JPH09232326A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] An impurity profile of a crystal substrate for epitaxial growth
Made from a diffusion substrate with the same impurity profile as the
To provide a semiconductor device having the above structure. SOLUTION: Light ions are n^-Substrates 1 and n⁺Is it the boundary of layer 2?
N⁺Irradiate into layer 2 and the irradiation dose at that time is near boundary 6
The irradiation dose is higher and the irradiation dose decreases as the distance from the boundary 6 increases.
Without irradiation, and the irradiation range is the minimum amount that can be converted into a donor.
There is 1 × 10 ¹²cm^-2From 1 × 10^Fifteencm^-2Done with heat
The processing temperature should be within the range of 350 ℃ to 600 ℃.
Result of epitaxial growth of impurity profile on surface 6
Almost the same as the crystal substrate.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which an FZ crystal is applied to a power device such as a high breakdown voltage diode.

2. Description of the Related Art FIG. 2 shows a conventional high breakdown voltage diode using a diffusion substrate. FIG. 2A shows a sectional structure and FIG. 2B shows an impurity profile. In FIG. 1A, n ⁻ substrate 1
N ⁺ layer 3 to the other, p ⁺ layer 5 to the other, p ⁺
A high breakdown voltage diode having an n ⁻ n ⁺ structure (commonly called a pin structure) is formed. In the figure (b), n ⁻
For n ⁺ impurity profile of the n ⁺ layer 3 in the vicinity of the interface 6 junction of the n ⁺ layer 3 is formed by diffusion, the shape as shown has a slope shape 7. When the diode is reverse recovery, the elongation of the depletion layer is suppressed at the n ⁺ layer 3, when the n ⁺ layer 3 has the inclined 7, elongation depletion layer at a low concentration region, the high area The growth is suppressed as it becomes. Therefore, the depletion layer extends to the depth of the n ⁺ layer 3 to some extent, so that the reverse recovery current decreases gradually and the reverse recovery loss increases. One of the measures to solve this inconvenience is to change the slope shape into a step shape. 3A and 3B show a conventional high breakdown voltage diode using an epitaxially grown crystal substrate. FIG. 3A shows a sectional structure and FIG. 3B shows a step-like impurity profile. This step-like impurity profile 9 is obtained by epitaxially growing the n ⁺ layer 4 on the n ⁻ substrate 1, and the reverse recovery loss of the high breakdown voltage diode manufactured using this crystal substrate is the same as that of the high breakdown voltage diode of FIG. Compared to.

However, the cost of the epitaxially grown crystal substrate is 2 compared with the ordinary diffusion substrate.
There is the inconvenience of being about twice as expensive. An object of the present invention is to provide a semiconductor device made of a diffusion substrate having an impurity profile similar to that of an epitaxially grown crystal substrate.

In order to achieve the above-mentioned object, a high-concentration first-conductivity-type impurity atom is diffused from one main surface of a low-concentration first-conductivity-type semiconductor substrate. -Shaped high concentration diffusion layer is formed, a predetermined amount of light ions are irradiated from the tip of the high concentration diffusion layer into the high concentration diffusion layer, and then heat treatment is performed at a predetermined temperature, so that The lattice defect is converted to a donor, and the concentration profile near the tip of the high concentration diffusion layer is formed in a step shape. The light ions are preferably protons or helium ions. In addition, the irradiation dose of light ions is 1 × 10 ¹² cm ^-2 to 1
The lattice defects formed by light ions are made into donors by setting the temperature to × 10 ¹⁵ cm ⁻² and setting the heat treatment temperature after irradiation with light ions to 350 ° C. to 600 ° C.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which FIG. 1 (a) shows a state in which light ions are irradiated, and FIG. 1 (b) shows impurity profiles before and after donor formation. Proton or helium ion, which is a light ion, is added to n ⁻ substrate 1
Irradiate into the n ⁺ layer 2 from the boundary between the n ⁺ layer 2 and the n ⁺ layer 2. The irradiation amount at that time is large near the interface 6, and the irradiation amount is small as the distance from the interface 6 increases. The range of the irradiation amount is from 1 × 10 ¹² cm ^−2, which is the minimum dose for making a donor, to 1 × 10 ¹⁵ cm ⁻² , which is the practical maximum value. The heat treatment temperature is in the range of 350 ° C., which is the lowest temperature at which donors are formed, to 600 ° C., at which donor formation is weakened. By carrying out such a treatment, the impurity profile after the donor formation shown in FIG. 6B was obtained, and the impurity profile almost the same as that of the epitaxially grown crystal substrate was obtained. That is, the step 7 is formed in the vicinity of the interface of the n ⁺ layer 2. As a result, the reverse recovery loss of the high breakdown voltage diode became the same as that using the epitaxially grown crystal substrate. Although the high breakdown voltage diode is shown as an embodiment of the present invention, the n ⁺ buffer layer of a MOS gate structure device such as an IGBT may of course be used as the n ⁺ layer 2 irradiated with light ions, and other semiconductor devices. Alternatively, a crystal substrate irradiated with light ions may be applied. The cost of the crystal substrate obtained by irradiating the diffusion substrate with light ions is about 30 to 40% lower than that of the epitaxial growth substrate, and the manufacturing cost of the semiconductor device manufactured using this substrate can be significantly reduced.

According to the present invention, light ions such as protons and helium ions are added to the high concentration region of the n-type diffusion substrate at 1 ×.
By irradiating 10 ¹² cm ^-2 or more and performing heat treatment at 350 ° C. or more, a crystal substrate having an impurity profile almost the same as that of the epitaxially grown crystal substrate is obtained. By using this crystal substrate, reverse recovery loss is small and A semiconductor device with low cost can be obtained.

[Brief description of drawings]

FIG. 1A is a diagram showing irradiation of light ions, and FIG. 1B is a diagram showing impurity profiles before and after conversion into a donor in an embodiment of the present invention.

FIG. 2 is a conventional high breakdown voltage diode using a diffusion substrate,
(A) is a cross-sectional structure diagram, (b) is a diagram showing an impurity profile

3A and 3B are conventional high breakdown voltage diodes using an epitaxially grown crystal substrate, in which FIG. 3A is a sectional structural view, and FIG.
Shows a step-like impurity profile

[Explanation of symbols]

1 n ^- Substrate 2 n ⁺ Layer 3 n ⁺ Layer 4 n ⁺ Layer 5 p ⁺ Layer 6 Interface 7 Steps 8 Gradient 9 Steps

Claims (3)

[Claims] 1. A high-concentration diffusion layer of the first conductivity type is formed by diffusing high-concentration impurity atoms of the first conductivity type from one main surface of a low-concentration semiconductor substrate of the first conductivity type. By irradiating a certain amount of light ions into the high-concentration diffusion layer from the tip of the diffusion layer, and then performing heat treatment at a predetermined temperature, the lattice defects in the region irradiated with the light ions are made into donors, and the vicinity of the tip of the high-concentration diffusion layer A method for manufacturing a semiconductor device, characterized in that the concentration profile of is formed stepwise. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the light ions are protons or helium ions. 3. The light ion irradiation dose is 1 × 10 ¹² cm ⁻² to 1 × 10 ¹⁵ cm ⁻² , and the heat treatment temperature after the light ion irradiation is 350 ° C. to 600 ° C. The method for manufacturing a semiconductor device according to claim 1.