JP2992596B2 - Method for pattern etching SiC and method for manufacturing laminar type SiC diffraction grating using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, SiC or SiC as a material for a blue semiconductor laser or an environment-resistant semiconductor material.
SiC that can be used when making diffraction gratings, etc.
(Silicon carbide) highly efficient etching method and
For manufacturing laminar-type SiC diffraction grating using the same
About.

[0002]

2. Description of the Related Art Diffraction gratings for synchrotron radiation (SR light) and short-wavelength, high-power lasers are stable up to a relatively high temperature with respect to a temperature rise due to these high-energy radiations, and have a high thermal conductivity. A SiC diffraction grating with good cooling efficiency is ideal because of its high rate. However, even if an attempt is made to scribe a diffraction grating pattern directly on the SiC substrate by dry etching such as an ion beam method, the resist is etched faster than the SiC substrate, so the diffraction grating pattern is formed directly on the SiC substrate. It was difficult to do. Therefore, conventionally, the following method has been devised.

One is as shown in FIG. 5, where a resist pattern 55 (5
3 is an original resist layer), and lift-off
1 to form a reverse pattern 56. By performing reactive ion etching (RIE) using CF ₄ and CF ₄ + O ₂ ion beams 57 using the Al pattern 56 as a mask, a desired pattern 58 is obtained on SiC (JW Palmour et al., “Dry Etching of β-SiC in C
F4 and CF4 + O2 mixtures ", J. Vac. Sci. Technol. A4
(3), May / Jun 1986, p.590-593). Alternatively, FIG.
As shown in FIG. 7, a PMMA 63 is applied on a SiC substrate 62 and an electron beam 65 is applied so as to form a diffraction grating pattern.
(Electron beam lithography)
A diffraction grating pattern 64 of PMMA is created. Similarly, a reverse pattern 66 of Cr is formed from the resist pattern 64 by lift-off, and reactive ion beam etching (RIB) using a reactive ion beam 67 of CF ₄ + O ₂ is performed.
E) to obtain a diffraction grating pattern on SiC62 (Shinji Matsui et al., "Reactive Ion-Beam Etchingo"
f Silicon Carbide ", Japanese Journal of Applied Phy
sics, Vol. 20, No. 1, January, 1981, pp. L38-L40).

[0004]

According to the method shown in FIG.
Since the etching of C is performed by RIE, the SiC 51 is exposed to the plasma during the etching, and the etched surface is very rough. For this reason, when used as a diffraction grating, there is a problem that high-precision spectroscopy cannot be performed. Further, the method of FIG. 6 has a drawback that it takes a long time to draw the pattern because the formation of the resist pattern 64 is performed by electron beam lithography. In particular, since a diffraction grating for SR (radiation light) needs to have a large area, it is difficult to employ electron beam lithography in terms of production efficiency. Also, FIG.
In both methods of FIG. 6, in order to increase the etching selectivity of the SiC substrate with respect to the mask ([etching rate of SiC substrate] / [etching rate of mask]), Al or Cr mask 56 is lifted off from photoresists 55 and 64. , 66, which has the disadvantage of requiring an extra lift-off step.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an SiC pattern capable of quickly etching a SiC substrate into a desired pattern by a simple process. An etching method is provided , and a laminar SiC diffractometer is provided using the etching method.
A method for manufacturing a child is provided.

[0006]

According to the present invention, there is provided a method for etching a pattern of SiC, which comprises forming a pattern mask on a SiC substrate using a resist material, and forming (CCl ₂ F ₂ + Ar). Etching is performed on a SiC substrate by irradiating a reactive ion beam generated from a mixed gas of CCl ₂ F ₂ and Ar with a partial pressure ratio of Ar to 55 to 85% with respect to the vertical direction of the substrate. is there. In addition, laminar type SiC diffraction
The method of manufacturing the grating is such that a parallel linear diffraction grating is formed on a SiC substrate.
A resist mask having a pattern is deposited, and (C
The partial pressure ratio of Ar to Cl ₂ F ₂ + Ar) is 55 to 85.
% Of a mixed gas of CCl ₂ F ₂ and Ar
The substrate is irradiated with a reactive ion beam
With this, a laminar groove for diffraction is etched in the SiC substrate.
It is to do.

[0007]

FIG. 1 shows various composition ratios of (CCl ₂ F ₂ + A
r) In the case of performing reactive ion etching using a mixed gas, a photoresist standardized by the Ar content in the mixed gas and the ion current density (here, OFPR5000 manufactured by Tokyo Ohka Co., Ltd.) and SiC The relationship with the etching rate is shown. As shown in FIG. 1, when only CCl ₂ F ₂ is used ([Ar / (CCl ₂ F ₂ + Ar)] = 0%),
Alternatively, in the case of only Ar ([Ar / (CCl ₂ F ₂ + A
r)] = 100%), the etching rate of the resist is more than twice that of SiC. In other words, under such conditions, SiC, which is the object of etching, is hardly etched, while the resist is etched at twice or more the rate. Therefore, conventionally, as described above, Al or C
An extra step of forming a mask of r is included.
Such a phenomenon also occurs when reactive ion etching is performed on SiC, even when another photoresist material is used.

On the other hand, [Ar / (CCl ₂ F ₂ + A)
r)] is in the range of 55 to 85%, the etching rate of SiC is specifically increased, and is substantially equal to the etching rate of the resist. Therefore, as shown in FIG. 2, the selectivity ([etching rate of SiC] / [etching rate of resist]) is 0.5 or less in other ranges, but is almost equal to 1 in this range. Becomes Therefore, by performing the reactive ion etching under such conditions, it is possible to reduce the S
The pattern etching of the iC substrate can be performed at high speed. The laminar type SiC diffraction grating uses this pattern edge.
It is manufactured using the chilling method.
Will be described in detail.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As a first embodiment of the present invention, a laminar Si
A method of manufacturing a C diffraction grating will be described with reference to FIG. First, a sintered SiC substrate 31 is prepared (a), and a β-SiC single crystal layer 32 is deposited on the surface thereof by CVD. This surface is optically polished to reveal a (2,2,0) -oriented surface on the surface (b). Further, a photoresist (here, OFPR5000 manufactured by Tokyo Ohka Co., Ltd.) layer 33 having a thickness of 300 nm is formed on this surface by spin coating (c). After coating, the substrate is placed in a 90 ° C. fresh air oven and baked for 30 minutes.
The CVD-SiC layer 32 is not β-SiC but α-
SiC may be used, and the orientation plane is not limited to (2, 2, 0), but may be (1, 1, 1) or a mixed orientation film. Further, amorphous SiC may be used. Further, the material of the photoresist is not limited to the above-mentioned OFPR5000, and other photoresists may be used.

Next, holographic exposure is performed to form a laminar type diffraction grating pattern. That is, by irradiating a plane wave 34 from two directions and forming interference fringes on the resist 33, a parallel-line latent image having a sine-wave cross-sectional exposure density is formed in the resist layer 33 (d). Here, He-Cd laser light (wavelength λ = 441.6 nm) was used as exposure light, and 1200 lines / m
Create m parallel line patterns. After exposure, the resist mask 35 having a parallel line shape and a half sinusoidal cross section is left on the substrate 32 by processing with a dedicated developer (e). Here, by appropriately adjusting the exposure time and the development time, the ratio of the portion covered with the resist 35 on the substrate 32 to the portion not covered (that is, the portion where the SiC substrate 32 is exposed) ( L & S ratio) can be arbitrarily set. Here, the L & S ratio is 1: 1. In the method of the present embodiment, since a diffraction grating pattern is created by holographic exposure, a periodic error, which is the most important characteristic of a diffraction grating, is unlikely to occur (this is likely to occur in electron beam lithography performed by the method of FIG. 6). , A highly accurate diffraction grating can be manufactured. The exposure wavefront by the holographic exposure method is a spherical wave or an aspherical wave when an aberration correction type diffraction grating is manufactured.

Using the resist 35 of the diffraction grating pattern formed as described above as a mask, a reactive ion beam 36 using a mixed gas of CCl ₂ F ₂ and Ar is irradiated from a direction perpendicular to the substrate 32 to dry etching. (F). The composition of this mixed gas is [Ar / (CCl ₂ F ₂
+ Ar)] = 75%. This ion beam etching is performed until the etching groove reaches a predetermined depth (10 nm) (the relationship between the etching time and the groove depth is determined in advance by an experiment). Finally, the photoresist 35 remaining on the surface is ashed and removed with O ₂ plasma (a resist stripper or a solvent may be used) to obtain a desired laminar diffraction grating 37.

The laminar diffraction grating 37 thus produced
Can be used on the surface as it is in a wavelength region where the reflectance of SiC is sufficiently high. In a wavelength region where the reflectance of SiC is low, the reflectance is increased by applying a coating of gold (Au) or platinum (Pt), or by coating an X-ray multilayer film.

The method according to the present invention can be used not only for producing a laminar type diffraction grating but also for producing an arbitrary pattern. For example, as shown in FIG.
Si with resist film formed in step (c) of the above embodiment
Pattern exposure is performed on the C substrate 32 (FIG. 4A) using a photomask 41 having an arbitrary pattern to form a resist 44 having an intended pattern (FIG. 4C). And, similarly,
(CCl ₂ F ₂ + Ar) reactive ion beam 45 ([Ar
/ (CCl ₂ F ₂ + Ar)] = 55 to 85%), the pattern 46 can be easily and efficiently formed on the SiC substrate 32, which has been difficult in the past.

[0014]

According to the SiC pattern etching method of the present invention, since the etching rate of SiC is substantially equal to the etching rate of resist, the direct etching of the SiC substrate by the resist mask can be performed without including an extra step of lift-off. Pattern etching becomes possible. Further, since the SiC substrate is not exposed to plasma, a smooth surface can be obtained. For this reason, a desired pattern can be etched on SiC by a simple and short process, for example, excellent heat resistance and
A laminar type diffraction grating made of only SiC having good cooling efficiency can be manufactured. Further, Ar contained in the mixed gas also has a function of removing impurities sputtered from inside the chamber during etching and cleaning the inside of the apparatus. For this reason, the maintenance interval of the etching apparatus becomes longer, and the maintenance becomes easier.

[Brief description of the drawings]

FIG. 1 shows a photoresist and S standardized by Ar content in a mixed gas and ion current density in reactive ion etching using a (CCl ₂ F ₂ + Ar) mixed gas.
4 is a graph showing a relationship between an iC and an etching rate.

FIG. 2 is a graph in which the data of FIG.

FIG. 3 shows a laminar type Si according to a first embodiment of the present invention.
Explanatory drawing of the process of producing a C diffraction grating.

FIG. 4 is an explanatory view of a step of forming an arbitrary pattern on a SiC substrate according to a second embodiment of the present invention.

FIG. 5 is an explanatory view of a step of performing pattern etching on a SiC substrate by a conventional method.

FIG. 6 is an explanatory view of a step of performing pattern etching on a SiC substrate by another conventional method.

[Description of Signs] 31 ... SiC substrate 32 ... β-Si
C single crystal layers 33 and 35 ... photoresist 34 ... holographic exposure plane wave _{36 ... (CCl 2 F 2 +} Ar) reactive ion beam 37 ... laminar type diffraction grating 41 ... photomask 44 ... photoresist pattern 46 ... SiC substrate Pattern

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-293234 (JP, A) JP-A-1-274430 (JP, A) JP-A-63-232335 (JP, A) JP-A-54- 102872 (JP, A) JP-A-52-127764 (JP, A) JP-A-60-124824 (JP, A)

Claims (2)

(57) [Claims] 1. A forming a pattern mask with a resist material on SiC _{substrate, (CCl 2 F 2 + Ar} ) and _CCl 2 _{F 2,} which was 55-85% the partial pressure ratio of Ar for Ar
Etching a SiC substrate by irradiating a reactive ion beam generated from a mixed gas of the SiC substrate and the substrate from vertically above the substrate. 2. A diffraction grating pattern having a parallel line shape on a SiC substrate.
A resist mask having a pattern is deposited, and (CCl
₂ F ₂ + Ar) with a partial pressure ratio of 55 to 85%
CCl ₂ F ₂ Generated from a mixed gas of
Irradiating the reactive ion beam perpendicular to the substrate
Etching the parallel linear grooves in the SiC substrate.
A method for producing a laminar type SiC diffraction grating.