JPS622673A - Semiconductor light receiving device - Google Patents

Abstract

PURPOSE:To obtain high speed response all the time, by covering a region, in which an intrinsic semiconductor layer is not converted into a depletion layer, by a light shielding layer. CONSTITUTION:A metal layer 11, which is a light shielding layer, is provided on an insulating film 5. The size of the metal layer 11 is determined so as to cover a region 9, which is not converted into a depletion layer. Namely, the inner end side of the metal layer 11 covers a P-N junction part 7. The outer end side is extended to a channel cutting region 4. Therefore, incident light to the region 9 can be shielded. Yield of an electric charge component, whose moving speed is slow, in the vicinity of the P-N junction can be prevented. Therefore, hole-electron pairs, which are excited by the incident light, are generated only in the depletion layer, which is moved under a high electric field. Thus, high speed response can be always obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light receiving device characterized by high-speed response.

[Conventional technology]

As a conventional semiconductor light receiving device characterized by high-speed response, there is, for example, a PIN type photodiode shown in FIG.

In the figure, 1 is an intrinsic semiconductor layer (hereinafter referred to as 1 layer), 2 is
is a P-type semiconductor layer (hereinafter referred to as P layer), 3 is an N-type semiconductor layer (hereinafter referred to as N layer), 1 layer 1 is sandwiched between 2 layers 2 and 8 layers 3, and a part of 1 layer 1 is exposed from the periphery of the second layer 2 to the main surface. Reference numeral 4 designates a channel cut region provided at the periphery of the first layer 1 exposed on the main surface, 5 an insulating film such as an oxide film covering the main surface, and 6 an electrode electrically connected to the second layer 2.

Next, the operation will be explained. When a voltage is applied, layer 1 becomes a depletion layer as shown by the broken line, and when light enters this region 8, hole-electron pairs are generated and move by drift under a high electric field. Therefore, high-speed response can be obtained and conversion efficiency is also good.

[Problem that the invention seeks to solve]

However, in the above photodiode, a positive interfacial charge exists at the interface between the layer 1 and the insulating film 5 exposed on the main surface, and this effect causes the surface of the layer 1 to become N-type. , the impurity concentration in that part becomes substantially high, so as shown in FIG.
The depletion layer becomes difficult to grow near the PN junction 7 with 1
A wide region 9 that was not converted into a depletion layer was likely to occur in the layer 1. Therefore, when light enters the region 9 that is not made into a depletion layer, the electron pairs of the excited holes move due to diffusion.
Because the movement speed is significantly slower than movement by drift,
There was a problem that high-speed response could no longer be obtained.

Conventionally, as a method to solve this problem, as shown in FIG.
There is a method of extending O around the surface of the insulating ItI 5 to prevent light from entering the region 9 which is not made into a depletion layer. In this case, the metal layer 10 prevents the charges adsorbed on the insulating film 5 from affecting the surface of the I layer 1, and also has the effect of preventing channel leakage. However, the metal layer 10 is electrically conductive with the channel cut region 4 and the insulating film 5
Since it extends upward, it becomes an electrode capacitance and the capacitance increases, which has the disadvantage that it is difficult to obtain high-speed response. Of course, if the extension width of the metal layer 10 onto the insulating film 5 is narrowed, the capacitance will be reduced, but this will reduce the effect of preventing light from entering the region 9 on the surface of the I layer 1 that is not a depletion layer. There was a problem.

This invention was made in order to solve these conventional problems, and it is possible to effectively block the incident light to the region where the depletion layer is not formed, and therefore, it is possible to create a semiconductor that can always provide high-speed response. The purpose is to provide a light receiving device.

[Means for solving problems]

In a semiconductor light-receiving device in which an intrinsic semiconductor layer is sandwiched between a P-type semiconductor layer and an N-type semiconductor layer, and a main surface of which a part of the intrinsic semiconductor layer is exposed around the P-type semiconductor layer is covered with an insulating film, A light-shielding layer is provided on the insulating film to block incident light to a region of the intrinsic semiconductor layer that is not made into a depletion layer.

[Effect]

In the semiconductor light-receiving device according to the present invention, when a voltage is applied, incident light to the region that is not formed into a depletion layer is blocked, so that light is incident only to the region that is formed into a depletion layer. Therefore, excited charges move exclusively by drift under a high electric field, and charge components that move by diffusion are removed. Therefore, high-speed response can always be ensured.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention. This embodiment is a PIN type photodiode similar to the conventional example. In the figure,
The same reference numerals as in FIG. 2 indicate the same or corresponding parts, and 11 is a light shielding layer provided on the insulating film 5. This layer 11 is an annular metal layer having a width ranging from a position covering the PN junction 7 on the inner end side to a channel car region 4 on the outer end side, and
It is made of the same metal as the metal that composes it. In this embodiment, aluminum is formed by vacuum deposition. Further, the light shielding layer 11 is configured so as not to be electrically connected to the channel car/upper region 4 and the electrode 6.

Next, the operation will be explained.

As mentioned above, in this embodiment as well, the depletion layer becomes elongated near the PN junction 7 when voltage is applied, and the I layer l
This results in a wide region 9 that is not depleted. However, since the gold m layer 11, which is a light shielding layer, is provided on the insulating film 5 with a size that is large enough to cover the region 9 that is not made into a depletion layer, that is, the inner end side of the metal layer 11 is located at the PN junction 7. Since the outer end side extends to the channel cut region 4, it is possible to block the incident light to the region 9, and to prevent the generation of slow-moving charge components in the vicinity of the PN junction portion 7. Therefore, hole-electron pairs excited by incident light are generated only in the depletion layer that moves due to drift under a high electric field, and high-speed response can always be obtained.

Furthermore, in this embodiment, the metal layer 11 is not electrically connected to the channel car/upper region 4 or the electrode 6, so its capacitance does not increase, and from this point of view, high-speed response can be ensured. .

Although the embodiments have been described using a PIN type photodiode as an example, this invention is intended to provide a light shielding layer that blocks light from entering a region that degrades high-speed response. Needless to say, the present invention can also be applied to semiconductor photodetectors that require high-speed response.

〔Effect of the invention〕

As explained above, according to the present invention, since the region of the intrinsic semiconductor layer that is not depleted is covered with the light shielding layer, it is possible to block the incident light to the region that is not depleted.
Therefore, high-speed responsiveness can always be obtained.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views showing a conventional semiconductor light receiving device, and FIG. 3 is a cross-sectional view showing an embodiment of the present invention. In the figure, N is an intrinsic semiconductor layer, 2 is a P-type semiconductor layer, and 3 is a P-type semiconductor layer.
is an N-type semiconductor layer, 4 is a channel cut region, 5 is an insulating film, 6 is an electrode, 7 is a PN junction, 8 is a depletion layer region, 9 is a non-depletion region, and 11 is a light shielding layer. It is a metal layer. Note that in Figure 1, round lights indicate the same or equivalent parts.

Claims (1)

[Claims] In a semiconductor light-receiving device in which an intrinsic semiconductor layer is sandwiched between a P-type semiconductor layer and an N-type semiconductor layer, and a main surface of which a part of the intrinsic semiconductor layer is exposed around the P-type semiconductor layer is covered with an insulating film, A semiconductor light-receiving device characterized in that a light-shielding layer is provided on the insulating film to block incident light to a region of the intrinsic semiconductor layer that is not converted into a depletion layer.