High-performance wafer-level lead sulfide near infrared photosensitive thin film and preparation method thereof

Abstract

Provided are a method for preparing a high-performance wafer-level lead sulfide near infrared photosensitive thin film. Firstly, a surface of the selected substrate material is cleaned; next, a vaporized oxidant is introduced into a vacuum evaporation chamber under a high background vacuum degree, and a PbS thin film is deposited on the clean substrate surface to obtain a microstructure with medium particle, loose structure and consistent orientation. Finally, under a given temperature and pressure, a high-performance wafer-level PbS photosensitive thin film is obtained by sensitizing the film prepared at step S2 using iodine vapor carried by a carrier gas. This preparation method is simple, low-cost and repeatable. The PbS photosensitive thin film has a high photoelectric detection rate. The 600K blackbody room temperature peak detection rate is >8×1010 Jones. The corresponding non-uniformity in a wafer-level photosensitive surface is <5%, satisfying the requirements of preparation of a PbS Mega-pixel-level array imaging system.

Claims

1. A method for preparing a wafer-level lead sulfide (PbS) near infrared photosensitive thin film, comprising the following steps: at step S1, selecting an appropriate substrate material, and cleaning a surface of the selected substrate material to obtain a substrate with clean surface; wherein the substrate has insulation property and temperature resistance; at step S2, introducing a vaporized oxidant into a vacuum evaporation chamber under a high background vacuum degree, and slowly depositing a PbS thin film from a PbS evaporation source on the clean substrate surface in step S1 to obtain a microstructure with medium particle, loose structure and consistent orientation; wherein a vacuum degree of the vacuum chamber is maintained at 2-5×10−2 Pa after introduction of the oxidant, and a flow rate of introducing the oxidant is controlled to 10-25 sccm; a deposition temperature of the PbS thin film is controlled at 50-120 degrees Celsius, a PbS deposition rate is controlled to 0.5-1.2 microns/hour, and a PbS thickness is controlled to 1.2-1.5 microns; at step S3, at a temperature of 200-400° C., obtaining a PbS photosensitive thin film by performing sensitization for the PbS thin film prepared at step S2 for 5-240 min by using iodine vapor carried by a carrier gas; wherein the oxidant introduced into the vacuum chamber at step S2 comprises halogen gas, ozone, and hydrogen peroxide.

2. The method according to claim 1, wherein the substrate in step S1 is resistant to treatment at a temperature 450° C. and comprises one of silicon (Si), Sapphire (Al2O3), fused quartz glass (SiO2), glass, zinc sulfide (ZnS), zinc selenide (ZnSe), and calcium fluoride (CaF2).

3. The method according to claim 2, wherein the cleaning in step S1 is performed by wet chemical cleaning or thermal cleaning; and the cleaning comprises: 1) Placing in acetone, ethanol and de-ionized water in sequence for ultrasonic cleaning; 2) Employing one or more of acid wash, alkali wash and plasma cleaning; and 3) cleaning the substrate by using de-ionized water and drying to obtain the substrate with clean surface.

4. The method according to claim 3, wherein the substrate surface treatment in step S1 is performed by wet chemical cleaning.

5. The method according to claim 4, wherein the deposition of the PbS thin film in the vacuum chamber in step S2 is performed by resistive thermal evaporation, electron beam thermal evaporation or magnetron sputtering, and a purity of a PbS evaporation source is not smaller than 99.99%.

6. The method according to claim 5, wherein the carrier gas in step S3 is air, high purity oxygen or inert gas, and the carrier gas is introduced at a flow rate of 1-10 sccm; a flow rate of iodine vapor is controlled at 0.01-1 sccm; and a pressure of sensitization treatment is controlled at 1.001-1.005 standard atmospheric pressures.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

(1) FIG. 1 is a SEM image of a section of a typical PbS photosensitive thin film.

(2) FIG. 2 shows an influence of an oxidant flow rate on a detection rate of a PbS photosensitive thin film.

(3) FIG. 3 shows an influence of a sensitization temperature on a detection rate of a PbS photosensitive thin film in a sensitization process.

(4) FIG. 4 shows an influence of a sensitization time on a detection rate of a PbS photosensitive thin film in a sensitization process.

(5) FIG. 5 shows an influence of an oxygen/iodine gas flow rate on a detection rate of a PbS photosensitive thin film in a sensitization process.

DETAILED DESCRIPTIONS OF EMBODIMENTS

(6) The present invention will be further detailed in combination with specific embodiments and accompanying drawings, but the present invention is not limited to these embodiments of the present invention.

Embodiment 1

(7) At step S1, a common glass of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation. Next, the glass substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a glass wafer substrate with clean surface.

(8) At step S2, the clean glass wafer substrate was conveyed into a PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 5×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS thin film deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the chlorine gas input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(9) At step S3, the glass wafer PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.001 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.1 sccm was introduced for 30 min. Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, 600k blackbody room temperature peak detection rate was 2.5×10.sup.11 Jones as shown by the point A in FIGS. 2, 3, 4, and 5.

Embodiment 2

(10) At step S1, a high resistivity silicon wafer was placed into a high temperature furnace to perform high temperature oxidation thermal cleaning at a temperature of 600° C. for 3 h at a flow rate of oxygen 10 sccm.

(11) At step S2, the clean Si wafer was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 5×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the chlorine gas input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(12) At step S3, the PbS thin film on the Si wafer substrate was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.01 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.1 sccm was introduced for 30 min Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 2.2×10.sup.11 Jones.

Embodiment 3

(13) At step S1, a common glass wafer of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a glass wafer substrate with clean surface.

(14) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 25 sccm and the vacuum degree of the reaction chamber was maintained at 5×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After three hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.4 microns/hour.

(15) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.005 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.1 sccm was introduced for 30 min. Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 0.8×10.sup.11 Jones as shown by the point B in FIG. 2.

Embodiment 4

(16) At step S1, a common glass of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the glass substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a substrate with clean surface.

(17) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(18) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.001 atmospheric pressures. Next, the sensitization furnace was heated to 200° C., and then iodine vapor of 0.1 sccm was introduced for 30 min. Afterwards, the temperature started to drop and the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 0.78×10.sup.11 Jones as shown by the point C in FIG. 3.

Embodiment 5

(19) At step S1, a common glass wafer of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the glass substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a glass wafer substrate with clean surface.

(20) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(21) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.001 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.1 sccm was introduced for 75 min. Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 0.92×10.sup.11 Jones as shown by the point D in FIG. 3.

Embodiment 6

(22) At step S1, a common glass of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a substrate with clean surface.

(23) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(24) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 1 sccm to enable a pressure inside the furnace to stay at 1.0001 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 1 sccm was introduced for 2 min. Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 0.76×10.sup.11 Jones as shown by the point E in FIG. 5.

Embodiment 7

(25) At step S1, a common glass of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a substrate with clean surface.

(26) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(27) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 1 sccm to enable a pressure inside the furnace to stay at 1.001 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.1 sccm was introduced for 10 min. Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 1.5×10.sup.11 Jones as shown by the point F in FIG. 5.

Embodiment 8

(28) At step S1, a common glass of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a substrate with clean surface.

(29) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 50° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 10 sccm and the vacuum degree of the reaction chamber was maintained at 2×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After two hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was 0.6 microns/hour.

(30) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.01 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.01 sccm was introduced for 240 min Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 2.0×10.sup.11 Jones as shown by the point G in FIG. 5.

Embodiment 9

(31) At step S1, a common glass wafer of 3 inches was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min, and then placed in a concentrated sulfuric acid for 2 h of impregnation, and then the glass substrate was washed repeatedly using flowing de-ionized water, and then ultrasonically cleaned for 10 min in de-ionized water and then dried to obtain a glass wafer substrate with clean surface.

(32) At step S2, the clean glass substrate was conveyed into the PbS evaporation reaction chamber and heated to 120° C. after a vacuum degree reached 2×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, chlorine gas was introduced at a flow rate of 20 sccm and the vacuum degree of the reaction chamber was maintained at 4×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After three hours, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the oxidant input was also stopped. The thin film had a thickness of 1.3 microns. The PbS deposition rate was 0.45 microns/hour.

(33) At step S3, the glass substrate PbS thin film was placed into a sensitization furnace, and oxygen was introduced at a flow rate of 10 sccm to enable a pressure inside the furnace to stay at 1.01 atmospheric pressures. Next, the sensitization furnace was heated to 400° C., and then iodine vapor of 0.1 sccm was introduced for 30 min. Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of oxygen was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 1.6×10.sup.11 Jones.

Embodiment 10

(34) At step S1, a sapphire (Al.sub.2O.sub.3) wafer was placed into a high temperature furnace to perform high temperature oxidation thermal cleaning at the temperature of 600° C. for 3 h at the flow rate of oxygen 10 sccm.

(35) At step S2, the clean sapphire wafer was conveyed into the PbS evaporation reaction chamber and heated to 120° C. after a vacuum degree reached 8×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, ozone was introduced at a flow rate of 18 sccm and the vacuum degree of the reaction chamber was maintained at 5×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After deposition, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the ozone input was also stopped. The thin film had a thickness of 1.2 microns. The PbS deposition rate was controlled to 0.8 microns/hour.

(36) At step S3, the PbS thin film on the sapphire wafer substrate was placed into a sensitization furnace, and air was introduced at a flow rate of 2 sccm to enable a pressure inside the furnace to stay at 1.001 atmospheric pressures. Next, the sensitization furnace was heated to 360° C., and then iodine vapor of 1 sccm was introduced for 3 min Afterwards, the temperature started to drop. After the temperature was decreased to 250° C., the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of air was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 1.1×10.sup.11 Jones.

Embodiment 11

(37) At step S1, a zinc sulfide (ZnS) wafer was placed in acetone, ethanol and de-ionized water in sequence for respective ultrasonic cleaning for 10 min and then dried to obtain a substrate with clean surface.

(38) At step S2, the clean ZnS wafer was conveyed into the PbS evaporation reaction chamber and heated to 80° C. after a vacuum degree reached 5×10.sup.−4 Pa, and then a PbS source temperature was gradually increased to an eruption temperature. Next, a hydrogen peroxide liquid was passed through at a flow rate of 25 sccm with oxygen as a carrier gas, and the vacuum degree of the reaction chamber was maintained at 3×10.sup.−2 Pa by adjusting a pumping force of a vacuum system. After vacuum stabilization, a growth baffle plate was opened to start to carry out PbS deposition. After deposition, the baffle plate was closed, a PbS source and a substrate heating power source were stopped, and the carrier gas and hydrogen peroxide input was also stopped. The thin film had a thickness of 1.5 microns. The PbS deposition rate was controlled to 1.2 microns/hour.

(39) At step S3, the PbS thin film on the ZnS wafer substrate was placed into a sensitization furnace, and argon gas was introduced at a flow rate of 5 sccm to enable a pressure inside the furnace to stay at 1.005 atmospheric pressures. Next, the sensitization furnace was heated to 250° C., and then iodine vapor of 0.01 sccm was introduced for 240 min. Afterwards, the temperature started to drop and the supply of iodine vapor was stopped. After the temperature was decreased to room temperature, the supply of argon gas was stopped. At this time, in a case of 600k blackbody, the room temperature peak detection rate of the PbS detector was 0.96×10.sup.11 Jones.

(40) The above descriptions are made only to the embodiments of the present invention and shall not be intended to limit the scope of protection of the present invention. It should be pointed out that several variations and improvements made by those skilled in the art without departing from the idea of the present invention shall all fall within the scope of protection of the present invention.