JPH02129970A - Photodiode and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve optical detection sensitivity by providing a plurality of electrodes on an active layer constituting an optical absorption layer and further providing lens layers each comprising a material where the refractive index of light is greater than that of air on the active layer between the electrodes. CONSTITUTION:A plurality of electrodes 3 are provided on the same surface of an active layer 2, separated away from each other, and lens layers 7 are provided on portions of the active layer 2 located among the electrodes 3. Once light 5 is illuminated through the lenses 7, light 5B impinging the electrode 3 in the vicinity of the center of the same is blocked by the electrode 3, while light 5C impinging the plurality of the electrode 3 is refracted by the lens action of the lens layer 7 and focused onto an optical absorption region 6. Thus, the rate of light reaching the optical absorption area 6 is increased., hereby, detection sensitivity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photodiode and a method for manufacturing the same.

[Conventional technology]

Conventionally, when integrating a photodiode and an electronic circuit,
As a photodiode, one having a horizontal structure as shown in FIG. 3(A) is generally used.

In this figure, (1) is a GaAs substrate, and (2) is an active layer formed on one surface of the substrate by ion implantation, which acts as an absorption layer when irradiated with light as described later. (3) is a plurality of Schottky electrodes provided on the surface of the active layer, made of Wsi,
They are arranged at a predetermined distance from each other. G4) is a passivation film provided to cover the entire surface of the active layer and Schottky electrode.

In such a configuration, when a bias is applied between the Schottky electrodes (3) and light (51) is irradiated as shown in FIG. 3(B), the active layer located between each Schottky electrode is Light is absorbed in the light absorption region (6), and as is well known, carriers are generated and a photocurrent is generated.

[Problem to be solved by the invention]

In order to achieve long-distance transmission in optical receivers that integrate photodiodes and electronic circuits, it is necessary to improve the sensitivity of the photodiodes and efficiently convert even low-power optical signals into electrical signals. When a conventional photodiode is irradiated with light, the photodiode shown in Fig. 3 (
As shown in B), the light (5A) incident between the Schottky electrodes (3) reaches the light absorption region (6) of the active layer (2) and acts effectively; The incident light (5B) is blocked by the Schottky electrode (3) and does not reach the light absorption region (6).

Therefore, there is a problem in that a considerable portion of the incident light does not work effectively, which is an obstacle to improving the sensitivity of the photodiode.

This invention has been made to solve the above-mentioned problems, and aims to provide a photodiode and a method for manufacturing the same that can increase the proportion of light that reaches the light absorption region and improve the light receiving sensitivity. It is something.

[Means to solve the problem]

In the photodiode according to the present invention, a plurality of electrodes are provided in the active layer constituting the light absorption layer, and a lens layer made of a material having a light refractive index higher than that of air is provided in the active layer between each of the electrodes. It was designed to be provided.

Further, the method for manufacturing a photodiode according to the present invention includes forming a resist film on the lens layer configured as described above, removing the resist film located above the electrode, and heating the remaining resist film. After that, the peripheral part is heated to create a wave-like cross-sectional shape that is thinner at the top of the electrode and thicker between the electrodes, and then a part of the resist film and lens layer is removed by etching to form a lens. This is what I did.

[For production]

According to this invention, since a lens is formed on the top surface of the photodiode, part of the incident light that hits the electrode is refracted by the lens and focused on the light absorption area, resulting in light receiving sensitivity. is improved. or,
When manufacturing photodiodes, a resist film is placed on the top surface of the lens layer, and the shape of the lens is created by heating this resist film and causing heat to sag around the resist film, reducing the number of steps and making the work easier. It is something that can be done.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figures show an example of a photodiode, (A) is a cross-sectional view showing a schematic configuration, (B) is an explanatory view showing a light condensing state,
Figure 2 shows an example of the manufacturing method of this invention (A)
-(F) each show a schematic configuration of the process order.

In these figures, parts corresponding to conventional photodiodes are given the same reference numerals.

First, an example of the manufacturing method of the present invention will be explained with reference to FIG. FIG. 2(A) is the same as the structure before providing the passivation film (4) in FIG. 3(A), so the explanation will be omitted. ) and the upper surface of the Schottky electrode (3), a lens layer m such as a 5iON film serving as a film for forming a lens is formed. As shown in the figure, this lens layer has unevenness on the surface of the film depending on the shape of the Schottky electrode (3).
The convex portion is scraped off to make it flat as shown in FIG. 2(C).

After that, a resist film is applied to the entire upper surface of the lens layer m,
As shown in Figure 2(D), each Schottky electrode (3)
The resist film located above is removed and patterned. Part (f) of FIG. 2(D) shows the remaining resist film.

When the remaining resist film (8) is heated in this state, the respective peripheral parts sag, and as shown in FIG. The cross-sectional wave shape becomes thicker in the middle.

Thereafter, by etching until the resist film (5) is removed, a part of the lens layer (2) is also removed, and the surface of the lens layer (7) becomes a second layer as shown in FIG.
The resist film is shaped to have the same shape as the surface of the resist film shown in FIG. 3E, and a lens is formed. FIG. 1(A) shows an example of a photodiode formed in this manner.

Now, as shown in Fig. 1<8), this photodiode is
When the light (5) is irradiated, the light (5B) that hits near the center of the Schottky electrode (3) is blocked by the Schottky electrode, but the light (5C) that hits the peripheral part of the Schottky electrode (3) is blocked. The light is refracted as shown in the figure by the lens action of the lens layer (7) and focused on the light absorption region (6). Therefore, the proportion of light reaching the light absorption region (6) is increased compared to the conventional one, and the light receiving sensitivity of the photodiode is improved. In addition, in the above embodiment, the lens layer (■) is 5i
Although we have given an example of ONJIGI, it is not limited to this, and any material that has a refractive index higher than air, has a low reflectance to incident light, and almost transmits light can be an insulator. The present invention can also be applied to semiconductors, and the same effects as those of the above embodiments can be expected. Also, the substrate (1) is GaAs, and the electrode e) is Ws.
Although the embodiment in which the Schottky electrode is formed by the substrate (1) may be formed of a compound semiconductor such as Si, Ge, or InGaAs, the substrate (1) may be formed of a compound semiconductor such as Si, Ge, or InGaAs.
) can be applied to either a Schottky junction or a ρn junction as long as it has a horizontal arrangement.

〔Effect of the invention〕

As described above, according to the present invention, a plurality of electrodes are provided on the same surface of the active layer at a distance from each other, and a lens layer is provided on the active layer located between the electrodes. It is possible to increase the proportion of light reaching the photodiode and improve the light receiving sensitivity of the photodiode. In addition, when manufacturing the photodiode, the lens is formed by buttering the resist film on the lens layer and heating the remaining resist film to cause the surrounding area to sag, resulting in fewer steps. It is easy to work with.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, in which (A) is a sectional view showing a schematic configuration, and (B) is an explanatory view showing a condensed state. Fig. 2 is a schematic diagram showing an example of the manufacturing method of the present invention in the order of steps, and Fig. 3 is a conventional photodiode, in which (A) is a cross-sectional view showing the schematic structure, and (B) shows the light condensing state. It is an explanatory diagram. In the figure, (1) is the substrate, (2) is the active layer, (3) is the Schottky electrode, G4) is the passivation film, and (6) is the Schottky electrode.
(9) is a light absorption region, (7) is a lens layer, and (f) is a resist film. In the figures, the same reference numerals indicate the same or corresponding parts. Figure 1 Agent: Patent Attorney Dai Iwa MasuoFigure 2Figure 3

Claims (2)

[Claims] (1) An active layer formed on one surface of a semiconductor substrate and constituting a light absorption layer, a plurality of electrodes formed on this active layer at a distance from each other, and a plurality of electrodes provided on the active layer between these electrodes to absorb light. A photodiode including a lens layer made of a material whose refractive index is larger than that of air. (2) A step of forming an active layer acting as a light absorption layer on one surface of a semiconductor substrate, a step of forming a plurality of electrodes spaced apart from each other on the active layer, and a step of forming a refractive index of light so as to cover each electrode. a step of forming a lens layer made of a material having a larger diameter than air on the active layer, a step of forming a resist film on the lens layer and removing a resist film located above each of the electrodes, a step of removing the resist film. A method for manufacturing a photodiode, which includes a step of heating to sag the periphery of the photodiode, and a step of removing a portion of the resist film and lens layer by etching.