JPS5910056B2 - Mask making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mask manufacturing method for manufacturing a photomask used in a semiconductor device manufacturing process using an electron beam.

In recent years, in the manufacture of semiconductor devices, especially semiconductor devices that require fine patterns, hard masks such as chrome used in the photolithography process can be thinner than conventional emulsion masks. In addition, it has many advantages, such as making it possible to miniaturize the pattern and increasing its lifespan.

For example, when the material of such a hard mask is chromium, a chromium film is formed as a photomask with a thickness of about 500 to 1000 Å on a transparent glass substrate by sputtering or vapor deposition. Further, with the progress of photomask technology, a mask manufacturing method using electron beam exposure technology has also been developed and put into practical use.

Using this electron beam exposure technology, it is possible to significantly shorten the design time of semiconductor devices such as LSI,
In addition, the mask manufacturing cost is lower than the conventional mask manufacturing method using light (ultraviolet light), and the width is 2 μm.
This makes it possible to process submicron fine patterns. However, when manufacturing fine patterns with a width of 2 μm or less using a mask manufacturing method using electron beam exposure, it is necessary to accurately perform resist processing, post-exposure development processing, etching processing, etc. used during pattern formation. arise.

In other words, even if a fine pattern is drawn using an electron beam,
Resist film removal due to overdevelopment or development during subsequent development processing, resist film removal during etching processing,
In the end, a fine pattern mask may not be obtained due to film erosion due to overetching or the like. Therefore, when dry etching is performed using gas plasma or reactive sputtering to obtain a fine pattern, as has been the case recently, resist film erosion becomes a problem.

Furthermore, when manufacturing a hard mask made of chromium, chromium oxide, etc., conventionally, as shown in FIG. , a resist material 3 for electron beam, for example PMMA (
Polymethyl methacrylate), PBS (polybutenesulfone), COP (glycidyl methacrylate-ethyl acrylate copolymer), etc. are applied.

Next, as shown by BM in FIG. 2B, a desired pattern is formed on the resist material 3 by irradiation with electron beams, X-rays, etc. After that, a pattern is formed through development processing,
A substrate shown in FIG. 1C is obtained.

When the photomask material 2 is chromium, conventionally, nitric acid 2
Cerium ammonium [Ce(NH4)2(NO2)6
] and perchloric acid [HClO4].

Furthermore, as already mentioned, with the miniaturization of patterns for semiconductor devices such as LSIs, etching technology has also advanced, and dry etching technology using gas plasma or reactive sputtering has been developed, so etching using this technology is also possible. j now applicable.

By the way, dry etching of chromium, which is widely used as photomask material 3, is performed by glow-discharging a mixed gas containing oxygen and a halogen element such as chlorine.
This is achieved by a reaction presumed to be 12.

A hard mask is manufactured in this way, and as described above, the resist material 3 is processed by development and etching.
Film burrs occur as shown at 3a in FIGS. 1C and 1D.

For this reason, a problem may arise in so-called pattern cutting. Furthermore, if the film thickness of the resist material 3 is increased in advance in consideration of film erosion, the resolution and contrast of the resist will be reduced, causing a big problem in microfabrication.
The present invention has been made to solve these problems, and provides a semiconductor device that simplifies the manufacturing process, improves yield, and improves pattern accuracy. The purpose is to provide a mask manufacturing method for The mask manufacturing method of the present invention includes the steps of depositing a photomask material, such as chromium, chromium oxide, a mixture of chromium and chromium oxide, iron oxide, etc., on a glass substrate by sputtering or vapor deposition; Polymer materials on top, such as river V Buddha (
The photomask material and the polymeric material react to form a desired pattern. The photomask material is further drawn by the electron beam, and the polymer material is removed by a gas plasma, for example, a plasma of a mixed gas containing a halogen element such as chlorine and oxygen. This process includes a step of selectively etching the area (or, conversely, the area that is not drawn), and the mask is manufactured in the above order. In this case, the chromium oxide may contain either or both of tungsten and molybdenum. An embodiment of the present invention will be described below with reference to FIG. FIG. 2 is a cross-sectional view of the substrate in each manufacturing process of the present invention. For the substrate, first, a chromium film 4, which is a commonly used low-reflection chromium, is deposited on a glass substrate 1 by sputtering or vapor deposition, and then a photomask material 5 made of chromium oxide is deposited in the same manner on top of the chromium film 4. It was deposited to a thickness of approximately 100A.

As shown in FIG. 2A, PM
A resist material 3 is formed by applying an electron beam resist such as MA, PBS, or COP.

As the resist material 3, photoresists such as OMR, KTFR, AZ, and other polymeric materials are used. Next, as shown in FIG. 2B, a desired pattern is formed using an electron beam BM.
Draw on the board with . In this case, the film thickness of the resist material 3 is preferably as thin as possible. This is an electron beam BM
This is to improve pattern accuracy by reducing scattering within the resist material 3 or back scattering by the substrate. The amount of electron beam varies depending on the types of resist material 3 and photomask material 5, but it is sufficient as long as it is high enough to cause a reaction between resist material 3 and photomask material 5. For example, when the resist material 3 is PBS and its film thickness is about 1000A, the electron beam amount is 0.5A/Cr
The current density is about A. However, since the above-mentioned reaction is also related to the writing speed of the electron beam BM, this writing speed must also be included in the determination of the current density. Next, the resist material 3 on the photomask material 5 is completely removed using oxygen plasma or the like, as shown in FIG. The reacted areas 5a of the photomask material 5 and the chromium film 4 are etched to form a substrate as shown in FIGS. 2D and 2E.

In this case, plasma etching can be performed, for example, using carbonate tetrachloride (
It is carried out using a gas mixture of CCl4) and air.

Substances generated by the decomposition of the resist material 3 by the irradiation with the etching electron beam BM, such as hydrogen and carbon monoxide, react with the photomask material 5, causing the photomask material 5 to volatilize in the gas plasma. It is presumed that this is achieved by changing the state to a state where it is easy to be etched, that is, easily etched.

Therefore, the region 4a of the chromium film 4 in contact with the region 5a irradiated with the electron beam BM is selectively removed by etching to form a substrate as shown in FIG. 2E.

This does not indicate that the substrate shown in FIG. 2E can be obtained without going through the conventional development process.

As is clear from the foregoing, the etching effect differs depending on the materials of the resist material 3 and photomask material 5.

That is, the etching rate is greatly influenced by the oxygen concentration contained in the photomask material 5, which is a chromium oxide film, and the presence of other impurities. This impurity may be tungsten, molybdenum, etc., and the photomask material 5 containing these is hardly etched in plasma etching using a mixed gas of carbon tetrachloride and air.
Non-volatile. FIG. 3 &ζShows cross-sectional views of a substrate at each step showing another embodiment of the present invention.

In this case, the chromium film 4 reacted by plasma etching
The area 4b is removed as shown in FIG. 3B. FIG. 4 shows a cross-sectional view of a substrate in each step without showing yet another embodiment of the present invention.

In this case, a region 4b reacted by &ζ plasma etching remains as shown in FIG. 4B. In the above description, the photomask material 5 is made of low-reflection chromium (chromium + chromium oxide), but it may also be made of a metal material such as chromium.

In addition, although the photomask material 5 that reacts with the resist material 3 is etched in a gas plasma of carbon tetrachloride or the like, the symmetry of the etching can be changed depending on the types of the resist material 3, the photomask material 5, and the plasma gas. Can be reversed. As described above, according to the present invention,
The development process can be omitted, which improves the yield.Furthermore, since there is no film burr of the resist material due to development and etching, pattern accuracy is improved and microfabrication becomes possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a substrate in each step of conventional mask manufacturing, FIG. 2 is a sectional view of a substrate in each step of mask manufacturing according to an embodiment of the present invention, and FIGS. 3 and 4 are sectional views of a substrate in each step of mask manufacturing according to an embodiment of the present invention. FIG. 7 is a cross-sectional view of a substrate in each step of mask manufacturing according to another embodiment. 1...Glass substrate, 2,5...Photomask material, 3...Resist film, 4...
・Chromium film.

Claims (1)

[Claims] 1. A step of depositing a photomask material on a glass substrate by sputtering or vapor deposition, a step of applying a polymer material on the deposited photomask material, and a step of applying an electron beam to the photomask material. a step of drawing a pattern by reacting the photomask material and the polymer material; and a step of etching away the region of the photomask material drawn by the polymer material and the electron beam using gas plasma. A mask manufacturing method comprising: manufacturing a mask in the above order. 2. The mask manufacturing method according to claim 1, wherein the photomask material is at least one of chromium and chromium oxide. 3. The mask manufacturing method according to claim 1, wherein the photomask material is iron oxide. 4. The mask manufacturing method according to claim 1, wherein the polymer material is an electron beam resist. 5. The mask manufacturing method according to claim 2, wherein the chromium oxide is a chromium oxide containing either tungsten or molybdenum, or both. 6. The mask manufacturing method according to claim 1, wherein the gas plasma is generated with a mixed gas containing a halogen element and oxygen. 7. A step of depositing a photomask material on a glass substrate by sputtering or vapor deposition, a step of applying a polymer material on the deposited photomask material, and a step of depositing the photomask material and the photomask material with an electron beam. Consisting of a step of drawing a pattern by reacting a polymeric material, and a step of etching away other regions of the photomask material by gas plasma using the polymeric material and the portions reacted by the electron beam as a mask. and manufacturing the mask in the above order.