JPS62269311A - Method for doping on crystal - Google Patents

Abstract

PURPOSE:To contrive improvement in doping efficiency by a method wherein the gas molecule containing the element to be turned to a dopant is decomposed with plasma, and a doping is performed by controlling the quantity of decomposed gas and by changing the high frequency power of a plasma generating source. CONSTITUTION:The gas molecule containing the element to be turned to a dopant is decomposed with plasma, and the density of doping is brought under control by controlling the quantity of decomposed gas by changing the power of a plasma generating source. For example, dopant gas is introduced into an MBE growing chamber 6 before the growth of GaAs or the GaAs is being grown, and 100W of the high frequency power of the frequency of 13.56 MHz is applied. The dopant gas is turned to a radical by partial or total decomposition by high frequency heating, and it reaches the GaAs substrate 7 which is heated up to 600 deg.C by the filament 9 to be used for heating of the substrate. Said radical is adhered to the GaAs substrate 7 and decomposed, and it is turned into Si or C and brought into the grown layer as a dopant. As a result, doping efficiency can be improved.

Description

[Detailed Description of the Invention] [Summary] In molecular beam epitaxial (MBE) crystal growth, etc.
By decomposing gas molecules containing dopant elements with plasma and performing doping by changing the amount of decomposed gas by changing the high frequency power of the plasma generation source, doping can be performed using any source gas. Doping efficiency can be increased even for gases with small coefficients or gases with high decomposition temperatures.

[Industrial application field]

The present invention uses Topan! gas in MBE crystal growth, etc.
-Relates to a method of doping crystals using raw materials.

[Prior Art] In MBE crystal growth, doping is usually performed using a solid source. For example, gallium 6th element (G
As a dopant for n-type silicon (St
), beryllium (Be), or carbon (C) for p-type
There is.

Solid-state doping with St is performed by heating solid Si at about 1200'C and irradiating the heated crystal substrate with molecular beams emitted from the surface by sublimation, thereby incorporating Si into the crystal.

Solid doping with Be is carried out in the same manner, but since Be is a highly toxic substance, it is desirable to use C, but doping is difficult because of its low vapor pressure.

For this reason, gas doping has recently been attempted.

A recent method of doping a crystal using a gas as a dopant raw material is to thermally decompose the gas adhering to the surface of the epitaxial layer (by heating the substrate) and incorporate it into the epitaxial layer. For example,
In the following literature, monosilane gas (S i I+ 4 ) is used to prepare GaAs, aluminum gallium arsenide (AIGa).
Doping of Si into As) has been reported.

Br1ones et al, Vac, Sci,
Technol, B3 (1985).

In this case, the doping efficiency (number of moles taken into the crystal/number of moles incident on the crystal) is extremely low at 10 −4 or less. Furthermore, the doping efficiency depends on the substrate temperature,
/ Group III (Ga) group ratio, making control difficult.

[Problem that the invention seeks to solve]

Conventional gas doping has the disadvantage that doping efficiency is extremely low when the dopant has a small adhesion coefficient or when the decomposition temperature is higher than the substrate temperature.

[Means for solving problems]

The solution to the above problem is to dope the crystal by decomposing the gas molecules containing the dopant element using plasma and controlling the amount of decomposed gas by changing the power of the plasma generation source to control the doping concentration. This is accomplished by a method.

[Effect]

The present invention utilizes the property that when gas molecules are irradiated with high frequency waves having an appropriate frequency, some or all of the gas molecules decompose and radicals are generated.

That is, by providing a means for high-frequency heating of the dopant gas, some or all of the dopant gas molecules are decomposed to create radicals, thereby increasing the gas adhesion coefficient and decomposition efficiency, thereby increasing the doping efficiency.

Furthermore, the doping concentration can be controlled by changing the radio frequency power.

〔Example〕

FIG. 1 is a sectional view of a gas furnace implementing the present invention.

In the figure, doping gas passes through a valve 2, enters a gas furnace 1 made of quartz, is ionized there, and is introduced into the MBE growth chamber from an outlet on the right side.

The flange 3 is for attaching the gas furnace 1 to the MBE growth chamber.

The doping gas in the gas furnace 1 is ionized by applying high frequency power to the high frequency generation coil 4 from the high frequency power supply 5, thereby generating plasma.

FIG. 2 is a sectional view of an MBE apparatus illustrating an embodiment of the present invention.

In the figure, GaA is mounted on a substrate support 8 in an MBE growth chamber 6.
Attach the s board 7. The GaAs substrate 7 is heated by a substrate heating filament 9.

On the other hand, in the MBE growth chamber 6, facing the substrate, there is a gas furnace 1 for doping gas, a Ga molecular beam source 10, and an A
An s molecular beam source 11 is arranged.

Si 1 is an example of n-type dopant gas for GaAs.
1 a. Methane gas (C
H4).

Molecular beam sources for Ga and As each use a normal metal as an evaporation source, or a gas source (for example, triethyl gallium (TEG, (CJs) 3 Ga) is used for Ga, and arsine (AS113) is used for 8S). Supplied.

Doping is performed as follows.

Before or during GaAs growth, the valve 2 is opened to introduce dopant gas into the MBE growth chamber 6, and the frequency 13.
100 pulses of 56 MHz high frequency power are applied. The dopant gas is partially or completely decomposed into radicals by high-frequency heating and reaches the GaAs substrate 7 heated to 600° C. by the substrate heating filament 9.

The radicals adhere to the GaAs substrate 7 and are decomposed, forming Si,
Alternatively, it becomes C and is incorporated into the growth layer as a dopant.

According to the embodiments of the present invention, there are advantages such as increasing the doping efficiency, controlling the doping concentration by high-frequency power, and controlling carbon doping, which has been difficult to control in the past.

FIG. 3 is a sectional view of an MBE apparatus illustrating another embodiment of the present invention.

In the figure, a gas furnace 1 for doping gas and an As molecular beam source 11 are arranged in an MBE growth chamber 6 facing a substrate.

C doping will be taken up as an example of p-type doping in GaAs.

Organic metals, e.g. T, as sources containing both Ga and C
MG ((CI+3):+Ga, trimethylgallium) or TEG is used.

The organometallic gas is introduced into the MBE growth chamber 6 from the gas furnace 1 .

The source of As is supplied from a normal metal source or a gas source.

Doping is performed as follows.

Similar to the embodiment shown in FIG. 2, the valve 2 is opened to introduce the organometallic gas into the MBE growth chamber 6, and high frequency power is applied.

The organometallic gas is partially or completely decomposed by high-frequency heating to become radicals, which reach the GaAs substrate 7 .

The radicals adhere to the GaAs substrate 7 and are decomposed to form Ga.

Alternatively, it becomes C and is incorporated into the growth layer.

This embodiment has the effect that both crystal growth (GaAs) and doping (C) can be controlled using one type of organometallic gas.

〔Effect of the invention〕

As described in detail above, according to the present invention, doping can be performed using any source gas, and for example, doping efficiency can be increased even for gases with a small adhesion coefficient or gases with a high decomposition temperature.

For this reason, carbon doping, which was difficult with solid doping, has become easier.

Furthermore, there is an advantage that the doping concentration can be controlled by high frequency power.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a gas furnace implementing the present invention, Fig. 2 is a sectional view of an MBE device illustrating one embodiment of the present invention, and Fig. 3 is a sectional view of an MBE device illustrating another embodiment of the present invention. FIG. In the figure, 1 is a gas furnace, 2 is a valve, 3 is a flange, 4 is a coil for high frequency generation, 5 is a high frequency power source, 6 is an MBE growth chamber, 7 is a striped GaAs substrate, 8 is a substrate support, 9 is for substrate heating filament, 10 is a Ga molecular beam source, 11 is an As molecular beam source MB
E'AX's? kra AA prisoner

Claims (1)

[Claims] A method for doping crystals, characterized by decomposing gas molecules containing an element to be a dopant by plasma, controlling the amount of gas decomposed by changing the power of a plasma generation source, and controlling the doping concentration.