JPH03203226A - Semiconductor thin-film forming method - Google Patents

Abstract

PURPOSE:To prevent contamination of the surface of a semiconductor thin film due to impurity atoms by forming the semiconductor thin film, forming a specific protection film on the surface, and then carrying it to a second growth chamber. CONSTITUTION:After forming an n-type III-V compound semiconductor thin film for example as a conductive type by the MBE method in a first growth chamber 2, a protection film consisting of a V element constituting this n-type III-V compound semiconductor thin film is formed on the surface, and then it is carried to a second growth chamber 3. Then, a III-V compound semiconductor multilayer structure with a pn junction is formed within the second growth chamber 3 by the MBE method. In that case, by increasing the temperature of the substrate, only the protection film consisting of V elements evaporates along with impurity atoms being adhered during transportation due to high evaporation pressure of the V element and omitted, thus keeping the surface of the n-type III-V compound semiconductor thin film to be clean.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a semiconductor thin film, and more specifically, when manufacturing a light emitting element, a bipolar transistor, etc., a pn junction is formed using a molecular beam epitaxial growth method. The present invention relates to a method for forming a semiconductor thin film in which a multilayered structure of a group II-V compound semiconductor and a multilayered structure of a group II-VI compound semiconductor are formed without contaminating the pn junction interface.

[Prior art] A semiconductor thin film forming method in which a semiconductor multilayer structure having a pn junction is formed by laminating n-type and p-type semiconductor thin films using the molecular beam epitaxial method (hereinafter referred to as MBE method). The following methods are conventionally known.

That is, FIG. 4 is an explanatory diagram of a schematic configuration of a molecular beam epitaxial apparatus (hereinafter referred to as an MBE apparatus) equipped with one growth chamber maintained in an ultra-high vacuum (Nikkei Electronics, January 17, 1983, Pb0 , by NaoT, Tsan
g).

In the figure, 51 is a growth chamber for performing the MBE method;
2 is a substrate holder, 53 is a semiconductor substrate, 54 is a cell containing ■ a raw material (e.g. Ga, AI), 55 is a cell containing a V raw material (e.g. As), 56 is a cell containing a p-type impurity (e.g. Be) a cell in which a source is housed; 57 is a cell in which an n-type impurity (for example, Si) source is housed; 54a;
57a is a cell shutter. Using such an MBE apparatus, in the same growth chamber 51 maintained at an ultra-high vacuum,
For example, an n-type compound semiconductor thin film is first formed on the semiconductor substrate 53, and then a p-type compound semiconductor fill) II is formed by supplying raw materials and impurities from independent cells, evaporating them, and irradiating them. Thus, a compound semiconductor multilayer structure having a pn junction is formed.

In this case, switching from an n-type compound semiconductor thin film to an n-type compound semiconductor thin film is achieved by closing the cell shutter 57a that was provided immediately before the n-type impurity cell 57 and closing the cell shutter 57a that was open until then. This is done by opening the shutter 56a. When the cell shutters 56a and 57a are open, heated and evaporated n-type or p-type
Type impurity atoms are supplied and incorporated into the thin film. At this time, not all of the evaporated impurity atoms are incorporated into the Wi film, but most of the n-type or p-type impurity atoms adhere to the substrate holder 52, the inner wall of the growth chamber 51, and the like.

On the other hand, No. 50 is a schematic configuration explanatory diagram showing an example of an MBE device modularized as a vacuum-through process (Molecular Beam Epitaxy Technology, Author: Kiyoshi Takahashi, Industrial Research Association, 19
84, Pb0). As shown in the figure, the MBE apparatus is modularized into a sample preparation chamber 71, a growth chamber 72 with a transfer mechanism, an analysis chamber 73 with a transfer mechanism, a transfer chamber 74 with a transfer mechanism, etc. These preparation chambers 71, growth chamber 72,
The analysis chamber 73 is connected to the transfer chamber 74 via a gate valve 75, and is evacuated to almost the same level of ultra-high vacuum. Therefore, by adding a growth chamber, it is possible to separate the growth chamber into a growth chamber for forming an n-type compound semiconductor thin film and a growth chamber for forming an n-type compound semiconductor thin film. As a result, an n-type compound semiconductor thin film, for example, is formed in one growth chamber by the MBE method, and this is generally transported into the other growth chamber while being kept in a vacuum, and then the MBE method is performed in this growth chamber. It has become possible to form a compound semiconductor multilayer structure having a pn junction by forming an n-type compound semiconductor thin film.

[Problem to be solved by the invention]

- However, in the former conventional technology mentioned above, since n-type and p-type impurities are used in the same growth chamber in the MBE method, contamination by the impurities deposited on the substrate holder, the growth chamber wall, etc. This has become a problem. That is,
For example, when forming an n-type compound semiconductor thin film, when the temperature of the substrate holder is raised, p
Type impurities are re-evaporated and incorporated into the n-type compound semiconductor thin film. Therefore, the electrical properties of the thin film deteriorate. That is, when forming a compound semiconductor multilayer structure having a pn junction, there is a problem of mutual contamination due to n-type and p-type impurities.

On the other hand, according to the latter conventional technology mentioned above, it is possible to separate the growth chamber using n-type impurities from the growth chamber using p-type impurities, so the degree of mutual contamination mentioned above can be greatly reduced. reduced. However, since the thin film growth is interrupted at the pn junction interface, which determines the quality of the device characteristics, there is a problem that this pn junction interface is easily contaminated and the device characteristics deteriorate. That is, when an n-type compound semiconductor thin film formed in one growth chamber is transferred to the other growth chamber for forming a p-type compound semiconductor thin film, the surface of the n-type compound semiconductor 'Ia film is in vacuum. There is a problem in that the growth chamber is contaminated by residual gas or impurity atoms (or molecules) caused by degassing from the inner wall of the growth chamber.

The present invention was made to solve the above-mentioned problems, and uses a molecular beam epitaxial growth method to produce a ■-■ group compound semiconductor multilayer structure having a p-n junction, and a II-VI compound semiconductor having a p-n junction. An object of the present invention is to provide a method for forming a semiconductor thin film that can form a group compound semiconductor multilayer structure without causing contamination at the pn junction interface.

[Means for Solving the Problems] In order to achieve the above-mentioned object, a first method for forming a semiconductor thin film according to the present invention includes forming a first semiconductor thin film on a semiconductor substrate by molecular beam epitaxial growth in a first growth chamber. A compound semiconductor thin film having a conductivity type of By forming a compound semiconductor thin film having a second conductivity type opposite to the first conductivity type by a line epitaxial growth method, p
In a semiconductor thin film forming method for forming a compound semiconductor multilayer structure having an n-junction, a -V group compound semiconductor thin film having a first conductivity type is formed on a semiconductor substrate in the first growth chamber. Immediately thereafter, by stopping the supply of the group II elements and impurity elements constituting the ■-V group compound semiconductor thin film, and supplying only the group ■ elements, the above-mentioned ■-V group compound semiconductor thin film is (2) Forming a protective film made of a group element, then transporting the obtained product into the second growth chamber, and increasing the substrate temperature in the second growth chamber to remove only the protective film. After that, the above ■-V
By forming a ■■ group compound semiconductor thin film having a second conductivity type opposite to the first on the surface of the group compound semiconductor thin film, a ■■ group compound semiconductor multilayer structure having a pn junction is formed. It is characterized by what it did.

Further, a second semiconductor Wi film type forming method is a semiconductor thin film forming method, in which a II-VI group compound semiconductor thin film having a first conductivity type is formed on the semiconductor substrate in the first growth chamber, Immediately after that, by stopping the supply of the Group II elements and impurity elements constituting the II-VI Group compound semiconductor thin film and supplying only the Group ■ elements, the
■ Group compound semiconductor film thin film I1 consisting of the above Group ■ elements
After forming a film, transporting the obtained product into the second growth chamber, and removing only the protective film by increasing the substrate temperature in the second growth chamber, VI
A II-VI group compound semiconductor multilayer structure having a pn junction is formed by forming a ■-■-■ compound semiconductor thin film having a second conductivity type opposite to the first on the surface of the group compound semiconductor thin film. It is characterized by the fact that it is made to do so.

[For production]

In the first method for forming a semiconductor thin film configured as described above, after forming, for example, an n-type conductivity type ■-V group compound semiconductor thin film by the MBE method in the first growth chamber, this N-type conversion 10- Since a protective film made of group V elements constituting the group V compound semiconductor thin film was formed before being transported to the second growth chamber, this semiconductor thin film was exposed to vacuum, which could be a source of contamination during transport. It can prevent contamination by impurity atoms (or molecules) such as residual gas atoms (or molecules) inside.

When forming a ■-■ group compound semiconductor multilayer structure having a pn junction in the second growth chamber by the MBE method, the substrate temperature is raised to increase the vapor pressure of the group V elements due to the high vapor pressure of the group Only the protective film consisting of this evaporates and leaves along with the impurity atoms (or molecules) attached to it during transportation.

As a result, the surface of the n-type -V group compound semiconductor thin film is maintained as a clean, uncontaminated surface, and the p-type group -
By forming a thin film of a group compound semiconductor, it is possible to avoid contamination at the p-n junction interface (with a p-n junction).
A group V compound semiconductor multilayer structure can be formed.

Similarly, in the second semiconductor thin film forming method, for example, the surface of the n-type 111-VI group compound semiconductor thin film formed in the first growth chamber is made of group Ⅰ elements constituting this semiconductor thin film. The protective film protects it from contamination by impurity atoms (or molecules) during transport. Then, pn is grown by MBE method in the second growth chamber.
When forming a ■-■ group compound semiconductor multilayer structure with junctions, by increasing the substrate temperature, a high vapor pressure ■
Only the protective film consisting of the group is removed together with the impurity atoms (or molecules) attached to it. By forming a p-type ■-■ group compound semiconductor thin film thereon, a II-VI
A group compound semiconductor multilayer structure can be formed.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a diagram for explaining the semiconductor thin film forming method according to the present invention, and FIG. 2 is a schematic diagram showing an example of an MBE apparatus for carrying out the semiconductor thin film forming method according to the present invention.

In FIG. 2, 1 shown in the figure is a sample preparation chamber, 22 is a first growth chamber for performing the MBE method, 2a is a gate valve of the first growth chamber 2, and 3 is a second growth chamber for performing the MBE method.
3a is a gate valve of the second growth chamber 3, and 4 is a transfer chamber with a transfer mechanism (+I feed path). The first growth chamber 2 and the second growth chamber 3 each have a gate valve 2a,
The growth chambers 2.3 and 4 are connected to each other by a transfer chamber 4 via 3a, and the interiors of both growth chambers 2.3 and transfer chamber 4 are maintained at approximately the same level of vacuum. Note that the configuration of the two grand chambers 2.3 is the same as the conventional one.

Next, the first semiconductor thin film forming method of the present invention, which is carried out using the MBE apparatus as described above, will be explained below with reference to FIG.

■ First, the first growth chamber 2 (background vacuum degree 5
XIO-th TOrr, ), an n-type GaAs substrate 5 (carrier density n = I x 10 ”cm-3)
An n-type GaAs thin film 6 was formed on top [Figure 1(a)]
. Note that Si was used as the n-type impurity, and the carrier density was set to n-I x 10'' cm-3.

- Immediately after this formation is completed, the cell shutters of the Ga raw material cell and the Si raw material cell are closed, and As atoms (or molecules) are supplied with only the cell shutter of the As raw material cell open,
Turn off the substrate heating heater power and raise the substrate temperature to 600°C.
The temperature is lowered from to room temperature, and As is deposited on the n-type GaAsfi film 6.
A bond 7 was formed by atoms (or molecules) [Fig. 1(b)]. After that, the cell shutter of the As raw material cell is closed.

■ Open the gate valve 2a and transfer the obtained material to the transfer chamber 4.
The sample is transported into the second growth chamber 3 through the tube. During this transportation,
Impurity atoms (or molecules) that cause contamination due to residual impurity gas, etc., indicated by black circles in FIG. 1 (C1), adhere to the surface of the protective film 7. FIG. 1 (C2) is a diagram schematically showing the situation of the outermost surface in this case, and A
The protective film 7 made of , s atoms (or molecules) is not dense, but if there is a certain amount of deposits, it will combine with impurity atoms (or molecules) and n-type GaAsF! Contact with the surface of the membrane 6 can be prevented.

(2) After the transfer, the protective film 347 is applied to the surface of the n-type CaAs thin film 6 on the substrate holder in the second growth chamber 3 (background vacuum level is 7×10-I Torr). The molded GaAs substrate 5 is set, and the gate valve 3a is closed. After that, the substrate temperature was increased from room temperature to 400°C.
By raising the temperature to about .degree. C. and waiting, only the protective film 7 made of As atoms (or molecules) was removed.

In this case, impurity atoms (or molecules) due to residual impurity gas etc. adhering to the protective film 7 can also be removed at the same time [FIG. 1(d)].

(2) After raising the substrate temperature to 600°C, p-type Ga is formed on the surface of the n-type GaAs thin film 6 from which the protective film 7 has been removed using Be as a p-type impurity.

AIo, 5AsF4 film 8 (carrier density n=lX108
cm-3), a ■-■ group compound semiconductor multilayer structure having a pn junction was formed [Figure 1 (
e)].

Thereafter, a light emitting diode (LED) was manufactured using the one obtained by the above method, and an LED was manufactured using the one that was transported and formed a p-n junction without forming a protective film made of As element. The luminescence intensity was compared with respect to the current value.

The results are shown in Figure 3. From the same figure, it can be seen that according to the method according to the present invention, an LED with a large emission intensity can be obtained for the same current value. In other words, in LP and D manufactured by transport without forming an insulation film, there is an interface state due to impurity atoms such as the above-mentioned residual impurity gas in the formed pn junction, and as a result, the current A part of it will flow through this interface state. Therefore, the current flowing through such interface states does not contribute to light emission, so even if the same current value flows, the light emission intensity becomes low.

On the other hand, in the LED manufactured based on the method according to the present invention, a clean pn junction interface can be obtained, so that the light emission intensity can be increased compared to the conventional method for the same current value.

In the above embodiment, n-type ■-V is grown in the first growth chamber 2.
A group compound semiconductor El film is formed, and p is grown in the second growth chamber 3.
However, conversely, a p-type ■-V group compound semiconductor thin film was formed in the first growth chamber 2 and an n-type ■-V group compound semiconductor thin film in the second growth chamber 3. It may also be formed.

In the above embodiment, ■-V having a GaAs-based pn junction
Although the method for forming a group compound semiconductor multilayer structure has been described, the method according to the present invention is not limited thereto. A ■-■ group compound semiconductor multilayer structure with a pn junction of the system, or a ! The present invention can also be applied to the formation of a -V group compound semiconductor multilayer structure having a GaSb-based or InSb-based pn junction, in which a protective film made of the sb element is formed as a film.

In addition, in the same manner as in the method for forming such a ■-■ group compound semiconductor multilayer structure, a ■-■ group compound semiconductor multilayer structure having a ZnS-based, Zn5e-based, or ZnTe-based pn junction can be prepared without contamination at the p-n junction interface. can be formed without being

(Effects of the Invention) As explained above, in the first semiconductor thin film forming method according to the present invention, a ■-V group compound semiconductor thin film of, for example, n-type conductivity is formed in the first growth chamber by the MBE method. After that, a protective film made of the group II elements constituting the ■-■ group compound semiconductor thin film was formed on the surface, and then this was transported to the second growth chamber, so that the surface of the semiconductor thin film was The protective film can prevent contamination by impurity atoms (or molecules) due to residual impurity gas, etc.Furthermore, after transportation, the M
When forming a multilayer structure of a ■■ group compound semiconductor having a pn junction by the BE method, only the above-mentioned protective film was removed together with the above-mentioned impurity atoms (or molecules) attached to it by increasing the substrate temperature. After that, p-type ■−■
Since a thin film of a group compound semiconductor is formed, it is possible to form a multilayer structure of a group compound semiconductor having a clean pn junction interface without contamination.

Further, in the second semiconductor thin film forming method according to the present invention, after forming a II-VI group compound semiconductor thin film of, for example, n-type conductivity in the first growth chamber, this II-VI group compound semiconductor thin film is deposited on the surface of the thin film. After forming a protective film made of group Ⅰ elements constituting the semiconductor thin film, this is transported to the second growth chamber.7=18= Therefore, in the same way as the above method, a clean pn junction without contamination can be formed. A multilayer structure of a ■-■ group compound semiconductor having an interface can be formed.

As a result, the method for forming a semiconductor thin film according to the present invention can improve the characteristics of a light emitting device, bipolar transistor, etc. compared to the conventional method, and can contribute to improving the device characteristics.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the method for forming a semiconductor thin film according to the present invention, FIG. 2 is a schematic configuration explanatory diagram showing an example of an MBE apparatus for carrying out the method according to the present invention, and FIG. 3 is a diagram for explaining the structure of the first semiconductor film. FIGS. 4 and 5 are diagrams showing the emission intensity characteristics of an LED manufactured based on the thin film forming method, and are diagrams for explaining the conventional method, and FIG. FIG. 5 is a schematic diagram illustrating an example of a modularized MBE device. 2. The 19th Kaicho room where the MBE method is carried out, 3- The second growth chamber where the MBE method is carried out, 9 3a--Gate valve, 4-=-Transfer chamber, n-type Cya
As substrate, 6-n-type GaA, s thin film, protective film made of As atoms, p-type Gao, 7Alo, +As thin film.

Claims (2)

[Claims] (1) A compound semiconductor thin film having a first conductivity type is formed on a semiconductor substrate by molecular beam epitaxial growth in a first growth chamber, and this is kept in a vacuum. A pn junction is formed by transporting the compound semiconductor thin film into a second growth chamber independent of each other, and forming a compound semiconductor thin film having a second conductivity type opposite to the first one by molecular beam epitaxial growth in the second growth chamber. In the semiconductor thin film forming method for forming a compound semiconductor multilayer structure having By stopping the supply of the Group III elements and impurity elements constituting the Group III-V compound semiconductor thin film and supplying only the Group V elements, the Group V element is formed on the Group III-V compound semiconductor thin film. After forming a protective film, transporting the obtained product into the second growth chamber, and removing only the protective film by increasing the substrate temperature in the second growth chamber, the third - A III-V compound semiconductor multilayer structure having a pn junction is formed by forming a III-V compound semiconductor thin film having a second conductivity type opposite to the first on the surface of the V group compound semiconductor thin film. A method for forming a semiconductor thin film, characterized in that: (2) A compound semiconductor thin film having a first conductivity type is formed on a semiconductor substrate by molecular beam epitaxial growth in a first growth chamber, and the first growth chamber is kept in a vacuum state. A pn junction is formed by transporting the compound semiconductor thin film into a second growth chamber independent of each other, and forming a compound semiconductor thin film having a second conductivity type opposite to the first one by molecular beam epitaxial growth in the second growth chamber. In a semiconductor thin film forming method for forming a compound semiconductor multilayer structure having a first conductivity type, a group II-VI compound semiconductor thin film having a first conductivity type is formed on a semiconductor substrate in the first growth chamber, and immediately thereafter By stopping the supply of the Group II elements and impurity elements constituting the Group II-VI compound semiconductor thin film and supplying only the Group VI elements, the Group VI element is formed on the Group II-VI compound semiconductor thin film. A protective film is formed, and then the obtained product is transported into the second growth chamber, and only the protective film is removed by increasing the substrate temperature in the second growth chamber, and then the II - Forming a II-VI compound semiconductor multilayer structure having a pn junction by forming a II-VI compound semiconductor thin film having a second conductivity type opposite to the first on the surface of the VI group compound semiconductor thin film. A method for forming a semiconductor thin film, characterized in that: