JPS6134927A - Growing process of compound semiconductor single crystal thin film - Google Patents

Abstract

PURPOSE:To make it feasible to grow single crystal growing layers subject to the precision of monomolecular layer on a substrate by a method wherein the pressure inside a growing vessel, heating temperature of substrate, optimum value for single crystal growing one cycle monomolecular layers or one cycle dimolecular layers of introducing gas are specified. CONSTITUTION:A gate valve 2 is opened to vacuum a growing vessel 1 up to around 10<-7>-10<-8> Pa by an ultrahigh vacuum pump 3 and after heating a GaAs substrate 12 up to 300-800 deg.C by a heater 10, one valve 6 is opened to introduce TMG8 for 0.5-10sec within the range boosting the pressure in the growing vessel 1 up to 10<-1>-10<-7> Pa. When, after closing the valve 6 to vacuum the gas inside the growing vessel 1, the other valve 7 is opened to introduce AsH3 for 2- 200sec within the range boosting the pressure in the growing vessel 1 up to 10<-1>-10<-7> Pa, at least one monomolecular layer of GaAs is formed on the substrate 12. Finally single crystal growing layers of GaAs with specific thickness may be grown subject to the precision of monomolecular layer by means of repeating said procedures for growing monomolecular layers one after another.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for growing a compound semiconductor single crystal thin film suitable for forming a compound semiconductor single crystal growth layer on the order of a monomolecular layer.

[Prior art and its problems] Metal-organic vapor phase epitaxy (hereinafter referred to as MO-C
VD method), molecular beam epitaxy method C, MBE
(hereinafter referred to as ALE method), atomic layer epitaxy (hereinafter referred to as ALE method), and the like are known. However, in the MO-CVD method, group (1) and (3) elements are introduced as a source into a reaction chamber simultaneously with hydrogen gas or the like as a carrier, and the growth layer is grown by thermal decomposition, so the quality of the grown layer is poor. Further, there are drawbacks such as difficulty in controlling the monolayer order.

On the other hand, the MBE method, which is well known as a crystal growth method using an ultra-high vacuum, uses physical adsorption as the first step, so the quality of the crystal is inferior to the vapor phase growth method using a chemical reaction. GaA
When growing compound semiconductors between the ■-V groups such as S, group ■ and group ■ elements are used as sources, and the sources themselves are installed in the growth chamber. For this reason, it is difficult to control the gas released by heating the source and the amount of evaporation, and to replenish the source, making it difficult to keep the growth rate constant for a long time. In addition, the vacuum equipment, such as exhausting evaporated matter, becomes complicated. Furthermore, it is difficult to precisely control the stoichiometric composition (stoichiometry) of the compound semiconductor, and as a result, high quality crystals cannot be obtained.

Furthermore, the ALE method was developed by T,5unLola et al.
As explained in Nn4058430 (1977), this method improves the MBE method and alternately supplies each semiconductor element in a pulsed manner, depositing monoatomic layers alternately on the substrate and growing a thin film atomic layer by atomic layer. , which has the advantage of being able to control the film thickness with atomic layer precision, is an extension of the MBE method.
Similar to E, crystallinity is not good. In addition, the grown thin film is also Cd
It is limited to II-IV group compound semiconductors such as Te and ZnTe, and currently includes Sl and G, which are the mainstay of semiconductor devices such as VLSI.
No success has been achieved with aAs. Attempts have been made to improve ALE to adsorb a molecular layer and use chemical reactions on the surface for growth, but these are only for the growth of polycrystalline ZnS or amorphous thin films of Ta 205, and this is not a single-crystal growth technology. do not have.

As described above, while it is difficult to form high-quality crystals that satisfy the stoichiometric composition on the order of a monomolecular layer using the MO-CVD method and the MBE method, the ALE method has the disadvantage that single crystals cannot be obtained. Ta.

[Object of the invention] The present invention eliminates the drawbacks of the above-mentioned prior art, improves the quality of a crystal growth layer by controlling the stoichiometric composition, and provides a compound that can form a growth film with the precision of a monomolecular layer. The purpose of this invention is to provide a method for growing single crystal thin films of semiconductors.

[Summary of the Invention] Therefore, in the ALE method, a single atomic layer of a single element is formed on a substrate, whereas a gas containing molecules containing the component elements desired to be grown on the substrate is alternately supplied from the outside. A crystal is grown on the substrate by repeating the introduction cycle, and at this time, the pressure in the growth tank, the substrate heating temperature, and the amount of gas introduced are adjusted such that a single crystal grows in one molecular layer per cycle or two molecular layers per cycle. Experimentally find the optimal value for
The feature is that a single crystal can be grown on the substrate.

[Embodiments of the invention] The present invention will be explained in detail below.

FIG. 1 shows a configuration diagram of a compound semiconductor single crystal growth apparatus according to an embodiment of the present invention, in which 1 is a growth tank made of metal such as stainless steel, 2 is a gate valve, and 3 is inside the growth tank 1. 4 and 5 are nozzles for introducing, for example, gaseous compounds of component elements of group Ⅰ and group Ⅰ of the ■-■ group compound semiconductor; 6 and 7 are nozzles 4 and 5; Valve that opens and closes, Group 8 is a gaseous compound containing a component element, 9 is a gaseous compound containing a component element of Group 2, 10 is a heater for heating the substrate, and tungsten (W) sealed in quartz glass. 11 is a thermocouple for temperature measurement, 12 is a compound semiconductor substrate, and 13 is a pressure gauge for measuring the degree of vacuum in the growth tank.

With the above configuration, the crystal growth state was investigated using parameters such as the pressure inside the growth tank 1, the heating temperature of the substrate 12, and the amount of gas introduced. As a result, it was found that when the crystal is grown under the following conditions, a high quality single crystal thin film can be obtained. It was experimentally confirmed that it is possible to form a monolayer with the precision of a monomolecular layer. That is.

To epitaxially grow a GaAs single crystal on a GaAs substrate 1, first open the gate valve 2 and use the ultra-high vacuum exhaust device 3 to vacuum the inside of the growth tank 1 at 10-7 to 10'.
Exhaust to about Pa5cal (hereinafter abbreviated as Pa).

Next, the GaAs substrate 12 is heated to 300 to 800°C by the heater 10, and TMG (
)-limethylgallium)8 when the pressure in the growth tank 1 is 10
-1 to 1O-7Pa, the valve 6 is opened for 0.5 to 10 seconds and the mixture is introduced. After that, the valve 6 is closed and the gas in the growth tank 1 is exhausted, and then the gas containing As is ASH! (Arsine) 9 and the pressure in growth tank 1 is 10-1
The valve 7 is opened for 2 to 200 seconds at a pressure of ~10"Pa. This allows at least one molecular layer of GaAs to grow on the substrate 12. By repeating the above operations, monomolecular layers are grown one after another. By doing so, a GaAs single crystal growth layer of a desired thickness can be grown with the precision of a monomolecular layer.

Figure 2 (a) shows the TM per cycle at a growth temperature of 600°C when TMG and GaAs are used as introduced gases.
Ga per cycle using the amount of G introduced as a parameter
It shows the growth thickness of the As film. As the amount of TMG introduced per cycle increases, the grown film thickness becomes saturated. If growth is performed with the amount of gas introduced above this saturation value, even if the amount of gas introduced varies from core to core, one molecular layer per cycle or two molecular layers per cycle will be grown, resulting in precision in atomic units. The film thickness can be controlled. Under this saturated condition, TMG
And A! 9H3 was introduced alternately, and the number of introductions and GaA
FIG. 2(b) shows the relationship between the film thicknesses of the s epitaxial growth layer. As is clear from this figure, the film exhibits very good linearity, indicating that any film thickness can be completely controlled. When the thus obtained epitaxially grown GaAs layer was examined by electron beam diffraction and X-ray diffraction, it was found that it was a thin film single crystal with extremely high integrity.

Note that the raw material gas containing Ga is not limited to TMG, but also TMG.
EG, ZEGaCfl, ZMGaCfl and CaCQ
3 +GaBr 3. Even when a gas such as GaT3 was used, a GaAs thin film with good crystallinity was similarly obtained.

FIG. 3 shows another embodiment of the present invention, which is for adding impurities. 14.15 is a nozzle that introduces a gaseous compound used for impurity addition, 16.17
18 is a gaseous compound containing a component element of group (1); and 19 is a gaseous compound containing a component element of group (2). Since the parts other than the addition of impurities are the same as the embodiment shown in FIG. 1, their explanation will be omitted.

When forming a P-type growth layer with this configuration, three gases, TMG (trimethyl gallium) 8 and AsHs (arsine) 9 as introduced gases, and ZMZn (dimethyl zinc) 18 as an impurity gas to be added, are introduced in a circulating manner. do.

Another method is to introduce T IG8 and ZMZnlB at the same time and alternately with AsH39, or to introduce AsH39 and 2
Impurities can be added by simultaneously introducing MZn18 and TMG8 alternately. Furthermore, another method is to simultaneously introduce TMG and ZMZn, vacuum evacuation, and AsH
The first cycle is 3 introduction, vacuum evacuation, and the second cycle is n4G only introduction, vacuum evacuation, AsHs introduction, and vacuum evacuation.
It is also possible to form alternating Zn doped and undoped layers or multiple layers by alternating cycles of Zn.

Note that impurity gases include ZMCd (dimethylcadmium), ZMMg (dimethylmagnesium), and SiHa.
(monosilane), GeH4 (germane), etc. may also be used.

Furthermore, ZMCd and ZMZn may be introduced at the same time.

Next, to form an n-type growth layer, 2MSe19 (dimethyl selenium) is added as an impurity gas to TMG8. AsH
39 and introduced in a circular manner. Another method is to add impurities by simultaneously introducing TMG8 and 2MSe19 alternately with TMG8.

Incidentally, as the impurity gas at this time, ZMS (dimethyl sulfur), H2S (hydrogen sulfide), H2Se (hydrogen selenide), etc. can be used.

In this case, the flow rate of impurity gas introduced is changed to AsH39, TMG
By setting the impurity concentration smaller, for example, by 10<-3> to 10<-6> than 8, and by setting the introduction time to 0.5 to 10 seconds, a molecular layer epitaxial growth layer having a desired impurity concentration distribution in the thickness direction can be formed. In addition, by adjusting the amount and time of the impurity gas added, it is possible to create pn junctions, non-uniform impurity density distributions, bipolar transistor structures such as npn, npin, pnp, pnip, n+in'', n''n''
Of course, field effect transistors such as -n+, static induction transistors, pnpn thyristor structures, etc. can be realized.

FIG. 4 shows yet another embodiment of the present invention,
This is to grow a mixed crystal compound semiconductor. Explanation will be given by taking Ga1-xAnxAs as an example of the mixed crystal. 20 is■
A nozzle for introducing a gaseous compound of Al of the group 21 is 20
The valve 22 for opening and closing is a gaseous compound containing 1 of group Ⅰ. 50 to 52 will be described later. The other parts are the same as the embodiment shown in FIG. 1, so their explanation will be omitted.

AsHs 8, TMG9, TNA Q as introduced gas
22 (trimethylaluminum TMA Q 22 is introduced in a circulation manner. At this time, TM
By adjusting the introduction flow rate and introduction time of A fl 22 with respect to TMG 9, a mixed crystal molecular layer epitaxially grown layer having a desired component ratio in the thickness direction can be formed.

Note that TMG9 and TMA Q22 may be introduced at the same time.

Further, the introduced gas 20 may be a mixture of TMG and TMA Q. In addition, although Ga 1-xA Q xAs was taken as an example, GaAs 1-xPx. InxGa
1-xP. Other m-v group mixed crystals such as InxGa1-xAa and II-Vl group mixed crystals such as Hg + -xcdxTe may also be used.

In addition, Ga + -xAlx as shown in FIG. 5(a)
To grow an As superlattice structure, a sequence as shown in FIG. 5(b) may be used. That is, TMG9 and AsH s 8 are alternately introduced in the first two cycles, TMA Q 22 and AsH s 8 are alternately introduced in the next five cycles, and TMG9 and AsH s 8 are alternately introduced in the next two cycles. The next four cycles are impurity introduction cycles, using the nozzle 50 and opening and closing the valve 51 to
4 (silane) 52 is introduced simultaneously with AsH s8 and alternating with TMG9. That is, the opening and closing phases of the valve 51 and the valve 6 are made to match, and four cycles are introduced. The next two cycles are the growth of undoped GaAs, TMG9 and AsH.
Alternating introduction with s 8, next 2 cycles are undoped A
With the growth of Q As, TMA Q 22 and AsH s 8
It would be better to introduce it alternately with

FIG. 6 shows yet another embodiment of the present invention,
The purpose is to grow a lattice strain-corrected mixed crystal compound semiconductor of quaternary mixed crystal or higher whose forbidden band width and lattice constant can be controlled independently. - For example, Gao. 7Alo. 3^so. gsP
o. It is known that lattice distortion is corrected when grown on a GaAs substrate with
This will be explained by taking nxAs + -yPy as an example.

23 and 24 are nozzles for introducing a gaseous compound of group Ⅰ A[, group Ⅰ P containing a mixed crystal element, 25.26 is nozzle 2
The valves 3 and 24 open and close, 27 and 28 are ■
It is a gaseous compound containing elements of AΩ of group V and P of group V. Since the other parts are the same as those in FIG. 1, their explanation will be omitted. AsH 38 and TMG9 were introduced as gases.

Using TMAΩ27, PI (3 (phosphine)28,
These gases are introduced in a circulating manner. At this time, the ■ group members and the ■ group members may be introduced at the same time. Alternatively, the gases may be mixed in advance. The growth temperature, growth pressure, etc. are almost the same as those in the embodiment shown in FIG. 1, and by adjusting the gas mixture ratio, introduction flow rate, and introduction time, a mixed crystal compound semiconductor epitaxial growth layer with lattice strain correction can be formed.

In each of the above embodiments, an example has been described in which the heating source for the substrate 12 is provided in the growth tank 1. For example, as shown in FIG. 7, an infrared lamp 3 is used as the heating source.
0 is installed in a lamp house 31 outside the growth tank 1, and by irradiating the substrate 12 with infrared rays output from the lamp house 31 via the quartz glass 32, the substrate I2 held on the susceptor 33 is It may also be heated. In this way, members unnecessary for crystal growth can be removed from the inside of the growth tank 1, and generation of unnecessary gas components such as heavy metals due to heater heating can be prevented.

Furthermore, an optical system 40 is attached to the growth tank 1, and a mercury lamp, deuterium lamp, Xe lamp, excimer lamp, etc. are installed on the outside of the optical system 40.
A light source 4I such as a laser or Ar laser is provided, and the wavelength is 180~
The substrate 12 may be irradiated with 600 nm light. In this case, the substrate temperature can be lowered, and as a result, a single crystal of even higher quality can be grown.

Incidentally, in the embodiments described above, a well-known ultra-high vacuum device such as an ion pump can be used. Furthermore, it goes without saying that an auxiliary vacuum chamber for loading and unloading the single crystal substrate, a crystal drawing device, etc. can be easily added, and the device can be easily mass-produced. Also,
Although the gas used for crystal growth has mainly been explained with respect to GaAs, it is of course applicable to other m-v group compounds such as InP, A(AP, GaP, etc.) or ■-■ group compounds. However, heteroepitaxial growth on other compound substrates may be used.

[Effects of the Invention] As described above, according to the present invention, it is possible to grow layer by layer, it is easy to satisfy the stoichiometric composition, and it is possible to form a high-quality single crystal on a substrate.

In addition, since impurities can be added layer by layer, a very steep impurity density distribution can be obtained.
It exhibits excellent effects in the production of extremely high-speed transistors, integrated circuits, diode light emitting devices, etc.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a crystal growth apparatus according to an embodiment of the present invention, and FIG. 2(a) shows the TM per cycle in FIG.
A graph showing the relationship between the amount of G introduced and the grown film thickness, Figure 2 (
b) is a graph showing the relationship between the growth layer thickness and the number of valve openings and closings in FIG. The figure is number 4
This is an explanatory diagram when forming a superlattice structure using the apparatus shown in the figure. Figure (a) is an explanatory diagram of the superlattice structure, Figure (b) is a gas introduction sequence diagram, and Figures 6 and 7 are respectively It is a block diagram of the crystal growth apparatus based on yet another Example of this invention. 1... Growth tank, 2 - Gate valve, 3... Exhaust device, 4, 5, 14, 15, 20, 23, 211...
Nozzle, 6, 7, 16° 17.21, 25.26...
Valve, 8, 9, 18, 19, 22, 27, 28...
Gaseous compound, 10... Heater, 11... Thermocouple, 12... Substrate, 13... Pressure gauge. Figure 1 Figure 3 Figure 4 Figure 6

Claims (15)

[Claims] (1) Gaseous molecules containing component elements of a compound semiconductor are introduced onto the substrate for 0.5 to 200 seconds at a pressure in the growth tank of 10^-^1 to 10^-^7 Pascals, and after evacuation. ,
A series of introducing gaseous molecules containing another component element of the compound semiconductor onto the substrate for 0.5 to 200 seconds at a pressure in the growth tank of 10^-^1 to 10^-^7 Pascals. A method for growing a compound semiconductor single crystal thin film, which is characterized by growing a compound semiconductor single crystal thin film of a desired thickness with monomolecular layer precision by heating the substrate to 300 to 800°C and repeating the above operations. . (2) A method for growing a compound semiconductor single crystal thin film according to claim 1, in which single crystal thin films of at least two types of compound semiconductors are successively grown on the substrate. (3) In claim 1 or 2, a gaseous molecule containing an impurity element of the compound semiconductor is introduced simultaneously or alternately with at least one of the gaseous molecules containing a component element of the compound semiconductor. A method for growing a compound semiconductor single crystal thin film in which a compound semiconductor single crystal thin film having a desired impurity concentration distribution in the thickness direction is continuously grown with monomolecular layer precision. (4) In claim 1 or 2, at least once in each predetermined repetition cycle, at least one of the gaseous molecules containing the component elements of the compound semiconductor is simultaneously A method for growing compound semiconductor single crystal thin films that periodically and continuously forms molecular layers containing impurity elements and molecular layers not containing impurity elements by introducing molecules. (5) A method for growing a compound semiconductor single crystal thin film according to claim 3 or 4, in which gaseous molecules containing at least two or more types of compound semiconductor impurity elements are introduced. (6) In claim 3 or 4, gaseous molecules containing component elements of a compound semiconductor in which impurity elements of at least two or more compound semiconductors are mixed are individually cycled in different cycles or in the same cycle. A method for growing compound semiconductor single crystal thin films in which different impurity elements are included in different molecular layers by introducing them for different times. (7) A method for growing a compound semiconductor single crystal thin film according to claim 1 or 2, wherein the compound semiconductor is composed of two or more components. (8) A method for growing a compound semiconductor single crystal thin film according to claim 1, wherein the compound semiconductor is GaAs. (9) In claim 2, one of the at least two types of compound semiconductors is GaAs, and the other is GaAs.
A method for growing a compound semiconductor single crystal thin film of a_1_-_xAl_xAs. (10) In a method of growing a compound semiconductor on a substrate by introducing a gas containing a crystal component element from the outside into a growth tank that is evacuated, the growth tank is evacuated to a predetermined pressure, while the substrate is Heat to specified temperature, TMG, TE
Introducing any one of G, ZEGaCl, GaBr_3GaI_3 into the growth tank at a predetermined pressure for a predetermined time,
After exhaust, TMAs, AsCl_3, AsBr_3, As
At least a cycle of growing at least one molecular layer by introducing any one of H_3 into the growth tank at a predetermined pressure for a predetermined time, and further repeating the above cycle to grow a GaAs single crystal thin film with a desired thickness. A method for growing compound semiconductor single crystal thin films with the precision of a monomolecular layer. (11) In claim 10, the compound semiconductor is a compound semiconductor crystal thin film consisting of two or more components containing Al, and the compound gas containing Al includes TMAl, T
EAl, ZMAlCl, ZMAlCl, AlCl_3,
Using either AlBr_3 or AlI_3, at least one molecular layer is grown by simultaneously or alternately introducing a gas containing a component other than Al of the compound semiconductor into the growth tank at a predetermined pressure for a predetermined time and evacuating it. 1. A method for growing a compound semiconductor single crystal thin film, comprising at least a cycle, and further repeating the above cycles to grow a single crystal thin film of a desired thickness with monomolecular layer precision. (12) In claim 10 or 11, ZMZn, ZEZn, ZECd, ZMH is used as the gaseous molecule containing the p-type impurity element of the compound semiconductor.
g, ZEHg, B_2H_6, or n
SiH_4, Ge as gaseous molecules containing type impurity elements
H_4, SnH_4, PbH_4, ZNSe, ZNTe
, H_2S, H_2Se, H_2Te, H_2Po simultaneously or alternately with at least one of gaseous molecules containing component elements of the compound semiconductor, the compound semiconductor has a desired impurity concentration distribution in the thickness direction. A compound semiconductor single crystal thin film growth method that grows single crystal thin films with monomolecular layer precision. (13) In any one of claims 10, 11, and 12, at least one of the gaseous molecules containing the component elements of the compound semiconductor is At the same time, a method for growing a compound semiconductor single crystal thin film in which a molecular layer containing the impurity element and a molecular layer not containing the impurity element are periodically formed by introducing gaseous molecules containing the impurity element of the compound semiconductor. (14) In claim 12 or 13, gaseous molecules containing component elements of a compound semiconductor in which at least two or more types of compound semiconductor impurity elements are mixed are individually cycled in different cycles or in the same cycle. A method for growing compound semiconductor single crystal thin films in which different impurity elements are included in different molecular layers by introducing them for different times. (15) A method for growing a compound semiconductor single crystal thin film according to any one of claims 1 to 14, in which a substrate is irradiated with light having a wavelength of 180 to 600 nm.