Boron ion implantation modified amorphous silicon thermosensitive structure and preparation method thereof

Abstract

The application provides a boron ion implantation modified amorphous silicon thermal sensitive structure and a preparation method thereof, and belongs to the technical field of infrared detection imaging. The boron ion implantation modified amorphous silicon thermal sensitive structure is characterized in that it comprises a substrate and a hydrogenated amorphous silicon film formed on the substrate. The hydrogenated amorphous silicon film is formed with a boron doped region through boron ion implantation. The boron doped region is non-uniformly distributed in the thickness direction of the hydrogenated amorphous silicon film. The concentration peak of boron elements is located between the upper surface and the lower surface of the hydrogenated amorphous silicon film and is far away from the upper surface and the lower surface, so as to form a buried layer conduction channel in the hydrogenated amorphous silicon film. The application realizes accurate control of the doped distribution, reduction of the defect density and low-frequency noise, and optimization of the square resistance and the resistance temperature coefficient.

Description

Technical Field

[0001] This invention relates to the field of infrared detection and imaging technology, and in particular to a boron ion implantation modified amorphous silicon thermistor structure and its preparation method. Background Technology

[0002] Uncooled infrared detectors, due to the elimination of the need for cryogenic cooling systems, offer advantages such as small size, light weight, low power consumption, high reliability, and low cost, leading to their widespread application in night vision devices, industrial temperature measurement, automotive driver assistance systems, and security monitoring. Hydrogenated amorphous silicon, as a thermistor structure, possesses excellent complementary metal-oxide-semiconductor process compatibility, good large-area uniformity, and low cost, making it easily integrated on a single chip. Crucially, the low-frequency noise of amorphous silicon systems is primarily dominated by 1 / f noise, with its noise power spectral density decreasing as the operating frequency increases. This characteristic effectively offsets the increase in thermal noise caused by increased bandwidth, enabling amorphous silicon detectors to maintain stable performance in high-speed imaging scenarios.

[0003] However, intrinsic amorphous silicon thin films contain numerous dangling bonds and defect states, resulting in extremely high sheet resistance and a low absolute value of the temperature coefficient of resistance. This severely limits the intrinsic sensitivity of the detector and generates significant noise. Traditional vapor-phase doping struggles to achieve precise control over doping concentration and depth, leading to poor film uniformity and batch repeatability. While high-temperature annealing can repair some defects, it easily triggers hydrogen escape or unintended crystallization of the film, thus worsening electrical properties. Furthermore, traditional modification methods often fail to significantly reduce sheet resistance while maintaining a high absolute value of the temperature coefficient of resistance. Summary of the Invention

[0004] This invention provides a boron ion implantation modified amorphous silicon thermistor structure and its preparation method, which achieves precise control of doping distribution, reduces defect density and low-frequency noise, and synergistically optimizes sheet resistance and temperature coefficient of resistance.

[0005] In a first aspect, the present invention provides a boron ion implantation modified amorphous silicon thermistor structure, comprising:

[0006] Substrate;

[0007] Hydrogenated amorphous silicon thin film formed on the substrate;

[0008] The hydrogenated amorphous silicon thin film has boron-doped regions formed by boron ion implantation. The boron-doped regions are non-uniformly distributed in the thickness direction of the hydrogenated amorphous silicon thin film. The peak concentration of boron is located between and away from the upper and lower surfaces of the hydrogenated amorphous silicon thin film, so as to form a buried conductive channel inside the hydrogenated amorphous silicon thin film.

[0009] In some embodiments, the peak concentration of boron is located in the region of one-third to two-thirds of the thickness of the hydrogenated amorphous silicon film; and / or, the thickness of the hydrogenated amorphous silicon film ranges from 50 nm to 200 nm.

[0010] In some embodiments, the sheet resistance of the boron ion implantation modified amorphous silicon thermistor structure at room temperature ranges from 5 MΩ / sq to 10 MΩ / sq, and the absolute value of the temperature coefficient of resistance of the boron ion implantation modified amorphous silicon thermistor structure at room temperature ranges from 2.8% / K to 3.8% / K.

[0011] In some embodiments, the 1 / f noise power spectral density of the boron ion implantation modified amorphous silicon thermistor structure decreases as the operating frequency increases, so that the noise equivalent temperature difference change rate of the detector using the boron ion implantation modified amorphous silicon thermistor structure in the operating frame frequency range of 30 Hz to 120 Hz is less than or equal to 20%.

[0012] In some embodiments, the boron-doped region exhibits a Gaussian distribution, a single-peak curve distribution, or a flat-top box distribution within the hydrogenated amorphous silicon thin film; wherein, corresponding to the flat-top box distribution, during the plateau period in the region of one-third to two-thirds of the thickness of the hydrogenated amorphous silicon thin film, the difference between the maximum and minimum concentrations of boron is less than or equal to ±10% of the average concentration during the plateau period.

[0013] In some embodiments, the hydrogen retention rate of bound state of silicon-hydrogen bonds in the hydrogenated amorphous silicon thin film is greater than or equal to 95% before ion implantation; and / or, the thermosensitive activation energy range of the boron ion implantation modified amorphous silicon thermosensitive structure is 0.22 eV to 0.32 eV.

[0014] In some embodiments, the surface electrode contact region of the hydrogenated amorphous silicon thin film is formed with a shallow, heavily doped contact region implanted twice, and the depth of the shallow, heavily doped contact region is less than or equal to 10 nm.

[0015] In a second aspect, the present invention also provides a method for preparing a boron ion implantation modified amorphous silicon thermistor structure, used to prepare the boron ion implantation modified amorphous silicon thermistor structure as described in the first aspect, the preparation method comprising:

[0016] Provide substrate;

[0017] A hydrogenated amorphous silicon thin film is deposited on the substrate;

[0018] The hydrogenated amorphous silicon thin film is subjected to global boron ion implantation, so that the concentration distribution of the implanted boron element in the thickness direction of the hydrogenated amorphous silicon thin film is concentrated inside the hydrogenated amorphous silicon thin film to form a buried layer conduction channel.

[0019] The hydrogenated amorphous silicon thin film after ion implantation is subjected to low-temperature annealing.

[0020] In some embodiments, at least one of the following is satisfied:

[0021] The energy range of the boron ion implantation is from 10 keV to 50 keV;

[0022] The implantation dose of the boron ions is in the range of 1×10⁻⁶. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 ;

[0023] The beam current density range during boron ion implantation is 1 μA / cm². 2 Up to 5μA / cm 2 ;

[0024] The annealing temperature range is 180°C to 280°C;

[0025] The annealing time for the annealing process is 30 min to 60 min;

[0026] The heating and cooling rates of the annealing process are both less than or equal to 3°C / min.

[0027] In some embodiments, global boron ion implantation is performed on the hydrogenated amorphous silicon thin film, including:

[0028] The boron ion implantation employs a single implantation to form a Gaussian distribution.

[0029] Alternatively, the boron ion implantation may employ at least two combinations of implantation with different energies and doses to form a flat-top box-shaped distribution of boron within the hydrogenated amorphous silicon thin film.

[0030] In some embodiments, before or during the annealing process of the hydrogenated amorphous silicon thin film, the method further includes:

[0031] The hydrogenated amorphous silicon thin film is subjected to in-situ hydrogen plasma treatment or hydrogen repassivation by introducing a hydrogen-nitrogen mixed gas.

[0032] In some embodiments, after performing full-domain boron ion implantation on the hydrogenated amorphous silicon thin film, the method further includes:

[0033] Secondary boron ion implantation is performed in the electrode construction region of the hydrogenated amorphous silicon thin film; wherein the energy of the secondary boron ion implantation is less than or equal to 5 keV and the implantation depth is less than or equal to 10 nm, so as to form a shallow, highly doped contact region in the electrode construction region.

[0034] Thirdly, the present invention also provides an uncooled infrared detector comprising a boron ion implantation modified amorphous silicon thermistor structure as described in the first aspect.

[0035] In this invention, because the peak boron concentration deviates from and is far from the upper and lower surfaces of the film, the carrier concentration and conductivity in the deep region inside the film are significantly higher than those in the surface and bottom layers. When an external bias voltage is applied, the conductive current mainly flows along the buried conduction channel in the middle of the film thickness. The top surface has dangling bonds and adsorption traps, while the bottom interface has interface stress and traps. The carrier concentration at these two locations is relatively low, reducing the probability of trapping and releasing conductive carriers by surface and interface defect states, thereby effectively suppressing the additional 1 / f low-frequency jumping conductivity noise caused by interface trap states. Furthermore, planar full-domain injection is used to establish buried conduction channels deep within the film thickness, eliminating the need for steep sidewall etching and angled sidewall injection. This allows for independent design of the volume-sensitive channel and contact area functions entirely within a planar process, reducing process complexity and improving batch uniformity in the fabrication of large-area focal plane arrays. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic cross-sectional view of a boron ion implantation modified amorphous silicon thermistor structure provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic flowchart of a method for preparing a boron ion implantation modified amorphous silicon thermosensitive structure according to an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of the boron ion implantation concentration distribution along the film depth in a boron ion implantation modified amorphous silicon thermosensitive structure provided in an embodiment of the present invention;

[0040] Figures 4 to 6 This is a schematic cross-sectional view of each step in the preparation method of a boron ion implantation modified amorphous silicon thermosensitive structure provided in this embodiment of the invention.

[0041] Figure 7 This is a schematic diagram of the sheet resistance of a boron ion implantation modified amorphous silicon thermistor structure at room temperature under different boron ion implantation doses, provided by an embodiment of the present invention, as a function of annealing temperature.

[0042] Figure 8This is a schematic diagram comparing the absolute value of the temperature coefficient of resistance of a boron ion implantation modified amorphous silicon thermistor structure and a plasma-enhanced chemical vapor deposition in-situ vapor phase doped structure at room temperature under the same sheet resistance, according to an embodiment of the present invention.

[0043] Figure 9 This is a schematic diagram comparing the 1 / f noise power spectral density of a boron ion implantation modified amorphous silicon thermosensitive structure and a gas-phase doped structure as a function of operating frequency, according to an embodiment of the present invention.

[0044] Figure 10 This is a schematic diagram comparing the noise equivalent temperature difference curves of a boron ion implantation modified amorphous silicon thermistor structure and a traditional vanadium oxide thermistor structure at different test frame frequencies, provided by an embodiment of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] Uncooled infrared detectors, due to the elimination of the need for cryogenic cooling systems, offer significant advantages such as small size, light weight, low power consumption, high reliability, and low cost, leading to their widespread application in night vision devices, industrial temperature measurement, automotive driver assistance systems, and security monitoring. Currently, vanadium oxide and amorphous silicon are the two mainstream choices for thermistor structures. Vanadium oxide is renowned for its high temperature coefficient of resistance, low noise, and high sensitivity. However, vanadium oxide fabrication processes have poor compatibility with standard CMOS processes, and large-area uniformity control is difficult, resulting in low supply chain self-control and high costs. In contrast, amorphous silicon thin films possess excellent CMOS compatibility, good large-area uniformity, and low cost, making monolithic integration extremely easy. Crucially, amorphous silicon exhibits unique advantages in dynamic frequency characteristics. Traditional detectors typically experience performance degradation when operating frequencies are increased, such as by raising imaging frame rates, due to the shortened integration time. However, because the noise of amorphous silicon thin films is primarily dominated by 1 / f noise, its noise power spectral density decreases significantly with increasing operating frequency. This characteristic effectively offsets the increase in thermal noise caused by increased bandwidth, allowing amorphous silicon detectors to maintain the stability of the noise equivalent temperature difference even in high-speed imaging scenarios. Therefore, amorphous silicon has strong competitive potential in high-speed, high-volume, and high-performance consumer applications.

[0047] However, intrinsic amorphous silicon thin films still have obvious physical defects, with high density of dangling bonds and defect states inside, resulting in extremely high sheet resistance and low absolute value of noise equivalent temperature difference. This severely limits the intrinsic sensitivity of the detector and generates large noise.

[0048] To improve its thermosensitive properties, existing technologies typically employ hydrogenation or the introduction of doping elements such as boron and phosphorus. However, current modification methods have significant limitations. Specifically, process control is difficult. Traditional vapor-phase doping, such as in-situ introduction of dopant gas in plasma-enhanced chemical vapor deposition (PECVD), makes precise control of dopant concentration and distribution depth difficult, resulting in poor film uniformity and batch repeatability. While high-temperature annealing can repair some defects, it easily triggers hydrogen escape or unintended film crystallization, which deteriorates electrical properties. Furthermore, traditional doping methods often fail to significantly reduce sheet resistance while maintaining a high temperature coefficient of resistance. Therefore, for amorphous silicon materials, there is an urgent need to develop a modification technology that can precisely control the doping composition, effectively reduce defect density and sheet resistance, and significantly improve the absolute value of the temperature coefficient of resistance, so as to fully leverage its advantages in high-frame-rate, high-performance infrared detection.

[0049] To address the shortcomings of existing technologies, this invention provides a boron ion implantation-modified amorphous silicon thermistor structure and its preparation method. By precisely controlling the boron ion implantation dose and energy, combined with an optimized annealing process, the defect density and room temperature sheet resistance of the thin film are effectively reduced while maintaining the amorphous structure. This significantly improves the temperature coefficient of resistance and the noise equivalent temperature difference, and reduces the intrinsic low-frequency noise of the material, thereby meeting the application requirements of high-sensitivity uncooled infrared detectors. For example, the boron ion implantation-modified amorphous silicon thermistor structure is prepared by implanting a boron ion dose of 1×10⁻⁶ ions into a hydrogenated amorphous silicon thin film. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 Boron ions are obtained by low-temperature annealing, for example, at 150°C to 250°C, which effectively reduces the defect density and sheet resistance of amorphous silicon thin films, significantly improves the temperature coefficient of resistance, and achieves a noise equivalent temperature difference of -4.5% / K to -5.2% / K. Moreover, the process is compatible with CMOS and is suitable for fabricating high-sensitivity uncooled infrared detectors.

[0050] Figure 1 This is a schematic cross-sectional view of a boron ion implantation-modified amorphous silicon thermistor structure provided in an embodiment of the present invention. Figure 1As shown, the boron ion implantation modified amorphous silicon thermistor structure includes a substrate 1 and a hydrogenated amorphous silicon thin film 2 formed on the substrate 1; wherein, the hydrogenated amorphous silicon thin film 2 has a boron doped region formed by boron ion implantation, the boron doped region is non-uniformly distributed in the thickness direction of the hydrogenated amorphous silicon thin film 2, and the concentration peak of boron element is located between the upper surface and the lower surface of the hydrogenated amorphous silicon thin film 2 and away from the upper surface and the lower surface, so as to form a buried conductive channel inside the hydrogenated amorphous silicon thin film 2.

[0051] Specifically, the boron ion implantation modified amorphous silicon thermistor structure refers to a solid structure comprising a substrate 1 and a hydrogenated amorphous silicon thin film 2 formed thereon, with modified doped regions of a specific spatial distribution formed within the film via boron ion implantation. Substrate 1 refers to the base component located at the bottom, providing physical support and electrical and thermal isolation. Hydrogenated amorphous silicon thin film 2 refers to a semiconductor thin film formed by a deposition process, containing silicon and bound hydrogen elements, with atoms arranged in a disordered amorphous structure. Boron-doped region refers to the modified region formed by introducing boron elements into the hydrogenated amorphous silicon thin film 2 via ion implantation. Non-uniform distribution refers to the non-isotropic, constant concentration distribution of boron elements along the thickness direction of the hydrogenated amorphous silicon thin film 2, where the concentration varies with depth. Buried conductive channels refer to the main conductive and signal transmission paths located in the middle, deep region of the hydrogenated amorphous silicon thin film 2, deviating from and far from the interface between the upper and lower surfaces.

[0052] A hydrogenated amorphous silicon thin film 2 is formed on a substrate 1. The substrate 1 can be, for example, a monocrystalline silicon substrate 1 or a silicon-based substrate 1 with a silicon dioxide and silicon nitride composite insulating layer grown on its surface, to provide electrical isolation and mechanical support. For example, in addition to the silicon dioxide and silicon nitride composite layer, the insulating layer material can also be a single layer or a composite layer of silicon oxynitride, aluminum oxide, hafnium oxide, or silicon carbide. Before the thin film patterning etching, planar global boron ion implantation is performed on the entire hydrogenated amorphous silicon thin film 2. By controlling the implantation energy and dose, the implanted boron ions penetrate the film surface and concentrate in the deep interior layer along the film thickness direction. That is, the peak boron concentration is located at the interior depth between the upper and lower surfaces, maintaining a physical distance from both the upper and lower surfaces.

[0053] Traditional plasma-enhanced chemical vapor deposition (PECVD) in-situ vapor phase doping involves introducing a dopant gas during deposition, resulting in a uniform and isotropic distribution of dopant elements across the entire film thickness. This leads to high doping concentrations at both the top and bottom surfaces of the film. Due to dangling bonds and / or adsorbed impurity traps on the top surface and stress lattice mismatch traps at the bottom interface, charge carriers are frequently trapped and released at these surfaces and interfaces, causing severe 1 / f low-frequency noise. Furthermore, conventional methods first etch the film into mesa resistors and then apply angled sidewall ion implantation to its vertical sidewalls to improve electrode-sidewall contact. However, sidewall implantation requires extremely high vertical steepness in photolithography and dry etching, has a narrow process window, and only improves the sidewall contact interface, failing to establish a low-noise bulk conduction path. This invention, however, performs planar implantation before film patterning. By controlling the depth distribution, the high-concentration doped region is placed within the film thickness, constructing a buried conduction channel far from the top and bottom surfaces.

[0054] Therefore, in this embodiment of the invention, because the peak boron concentration deviates from and is far from the upper and lower surfaces of the film, the carrier concentration and conductivity in the deep region inside the film are significantly higher than those in the surface and bottom layers. When an external bias voltage is applied, the conductive current mainly flows along the buried conduction channel in the middle of the film thickness. The top surface has dangling bonds and adsorption traps, while the bottom interface has interface stress and traps. The carrier concentration at these two locations is low, reducing the probability of trapping and releasing conductive carriers by surface and interface defect states, thereby effectively suppressing the additional 1 / f low-frequency jumping conductivity noise caused by interface trap states. Furthermore, by using planar full-domain injection to establish buried conduction channels deep within the film thickness, without relying on steep sidewall etching and angled sidewall injection, the independent design of the volume-sensitive channel and contact area functions is achieved entirely under planar processing, reducing process difficulty and improving batch uniformity in the fabrication of large-area focal plane arrays.

[0055] In some embodiments, the peak concentration of boron is located in the region of one-third to two-thirds of the thickness of the hydrogenated amorphous silicon film 2; and / or, the thickness of the hydrogenated amorphous silicon film 2 ranges from 50 nm to 200 nm.

[0056] Specifically, the one-third to one-third region refers to the intermediate depth range along the thickness direction of the hydrogenated amorphous silicon thin film 2, measured from the upper surface of the film, between one-third and two-thirds of the total thickness of the film. The thickness range of the hydrogenated amorphous silicon thin film 2 from 50 nm to 200 nm means that the total geometric thickness of the hydrogenated amorphous silicon thin film 2 is defined between 50 nm and 200 nm.

[0057] In a hydrogenated amorphous silicon thin film 2 with a thickness of 50 nm to 200 nm, the peak concentration of boron is located in the depth region of one-third to two-thirds. Specifically, the film surface, for example, at a depth of zero to one-third, is exposed to the environment or in contact with the subsequent protective layer, and has a high density of dangling bonds, adsorbed impurities, and interface traps. If the doping peak is located on the surface, surface traps will induce frequent charge trapping and releasing processes, generating strong 1 / f noise. At the bottom of the film, for example, at a depth of two-thirds to one-third, it is in contact with the insulating substrate 1, and has stress and interface traps. If the doping peak is close to the bottom, interface defects will also worsen the noise characteristics. By injecting boron ions into the deep central region of one-third to two-thirds, a bulk conduction channel is formed under the relatively pure amorphous silicon on both sides, away from the upper and lower interface defect traps, reducing jump conductance noise.

[0058] During the fabrication process, Monte Carlo particle transport simulation programs can be used. By inputting the target material density (e.g., approximately 2.1 g / cm³ to 2.2 g / cm³ for hydrogenated amorphous silicon), along with the implanted ion type, film thickness, and implantation tilt angle, the projected range and standard deviation of the range at different acceleration energies can be calculated. For example, for a 100 nm film, an acceleration energy of 25 keV can achieve a projected range of approximately 65 nm, located at about two-thirds of the depth. Using simulation programs to guide and precisely control the peak projected range to the depth range of one-third to two-thirds of the film thickness (from 50 nm to 200 nm) is a crucial technological mechanism for achieving low-noise buried layer structures.

[0059] Therefore, this embodiment of the invention defines the film thickness as 50nm to 200nm, ensuring that the thermosensitive structure has a small heat capacity, which is beneficial to improving the thermal response speed of the infrared detector. At the same time, this thickness range provides suitable space for the projection range distribution of ion implantation. Precisely limiting the boron concentration peak to one-third to two-thirds of the depth region ensures spatial isolation between the main conductive path and the top surface states and bottom interface states, effectively reducing low-frequency jumping conductivity noise and improving the signal-to-noise ratio.

[0060] In some embodiments, the sheet resistance of the boron ion implantation modified amorphous silicon thermistor structure at room temperature ranges from 5 MΩ / sq to 10 MΩ / sq, and the absolute value of the temperature coefficient of resistance of the boron ion implantation modified amorphous silicon thermistor structure at room temperature ranges from 2.8% / K to 3.8% / K.

[0061] Specifically, the sheet resistance range of 5 MΩ / sq to 10 MΩ / sq at room temperature refers to the resistance per unit square area of ​​the modified thermistor structure measured at room temperature, i.e., 20°C to 25°C, such as 23°C, being between 5 MΩ / sq and 10 MΩ / sq. The absolute value range of the temperature coefficient of resistance at room temperature is 2.8% / K to 3.8% / K, meaning that at room temperature, for every 1 K change in temperature, the absolute value of the relative change in resistance of the modified thermistor structure is between 2.8% / K and 3.8% / K.

[0062] The boron ion implantation dose has a decisive influence on the absolute values ​​of the sheet resistivity and temperature coefficient of resistance of the material. Specifically, when the implantation dose is less than 1 × 10⁻⁶, the impact is more pronounced. 14 ions / cm 2 At this point, the concentration of substitute boron atoms is too low to effectively fill defects and increase carrier concentration, resulting in extremely high sheet resistance, making it difficult to match with subsequent readout circuits, and causing significant system noise. When the injected dose is greater than 5 × 10⁻⁶, 15 ions / cm 2 Overdoping causes the Fermi level to approach the band tail state too closely, resulting in an excessively low activation energy. This leads to a drop in the absolute value of the temperature coefficient of resistance to below 2% / K, reducing temperature sensitivity. Furthermore, high-dose implantation generates significant and difficult-to-repair lattice displacement damage. When the implantation dose is controlled at 1×10⁻⁶, the situation becomes more challenging. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 Within this range, an appropriate amount of boron atoms occupy substitution sites, which lowers the sheet resistance to the ideal range of 5 MΩ / sq to 10 MΩ / sq that matches the readout circuit, while maintaining the absolute value of the temperature coefficient of resistance at a relatively high level of 2.8% / K to 3.8% / K.

[0063] Therefore, the embodiments of the present invention overcome the technical contradiction that reducing sheet resistance in traditional vapor-phase doping inevitably leads to a significant decrease in the absolute value of the temperature coefficient of resistance. While ensuring that the impedance matches the readout circuit, a high absolute value of the temperature coefficient of resistance is maintained, achieving synergistic optimization of sensitivity and conductivity.

[0064] In some embodiments, the 1 / f noise power spectral density of the boron ion implantation modified amorphous silicon thermistor structure decreases with increasing operating frequency, so that the noise equivalent temperature difference change rate of the detector using the boron ion implantation modified amorphous silicon thermistor structure is less than or equal to 20% in the operating frame frequency range of 30Hz to 120Hz.

[0065] Specifically, the decrease in 1 / f noise power spectral density with increasing operating frequency indicates that the intrinsic scintillation noise power of the thermistor structure exhibits a physical characteristic of attenuation with increasing operating frequency in the frequency domain. A noise equivalent temperature difference variation rate of less than or equal to 20% means that, within the operating frame frequency range of 30Hz to 120Hz, the ratio of the maximum fluctuation amplitude of the noise equivalent temperature difference to the average value is less than or equal to 20%.

[0066] The low-frequency noise of hydrogenated amorphous silicon materials is dominated by 1 / f noise, and the 1 / f noise power spectral density decreases inversely with increasing operating frequency. When the operating frame frequency of the infrared detector increases, such as from 30Hz to 120Hz, the integration time of a single frame signal shortens, resulting in a reduction in the amount of thermal radiation signal collected by each pixel. For conventional thermistor structures, such as vanadium oxide, noise increases with increasing frame frequency, shortening integration time, and increasing bandwidth, leading to a steep increase in the noise-equivalent temperature difference and performance degradation. However, the modified amorphous silicon thermistor structure provided in this invention, dominated by 1 / f noise, exhibits a significant reduction in the intrinsic noise power spectral density as the operating frequency increases. This reduction in noise power density at high frequencies offsets the signal collection loss caused by the shortened integration time, forming a dynamic hedging effect that reduces noise to compensate for signal loss.

[0067] Therefore, the embodiments of the present invention enable the infrared detector based on the thermal structure to maintain a flat and stable noise equivalent temperature difference with a change rate of less than or equal to 20% in the high-speed operating frame frequency range of 30Hz to 120Hz, thus solving the problem of sharp decrease in detector sensitivity in high-speed imaging scenarios.

[0068] In some embodiments, the boron-doped region exhibits a Gaussian distribution, a single-peak curve distribution, or a flat-top box distribution within the hydrogenated amorphous silicon thin film 2; wherein, corresponding to the flat-top box distribution, in the plateau period within one-third to two-thirds of the thickness of the hydrogenated amorphous silicon thin film 2, the difference between the maximum and minimum concentrations of boron is less than or equal to ±10% of the average concentration during the plateau period.

[0069] Specifically, a Gaussian distribution refers to a symmetrical curve of boron atomic concentration along the film thickness direction. A unimodal distribution refers to a distribution where boron atomic concentration has only one peak along the film thickness direction. A box-shaped distribution refers to a box-shaped distribution where boron atomic concentration maintains a relatively flat plateau in the middle region along the film thickness direction. The plateau period refers to the middle depth range where boron atomic concentration remains high and relatively flat in the box-shaped distribution. The difference between the maximum and minimum concentration values ​​being less than or equal to ±10% of the average concentration during the plateau period means that the extreme deviation of concentration fluctuations from the average concentration is strictly controlled within ±10% during the plateau period. It is important to clarify that the distribution patterns mentioned here all refer to the boron atomic concentration distribution curve along the film thickness direction, i.e., the depth direction from the top surface to the bottom surface.

[0070] A single implantation can result in a Gaussian or single-peak distribution of the boron-doped region within the hydrogenated amorphous silicon thin film 2, with a concentration gradient on both sides of the concentration peak. A flat-topped box-shaped distribution is achieved through at least two combined ion implantations with different energies and doses. The boron atoms implanted in two or more implantations physically superimpose in the depth direction, flattening the concentration curve within one-third to two-thirds of the thickness region, forming a plateau period. Within the flat-topped plateau period, the deviation between the extreme concentration and the average concentration is controlled within ±10%.

[0071] Therefore, the embodiments of the present invention eliminate the steep concentration gradient along the depth direction inside the conduction channel by the flat-top box-shaped distribution, avoid the microscopic built-in electric field and charge fluctuations caused by concentration difference, construct a more uniform and wide volume conduction path, and further reduce the noise of microscopic charge fluctuations.

[0072] In some embodiments, the hydrogen retention rate of bound state of silicon-hydrogen bonds in the hydrogenated amorphous silicon thin film 2 is greater than or equal to 95% before ion implantation; and / or, the thermosensitive activation energy range of the boron ion implantation modified amorphous silicon thermosensitive structure is 0.22 eV to 0.32 eV.

[0073] Specifically, a hydrogen retention rate in the silicon-hydrogen bonded state greater than or equal to 95% of that before ion implantation means that after modification, the number of hydrogen atoms in the thin film existing in the silicon-hydrogen bonded state remains above 95% of the original hydrogen content before implantation. A thermistor activation energy range of 0.22 eV to 0.32 eV means that the thermal activation energy required for charge carriers in the thermistor structure to overcome the energy barrier and participate in conduction is defined between 0.22 eV and 0.32 eV.

[0074] In hydrogenated amorphous silicon, hydrogen atoms passivate dangling bonds in the silicon network by forming silicon-hydrogen bonds. If the process temperature is too high, these silicon-hydrogen bonds will break, causing hydrogen to escape and increasing the defect state density. This invention avoids rapid hydrogen escape by controlling the injection beam current density and using low-temperature window annealing, achieving a hydrogen retention rate of over 95% in the bound state. The electrical conductivity and temperature coefficient of resistance of the material are closely related to the thermodynamic activation energy. By precisely controlling the boron doping amount and hydrogen retention rate, the thermodynamic activation energy is stabilized within the range of 0.22 eV to 0.32 eV.

[0075] Therefore, in this embodiment of the invention, a hydrogen retention rate of greater than or equal to 95% ensures continuous passivation of dangling bonds, maintains a low defect state density, and enhances the thermal stability and long-term reliability of the thin film. Controlling the thermistor activation energy between 0.22 eV and 0.32 eV allows the material to possess both a high absolute value of the temperature coefficient of resistance and a suitable impedance matching the readout circuit.

[0076] In some embodiments, the surface electrode contact region of the hydrogenated amorphous silicon thin film 2 is formed with a shallow, heavily doped contact region implanted twice, and the depth of the shallow, heavily doped contact region is less than or equal to 10 nm.

[0077] Specifically, the surface electrode contact area refers to the local region on the upper surface of the hydrogenated amorphous silicon thin film 2 where an electrical connection is to be established with the subsequent electrode. The shallow, highly doped contact area refers to an extremely shallow region with a high boron concentration, less than or equal to 10 nm, formed in the surface electrode contact area through secondary implantation. After completing the full-domain main implantation and constructing a buried conduction channel to a depth of one-third to two-thirds, a mask is used to block the non-electrode area, and a secondary ion implantation with an energy of less than or equal to 5 keV is applied to the electrode contact area. Due to the extremely low implantation energy, the secondary implanted boron atoms are concentrated in the extremely shallow surface layer within 10 nm of the upper surface. Compared to the method of implantation by etching the mesa and applying oblique sidewalls, this embodiment of the invention can directly perform shallow secondary implantation on the upper surface of the planar thin film without the need for complex vertical etching processes, and can be completed under planar processes.

[0078] Therefore, in this embodiment of the invention, the shallow, highly doped contact region with a depth of less than or equal to 10 nm effectively reduces the Schottky barrier height and contact resistance at the interface between the metal electrode and amorphous silicon, establishing a good ohmic contact and reducing low-frequency contact noise. Since the secondary implantation depth is strictly limited to within 10 nm, it is spatially independent of the main conduction channel of the buried layer located at one-third to two-thirds depth, and will not disrupt the low-noise transmission characteristics of the buried layer channel.

[0079] This invention also provides a method for preparing a boron ion implantation modified amorphous silicon thermistor structure, used to prepare the boron ion implantation modified amorphous silicon thermistor structure as described in the above embodiments. Figure 2This is a schematic flowchart of a method for preparing a boron ion implantation modified amorphous silicon thermistor structure according to an embodiment of the present invention. Figure 2 As shown, the preparation method includes:

[0080] Step 101: Provide a substrate.

[0081] Step 102: Deposit a hydrogenated amorphous silicon thin film on the substrate.

[0082] Step 103: Perform global boron ion implantation on the hydrogenated amorphous silicon thin film, so that the concentration distribution of the implanted boron element in the thickness direction of the hydrogenated amorphous silicon thin film is concentrated inside the hydrogenated amorphous silicon thin film to form a buried layer conduction channel.

[0083] Step 104: Perform low-temperature annealing on the hydrogenated amorphous silicon thin film after ion implantation.

[0084] Specifically, full-area boron ion implantation refers to the unmasked or full-planar ion implantation operation performed on the entire planar thin film area before thin film patterning and etching separation. Low-temperature annealing refers to a heat treatment operation performed in the range below the hydrogen escape temperature threshold and above the impurity activation temperature.

[0085] First, a substrate 1 is provided. A hydrogenated amorphous silicon thin film 2 is deposited on the substrate 1 using plasma-enhanced chemical vapor deposition (PECVD). Before patterning the film, full-area planar boron ion implantation is performed on the entire planar film, followed by low-temperature annealing. This invention resolves the technical contradiction between ion implantation damage and hydrogen escape. Traditional semiconductor concepts hold that lattice displacement damage caused by ion implantation must be repaired by high-temperature annealing, such as annealing above 350°C to 600°C. However, in hydrogenated amorphous silicon, high temperatures easily induce hydrogen escape and unintended crystallization. This invention employs low-energy ion implantation, resulting in mostly simple point defects rather than complex damage clusters. The subsequent low-temperature annealing, such as annealing at 180°C to 280°C, provides thermal energy that activates boron atoms to occupy substitution sites and repair point defects. Simultaneously, this temperature is below the hydrogen escape thermal kinetic energy threshold and crystallization temperature, thus opening up a technical path that both activates impurities, repairs damage, and protects the hydrogenated structure.

[0086] Therefore, the global planar implantation method of this invention establishes buried layer channels before patterning, eliminating the need for complex sidewall etching and bevel implantation, thus simplifying the process. Low-temperature annealing enables effective activation of boron atoms and repair of displacement damage, while avoiding the rapid escape of bound hydrogen and thin film crystallization, ensuring the compactness of the amorphous network structure.

[0087] In some embodiments, the method for preparing boron ion implantation modified amorphous silicon thermosensitive structures satisfies at least one of the following: the energy range of boron ion implantation is 10 keV to 50 keV; the implantation dose of boron ions is 1 × 10⁻⁶. 14Up to 5×10 15 ions / cm 2 The beam current density range during boron ion implantation is 1 μA / cm. 2 Up to 5μA / cm 2 The annealing temperature range is 180°C to 280°C; the annealing time is 30 min to 60 min; and the heating and cooling rates are both less than or equal to 3°C / min.

[0088] Specifically, the energy range of 10 keV to 50 keV refers to the accelerating voltage during boron ion implantation being defined between 10 keV and 50 keV. The implantation dose range is 1 × 10⁻⁶. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 The total number of boron ions injected per unit area is defined as 1×10⁻⁶. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 Between. The beam current density range is 1 μA / cm. 2 Up to 5μA / cm 2 This refers to the ion beam current per unit area during the implantation process being defined as 1 μA / cm². 2 Up to 5μA / cm 2 The annealing temperature range of 180°C to 280°C refers to the holding temperature during the annealing process being between 180°C and 280°C. The annealing time of 30 min to 60 min refers to the holding time at the annealing temperature being between 30 min and 60 min. Both the heating rate and cooling rate being less than or equal to 3°C / min means that both the heating rate and cooling rate during the annealing process are no greater than 3°C / min.

[0089] Energy was controlled between 10 keV and 50 keV to ensure the projection range was concentrated in the depth range of one-third to two-thirds of the film thickness, from 50 nm to 200 nm. Dose was controlled at 1 × 10⁻⁶. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 This ensures an appropriate amount of boron atoms replace silicon atoms. The beam current density is controlled at 1 μA / cm². 2 Up to 5μA / cm 2To prevent the thermal effect of high beam current density from causing localized heating of the film and triggering hydrogen escape, the annealing temperature is controlled between 180°C and 280°C, preferably between 220°C and 250°C, and the time is set to 30 min to 60 min. Within this energy window, boron atoms are fully activated and point defects are repaired. The heating and cooling rate is controlled to be less than or equal to 3°C / min, allowing the internal thermal stress of the film to be released slowly.

[0090] Therefore, through the synergy of various process parameters, the embodiments of the present invention achieve precise embedding by controlling energy, balance the sheet resistance and temperature coefficient of resistance by controlling the dosage, avoid hot hydrogen escape during the injection process by controlling the beam density, achieve low thermal budget activation by controlling the annealing temperature and time, and eliminate thermal stress by controlling the heating and cooling rates to prevent large-area film peeling.

[0091] In some embodiments, global boron ion implantation is performed on the hydrogenated amorphous silicon thin film 2, including: boron ion implantation using a single implantation to form a Gaussian distribution; or, boron ion implantation using at least two combined implantations with different energies and doses to form a flat-top box-shaped distribution of boron elements within the hydrogenated amorphous silicon thin film 2.

[0092] Specifically, global boron ion implantation refers to the overall ion implantation process performed on the entire undivided planar surface of the hydrogenated amorphous silicon thin film 2 before patterning and etching. Single implantation refers to a single-step ion implantation using a single fixed implantation acceleration energy and a single implantation dose. Gaussian distribution refers to the concentration distribution of implanted boron in the thickness direction of the hydrogenated amorphous silicon thin film 2, i.e., the depth direction from the upper surface to the lower surface, exhibiting a normal bell-shaped curve with depth. Combined implantation refers to multi-step ion implantation performed sequentially using at least two different implantation acceleration energies and correspondingly matched implantation doses. Flat-top box-shaped distribution refers to the concentration distribution of boron in the middle region of the film thickness, formed by the physical superposition of at least two ion implantations with different energies and doses in the thickness direction of the hydrogenated amorphous silicon thin film 2, where the boron concentration maintains a flat plateau period and the top of the curve exhibits a flat trapezoidal shape.

[0093] Before patterning and etching the thin film, global boron ion implantation is performed. The implantation method can be either single implantation or combined implantation. For the single implantation mechanism, a single acceleration energy is set, such as a fixed energy within the range of 10keV to 50keV, along with a single dose. After high-energy boron ions penetrate the thin film, they undergo elastic and inelastic collisions with silicon atoms, gradually decelerating and resting. The ion resting positions exhibit a Gaussian distribution along the depth direction, and the peak resting position is the projected range. Single implantation is simple to operate and can quickly form a single Gaussian concentration peak at a predetermined depth. For the combined implantation mechanism, a smaller first acceleration energy, such as 20keV, is first injected to allow boron to rest at a shallower depth, such as near one-third of the film thickness, forming the first Gaussian distribution peak. Immediately afterwards, a larger second acceleration energy, such as 45keV, is injected to allow boron to rest at an even deeper depth, such as near two-thirds of the film thickness, forming the second Gaussian distribution peak. The boron atom concentrations from the two implantations are physically superimposed in the depth space. Since the rear wing of the first peak and the front wing of the second peak overlap in the middle of the depth, the total concentration after superposition is flattened in the range of one-third to two-thirds of the film thickness, so that the concentration ordinate remains flat in a relatively wide depth range, forming a box-shaped flat top.

[0094] Conventional plasma-enhanced chemical vapor deposition (PECVD) in-situ vapor phase doping introduces dopant gas during deposition, resulting in an isotropic and uniform distribution of dopant elements across the entire film thickness. This makes it impossible to artificially control the concentration distribution at depth. Sidewall implantation, on the other hand, involves oblique implantation into the vertical sidewalls after etching the film into mesa, making it impossible to construct box-shaped channels along the planar film thickness. Therefore, the single-implantation mode of this invention has fewer process steps and simpler control, enabling rapid formation of buried conduction channels at a specified depth, reducing production costs and ensuring good batch repeatability. In the combined implantation mode, the flat-top box-shaped distribution widens the effective geometric width of the buried conduction channel in the depth direction, increasing the effective cross-sectional area for the main conduction current and reducing bulk resistance. Simultaneously, the flat-top box-shaped distribution eliminates the steep boron concentration gradient on both sides of the peak value of the single-peak distribution, reducing the uneven diffusion of micro-charges and local electric field fluctuations caused by the concentration gradient. This further reduces 1 / f low-frequency noise caused by micro-charge fluctuations, improving the signal-to-noise ratio.

[0095] Figure 3 This is a schematic diagram showing the distribution of boron ion implantation concentration along the film depth in a boron ion implantation modified amorphous silicon thermistor structure provided in an embodiment of the present invention. Figure 3As shown, the horizontal axis represents the film depth: 0 nm represents the upper surface of the hydrogenated amorphous silicon film, 33 nm represents one-third of the film thickness, 66 nm represents two-thirds of the film thickness, and 100 nm represents the lower surface of the film in contact with the substrate. The vertical axis represents the boron atomic concentration, indicating the doping concentration of boron at different film depths. The dashed line on the left corresponds to the first implantation, with an energy of, for example, 20 keV, representing the first Gaussian distribution curve formed by the first ion implantation with a relatively low initial acceleration energy, and its concentration peak is located near one-third of the film thickness. The dashed line on the right corresponds to the second implantation, with an energy of, for example, 45 keV, representing the second Gaussian distribution curve formed by the second ion implantation with a relatively high initial acceleration energy, and its concentration peak is located near two-thirds of the film thickness. The solid line at the top represents the total concentration distribution curve after the physical superposition of the first and second implantations in the film depth space. The curve rises sharply from low concentration at the surface to deeper layers from 0 nm to 33 nm, remains flat and level from 33 nm to 66 nm, and drops sharply from deeper layers to the bottom interface from 66 nm to 100 nm. The blue shaded area in the middle represents the buried conductive channel region located between one-third and two-thirds of the film thickness, while the low-concentration areas on both sides represent the low-concentration isolation regions on the upper and lower sides away from the main conductive channel.

[0096] In some embodiments, before or during the annealing process of the hydrogenated amorphous silicon thin film 2, the method further includes: performing in-situ hydrogen plasma treatment on the hydrogenated amorphous silicon thin film 2 or introducing a hydrogen-nitrogen mixed gas for hydrogen repassivation.

[0097] Specifically, annealing refers to the process of heating and holding the ion-implanted hydrogenated amorphous silicon thin film 2 at a predetermined temperature and atmosphere to repair lattice displacement damage and activate substituted boron atoms. In-situ hydrogen plasma treatment refers to the thermochemical treatment in which highly active hydrogen ions and hydrogen radicals are generated by exciting hydrogen gas with an electric field within the same reaction chamber or high-vacuum combined chamber, and then bombard and penetrate the hydrogenated amorphous silicon thin film 2. Hydrogen-nitrogen mixed gas refers to a reducing passivating protective gas formed by mixing high-purity hydrogen gas and high-purity nitrogen gas in a predetermined ratio, such as 5% to 10% by volume of hydrogen gas. Hydrogen repassivation refers to the process of introducing external active hydrogen atoms into the interior of the thin film, where they recombine with the dangling bonds broken by high-energy particle bombardment during ion implantation to form bound silicon-hydrogen bonds, thus repairing the damage.

[0098] When high-energy boron ions are injected into the hydrogenated amorphous silicon thin film 2, although low energy and low beam current density are used, the high-energy particles inevitably undergo inelastic collisions with bound hydrogen in the silicon network as they pass through the lattice. This results in the breakage of a small number of bound silicon-hydrogen bonds, forming microscopic dangling bonds and defect traps. In this embodiment of the invention, in-situ hydrogen plasma treatment is introduced before or during annealing. Utilizing the high diffusion capacity of excited highly active hydrogen radicals, they rapidly diffuse from the film surface to deeper layers. Alternatively, a hydrogen-nitrogen mixed gas is introduced into the annealing atmosphere. Under thermal activation at 180°C to 280°C, hydrogen molecules in the gas dissociate into active hydrogen atoms and penetrate the film. The penetrated active hydrogen atoms actively seek out unsaturated silicon dangling bonds generated by the injection collisions within the film and re-covalently bond with them, repairing the broken silicon-hydrogen bonds and achieving in-situ hydrogen repassivation.

[0099] Therefore, the in-situ hydrogen plasma treatment or hydrogen repassivation process of introducing a hydrogen-nitrogen mixed gas in the embodiments of the present invention timely strengthens the bound state silicon-hydrogen bonds damaged during ion implantation collisions, so that the bound state hydrogen retention rate of silicon-hydrogen bonds in the film after annealing is stably maintained above 95%. This hydrogen repassivation mechanism reduces the density of residual dangling bond traps inside the film, weakens the 1 / f low-frequency jumping conductivity noise caused by the capture and release of charge carriers by dangling bond traps, and improves the absolute value of the temperature coefficient of resistance and the thermal stability of the thermistor structure.

[0100] In some embodiments, after performing global boron ion implantation on the hydrogenated amorphous silicon thin film 2, the method further includes performing secondary boron ion implantation in the electrode construction region of the hydrogenated amorphous silicon thin film 2; wherein the energy of the secondary boron ion implantation is less than or equal to 5 keV and the implantation depth is less than or equal to 10 nm, so as to form a shallow highly doped contact region in the electrode construction region.

[0101] Specifically, the electrode construction region refers to the local surface area on the upper surface of the hydrogenated amorphous silicon thin film 2 where a magnetron sputtered metal electrode is to be deposited and an electrical connection established. Secondary boron ion implantation refers to a second localized low-energy ion implantation performed only on the electrode construction region after the buried layer channel has been constructed through full-domain main implantation. The shallow, highly doped contact region refers to an extremely shallow, locally highly conductive region with a depth limited to within 10 nm of the upper surface of the film and a boron doping concentration higher than that of the main film surface layer.

[0102] After full-area boron ion implantation of the hydrogenated amorphous silicon thin film 2, the non-electrode areas were shielded using a photoresist mask, exposing the electrode construction area. A secondary boron ion implantation was then performed on the exposed electrode construction area using an ultra-low acceleration energy of less than or equal to 5 keV. Due to the extremely low acceleration energy, the boron ions had weak penetration and remained in a very shallow layer within 10 nm of the film's surface, resulting in a boron ion implantation dose greater than 1 × 10⁻⁶. 15 ions / cm 2The highly doped contact region is then constructed. After the secondary implantation, the photoresist is stripped, and a titanium-gold or nickel-chromium composite metal electrode is deposited over this shallow, highly doped contact region. The shallow, highly doped surface narrows the depletion layer at the interface between the amorphous silicon and the metal electrode, allowing charge carriers to pass smoothly through the quantum tunneling effect or the reduced potential barrier, thus forming a good ohmic contact. Compared to existing technologies that involve etching a thin film onto a surface and then applying complex oblique sidewall implantation, this invention is implemented entirely in a planar process, avoiding the risk of uneven implantation caused by uneven etching sidewalls.

[0103] Therefore, in the planar process flow, this invention significantly reduces the Schottky barrier and contact resistance between the metal electrode and the modified hydrogenated amorphous silicon thin film 2 through a shallow, highly doped contact region, eliminating the influence of nonlinear contact characteristics at the electrode interface and reducing low-frequency contact noise caused by system electrode contact. The secondary implantation energy is less than or equal to 5 keV, and the implantation depth is less than or equal to 10 nm. The high doping exists only in a very thin surface layer and does not penetrate to the buried conduction channels located at one-third to two-thirds depth. Therefore, it does not damage the low-defect and low-noise transmission characteristics of the deep buried conduction channels, achieving decoupling and synergy between contact resistance optimization and bulk thermally sensitive low-noise characteristics.

[0104] The following is a detailed explanation of the boron ion implantation modified amorphous silicon thermistor structure and its preparation method using a specific example:

[0105] A boron ion implantation modified amorphous silicon thermistor structure includes: a substrate 1, such as a single-crystal silicon wafer, or a silicon-based substrate 1 with a composite insulating layer formed by growing a silicon dioxide insulating layer 3 and a silicon nitride insulating layer 4 on its surface, for providing electrical isolation and mechanical support; a hydrogenated amorphous silicon thin film 2, such as a hydrogenated amorphous silicon thin film 2 deposited on the substrate 1 with a thickness ranging from 5 nm to 200 nm, wherein the hydrogen content is controlled to obtain an optimized value; and a boron-doped region, such as a boron-doped region located inside the hydrogenated amorphous silicon thin film 2, introduced by an ion implantation process. For the boron-doped region, the boron ion implantation dose is, for example, 1 × 10⁻⁶. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 5×10 is preferred 14 ions / cm 2 Up to 2×10 15 ions / cm 2 This balances the sheet resistance at room temperature with the absolute value of the temperature coefficient of resistance at room temperature. For boron ion implantation energies, such as 10keV to 50keV, the projected range peak of the dopant ions is ensured to be located at a depth of one-third to two-thirds of the film thickness. This embedded distribution avoids the additional noise caused by surface states and bottom interface states, and is the physical basis for achieving a stable noise equivalent temperature difference at high frequencies.

[0106] Figures 4 to 6 This is a schematic cross-sectional view of each step in the preparation method of a boron ion implantation modified amorphous silicon thermistor structure provided in this embodiment of the invention. Combined with... Figure 4 and Figure 5 First, the substrate 1 undergoes deep cleaning and surface passivation. Specifically, the first step involves organic cleaning, for example, placing the silicon substrate 1 with silicon dioxide and silicon nitride insulating layers 4 sequentially in acetone, anhydrous ethanol, and deionized water, and ultrasonically cleaning each for 10 to 15 minutes to thoroughly remove adsorbed organic contaminants and microparticles from the surface. The second step involves surface activation. After drying with nitrogen, the substrate is immersed in, for example, hydrofluoric acid diluted 1:100 by volume for 30 to 60 seconds to micro-etch the extremely thin silicon oxynitride layer on the silicon nitride surface and form highly chemically active dangling bonds on the insulating layer surface, thereby significantly enhancing the interfacial adhesion between the subsequently deposited hydrogenated amorphous silicon film 2 and the insulating layer. For example, an 8-inch N-type single-crystal silicon wafer can be selected, and a 300nm silicon dioxide layer can be grown on the surface by thermal oxidation. Then, a 100nm silicon nitride layer can be grown by plasma-enhanced chemical vapor deposition to form a composite insulating substrate 1. The substrate 1 is ultrasonically cleaned in acetone, ethanol and deionized water for 12 minutes each. After being dried with nitrogen, it is immersed in a 1:100 diluted hydrofluoric acid solution for 45 seconds to micro-etch the silicon nitride surface and form active dangling bonds to enhance the interfacial adhesion.

[0107] like Figure 6 As shown, the hydrogenated amorphous silicon thin film 2 is deposited using plasma-enhanced chemical vapor deposition (PECVD). A key aspect of PECVD is controlling the hydrogen dilution ratio to reduce defect state density. The reactant gas, for example, is silane with a purity of 99.999%, with a flow rate of 20 to 50 sccm. The dilution gas, such as hydrogen, has a flow rate of 100 to 200 sccm. This high hydrogen dilution ratio effectively passivates silicon dangling bonds, reducing intrinsic noise. The process environment includes a substrate temperature of 200°C to 250°C, an RF power of 20 W to 50 W, and a chamber pressure of 50 Pa to 150 Pa. The goal is to control the deposition rate at 2 nm / min to 5 nm / min to obtain a dense hydrogenated amorphous silicon thin film 2 with uniform hydrogen distribution. For a specific example, plasma-enhanced chemical vapor deposition was used. The substrate temperature was 220°C, the silane flow rate was 30 sccm, the hydrogen flow rate was 150 sccm, the RF power was 30 W, the cavity pressure was 80 Pa, and the deposition time was 40 minutes to obtain a hydrogenated amorphous silicon thin film 2 with a thickness of 100 nm.

[0108] like Figure 1As shown, ion implantation modification is performed using a neutral or weak current ion implanter to prevent irreversible damage to the amorphous network caused by high-energy particles. Implanted ions are, for example, monovalent boron ions. The parameters in the above structure are strictly adhered to, and particle transport simulation software is used to ensure that the doping peak is located in the central region of the film. The beam current density is controlled, for example, at 1 μA / cm². 2 Up to 5μA / cm 2 To prevent hydrogen escape due to thermal effects caused by high beam current density during implantation, it is crucial to ensure the hydrogenation stability of the thin film. For example, monovalent boron ion implantation is used with an implantation dose of 2 × 10⁻⁶ ions. 15 ions / cm 2 The injection energy was 25 keV, ensuring a projected range of approximately 65 nm, located at about two-thirds of the film thickness, with a beam current density of 5 μA / cm. 2 The injection angle is 7°.

[0109] like Figure 6 As shown, carrier activation and damage repair annealing are then performed. This is a crucial step determining the absolute value of the temperature coefficient of resistance and noise characteristics at room temperature. The annealing environment is, for example, high-purity nitrogen or a vacuum atmosphere, with a temperature gradient of, for example, 180°C to 280°C, preferably 220°C to 250°C. This temperature range effectively activates boron atoms to enter substitution sites, repairs displacement damage caused by implantation, and does not trigger rapid hydrogen escape, while avoiding the crystallization of hydrogenated amorphous silicon. The time and cooling, for example, annealing for 30 to 60 minutes, with a heating / cooling rate of less than or equal to 3°C / min, are used to eliminate internal thermal stress in the film and prevent large-area uniformity deterioration. Specifically, in a vacuum atmosphere, i.e., less than 1 × 10⁻⁶... -3 Under Pa conditions, the temperature was increased to 250°C at a rate of 3°C / min, held for 60 minutes, and then cooled with the furnace. The final test results were as follows: sheet resistance at room temperature was 7.5 MΩ / sq, absolute value of temperature coefficient of resistance at room temperature was 3.2% / K, and noise equivalent temperature difference stability was 40.2 mK at 30 Hz and 58.5 mK at 120 Hz, with minimal fluctuation, reflecting the 1 / f noise offset effect.

[0110] Finally, high-performance electrodes are constructed by depositing titanium-gold or nickel-chromium composite electrodes with a thickness of, for example, 20 nm to 100 nm, via magnetron sputtering. A short in-situ plasma cleaning is performed before electrode deposition to reduce the Schottky barrier between the electrode and the modified hydrogenated amorphous silicon, ensuring good ohmic contact and further reducing low-frequency noise in the system.

[0111] The following is a detailed example of the preparation method for a boron ion implantation modified amorphous silicon thermistor structure. In one embodiment, the preparation method includes the following steps: substrate activation, in which a substrate 1 with a silicon dioxide and silicon nitride insulating layer 4 is activated using a diluted hydrofluoric acid solution to remove surface oxides and form active dangling bonds; thin film deposition, in which a hydrogenated amorphous silicon thin film 2 is deposited using plasma-enhanced chemical vapor deposition at a deposition temperature of 200°C to 250°C, and the hydrogen to silane flow ratio is greater than or equal to 3:1; and ion implantation, in which boron ions are implanted into the thin film at an implantation dose of 1×10¹⁴ to 5×10¹⁴. 15 ions / cm 2 The beam current density was controlled at 1 μA / cm. 2 Up to 5μA / cm 2 To suppress hydrogen escape; for defect repair, annealing is performed at 150°C to 250°C in a vacuum or inert gas atmosphere, with a heating rate of 2°C / min to 5°C / min, and cooling is performed in-furnace to eliminate thermal stress. In another embodiment, the injection dose can be 1×10⁻⁶. 15 ions / cm 2 The energy can be 20keV, the annealing temperature can be 220°C, and the test results show a sheet resistance of 9.8 MΩ / sq at room temperature and an absolute temperature coefficient of resistance of 3.6% / K at room temperature. In another embodiment, the thickness of the hydrogenated amorphous silicon thin film 2 can be set to 150 nm, and the implantation dose can be 4 × 10⁻⁶. 15 ions / cm 2 The energy can be 40keV, the annealing temperature can be 250°C, and the test results are a sheet resistance of 5.2MΩ / sq at room temperature and an absolute value of the temperature coefficient of resistance of 2.9% / K at room temperature.

[0112] Below are two comparative examples relative to the embodiments of the present invention. The first comparative example is an intrinsic comparative example, i.e., without implantation and annealing, with a sheet resistance greater than 100 MΩ / sq at room temperature and an absolute value of the temperature coefficient of resistance of approximately 2.0% / K at room temperature. The second comparative example is a vapor-phase doped comparative example, with in-situ introduction of diborane doping, exhibiting a sheet resistance of 15 MΩ / sq at room temperature and an absolute value of the temperature coefficient of resistance of only 2.4% / K at room temperature.

[0113] Figure 7 This is a schematic diagram showing the sheet resistance of a boron ion implantation-modified amorphous silicon thermistor structure at different boron ion implantation doses at room temperature as a function of annealing temperature, according to an embodiment of the present invention. Figure 7As shown, the horizontal axis represents the annealing temperature, indicating the heat treatment temperature applied during the low-temperature activation and damage repair annealing process of the hydrogenated amorphous silicon thin film 2. The vertical axis represents the sheet resistance at room temperature, representing the impedance characteristics of the modified hydrogenated amorphous silicon thin film 2. The topmost curve represents the intrinsic hydrogenated amorphous silicon thin film 2 without boron ion implantation and annealing, and the second curve represents the intrinsic hydrogenated amorphous silicon thin film 2 with a boron ion implantation dose of 1×10⁻⁶. 14 ions / cm 2 The modified structure showed a significant decrease and plateauing of sheet resistance at room temperature as the annealing temperature increased from 150°C to 220°C. The third curve represents a boron ion implantation dose of 5 × 10⁻⁶. 14 ions / cm 2 The modified structure further reduces the sheet resistance at room temperature. The lowest curve represents a boron ion implantation dose of 1×10⁻⁶. 15 ions / cm 2 The modified structure can enter a stable low-resistivity state at relatively low temperatures. The yellow shaded area in the figure represents the preferred annealing window, indicating that annealing within this temperature range effectively activates the substituted boron atoms and repairs displacement damage, resulting in a sheet resistance at room temperature that changes gradually and is highly controllable. Figure 7 This demonstrates that the electrical properties of the material can be adjusted by controlling the annealing temperature, and that a stable and highly controllable process range is reached around 180°C. For high-dose doping, the material can achieve a relatively stable low-resistivity state at lower temperatures.

[0114] Figure 8 This is a schematic diagram comparing the absolute value of the temperature coefficient of resistance as a function of operating temperature at room temperature for a boron ion implantation modified amorphous silicon thermistor structure and a plasma-enhanced chemical vapor deposition in-situ vapor-doped structure, both under the same sheet resistance. Figure 8 As shown, the horizontal axis represents the operating temperature, simulating the ambient temperature variation during the actual operation of an uncooled infrared detector. The vertical axis represents the absolute value of the temperature coefficient of resistance, indicating the sensitivity of the thermistor structure to temperature changes. Both curves are compared under the premise that they have the exact same sheet resistance of 7.5 MΩ / sq at room temperature. The upper solid line corresponds to the ion implantation modification in this embodiment of the invention. At room temperature (23°C), the absolute value of the temperature coefficient of resistance reaches 3.2% / K, and within the full operating temperature range of -55°C to 60°C, the absolute value of the temperature coefficient of resistance remains at a high level of 2.0% / K to 4.0% / K. The lower dashed line corresponds to the second comparative example of in-situ vapor phase doping using conventional plasma-enhanced chemical vapor deposition. At room temperature (23°C), the absolute value of the temperature coefficient of resistance is only 2.2% / K, significantly lower than the ion implantation modified structure of this invention across the entire operating temperature range. Figure 8The effects of ion implantation modification and plasma-enhanced chemical vapor deposition (PECVD) vapor phase doping on the absolute value of the temperature coefficient of resistance of materials at different operating temperatures were compared. Under the premise of the same sheet resistance at room temperature, the ion implantation process showed a higher absolute value of the temperature coefficient of resistance across the entire operating temperature range, which means that this technology can enable infrared detection materials to obtain higher temperature sensitivity while maintaining the same impedance.

[0115] Figure 9 This is a schematic diagram comparing the 1 / f noise power spectral density curves of a boron ion implantation modified amorphous silicon thermistor structure and a vapor-phase doped structure as a function of operating frequency, according to an embodiment of the present invention. Figure 9 As shown, the horizontal axis represents the operating frequency f, and the vertical axis represents the noise power spectral density. The upper curve represents the plasma-enhanced chemical vapor deposition (PECVD) vapor-doped structure, corresponding to the second comparative example, while the lower curve represents the ion implantation modified structure of this invention. The overall downward shift of the lower curve across the entire frequency band indicates significant low-frequency noise suppression. Simultaneously, both curves steeply descend, demonstrating the physical characteristic that 1 / f noise decreases with increasing operating frequency. The negative noise growth at high frequencies creates a dynamic offsetting effect to compensate for high frame rate signal loss. Figure 9 The study demonstrated the advantages of ion implantation over conventional plasma-enhanced chemical vapor deposition (PECVD) in noise suppression. Materials implanted with high-dose ion implantation and annealed at 200°C exhibited lower noise levels across the entire frequency band, with particularly superior noise suppression in the low-frequency band. Furthermore, negative growth compensation was achieved in the high-frequency band through noise offsetting effect, thereby improving detector sensitivity and optimizing signal-to-noise ratio performance.

[0116] Figure 10 This is a schematic diagram comparing the noise equivalent temperature difference curves of a boron ion implantation modified amorphous silicon thermistor structure and a traditional vanadium oxide thermistor structure at different test frame frequencies, as provided in an embodiment of the present invention. Figure 10 As shown, the horizontal axis represents the test frame rate, and the vertical axis represents the noise equivalent temperature difference. The green curve corresponds to the traditional vanadium oxide material; as the frame rate increases from 30Hz to 120Hz, the noise equivalent temperature difference rises sharply from 30mK to 116mK. The black curve corresponds to the modified structure of this invention; within the range of 30Hz, 60Hz, and 120Hz, the curve is flat, with a change rate less than or equal to 20%. For vanadium oxide, the noise equivalent temperature difference increases sharply with the operating frequency from 30Hz to 120Hz, indicating a deterioration in sensitivity during high-speed imaging. The modified structure of this invention maintains a flat noise equivalent temperature difference curve across the entire operating frequency range of 30Hz to 120Hz, effectively verifying the dynamic offsetting effect of negative noise growth compensating for signal loss at high frequencies.

[0117] In summary, the boron ion implantation modified amorphous silicon thermistor structure is fabricated by depositing a hydrogenated amorphous silicon thin film 2 on a substrate 1 with a silicon dioxide and silicon nitride composite insulating layer, followed by boron ion buried layer implantation using energies of 10keV to 50keV, and then low-temperature annealing treatment at 150°C to 250°C. This achieves synergistic optimization of sheet resistance at room temperature from 5MΩ / sq to 10MΩ / sq and absolute value of temperature coefficient of resistance at room temperature from 2.8% / K to 3.8% / K. Crucially, by utilizing the physical characteristic that the 1 / f noise of this structure decreases with increasing operating frequency, a high degree of stability of the noise equivalent temperature difference is achieved in a high-speed detection environment from 30Hz to 120Hz. This overcomes the technical bottleneck of significant performance degradation of traditional structures at high frame rates, making it suitable for uncooled infrared focal plane arrays with high sensitivity and high dynamic response.

[0118] This invention also provides an uncooled infrared detector comprising a boron ion implantation-modified amorphous silicon thermistor structure as described in the above embodiments, thus possessing the beneficial effects described in the above embodiments, which will not be repeated here. Specifically, the thermistor layer is integrated into the uncooled infrared detector, which supports high frame rate imaging modes above 60Hz, and the noise equivalent temperature difference performance remains stable in this mode.

[0119] In summary, this invention provides a boron ion implantation-modified amorphous silicon thermistor structure, its preparation method, and its applications. This material is prepared by depositing hydrogenated amorphous silicon on a substrate 1 with a silicon dioxide and silicon nitride composite insulating layer, followed by precise buried boron ion implantation using energies from 10keV to 50keV, and then annealing at low temperatures from 150°C to 250°C. This achieves synergistic optimization of room temperature sheet resistance from 5 MΩ / sq to 10 MΩ / sq and absolute noise equivalent temperature difference from 2.8% / K to 3.8% / K. Crucially, by utilizing the material's physical property that 1 / f noise decreases with increasing frequency, a highly stable noise equivalent temperature difference is achieved in a high-speed detection environment from 30Hz to 120Hz. This overcomes the technical bottleneck of significant performance degradation of traditional materials at high frame rates, making it suitable for high-sensitivity, high-dynamic-response uncooled infrared focal plane arrays.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A boron ion implantation modified amorphous silicon thermistor structure, characterized in that, include: Substrate; Hydrogenated amorphous silicon thin film formed on the substrate; The hydrogenated amorphous silicon thin film has a boron-doped region formed by boron ion implantation. The boron-doped region is non-uniformly distributed in the thickness direction of the hydrogenated amorphous silicon thin film. The peak concentration of boron is located between the upper and lower surfaces of the hydrogenated amorphous silicon thin film and away from the upper and lower surfaces, so as to form a buried conductive channel inside the hydrogenated amorphous silicon thin film.

2. The boron ion implantation modified amorphous silicon thermistor structure according to claim 1, characterized in that, The peak concentration of boron is located in the region of one-third to two-thirds of the thickness of the hydrogenated amorphous silicon film; and / or, the thickness of the hydrogenated amorphous silicon film ranges from 50 nm to 200 nm.

3. The boron ion implantation modified amorphous silicon thermistor structure according to claim 1, characterized in that, The boron ion implantation modified amorphous silicon thermistor structure has a sheet resistance ranging from 5 MΩ / sq to 10 MΩ / sq at room temperature, and an absolute value of the temperature coefficient of resistance ranging from 2.8% / K to 3.8% / K at room temperature.

4. The boron ion implantation modified amorphous silicon thermistor structure according to claim 1, characterized in that, The 1 / f noise power spectral density of the boron ion implantation modified amorphous silicon thermistor structure decreases as the operating frequency increases, so that the noise equivalent temperature difference change rate of the detector using the boron ion implantation modified amorphous silicon thermistor structure in the operating frame frequency range of 30Hz to 120Hz is less than or equal to 20%.

5. The boron ion implantation modified amorphous silicon thermistor structure according to any one of claims 1-4, characterized in that, The boron-doped region exhibits a Gaussian distribution, a single-peak curve distribution, or a flat-top box distribution within the hydrogenated amorphous silicon thin film; wherein, corresponding to the flat-top box distribution, during the plateau period in the region of one-third to two-thirds of the thickness of the hydrogenated amorphous silicon thin film, the difference between the maximum and minimum concentrations of the boron element is less than or equal to ±10% of the average concentration during the plateau period.

6. The boron ion implantation modified amorphous silicon thermistor structure according to any one of claims 1-4, characterized in that, The hydrogen retention rate of bound hydrogen in the hydrogenated amorphous silicon thin film is greater than or equal to 95% of that before ion implantation; and / or, the thermosensitive activation energy range of the boron ion implantation modified amorphous silicon thermosensitive structure is 0.22 eV to 0.32 eV.

7. The boron ion implantation modified amorphous silicon thermistor structure according to any one of claims 1-4, characterized in that, The surface electrode contact region of the hydrogenated amorphous silicon thin film has a shallow, highly doped contact region formed by secondary implantation, and the depth of the shallow, highly doped contact region is less than or equal to 10 nm.

8. A method for preparing a boron ion implantation modified amorphous silicon thermistor structure, characterized in that, The method for preparing the boron ion implantation modified amorphous silicon thermistor structure as described in any one of claims 1-7 includes: Provide substrate; A hydrogenated amorphous silicon thin film is deposited on the substrate; The hydrogenated amorphous silicon thin film is subjected to global boron ion implantation, so that the concentration distribution of the implanted boron element in the thickness direction of the hydrogenated amorphous silicon thin film is concentrated inside the hydrogenated amorphous silicon thin film to form a buried layer conduction channel. The hydrogenated amorphous silicon thin film after ion implantation is subjected to low-temperature annealing.

9. The method for preparing a boron ion implantation modified amorphous silicon thermistor structure according to claim 8, characterized in that, Meet at least one of the following: The energy range of the boron ion implantation is from 10 keV to 50 keV; The implantation dose of the boron ions is in the range of 1×10⁻⁶. 14 ions / cm 2 Up to 5×10 15 ions / cm 2 ; The beam current density range during boron ion implantation is 1 μA / cm². 2 Up to 5μA / cm 2 ; The annealing temperature range is 180°C to 280°C; The annealing time for the annealing process is 30 min to 60 min; The heating and cooling rates of the annealing process are both less than or equal to 3°C / min.

10. An uncooled infrared detector, characterized in that, It includes the boron ion implantation modified amorphous silicon thermistor structure as described in any one of claims 1-7.

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