JPS63271990A - Manufacture of semiconductor diffraction grating - Google Patents

Abstract

PURPOSE:To improve the diffraction efficiency by forming a semiconductor layer on a substrate by epitaxial growth while irradiating a laser two-beam interference light on the surface of the substrate. CONSTITUTION:While irradiating two interference beams of laser light on the surface of a substrate, a normal epitaxial growth is performed, for example, a crystal growth by an organic metal vapor technique. When the two interference beams of laser is irradiated, the laser beams are irradiated alternately in cycles on the substrate and the laser beams permit the epitaxial layer where regions having different compositions, conductivity types, and carrier concentrations are formed alternately in cycles to grow. In this way, as the regions having the different compositions, conductivity types, and carrier concentrations are formed under the action of the light, an interface between laser irradiation and irradiationless parts is so steep that its diffraction efficiency becomes higher than conventional ones.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is useful in the optical communication field, optical disk related field,
In particular, the present invention relates to a method of manufacturing a semiconductor diffraction grating that can be used as a diffraction grating for a distributed feedback semiconductor laser and a black reflection feedback semiconductor laser, which are wavelength stabilized light sources and light sources for optical ICs.

Conventional technology In recent years, in order to stabilize the oscillation wavelength of semiconductor lasers, research and development has been conducted in various places on devices that monolithically integrate a semiconductor laser and a semiconductor diffraction grating, that is, distributed feedback semiconductor lasers or black reflective feedback semiconductor lasers. It is being actively carried out.

Conventionally, this semiconductor diffraction grating has been manufactured by a process as shown in FIG. 3, for example.

First, a resist film is applied onto a semiconductor substrate, and then a periodic striped pattern is formed on the resist film by a two-beam interference exposure method using a laser beam using an optical system arrangement as shown in FIG. In Fig. 3, 1 is GaAs, 1
A semiconductor crystal substrate such as nP, 2 a resist film, 3 a laser beam generator, 4 a beam expander, 6 a half mirror, 16 a mirror, and 7 a laser beam. Thereafter, the semiconductor crystal substrate was chemically etched using the resist film 2 on which the striped pattern was formed as a mask to form periodic irregularities on the surface of the semiconductor substrate, thereby manufacturing a semiconductor diffraction grating.

Problems to be Solved by the Invention However, when semiconductor diffraction gratings are manufactured using the method described above, the unevenness on the surface of the semiconductor substrate is formed by chemical etching, which makes it difficult to make large changes in the unevenness, resulting in a decrease in diffraction efficiency. There was a problem with this. Further, when the semiconductor diffraction grating is used in a distributed feedback semiconductor laser, a Bragg reflective feedback semiconductor laser, an optical IC, etc., it is necessary to epitaxially grow a semiconductor crystal on the diffraction grating. In that case, the removal of the resist after forming irregularities on the surface of the semiconductor substrate is often incomplete, and as a result, epitaxial growth on the diffraction grating becomes difficult, and the surface of the diffraction grating is damaged during the removal of the resist. Alternatively, since it is exposed to air, an oxide film may be formed on its surface, resulting in a problem in that the crystallinity of the epitaxial layer on the diffraction grating is reduced. Furthermore, when epitaxial growth is performed on a diffraction grating using a liquid phase epitaxial growth method in particular, there is a problem in that the diffraction grating is partially dissolved due to meltback, and as a result, changes in unevenness are reduced and diffraction efficiency is reduced.

Means for Solving the Problems The present invention solves the above-mentioned conventional problems by performing normal epitaxial growth, for example, crystal growth using an organometallic vapor phase method, while irradiating the substrate surface with two-beam laser interference light. This is a method of manufacturing a semiconductor diffraction grating.

For production The effect of this technical means is as follows.

By irradiating the substrate surface with laser light during epitaxial growth using the organometallic vapor phase method, it is possible to change the composition, carrier concentration, and conductivity type only in the area irradiated with the laser light, and the magnitude of the change depends on the irradiation. Almost proportional to laser power.

When irradiating with laser beam interference light, the laser beams are alternately and periodically irradiated onto the substrate, which changes the composition.

An epitaxial layer is grown in which regions having different conductivity types and carrier concentrations are alternately and periodically formed.

Note that since the light intensity distribution of the laser beam interference light is a square distribution of a sine wave, the composition, conduction type, and carrier concentration distribution also become a sine wave distribution. That is, the structure of these epitaxial layers has a function as a semiconductor diffraction grating.

In this case, regions with different compositions, conductivity types, and carrier concentrations are formed by the action of light, so the interface between the laser irradiated part and the non-irradiated part is steep, and the diffraction efficiency is higher than in the conventional case.

Embodiments The method for manufacturing a semiconductor diffraction grating according to the present invention is realized by the embodiments described below.

FIG. 1 shows a schematic diagram of a case where laser interference light is introduced into an apparatus used for manufacturing a semiconductor diffraction grating, that is, a crystal growth chamber for metal organic vapor phase epitaxy. 8 is a crystal growth chamber, 9 is a laser beam entrance window of the crystal growth chamber, 10.11 is a source gas inlet, 12 is an exhaust port, 13 is a high frequency coil, and 14 is a carbon susceptor. Note that the optical system for forming laser interference light is the same as the conventional one.

Using this device, more Ga Ats shown in Figure 2 can be obtained.
The case of creating a diffraction grating on a substrate will be described below.

In this case, the raw material gases for Ga, Al, and As are Ga (CH3) 3. Al (CH3)
3. AsH3 was used as the n-type and p-type impurity raw materials, and S i (CH3) 4°zn(CH3)2 was used as the carrier gas. Furthermore, ArF excimer laser light (wavelength: 1 ssnm) was used as the laser light.

Further, in this case, a diffraction grating can be considered in which the laser irradiated part and the non-irradiated part have different compositions, carrier concentrations, and conductivity types, respectively. The creation conditions for each case are summarized in the table below.

Substrate GaAs
Growth temperature 700℃ 70011m 700
℃ growth pressure 100Torr 100Torr
r 100TorrGa(CH3)3 supply amount 0.2
8sccm 0.4sccm 0.4sccmA
l(CH3)3 supply amount 0.12sccm--AsH3
Supply amount 101005c 20s+ccm
20sccmZ n (CH,I)2 supply amount
6.25X10″mcamSi
(CH3)4 supply amount 0.012s+c
cm 0.012gc (In total H2 flow rate 5
sdm 5sJm 5sJm Laser wavelength 193nm 193nm 1
In the 93 nm manufacturing process, a GaAs substrate 1 is first placed on a carbon susceptor 14 in a crystal growth chamber 8.

Next, the substrate is heated to the growth temperature while supplying A m Ha, and after reaching the growth temperature, if the composition changes periodically, G a (CHa) 3 and AJ (CH3)
3, and when the carrier concentration changes periodically, Ga(CH3)3 and Si(CH3
) 4, and when the conduction type changes periodically, Ga
(CH3)3, 5l(CH3)4, and Zn(CH3)3, which is a p-type impurity raw material, are supplied, and at the same time, KArF excimer laser beam interference light (wavelength 193 nm) is applied to the substrate 1.
irradiate. In this state, epitaxial growth is performed for minutes, and in the case of a composition change, an AI Ga As layer is grown in the laser irradiated part, the GaAs layer is grown in the non-irradiated part, and in the case of a carrier concentration change, a Ga with a carrier concentration of ~1018 cm-' is grown in the laser irradiated part.
A1 layer, non-irradiated part has a carrier concentration of ~103G
In the case of a conductivity change, the aAs layer is an n-type GaAs layer in the laser irradiated area, and the p-type GaAs layer is in the non-irradiated area.
A layer was formed. The above method takes advantage of the fact that ArF excimer laser irradiation increases the decomposition efficiency of Al(CH3)3°Si(CH3)4 and that zn(CH3)2 is hardly affected by laser irradiation.

The semiconductor diffraction gratings created in this way have a steep change in composition, carrier concentration, and conductivity type at the interface between the laser irradiated and non-irradiated areas, and changes in the unevenness cannot be achieved using conventional chemical etching methods. It has a high diffraction efficiency, which is improved by about 60%.

In the embodiments described above, GaAt5-AlGaA
The method for manufacturing an s-based semiconductor diffraction grating has been explained, but
Semiconductor diffraction grating InP-InGaAsP system according to the invention,
AIGaInP-GaAs system, InGaAsP-GaA
S-type.

It can be used not only for other (1)-v group semiconductor crystals, but also for n-2 group compound semiconductor crystals and mixed crystals such as Zn5e+Zn5se. Furthermore, in the embodiments described above, metal organic vapor phase method was used as the epitaxial growth technique, but other compound semiconductor vapor phase epitaxial growth methods such as hydride vapor phase epitaxy, jar growth method, and chloride vapor phase epitaxial growth method may also be used. It is possible not only when using a molecular beam epitaxy method or an organometallic molecular beam epitaxy method. Furthermore, in the above-described embodiments, the case where an ArF excimer laser was used as the laser was described, but an excimer laser or a Co2 laser using other gases such as KrF or XeF may also be used.

The present invention can be realized even when using a He-Cd laser, an Ar laser, or the like.

Effects of the Invention The method for manufacturing a semiconductor diffraction grating according to the present invention is a method in which the surface of a substrate is simply irradiated with laser beam interference light during normal epitaxial growth.

The diffraction efficiency of this semiconductor diffraction grating is high, and since the surface of the diffraction grating is not exposed to the air during fabrication and no resist remains as in conventional methods, epitaxial growth on the diffraction grating can be performed without any problems. Can be done. Furthermore, the position at which the diffraction grating is fabricated on the substrate can be determined by the position at which the laser interference light is irradiated and the size of the laser interference light on the substrate. is expensive. As described above, the manufacturing method according to the present invention has a very large practical effect.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining a method for manufacturing a semiconductor diffraction grating according to an embodiment of the present invention, FIG. FIG. 3 is a schematic diagram for explaining a typical conventional method of manufacturing a semiconductor diffraction grating. 1...Semiconductor crystal substrate, 2...Resist film, 3...Laser light generator, 7...
・Laser light, 8...Crystal growth chamber, 9...
・Laser light introduction window. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure E-F4 ()

Claims (4)

[Claims] (1) While irradiating the substrate surface with two-beam laser interference light,
A method of manufacturing a semiconductor diffraction grating, which comprises epitaxially growing a semiconductor layer on the substrate. (2) The method for manufacturing a semiconductor diffraction grating according to claim 1, wherein the laser used is an Ar laser or an excimer laser. (3) The method for manufacturing a semiconductor diffraction grating according to claim 1, wherein the epitaxial growth is a metal organic vapor phase epitaxy method. (4) The method for manufacturing a semiconductor diffraction grating according to claim 1, wherein the semiconductor is a III-V compound semiconductor.