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EP-4496010-B1 - LIGHT DETECTION DEVICE

EP4496010B1EP 4496010 B1EP4496010 B1EP 4496010B1EP-4496010-B1

Inventors

  • KURACHI, IKUO
  • TAKANO, HIROSHI
  • KASHIMA, YASUMASA

Dates

Publication Date
20260506
Application Date
20220316

Claims (4)

  1. A photo detection device detecting an incident light from an object, comprising: (i) a P-type silicon (Si) substrate (101); (ii) a P-type germanium (Ge) layer (102) formed by epitaxial growth on a first surface serving as a front surface of the P-type silicon (Si) substrate; and (iii) a P-type thin film silicon (Si) (103) layer formed on the P-type germanium (Ge) layer, (iv) wherein the P-type thin film silicon (Si) layer is divided into a first region and a second region by a Shallow Trench Isolation (STI) (104), multiple single photon avalanche diodes (SPADs) (202) arranged in an array are formed in the first region, and a CMOS transistor circuit (201) driving the SPADs is formed in the second region.
  2. The photo detection device according to claim 1, the P-type thin film silicon (Si) layer is formed by surface activated bonding technique and smart-cut technique using hydrogen ion implantation.
  3. The photo detection device according to claim 1, the P-type thin film silicon (Si) layer is thinned and formed on the P-type germanium (Ge) layer by epitaxial growth of silicon (Si).
  4. The photo detection device according to any of claims 1 to 3, configured to receive the incident light from a second surface serving as a back surface of the P-type silicon (Si) substrate.

Description

Technical Field The present invention relates to a photo detection device containing multiple photo detection elements that detects a single photon of incident light, in particular, infrared light whose wavelength is about 0.9 to 1.6 µm, from an object, and a driving circuit that drives the photo detection elements. Background Art Conventionally, a photo detection element capable of detecting a single photon is generally realized as a SPAD (Single Photon Avalanche Diode) using silicon (refer to Patent Document 1). However, in this case, only a photon with a wavelength (λ) shorter than about 1 µm can be detected due to a bandgap (Eg = 1.12 eV) specific to silicon. It is necessary to use a semiconductor with a bandgap narrower than that of silicon as a detection element in order to detect a photon of infrared light whose wavelength is equal to or greater than 1 µm. Thus, indium gallium arsenide (InGaAs) or germanium (Ge) is generally used in order to detect a photon of infrared light whose wavelength is equal to or greater than 1 µm. There are many crystal defects in the former InGaAs and in particular, deep level traps are formed therein. Thus, it is known that when it is operated as an avalanche photodiode (APD), many faults called afterpulses ("noise") occur. In addition, InGaAs cannot be produced as a single crystal and are generally formed on an Inp substrate by epitaxial growth using metal organic chemical vapor deposition (MOCVD). Thus, it is disadvantageous in that a substrate-manufacturing cost becomes expensive. Furthermore, it is difficult to sufficiently enhance crystal quality In addition, it was impossible to integrate a driving circuit for amplifying and processing a signal from an APD with the APD and configure them in the same chip. In the latter Ge, since an avalanche region has to be formed in Ge and Ge has a narrow bandgap as mentioned above, a thermally excited carrier is easily generated, the carrier causes avalanche amplification, and "photon" counting can be performed even without light, i.e., in the "dark." This is called a dark count rate (DCR) and there was a problem that the DCR could be high. In addition, for example, when the photo detection device is used as a Laser Imaging Detection and Ranging (LiDAR), two-dimensional range information is needed and multiple SPADs must be arranged in an array. However, in the case of the detection device using InGaAs or Ge, it was difficult to arrange the plurality of SPADs in an array in the same chip. Non-Patent Document 1 discloses forming a single photon avalanche diode (SPAD) in a germanium (Ge) layer formed on a silicon substrate. Non-Patent Document 2 discloses a separate absorption, charge and multiplication avalanche photodiode (SACM-APD) that is composed of a Ge absorption layer and an Si multiplication layer, and configured to be separated by a p-doped Si charge layer. However, the SPAD as disclosed in Non-Patent Documents 1 and 2 is of a single diode structure, multiple diodes are not arranged in an array, and a circuit that drives the SPAD, is not formed on the same substrate. Non-Patent Document 3 discloses a circuit for active reset of an N+P single-ended SPAD that is used in an NIR LiDAR receiver. However, it does not disclose in detail how to configure the SPAD and the resetting circuit thereof on the same substrate. Non-Patent Document 4 discloses a characteristic evaluation result of germanium (Ge) epitaxially grown on a silicon (001) with 0° and 6° offcut. Non-Patent Document 5 discloses epitaxially growing a germanium (Ge) thin film on a silicon (100) using a two-step process. Non-Patent Documents 4 and 5 just evaluate a characteristic of the Ge layer epitaxially grown on the silicon layer but do not disclose any structure of the photo detection device. Non-patent Document 6 shows another photon detection device according to the prior-art. Prior Art Literature Patent Documents Patent document 1: Japanese Patent Application Publication No. 2021-150359 Non-Patent Documents Non-patent document 1: "High performance planar germanium-on-silicon single-photon avalanche diode detectors", Peter Vines, etc. ┌nature communications, (2019)10;1086┘Non-patent document 2: "Modelling Ge/Si Avalanche Photodiodes", F.Gity etc. ┌Science Foundation Ireland (SF1) under grand 07/SRC/11173┘Non-patent document 3: "Active-Reset for the N+P Single-Ended SPAD Used in the NIR LiDAR Receivers", A.Katz, etc. ┌IE3 TRANSACTIONS ON ELECTRON DEIVES, Vol. 66, No. 12 December 2019┘Non-patent document 4: "Comparative Studies of the Growth and Characterization of Germanium Epitaxial Film on Silicon (001) with 0° and 6° Offcut." Kwang Hong Lee, etc. ┌Journal of Electronic Materials, vol 42, No. 6, 2013┘Non-patent document 5: "Epitaxial Germanium thin films of Silicon (100) using two-step process", Saloni Chaurasia, etc. "VTC from IEEE Xplore"Non-patent document 6 : "GAO S ET AL: "3D Electro-optical Simulations for Improving the Photon Detection Probability of S