Laser-Activated Chemical-Depositing Method and Apparatus

The present invention relates to chemical deposition, also called electroless deposition, and more particularly to a new and improved chemical or electroless deposition method and apparatus whereby a local depositability of the surfaces is controlled or enhanced. The invention is particularly advantageous in forming, among others, an intricate pattern of deposit upon a surface without masking or a uniform layer of deposit upon a substrate regardless of the complexity of the contour thereof.

Chemical deposition has been known to be a slow deposition process. Moreover, the process has been recognized to be generally inefficient. For example, when a pattern of metal deposit is to be chemically formed on a substrate as practiced in the manufacture of electronic circuit devices, masking has been commonly required and is quite often highly intricate. Not only does the conventional masking procedure make the total process inefficient and costly, it imposes serious restriction on the size of the pattern which can be batch-deposited.

With the chemical deposition process, difficulties have also been encountered in assuring uniformity of a layer of deposit, especially where the receiving substrate is shaped with an intricate contour having ridges or edges and recesses. Generally, the deposit tends to build up predominantly on relatively projecting areas and may occur hardly at all at a recessed corner portion, resulting in an irregularity of deposition over the entire surface and this tendency is generally accentuated as the process continues. While various techniques have been proposed to reduce the deposit irregularity, none of them has been found to be satisfactory on account of efficiency and economy.

In general, there is a consistent desire in the art of chemical or electroless deposition to increase the rate of deposition, to enhance the efficiency of the process and to develop a high-precision layer of deposit which is uniform or controllable in thickness.

The present invention seeks to provide a novel and improved chemical or electroless deposition method which affords an increased rate of deposition over the prior art and which also allows any desired pattern of metal deposit or a desired uniform layer of metal deposit to be achieved readily and with due precision.

The present invention also seeks to provide a novel and improved chemical or electroless deposition apparatus whereby a desired pattern or layer of metal deposit is obtainable with due precision and yet with greater efficiency than with the prior art.

In accordance with the present invention there is provided in a first aspect thereof a method of chemically depositing a metal on a substrate, which comprises: bringing a solution containing the metal into contact with the substrate; irradiating a localized area on the substrate with a light beam, thereby activating an interface between the area and the solution to allow the metal to be chemically deposited therefrom selectively on that area; and relatively displacing the light beam and the substrate to shift the localized area of interception of the incident light beam successively over a desired surface region of the substrate whereby the metal is sequentially deposited on the surface region.

Preferably, the chemical-depositing solution should be forced to flow at a high velocity, viz. in excess of 5 meters/sec and less than 100 meters/sec, preferably not greater than 25 meters/sec, in the region of the localized area.

Specifically, the light beam is advantageously a laser beam but may be a narrow beam of intense light in any other form such as from a xenon lamp. It has been found to be desirable to maintain the thickness of the solution traversed by the laser or light beam incident upon the localized area to be not greater than 5 cm and preferably not to exceed 1 cm. With an ordinary chemical depositing solution, such thickness limitation is generally satisfactory with the laser beam being derived from an argon gas laser but is desirably limited further not to exceed 5 mm or 1 mm when the laser is a carbon dioxide gas laser.

It has also been found to be desirable that the chemical-depositing solution contain one or more light-sensitizing substances for the purposes of the present invention. Such substances include CdS, ZnO, TiO.sub.2, SnO.sub.2, Se, SbGa, chlorophyll and other known organic or inorganic sensitizing agents.

The narrow light beam is emitted from a source thereof which may be fixed in position, the beam in its optical path being reflected by a mirror so as to be incident upon the localized area. The displacement of the mirror is advantageously used to effect at least a portion of the required relative displacement between the beam and the workpiece.

According to a further feature of the invention, the light beam in its optical path is passed through a lens and the lens is positioned to have its focal plane for the beam coincident with the localized area.

The invention also provides, in a second aspect thereof, an apparatus for chemically depositing a metal onto a substrate, which apparatus comprises: means (a) for bringing a solution containing the metal into contact with the substrate; means (b) for irradiating a localized area on the substrate with a light beam, thereby activating the interface between the area and the solution to allow the metal to be chemically deposited therefrom selectively onto that area; and means (c) for relatively displacing the light beam and the substrate to shift the localized area of interception of the beam successively over a desired surface region on the substrate whereby the metal is sequentially deposited on the surface region.

Preferably, pumping means is provided for passing the chemical-depositing solution at a high velocity in the region of the workpiece surface.

Specifically, the means (b) advantageously includes a laser constituting a source of the light beam.

The means (b) may also advantageously include a source of the narrow light beam together with mirror means for reflecting the beam from the source onto the substrate. The means (c) then includes means (c') for displacing the mirror means. The source may be fixed in position. The means (b) may also advantageously include lens means disposed in the optical path between the source and the substrate for establishing a focal plane for the beam from the source. The apparatus may then further comprise means (d) for displacing the lens means so as to maintain the focal plane coincident with the localized area as the beam and the substrate are relatively displaced by means (c).

In accordance with a further feature of the apparatus aspect of the invention, the means (b) comprises an assembly including a source of the light beam and a hollow optical guide means having its one open end connected to a source of the beam and its other open end adapted to be closely spaced from the localized area for projecting the beam transmitted from the source onto the localized area on the substrate. The said other open end of the hollow guide means is advantageously fitted with a transparent or semi-transparent solid member for preventing entry therein of the depositing solution in the region of the substrate. The solid member is preferably shaped so as to serve as a lens for the beam to be passed therethrough onto the localized area on the substrate from the source. Alternatively, means may be used for filling the hollow space in the guide means with a pressurized gas to prevent entry thereto of the depositing solution in the region of the substrate.

These and other features of the present invention as well as advantages thereof will become more readily aparent from a reading of the following description of certain exemplary embodiments thereof when taken with reference to the accompanying drawing in which:

FIG. 1 is a diagrammatic view, partly in section, illustrating an apparatus according to the present invention;

FIG. 2 is a similar view illustrating a simplification of the apparatus of FIG. 1;

FIG. 3 is a similar view illustrating an arrangement of the invention in which a plurality of beam irradiation units are accommodated in a solution delivery chamber;

FIG. 4 is a generally cross-sectional view of such a plural unit assembly chamber;

FIG. 5 is a diagrammatic view, partly in section and partly in perspective, illustrating another apparatus for practicing the method of the invention;

FIG. 6 is a generally top plan view of a portion of the apparatus shown in FIG. 5;

FIG. 7 is a diagrammatic view, partly in section, illustrating a further embodiment of the apparatus according to the invention;

FIGS. 8(A) and 8(B) are longitudinal sectional views of two possible forms of the tubular optical guide member shown in FIG. 7;

FIG. 9 is a diagrammatic and partly sectional view illustrating the apparatus of FIG. 7 including means for measuring the thickness of a layer of chemical deposit according to the invention;

FIG. 10 is a similar view illustrating the apparatus of FIG. 7 including an additional measure according to the invention an;

FIG. 11 is a similar view illustrating another form of the arrangement for carrying out the method of the invention.

Referring now to FIG. 1 there is shown a chemical- or electroless-depositing apparatus 1 embodying the present invention. The apparatus 1 includes a worktank 2 which accommodates a workpiece or substrate 3 which is shown immersed in a chemical-depositing solution 4 which contains a metal to be deposited upon the substrate 3. The solution 4 is supplied by a pump (not shown) from a source thereof (not shown) through an inlet pipe 5 into a delivery chamber 6 for temporary storage therein and thence onto a surface of the workpiece 3 through an opening 7 formed at the lower end of the delivery chamber 6. It is desirable that the solution 4 be passed at a high velocity, e.g. between 5 and 25 meters/sec, in the region of the surface of the workpiece 3. The workpiece 3 is secured in position by a clamp 8 within the worktank 2. The worktank 2 is provided at an upper end portion thereof with a drain outlet 9 to accept the overflowing solution and to feed it to a suitable treatment vessel (not shown).

The solution delivery chamber 6 is formed with an opening or passage 10 through which a laser beam 11 from a laser beam source or gun 12 is passed to irradiate a localized area on the surface 3a of the workpiece 3. The laser gun 12 has a focusing knob 12a for the beam 11 and is carried by a holder 13 which is in turn secured to a support member 14 attached to a semi-circular disk 15. The latter is a semi-circular worm wheel rotatably mounted to a head 16 which depends from a spindle 17. The worm wheel 15 is rotatable about an axis 18, i.e. a Y-axis, to swing the laser gun 12 and hence the laser beam 11 in an X-Z plane orthogonal to the Y-axis 18. The angle of swing is established by the operation of a motor 19 which is drivingly coupled with a worm 20 in mesh with the worm wheel 15. It should be noted that the gun holder 13 or the support member 14 therefor and the solution delivery chamber 6 are mechanically coupled with each other.

The worktank 2 is securely mounted on a rotary table 21 which is driven by a motor 22 to angularly displace the workpiece 3 in a predetermined polar coordinate system in the X-Y plane. The rotary table 21 is in turn carried on X-axis and Y-axis tables 23 and 24 in a cross-slide arrangement to rectilinearly displace the workpiece 3 in the X-Y plane coordinate system. The tables 23 and 24 are driven by motors 25 and 26, respectively. A control unit 27 is provided to furnish the motors 19, 22, 25 and 26 with respective drive signals based upon preprogrammed data to displace the workpiece 3 so that the laser beam 11 sweeps in a scanning manner with the four degrees of freedom along a predetermined path on the surface thereof. The control unit 27 is also stored with velocity commands for the displacement. Furthermore, the beam gun 12 has a parameter setting circuit 28 sequence-controlled by the control unit 27 to sequentially alter the diameter and/or the energy of the irradiating laser beam 11 in accordance with a predetermined program.

In operation, the delivery chamber 6 is furnished with a chemical-depositing solution, e.g. nickel or copper plating solution to deliver it to the surface of the workpiece 3 at a high velocity as previously indicated. Chemical-depositing conditions, including the temperature of the solution, are set up such that without irradiation with a laser beam, deposition takes place uniformly over the workpiece surface 3a and slowly as usual or at a rate much slower than a customarily attainable optimum or highest deposition rate, or even such that practically no deposition continues without irradiation with a laser beam.

FIG. 2 shows an arrangement which is essentially the same as that shown in FIG. 1 except that the solution delivery chamber 6 is dispensed with and the workpiece 3 is immersed in an essentially static mass of the solution 4 retained in the worktank 2. The solution may be caused to flow slowly between an inlet and an outlet which are formed in the worktank 2 but not shown.

It has been found that the laser beam 11 acts as a narrow thermal beam to heat the depositing solution up to a temperature from 45.degree. to 60.degree. C. or higher in the region of a localized area on the workpiece surface 3a through which the solution 4 is forced to flow and that it impinges and thereby selectively activates that interface to enhance the chemical-depositability thereof. The focusing knob 12a for the laser beam 11 provided on the gun holder 13 may be used to control the size of the localized activation or depositability-enhanced area on the workpiece surface 3a. By relatively displacing the laser beam 11 and the workpiece 3, it follows that chemical deposition develops on the workpiece surface 3a selectively along the path of displacement of the laser beam 11 relative to the workpiece 3. Thus, a pattern of deposition defined by the size of the beam 11 and the path of the relative displacement is created on the workpiece surface 3a. The rate of the relative displacement is determined according to the thickness of a deposition pattern desired. Not only is it possible in this manner to achieve a continuous deposition pattern of any shape desired but a set of discontinuous or discrete such patterns is obtainable. To the latter end, the control unit 27 operates to turn off the laser source 12 during programmed time intervals in the course of the scanning operation selectively to leave intact those areas which are within the path of the relative displacement but not to be chemically deposited. Thus, the laser gun 12 may be deactuated selectively during those time intervals or for the corresponding sections of the relative displacement. It is, of course, desirable that minimum time intervals be employed to traverse these sections.

It will be apparent that the method of the invention is useful for producing a print-form circuit or wiring on a board for electronic devices. The method is also advantageously used for metal plating or forming on a substrate which is of an intricate contour or has one or more recesses or grooves which could be chemically plated only with difficulty by the conventional technique. Accordingly, thanks to the invention, a metal deposit is achieved uniformly over such a substrate by controlling the time of irradiation or the rate of scan with the laser beam 11 or the local point thereof according to the position on the workpiece surface or substrate 3a. Generally, a recessed area or corner portion in a recess may be irradiated for a longer time than other areas.

Referring to FIG. 3 in which the same reference numerals as those in FIGS. 1 and 2 are used to designate the same or functionally same parts, a modified apparatus embodying the present invention is illustrated. The apparatus 2 makes use of a relatively large solution delivery chamber 30 in which a plurality of laser irradiation units 31-44 (FIG. 4) are accommodated. Each of these units, of which only 31-34 appear in FIG. 3, comprises a laser source 45, 46, 47, 48, . . . connected via a rotary switch 59 to an energization power supply 60 and an optical guide 61, 62, 63, 64, . . . connected at its upper end to the laser source and having its lower end juxtaposed with the workpiece surface 3a and fitted with a disk 75, 76, 77, 78, . . . . These disks are positioned to be flush with one another, defining the lower end surface of the delivery chamber 30 and are spaced apart from one another with a spacing 89 serving as a solution delivery passage. Here again, the solution 4 is forced to pass in the region of the workpiece 3a at a high velocity as indicated.

The rotary switch 59 comprises a rotary arm 59a actuated by a switching circuit 90 and arranged for engagement with fixed contacts 91, 92, 93, 94, . . . , which are connected to the laser sources 45, 46, 47, 48, . . . , respectively. The switching circuit 90 is operated by the control unit 27 in accordance with a predetermined program stored therein to selectively energize the laser sources 45, 46, 47, 48, . . . from the power supply 60. The control unit 27 also acts on the power supply 60 to control the intensity of the laser beam emitted from each of the sources 45, 46, 47, 48, . . . in accordance with a predetermined stored program. In each of the units 31, 32, 33, 34, . . . the laser beam emitted from the source 45, 46, 47, 48, . . . passes through the optical guide 61, 62, 63, 64, . . . to irradiate a localized area on the workpiece surfaces 3a in the presence of a high-velocity stream of the depositing solution supplied from the inlet conduit 5 through the delivery chamber 30 and the outlet passage 89 thereof. The localized areas on the surface 3a of the workpiece 3 are thereby activated and selectively chemically deposited.

In the further embodiment shown in FIGS. 5 and 6 the laser beam 11 emitted from a laser gun 12, upon reflection by a mirror 111, impinges on a workpiece 3 immersed in chemical-depositing solution 4 in a worktank 106 through which it is forced to flow at a high velocity as indicated. The latter is securely mounted on a slide table 107 with which is drivingly coupled a feed screw 108 extending in the direction normal to the sheet of the drawing to position the workpiece 3 in that direction along a predetermined coordinate axis, i.e. a Y-axis. The feed screw 108 is driven by a motor 109 (FIG. 6) which operates in response to drive signals furnished from a control unit 27, e.g. a numerical controller.

The mirror 111, having its mirror face vertical, is carried on a horizontal support member 112 which is supported on a pedestal 113 so as to be movable horizontally along a predetermined coordinate axis, i.e. an X-axis. The support member 112 is carried by a lead screw 114 which is slidably supported on a pedestal 115. The lead screw 114 is in mesh with a nut 116 fitted in the center of a large gear 117 in mesh with a small gear 118. The latter is carried on the drive shaft 119a of a motor 119 which operates in response to drive signals furnished from the control unit 27. As the motor 119 is driven, the lead screw 114 is rotated to displace the support member 112 and hence the mirror 111 in the direction of the X-axis to displace the position of the laser beam 11 reflected thereby and impinging on the workpiece surface 3a.

The control unit 27 has path data for relative displacement of the reflected laser beam 11 and the workpiece 3 preprogrammed therein and operates to produce from those data drive signals for the operation of the X-axis motor 119 and the Y-axis motor 109.

The solution may, of course, be any conventional chemical depositing solution. For example, copper sulfate solution may be used for copper deposition. For nickel deposition, sulfonic nickel solution may be used. The laser should preferably be an argon gas laser (having a wavelength between 4880 and 5145 angstroms, green), which has a high transmissivity to such a solution. A beam of the laser can penetrate a solution as thick as 1 to 5 cm and, without substantial heating thereof, is capable of selectively activating a localized area on the workpiece surface to enhance its depositability. By contrast, a carbon-dioxide gas laser (having a wavelength of 10.6 .mu.m) is relatively low in transmissivity to the solution mentioned and requires that the solution should be present in a thickness as small as 5 mm or less. For example, a laser beam from a carbon-dioxide gas laser of 50 watt output can successfully be used to scan a workpiece at a rate of 30 mm/min in deposition of nickel upon the workpiece from a sulfonic nickel chemical-depositing solution when the thickness of the solution on the workpiece is 0.5 mm. The solution of that thickness through which the beam travels is then heated up to 60.degree. C. When the thickness is increased to 5 mm, the degree of the localization of deposition is largely reduced.

Since the size of a laser beam spot can be reduced down to twice the wavelength of the beam, the method of the invention is advantageously applicable to printing-type deposition wiring of tiny electronic devices and also to high-precision localized deposition. In chemical-deposition of nickel from a sulfonic nickel solution, an argon gas laser can be used to provide a beam spot of 0.2 mm diameter and thereby a localized deposition of the same area. This area is increased to 4 mm when the laser is replaced by a carbon-dioxide gas laser.

In the embodiment of FIG. 7, an elongate tubular optical guide member 120 is juxtaposed with the surface 3a of a workpiece 3 immersed in the chemical-depositing solution 4 retained in the worktank 2. The solution 4 is introduced into the worktank 2 via an inlet conduit 5 and drawn out through a drain outlet 9. The elongate tubular guide member 120 has at its lower or forward end a transparent or semi-transparent member 122 fitted therein which may be a plain glass plate as shown at 122a in FIG. 8(A) but is preferably shaped, as shown at 122b in FIG. 8(B), to serve as a convex lens for a laser beam 11 emitted from a laser gun 12. The tubular guide member 120 is secured via a coupling ring 123 to the laser gun 12 so that the laser beam emitted from the laser source 12a is passed through the inner bore 121 of the tubular guide member 120 and the transparent or semi-transparent member 122 for irradiation of a localized area on the surface 3a of the workpiece 3. The member 122 is designed also to prevent chemical-depositing solution 4 in the tank 2 from entering into the inner bore 121 of the guide member 120.

The unit structure comprising the laser gun 12, the annular coupling 123 and the tubular optical guide member 120 in combination is carried by a vertical positioner 124 seated on a wheeled carriage 125. The vertical positioner 124 operates in response to drive signals furnished from the control unit 27 to position the forward end of the tubular guide member 120 in closely spaced juxtaposition with the surface 3a of the workpiece 3 which is shown to be planar but may be of an intricate three-dimensional contour.

The wheeled carriage 125 is displaceable by a motor 126 so as to roll over a track 127 in the direction of the X-axis indicated. The track 127 is securely supported on a wheeled carriage 128 with wheels indicated at 129 and 130 and adapted to roll on a pair of rails 131 and 132 to displace the carriage 128 in the direction of the Y-axis indicated. The rails 131 and 132 are mounted to stand vertically on the upper edges of the two opposed walls of the worktank 2, respectively and to extend in parallel with each other. A motor 133 mounted on the track 127 has on its output shaft a pulley 134 which is coupled via a belt 135 with a pulley 136 secured to the rotary shaft 137 carrying the wheels 129 and 130 for the carriage 128. As the motor 133 is driven in response to drive signals furnished from the control unit 27, the carriage 128 is thus driven to position the axis of the tubular electrode in the Y-axis coordinate.

The workpiece 3 may, for example, be a silica board for formation of an electronic circuit thereon. The board 3 has been pre-treated according to the conventional techniques, viz. washing, de-greasing with a 10% sodium hydroxide solution, washing, acid-washing with a 3.5% HCl solution, washing and drying in sequence. The board is then sensitized with a sensitizing agent consisting of 10 gr/l SnCl.sub.2 and 20 to 50 gr/l HCl. Thereafter, upon washing, the board is activated at 50.degree. C. with an activating agent composed of 0.5 gr/l PdCl.sub.2 which has added thereto HCl to make its pH 3 to 4 to substitute Sn with Pd which constitutes nuclei for chemical deposition with a desired metal. The activated board is then washed and dried.

The subsequent step of actually depositing the desired metal, say, copper upon the pretreated board may also make use of a known chemical-depositing solution which is, for example, composed of 0.1 mol/cm.sup.3 of (HCHO)n where n is normally 3, 0.05 mol/cm.sup.3 of CuSO.sub.4 and 0.15 mol/cm.sup.3 of Na.sub.2 EDTA salt. As is common, the solution further contains NaOH in an amount to adjust the pH value at 12.5 The solution has a temperature of 5.degree. C. and is introduced through the inlet 5 into the worktank 2 to flow rapidly in the region of the upper surface of the board 3 so that little deposition of the copper metal from the solution is caused thereon. The flowing solution 4 is drained out of the worktank through the outlet 9.

In the state described, the laser 12 is actuated to project a laser beam. The laser 12 may be an argon laser and the beam intensity adjusted at 15 watts. The lens 122b is used to focus the beam so that the beam has a cross section of 15 .mu.m diameter. The laser beam is focused at a localized area on the board surface 3a so that it impinges and thereby selectively activates the interface between the surface 3a and the solution 4 to enhance the chemical-depositability of the localized region. By relatively displacing the laser beam and the board, it follows that chemical deposition develops on the board surface 3a selectively along the path of displacement of the laser beam relative to the board. Thus, a pattern of deposition defined by the size of the laser beam and the path of the relative displacement is created on the board surface 3a. In this manner, it has been found that deposition proceeds at a rate up to 15 times greater than that obtainable by the conventional technique or without the use of a laser beam. The rate of the relative displacement is determined according to the thickness of a deposition pattern desired. Not only is it possible in this manner to achieve a continuous deposition pattern of any shape desired but a set of discontinuous or discrete such patterns is obtainable. To the latter end, the control unit 27 operates to turn off the laser source 12a during programmed time intervals in the course of the scanning operation selectively to leave intact those areas which are within the path of the relative displacement but not to be chemically deposited. Thus, the laser gun 12 may be deactuated selectively during those time intervals or for the corresponding sections of the relative displacement. It is, of course, desirable that minimum time intervals be employed to traverse these sections.

In copper chemical-deposition, it is desirable that the solution of the type described be held at a relatively low temperature, e.g., in a range between 3.degree. C. to 10.degree. C., say, at 5.degree. C. In this case it is desirable that a suitable cooling means be disposed in contact with the workpiece 3, say, at the rear side thereof to hold it cooled at the low temperature. In nickel chemical-deposition, a solution may be held at a relatively high temperature, say, 80.degree. C. In the practice of the invention, the nickel chemical-deposition may be held at room temperature, say, at 20.degree. C. and then no cooling means may be provided.

The arrangement of FIG. 9 is the same as in FIG. 7 except that it includes a further provision for measuring the thickness of a deposited layer on the workpiece surface 3a behind the tubular guide member 120. Thus, there is provided a measuring electrode assembly 140 comprising an electrode 141 coated with an insulating film 142, which assembly extends in parallel with the tubular guide member 120 and is carried by its vertical positioner 143 seated on the wheeled carriage 125. The vertical positioner 143 operates in response to drive signals furnished from the control unit 27 to position the forward end of the measuring electrode 141 in contact or closely spaced juxtaposition with the deposited workpiece surface 3a. Since the single carriage 125 is used to carry both the tubular guide member 120 and the measuring electrode assembly 140, the axis of the latter is held to be adjacent to the axis of the tubular guide member 120.

The measuring electrode 141 is adapted to sense its contact or proximate relationship with the deposited workpiece surface 3a by measuring, for example, the electrical resistance therebetween, and to transmit a sensed signal to the control unit 27. The latter continues to furnish drive signals to cause the vertical positioner 125 to advance the measuring electrode assembly 140 until its preselected contact or proximity relationship with the deposited workpiece surface 3a is attained. The distance of advance required may be registered in the control unit 27 to produce control signals which act on the laser gun 12 to control the intensity of the light emitted from the laser source 12a.

FIG. 10 shows a modification of the embodiment of FIG. 7 and again uses the same reference numerals used therein to indicate the same parts. In ths arrangement of FIG. 10, the inner bore 121 of the tubular guide member 120 communicates with a source of pressure gas 145, such as a compressor, via a throttle valve 146 and a pressure-regulating valve 147. In this manner, the inner bore 121 is filled with the pressurized gas to prevent entry of the depositing solution 4 therein. The pressure-regulating valve 147 operates in response to command signals furnished from the control circuit 27. The control circuit 27 operates to control the pressure-regulating valve 147 so that the pressure of compressed gas within the inner bore 121 of the tubular guide member 120 always exceed the pressure of the solution 4 in the open end region of the tubular guide member 120 to prevent entry of the solution into the bore 121 thereof.

FIG. 11 shows a laser-assisted chemical-depositing apparatus embodying the present invention and again makes use of the same reference numerals as used in the previous FIGURES to designate the same or functionally same parts. In this arrangement, a laser gun 12 securely mounted via its holder 13 to a spindle or ram head 17 is designed to project a vertical laser beam 11 for irradiation of a localized area on the workpiece surface 3a therewith. In the path of the laser beam 11 there is provided a beam-focusing assembly 154 in which a plurality of lenses 155 are arranged. The assembly 154 is supported by a horizontal arm 156 which is in turn supported by a vertical lead screw 157 at its lower end. The lead screw 157 is in mesh with a nut 158 which is geared on its periphery 159 in mesh with a gear 160 secured to the output shaft of a motor 161. By its holder the motor 161 is secured to the spindle 17. The nut 158 is, for its vertical position to be fixed, retained between a pair of bearing surfaces of a support member 162 secured to the spindle 17. Further, the lead screw 157 formed with a key-in groove engaged by a projection 163 on the support member 162 is held against rotation. The motor 161 operates in response to drive signals furnished from the control unit 27, e.g. a numerical controller, to position the lens assembly 154 so that the laser beam 11 projected from the laser gun 12 is focused on the localized area on the workpiece surface 3a.

The arrangement of FIG. 11 is particularly advantageous for chemical-deposition of a workpiece with recessed surfaces or of an intricate contour as shown. The control unit 27 provides the motors 22, 25 and 26 with drive signals to displace the workpiece 3 along a preprogrammed path in the X-Y plane as that its surface 3a is swept over by the laser beam 11 from the laser gun 12. During the planar displacement of the workpiece 3 in the X-Y plane, the motor 161 is responsive to Z-axis positioning signals from the control unit 27 to regulate the position of the lens assembly 154 so as to focus the laser beam 11 onto a localized area.

Here again, the chemical-depositing solution may be a conventional copper chemical-depositing solution held at a relatively low temperature, say, 5.degree. C. In order to enhance the light sensitivity to the beam 1, it has been found to be desirable that the solution contain, for example, Ru.sub.2 (bpy).sub.3 X.sub.2 (obtained by fixing ruthenium to silicate ester of polyvinyl alcohol) in an amount of 2.8.times.10.sup.-6 mol/l. In this case, the light-beam source 12 can be served by a xenon lamp. The light beam 11 from the xenon lamp 12 is focused by the lens system 154 into a cross section of 3.5.mu. diameter as it impinges on the workpiece surface 3a. It has been found that the focused xenon light beam when used with the solution containing such a sensitizing substance yields substantially the same rate of chemical deposition as that obtained with an argon laser beam used with the solution omitting the sensitizing substance. When used with the solution containing the sensitizing substance, the laser beam yields a rate of chemical deposition up to three times as great as that obtainable with the xenon light beam used with the solution containing the sensitizing substance.