JP2551079B2 - Method of manufacturing low reflection molybdenum silicide mask material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention further forms a molybdenum silicide oxide film on a substrate on which a molybdenum silicide film is formed, by sputtering using argon gas containing oxygen gas. And a method for manufacturing a low-reflection molybdenum silicide mask material.

[Prior Art] A low-reflection photomask is desired in manufacturing a semiconductor device. This is because when a photomask having a high reflectance is used, when the pattern of the mask is transferred onto a wafer, for example, a silicon wafer, the reflected light from the wafer is reflected again on the surface of the mask, which causes a decrease in accuracy of the resist pattern. Is caused.

For example, JP-A-57-157247 and JP-A-57-157247
In the hard mask formed with a metal film such as the Cr mask disclosed in Japanese Patent Publication No. 157249, the above-mentioned problem has remarkably appeared due to the high reflectance of the surface thereof. Therefore,
By further forming an oxidized Cr film on the Cr film, the reflectance on the mask surface is reduced. However, since the Cr film does not have good adhesion to the glass substrate, pattern defects may occur due to peeling of the film, or
Since the etching rate of the Cr film during the dry etching is slow, the resist pattern of the organic polymer may disappear first. Therefore, it becomes difficult to dry the process and increase the throughput.
I) I could not expect as a corresponding mask material.

Therefore, a newly proposed film is a molybdenum silicide film (hereinafter abbreviated as MoSi film), which is a VLSI compatible photomask material that solves the above problems of the Cr film.
Then, in order to reduce the surface reflectance of the MoSi mask,
An oxidized MoSi film is formed on the MoSi film by a sputtering method.

[Problems to be Solved by the Invention] Now, the above-mentioned oxidized Mo by the sputtering method is used.
In order to form a Si film, it is necessary to target MoSi and mix oxygen into Ar gas that is a sputtering gas. However, when the amount of oxygen in Ar gas is excessive, the target of MoSi is oxidized on the contrary, and there is a problem that sputtering is suddenly impossible. In the conventional sputtering method, since the upper limit of the oxygen partial pressure in Ar gas was not clarified, the above problems were always present, and the oxidized MoSI film could not be formed stably with good reproducibility. .

The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing a low-reflection molybdenum silicide mask material, which stably forms an oxidized MoSi film with good reproducibility. To do.

[Means for Solving the Problems] The present invention is directed to a molybdenum silicide film (molybdenum silicide oxide film) which is oxidized on a substrate on which a molybdenum silicide film is formed by a sputtering method using argon gas containing oxygen gas. Is further formed to manufacture a low-reflection molybdenum silicide mask material.

Then, when the ratio of the oxygen partial pressure in the argon gas to the total pressure is γ and the power of the sputtering is Qkw, the value of γ is the inequality below. It is characterized in that the sputtering is carried out by adjusting so as to satisfy the above condition.

The value of Q described above is not particularly limited, but in general,
The range of 0 to 1.0 is most preferable.

[Operation] The above inequality (1) is a conditional expression obtained by actually conducting an experiment, and if the value of γ is adjusted within this range, a stable low-reflection MoSi mask material with good reproducibility can be manufactured. It was found that it could be done.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a low reflection molybdenum silicide mask material manufactured according to an embodiment of the present invention. In the figure, 1 is a substrate, for example, a synthetic quartz glass substrate. A MoSi film 2 formed by a sputtering method is formed on a substrate 1. An oxidized MoSi film 3 is further formed on the MoSi film 2. Low reflectance can be achieved by forming the oxidized MoSi film 3 to have an appropriate film thickness. This reduction in reflection is based on the result that the incident light is synergistically affected by the two effects of attenuation and interference by absorption inside the oxidized MoSi film 3. The oxidized MoSi film 3 that causes such attenuation and interference of incident light is obtained by mixing oxygen in Ar in sputtering using MoSi as a target using argon gas (hereinafter referred to as Ar). However, as described above, when the partial pressure of oxygen in Ar exceeds a certain value, a phenomenon occurs in which the MoSi target is not sputtered but is oxidized in reverse. This happens when,
A low reflection film cannot be formed with good reproducibility and stability.
This has been a big problem in the past. Therefore, the partial pressure of oxygen in Ar and the oxidized MoSi film (hereinafter referred to as the low reflection film)
I investigated the relationship with the deposition rate of.

Figure 2 is a graph of the results of this investigation, where the horizontal axis is 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 is the low The film forming speed of the reflective film is shown. In this experiment, a planar magnetron sputtering device was used,
It was performed under the condition of 10 mTorr. From the results of this experiment, as for the deposition rate of the low reflection film, the sputtering power Q was 0.5 kW.
Was found to be proportional to the oxygen partial pressure ratio γ in the range of 1.0 kW to 1.0 kW. Then, as is clear from the figure, when γ exceeds a certain value or more according to the value of the power Q,
It was also found that the film formation rate rapidly decreased to zero. The rapid decrease in film formation rate to zero indicates that target oxidation is occurring.

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

q / γ = k (constant) (2) The above relational expression (2) is obtained by an experiment, and shows the upper limit of γ with which the low reflection film can be stably formed. Actually applying the experimental values, k · Qs = Q / γ = 25/9 was obtained, and in order to stably form the low reflection film in the sputtering power range up to 1 kW, γ and Q Between
It was derived that the following inequality must hold.

That is, it was revealed that the use of the condition given by the above inequality (3) makes it possible to prevent the oxidation of the target and form a reproducible and stable low reflection film. In the above formula (3), the reason why Q is limited to a value of 1.0 or less is that if the value of Q is larger than this, there is a problem that film burning occurs.

Further, in the above embodiment, the description was given of the case where the pressure was set to 10 mTorr in the planar magnetron sputtering apparatus, but the present invention is not limited to this, and the relationship between γ and Q is the above inequality ( Other types of equipment may be used and pressures of 10
It doesn't have to be mTorr.

[Effects of the Invention] As described above, according to the present invention, a molybdenum silicide oxide film is further formed on a substrate on which a molybdenum silicide film is formed by a sputtering method using argon gas containing oxygen gas. In manufacturing a low-reflection molybdenum silicide mask material, sputtering is carried out under the condition that the oxygen partial pressure ratio γ is smaller than the condition value at which target oxidation occurs, so that target oxidation does not occur. The effect that a stable low-reflection film that is always reproducible can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a low-reflection molybdenum silicide mask material obtained according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the oxygen partial pressure ratio γ and the film formation rate of the low reflection film. In the figure, 1 is a synthetic quartz glass substrate, 2 is a MoSi film, 3
Is a low reflection film.

Claims (1)

(57) [Claims] 1. A method of manufacturing a low-reflection molybdenum silicide mask material by further forming a molybdenum silicide oxide film on a substrate on which a molybdenum silicide film is formed by a sputtering method using argon gas containing oxygen gas. When the ratio of the oxygen partial pressure in the argon gas to the total pressure is γ and the power of the sputtering is Qkw, the value of γ is the inequality below. The method for producing a low-reflection molybdenum silicide mask material, wherein the sputtering is performed so as to satisfy the above condition.