JPS6055827B2 - Photomask substrate processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, photomasks used in the manufacture of semiconductor devices are manufactured by chamfering the edges of the surfaces of the glass substrate using a grindstone, etc., and by applying chromium and oxide on the substrate surface. Substrate processing consists of forming a photomask made of a thin chromium film, but in recent years there has been an increasing demand for photomasks that can produce highly accurate and fine patterns with high efficiency and reliability. Therefore, the number of pinholes in the photomask must be reduced as much as possible.

However, the conventional glass substrate processing method described above tends to produce pinholes that exceed inspection standards, resulting in many rejected products, and it is extremely difficult to obtain a substrate with a photo film that satisfies the above requirements. There is. The present invention investigates the cause of pinholes that occur during such substrate processing, and based on this, provides a method for processing a photomask substrate that aims to significantly reduce the occurrence of pinholes. A semiconductor device consisting of a process of chamfering a photomask substrate and a process of forming a photomask on the substrate surface.
A method of processing a photomask substrate for manufacturing a semiconductor device is characterized in that, prior to the photomask forming step, a large number of minute protrusions constituting microcracks on a chamfered surface are erased.

Next, the present invention will be explained in detail.

Conventionally, substrate processing has been carried out by chamfering the four sides and the top and bottom corners of a glass substrate, then cleaning the surface on which a photomask is to be formed, and then forming a photomask on that surface. However, the number and size of pinholes in the photomask that exceeded the standards often occurred.

The inventor of the present invention has been investigating the cause of this problem and has discovered the following fact. That is, when the glass substrate is chamfered using a conventional method using a grindstone, it is observed with a microscope that micro-cracks caused by countless delicate glass protrusions are generated on the processed surface due to the grinding process. The microscopic glass protrusions that make up the cracks not only remain even after a thorough cleaning process to purify the surface of the substrate on which the photomask is to be applied, but they also remain during subsequent drying, transportation, and other handling processes and coatings. It has been found that during the process, these microscopic glass protrusions are broken and a state is created where the crushed particles are transferred to the surface of the substrate to be coated, and this is one of the major causes of forming pinholes. It has been found. Based on such knowledge, the present inventors have found that, especially when performing a process of erasing such easily broken fine glass protrusions prior to the photomask forming process, the generation of pinholes can be significantly reduced. Compared to the past,
It has been found that this reduces the number of defective products and therefore significantly improves product yield. As for the erasing process, the chamfered surface is subjected to (1) mirror polishing process, (1)
1) etching treatment, (iii) flame melting treatment, etc. In the mirror polishing process (1), after chamfering is performed using a conventional grindstone, mirror polishing is performed using a buff, leather, wood, or the like. In this case, it is preferable to round the chamfer with a grindstone and not make any corners. As a result, fine glass fluff-like protrusions generated on the machined surface during the chamfering process are removed, and a smooth chamfered surface with no microcracks is obtained. (Ii) In the etching process, an alkali such as HF', HBF4, NaOH, Na2CO3, etc. is used as an etching agent in the form of liquid or vapor.

Although it differs depending on the type of glass, for example, for a soda-coal based glass substrate, 1% HF or 0.9% water x 6% H
The chamfered surface of the substrate is etched using an aqueous NO3 solution. In such a case, the fine glass protrusions in the micro-crack portions will melt, adhere, etc., and disappear. In this way, even if a large eroded surface is formed, a chamfered surface is obtained in which numerous microcracks have completely or almost disappeared. Note that the surface of the substrate is also slightly eroded by the etching vapor, but this can be resolved by mild polishing with polyurethane or the like. (III) In the flame solution treatment, if a suitable flame such as a small burner is run along the chamfered surface, the minute glass protrusions forming the microcracks will melt and disappear, producing a smooth machined surface. .

! After carrying out the appropriate erasing process as described above, there are virtually no or almost no microscopic protrusions that will be destroyed by subsequent handling, so it is possible to coat the surface of the substrate with a thin film of chromium or chromium oxide. When forming a photomask,
Compared to conventional products, high-quality products without pinholes can be obtained at a higher yield. The number of pinholes on conventionally processed substrates has been reduced to 10.
0, it is possible to reduce the number to 20 to 30 by using the substrate treated with this method.

The drawings show processed substrates obtained by an example of the implementation of this method, in which (1) is a glass substrate, and (2) is a glass substrate that has been chamfered by grinding with a grindstone as in the past and then etched. (3) shows a photomask with a film made of chromium and chromium oxide applied to the surface by a conventional method. The thus obtained thin film substrate can be formed with highly accurate fine patterns with high efficiency and reliability, and can be used in the production of semiconductor integrated circuits to improve the yield. As described above, according to the present invention, after the micro-cracks are erased on the chamfered surface of the substrate, the surface is subjected to photomask processing, so the pinholes generated in the photomask are significantly reduced. This has the effect of significantly improving product yield and producing a processed substrate that can be applied to the manufacture of high-precision patterns and highly integrated semiconductor devices.

[Brief explanation of drawings]

The drawing shows a partially cutaway perspective view of a photo film substrate obtained by the processing method of the present invention. 1... Glass substrate, 2... Chamfered surface, 3...
Photo mask.

Claims (1)

[Claims] 1. In a method for processing a photomask substrate for semiconductor device manufacturing, which comprises the steps of chamfering a photomask substrate and forming a photomask on the surface of the substrate, the chamfered surface is chamfered prior to the photomask forming step. A photomask substrate processing method characterized by erasing a large number of minute protrusions that constitute microcracks.