JP2987405B2 - Method for manufacturing compound semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device based on a compound semiconductor and a method of manufacturing the same.
The most effective technique to use when manufacturing a compound semiconductor device having a P single crystal and a Schottky electrode such as a Schottky diode and a MESFET (MES field effect transistor) on a ternary or quaternary mixed crystal substrate. About.

[0002]

2. Description of the Related Art Compound semiconductors such as GaAs and InP have higher electron mobility than Si, and are excellent in radiation resistance and heat resistance, and are expected to be used as high-frequency, high-speed electronic devices replacing Si. Although many studies have been made, MOSFETs have not yet been put to practical use because a stable oxide film having a low interface state density cannot be obtained. Therefore, in GaAs, a MESFET (metal-semiconductor junction type FET) using a Schottky electrode has been put to practical use, and a discrete high-frequency FET and a small-scale digital IC have been put to practical use. However, GaAsM
Since the Schottky barrier potential is small, the ESFET has a drawback that a large logic amplitude cannot be obtained and a large-scale digital IC cannot be manufactured with a high yield.
On the other hand, InP is expected to be used as a material for ultra-high-speed devices, particularly high-power ultra-high-frequency devices, because it has a high electron saturation speed, a thermal conductivity as large as 1.5 times that of GaAs, and a large breakdown voltage. Application to FETs is under consideration.

[0003]

SUMMARY OF THE INVENTION However, InP
Since the Schottky barrier height is smaller (0.3 to 0.4 eV) than GaAs (0.8 eV), it has a large practical disadvantage such as a large reverse leakage current and a small gate breakdown voltage. Therefore, InP uses SiO ₂ , Si
Nx, Al ₂ O _3, a CVD method an insulating film such as PNx, plasma CVD, photo-excited CVD method, a sputtering method, have been many studies of the MISFET for low temperature deposition by vapor deposition or the like. However, in the case of a MISFET having an insulating film deposited at a low temperature, the interface state density between the insulating film and the substrate becomes considerably large, and a MISFET having good characteristics has not been obtained.

Further, a technique related to a diode and a MESFET in which a metal Cd is stacked on an InP substrate or an InGaAs substrate by 200 mm and a Schottky electrode is formed thereon to improve the Schottky barrier height is disclosed in Lica.
(American I.
nstate of Physics Appl.
Phys. Lett. 58 (8), 25 February
ry 1991). However, according to this technique, although the height of the Schottky barrier can be considerably increased, the height of the Schottky barrier can be increased.
It is about 55 to 0.70 eV.

The present invention has been made in view of the above background, and has as its object to provide a III-V compound semiconductor substrate having a Schottky gate electrode having a small reverse leakage current and a high gate breakdown voltage. Good M
An object of the present invention is to provide a method for manufacturing an ESFET and a Schottky diode. It is another object of the present invention to provide a method of manufacturing an InP MESFET and an InP Schottky diode having a Schottky gate electrode having a Schottky barrier height comparable to that of GaAs.

[0006]

In order to achieve the above object, the present invention relates to a substrate having a group III-V compound semiconductor layer such as InP epitaxially grown on its surface, or a group III-V compound semiconductor substrate. The carrier gas is controlled such that the temperature of the substrate installation section is 250 to 450 ° C. and the temperature of the substrate installation section is higher than the temperature of the raw material installation section by 0.1 ° C. to 10 ° C. Is flowed from the raw material installation part side to the substrate installation part side to transport Cd as a raw material and deposit a Cd thin film on the substrate in a thickness of 10 atomic layers or less, and then oxidize the Cd thin film to form a Cd oxide layer. A Schottky electrode is formed thereon.

[0007]

According to the above-mentioned means, the Cd oxide layer is interposed between the semiconductor substrate and the Schottky electrode and is as thin as 10 atomic layers or less. And a Schottky electrode having a sufficiently high Schottky barrier height is obtained, whereby a MESFET and a Schottky electrode having good characteristics having a Schottky gate electrode having a small reverse leakage current and a high withstand voltage are obtained. A diode can be manufactured. With a Cd oxide layer having a thickness exceeding 10 atomic layers, its elastic limit is exceeded, stress acts on the interface, and unpaired bonding occurs at the interface, resulting in a defect level.

In a conventional method of forcibly depositing an insulating film by a CVD method, a plasma CVD method, a photo-excited CVD method, a sputtering method, a vapor deposition method, or the like, a defect due to lattice disorder is generated on a substrate surface. Although only an insulating film having a high potential density could be formed, according to the means described above, C
Since a thin film of d is deposited and this Cd thin film is oxidized, an oxide layer having a thickness of 10 atomic layers or less is formed without causing surface defects, and the interface state density is low and the Schottky barrier height is low. It is possible to obtain a Schottky electrode having a sufficiently high resistance. Further, as a method of depositing a Cd thin film, the temperature is controlled so that the temperature of the substrate installation portion is higher than the temperature of the raw material installation portion by 0.1 ° C. or more and 10 ° C. or less, so that the Cd thin film is applied. , Cd is chemisorbed on the substrate at most 2-3 atomic layers, usually 1 atomic layer, independent of the deposition time,
Cd of 10 atomic layer or less is not stably deposited
A thin film can be applied. Further, the adhesion to the substrate is also increased. Further, the temperature of the substrate installation part is set to 250 to 450 ° C.
By doing so, the height of the Schottky barrier can be made higher than before.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a case where a Schottky electrode is formed on an InP substrate will be described as an example. Example 1 First, a non-doped n-type InP substrate (N = 5 × 10 ¹⁵ cm ⁻³ ) having an ohmic electrode made of AuGe / Ni / Au or the like on its back surface is prepared. Next, after etching the substrate surface, a Cd thin film is formed using an apparatus as shown in FIG. In FIG. 1, reference numeral 1 denotes a cylindrical quartz reaction tube, and one end of the quartz reaction tube 1 (the left end in the figure).
Is connected to a gas introduction pipe 2, and the other end (right end in the figure) of the quartz reaction pipe 1 is connected to a gas exhaust pipe 3. A mass flow controller 4 is provided in the middle of the gas introduction pipe 2 so as to be able to adjust the flow rate of the gas flowing into the quartz reaction tube 1.
The heaters 5a and 5b are arranged so that the temperature in the reaction tube can be controlled.

In this embodiment, a boat 7 containing cadmium 6 as a raw material is installed upstream of the quartz reaction tube 1 and an n-type InP substrate 8 is installed downstream of the quartz reaction tube 1. Then, power is supplied to the heaters 5a and 5b so as to control the temperature T2 of the substrate installation portion to be higher than the temperature T1 of the raw material boat portion by 0.1 ° C. or more and 10 ° C. or less. In addition, an inert gas such as hydrogen or argon is supplied from the gas introduction pipe 2, and the vapor of Cd in the boat 7 is carried to the downstream side, and is chemically adsorbed on the InP substrate 8, and Cd of 10 atomic layers or less is formed. Grow a thin film.

As described above, the temperature T2 of the substrate setting part is controlled so as to be higher than the temperature T1 of the raw material boat part by 0.1 ° C. or more and 10 ° C. or less, and the Cd vapor is carried to the substrate side by the carrier gas. By doing so, a Cd thin film having 10 atomic layers or less can be grown on the InP substrate 8. That is, the temperature T2 of the substrate setting part is equal to the temperature T of the raw material boat part.
When the temperature is lower than 1 (T2 <T1), the deposition reaction of the raw material Cd on the substrate proceeds unilaterally, so that the thickness cannot be controlled in a unit of several atomic layers, and the difference between the temperatures T2 and T1 is reduced. When the temperature is lower than 0.1 ° C., the fluctuation of temperature causes unevenness in the deposition rate, so that the thickness cannot be controlled in units of several atomic layers. Further, if the difference between the temperatures T2 and T1 exceeds 10 ° C., the deposition reaction of Cd on the substrate does not proceed.

On the other hand, after forming a Cd thin film of several atomic layers on the substrate, the gas introduced from the gas introduction pipe 2 is switched to oxygen, and the Cd thin film on the InP substrate 8 is oxidized under the same temperature conditions. After the formation of the Cd oxide layer 12, a Schottky electrode 13 is formed on the Cd oxide layer 12 by an electron beam evaporation apparatus or the like (see FIG. 2). 14 is an ohmic electrode formed in advance.

As an example, the temperature difference ΔT between the temperature T2 of the substrate installation part and the temperature T1 of the raw material boat part is 2 ° C. (where T
2> T1), Cd is 10 on the surface of the InP substrate.
After being adsorbed so as to have an atomic layer or less and then being oxidized, a gold electrode 13 is placed on the Cd oxide layer 12 by 150 nm.
0 ° was formed to produce a Schottky diode as shown in FIG. The temperature T2 of the substrate installation part is 200 to 500 ° C.
About the device obtained by changing in the range of
The voltage-current characteristics were measured while changing the voltage applied between 3 and 14. The result is shown in FIG. As shown in the figure, when the temperature T2 of the substrate installation part is in the range of 250 to 450 ° C., the Schottky barrier is 0.5 e of the general InP Schottky electrode.
V, and the maximum is 0.80 eV.
Also, the leakage current in the reverse direction voltage 2V is 1 × 10- ⁶ A /
cm ² , the withstand voltage was as good as about 90V.

Further, Cd is applied to the substrate surface as described above.
When the surface of the substrate after the formation of the Cd oxide film formed by adsorbing and oxidizing the thin film was measured by an Auger electron spectrometer, it was found that a Cd oxide film of several atomic layers was formed. Further, in the above embodiment, the formation of the Schottky electrode on the InP substrate has been described as an example. However, the present invention is not limited to the InGaAs substrate and other III-V substrates.
The present invention can be applied to a case where a Schottky electrode is formed on a group III compound semiconductor substrate or a substrate on which a III-V group compound semiconductor layer is epitaxially grown.

[0015]

As described above, according to the present invention, the temperature of the substrate mounting portion is set at 250 to 450 on a substrate having a III-V compound semiconductor layer epitaxially grown on its surface or a III-V compound semiconductor substrate. ° C and the temperature of the substrate installation part is 0.1 ° C or more than that of the raw material installation part.
While controlling the temperature so as to be higher than ℃, the carrier gas flows from the raw material installation part side to the substrate installation part side, and the Cd of the raw material is changed.
Was transported to deposit a Cd thin film on the substrate in a thickness of 10 atomic layers or less, and then the Cd thin film was oxidized to form a Schottky electrode on the Cd oxide layer. Since a thin Cd oxide layer is interposed between the electrodes and is as thin as 10 atomic layers or less, the occurrence of unpaired coupling at the interface due to elastic strain acting between the substrate and the Cd oxide layer is prevented. Thus, a Schottky electrode having a sufficiently high Schottky barrier height can be obtained, thereby making it possible to manufacture a MESFET and a Schottky diode having good characteristics having a Schottky gate electrode having a small reverse leakage current and a high withstand voltage. Further, since a Cd thin film is deposited on the surface of the compound semiconductor substrate and the Cd thin film is oxidized, the Cd thin film can be oxidized without causing surface defects.
By forming a Cd oxide layer having a thickness of 0 atomic layer or less, a Schottky electrode having a low interface state density and a sufficiently high Schottky barrier height can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional front view showing an example of an apparatus suitable for use in forming a Cd thin film in the method of the present invention.

FIG. 2 is a cross-sectional view showing a structure of a device manufactured in an example.

FIG. 3 is a graph showing a measured value of a Schottky barrier height of a device (diode) manufactured by a method of an example in relation to an oxidation temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz reaction tube 2 Gas introduction tube 3 Gas exhaust tube 4 Mass flow controller 5a, 5b Heater 6 Cd raw material 7 Boat 8 Growth substrate (InP substrate) 12 Cd oxide layer 13 Schottky electrode (gold electrode) 14 Ohmic electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/338 C23C 16/46 H01L 21/205 H01L 29/812 H01L 29/872

Claims (1)

(57) [Claims] 1. A substrate having a III-V group compound semiconductor layer epitaxially grown on its surface or a III-V group compound semiconductor substrate, wherein the temperature of the substrate setting part is 250-45.
While controlling the temperature so that the temperature is 0 ° C. and the temperature of the substrate installation portion is higher than the temperature of the material installation portion by 0.1 ° C. or more and 10 ° C. or less, the carrier gas is transferred from the material installation portion side to the substrate installation portion side. Cd (cadmium) as a raw material is transported and a Cd thin film is deposited on the substrate in a thickness of 10 atomic layers or less.
A method for manufacturing a compound semiconductor device, comprising oxidizing a thin film and forming a Schottky electrode on the Cd oxide layer.