A method for recycling cadmium zinc telluride substrates
By performing thickness detection, bonding, diamond wheel thinning, and polishing on cadmium zinc telluride substrates, the problems of surface defects and mother liquor residue in the reuse of cadmium zinc telluride substrates were solved, improving the reuse rate and quality consistency, and reducing processing difficulty and cost.
Patent Information
- Application Number
- CN202211521174.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-30
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2042-11-30
AI Technical Summary
In the existing technology, zinc zinc cadmium substrates cannot be effectively reused. They have surface defects, scratches and mother liquor residue, which makes processing difficult and costly. In addition, ordinary grinding and polishing methods are prone to crystal orientation deviation and cracking, resulting in low reuse rate.
The zinc cadmium telluride substrate is processed through steps such as thickness detection, bonding to a carrier, diamond wheel thinning, and polishing to remove the mercury cadmium telluride epitaxial film and mother liquor residue, ensuring thickness uniformity and surface quality.
This enables the reuse of zinc cadmium telluride substrates, improving utilization and reuse efficiency, and reducing processing costs and resource waste.
Smart Images
Figure CN115799100B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of cadmium zinc telluride wafer processing technology, and more particularly to a method for reusing cadmium zinc telluride substrates. Background Technology
[0002] The liquid-phase epitaxy process of mercury cadmium telluride (CdZnTe) can be summarized as follows: A pre-treated CdZnTe substrate is placed in a substrate tank within a graphite boat. The growth solution is then added to the mother liquor tank of the graphite boat. The graphite boat is then placed in the growth temperature zone of the epitaxial system. A sufficient amount of pure mercury is added to the mercury source temperature zone of the epitaxial system. After the entire epitaxial system is evacuated, hydrogen gas is introduced into the epitaxial equipment. Hydrogen gas acts as a carrier gas through the pure mercury in the mercury source temperature zone, maintaining a certain mercury vapor pressure on the surface of the growth liquid, thus effectively avoiding losses caused by mercury evaporation in the growth solution. During epitaxial growth, the temperature of the growth temperature zone in the equipment is first raised to melt the growth solution. After maintaining this temperature for a period of time, the solution temperature is lowered slightly below the liquidus point. Then, the growth solution is brought into contact with the substrate for cooling growth. After growth is complete, the solution is removed from the substrate, and the epitaxial layer is cooled as quickly as possible.
[0003] Cadmium zinc telluride (CZN) substrates are a superior substrate material for liquid-phase epitaxial mercury cadmium telluride (HgCdTe) thin films. However, after HgCdTe epitaxy on CZN substrates, the resulting HgCdTe films may suffer from surface defects, scratches, and residual growth solution due to epitaxial process issues. These defects may be inherited from the CZN substrate or originate from second-phase inclusions caused by uneven growth solution. Furthermore, severe scratches on the film surface due to operational factors, and large-area residues of growth solution leaving the substrate, render the HgCdTe films unusable in subsequent processes. These surface defects are difficult to remove even with polishing. In such cases, the HgCdTe film cannot be used for subsequent device fabrication.
[0004] Growing cadmium zinc telluride (CdZT) crystals is challenging, involves a long growth cycle, and requires highly pure raw materials. Furthermore, CdZT is a typical soft and brittle material with a hardness of approximately 0.8–1.5, making it highly susceptible to chipping, breakage, and even cracking during machining. In summary, the fabrication of CdZT substrates is difficult and costly. Therefore, if qualified substrates become unusable due to epitaxial process issues, recycling and reusing the CdZT substrates can effectively save costs and processing time.
[0005] Currently, there is no systematic processing method for reusing cadmium zinc telluride (CZN) substrates. Ordinary grinding and polishing methods, when processing substrates with residual CZN mother liquor, suffer from uneven stress distribution during processing due to significant thickness variations in the CZN substrate to be reused. This leads to the formation of oblique surfaces on the substrate, causing crystal orientation deviations in the pre-epitaxy substrate, or even cracks and fragmentation during grinding and polishing. Consequently, the reuse rate is low, making it unsuitable as a method for reusing CZN substrates after CZN epitaxy. Summary of the Invention
[0006] To solve or partially solve the above problems, this application provides a method for reusing cadmium zinc telluride substrates.
[0007] This application proposes a method for reusing a cadmium zinc telluride (CZN) substrate. The method includes: measuring the thickness of the CZN substrate to be reused to obtain its thickness; bonding the CZN substrate to a carrier; fixing the carrier with the CZN substrate bonded to it onto the stage of a diamond wheel thinning device; processing the CZN substrate according to its thickness using the diamond wheel thinning device; and polishing the processed CZN substrate to achieve reuse.
[0008] In some examples, the thickness of the reusable cadmium zinc telluride substrate is measured to obtain its thickness. This includes: selecting multiple detection points on the edge and middle regions of the substrate surface according to its size, and measuring the thickness of the substrate at each detection point. The maximum value is obtained by measuring the thickness at the residual position of mercury cadmium telluride mother liquor on the substrate. The maximum thickness of the reusable cadmium telluride substrate is then determined based on the above measurements.
[0009] In some examples, after the reusable cadmium zinc telluride substrate is bonded to the carrier, the method further includes: performing a thickness test on the reusable cadmium zinc telluride substrate again to confirm that the thickness variation value of the reusable cadmium zinc telluride substrate is within a preset range.
[0010] In some examples, the diamond wheel thinning device performs a thinning process on the reusable cadmium zinc telluride substrate based on its thickness, including: obtaining the thickness of the mercury cadmium telluride epitaxial film and the thickness of the mercury cadmium telluride mother liquor residue on the reusable cadmium telluride substrate based on the thickness of the reusable cadmium telluride substrate and its thickness before the first epitaxy; determining a removal thickness based on the thickness of the mercury cadmium telluride epitaxial film and the thickness of the mercury cadmium telluride mother liquor residue on the reusable cadmium telluride substrate; and removing the thickness of the mercury cadmium telluride epitaxial film and the mercury cadmium telluride mother liquor residue on the reusable cadmium telluride substrate based on the thickness of the reusable cadmium telluride substrate and the removal thickness.
[0011] In some examples, edge removal of the reusable cadmium zinc telluride (CZNC) substrate is performed using the dicing device, including: removing the edges of the CZNC substrate where residual mercury cadmium telluride mother liquor remains, based on the location of residual mercury cadmium telluride mother liquor on the edge of the reusable CZNC substrate. In some examples, the thickness of the processed CZNC substrate is measured to obtain the average thickness of the processed CZNC substrate. This includes: selecting multiple detection points on the edge and middle regions of the processed CZNC substrate surface according to its size, and measuring the thickness of the processed CZNC substrate at each of the multiple detection points to obtain the average thickness, as well as the difference between the maximum and minimum thicknesses in the measured values, TTV (Total Thickness Variation). Based on the average thickness of the processed cadmium zinc telluride (CZT) substrate, it is confirmed that the thickness of the processed CZT substrate is within a preset range. Based on the TTV value of the processed CZT substrate, it is confirmed that the TTV value of the processed CZT substrate is within a standard range.
[0012] In some examples, polishing the processed cadmium zinc telluride substrate to be reused includes: sequentially performing mechanical polishing and chemical mechanical polishing on the cadmium zinc telluride substrate to be reused.
[0013] In some examples, attaching the reusable cadmium zinc telluride substrate to the carrier includes using adhesive wax to attach the reusable cadmium zinc telluride substrate to the carrier.
[0014] Compared with the prior art, this application has the following beneficial effects:
[0015] The technical solution provided in this application discloses a method for reusing a cadmium zinc telluride (CZT) substrate. The method includes: measuring the thickness of the CZT substrate to be reused to obtain its thickness; bonding the CZT substrate to a carrier; fixing the carrier with the bonded CZT substrate on a stage of a diamond wheel thinning device; thinning the CZT substrate according to its thickness using the diamond wheel thinning device; removing the edges of the CZT substrate; measuring the thickness of the processed CZT substrate; and polishing the processed CZT substrate to achieve reuse. This method enables the reuse of CZT substrates, improves their utilization rate, increases reuse efficiency, and ensures consistent quality control of reused substrates. Given the challenges of growing and processing cadmium zinc telluride single crystals, this method can effectively save costs and resources. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the basic process of a method for reusing a zinc cadmium telluride substrate, as shown in an embodiment of this application. Detailed Implementation
[0017] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.
[0018] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.
[0019] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.
[0020] It should also be noted that "multiple" as mentioned in this application refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.
[0021] Example 1
[0022] Please see Figure 1 , Figure 1 This is an exemplary embodiment illustrating a method for reusing a zinc-cadmium substrate, the method comprising:
[0023] S101. The thickness of the cadmium zinc telluride substrate to be reused is measured to obtain the thickness of the cadmium zinc telluride substrate to be reused.
[0024] S102. The reusable zinc cadmium telluride substrate is bonded to the carrier.
[0025] S103. The carrier sheet with the reusable zinc-cadmium telluride substrate bonded to it is fixed on the carrier stage of the diamond wheel thinning device, and the reusable zinc-cadmium telluride substrate is thinned according to the thickness of the reusable zinc-cadmium telluride substrate by the diamond wheel thinning device.
[0026] S104. Polish the processed cadmium zinc telluride substrate to be reused to achieve reuse of the cadmium zinc telluride substrate.
[0027] In some examples, the thickness of the reusable cadmium zinc telluride substrate is measured to obtain its thickness. This includes: selecting multiple detection points on the edge and middle regions of the substrate surface according to its size, and measuring the thickness of the substrate at each detection point. The maximum value is obtained by measuring the thickness at the residual position of mercury cadmium telluride mother liquor on the substrate. The maximum thickness of the reusable cadmium telluride substrate is then determined based on the above measurements.
[0028] First, the thickness of the cadmium zinc telluride substrate to be reused is measured. Based on the size of the cadmium zinc telluride substrate, multiple points are selected on the edge and middle of the substrate surface for measurement. The thickness of the residual cadmium telluride mercury mother liquor is also measured to obtain the maximum value, which reflects the general trend of the thickness of the cadmium zinc telluride substrate to be reused and obtains the maximum thickness value.
[0029] Following step S101, the reusable zinc-cadmium telluride (CdC) substrate is bonded to a carrier wafer. Specifically, the reusable CdC substrate is bonded to the carrier wafer (the carrier wafer facilitates substrate bonding and has a flatness ≤2μm), ensuring no air bubbles remain between the reusable CdC substrate and the carrier wafer during the bonding process. In some examples, bonding the reusable CdC substrate to the carrier wafer includes using adhesive wax. Specifically, the reusable CdC substrate with the defective mercury cadmium telluride (MCH) epitaxial film is bonded to the silicon wafer using adhesive wax, ensuring the center of the silicon wafer is at the midpoint between the reusable CdC substrates. The size of the silicon wafer can be determined based on the size of the reusable CdC substrate itself or the size of the wafer stage of the diamond wheel thinning device. During bonding, the wax layer must be applied evenly to ensure that there are no air bubbles, particles, or other defects affecting the flatness between the reusable cadmium zinc telluride substrate and the wafer. When placing the silicon wafer, align the center of the wafer with the center of the wafer stage. After completion, turn on the vacuum to firmly adhere the silicon wafer to the wafer stage.
[0030] In some examples, the reusable cadmium zinc telluride substrate is bonded to a carrier. The method further includes: measuring the thickness of the reusable cadmium zinc telluride substrate again to confirm that the thickness variation value of the reusable cadmium zinc telluride substrate is within a preset range. After bonding, the thickness value at the corresponding point is measured again to confirm that the variation value of each point difference is within 5 μm, and the maximum thickness of the reusable cadmium zinc telluride substrate after bonding is obtained (if the variation value is greater than 5 μm, the reusable cadmium zinc telluride substrate is removed, and step S102 is repeated). Multiple reusable cadmium zinc telluride substrates with similar thicknesses can be selected and bonded simultaneously on the carrier. The average thickness deviation between the reusable cadmium zinc telluride substrates is less than 20 μm, preferably 2 to 4 substrates. Specifically, a batch (taking two wafers as an example) of reusable zinc-cadmium telluride (CdC) substrates with similar thickness and containing substandard CdC epitaxial films are bonded side-by-side to a silicon wafer using adhesive wax, ensuring the center of the silicon wafer is positioned midway between the two CdC substrates. The size of the silicon wafer can be determined based on the size of the CdC substrates themselves or the size of the wafer stage in the diamond wheel thinning device. During bonding, the wax layer must be applied evenly to ensure there are no air bubbles, particles, or other defects affecting flatness between the CdC substrates and the wafer. When placing the silicon wafer, align the center of the wafer with the center of the wafer stage. After completion, activate the vacuum to firmly adhere the silicon wafer to the wafer stage.
[0031] In some examples, the diamond wheel thinning device performs a reuse process on the reusable cadmium zinc telluride substrate based on its thickness, including: obtaining the thickness of the mercury cadmium telluride epitaxial film and the thickness of the mercury cadmium telluride mother liquor residue on the reusable cadmium telluride substrate based on the thickness of the reusable cadmium telluride substrate and its thickness before the first epitaxy; determining a removal thickness based on the thickness of the mercury cadmium telluride epitaxial film and the thickness of the mercury cadmium telluride mother liquor residue on the reusable cadmium telluride substrate; and removing the thickness of the mercury cadmium telluride epitaxial film and the mercury cadmium telluride mother liquor residue on the reusable cadmium telluride substrate based on the thickness of the reusable cadmium telluride substrate and the removal thickness.
[0032] Specifically, the substrate is fixed on the stage of the diamond wheel thinning device using vacuum adsorption. The diamond wheel thinning device removes the mercury cadmium telluride (MCH) epitaxial film and residual MCH mother liquor from the reusable cadmium zinc telluride (CZC) substrate. The diamond wheel thinning device can be an abrasive wheel thinning device, preferably using a diamond wheel with a rotation speed of 1000 rpm to 2000 rpm; the stage rotation speed is preferably 50 rpm to 100 rpm. Because the height of the residual MCH mother liquor is inconsistent with the height of the MCH film, during rapid wheel feeding, the feed rate must be changed 20 μm to 150 μm above the highest point of the reusable CZC substrate and epitaxial film. Depending on the thickness to be removed, the wheel feed rate is decreased stepwise from 0.5 μm / s to 0.01 μm / s. The selection of the grinding wheel feed rate was determined through multiple experiments. If it is too high, it will cause cleavage or cracking of the cadmium zinc telluride substrate; if it is too low, it will not achieve the goal of rapid removal. Finally, the grinding wheel feed can be stopped at the target thickness (the thickness to be removed from the cadmium zinc telluride substrate to be reused), and the grinding wheel and stage can be kept rotating for a period of time to obtain a better surface condition. Specifically, the starting position and target position of the grinding wheel (the position where the target thickness is located) are set. Based on the above settings, the rotation speeds of the grinding wheel and stage are set, and the removal thickness is set according to the specific thickness of the substrate. The diamond grinding wheel thinning device is then started. Water is used as a coolant during the thinning process. After the cadmium telluride film is removed, because the subsequent mechanical polishing pressure is high and the silicon wafer as a carrier is fragile, the substrate is removed from the silicon wafer and bonded to a new carrier glass plate using adhesive wax.
[0033] In some examples, after removing the thickness of the mercury cadmium telluride epitaxial film and the residual mercury cadmium telluride mother liquor on the reusable cadmium telluride substrate based on the thickness of the substrate to be reused and the removal thickness, the method further includes: edge removal of the reusable cadmium telluride substrate using a dicing device; specifically, this includes: removing the edge of the residual mercury cadmium telluride mother liquor on the reusable cadmium telluride substrate based on the location of the residual mercury cadmium telluride mother liquor at the edge of the substrate to be reused. Specifically, the removal amount of the cadmium telluride substrate edge is set. Considering the influence of the epitaxial mercury cadmium telluride process, the removal amount of the cadmium telluride substrate edge is preferably 50-150 μm. After multiple rounds of experimental verification, this removal range can completely remove the residual mercury cadmium telluride mother liquor while remaining within the allowable error of the cadmium telluride substrate size in the epitaxial mercury cadmium telluride process.
[0034] In some examples, the thickness of the processed cadmium zinc telluride (CZT) substrate to be reused is measured to obtain its thickness. This includes: selecting multiple detection points on the edge and middle regions of the processed CZT substrate according to its size; measuring the thickness at each detection point; obtaining the average thickness; and the difference between the maximum and minimum thicknesses, TTV (Total Thickness Variation). Based on the average thickness of the processed CZT substrate, it is confirmed that the thickness value is within a preset range. Based on the TTV value of the processed CZT substrate, it is confirmed that the TTV value is within a standard range. Specifically, the average thickness of the finished reusable cadmium zinc telluride substrate should be lower than the thickness of the reusable cadmium zinc telluride substrate before the first epitaxy, and the difference is preferably greater than 5 μm; the measured TTV value of the finished reusable cadmium zinc telluride substrate should be within the processing standard range of the corresponding size of the cadmium zinc telluride substrate before polishing.
[0035] In some examples, the polishing of the processed reusable cadmium zinc telluride substrate includes: sequentially performing mechanical polishing and chemical mechanical polishing on the reusable cadmium zinc telluride substrate. The mechanical polishing process uses a soft polishing cloth and a polishing slurry containing diamond. The chemical mechanical polishing process uses a different type of soft polishing cloth and a polishing slurry containing silica. The surface condition of the substrate after polishing is comparable to its surface condition before the initial epitaxy. Specifically, diamond polishing slurry is used for mechanical polishing, and the flow rate of the polishing slurry is adjusted appropriately to ensure that the polishing pad is evenly covered with polishing slurry, at a rate of 100 g / cm³. 2~400g / cm 2 The unit pressure is set to determine the polishing pressure for the mechanical polishing process. After multiple rounds of experimental verification, it was found that the material removal rate on the substrate surface during the mechanical polishing process for the reusable zinc-cadmium telluride substrate should be no less than 10 μm to remove surface damage caused by the diamond wheel thinning device. Chemical mechanical polishing uses a silica sol polishing slurry with added oxidants and additives. The flow rate of the polishing slurry is adjusted to ensure even distribution on the polishing pad, at a rate of 200 g / cm³. 2 ~500g / cm 2 The unit pressure setting is the polishing pressure for the mechanical polishing process.
[0036] This embodiment provides a method for reusing cadmium zinc telluride (CZT) substrates. The method includes: measuring the thickness of the CZT substrate to be reused to obtain its thickness; bonding the CZT substrate to a carrier; fixing the carrier with the CZT substrate to be reused onto the stage of a diamond wheel thinning device; and performing reuse processing on the CZT substrate according to its thickness using the diamond wheel thinning device; and polishing the processed CZT substrate to achieve reuse. This method enables the reuse and recycling of CZT substrates, improving their utilization rate, reuse efficiency, and consistency in quality control. It can effectively save costs and resources, especially given the challenges of growing and processing CZT single crystals.
[0037] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used in this patent to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for recycling of a cadmium zinc telluride substrate, characterized in that, The method comprises: thickness detection on the to-be-reused CdZnTe substrate to obtain the thickness of the to-be-reused CdZnTe substrate; bonding the to-be-reused CdZnTe substrate to a slide; fixing the slide with the to-be-reused CdZnTe substrate bonded thereon on a slide table of a diamond grinding wheel thinning device, and performing thinning processing on the to-be-reused CdZnTe substrate by the diamond grinding wheel thinning device according to the thickness of the to-be-reused CdZnTe substrate; polishing the processed to-be-reused CdZnTe substrate to realize reuse of the to-be-reused CdZnTe substrate; the thickness detection on the to-be-reused CdZnTe substrate to obtain the thickness of the to-be-reused CdZnTe substrate comprises: selecting multiple detection points on the surface edge portion and the middle region of the to-be-reused CdZnTe substrate according to the size of the to-be-reused CdZnTe substrate, and detecting the to-be-reused CdZnTe substrate at the multiple detection points respectively to obtain the maximum value of the thickness of the to-be-reused CdZnTe substrate at the position of the residual CdHgTe mother liquor on the to-be-reused CdZnTe substrate; obtaining the maximum value of the thickness of the to-be-reused CdZnTe substrate based on the above detection; the thinning processing on the to-be-reused CdZnTe substrate by the diamond grinding wheel thinning device according to the thickness of the to-be-reused CdZnTe substrate comprises: based on the thickness of the to-be-reused CdZnTe substrate and the thickness of the to-be-reused CdZnTe substrate before epitaxy, obtaining the thickness of the CdHgTe epitaxial film on the to-be-reused CdZnTe substrate and the thickness of the residual CdHgTe mother liquor, and determining the removal thickness based on the thickness of the CdHgTe epitaxial film on the to-be-reused CdZnTe substrate and the thickness of the residual CdHgTe mother liquor; based on the removal of the thickness of the CdHgTe epitaxial film on the to-be-reused CdZnTe substrate and the residual CdHgTe mother liquor according to the thickness of the to-be-reused CdZnTe substrate and the removal thickness; performing edge removal on the to-be-reused CdZnTe substrate by a scribing device; when the grinding wheel is rapidly fed, the grinding wheel changes the feeding rate at 20 μm-150 μm above the highest position of the to-be-reused CdZnTe substrate and the epitaxial film, and the feeding rate of the grinding wheel is decreased step by step by 0.5 μm / s-0.01 μm / s according to the removal thickness.
2. The method of claim 1, wherein, after the bonding of the to-be-reused CdZnTe substrate to the slide, the method further comprises: detecting the thickness of the to-be-reused CdZnTe substrate again to confirm that the thickness change value of the to-be-reused CdZnTe substrate is within a preset range.
3. The method of claim 1, wherein, the method further comprises: detecting the thickness of the processed to-be-reused CdZnTe substrate to obtain the average thickness of the processed to-be-reused CdZnTe substrate.
4. The method of claim 1, wherein, the polishing of the processed to-be-reused CdZnTe substrate comprises: mechanical polishing and chemical mechanical polishing are performed on the to-be-reused CdZnTe substrate in sequence.
5. The method of claim 1, wherein, the bonding of the to-be-reused CdZnTe substrate to the slide comprises: the to-be-reused CdZnTe substrate is bonded to the slide by using bonding wax.