JP2000308961A - Affixing plate and manufacture of same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an affixing plate with a was-free holding device that prevents maldistribution of water and has no influence upon the form of wafers during polishing by polishing machines. SOLUTION: In a polishing machine with a rotatable surface plate for polishing and a pressure plate, an affixing plate 11 for holding and pressing a workpiece surface against the surface of the polishing surface plate in parallel relation comprises an appreciably rigid and dense ceramics plate, one or more porous ceramics plates 15 having gas-and-water-permeabilities, and a backing pad 12 consisting of a layer 13 of soft foam and a collar 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a silicon wafer or a compound semiconductor wafer as a material of a semiconductor device such as an IC, an LSI or a super LSI, an aluminum disk as a carrier of a computer external storage device, and an LCD. The present invention relates to an attaching plate attached to a polishing machine used in a process of processing an ultra-thin glass wafer or the like, and more specifically, means for gripping a workpiece to be polished (hereinafter abbreviated as a workpiece) is, for example, wax. The present invention relates to a structure of a sticking plate and a method of manufacturing the same by a method of adsorbing and holding by using a backing pad and water instead of an adhesive method using a method such as the above.

[0002]

2. Description of the Related Art In recent years, in the semiconductor industry, for example, ICs,
The degree of integration of semiconductor devices such as LSIs or super LSIs (hereinafter referred to as ICs, etc.) has dramatically increased, and 16 Mbits,
Progress is being made to 64 Mbits, 256 Mbits and even G (giga) bit units above them. Under such circumstances, the demand for improving the quality of the surface of the wafer as the substrate has been increasingly sophisticated. Along with this, it is natural that there is a demand for the advancement of chemical and electrical properties, but in order to increase the degree of integration of ICs and the like, the minimum line width of a circuit diagram constituting a device provided on a wafer is required. However, the requirements are becoming increasingly finer, and the requirements are increasing from 0.5 μm to 0.25 μm and further to 0.18 μm. Furthermore, in order to increase the productivity, there is an increasing movement to increase the wafer size. At present, the wafer size is generally 8 inches, but the processing technology is urgently required for large diameter wafers of 12 inches or more, which are planned to be introduced in the future.

In order to enable such high-precision processing, there is an increasing demand that the requirement for physical flatness of the wafer surface, that is, the shape accuracy in the thickness direction must be achieved simultaneously with high cleanliness. It has become to. That is, the wafer after the final mirror finishing is
It is required that the thickness floating (total thickness variation, TTV) over the entire area is 1 μm or less, and that the thickness floating (site thickness indication reading, STIR) over the entire size to be one IC chip is 0.2 μm or less. It is coming. In order to achieve such high required accuracy, in the processing step of the wafer, processing is performed in multiple stages, and a wafer having excellent surface roughness and flatness of the wafer is manufactured. Normally, only one side is processed in the polishing step in which both sides of a thin wafer are processed at the same time and the latter half, particularly, the final mirror finish is performed. Conventionally, when polishing only one surface as described above, wax is applied to the surface of the work not to be polished and adhered to the surface of the sticking plate made of hard (high rigidity / high density) ceramics. The gripping method has been used as the most effective means for ensuring the flatness described above. In other words, the work surface held by the extremely thin wax adhesive layer on the highly accurate flat surface of the attachment plate made of hard (high rigidity / high density) ceramics is copied by polishing. Have been. That is, the work has been performed with the back surface of the work as the reference plane.

[0004] In the case of using such a means for gripping a work by a bonding method using wax, after the polishing work is completed, the work is peeled off from the adhering plate, and then the adhesive residue remaining on the back surface of the work and the surface of the adhering plate is removed. Huge equipment is needed for cleaning and removal,
Since these residues or cleaning substances become dust and contaminate the work itself and the surrounding environment, it has become extremely difficult to achieve a high degree of cleanliness of the work required in the future.

[0005] In order to solve the above-mentioned problems, the soft foam layer of the backing pad is impregnated with water, and the work is placed on the soft foam layer. A so-called waxless mounting method has been proposed in which a work is adsorbed by utilizing the surface tension of the foam and the negative pressure generated when water is extruded from the foam layer (for example, Japanese Patent Application Laid-Open No. 7-58066). ), Any of the methods cannot achieve the expected processing accuracy, and furthermore, when the backing pad is attached to the attaching plate, there is a problem that air is involved and bubbles are generated and wrinkles are generated. This causes the surface accuracy to be significantly impaired, and the undesired surface shape is directly transferred to the work, which is a factor that lowers the surface accuracy of the work. In addition, since there is no way for excess water contained in the soft foam layer to escape, water is collected between the soft foam and the work, which also adversely affects the processing accuracy, and is a difficult method to handle. Was.

FIG. 1 is a view showing an example of a general waxless polishing machine. A polishing pad 2 is attached to the surface of an annular metal platen 1, and has a rotating shaft 3 in the center. Four rotatable pressure plates 5 are evenly arranged on the upper part of the surface plate (only one is shown in the drawing), and are arranged so as to face the pad surface 2 of the surface plate. The pressure plate is provided with a sticking plate 11 on which a work 4 such as a silicon wafer is sucked by the suction force of a backing pad 12, and is pressed against the polishing pad 2 on the surface plate via a pressure plate 5. The pressure plate 5 has a structure that rotates around the rotation shaft 17, and a method of applying a load related to processing is, for example, a pressure cylinder method using air pressure, a method of putting a weight on the pressure plate, or a weight of the pressure plate. It is adjusted so as to have a constant load by using a method. The working fluid required for the polishing process is supplied from the nozzle 6 onto the polishing pad. During polishing, the surface plate 1 rotates about the rotating shaft 3, and the work 4 is pressed against the polishing pad with the work 4 being adsorbed on the attaching plate 11. Pressure plate 5
Rotates following the rotation of the surface plate 1, but may be of a type that rotates itself. Working fluid is polishing pad 2
It is supplied to the upper side and enters the gap between the workpiece 4 and the polishing proceeds by the action of the rotating force, the processing pressure and the processing liquid.

FIG. 3 shows an outline of a general waxless holding method using a backing pad using a soft film for a soft foam layer. The layer of the flexible foam film 13 is adhered to the attaching plate 11 via a layer of an adhesive tape 14 or the like, and a collar 16 is adhered on the flexible foam film layer 13 to determine the position of the work 4 such as a wafer and to prevent popping out. ing. As the soft foam film for the backing pad, a backing pad having a nap layer or a micropore layer is used, but the compression elastic modulus and viscoelasticity change due to the polishing load during processing occurs, and the backing pad shape It has been pointed out that the change affects the processing accuracy and is inferior to the conventional wax method in processing accuracy. In response to this problem, the thickness of a soft foam layer such as a nap layer and the thickness of an adhesive have been reduced to the utmost. However, the thinned backing pad material has low rigidity itself, and when it is attached to the attachment plate, it becomes wrinkled or contains air bubbles, and it expands and plastically deforms when it is peeled off and reattached. In many cases, there is a new problem that the difficulty in the pasting operation becomes extremely high.

In the case of such a structure, the mechanism for attaching the wafer is as follows. After a soft foamed film contains an appropriate amount of water and is uniformly dispersed, the wafer is placed with the non-processed surface as an adsorption surface, and the wafer is uniformly placed from above. The wafer is adsorbed by the negative pressure generated when the water of the soft foam layer (nap layer or micropore layer) is extruded by a small pressing force. Part of the water pushed out by the pressing is discharged out of the system from the gap between the collar and the wafer, but most of it is concentrated between the wafer and the nap layer or micropore layer, and the center of the wafer becomes convex. There is also a problem that the protrusion is formed into a concave shape after polishing and polishing. Similarly, the water extruded to the outer periphery of the wafer loses a relief area due to the edge of the collar and locally accumulates, pushes up the wafer, and is subjected to stress concentration and polished, thereby causing sagging of the outer periphery. .

As another measure against the problem of the wax bonding method, for example, a hard ceramic having a large number of small holes is used as a sticking plate for bonding and fixing a wafer, and suction pressure is applied from the back surface of a pressure plate to utilize the suction power. There is a method of gripping the wafer. In the case of this method, the wafer is sucked and gripped on the surface of the bonding block by applying the suction force by vacuum, so the wafer is slightly deformed by the suction force, and the uneven shape of the small hole of the holder is changed to the wafer after polishing. It is not preferable because it remains, and it is necessary to provide a line for evacuation in the pressure plate, which is not preferable because the equipment becomes complicated and large.

[0010]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the general waxless holding method using a soft foam backing pad, the present inventors have made intensive studies to complete the present invention. The purpose of that is when polishing with a polishing machine,
It is an object of the present invention to provide an adhesive plate having a waxless holding device that prevents uneven distribution of water and does not affect the shape of a wafer. Another object of the present invention is to provide a method of manufacturing the adhesive plate. is there.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing machine having a rotatable polishing surface plate and a pressure plate, wherein a surface of a workpiece is formed with respect to the surface of the polishing surface plate. The backing pad consists of a high-rigidity, high-density ceramic plate, one or more porous and air-permeable ceramic plates, and a layer of soft foam and a collar. This is achieved by a sticking plate characterized by comprising: Another object of the present invention is to bond a high-rigidity, high-density ceramic plate and a porous ceramics plate with a synthetic resin-based thermosetting adhesive or a silicon oxide-based binder, and then the porous ceramics plate. This is achieved by a method of manufacturing a sticking plate, wherein a backing pad made of a layer of a soft foam and a collar is stuck to the surface of the plate.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A polishing machine referred to in the present invention is a semiconductor material such as a silicon wafer or a compound semiconductor wafer, a carrier of a computer external storage device such as an aluminum disk substrate or a glass disk substrate, a glass wafer, a quartz crystal. Among devices for processing thin plate-like articles such as those used for LCDs such as wafers, it refers to a device for performing a final mirror finish, and refers to a device for finishing one side of a work to a mirror surface.

FIG. 2 is a drawing specifically showing a pressure plate provided with an embodiment of the sticking plate according to the present invention. The pressure plate 5 has a structure rotatable by a rotating shaft 17. The surface of the sticking plate 11 made of high-rigidity and high-density ceramics, which is gripped by the pressure plate, faces the work 4, and has ventilation and water permeability. Is adhered to the porous ceramic plate 15 via the layer of the adhesive tape 14. The porous ceramic plate 15 is the attachment plate 1
The fixing means is not particularly limited, but is preferably a synthetic resin-based thermosetting adhesive or a silicon oxide-based binder for the purpose of suppressing the adhesive strength and elution of trace components. It is preferable to bond them by using the method described above. Further, a collar 16 is attached to the surface of the layer of the flexible foam 13 for holding and preventing the work from jumping out. The layer of the adhesive tape for bonding to the porous ceramic plate and the above-described flexible foam and the collar are used. The backing pad 12 is configured. FIG. 3 is a view showing a structure of a pressure plate according to a conventional general waxless holding method.
Is directly stuck on the sticking plate 11 via the above layer.

As shown in the embodiment of FIG. 2, there is a single work as shown in FIG.
Depending on the size of the work, a plurality of pieces may be stored. In this case, prepare a porous ceramic plate that is the same size or a little larger than the size of the work, attach it to the high-rigidity, high-density ceramic plate so that it fits into the perforated hole, and glue the soft foam with the collar. It may be used, or a porous ceramic plate with a diameter slightly smaller than that of the high-rigidity / high-density ceramic plate is attached to the surface of the high-rigidity / high-density ceramic plate, and a backing pad of the same size or smaller is further placed thereon. May be attached, and a collar having a shape corresponding to the size and the number of the workpieces may be attached thereon.

A flexible foam 13 (a nap layer or a micropore layer) having water permeability and air permeability, an adhesive or adhesive material 14 in its inner layer, and a collar bonded to the surface of the flexible foam 13 are provided. In the backing pad, by applying a load while placing the work 4 in a state where the soft foam 13 contains water, the work 4 is firmly adsorbed on the suction surface of the soft foam 13 and does not easily peel off. This is due to the negative pressure generated when water in the soft foam layer is extruded due to external stress and the surface tension of the thin water. The force is not effective against the stress in the lateral direction (the plane parallel to the attaching plate), and the lateral force is shifted by a small force.
A collar 16 is attached in order to prevent the displacement phenomenon and the phenomenon of jumping out in a severe case. By adsorbing the work 4, the water excessively contained in the layer of the soft foam 13 is discharged from a slight gap between the work and the collar, and the porous material disposed in the upper layer of the soft foam is removed. It enters the pores of the ceramic plate 15 or is discharged further out of the sticking plate. Therefore, the undesirable phenomenon of the conventional apparatus that excessive water protrudes from the center of the work in a convex shape or collects intensively on the outer periphery of the work and adversely affects the processing accuracy, the processed shape, and the outer peripheral sag. It can be prevented beforehand. In other words, it has an effect as a buffer against excessively contained water. As described above, since the flatness of the soft foam layer is better as the flatness is better, the soft foam layer is attached to the porous ceramic plate, and then the surface is ground to form a reference surface, Thereafter, the collar may be bonded.

It is also effective to provide a plurality of small holes 18 vertically penetrating the sticking plate 11 as shown in FIG. 4 in order to enhance the effect of draining excess water. In this case, through this small hole to further increase the drainage effect,
It is also possible to perform vacuum suction from the back of the pressure plate. As shown in the drawing, in this case, the outer peripheral dimension of the porous ceramic plate 15 is set to be equal to or smaller than the outer peripheral dimension of the backing pad 12. By doing so, leakage can be prevented and the above-mentioned suction effect can be enhanced.

The sticking plate gripped by the pressure plate of the polishing machine according to the present invention uniformly presses the surface of the work, rotates smoothly, and withstands the chemical contained in the working fluid. It is required that the dimensional change is small and that the abrasion resistance is excellent. In the present invention, it is preferable to select a high-rigidity, high-density ceramic material for the attachment plate 11, particularly, a high-rigidity, hard-to-break and chemically-resistant ceramic, specifically, an acid- and alkali-resistant alumina. It is preferable to select a high-density ceramics material such as porcelain, boron carbide, zirconia, boron nitride, and aluminum nitride, or a Pyrex glass material. Further, as described above, the porous ceramic plate 15 used here is required to have a function of absorbing and retaining water and easily transferring and quickly dispersing and averaging, so that it has a fine continuous pore structure. . Further, since it is for finishing a work such as a wafer, which is a hard and brittle material, with high dimensional accuracy, the work itself must not be deformed by an external force, and is the same as that required for the above-mentioned attachment plate. Performance is required. Therefore, as a material for a porous ceramic plate, high-rigidity ceramics such as alumina, boron carbide, zirconia, boron nitride, aluminum nitride, etc., which are highly rigid, hard to break, and chemically strong, are also used as materials for porous ceramic plates. It is preferable to select a raw material, a Pyrex glass material or a quartz glass material, or a material formed on a plate having pores after molding the above-mentioned material into a bead shape.

A layer of the flexible foam 13 having ventilation and water permeability is attached to a porous ceramic plate 15,
The means for sticking is not particularly limited, and a method using an adhesive, a method using an adhesive tape, or the like can be appropriately used. However, the porous ceramic layer must not have a high hermeticity that hinders the action of absorbing water contained in the soft foam, and should be based on a porous film. Is preferred. In the case where the airtightness is high, a large number of small holes may be formed in the surface.

[0019]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention thereto. In the following Examples and Comparative Examples, polishing is performed using a 200 mm-sized etched silicon wafer as a work.
Sheets of work are attached, and specific conditions are as follows. <Processing conditions>-Polishing machine: Polishing device 59SPAW
-II type (manufactured by Speed Fam Japan) Surface plate diameter: 1504 mm Processing pressure: 25 kPa or less Surface plate rotation speed: 40 rpm Processing fluid flow rate: Nalco 2371-10 times pure water dilution Processing fluid flow rate: 10 to 20 L / min circulation processing Liquid temperature: 20-23 ° C

The configuration of the pasting plate and other main parts used is as follows. <Attachment plate configuration>-High rigidity and high density ceramics: Alumina A479 (manufactured by Kyocera Corporation) A479 size: φ586 x 22 mm-Porous ceramics: Porous alumina prototype (porosity: 40%) Size: φ580 x thickness 10mm Surface-polished after fitting into a high-rigidity, high-density alumina plate with a vitreous binder.・ Backing pad: R305 prototype (Rodel Nitta) Soft foam thickness: 80 μm Adhesive thickness: 20 μm Color thickness: 550 μm <Polishing pad> SUBA400 (Rodel Nitta)

Examples and Comparative Examples Using the pasting plate having the above-described structure according to the present invention as an example, and using a conventional structure as a comparative example, a 200 mm-sized etched silicon under the above-described processing conditions was used. Polishing was performed using the wafer as a work. Take 5 samples, T before and after polishing
The TV value was measured. Table 1 shows the measurement results.

[0022]

[Table 1]

As is clear from the results shown in Table 1, in the embodiment using the sticking plate according to the present invention, the TTV value of the polished work shows a good value of 1 μm or less. The variation is extremely small, and the problem of the polishing machine equipped with the conventional waxless type attaching plate is sufficiently solved. In addition, there was no difference between the attachment and detachment of the work and the easiness of handling, and there was no difference from the conventional waxless type attachment plate.

[0024]

As is evident from the above results, if a silicon wafer is processed by the apparatus according to the present invention, it is extremely easy to attach / detach the wafer, there is no contamination of the wafer, and moreover, it is possible to use a single wafer. It is clear that polishing processing can be performed with high precision while suppressing variations in quality and poor shape accuracy. That is, the conventional bonding method using the wax method is a manual operation that requires the most skill in the processing step of a silicon wafer, and is simplified and automation is facilitated. In addition, the waxless method, which was an insufficient method, was completed, and the efficiency of polishing processing was improved, the yield was improved, labor was saved, and time was shortened. The effect on the industry was extremely large.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a general waxless polishing machine.

FIG. 2 is an enlarged side view of a main part of an embodiment of a pressure plate of the polishing machine according to the present invention.

FIG. 3 is an enlarged side view of a main part of a pressure plate by a conventional general waxless holding method.

FIG. 4 is an enlarged side view of a main part of another embodiment of the pressure plate of the polishing machine according to the present invention.

[Explanation of symbols]

1: Metal surface plate, 2: Polishing pad, 3: Rotation axis, 4: Workpiece, 5: Pressure plate, 6:
Nozzle, 11: sticking plate, 12: backing pad, 13: flexible foam, 14: adhesive tape, 15:
Porous ceramic plate, 16: color, 17:
Rotation axis, 18: fine through hole

Claims (5)

[Claims] 1. A polishing machine comprising a rotatable polishing surface plate and a pressure plate, wherein an attaching plate grips and presses a surface of a workpiece in parallel with a surface of the polishing surface plate. Is composed of a high-rigidity and high-density ceramic plate, one or more porous ceramic plates having air permeability and water permeability, and a backing pad made of a layer of a soft foam body and a collar having air permeability and water permeability. An attachment plate, characterized in that: 2. The method according to claim 1, wherein the outer peripheral dimension of the porous ceramic plate is set to be equal to or larger than the outer peripheral dimension of the backing pad composed of the layer of the soft foam and the collar. An attachment plate according to the item. 3. A porous ceramic plate is installed such that its outer peripheral dimension is equal to or smaller than the outer peripheral dimension of a backing pad made of a layer of a soft foam and a collar. The attachment plate according to claim 1, wherein the attachment plate is provided. 4. A high-rigidity, high-density ceramic plate and a porous ceramics plate are bonded with a synthetic resin-based thermosetting adhesive or a silicon oxide-based binder, and then a soft foam is formed on the surface of the porous ceramics plate. 4. The method of claim 1, wherein a backing pad comprising a body layer and a collar is attached. 5. A high-rigidity, high-density ceramic plate and a porous ceramic plate are bonded to each other with a synthetic resin-based thermosetting adhesive or a silicon oxide-based binder. 2. The method according to claim 1, further comprising: attaching a layer, grinding the surface to form a reference surface, and then bonding a color material thereon.
Item 4. The method for producing a sticking plate according to Item 3.