JPS5952532B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of doping aluminum (Al) into a semiconductor to obtain a p-type semiconductor layer.

Conventionally, Al has a large diffusion coefficient and deep junctions.
It has been said that this impurity is suitable for forming a semiconductor layer. However, on the other hand, it has been considered difficult to put Al into practical use because it is difficult to electrically activate Al and there is no suitable diffusion method with good controllability. In recent years, with the development of ion implantation methods, it has become possible to dope Al in a fairly quantitative manner, but the drawback of being difficult to electrically activate remains a problem that is extremely difficult to overcome. . The reason why Al is difficult to electrically activate is mainly due to the following reasons.

That is, as shown in the following formula [1], Al is an interstitial atom (s) present in a semiconductor (for example, silicon Si) crystal.
Therefore, Al at the substitution position is driven out by the interstitial device, so that it no longer functions as an acceptor and is no longer electrically activated. A
l (substitution position) + si (interstitial position) → Al (interstitial position) + Si (substitution position) [1] If this reaction can be sufficiently inhibited, the activation rate of Al can be greatly improved.

To this end, it is necessary to supply sufficient vacancies to the semiconductor (Si) crystal, while minimizing the number of interstitial Si atoms. If these conditions are met, the following reaction will produce A.
The electrical activity of l is significantly enhanced. Al (interstitial position) ten pores → Al (substitution position) [2] Si (interstitial position)
10 vacancies → Si (substitution position) [3] This invention was made based on the above basic concept, and has developed a method to make a p-semiconductor layer doped with Al and capable of forming deep junctions into practical use. The purpose is to provide

5 First, the basic operation of this invention will be described.

First, a Si crystal is doped with Al by ion implantation or thermal diffusion, and the Al-doped region is irradiated with light particle ions such as protons or helium (He+) ions. Although approximately the same number of interstitial Si atoms and vacancies are created in the Si of the host crystal by irradiation with light particle ions, the distribution of the two is greatly different due to the difference in diffusion rate. Figure 1 shows the Al content in the Si crystal at this time. 1 is a diagram showing concentration distributions of vacancies and interstitial Si atoms in the depth direction, shown by curves A, B, and C, respectively.

As shown in the figure, an overwhelming number of vacancies are left in the Al doped region. Therefore, the reactions of the above formulas [2] and [3] are promoted, the electrical activation rate of Al is significantly improved, and a practical p-type semiconductor layer can be obtained. Figure 2 a-d
1A and 2B are cross-sectional views at each stage for explaining the method for creating an A1 diffusion layer used for isolation between Pn junction elements in a bipolar integrated circuit as an application example of the present invention. After forming the layer 2, an n-type epitaxial layer 3 is grown thereon, giving the collector layer 2 a buried configuration (FIG. 2a).

Next, as in the usual process, an oxide film 4 is formed on the surface, a window 5 for isolation and diffusion is opened in this oxide film 4, and Al+ ions 6 are implanted over the entire surface of the oxide film 4 and the window 5 ( Figure 2 b). This implantation amount only needs to be greater than the amount that enables the desired isolation between Pn junction elements, but it is usually 1×101
A range of 5 to 1×10 16 /ba is used. Further, although it is desirable that the implantation energy be as high as possible, it must be set to such an extent that the A ions do not penetrate through the oxide film 4 used as a mask. Usually, the injection energy is 100~
200keV is desirable, 5000 people at 100keV,
At 200 keV, an oxide film 4 of 1 μm thickness is required.
Then, heat diffusion of A1 is performed to form the Al diffusion layer 7.
It is formed so as to penetrate through the p-type epitaxial layer 3 and reach the p-type substrate 1.

To give an example of this diffusion condition, for the epitaxial layer 3 with a thickness of 4μ, the energy is 100keV and 1×101
For the A1+ ion-implanted layer implanted with an amount of 6/CIn3, drive diffusion at 1100° C. for 3 hours or more is required. However, recently, the activation rate of Al was only 1.
Since it is about 0%, in order to activate it, protons (or H+-8 ions) 8, which is the main step of this invention, are
Perform irradiation injection (Figure 2c). This irradiation implant energy separates the epitaxial layer 3 with a thickness of 4μ from A1.
Approximately 200 keV is required to activate the diffusion layer 7,
Since 200 keV protons create several dozen vacancies per particle, the proton injection amount is 1 x 1014 to 5 x 101.
A concentration of about 5/CIIl3 is sufficiently effective. Thereafter, as shown in FIG. 2d, a space region 10 and the like are diffused through an oxide film mask 9 of a desired pattern to complete the semiconductor device.

The A1 diffusion layer 71 activated by irradiation with light particle ions such as protons and H+←8 ions is preferably subjected to appropriate heat treatment in order to promote the reaction of formula [2]. Heat treatment during formation may also be used.

FIG. 3 is a diagram showing the distribution of various particles in the Al diffusion layer 71, where the horizontal axis shows the depth from the surface and the vertical axis shows the concentration.

Curve A is Al atoms, curve B is vacancies, and curve C is interstitial Si.
Atom, curve D shows the concentration distribution of protons.
In this way, by the method of the present invention, A
The activation rate of A can be improved to 30-60%, and
It has become possible to use l diffusion layers for isolation between Pn junction elements.

By the way, since A1 is easily diffused in subsequent steps, it is desirable to keep the subsequent heat treatment temperature as low as possible, and when forming the first A1 diffusion layer, the width is formed to be narrow in consideration of subsequent spreading. It is also necessary. The diffusion coefficient of this Al is much larger for interstitial Al atoms than for substituted Al atoms, but since the method of this invention reduces the number of interstitial Al atoms, the above-mentioned problem of spreading of the diffusion layer is greatly resolved. eased. The method of the present invention can be effectively used not only in the above-mentioned embodiments but also in separating thyristors having Npnp junctions.

As detailed above, in this invention, by doping aluminum into a semiconductor and irradiating the doped region with light particle ions, it is possible to activate the aluminum diffused into the semiconductor, which was previously considered difficult. This makes it possible to effectively form a deep p-type diffusion layer by taking advantage of aluminum's large diffusion coefficient, and if this is applied to device isolation, etc.
The heat treatment time for separation and diffusion can be reduced to 1/3 to 1/5,
The effect of heat treatment on other parts of the semiconductor device can be significantly reduced, helping to improve the performance of the product and also making the process more efficient.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the concentration distribution in the depth direction of aluminum, vacancies, and interstitial silicon atoms in a silicon crystal when aluminum is doped into silicon and light particle ions are irradiated to that region. Figures a to d are cross-sectional views at each process step to show an example of application of the present invention, and Figure 3 is a diagram showing the concentration distribution of various particles in the aluminum diffusion layer in the example of application shown in Figure 2. . In the figure, 1 is a p-type substrate, 3 is an n-type epitaxial layer, 4 is an oxide film mask, 5 is a window, 6 is an aluminum ion, 7 is an aluminum doped region, 8 is a light particle ion, and 71 is an activated region. This is an aluminum diffusion layer.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a semiconductor device, comprising the steps of doping aluminum into a semiconductor and then irradiating the aluminum-doped semiconductor region with light particle ions to form a p-type semiconductor region. 2. The method of manufacturing a semiconductor device according to claim 1, wherein aluminum is ion-implanted and then doped by thermal diffusion. 3. A method for manufacturing a semiconductor device according to claim 1 or 2, characterized in that protons are irradiated to a semiconductor region doped with aluminum. 4 Claim 1 characterized in that helium ions are irradiated onto a semiconductor region doped with aluminum.
A method for manufacturing a semiconductor device according to item 1 or 2.