JPH01303770A - Manufacture of superconductive base transistor - Google Patents

Abstract

PURPOSE:To prevent an element from deteriorating in a characteristic by a method wherein a superconductive base region of an oxide superconductor is so formed as to bring only a compositional element of the oxide superconductor such as a group IIIA, a lanthanoid group, a group IIIB or a group VB elements into contact with a semiconductor interface through a growth method that the compositional element concerned is made to grow by an atomic layer at a time. CONSTITUTION:When a superconductive base region of an oxide is formed, each compositional element of the superconductive thin film is made to grow by an atomic layer at a time to form the oxide superconductive thin film, and at the start and the end of this process, one of the elements of the thin film components such as group IIIB, a lanthanoid group, a group IIIA and a group VA elements is formed into an atomic layer which constitutes a junction face that is in contact with a semiconductor face. Therefore, the superconductive base region can be formed without oxidizing the surface of the semiconductor. Moreover, this thin film manufacturing method is the application of an atomic layer control epitaxial growth method and a very soft way to make a thin film grow as compared with a sputtering method, so that the surface of the semiconductor is protected against damage. By these processes, a junction interface between a semiconductor and an oxide superconductor excellent in quality and practcality can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a superconducting base transistor having a structure in which an oxide superconductor is used as a base region and a semiconductor is used in a collector region and an emitter region.

[Prior art] Superconductor bases, which have been proposed for conventionally developed superconductor-based transistors and are mainly made of metal materials such as Nb (Ob)-based materials, have a low critical temperature (Tc) of superconductors, so liquid helium cannot be used. Development has been progressing with the assumption that it will operate at a temperature of (4, near K).

On the other hand, as is well known, research and development of superconducting materials, particularly aimed at raising the critical temperature, has recently made revolutionary progress, and in 1986 Bednorz (J.

G, Bednorz) and Müller (K, A, Mijl)
Starting with the discovery of high-temperature superconductors by Ier et al.
In 988, the critical temperature of oxides containing TD elements was 12
It became possible to stably obtain more than 0. The circumstances during this period are outlined in the following publication.

Superconductivity Engineering (Revised Edition); Written by IEEJ Correspondence Education Society; 27~
34 pages, published May 31, 1988.

The high-temperature oxide superconductor described above has an energy gap Eg that increases in proportion to Tc, which is several tens of meV or more, a coherence length as small as Inn, and a critical current that has a large value of ~1o7A/c-. Considering the following points:

That is, the greatest advantage is that it can operate satisfactorily at the temperature of liquid nitrogen without using expensive liquid helium, which has a high Tc (critical temperature). Furthermore, since excited carriers caused by impurities in semiconductors do not freeze at liquid nitrogen temperatures, semiconductors can be used as superconducting-based devices in the same way as semiconductor devices at room temperature.
It can be used for constituent parts such as the emitter region and collector region of a transistor.

In this case, a thin film of an oxide superconductor is formed as a base region on a collector region made of semiconductor, and then a semiconductor is deposited on top of this thin film to form an emitter region and a superconducting base transistor. are doing. A widely used method for forming this thin film is the sputtering method using a sputtering device, in which an oxide superconductor placed in a sputtering device is sputtered and the sputtered particles are deposited on the semiconductor surface to form an oxide thin film with the same composition as the bulk. It is something that forms.

[Problems to be Solved by the Invention] However, as mentioned above, the conventional method for forming thin films of superconducting oxides is mainly by sputtering; There is a problem in that damage is formed on the semiconductor surface. Moreover, the surface of the semiconductor is oxidized by oxygen in the atmosphere during sputtering, and this oxide film forms interface states, resulting in deterioration of device characteristics. This has made it difficult to manufacture composite elements of superconductors and semiconductors that take full advantage of the advantages of high-temperature superconductors, and it has not been possible to obtain anything that is technically satisfactory.

This invention provides a method for manufacturing superconducting base transistors that eliminates the problems such as damage and oxidation at the semiconductor interface described above and realizes a junction interface between a semiconductor and an oxide superconductor in a highly practical and good condition. The purpose is to

[Means for Solving the Problems] A method for manufacturing a superconducting base transistor according to the present invention includes a superconducting base transistor in which a base region located between an emitter region and a collector region composed of a semiconductor is composed of an oxide superconductor. When forming the region, first, one atomic layer of an element corresponding to one of the group 3A, lanthanide, group 3B, and group 5B elements of the compositional elements of the oxide superconductor is deposited on the surface of the collector semiconductor. Then, on this monoatomic layer, monoatomic layers of the constituent elements of the oxide superconductor are alternately deposited in a predetermined order for each constituent element to form an oxide superconductor layer of a predetermined thickness, Further, after depositing a single atomic layer of the appropriate element mentioned above, an emitter semiconductor layer is grown and deposited to form the basic element of the superconducting base transistor.

That is, by the method of growing one atomic layer at a time as described above, only the 3A group, lanthanoid group, 3B group, and 5B group elements among the constituent elements of the oxide superconductor are brought into contact with the semiconductor interface, and the oxide superconductor is grown. The above-mentioned problem has been solved by the method of forming the base region.

[Function] In this invention, especially when forming an oxide superconducting base region, each constituent element of this superconducting thin film is grown one atomic layer at a time to form an oxide superconducting thin film. Finally, one atomic layer of one element from the 3B group, lanthanoid group, 3A group, and 5A group, which are the constituent components of this thin film, is formed to form a bonding surface that contacts the semiconductor surface, so that the semiconductor surface is not oxidized. A superconducting base region is formed in this state. Furthermore, this thin film manufacturing method
This is an application of atomic layer controlled epitaxial growth, which is an extremely soft thin film growth method compared to sputtering, so it does not damage the semiconductor surface.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Example 1; FIG. 1 is a schematic explanatory diagram of an epitaxial growth apparatus for implementing an example of the present invention. In the figure, 1 is a growth chamber, 2 is a gate valve, and 3 is an exhaust system for evacuating the growth chamber 1 by opening the gate valve 2. 4 is a semiconductor substrate on which a superconducting base transistor is to be formed, and 5 is a susceptor that includes a heating system for the substrate 4. 6 is growth chamber 1
7 is a valve attached to the nozzle 6, and 8 contains constituent elements of the oxide superconductor to be grown on the substrate 4. The source gas is ejected from the nozzle 6 into the growth chamber 1 via the valve 7 . Note that the source gas 8 is introduced into the growth chamber 1 from a plurality of source gas cylinders (not shown) via a switching valve.

FIG. 2 is a schematic diagram illustrating the structure of a superconducting base transistor formed using the epitaxial growth apparatus shown in the embodiment of FIG. 1. The basic structure of this transistor is a three-layer structure consisting of a collector region 3L, a superconducting base region 32, and an emitter region 33. A Schottky contact is established between the collector region 31 made of a semiconductor and the emitter region 33, which is made of a superconducting oxide superconductor. A base region 32 is formed. And the collector area 31
A collector electrode 34 is formed in the region, and an emitter electrode 35 is formed in the emitter region 33 by ohmic contact.'
There is C. Further, a base electrode 3 is provided in the superconducting base region 32.
G is connected and each is connected to an electrode terminal (white circle mark). Note that in the transistor, the collector region 3
1 and the superconducting base head 32, and the superconducting base region 32 and the emitter region 33 do not need to be in ohmic contact. any one of them
The two elements are joined by a Schottky contact.

Hereinafter, with reference to FIGS. 1 and 2, the oxide superconductor used for the superconducting base region 32 is YBa2Cu07-J.
The manufacturing method in the case of (δ×1) will be explained.

During this manufacturing process, the collector electrode 34 and the collector region 31
, the bonding and forming methods of the emitter electrode 35 and the emitter region 33 and the base electrode 36 and the superconducting base region 32 are the same as those in the conventional technology, so detailed explanations will be omitted. I will explain about it.

First, a semiconductor substrate 4 (corresponding to the collector region 31 in FIG. 2) is placed on the susceptor 5, and then the growth chamber 1
30 while opening gate valve 2 and exhausting with exhaust system 3.
Heat and maintain at a temperature range of 0 to 700°C. Next, after closing the gate valve 2, a source gas 8 containing Y (yttrium) is introduced into the growth chamber 1 through the nozzle 6 by opening the valve 7, so that a monolayer of the gas containing Y is formed on the surface of the substrate 1. After depositing one atomic layer of metallic yttrium (Y) so that only yttrium (Y) is adsorbed, the valve 7 is closed, the gate valve 2 is opened, and the growth chamber 1 is evacuated by the exhaust system 3.

Subsequently, 27- containing each compositional element of YBu CuO
The δ source gas 8 is sequentially introduced into the growth chamber 1 to form a single atomic layer of each constituent element, and then exhausted, but since the valve operation is the same as in the case of Y, the explanation of the procedure will be simplified below. Only the main points of the procedure will be described.

After forming a monoatomic layer of Y, a source gas 8 containing Cu and a gas 8 containing oxygen (for example, argon gas, etc.) are introduced to form a Cu-0 plain consisting of a single atomic pair of Cu and O, and then exhausted. do.

Subsequently, a source gas 8 containing Ba is introduced to form a single atomic layer of Ba, and then exhausted.

Next, a source gas 8 containing Cu and a gas 8 containing oxygen are introduced to form a Cu-0 plane, and then exhausted.

Further, a source gas 8 containing Y is introduced to form a single atomic layer of Y, and then exhausted.

One molecular layer of YBa Cu O is formed by the above-described series of steps for forming each atomic layer of Y--CuO--Ba--CuO--Y.

Note that FIG. 3 is a schematic diagram showing how monoatomic layers of each compositional element of YBa2Cu307-δ are sequentially formed on the substrate 4 (collector region 31 in FIG. 2) by the above-described procedure. In the figure, 4 is a substrate, the O symbol represents a Y atom, the X symbol represents a Cu-0 atom pair, and Δ represents a Ba atom.

By repeating this series of steps, YBa2Cu
A monomolecular layer of O is laminated to a predetermined thickness to form a YBa2Cu30 thin film constituting the superconducting base region 31.

In conclusion, the oxide superconducting thin film forming the superconducting base region 32 is completed by leaving a surface formed by a Y monoatomic layer on the surface using the same procedure as described above.

That is, the basic element portion of the superconducting base transistor is completed by subsequently depositing a semiconductor on the seven surfaces of the final stage by epitaxial growth to form an emitter region 33.

The embodiments of the manufacturing method of the present invention have been described above, and the source gases used in these embodiments include, for example, the following gases containing Y. That is, Y(C1l
-CH) :) Limethylcyclopentagenyl yttrium, Y-((H2C)3cOCO(CH3)3
) yttrium nidipivaloylmethane, yttrium acetylacetone, Y-(thd): yttrium tetramethylhebutandionate, and the like. Although detailed description is omitted, source gases having the same ligands as in the case of Y are also applied to gases containing Ba and Cu.

Embodiment 2; FIG. 4 is a schematic explanatory diagram of an oxide superconducting thin film growth apparatus for carrying out another embodiment of the present invention. In the figure, 11 is a growth chamber, 12 is a gate valve, 13 is an exhaust system,
14 is a semiconductor substrate, 15 is a susceptor for holding and heating the substrate 14, 1B, 17.18 are Y and Ba, respectively.
, are Knudsen cells (also called K cells) for evaporating Cu and injecting each atomic beam in the direction of the substrate 14, and 22, 23, and 24 are cell 1G, cell 17. This is the shutter for the atomic beam from the cell 18. 19 is a nozzle for introducing gas, 2o is a valve, and 21 is a gas, which in this case is mainly oxygen gas.

Hereinafter, as in Example 2, YBa Cu O super 237-
The case of forming a δ conductive thin film will be explained. In this example, the formation of a monoatomic layer of each compositional element other than oxygen (0) in the superconductor is performed by vapor deposition on the substrate 14 using an atomic beam (in the case of oxygen gas, adsorption of oxygen atoms by a molecular beam). The operation of evacuation of the growth chamber 11 using the gate valve 12 and the evacuation system 13 only needs to be performed after placing the substrate 14 on the susceptor 15, and all deposition steps are performed in a vacuum state while evacuation is performed with the gate valve 12 open. be exposed.

Hereinafter, only the procedure for forming the superconducting thin film of the superconducting base region 32 of the superconducting base transistor (see FIG. 2) according to the embodiment shown in FIG. 4 will be described. The other methods for forming the superconducting base transistor are the same as the method shown in Example 1, and will therefore be omitted.

First, after installing the substrate 14 on the susceptor 15,
Heating and holding at a predetermined temperature in the range of ~700°C.

First, the shutter 22 is opened, and the surface of the substrate 14 is irradiated with the Y atomic beam emitted from the cell 16 for a predetermined period of time to deposit one atomic layer of Y, and then the shutter 22 is closed. During this time, the shutters 23, 24 and the valve 20 remain closed.

Next, the shutter 24 is opened, and the surface of the substrate 14 is irradiated with the Cu atomic beam emitted from the cell 18 for a predetermined time to deposit one atomic layer of Cu on one atomic layer of Y, and then the shutter 24 is opened. close. Subsequently, the valve 20 is opened and oxygen gas 21 is supplied to the surface of the substrate 14 through the nozzle 19 to form a Cu-0 plane with Cu-0 atomic pairs, and then the valve 20 is closed. In this case, to form the Cu -0 plane, oxygen gas 20 may be introduced into the substrate simultaneously with the emission of the Cu atomic beam, or may be introduced subsequently as described above.

Next, the shutter 23 is opened for a predetermined period of time, and the Ba atomic beam from the Ba cell 17 is irradiated onto the substrate, and Cu-0
After depositing one atomic layer of Ba on the plane, the shutter 2
Close 3.

Subsequently, in the subsequent steps, a Cu-0 plane is deposited on a single atomic layer of Ba in the same manner as the above-mentioned deposition process procedure for each compositional element, and then a Y
Deposit one atomic layer of .

The above exemplary deposition procedure forms a monolayer of YBa2Cu30. By repeating this series of steps 7-δ, YBa Cu O molecule 2
The 37-δ layer is deposited a predetermined number of times to form a thin film of superconducting base region 32 (see FIG. 2) of this oxide superconductor.

FIG. 5 is a schematic diagram of the potential structure of the superconducting base transistor shown in FIG. 2 manufactured according to an embodiment of the present invention. The figure shows the driving state of this transistor when it is in operation with a current flowing through it; the solid line shows the potential, and the dotted line shows the Fermi level EF. In other words, the reverse bias between the emitter and the base is v1base.
This shows a state where a forward bias is applied between the collectors B, and the E
g is the energy gap according to the semiconductor model of the oxide superconductor. Furthermore, A indicates the height of the Schottky barrier existing between the emitter semiconductor and the base superconductor, and B indicates the height of the Schottky barrier existing between the base superconductor and the collector semiconductor.

As described above, by the methods shown in Examples 1 and 2, oxides such as oxide superconductors, which have been a problem in the past, can be formed on semiconductors, and semiconductors can be grown and deposited on oxides. This solves the problems of the semiconductor interface being sometimes oxidized, which adversely affects device performance and damaging the semiconductor interface.

In the above example, the case where YBa2Cu30 was used as the thin film of the oxide superconductor forming the base region was explained, but instead of the 3A group element Y7-δ, Yb, Tm, Er, Ho, Dy,
Tb, Gd, Eu, Sm.

The base region of the oxide superconductor thin film can be similarly formed using lanthanide group elements such as Pm, Nd, Pr, Ce, and La. Also, superconductors containing Bi and TΩ elements, which are 3B and 5B elements, respectively. S
r 2Ca Cu Oy or TD Ba CaCu O
A base region made of an oxide superconductor such as , TR2Ba2Ca2CuaOto can also be formed satisfactorily by a similar method.

[Effects of the Invention] As described above, according to the present invention, in a method for manufacturing a superconducting base transistor of a composite element of a superconductor and a semiconductor, which assumes a stacked structure of a semiconductor, a superconductor, and a semiconductor, Depending on the growth method, 3A group, lanthanide group, and 3B, which are one of the constituent elements of oxide superconductors,
Since the manufacturing method was used to form a superconducting base region made of an oxide superconductor so that only Group 5B or Group 5B elements come into contact with the semiconductor interface, oxidation and damage to the semiconductor can be avoided in the transition region of the oxide superconductor/semiconductor interface. An excellent superconducting base transistor can be obtained that can prevent deterioration of device characteristics due to Therefore, it is possible to realize a superconducting base transistor whose cut-off frequency is particularly driven in the terahertz (to 12 Hz) region.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an epitaxial cell growth apparatus for carrying out an embodiment of the present invention, FIG. 2 is an explanatory diagram of the configuration of a superconducting base transistor formed using this epitaxial growth apparatus, and FIG. 3 is a schematic diagram of the invention. FIG. 4 is a schematic diagram showing how one atomic layer of each constituent element of YBa2Cu307-8 is sequentially deposited in the manufacturing method of FIG. 5 is a schematic explanatory diagram of the growth apparatus, and is a schematic diagram of the potential structure of a superconducting base transistor manufactured according to an embodiment of the present invention. In Figures 1 and 4, 1.11 is the growth chamber, 2°12
is the gate valve, 3 and 13 are the exhaust system, 4 and 14 are the board,
5.15 is the susceptor, 6.19 is the nozzle, 7°20 is the valve, 8 is the source gas, 21 is the gas (oxygen), 16 is the Y cell, 17 is the Ba cell, 18 is the Cu cell , 21.23.24 are shutters. In addition, in FIG. 2, 31 is a collector area (targeted to the substrate 4);
2 is a superconducting base region, 33 is an emitter region, 34 is a collector electrode, 35 is an emitter electrode, and 36 is a base electrode. ≦ Fig. 3 Δ This heron May's Bπ 1 Mars transi' and evening's P tensile Fig. 5 O2 Ohe base 1, Indication of the incident Patent application No. 132850/1986 2, Name of the invention Superconducting base transistor Manufacturing method 3, relationship with the case of the person making the amendment Patent applicant address: 1-7-12 Toranomon, Minato-ku, Tokyo
Name (029) Oki Electric Industry Co., Ltd. Representative: Nobumitsu Kosugi 4, Agent address: 4-10-3-5, Shibaura, Minato-ku, Tokyo, Column 6 of “Detailed Description of the Invention” of the specification to be amended, Amendment Contents (1) rYBa C on page 9, lines 1 to 2 of the specification
u07-δ(δku1)” to “YBa Cu O(δ
1)' 237 δ. (2) rYBu CuO-J on page 10, line 1 of the specification
2 7 δ as ry Ba2Cua o 7. Correct as y J.

Claims (1)

[Claims] A method for manufacturing a superconducting base transistor in which a base region located between two semiconductor layers constituting an emitter region and a collector region is made of an oxide superconductor; , the compositional elements of the oxide superconductor, which include group 3A, lanthanide group, and group 3B.
One atomic layer of an element corresponding to one of the Group and 5B elements is formed, and on top of this one atomic layer, one atomic layer of a constituent element including the above-mentioned applicable element is formed for each constituent element. A superconducting base region having a predetermined thickness is formed by depositing in a predetermined order, a monoatomic layer of the above-mentioned element is deposited on the superconducting base region, and then a semiconductor layer forming the emitter region is deposited. A method for manufacturing a superconducting base transistor, comprising forming a basic element of the above-mentioned superconducting base transistor.