JPS625632A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To dope arsenic of high density, to reduce the defect density of an epitaxial film, to abruptly increase the profile of an impurity by ionizing part of arsenic when evaporating from InAs, GaAs or InGaAs, and emitting a silicon molecular beam on a substrate. CONSTITUTION:Part of arsenic evaporated from InAs, GaAs or InGaAs is ionized, emitted together with a silicon molecular beam on a substrate, and doped with the arsenic. For example, arsenic molecules evaporated from an arsenic evaporation source 41 heated by a filament 40 is partly ionized by thermions from the filament near a grid 42. These ions are drawn by a lead out electrode 43, and then accelerated toward the substrate since an accelerating voltage 44 (1-2kV) is applied to the substrate potential. A Faraday cup 45 is disposed as required between the electrode 43 and the substrate to measure the ion current.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a semiconductor thin film.

(Conventional technology) In recent years, growth has been performed at lower temperatures than conventional silicon thin film growth techniques for the purpose of application to high-speed bipolar devices, microwave devices, and superlattice structure devices.
Therefore, silicon molecular beam growth (8iMEB) in a high vacuum is characterized by hardly disturbing the impurity distribution.
) technology is being actively researched and developed.

(Problems to be Solved by the Invention) In such a silicon molecular beam growth technique, the doping method generally involves blowing molecular or atomic impurities out of the molecular beam cell at the same time as silicon. Therefore, the N-type impurity for doping has been limited to antimony, which can be easily removed from the molecular beam cell.

However, in the current semiconductor device manufacturing process, N
Arsenic and phosphorus are mainly used as type impurities, and many technologies have been accumulated for dealing with these impurities. However, K.
- When doping single arsenic by heating it in a cell, the heating temperature of arsenic is low;
It must be minutely controlled at around 0°C, which is extremely difficult. Furthermore, even if the main body of the device is simply baked at 200° C., the vapor pressure of arsenic is high and the amount of arsenic circulates around the device, causing it to fill and contaminate the device. Further, even during doping, since the adhesion coefficient of neutral arsenic molecules to silicon is very small, in order to perform high concentration doping, a large amount of arsenic must be blown away, which also contaminates the inside of the device. Furthermore, when doping is performed using neutral arsenic, even if the impurity profile is changed by opening and closing the shutter, a pile-up of impurities (surface high concentration layer) will occur on the substrate surface, so the actual impurity profile will change when the shutter opens and closes. The carrier concentration changes slowly without following the current, and as a result, a steep impurity profile cannot be obtained.

Therefore, Iyer (8, S, Iyer) et al.
-Phys, ) 52 (1981) 5608, when growing a new layer, silicon is not evaporated first, but only impurities are evaporated and deposited to create a pile-up of impurities on the substrate surface. "prebuild up" and "flashoff", a method in which when the growth of one layer is finished, a high temperature treatment of 950 to 1000 degrees Celsius is performed for a short period of time to remove impurities remaining on the surface. However, this would require high-temperature heat treatment, which would undermine the original advantage of silicon molecular beam growth, which is low-temperature growth, and would likely lead to changes in impurity distribution due to high-temperature heat treatment.

In order to overcome the above drawbacks, Be1l Lab's J.
C-Bean et al., Journal of Vacuum Science and Technology (J-Vac-8ci, Technol-) 20
(2) (1982) 137, proposes a method of performing slow ion implantation of boron and arsenic during growth. However, in this method, the ion implantation device must be combined with the MBE device, which increases the size of the device and poses problems such as deterioration of the degree of vacuum on the λIBk device side.

The purpose of the present invention is to eliminate such conventional drawbacks,
To provide a method for manufacturing a single conductor thin film which is doped with arsenic at a high concentration, reduces the defect density of the epitaxial film, makes the impurity profile steeper, and does not contaminate the inside of the device with arsenic. .

(Means for Solving the Problem) According to the present invention, in impurity doping in silicon molecular beam growth, a part of arsenic evaporated from indium arsenide or gallium arsenide (or indium gallium arsenide) is ionized and transferred onto a substrate. A method for manufacturing a semiconductor thin film is obtained, characterized in that doping is performed by irradiation with a silicon molecular beam.

(Function) According to this method, when doping with arsenic, by using an arsenic compound instead of using arsenic alone, the required vapor pressure can be obtained within a normal temperature range, thereby preventing contamination within the device. In addition, by using an ionization cell, the adhesion coefficient of arsenic molecules that can be doped effectively increases significantly, and when the degree of doping is varied, the width of the transition region becomes extremely small, resulting in a steep impurity distribution. Furthermore, the doping concentration can be significantly increased compared to the case where only neutral molecules are used. Furthermore, at the same time, ionization reduces the factors that cause lattice defects, and the defect density can also be reduced.

(Example) Next, an example of the present invention will be described with reference to the drawings. Figure 1 (a) shows that InAa near the filament is heated by thermal radiation, and only arsenic molecular beams are generated by utilizing the difference in sublimation temperature between indium and arsenic in InAs, and electron beams are applied to the generated arsenic molecular beams. This figure shows the relationship between the amount of arsenic doped and the ion acceleration voltage when doping is performed using a cell that ionizes a part of the arsenic molecular beam by emitting .

The ionization cell used here has a structure as shown in FIG. 4, with an arsenic evaporation source 4 heated by a filament 40
The arsenic molecules evaporated from 1 are partially ionized near the grid 42 by hot electrons from the filament. After these ions are extracted by the extraction electrode 43,
Furthermore, an accelerating voltage 44 (
0 to 2 KV) is applied, so it is accelerated toward the substrate. 7 between the extraction electrode and the substrate as necessary.
It is possible to position the Aradeca 45 and measure the ion current.

Further, FIG. 1(b) shows the relationship between the density of dislocations formed in the epitaxial film and the accelerating voltage. The substrate is a P-type single crystal silicon wafer with (100) plane orientation.
Growth temperature is 750℃, silicon growth rate is 10X/8
It is. As can be seen from the results shown in Figure 1(a),
The doping amount of arsenic has an accelerating voltage dependence; when the acceleration is O, it is 4 x 10"cm-", but it increases as the accelerating voltage increases, and when the acceleration is 1.5 KV, it is 8 x
The maximum is 10"am", and 2. Above OKV, it decreases rapidly. Furthermore, as can be seen from the results shown in Figure 1(b), the dislocation density at this time also has a dependency on the acceleration voltage, with a minimum value of 2000 cm'' when the acceleration is IKV, and 2
．． Above OKV, the dislocation density increases rapidly. Therefore,
It can be seen that if ionization doping is performed at an accelerating voltage of 0.5 to 1.5 KV, high concentration doping can be achieved and the dislocation density can also be reduced. Furthermore, the sublimation temperature of arsenic from InAs is approximately 400°C, so baking the main body of the device at 150°C will not release arsenic and contaminate the inside of the device, and the ionization effect increases the adhesion coefficient, so excess arsenic High concentration arsenic doping can be performed without blowing off and contaminating the inside of the device. In addition, when arsenic is removed from arsenic alone, the cell temperature must be slightly controlled at around 100°C, which is very difficult, but by removing it from InAsT, the cell temperature can be lowered to 40°C.
The temperature can be raised to around 0°C, making it easier to control the temperature.

The reason why it is preferable for the accelerating voltage to be between 0.5 and 15 KV is considered as follows. When the accelerating voltage is lower than this range,
This is because each arsenic ion does not have the energy necessary for doping, and when the accelerating voltage is high, there is too much energy and either reevaporation occurs, or it is implanted into the substrate and remains in an inactive state. It is believed that there is. Further, when a Faraday cup was placed in front of this arsenic ionization cell and the ion current was measured, it was 0.1 μA regardless of the accelerating voltage. Therefore, assuming that the adhesion coefficient of arsenic ions is 1, that all 0.1 μA arsenic ions reach the substrate, and that only these arsenic ions contribute to the carrier concentration, the calculation results in 8 x 10"cm-'. This calculated value is two orders of magnitude lower than the experimental value.This can be explained as follows.On the silicon surface,
It is thought that arsenic molecules and arsenic ions are mixed,
In this state, energy is transferred from the ions to the molecules, activating many arsenic molecules and making high-concentration doping possible. Therefore, by mixing a neutral arsenic molecular beam and arsenic ions, it is possible to achieve doping at a concentration X5≧about 100 times higher than when a neutral molecular beam or arsenic ions are used alone.

FIG. 2 shows the results of spreading resistance measurements when changing the impurity profile between the molecular beam cell and the ionization cell.

From this, in case 3 of the molecular beam cell, a carrier distribution corresponding to the doping conditions was not obtained, but in case 4 of the ionization cell, a steep carrier distribution corresponding to the doping conditions was obtained.

Next, as shown in FIG. 3, an N type epitaxial layer 32, which is a collector, is formed on the N+ silicon substrate 31.
The P-type epitaxial layer 33 that is the base of oX and the N-type epitaxial layer 34 that is the emitter are all made using a silicon molecular beam epitaxial layer, and the doping is accelerated 1. When using an OKV ionization cell, a steep impurity distribution is possible, so the transition region can be made thinner than when using a molecular beam cell, and the active region can be effectively made thinner. It is now possible to operate approximately five times faster than before.

In the above embodiments, only the case of arsenic doping from InAs was described, but it is also possible to dope from GaAs or InAs.
GaAs can also be doped with arsenic.

(Effects of the Invention) As described above in detail, if the present invention is carried out as intended, it is possible to perform high-concentration arsenic doping without contaminating the inside of the device with arsenic, reduce the defect density of the epitaxial film, and further reduce the steep impurity It is possible to get a profile of.

[Brief explanation of the drawing]

Figure 1 shows the accelerating voltage, arsenic doping amount, and width when arsenic ionization doping is performed. FIG. 2 is a diagram showing the result of spreading resistance measurement for comparing impurity profiles between a molecular beam cell and an ionization cell. FIG. 3 is a cross-sectional view of a bipolar transistor manufactured using the present invention. FIG. 4 is a schematic diagram of the structure of the ionization cell. In the figure, 3... Doping profile by molecular beam cell, 4... Dobin by ionization cell, Figure 1, Toguchi pressure (XV), Figure 2, I

Claims (1)

[Claims] In impurity doping in silicon molecular beam growth, indium arsenide (InAs) or gallium arsenide (
GaAs) or indium gallium arsenide (InGa
A method for manufacturing a semiconductor thin film, characterized in that arsenic doping is performed by ionizing a portion of arsenic evaporated from As) and irradiating it onto a substrate together with a silicon molecular beam.