JPS6360536A - Manufacture of semiconductor superlattice - Google Patents

Abstract

PURPOSE:To manufacture a thin film of high quality in a mass production by using an additive combined by dialkyl zinc, dialkyl sulfur or dialkyl selenium, and forming a thin zinc sulfide film and a thin zinc selenium by an organic metal vapor thermal decomposing method using hydrogen sulfide and hydrogen selenium. CONSTITUTION:The quantity of lower boiling point of R2Zn, R2S and R2Se is excessively mixed, reacted and ripened by heating, and excessive component is then distilled to be removed to synthesize the additive. The dialkyl zinc is formed with dialkyl sulfur or dialkyl selenium to form an additive to remarkably reduce the reactivity as a Lewis acid. Thus, even if it is coexisted with hydrogen sulfide or hydrogen selenide near at room temperature, its reaction is not advanced at all. When the additive introduced into a reaction furnace 1 arrives at a heating zone near the substrate 3, it is ionized to generate dialkyl zinc, which is reacted with hydrogen sulfide or hydrogen selenide, thereby growing a thin film. Thus, the formation of fine particles of ZnS, ZnSe is suppressed and a thin film of high quality is grown.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to the production of semiconductor superlattices, which are important components of visible short wavelength light emitting devices that are desired to be put to practical use as light sources for color sensors, full color displays, etc. Regarding the law.

<Prior Art> Since the optical and electrical properties of a compound semiconductor superlattice can be controlled by the laminated structure of thin films, it is possible to fabricate devices with properties that cannot be obtained with bulk semiconductor crystals or epitaxial thin films. Furthermore, if the thickness of the individual thin films constituting the superlattice is reduced to about 50χ or less, even if materials with different lattice constants of the individual thin films are stacked, they will be distorted so that the lattice constants in the plane direction match each other. Therefore, crystal growth can be performed without causing misfit dislocations or the like. Such a superlattice is called a strained superlattice. Unlike conventional epitaxial growth, there is no need to consider lattice matching conditions, so it has the advantage of widening the range of material combinations and selections when designing devices. m − of strained superlattice
An example of application to a V-group compound semiconductor is shown below.

Conventional technology 1゜A strained superlattice consisting of ZnS and Zn5e, ZnSθ and Zn
A strained superlattice made of Te was formed. (For example, J, C!
rystal Growth Uni (1985) 299
．． Appl, PhysLetto, Dan (1986) 23
6. (See, etc.) Conventional technology Strained supersons made of Zn5e and Zn'I'e were formed on a two-dimensional nP substrate using a 2° molecular beam epitaxy method (MBI method).

(For example, Appl, Phys, Lett, 1i(1
986) 296. Prior art 3゜Zn5e and Znso,! A strained superlattice consisting of Se was formed.

(For example, Appl, Phys, Lett, and (
1985) 955. (See, etc.) <Problems to be solved by the invention> The above-mentioned prior art has the following problems.

Prior Art 1. The hot wall epitaxy method is a crystal growth method that applies a vacuum evaporation method, and supplies raw materials to a growth substrate by evaporating heated and melted raw materials in a vacuum.

Since the amount of evaporation from the surface of the molten raw material depends on the surface area of the raw material and the heating method, it is difficult to control the growth rate of the film. In addition, it is difficult to control the 7 lux of evaporated raw material because it depends on the shape of the reservoir containing the raw material.
, the amount of raw material reaching the substrate tends to be non-uniform. This tends to cause film thickness distribution. Therefore, large-diameter substrates cannot be processed, and mass production capacity is low.

Conventional technology 2° Molecular Beam Epitaxy (MBI!) is a growth method with excellent film thickness controllability, but
Since it consists of an exhaust system and a vacuum chamber to obtain an ultra-high vacuum called RR, the equipment itself is expensive, and
Maintenance costs are also high.

Conventional technology 3° Metal-organic vapor phase pyrolysis (MoavD method) is a technology for mass production because the raw material is supplied as a gas, so it suffers from poor film thickness controllability and is capable of processing a large number of large-sized substrates. However, Z
When dimethyl zinc and hydrogen sulfide or hydrogen selenide are used as the growth raw materials for n S e sZ n S 04 S e 0°, the raw materials introduced into the reactor react with each other in the gas phase, and Z n -S Z n Se and other fine particles are generated. The fine particles adhere to the thin film growth surface on the substrate and impair the crystal growth process, resulting in poor properties of the resulting film.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and its purpose is to provide a manufacturing method for mass-producing a superlattice structure made of a high-quality -W group compound semiconductor thin film.

<Function> In the MOOVD method, the growth of a thin film is controlled by the amount of raw material supplied. Since the raw material supply amount is precisely controlled by the mass 70 controller, the growth rate, film thickness controllability, and composition controllability of the thin film are extremely high. Furthermore, by optimizing the shapes of the growth reactor and the pod that holds the substrate, it is possible to process a large number of large-diameter wafers.

When dialkyl zinc forms an adduct with dialkyl sulfur or dialkyl selenium, its reactivity as a Lewis acid is significantly reduced, so the reaction does not proceed at all even if it is present with hydrogen sulfide or hydrogen selenide at around room temperature.

When the adduct introduced into the reactor reaches the heating zone near the substrate, it dissociates to produce dialkylzinc, which reacts with hydrogen sulfide or hydrogen selenide, resulting in the growth of a thin film. The dialkyl sulfur or dialkyl selenium produced by the dissociation of the adduct is not thermally decomposed and therefore does not participate in thin film growth. Due to the above mechanism, ZnS became a problem when dialkyl zinc was used as the zinc source.

The formation of Zn5e* particles can be suppressed, making it possible to grow high-quality thin films.

<Example> Dialkyl zinc (R, zn) dialkyl sulfur (R2S) used in synthesizing the adduct used in the present invention,
Dialkylselenium (R2Se) is summarized in Table 1.

(Table 1) R2Zn and R,S or R,Ss are mixed with a roughly excessive amount of the low boiling point component of both, and after reaction and aging are performed by heating, the excess component is removed by distillation. The adduct was synthesized. General formula of adduct %Formula % Each synthesized adduct exhibits a unique vapor pressure, and its purity can be improved by repeating distillation. Table 2 shows specific examples of vapor pressure.

(Table 2) The synthesis of adducts is not limited to the compounds shown in Table 1. It is possible to synthesize with R, Zns R, Ss R, Ss other than those in Table 1, and all of them are included in the scope of the present invention. FIG. 1 shows a schematic diagram of the configuration of the MOO'VD device used in the present invention.

A graphite holder 2 is set inside a horizontal reactor 1 made of transparent quartz, and a substrate 3 is placed thereon. The substrate 3 is heated by a high frequency induction heating coil 4. The substrate temperature is monitored by a thermocouple 5 whose tip is embedded inside the pod. The reactor 1 is connected to a high vacuum evacuation system 7 via a pulp 6. Further, the reaction gas leaving the reactor 1 is connected to a rotary pump 9 via a pulp 8 and reaches a gas treatment device 10. The pulp 8 has the function of keeping the internal pressure of the reactor 1 constant.

/<Lua'11 to 16, the gas introduced by the three-way pulp is sent to the main line 1g, 18 or the waste line 19.20
Supply to either one of the following. The main lines 17, 18 are introduced into the reactor 1 after merging.

The waste lines 19 and 20 reach the rotary pump 23 via the pulps 21 and 22, respectively, and are introduced into the gas treatment device 10. The valves 22 and 21 are connected to the waste line 1, respectively.
It has the function of adjusting the internal pressures of the waste lines 19 and 2o, so that the internal pressures of the waste lines 19 and 2o are equal to those of the main lines 17 and 18, respectively. 24 is a mass flow controller that precisely controls the gas flow rate. The cylinder 25 is filled with hydrogen gas, which is a carrier gas, and is supplied after being highly purified by a purifier 26 .

The bubbler 27 is filled with additives, and the thermostatic chamber 28
is maintained at a predetermined temperature. The adduct is -20℃
Since it is a liquid in the temperature range around room temperature, it can be supplied as vapor of the carrier gas.The supply amount can be controlled by the flow rate of the bubbling gas and the temperature of the bubbler.The valve 30 adjusts the pressure. Has a function,
The upstream side of the pulp 50, including the surface of the added body fluid inside the bubbler, is maintained at atmospheric pressure. The cylinders 31 and 52 are each filled with hydrogen sulfide and hydrogen selenide diluted with hydrogen gas, and the supply amount is controlled by the mass 70-controller 24.

The manufacturing procedure of the semiconductor superlattice is described below.

A carrier gas containing adduct vapor is supplied to the pulp 12, and a carrier gas of the same flow 1 is supplied to the pulp 11. In addition, hydrogen selenide and hydrogen sulfide are supplied to pulps 15 and 15, respectively, and pulps 14 and 145 are supplied with hydrogen selenide and hydrogen sulfide, respectively.
A carrier gas is supplied at the same flow rate as the pulp 13.15, respectively. The same flow rate of carrier gas for diluting the raw material flows through the main line 17.18 and the waste line 19.20, respectively. The internal pressures of the main lines 17, 18 show values corresponding to the internal pressures of the reactor 1 determined by the gas flow rate and the pulp 8, and the internal pressures of the waste lines 19.20 are 17.1, respectively, determined by the pulp 22.21.
It is set equal to the internal pressure of 8. Pulp 11 and 1
2.13, 14.15 and 16 are operated in pairs, respectively. That is, when one side is connected to the main line,
The other is connected to the waste line. When switching gases, switch both at the same time. With this operation, reactor 1, main line 17.18 and waste line 19.20
The raw material gas can be switched between the main line and waste line while keeping the internal pressure constant. Fluctuations in the internal pressure of the reactor 1 due to gas switching induce fluctuations in the growth rate, resulting in uneven film thickness and in-plane thickness distribution of the film that constitutes the superlattice structure, so it should be suppressed as much as possible. is desirable.

When creating a superlattice by switching between hydrogen sulfide and hydrogen selenide, the process is as follows. When supplying hydrogen sulfide, pulp 15. Connect j4 to main line 18,
Pulp 13,16 is connected to waste line 20. At this time, hydrogen sulfide is supplied to the reactor 1 via the main line 18, and hydrogen selenide is discarded. Next: Pulp 15.1
6 at the same time. At this time, only the carrier gas is supplied to the reactor 1, and the growth is interrupted, resulting in an interval state. Hydrogen selenide is then supplied to the reactor 1 by simultaneously switching the pulps 13, 14. Thereafter, in the same manner, hydrogen sulfide and hydrogen selenide can be alternately supplied to the reactor 1 by continuing to switch the pulp at intervals of an appropriate length.

FIG. 2 shows an embodiment of the sequence of supplying raw material gas to the reactor 1 according to the present invention. The superlattice is formed by continuously supplying the adduct and alternately supplying hydrogen sulfide and hydrogen selenide. In FIG. 2, the horizontal axis indicates the time axis. 55.56.

39 indicates the supply timing of the adduct, hydrogen selenide, and hydrogen sulfide, respectively. 34, 57.40 indicate a state in which raw materials are being supplied to the reactor, and 35.38.41 indicate a state in which no raw materials are supplied. As is clear from the combination of raw material supplies, growth starts from time zero.
42 indicates a time period in which ZnS 44 is growing on top of ZnS, and 43 indicates an interval at which growth is interrupted.

The thickness of Zn5es ZnS can be arbitrarily changed by the time setting of 42.44. If the three-way pulps 11 to 16 are driven by a sequencer, the above-described growth sequence can be easily carried out.

FIG. 3 shows an example of the sequence of supplying raw material gas to the reactor 1 in the present invention. A superlattice is formed by alternately repeating the simultaneous supply of the adduct and hydrogen selenide and the adduct and hydrogen sulfide.

In FIG. 3, the horizontal axis indicates the time axis.

45.48.51 indicates the supply timing of adduct, hydrogen selenide, and hydrogen sulfide, respectively, and 46.49.5
2 is a state in which raw materials are being supplied to the reactor, 47, 50.
53 indicates a state in which the raw material is not supplied. Growth starts from time zero, 54 is Zn5g, 56
indicates the time period during which ZnS is grown, and 55 indicates the interval at which the growth is interrupted.

Specifically, a superlattice structure was manufactured under the following growth conditions according to the sequence shown in FIG. 2 or 3.

Growth substrate: (100) plane of gallium arsenide Growth temperature: 62
5℃ Reactor internal pressure Crab 70 Torr (OH3)2Zn5e(CH3),' Bubbling gas flow rate: joall at bubbler temperature -15℃
/ m (vapor pressure at -15°C is 21 ar) Hydrogen base 10%) I2Se supply amount: sov / = hydrogen page hydrogen pace 2 supply H2S supply amount = 250 s + s17.1
8, 19. Hydrogen flow rate flowing to 20; 2.5 per each line
Under the above conditions, the growth rate of Zn5e and ZnS was about IX/see. Based on the growth rate, the supply times of hydrogen sulfide and hydrogen selenide were set to determine the structure of the superlattice. The interval is 1-291! lc, closed.

Figure 4 shows a diffraction X-ray chart of a superlattice structure consisting of znse5X, zns50XSa repeating layers with a period of 400. A diffraction peak reflecting the long period structure of a 0 superlattice is observed, indicating that a superlattice is formed. It shows.

Figure 5 shows the 7 otoluminescence spectrum at 77°K of a superlattice structure consisting of Zn5e 10χ, ZnS 45χ, and a repeating period of 560 layers. Due to the quantum effect in the 0 superlattice structure, the emission peak energy is
The band gap energy is shifted to the higher energy side compared to the band gap energy of n S e. In addition, the light emission is due to quantized electron-hole pairs, and no light emission involving deep levels on the long wavelength side has been observed, indicating that the obtained superlattice is of high purity and quality. It shows that.

In the method for manufacturing a superlattice according to the present invention, the above-mentioned (aa
, ), zn-Se (OH,), adducts, but also adducts obtained by all combinations of R2Zn, R23% R, Se shown in Table 1 can be used to produce superlattice structures. When the supply amount determined by the vapor pressure of the adduct and the bubbling gas flow rate was the same, a superlattice structure exhibiting characteristics similar to those of the above example could be manufactured.

In addition, the MOC shown in Figure 1! In the schematic diagram of the VD device, ZnSe1aX-ZnS0. SEO
It is also possible to fabricate a superlattice structure including a mixed crystal layer such as g 50 X. In addition, by installing a dopant, Zn
Doping of the 5e layer or the ZnS layer is also possible. Example of application of superlattice structure to device Zn5e 25
A light emitting device was fabricated by selectively doping only the superlattice Zn5e layer made of -ZnS 25 X. Z
N5e layer doped with A2, repetition period 300
After a superlattice consisting of layers was formed on the (100) plane of knee-type gallium arsenide, a superlattice consisting of 300 repeating period layers of a Zn5e layer doped with N was laminated. Each superlattice layer exhibited N-type and P-type conductivity. When an ohmic contact was formed on the gallium arsenide substrate and the P − type superlattice layer, and a forward bias was applied.
Emission was observed from around 2.5V with a peak wavelength of 460V.
It exhibited a pure blue emission of nm. The fact that no emission in the long wavelength region is observed indicates that the superlattice according to the present invention is of high purity and quality and can be applied to blue light emitting devices.

The present invention is not limited to the ZnS layer and the superlattice made of ZnS shown in the above-mentioned embodiments.
superlattice systems containing Te), for example ZnS layers - Z n T
e series, ZnS-ZnTe, %, Zn5zSe+-2(
It is also applicable to the 0<π<1)-ZnTe system and is included in the present invention.

<Effects of the Invention> As described above, according to the present invention, in the method for manufacturing a semiconductor superlattice formed by alternately stacking a large number of II-4 group compound semiconductor thin films, dialkylzinc and dialkylsulfur or dialkylselenium are used as zinc sources. ■-W group compound by forming zinc sulfide thin film and zinc selenide thin film by organometallic vapor phase pyrolysis using hydrogen sulfide as a sulfur source and hydrogen selenide as a selenium source. It has become possible to mass-produce high-quality superlattice structures made of semiconductor thin films. We are confident that the present invention will greatly contribute to visible short wavelength light emitting devices, typically in the blue region.

[Brief explanation of drawings]

FIG. 1 shows MOf:! according to the present invention. FIG. 2 is a schematic configuration diagram of a VD device. 1.0 reactor, 2...Graphite Sayabuta-1
3... Board, 4... High frequency induction heating coil, 5...
・Thermocouple, 6...Pulp, 7...High vacuum exhaust system, 8
...Pulp, 9...Rotary pump, 10...
Gas treatment equipment, 11-16... three-way pulp, 17.1
8... Main line, 19, 20... Disposal line,
11.22... Pulp, 23... Rotary pump, 24... Mass 70-controller, 25... Cylinder containing carrier gas, 26... Purifier, 27...
・Bubbler containing adduct, 2B... constant temperature bath, 29・
...Pulp, 5o...Pulp, 31...Cylinder containing hydrogen sulfide diluted with hydrogen, 32...Pompero containing hydrogen selenide diluted with hydrogen. Figure 2 shows the raw material gas in the present invention. Supply sequence diagram to the reactor. 33... Adduct supply timing! +6... Timing of supplying hydrogen selenide, 39... Timing of supplying hydrogen sulfide, 34.57.40... State where raw materials are being supplied to the reactor, 35.38.41... Reactor 42... Time period during which Zn5e is growing, 43... Interval, 44...
Time period during which ZnS is grown. FIG. 3 is a sequence diagram of the supply of raw material gas to the reactor in the present invention. 45...Adduct supply timing, 48...Hydrogen selenide supply timing, 51...Hydrogen sulfide supply timing, 46 , 49.52... State where the raw material is supplied to the reactor, 47, 50.53... State where the raw material is not supplied to the reactor, 54... Time period during which ZnS9 is grown. 55...Interval, 56...Z
Time period during which nS is grown @ Figure 4 is a diffraction X-ray diagram of the superlattice fabricated according to the present invention. FIG. 5 shows the 7 otoluminescence spectrum at 77°K of the superlattice fabricated according to the present invention. Applicant: Seiko Epson Co., Ltd. Agent, Patent Attorney Tsutomu Mogami, and 1 other person:
；＜ / rshiw= 5′″th concave

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor superlattice formed by alternately stacking a large number of II-VI group compound semiconductor thin films, using an adduct synthesized from dialkylzinc and dialkylsulfur or dialkylselenium as a zinc source. A method for producing a semiconductor superlattice, comprising forming a zinc sulfide thin film and a zinc selenide thin film by an organometallic vapor phase pyrolysis method using hydrogen sulfide as a sulfur source and hydrogen selenide as a selenium source. 2. It is characterized by continuously supplying adducts to a semiconductor superlattice formation reactor and alternately supplying hydrogen sulfide and hydrogen selenide to alternately stack zinc sulfide thin films and zinc selenide thin films. A method for manufacturing a semiconductor superlattice according to claim 1. 3. A zinc sulfide thin film and a zinc selenide thin film are formed by alternately repeating a state in which an adduct and hydrogen sulfide are supplied and a state in which an adduct and hydrogen selenide are supplied to a reactor for forming a semiconductor superlattice. A method for manufacturing a semiconductor superlattice according to claim 1, characterized in that the semiconductor superlattice is laminated alternately.