JP3437389B2 - Mask membrane for electron beam and X-ray lithography - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask membrane for electron beam and X-ray lithography.

[0002]

2. Description of the Related Art With the miniaturization of pattern formation in the fabrication of semiconductor devices, X-ray lithography technology is regarded as a promising future lithography technology. The structure of a general mask substrate for X-ray lithography is shown in FIG. The mask substrate of FIG. 3 has an absorber pattern 15, an X-ray transparent film (hereinafter,
Membrane) 16, support substrate 13, backside protective film 1
It consists of 4.

The characteristics required for the membrane are shown below. 1) High mechanical strength. 2) Withstand irradiation of high energy beams such as high energy electron beams and synchrotron radiation (hereinafter abbreviated as SOR light). 3) High visible light transparency required for highly accurate alignment. Conventionally, as a mask membrane material for X-ray lithography, boron nitride (BN), boron-doped silicon, silicon nitride (SiN), silicon carbide (SiC), silicon carbonitride (SiCN), diamond and the like have been proposed. Among them, diamond having high crystallinity is excellent in the characteristics 1) to 3), and is considered to be most suitable as a mask membrane material for X-ray lithography.

On the other hand, the membrane needs to be a self-supporting film having a thickness of 1 to 2 μm in order to minimize the absorption of X-rays. Therefore, it is known that the membrane stress of the membrane must be 0.0 to 5.0 × 10 ⁹ dyn / cm ² (tensile force) in order to manufacture the membrane.

[0005]

Generally, as a method for forming a diamond film, 1) DC, arc discharge, 2) DC,
Glow discharge, 3) combustion flame, 4) high frequency (13.56MHz),
5) microwave (2.45 GHz), 6) hot filament, etc. However, in all of these film forming methods, since plasma is used, many film forming parameters are related to the plasma state, so that plasma necessary for forming a desired film can be obtained. Have difficulty. In particular, it has been extremely difficult to simultaneously satisfy the two characteristics of mechanical strength, SOR light irradiation resistance, high crystallinity for enhancing visible light transmittance, and film stress for membrane formation.

[0006]

The inventors of the present invention have made extensive studies in view of the above problems, and as a result, as a main constituent material of a membrane, a vapor phase synthetic diamond film is used for stress correction on one side or both sides. The present invention has been completed, focusing on the fact that the above two characteristics can be satisfied at the same time by forming a film to form a laminated structure. That is, the present invention is Ri Do a laminated structure film was formed for the stress compensation on one or both surfaces of the CVD diamond film, for the stress compensation
The film is silicon carbide, silicon nitride, or silicon carbonitride
A mask membrane consisting of the above laminated structure.
The stress of the laminated film is 0.0 to 5.0 × 10 ⁹ dyn / cm ² (tensile)
And / or a film of said vapor phase synthetic diamond film
Ratio of thickness (t _dia ) to film thickness (t _Si ) for stress compensation
The gist is a mask membrane for electron beam and X-ray lithography (hereinafter, simply referred to as a mask membrane for X-ray lithography), which has a ratio of t _dia / t _Si ≧ 1.0 . In the above equation, t _Si is
Silicon carbide film or silicon nitride film or charcoal for force correction
This is the film thickness of the silicon nitride film.

[0007]

DETAILED DESCRIPTION OF THE INVENTION This will be described in detail with reference to the drawings. 1 and 2 are schematic sectional views showing the structure of a mask substrate for X-ray lithography according to the present invention. In the present invention, when the stress of the highly crystalline diamond film 1, which has been the main constituent material of the membrane 6 in the past, is an unsuitable value for membrane production, that is, the tensile stress of 0.0 to 5.0 × 10 ⁹ dyn / cm ² If it is not within the range of,
The stress correction film 2 having an appropriate stress is formed on one side or both sides of the diamond film 1 to form the membrane 6 in a laminated structure. Thereby, the tensile stress of the laminated film composed of the diamond film 1 and the stress correction film 2 is 0.0 to 5.0 ×.
Correct to 10 ⁹ dyn / cm ² .

The film 2 for stress compensation may be formed on either surface of the diamond film as shown in FIGS. 1 and 2, or may be formed on both surfaces. Also, as materials, SiC, SiN
, SiCN, etc., among which mechanical strength and SO
A SiC film is preferable because it has excellent resistance to R light irradiation.

The SiC film will be described in more detail below. SiC
Although it is easier to control stress than diamond and has mechanical strength and SOR light irradiation resistance second to diamond, visible light transmission is slightly lower than that of diamond. Therefore, diamond film thickness t _dia and SiC film thickness t
_{By making SiC} as thin as possible within the range of the film thickness ratio t _dia / t _SiC ≧ 1.0, it is possible to obtain practically sufficient visible light transmittance. If t _dia / t _SiC is less than 1.0, the excellent properties of diamond cannot be fully utilized, and there is a problem that desired mechanical strength, SOR light irradiation resistance, and visible light transmission cannot be obtained, so it is 1.0 or more. There is a need. Further, when t _dia / t _SiC exceeds 2000, a very high stress is required for the SiC film for diamond stress correction, and there is a problem that cracks easily occur in such a high stress SiC.

When t _dia is less than 0.01 μm, there is a problem of mechanical strength, and when it exceeds 100 μm, there is a problem of X-ray absorption. Therefore, 0.01 to 100 μm is preferable, and 0.01 to 10 μm is more preferable. If _tSiC is less than 0.01 μm, the stress correction effect is small, and if it exceeds 100 μm, there is a problem of pinhole defects.
˜10 μm is more preferred. The SiC film may be formed by a known method such as a sputtering method or a thermal CVD method.

[0011]

EXAMPLES Next, examples of the present invention will be described. However, the present invention is not limited to this. Note that the stress is measured by the wafer curvature radius.
Done by law. Example 1 An X-ray lithography mask substrate having the structure shown in FIG. 2 is produced. A double-side polished silicon wafer (100) having a diameter of 3 inches and a thickness of 600 μm was used as the supporting substrate 3. On the first layer on the support substrate 3, the vapor phase synthetic diamond film 1 is formed by the microwave plasma CVD method. First, the surface of the supporting substrate 3 was treated with a fluidized bed of diamond particles for the purpose of increasing the nucleus density of diamond before film formation. 400μ for diamond particles
3m by flowing nitrogen gas at a flow rate of 366cm / sec.
Time processing was performed. Next, the pretreated substrate 3 is set in a microwave CVD chamber and evacuated to a base pressure of 10 ⁻³ Torr or less by a rotary pump,
1000 sc of hydrogen diluted methane (0.5% by volume), which is the source gas
cm introduced. After adjusting the opening degree of the valve communicating with the exhaust system to 30 Torr in the chamber, microwaves with an electric power of 3000 W were input to perform film formation for 20 hours. The substrate surface during film formation was 850 ° C. as measured by a pyrometer.
The obtained film thickness is 1.5 μm, and the film stress is −5.0 × 10 ⁹ d.
It was yn / cm ² (compressed). As a result of evaluation by X-ray diffraction and Raman spectroscopy, this diamond film was confirmed to be polycrystalline diamond having high crystallinity. However, with the above-mentioned stress, when the back etching is performed, wrinkles are generated in the membrane, or the membrane is broken, so that the membrane cannot be manufactured.

Then, the second layer for stress compensation is
The SiC film 2 is formed. 6 inch diameter and 5 m thickness
An RF (13.56 MHz) magnetron sputtering method was used with a target of a SiC sintered body having m and a purity of 99.9% or more (excluding C, O, and N). 55 substrates with diamond film formed
After heating to 0 ° C. and confirming that the base pressure was 1 × 10 ⁻⁷ Torr or less, argon gas was introduced at 10 sccm. Adjust the opening of the valve leading to the exhaust system to 8 x 10 ^-3
After setting to Torr, RF power of 1600 W was input and film formation was performed for 6 minutes. The obtained SiC film has a thickness of 0.3 μm and a stress of 3.1 ×
It was 10 ¹⁰ dyn / cm ² (pull). Diamond film 1
The thickness of the membrane 6 made of a laminated film of
The thickness was 1.8 μm, the stress was 1.6 × 10 ⁹ dyn / cm ² (tensile), and the film thickness ratio t _dia / t _SiC was 5.0.

Finally, after forming an amorphous BN film as the back surface protective film 4 on the area other than the central 35 mm square of the rear surface of the silicon substrate 3, the central 35 mm square area is etched from the rear surface with a KOH aqueous solution at 95 ° C. The mask substrate for X-ray lithography shown in (4) was completed. The visible light transmittance of this X-ray lithography mask membrane was 41% (wavelength 633 nm). Furthermore, as a result of irradiating the membrane with SOR light at 100 MJ / cm ³ , no damage due to SOR light irradiation was observed,
It was confirmed that the membrane was extremely excellent in SOR light irradiation (see Table 1).

Comparative Example 1 For comparison, the conditions for forming a diamond film without forming a SiC film were as follows: input power 1000 W, hydrogen diluted methane concentration.
A mask substrate for X-ray lithography was prepared in the same manner as in Example 1 except that 0.5% by volume and the substrate temperature during film formation were 850 ° C.
The characteristics of the membrane were evaluated. The results are shown in Table 1 together with the results of Example 1.

Comparative Example 2 An X-ray lithography mask substrate was prepared in the same manner as in Comparative Example 1 except that the diamond film forming conditions were input power of 3000 W, and the characteristics of the membrane were evaluated. The results are also shown in Table 1.

Comparative Example 3 An X-ray lithography mask substrate was prepared in the same manner as in Comparative Example 1 except that the diamond film formation conditions were an input power of 3000 W and a substrate temperature during film formation of 950 ° C., and the characteristics of the membrane were evaluated. did. The results are also shown in Table 1.

Comparative Example 4 An X-ray lithography mask substrate was prepared in the same manner as in Comparative Example 1 except that the diamond film formation conditions were an input power of 3000 W and a hydrogen diluted methane concentration of 2.0% by volume, and the characteristics of the membrane were evaluated. did. The results are also shown in Table 1.

[0018]

[Table 1]

It can be seen from Table 1 that none of the comparative examples satisfy both the film stress and the crystallinity at the same time. That is, Comparative Examples 1 to 3 are not suitable for film stress,
On the other hand, Comparative Example 4 has a film stress capable of producing a membrane, but has poor crystallinity.

[0020]

According to the present invention, and the diamond, SiC
Alternatively , a membrane composed of a laminated film of SiN or SiCN has mechanical strength, resistance to SOR light irradiation, and visible light transmission that are almost the same as diamond. Furthermore, for stress compensation, the stress of the membrane can be controlled with high precision using SiC, SiN, or SiCN .

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the structure of an example of a mask substrate for X-ray lithography according to the present invention.

FIG. 2 is a schematic sectional view showing the structure of another example of the mask substrate for X-ray lithography according to the present invention.

FIG. 3 is a schematic sectional view showing a structure of a conventional mask substrate for X-ray lithography.

[Explanation of symbols]

1 ... Diamond film 2 SiC film (stress correction film) 3, 13 ... Supporting substrate 4, 14 ... Backside protective film 5, 15 ... Absorber pattern 6 Membrane (laminated film) 16: Membrane (diamond film)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-338628 (JP, A) JP-A-7-74078 (JP, A) JP-A-7-99154 (JP, A) JP-A-8- 54726 (JP, A) JP-A 8-250392 (JP, A) JP-A 61-32425 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 1 / 16 G03F 7/20

Claims (3)

(57) [Claims] 1. A ne from the membrane formed was laminated structure for one or both surfaces to stress correction of CVD diamond films
The film for the stress correction is made of silicon carbide or silicon nitride.
It is a mask membrane made of silicon carbide nitride.
The stress of the laminated film having the above laminated structure is 0.0 to 5.0 ×
A mask membrane for electron beam and X-ray lithography, which is 10 ⁹ dyn / cm ² (pull) . 2. One side of a vapor phase synthetic diamond film or
It consists of a laminated structure with a film for stress compensation on both sides.
Ri, a mask membrane made of a film of silicon carbide or silicon nitride, or carbide of silicon nitride for the stress compensation
And the film thickness (t _dia ) of the vapor phase synthetic diamond film
The ratio with the film thickness (t _Si ) for force correction is t _dia / t _Si
A mask membrane for electron beam and X-ray lithography, wherein ≧ 1.0 . 3. One side of a vapor phase synthetic diamond film or
It consists of a laminated structure with a film for stress compensation on both sides.
The film for the stress correction is made of silicon carbide or silicon nitride.
It is a mask membrane made of silicon carbide nitride.
The stress of the laminated film having the above laminated structure is 0.0 to 5.0 ×
10 ⁹ dyn / cm ² (pull), and the vapor phase synthetic diamond
Film thickness (t _dia ) and film thickness for stress correction (t _Si
) And the ratio t _dia / t _Si ≧ 1.0
A mask membrane for electron beam and X-ray lithography.