JPH09237905A - Semiconductor device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain desired characteristics at low cost, without increasing man- hours by implanting B at an ion implanting energy in specified range to change he surface concn. of an epitaxial layer as little as not to invert it. SOLUTION: The specific resistance of an epitaxial layer 15 to 0.5-1.0Ω, an oxide layer 16 is grown for selective diffusion in a thickness range of 300-600nm, the guard ring diffusion for ensuring a breakdown voltage is made by the ion implanting method to form a layer having a reverse conductivity to that of a semiconductor substrate on the guard ring. B is implanted into the other main face of the film 16 in the implanting condition that the implanting energy is 50-150keV and dosage is 5×10<14> -1×10<16> /cm<-1> so that the concn. of B implanted through the film 16 into the skirt has influence on the surface concn. of the layer 15. Thus, desired characteristics can be attained, without increasing man-hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a Schottky barrier diode (hereinafter abbreviated as SBD).

[0002]

2. Description of the Related Art The manufacturing process of a conventional SBD of this type is shown in FIG.
2 to FIG. By the way, in order to change the characteristics of the SBD, conventionally, the barrier metal is changed, or barrier metals 2 and 3 having different barrier heights are formed through two steps as shown in FIG. 19 to meet the desired characteristics. Was producing SBD. Below, FIG. 12 to FIG.
A detailed description will be given of a conventional SBD manufacturing procedure with reference to FIG. FIG.
In order to manufacture the SBD 1 as shown in (1), first, the N ↑ -epitaxial layer 5 is grown on the N ↑ + semiconductor substrate 4 in such a concentration and thickness as to obtain the target characteristics (FIG. 12). Next, in order to form an oxide film on the surface, it is heated in an oxidation furnace,
An oxide film 6 is attached (FIG. 13). Next, masking is performed so that the oxide film 6 at the target location can be removed by the photolithography process, and the oxide film 6 at the location is removed by buffer hydrofluoric acid (B-HF) (FIG. 14). Next, boron deposition and boron drive-in are performed for the purpose of ensuring withstand voltage, etc., and diffusion is performed to achieve the target characteristics, and the guard ring 7
Are formed (FIG. 15).

Next, masking is carried out again in the photolithography process so that the oxide film 6 at the portion to which the barrier metal is attached can be removed, and the target oxide film 6 is removed by buffer hydrofluoric acid (FIG. 16). Next, the first barrier metal 2 is entirely vapor-deposited on the surface of the guard ring and the surface of the epitaxial layer. Then, the first barrier metal 2 is selectively removed by a photolithography process. A second barrier metal 3 having a different barrier height is selectively formed by photolithography on the selectively removed portion (FIG. 17). Next, vapor deposition is performed on both main surfaces of the ohmic metal 8 for connecting to the electrode leads, masking is performed using a mask capable of removing metals other than the ohmic metal 8, and unnecessary portions of metal are removed by etching. (FIG. 18), the target SBD as shown in FIG. 19 is completed.

[0004]

Since the conventional SBD 1 is manufactured through the steps shown in FIGS. 12 to 18, the barrier metal 2 and the barrier metal 3 are vapor-deposited twice,
Along with that, there are steps such as masking and etching twice, which increases the man-hours and increases the manufacturing cost, which is a problem to be solved.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and by using the ion implantation method to change the surface concentration of the epitaxial layer to such an extent that it does not invert, the via height changes and the target It is an object of the present invention to provide a method of manufacturing a semiconductor device, especially an SBD, which can be manufactured at low cost without increasing the number of steps.

[0006]

According to a method of manufacturing a semiconductor device of the present invention, a specific resistance of an epitaxial layer formed by epitaxial growth on one main surface of a semiconductor substrate is 0.4 to 0.4.
A first step of setting the resistance to 1.0 Ωcm, a second step of growing an oxide film to be grown for selective diffusion within a range of 300 to 600 nm, and a second step of securing a breakdown voltage. Diffusion of the guard ring used is carried out by an ion implantation method, and a conductivity type layer having a conductivity type opposite to the conductivity type of the semiconductor substrate is formed on the portion of the guard ring formed by the ion implantation method, and the other main surface The ion implantation energy is 50 to 15 so that the concentration of the hem portion of the boron implanted through the oxide film affects the epitaxial layer surface concentration.
The dose amount is 5 × 10 ↑ 14 to 1 × 1 in the range of 0 keV.
And a third step of implanting boron under ion implantation conditions in the range of 0 ↑ 16 cm ↑ -2.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, the feature of the present invention is to control the surface concentration such that the barrier height is changed by the ion implantation I of boron as shown in FIG. For this purpose, it is conceivable to form the two-stage epitaxial layers 5a and 5b as shown in FIG. 2 from the beginning, but there is a drawback that the material becomes expensive. By the way, in order to control the surface concentration, it is necessary to find a condition in which the resistivity of the epitaxial layer used, the oxide film thickness, and the ion implantation conditions of ions match. If these conditions do not match, for example, if the ion implantation conditions are strong (FIG. 3) or the oxide film is thin (FIG. 4),
The epitaxial layer may or may not be inverted to the P layer on the entire surface, resulting in a short-circuit of the breakdown voltage and a high forward voltage drop. On the other hand, if the oxide film is too thick, boron is completely blocked, so that the concentration change layer is not formed and only normal characteristics may be obtained.

Therefore, in order to obtain the concentration changing layer by the ion implantation method as shown in FIG. 1, it is necessary to perform the procedure as shown in FIGS. That is, first, 1 × 10 ↑ 1
An epitaxial layer 15 is grown on an arsenic substrate 14 (As sub) having a size of 9 cm ↑ -3 or more so as to have a specific resistance of 0.45 to 0.5 Ωcm (FIG. 5). As a result of the experiment, a matching condition could be found within a range of the lower limit of 0.4 Ωcm and the upper limit of 1.0 Ωcm.
Next, an oxide film is grown in an oxidizing furnace under conditions such that the oxide film thickness becomes 490 to 520 nm (FIG. 6). As a result of an experiment, the lower limit of the oxide film thickness is 300 nm and the upper limit thereof is 5 nm.
The matching condition could be found up to 20 nm.
Next, masking is performed to form a guard ring portion, and then the oxide film of the guard ring portion is etched (FIG. 7).

Next, the P ↑ + layer 17 is formed on the guard ring portion.
And boron is implanted to form the surface concentration change layer 18.

As long as the above-mentioned boron implantation conditions are within the above-mentioned specific resistance and oxide film thickness, the experimental result shows that the implantation energy is 1
00 keV and a dose amount of 1 × 10 ↑ 15 cm ↑ -2 were suitable. However, when various experiments were conducted in correspondence with the range of the specific resistance and the range of the oxide film thickness, the lower limit was 5 ×.
10 ↑ 14 pieces cm ↑ -2, the upper limit is 1 × 10 ↑ 16 pieces cm
With the dose amount of ↑ -2, matching of 3 conditions was obtained. Then, annealing treatment, oxidation, etc. are performed to obtain a P ↑ layer 17 having a target guard ring diffusion depth and a target surface concentration change layer 18 (FIG. 8). Subsequently, masking is performed to form a portion to which a barrier metal is attached, and the oxide film 16 in the barrier portion is removed by etching (FIG. 9).

Next, a barrier metal 19 is deposited, masking is performed to form a barrier, and unnecessary barrier metal 19 is removed by etching (FIG. 10). Then, ohmic metal 20 for connecting to the electrode lead
Is vapor-deposited, and unnecessary portions are removed by etching to obtain the desired SBD (FIG. 11).

[0012]

As described above, according to the present invention, the low concentration portion can be formed on the surface of the epitaxial layer by controlling the epitaxial layer resistivity, the oxide film thickness and the ion implantation conditions. The material cost is not expensive, and the semiconductor device having the desired characteristics can be manufactured at low cost without increasing the number of steps.

[Brief description of drawings]

FIG. 1 is a sectional view of an SBD showing one step of a manufacturing method of the present invention.

FIG. 2 is a sectional view of an SBD having a two-step epitaxial layer shown for comparison with the method of the present invention.

FIG. 3 is an explanatory cross-sectional view when the ion implantation condition, which is one of the essential conditions in the method of the present invention, does not match.

FIG. 4 is a cross-sectional view for explaining a case where the oxide film thickness, which is one of the essential conditions in the method of the present invention, is thin and the conditions do not match.

FIG. 5 is a sectional view showing a first step for explaining the method of the present invention.

FIG. 6 is a sectional view showing a second step for explaining the method of the present invention.

FIG. 7 is a sectional view showing a third step for explaining the method of the present invention.

FIG. 8 is a sectional view showing a fourth step for explaining the method of the present invention.

FIG. 9 is a sectional view showing a fifth step for explaining the method of the present invention.

FIG. 10 is a sectional view showing a sixth step for explaining the method of the present invention.

FIG. 11 is a cross-sectional view of an SBD obtained by the method of the present invention.

FIG. 12 is a cross-sectional view showing a first step for explaining a conventional method.

FIG. 13 is a cross-sectional view showing a second step for explaining the conventional method.

FIG. 14 is a cross-sectional view showing a third step for explaining the conventional method.

FIG. 15 is a cross-sectional view showing a fourth step for explaining the conventional method.

FIG. 16 is a sectional view showing a fifth step for explaining the conventional method.

FIG. 17 is a cross-sectional view showing a sixth step for explaining the conventional method.

FIG. 18 is a sectional view showing a seventh step for explaining the conventional method.

FIG. 19 is a cross-sectional view showing the structure of a conventional SBD.

[Explanation of symbols]

 14 Silicon Substrate 15 Epitaxial Layer 16 Oxide Film 17 P ↑ + Layer 18 Surface Concentration Change Layer 19 Barrier Metal 20 Ohmic Metal

Claims (1)

[Claims] 1. A specific resistance of an epitaxial layer formed by epitaxial growth on one main surface of a semiconductor substrate is 0.
The first step is 4 to 1.0 Ωcm, and then the oxide film thickness to be grown for selective diffusion is 30
The second step of growing in the range of 0 to 600 nm, and then the guard ring diffusion used to secure the breakdown voltage is performed by the ion implantation method. A conductivity type layer having a conductivity type opposite to the conductivity type of the semiconductor substrate is formed, and the concentration of the hem portion of the boron implanted through the oxide film on the other main surface affects the epitaxial layer surface concentration. Ion implantation energy is 50 to 150 keV and dose is 5 × 10 ↑
A third step of implanting boron under ion implantation conditions in a range of 14 to 1 × 10 ↑ 16 pieces cm ↑ 2, and a method of manufacturing a semiconductor device.