JP2979832B2 - Manufacturing method of low stress metal film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a stable metal film having a small internal stress.

[0002]

2. Description of the Related Art Conventionally, a metal film has been formed by a chemical vapor deposition method, a sputtering method, and a vacuum evaporation method. Method is used.

[0003]

For example, in the production of an X-ray mask used for X-ray lithography, a low-stress X-ray absorber having an internal stress of about 1 × 10 ⁷ N / m ² or less is indispensable. . However, the internal stress of the Ta film and the W film changes to the compressive stress side in the atmosphere after the film is formed, and it takes a long period of several months to be stabilized. Could not.

[0004]

SUMMARY OF THE INVENTION The present invention aims to stabilize internal stress in a short time by annealing a metal film having a predetermined tensile stress by sputtering in oxygen immediately after the formation.

[0005]

The change in the internal stress of a metal film such as Ta and W occurs due to the diffusion of oxygen into the film. When annealing is performed in an oxygen atmosphere, diffusion of oxygen is accelerated, and a stable absorber can be obtained in a short time. Further, the amount of change in the internal stress varies depending on the film forming conditions, but is substantially constant in a region where the internal stress is small. Therefore, by forming a film having a predetermined tensile stress in advance so that the internal stress after annealing becomes zero or close to zero, a low stress and stable metal film can be manufactured.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method by a sputtering method will be described below as an embodiment of the present invention. For example, T
When the a film is formed, the internal stress changes as shown in FIG. 1 depending on the Ar gas pressure. The internal stress becomes zero at 3 Pa
There are two regions, namely, the vicinity and 6 Pa or more. However, if the pressure is 6 Pa or more, the film becomes a low-density film. In order to obtain a high-density, low-stress Ta film, it is necessary to optimize the sputtering gas pressure and other parameters at around 3 Pa to form a film. FIG. 2 shows the variation of the internal stress with respect to the sputtering gas pressure. Ar was used as a sputtering gas, the substrate temperature was room temperature, and the RF power was 1 kW. 3.5P
Below a, it changes to a substantially constant value (3 × 10 ⁷ N / m ² ) to the compressive stress side. Therefore, a Ta film having a tensile stress of 3 × 10 ⁷ N / m ² is formed by setting the sputtering gas pressure to 2.7 Pa, and annealing is performed for 1 hour in an oxygen atmosphere at 100 ° C., whereby the internal stress is zero and stable. Ta is obtained.

[0007]

As described above, by using this method, a stable metal film with low stress can be formed in a short time.

[Brief description of the drawings]

FIG. 1 shows a sputtering gas (Ar) by a sputtering method.
FIG. 4 is a diagram showing a relationship between the pressure of the Ta film and the stress of the Ta film.

FIG. 2 is a diagram showing the pressure of a sputter gas (Ar) and the amount of change in the internal stress of a Ta film during film formation.

Claims (1)

(57) [Claims] 1. A method for producing a low-stress metal film, comprising: forming a metal film having a predetermined tensile stress by a sputtering method; and annealing the film in an oxygen atmosphere to reduce the stress.