Method for Removing Sub-Micron Particles From a Semiconductor Wafer Surface by Exposing the Wafer Surface to Clean Room Adhesive Tape Material

The present invention relates to semiconductor processing in general, and more specifically to removing residues and particles from a surface of a semiconductor wafer.

As geometries of integrated circuit devices decrease, and integration levels increase in number, the generation and removal of particles on a semiconductor wafer becomes a more important issue to improve integrated circuit yield. Particles which are generated through various steps in the manufacturing process, for example, during etch steps or polishing steps, must be removed from the wafer to avoid defects and reliability problems.

Conventional removal of particles from semiconductor wafers comes in a variety for forms. One of the most common cleaning or particle removal process is the use of a spin-rinse-dry (SRD) process. In an SRD process, a wafer is sprayed with fluid (for example, in water or alcohol) while being spun. A combination of dynamic forces caused by the spinning, and fluid drag forces are used to pull the particles from the wafer surface. Following the rinse, the wafers are dried by spinning. While SRD has wide spread use in semiconductor manufacturing, a disadvantage of the technique is that as the radius of the particles to be removed becomes smaller, the effectiveness of the removal or cleaning process is reduced. The dynamic force removal of particles is proportional to the cube of the radius of the particles, while the fluid drag forces used to remove particles is proportional to the radius squared. Therefore, for small sub-micron particles, SRD is an incomplete solution to particle removal.

Other particle removal techniques have similar limitations. For example, ultrasonic cleaning is an immersion cleaning process whereby instead of spinning or rotating the wafer, the wafers are placed in a liquid bath where the liquid within the bath is ultrasonically vibrated. Again, however, forces used to remove particles from the wafer diminish with decreasing particle radius, as is the case for SRD cleaning.

Another known technique for particle removal is one which relies upon differential surface energy of two fluids. For example, a combination of fluids (for example, isopropyl alcohol and water) are combined in a bath. The wafer is dipped in this bath, and as particles on the wafer reach an interface between the two fluids in the bath, the differences in surface tension between the two fluids and the particles causes the particles to be lifted or pulled from the wafer. A problem with this technique is that a limited number of solutions are available for use in achieving the differential surface energies, and the forces created by the these limited fluids are not sufficient to remove a significant amount of particulates from the wafer surface.

Further disadvantages with each of the above techniques described relates to the ability to manufacture semiconductor devices in a timely and cost effective manner. Many of the prior art cleaning techniques are single wafer techniques which require on the order of minutes to perform. Further, these techniques typically involve chemicals which must not only be purchased but must somehow be disposed of in large quantifies. Therefore, it would be advantageous to have a particle removal process for semiconductor wafers which effectively removes even small particles, while at the same time can be implemented in a manufacturing environment with minimal processing time, minimal chemical waste, and with minimal equipment or supply cost.

FIGS. 1-3 illustrate in partial cross-sectional view a planar surface of a semiconductor wafer having particles which are removed by an adhesive tape in accordance with one embodiment of the present invention.

FIGS. 4-7 illustrate, in partial cross-sectional view, another embodiment of the present invention wherein particles can be removed from a non-planar surface of a semiconductor wafer using an adhesive tape in accordance with the present invention.

FIG. 8 illustrates in cross-section a schematic view of a roller system suitable for applying and removing tape to a semiconductor wafer in accordance with the present invention.

Generally, the present invention involves applying tape to a semiconductor wafer in order to reduce a number of particles on a top surface (also referred to as an active surface) of the wafer. In a preferred form, a semiconductor wafer is provided which has a top surface which contains a plurality of particles. This semiconductor wafer is placed on a vacuum chuck and brought into contact with tape material. The tape has a carrier film and an adhesion layer. The adhesion layer portion of the tape is placed face down onto the wafer so that glue molecules in the adhesion layer will adhere to the particles on a top surface of the wafer. The tape is then removed from the surface of the wafer whereby the particles on a top surface of the wafer are removed due to the adhesion between the particles and the adhesion layer of the tape.

The present invention will be further understood with reference to FIGS. 1-8. FIG. 1 illustrates a substrate 10. The substrate 10 may be single crystalline silicon, gallium arsenide, silicone-on-insulator material, epitaxial formations, germanium, germanium silicon, polysilicon, and/or like substrate materials used in semiconductor manufacturing. In a preferred form, substrate 10 is a silicon semiconductor wafer. Within the substrate 10, there may be formed diffusion regions for source and drain electrodes of MOS transistors, well regions, bipolar transistor electrodes, and any other doped region which allows for the formation of active circuitry within the substrate 10. One or more integrated circuit layers 12 are formed overlying the substrate 10. The one or more integrated circuit layers 12 may include dielectric layers. For example, these dielectric layers may include, wet or dry silicon dioxide, silicon nitride, nitride materials, tetraethylorthosilicate (TEOS) based oxide, borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), oxide-nitride-oxide (ONO) films, oxynitride, or a like dielectric materials. In addition, the one or more integrated circuit layers 12 may contain conductive regions. These conductive regions may include polysilicon, silicide or salicide regions, metallic regions, refractory metals, or like conductive materials used for integrated circuit fabrication. Layers 12 are deposited, patterned, and etched to form active circuitry overlying the substrate 10. The details of forming layers 12 are not important to gain an understanding of the invention. It is important to note, however, that the present invention may be utilized at any point in time and on any material surface during wafer processing.

In FIG. 1, a top layer with the one or more integrated circuit layer 12 is chemically mechanically polished using a slurry to form a top polished surface 12A. When performing a chemical mechanical polishing (CMP) operation, residue and particulates such as particles 21, 22, 23, and 24 (hereafter particles 21-24) are left on the polished surface 12A as illustrated in FIG. 1. These particles 21-24 may be particles from the layer which is polished, abrasive particles from the polishing slurry, particles from the ambient, particles from the CMP tool, or any other contaminants. If these particles 21-24 remain on the surface and are not removed by subsequent processing, then integrated circuit yield will be reduced. Therefore, a need exists for a cost effective and efficient method for removal of the particles 21-24.

FIG. 2 illustrates that a tape 14 is applied to the polished surface 12A in order to remove the particles 21-24. Tape 14 comprises an adhesion layer 16 and a carrier film 18. In one form, tape 14 can be cleanroom tape publicly available from the Advanced Laminated Material Applications (ALMA), Inc. When using this cleanroom tape, the carrier film 18 is a polyolefin film and the adhesion layer 16 is an acrylic based adhesive. Another tape which can be used is available from Label Graphics, Inc. and is referred to as tape P3WTCLG18. This tape comprises a carrier film made of polypropylene and an adhesive layer made from LG18 adhesive. In another form, LG19 adhesive may also be used. It is important to note that other corporations such as 3M, provide alternative tapes to those listed herein which can also be suitably used to remove particles in accordance with the invention.

Generally, in a preferred form, the tape used as tape 14 in FIG. 2 should have certain characteristics. First, the tape should be compatible with a cleanroom environment. Second, the adhesive layer of the tape should adequately adhere to particles on the surface of a wafer. Third, it is preferable that the adhesive layer 16 has a greater adhesive force with the carrier 18 than with the layers 12. If the adhesive layer 16 has greater adhesive force to the carrier 18 than to the layers 12, then adhesive residue remaining on the wafer after the tape 14 is removed from the substrate is reduced. Fourth, it is desirable to use a tape wherein the adhesive force between glue molecules in the adhesive layer 16 is greater than an adhesive force between the glue molecules and the particles 21-24 and the wafer surface 12A. This will also ensure that glue residue remaining on the wafer is minimized when the wafer and the tape are separated. It is important to note that any glue residue remaining on the surface 12A after removal of the tape can be dissolved by exposing the surface 12A to a solvent, such as acetone, alcohol, or other organic solvent.

Therefore, in summary, FIG. 2 illustrates that a tape 14 containing an adhesive layer 16 is brought into contact with the surface 12A. The adhesive layer 16 adheres to the particles 21-24 as illustrated in FIG. 2.

FIG. 3 illustrates that the tape 14 is removed from the surface 12A. This removal process will result in the particles 21-24 being removed from the surface 12A via adhesion to the adhesion layer 16 as illustrated in FIG. 3. Therefore, a total number of particle resident on the surface 12A of the substrate 10 are effectively and efficiently removed from the surface 12A to increase yield of an integrated circuit. As previously discussed, the removal of the tape 14 may or may not result in a glue residue remaining on the surface 12A. This residue may easily be removed by exposing the surface 12A to a solvent to remove this residue effectively. Therefore, FIGS. 1-3 illustrate a method by which particulates are removed from a top surface 12A which has been chemically mechanically polished using tape 14.

FIGS. 4-7 illustrate that the tape method described and illustrated in reference to FIGS. 1-3 can also be used for removing particles from a non-planar topography surface. FIG. 4 illustrates a substrate 30 which is similar to the substrate 10 of FIG. 1. One or more integrated circuit layers 32, comparable to layers 12, are illustrated in FIG. 4, wherein a top layer of layers 32 is an interlevel dielectric layer. Below the interlevel dielectric layer, there may be formed a plurality of conductive and dielectric layers to form active devices overlying the substrate 30. Conductive interconnects 34 and 36 are formed overlying the layers 32 using conventional lithographic and etch processing. Overlying the conductive interconnects 34 and 36 is formed a dielectric layer 38. Dielectric layer 38 is a conformal dielectric layer which forms high areas 37 overlying the conductive interconnects 34 and 36 and low areas 39 as illustrated in FIG. 4. FIG. 4 also illustrates a plurality of particles 40, 41, 42, and 43 (hereafter particles 40-43), wherein some of the particles reside on top of high areas 37 and other particles reside in low areas 39.

FIG. 5 illustrates that a tape 46 is brought into contact with the dielectric layer 38. If a minimal amount of force is applied to the tape 46, then the tape 46, which comprises an adhesion layer 48 and a carrier film 50, will only come in contact with the high areas 37. Therefore, when using minimal force, the particles 41, 42, and 43 residing in the low areas 39 will not come into contact with the adhesion layer 48 and remain on a surface of the dielectric layer 38. To solve this issue and enable removal of particles in the low areas 39, a tape 46 may be used which has an adhesion layer 48 with a thickness "X" where X is greater than a difference in height between the high areas 37 and low areas 39. For example, an adhesive layer thickness of about 1 mil (25 .mu.m) is sufficient. Thus, the thickness of the adhesive layer will be great enough to ensure that pressure applied to the tape 46 will result in adhesive material coming in contact with the entire surface of the layer 38, as demonstrate in FIG. 6.

FIG. 6 illustrates that positive force can be applied to the tape 46 so that material of the adhesive layer will deform from the high areas 37 to low areas 39. Consequently, the glue molecules of the adhesive layer 48 will come into contact with particles 40-43 in both the high surfaces 37 and the low surfaces 39 of the dielectric layer 38.

As illustrated in FIG. 7, the tape 46 is then removed from the surface of the layer 38 whereby the particles 40-43 are effectively removed from both the high areas 37 and the low areas 39. As mentioned previously, if any adhesive residue remains on the surface of the substrate upon removing the tape, such residue can be dissolved using a solvent.

FIG. 8 illustrates an apparatus which can be used to apply tape to a semiconductor wafer in accordance with the present invention. FIG. 8 illustrates a vacuum chuck 61 which is used to hold a wafer 60 in place. Tape is provided from a feed reel 66 to a tape application roller 62. Therefore, feed reel 66 provides new tape 70 to the tape application roller 62 for application to the wafer 60. The wafer 60 is moved laterally beneath the surface of the roller, or the roller is moved laterally across the surface of the wafer, so that new tape 70 is brought into contact with the top surface of the wafer 60 with sufficient pressure. The wafer or roller continue lateral movement, thereby causing the tape to be peeled or released from the wafer surface. As a result of removing the tape, particles from the surface of the wafer 60 are removed. The particles will attach to the adhesive layer of the tape 68, and this used tape 68 will be collected by a take-up reel 64 for proper disposal or reclamation. Therefore, FIG. 8 illustrates a tape providing apparatus for effectively removing particles from the surface of the semiconductor wafer 60.

From the foregoing, it is apparent that the present invention provides a simple method for effectively removing particles from a surface of a semiconductor wafer. Particles and residue may be effectively removed from either a topographic surface or a planar surface of a semiconductor wafer by bringing the semiconductor surface in contact with an adhesive tape. The tape is an inexpensive and effective way for removing particles, including sub-micron particles, from a surface of a wafer whereby chemical waste is reduced, throughput is increased, and yield is enhanced.

While the present invention has been illustrated and described with reference to specific embodiments, further modifications and improvements will occur to those skill in the art. For example, any type of tape which is compatible with the cleanroom environment may be used to remove particles as taught herein. The tape removal process taught herein can be run in a batch process to remove particles from a plurality of wafers in a simultaneous fashion. The particle removal process taught herein can be used at any stage during the manufacture of a semiconductor wafer. The particle removal process as taught herein can also be used on other objects such as components within a deposition chamber, wafer clamps, electrodes, or the like to effectively remove particles from semiconductor equipment components. It is to be understood, therefore, that this invention is not limited to the particular forms illustrated and that is intended in the appended claims to cover all modifications that do not depart from the spirit and scope of this invention.