JP2551078B2 - Method for manufacturing low reflection mask material - Google Patents

Description

TECHNICAL FIELD The present invention further forms a transition metal silicide oxide film on a substrate on which a transition metal silicide film is formed by sputtering using argon gas containing oxygen gas. And a method for manufacturing a low reflection mask material.

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

For example, JP-A-57-157247 and JP-A-57-157247
In a hard mask having a metal film such as a Cr mask formed therein as disclosed in Japanese Laid-Open Patent Publication No. 157249, the above problem remarkably occurs due to the high reflectance on the surface thereof. Therefore, the reflectance of the mask surface is reduced by further forming an oxidized Cr film on the Cr film. However, since the Cr film does not have good adhesion to the glass substrate, pattern defects due to peeling of the film may occur,
In addition, since the etching rate of the Cr film during dry etching is slow, the organic polymer resist pattern may disappear first. Therefore, it is difficult to dry the process and increase the throughput.
It could not be expected as a mask material for (VLSI).

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. In order to reduce the surface reflectance of this MoSi mask, an oxidized MoSi film (hereinafter abbreviated as MoSi oxide film) is formed on the MoSi film by the sputtering method. The details of the sputtering method are described in the Encyclopedia of Electrical and Electronic Engineering, Vol. 4, page 105 (published by Densho Shoin Co., Ltd. in 1983).

[Problems to be Solved by the Invention] Now, in order to form the above-mentioned MoSi oxide film by the sputtering method, it is necessary to target MoSi and mix an appropriate amount of oxygen into Ar gas which 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, the upper limit of the partial pressure of oxygen in Ar gas has not been clarified, so that the above problems are always present, and the MoSi oxide film cannot be stably formed with good reproducibility.

The present invention has been made to solve the above problems, and provides a method of manufacturing a low reflection mask material, which can stably form a transition metal silicide oxide film including a MoSi oxide film with good reproducibility. The purpose is to do.

[Means for Solving the Problems] The present invention further forms a transition metal silicide oxide film on a substrate on which a transition metal silicide film is formed by a sputtering method using argon gas containing oxygen gas, The present invention relates to a method of manufacturing a low reflection mask material.

When the ratio of the oxygen partial pressure in the Arungon gas to the total pressure is γ and the sputtering power is Qkw, the value of γ is the inequality below. The above-mentioned sputtering is performed so as to satisfy the above condition.

The transition metal used in the present invention may be used regardless of the group or period to which the element belongs or the atomic weight thereof. Of these, Mo, Ta, W are always preferred.
And Mo is particularly preferable.

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

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

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. In this example, a case where Mo is used as a transition metal will be described as an example.

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. The MoSi film 2 is formed on the substrate 1 by the sputtering method. A MoSi oxide film 3 is further formed on the MoSi film 2. Low reflectance can be achieved by forming the MoSi oxide film 3 to have an appropriate thickness. This low reflection is based on the result that the incident light receives two effects of attenuation and interference due to absorption in the MoSi oxide film 3 synergistically. The MoSi oxide film that causes such attenuation and interference of incident light can be obtained by mixing oxygen in Ar in sputtering using Mo as a target using Ar. However, as mentioned 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. In this case, the low reflection film cannot be formed stably with good reproducibility. This is a big problem of the conventional method. Therefore, the partial pressure of oxygen in Ar and the MoSi oxide film 3
I investigated the relationship with the deposition rate (hereinafter referred to as the low reflection film).

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 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) (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. By actually applying the experimental values, we obtain k · Qs = Q / γ = 25/9 (3). Therefore, the oxygen partial pressure ratio γ with which the low reflection film can be formed under the power Q is given by the following inequality.

That is, as long as the condition given by the above inequality (4) is used, the oxidation of the target can be prevented, and the reproducible and stable low reflection film can be formed. In the above equation (4), Q is limited to a value of 1.0 or less because
This is because if the value of Q is larger than this, the problem of film burning occurs.

In addition, although the case where Mo is used as the transition metal has been described as an example in the above-mentioned embodiment, the same tendency is observed even when the transition metal is Ta or W, and the same effect as that of the embodiment is realized. I also understood that.

Further, in the above-mentioned embodiment, the case where the pressure is set to 10 mTorr in the planar type magnetron sputtering apparatus has been described. However, the present invention is not limited to this, and the relation between γ and Q is expressed by the above equation. Other types of devices may be used and pressures may be used, as long as inequality (4) holds.
It doesn't have to be 10mTorr.

Furthermore, in the above embodiment, the case where the synthetic quartz substrate is used as the substrate material has been described, but the present invention is not limited to this, and any material that can be a silicon wafer or other substrates can be used.

Further, in the above embodiments, the method of forming the low reflection film on the mask has been described, but the present invention can be applied to the case where an oxide film other than the mask is required.

Although the method for manufacturing the low-reflection mask material according to the present invention has been described above with reference to specific examples, the present invention can be carried out in various other forms without departing from the spirit or characteristics of the invention. it can. Therefore, the above embodiments are merely examples in all respects, and should not be construed in a limited manner. The scope of the present invention is defined by the claims and is not bound by the text of the specification. Furthermore, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

[Effect of the Invention] As described above, according to the present invention, a transition metal silicide oxide film is further formed on a substrate on which a transition metal silicide film is formed by a sputtering method using an argon gas containing oxygen gas. Therefore, in manufacturing the low reflection mask material, the sputtering is performed under the condition that the oxygen partial pressure ratio γ becomes a value smaller than the condition value at which the target oxidation occurs. The effect is that a reproducible and stable low-reflection mask material can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a low reflection 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 (MoSi oxide film).

Claims (1)

(57) [Claims] 1. A method for producing a low-reflection mask material by further forming a transition metal silicide oxide film on a substrate on which a transition metal silicide film is formed by sputtering using argon gas containing oxygen gas, When the ratio of the partial pressure of oxygen 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 mask material, wherein the sputtering is performed so as to satisfy the above condition.