JPH061371B2 - How to repair molybdenum silicide mask - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of repairing defects existing in a mask used for manufacturing a semiconductor device, and particularly to defects existing in a molybdenum silicide (hereinafter referred to as MoSi) mask. It relates to a method of correcting a defect.

[Prior Art] With the progress of miniaturization and densification of semiconductor devices, hard masks having metallic chromium as a pattern material are widely used as masks used in the manufacture of semiconductor devices. 157247, JP-A-57-
No. 157249. As a mask to be used, a defect existing in the mask has a great influence on the manufacturing yield of semiconductor elements, and thus a defect-free mask is preferable. Therefore, the probability of obtaining a defect-free mask in a normal mask manufacturing process is extremely low and often includes several defects. Therefore, in order to obtain a defect-free mask, it is necessary to correct these defects by some method after manufacturing the mask.

In the chromium hard mask as described above, there are two types of defects, a residual defect in which a black spot of chromium remains and a defect defect in which a pinhole is generated in the chromium film. Among these, the residual defects can be easily corrected by irradiating the defective portion with laser light to evaporate the residual chromium. on the other hand,
The defect defect can be repaired by a method including the following steps called a chromium lift-off method.

(a) Applying a positive photoresist on the entire surface of the mask,
Step of forming a photoresist film.

(b) A step of irradiating a spot including a defective defect with spot light.

(c) A step of exposing the defective defect portion from the photoresist film by subjecting the photoresist film to a development treatment.

(d) A step of depositing metallic chromium on the surface of the photoresist film and the exposed portion by a vapor deposition method or a sputtering method.

(e) A step of removing the chromium metal deposited on the surface of the photoresist film by peeling it off, and leaving only the chromium metal deposited on the exposed portion, that is, the defective defect portion (chrome lift-off step).

In this method, defects are eventually corrected by depositing metallic chromium only at defective defect portions.

[Problems to be Solved by the Invention] However, since the adhesion between the deposited metal chromium and the exposed glass substrate surface after the development processing is poor, the metal chromium deposited at the defective defect portion may cause mask cleaning or the like. In the work process, there is a drawback that it peels off.

Therefore, as a means for solving the above problems, a method of using MoSi as a mask material can be considered. This is due to the Si in the glass substrate and the Si in MoSi as the mask material.
The fact that (1) and (2) are effectively bonded to each other to obtain a material having high adhesive strength is utilized.

However, since MoSi has a high melting point, it is difficult to form a stable film by a resistance heating method or an evaporation method using an electron beam (EB). On the other hand, according to the sputtering method, a stable MoSi film is formed. Therefore, in the step (d) shown as the method for repairing the defective defect portion as described above, the M method is performed by the sputtering method.
Deposit oSi. However, since the formed MoSi film has good coverage for the step, the next step (e)
It is difficult to lift off MoSi in. That is, when the conventionally used lift-off process or the method of immersing in a solvent is used, it is difficult to dissolve and peel the underlying photoresist film because of good coverage of the step portion of the MoSi film. When a photoresist film is actually formed using a positive type resist of AZ-1350 under the sputtering method, MoSi is deposited thereon, and then it is immersed in acetone, it is peeled off together with the photoresist film. It took 30 minutes or more to remove the MoSi film.

The present invention has been made in order to solve the above problems, and provides a method for repairing a MoSi mask that facilitates lift-off of deposited MoSi and that also provides good adhesion between the deposited MoSi and the glass substrate surface. The purpose is to do.

[Means for Solving Problems] A method for repairing a MoSi mask according to the present invention includes the following steps.

(a) A step of forming a photoresist film on the entire surface of the MoSi mask.

(b) A step of exposing a portion including a defect defect to be repaired from the photoresist film.

(c) A step of etching the exposed portion.

(d) A step of depositing MoSi on the surface of the photoresist film and the exposed portion by a sputtering method.

(e) A step of heat treating the entire MoSi mask at the softening point temperature of the photoresist.

(f) A step of removing the photoresist film and MoSi deposited on the surface of the photoresist film (MoSi lift-off).

[Operation] In the present invention, MoS is formed on the surface of the photoresist film and the defective defect portion exposed from the photoresist film.
After i is deposited, the entire mask is heat-treated at the softening temperature of the photoresist. After this heat treatment, MoS
i is being lifted off. When heat treated,
The photoresist film can be easily stripped. Therefore, MoSi deposited on the surface of the photoresist film can be easily removed together with the photoresist film in a short time. Further, since the deposited MoSi has good adhesion to the glass substrate, it is difficult to peel it off even when cleaning the mask.

[Embodiment] FIG. 1 is a process diagram showing a method of repairing a MoSi mask in an embodiment of the present invention.

As shown in FIG. 1, the embodiment of the present invention comprises the following steps.

(1) A photoresist film is formed on the entire surface of the MoSi mask. In this embodiment, a positive type photoresist having a trade name of AZ-1350 is applied.

In this embodiment, the step of exposing the portion including the defect defect existing in the MoSi mask from the photoresist film is performed in this embodiment.
It consists of steps (2) and (3).

(2) Irradiate spot-like light on the defective portion.

(3) Perform development processing.

In this embodiment, since a positive type photoresist is used as the photoresist, the defective portion is exposed from the photoresist film by irradiating only the defective portion with spot-shaped light and then performing development processing.

(4) Lightly etch exposed areas.

(5) MoSi is deposited on the photoresist film surface and exposed portions by a sputtering method.

(6) Heat the entire MoSi mask at the softening temperature of the photoresist. In this embodiment, the heat treatment is performed in a nitrogen atmosphere.

(7) Peel off the photoresist film. At this time, MoSi deposited on the surface of the photoresist film is also removed (MoSi
Lift off Si). In this embodiment, this treatment is carried out in an ultrasonic bath containing acetone as a solvent.

As described above, after the heat treatment (6), the peeling of the photoresist film is performed.
(7) That is, if the lift-off of MoSi is performed, the lift-off can be easily achieved in a short time.

Since the MoSi film formed by the sputtering method has good coverage, it is difficult to lift off. Lift off is MoS
This is done by dissolving the photoresist film, which is the base of the i film, in a solvent. For that purpose, the solvent must be easily diffused into the photoresist film.

Fig. 2 shows the product name AZ-13 on a 5 "square quartz glass plate.
Graph showing the experimental results of applying 50 photoresist with a film thickness of 800 nm, forming a MoSi film on it by sputtering, and then lifting off the MoSi film in an ultrasonic cleaner containing acetone. Is. This graph shows the relationship between the lift-off time of the MoSi film and the Ar gas flow rate, which is one of the sputtering conditions when the MoSi film is formed. According to this, the time required for lift-off of the MoSi film largely changes depending on the Ar gas flow rate or Ar atmospheric pressure. The lift-off is extremely difficult for the MoSi film formed by the sputtering method when the Ar pressure is around 25 mTorr, and it takes 20 minutes or more to remove it. On the other hand, the MoSi film formed with Ar pressure of 5 mTorr was removed in about 7 minutes, and the film was formed under the conditions most suitable for lift-off in the present experiment.

The time required for lift-off of the MoSi film is influenced by the heat treatment performed before the lift-off. FIG. 3 shows the experimental results of the MoSi film having a thickness of 140 nm formed by the sputtering method under the Ar pressure of 5 mTorr and subjected to the heat treatment before the lift-off of the MoSi film in the ultrasonic cleaning device. It is a graph. At this time, product name AZ-
The photoresist film thickness of 1350 is 800 nm, and the heat treatment time is 15 minutes. This graph shows the relationship between the lift-off time of the MoSi film and the heat treatment temperature. Also,
In the graph, the solid line shows the extrapolation of the experimental value (marked with ○). This shows that the heat treatment temperature for reducing the lift-off time of the MoSi film is around 140 ° C. This temperature corresponds to the softening point of the photoresist of AZ-1350 under the trade name used in this experiment. If the heat treatment is performed for 15 minutes at the softening point temperature of the photoresist, lift-off of the MoSi film can be achieved in a short time of about 1 minute.

Further, FIG. 4 shows that the film thickness of 1 is obtained by the sputtering method at the Ar gas flow rate of 10 cm ³ / min (standard condition) in the same manner as the above result.
After forming a MoSi film of 00 nm and heat-treating it at a temperature of 140 ° C, MoSi in an ultrasonic cleaner at a frequency of 27 kHz.
7 is a graph showing the results of an experiment in which the film was lifted off. This graph shows the relationship between the lift-off time of the MoSi film and the heat treatment time at a temperature of 140 ° C. The lift-off time is clearly the minimum when the heat treatment time is 15 minutes. In addition, according to the result of this experiment
When the heat treatment is carried out at, the lift-off time is within 7 minutes regardless of the heat treatment time.

The present invention was made based on the above experimental results by the inventors of the present application. In the method of repairing the MoSi mask, the condition for facilitating the lift-off of the MoSi film deposited by the sputtering method is to perform the lift-off of the MoSi film after the heat treatment at the softening point temperature of the photoresist.
Under these conditions, lift-off can be achieved within 7 minutes. Furthermore, the sputtering conditions for forming the MoSi film are Ar
The atmospheric pressure is preferably 5 mTorr, and the heat treatment time is preferably 15 minutes. When forming a photoresist film on the entire surface of the MoSi mask, it is desirable to use a positive type photoresist. With a positive photoresist,
In the step of exposing the defective defect portion, spot-shaped light may be irradiated only to the defective defect portion.

The MoSi film used for the correction needs to shield the defective defect portion from light. Therefore, FIG. 5 shows the result of measuring the optical density of the MoSi film deposited under the sputtering conditions in which the lift-off is easy as described above. This graph shows the relationship between optical density and MoSi film thickness. According to this, the film thickness is 1
The optical density of 3.0 or more at 00 nm and the MoSi film at the portion corrected by lift-off show practical light-shielding characteristics.

Further, since the MoSi film deposited by the sputtering method has denser crystal grains than the film deposited by the evaporation method, it has excellent mechanical strength and adhesion to the substrate.

[Effects of the Invention] As described above, according to the present invention, the lift-off of the MoSi film is performed after the heat treatment of the photoresist at the softening point temperature, so that the lift-off time is shortened. Therefore, the lift-off time becomes a practical time. Therefore, this is a method of repairing a MoSi mask suitable for mass production, and a defect-free mask can be easily obtained.

[Brief description of drawings]

FIG. 1 is a process diagram of a method of repairing a MoSi mask that is an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the Ar gas flow rate, which is one of the sputtering conditions for forming a MoSi film, and the lift-off time of the MoSi film. FIG. 3 is a graph showing the relationship between the heat treatment temperature and the lift-off time of the MoSi film when the heat treatment time is 15 minutes. FIG. 4 is a graph showing the relationship between the heat treatment time and the lift-off time of the MoSi film when the heat treatment temperature is 140 ° C. FIG. 5 is a graph showing the relationship between the film thickness of the correction MoSi film and the optical density.

Claims (4)

[Claims] 1. A method for repairing a defect defect existing in a molybdenum silicide mask in which a molybdenum silicide film is formed in a predetermined region on a glass substrate, wherein a photoresist film is formed on the entire surface of the molybdenum silicide mask. A step of forming, a step of exposing a portion including the defect defect from the photoresist film, a step of etching the exposed portion, and a step of depositing molybdenum silicide on the photoresist film surface and the exposed portion by a sputtering method. A heat treatment of the entire molybdenum silicide mask at the softening point temperature of the photoresist; and a step of removing the molybdenum silicide deposited on the photoresist film and the photoresist film surface. How to fix. 2. The method for repairing a molybdenum silicide mask according to claim 1, wherein the photoresist is a positive type. 3. The method for repairing a molybdenum silicide mask according to claim 1, wherein the deposited molybdenum silicide is formed by a sputtering method in which an argon pressure is 5 mTorr. 4. The method for repairing a molybdenum silicide mask according to claim 1, wherein the heat treatment time at the softening point temperature of the photoresist is 15 minutes.