CN107527958A - A kind of superlattices infrared detector surface passivation method - Google Patents

Abstract

A surface passivation method of a superlattice infrared detector of the present invention, step 1: take the superlattice material sample that has been etched on the table surface without passivation, and put the sample into a high vacuum chamber after cleaning, and the vacuum degree Higher than 10 ^‑6 Torr; step 2: use atomic layer etching technology to clean the surface and sidewall of the superlattice mesa at a temperature of 0‑150 ° C, to etch and remove the oxide layer on the surface and sidewall and Residual pollutants from the previous process; Step 3: After the atomic layer etching step, use atomic layer deposition technology in the same vacuum system to deposit and grow a passivation layer layer by layer at a temperature of 0-280°C to passivate the superlattice The surface and side walls of the countertop. The invention can effectively increase the lateral resistivity of the mesa, thereby suppressing the lateral leakage of the device and improving the performance of the detector.

Description

A method for surface passivation of superlattice infrared detectors

technical field

The invention belongs to the technical field of semiconductor materials and devices, in particular to a method for passivating the surface of a superlattice infrared detector, which can be applied to the surface passivation of class II superlattice infrared detector devices.

Background technique

The class II superlattice material based on III-V semiconductor InAs/GaSb is a new type of infrared detector material. Compared with the mercury cadmium telluride and superlattice detectors currently on the market, it has The lattice structure can adjust the detection wavelength in a large range; 2) the Auger recombination probability is low, which is beneficial to increase the working temperature; 3) the infrared absorption coefficient of the material is high, and the photoelectric efficiency of the interband transition is high; 4) the electron tunneling of the superlattice structure 5) There are many advantages such as low cost and difficulty in making large area array devices, so the application range of infrared detectors in military and civilian fields is expanding day by day, covering strategic early warning, battlefield surveillance , Atmospheric monitoring, space communication, spaceborne detection, security monitoring, intelligent transportation and medical treatment and other fields.

When making a superlattice infrared detector device, it is necessary to etch the grown superlattice epitaxial wafer into discrete mesas, and at this time the side walls of the mesas become new surfaces exposed to the environment. Due to the small effective bandgap width of the second type superlattice material (less than 0.3eV, some even less than 0.03eV), the energy band will be bent on the surface of the material due to the existence of the interface, and the bending of the energy band is easy to occur in the narrow bandgap A potential well of carriers is generated on the surface of the material, thereby forming a surface conductive layer; at the same time, both InAs and GaSb are easily oxidized, and form a single semi-metal As and metal Sb remaining on the side of the mesa, making the surface rough and introducing Surface states increase surface non-radiative recombination and sidewall leakage, so the surface passivation process is crucial to the performance of type II superlattice infrared detectors. In addition, it should be noted that InAs/GaSb superlattice materials cannot tolerate high-temperature processes, and the process temperature greater than 300°C in the current common passivation layer growth process will cause damage to the superlattice structure and affect its performance. It is very necessary to develop a low temperature surface passivation process.

Contents of the invention

The purpose of the present invention is to provide a surface passivation method of a superlattice infrared detector, which can effectively increase the lateral resistivity of the mesa, thereby suppressing the lateral leakage of the device and improving the performance of the detector.

The present invention realizes above-mentioned purpose through following technical scheme:

A method for passivating the surface of a superlattice infrared detector, comprising the following steps:

Step 1: Take a sample of the superlattice material that has been etched on the mesa without passivation, and put the sample into a high vacuum chamber after cleaning, and the vacuum degree is higher than 10 ^-6 Torr;

Step 2: Use atomic layer etching technology to clean the surface and sidewall of the superlattice mesa at a temperature of 0-150°C to etch and remove the oxide layer on the surface and sidewall as well as residual pollutants from the previous process ;

Step 3: After the atomic layer etching step is completed, the atomic layer deposition technology is used in the same vacuum system to deposit and grow a passivation layer layer by layer at a temperature of 0-280° C. to passivate the surface and side walls of the superlattice mesa.

Further, the superlattice material is an antimonide-based type II superlattice infrared detector material.

Further, the atomic layer etching in the second step is to expose the sample to alternating pulses of chlorine-containing plasma, argon-containing or neon-containing plasma to etch the surface and sidewall of the sample layer by layer, and the alternating pulses The recurrence period is greater than or equal to 1.

Further, the material of the passivation layer grown by the atomic layer deposition process in the step 3 includes aluminum oxide, silicon oxide, silicon nitride or III-V group compounds, and the passivation layer consists of a single layer, two layers or multiple layers The passivation layer materials are stacked,

Further, the total thickness of the passivation layer is 2-1000 nanometers.

Compared with the prior art, the beneficial effects of the superlattice infrared detector surface passivation method of the present invention are: 1) the whole process is carried out in the same high-vacuum system, the atmosphere is not exposed midway, and the material surface after cleaning will not 2) The surface and side walls of the mesa are cleaned by atomic layer etching technology, and the oxide layer and impurity pollutants are removed, which ensures the quality of the interface between the passivation layer and the superlattice, which can Obtain higher lateral resistivity, suppress device lateral leakage, and improve device performance; 3) When the atomic layer deposition technology grows the passivation layer, the deposition temperature used is low, so the passivation process has no damage to the superlattice structure ; 4) The thickness of the passivation layer deposited by atomic layer deposition technology is uniform, the ratio of elements is accurate, and the resistivity is high, which can realize high-quality passivation of large area array devices; 5) atomic layer etching and atomic layer deposition technology are both effective Self-limiting, isotropic and conformal process, the process thickness can be controlled by the number of reaction cycles, and etching or growth is not affected by the shape or height of the mesa, so the passivation process is easy to control and repeatable High, it can be applied to the surface passivation of superlattice infrared detector devices in various bands.

Description of drawings

Figure 1 is a schematic diagram of a passivated superlattice mesa.

Figure 2 is a comparison of the mesa lateral resistivity of unpassivated and passivated devices at 83K.

detailed description

The technical scheme of the present invention will be further described below in conjunction with the accompanying drawings.

This embodiment shows a method for passivating the surface of a superlattice infrared detector. In order to show the passivation effect of the present invention, the steps of this embodiment include:

Step 1: Take four samples of superlattice materials that have completed mesa etching without passivation. The superlattice materials are antimonide-based Class II superlattice infrared detector materials, including but not limited to InAs/GaSb supercrystals Lattice, InAs/InAsSb superlattice, etc. The sample is a long-wave infrared detector material with a 90% cut-off wavelength of 12.3 microns. After cleaning with acetone, put it into a high vacuum chamber, the vacuum degree is higher than 10 ^-6 Torr, preferably 5×10 ^-7 Torr;

Step 2: Use atomic layer etching (Atomic Layer Etching, ALE) technology to clean the surface and sidewall of the superlattice mesa at 0-150°C, preferably 30°C, to etch and remove the surface and sidewall The oxide layer and the residual pollutants of the previous process, the atomic layer etching uses alternating pulses of chlorine-containing plasma and argon-containing plasma, and the repetition period of the alternating pulse is greater than or equal to 1, preferably 5 cycles of repeated etching , the etching thickness is about 1 nanometer;

Step 3: Immediately after the atomic layer etching step is completed, the passivation layer material is grown by atomic layer deposition (Atomic Layer Deposition, ALD) technology in the same vacuum system. The passivation layer material includes aluminum oxide, silicon oxide, silicon nitride or III - Group V compounds, the passivation layer can be composed of a single above-mentioned material, or can be formed by stacking two or more layers of the above-mentioned materials, and the total thickness of the passivation layer is 2-1000 nanometers. The passivation layer is preferably an aluminum oxide passivation layer, the deposition temperature is 0-280°C, preferably 120°C, and the deposition is carried out by alternating pulses of trimethylaluminum and water molecules, and the thickness of the deposited aluminum oxide passivation layer is 10 nanometers .

As a comparison, four other superlattice material samples of the same size as those in step 1 were taken for testing.

Figure 1 is a schematic diagram of a passivated superlattice device, where P1 represents the superlattice mesa, P2 represents the passivation layer, P3 represents the sample substrate where the superlattice is located, and P4 and P5 represent a pair of electrodes of the device.

Using liquid nitrogen as a cooling source, the R ₀ A values of all unpassivated and passivated samples were measured at a temperature of 83K, and then as shown in Figure 2, the perimeter area ratio P/A and R ₀ A of each sample For a linear fit to the reciprocal of the value, use the formula:

The ρ _Surface value of the unpassivated and passivated samples can be obtained, that is, the lateral resistivity of the mesa. It can be seen from the comparison that after adopting the passivation method of the present invention, the lateral resistivity of the mesa of the device is increased from 10.5kΩ cm to 137kΩ cm, which is an order of magnitude improvement, and the quality of the superlattice material is not degraded at the same time, which shows that the passivation method of the present invention The oxidation process effectively suppresses the sidewall leakage of the device and plays a good passivation role.

What has been described above is only one embodiment of the present invention. For those skilled in the art, without departing from the inventive concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims (5)

1. a superlattice infrared detector surface passivation method, is characterized in that, comprises the following steps: Step 1: Take a sample of the superlattice material that has been etched on the mesa without passivation, and put the sample into a high vacuum chamber after cleaning, and the vacuum degree is higher than 10 ^-6 Torr; Step 2: Use atomic layer etching technology to clean the surface and sidewall of the superlattice mesa at a temperature of 0-150°C to etch and remove the oxide layer on the surface and sidewall as well as residual pollutants from the previous process ; Step 3: After the atomic layer etching step is completed, the atomic layer deposition technology is used in the same vacuum system to deposit and grow a passivation layer layer by layer at a temperature of 0-280° C. to passivate the surface and side walls of the superlattice mesa. 2 . The surface passivation method for superlattice infrared detectors according to claim 1 , wherein the superlattice material is an antimonide-based Class II superlattice infrared detector material. 3 . 3. The superlattice infrared detector surface passivation method according to claim 1, characterized in that: the atomic layer etching in the step 2 is to expose the sample to chlorine-containing plasma, argon-containing or neon-containing plasma In the alternating pulse of the body, the surface and sidewall of the sample are etched layer by layer, and the repetition period of the alternating pulse is greater than or equal to 1. 4. superlattice infrared detector surface passivation method according to claim 1, is characterized in that: the passivation layer material that the atomic layer deposition technique growth in described step 3 comprises aluminum oxide, silicon oxide, silicon nitride Or III-V compound, the passivation layer is formed by stacking a single layer, two or more layers of passivation layer materials. 5. The surface passivation method of the superlattice infrared detector according to claim 4, characterized in that: the total thickness of the passivation layer is 2-1000 nanometers.