EP-4737416-A1 - METHOD FOR PRODUCING SYNTHETIC QUARTZ GLASS SUBSTRATE

Abstract

Provided is a method for producing a synthetic quartz glass substrate, including an evaluation step of evaluating a depth of a machining damaged layer at a machined surface of a synthetic quartz glass substrate, and a removal step of removing the machining damaged layer on the basis of a result of evaluation of the depth of the machining damaged layer. A machining damaged layer is removed on the basis of evaluation of the depth of the machining damaged layer at a machined surface. The machining damaged layer can be reliably and efficiently removed, and the productivity of a synthetic quartz glass substrate can be improved.

Inventors

• ANDO, MASAO

Assignees

• SHIN-ETSU CHEMICAL CO., LTD.,

Dates

Publication Date

20260506

Application Date

20251020

Claims (7)

1. A method for producing a synthetic quartz glass substrate, comprising an evaluation step of evaluating a depth of a machining damaged layer at a machined surface of a synthetic quartz glass substrate, and a removal step of removing the machining damaged layer on the basis of a result of evaluation of the depth of the machining damaged layer.
2. The method for producing a synthetic quartz glass substrate according to claim 1, wherein in the evaluation step, whether the synthetic quartz glass substrate has predetermined values of an arithmetic average height (Sa), a skewness (Ssk) and a kurtosis (Sku) at the machined surface is evaluated, and depending on a result of the evaluation, the removal step is performed.
3. The method for producing a synthetic quartz glass substrate according to claim 2, wherein a synthetic quartz glass substrate satisfying the predetermined values is selected in the evaluation step, and the removal step is performed under a predetermined condition set in advance on the synthetic quartz glass substrate satisfying the predetermined values.
4. The method for producing a synthetic quartz glass substrate according to claim 2 or 3, wherein the predetermined values of the arithmetic average height (Sa), the skewness (Ssk) on an absolute value basis, and the kurtosis (Sku) are 2.0 µm or less, 0.8 or less and 5.0 or less, respectively.
5. The method for producing a synthetic quartz glass substrate according to claim 4, wherein the removal step in which a depth of removal is set to 30 µm is performed on the synthetic quartz glass substrate satisfying the predetermined values.
6. The method for producing a synthetic quartz glass substrate according to any one of claims 1 to 5, wherein the removal step comprises mirror polishing or wet etching.
7. The method for producing a synthetic quartz glass substrate according to any one of claims 1 to 6, wherein the depth of the machining damaged layer is 30 µm or less.

Description

TECHNICAL FIELD The present invention relates to a method for producing a synthetic quartz glass substrate. BACKGROUND Synthetic quartz glass substrates to be used for semiconductor substrates, optical members, microfluidics, microlens arrays, and the like undergo cutting machining for forming through holes or blind holes, grooves, level differences and the like, and are put to practical use. When such cutting machining is performed, a tool such as grinding stone or a drill is commonly used. Here, a machining damaged layer is generated at the machined surface. For removing the machining damaged layer, it is required that the amount of grinding, the amount of polishing or the like be made large in a subsequent grinding step, polishing step or the like, which causes deterioration of productivity. A fixed abrasive grain tool that is typically used for such cutting machining is dressed before the start of the cutting machining or during the machining for adjusting the amount of protrusion of abrasive grains or forming a cutting edge of abrasive grains. Since the state of the tool after the dressing is not always constant, a deep machining damaged layer may be exceptionally generated or there may be a large variation in the depth of the machining damaged layer depending on the life of the fixed abrasive grain tool. To address such a problem, for example, JP-A 2012-035330 (Patent Document 1) discloses a method in which in production of a glass substrate for a magnetic recording medium, an abrasive grain size distribution width of abrasive grains contained in grinding stone is set equal to or less than a predetermined value to suppress generation of a deep machining damaged layer at a machined surface. JP-A 2012-027976 (Patent Document 2) discloses a method in which in production of a glass substrate for a magnetic recording medium, the surface roughness of a cutting surface of a fixed abrasive grain tool is defined to suppress generation of a deep machining damaged layer at a machined surface. Citation List Patent Document 1: JP-A 2012-035330Patent Document 2: JP-A 2012-027976 SUMMARY OF THE INVENTION However, in the method described in Patent Document 1 or 2, a deep machining damaged layer exceptionally generated or a variation in the depth of the machining damaged layer, which depends on the dressing condition and life of grinding stone and a fixed abrasive grain tool, is not considered. Deep cracks or the like may remain even after the machining damaged layer removing step. Measurement of the depth of the machining damaged layer requires additional steps of precision cleaning, etching and the like, which may deteriorate productivity. The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a production method capable of reliably and efficiently removing a machining damaged layer, and producing a synthetic quartz glass substrate with good productivity. The present inventor has conducted intensive studies, and resultantly found that by evaluating the depth of a machining damaged layer at a machined surface of a synthetic quartz glass substrate, and removing the machining damaged layer on the basis of the result of the evaluation, the machining damaged layer can be reliably and efficiently removed, and the productivity of the synthetic quartz glass substrate can be improved, leading to completion of the present invention. Accordingly, the present invention provides the following method for producing a synthetic quartz glass substrate. 1. A method for producing a synthetic quartz glass substrate, including an evaluation step of evaluating a depth of a machining damaged layer at a machined surface of a synthetic quartz glass substrate, and a removal step of removing the machining damaged layer on the basis of a result of evaluation of the depth of the machining damaged layer.2. The method for producing a synthetic quartz glass substrate according to 1, wherein in the evaluation step, whether the synthetic quartz glass substrate has predetermined values of an arithmetic average height (Sa), a skewness (Ssk) and a kurtosis (Sku) at the machined surface is evaluated, and depending on a result of the evaluation, the removal step is performed.3. The method for producing a synthetic quartz glass substrate according to 2, wherein a synthetic quartz glass substrate satisfying the predetermined values is selected in the evaluation step, and the removal step is performed under a predetermined condition set in advance on the synthetic quartz glass substrate satisfying the predetermined values.4. The method for producing a synthetic quartz glass substrate according to 2 or 3, wherein the predetermined values of the arithmetic average height (Sa), the skewness (Ssk) on an absolute value basis, and the kurtosis (Sku) are 2.0 µm or less, 0.8 or less and 5.0 or less, respectively.5. The method for producing a synthetic quartz glass substrate according to