JPH08264443A - Formation of microminiature buried structure of compound semiconductor - Google Patents

Abstract

PURPOSE: To provide a method for the formation of a microminiature buried structure wherein a high quality microminiature buried structure is stably formed through a vacuum consistent process, including re-growth by MBE. CONSTITUTION: A compound semiconductor layer 11 to be processed is grown on a GaAs (100) substrate 10. The surface of the compound semiconductor layer 11 is exposed to oxygen and irradiated with light from a halogen lamp to form an oxide film 12. The surface of the oxide film is subjected to etching gas 13 and scanned with an electron beam 14. The scanning is performed in the [1-10] direction. The electron beam irradiation is stopped, and the compound semiconductor layer is etched in the etching gas 13 to form a stripe. Thereafter, a buried growth layer 15 is grown to fill the stripe.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a fine embedded structure of a compound semiconductor, and more particularly to a fine embedded structure of a compound semiconductor used in an integrated vacuum process for processing a compound semiconductor under ultrahigh vacuum. And a method of forming the same.

[0002]

2. Description of the Related Art In recent years, as a method for producing a microdevice utilizing a fine structure and an integrated device such as an OEIC (Optical Electronic Integrated Circuit) made of a compound semiconductor, a vacuum consistent process for continuously processing a compound semiconductor in a vacuum atmosphere. Attention is paid to the process, and various studies are being conducted.

Focused ion beams (FIB) and electron beams (E) are typical of conventional vacuum integrated processes.
A combination of B) and molecular beam crystal growth method (MBE) is known, and this process is actually used for manufacturing some fine structures and devices.

As an example of the conventional vacuum integrated process, a process of manufacturing a buried structure or the like by the EB-MBE process using an oxide film will be described. This process starts with MB on a substrate, eg, GaAs (001) substrate.
The E method is used to grow a GaAs / AlGaAs system epitaxial layer. Next, the surface of the epitaxial layer is exposed to an oxygen gas atmosphere and irradiated with light to form an oxide film on the surface of the epitaxial layer. Next, in a high vacuum or in a chlorine gas atmosphere, the formed oxide film is selectively irradiated with an electron beam for patterning. Then, using the patterned oxide film as a mask, the epitaxial layer is etched using chlorine gas. Finally, if the temperature of the substrate is raised in an As atmosphere, all the oxide film on the surface of the epitaxial layer is removed. After this, continue with Al
A buried structure can be produced by epitaxially growing a wide gap material such as GaAs.

As described above, the vacuum integrated process by EB-MBE does not expose the substrate to the atmosphere and does not use an organic resist material, so that the surface contamination of the work material can be remarkably avoided, and the high efficiency is achieved. A quality embedded structure can be realized.
In addition, not only the buried structure but also various fine structures can be manufactured by this process. Therefore, this type of vacuum integrated process is considered to be an indispensable technique for manufacturing future microdevices and integrated devices using a fine structure.

[0006]

However, the fine structure produced by such a vacuum integrated process is of high quality (no contamination, excellent optical and electrical characteristics) as compared with the conventional method. The inventors of the present invention have investigated and confirmed that it is not possible to obtain a high quality product simply by using the vacuum integrated process.

For example, when a stripe-shaped GaAs / AlGaAs quantum thin wire is formed by using the above-mentioned process, when a stripe direction is formed along the [110] direction, a high quality product cannot be obtained at all. . This is because when a stripe is formed by etching along the [110] direction, an undercut called an inverted mesa is formed in the lower portion of the stripe, or even if it does not reach that point, the side wall becomes steep, and This is because there is a shadow portion where the molecular beam does not hit during the growth, and the completeness of the regrown crystal on the side wall of the stripe is hindered.

As described above, the conventional method of forming a fine embedded structure of a compound semiconductor using the vacuum consistent process has a problem that it is not always possible to form a high quality fine embedded structure.

It is an object of the present invention to provide a method for forming a fine embedded structure capable of stably forming a high quality fine embedded structure in a vacuum integrated process including regrowth by MBE. .

[0010]

According to the present invention, a first step of forming a stripe on a compound semiconductor layer, and a second step of regrowth of a new compound semiconductor layer by MBE thereafter to embed the stripe. In the method for forming a fine embedded structure of a compound semiconductor, which is continuously performed under a high vacuum, the stripe forming direction in the first step is [1
A method of forming a fine embedded structure of a compound semiconductor, characterized in that the bar 10] direction is employed.

Further, according to the present invention, a first step of forming a stripe on the compound semiconductor layer, and a second step of regrowth of a new compound semiconductor layer by the MBE method to bury the stripe after that are carried out. In the method of forming a fine embedded structure of a compound semiconductor, which is continuously performed under a high vacuum, the step of embedding the stripe is performed using a plurality of group V sources arranged at different angles with respect to the stripe. And a method for forming a finely embedded structure of a compound semiconductor.

[0012]

When the stripes are formed by etching along the [1 bar 10] direction, the side walls of the stripes become gentle side walls called pure mesas. Therefore, MBE
When the source beam is irradiated, no shadow appears on the side wall, a good regrown crystal can be formed on the side wall, and a high-quality buried structure can be realized.

Beams from a plurality of group V sources are
By irradiating the stripes at different angles, shadows do not appear even on the side walls with a sharp slope called reverse mesa, and good recrystallization can be formed on the side walls, resulting in a high-quality embedding. The structure can be realized.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. First, a device used in an embodiment of the present invention will be briefly described. As shown in FIG. 2, this device
An introduction chamber 21 for loading and unloading a sample, an MBE chamber 22 for epitaxial growth, an etching chamber 23 for etching, a surface treatment chamber 24 for forming an oxide film, and an Auger analysis chamber 25 are provided. These chambers are connected to a sample exchange chamber 28 via passages 27 each having a gate valve 26. A sample heating chamber 29 is also connected to the sample exchange chamber 28.

A gas introduction control system 231 for introducing an etching gas, an electron beam generator 232 for generating a patterning electron beam, and a manipulator 23 for moving the sample introduced into the etching chamber 23.
3 and the like are provided. In addition, the surface treatment chamber 24 has a variable leak valve 241 for introducing oxygen gas.
And a quartz window 242 for taking in light from the light source.

A vacuum pump (not shown) such as a turbo molecular pump or an ion pump is connected to each chamber so that each chamber can be evacuated independently. In addition, this device has a magnet feedthrough 3
0 is provided in the sample exchange chamber 28 and other chambers so that the sample can be transported to any chamber.

Next, the etching chamber will be described with reference to FIG. Inside the etching chamber 23, the sample 31
A holder 32 for holding the sample, a heater 33 for heating the holder 32, and a gas nozzle 34 for irradiating the sample 31 with gas are provided. The holder 32 is
It is connected to the manipulator 233.

Next, an embodiment of the present invention will be described with reference to FIGS. First, GaAs is placed in the sample introduction chamber 21.
The (001) substrate 10 was introduced and conveyed to the sample heating chamber 29 using the magnet feedthrough 30. And
The sample heating chamber 29 was decompressed to 1 × 10 ⁻⁸ Torr or less, and the GaAs substrate 10 was heated to 200 ° C. by the heating device provided in the sample heating chamber 29 and held for 10 minutes. By this treatment, the water adsorbed on the GaAs substrate 10 was removed, and a clean surface could be obtained.

Next, the substrate 10 was transferred to the MBE chamber 22 using the magnet feedthrough 30. Then, as shown in FIG. 1A, the compound semiconductor layer 11 to be processed was MBE-grown on the substrate 10 to a predetermined thickness. Here, AlG is used as the compound semiconductor layer 11.
aAs layer 11a, GaAs layer 11b, and AlGaAs
It is assumed that a GaAs / AlGaAs quantum well structure having the layer 11c is formed. Furthermore, in order to form an oxide film,
A GaAs layer 11d was formed on the surface of the AlGaAs layer 11c.

Next, the substrate 10 (hereinafter referred to as a wafer) on which the compound semiconductor layer 11 was grown was transferred to the surface treatment chamber 24 via the sample exchange chamber 28 using the magnet feedthrough 30. In the surface treatment chamber 24, oxygen gas is introduced through the variable leak valve 241 to 1 atm, and the light from the halogen lamp is irradiated through the quartz window 242 onto the surface of the wafer to form the photo-oxidized film 1.
Formed 2. After that, the inside of the surface treatment chamber 24 is 1 × 10 ⁻⁸
After re-evacuating to Torr, the wafer was transferred to the etching chamber 23 via the sample exchange chamber.

After the wafer was loaded into the etching chamber 23, the etching gas 13 was introduced into the etching chamber 23 from the gas nozzle 34. At this time, the pressure in the etching chamber 23 increased to 8 × 10 ⁻⁵ Torr. The etching gas is Cl ₂ , Br ₂ , HCl, HBr, CH ₃
Br, CF ₃ Br, or a mixed gas thereof can be used.

Further, while introducing the etching gas 13 into the etching chamber 23, at the same time, the electron beam 14 from the electron beam generator 232 is projected on the surface of the wafer [1 bar 1].
Irradiation along the [0] direction. Here, the [1 bar 10] direction is the direction represented by Expression 1.

[0023]

[Equation 1] The etching gas 13 is broadly irradiated on the surface of the wafer over a range of several mm in diameter, but the electron beam 1
4 is narrowed down to a few nm in diameter and scanned on the wafer surface. Thus, when the wafer surface is irradiated with the electron beam 14 in the atmosphere of the etching gas 13, as shown in FIG.
As shown in (b), the oxide film 12 was removed and the oxide film 12 was patterned only in the region irradiated with the electron beam 14. It has been confirmed by other experiments that the patterning of the oxide film can be similarly realized even when the surface of the wafer is first irradiated with only the electron beam and then the surface of the wafer is exposed to the etching gas.

Next, when the irradiation of the electron beam is stopped and only the irradiation of the etching gas 13 is continued, the compound semiconductor layer 11 is changed to the etching gas 13 at the opening of the oxide film as shown in FIG. 1 (c). Exposed and etched. That is,
The oxide film 12 served as an etching mask. The etching rate at this time is 100 nm at a wafer temperature of 70 ° C.
/ min. After that, etching is performed to a depth reaching the AlGaAs layer 11a, that is, until the GaAs layer 11b has a fine line structure, the irradiation of the etching gas is stopped, the inside of the etching chamber 23 is evacuated, and the wafer is again MBE. It was transported to the chamber 22.

Next, the wafer transferred to the MBE chamber 22 was heated to 500 ° C. in vacuum or under an As atmosphere and held for several minutes. Then, the oxide film 12 on the surface of the wafer was completely removed as shown in FIG. After that, when the desired buried growth layer (for example, AlGaAs layer) 15 is continuously formed in the MBE chamber 22, as shown in FIG.
An embedded structure could be formed as shown in (e).
It was also confirmed that an insulating film, a metal film, etc. could be formed.

The quality of the buried structure formed as described above was evaluated by the photoluminescence method. Here, evaluation was performed by comparing with a sample in which a GaAs / AlGaAs quantum well structure was etched and processed into a stripe shape.

In the quantum well stripe just etched, the quantum well is exposed, and in this case, the recombination level is formed on the exposed surface. As a result, the excited carriers recombine at this exposed surface, so that their emission intensity decreases as the stripe width decreases. On the other hand, when the quantum well stripe is filled with a wide gap material, it is possible to suppress the decrease in emission intensity due to the decrease in stripe width. Therefore, the quality of the buried structure can be evaluated by observing the degree of decrease in photoluminescence intensity as the stripe width decreases. The results are shown in FIG.

As shown in FIG. 4, in the quantum well stripe manufactured according to the present embodiment, the decrease in photoluminescence intensity in the region where the stripe width is very small is greatly improved as compared with the case where no embedding is performed. ing. It is also clear that the stripes are greatly improved as compared with the case where the stripes are formed in the [110] direction.

As described above, according to this embodiment, the stripe forming direction is the [1 bar 10] direction.
The sidewalls of the stripes formed by etching had a gentle inclination, and good regrown crystals could be formed on the sidewalls.

Next, a second embodiment of the present invention will be described. Here, the description of the same steps as those in the first embodiment will be omitted, and only the growth of the buried growth layer will be described below.

The MBE chamber 22 used in this embodiment is provided with a substrate heater block 52 for heating the wafer 51 and a plurality of knudsen cells 53 directed to the wafer 51, as shown in FIG. Has been. A shutter 54 is provided in each of the Knudsen cells 53. Usually, different raw materials are loaded in the plurality of knudsen cells 53. However, in this example, the two Knudsen cells 53 were loaded with As and used as a group V element source cell. The other Knudsen cell 53 was loaded with Ga, Al, and a dopant, respectively.

The two knudsen cells 53 loaded with As are arranged at different angles with respect to the wafer 51 (preferably, positions symmetrical with respect to the stripe), and like the inverted mesas. Even if the sidewalls of the stripe are steeply inclined, the shadow of the molecular beam is not generated on the sidewall of the stripe. As a result, in this example, good regrowth crystals could be obtained regardless of the stripe forming direction, even if the stripe was formed in a direction other than the [1 bar 10] direction.

In the above embodiment, an example in which the oxide film is patterned by an electron beam to be used as an etching mask has been described. However, the method is not limited to this, and any method capable of avoiding contamination of the surface of the material to be processed can be used. Good.

[0034]

According to the present invention, in the vacuum integrated process,
In the method of forming the fine embedded structure for embedding the stripes, the stripes are formed in the [1 bar 10] direction, so that high-quality regrown crystals can always be obtained.

Further, according to the present invention, the group V element is supplied from a plurality of different directions when the stripes are embedded in the vacuum consistent process, so that high quality is always achieved regardless of the stripe formation direction. Regrown crystals can be obtained.

[Brief description of drawings]

FIG. 1 is a process drawing of a first embodiment of the present invention.

FIG. 2 is a schematic view of an apparatus used in the method for forming the fine embedded structure of the compound semiconductor of FIG.

FIG. 3 is an enlarged schematic view of an etching chamber 23 of the apparatus shown in FIG.

FIG. 4 is a graph showing the relationship between the stripe width of the quantum well stripe formed by the method of FIG. 1 and the photoluminescence intensity.

FIG. 5: MB of the device used in the second embodiment of the present invention
FIG. 9 is a layout view of source cells provided in an E chamber.

[Explanation of symbols]

 10 GaAs (001) substrate 11 Compound semiconductor layer 11a AlGaAs layer 11b GaAs layer 11c AlGaAs layer 12 Photo-oxidized film 13 Etching gas 14 Electron beam 15 Embedded growth layer 21 Introduction chamber 22 MBE chamber 23 Etching chamber 231 Gas introduction control system 232 Electron Beam generator 233 Manipulator 24 Surface treatment chamber 241 Variable leak valve 242 Quartz window 25 Auger analysis chamber 26 Gate valve 27 Passage 28 Sample exchange chamber 29 Sample heating chamber 30 Magnet feedthrough 31 Sample 32 Holder 33 Heater 34 Gas nozzle 51 Wafer 52 Substrate heater Block 53 Knudsencell 54 Shutter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Lopez Lopez Maximo 7-3 Higashiarai Tsukuba, Ibaraki Prefecture President Tsukuba 304

Claims (3)

[Claims] 1. A first step of forming a stripe on a compound semiconductor layer, and a second step of growing a new compound semiconductor layer by an MBE method to embed the stripe.
In the method for forming a fine embedded structure of a compound semiconductor which is continuously performed under a high vacuum, the direction of forming a stripe in the first step is [1 bar 10] direction. Method of forming embedded structure. 2. A first step of forming a stripe on a compound semiconductor layer, and a second step of growing a new compound semiconductor layer by an MBE method to fill the stripe.
In the method of forming a fine embedded structure of a compound semiconductor, which is continuously performed in a high vacuum, the second step is performed using a plurality of group V sources arranged at different angles with respect to the stripe. And a method for forming a finely embedded structure of a compound semiconductor. 3. The method for forming a fine embedded structure of a compound semiconductor according to claim 1, wherein the first step is performed using a gas containing at least one of chlorine and bromine. .