JPH02260467A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To improve a defect on the surface of a semiconductor photodetector, to reduce a dark current and to improve short wavelength sensitivity by removing the surface of a substrate with a p-n junction to reduce the thickness of a p-type or n-type layer. CONSTITUTION:A pattern 3 which becomes a photodetector part is formed of resist on an n-type Si substrate 1, boron (B<+>) is implanted, annealed, a p-n junction is formed, phosphorus (P<+>) is. implanted in a ring state around the junction to form a guard ring 4, and an ohmic contact layer 5 is formed on the rear face of the substrate 1. Then, the layers 3-5 are oxidized by low temperature high pressure oxidation, an oxide film (a) is then removed to reduce the thicknesses of the layers 3-5, and then a reflection preventive film 6, an Al electrode 7 are formed. Thus, the defect of the surface is removed, and short wavelength sensitivity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a semiconductor photodetection element, and is intended to reduce damage caused by ion implantation and to improve high and short wavelength sensitivity.

<Prior art> In order to realize a semiconductor photodetector element with high short wavelength sensitivity, it is necessary to form a shallow p-n junction.The conventional method for realizing such a shallow junction is ion implantation using low acceleration energy. implantation method using ions with large atomic radius (for example, As for n-type, B for p-type)
Fco+) was used.

Such an element is, for example, an n-type S as shown in FIG. 3(a).
1 Boron (B) ions are implanted into the substrate.

As shown in (b), a pn junction is formed by applying an annealing temperature of about 900°C.

<Problem to be solved by the invention> However, annealing at a temperature of about 900°C does not fully recover defects generated during ion implantation, so it is necessary to anneal at a higher temperature. Because the layer extends deep (for example, 5 μm), it is difficult to create a device with high short wavelength sensitivity.Furthermore, defects on the surface A that occur during ion implantation remain even after annealing, resulting in a large dark current. was there.

The present invention has been made in view of the problems of the prior art described above, and an object of the present invention is to eliminate defects on one surface and to realize a semiconductor photodetecting element having high short wavelength sensitivity.

Means for Solving the Problems> The structure of the present invention for solving the above problems is such that, in a semiconductor photodetecting element having a pn junction formed on a substrate by ion implantation, the surface of the substrate is removed. This feature is characterized in that the thickness of the p or n layer is reduced by doing so.

<Example> DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device of the present invention will be explained below based on the drawings.

FIGS. 1(a) to 1(d) are diagrams schematically showing the manufacturing process of the present invention.

Step (a) A pattern to be a light receiving portion is formed on the mouth-shaped St substrate using a lens 1-, boron (B+) is implanted, and annealing is performed to form a pn junction.

Step (b) Phosphorus (P+) is implanted in a ring shape around the pn junction to form a guard ring and an ohmic contact layer is formed on the back surface of the substrate. (Up to this point, the same as before) Step (c) Perform tympanic high-pressure oxidation to oxidize the surface of the upper p layer. At this time, set the time so that the thickness of the oxide film is twice the thickness you want to etch. , ρ The thickness of the upper layer is set to about 0.1 μm.

Step (d): Form an antireflection film and an Al electrode. In this case, the electrode on the back surface is formed after removing the oxide film, but the anti-reflection film 5 may be formed using an oxide film instead, or may be formed after removing the oxide film.

Figure 2 shows the relationship between the oxide film thickness and the oxidation pressure/time product using the high-pressure oxidation equipment used in step (c). According to Figure 1, the growth rate increases at around 800"C, resulting in a thick oxide film. can be formed.

Therefore, an oxide film with a desired thickness can be obtained without changing the blower aisle after ion implantation. Note that oxidation occurs when the surface of the 81 substrate grows by reacting with oxygen.The surface of the 1 surface is etched by approximately 1/2 of the thickness of the grown oxide film (in the diagram of process C, the thickness of the oxide film (
In contrast to (a), the second layer (b) is etched, and the p layer becomes thinner accordingly).

Note that in step (c), for example, after polishing the surface of the substrate with an abrasive, a processing method such as mechanochemical etching may be used to remove defective portions on the surface.

Furthermore, although this embodiment has been described with reference to an example in which two layers are formed on an n-type substrate, an n-layer may be formed on a p-type substrate.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the surface of the substrate on which the +P n junction is formed is removed to reduce the thickness of the p or n layer. It is possible to eliminate such defects, reduce dark current, and realize a semiconductor photodetector element having high short wavelength sensitivity.

[Brief explanation of drawings]

Figure 1 is a diagram showing the manufacturing process of the semiconductor photodetector element of the present invention, and Figure 2 is a diagram showing the relationship between oxide film thickness and oxidation pressure/time product when a high-pressure oxidation apparatus is used. ) and (b) are diagrams showing general manufacturing examples of semiconductor photodetecting elements. 1...N-type S1 substrate, 3...P upper layer 1st diagram A-no-electronic

Claims (1)

[Claims] A semiconductor photodetector having a p-n junction formed on a substrate by ion implantation, characterized in that the thickness of the p or n layer is reduced by removing the surface of the substrate. .