JPH06100823B2 - See-through mask blanks and see-through masks - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a see-through mask blank, and more particularly to a see-through mask blank that provides a see-through mask having excellent chemical resistance used for manufacturing a semiconductor device. is there. The present invention also relates to a see-through mask formed using such a see-through mask blank.

[Prior Art] Among photomasks used for various wide-ranging applications such as manufacturing of semiconductor devices such as ICs and LSIs, there is a so-called see-through mask in which a mask pattern is formed of a semitransparent layer. With a mask pattern having a normal light-shielding pattern, when the light-shielding pattern and the alignment mark overlap, alignment becomes difficult. Therefore, a see-through mask having a mask pattern formed of a semi-transparent layer that allows visible light to pass therethrough but does not pass near-ultraviolet light that hardens the resist is required.

Next, the manufacturing process of the conventional see-through mask will be described with reference to the drawings.

6 to 11 are cross-sectional views showing a conventional process for manufacturing a see-through mask, which is a technique disclosed in Japanese Patent Laid-Open No. 61-11747. The manufacturing method will be briefly described with reference to the drawings. In FIG. 6, reference numeral 1 is a light transmissive substrate such as a glass substrate. First, the amorphous silicon 2 is deposited on the light transmissive substrate 1 (seventh embodiment).
Figure). As the deposition method, a sputtering method, a CVD method, a vacuum deposition method, or the like is adopted. Next, the amorphous silicon film 2
A resist pattern 3 is formed on it (FIG. 8). Then, using the resist pattern 3 as a mask, the amorphous silicon film 2 is etched to form a semitransparent pattern 2 '(FIG. 9). Then, after removing the resist pattern 3, a chromium film 4 is deposited on the entire surface by a sputtering method or the like (FIG. 10). After that, when heat treatment is performed at 200 ° C. for 30 minutes in a nitrogen atmosphere, amorphous silicon reacts with chromium at the interface to form chromium silicide. Then, the unreacted chromium 4 is removed by using a chromium etching solution (an aqueous solution of ceric ammonium nitrate with perchloric acid), and the surface is covered with chromium silicide 5 as shown in FIG. A light-shielding film pattern 2'made of amorphous silicon is obtained.

[Problems to be Solved by the Invention] Since the conventional manufacturing process of the see-through mask is configured as described above, the process is very complicated, and there is a demand for simplification. Further, since the formation of the light-shielding film pattern 2'is a wet method having a characteristic of isotropic etching, miniaturization is extremely difficult, and it is necessary to dry it so that the characteristic of anisotropic etching can be exhibited. Further, in the above heat treatment for forming the chromium silicide 5 by the reaction of amorphous silicon and chromium, a uniform reaction does not occur, and the pattern 2 '
However, there is a problem that it is not possible to achieve high precision and miniaturization.

This invention was made to solve the above problems, excellent chemical resistance, and a simple manufacturing process,
Moreover, it is an object of the present invention to provide a see-through mask blank which can use a dry etching method for pattern formation and can provide a see-through mask having a high precision and a fine pattern. Another object of the present invention is to provide a see-through mask formed by using such a see-through mask blank.

[Means for Solving the Problems] A see-through mask blank according to the first aspect of the present invention includes a light-transmissive substrate and a molybdenum silicide oxide film layer deposited on the light-transmissive substrate. The molybdenum silicide oxide film layer is formed by a sputtering method using a sputtering gas containing oxygen gas.
The sputtering method, the ratio of the partial pressure of the oxygen to the total pressure is γ, and the power of the sputtering is Qkw
And the following inequality It is carried out under the conditions that satisfy.

A see-through mask according to a second aspect of the present invention includes a light transmissive substrate and a fine pattern formed on the light transmissive substrate and formed of a molybdenum silicide oxide film. The molybdenum silicide oxide film layer is formed by a sputtering method using a sputtering gas containing oxygen gas. The sputtering method, the ratio of the partial pressure of the oxygen to the total pressure is γ, and the power of the sputtering is Qkw, the following inequality It is carried out under the conditions that satisfy.

[Operation] According to the see-through mask blank according to the first aspect of the present invention, since the molybdenum silicide oxide film layer is formed under the above-described sputtering conditions, it becomes a reproducible and stable molybdenum silicide oxide film. There is.

According to the see-through mask according to the second aspect of the present invention, the molybdenum silicide oxide film layer can be formed by a simple process of dry etching using a resist pattern. Further, since the dry etching method can be used, the characteristic of anisotropic etching can be exhibited, and a see-through mask including a highly precise fine pattern can be formed. Further, since the pattern is made of molybdenum silicide oxide, it has high chemical resistance.

[Examples] Next, a see-through mask blank according to the present invention and a method of manufacturing a see-through mask from the see-through mask blank will be described.

FIG. 1 is a sectional view of a see-through mask blank according to the present invention. As described above, the see-through mask blanks are precursors before the see-through mask is manufactured. As is apparent from the figure, the see-through mask blank 10 according to the present invention comprises a light-transmissive substrate 1 and a molybdenum silicide oxide film layer 6 deposited on the light-transmissive substrate 1. For example, a synthetic quartz glass substrate is preferably used as the light transmissive substrate 1. The molybdenum silicide oxide film layer 6 is deposited by the sputtering method. The conditions of this deposition method will be described in detail later.

In order to use the above see-through mask blanks 10 as a see-through mask, it is only necessary to go through the process shown in FIGS. 2 and 3. Therefore, the use of the see-through mask blank according to the present invention has an advantage that the manufacturing process of the see-through mask is greatly simplified. The process will be described with reference to FIGS. 2 and 3.

First, after forming a resist pattern 3 on the see-through mask blanks 10, a CF ₄ gas containing 5% O ₂ is used as an etchant with the resist pattern 3 as a mask to dry the molybdenum silicide oxide film layer 6 by a plasma etching apparatus. The semi-transparent pattern 6 is formed by etching (FIG. 2). The peeling of the resist pattern 3 is performed by O ₂ prisma. Then, the see-through mask 20 as shown in FIG. 3 is obtained.

As described above, the see-through mask blanks 10 of the present invention
If the above is used, the manufacturing process of the see-through mask 20 is simple, the dry process can be easily performed as described above, and the see-through mask 20 having a high precision and fine pattern can be obtained.

Next, a method for manufacturing the see-through mask blanks shown in FIG. 1 will be described in detail.

A molybdenum silicide oxide film layer 6 is formed on the transparent substrate 1.
Is formed by targeting MoSi by a sputtering method and mixing oxygen in Ar gas which is a sputtering gas. This is the usual way. However, if the amount of oxygen in the Ar gas becomes excessive, the MoSi target may be oxidized in the opposite direction, suddenly making sputtering impossible, and making film formation impossible. Therefore, the conditions for forming the molybdenum silicide oxide film layer 6 stably with good reproducibility were investigated.

Fig. 4 is a graph of the results of this survey.
FIG. 5 is a relationship diagram between the partial pressure of oxygen in the inside and the deposition rate of a molybdenum silicide oxide film. In the figure, the horizontal axis represents the ratio γ of the oxygen gas pressure to the total pressure (Ar gas pressure + oxygen gas pressure) in the space where deposition occurs, and the vertical axis represents the deposition rate of the molybdenum silicide oxide film. .
The experiment was conducted using a planar type magnetron sputtering apparatus under a pressure of 10 mTorr. From this experimental result, it was found that the deposition rate of the molybdenum silicide oxide film 6 is proportional to the oxygen partial pressure ratio γ when the sputtering power Q is in the range of 0.5 kW to 1.0 kW. From the figure, it was also found that when γ exceeds a certain value or more in accordance with the value of the power Q, the film formation rate sharply decreases to zero. The rapid decrease in film formation rate to zero indicates that the target MoSi is being oxidized.

Considering the above experimental results, if q (= Q / Qs) is the ratio of the threshold power Qs (kW) that enables normal film formation and the power Q that is actually input, then γ and q In the meantime, it was found that the following relational expression holds.

q / γ = k (constant) (1) The above relational expression (1) is obtained by experiment, and shows the upper limit of γ with which the molybdenum silicide oxide film can be stably formed. Applying the experimental values to the experiment, k
Qs = Q / γ = 25/9 is obtained, and the sputtering power Q is
It was derived that the following inequality must be established between γ and Q in order to stably form the molybdenum silicide oxide film 6 in the range of up to 1 kW.

O <γ ≦ 9 / 25Q O <Q ≦ 1.0 (2) That is, if sputtering is performed under the conditions given by the above inequality (2), oxidation of the target can be prevented and stable molybdenum with reproducibility can be prevented. It has been clarified that a silicide oxide film can be formed. In the above formula (2), the reason why Q is set to 1.0 or less is that if the value of Q is larger than this, the problem of film burning occurs.

Further, in the above-mentioned method, the sputtering is performed with a planar type magnetron sputtering device at a pressure of 10 mTor.
Although the case of performing under the condition of r has been described, other types of devices may be used and the pressure does not have to be 10 mTorr as long as the relationship between γ and Q applies to the above inequality (2).

Next, the transmittance of the film obtained under the above-mentioned sputtering conditions was plotted in relation to the ratio γ of the partial pressure of oxygen used. FIG. 5 is a correlation diagram at that time.
The vertical axis represents the light absorption coefficient, and the horizontal axis represents the oxygen partial pressure ratio γ when sputtering is performed. As is clear from FIG. 5, a linear relationship is established between the two. From this result, it is understood that the see-through mask blanks 10 having various transmittances can be arbitrarily manufactured by controlling the ratio γ of the partial pressure of oxygen to the total pressure. When exposing using a see-through mask, it may be necessary to change the transmittance depending on the light source. In consideration of such a case, this method of freely controlling the transmittance is extremely useful.

As described above, according to the see-through mask blank according to the present invention, since the molybdenum silicide oxide film is formed under the condition given by the above inequality (2), stable and reproducible molybdenum is formed. A silicide oxide film is provided.

Further, according to the see-through mask according to the present invention, the molybdenum silicide oxide film layer can be formed only through a simple process of dry etching using a resist pattern. Further, since the dry etching method can be used, anisotropic etching characteristics can be obtained, and a see-through mask having a high precision and a fine pattern can be realized. Further, since the semi-transparent pattern is made of molybdenum silicide oxide, it has high chemical resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a see-through mask blank according to the present invention. 2 and 3 are cross-sectional views showing the steps for manufacturing a see-through mask using the see-through mask blanks of the present invention. FIG. 4 is a diagram showing the relationship between the film formation rate of the molybdenum silicide oxide film and the oxygen partial pressure ratio.
FIG. 5 is a relationship diagram between the light absorption coefficient of the obtained molybdenum silicide oxide film and the oxygen partial pressure ratio when the molybdenum silicide oxide film is obtained. 6, 7 and 8
FIG. 9, FIG. 10, FIG. 10 and FIG. 11 are sectional views showing the steps of manufacturing a conventional see-through mask. In the figure, 1 is a light transmissive substrate, 6 is a molybdenum silicide oxide film layer, 10 is a see-through mask blank, and 20 is a see-through mask.

Claims (2)

[Claims] 1. A sputtering method, comprising: a light-transmissive substrate; and a molybdenum silicide oxide film layer deposited on the light-transmissive substrate, wherein the molybdenum silicide oxide film layer uses a sputtering gas containing oxygen gas. Is formed by a sputtering method, the ratio of the partial pressure of oxygen to the total pressure is γ, and the sputtering power is Qkw.
And the following inequality See-through mask blanks that are performed under the conditions that satisfy 2. A light-transmissive substrate, and a pattern formed on the light-transmissive substrate and formed of a molybdenum silicide oxide film, wherein the molybdenum silicide oxide film includes a sputtering gas containing oxygen gas, Is formed by a sputtering method using, the sputtering method, the ratio of the partial pressure of the oxygen to the total pressure is γ, and the power of the sputtering Qkw
And the following inequality See-through mask that is performed under the conditions that satisfy