JPS6140100B2 - - 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 glass substrate using a grindstone or the like, and by applying chromium or chromium oxide to the substrate surface. In recent years, there has been an increasing demand for photomasks that can reliably produce highly accurate, fine patterns with high efficiency. To achieve this, 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 the 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. It is.

The present invention investigates the causes of pinholes that occur during such substrate processing, and based on this, provides a photomask substrate processing method that aims to significantly reduce the occurrence of pinholes. In the photomask substrate processing method, which includes the steps of chamfering the photomask substrate and forming a photomask on the surface of the substrate, a large number of fine protrusions constituting microcracks are formed prior to the photofilm forming step. The chamfered surface is covered with a covering material. 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. Photomasks often had pinholes that exceeded the standard in number and size. 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 microcracks due to countless fine glass protrusions are generated on the processed surface due to grinding with the grindstone. In addition, the fine glass protrusions that make up these microcracks 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. It has been found that these minute glass protrusions are broken during the coating process, etc., and a state is created in which the crushed particles are transferred to the surface of the substrate to be coated, and this creates a large one that makes up the pinhole. It turned out to be the cause. Based on such knowledge, the present inventors have found that the formation of pinholes can be extremely significantly reduced, especially when coating such easily broken fine glass protrusions with a coating film prior to the photomask forming process. It has been found that this method reduces the number of defective products compared to the conventional method, and therefore significantly improves the product yield. As for the coating formation treatment of the coating film, on the chamfered surface,
(i) Application treatment of paste, synthetic resin liquid, etc., (ii) Formation treatment of vapor deposited film by vapor deposition of metal or metal oxide, (iii)
This includes coating treatment using a separately prepared coating material.

The coating process (i) uses a coating material such as paste or synthetic resin liquid, such as silicone resin or epoxy resin, and applies it to the entire surface of the chamfered surface.
After drying, the surfaces of the numerous fine glass protrusions are coated and bonded. In forming the deposited film (ii), a metal such as chromium or a metal oxide is deposited using an appropriate vacuum deposition apparatus to cover the fine glass protrusions.

(iii) Covering treatment with separately prepared covering material:
This means that a separately produced plate-shaped, groove-frame-shaped, etc.-shaped covering material is fixedly attached to the chamfered surface of the substrate, or is fitted and coated in a removable manner.

After the above-mentioned coating treatment is performed, the fine protrusions are prevented from escaping and moving due to breakage due to the coating material, so when a photomask made of a thin film of chromium or chromium oxide is formed on the surface of the substrate. Compared to the conventional method, high-quality products with no or almost no pinholes can be obtained at a higher yield.

If the number of pinholes on a conventionally treated substrate is 100, the number can be reduced to 20 to 20 by using a substrate treated with this method.
It is possible to reduce it to 30.

Note that after the above-mentioned erasing process, the substrate may be cleaned.

In the drawings, Figure 1 shows processed substrates obtained by an example of implementing this method, 1 is a glass substrate, 2 is a glass substrate that has been chamfered by grinding with a grindstone as in the past, and then a coating film is formed. a chamfered surface treated with a coating film 3 that covers and protects microcracks;
4 shows a photomask with a coating made of chrome and chromium oxide applied on its surface by a conventional method.

FIG. 2 shows another embodiment, in which a fitting groove 5a having a U-shaped cross section as shown in FIG.
In this method, a longitudinal groove frame covering material 5 having a diameter is fitted as shown in FIG. 2b. The material is a flexible thin soft material such as gold, copper, pure aluminum, lead, synthetic resin such as Teflon, etc., and its flexible elasticity allows it to be tightly fitted and removed, and can be used repeatedly. It is preferable to make it possible. The width of the groove frame is, for example, approximately 0.1 mm smaller than the thickness of the substrate so that it can be removably fitted tightly. Such a removable coating type is advantageous because it can be used repeatedly, reduces impact during handling, and provides good protection against damage to the edges of the substrate.

On the thus obtained thin plate substrate, a highly accurate fine pattern can be formed with high efficiency and reliability, resulting in an increase in the integration density with silicon wafers. In this way, according to the present invention, after coating the microcrack surface on the chamfered surface of the substrate, the photomask process is applied to that surface, 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 the drawing]

Figure 1 is a partially cutaway perspective view of a photo film substrate obtained by one example of the processing method of the present invention;
Figure a is a slope view of the covering material used in another example, Figure 2 b
shows a cutaway side view of another example. 1... Glass substrate, 2... Chamfered surface, 3...
...Protective coating film, 4... Photomask, 5... Groove frame covering material.

Claims (1)

[Claims] 1. In a method of processing a photomask substrate, which consists of a step of chamfering a photomask substrate and a step of forming a photomask on the surface of the substrate, a large number of fine cracks constituting microcracks are formed prior to the photofilm forming step. A method for processing a photomask substrate, characterized in that a chamfered surface having protrusions is covered with a coating material.