JPH04352330A - Manufacture of mis semiconductor device - Google Patents

Abstract

PURPOSE:To make the surface of a GaAs substrate nitride and to form efficiently a GaN film by a method wherein As atoms are made to evaporate from the surface of the GaAs substrate to make the surface rich in Ga by annealing first the GaAs substrate surface at a high temperature for a short time in an H2 gas atmosphere and thereafter, the GaAs substrate surface is annealed in an NH3 gas atmosphere. CONSTITUTION:A GaAs substrate 1 is mounted on a carbon boat 3 provide with a thermocouple monitor 2 in an infrared ray lamp annealing device, with the substrate surface up. The substrate 1 surface is annealed at a high temperature for a short time in an H2 gas atmosphere. Whereby As atoms are made to evaporate from the surface of the GaAs substrate and the surface becomes rich in Ga. Moreover, the H2 gas is changed to NH3 gas keeping the substrate 1 intact and the substrate 1 surface is annealed at a high temperature for a short time. Thereby, GaAs substrate surface is efficiently nitrided and a GaN film 9 is formed on the surface in a thickness of about 50nm.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to compound semiconductor GaAs (
Metal-insulating film-semiconductor (MIS) using gallium arsenide
) type element manufacturing method.

0002

2. Description of the Related Art Various MIS type devices using compound semiconductor GaAs have been reported to date. As insulating films, plasma oxide films of SiO2, SiN, AlN, GaAs, and semiconductor layers such as AlGaAs have been reported.

0003

[Problem to be Solved by the Invention] However, in MIS type devices using such conventional insulating films, the interface state density is 10.
It was often 12 cm-2 eV-1 or more, and it was difficult to form an inversion layer. This is because a large number of surface levels exist on the GaAs surface, such as donors due to As atoms (AsGa) at Ga lattice positions and acceptors due to Ga atoms (GaAs) at As lattice positions. On the other hand, in MIS type devices using semiconductors such as AlGaAs, the interface state density is
Although it is as small as an OS element, the maximum energy gap is only about 2 eV, and as the bias voltage increases, the leakage current increases and the bias margin is small.

0004

[Means for solving the problem] MIS according to claim 1
The method for manufacturing a type semiconductor device is to manufacture a GaA type semiconductor device in a hydrogen gas atmosphere.
The method is characterized by including a step of annealing at least one main surface of the GaAs substrate at high temperature for a short time in an ammonia gas atmosphere, and then annealing one main surface of the GaAs substrate at high temperature for a short time in an ammonia gas atmosphere.

The method for manufacturing an MIS type semiconductor device according to the second aspect includes generating plasma using a gas containing oxygen, exposing at least one principal surface of a GaAs substrate in the plasma gas, and then processing the GaAs substrate. It is characterized by including a step of annealing one main surface of the GaAs substrate at high temperature in an ammonia gas atmosphere for a short time.

[0006] In the method for manufacturing an MIS type semiconductor device according to claim 4, plasma is generated using a gas containing nitrogen trifluoride, and at least one main surface of a GaAs substrate is exposed and processed in the plasma gas. It is characterized by including a process.

[0007]

[Operation] In the first method as claimed in claim 1, the As atoms on the surface of the GaAs substrate are evaporated by first short-time annealing at high temperature in hydrogen gas to make the surface Ga-rich, and then the surface is made Ga-rich. A gallium nitride (GaN) layer is efficiently formed by annealing at a high temperature for a short time.

In the second method described in claim 2, a gallium oxide (Ga2 O3) layer is formed on the GaAs surface by a first oxygen-containing gas plasma treatment, and then a short time annealing at a high temperature in annimore gas is performed. The gallium oxide layer is efficiently nitrided to form a gallium nitride (GaN) layer.

In the third method according to claim 4, GaA
A GaFN film is formed by fluoridating and nitriding GaAs by plasma treatment of nitrogen trifluoride (NF3) gas on the surface of the s-substrate.

GaN formed by the first and second methods has a large energy gap of approximately 3.4 eV, and thus plays a sufficient role as an insulating film. Also, G formed by the third method
Similarly, the aFN film has an energy gap of 3.4 to 9.
．． Similarly, the film sufficiently functions as an insulating film between 6 eV and 6 eV. Furthermore, since the interface between these insulating films and GaAs is formed inside the GaAs, it is not affected by the GaAs surface, and the interface state density is very low, making it possible to obtain a good MIS type element.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing an MIS type semiconductor device according to the present invention will be explained below based on specific examples.

FIGS. 1A to 1D show an embodiment of the first manufacturing method according to claim 1. As shown in Figure 1(a), n-type (carrier concentration is approximately 1 x 1017 cm-3)
A GaAs substrate 1 is placed with the substrate surface upward on a carbon boat 3 equipped with a thermocouple monitor 2 in an infrared lamp annealing apparatus, and is annealed at a high temperature and for a short time in an H2 gas atmosphere. High temperature is approximately 700℃ ~ 85
At 0°C, the short time is in the range of about 5 seconds to 10 seconds, and in this example, annealing was performed in an atmosphere of 750°C for 5 seconds.

As a result, As atoms evaporate from the GaAs surface, making the surface rich in Ga. In this manufacturing equipment, 4
5 is an infrared lamp, 5 is a reflector, 6 is a susceptor made of quartz glass, and 7 and 8 are a gas inlet and an outlet, respectively.

Furthermore, as shown in FIG. 1(b), Ga
The As substrate 1 is subjected to high-temperature, short-time annealing by switching to NH3 gas while maintaining its position. High temperature is about 700
C to 850 C, and the short time ranges from about 5 seconds to 15 seconds, and in this example, it was annealed at 800 C for 5 seconds.

As a result, the surface of the GaAs substrate is efficiently nitrided, and a GaN layer 9 of about 50 nm is formed on the surface. Furthermore, as shown in FIG. 1(c), AuGe was evaporated on the back surface of the GaAs substrate and argon (A
r) Form an ohmic electrode 10 by sintering in a gas, and then apply a lift-off method to a predetermined region of the GaN layer to form a gate electrode 11 made of aluminum (Al) metal, as shown in FIG. 1(d). is formed to complete the MIS diode.

FIGS. 2A to 2D show an embodiment of the second manufacturing method according to claim 2. As shown in FIG. 2(a), an n-type GaAs substrate 1 is placed on a heater 12 in a plasma CVD apparatus, nitrous oxide (N2O) gas is introduced into a chamber 13, and a high frequency power source 14 is used to
13.56MHz, high frequency output 100W to electrode 14a
, 14b to generate plasma and plasma-treat the surface of the GaAs substrate. The plasma conditions are N
2 O gas flow rate of 20 sccm, vacuum degree of 40 Pa, substrate temperature of 300° C., and processing time of 5 minutes were used.

As a result, a GaAs oxide film 15 (about 40 nm thick) containing gallium oxide (Ga2 O3) as a main component is formed on the GaAs surface. In the same figure, 16
, 17 indicate a gas inlet port and an exhaust port, respectively.

Although this GaAs oxide film 15 is unstable, next, as shown in FIG. 2(b), the GaAs substrate 1 is placed in an infrared lamp annealing device and subjected to high-temperature and short-time annealing in an NH3 gas atmosphere. undergo annealing. High temperature is about 7
The short time ranges from about 5 seconds to 15 seconds, and in this example, it was annealed at 800 degrees Celsius for 5 seconds.

As a result, the oxide film 15 on the GaAs surface is efficiently nitrided, and a more stable GaN layer 9 (with a thickness of about 50 mm) is formed.
nm). Next, as shown in FIG. 2(c), AuGe was deposited on the back surface of the GaAs substrate at 450°C.
The ohmic electrode 10 is formed by sintering in argon (Ar) gas for 30 seconds. Furthermore, as shown in FIG. 2(d), a gate electrode 11 made of aluminum (Al) metal is applied to a predetermined region of the GaN layer using a lift-off method.
is formed to complete the MIS diode.

In this example, N2 is used as the oxygen-containing gas.
Although O was used, NO2 gas or NO gas may also be used. FIGS. 3A to 3C show an embodiment of the third manufacturing method according to claim 4.

As shown in FIG. 3(a), n-type GaAs
A substrate 1 is placed on a heater 12 in a plasma CVD apparatus, and nitrogen trifluoride (NF3) gas is injected into a chamber 13.
The frequency is 13.56MH from the high frequency power supply 14.
z, high-frequency power of 100 W is applied between the electrodes 14a and 14b to generate plasma, and the surface of the GaAs substrate is plasma-treated. The plasma conditions were: NF3 gas flow rate 20 sccm, vacuum degree 40 Pa, substrate temperature 300°C,
A treatment time of 15 minutes was used.

As a result, the GaAs surface was fluoridated and nitrided to form a GaFN film 18 with a thickness of about 50 nm. Next, as shown in FIG. 3(b), A
uGe was evaporated and heated at 450°C for 30 seconds using argon (Ar).
) sintering in a gas to form an ohmic electrode 10;
Furthermore, as shown in FIG. 3C, a gate electrode 11 made of aluminum (Al) metal is formed in a predetermined region of the GaFN layer using a lift-off method to complete the MIS diode.

FIG. 4 shows the C-V (capacitance-voltage) characteristics at high frequency (1 MHz) and low frequency (10 Hz) of three types of MIS diodes manufactured by each of the manufacturing methods shown in FIGS. 1 to 3. The vertical axis is normalized by the insulating film capacitance Ci.

As is clear from FIG. 4, all samples have a withstand voltage of up to ±5 V, the formation of an inversion layer is observed, and the transition from the accumulation region to the depletion region is steep.

FIG. 5 shows the interface state density distribution obtained for the three samples shown in FIG. 4, and the lowest interface state is 1 for both samples.
It shows a very low value of the order of 0.010 cm-2 eV-1, indicating that good interfacial properties are obtained.

In each of the above embodiments, the substrate 1 is made of n-type Ga.
Although the As substrate has been described, it goes without saying that the same applies to a p-type GaAs substrate. Moreover, although the MIS type diode has been described, it goes without saying that the same applies to the MIS type FET.

[0027]

According to the first manufacturing method described in claim 1, the GaAs surface is first annealed at high temperature in an H2 gas atmosphere for a short time, thereby evaporating As atoms from the GaAs surface and making the surface rich in Ga. By subsequently annealing in an NH3 gas atmosphere, the GaAs surface can be nitrided and a GaN film can be efficiently formed.

According to the second manufacturing method described in claim 2, a GaAs oxide film is formed on the GaAs surface by plasma treatment with a gas containing oxygen (O2), and then annealing is performed in an NH3 gas atmosphere to form a GaAs oxide film. An oxide film can be efficiently converted into a stable GaN film.

According to the third manufacturing method described in claim 4, the GaAs surface is subjected to plasma treatment with NF3 gas, thereby fluoridating and nitriding the GaAs surface to form GaF.
An N film can be formed.

The GaN and GaFN films formed by these manufacturing methods have a large energy gap and sufficiently serve as an insulating film, and the interface with GaAs has a large energy gap.
Since it is formed inside the GaAs surface, a MIS type element with a low density of interface states can be created without being affected by the GaAs surface. The thickness of these GaN and GaFN films can be adjusted by adjusting annealing conditions, plasma conditions, and the like.

[Brief explanation of drawings]

FIG. 1 shows a process diagram of a method for manufacturing an MIS type element according to a first embodiment of the present invention.

FIG. 2 shows a process diagram of a method for manufacturing an MIS type element according to a second embodiment of the present invention.

FIG. 3 shows a process diagram of a method for manufacturing an MIS type element according to a third embodiment of the present invention.

FIG. 4 shows a capacitance-voltage characteristic diagram of each MIS type element of the first to third embodiments of the present invention.

FIG. 5 shows an interface state density distribution characteristic diagram of each MIS type device according to the first to third embodiments of the present invention.

[Explanation of symbols]

1 N-type GaAs substrate 2 Thermocouple monitor 3 Carbon boat 4 Infrared lamp 5 Reflector plate 6. Quartz glass susceptor 7 Gas inlet 8 Gas outlet 9 GaN layer 10 Ohmic electrode 11 Gate electrode 12 Heater 13 Chamber 14 High frequency power supply 15 GaAs oxide film 16 Gas inlet 17 Gas exhaust port 18 GaFN film

Claims (4)

[Claims] 1. The method includes the step of annealing at least one main surface of the GaAs substrate at high temperature for a short time in a hydrogen gas atmosphere, and then annealing one main surface of the GaAs substrate at high temperature for a short time in an ammonia gas atmosphere. Featured MIS
A method for manufacturing a type semiconductor device. 2. After generating plasma using a gas containing oxygen and exposing at least one main surface of the GaAs substrate in the plasma gas, one main surface of the GaAs substrate is exposed to high temperature in an ammonia gas atmosphere. 1. A method for manufacturing an MIS type semiconductor device, comprising a step of annealing for a short time. [Claim 3] The gas containing oxygen is N2O, NO2
, NO. 4. A MIS type semiconductor device, comprising the step of generating plasma using a gas containing nitrogen trifluoride, and exposing and processing at least one principal surface of a GaAs substrate in the plasma gas. Production method.