KR20010049553A - An edge polishing machine and edge polishing method thereby - Google Patents

Abstract

PURPOSE: To provide an edge polishing device and an edge polishing method capable of improving and stabilizing the polishing speed, and increasing the service life of a polishing pad. CONSTITUTION: In a wafer edge polishing device comprising a rotary drum 2 to a surface of which a polishing pad 1 is attached, a wafer rotating device to press its end face against the rotary drum 2 at a specified angle while rotating a wafer 3, and a nozzle 7 to feed a polishing solution to a contact part of the wafer with the polishing pad, the polishing pad is a sheet of a multi- layered structure in which a sheet 11 comprising at least one of a synthetic resin foam, a non-woven fabric, a resin-worked non-woven fabric, a synthetic leather or a composite product thereof is combined with a sheet 12 of 50-500 kgf/cm2 in compressive modulus of elasticity.

Description

An edge polishing machine and edge polishing method

TECHNICAL FIELD The present invention relates to an apparatus and a method for performing polishing of an edge portion of a semiconductor substrate made of a silicon wafer, a compound wafer, or the like. More specifically, the present invention relates to a material and a structure of a polishing pad attached to the polishing apparatus.

Electronic components such as ICs, LSIs, or ultra-LSIs that use semiconductor materials such as silicon single crystals as raw materials are obtained by dividing delicate electrical circuits into wafers in which single crystal ingots of silicon or other compound semiconductors are sliced into thin discs. It is manufactured based on a small piece of semiconductor device chip. An as cut wafer sliced from an ingot is processed into a mirror surface wafer having at least one surface finished with a mirror surface through a process of lapping, etching and further polishing. In the subsequent device process, a fine electric circuit is written on the mirror-finished surface in a subsequent device process, but the wafer is processed while maintaining the original disc shape until divided into semiconductor device chips. Operation, such as washing, drying, and conveyance, enters. In the meantime, if the shape of the outer peripheral side edge of the wafer is shaved and is a rough surface, it is in contact with a device or other object during each process, and microdestructive occurs due to fine particles, or contaminated in the rough surface. In many cases, the particles are attracted and dissipated in the subsequent process to contaminate the surface subjected to the precision processing, which greatly affects the production yield and quality of the product. In order to prevent this, it is generally carried out to chamfer the edge portion in the initial stage of wafer processing and to mirror finish (edge polishing) the portion.

The above-mentioned edge grinding is generally a polishing machine having a polishing machine made of a synthetic resin foam, a nonwoven fabric, a non-woven resin processed product, a synthetic leather or a composite or synthetic leather thereof, or the like on a rotatable drum surface. It is performed by the method of performing the grinding | polishing process of an edge part, pressing at the inclination of a fixed angle, rotating the edge part, such as a beveling), and supplying the polishing composition solution which mainly contains colloidal silica.

The chamfering of the above-mentioned edge part and the process after that are specifically performed as follows conventionally. That is, the circumferential edge part of the cut wafer which sliced the ingot first is beveled using a diamond grindstone. The shape after chamfering is made to have an angle of about 22 degrees with respect to the upper and lower surfaces, respectively, or it is circular arc shape. The etching step is performed in this state, and the edge chamfered portion is polished before the polishing of the wafer surface is started. As shown in Fig. 1, edge polishing uses an edge polishing apparatus having a polishing pad attached to an outer surface of a rotatable drum. It is polished while dropping the polishing liquid onto the machined part by pressing firmly at a constant angle while rotating the wafer to the drum which gradually rises and rotates while rotating. The edge portion of the pressed wafer is buried in the polishing pad by the flexibility and elasticity of the polishing pad, and the edge portion is processed. The polishing pad used herein is the same as that used for the primary polishing of the wafer. Specifically, for example, a porous pad obtained by impregnating a polyurethane felt with a polyester felt is one having a thickness of about 1 to 1.5 mm. Is used. In general, the roughness of the surface before polishing is about 350 to 400 kPa in Ra, and is improved to about 10 to 100 kPa after processing.

Also with the above apparatus and method, the recent improvement of performance, the improvement of productivity, and the correspondence to a large diameter wafer are urgently required. Specifically, there has been a demand for improvement and stabilization of the polishing rate and the extension of the life of the polishing pad. In addition, for example, in the case where there is a potential flaw or distortion in the wafer, the wafer may rarely be broken during processing, in which case fragments of the wafer may be lodged and damage not only the polishing pad but also the drum, thereby effectively Prevention is also required.

As a method of uniformly polishing the entire edge surface of a large-diameter wafer, for example, a 12-inch wafer, as shown in, for example, Japanese Patent Application Laid-Open No. 11-188590, it has a multilayer structure in which a polishing pad and a sheet having elasticity are combined. The method of absorbing sinking of the edge part of a large diameter wafer and making it possible to perform the homogeneous processing of the whole edge surface is mentioned. At the same time, this method can be expected to some extent in terms of the demands of the above-described conventional apparatus, that is, the improvement and stabilization of the polishing rate and the extension of the life of the polishing pad.

In view of the problems of the conventional edge polishing apparatus, the present inventors have made further studies on the above-described multilayer structure polishing pad and have developed the edge polishing apparatus of the present invention. It is an object of the present invention to provide an edge polishing apparatus and an edge polishing method capable of improving and stabilizing the polishing rate and extending the life of the polishing pad, as compared with the above devices.

The above object is a rotating drum having a polishing pad attached to a surface thereof, a wafer rotating device which rotates the wafer while pressing the cross section at a constant angle with respect to the rotating drum, and polishes the contact portion between the wafer and the polishing pad. A wafer edge polishing apparatus having a nozzle for supplying a polishing liquid for polishing, wherein the polishing pad is a sheet made of at least one of a synthetic resin foam, a nonwoven fabric, a non-woven resin processed product, a synthetic leather, or a composite product thereof (hereinafter referred to as 'for polishing' Sheet ') and a sheet having a resilient sheet having a compressive modulus of elasticity in the range of 50 to 500 kgf / cm ² .

The material of the sheet having elasticity described above is not particularly limited, and any material can be used as long as it is in the shape of a sheet. However, a sheet of synthetic rubber, natural rubber, or sponge having particularly good resilience and excellent chemical resistance is preferable. Do. The reason why chemical resistance is important is that corrosive components such as alkali are contained in the polishing composition solution used for polishing.

What is important in this invention is that the sheet | seat combined with the grinding | polishing sheet | seat is a sheet | seat which has elasticity whose compressive modulus is in the range of 50-50 kgf / cm <^2> . The compressive elastic modulus in this invention is a numerical value which shows the repulsive force with respect to compression, and is measured based on the measuring method shown to JIS-K6254. The higher the value, the harder the elasticity is, and the lower the value, the lower the elasticity. If the compressive elastic modulus is less than 50 kg / cm ² , the elastic modulus is too low, the repulsion to the stress is not sufficient, and the bottoming phenomenon appears, and the meaning of using the sheet having elasticity in the present invention is lost. When the compressive elastic modulus exceeds 50 kg / cm ² , the elastic modulus is too high and stress absorption as an elastic body is not sufficient, and the effect as an appropriate elastic body cannot be exhibited.

Although it does not specifically limit about the thickness of the sheet | seat which has elasticity, Preferably it is 4 mm or less. If it is more than that, the thickness as the whole polishing pad becomes too thick, and it becomes difficult to homogeneous adhesion to a rotating drum. Therefore, the gap between the joint line portions cannot be narrowed so as to be negligible, and it is difficult to obtain sufficient dimensional accuracy, and the surface roughness of the wafer edge portion after polishing tends to be irregular.

In addition, the method is not particularly limited in combination of the polishing sheet constituting the polishing pad and the sheet having elasticity, but the method is not particularly limited. However, since a large mechanical force is applied in actual use, an adhesive or It is preferable to use a double-sided tape or to laminate by means such as heat fusion.

1 is a side view of the wafer edge polishing apparatus of the present invention.

Fig. 2 is a graph showing the transition of the polishing results of long-term continuous use by the edge polishing apparatus using the polishing pads of Examples 1, 2 and Comparative Example 1;

<Brief description of the symbols in the drawings>

1 polishing pad 2 rotating drum 3 silicon wafer

4 rotary drum rotary shaft 5 wafer rotator

6 wafer axis of rotation 7 nozzles

11 Polishing sheet 12 Elastic sheet

Although the implementation example of this invention is demonstrated below by drawing, it does not specifically limit by this. 1 is a side view of the wafer edge polishing apparatus of the present invention. The rotating drum 2 has a structure that rotates at a high speed of about 1000 to 3000 times per minute about the rotating shaft 4, and has a polishing pad 1 composed of the polishing sheet 11 and the sheet 12 having elasticity. ) Is attached to cover the front surface close to the outer peripheral surface. The wafer 3 rotates at a high speed about the rotation shaft 6 in a state of being fixed to the wafer rotating apparatus 5. The wafer rotation shaft 6 is inclined at an angle of about 45 degrees with respect to the drum rotation shaft 4. The rotary drum 2 is structured to move little by little in the vertical direction while maintaining a constant rotational speed, thereby traversing the contact point between the wafer 3 and the polishing pad 1 up and down. The nozzle 7 is arrange | positioned on the contact point of the wafer 3 and the polishing pad 1, and the processing liquid is supplied quantitatively from this nozzle.

In the polishing process, the wafer 3 is inclined by about 45 degrees while the rotating drum 2 and the wafer 3 are both rotated to contact the rotating drum 2. The tip of the edge portion of the wafer 3 is polished in the state of being embedded in the polishing pad 1. In the case of the polishing apparatus of the present invention, that is, the apparatus having a polishing pad in which a composite of a polishing sheet and a sheet having elasticity is combined, as shown in FIG. 1, the edge of the wafer 3 is sufficiently buried, and the inclined surface of the wafer upper surface is shown. It is obvious that it is processed to about two thirds of the position from the top of the front and the end face. If the wafer is inverted and processed, the edge surface can be sufficiently processed.

In the polishing process, high contact pressure is applied to the polishing sheet 11 as the wafer edge surface is pressed and rotated, but this stress is absorbed by the elastic sheet 12 existing inside and is greatly compressed and deformed. Therefore, compared with the normal polishing pad, that is, without the elastic sheet, the surface damage is extremely slight and there is little change in shape and physical properties. In addition, it is relatively easy to cope with severe conditions such as increasing the polishing processing speed in order to improve productivity.

In addition, there are potential scratches and distortions on the wafer, which may cause an unexpected situation such as breakage of the wafer during polishing, so that the wafer fragments remain in the elastic sheet even when the wafer fragments are stuck. No damage to the drum.

Edge grinding methods, such as a wafer, which are another objective of this invention are clarified in the Example described below.

Hereinafter, although an Example and a comparative example are given and the wafer edge grinding apparatus and grinding | polishing method of this invention are demonstrated concretely, it does not specifically limit by this.

In addition, the apparatus used in the present Example and the comparative example is edge grinding apparatus V type | mold by Speed Palm Co., Ltd. As an abrasive | polishing sheet | seat, the thing of 1.27 mm thickness of the sheet SUBA400 made from Rodel-Nita Corporation was used. The sheet and the sheet having elasticity were bonded together to perform edge polishing of an 200 mm diameter acut silicon wafer as a polishing pad. As the polishing solution, a colloidal silica having a pH of 10.2 and an average particle diameter of 50 nm was supplied at a flow rate of 30 mL / min using a 5% concentration.

Example 1

As a sheet having elasticity, a natural rubber sheet having a compressive modulus of 287 kgf / cm ² at a thickness of 2 mm and the above-described polishing sheet were combined and laminated to form a two-layer polishing pad, which was attached to a drum. The edge chamfered part of the silicon wafer after processing became a homogeneous mirror surface state in the whole area | region, and the remainder which was not processed was not seen. This polishing was carried out continuously, and the change in the polishing rate for each elapsed time was measured. The results are shown in the graph of FIG.

Example 2

As a sheet having elasticity, a natural rubber sheet having a compressive modulus of 346 kgf / cm ² at a thickness of 2 mm and the above-described polishing sheet were combined and laminated to form a two-layer polishing pad, which was attached to a drum. The edge chamfered part of the silicon wafer after processing became a homogeneous mirror surface state in the whole area | region, and the remainder which was not processed was not seen. This polishing was carried out continuously, and the change in the polishing rate for each elapsed time was measured. The results are shown in the graph of FIG.

Comparative Example 1

As a sheet | seat having elasticity, it carried out similarly to Example 1 except having used the urethane sponge sheet of compressive elastic modulus 0.5kgf / cm <^2> at thickness 2mm instead of the natural rubber sheet | seat. The edge chamfer part of the silicon wafer in the initial grinding | polishing process became the mirror surface state homogeneously in the whole area | region, and the remainder which was not processed was not seen. This polishing was carried out continuously, and the change in the polishing rate for each elapsed time was measured. The results are shown in the graph of FIG. In the step after 600 minutes, the edge chamfered part of the silicon wafer after polishing was slightly deteriorated in surface roughness, and the center portion in the thickness direction of the peripheral edge portion of the wafer was not polished.

As is clear from the graph of Fig. 2, the polishing pads of Examples 1 and 2 show no deterioration in the polishing rate even in long-term continuous use, and the damage to the surface of the polishing pad is extremely slight, and the polishing results are also compared with the first. Even if not inferior at all, the continuity of the processing force was enough. On the other hand, in the case where the polishing pad of Comparative Example 1 is used, as shown in the graph, the decrease in the processing speed is obvious from the time point exceeding 300 minutes, and the damage of the polishing pad is also remarkable, and even the edge processing can be performed. It became impossible.

As described above, according to the apparatus of the present invention, in edge polishing, which is late in development in the processing of semiconductor materials such as silicon wafers, it is only necessary to devise the configuration of the polishing pad without significantly changing the structure of the edge polishing apparatus itself. It is possible to improve productivity, that is, to improve and stabilize the polishing rate, to cope with larger wafer diameters, and to extend the life of the polishing pad.

Claims (2)

A rotating drum having a polishing pad attached to a surface thereof, a wafer rotating device for pressing the wafer while the cross section is held at a constant angle with respect to the rotating drum, and a polishing liquid applied to the contact portion between the wafer and the polishing pad. A wafer edge polishing apparatus having a nozzle to supply, wherein the polishing pad is a sheet made of at least one of a synthetic resin foam, a nonwoven fabric, a resin processed product of a nonwoven fabric, a synthetic leather, or a composite product thereof, and a compressive modulus of 50-50 kgf / Wafer edge polishing apparatus, characterized in that the multi-layered sheet is a combination of sheets in the range of cm ² . Rotating the rotating drum of the wafer edge polishing apparatus of claim 1, while pressing the edge portion while maintaining a constant angle with respect to the rotating drum while rotating the wafer, the edge portion of the wafer while supplying the liquid of the polishing composition from the liquid supply nozzle Edge grinding method for polishing.