Preparation method and equipment of cadmium telluride film

Abstract

The invention relates to a method and equipment for preparing a cadmium telluride thin film, the cadmium telluride thin film is prepared by using vertical magnetron sputtering equipment, the distance between a sample table and a radio frequency table is adjusted to a theoretical optimal value, then the sputtering power, the process pressure and the substrate temperature are adjusted, and the high-quality thin film is obtained. The problem that many holes appear after mutual diffusion annealing is carried out on the cadmium telluride film prepared in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip processing, and relates to a method and device for preparing cadmium telluride thin films. Background Art

[0002] A large number of dangling bonds will be generated on the surface of untreated mercury cadmium telluride. When exposed to air, an oxide layer will form on the surface. This as-grown oxide layer is very unstable. If no treatment is carried out, it will seriously affect the device performance. Therefore, a cadmium telluride film needs to be covered on its surface to eliminate surface dangling bonds and protect the surface of mercury cadmium telluride. After R. PAL et al. grew a cadmium telluride passivation layer on the surface of mercury cadmium telluride and annealed it, tellurium and mercury at the cadmium telluride / mercury cadmium telluride interface would interdiffuse between the two. Mercury in mercury cadmium telluride diffused into the passivation layer cadmium telluride, and tellurium in cadmium telluride diffused into the interior of mercury cadmium telluride, thereby forming a region with a compositional gradient change near the cadmium telluride / mercury cadmium telluride interface. The gradient change of the composition caused the energy band near the cadmium telluride / mercury cadmium telluride interface to bend, forming a built-in electric field near the cadmium telluride / mercury cadmium telluride interface, and the band gap width near cadmium telluride was relatively large. Under the same passivation layer charge density, it was not easy for mercury cadmium telluride to form an inversion state (Pal R, Malik A, Srivastav V, et al. Compositionally graded interface for passivation of HgCdTe photodiodes[J]. Journal of Electronic Materials, 2006, 35(10): 1793-1800). Therefore, annealing is usually carried out to improve the passivation effect and thus improve the performance of the detector.

[0003] However, the cadmium telluride thin films prepared under conventional process conditions usually have poor compactness and are very prone to a lot of holes after interdiffusion annealing, as Figure 1a is the surface SEM image after annealing, Figure 1b and is the cross-sectional SEM image. It can be seen from the figure that there are many holes in the cadmium telluride thin film after interdiffusion annealing, indicating that the film quality is very poor and affects the device performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for preparing cadmium telluride thin films, which solves the problem that a lot of holes appear in the cadmium telluride thin films prepared in the prior art after interdiffusion annealing.

[0005] To achieve the above purpose, the technical solution of the present invention is:

[0006] A method for preparing cadmium telluride thin films, which uses a vertical magnetron sputtering device to prepare cadmium telluride thin films. The vertical magnetron sputtering device includes a vacuum chamber, a radio frequency stage for placing a target material and a sample stage for fixing a metal carrier plate, which are oppositely placed and the distance between them can be adjusted. The vacuum chamber is also provided with a rotating shaft for driving the sample stage to rotate and a temperature control component for controlling the temperature of the sample stage; the radio frequency stage is connected to the cathode of the radio frequency power supply, and the sample stage is connected to the anode of the radio frequency power supply;

[0007] The specific method steps are as follows:

[0008] Step 1: Fix the cadmium telluride target on the radio frequency stage, and fix the metal carrier plate loaded with the sample on the sample stage; adjust the distance between the radio frequency stage and the sample stage;

[0009] Step 2: Evacuate the vacuum chamber to make the vacuum degree reach the set value;

[0010] Step 3: Heat the temperature of the sample stage to 100°C - 130°C; set the sputtering power to 50W - 100W; set the deposition time to 900s - 3000s;

[0011] Step 4: Fill the vacuum chamber with argon and adjust the pressure of the vacuum chamber;

[0012] Step 5: Start the rotating shaft to drive the sample stage to rotate, turn on the radio frequency power supply, and start sputtering;

[0013] Step 6: After reaching the deposition time, turn off the radio frequency power supply, stop filling argon, stop heating the sample stage, and turn off the rotating shaft; naturally cool to room temperature, and take out the sample covered with cadmium telluride thin films.

[0014] The sample described in one is a mercury cadmium telluride material on a cadmium zinc telluride substrate.

[0015] In step 2, the vacuum degree of the vacuum chamber is set to 5.0×10 -7 mbar.

[0016] In step 3, heat the sample stage to keep the temperature of the metal carrier plate at 100°C - 125°C; set the sputtering power to 50W - 80W; set the deposition time to 1200s - 3000s.

[0017] In step 4, fill 200sccm of argon into the vacuum chamber and adjust the pressure to 3.0×10 -3 mbar.

[0018] In step 6, the thickness of the cadmium telluride thin film of the sample is 298nm - 312nm.

[0019] A vertical magnetron sputtering device for implementing the preparation method of cadmium telluride thin films as described above. The device includes a vacuum chamber, a radio frequency stage for placing a target and a sample stage for fixing a metal carrier plate, which are oppositely placed and the distance between them can be adjusted. The vacuum chamber is also provided with a rotating shaft for driving the sample stage to rotate and a temperature control component for controlling the temperature of the sample stage; the radio frequency stage is connected to the cathode of a radio frequency power supply, and the sample stage is connected to the anode of the radio frequency power supply.

[0020] The advantages of the present invention are as follows: By applying the method of the present invention, the growth rate of cadmium telluride on mercury cadmium telluride is relatively fast, reaching 2.5 Å / s. The growth of cadmium telluride on mercury cadmium telluride is uniform, significantly improving the density of the cadmium telluride thin film, and it can be achieved that there are no holes on the cadmium telluride thin film after interdiffusion annealing. Description of the Drawings

[0021] Figure 1a and Figure 1b are SEM images after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in the prior art, where Figure 1a is the surface SEM image, Figure 1b is the cross-sectional SEM image.

[0022] Figure 2 is a schematic structural diagram of the vertical magnetron sputtering device used in the present invention;

[0023] Figure 3a and Figure 3b are SEM images after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in Example 1 of the present invention, where Figure 3a is the surface SEM image, Figure 3b is the cross-sectional SEM image.

[0024] Figure 4a and Figure 4b are SEM images after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in Example 2 of the present invention, where Figure 4a is the surface SEM image, Figure 4b is the cross-sectional SEM image.

[0025] Figure 5a and Figure 5b are SEM images after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in Example 3 of the present invention, where Figure 5a is the surface SEM image, Figure 5b is the cross-sectional SEM image.

[0026] Figure 6a and Figure 6b are SEM images after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in Example 4 of the present invention, where Figure 6a is the surface SEM image, Figure 6b is the cross-sectional SEM image.

[0027] Figure 7a And Figure 7b FIG. is the SEM image after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in Example 5 of the present invention, where Figure 7a is the surface SEM image, Figure 7b is the cross-sectional SEM image.

[0028] Figure 8a And Figure 8b FIG. is the SEM image after annealing the cadmium telluride passivation layer grown on the surface of a mercury cadmium telluride substrate in Example 6 of the present invention, where Figure 8a is the surface SEM image, Figure 8b is the cross-sectional SEM image.

[0029] In the figure: 1 - radio frequency stage; 2 - sample stage; 3 - vacuum chamber; 4 - rotating shaft. Detailed implementation manners

[0030] The present invention will be further described below with reference to the accompanying drawings. The accompanying drawings are only for illustrative purposes and should not be construed as a limitation of this patent.

[0031] To more concisely illustrate this embodiment, some components that are well-known to those skilled in the art but not relevant to the main content of this creation will be omitted in the drawings or descriptions. Additionally, for ease of expression, some components in the drawings will be omitted, enlarged, or reduced, but this does not represent the dimensions or entire structure of the actual product.

[0032] The present invention discloses a method for preparing a cadmium telluride thin film, using a vertical magnetron sputtering device as shown in Figure 2 to prepare a cadmium telluride thin film. The vertical magnetron sputtering device includes a vacuum chamber 3, a radio frequency stage 1 for placing a target and a sample stage 2 for fixing a metal carrier plate, which are oppositely placed and the distance between them can be adjusted, and are arranged in the vacuum chamber 3. The vacuum chamber 3 is further provided with a rotating shaft 4 for driving the sample stage 2 to rotate and a temperature control component for controlling the temperature of the sample stage 2; the radio frequency stage 1 is connected to the cathode of a radio frequency power supply, and the sample stage 2 is connected to the anode of the radio frequency power supply.

[0033] The specific method steps are as follows:

[0034] Step 1, fix the cadmium telluride target on the radio frequency stage 1, and fix the metal carrier plate loaded with the sample on the sample stage 2; the sample is a mercury cadmium telluride material on a cadmium zinc telluride substrate.

[0035] Adjust the distance between the radio frequency stage 1 and the sample stage 2; preferably, the distance between the radio frequency stage 1 and the sample stage 2 is 78 mm - 82 mm.

[0036] Step 2, evacuate the vacuum chamber 3 to make the vacuum degree reach the set value. Preferably, the vacuum degree is set to 5.0 × 10 - 7 mbar.

[0037] Step 3: Heat the temperature of the sample stage 2 to 100°C - 130°C; preferably, heat the sample stage 2 to keep the temperature of the metal carrier plate at 100°C - 125°C.

[0038] Set the sputtering power to 50W - 100W; preferably, the sputtering power is 50W - 80W.

[0039] Set the deposition time to 900s - 3000s; preferably, the deposition time is 1200s - 3000s.

[0040] Step 4: Fill the vacuum chamber 3 with argon and adjust the pressure of the vacuum chamber; preferably, fill the vacuum chamber 3 with 200 sccm of argon and adjust the pressure to 3.0×10 -3 mbar.

[0041] Step 5: Start the rotating shaft 4 to drive the sample stage 2 to rotate, and set the rotation speed to 8 rpm. Turn on the RF power supply and start sputtering;

[0042] Step 6: After reaching the deposition time, turn off the RF power supply, stop the argon filling, stop heating the sample stage 2, and turn off the rotating shaft 4; naturally cool to room temperature, take out the sample covered with the cadmium telluride thin film, and the thickness of the cadmium telluride thin film of the sample is 298nm - 312nm.

[0043] The effects of the method of the present invention are compared with the prior art through the following examples:

[0044] Example 1: Evacuate the vacuum chamber 3 to make the vacuum degree reach the set value of 5.0×10 -7 mbar; heat the sample stage 2 to 115°C; rotate the sample stage 2 through the rotating shaft 4, and set the rotation speed to 8 rpm; fill the vacuum chamber 3 with 200 sccm of argon, adjust the pressure to 3.0×10 -3 mbar, adjust the sputtering power to 50W, and the deposition time is 2210s. The thickness of the cadmium telluride thin film measured by an infrared ellipsometer is 300nm.

[0045] After preparation, turn off the RF power supply, close the argon valve, turn off the heating stage, slowly adjust the rotation speed to zero, and take out the mercury cadmium telluride material with the cadmium telluride thin film prepared on the metal carrier plate after cooling for 2 - 3h.

[0046] Perform interdiffusion annealing on the prepared material, and use a scanning electron microscope to characterize the annealed material. Figure 3a is the surface SEM image after annealing. Figure 3b is the cross-sectional SEM image. It can be seen from the figure that the holes in the cadmium telluride thin film prepared by this method are much smaller than those of the prior art Figure 1a and Figure 1b are much smaller.

[0047] Example 2: The vacuum chamber 3 was evacuated until the vacuum degree reached the set value of 5.0×10 -7 mbar; the sample stage 2 was heated to 100 °C; the sample stage 2 was rotated through the rotating shaft 4, and the rotation speed was set to 8 rpm; 200 sccm of argon gas was introduced into the vacuum chamber 3, and the pressure was adjusted to 9.0×10 -3 mbar, the sputtering power was adjusted to 50 W, the deposition time was 3000 s, and the thickness measured by the infrared ellipsometer was 298 nm.

[0048] After preparation, the radio frequency power supply was turned off, the argon gas valve was closed, the heating stage was turned off, the rotation speed was slowly adjusted to zero, and after cooling for 2 - 3 h, the mercury cadmium telluride material with cadmium telluride thin film prepared on the metal carrier disk was taken out.

[0049] The prepared material was subjected to interdiffusion annealing, and the annealed material was characterized by a scanning electron microscope. Figure 4a This is the surface SEM image after annealing. Figure 4b This is the cross-sectional SEM image. Compared with that of Example 1 Figure 3a 、 Figure 3b The cadmium telluride thin film prepared by this method had fewer holes and improved film quality after annealing.

[0050] Example 3: The vacuum chamber 3 was evacuated until the vacuum degree reached the set value of 5.0×10 -7 mbar; the sample stage 2 was heated to 125 °C; the sample stage 2 was rotated through the rotating shaft 4, and the rotation speed was set to 8 rpm; 200 sccm of argon gas was introduced into the vacuum chamber 3, and the pressure was adjusted to 9.0×10 -3 mbar, the sputtering power was adjusted to 50 W, the deposition time was 3000 s, and the thickness measured by the infrared ellipsometer was 304 nm.

[0051] After preparation, the radio frequency power supply was turned off, the argon gas valve was closed, the heating stage was turned off, the rotation speed was slowly adjusted to zero, and after cooling for 2 - 3 h, the mercury cadmium telluride material with cadmium telluride thin film prepared on the metal carrier disk was taken out.

[0052] The prepared material was subjected to interdiffusion annealing, and the annealed material was characterized by a scanning electron microscope. Figure 5a This is the surface SEM image after annealing. Figure 5b This is the cross-sectional SEM image. Compared with that of Example 2 Figure 4a 、 Figure 4b The cadmium telluride thin film prepared by this method had occasional tiny holes and significantly improved film quality after annealing.

[0053] Example 4: The vacuum chamber 3 was evacuated until the vacuum degree reached the set value of 5.0×10 -7mbar; The sample stage 2 is heated to 120 °C; The sample stage 2 is rotated through the rotating shaft 4, and the rotation speed is set to 8 rpm; 200 sccm of argon gas is filled into the vacuum chamber 3, and the pressure is adjusted to 3.0 × 10 -3 mbar, the sputtering power is adjusted to 80 W, the deposition time is 1200 s, and the thickness of the cadmium telluride thin film measured by the infrared ellipsometer is 301 nm.

[0054] After preparation, turn off the radio frequency power supply, close the argon gas valve, turn off the heating stage, slowly adjust the rotation speed to zero, and take out the mercury cadmium telluride material with the cadmium telluride thin film prepared on the metal carrier after cooling for 2 - 3 h.

[0055] The prepared material is subjected to interdiffusion annealing, and the annealed material is characterized by a scanning electron microscope. Figure 6a is the surface SEM image after annealing. Figure 6b is the cross-sectional SEM image. It can be seen from the figure that the pore diameter of the cadmium telluride thin film prepared by this method after annealing is significantly smaller than that of Example 1. Figure 3a 、 Figure 3b The pores are significantly reduced, and the film quality is further improved.

[0056] Example 5: The vacuum chamber 3 is evacuated to make the vacuum degree reach the set value of 5.0 × 10-7 mbar; The sample stage 2 is heated to 115 °C; The sample stage 2 is rotated through the rotating shaft 4, and the rotation speed is set to 8 rpm; 200 sccm of argon gas is filled into the vacuum chamber 3, and the pressure is adjusted to 3.0 × 10 -3 mbar, the sputtering power is adjusted to 80 W, the deposition time is 1200 s, and the thickness of the cadmium telluride thin film measured by the infrared ellipsometer is 312 nm.

[0057] After preparation, turn off the radio frequency power supply, close the argon gas valve, turn off the heating stage, slowly adjust the rotation speed to zero, and take out the mercury cadmium telluride material with the cadmium telluride thin film prepared on the metal carrier after cooling for 2 - 3 h.

[0058] The prepared material is subjected to interdiffusion annealing, and the annealed material is characterized by a scanning electron microscope. Figure 7a is the surface SEM image after annealing. Figure 7b is the cross-sectional SEM image. Compared with that of Example 4 Figure 6a 、 Figure 6b After annealing, the cadmium telluride thin film prepared by this method basically has no pores, and the film quality is good.

[0059] Example 6: The vacuum chamber 3 is evacuated to make the vacuum degree reach the set value of 5.0 × 10-7 mbar; The sample stage 2 is heated to 125 °C; The sample stage 2 is rotated through the rotating shaft 4, and the rotation speed is set to 8 rpm; 200 sccm of argon gas is filled into the vacuum chamber 3, and the pressure is adjusted to 3.0 × 10 -3mbar, adjust the sputtering power to 80 W, deposition time 1200 s. The thickness of the cadmium telluride thin film measured by an infrared ellipsometer is 299 nm.

[0060] After preparation, turn off the radio frequency power supply, close the argon gas valve, turn off the heating stage, slowly adjust the rotation speed to zero, and take out the mercury cadmium telluride material with the cadmium telluride thin film prepared on the metal carrier plate after cooling for 2 - 3 h.

[0061] Perform interdiffusion annealing on the prepared material, and characterize the annealed material using a scanning electron microscope. Figure 8a It is the surface SEM image after annealing. Figure 8b It is the cross - section SEM image. Compared with that of Example 5 Figure 7a 、 Figure 7b After annealing, the cadmium telluride thin film prepared by this method has no holes at all, and the film quality is very good.

[0062] The above embodiments show that from the effect of interdiffusion annealing, compared with the cadmium telluride thin film prepared by the prior art, when using the method of the present invention to prepare the cadmium telluride thin film, not only can a cadmium telluride thin film with significantly fewer holes and better quality than the prior art be prepared, but also an excellent cadmium telluride thin film without holes and with excellent quality can be prepared.

[0063] A vertical magnetron sputtering device for implementing the preparation method of the cadmium telluride thin film as described above, as Figure 2 shown, the device includes a vacuum chamber 3, a radio frequency stage 1 for placing a target and a sample stage 2 for fixing a metal carrier plate, which are oppositely placed and the distance between them can be adjusted in the vacuum chamber 3. The vacuum chamber 3 is also provided with a rotating shaft 4 for driving the sample stage 2 to rotate and a temperature control component for controlling the temperature of the sample stage 2; the radio frequency stage 1 is connected to the cathode of the radio frequency power supply, and the sample stage 2 is connected to the anode of the radio frequency power supply.

[0064] In summary, the above are only the preferred embodiments of the present invention, and are not used to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made according to the content of the patent application scope of the present invention should fall within the technical scope of the present invention.

Claims

1. A method for preparing a cadmium telluride thin film, characterized in that: A cadmium telluride thin film is prepared by using a vertical magnetron sputtering device, the vertical magnetron sputtering device comprising a vacuum chamber (3), a radio frequency table (1) for placing a target material and a sample table (2) for fixing a metal carrier, which are arranged in the vacuum chamber (3) and are arranged relative to each other and have an adjustable distance, the vacuum chamber (3) also being provided with a rotating shaft (4) for driving the sample table (2) to rotate and a temperature control component for controlling the temperature of the sample table (2); the radio frequency table (1) is connected to a cathode of a radio frequency power source, and the sample table (2) is connected to an anode of the radio frequency power source; The specific steps are: Step 1: fix the cadmium telluride target on a radio frequency stage (1), fix a metal carrier plate loaded with a sample on a sample stage (2); and adjust the distance between the radio frequency stage (1) and the sample stage (2); Step 2: evacuate the vacuum chamber (3) to make the vacuum degree reach a set value; Step 3, heating the temperature of the sample stage (2) to 100°C-130°C; setting the sputtering power to 50W-100W; setting the deposition time to 900s-3000s; Step 4, filling the vacuum chamber (3) with argon gas and adjusting the pressure of the vacuum chamber; Step 5, starting the rotating shaft (4) to drive the sample stage (2) to rotate, turning on the radio frequency power supply, and starting sputtering; Step 6: After the deposition time is reached, turn off the RF power supply, stop filling with argon gas, stop heating the sample stage (2), and turn off the rotating shaft (4); cool naturally to room temperature, and take out the sample covered with the cadmium telluride film.

2. The method for preparing a cadmium telluride thin film according to claim 1, characterized in that: The sample described in step 1 is a mercury cadmium telluride material on a cadmium zinc telluride substrate.

3. The method for preparing a cadmium telluride thin film according to claim 1, characterized in that: The vacuum degree of the vacuum chamber (3) in step 2 is set to 5.0 x 10 -7 mbar.

4. The method for preparing a cadmium telluride thin film according to claim 1, characterized in that: In step 3, the sample stage (2) is heated to keep the temperature of the metal carrier at 100°C-125°C; the sputtering power is set to 50W-80W; and the deposition time is set to 1200s-3000s.

5. The method for preparing a cadmium telluride thin film according to claim 1, characterized in that: In step 4, 200 sccm of argon gas is filled into the vacuum chamber (3) and the pressure is adjusted to 3.0 x 10 -3 mbar.

6. The method for preparing a cadmium telluride thin film according to claim 1, characterized in that: The thickness of the cadmium telluride film of the sample in step six is ​​298nm-312nm.

7. A vertical magnetron sputtering device for implementing the method for preparing a cadmium telluride thin film according to any one of claims 1 to 6, characterized in that: The device comprises a vacuum chamber (3), a radio frequency table (1) for placing a target material and a sample table (2) for fixing a metal carrier plate, which are arranged in the vacuum chamber (3) and are arranged relative to each other and have an adjustable distance. The vacuum chamber (3) is also provided with a rotating shaft (4) for driving the sample table (2) to rotate and a temperature control component for controlling the temperature of the sample table (2); the radio frequency table (1) is connected to the cathode of a radio frequency power source, and the sample table (2) is connected to the anode of the radio frequency power source.

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