Low-damage high-compactness cadmium telluride passive film and preparation method and application thereof

Abstract

The invention provides a low-damage high-compactness cadmium telluride passive film and a preparation method and application thereof.The preparation method comprises the steps that multiple thin-layer CdTe films are deposited on the surface of a substrate material in a step-by-step magnetron sputtering mode, and every two adjacent thin-layer CdTe films are deposited through different sputtering powers, the CdTe passive film is obtained until the total thickness of the multiple thin CdTe films on the substrate material reaches the designed thickness of the CdTe passive film; wherein the sputtering power adopted for deposition of the thin CdTe film close to the substrate material does not exceed a threshold value causing damage to the surface of the substrate material. According to the method, the cadmium telluride passivation film is deposited through step-by-step magnetron sputtering with different powers, the problem that a large number of pores exist in the cadmium telluride passivation film prepared through traditional single sputtering power deposition is effectively solved, the high-compactness cadmium telluride passivation film can be obtained, low sputtering power is adopted when the design is close to a substrate material for magnetron sputtering deposition, and the high-compactness cadmium telluride passivation film is obtained. The problem that the surface of a substrate material is damaged due to fixed high-sputtering-power deposition in the sputtering deposition process of a traditional cadmium telluride passive film is solved.

Description

Technical Field

[0001] This invention belongs to the field of infrared detector technology, specifically relating to a low-damage, high-density cadmium telluride passivation film, its preparation method, and its application. Background Technology

[0002] Mercury cadmium telluride (HgCdTe) infrared detectors remain among the highest-performing infrared detectors, and surface passivation of HgCdTe is a crucial method for reducing surface leakage current in HgCdTe chips. Cadmium telluride (CdTe) is considered the most ideal surface passivation material for HgCdTe focal plane array devices because its crystal structure, lattice constant, and chemical composition are very similar to those of HgCdTe, and it also exhibits good stability.

[0003] The most common methods for preparing cadmium telluride (CdTe) passivation films include magnetron sputtering deposition, thermal evaporation deposition, electron beam deposition, and molecular beam epitaxy (MBE) in-situ deposition. Thermal evaporation and electron beam deposition of CdTe passivation films suffer from poor adhesion and porous film quality, failing to meet the requirements for high-performance HCTM infrared detectors. MBE in-situ deposition of CdTe passivation films is suitable for in-situ passivation of HCTM materials grown by MBE. However, for HCTM materials prepared using other growth processes, MBE deposition of CdTe films is complex and costly, making it difficult to meet the needs of mass passivation of HCTM materials. Magnetron sputtering deposited CdTe films have high density, fast deposition rate, and strong adhesion, thus finding widespread application in the development and production of HCTM focal plane array devices.

[0004] The traditional method for magnetron sputtering deposition of cadmium telluride (CdTe) passivation films on the surface of mercury cadmium telluride (HCDT) materials involves depositing a CdTe passivation film of a certain thickness on the HCDT material surface under a fixed sputtering power, chamber pressure, and substrate temperature. To ensure a fast deposition rate, traditional magnetron sputtering deposition methods typically employ a high sputtering power and a low chamber pressure to deposit the CdTe passivation film. However, CdTe films prepared by traditional high-power magnetron sputtering deposition methods suffer greater damage to the HCDT substrate material during the sputtering deposition process due to the high sputtering kinetic energy of CdTe molecules, which can easily lead to increased leakage current on the surface of HCDT devices. Simultaneously, while higher sputtering power achieves a high deposition rate, it also results in larger CdTe molecular clusters, creating more porosity during the accumulation process. During subsequent heat treatment, the recrystallization of CdTe molecules generates more porosity in the CdTe film, thus reducing the passivation effect of the CdTe passivation film. However, if a lower sputtering power is used throughout the process, the deposition rate of the CdTe passivation film is lower, resulting in a slower deposition rate and reduced CdTe film deposition efficiency. Simultaneously, when low power deposition is used throughout, the initial kinetic energy of CdTe molecules is low, leading to weaker intermolecular bonding in the CdTe passivation film and a porous CdTe film, which also affects the surface passivation effect of the mercury cadmium telluride (HCDT) device. Therefore, traditional cadmium telluride sputtering deposition processes cannot simultaneously achieve low-damage, high-density deposition of the CdTe passivation film. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a low-damage, high-density cadmium telluride passivation film, which can at least solve some of the defects existing in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a low-damage, high-density cadmium telluride passivation film includes the following steps:

[0008] Multiple thin CdTe films are deposited sequentially from bottom to top on the surface of the substrate material by magnetron sputtering, with different sputtering powers used for each adjacent pair of thin CdTe films, until the total thickness of the multiple thin CdTe films on the substrate material reaches the designed CdTe passivation film thickness, thus obtaining the CdTe passivation film; wherein, the sputtering power used for the deposition of the thin CdTe film close to the substrate material does not exceed the threshold that would cause damage to the surface of the substrate material.

[0009] Furthermore, the magnetron sputtering deposition process of the CdTe passivation film includes at least one deposition cycle, and the sputtering power is gradually increased from low to high within each deposition cycle, with each sputtering power corresponding to the sputtering deposition of a thin CdTe film.

[0010] Furthermore, the sputtering power controlled within each deposition cycle, from low to high, is P1, P2, ... P n-1 P n Where n is the number of times the sputtering power is adjusted within a single deposition cycle, n≥3, P1 is 30-50W, P n ≤250W, the difference in sputtering power between two adjacent adjustments (P) n -P n-1 The value is 10-30W.

[0011] Furthermore, the thickness of the CdTe film deposited by magnetron sputtering at various sputtering powers is 20-50 nm.

[0012] Furthermore, the CdTe films deposited by magnetron sputtering at various sputtering powers have the same thickness.

[0013] Furthermore, the temperature of the substrate material is 60-100℃, and the pressure in the growth chamber is controlled to be 0.03-9 mBar during the magnetron sputtering process.

[0014] Furthermore, the preparation method of the aforementioned low-damage, high-density cadmium telluride passivation film also includes chemical etching and degassing treatment of the substrate material surface.

[0015] Furthermore, the substrate material is a mercury cadmium telluride (MDT) substrate. The MDT substrate is chemically etched using a bromoethanol or bromomethanol solution. Then, the chemically etched MDT substrate is placed in a magnetron sputtering CdTe growth chamber for 5-20 minutes, while maintaining a vacuum level of less than 3 × 10⁻⁶. -6 Pa, the temperature of the mercury cadmium telluride substrate is 60-100℃.

[0016] In addition, the present invention also provides a low-damage, high-density cadmium telluride passivation film, which is prepared by the above-described method for preparing the low-damage, high-density cadmium telluride passivation film.

[0017] The present invention also provides the application of the above-mentioned low-damage, high-density cadmium telluride passivation film in mercury cadmium telluride infrared detectors or solar cells.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] This invention employs a stepwise magnetron sputtering deposition method with varying power to prepare cadmium telluride passivation films. This effectively solves the problem of numerous pores in cadmium telluride passivation films prepared by traditional single-power sputtering deposition, thus facilitating the production of highly dense cadmium telluride passivation films. Furthermore, the invention utilizes a low sputtering power during magnetron sputtering deposition close to the substrate material to address the damage to the substrate surface caused by consistently high sputtering power deposition in traditional cadmium telluride passivation film sputtering processes. This method for preparing cadmium telluride passivation films can simultaneously achieve low damage to the substrate surface and high-efficiency deposition of the cadmium telluride passivation film, resulting in cadmium telluride passivation films with both low damage and high density.

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is the XRD pattern of the cadmium telluride passivation film prepared in the embodiments of the present invention.

[0022] Figure 2 This is an XRD pattern of a cadmium telluride passivation film prepared using conventional fixed sputtering power. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation", "connection", and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, an abutting connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0027] To address the issue that existing traditional cadmium telluride sputtering deposition processes cannot simultaneously achieve low-damage and high-density deposition of CdTe passivation films, this invention provides a method for preparing a low-damage, high-density cadmium telluride passivation film, specifically comprising the following steps:

[0028] Multiple thin CdTe films are deposited sequentially from bottom to top on the surface of the substrate material by magnetron sputtering, with different sputtering powers used for each adjacent pair of thin CdTe films, until the total thickness of the multiple thin CdTe films on the substrate material reaches the designed CdTe passivation film thickness, thus obtaining the CdTe passivation film; wherein, the sputtering power used for the deposition of the thin CdTe film close to the substrate material does not exceed the threshold that would cause damage to the surface of the substrate material.

[0029] In this invention, a thin CdTe film is first deposited on the surface of a substrate material using magnetron sputtering with a low sputtering power. Specifically, the sputtering power is designed not to exceed the threshold that would damage the substrate material surface. Due to the low sputtering power, the deposition rate is relatively slow. At this time, the sputtered CdTe particles have low energy and cause less damage to the substrate material, overcoming the problem of significant damage to the substrate material caused by traditional sputtering deposition with a fixed high power. Subsequently, not only is the sputtering power increased, but different sputtering powers are also used for alternating sputtering deposition. The increase in sputtering power increases the deposition rate, thereby improving the deposition efficiency of the CdTe passivation film. Moreover, since different sputtering powers can produce CdTe particles of different sizes, the alternating sputtering deposition method allows CdTe molecules or particles of different sizes to be deposited and stacked alternately. This alternating stacking forms a multilayer structure, reducing the porosity of the thin CdTe film. Each layer has different microstructures and properties, thus combining the advantages of CdTe particles of different sizes and improving the overall performance of the CdTe passivation film.

[0030] In the optimized implementation, the magnetron sputtering deposition process of the CdTe passivation film includes at least one deposition cycle, and within each deposition cycle, the sputtering power is gradually increased from low to high, with each sputtering power corresponding to the sputtering deposition of a thin CdTe film; specifically, the sputtering power controlled within each deposition cycle is defined as P1, P2, ... P1, P2, ... P2, from low to high. n-1 P nThe process involves first sputtering a first thin CdTe film onto the substrate surface using a low sputtering power P1. Then, a second thin CdTe film is sputtered onto the first CdTe film using a sputtering power P2 (P2 > P1). Next, a third thin CdTe film is sputtered onto the second CdTe film using a sputtering power P3 (P3 > P2), and so on. The sputtering power P... n (P) n >P n-1 After sputtering and depositing the nth thin CdTe film, one CdTe film sputtering deposition cycle with sputtering power increasing from low to high is completed. Repeating this process several times yields a CdTe passivation film of a certain thickness. Here, n represents the number of times the sputtering power is adjusted within a single deposition cycle, n≥3, and the specific value of n is designed and selected according to actual needs; P1 is designed to be 30-50W to ensure minimal damage to the substrate material during the deposition of the first thin CdTe film; P n ≤250W, the difference in sputtering power between two adjacent adjustments (P) n -P n-1 The sputtering power is 10-30W to ensure a denser CdTe passivation film. In this embodiment, multiple deposition cycles are used for repeated deposition, and different sputtering powers are used alternately in each deposition cycle. This allows CdTe molecules or particles of different sizes to alternate, which can effectively fill the pores generated during the CdTe particle accumulation process, resulting in a denser CdTe passivation film.

[0031] Specifically, the thickness of the CdTe film deposited by magnetron sputtering at various sputtering powers is designed to be 20-50 nm. Preferably, the thickness of the CdTe film deposited by magnetron sputtering at various sputtering powers is the same. The thickness of the CdTe passivation film is 300-500 nm.

[0032] Furthermore, in the magnetron sputtering deposition process, in addition to sputtering power, the substrate material temperature and sputtering pressure (i.e., growth chamber pressure) also have a significant impact on the structure (such as CdTe particle size, density, surface roughness, etc.) and properties (such as adhesion, internal stress, etc.) of the CdTe passivation film. Therefore, in this embodiment, the substrate material temperature for magnetron sputtering deposition is designed to be 60-100℃ and the growth chamber pressure is 0.03-9mBar. By synergistically controlling the sputtering power, substrate material temperature, and sputtering pressure, the CdTe passivation film is ensured to have characteristics such as high density, fast deposition rate, and strong adhesion.

[0033] To improve the adhesion between the CdTe passivation film and the substrate material during sputtering deposition, it is preferable to pre-treat the surface of the substrate material by cleaning. In some embodiments, the cleaning pre-treatment may include chemical etching and degassing of the substrate material surface. Specifically, taking a mercury cadmium telluride (MDT) substrate as an example, the MDT substrate can be chemically etched with a 0.2-0.5% (v / v) bromoethanol or bromomethanol solution for 5-20 seconds. After drying, the MDT substrate sample is immediately transferred to a nitrogen environment for storage. Before magnetron sputtering deposition of the CdTe passivation film, the stored chemically etched MDT substrate is transferred to the magnetron sputtering CdTe growth chamber, maintaining a vacuum level of less than 3 × 10⁻⁶ within the growth chamber. -6 Pa, the temperature of the mercury cadmium telluride substrate is 60-100℃, and the mercury cadmium telluride substrate is placed in the growth chamber for 5-20 minutes. During this process, water vapor, air and other substances adsorbed on the surface of the mercury cadmium telluride substrate can be removed.

[0034] The following experiments, A and B, illustrate the preparation process and effects of the low-damage, high-density cadmium telluride passivation film of this invention.

[0035] Group A used the method of this invention to magnetron sputter-deposit a cadmium telluride passivation film on a mercury cadmium telluride substrate. The specific process is as follows: 1) Pretreatment of the mercury cadmium telluride substrate: The mercury cadmium telluride substrate was etched with a 0.2-0.5% (v / v) bromoethanol solution for 5-20 seconds. After drying, the mercury cadmium telluride substrate sample was immediately transferred to a nitrogen environment for storage. The mercury cadmium telluride substrate sample was then transferred to the magnetron sputtering CdTe growth chamber, maintaining a vacuum of less than 3 × 10⁻⁶ ppm in the growth chamber. -6 Pa, the temperature of the mercury cadmium telluride substrate is 60-100℃, and the mercury cadmium telluride substrate sample is placed in the growth chamber for 5-20 minutes; 2) Periodic gradient sputtering power deposition of CdTe passivation film: the temperature of the mercury cadmium telluride substrate sample is maintained in the range of 60-100℃, argon gas is introduced into the growth chamber to keep the pressure in the growth chamber range of 0.03-9 mBar, a thin CdTe film with a thickness of 30nm is sputtered using sputtering power P1=40W, and then sputtered using sputtering power P2=70W. A 30 nm thick CdTe film is deposited, followed by another 30 nm thick CdTe film deposited by sputtering with a power of P3=100W, a third 30 nm thick CdTe film deposited by sputtering with a power of P4=130W, and a fourth 30 nm thick CdTe film deposited by sputtering with a power of P5=160W. This completes one deposition cycle with sputtering power increasing from low to high. This process is repeated for two deposition cycles to obtain a 300 nm thick CdTe passivation film.

[0036] The method used by Group B is roughly the same as that used by Group A. The difference is that in step 2), a fixed sputtering power is used to deposit the CdTe passivation film in one step. The temperature of the mercury cadmium telluride substrate sample is in the range of 60-100℃, the pressure in the growth chamber is maintained in the range of 0.03-9mBar, and the sputtering power is 100W.

[0037] XRD tests were performed on the CdTe passivation films prepared in groups A and B, and the results are as follows: Figure 1 and Figure 2 As shown. By Figure 1 and Figure 2 The comparison shows that the CdTe passivation film prepared by the method of the present invention has higher CdTe crystallinity and lower stress, and its performance is superior.

[0038] The CdTe passivation film sputtering deposition process of this invention can be applied not only to the production process of mercury cadmium telluride infrared detectors, but also to the deposition process of CdTe passivation films on the surface of solar cells in the photovoltaic industry.

[0039] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method for preparing a low-damage, high-density cadmium telluride passivation film, characterized in that, The process includes the following: Multiple thin CdTe films are deposited sequentially from bottom to top on the surface of the substrate material by magnetron sputtering, with different sputtering powers used for each adjacent pair of thin CdTe films, until the total thickness of the multiple thin CdTe films on the substrate material reaches the designed CdTe passivation film thickness, thus obtaining the CdTe passivation film; wherein, the sputtering power used for the deposition of the thin CdTe film close to the substrate material does not exceed the threshold that would cause damage to the surface of the substrate material.

2. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 1, characterized in that, The magnetron sputtering deposition process of the CdTe passivation film includes at least one deposition cycle, and the sputtering power is gradually increased from low to high within each deposition cycle, with each sputtering power corresponding to the sputtering deposition of a thin CdTe film.

3. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 2, characterized in that, The sputtering power adjusted within each deposition cycle, from low to high, is P1, P2, ... P. n-1 P n Where n is the number of times the sputtering power is adjusted within a single deposition cycle, n≥3, P1 is 30-50W, P n ≤250W, the difference in sputtering power between two adjacent adjustments (P) n -P n-1 The value is 10-30W.

4. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 3, characterized in that, The thickness of the CdTe film deposited by magnetron sputtering at various sputtering powers is 20-50 nm.

5. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 3, characterized in that, The CdTe films deposited by magnetron sputtering at various sputtering powers have the same thickness.

6. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 1, characterized in that, The temperature of the substrate material is 60-100℃, and the pressure of the growth chamber is controlled at 0.03-9 mBar during magnetron sputtering.

7. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 1, characterized in that, It also includes chemical etching and degassing treatment of the substrate material surface.

8. The method for preparing the low-damage, high-density cadmium telluride passivation film as described in claim 7, characterized in that, The substrate material is mercury cadmium telluride (MDT) substrate. The MDT substrate is chemically etched using bromoethanol or bromomethanol solution. The chemically etched MDT substrate is then placed in a magnetron sputtering CdTe growth chamber for 5-20 minutes, during which the vacuum level within the growth chamber is maintained at less than 3 × 10⁻⁶. -6 Pa, the temperature of the mercury cadmium telluride substrate is 60-100℃.

9. A low-damage, high-density cadmium telluride passivation film, characterized in that, The low-damage, high-density cadmium telluride passivation film was prepared using the method described in any one of claims 1-8.

10. The application of the low-damage, high-density cadmium telluride passivation film as described in claim 9 in mercury cadmium telluride infrared detectors or solar cells.

Images