CN103779437A - Single-photon-level resolution ratio sensor unit structure based on standard CMOS technology - Google Patents

Abstract

A single-photon-level resolution sensor unit structure based on a standard CMOS process, the sensor unit structure uses a single-photon avalanche diode (SPAD), and its basic structure includes: a deep N well is arranged above a P-type silicon substrate (4) (3); the P-well region (2) is formed above and surrounded by the deep N-well (3); the anode contact (9) is connected to the P-well through the heavily doped P-type region (1) region (2); the cathode contact (10) is connected to the N-well region (6) and the deep N-well region (3) through the heavily doped N-type region (5); the shallow trench isolation region (7) is located in the P-well region ( 2) between the N well region (6), the P well is isolated from the N well; the shallow trench isolation region (7) is provided with a P-type doped guard ring (8) around to prevent the shallow trench isolation Dark noise due to defects; PN junction (11) between the bottom of the P well region (2) and the deep N well (3), when a proper bias voltage is applied between the cathode and anode, the PN junction produces a high voltage region , forming a SPAD multiplication region to detect photons, and controlling the concentration gradient of the deep N well (3) to make the edge breakdown voltage of the PN junction higher than the breakdown voltage of the planar multiplication region of the SPAD.

Description

A single-photon-level resolution sensor unit structure based on standard CMOS process

technical field

The invention is a unit structure of a single-photon-level resolution sensor, and its manufacturing method is specifically implemented in a standard CMOS process.

Background technique

High-efficiency, low-noise single-photon detectors are needed in the fields of weak light imaging, high-speed imaging, and quantum communication. The photomultiplier tube (PMT) commonly used now needs high operating voltage, and the unit structure is bulky, so it cannot be integrated on a large scale. A silicon avalanche photodiode (APD) works in the linear region of the PN junction, and its working voltage is lower than the avalanche voltage, so its gain is generally not higher than 1000, and single photon detection cannot be realized. The gain of electron multiplier CCD (EM-CCD) can be applied to weak light detection, but its operating frequency is low, and the time resolution cannot reach the application of photon counting.

Single-photon avalanche diode (SPAD), namely Geiger mode avalanche photodiode (GM-APD), its basic structure is a planar PN junction, and its working voltage is above the avalanche breakdown voltage of the PN junction. When the working voltage of the planar PN junction gradually approaches the avalanche voltage, the avalanche multiplication factor will tend to infinity in theory, but in practice, when the working voltage is lower than the avalanche voltage, the multiplication factor will be saturated when it reaches about 1000. Only in Geiger mode, that is, when the operating voltage is higher than the avalanche breakdown voltage, can the multiplication factor be large enough to capture single photons.

Single-photon avalanche diodes can be realized with a variety of structures, and the final device characteristics of each structure are low dark noise, high time resolution, and integration. At the same time, while ensuring the good performance of the device, its manufacturing process also needs to be simple, convenient and economical. Therefore, the single photon avalanche diode that can be realized by standard CMOS technology meets the market demand.

The single-photon-level resolution sensor unit structure proposed by the present invention is completely based on the standard CMOS process design while ensuring the excellent performance of the device, so it can conveniently carry out large-scale integration and solve the difficulties and problems existing in the prior art.

Contents of the invention

The invention provides a single-photon-level resolution sensor unit structure based on a standard CMOS process. The sensor unit structure uses a single-photon avalanche diode (SPAD), and its basic structure is: a P-type silicon substrate (4) is provided with There is a deep N-well (3); the P-well region (2) is formed above and surrounded by the deep N-well (3); the anode contact (9) is through the heavily doped P-type region (1) Connected to the P-well region (2); the cathode contact (10) is connected to the N-well region (6) and the deep N-well region (3) through the heavily doped N-type region (5); the shallow trench isolation region (7) is located Between the P well region (2) and the N well region (6), the P well is isolated from the N well; the shallow trench isolation region (7) is provided with a P-type doped guard ring (8) around to contain the shallow Dark noise due to defects in trench isolation; the PN junction (11) between the bottom of the P well region (2) and the deep N well (3), when an appropriate bias voltage is applied between the cathode and anode, Make the PN junction work in the Geiger mode, the PN junction generates a high voltage region, forming a SPAD multiplication region to detect photons, and by controlling the concentration gradient of the deep N well (3), the edge breakdown voltage of the PN junction is higher than that of the SPAD The breakdown voltage of the planar multiplication region ensures that the device works normally in the Geiger mode for photon detection.

The beneficial effects of the present invention are: (1) the structure of the device is simple, the manufacturing process is fully compatible with the standard CMOS process, economical and practical; (2) the dark noise of the device is effectively reduced through shallow trench isolation and P-type doping guard ring ; (3) The device has good scalability, which is conducive to improving the large-scale integration of the device.

Description of drawings

The subject matter of the present invention will now be described in detail with reference to the following drawings, and clearly understand the relevant structures and implementation methods of the present invention as well as its purpose, features and advantages:

FIG. 1 is a schematic diagram of the structure of a single-photon-level resolution sensor unit based on a standard CMOS process in the present invention.

Fig. 2 is a working voltage mode diagram of the single-photon level resolution sensor of the present invention.

Fig. 3 is a working principle diagram of the single-photon level resolution sensor of the present invention.

Fig. 4 is a schematic diagram of the principle of avalanche multiplication.

Detailed ways

In the following detailed description, specific details are described in order to provide a comprehensive understanding of the invention. As previously stated, it will be understood that if the type of semiconductor doping is reversed (i.e., N-type doping replaces P-type doping), the voltage, Where the anode and cathode etc. are appropriately reversed, the examples given for P-type and N-type materials are used equally. The present invention assumes the use of a P-type substrate, which is the most standard substrate type used in standard CMOS processes.

Fig. 1 is the single-photon-level resolution sensor unit structural representation based on standard CMOS technology of the present invention, and the composition of described single-photon-level resolution sensor unit structure is: P-type silicon substrate (4) top is provided with deep N well ( 3); the P-well region (2) is formed above and surrounded by the deep N-well (3); the anode contact (9) is connected to the P-well region through the heavily doped P-type region (1) (2); the cathode contact (10) is connected to the N well region (6) and the deep N well (3) through the heavily doped N-type region (5); the shallow trench isolation region (7) is located in the P well region (2 ) and the N well region (6), the P well is isolated from the N well; the shallow trench isolation region (7) is provided with a P-type doped guard ring (8) around the perimeter to prevent the shallow trench isolation from Dark noise generated by defects; the PN junction (11) between the bottom of the P well region (2) and the deep N well (3), when an appropriate bias voltage is applied between the cathode and the anode, the PN junction produces a high voltage region, The SPAD multiplication region is formed to detect photons, and the edge breakdown voltage of the PN junction is higher than the breakdown voltage of the SPAD plane multiplication region by controlling the concentration gradient of the deep N well (3).

The working mechanism and process of the single-photon-level resolution sensor based on the standard CMOS process are as follows:

As shown in Figure 2, an appropriate bias voltage is applied between the anode and cathode of the sensor, so that the voltage difference ensures that the planar multiplication region PN junction (11) of the device is in the Geiger mode, that is, the operating voltage is higher than the strike of the PN junction. High voltage. Under this voltage difference, a depletion region is generated at the PN junction (11), as shown in Figure 3, there is a strong electric field in the depletion region, which is sufficient to ensure that the carriers in this region can obtain sufficient The energy creates an avalanche through the impact ionization effect, which creates a large avalanche current.

When light is incident into the depletion region, the energy of the incident photons is absorbed by the semiconductor silicon to generate electron-hole pairs, as shown in FIG. 4 . Under the action of a strong electric field, the generated electrons accelerate upwards to obtain enough energy. When the electrons collide with the silicon lattice atoms, they can collide the electrons on the valence bond and become conductive electrons, and at the same time generate a hole. , so one carrier becomes three carriers. In the same way, the generated electrons and holes will continue to collide, and if this continues, the carriers will increase greatly, resulting in an avalanche effect. From its final result, the sensor converts an incident photon into countless carriers, thereby generating a large observable current between the cathode and anode, and realizing the detection of a single photon.

An important performance of the single-photon resolution sensor is its dark noise, that is, the avalanche effect caused by the carriers inside the sensor itself. If the dark noise is high, it will cover up the weak light signal, confuse the light signal with the dark noise, and make it difficult to distinguish whether there are photons incident. Therefore, suppression of dark noise is extremely important. In the present invention, there is a P-type doped guard ring around the shallow trench isolation region, and this guard ring effectively suppresses the contribution of a large number of defects in the shallow trench isolation to the dark noise of the device, thereby significantly reducing the The dark noise of the sensor improves the working performance of the sensor.

In summary, based on the standard CMOS process, the present invention designs a single-photon-level resolution sensor unit structure, realizes the detection of weak light or even a single photon, simplifies the production process of the single-photon-level resolution sensor, and reduces The production cost is reduced and the detection efficiency is improved. It will therefore be understood that the examples given with respect to P-type and N-type materials would be understood if the type of semiconductor doping was reversed (i.e. N-type doping instead of P-type doping), and the voltage, anode and cathode, etc. Equal use does not exceed the core connotation of the device structure described in the present invention. The present invention assumes the use of a P-type substrate, which is the most standard substrate type used in standard CMOS processes.

Claims (4)

1. a single photon level resolution sensor unit structure based on standard CMOS technology, this sensor unit structure uses a kind of single photon avalanche diode (SPAD), and described SPAD structural feature is: P-type silicon substrate (4) top is set There is a deep N-well (3); the P-well region (2) is formed above and surrounded by the deep N-well (3); the anode contact (9) is through the heavily doped P-type region (1) Connected to the P-well region (2); the cathode contact (10) is connected to the N-well region (6) and the deep N-well region (3) through the heavily doped N-type region (5); the shallow trench isolation region (7) is located Between the P well region (2) and the N well region (6), the P well is isolated from the N well; the shallow trench isolation region (7) is provided with a P-type doped guard ring (8) around to contain the shallow Dark noise due to defects in trench isolation; the PN junction (11) between the bottom of the P well region (2) and the deep N well (3), when an appropriate bias voltage is applied between the cathode and anode, Make the PN junction work in the Geiger mode, the PN junction generates a high voltage region, forming a SPAD multiplication region to detect photons, and by controlling the concentration gradient of the deep N well (3), the edge breakdown voltage of the PN junction is higher than that of the SPAD The breakdown voltage of the planar multiplication region ensures that the device works normally in the Geiger mode for photon detection. 2. The SPAD according to claim 1, wherein the shallow trench isolation region (7) is characterized in that it effectively isolates the P well region (2) from the N well region (6). 3. The SPAD according to claim, wherein the guard ring (8) of P-type doping is characterized in that it is located around the shallow trench isolation region (7) to generate defects in the shallow trench isolation region Carriers are isolated outside the multiplication region of the PN junction (11). 4. The SPAD according to claims 1 to 3, characterized in that, an appropriate bias voltage is applied between the cathode and the anode, so that the PN junction (11) works in the Geiger mode, so that the incident light is detected .

Images