JPS62137871A - Manufacture of compound semiconductor device - Google Patents

Abstract

PURPOSE:To uniformly manufacture a field effect transistor (FET) having the desired characteristics and the degree of integration with excellent productivity by a method wherein an excimer laser beam is made to irradiate on the surface of a substrate while an epitaxial process is being performed on GaAs crystal. CONSTITUTION:A completely cleaned semiinsulative GaAs substrate 301 is prepared and it is set in a metal oxide chemical vapor deposition (MOCVD) device. The set substrate is heated up and, at the same time, AsH3 gas is allowed to flow. Then, an excimer laser 303, which is patternized by a metal mask 303 and the like in advance, is made to irradiate on the surface of the substrate, and the growth of crystal is started immediately after said irradiation by passing TMG into the MOCVD device. After lapse of the desired time, first, the flow of TMG is stopped, and then the irradiation of the excimer laser is stopped. After the temperature of the substrate has been dropped completely, the substrate is picked out from the MOCVD device, an etching is performed, an ohmic electrode 309 is formed, and Schottky electrode 310 is formed. This invention can be applied not only to the GaAs crystal but also to InP, InGaAs and the like. Also, this invention can be used not only for the manufacture of III-V compound semiconductor but also for the growth of crystal such as a II-VI group, a IV-VI group, a IV-IV group, chalcopyrite and the like.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the threshold voltage of a metal-semiconductor field effect transistor (hereinafter referred to as MES?FXT) made of, for example, a gallium arsenide crystal (hereinafter referred to as GaAθ crystal). The present invention relates to a method for manufacturing a compound semiconductor device, which is characterized in that characteristics such as conductivity and conduction type can be controlled within the crystal plane during growth of a GaA3 crystal thin film.

[Summary of the invention]

In the method of manufacturing a compound semiconductor device such as a MISFET made of a compound semiconductor crystal, the present invention mainly involves irradiating ultraviolet light during the epitaxial growth process of a crystal thin film used for a PET channel, thereby producing a photochemical reaction caused by the ultraviolet light on the substrate surface. By controlling the carrier concentration and conductivity type in the crystal thin film, it has become possible to manufacture enhancement type and depletion type MESFETs at high density within the substrate surface.

[Conventional technology]

GaAsMKSFIT, which is attracting attention as a high-speed device, is being developed to 16 bits or more by making full use of the integration technology cultivated in silicon LSI.GaAsFET uses high-quality gate insulating films like those used in silicon FIT Since this cannot be obtained, a Mis type that utilizes a metal-semiconductor Schottky contact is used. MES
In the case of type FETs, the Schottky barrier is at most a few electron volts, so a voltage of more than a few volts cannot be applied to the gate electrode, and therefore the characteristics are uniform within the integrated circuit. 'When manufacturing an ET, the threshold voltage ~ of the FIT must be controlled with good uniformity. Furthermore, in order to assemble a logic circuit, PETs having two types of threshold voltages, a depletion type and an enhancement type, are required. Furthermore, in order to prevent heat generation even in the case of high integration, the conductivity types of the FICT channels must be P-type and 2-type to be complementary.

Conventionally, to control the threshold 7u pressure and conduction type of f:rGaAs FET, a technique called ion implantation was used to implant elements that could become donors or acceptors into the PET channel region and its surroundings. , controlled the channel characteristics of each 1i'ET.

[Problems and objectives to be solved by the invention] However,
This ion implantation method has problems with crystallinity and uniformity because the implanted atoms generate defects inside the crystal and the distribution of the implanted atoms in the depth direction varies. In addition, in order to activate the ion-implanted atoms, a heat treatment process that takes a long time is necessary, and in order to create a difference in threshold voltage between each FET, ions must be implanted separately, and equipment handling is required. There was a problem in that productivity was extremely low because it took a long time. moreover,
This method involves the step of exposing the compound semiconductor thin film to the atmosphere after it has been epitaxially grown, which has the problem of degrading the characteristics of the semiconductor.

The present invention is intended to solve these problems, and its purpose is to provide a method for manufacturing FETs with desired characteristics and degree of integration uniformly and with high productivity. .

[Effect]

Metal-organic pyrolysis crystal growth method (hereinafter referred to as MOOVD method)
By irradiating the substrate surface with an excimer laser during the epitaxial process of GaA3 crystal, the electrical characteristics of the epitaxial layer in the portion irradiated with the excimer laser change. This is because impurity raw materials that are difficult to decompose by heat contained in metal alkyl compounds and hydrides, which are gas phase raw materials, are easily decomposed by excimer laser, and impurities are not taken into crystals by excimer laser. As a result of being promoted or suppressed by the laser, the impurity concentration in the crystal differs only in the excimer laser irradiated area. Since the excimer laser is irradiated during the crystal growth process, the impurity concentration distribution in the film thickness direction is uniform and the crystallinity is good. Furthermore, by changing the wavelength and intensity of the excimer laser, the type and concentration of impurities that are taken in can be changed.

〔Example〕

trimethylgallium (TMC)) and arsine (A
AeH,/TMG of the carrier concentration in the GaAθ crystal grown by the MOCjVD method using sH3 as the raw material
The molar ratio dependence is shown in FIG. The solid line in the figure shows the crystal grown by the normal pyrolytic MOCVD method, and the dotted line shows the crystal grown by the normal pyrolytic MOOVD method.
The results are shown when the rF excimer laser is irradiated with an intensity of 1.5 W/, -j, respectively. Because the rate of impurity incorporation into the crystal varies depending on excimer laser irradiation,
The curve has shifted to the left. When the AeH,/TMG molar ratio is at point A in the figure, the electron concentration is high in the part irradiated with the excimer laser. FIG. 2 shows the relationship between the excimer laser intensity and the change in carrier concentration. The change in carrier concentration is calculated by dividing the carrier concentration in the crystal by the carrier concentration in the crystal not irradiated with excimer laser. When the excimer laser intensity is increased, the electron concentration increases when the conductivity type is n-type, and the hole concentration decreases when the conductivity type is p-type.

An embodiment of the present invention utilizing these effects of excimer laser irradiation is shown in FIG. 5(α) and FIG. 3(b). G
The manufacturing process of aAsIFKT will be explained. First, a sufficiently cleaned semi-insulating GaA3 substrate is prepared and set in the MOOVD apparatus. While heating the set board,
Flow AsH gas. Next, an excimer laser patterned in advance using a metal mask or the like is irradiated onto the substrate surface.
Immediately after that, TMG is poured into the MOOVD apparatus and crystal growth is started. After a desired time has elapsed, the flow of TMG is first stopped, and then the irradiation partial pressure of the excimer laser is reduced. After the substrate temperature has dropped sufficiently, the substrate is taken out of the equipment and etched.
Formation of ohmic electrodes and Schottky electrodes completes the process. FIG. S (α) shows a schematic cross-section of a semiconductor during crystal growth. 501 is a semi-insulating GaA3 crystal substrate.

502 is a metal mask for patterning the excimer laser. 303 is an excimer laser patterned by the metal mask described above.

304 is a normal MO (!5E formed by the VD method)
It is a GaAθ crystal. 305 is a part irradiated with excimer laser, which has a higher electron concentration than the n-type GaAs crystal.
It is a type GaA3 crystal.

FIG. 5<b> is a diagram of a completed structure when two types of FETs having different threshold voltages are formed on the same substrate. 306 is a semi-insulating GaA3 substrate like 301, 507 is 304
Similarly to 505, 308 is an n-type GaAS crystal, and like 505, it is a nine-type GaAB crystal. 509 is a metal for making ohmic contact with each GaAs crystal layer, and in this case, Au-Ge/Ni was used. 5o9
correspond to the source and drain of PET. 510 is gate gold fm (Au) and 307 or 508 GaAs
It is in direct contact with the crystal. The 2161 class n-nayanel GaAs produced in this way? Figure 4 shows the characteristics from VU- of ET. Do not irradiate with excimer laser 5
IPET using - type GaA3 crystal was an enhancement type, whereas external type G with excimer laser irradiation
The aAs crystal PET has become a depression type.

The present invention is applicable not only to GaAs crystal system but also to In2 system and InG crystal system.
It can also be applied to aAs thread. In addition to manufacturing m-■ group compound semiconductors, we also manufacture n-VI group compound semiconductors.

■Applicable to crystal growth of group VI, group IV-tV, chalcobyrite, etc. In this example, the MOOVD method was used as a crystal growth method, but MOOVD method, which is a vapor phase growth method, was used.
It can be applied to the MBK method, general VPE method, and reduced pressure OVD method. Although 193 mm of ArIF was used as the wavelength of the excimer laser, it is possible to use Ar, Kr, and Xe-based fluoride and chloride, which can selectively decompose the source gas, as the filler gas of the excimer laser.

〔Effect of the invention〕

The effects of the present invention include the following.

(1) Since impurity doping can be performed during the crystal growth process, a crystal with good crystallinity and uniform film quality can be obtained.

(2) Since the crystal value and conductivity type can be controlled simultaneously during the crystal growth process, productivity is high and equipment can be inexpensive.

(3) Since an excimer laser is used, the intensity of the light is strong, and since it is parallel light, it is effective for fine/zetaturns.

(4) The threshold voltage can be freely controlled by changing the intensity of the excimer laser.

(5) Devices with superior characteristics can be manufactured because the number of steps in which the crystal is exposed to the atmosphere is reduced.

[Brief explanation of drawings]

Figure 1 is MOC! 2 is a graph showing the dependence of the carrier concentration in a GaAl3 crystal grown by the VD method on the (ASH,)/CTMG) molar ratio. The solid line shows the characteristics of the part not irradiated with the excimer laser, and the dotted line shows the characteristics of the part irradiated with the excimer laser. FIG. 2 is a graph showing the relationship between excimer laser intensity and carrier concentration change. 201 force type 1, 20
2 is the P type. FIG. 3 is a schematic diagram of the FF1T structure manufactured according to the present invention, FIG. 3 (α) is a cross-sectional view during crystal growth, and FIG. 3 (b) is a cross-sectional view of the completed structure. . 301.306...Semi-insulating GaAθ crystal substrate 302...Metal mask 503...Excimer laser 304, 307==ts-type GaAe crystal 305,
308-=s type GaAs crystal 509...Ohmic electrode (source, drain 510...Schottky electrode (gate)) Figure 4 shows the manufactured GaAsME
S? This is the gate % needle drain current characteristic of ET. 40
1 does not irradiate excimer laser? ]Characteristics of lCT, 4
02 is a characteristic diagram of the FET irradiated. Applicant Seiko Epson Co., Ltd. Figure 1 - IT ``J' History i Bi ~ String'' υ Support arrogant'' Mountain map 3rd figure (Ku) Light entrance lecture round/S front darkness concave 2 FW <F,; Date "den) L V@- '!i1shi+5Cra8s HE5FETnVc, -ko *t)I-' iFigure 4

Claims (2)

[Claims] (1) A method for manufacturing a compound semiconductor device comprising stacking at least one compound semiconductor thin film on a semiconductor substrate, including the step of irradiating the surface of the semiconductor substrate with ultraviolet light during epitaxial growth of the compound semiconductor thin film, The step of forming an n-type depletion field effect transistor on the compound semiconductor thin film in the region irradiated with the ultraviolet light, and forming an n-type enhancement field effect transistor in the compound semiconductor thin film in the region not irradiated with the ultraviolet light. A method for manufacturing a compound semiconductor device characterized by: (2) The method for manufacturing a compound semiconductor device according to claim 1, characterized in that an alkyl compound and an aqueous compound of metal are used as raw materials for the epitaxial growth, and an excimer laser is used as the ultraviolet light. .