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EP-4131940-B1 - SOLID-STATE IMAGE SENSOR AND IMAGING SYSTEM

EP4131940B1EP 4131940 B1EP4131940 B1EP 4131940B1EP-4131940-B1

Inventors

  • GOTO, HIROSHIGE

Dates

Publication Date
20260506
Application Date
20210310

Claims (6)

  1. A solid-state image sensor (1) comprising: a first semiconductor (10) having a first composition and including: a photodiode (11) configured to convert light incident on the photodiode into charge carriers; and a plurality of first carrier storages (12) for storing the charge carriers; and a transfer controller (13; 17) configured to transfer the charge carriers to a selected one of the first carrier storages (12); a second semiconductor (30) having a second composition different from the first composition, the second semiconductor being electrically connected to the first semiconductor (10), the second semiconductor including: a plurality of second carrier storages (33) corresponding to the respective first carrier storages (12), each of the second carrier storages being configured to store charge carriers based on the charge carriers stored in a corresponding one of the first carrier storages; and a potential detector configured to detect an electric potential of each of the second carrier storages (33); and a resetter (35) configured to reset an electric potential of each of the first carrier storages (12) to a predetermined electric potential, characterized in that the first composition and the second composition are different in constituent elements and in lattice constants, and in that the plurality of first carrier storages (12) and the transfer controller (13; 17) are included in the first semiconductor (10) having the first composition.
  2. The solid-state image sensor (1) according to claim 1, wherein the first semiconductor (10) is composed of germanium, germanium-silicon or gallium antimonide, and the second semiconductor (30) is composed of silicon, and wherein the second semiconductor (30) is electrically connected to the first semiconductor (10) by interconnection through diffusion layers.
  3. The solid-state image sensor (1) according to claim 1 or 2, wherein the resetter (35) is mounted to the first semiconductor (10).
  4. The solid-state image sensor (1) according to one of claims 1 to 3, wherein the photodiode (11) comprises germanium as a main element thereof.
  5. An imaging system (100) comprising: a light source unit (110) configured to emit light having a predetermined wavelength profile; and a solid-state image sensor (1) according to any one of claims 1 to 4.
  6. The imaging system (100) according to claim 5, wherein the light source unit (110) is configured to emit, as the light, near-infrared light or short-wave infrared light.

Description

[Technical Field] The present invention relates to solid-state image sensors and imaging systems. [Background Art] Solid-state imaging devices are used in various fields. As one example, solid-state imaging devices are used in imaging systems that can measure distances to objects. Such imaging systems typically include a light source for producing light to be emitted toward an object, and a solid-state imaging device. The imaging device functions as an image sensor that captures an image of light reflected from the object. One issue with the above imaging device is noise due to external light. One measure which has been considered to reduce this noise is to use near-infrared or short-wave infrared light at wavelengths that sunlight contains little of (preferably, light at wavelengths of about 1350 nm to 1400 nm that sunlight contains little of). This allows the above imaging device to be substantially unaffected by many types of external light, including sunlight. Providing an imaging system capable of measuring distances to objects using light in such a wavelength range requires a solid-state imaging device that efficiently converts light in that range into charge carriers. For this reason, germanium (Ge) and the like having a high absorption coefficient have been considered for use. PTL 1 discloses a device having photodiodes formed in a layer containing Ge and silicon (Si). [Citation List] [Patent Literature] PTL 1: US 2017/0040362 APTL 2: EP 3610 510 [Summary of the Invention] [Technical Problem] The device disclosed in PTL 1 includes a first semiconductor with photodiodes formed therein, and a second semiconductor disposed on a silicon substrate. Although charge carriers generated by the photodiodes in the first semiconductor are transferred to the second semiconductor for subsequent carrier-to-voltage conversion, PTL 1 does not specifically describe the manner in which the charge carriers are transferred from the first semiconductor to the second semiconductor, but it only illustrates, by way of example, a known interconnection using conductive wiring and a diffusion layer. In a solid-state imaging device, charge carriers generated in a photodiode may be subjected to selective transfer to one of a plurality of carrier-storage regions. PTL 1 discloses a time-of-flight (ToF) optical sensor in which charge carriers transferred to a second semiconductor are subjected to selective transfer to one of two carrier-storage regions. However, when the first and second semiconductors of the device disclosed in PTL 1 are coupled to each other in the above example manner, the presence of a diffusion layer between the photodiode and gates that perform selective carrier transfer may actually interfere with appropriate selective carrier transfer. In view of the above circumstances, the present invention aims to provide a solid-state image sensor that efficiently uses near-infrared or short-wave infrared light and that performs appropriate selective carrier transfer. [Solution to Problem] A solid-state image sensor according to a first aspect of the present invention includes a first semiconductor having a first composition, and a second semiconductor having a second composition different from the first composition and electrically connected to the first semiconductor. The first semiconductor includes a photodiode configured to convert light incident on the photodiode into charge carriers; a plurality of first carrier storages for storing the charge carriers; and a transfer controller configured to transfer the charge carriers to a selected one of the first carrier storages. The second semiconductor includes a plurality of second carrier storages and a potential detector. The second carrier storages correspond to the respective first carrier storages and are each configured to store charge carriers based on the charge carriers stored in a corresponding one of the first carrier storages. The potential detector is configured to detect the electric potential of each of the second carrier storages. The solid-state image sensor further includes a resetter configured to reset the electric potential of each of the first carrier storages to a predetermined electric potential. An imaging system according to a second aspect of the present invention includes a light source unit configured to emit light having a predetermined wavelength profile; and a solid-state image sensor according to the first aspect. [Advantageous Effects of the Invention] The above aspects of the present invention enable efficient use of near-infrared or short-wave infrared light and appropriate selective carrier transfer. [Brief Description of the Drawings] Fig. 1 is a schematic diagram illustrating a solid-state image sensor according to an embodiment of the present invention.Fig. 2 is a schematic diagram illustrating a modification of the solid-state image sensor.Fig. 3 is a diagram illustrating an example of a solid-state imaging device including a plur