JPS638900Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a photomask substrate used for selectively exposing a photoresist film on a processing medium, such as a silicon wafer, in an integrated circuit manufacturing process.

In general, as a photomask for selective exposure such as a photomask for integrated circuits, a so-called metal mask using a metal such as chromium is often used instead of a so-called emulsion mask using an emulsion of a silver halide compound. This metal mask is durable,
It is superior to emulsion masks in terms of resolution and chemical resistance, and is becoming indispensable for manufacturing semiconductor parts such as ultra-LSIs that have high precision and include fine patterns of about 1 to 2 μm. . This metal mask is manufactured by forming a metal layer of chromium or chromium oxide with a thickness of 500 Å to 3000 Å on a transparent substrate such as glass by vapor deposition or sputtering, and then selectively applying photoresist or electron beam resist on this metal layer. This is carried out by exposing and developing using a commonly used method, and then selectively removing the metal layer using the photoresist or electron beam resist as an etching mask. Usually, in order to manufacture integrated circuits, several types of masks (generally 8 to 10 masks) having such a structure are configured as a set.

The transparent substrate used in the manufacturing process of the metal mask mentioned above is conventionally made of soda-lime glass (mainly composed of silicic acid (SIO ₂ ), soda (Na ₂ O), and lime (CaO)).
etc.) are used, but although they are cheap, they have large thermal expansion (92×10 ^-7 /℃)
It has the following drawbacks.

Recently, as the density of integrated circuits has increased, fine patterns have become required.
As mentioned above, in order to manufacture integrated circuits, it is necessary to precisely overlap 8 to 10 metal masks.

High silicate glass (96% silicic acid), which has a small thermal expansion (8 x 10 ^-7 /°C), is being used instead of conventional soda lime glass. An example of this is LE30 glass manufactured by Hoya Denshi.

For example, if we take a 5-inch (127 cm) square metal mask substrate as an example, if the metal masks are stacked one on top of the other and used one after another to create an integrated circuit,
It can be seen that overlaying can be performed with approximately 10 times higher precision than in the case of soda lime glass (5.8μ), which is subject to temperature changes of

Furthermore, with the recent increase in the density of integrated circuits, fine patterning has progressed and patterns of about 1μ have come to be used, but the light used for exposure when transferring from a metal mask to a silicon wafer has traditionally been 436nm or Although it was around 405 nm, there is a disadvantage that fine patterns of about 1 μm cannot be accurately transferred due to light diffraction phenomenon. In other words, the longer the wavelength of the exposure light, the worse the resolution of the pattern becomes due to the diffraction phenomenon. To solve this problem, recently, instead of the 436nm or 405nm light that was conventionally used for exposure, short wavelength light has been used to reduce the diffraction phenomenon.
A method using light around 250 nm is being adopted (Reference: NIKKEI ELECTRONICS 1978.7.10
P81).

With this method, a fine pattern of about 1 μm can be transferred with high precision because there is little diffraction phenomenon. This method is generally called deep UV exposure. However, when using this deep UV exposure method, a short wavelength band around 250 nm is used, so the soda lime type or silicate glass used as the conventional transparent substrate is not used as shown in 1.
Cannot be used due to poor transmittance near 250nm. on the other hand,
When quartz glass is used as the transparent substrate of the metal mask, the transmittance is about 90% even at around 250 nm, as shown by 2 in Figure 1, making it sufficiently usable.
However, as mentioned above, soda lime glass, high silicate glass, and quartz glass are all transparent substrates when observed with the naked eye, and cannot be distinguished at all by the naked eye.

Furthermore, it goes without saying that even if a metal film is applied to these transparent substrates or a metal mask substrate is used, the two cannot be distinguished in the same way.

These transparent substrates are different in price by several times, and also have different spectral transmittances as mentioned above, so it is clear that problems will occur unless they are used clearly.

In view of the above-mentioned conventional disadvantages, the present invention provides a metal mask substrate that allows the material of the metal mask substrate to be easily determined. That is, the present invention provides a mask substrate for semiconductor device manufacturing having a metal coating on one principal plane of a transparent substrate.
The corner portions of this mask substrate have marks for identifying the material of the transparent substrate using the three sides forming the corner portions.

The details of the present invention will be explained below with reference to Examples.

For example, as shown in FIG. 2, a metal mask substrate used for manufacturing an integrated circuit is a substrate 3 made of a transparent substrate, and chromium (Cr), chromium oxide (CrmOn), nickel (Ni), iron oxide ( FexOy)
A thin metal oxide film 4 such as the above is formed, and one set is usually composed of several types of metal masks having the same structure and the same material.

Example: When polishing a transparent substrate, a corner portion 3 is formed on the corner portion of the metal mask substrate so that the type of transparent substrate can be identified as shown at 5 in FIG.
A mark using a surface is made in at least one or more places using a grinder or the like. A thin metal film is then deposited.

In this way, the present invention has a mark on the corner of the metal mask substrate that allows you to identify the material of the transparent substrate, so it is easy to identify the material of the transparent substrate, and the material can be easily identified depending on the wavelength of the light used. Transparent substrates can be sorted without error.

In addition, since the mark according to the present invention is provided at the corner of the metal mask substrate, even if the mark is provided on the mask in this way, there is no mark on the part corresponding to the wafer, and the entire wafer is effectively used. It can be used for. Furthermore, according to the present invention,
Marks on the corners can be easily confirmed from three sides. Therefore, even when a plurality of masks are stored in a mask holder with their surfaces vertically, the material of each mask can be easily identified in the same state.

As described above, forming marks on a transparent substrate can be easily realized using current technology, and the above-mentioned inconvenience caused by difficulty in distinguishing between materials can be easily resolved with this invention. .

[Brief explanation of the drawing]

FIG. 1 shows the spectral transmission characteristics of glass such as soda lime and quartz glass, and FIG. 2 shows the structure of a metal mask substrate. Figure 3a,
FIG. 1B is a plan view and a cross-sectional view showing an example in which a mark is placed in at least one corner of a transparent substrate by a grinder using a surface forming the corner, which can be used to identify the type of metal mask substrate. 1... Spectral transmittance characteristics of soda lime glass, 2... Spectral transmittance characteristics of quartz glass, 3...
Transparent substrate, 4...Metal or metal oxide coating, 5
...Identification mark attached to a transparent substrate.

Claims (1)

[Scope of utility model registration request] In a mask substrate for semiconductor device manufacturing having a metal coating on one principal plane of a transparent substrate, the material of the transparent substrate is determined at a corner portion of the mask substrate using three surfaces forming the corner portion. 1. A mask substrate for manufacturing a semiconductor device, characterized in that it has a mark for manufacturing a semiconductor device.