Method and apparatus for drying substrate

[0002] The present invention relates to a method and apparatus for drying a substrate such as a semiconductor wafer and a liquid crystal display glass after the substrate has been cleaned.

[0003] FIG. 28 illustrates one example of a drying process known in the art. This known process is called the “direct displacement isopropyl alcohol (IPA) drying process”, also known as the “Marangoni drying process”. A rinsing bath 92 is closed by a lid 91 and filled with pure water 93. After a semiconductor wafer W (hereinafter, simply referred to as a “wafer”) has been cleaned by a chemical agent, it is immersed in the pure water 93 for rinsing purposes. A gas mixture of isopropyl alcohol vapor and nitrogen is then fed to the upper interior space of the rinsing bath 92 through gas inlet and outlet ports 95aand 95bto fill the upper interior space with the mixture.

[0004] Thereafter, a holder 94 on which the wafer W is placed is raised toward the upper interior space of the rinsing bath 92 as shown by phantom line in FIG. 28. When the wafer W upwardly passes past the level of the pure water, isopropyl alcohol is attached to the surface of the wafer W. A change in the surface tension of water due to concentration gradient of isopropyl alcohol causes a film of water attached to the surface of the wafer to be forced back to the pure water. This enables the surface of the wafer to be quickly dried out. In this example, the holder 94 is raised within the rinsing bath. Alternatively, the pure water 93 may be withdrawn from the rinsing bath 92 whereas the holder 94 is fixed in place.

[0005] FIG. 29 illustrates another example of a drying process known in the art. In this example, the holder 94 is fixed in place. A gas mixture of isopropyl alcohol vapor and nitrogen is fed to the upper interior space of the rinsing bath 92 through the gas inlet and outlet ports 95aand 95b. The gas pressure causes the pure water 93 to be displaced from the rinsing bath 92 through a drain valve 96. After the pure water 93 has been withdrawn, heated nitrogen is fed to the rinsing bath through second gas inlet and outlet ports 97aand 97bto thermally dry out the surface of the wafer. In this example, the pure water 93 is withdrawn. The holder 94 may alternatively be lifted.

[0006] FIG. 30 illustrates a further example of a drying process known in the art. This known process is called the “hot water drying process”. The pure water 93 within the rinsing bath 92 is heated to a predetermined temperature. The wafer W is immersed in the resulting hot water after it has been cleaned by a chemical agent. After the wafer has been rinsed, the holder 94 on which the wafer W is placed is raised to a position shown by phantom line in FIG. 30. The wafer is then dried by air or hot air. In this example, the holder 94 is lifted. The pure water 93 may alternatively be withdrawn from the rinsing bath 92 while the holder 94 may be fixed in place.

[0007] All of the known drying processes present the following common problems. As shown in FIG. 31A, the holder 94 includes a pair of support arms 94a. A plurality of Y-shaped wafer holding grooves 94bare formed in the upper ends of the support arms 94a. The wafer W is inserted into the grooves 94bwhereby the wafer W is held in a vertical orientation. As shown, on an enlarged scale, in FIG. 32, the wafer W is constantly in contact with a portion of the wafer holding groove 94b.

[0008] As shown in FIG. 32, a water droplet 98 remains between the wafer W and the groove 94bwhen the wafer W is moved out of the pure water, or the pure water is withdrawn from the rinsing bath.

[0009] In such a case, a certain period of time is required to dry out the water droplet 98. This results in an increase in the time required to complete the drying process and brings about a reduction in the throughput of the apparatus. Moreover, watermarks are left on the surface of the wafer due to foreign substance contained within the water droplet while the water droplet 98 is being dried. Such watermarks may cause the wafer to malfunction.

[0010] Accordingly, it is an object of the present invention to provide a method and apparatus for drying a substrate such as a semiconductor wafer, a liquid crystal display glass and the like, which prevent water droplets from remaining between the substrate and a holder on which the substrate is held when the substrate is rinsed by pure water or a similar rinsing liquid.

[0011] According to one aspect of the present invention, there is provided a method for drying a substrate by displacing the substrate relative to a rinsing liquid after the substrate is rinsed in a rinsing bath in which the rinsing liquid is contained. The method comprises the steps of: providing a first holder vertically movably arranged in the rinsing bath and including at least one substrate holding groove, and a second holder vertically movably arranged in the rinsing bath below the first holder and including at least one substrate holding groove; substantially vertically holding the substrate solely by the second holder, with the substrate engaged with the substrate holding groove of the second holder, when a level of the rinsing liquid passes past the substrate holding groove of the first holder; and after the level of the rinsing liquid has passed the substrate holding groove of the first holder, raising the first holder to bring the substrate holding groove thereof into engagement with the substrate and lowering the second holder to disengage the substrate holding groove of the second holder from the substrate, to thereby substantially vertically hold the substrate solely by the first holder, with the substrate engaged with the substrate holding groove of the first holder, when the level of the rinsing liquid downwardly passes past the substrate holding groove of the second holder.

[0012] According to the method of the present invention, the substrate is maintained out of contact with each of the holders when the level of the rinsing liquid passes past the substrate holding groove of a corresponding one of the holders. This prevents water droplets from being left between the holder and the substrate.

[0013] In a preferred embodiment, after the level of the rinsing liquid has passed past the substrate holding groove of the first holder, the substrate holding groove of the first holder is dried and then brought into contact with the substrate.

[0014] In a preferred embodiment, when the level of the rinsing liquid passes a lower end of the substrate, the lower end of the substrate is kept in contact with a triangular edged member to make a portion of the rinsing liquid remaining on the lower end of the substrate flow away therefrom.

[0015] According to another aspect of the present invention, there is provided an apparatus for drying a substrate by displacing the substrate relative to a rinsing liquid after the substrate is rinsed in a rinsing bath in which the rinsing liquid is contained. The apparatus comprises a first holder arranged in the rinsing bath to hold the substrate in a substantially vertical orientation and including at least one substrate holding groove with which the substrate is engageable, a second holder arranged in the rinsing bath below the first holder so as to hold the substrate in a substantially vertical orientation and including at least one substrate holding groove with which the substrate is engageable, and a holder lifting mechanism arranged to substantially vertically move the first holder and the second holder. The holder lifting mechanism is operable to substantially vertically move the first holder and the second holder, so that the substrate is held solely by the second holder when a level of the rinsing liquid downwardly passes past the substrate holding groove of the first holder, and the substrate is held solely by the first holder when the level of the rinsing liquid downwardly passes past the substrate holding groove of the second holder.

[0016] According to the apparatus of the present invention, the substrate is maintained out of contact with each of the holders when the level of the rinsing liquid passes past the substrate holding groove of a corresponding one of the holders. This arrangement prevents water droplets from being left between the holder and the substrate and brings about a reduction in the time required to dry out the substrate. Also, no watermark remains on the surface of the substrate, thus preventing a reduction in yieldability of the substrate.

[0017] In a preferred embodiment, the holder lifting mechanism is located in the vicinity of a bottom of the rinsing bath. The holder lifting mechanism includes a housing for defining a sealed space therein. The holder lifting mechanism further includes, within the sealed space, a first eccentric cam, a second eccentric cam, a third eccentric cam, a first guide plate, a second guide plate and a third guide plate. The second eccentric cam and the third eccentric cam are located at opposite sides of the first eccentric cam. The first, second and third guide plates are connected to the first, second and third eccentric cams, respectively and vertically moved when the first, second and third eccentric cams are rotated. The holder lifting mechanism further includes an actuator means for rotating the first, second and third eccentric cams. The first holder is composed of two holder members between which the second holder is interposedly located. One of the holder members is connected to the second guide plate, and the other holding member is connected to the third guide plate. The second holder is connected to the first guide plate. The housing may include a pair of upper and lower flexible sheets through which the second holder and the holder members are sealingly mounted on the first guide plate and the second and third guide plates, respectively. By such arrangement, the holder lifting mechanism is maintained out of direct contact with the rinsing liquid. Under the circumstances, no contaminant or foreign substance is introduced from the holder lifting mechanism into the rinsing liquid. The substrate can thus be dried with a high degree of cleanability.

[0018] In a preferred embodiment, the first holder and the second holder are vertically moved synchronously in opposite directions. When one of the first and second holders is raised, the other holder is lowered. This arrangement prevents a change in the volume of the rinsing liquid which may occur when the flexible sheets are vertically moved as well as a change in the level of the rinsing liquid which may occur when the first and second holders are vertically moved in opposite directions. The substrate can thus be dried with a high degree of cleanability since the rinsing water will in no way bubble or splash.

[0019] In a preferred embodiment, the holder lifting mechanism includes a pair of sealed casings spaced apart at a predetermined distance and located in the vicinity of a bottom of the rinsing bath. The holder lifting mechanism further includes a pair of first eccentric cams, a pair of second eccentric cams, a pair of third eccentric cams, a pair of first guide plates, a pair of second guide plates and a pair of third guide plates. The pairs of first, second and third eccentric cams and the pairs of first, second and third guide plates are located within the pair of respective sealed casings. The pairs of second and third eccentric cams are located at opposite sides of the pair of first eccentric cams. The pairs of first, second and third guide plates are connected to the pairs of first, second and third eccentric cams, respectively and vertically moved when the pairs of first, second and third eccentric cams are rotated. The holder lifting mechanism includes a first pipe extending between the pair of sealed casings in a watertight manner, a first rotary actuator contained within the first pipe and connected to the pair of first eccentric cams, a second pipe extending between the pair of sealed casings in a watertight manner and a second rotary actuator contained within the second pipe and connected to the pair of second eccentric cams. The holder lifting mechanism further includes a third pipe extending between the pair of sealed casings in a watertight manner and a driven shaft extending through the third pipe. The pair of third eccentric cams are connected to the driven shaft. The driven shaft has one end thereof linked to the second rotary actuator, whereby the driven shaft is rotated synchronously with the second rotary actuator. The first holder is composed of two holder members between which the second holder is interposedly located. One of the two holder members extends between the pair of second guide plates, and the other holder member extends between the pair of third guide plates. The second holder extends between the pair of third guide plates. By this arrangement, no obstacle which may inhibit the flow of the rinsing liquid exists between the bottom of the rinsing bath and the substrate. Thus, the substrate can be more efficiently dried out.

[0020] In a preferred embodiment, the second holder is formed with a central opening extending vertically therethrough. The holder lifting mechanism includes a floating member floatable on the rinsing liquid and having a triangular edged top inserted into the central opening and adapted to be brought into contact with a lower end of the substrate by buoyancy thereof. The rinsing liquid may remain in the lower end of the substrate when the level of the rinsing liquid is downwardly moved away from the lower end of the substrate. However, this arrangement causes the rinsing liquid to flow along the edged top of the floating member and then, into the rinsing liquid. No water droplet thus remains at the lower end of the substrate, enabling the surface of the substrate and the grooves to be dried in a significantly short period of time.

[0021] The principle of the present invention will be explained with reference to FIGS. 1A to 1E.

[0022] As shown, wafers W are fixed in place, whereas pure water 26 is withdrawn from a rinsing bath 1. To carry out the present invention, first and second holders 2 and 3 are required to hold the wafers W. The second holder 2 is located below the first holder 3.

[0023] After the wafers W have been cleaned by a suitable chemical agent, the wafers W are vertically placed on the first and second holders 2 and 3 within the rinsing bath 1 as shown in FIG. 1A.

[0024] At the initial stage of the process, the wafers W may be held by the both first and second holders 2 and 3 or may be held by either the first holder 2 or the second holder 3. However, it is preferable that the wafers W be held solely by the second holder 3. This arrangement facilitates movement of the holders in the following steps.

[0025] After the wafers W are placed on the second holder 3, the pure water or a similar rinsing liquid 26 is introduced into the rinsing bath 1, as shown in FIG. 1B, so as to rinse out or remove the chemical agent and the like from the surfaces of the wafers W. After the wafers W have been rinsed, as the pure water 26 is withdrawn from the rinsing bath 1, the wafers W are dried by using the direct displacement IPA drying process or hot water drying process as explained above.

[0026] Then, as shown in FIG. 1C, when a level of the pure water 26 reaches the upper end of the first holder 2 or wafer holding grooves thereof as indicated at L₁, the first holder 2 is lowered by a predetermined distance, and the second holder 3 is controlled so as to hold the wafers W solely thereby, resulting in the wafers W being out of contact with the first holder 2. The second holder 3 has a height less than that of the first holder 2 and is located inside the first holder 2.

[0027] With the wafers W maintained out of contact with the first holder 2, no water droplet remains between the wafers W and the first holder 2 when the level of the pure water 26 is further lowered. As such, the wafers W and the grooves of the first holder 2 can be cleanly dried out in a significantly short period of time.

[0028] Next, as shown in FIG. 1D, when the level of the pure water 26 is lowered to the upper end of the second holder 3. or wafer holding grooves thereof as indicated at L₂, the first holder 2 is raised to hold the wafers W, and at the same time, the second holder 3 is moved down by a predetermined distance, so that the wafers W are held solely by the first holder 2. The wafers W are now maintained out of contact with the second holder 3 and held solely by the first holder 2.

[0029] With the wafers W maintained out of contact with the second holder 3, no water droplet remains between the wafers W and the second holder 3 when the level of the pure water 26 is further lowered. As such, the wafers W and the grooves of the second holder 3 can be cleanly dried out in a significantly short period of time.

[0030] Referring to FIG. 1E, the drying process is completed when the level of the pure water 26 reaches the lower ends of the wafers W as indicated at L₃, or when the pure water 26 has been fully withdrawn from the rinsing bath 1. Thereafter, the wafers W are transferred for a next step by means of a conveyor mechanism (not shown).

[0031] FIGS. 1A to 1E illustrate the principle of a method according to the present invention;

[0032] FIG. 2 is a schematic vertical sectional view of a drying apparatus according to a first embodiment of the present invention;

[0033] FIG. 3 is a schematic plan view of the drying apparatus shown in FIG. 2;

[0034] FIG. 4 is a sectional view taken along the line 4—4 in FIG. 2;

[0035] FIG. 5 is a sectional view taken along the line 5—5 in FIG. 2;

[0036] FIG. 6 is a front view of a first holder;

[0037] FIG. 7 is a plan view of the first holder shown in FIG. 6;

[0038] FIG. 8 is a side view of the first holder shown in FIG. 6;

[0039] FIG. 9 is an enlarged view of a plurality of wafer holding grooves of the first holder;

[0040] FIG. 10 is a front view of a second holder;

[0041] FIG. 11 is a plan view of the second holder shown in FIG. 10;

[0042] FIG. 12 is a side view of the second holder shown in FIG. 10;

[0043] FIGS. 13A and 13B show the manner in which a wafer is separated from the grooves of the first holder;

[0044] FIG. 14 is a schematic sectional view of a drying apparatus according to a second embodiment of the present invention;

[0045] FIG. 15 is a schematic plan view of the drying apparatus shown in FIG. 14;

[0046] FIG. 16 is a sectional view taken along the line 16—16 in FIG. 15;

[0047] FIG. 17 is a schematic sectional view of a drying apparatus according to a third embodiment of the present invention;

[0048] FIG. 18 is a schematic plan view of the drying apparatus shown in FIG. 17;

[0049] FIG. 19 is a sectional view taken along the line 19—19 in FIG. 17;

[0050] FIG. 20 is a sectional view taken along the line 20—20 in FIG. 19;

[0051] FIG. 21 is a sectional view taken along the line 21—21 in FIG. 19;

[0052] FIG. 22 is a perspective view showing the manner in which a link mechanism is connected;

[0053] FIGS. 23A and 23B are side and plan views of a second holder;

[0054] FIG. 24 is a perspective view of a floating member;

[0055] FIG. 25 shows the manner in which the floating member is operated;

[0056] FIG. 26 shows the manner in which a guide plate, centrally located in FIG. 17, is operated;

[0057] FIG. 27A shows the manner in which a guide plate, located at the right side in FIG. 17, is operated;

[0058] FIG. 27B shows the manner in which a guide plate, located at the left side in FIG. 17, is operated;

[0059] FIG. 28 illustrates one example of a drying process known in the art;

[0060] FIG. 29 illustrates another example of a drying process known in the art;

[0061] FIG. 30 illustrates a further example of a drying process known in the art;

[0062] FIG. 31A is a front view of a holder used in the prior art;

[0063] FIG. 31B is a sectional view taken along the line 31B—31B in FIG. 31A; and

[0064] FIG. 32 shows the manner in which a wafer is engaged with wafer holding grooves of the holder.

[0065] The present invention will now be described, by way of example, with reference to the accompanying drawings.

[0066] FIGS. 2 to 13B illustrate a drying apparatus according to a first embodiment of the present invention.

[0067] Illustratively, the present invention is applied to a drying apparatus of the type in which pure water or a rinsing liquid is withdrawn from a rinsing bath whereas two holders for supporting substrates are fixed in place.

[0068] Referring specifically to FIGS. 2 and 3, pure water is contained in a rinsing bath 1. A holder lifting mechanism 4 is arranged in the vicinity of the bottom of the rinsing bath 1 so as to selectively move up and down a pair of first holders 2aand 2band a second holder 3. A pair of actuator containers 7aand 7bare disposed at opposite sides of the holder lifting mechanism 4. A pair of pneumatically driven actuators 6aand 6bare contained within the corresponding actuator containers 7aand 7band adapted to drive the holder lifting mechanism 4.

[0069] Although not specifically shown, the actuator containers 7aand 7beach include an air inlet for feeding air under pressure to the actuators 6aand 6b, an air outlet, and an air vent through which the interior of each of the holder lifting mechanism 4 and the actuator containers 7aand 7bis communicated with ambient atmosphere.

[0070] The first actuator 6aincludes a drive shaft 8awhich is connected through a coupling 9ato a first drive shaft 10aof the holder lifting mechanism 4. A pair of eccentric cams 11aand 11bare fixedly mounted on the first drive shaft 10aimmediately below the corresponding first holders 2aand 2bso as to move up and down the first holders 2aand 2b, respectively.

[0071] Similarly, the second actuator 6bincludes a drive shaft 8bwhich is connected through a coupling 9bto a second drive shaft 10bof the holder lifting mechanism 4. An eccentric cam 11cis fixedly mounted on the second drive shaft 10bimmediately below the second holder 3 so as to move up and down the second holder 3.

[0072] The first drive shaft 10aand the second drive shaft 10bextend through and are held in place by two reinforcing plates 12aand 12b. The two reinforcing plates 12aand 12bthus serve as bearings as well as positioning plates.

[0073] The holder lifting mechanism 4 includes a front plate 13a, a rear plate 13b, a right side plate 14a, and a left side plate 14b. These four plates are assembled as a sealed housing. A pair of flexible sheets 15aand 15b, made for example of polytetrafluoroethylene, are sealingly attached to the upper and lower sides of the housing through gaskets (not shown). A pair of linear sliders 16aand 16bare mounted to the inner side of the rear plate 13bso as to guide vertical movement of the corresponding first holders 2aand 2b. Similarly, a linear slider 16cis mounted to the inner side of the rear plate 13bso as to guide vertical movement of the second holder 3.

[0074] Three guide plates 17ato 17care slidably mounted to the corresponding linear sliders 16ato 16cfor vertical sliding movement. As shown in FIG. 4, the upper end of each of the guide plates 17aand 17bis sealingly secured to the first holders 2aand 2bthrough the upper flexible sheet 15a. The lower end of each of the guide plates 17aand 17bis sealingly secured to the lower flexible sheet 15bthrough retainer plates 18aand 18b.

[0075] The guide plates 17aand 17binclude horizontal U-shaped recesses 19aand 19bwithin which the eccentric cams 11aand 11bfixed on the first drive shaft 10aare rotatably received, respectively.

[0076] With this arrangement, the first actuator 6ais controllably operated to rotate the first drive shaft 10atogether with the eccentric cams 11aand 11bincrementally by 180°. This causes the guide plates 17aand 17bto be vertically moved by a distance corresponding to the amount of displacement of the eccentric cams 11aand 11bfrom the axis of rotation of the drive shaft 10a. The first holders 2aand 2bare vertically moved with the guide plates 17aand 17b.

[0077] As shown in FIG. 5, the upper end of the guide plate 17cis sealingly secured to the second holder 3 through the upper flexible sheet 15a. The lower end of the guide plate 17cis sealingly secured to the lower flexible sheet 15bthrough a retainer plate 18c.

[0078] The guide plate 17cincludes a horizontal U-shaped recess 19cwithin which the eccentric cam 11cfixed on the second drive shaft 10bis rotatably received.

[0079] With this arrangement, the second actuator 6bis controllably operated to rotate the second drive shaft 10btogether with the eccentric cam 11cincrementally by 180°. This causes the guide plate 17cto be vertically moved by a distance corresponding to the amount of displacement of the eccentric cam 11cfrom the axis of rotation of the second drive shaft 10b. The second holder 3 is vertically moved with the second guide plate 17c.

[0080] Referring specifically to FIGS. 6 to 8, the first holders 2aand 2beach include two support projections or arms 20aand 20b. The length of the two support arms 20aand 20band the space between the two support arms 20aand 20bare selected depending upon the size of a wafer W. A predetermined number of wafer holding grooves 21aand 21bare formed in the respective upper ends of the support arms 20aand 20bto receive the wafers W. The reference numeral 22 designates a bolt hole through which a bolt extends so as to secure the first holders 2aand 2bto the upper ends of the guide plates 17aand 17b, respectively.

[0081] As shown, on an enlarged scale, in FIG. 9, the grooves 21aand 21beach have a width significantly greater than the thickness of the wafer W. The grooves 21aand 21bhave respective slant surfaces inclined in opposite directions and slightly laterally displaced so as to hold the wafer W in its vertical orientation while the wafer W is interposed between the grooves 21aand 21b.

[0082] This particular shape of the grooves 21aand 21benables tight holding of the wafer W. When the wafer W is spaced away from the grooves 21aand 21b, a sufficient space is left between the wafer W and the grooves 21aand 21bas shown in FIGS. 13A and 13B, to thereby minimize the risk that water droplets remain within the grooves 21aand 21b.

[0083] As shown in FIGS. 10 to 12, the second holder 3 includes four support arms 23ato 23d. A plurality of wafer holding grooves 24ato 24dare formed in the respective upper ends of the support arms 23ato 23dand are similar in shape to the grooves 21aand 21bof the first holders 2aand 2b. The reference numeral 25 designates a bolt hole through which a bolt extends so as to secure the second holder 3 to the upper end of the guide plate 17c.

[0084] Reference will next be made to a drying process carried out by the drying apparatus.

[0085] At the initial stage of the process, the wafers W are held solely by the second holder 3, and the first holders 2aand 2bare located downwardly from the wafer W.

[0086] The wafers W are transferred to the rinsing bath 1 by means of a conveyor mechanism and a chuck (not shown) after they have been cleaned by a suitable chemical or washing agent. The wafers W are vertically placed on the second holder 3 within the rinsing bath 1. The rinsing bath 1 is covered by an upper lid (not shown). Pure water 26 is then fed from a supply of pure water (not shown) so as to rinse the surfaces of the wafers W.

[0087] After the wafers W have been rinsed, a mixture of isopropyl alcohol and nitrogen is fed from a gas resource (not shown) to the upper interior space of the rinsing bath 1. A drain valve (not shown) is then opened to withdraw the pure water from the rinsing bath 1.

[0088] The pure water may be withdrawn at the highest possible speed until the level of the water reaches the upper ends of the wafers W. After the water level reaches the upper ends of the wafers W, the drain valve should be controlled to allow the pure water to be withdrawn at a speed, for example, 1.5 cm/sec, suitable for achieving the Marangoni effect.

[0089] When the water level becomes below the tops of the wafers W, a portion of a surface of each of the wafers W above the water level is cleanly dried under the Marangoni effect as the water level is lowered along the surfaces of the wafers W. When the water level reaches the upper ends of the first holders 2aand 2bor position of the grooves 21aand 21b, as indicated at L₁, the pure water will barely be left in the grooves 21aand 21bsince the wafer W is spaced away from the grooves 21aand 21b(see FIGS. 13A and 13B).

[0090] As such, the wafer W and the grooves 21aand 21bcan be dried in a significantly short period of time after the wafer W and the grooves 21aand 21bare located above the water level. In the prior art arrangement, a substantial number of water droplets are left at contact portions between a wafer and wafer holding grooves. Watermarks thus remain when such water droplets are dried. In the present invention, no watermark remains since water droplets are barely left between the wafer and the grooves 21aand 21b.

[0091] When the water level is further lowered to the upper end of the second holder 3 or position of the grooves 24aand 24b, as indicated at L₂, a controller (not shown) is operable to control the actuators 6aand 6bso as to rotate the first drive shaft 10aand the second drive shaft 10bby 180°.

[0092] As the eccentric cams 11ato 11care rotated with the first and second drive shafts 10aand 10b, the guide plates 17aand 17bare moved up by a distance corresponding to the amount of displacement of the cams 11aand 11bfrom the axis of rotation, whereas the guide plate 17cis moved down by a distance corresponding to the amount of displacement of the cam 11cfrom the axis of rotation.

[0093] The first holders 2aand 2bare moved up with the guide plates 17aand 17b, respectively through the flexible sheet 15a. Also, the second holder 3 is moved down with the guide plate 17cthrough the flexible sheet 15a. When the water level reaches the upper end of the second holder 3, as indicated at L₂, the wafers W are separated from the grooves 24ato 24dof the second holder 3 and instead, held by the first holders 2aand 2b, i.e. the wafers W are held by the grooves 21aand 21bof the first holders 2aand 2bwhich grooves are dried.

[0094] When the water level is further lowered to the grooves 24ato 24bof the second holder 3, the pure water 26 will barely be left between the wafer W and the grooves 24ato 24dsince the wafer W has already been disengaged from the grooves 24ato 24das described above.

[0095] As such, the wafer W and the grooves 24ato 24dcan be dried in a significantly short period of time after the wafer W and the grooves 24ato 24dare located above the water level. As stated above, in the prior art arrangement, a substantial number of water droplets are left between a wafer and wafer holding grooves. Watermarks remain when such water droplets are dried. In the present invention, no watermark remains since water droplets are barely left between the wafer W and the grooves 24ato 24d.

[0096] This drying process is completed when the level of the pure water 26 is lowered below the lower ends of the wafers W, as indicated at L₃, or when the pure water 26 is fully discharged from the rinsing bath 1. The wafers W are thereafter moved out of the rinsing bath 1 and transferred for a next processing step by means of a chuck and a conveyor mechanism (not shown).

[0097] It should be noted that the flexible sheets 15aand 15bin their entirety are vertically moved with the first holders 2aand 2band the second holder 3. This results in variations in the volume of the rinsing bath 1 and thus, the level of the pure water within the rinsing bath 1. To this end, in this embodiment, the first holders 2aand 2band the second holder 3 are moved in opposite directions. That is, when the first holders 2aand 2bare raised, the second holder 3 is simultaneously lowered. When the first holders 2aand 2bare lowered, the second holder 3 is simultaneously raised. This accommodates a change in the volume of the rinsing bath 1, eliminates a corresponding change in the water level and thus, prevents the pure water from bubbling or splashing. The wafers can thus be cleaned with a higher degree of cleanability.

[0098] FIGS. 14 to 16 illustrate a second embodiment of the present invention.

[0099] The second embodiment includes a holder lifting mechanism which is different in structure from that used in the first embodiment.

[0100] In the second embodiment, a holder lifting mechanism includes a first linear drive mechanism 33 connected through a connecting rod 32 to a first holder 2, and a second linear drive mechanism 35 connected through a connecting rod 34 to a second holder 3. The first and second linear drive mechanisms 33 and 35 are controllably operated to vertically move the first and second holders 2 and 3, respectively.

[0101] The timing of vertical movement of the first and second holders 2 and 3 and the drying process are identical to those referred to in the first embodiment and will not be described herein.

[0102] FIGS. 17 to 25 illustrate a drying apparatus according to a third embodiment of the present invention. In FIG. 17, the drying apparatus is shown with an upper lid removed for clarity. Like parts are given like reference numerals used in the first embodiment.

[0103] As shown in FIGS. 17 to 19, a holder lifting mechanism 4 of the third embodiment includes a pair of sealed casings 41aand 41binterconnected by three pipes 42 to 44. A suitable mechanism is arranged in the sealed casings 41aand 41bto vertically move first holders 2aand 2band a second holder 3.

[0104] Disposed within the centrally located pipe 42 (see FIG. 19) is a first rotary actuator 45 as a drive means for vertically moving the second holder 3. As shown in schematic section in FIG. 21, the first rotary actuator 45 includes a rotor 45brotatably mounted within a cylindrical member 45a. The cylindrical member 45aincludes an air inlet 45cand an air outlet 45d. Air under pressure is selectively fed into and discharged from the first rotary actuator 45 through the air inlet 45cand the air outlet 45dso as to reversibly rotate the rotor 45bby 180°.

[0105] A second rotary actuator 46 is mounted within the pipe 43 (right side in FIG. 19) and serves as a drive means for vertically moving the first holders 2aand 2b. As in the first rotary actuator 45 shown in FIG. 21, the second rotary actuator 46 includes an air inlet 46cand an air outlet 46d. Air under pressure is fed into and discharged from the second rotary actuator 46 so as to reversibly rotate a rotor 46bby 180°.

[0106] Disposed within the pipe 44 (left side in FIG. 19) is a driven shaft 48 driven by the second rotary actuator 46 through opposite links 47aand 47b.

[0107] Two shafts 49aand 49bare connected to opposite ends of the first rotary actuator 45 within the pipe 42. As the rotor 45bis rotated by 180°, the shafts 49aand 49bare also rotated by 180° in the same direction. The shafts 49aand 49bextend into the left and right sealed casings 41aand 41bthrough a pair of opposite bearings 50aand 50b, respectively. A pair of eccentric cams 51aand 51bare fixedly mounted on the distal ends of the shafts 49aand 49b, respectively.

[0108] A pair of guide plates 53aand 53bare vertically moved along a corresponding pair of linear sliders 52aand 52band include respective horizontal U-shaped recesses 54aand 54bwithin which the eccentric cams 51aand 51bare respectively received. The guide plates 53aand 53bare designed to convert rotary movement into vertical movement. When the eccentric cams 51aand 51bare rotated by 180°, the guide plates 53aand 53bare vertically moved by a distance corresponding to the offset amount of the eccentric cams 51aand 51b. To minimize frictional resistance between the eccentric cams 51aand 51band the recesses 54aand 54b, a pair of bearings 55aand 55bare fitted around the two eccentric cams 51aand 51b, respectively.

[0109] To vertically move the second holder 3, a pair of drive shafts 56aand 56beach have one end thereof connected to the upper surface of a corresponding one of the guide plates 53aand 53band the other end thereof connected to the second holder 3. The drive shafts 56aand 56bextend into the rinsing bath 1 through the tops of the sealed casings 41aand 41b. A pair of bellows 57aand 57bare disposed around the corresponding drive shafts 56aand 56bso as to prevent entry of the pure water into the sealed casings 41aand 41b. The drive shafts 56aand 56bare freely moved up and down through the bellows 57aand 57b.

[0110] Two shafts 58aand 58bare connected to opposite ends of the second rotary actuator 46 within the pipe 43. As the rotor 46bis rotated by 180°, the shafts 58aand 58bare also rotated by 180° in the same direction. The shafts 58aand 58bextend into the left and right sealed casings 41aand 41bthrough a pair of bearings 59aand 59b, respectively. A pair of eccentric cams 60aand 60bare fixedly mounted on the distal ends of the shafts 58aand 58b, respectively.

[0111] A pair of guide plates 62aand 62bare vertically moved along a corresponding pair of linear sliders 61aand 61band include respective horizontal U-shaped recesses 62aand 62bwithin which the eccentric cams 60aand 60bare respectively received. The guide plates 62aand 62bare designed to convert rotary movement into vertical movement. When the eccentric cams 60aand 60bare rotated by 180°, the guide plates 62aand 62bare vertically moved by a distance corresponding to the offset amount of the eccentric cams 60aand 60b. To minimize frictional resistance between the eccentric cams 60aand 60band the recesses 63aand 63b, a pair of bearings 64aand 64bare fitted around the two eccentric cams 60aand 60b, respectively.

[0112] To vertically move the first holder 2a, a pair of drive shafts 65aand 65beach have one end thereof connected to the upper surface of a corresponding one of the guide plates 62aand 62band the other end thereof connected to the first holders 2a. The drive shafts 65aand 65bextend into the rinsing bath 1 through the tops of the sealed casings 41aand 41b. A pair of bellows 66aand 66bare disposed around the corresponding drive shafts 65aand 65bso as to prevent entry of the pure water into the sealed casings 41aand 41b. The drive shafts 65aand 65bare freely moved up and down through the bellows 66aand 66b.

[0113] The driven shaft 48 is received within the pipe 44. The driven shaft 48 extends into the sealed casing 41aand 41b. The links 47aand 47bare connected to opposite ends of the driven shaft 48. The driven shaft 48 is driven by the second rotary actuator 46 through the links 47aand 47b. The eccentric cams 68aand 68bare fixedly mounted on the opposite ends of the driven shaft 48.

[0114] A pair of guide plates 70aand 70bare vertically moved along a corresponding pair of linear sliders 69aand 69band include respective horizontal U-shaped recesses 71aand 71bwithin which the eccentric cams 68aand 68bare respectively received. The guide plates 70aand 70bare designed to convert rotary movement into vertical movement. When the eccentric cams 68aand 68bare rotated by 180°, the guide plates 70aand 70bare vertically moved by a distance corresponding to the offset amount of the eccentric cams 68aand 68b. To minimize frictional resistance between the eccentric cams 68aand 68band the recesses 71aand 71b, a pair of bearings 72aand 72bare fitted around the two eccentric cams 68aand 68b, respectively.

[0115] To vertically move the first holder 2b, a pair of drive shafts 73aand 73beach have one end thereof connected to the upper surface of a corresponding one of the guide plates 70aand 70band the other end thereof connected to the first holder 2b. The drive shafts 73aand 73bextend into the rinsing bath 1 through the tops of the sealed casings 41aand 41b. A pair of bellows 74aand 74bare disposed around the corresponding drive shafts 73aand 73bso as to prevent entry of the pure water into the sealed casings 41aand 41b. The drive shafts 73aand 73bare freely moved up and down through the bellows 74aand 74b.

[0116] As shown in FIG. 22, the links 47aand 47beach have one end thereof connected to a corresponding one of the shafts 58aand 58bthrough a respective one of levers 75aand 75band the other end thereof connected to the driven shaft 48 through a respective one of opposite levers 76aand 76b. The levers 75aand 76aand the levers 75band 76bare displaced from each other by 90° so as to promote smooth reciprocating movement of the links 47aand 47b.

[0117] The first holders 2aand 2band the second holder 3 used in the third embodiment are basically similar in structure to those used in the first embodiment, but the following attempts are made to the second holder 3 used in the third embodiment.

[0118] Referring specifically to FIGS. 23A and 23B, the second holder 3 includes a central opening 80 to receive a floating member 81.

[0119] The floating member 81 includes a floating body 81bwith a triangular edged top 81a, and a pair of side arms 81cextending horizontally from opposite sides of the floating body 81b. The floating body 81bis much hydrophilic to the pure water than the wafer W. The floating body 81bis made of synthetic resin having a specific gravity less than that of the pure water. Alternatively, the floating body 81bmay be made of metal. In such a case, however, the floating body 81bshould be hollow so that it may float on the surface of the pure water. In this instance, the floating body 81bis made of, for example, polyetherethrketone (PEEK).

[0120] As shown in FIGS. 17 and 18, the side arms 81cand 81cof the floating member 81 are pivotally mounted at their one ends to the side wall of the sealed casings 41aand 41bthrough pins 83aand 83b, respectively. As shown in FIG. 25, when a level La of the pure water is located above the floating member 81, the floating body 81bis upwardly pivoted about the pins 83aand 83bby buoyancy thereof, as shown by solid line, to cause the edged top 81aof the floating body 81bto make contact with the lower end of the wafer W.

[0121] On the other hand, when the level Lb of the pure water is located below the floating member 81, the floating body 81bis downwardly pivoted by its weight, as shown by phantom line, to cause the edged top 81ato moved away from the lower end of the wafer W. This arrangement enables the edged top 81aof the floating body 81bto make water droplets, which may, otherwise, remain on the lower end of the wafer W, flow away therefrom when the level of the pure water passes past the lower end of the wafer W, resulting in no water droplet remaining on the lower edge of the wafer W.

[0122] Reference will now be made to the process carried out by the drying apparatus according to the third embodiment.

[0123] At the initial stage of the process, all of the guide plates 53a, 53b, 60a, 60b, 70aand 70bare located in their uppermost position as shown by solid line in FIGS. 26, 27A and 27B, and the wafer W is held by all of the first holders 2aand 2band the second holder 3.

[0124] After the wafers W have been cleaned by a suitable chemical agent, the wafers W are transferred to the interior of the rinsing bath 1 by means of a conveyor mechanism and a chuck (not shown). The wafers W are then vertically placed on the first holders 2aand 2band the second holder 3. After the open top of the rinsing bath 1 is closed by an upper lid (not shown), the pure water is introduced from a supply of pure water (not shown) so as to rinse the surfaces of the wafers W.

[0125] After the wafers W have been rinsed out, a gas mixture of isopropyl alcohol vapor and nitrogen is fed from a gas resource (not shown) to the upper interior space of the rinsing bath 1, and a drain valve (not shown) is opened to withdraw the pure water from the rinsing bath 1 at a predetermined speed. When the level of the pure water is lowered and then, passes past the surfaces of the wafers W, the wafers are efficiently dried under the Marangoni effect as described above.

[0126] When the level of the pure water is lowered to near the upper ends of the first holders 2aand 2b, the second rotary actuator 46 is driven to rotate the rotor 46bby 180°. This causes the shafts 58aand 58bto be rotated by 180° in the same direction.

[0127] The eccentric cams 60aand 60bare rotated with the shafts 58aand 58bby 180° as shown by phantom line in FIG. 27A to thereby move the guide plates 62aand 62bfrom a position shown by solid line to the lowermost position shown by phantom line. As a result, the first holder 2aconnected to the end of the drive shafts 65aand 65bis lowered to the lowermost position and separated from the wafers W (see FIGS. 13A and 13B).

[0128] The rotation of the shafts 58aand 58bis transmitted to the driven shaft 48 through the links 47aand 47b, whereby the driven shaft 48 is rotated by 180° in the same direction simultaneously with the rotor 46b. The eccentric cams 68aand 68bare rotated with the driven shaft 48 by 180° as shown by phantom line in FIG. 27B to thereby move the guide plates 70aand 70bto the lowermost position shown by phantom line. As a result, the first holder 2bconnected to the end of the drive shafts 73aand 73bis also lowered to the lowermost position and separated from the wafers W (see FIGS. 13A and 13B).

[0129] The wafers W are then held only by the second holder 3. As described above, the links 47aand 47bare mounted to the shafts 58aand 58band the driven shaft 48 with the levers 75aand 76aand the levers 75band 76bwhile being displaced from each other by 90°. Thus, the links 47aand 47bcan be smoothly rotated at this time.

[0130] When the level of the pure water is lowered to the grooves 21aand 21bof the first holders 2aand 2b(see FIGS. 6 to 8), the pure water will in no way remain in the grooves 21aand 21bsince each of the wafers W has already been separated from the grooves 21aand 21b.

[0131] As such, the wafers W and the grooves 21aand 21bcan be dried in a significantly short period of time, and no watermark will be left on the surfaces of the wafers W.

[0132] When the level of the pure water is further lowered to near the upper end of the second holder 3, the second rotary actuator 46 is rotated by 180° and returned to its initial position. This causes the guide plates 62a, 62b, 70aand 70bto be returned to their uppermost position as shown by solid line in FIGS. 27A and 27B. At the same time, the first rotary actuator 45 is driven to rotate the rotor 45bby 180°. This causes the shafts 49aand 49bto be rotated by 180° in the same direction.

[0133] Also, the eccentric cams 51aand 51bare rotated with the shafts 49aand 49bso as to move the guide plates 53aand 53bto their lowermost position as shown by phantom line in FIG. 26. This movement causes the second holder 3 to be moved to its lowermost position and separated from the wafers W.

[0134] Under the circumstances, the wafers W are held only by the first holders 2aand 2brather than the second holder 3.

[0135] Although the second holder 3 is separated from the wafers W, the floating body 81bof the floating member 81 is upwardly pivoted about the pins 83aand 83bby its buoyancy to allow the edged top 81ato be in contact with the lower ends of the wafers W, as shown in FIG. 25.

[0136] By this arrangement, the pure water will in no way remain in the grooves 24ato 24d, as opposed to the prior arrangement, when the level of the pure water passes past the grooves 24ato 24dof the second holder 3 (see FIG. 10). This is because the grooves 24ato 24dhave already been separated from the wafers W.

[0137] When the level of the pure water is moved downwardly to leave the lowermost ends of the wafers W, the last water droplet attached to the lower end of each of the wafers W is caused to flow away along the edged top 81aof the floating body 81band is, then, directed to the pure water. In this way, substantially all of the water droplets can be removed from the lower ends of the wafers W.

[0138] Accordingly, the surface of the wafer W and the grooves 24ato 24dwill be dried in a significantly short period of time.

[0139] This drying process is completed when the level of the pure water is moved below the lower ends of the wafers W or when the pure water is completely withdrawn from the rinsing bath 1. After this process is carried out, the wafers W are transferred for a next step by means of the chuck and the conveyor mechanism.

[0140] In the third embodiment, the sealed casings 41aand 41bare connected by the three pipes 42 to 44 only, and no such obstacle as the flexible sheets 15aand 15bused in the first embodiment (see FIG. 2) exist between the bottom of the rinsing bath 1 and the wafers W. This advantageous arrangement promotes rinsing of the wafers.

[0141] It should be understood that the floating member 81 may be employed in the first and second embodiments.

[0142] In all of the three embodiments, the pure water is used as a rinsing liquid. However, the present invention is not limited thereto. A wide variety of rinsing liquids may be used depending upon the types of wafers and rinsing requirements.

[0143] Also, the semiconductor wafer is used as a substrate to be rinsed and dried. However, the present invention is not limited thereto. For example, there may be employed a liquid crystal display glass or other disks.

[0144] Illustratively, the present invention is applied to a direct displacement IPA drying apparatus. However, the present invention is not limited thereto. The present invention is equally applicable to any types of drying apparatus in which a substrate is dried by moving the substrate out of a rinsing liquid or discharging the rinsing liquid after the substrate is immersed in the rinsing liquid while being held in a vertical orientation by holders.

[0145] The present invention has been described with respect to its preferred embodiments. It is to be understood, however, that various modifications and changes may be made without departing from the scope of the appended claims.