JPH02202020A - Arsenic diffusing agent and manufacture thereof, and manufacture of semiconductor element using the diffusing agent - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an arsenic diffusing agent and a method for producing the same, particularly an arsenic diffusing agent that is easy to mold, easy to handle, difficult to scatter, and therefore has no risk of environmental pollution. The present invention relates to a novel arsenic diffusing agent that is useful as an arsenic diffusing agent for semiconductor devices such as semiconductor substrates, such as silicon, because it has a long life as a diffusion source and is inexpensive, as well as a method for producing the same. The present invention relates to a method of manufacturing a semiconductor device by diffusing arsenic into a semiconductor substrate.

(Prior art) A method for doping a semiconductor substrate such as a silicon wafer with arsenic is to vacuum seal the silicon wafer and powdered arsenic in a capsule. It has also been proposed to use crystals (see Japanese Patent Publication No. 53-44789). Especially, if silicon arsenide is used, it is possible to precisely control the doping amount without creating crystal defects on the wafer surface with easy pretreatment. Regarding the manufacturing method of semiconductor devices using this silicon arsenide, it has been proposed to use this silicon arsenide in the form of an easy-to-handle plate, or to use it in the form of a pellet. 57-222
09, Japanese Patent Publication No. 57-22210), however, this silicon arsenide itself has a thin multi-layered structure, so it easily peels off, and its softness makes it difficult to work with, making it difficult to use repeatedly. Therefore, there is a disadvantage that its use is limited.

(Structure of the Invention) The present invention relates to an arsenic diffusing agent that solves such disadvantages, a method for manufacturing the same, and a method for manufacturing semiconductor devices using the same. An arsenic diffusing agent characterized by being mixed with a polysilicate, dried and sintered after hydrolysis, and sintered at a temperature of 800 to 1,500°C and an atmospheric gas pressure of 1.5 kg/cm' or more. The present invention relates to a method for manufacturing the arsenic diffusing agent, which is characterized in that the semiconductor substrate and the arsenic diffusing agent are heated in an inert gas containing gas or under reduced pressure to diffuse arsenic into the semiconductor substrate. The present invention relates to a method for manufacturing a semiconductor device.

That is, as a result of various studies on arsenic diffusing agents for diffusing arsenic into semiconductor substrates, the present inventors found that silicon arsenide, arsenic oxide, and/or silicon are mixed with alkyl polysilicate, hydrolyzed, and then dried. , discovered that when sintered, an extremely uniform and strong solid molded product was obtained, and that this product had good workability because only the silicon arsenide did not peel off or vaporize. It was confirmed that if this material was sealed in a capsule with a semiconductor substrate, such as a silicon wafer, and heat-treated, it would easily release arsenic, so the silicon wafer could be easily doped with arsenic. The present invention was completed by conducting research on the types and amounts of each component constituting the molded product, the method for manufacturing the molded product, etc.

The silicon arsenide as the first component constituting the arsenic diffusing agent of the present invention may be a known silicon arsenide. Therefore, it can be used by vacuum sealing arsenic and metal silicon to heat the silicon to 1,083°C or higher and the arsenic to 640°C or higher. Each may be heated, melted, and cooled to form 5iAs (see Japanese Patent Laid-Open No. 43326/1983).

Next, arsenic oxide as the second component constituting this arsenic diffusing agent is vitrified with a hydrolysis product of alkyl polysilicate as the third component constituting this arsenic diffusing agent, and silicon is vitrified as the first component. A eutectic mixture is formed with silicon arsenide as a component, and the strength of the compact after sintering is improved by the addition of these ingredients.

The arsenic oxide used here is arsenous acid (AS203).
- Arsenic oxide such as arsenic acid (^52Ql) may be used, but from the viewpoint of toxicity and economics, arsenic acid (AS205) is preferable, and its particle size is 1 to 1.
A thickness of approximately 50 μm is preferred from the viewpoint of moldability. Further, this arsenic oxide and silicon may be used together, or either arsenic oxide or silicon may be used alone, and this silicon may be a known silicon, but it is also preferable that the particle size is about 1 to 50 μm. It is better to make it as fine as possible.

Next, the alkyl polysilicate as the third component constituting this arsenic diffusing agent is a polysilicate obtained by condensing alkyl silicates such as methyl silicate, ethyl silicate, propyl silicate, etc., or a mixture thereof by a conventional condensation method. However, ethyl polysilicate is preferred from the viewpoint of stability and economy.

When this alkyl polysilicate is hydrolyzed, its alkyl group is removed, and when it is dried and sintered, it becomes extremely fine silica. Therefore, this alkyl polysilicate is mixed with silicon arsenide, arsenic oxide, and/or silicon, and then hydrolyzed. Then, molecular-order silica is attached to the surface of the particles of silicon arsenide as the first component, arsenic oxide as the second component, and/or silicon, and the surface is covered with extremely uniform particles. Therefore, a glass phase of arsenic oxide and a hydrolysis product of an alkyl polysilicate produced by drying and sintering this, or a eutectic mixture of a hydrolysis product of silicon and an alkyl polysilicate are ideal. A mixed sintered state is obtained, and the resulting molded product has high strength and excellent stability, and this product also has no warping due to uneven distribution of the composition.

The first to third parts required to obtain such a molded body
If the amount of arsenic oxide and/or silicon as the second component is less than 0.5 parts by weight per 1 part by weight of silicon arsenide as the first component, it will be difficult to maintain the strength of the sintered body. If the amount is more than 0.5 parts by weight, the content of silicon arsenide, which effectively acts as an arsenic source in the diffusing agent, will decrease, resulting in an insufficient arsenic generation rate as a diffusing agent. , As for the alkyl polysilicate as the third component, it improves the strength of the molded product,
It is added for the purpose of improving heat resistance, and if it is less than 1 part by weight to 1 part by weight of silicon arsenide, the strength and heat resistance of the molded product will not be practical, and if it is more than 10 parts by weight, Since excessive voids increase and the molded product becomes brittle, the amount is preferably in the range of 1 to 10 parts by weight.

In addition, the production of this arsenic diffusing agent involves mixing the silicon arsenide, arsenic oxide, and/or silicon described above with an alkyl polysilicate, adding enough water to hydrolyze the alkyl polysilicate, and then using a ball mill or the like. After mixing and pulverizing the mixture in a mixer and hydrolyzing it, it is dried, and the dried product is adjusted to a certain particle size using a granulator or the like, then pressed to form a molded body, and then sintered. However, if this sintering is performed at a temperature lower than 800°C, the resulting compact will lack strength, and if the temperature is higher than 1,500°C, the decomposition of silicon arsenide will increase; It is preferable to carry out the process at high temperature, but in this atmosphere, for example, if it is carried out under vacuum or under the flow of an inert gas atmosphere, the decomposition of silicon arsenide,
Because the amount of scattering increases and it becomes impossible to obtain the desired arsenic diffusing agent, the auspicious gas pressure should be set at 1.5 kg/cI112.
The above is preferable, and since decomposition of silicon arsenide can be suppressed in this way, the desired arsenic diffusing agent can be obtained efficiently. Note that this sintering time may be determined depending on the amount of material to be treated and the treatment temperature.

The arsenic diffusing agent obtained in this way is heat resistant and strong because the molded body is heated and fired, and is therefore easy to handle industrially.However, regarding the formation of this molded body, In order to improve moldability, various organic binders and various inorganic substances for the purpose of improving sinterability may be added.

Since the arsenic diffusing agent of the present invention described above contains silicon arsenide as an arsenic supplying agent, it is said to be useful as an arsenic doping agent for silicon wafers, for example. A semiconductor substrate such as a silicon wafer and a molded product of this arsenic diffusing agent are placed facing each other in an electric furnace and heated to 900 to 1,200°C, or heated in an inert gas or oxygen-added inert gas stream. or 30 doped with arsenic by heat treatment under reduced pressure
N-type silicon wafers with a sheet resistance of ~300 Ω/mouth can be easily obtained.

Next, examples of the present invention will be given, and parts in the examples indicate parts by weight.

Example 100 parts of silicon arsenide and 50 parts of arsenic oxide (AS205)
50 parts of silicon, 200 parts of ethyl polysilicate, and 400 parts of water were ground and mixed in a ball mill for 20 hours, and simultaneously hydrolyzed. This mixture was made into granules with a particle size of 0.5 mm using a granulator. , dried at 110°C. Next, this dried body was press-molded with a pressing force of 2.5 t/cm' to make a wafer-like molded body with a diameter of 6 inches and a thickness of 2ffi, and this was heated at 260°C for 8 hours at 600°C.
It was heated and sintered at 950°C for 4 hours and 950°C for 12 hours to produce an arsenic diffusing agent.

Next, this arsenic diffuser and a 6 inch diameter, 500μ thick
When silicon semiconductor wafers of 5 m were placed alternately at a distance of 3 II 11 on a quartz boat and heated at 1,000°C for 60 minutes in a nitrogen gas atmosphere to diffuse arsenic, a resistance of about 150 Ω/mouth was obtained. An N-type silicon wafer with sheet resistance was obtained.

Example 2 100 parts of silicon arsenide, 500 parts of silicon, 500 parts of ethyl polysilicate, and 150 parts of water were pulverized and mixed in a ball mill for 30 hours, and hydrolyzed until the average particle size was 2.
After making a mixture of 5 μm, it was dried and granulated in the same manner as in Example 1, and then molded using a press to form a mixture with a diameter of 6 inches and a thickness of 1.5 mm.
A wafer-shaped compact was produced, and then this compact was heated and sintered at 1.400° C. for 5 hours under an argon pressure of 10 kg/cm 2 to produce an arsenic diffusing agent.

Next, when this arsenic diffusing agent was used to diffuse arsenic into a silicon semiconductor wafer in the same manner as in Example 1, an average of 60.
A silicon wafer with a sheet resistance of Ω/Ω is obtained,
Even when this product was repeatedly used 50 times, the sheet resistance of the silicon wafer obtained was within ±20%, and it was confirmed that it could be used for a long period of time.

Claims (1)

[Claims] 1. Mixing silicon arsenide, arsenic oxide and/or silicon with alkyl polysilicate, drying after hydrolysis,
An arsenic diffusing agent characterized by being made by sintering. 2. The weight ratio of silicon arsenide to arsenic oxide and/or silicon to alkyl polysilicate is 1:0.5 to 5:
The arsenic diffusing agent according to claim 1, which has a molecular weight of 1 to 10. 3. The arsenic diffusing agent according to claim 1, wherein the alkyl silicate is ethyl polysilicate. 4. The method for producing an arsenic diffusing agent according to claim 1, wherein the sintering is carried out at a temperature of 800 to 1,500°C and an atmospheric gas pressure of 1.5 kg/cm^2 or more. 5. A method for manufacturing a semiconductor device, which comprises heating a semiconductor substrate and the arsenic diffusing agent according to claim 1 in an inert gas stream containing gas or under reduced pressure to diffuse arsenic into the semiconductor substrate. .