JPH01185917A - Doping of arsenic - Google Patents

Abstract

PURPOSE:To form a high-concentration doped region without executing a high- temperature heating operation by a method wherein arsenic gas whose metal arsenic has been sublimated is introduced between counter electrodes together with a carrier gas and a plasma doping operation is executed to a semiconductor substrate on the electrode on one side. CONSTITUTION:A reaction tank 1 is evacuated by using a vacuum evacuation system 61; substrates 4 are heated by using a heater 51 ; a metal arsenic heating container 8 is evacuated by using an evacuation system 62; after metal arsenic 81 has been heated by using a heater 52, it is sublimated. Then, a vacuum valve 64 is throttled; an evacuation speed of the evacuation system 61 is reduced and a valve 66 is shut simultaneously; a valve 65 is opened; an inert carrier gas flows through a regulating circuit 91 from a bomb 9; the carrier gas containing arsenic is introduced into the reaction tank 1; a pressure of the reaction tank is adjusted. After that, a discharge input of a direct current is supplied between counter electrodes 21, 22 from a power supply 3; a glow discharge is actuated. By this setup, a high-concentration arsenicdoped region can be formed inside a semiconductor substrate without executing a high- temperature heating operation for activation use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for doping arsenic in a semiconductor substrate for forming an N-type region or for forming an N layer.

[Conventional technology]

One method for doping arsenic is to diffuse arsenic into the oxide film on the surface of a semiconductor substrate in a vapor phase, and then heat the substrate using an open tube method to diffuse arsenic into the substrate.
A method of diffusion using an open tube method using an arsenic compound gas such as (arsine), or a method of sealing the semiconductor substrate together with a solid metal arsenic, a liquid compound such as ^scIg, or silicon in which arsenic is diffused. There are diffusion methods such as diffusion using a tube method. Alternatively, during epitaxial growth of a semiconductor, there is a method of mixing a liquid hexagonal compound with a liquid semiconductor raw material compound such as SIA 4, or a method of mixing a gaseous compound such as ^sH@ with a semiconductor raw material compound gas. Furthermore, an ion implantation method in which arsenic is ionized and implanted is also known.

[What the invention seeks to solve; a]

However, in all of these methods, the semiconductor substrate is
It is necessary to heat to a high temperature of ~1250°C. Such high temperature heat treatment has the disadvantage of generating crystal defects in the semiconductor substrate. Furthermore, as devices become smaller, it becomes necessary to form shallow doping regions, but in these methods that involve high-temperature heat treatment, for example, when considering Si as the semiconductor substrate, the diffusion coefficient of arsenic in Si is large. Therefore, it is not possible to obtain a shallow doping region, and in ion implantation, a shallow doping layer cannot be obtained.
It is difficult to stably drive at low accelerations below V to 0, and 10 to 1 to 103! There are problems in that it becomes difficult to obtain a high surface impurity concentration such as atomic/-. Furthermore, arsine used in gas phase diffusion is known to be highly toxic and requires extreme care when handling.

The purpose of the present invention is to solve the above-mentioned problems and to provide arsenic that can form a shallow, highly doped region in the substrate without using highly toxic gases such as arsine, without heating the semiconductor substrate to high temperatures. In order to achieve the above object, the method of the present invention involves placing a semiconductor substrate on one of the opposing electrodes in a vacuum container and maintaining it at a predetermined temperature to heat and sublimate metal arsenic. Gas is introduced between opposing electrodes together with a carrier gas, and a voltage is applied between the opposing electrodes to generate glow discharge.

[Operation] By introducing arsenic gas produced by sublimating a metal element into the plasma space, activation can be achieved by plasma doping as described in Japanese Patent Application Laid-Open No. 59-218727 filed by the present applicant. A shallow, highly doped region of arsenic can be formed within a semiconductor substrate without the need for high-temperature heat treatment for chemical conversion.

〔Example〕

FIG. 1 shows an apparatus used in an embodiment of the present invention, in which counter electrodes 21 and 22 connected to a DC power source 3 are arranged in a reaction tank 1 that can be evacuated, and a counter electrode 21 and 22 are placed on the ti 21. A built-in heater 51 that can heat the St substrate 4 to be heated is connected to the power source 3.
The 0 reaction tank 1 connected to 1 has an exhaust pipe 63. A vacuum exhaust system 61 is connected via a vacuum valve 64 . Further, a gas introduction pipe 76-' opens into the reaction tank 1, and a vacuum heating container 8 is connected to this via a vacuum valve 65. The vacuum heating container 8 can be evacuated by an evacuation system 62 connected through a vacuum valve 66, and is connected to a power source 32 in order to heat and sublimate the dish 82 containing metal arsenic 81 therein. A heated heater 52 is housed therein. Furthermore, an inert carrier gas cylinder 9 is connected to this vacuum heating container 8 via a gas adjustment circuit 91 such as a mass flow.
are connected to vacuum gauges 11 and 12 for adjusting the internal vacuum degree.

Using this apparatus, a doped region was formed according to the following procedure. First, the inside of the reaction tank 1 is evacuated to about I x 10-' Torr by the vacuum evacuation system 61 . si board 4
The metal arsenic heating container 8, which has been heated to about 200°C by the heater 51, is heated to about I x 10-”T by the exhaust system 62.
The metal arsenic 81 was heated to 50° C. with the heater 52 and sublimated. Then, the vacuum valve 64 was throttled to lower the exhaust speed of the exhaust system 61, and at the same time the valve 66 was closed, and the pulp 65 was opened. He as an inert carrier gas was passed through the adjustment circuit 91 from the cylinder 9, a carrier gas containing arsenic was introduced into the reaction tank 1, and the pressure of the reaction tank was adjusted to 2 Torr. After that, a direct current (ioO
A discharge input of 0.6 mA/alI was applied for 5 minutes. St substrate 4 has a specific resistance of 10 to 3
It was single crystal silicon with a resistance of 0 kΩ1.

FIG. 2 is a profile showing the concentration distribution of arsenic in the depth direction in the substrate 4 doped in this manner. This was measured using an ion microanalyzer. As can be seen from FIG. 2, the arsenic content formed by the method according to the invention has a high surface impurity concentration of more than 101 m atoms/-. Moreover, this impurity concentration decreases by 101 atoms/-2 at a depth of about 50 = 1100 nm, whereas in the normal diffusion method, the surface concentration is 10''
When compared with the case where the depth is 0.5μ or more, it can be said that this is a very high concentration and shallow doping region.

〔Effect of the invention〕

According to the present invention, by introducing arsenic gas obtained by sublimating metallic arsenic together with a carrier gas between opposing electrodes and plasma-doping the semiconductor substrate on one electrode, high-temperature heat treatment that causes crystal defects as in the conventional method is avoided. Without undergoing any process, the surface has a high concentration of 108' atoms/- or more, and 0
．． A shallow arsenic doping region of about 1.0 mm can be formed.

It has been impossible to perform extremely shallow doping with arsenic at such a high concentration because of the large diffusion coefficient of arsenic in Si. Moreover, since metallic arsenic is used as an impurity source in the present invention, there is no need to worry about highly toxic gas leaking from the piping system, which is the case when gases such as arsine (AsHs) are used, resulting in less danger and ease of handling. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of an apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing the arsenic concentration distribution in the depth direction in a Si substrate obtained according to an embodiment of the present invention. 1: Reaction tank, 21.22: @pole, 4: Si substrate, 51°52: Heater, 61, 62: Vacuum exhaust system, 7: Gas introduction tube, 8: Vacuum heating container, 81: Metallic arsenic, 9: carrier gas cylinder.

Claims (1)

[Claims] 1) A semiconductor substrate is placed on one of the opposing electrodes in a vacuum container, maintained at a predetermined temperature, and a gas in which metallic arsenic is heated and sublimated is introduced between the opposing electrodes together with a carrier gas. An arsenic doping method characterized by applying a voltage between the two to generate a glow discharge.