JPS5910055B2 - Mask making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a chrome mask, which is a photomask used mainly in the manufacturing process of semiconductor devices.

In recent years, in the manufacture of semiconductor devices, especially semiconductor devices that require fine patterns, chrome plates as a photomask material used in the photolithography process are inferior to conventional emulsion masks in terms of lifespan, possibility of forming fine patterns, etc. Has many advantages.

Such a chrome plate is made by depositing a 500 to 100 chrome film on a transparent glass substrate by sputtering or vapor deposition.
It is formed to a thickness of about 0A. This chrome plate is further coated with a photoresist such as OMR, KTFR, or AZ, or an electronic material such as PMMA (polymethyl methacrylate), PBS (polybutene sulfonate), or COP (glycidyl methacrylate-ethyl acrylate copolymer). A photomask is manufactured by applying a line resist and irradiating a desired pattern with light or electron beams. When forming a pattern, ceric ammonium nitrate [Ce(NH4)2(N02
)6] and perchloric acid [HCl04], i.e., wet chemical etching using chemicals, but in recent years, with the development of dry etching technology using gas plasma or reactive sputtering, this Etching techniques also began to be applied. By the way, dry etching of a chromium film is performed mainly by glow discharging a mixed gas containing a halogen element such as chlorine and oxygen.
This is achieved by a reaction presumed to be 12. The reason why such etching of chromium films, that is, dry etching, has come to be widely used is that microfabrication has become necessary in the manufacture of VLSIs.

This is because, with pick-up and wet etching, the adhesion between the substrate of the semiconductor device and the resist becomes a problem, making it difficult to miniaturize the pattern. When manufacturing chrome film masks, conventionally, positive resists and negative resists are used depending on the purpose of the mask.

However, such selective use complicates the manufacturing process, and there is a considerable risk of using the wrong resist. For this reason, it has become necessary to separate each treatment process such as development and etching, resulting in a complicated mask manufacturing process. In this case, the etching speed in dry etching of the chromium film depends on the impurities contained in the chromium film.
For example, it is known to be strongly related to oxygen impurities.

This impurity may be a metal impurity such as tungsten or molybdenum, which has been found to further change the etching speed. Such impurities are
This seems to be caused by the material of the heater during the vapor deposition process. According to Auger analysis, it was found that when tungsten, molybdenum, etc. were mixed at a ratio of 1/10 to 1/5 of chromium, the etching speed of the chromium film was extremely reduced. Therefore, the present invention has been made to improve the prior art by paying attention to the above-mentioned fact, and aims to provide a mask manufacturing method with a simple manufacturing process.

The mask manufacturing method of the present invention includes the steps of forming a chromium film on a glass substrate by sputtering or vapor deposition, and after applying a resist on the chromium film, irradiating it with X-rays or electron beams and developing it. It consists of a step of forming a pattern, a step of implanting metal ions such as tungsten, molybdenum, iron, copper, etc., and a step of dry etching using gas plasma or reactive sputtering after removing the resist. and manufactured according to the above order. In this case, it is also possible to use a chromium oxide film as the chromium film.

Hereinafter, an embodiment of the present invention will be explained with reference to FIG. 1.

FIG. 1 shows a cross-sectional view of the substrate in each mask manufacturing process. In FIG. 1A, a chromium film 2 is formed on a glass substrate 1 by sputtering or vapor deposition. Next, a resist film 3 is applied onto the chromium film 2 as shown in FIG. 1B. The resist film 3 is, for example, a positive type AZ
135O, negative type 0MRsKTFR may be used, and
PMMRs are attracting attention in terms of recent pattern refinement.
It may be a positive resist for electron beams such as PBS or a negative resist for electron beams such as COP. Next, after irradiating the resist film 3 with light or electron beams, a pattern is formed by a development process to obtain the substrate shown in FIG. 1C.

Next, metal ions I such as tungsten, molybdenum, iron, copper, etc. are implanted by ion implantation technology as indicated by arrows in FIG. 1D.

The ion implantation may be carried out at a distance of several tens to hundreds of λ from the surface of the chromium film 2, and the acceleration energy varies depending on the type of metal ion I, but is approximately 50 to 100 KeV. Next, the resist film 3 on the chromium film 2 is removed (Fig. 1E), and the chromium film 2 is further removed by plasma etching in which a mixed gas containing a halogen element such as chlorine and oxygen is glow-discharged. Process to remove. In this case, as shown in FIG. 1F, the region 2a of the chromium film 2 into which the metal ions I have not been implanted is selectively removed, and the region 2b of the chromium film 2 into which the metal ions I have been implanted is removed. remain. This is based on the fact that the etching speed of region 2b is slower than that of region 2a. FIG. 2 shows cross-sectional views of the substrate at each step of performing such so-called reverse etching, and shows another embodiment of the present invention.

In FIG. 2, ions are implanted into a chromium oxide film 4 formed on a glass substrate 1, and an ion-implanted region 4a as shown in FIG. 2 AVC is formed. next,
A resist film 3 is formed on the region 4a as shown in FIG. 2B, and the substrate is etched using gas plasma. In this etching, the resist film 3 decomposes to generate hydrogen, carbon monoxide, etc., which react with the chromium oxide film 4 and the region 4a, so that etching progresses from the periphery of the resist film 3. By this,
When a substrate as shown in FIG. 2C is formed and further etching progresses, the chromium oxide film 4 and the region 4a covered with the resist film 3 are finally removed, as shown in FIG. 2D. Obtain a substrate from which all of the In this way,
The reason why the portion of the chromium oxide film 4 and the region 4a covered with the resist film 3 are etched has not been fully elucidated.

However, as mentioned above, the resist film 3 decomposes in the gas plasma, and the resulting substances, such as hydrogen and carbon monoxide, react with the chromium oxide film 4 and the region 4a containing tungsten, etc. On the other hand, it is presumed that etching progresses by reacting with halogen elements in the gas plasma. FIG. 3 shows still another embodiment of the present invention.

In this case, a chromium film 2, a chromium oxide film 4, and a region 4a in which ions are implanted into the chromium oxide film 4 are formed in this order on the glass substrate 1 to obtain the substrate shown in FIG. 3A. Next, the substrate is etched using gas plasma to obtain a substrate as shown in FIG. 3B. However, if the ion implantation process is not performed, normal etching using the resist film 3 as a mask is of course effective.

As described above, in the present invention, pattern reversal is achieved using only positive or negative resist.

Furthermore, the resulting pattern has good so-called sharpness due to the linearity of the ions, and side etching is reduced. Therefore, the present invention is applicable to LSI. This method can also be suitably applied to resists with large film burrs due to mask fabrication and dry etching for VLSIs and the like. Further, in the present invention, by using chromium oxide into which metal ions such as tungsten or molybdenum are implanted, reverse etching can be performed to etch the region covered with resist.

Therefore, in the present invention, the process of removing the resist film can be omitted, so the mask manufacturing process can be simplified. That is, in the present invention, since the chromium film or region covered with the resist film can be removed by etching, there is no need for the resist reversal process that is disadvantageous in the conventional technology, and microfabrication is facilitated. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a substrate in each step showing an embodiment of the present invention, FIG. 2 is a cross-sectional view of a substrate in each step of reverse etching using a chromium oxide film, and FIG. FIG. 7 is a cross-sectional view of a substrate in still another embodiment. 1...Glass substrate, 2...Chromium film,
3...Resist film, 4...Chromium oxide film.

Claims (1)

[Claims] 1. A step of forming a chromium film or chromium oxide film on a glass substrate by sputtering or vapor deposition, and a step of applying X-rays or electron beams after applying a resist on the chromium film or chromium oxide film. A step of forming a pattern by irradiation and development, a step of implanting metal ions, and after removing the resist, the portion of the chromium film or chromium oxide film into which the metal ions are implanted by gas plasma or reactive sputtering. A method for manufacturing a mask, comprising the step of performing dry etching to remove other parts as a mask. 2. The mask manufacturing method according to claim 1, wherein the metal ions are tungsten ions. 3. The mask manufacturing method according to claim 1, wherein the metal ions are molybdenum ions. 4. The mask manufacturing method according to claim 1, wherein the metal ions are iron ions. 5. The mask manufacturing method according to claim 1, wherein the metal ions are copper ions.