JPH0787179B2 - Method for manufacturing superlattice semiconductor device - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device having a superlattice of a molecular layer unit having a self-stop function.

[Prior art and problems]

A semiconductor device having a superlattice structure is known as one in which different semiconductors are periodically formed in order to realize characteristics that cannot be obtained by a single semiconductor. However, this superlattice structure semiconductor device must have a structure in which a periodic potential is provided in the one-dimensional direction of the crystal that is sufficiently longer than the lattice constant of the host crystal and shorter than the mean free path of electrons. Therefore, it is difficult to manufacture, and so far, the manufacturing has stopped at the experimental stage and has not been industrialized. This is because the molecular beam epitaxial method (hereinafter referred to as MB
Abbreviated as E method), crystal growth method using organic metal (hereinafter MO-C
Atomic layer epitaxial method (abbreviated as VD method) (hereinafter abbreviated as ALE) and the like are known, but in both cases, it is not easy to form a superlattice structure because of poor film thickness controllability and crystallinity. is there. In other words, in the case of the MBE method, it is difficult to completely satisfy the stoichiometric composition (stoichiometry) because the molecular beam source is applied to the substrate for growth, and the atoms adsorbed on the substrate do not undergo liquid phase growth. As described above, since the crystal surface does not move freely, there is a drawback that a good crystal structure cannot be obtained.

In the MO-CVD method, Japan.J.Appl.Phys.19, (1980) L551 ~
An example of forming a superlattice structure is shown in L554, etc., but as the thickness of the boundary layer (transition layer) between different semiconductors is shown to be 60Å (about 29 molecular layers), it is It has the drawbacks that the crystallinity is originally poor because it is difficult to control the grown film thickness, a high substrate temperature of 600 ° C is required, and because of the thermal decomposition reaction. The ALE method is disclosed in JP-A-55-1.
As shown in Japanese Patent No. 30896, vapors containing component elements of a compound semiconductor are alternately introduced to the surface of a glass substrate to form a thin film by an exchange surface reaction, but the lattice constant is defined because it is polycrystalline or amorphous. Therefore, there is a drawback that a superlattice structure cannot be formed. In addition, the ALE method has a drawback that only one-third molecular layer or less can grow in one cycle of alternate steam introduction. Furthermore, in the ALE method, III-V compound semiconductors and Si
Had the drawback that it could not grow.

[Object of the Invention]

In view of the above points, an object of the present invention is to provide a method for industrially precisely manufacturing a semiconductor device having a superlattice structure on a molecular layer basis by a novel method.

[Outline of Invention]

According to the present invention, at least one molecular layer is formed in one cycle of gas introduction by alternately introducing a gas containing a crystal component element from the outside into a growth tank that is evacuated to a vacuum, and the growth film thickness is measured in molecular layer units. It is characterized in that a superlattice semiconductor device which can be designed by the number of molecular layers can be obtained by controlling and growing a crystal satisfying the stoichiometric composition.

EXAMPLE OF THE INVENTION In the following, will be described taking as an example a case of manufacturing a superlattice semiconductor device of _{GaAs-Ga 1-x Al x} As 1-y P y an embodiment of the present invention.

FIG. 1 is a block diagram of a crystal growth apparatus according to an embodiment of the present invention. In the figure, 1 is a growth tank, the material is metal such as stainless steel, 2 is a gate valve, 3 is a growth tank 1
To an ultra-high vacuum, 4 is a nozzle for introducing a compound gas containing Ga such as GaCl ₃ or TMG (trimethylgallium), 5 is a nozzle for introducing a compound gas containing As such as AsH ₃ , 6 is TMA (trimethylaluminum)
Such as a nozzle for introducing a compound gas containing Al, 7 is PH ₃ , P
Nozzle for introducing a compound gas containing P such as Cl ₃ , 8, 9, 10,
11 is a valve that opens and closes the nozzle, and is a gas source 12 (GaCl ₃
Etc.), 13 (AsH ₃ ), 14 (TMA etc.), 15 (PH ₃ etc.), 16 is a heater for heating the substrate and is a tungsten (W) wire enclosed in quartz glass Are not shown in the figure, 17 is a thermocouple for temperature measurement, 18 is a GaAs substrate, and the tip openings of the nozzles 4, 5, 6 and 7 face the surface of the GaAs substrate,
Moreover, they are arranged as close to the substrate surface as possible.
Reference numeral 19 is a pressure gauge for measuring the pressure in the growth tank.

In the case of epitaxially growing GaAs on the GaAs substrate 18 with this configuration, first, the gate valve 2 is opened, and the inside of the growth tank 1 is 10 ^-7 to 10 ^-8 Pascal (hereinafter abbreviated as Pa) by the ultrahigh vacuum exhaust device 3. ) Exhaust to the extent. Next, the GaAs substrate 18 is
After heating to 0 to 800 ° C, preferably 300 to 500 ° C by the heater 16, TMG12 is sufficiently more than the number of molecules necessary for forming one molecular layer within the range where the pressure in the growth tank 1 is 10 ^-1 to 10 ⁷ Pa. Many 0.
The valve 8 is opened and introduced for 5 to 10 seconds to form a monomolecular adsorption layer. Next, after exhausting excess TMG left over from the formation of the one-molecule adsorption layer from the inside of the growth tank 1, the AsH ₃ 13 pressure is increased to 10%.
^{In the} range of ^-1 to 10 < ⁷ > Pa, the number of molecules is sufficiently larger than the number of molecules required for forming one molecule adsorption layer, and the valve 5 is opened for 2 to 200 seconds for introduction. Excess AsH ₃ 13 left over to form the monomolecular adsorption layer is then exhausted. By the exchange surface reaction accompanying this gas introduction 1 cycle
GaAs monolayer can grow with self-stop function. By repeating this gas introduction cycle a desired number of times, GaAs having a desired number of molecular layers can be formed without using a special film thickness monitor.

Then, Ga is deposited on the GaAs molecular layer thus grown.
_{In the} case of heteroepitaxial growth of _-x Al _x As _1-y P _y , a single molecular layer is formed by introducing Group III Ga and Al and then introducing Group V As and P as in the case of GaAs growth. Growth is possible, and by repeating this, a desired number of molecular layers can be obtained.

Figure 2 is shows the manufacturing process of _{Ga -x Al x As 1-y} P y superlattice semiconductor device according to the molecular layer epitaxy or hetero-epitaxial growth, first, as shown in FIG. (A), GaAs A GaAs layer 21 is epitaxially grown on the substrate 20 in a predetermined number of molecular layers, for example, 30 molecular layers in a molecular layer unit. Subsequently, as shown in FIG. (B), to control the _{Ga -x Al x As 1-y} P y layer 22 given molecular layer number also on a molecular basis, for example 40 molecule layer thereon GaAs layer 21 Heteroepitaxial growth is performed. In addition, the above operation is performed in a predetermined cycle, for example 100
By repeating the cycle, a superlattice structure is formed. FIG. 3C shows three GaAs layers 21 and Ga _1-x Al _x.
This is an example in which As _1-y P _y layers 22 are alternately grown in molecular layer units. At this time, Ga _1-x Al _x As for lattice matching with GaAs
The composition of the mixed crystals of _1-y P _y is x = 0.3, and y = 0.01. On the superlattice structure thus formed, as shown in FIG. 4D, an Au—Ge alloy is vacuum-deposited by several hundred Å to form electrodes 23 and 24. This is formed, for example, by heat treatment at 450 ° C. in a H ₂ gas flow for 1 minute. Thereby, the superlattice diode 25 can be manufactured. As shown in FIGS. 2 (c) and (d), the GaAs layer 21
Since there is no transition layer between the Ga _1-x Al _x As _1-y P _y layer 22 and the superlattice structure can be accurately manufactured in a molecular layer unit.

By the way, when manufacturing the superlattice semiconductor as described above, by irradiating the substrate with ultraviolet rays during the growth, the growth temperature can be lowered to a low temperature such as 300 ° C. or lower, and the crystal quality can be improved. . As the ultraviolet ray source, a mercury lamp, a Xe lamp, an excimer laser, an argon ion laser, or the like can be used, and a window may be provided in the growth tank 1 to irradiate the substrate 18 from the outside.

In the above embodiments, the superlattice semiconductor device of Ga _1-x Al _x As _1-y P _y has been described, but by introducing a gas containing impurities into the growth layer, GaAs, Ga
It goes without saying that impurities can be added to _1-x Al _x As _1-y P _y . In this case, for both GaAs and Ga _1-x Al _x As _1-y P _y , a hydride or fluoride of H ₂ S group VI Te, Se or the like can be used as a gas containing n-type impurities. . Further, as p-type impurities, a gas such as ZnCl ₃ or demethylzinc may be introduced together with a group III or group V gas.

In addition, the combination of semiconductors to be a superlattice, in addition to the above examples, InAs-GaSb, GaSb-AlSb, InAs-AlSb, InP-In _1-x Ga _x P _1- zAsz, InP-In _1-x. Ga _x As, GaAs-GaAs _1-x P _x , GaP-GaP _1-x As _x , GaAs-Ga _1-x In _x As, GaP-AlP, GaSb-InSb, Ge-GaAs, Si-GaP, Si- _{Si 1-x Ge x, CdTe} -HgTe, PbTe-Pb -x Sn x Te, PbTe-Pb 1-x Ge x Te such combinations, p-type and n-type semiconductor combination, three semiconductor combinations, for example, InAs -Applicable to GaSb-AlSb, etc.

〔The invention's effect〕

As described above, according to the present invention, since it is possible to grow a semiconductor crystal film having a self-stop function and having good crystallinity in a molecular layer unit at low temperature, a vapor phase growth method such as a conventional MO-CVD method. The superlattice semiconductor device having no transition layer between different semiconductors existing in the case of the superlattice structure formed in 1. can be industrially produced. According to the present invention, there is no need to use an inert gas other than a raw material gas such as a carrier gas in ordinary vapor phase growth or a gas phase diffusion barrier in the ALE method, and the apparatus configuration is simplified. Furthermore, according to the present invention, since the growth is performed by the self-stop function, only gas introduction cycles are counted and a film thickness monitor is not required.
The configuration and operation of the device are easy, and the control of each molecular layer is possible, which is a great industrial advantage. Furthermore, according to the invention, GaAs and Ga
It is also possible to form a new superlattice structure in which _1-x Al _x As _1-y P _y and _1-x Al _x As _1-y P _y are alternately formed.

[Brief description of drawings]

FIG. 1 is a block diagram of a crystal growth apparatus according to an embodiment of the present invention, and FIGS. 2A to 2D are explanatory views of a manufacturing process of a superlattice semiconductor device manufactured by the apparatus of FIG. . 1 ... Growth tank, 2 ... Gate valve, 3 ... Exhaust device,
4-7 ... Nozzle, 8-11 ... Valve, 12-15 ... Gas source, 16 ... Heater, 17 ... Thermocouple, 18,20 ... GaAs substrate, 19 ... Pressure gauge, 21 ... GaAs layer, 22 …… Ga _1-x Al _x As
_1-y P _y layer, 23,24 …… electrode, 25 …… superlattice diode.

 ─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-55-130896 (JP, A) JP-A-58-98917 (JP, A) Japan. J. Appl. Phy s. , 19 [9], (1980-9), L551 to L554, 43rd Proceedings of the Society of Applied Physics, (1982-9-28), p. 539, 28P-Z-16 "Applied Physics" vol. 53, No. 6, 1984-6, P.P. 516-520

Claims (2)

[Claims] 1. A semiconductor single crystal substrate is heated to 300 to 800 ° C.,
The pressure of the group III compound gas and the group V compound gas in the growth tank is 10 ^-1 to 10 ^-7 pascals through at least two nozzles whose tip openings are located near the surface of the semiconductor single crystal substrate. In the range of the above, the semiconductor single crystal substrate is retreatly introduced into the surface of the semiconductor single crystal substrate from the outside of the growth tank, and the semiconductor single crystal substrate is opened and closed by opening and closing the valves and evacuating the inside of the growth tank only. An exchange surface reaction on the surface of the crystal substrate is realized, and one molecule layer of a group III-V compound semiconductor crystal is formed in a small amount in one cycle of the exchange surface reaction, and the cycle is repeated to obtain a desired number of molecular layers. A method for obtaining crystals, wherein the introduction time of the group III compound gas is 0.5 to 10 seconds, the introduction time of the group V compound gas is 2 to 200 seconds, and (i) the first III-V group The compound semiconductor is composed of a predetermined number of molecular layers in units of one to several molecular layers. And (ii) 1 to several second III-V group compound semiconductors having different constituent elements from the first III-V group compound semiconductors are provided on the first III-V group compound semiconductor. A method of manufacturing a superlattice semiconductor device, which comprises forming a superlattice semiconductor structure by alternately repeating a step of growing a predetermined number of molecular layers in a molecular layer unit a predetermined number of times. 2. The method according to claim 1, wherein
A method of manufacturing a superlattice semiconductor device, characterized in that the crystal quality is improved by irradiating the surface of the substrate with ultraviolet light when forming a III-V compound semiconductor crystal.