JPS61237476A - Manufacture of compound semiconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for manufacturing a compound semiconductor.

[Description of prior art]

Many compound semiconductors are expected to be useful as thin film optoelectronic devices. For example, CuIn8.2 has a band gear y7' (Eg) of 1.04 eV and can absorb almost the entire spectrum of sunlight at a thickness of 1 μm or less. U.S. Patent Office 4.335,266 has thin film C.
It is said that the photoelectric efficiency of the uIn5@/CdS device exceeds 10 cm.

CuInSe2 has structural defects and its electrical properties are significantly dependent on its composition. It is difficult to dope and forms many phases in the solid. The conductivity type also changes depending on the ratio of its component elements; for example, if there is a large amount of Cu or S., the conductivity type becomes - type and the stain resistance is small. On the other hand,
When In is high or Se is low (compared to the stoichiometric case), the n-type stain resistance is relatively large.

The electrical resistance of CuIn5a□, which is intended for use as a photoelectric device, significantly depends on its composition, but it is extremely difficult to control it using normal formation methods.

The relationship between this composition and electrical resistance is shown in FIG. 2 with respect to the CU to In ratio. As shown in the figure, the slope of the curve is steep and Cu
A slight change in the /In ratio significantly changes the stain resistance.

The above US Pat. No. 44,335,266 has Cu1nSe2
A method of forming two thermally evaporated layers is described as a method of forming a 7 ilm. First, as the first film, 4
A low resistance vapor deposition of p-type (Cu-enriched) is carried out at 00°C, followed by n-type (Cu-enriched) as a second film at 450°C.
This is a method in which high-resistance evaporation of a film (U-poor) is performed, and the bonding at the interface of these films is further dissolved by diffusion. However, this method requires extremely complicated control during vapor deposition of these two films, and is not easy to implement industrially for use in low-cost solar cells.

Regarding CdT@/CdS batteries, U.S. Patent No. 703-7
It is described on page 12. In these cases the semiconductor layer is deposited in compound form. In the latter method, a strip containing S and Cd is screen printed, then fired to form a CdS film, and then similarly coated with Cd.

This is a method of screen printing a paste containing To.

However, this method may cause pinholes due to evaporation of organic components in the paste.

Literature, J, Electrochem, 5ac-e
April 1978*, pages 566-572, and U.S. Pat. No. 4,260,427 describe a method of electrodepositing CdTe in an alloyed state. However, it is extremely difficult to electrodeposit a multicomponent semiconductor in the form of a compound because the electrodeposition characteristics of each component are significantly different.

Control of the specific electrodeposition rate of each component and the composition of the film formed cannot be achieved unless the electrolyte solution and current density distribution in the bath are carefully controlled, and it is industrially difficult to do so. LiteratureJapanese Journal o
f Applied Phyalcsp Vol.

13.49, (1979), pp. 1757-1766.

describes a method for depositing a Cd layer on a Te substrate. In this case, diffusion between the substrate and the Cd layer is performed by annealing to form CdTe.

Pages 24 to 26 describe a method for forming a Cu In S 2 film. A film is formed from a Cu-In alloy by sputtering, heated in argon mixed H2S gas, and S is introduced into the film to form a film using sputtering.
This is a method of forming InS2.

However, neither method provides suitable control and economics for producing solar cells made of multilayer films such as CuIn8e2. Therefore, it is desired to manufacture highly accurate compound semiconductors with good controllability and by a method suitable for mass production.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method for forming a compound semiconductor device easily and with good controllability.

That is, the present invention involves electrodepositing a layer containing at least one constituent element on a substrate, then electrodepositing at least one other constituent element, and then heating these electrodeposited layers to form a semiconductor compound. The present invention provides a method for manufacturing a compound semiconductor characterized by the following.

Note that the electrodeposition described above may be continuous or simultaneous.

Further, the heating step may be performed in an atmosphere containing other components of the compound semiconductor. Cu as a semiconductor compound
InSe2+CdTe and other compositions can be formed according to the present invention.

An important feature of this invention is that a compound semiconductor having a composition exceeding stoichiometry can be formed with good controllability. Since the component elements can be formed as a distinct deposit such as a film, the amount of each component element can be highly controlled. Further, the deposition of the component elements is not complicated and is not inhibited in any way by the deposition of other component elements. The amount of each component element deposited is determined by its deposited thickness, and is not changed by deposition of other component elements or heat treatment. The heat treatment causes the component elements to interdiffuse and react with each other in the solid phase, forming a homogeneous thin layer as a compound semiconductor. Further, component elements in the atmosphere may be incorporated into the compound semiconductor by reaction during heating.

For example, Cu and In are electrodeposited separately and then H
It is also possible to form a homogeneous thin film of CuInSe2 by heating in a reactive atmosphere of 2S.

In this case, the ratio of Cu and In is precisely controlled. This controls the resistance of the compound semiconductor and eliminates the need to deposit two separate compositions (of CuInSe2) as in conventional methods.

The component elements are deposited by electrodeposition (unless a reactive atmosphere is used). In this case, the current and time are milliamps (1O-3A) and milliseconds (10-3 seconds) respectively
can be controlled on the order of. Therefore, the charge transferred in this electrodeposition process can be controlled within the order of 10 coulombs. In a single-charge or “10th order” reaction, 1 coulomb is 6.25
When the number of electrons is x1018, this electrodeposition reaction can be easily controlled on the order of about 1013 atoms.

In fact, the current and time can be controlled to values well below the order of milliamperes and milliseconds, and the number of atoms electrodeposited can also be better controlled. For comparison, a film with a -atom thickness and an area of 16n will have 1015 atoms, assuming that the size of the atoms is 3 to 4X.

In the present invention, the diffusion of the component elements takes place at a temperature considerably lower than the melting point of the compound semiconductor made of them. For example, the melting point of CuInSe2 is about 1000°C, but diffusion of component elements can be performed at about 400°C. The resulting product is a polycrystalline thin film of fine particle size (1-5 μm), making it extremely useful for CuInSe2/CdS photovoltaic devices.

In the heating step of the present invention, diffusion and chemical reactions occur simultaneously in the solid phase to obtain the desired compound semiconductor. As used herein, "component element" refers to a basic chemical constituent in a semiconductor material, such as Cu in CuIn8e2, and does not mean a mere donor or quantitative component. The method of the present invention therefore differs significantly from the simple diffusion found in many solid phase doping processes.

The method of the present invention is applicable to an extremely thin semiconductor film whose thickness is preferably 1 to 5 μm, but can also be applied to a thickness of about 10 μm. The invention is particularly suitable for the formation of CuInSe2. The reason for this is that Cu and Se have extremely high diffusion rates. Therefore, a desired homogeneous compound semiconductor can be formed in a relatively short time.

[Preferred specific examples of the invention]

Figure 1 shows a thin film solar cell 1 produced by the method of the present invention.
0, the substrate 12, metal pad, contact 14
, a pair of laminated p-type and n-type layers 16, 18, and a surface electrode 20. An antireflection (AR) coating 22 may be applied to the surface (upper surface) of this battery 10. Layer 16.18 is a thin film semiconductor layer forming a photoelectric junction 24 which converts the incident light (hma) into an electrical signal which is collected by electrode 14.20. One or both of these layers 16, 18 may be comprised of a compound semiconductor made in accordance with the present invention. Since the method of the present invention is quick in terms of process and has good controllability, a compound semiconductor of high quality can be obtained at low cost.

The method of the present invention involves electrodepositing a layer containing a part of the component elements of a desired compound semiconductor and a layer containing another part, respectively;
This is then heated to cause diffusion and chemical reactions between the component elements to form a homogeneous layer.

This heating step is performed in an inert atmosphere or a reactive atmosphere (containing other component elements of the compound semiconductor), and other component elements are introduced into the layer from the atmosphere and reacted to obtain the desired compound semiconductor. You can do it like this.

FIG. 3 explains the method of the present invention step by step.

In the battery 10 of FIG. 1, step 26 includes cleaning and preparing the substrate 12 for applying the puck contacts 14. The substrate 12 may be electrically conductive or non-conductive, and may be made of glass, ceramic, or other materials, for example. If this substrate is non-conductive, a conductive layer is formed on it and used as an electrode for a later electrodeposition process.

For example, when alumina (At20s) is used as the substrate 12, the contact 14 can be a thin film of Mo or other metal. This film 14 is formed to have a thickness of 1.0 to 1.5 μm by sputtering or the like.

After this contact 14 has been formed on the substrate 12, a layer 16 containing two constituent elements is successively formed in step 28.30. The resulting shape is clearly shown in Figure 41, with the first film being 34" and the second film being 36".
The thickness of these films is approximately 3.0001 cm.
6, the films 34 and 36 are each Cu
.

In, these are stained by the method of the invention.

In this embodiment, films 34,36 are separately and sequentially electrodeposited. Therefore, they are stacked separately.

After this electrodeposition, the films s 4 and s 6 are sufficiently heated to form a semiconductor through mutual diffusion and chemical reaction between the component elements. When electrodepositing Cu and In, it is heated to about 400°C. At this temperature, Cu diffuses rapidly,
MO contact 14 remains unchanged. In this heating step, the film is exposed to a reactive atmosphere containing Se. This allows Se to be introduced into the film and react to form CuInSe with the correct atomic ratio. As shown in Figure 4b, film 16 is thicker than the combination of films 34 and 36. This is because the third component Se is layer 16.
This is because the dopant is added to an extent that contains about 50 atoms of the final semiconductor material.

This selenization can be carried out in various ways. For example, it can be carried out in the atmosphere of a diffusion furnace similar to that shown at 38'' in FIG. In the block 42, a fourth
A large number of samples 46 shown in FIG. 1 are heated to a predetermined temperature.

In this heating step, alcohol is sent from the spar chamber 40 to the chamber 42. Note that this alco gas is supplied from the raw material source 5.
With Sv from 0. Is this raw material source 50 heated to 200°C for vapor deposition? - or H2Se gas. In any case, the sample 46 is exposed to a reactive S@ atmosphere during this heating step, causing Se to diffuse and react within the film 34.36. The obtained film 16 consists of a homogeneous film of CuInSe2 with a thickness of 1 to 3 μm.

This layer 16 preferably has a thickness of approximately 2 μm, thereby avoiding short circuits due to structural defects.

An n-type layer 18 is applied over layer 16, followed by electrode 2.
0. An AR coating 22 is applied to complete the cell.

Layer 16 is p-WCuInSe2 with electrical resistance of 20-2
000-, this n-fi layer has a thickness of 3μ, for example.
A CdS layer of m may be sufficient. Layer 18 can be applied by evaporation, snoccuttering, and front electrode 20 can be applied by evaporation or screen printing.

According to the present invention, a highly efficient CuInSe2/CdS solar cell can be obtained. In this case, Cu and In are replaced by Mo
It is electrodeposited as a separate layer on the puck contact 14 to a thickness of 1 μm. The Cu film 34 is heated in an electrolytic bath (0.5M (Cu
SO4) +0.8 M (with H2SO4)) can be deposited at a steady current density of 80 mA/cm2. This C
u is formed on the deposition site with a thickness of 0.711n9. Then, an In film 36 is formed using an electrolytic bath of indium sulfamino acid. This indium uses the T4 Luz plating method, with a base current of 0 and a peak current of 40 mA.
/'crn. The time for each of these nine hours is 0.1
seconds, and the rest time between pulses is 0.2 seconds. The film 36 is approximately 0.4 μm thick, or 1.311 F above the deposition site! Apply at p.

Therefore, the Cu/In ratio (between layers 34 and 36)
is approximately 0.92.

After deposition, the films 34,36 are placed in a diffusion furnace 38;
Heated for selenization. This selenization is at 400℃
for 1 hour at autogenous pressure and annealed at the same temperature for 2 hours.

Finally, the furnace is closed and the film and substrate are cooled at room temperature under a flow of alden gas. Selenide H2S e is 1.5
% of argon at a flow rate of 50 cIns/min (STP).
is obtained. Cd8 layer 18 is deposited on layer 16 by thermal evaporation.
It is formed with a thickness of 2 μm.

For the experiment, the front electrode 20 and the AR coating 22 were removed from the battery, and a transparent indium tin oxide (xTo) conductive layer with a sheet resistance of 41Ω/IR2 was formed.

A transparent conductive layer on this Cd8 layer 18 forms the front contact of the cell.

Note that although the above example includes the step 32 of heating the film in a reactive atmosphere containing Se, the component elements containing Se may be electrodeposited as individual films instead of this step.

In this case, the three-layer film stack is heated to 400'C to cause interdiffusion, reaction, and to form the film 16 as a homogeneous film. This method is 3
Although used for forming compound semiconductors consisting of more than one component, the heating process can also be applied to forming two-component semiconductor materials, such as CdTe, by using an inert atmosphere.

Examples of compound semiconductors that can be formed by the present invention are shown below in Chemi.
stry & Physics 60th Edlt
Based on ion.

Table CdOGaAs ZnSnP2CuInSe2Cd
S InAs ZnGeP2CuInS2Cd
's InP Zn5iP2CuInTe2Cd
Ts GaP Cd5nP2CuALS2Zn
OAtSb Cd51Aa2CuGaSe2ZnS
AgIn52ZnSe
AgGa552nTe Preferred elements are Zn+Cd, Cu*AgJ+At5Ga
*In+C+5i, Ge*Sn+P, As+Sb+Bi
, S, Se and To.

The above compounds can be formed and are useful in the present invention as a semiconductor layer 16.18.

As mentioned in connection with CuInSe2, the semiconductor materials listed above have properties that are sensitive to changes in the stoichiometry of the elements. According to the method of the present invention, the ratio of component elements can be controlled more accurately than conventional methods. By sequentially electrodepositing component elements, each component in the final product can be precisely regulated.

Deposition and atomic ratios can be easily controlled. This is because the movement mechanism in electrodeposition is well known and complex electroplating systems are commercially available.

Figures 6 and 7 show a substrate holder 5 for use in electrodepositing the components of layer 16. This hole/-52 has a frame portion 54, a back plate 56 and a handle 58. Of these, the frame portion 54 and the handle 58 are made of a substantially inert, non-conductive material, such as a fluorine-based polymer. The seven frames 54 form a chamber 60 that receives the substrate 12 and pressure plate 62.

The frame 54 also has seven inwardly directed langes 64. This seven flange forms a square opening 66 and carries a resilient seal 68 and a metal strip, f70, facing the chamber. The pressure plate and substrate are biased outward against the 7 langes by springs 72 (restrained by the bag grate). This pack plate is sealed to the frame by an elastic member 76.

In this configuration, the IJ tag 70 contacts the Mo74 lumen of the substrate and applies an electrodeposition potential to the film. This seal 68 is S) IJ
It is located inside the pad 70 and maintains a liquid-tight state together with the Mo film, separating the strip from the surrounding electrolytic bath. This strip is preferably made of platinum and is connected to a conductive wire 78. This wire 78 extends from the handle portion 58 and connects to a power source.

In operation, a substrate 12 having a Mo contact film applied to its outer surface is placed in a holder 52 to allow continuous electrodeposition of predetermined elements. Terminal contact to the Mo film is made through a holder to allow uniform deposition without the need for permanent electrical connections to the film. A substrate can be placed in the holder and moved with the holder from one electrolytic bath to another to deposit films of different component elements. After electrodeposition, remove the substrate from the holder and
Placed in the furnace 38 shown in the figure, diffusion and reaction occur.

It should be noted that electrodeposition can be performed on a conductive back electrode, such as the contact film 14 of the battery 10, or on a transparent conductive oxide layer. This oxide layer is deposited on the glass prior to electrodeposition of the component elements and must be sufficiently conductive to provide a uniform current density distribution during electrodeposition.

The heating step to finally form the semiconductor is carried out in either an inert or reactive atmosphere, either at atmospheric pressure or under autogenous pressure.
It can be carried out at a temperature of 150-5501:. As the inert gas, argon, xenon, helium, etc. are used, and as the reactive atmosphere, an inert gas mixed with predetermined component elements is used.

The electrolyte used for electrodeposition is one that contains component elements, and can be changed without being chemically or physically harmful to the substrate, and can be an aqueous solution containing component elements, or an aqueous solution containing component elements, or an electrolyte that can be changed without chemically or physically harmful to the substrate. Non-aqueous salts can be used. When using an aqueous type, the temperature is below 90C, and when using a non-aqueous type, the temperature is 500℃.
It can be carried out at the following temperatures:

There is no particular limit to the current density, but 1 to 300 = n1
A range of 4-7 cm is common.

According to the present invention, a semiconductor compound containing component elements in any stoichiometric ratio can be produced, for example, an atomic ratio of I Cu/ 11 n/2 S@.

The present invention makes it possible to manufacture compound semiconductors which are extremely advantageous in terms of cost, time, and controllability of component ratios.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a solar cell for explaining one embodiment of the present invention; Figure 2 is a diagram showing the electrical resistance of Cu1nS*2 in relation to the amount of Cu and In; Figures 4a and 4b are cross-sectional views showing stages in the process of forming the device of Figure 1; Figure 5 is a perspective view of the diffusion furnace used in the present invention; Figure 6 The figure is a perspective view of the substrate holder used in the present invention; FIG.
10 is a sectional view taken along line 10. FIG. In the figure, 10... solar cell, 12... substrate, 14...
- Pack contact, 16...layer, 34...film, 36...film, 38...furnace. Applicant's representative Patent attorney Takehiko Suzue Notes to the drawings (no changes in content) FIG, / CII/I11 Island-11- FIG, 2 FIG, J FIG, 4σ FIG,
4bFIG, 5 FIG, 7 Procedural amendment (method) % formula % 1. Indication of the case Japanese Patent Application No. 1987-078222 2. Name of the invention Method for manufacturing compound semiconductors 3. Person making the amendment Relationship to the case Patent applicant Atlantic Litchfield Company 4,
Agent No. 17JL Building, 1-26-5 Toranomon, Minato-ku, Tokyo June 25, 1985 6 No drawings subject to amendment

Claims (28)

[Claims] (1) A step of electrodepositing at least one of the component elements onto the substrate; A step of separately electrodepositing other component elements onto the substrate; A step of heating these electrodeposited component elements; A method for manufacturing a compound semiconductor comprising a plurality of component elements. (2) Forming a first film mainly composed of at least one component element on the substrate; Forming a second film mainly composed only of other component elements on the first film; and: 2. The method according to claim 1, comprising: forming a compound semiconductor through diffusion and chemical reaction of the component elements through a heating step. (3) The method according to claim 1, wherein the component elements are continuously electrodeposited. (4) The method according to claim 1, wherein the electrodeposition of the component elements is performed substantially simultaneously. (5) The component element is an element selected from Group IIB and Group VIB of the periodic table, and the compound semiconductor is at least partially
The method according to claim 1, which comprises a compound of compositional formula (IIB)/(VIA) group. (6) The method according to claim 5, wherein the IIB group element is selected from Zn and Cd, and the VIA group element is selected from S, Se and Te. (7) The method according to claim 6, wherein the component elements are Cd and Te, and the semiconductor compound is at least partially composed of CdTe. (8) The component elements are selected from Group IIIA and Group VA elements, and the compound semiconductor has a compositional formula of (IIIA)・(
The method according to claim 1, which comprises a compound of group VA). (9) The method according to claim 8, wherein the IIIA group element is selected from B, Al, Ga and In, and the VA group element is selected from P, As and Sb. (10) The method according to claim 9, wherein the component elements consist of Ga and As, and the compound semiconductor is at least partially GaAs. (11) The method according to claim 1, wherein a third component element is further electrodeposited on the substrate before the heating step. (12) Component elements are Group IB, Group IIIA, and Group VIA
12. The method according to claim 11, wherein the compound semiconductor is selected from group elements, and the compound semiconductor has a compound having a compositional formula of groups (IB), (IIIA), and (VIA). (13) The Group IB element is selected from Cu and Ag, the Group IIIA element is selected from B, Al, Ga, and In, and the Group VIA element is S, Se, Te.
13. The method of claim 12, wherein the method is selected from: (14) The method according to claim 12, wherein the component elements are Cu, In and Se, and the semiconductor compound is at least partially composed of CuInSe_2. (15) The component elements are selected from Group IIB, Group IVA, and Group VA, and the semiconductor compound is at least partially
12. The method according to claim 11, wherein the method is composed of the group (IIB), (IVA), and (VA)_2. (16) The Group IIB element is selected from Zn and Cd, and
Group IVA elements are selected from C, Si, Ge, Sn,
16. The method according to claim 15, wherein the group element is selected from P, As, Sb and Bi. (17) The method according to claim 15, wherein the component elements are Zn, Sn, and P, and the semiconductor compound is at least partially composed of ZnSnP_2. (18) The method according to claim 1, wherein the heating step is performed in a reactive atmosphere containing other component elements of the semiconductor compound. (19) The component elements are selected from Group IB, Group IIIA, and Group VIA, and the compound semiconductor is at least partially (
19. The method according to claim 18, wherein the method is comprised of the group IB), (IIIA), and (VIA)_2. (20) Group I B element is selected from Cu and Ag, and Group II
20. The method of claim 19, wherein the Group IA element is selected from Al, Ga, and In, and the Group VIA element is selected from S, Se, and Te. (21) The method according to claim 19, wherein the semiconductor compound consists of CuInSe_2, the electrodeposited films each consist of Cu and In, and the reactive atmosphere contains Se. (22) The component elements are selected from Group IIB, Group IVA, and Group VA, and the semiconductor compound has a composition formula, (I
19. The method according to claim 18, wherein the method has IB), (IVA), and (VA)_2. (23) The Group IIB element is selected from Zn and Cd, and the Group IIB element is selected from Zn and Cd.
23. The method of claim 22, wherein the group element is selected from C, Si, Ge, Sn and the group VA element is selected from P, As, Sb, Bi. (24) The method according to claim 23, wherein the semiconductor compound consists of ZnSnP_2, the electrodeposited film contains Zn and Sn, and the reactive atmosphere contains P. (25) The method according to claim 1, wherein the heating step is performed in an inert atmosphere or in a reactive atmosphere containing further component elements of the semiconductor compound. (26) Electrodeposition process at a current density of 1 to 300 mA/cm^2
The method according to claim 1, wherein the method is carried out in an electrolyte that is harmless to the substrate. (27) The method according to claim 1, wherein the electrodeposition step is carried out under atmospheric pressure in an electrolyte aqueous solution at a temperature of 90° C. or lower, or in an electrolyte non-aqueous solution at a temperature of 500° C. or lower. (28) The heating step is performed under atmospheric pressure at a temperature of 150 to 500
The method according to claim 1, wherein the method is carried out at a temperature of 0.degree.