JPS6161664B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photomask plate with a transparent conductive film used in the manufacturing process of semiconductor integrated circuits and high-density integrated circuits. In general, this type of photomask plate includes a transparent glass substrate 1 as shown in FIG.
It has been proposed that a transparent conductive film such as indium oxide or tin oxide be applied to the
No. 117682). When making a photomask using this photomask plate, a pattern-forming film 3 of chromium, chromium oxide, iron oxide, etc. is formed on the transparent conductive film 2, as shown in FIG. When such a photomask plate is used, static electricity generated during the manufacturing process of semiconductor devices is grounded and released, thereby preventing the mask from being charged. Preventing static electricity on the mask prevents dust from accumulating on the mask and prevents pattern damage due to discharge between mask patterns, extending the life of the mask and improving the yield of wafers subjected to printing exposure (contact printing). improve. Currently, photomasks used in the manufacturing process of semiconductor devices are mainly used by contact printing, and the mask cleaning process includes scrub cleaning and cleaning by applying pressurized water to the mask. Hot concentrated sulfuric acid with extremely high strength and oxidizing hot concentrated sulfuric acid with hydrogen peroxide added are often used. Therefore,
The above-mentioned transparent conductive film is required not only to have good transparency and conductivity to the light used for exposure, and not to dissolve in the etching solution used for pattern creation, but also to have strong adhesion to glass and acid resistance. There is a strong demand for excellence in Conventional transparent conductive films use films mainly made of indium oxide, which has excellent conductivity, from the viewpoint of reducing sheet resistance, but have poor acid resistance. For example, a film with a thickness of about 200 Å formed on a glass substrate.
When an indium oxide film containing about 10% by weight of tin oxide is immersed in hot concentrated sulfuric acid at 80°C for 5 minutes and its sheet resistance is measured, it loses conductivity and the transparent conductive film peels off. On the other hand, when tin oxide is used, it has excellent acid resistance but poor adhesion. For example, a film thickness containing about 10% by weight of antimony oxide in tin oxide
A photomask blank was created by forming a transparent conductive film of about 200 Å on a soda lime glass substrate using a sputtering method, and a chromium film of about 800 Å on top of it using a sputtering method, and a scratch test with a sand eraser was performed. Then, the transparent conductive film is peeled off. Furthermore, when a blank chromium film prepared in the same manner is removed with a cerium nitrate-based etching solution and then immersed in hot concentrated sulfuric acid at 110°C, it loses its conductivity within about 4 hours and the transparent conductive film peels off. As described above, a transparent conductive film mainly composed of indium oxide has poor acid resistance, and a transparent conductive film mainly composed of tin oxide has poor adhesion. This invention eliminates the above-mentioned conventional drawbacks,
This was done in order to further improve the process, using a glass substrate that contains an alkali metal element of 3 mol percent or less in terms of its oxide (R ₂ O), or a glass substrate that does not contain an alkali element.
A transparent conductive film mainly made of tin oxide is formed on top of the film by sputtering, ion plating, or vacuum evaporation to improve adhesion and provide photomasks with a transparent conductive film that has excellent acid resistance. The purpose is to create a plate and further improve the acid resistance of the transparent conductive film itself, which is mainly made of tin oxide. FIG. 3 is a diagram showing a process of manufacturing a plate with a transparent conductive film from glass cut to a certain size. Referring to FIG. 3, the glass substrate is first precision polished (S ₁ ) and then acid-cleaned using sulfuric acid, hydrofluoric acid, etc. (S ₂ ). Subsequently, after alkali cleaning using sodium hydroxide, potassium carbonate, etc. (S ₃ ), a film containing tin oxide as the main component was produced on the glass substrate by reactive DC magnetron sputtering (S ₄ ). , a photomask plate having a structure similar to that shown in FIG. 1 is manufactured. in this case,
A glass substrate 1 containing 3 mole percent or less of an alkali metal oxide was used, and the produced film 2 contained about 10 weight percent of antimony oxide in addition to tin oxide. This film 2 is 200Å
The film had a film thickness of about 10 KΩ/□ and a sheet resistance of about 10 KΩ/□, and the transmittance for light with a wavelength of 436 nm was 85% or more. Oxygen was used as the reactive gas during sputtering. Note that ion plating and vacuum evaporation can be used as the film forming method, but in the case of vacuum evaporation, a glass substrate containing no alkali metal is used. As a result of an experimental analysis of the cause of the weak adhesion of conventional transparent conductive films made mainly of tin oxide, we found that the cause was the presence of a certain amount of alkali metal elements in the glass substrate. I understand. In other words, stannate salts (e.g., sodium hexahydroxostan(IV)) are formed at the interface between tin oxide and glass, and this inhibits the reaction of tin with silanol groups on the glass.
It is expected that the network structure in the glass will be expanded and the number of bondable silanol groups etc. per unit area will be reduced. Therefore, it is better not to include alkali metals in the glass, but according to experiments, the sputtering method,
The ion plating method can be defined as a glass substrate containing 3 mol percent or less of an alkali metal oxide, and the vacuum evaporation method can be defined as a glass substrate containing no alkali metal. This is expected to be because the sputtering method and ion plating method sputter the alkali metal elements on the surface a little more than the vacuum evaporation method, and the attached atoms are implanted deeply into the substrate, which is also more effective in activating the glass surface. be done. A chromium film is further applied by a sputtering method on the transparent conductive film mainly composed of tin oxide, which is formed on the glass substrate with an alkali metal oxide content of 3 mol percent or less or no alkali metal element. Even when the formed chrome blank is subjected to a scratch test using a sand eraser, the transparent conductive film and the chrome film do not peel off. In addition, because of its strong adhesion, the chromium film will not lose its conductivity even if it is immersed in hot concentrated sulfuric acid at 110°C for more than 8 hours after being peeled off with a cerium nitrate-based etching solution from a chromium blank made in the same way. . Next, another embodiment will be described. Example 1 A~ whose content of alkali metal oxide is shown in Table 1
A transparent conductive film of about 200 Å of tin oxide containing about 10% by weight of antimony oxide was formed on nine types of glasses of I in the process shown in FIG. 3, and then heat treated at 400° C. for 1 hour. The film forming method is DC and magnetron sputtering using a mixed gas of argon and oxygen. 800% chromium film on this transparent conductive film
A photomask blank having a thickness of about Å thick was prepared. When this was tested by a scratch test with a sand eraser, the transparent conductive film and chromium film were peeled off from glass substrates A to F containing 3 mol percent or more of alkali metal oxides, but G with 3 mol percent or less of alkali metal oxides peeled off. ~I did not peel off.

[Table] Figures 4, 5, 6, and 7 show samples using a scratch tester using glass substrates D, E, G, and H in Table 1. The surface condition of the chrome blank was examined using an optical microscope (transmitted light,
This is a photograph observed using a ×32.5). As is clear from Figure 4, peeling was observed in the samples using D and E, which contain alkali metal oxides of 3 mol percent or more;
It can be seen that no peeling was observed in the samples using H and H. Here, the conditions for the scratch test are listed below. Load: 600g Sand eraser No.72 Dark gray ink eraser
(Manufactured by Faber-castell) Scratching speed: 50 mm/min In the same manner, a chromium blank was prepared using D, F, G, H, and I glass substrates, and then only chromium was etched using a cerium nitrate-based etching solution. The removed sample was immersed in hot concentrated sulfuric acid at 110°C for a certain period of time, and its sheet resistance was measured. The results are shown in Table 2.

[Table] As shown above, glasses containing 3 mole percent or less of alkali metal oxides have strong adhesion to the transparent conductive film mainly composed of tin, and strong acid resistance. Example 2 A transparent conductive film of tin oxide containing 10% by weight of antimony oxide was created by vacuum evaporation on nine types of glasses A to I shown in Table 1 in the process shown in Figure 3, and then coated on the transparent conductive film. A chrome blank with a chromium film of approximately 800 Å thick was fabricated using the sputtering method. Note that the transparent conductive film was formed to have a thickness of about 200 Å. When this chrome blank was subjected to a scratch test using a sand eraser under the conditions described above, it was found that chromium on glass substrates A to G containing alkali metals,
Although the transparent conductive film peeled off, the chromium film and the transparent conductive film on the H and I glass substrates, which do not contain alkali metals, did not peel off (see FIGS. 8 and 9). Example 3 Using G, H, and I containing alkali metal oxides of 3 mole percent or less, a tin oxide film of about 200 Å containing about 10 weight percent of antimony oxide was formed on a glass substrate in the process shown in FIG. After that, 10
An indium oxide film containing approximately 100 Å of tin oxide was formed in a thickness of approximately 100 Å by weight. The film forming method is a sputtering method. A chrome blank was prepared by forming a chromium film on this photomask plate by a sputtering method, and the following two tests were conducted. 1. After removing chromium by dry etching using a mixed gas of carbon tetrachloride and oxygen (2 to 3 minutes), dry etching is further performed for 5 minutes.
Thereafter, as shown in Example 1, acid resistance was examined using hot concentrated sulfuric acid. 2. After removing the chromium film with a cerium nitrate-based etching solution, asheing was performed for 30 minutes in oxygen plasma (RF plasma, input is approximately 100 W) at an oxygen pressure of approximately 300 mtorr. Thereafter, as shown in Example 1, acid resistance was examined using hot concentrated sulfuric acid. As a result of tests 1 and 2, all the transparent conductive films did not lose their conductivity even when immersed in hot concentrated sulfuric acid for 6 hours or more. As described above, according to the present invention, when forming a transparent conductive film mainly composed of tin oxide by a sputtering method or an ion plating method, a glass substrate having an alkali metal oxide content of 3 mol percent or less, When forming by vacuum evaporation method,
Because it was formed on a glass substrate that does not contain alkali metals, it has strong adhesion, and its acid resistance is several times higher than that of the transparent conductive film, which is mainly made of tin oxide and is formed on ordinary glass substrates. This is more than 50 times better than a transparent conductive film based on indium (Figure 10).

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a photomask plate with a transparent conductive film, and FIG. 2 is a sectional view of a photomask with a light-shielding pattern formed on the photomask plate with a transparent conductive film. FIG. 3 is a schematic diagram of the manufacturing process of a photomask plate with a transparent conductive film. FIGS. 4 to 7 are micrographs showing the results of a scratch test on a sample in which a film was formed by sputtering. FIGS. 8 and 9 are micrographs showing the results of a scratch test of a vacuum-deposited film. FIG. 10 is a graph showing changes in sheet resistance when the indium oxide and tin oxide transparent conductive films formed on the glass G were treated with concentrated sulfuric acid at 110°C. 1...Transparent glass substrate, 2...Transparent conductive film,
3...Light-shielding pattern, _C1 ...Indium oxide film, _C2 ...Tin oxide film.

Claims (1)

[Scope of Claims] 1. A transparent glass substrate containing an alkali metal element of 3 mol percent or less in terms of its oxide (R ₂ O), and a transparent glass substrate containing an alkali metal element by either sputtering or ion plating on the transparent glass substrate. A photomask plate having a transparent conductive film mainly made of tin oxide. 2. A photomask plate comprising a transparent glass substrate substantially free of an alkali metal element, and a transparent conductive film mainly made of tin oxide formed on the transparent glass substrate by vacuum deposition.