JPH04213819A - Etching method for compound semiconductor - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of a semiconductor substrate in which crystal is grown continuously in a vacuum atmosphere after a pattern has been formed by etching without exposing a compound semiconductor to the atmospheric air. CONSTITUTION:The gas 53, containing hydrogen chloride, is projected to or brought into contact with the surface of a wafer 14 of compound semiconductor in a vacuum atmosphere, the above-mentioned wafer 14 is etched by projecting at least one of electron beam, a visible light, ultraviolet rays and X-rays on the surface of the wafer 14, and at least one of a semiconductor thin film, an insulating thin film and a metal thin film is formed on the surface of the wafer 14.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for etching compound semiconductors, which is carried out continuously under a vacuum atmosphere.

0002

2. Description of the Related Art Conventionally, elements using compound semiconductors have been fabricated through processes such as repeating crystal growth and etching several times and, in some cases, diffusing impurities. For example, to create an embedded semiconductor laser chip, the following steps are taken. First, a GaAs buffer layer, an AlGaAs cladding layer, a GaAs active layer, an Al
A GaAs cladding layer and a GaAs electrode layer are grown while adding necessary impurities at the same time. Second, a protective film such as a SiO2 film is formed on the surface of the semiconductor on which each layer has been grown, and a resist is applied to the surface. Next, a pattern corresponding to the laser stripes is exposed, followed by development to form a resist pattern. Third, hydrofluoric acid (H
F) The semiconductor is brought into contact with the resist pattern and the protective film such as the SiO2 film is removed from the area where there is no resist pattern. Thereafter, the resist remaining in the pattern is removed using an organic solvent or the like. Fourth, the semiconductor is brought into contact with an etching solution containing sulfuric acid (does not etch the protective film), and the G of the epitaxial layer is removed.
Etch to a depth that reaches the aAs buffer layer. Fifth, an AlGaAs layer is grown by a liquid phase epitaxial method or the like to fill in the etched portion. Sixth, the protective film remaining on the surface is removed. As described above, the conventional method for forming a semiconductor structure requires many steps, and as a result, there is a problem in that it takes a long time to fabricate. Furthermore, when a pattern is formed by wet etching using a solution, the semiconductor surface is exposed to the atmosphere, so there is a problem that the surface is contaminated by the atmosphere.

[0003] Therefore, the inventors invented a method for forming a compound semiconductor structure that solved these problems (Japanese patent application No.
162683 and Japanese Patent Application No. 1-332640). This invention continuously irradiates the surface of a compound semiconductor wafer with a first gas in a vacuum container to form a mask layer on the wafer surface, and then forms a pattern on the mask layer with a second gas and an electron beam. The compound semiconductor is then etched with a second gas to form a pattern on the wafer, and after the mask layer is removed by heating, a semiconductor thin film or the like is grown as a crystal on the patterned wafer surface. .

0004

However, the conventional method for forming a semiconductor structure requires many steps as described above, and as a result, there is a problem in that it takes a long time to fabricate. Furthermore, etching using a solution has the problem that the semiconductor surface is exposed to the atmosphere, and thus the surface is contaminated by the atmosphere. Further, the invention of the inventors (Japanese Patent Application No. 2-169983) also has a problem in that a long process is required for forming and removing the mask layer. An object of the present invention is to simplify the steps of a semiconductor substrate manufacturing method in which pattern formation by etching and subsequent crystal growth are performed continuously in a vacuum atmosphere without exposing a compound semiconductor to the atmosphere.

[0005]

[Means for Solving the Problems] A compound semiconductor etching method and a compound semiconductor substrate manufacturing method of the present invention include:
It has aspects (1) to (4) described below. (1) In a vacuum atmosphere, the surface of a compound semiconductor wafer is irradiated with or brought into contact with a gas containing hydrogen chloride, and the wafer surface is irradiated with at least one selected from electron beams, visible light, ultraviolet rays, and X-rays. A method for etching a compound semiconductor, comprising the step of etching the wafer by irradiating the wafer. (2) In (1), the focused electron beam scans and irradiates only a predetermined region of the substrate wafer, thereby etching the predetermined region and forming a pattern on the wafer. 1) Compound semiconductor etching method. (3) In (1), at least one selected from the electron beam, visible light, ultraviolet rays, and X-rays is projected through a beam blocking mask having a pattern to irradiate only a predetermined region of the wafer surface. The compound semiconductor etching method according to (1), characterized in that a pattern is formed on the wafer by etching the predetermined region. (4) Following the etching of (1) to (3), at least one selected from a semiconductor thin film, an insulating thin film, and a metal thin film is formed on the etched surface of the wafer in the vacuum atmosphere. A method for manufacturing a compound semiconductor substrate, characterized in that:

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. First, the apparatus used in the etching method and compound semiconductor substrate manufacturing method of the present invention will be briefly explained. The apparatus shown in FIG. 2 includes an introduction chamber 21 for loading and unloading wafers into the apparatus and for forming an etching mask, and an MBE chamber 2 for performing epitaxial growth.
2. It has an etching chamber 23 for selectively etching the semiconductor to form a pattern. These introduction chambers 21,
The MBE chamber 22 and the etching chamber 23 are each connected to a sample exchange chamber 24 via a passage. Each passage is provided with gate valves 25a, 25b, and 25c. Further, each chamber 21, 22, 23, and 24 is provided with a vacuum pump (not shown) such as a turbo molecular pump or an ion pump. Thereby, the wafer introduced into the apparatus can be transported to any chamber using the magnetic feedthroughs 26a, 26b, and 26c without being exposed to the atmosphere. Further, a sample heating chamber 20 is attached to the sample exchange chamber 24 via a passage. Furthermore, the etching chamber 23 is equipped with an electron beam generator 231 that generates an electron beam, a gas introduction section 28 that introduces a gas used for etching, and a manipulator 29 that adjusts the sample position. Etching chamber 23
FIG. 4 shows this in detail. Referring to FIG. 4, an electron beam generator 23 is installed in the upper part of the etching chamber 23.
1 is installed to irradiate a sample 48 with a focused electron beam 41. A heater 47 is provided below the sample 48, and the sample 48 can be heated by supplying electricity to the heater 47 through the current introduction terminal 44. In addition, the nozzle 46 of the gas introduction section 28
is provided so that the surface of the sample 48 can be irradiated with gas.

A first embodiment of the method for manufacturing a compound semiconductor substrate of the present invention will be described below with reference to FIGS. 1, 2, and 4. First, Ga introduced from the introduction chamber 21
The As substrate 10 is connected to the magnet feedthroughs 26a and 2
6b was used to transport the sample to the sample heating chamber 20. Sample heating chamber 2
0 to 1 x 10-8 Torr or less, and sample heating chamber 2.
The GaAs substrate 10, which had been transported to a temperature of 200° C., was heated to about 200° C. by a heating device installed inside and maintained at that state for 10 minutes. Through this treatment, water molecules adsorbed on the surface of the GaAs substrate 10 could be removed. Next, the substrate 10 is transferred to the MBE chamber 22 by the magnet feedthrough 26b.
Transported to. GaAs substrate 1 transported to MBE chamber 22
As shown in FIG. 1(a), a GaAs buffer layer 1 is formed on
1 to 0.2 μm, Alx Ga1-x As cladding layer 12 (0<x<1) to 1.2 μm, and GaAs guide layer 13 to 0.2 μm. This wafer 1
4 was transported to the etching chamber 23 connected to the MBE chamber 22 by an ultra-high vacuum passage using a magnetic feedthrough 26b or the like. The wafer 14 transferred to the etching chamber 23 is attached to a wafer holder (not shown), the temperature is set to 70° C. by the heater 47, and the wafer 14 is transferred to the etching chamber 23.
Hydrogen chloride gas 53 was introduced into the chamber from a nozzle 46. At this time, the pressure inside the etching chamber 23 rose to 8 x 10-5. Simultaneously with the introduction of hydrogen chloride gas 53, the electron beam 41
was irradiated onto the surface of the wafer 14. This electron beam 41 has a diameter of 50 nm and a current of 10 pA.
It was scanned to draw a line and space pattern with a width of nm. Ga formed on the surface of the wafer 14
The As guide layer 13 contains hydrogen chloride gas 53 and the electron beam 4.
Etching progressed only in the portions where both of No. 1 and No. 1 were irradiated. The hydrogen chloride gas 53 is irradiated broadly over a range of several mm in diameter on the surface of the GaAs guide layer 13, but the electron beam 41 draws very narrow lines and spaces as described above. Therefore, a line and space pattern was formed in the GaAs guide layer 13 according to the scanning of the electron beam 41. Etching by this hydrogen chloride gas 53 extends not only to the uppermost GaAs guide layer 13 but also to the lower AlGaAs cladding layer 12, and the etching rate is higher than that of the GaAs guide layer 13 and the AlGaAs cladding layer 12. It was the same though. In this way, as shown in FIG. 1(b), AlG
Etching was performed using hydrogen chloride gas 53 until the aAs cladding layer 12 was reached.

Subsequently, the wafer 14 having the GaAs guide layer 13 and the AlGaAs cladding layer 12 patterned on its surface in this manner was transferred to the MBE chamber 22 again. M
The wafer 14 transferred to the BE chamber 22 was heated to 550° C. or higher while irradiating the surface with an arsenic molecular beam, and the surface was cleaned for about 1 hour. This surface cleaning
During etching, the GaAs layer 13 and the AlGaAs layer 12
Hydrogen chloride etc. attached to the surface of the GaA are removed and pure GaA
We were able to obtain the s crystal plane. (Reflected electron diffraction (RHEED) method was used to monitor the degree of cleaning.) Next, the AlX Ga1-X As upper cladding layer 16 was coated with a thickness of 1.5 μm, and the GaAs oxidation prevention layer 17 was coated with a thickness of 0.0 μm.
It was grown to 1 μm. In this way, a desired buried structure as shown in FIG. 1(c) was obtained without taking the wafer out of the ultra-high vacuum apparatus into the atmosphere. As described above, in this embodiment, patterned etching is possible without using an etching mask using organic resist, SiO2, etc., and there is no etching mask that must be removed after forming the pattern. Therefore, there is no contamination of the surface due to the removal of the mask, and there is no process of removing the mask, and a semiconductor thin film or the like can be continuously grown on the patterned surface. Although a narrow electron beam is used in this embodiment, it is also possible to irradiate the entire surface of the substrate with a broad electron beam to etch the surface. Furthermore, instead of an electron beam, visible light, ultraviolet rays, X-rays, or the like can be projected onto the substrate surface through a beam blocking mask to perform etching and form a pattern. Furthermore, in addition to epitaxially growing a semiconductor thin film on the patterned surface, it was also possible to form an insulating thin film or a metal thin film without exposing it to the atmosphere.

Next, a second embodiment will be explained with reference to FIG. FIG. 3 is a schematic diagram showing the steps of this embodiment. The equipment used was the same as in the first example. First, an InP substrate 31 is carried into the MBE chamber 22, and an InGaAsP layer 32 is deposited on its surface using gas source MBE.
．． It was grown to 5 μm. This wafer 33 is placed in the etching chamber 2.
Transported to 3rd. The etching conditions in this example were as follows. That is, the substrate temperature was 130°C, and the etching gas was
Hydrogen chloride was used as 7, and the electron beam was scanned to form lines and spaces (grating) with a width of 200 nm. As a result of this etching, Figure 3 (b)
), the area of InGaA irradiated with the electron beam
The sP layer 32 was removed and an InGaAsP light guide layer was formed. After that, as in the first embodiment, the wafer 33 is
The InGaAsP active layer 38 is transferred to the BE chamber 22, and then the InGaAsP active layer 38 is
, an InP confinement layer 39, and an InGaAsP contact layer 40 were grown. As a result, a mesa was formed in the electron beam irradiation area as shown in FIG. 3(c). In this etching, the etching depth of the portion irradiated with the electron beam was approximately 0.3 μm, and the etched surface was a mirror surface. Note that the present invention is not limited to the above embodiments, and InAs, InS as the semiconductor material.
It may also be a compound semiconductor such as GaP, InGaAlP, and AlGaSb.

0010

[Effects of the Invention] According to the present invention, a pattern is formed by etching the surface of a compound semiconductor by irradiating it with an electron beam and hydrogen chloride gas, without causing crystal defects near the surface of the compound semiconductor. Fine patterns can be formed. In addition, in a series of substrate processing processes and crystal growth processes, each step can be performed continuously in a controlled atmosphere without exposing the substrate to the atmosphere. Contamination or the incorporation of impurities at the interface can be suppressed. Furthermore, since no mask layer is used for etching, there is no need for the formation and removal of a mask layer, and surface contamination can be suppressed.

[Brief explanation of the drawing]

FIG. 1 is a process diagram of a first embodiment of the pattern forming method of the present invention.

FIG. 2 is a schematic diagram of a vacuum system used in the processes of the first and second embodiments.

FIG. 3 is a process diagram of a second embodiment of the pattern forming method of the present invention.

4 is a perspective view for explaining in detail the etching chamber 23 of FIG. 2. FIG.

[Explanation of symbols]

10 GaAs substrate 11 GaAs buffer layer 12 Alx Ga1-x As cladding layer 13
GaAs guide layer 14 Wafer 16 AlX Ga1-X As upper cladding layer 17
GaAs antioxidant layer 20 Sample heating chamber 21 Introduction chamber 231 Electron beam generator 22 MBE chamber 23 Etching chamber 24 Sample exchange chambers 25a, 25b, 25c Gate valves 26a, 26
b, 26c Magnet feedthrough 28 Gas introduction part 29 Manipulator 31 InP substrate 32 InGaAsP layer 33 Wafer 37 Etching gas 38 InGaAsP active layer 39 InP confinement layer 40 InGaAsP contact layer 41 Electron beam 44 Current introduction terminal 46 Nozzle 47 Heater 48 GaAs substrate 53 hydrogen chloride gas

Claims (4)

[Claims] 1. In a vacuum atmosphere, the surface of a compound semiconductor wafer is irradiated with or brought into contact with a gas containing hydrogen chloride, and the wafer surface is irradiated with at least one selected from electron beams, visible light, ultraviolet rays, and X-rays. A method for etching a compound semiconductor, the method comprising the step of etching the wafer by irradiating the wafer. 2. The method according to claim 1, wherein the focused electron beam scans and irradiates only a predetermined region of the substrate wafer, thereby etching the predetermined region and forming a pattern on the wafer. The method of etching a compound semiconductor according to claim 1. 3. The electron beam according to claim 1,
etching the predetermined region on the wafer by projecting at least one selected from visible light, ultraviolet light, and X-rays through a patterned beam-blocking mask to irradiate only the predetermined region of the wafer surface; 2. The compound semiconductor etching method according to claim 1, further comprising forming a pattern. 4. Following the etching according to claims 1 to 3, at least one selected from a semiconductor thin film, an insulating thin film, and a metal thin film is formed on the etched surface of the wafer in the vacuum atmosphere. A method for manufacturing a compound semiconductor substrate, characterized in that: