PIN diode with overcurrent protection

Abstract

This invention discloses a PIN diode with overcurrent protection. A system includes a pixel comprising a diffusion layer in contact with an absorption layer. A transparent conductive oxide (TCO) is electrically connected to the diffusion layer. An overflow contact is electrically connected to the TCO. The overflow contact may be laterally spaced from the diffusion layer. The pixel may be one of a plurality of similar pixels arranged in a grid pattern, wherein each pixel has a corresponding overflow contact, thereby forming an overflow contact grid offset from the grid pattern.

Description

Background Technology

[0001] 1. field

[0002] This disclosure relates to diodes, and more particularly to photodiodes such as those used in pixels for imaging.

[0003] 2. Related technical specifications

[0004] The lower the dark current of the photodiode in an imaging device, the better the image quality. Similarly, the higher the sensitivity of the photodiode in an imaging device, the better the image quality. Under high light levels, excessive photons generate high currents, which can damage the detector and / or put greater stress on the readout integrated circuit (ROIC).

[0005] These conventional techniques have been considered satisfactory for their intended purpose. However, there has been a persistent need for improved systems and methods for using photodiodes in imaging devices. This disclosure provides a solution to this need. Summary of the Invention

[0006] A system includes a pixel comprising a diffusion layer in contact with an absorption layer. A transparent conductive oxide (TCO) is electrically connected to the diffusion layer. An overflow contact is electrically connected to the TCO.

[0007] The overflow contacts may be laterally spaced from the diffusion layer. The pixel may be one of a plurality of similar pixels arranged in a grid pattern, each pixel having a corresponding overflow contact, thereby forming an overflow contact grid offset from the grid pattern. The overflow contacts may be metallic. A capping layer may be deposited on the absorption layer opposite to the substrate. The capping layer may contain InP. A SiNx layer may be deposited on the capping layer. The TCO may be deposited on the SiNx layer, wherein the TCO surrounds the SiNx layer to contact the diffusion layer. At least one additional SiNx layer may be deposited on the TCO, wherein the overflow contacts extend through the at least one additional SiNx layer. An antireflective layer may be deposited on the substrate opposite to the absorption layer. Contact metal may be electrically connected to the diffusion layer and configured to electrically connect the diffusion layer to a readout integrated circuit (ROIC). The overflow contacts may be electrically connected to the ROIC.

[0008] The overflow contact may be electrically isolated from the contact metal, and the TCO may be electrically connected to the current tank of the ROIC. The TCO may comprise multiple layers of ZnO, TiO2, and / or indium tin oxide (ITO). The absorption layer may comprise InGaAs, for example, where the pixel is sensitive to illumination in infrared wavelengths. It is also conceivable that the absorption layer may comprise Si, for example, where the pixel is sensitive to illumination in visible light wavelengths.

[0009] A method includes forming a pixel array comprising a plurality of pixels, each pixel including a diffusion layer in contact with an absorption layer. The method further includes forming a corresponding overflow contact electrically connected to each respective pixel of the plurality of pixels, wherein the overflow contact follows an overflow contact grid.

[0010] The method may include: depositing a SiNx layer on a capping layer deposited on the absorber layer, and depositing a transparent conductive oxide (TCO) on the SiNx layer, wherein the overflow contact is electrically connected to the TCO. The method may also include: depositing at least one additional SiNx layer on the TCO.

[0011] These and other features of the systems and methods of this disclosure will become more readily apparent to those skilled in the art from the following detailed description of preferred embodiments taken in conjunction with the accompanying drawings. Attached Figure Description

[0012] Therefore, those skilled in the art will readily understand how the apparatus and methods of this disclosure can be made and used without excessive experimentation. Preferred embodiments thereof will be described in detail below with reference to specific accompanying drawings, in which:

[0013] Figure 1 This is a schematic cross-sectional front view of an embodiment of the system constructed according to this disclosure, showing the overflow contact; and

[0014] Figure 2 yes Figure 1 A schematic plan view of the system, showing a grid pattern of multiple pixels. Detailed Implementation

[0015] Reference will now be made to the accompanying drawings, wherein similar reference numerals identify similar structural features or aspects of this disclosure. For purposes of explanation and illustration, and not limitation, Figure 1 A partial view of an embodiment of the system according to this disclosure is shown and is generally labeled with reference numeral 100. Figure 2 Other embodiments or aspects thereof of the system according to this disclosure are provided, as will be described. The systems and methods described herein can be used to reduce overcurrent, improve sensitivity, and reduce stress on readout integrated circuits (ROICs) in imaging devices.

[0016] System 100 includes a pixel 102, which includes a diffusion layer 104 in contact with an absorption layer 106. A transparent conductive oxide (TCO) 108 is electrically connected to the diffusion layer 104. An overflow contact 110 is electrically connected to the TCO 108. The overflow contact 110 is laterally grounded to the diffusion layer 104 (i.e., as in...). Figure 1 (Separated in the horizontal direction of the center orientation).

[0017] Now for reference Figure 2 , Figure 1 Pixel 102 is arranged in a grid pattern 112 (which in Figure 2 One of a plurality of similar pixels 102 (indicated by imaginary lines), wherein each pixel 102 has a corresponding overflow contact 110, thereby forming an overflow contact grid 114 that is offset from the grid pattern 112.

[0018] Refer again Figure 1 A capping layer 116 may be deposited on the absorber layer 106 opposite to the substrate 118. The capping layer 116 may contain InP. A SiNx layer 120 may be deposited on the capping layer 116. A TCO 108 may be deposited on the SiNx layer 120, wherein the TCO 108 surrounds the SiNx layer 120 to contact the diffusion layer 104 (i.e., the TCO wraps downwards around the SiNx layer 120 to contact the diffusion layer 104, as in...). Figure 1 The orientation is as follows. Two additional SiNx layers 122 and 124 are deposited on the TCO 108. Overflow contact 110 extends through the additional SiNx layers 122 and 124. Antireflective layer 126 is optionally deposited on substrate 118 opposite to absorber layer 106. Contact metal 128 is electrically connected to diffusion layer 104, thereby electrically connecting diffusion layer 104 to readout integrated circuit (ROIC) 130. Overflow contact 110 is electrically connected to ROIC 130.

[0019] TCO 108 is typically used as an insulator, but when the current reaches a predetermined maximum level, the resistive barrier of TCO 108 is broken, and excess current flows through TCO 108 to the common current tank 132 on ROIC 130. The thin-film resistivity of TCO 108 can be designed according to the detector operating conditions, which can be achieved by adjusting the doping level of TCO 108. Overflow contact 110 can be metallic and electrically isolated from contact metal 128. TCO 108 may contain multiple layers of ZnO, TiO2, and / or indium tin oxide (ITO).

[0020] The absorption layer 106 may comprise InGaAs, for example, in which pixel 102 is sensitive to illumination in infrared wavelengths. It is also conceivable that the absorption layer 106 may comprise Si, for example, in which pixel 102 is sensitive to illumination in visible light wavelengths. Those skilled in the art will readily understand that any other suitable material can be used to provide sensitivity to any other suitable wavelength.

[0021] One method includes: forming a pixel array comprising multiple pixels (e.g., Figure 2 An array of pixels 102 in a square tiled grid pattern 112. Each pixel includes a diffusion layer (e.g., diffusion layer 104) in contact with an absorption layer (e.g., absorption layer 106). The method includes: forming a corresponding overflow contact (e.g., overflow contact 110) electrically connected to each corresponding pixel in the plurality of pixels, wherein the overflow contact follows an overflow contact grid (e.g., ... Figure 2 Overflow contact mesh 114).

[0022] The method may include: depositing a SiNx layer (e.g., SiNx layer 120) on a capping layer (e.g., capping layer 116) deposited on an absorber layer, and depositing a transparent conductive oxide (TCO) (e.g., TCO 108) on the SiNx layer, wherein an overflow contact is electrically connected to the TCO. The method may also include: depositing at least one additional SiNx layer (e.g., additional SiNx layers 122, 124) on the TCO. The diffusion layer 104 is the P-part of the PIN diode, the absorber layer 106 is the I-part of the PIN diode, and the substrate 118 is the N-part of the PIN diode.

[0023] The methods and systems of this disclosure, as described above and illustrated in the accompanying drawings, allow for reduced overcurrent, increased sensitivity, and reduced stress on the readout integrated circuit (ROIC) in the imaging apparatus. This improves image quality and reduces ROIC design requirements and signal processing complexity compared to conventional configurations. While the apparatuses and methods of this disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily understand that changes and / or modifications can be made to this disclosure without departing from its scope.

Claims

1. A system comprising: A pixel, the pixel including a diffusion layer in contact with an illumination-sensitive absorption layer; A transparent conductive oxide (TCO) electrically connected to the diffusion layer; A contact metal, electrically connected to the diffusion layer, is configured to electrically connect the diffusion layer to a readout integrated circuit (ROIC); as well as An overflow contact is configured to be electrically connected to the ROIC and electrically connected to the diffusion layer via the TCO; The overflow contact is electrically isolated from the contact metal.

2. The system of claim 1, wherein the overflow contact is laterally spaced from the diffusion layer.

3. The system of claim 1, wherein the pixel is one of a plurality of pixels arranged in a grid pattern, wherein each pixel has a corresponding overflow contact, thereby forming an overflow contact grid offset from the grid pattern.

4. The system of claim 1, wherein the overflow contact is metallic.

5. The system of claim 1, further comprising a capping layer deposited on the absorber layer opposite to the substrate.

6. The system of claim 5, wherein the overlay layer comprises InP.

7. The system of claim 5, further comprising a SiNx layer above the capping layer.

8. The system of claim 7, wherein the TCO is deposited on the SiNx layer, and wherein the TCO is wrapped around the SiNx layer to contact the diffusion layer.

9. The system of claim 7, further comprising at least one additional SiNx layer deposited on the TCO, wherein the overflow contact extends through the at least one additional SiNx layer.

10. The system of claim 5, further comprising an antireflective layer deposited on the substrate opposite to the absorbing layer.

11. The system of claim 1, further comprising the ROIC, the ROIC being electrically connected to the contact metal.

12. The system of claim 11, wherein the TCO is electrically connected to the current tank of the ROIC.

13. The system of claim 1, wherein the TCO comprises multiple layers of ZnO, TiO2 and / or indium tin oxide (ITO).

14. The system of claim 1, wherein the absorption layer comprises InGaAs, and wherein the pixel is sensitive to illumination in an infrared wavelength.

15. The system of claim 1, wherein the absorption layer comprises Si, and wherein the pixel is sensitive to illumination in the visible light wavelength range.

16. A method comprising: A pixel array comprising multiple pixels is formed, each pixel including a diffusion layer in contact with an illumination-sensitive absorption layer, and each respective diffusion layer being electrically connected to a readout integrated circuit (ROIC) via a respective contact metal; Deposit a corresponding transparent conductive oxide (TCO), wherein the TCO is electrically connected to a corresponding diffusion layer for each corresponding pixel; as well as A corresponding overflow contact is formed to be electrically connected to each of the plurality of pixels, wherein the overflow contact follows an overflow contact grid, each corresponding overflow contact is electrically connected to the ROIC and electrically connected to the corresponding diffusion layer of each corresponding pixel through a corresponding TCO; The respective overflow contact is electrically isolated from the respective contact metal.

17. The method of claim 16, further comprising: A SiNx layer is deposited on the capping layer deposited on the absorber layer; as well as The TCO is deposited on the SiNx layer.

18. The method of claim 17, further comprising: At least one additional SiNx layer is deposited on the TCO.

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