JPH02224326A - Manufacture of semiconductor device - 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 a method for manufacturing a semiconductor device in which an aluminum impurity diffusion region is formed in a silicon semiconductor substrate by aluminum ion implantation.

[Conventional technology]

When forming a p-type impurity region in a silicon semiconductor substrate,
Group MB elements of the periodic table as dopants.

In particular, boron, gallium, aluminum, etc. are used.

Among these, aluminum has the largest diffusion coefficient in silicon, and compared to boron and gallium, the diffusion time is shorter and a deep diffusion layer can be formed at a lower concentration, making it suitable for manufacturing silicon semiconductor devices that require high breakdown voltage. It can be said that it is the most suitable element for

However, when trying to form an aluminum diffusion region by ion implantation, the implantation of aluminum ions concentrates on the surface of the silicon semiconductor substrate and also causes silicon lattice defects. An annealing step is required, and this annealing step causes out-diffusion in which aluminum in the semiconductor substrate is released to the outside of the substrate, resulting in a problem in that the desired impurity concentration cannot be obtained. As a method to solve this problem, as described in Japanese Patent Application No. 62-310504 filed by the applicant, an aluminum impurity doped region is formed in a silicon semiconductor substrate by aluminum ion implantation, and then an aluminum impurity doped region is formed in a silicon semiconductor substrate. , sequentially coating the semiconductor substrate surface with a first oxide film, a nitride film, and a second oxide film, and then annealing.
In this method, a dense nitride film prevents out-diffusion, the first oxide film serves as a buffer layer between the semiconductor substrate and the nitride film, and the second oxide film is in balance with the first oxide film. This helps prevent thermal stress from occurring in the nitride film.

[Problem to be solved by the invention]

The effect of preventing out-diffusion by forming a dense protective film as described above is relatively small in the case of aluminum ion implantation.
- implanted, using silicon nitride as a protective film, at 1250°C
When annealing for 16 hours at

The reason for this is that the substrate single crystal becomes amorphous through aluminum ion implantation, and when this amorphous layer is annealed, aluminum segregates to the surface side in the process of epitaxial recrystallization from the interface with the single crystal. , is due to outward diffusion.

An object of the present invention is to provide a method for manufacturing a semiconductor device that more effectively prevents the outdiffusion of aluminum during the 7th period after aluminum ion implantation without using a protective film as described above. .

[Means to solve the problem]

In order to achieve the above object, the method for manufacturing a semiconductor device of the present invention involves forming an aluminum atom-doped region in a semiconductor single crystal substrate by aluminum ion implantation, and then forming a crystal film made of the same semiconductor material on the surface of the semiconductor substrate. and then annealing to form an aluminum diffusion region.

[Operation] The surface of the aluminum atom-added region of the semiconductor single crystal substrate by ion implantation is covered with a crystal film of the same semiconductor, and recrystallization of the amorphous region that occurs during ion implantation occurs only from the substrate single crystal side. Rather, it also progresses from the crystalline film on the surface.

Therefore, segregation of aluminum progresses in the center of the amorphous region due to ion implantation, so that significant outward diffusion during the recrystallization process can be prevented.

(Example) Figures 1 (♂) to (61 conceptually show the steps of an embodiment of the present invention. First, aluminum ions 2 are implanted into the silicon substrate 1 (Figure +8)). Implantation conditions are acceleration voltage 40~60kV, dose amount 5X10I4
~5X10" atoms/-, ion species "kl". At this time, an amorphous region 3 is formed on the silicon substrate surface by ion implantation (Figure (bl), then an amorphous region 3 is formed on the silicon substrate surface. Form a silicon film 4 (Figure (el)).

Note that this amorphous silicon film 4 is formed at 600° C., for example, by a vapor phase growth method using silane gas (Sill#).
The temperature is as follows: At 600° C. or higher, outward diffusion of aluminum occurs. The thickness of the amorphous silicon film 4 is determined based on the consideration of crystallization by laser irradiation, which will be described later, and minimizing the thermal effect of laser irradiation on the amorphous region 3 by M ion implantation. The surface amorphous silicon film 4 is turned into a single crystal silicon film 6 by irradiation with the primary laser beam 5, which is normally desirably about 0.5 to 1n (Figure + d)) *Annealing is performed by
It is carried out at 200-1250°C in a nitrogen atmosphere for 10-30 hours. During the annealing process, the amorphous region 3 due to ion implantation is gradually sandwiched by recrystallization, and eventually it is all crystallized (11J(a)).Aluminum segregates into the amorphous region, but in the end After all crystallization, approximately 50% diffuses into the silicon substrate, and approximately 50% diffuses outward.

Figure 2 shows the concentration distribution of aluminum in the depth direction obtained through the above process.
Xl01? An impurity diffusion distribution for an atom/- and a diffusion depth of 50n is obtained.

[Effect of the invention] For example, a crystalline film is formed by laminating an amorphous film on the top surface into which aluminum ions have been implanted and then irradiating it with laser light.
By sandwiching the amorphous layer produced during ion implantation between the crystal substrate and the crystal film, aluminum segregates in the amorphous region that narrows from both sides during annealing, reducing the outward diffusion by 50%. can be suppressed to This allows aluminum to be effectively diffused into the semiconductor substrate.

In addition to the method according to the present invention, 5l of the above patent application
If a diffusion prevention protective film coating with an ot/SiN/5ift structure is used in combination, the effect of preventing aluminum from outward diffusion is further improved.

[Brief explanation of the drawing]

FIGS. 1 ial to 1 are cross-sectional views conceptually showing sequentially the steps of an embodiment of the present invention, and FIG. 2 is a diagram showing the concentration distribution of aluminum in a silicon substrate obtained according to an embodiment of the present invention. t silicon + 8-, 2: 7tv mini? A Even, 3. Aeon 9 to Nyukanhanawa, 4 Hai quality chic/Katara, 5, I/-pu・tzG”%♂9 (Shisoko/Monthly table)
7 °°tsu drunk A shisotsun.

Claims (1)

[Claims] 1) Including the step of forming an aluminum atom-doped region in a semiconductor single crystal substrate by aluminum ion implantation, forming a crystal film made of the same semiconductor material on the surface of the semiconductor substrate, and then performing annealing to form an aluminum diffusion region. A method for manufacturing a semiconductor device, characterized in that: