CN-114846606-B - Ranging image sensor

CN114846606BCN 114846606 BCN114846606 BCN 114846606BCN-114846606-B

Abstract

In a range image sensor, each pixel has an avalanche multiplication region, a charge distribution region, a pair of first charge transfer regions, a pair of second charge transfer regions, a well region, a photogate electrode, a pair of first transfer gate electrodes, and a pair of second transfer gate electrodes. The first multiplication region of the avalanche multiplication region is formed so as to overlap with the charge distribution region and not overlap with the well region in the Z direction. The second multiplication region of the avalanche multiplication region is formed to overlap with the charge distribution region and the well region in the Z direction.

Inventors

MASE MITSUHITO
Ping Guangchun
SHIMADA AKIYO
ISHII HIROAKI
ITO YOSHINORI
TANAKA YUSUKE

Assignees

浜松光子学株式会社

Dates

Publication Date: 20260508
Application Date: 20201207
Priority Date: 20191226

Claims (12)

1. A ranging image sensor is characterized by comprising: a semiconductor layer having a first surface of a first side and a second surface of a second side opposite to the first side for constituting a plurality of pixels arranged along the first surface, and An electrode layer provided on the first surface for constituting the plurality of pixels, Each of the plurality of pixels has: An avalanche multiplication region including a first multiplication region of a first conductivity type formed in the semiconductor layer, and a second multiplication region of a second conductivity type formed in the semiconductor layer on a side of the first multiplication region proximate the first side; A charge distribution region of a second conductivity type formed in the semiconductor layer on a side of the second multiplication region near the first side, the charge distribution region being connected to the second multiplication region; a first charge transfer region of a second conductivity type connected to the charge distribution region, formed in the semiconductor layer on a side of the second multiplication region near the first side; A second charge transfer region of a second conductivity type connected to the charge distribution region, formed in the semiconductor layer on a side of the second multiplication region near the first side; a well region of the first conductivity type formed in the semiconductor layer on a side of the second multiplication region near the first side; A photogate electrode formed in the electrode layer on a side of the charge distribution region proximate the first side; A first transfer gate electrode formed in the electrode layer on a side of the charge distribution region near the first side in such a manner as to be located on the first charge transfer region side as compared with the photogate electrode, and A second transfer gate electrode formed in the electrode layer on a side of the charge distribution region near the first side in such a manner as to be located on the second charge transfer region side as compared to the photogate electrode, The first multiplication region is formed so as to overlap the charge distribution region and not overlap the well region in the thickness direction of the semiconductor layer, The second multiplication region is formed to overlap with the charge distribution region and the well region in a thickness direction of the semiconductor layer.
2. The ranging image sensor as defined in claim 1, wherein: Each of the plurality of pixels further has a barrier region of a second conductivity type formed in the semiconductor layer between the second multiplication region and the well region.
3. The ranging image sensor as recited in claim 2 wherein: The barrier region includes the well region when viewed in a thickness direction of the semiconductor layer.
4. A range image sensor according to claim 2 or 3, characterized in that: Each of the plurality of pixels further has a second-conductivity-type sink region connected to the barrier region formed in the semiconductor layer on a side of the barrier region near the first side.
5. The ranging image sensor as defined in claim 4, wherein: the sink region is connected with the second charge transfer region.
6. The ranging image sensor as defined in claim 1, wherein: The second multiplication region includes a first region overlapping the charge distribution region in a thickness direction of the semiconductor layer and a second region overlapping the well region in the thickness direction of the semiconductor layer, The second region has a higher concentration of impurities than the first region.
7. The range image sensor of claim 6, wherein: The second region includes the well region when viewed in a thickness direction of the semiconductor layer.
8. The ranging image sensor as recited in claim 6 or 7 wherein: each of the plurality of pixels further has a sink region of a second conductivity type connected to the second region formed in the semiconductor layer on a side of the second region near the first side.
9. The ranging image sensor as recited in claim 8 wherein: the sink region is connected with the second charge transfer region.
10. The ranging image sensor as defined in any one of claims 1-9, wherein: A trench separating each of the plurality of pixels from each other is formed in the first surface of the semiconductor layer.
11. The ranging image sensor as defined in any one of claims 1-10, wherein: The first multiplication region is divided by each of the plurality of pixels.
12. The ranging image sensor as recited in any one of claims 1-11, further comprising: and a wiring layer provided on the first surface so as to cover the electrode layer and electrically connected to each of the plurality of pixels.

Description

Ranging image sensor Technical Field The present invention relates to a range image sensor. Background As a range-finding image sensor that acquires a range image of an object by an indirect TOF (Time of Flight) system, there is known a range-finding image sensor including a semiconductor layer provided with a light-sensing region, and a photogate electrode (photogate electrode) and a transfer gate electrode provided for each pixel on the semiconductor layer (for example, refer to patent documents 1 and 2). According to such a range image sensor, the electric charges generated in the light sensing region can be transferred at high speed by incidence of light. Prior art literature Patent literature Patent document 1 Japanese patent application laid-open No. 2011-133464 Patent document 2 Japanese patent application laid-open No. 2013-206903 Disclosure of Invention Technical problem to be solved by the invention In the distance measurement image sensor described above, for example, in order to make the measurable distance longer, it is sometimes required to improve the light receiving sensitivity. The invention aims to provide a ranging image sensor capable of improving light receiving sensitivity while maintaining signal reading accuracy. Technical scheme for solving technical problems In one aspect, the present invention provides a ranging image sensor comprising a semiconductor layer having a first surface on a first side and a second surface on a second side opposite to the first side for constituting a plurality of pixels arranged along the first surface, and an electrode layer provided on the first surface for constituting the plurality of pixels, each of the plurality of pixels having an avalanche multiplication region including a first conductive type first region formed on the semiconductor layer and a second conductive type second multiplication region formed on the first side of the first multiplication region in the semiconductor layer, a second conductive type charge distribution region formed on the first side of the second multiplication region in the semiconductor layer and connected to the second multiplication region, a second conductive type first charge transfer region formed on the first side of the second multiplication region in the semiconductor layer and connected to the charge distribution region, a second conductive type second transfer region formed on the first side of the second multiplication region in the semiconductor layer and connected to the charge distribution region, a charge transfer region formed on the first side of the semiconductor layer and overlapping the charge distribution region in such a manner that the charge transfer region is formed on the first side of the gate electrode layer and the charge distribution region in a manner that the charge transfer region is formed on the first side of the semiconductor layer is not overlapped with the first gate electrode region in the first side of the charge distribution region, the second multiplication region is formed to overlap the charge distribution region and the well region in the thickness direction of the semiconductor layer. In the ranging image sensor, an avalanche multiplication region is formed in the semiconductor layer. This can realize high sensitivity in each of the plurality of pixels. Further, on the second side of the well region of the first conductivity type, a second multiplication region of the second conductivity type is formed so as to overlap the well region in the thickness direction of the semiconductor layer, and on the second side of the second multiplication region of the second conductivity type, the first multiplication region of the first conductivity type is formed so as not to overlap the well region in the thickness direction of the semiconductor layer. Thus, when a reverse bias is applied to the semiconductor layer, the depletion layer formed in the second multiplication region at a portion not overlapping the first multiplication region in the thickness direction of the semiconductor layer is less likely to spread toward the well region, and the depletion layer can be prevented from reaching the well region. That is, it is possible to prevent a current from flowing between the avalanche multiplication region and the well region due to the depletion layer reaching the well region. Therefore, the light receiving sensitivity can be improved while maintaining the signal reading accuracy. In the range image sensor according to one aspect of the present invention, each of the plurality of pixels may further include a second conductivity type barrier region formed between the second multiplication region and the well region in the semiconductor layer. Thus, even if the depletion layer formed in the second multiplication region expands toward the well region due to the application of the reverse bias to the semiconductor layer, the depletion layer can be prevented from reaching the well reg