JPS6025024B2 - Original plate for photomask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a photomask original plate used for producing a photomask for photolithography.

Photolithography technology is widely used in the manufacture of semiconductor devices, in which a pattern is transferred onto a wafer using a photomask for photolithography.The original plate for the photomask is a so-called hard surface plate that has a metal film made of chromium or the like. is often used.

FIGS. 1, 2, and 3 are each a longitudinal cross-sectional view of an example of a conventional hard surface plate.

In the figure, 1 is a substrate that is optically transparent to the light used to expose the photoresist coated on the wafer, and 2
, 2a, 2b are metal oxide films formed by reactive evaporation, reactive sputtering, etc.;
is a metal film such as a chromium film formed by a vapor deposition method, a sputtering method, or the like. FIG. 1 shows a hard surface plate having a metal oxide film 2 deposited directly on a substrate 1, the metal oxide film 2 being either a red and colored ferric oxide film or a black and colored ferric oxide film. A typical example is a colored chromium oxide film.

FIG. 2 shows a hard surface plate having a two-layer structure consisting of a metal film 3 deposited on a substrate 1 and a metal oxide film 2 deposited thereon. A typical film is a film consisting of a chromium film and a chromium oxide film.

FIG. 3 shows a first metal oxide film 2a deposited on a substrate 1.
, shows a hard surface plate having a three-layer structure consisting of a metal film 3 deposited on a metal oxide film 2a and a second metal oxide film 2b deposited on the metal film 3. A typical example of a three-layer film is a film in which a chromium film is surrounded by two layers of chromium oxide film.

The coatings on the various hard surface plates mentioned above are extremely thin, around 1000A, and have a very low surface reflectance of around 10% for the light used to expose the photoresist, making them effective for forming fine patterns. It is widely used because it is. To produce a photomask for semiconductor device manufacturing using a hard surface plate, first, a resist such as P(GMA-CO-EA) poly(glycidyl methacrylate-coethyl acrylate) is coated on the hard surface plate. [P(G
MA-CO-EA) poly(glycidylmet
hacrylate-co-ethylac)
: Copolymer (trade name of Mead Chemical Company)
mer)] to a thickness of 0.6r, and the resist is exposed to an electron beam using an electron beam exposure device. At that time, the electron beam that has reached the resist is exposed, and the resist layer is transmitted through the resist. to reach the top metal oxide film of the hard surface plate.

Since the electrical resistance of this metal oxide film is extremely high, the incident electrons cannot escape through conduction, causing a potential drop and blocking the arrival of subsequent incident electrons, which reduces the amount of exposure to the resist film. As a result, the resist film becomes weak and unstable, and uneven exposure occurs in the pattern formed on the resist film, making it difficult to form a fine pattern with high precision. Therefore, it is difficult to form a highly accurate fine pattern on a photomask that is finally obtained by etching the Hard Surf Ace plate using a mask obtained by developing this resist film.

In this way, conventional hard surface plates have difficulty forming highly accurate resist patterns due to uneven exposure due to potential drop during exposure using an exposure device that uses charged particles such as an exposure beam. It had the disadvantage of not being able to do so.

This invention involves forming a transparent conductive film on a transparent substrate, depositing on this film a pattern-forming film made of a metal oxide film with high electrical resistance at least on the surface side, and further depositing a pattern-forming film on the pattern-forming film. By forming a conductive film, charge accumulation in the pattern forming film and resist film does not occur during exposure to charged particles of the resist film formed on the surface, improving the accuracy of exposure and ultimately increasing the yield. The object of the present invention is to provide a photomask original plate that can improve the pattern accuracy of a photomask.

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

FIG. 4 is a longitudinal sectional view of a first embodiment of a photomask original plate (hard surface plate) according to the present invention. In FIG. 4, 4a is a transparent conductive film made of, for example, Nesa, formed on the substrate 1, and 4b is a transparent conductive film formed on the metal oxide film 2 adhered to the transparent conductive film 4a. It is a conductive film. The method of manufacturing the hard surface plate of this example will be briefly explained.

For example, a transparent conductive substrate 1 made of glass or the like that is transparent to the light used for exposing the photoresist is pre-heated, and a mixture of a tin chloride solution and an antimony chloride solution is sprayed onto it. sexual membrane 4
form a. Next, a metal oxide film 2, such as a chromium oxide film, is deposited on the transparent conductive film 4a by vapor deposition or sputtering. Further, the hard surface plate of the embodiment is manufactured by forming a transparent conductive film 4b made of a tin oxide film on the metal oxide film 2 by, for example, vacuum-depositing tin oxide powder. By attaching contact terminals to the transparent conductive film 4b on the upper surface of the hard surface plate in this embodiment to obtain electrical conduction, the resist film and the resist film formed on the hard surface plate are exposed to light by charged particles. It is possible to prevent charge accumulation on the surface of the metal oxide film 2, without causing a decrease or destabilization of the exposure amount to the resist film, and without causing exposure unevenness in the pattern formed on the resist film. It becomes possible to form highly accurate fine patterns on the photomask that is finally obtained. Figure 5 shows a hard surface playback according to this invention.
FIG.

In this embodiment, transparent conductive films 4a and 4b are formed on the conventional hard surface plate shown in FIG. FIG. 6 is a longitudinal sectional view of a third embodiment of the hard surface plate according to the invention.

In this embodiment, the metal oxide film 2a is completely surrounded by the transparent conductive layers 4a and 4b, and by keeping the potential of all layers at the same potential, the effect of preventing charge accumulation is further improved, and the final The pattern accuracy of the photomask obtained can be significantly improved. In each of the above embodiments, the transparent conductive films 4a and 4b have a thickness of 20 mm.
A thin conductive film such as a chromium film or an aluminum film having a thickness of about 0△ may be used.

Furthermore, it goes without saying that the metal film in the second embodiment may be a metal film made of a metal alloy instead of a metal film made of a single metal. As described in detail above, the photomask original plate according to the present invention includes a transparent substrate, a transparent first conductive film formed on the substrate, and a transparent conductive film formed on the transparent conductive film with at least the surface side having electrical resistance. Since it is equipped with a pattern-forming film made of a large metal oxide film and a transparent second conductive film formed on this pattern-forming film, a resist film is coated on this original plate and charged particles are When exposing the resist film of the lever, a contact terminal is attached to the conductive base to obtain electrical conduction.
It is possible to prevent charge accumulation in the pattern forming film and resist film, and it is possible to form highly accurate fine patterns on the final photomask without uneven exposure in the pattern formed on the resist film. Become.

[Brief explanation of the drawing]

1, 2, and 3 are longitudinal sectional views of an example of a subordinate photomask original plate, and FIGS. 4, 5, and 6 are respectively longitudinal sectional views of an example of a photomask original plate according to the present invention. FIG. In the figure, 1 is a substrate, 2, 2a, and 2b are metal oxide films, 3 is a metal film, and 4a, 4b are transparent conductive films. Note that the same reference numerals in the figures indicate the same or corresponding parts.
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. A substrate transparent to the light used for exposing the photoresist, a first conductive film formed on this substrate and transparent to the light, and on the first conductive film. a pattern-forming film formed on a metal oxide film having high electrical resistance at least on its surface side and opaque to the light; and a second conductive film formed on the pattern-forming film and transparent to the light. A photomask original plate comprising a film and in which a resist film formed on the second conductive film is exposed to a charged particle beam. 2. The original plate for a photomask according to claim 1, wherein the pattern forming film is surrounded by a first conductive film and a second conductive film. 3. The original plate for a photomask according to claim 1 or 2, wherein the pattern forming film is a metal oxide film. 4. The original plate for a photomask according to claim 1 or 2, wherein the pattern forming film is a two-layer structure film consisting of a metal film and a metal oxide film. 5. The method according to claim 1 or 2, wherein the pattern forming film is a three-layer structure film consisting of a first metal oxide film, a metal film, and a second metal oxide film. Original plate for photomask.