Device and method for thinning wafer

Abstract

The present disclosure discloses a device and method for thinning a wafer. The device includes: a wafer etching chamber, for placing a wafer and etching the wafer using an etching solution; a solution recovery tank, for containing a dirty etching solution formed by etching the wafer, wherein the dirty etching solution contains negatively charged residues; a first recovery pipeline, one end of which is connected to the wafer etching chamber and the other end is connected to the solution recovery tank, so as to transport the dirty etching solution from the wafer etching chamber to the solution recovery tank; and a second recovery pipeline, one end of which is connected to the solution recovery tank, so as to extract the dirty etching solution from the solution recovery tank; a particle separation device is provided on the second recovery pipeline, and a positive electrode plate and a negative electrode plate are provided in the particle separation device, and the positive electrode plate is used to adsorb the residues to filter the dirty etching solution into etching solution. Through the scheme of the embodiment of the present disclosure, the acid replacement cycle can be shortened, the time and raw materials consumed by the entire process can be reduced, and the process cost can be reduced.

Description

Technical Field

[0001] The present disclosure generally relates to the field of semiconductor manufacturing technology. More specifically, the present disclosure relates to an apparatus and method for thinning a wafer. Background Art

[0002] Back Side Illumination (BSI) 3D stacked CMOS image sensors place photosensitive elements on the back of the chip, allowing light to directly enter the photosensitive elements, improving light receiving efficiency and image quality. They have attracted much attention in various application fields such as light detection and ranging. In the BSI process, backside thinning is a key step, which requires grinding the backside of the wafer to the micron level to more effectively couple incident photons.

[0003] In the prior art, the BSI backside thinning process usually uses chemical mechanical polishing technology to complete rough grinding, and then uses an HNA solution composed of hydrofluoric acid, nitric acid and acetic acid to perform isotropic wet etching to remove part of the silicon on the back of the wafer to achieve the effect of thinning the wafer.

[0004] However, as the etching time increases, the effective etching components in the HNA solution are continuously consumed, the silicon particles removed by etching continue to accumulate, the etching effect decreases, and the silicon particles also contaminate the wafer. In order to ensure the stable operation of the thinning process, the HNA solution needs to be replaced frequently. Each acid change cycle requires the use of a new warm-up wafer (season wafer) and a control wafer (monitor wafer). Therefore, an acid change cycle that is too short will increase the process time and also cause a large amount of consumables loss, increasing the process cost.

[0005] In view of this, there is an urgent need to provide a wafer thinning solution so as to extend the acid replacement cycle while ensuring the etching effect, thereby reducing consumables loss and reducing process costs. Summary of the invention

[0006] In order to at least solve one or more of the technical problems mentioned above, the present disclosure proposes a wafer thinning solution in multiple aspects.

[0007] In the first aspect, the present disclosure provides an apparatus for thinning wafers, including: a wafer etching chamber, for placing wafers and etching wafers using an etching solution; a solution recovery tank, for accommodating dirty etching solution formed by etching the wafers, wherein the dirty etching solution contains negatively charged residues; a first recovery pipeline, one end of which is connected to the wafer etching chamber, and the other end is connected to the solution recovery tank, so as to transport the dirty etching solution from the wafer etching chamber to the solution recovery tank; and a second recovery pipeline, one end of which is connected to the solution recovery tank, so as to extract the dirty etching solution from the solution recovery tank; a particle separation device is provided on the second recovery pipeline, in which positive electrode plates and negative electrode plates are respectively provided on both sides of the conveying direction of the second recovery pipeline, and the positive electrode plates are used to adsorb residues to filter the dirty etching solution into etching solution.

[0008] In some embodiments, the equipment for thinning the wafer also includes: a solution holding tank, which is connected to the other end of the second recovery pipeline, for receiving the etching liquid formed by filtering the dirty etching liquid; and a liquid delivery pipeline, one end of which is connected to the solution holding tank and the other end is connected to the wafer etching chamber to transport the etching liquid in the solution holding tank to the wafer etching chamber.

[0009] In some embodiments, the device for thinning a wafer also includes: a fluid replenishing device; a light detection device, which is arranged inside a solution containing tank and is used to collect spectral information of the etching solution; and a control device, which is respectively communicated with the light detection device and the fluid replenishing device to control the fluid replenishing device to replenish effective etching components to the etching solution in the solution containing tank according to the spectral information.

[0010] In some embodiments, the device for thinning a wafer further includes: a filtering device; the filtering device is disposed on the second recovery pipeline and is used to filter out waste particles in the dirty etching solution whose particle size is larger than the filtering size.

[0011] In some embodiments, the particle separation device and the filtering device are sequentially arranged on the second recovery pipeline along the conveying direction of the second recovery pipeline.

[0012] In a second aspect, the present disclosure provides a method for thinning a wafer, comprising: recovering the dirty etching liquid formed by etching the wafer in a wafer etching chamber to a solution recovery tank through a first recovery pipeline, wherein one end of the first recovery pipeline is connected to the wafer etching chamber, and the other end is connected to the solution recovery tank, and the dirty etching liquid contains negatively charged residue; transporting the dirty etching liquid in the solution recovery tank to a particle separation device through a second recovery pipeline, wherein one end of the second recovery pipeline is connected to the solution recovery tank, the particle separation device is arranged on the second recovery pipeline, and in the particle separation device, positive electrode plates and negative electrode plates are respectively provided on both sides of the transport direction of the second recovery pipeline; using the positive electrode plate to adsorb the residue to obtain filtered etching liquid; and transporting the etching liquid to the wafer etching chamber through the second recovery pipeline to etch the wafer.

[0013] In some embodiments, transporting the etching liquid to the wafer etching chamber through the second recovery pipeline to etch the wafer includes: transporting the filtered etching liquid to the solution holding tank through the second recovery pipeline, wherein the other end of the second recovery pipeline is connected to the solution holding tank; and transporting the etching liquid in the solution holding tank to the wafer etching chamber through the liquid delivery pipeline to etch the wafer in the wafer etching chamber, wherein one end of the liquid delivery pipeline is connected to the solution holding tank, and the other end is connected to the wafer etching chamber.

[0014] In some embodiments, a light detection device is provided in the solution holding tank, the light detection device is communicatively connected to the control device, and the control device is also communicatively connected to the liquid replenishing device. The method for thinning the wafer also includes: using the light detection device to collect spectral information of the etching solution in the solution holding tank; using the control device to analyze the spectral information to obtain concentration information of effective etching components in the etching solution; using the control device to compare the concentration information with the concentration reference information; and using the control device to control the liquid replenishing device to replenish the effective etching components into the solution holding tank according to the comparison results.

[0015] In some embodiments, a filtering device is also provided on the second recovery pipeline, wherein after the dirty etching liquid formed by etching the wafer in the wafer etching chamber is recovered to the solution recovery pool through the first recovery pipeline, the method for thinning the wafer also includes: transporting the dirty etching liquid to the filtering device through the second recovery pipeline; and using the filtering device to filter out waste particles in the dirty etching liquid whose particle size is larger than the filtering size.

[0016] In some embodiments, on the second recovery pipeline, a particle separation device and a filtering device are sequentially arranged along the conveying direction of the second recovery pipeline, wherein using the positive electrode plate to adsorb the residue to obtain a filtered etching solution includes: using the positive electrode plate to adsorb the residue to obtain a filtered etching solution with reduced viscosity; conveying the filtered etching solution to the filtering device through the second recovery pipeline; and using the filtering device to filter out waste particles in the filtered etching solution whose particle size is larger than the filtering size to obtain an etching solution.

[0017] The unexpected technical effects of the present invention are:

[0018] Through the device for thinning wafers provided above, the embodiment of the present disclosure forms a recovery channel for the etching solution through a solution recovery pool, a first recovery pipeline and a second recovery pipeline. The first recovery pipeline can recycle the etching solution used in the wafer etching chamber and store it in the solution recovery pool, and the particle separation device on the second recovery pipeline can filter the dirty etching solution stored in the solution recovery pool to purify it into a clean etching solution and reuse it. Since different particles will present different electrical properties in solutions with different pH values, silicon-containing particles have a negative potential in the HNA solution, so the positive and negative electrode plates located on both sides of the conveying direction in the particle separation device can adsorb silicon-containing particles, separate silicon-containing particles from the recovered etching solution to form a clean etching solution for thinning the wafer, thereby effectively preventing the residues of the etching process from contaminating the wafer and ensuring the etching effect. At the same time, since the etching solution can be recovered, filtered and reused through the recovery channel, the frequency of acid change is greatly reduced, the acid change cycle is extended, thereby reducing the loss of consumables and reducing the process cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0020] Figure 1 An exemplary structural diagram showing an apparatus for thinning a wafer according to some embodiments of the present disclosure;

[0021] Figure 2 An exemplary flow chart showing a method for thinning a wafer according to some embodiments of the present disclosure is shown;

[0022] Figure 3 An exemplary structural diagram showing an apparatus for thinning a wafer according to some embodiments of the present disclosure;

[0023] Figure 4 An exemplary flow chart showing a method for thinning a wafer according to some embodiments of the present disclosure is shown;

[0024] Figure 5 An exemplary flow chart showing a method for thinning a wafer according to yet other embodiments of the present disclosure;

[0025] Figure 6 An exemplary structural diagram showing an apparatus for thinning a wafer according to yet other embodiments of the present disclosure;

[0026] Figure 7 An exemplary flow chart showing a method for implementing the additional acid replenishment mechanism according to some embodiments of the present disclosure;

[0027] Figure 8 An exemplary structural block diagram of an electronic device according to an embodiment of the present disclosure is shown;

[0028] Description of reference numerals:

[0029] 10-wafer etching chamber; 11-wafer; 20-solution recovery tank; 30-first recovery pipeline; 40-second recovery pipeline; 41-particle separation device; 42-filtering device; 43-water pump; 50-solution holding tank; 60-liquid delivery pipeline; 70-liquid replenishing device; 80-light detection device; 800-electronic device; 810-processor; 820-memory. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0031] It should be understood that the terms "include" and "comprising" used in the specification and claims of the present disclosure indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections thereof.

[0032] It should also be understood that the terms used in this disclosure are only for the purpose of describing specific embodiments and are not intended to limit the disclosure. As used in this disclosure and claims, the singular forms of "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" used in this disclosure and claims refers to any combination of one or more of the associated listed items and all possible combinations, including these combinations.

[0033] As used in this specification and claims, the term "if" can be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0034] The specific implementation of the present disclosure is described in detail below with reference to the accompanying drawings.

[0035] Example application scenarios

[0036] The steps of the backside thinning process of a back-illuminated 3D stacked CMOS image sensor are generally as follows: first, the P-type heavily doped area is coarsely ground by chemical mechanical polishing, and then the P-type heavily doped area and the P-type lightly doped area are wet-etched by HNA solution to achieve the effect of thinning the wafer by taking advantage of the high selectivity characteristics of the P-type heavily doped area and the P-type lightly doped area.

[0037] During the execution of the above processes, the silicon material removed by etching will continue to accumulate, thus contaminating the HNA solution used in wet etching. At the same time, with the consumption of HNA solution, the etching rate of the P-type heavily doped area and the P-type lightly doped area will drop significantly in the later stage of the process. Even more, the accumulated silicon material will contaminate the wafer in the wet etching process, affecting product quality.

[0038] In order to solve the above problems, the existing solution has to ensure the stable operation of the thinning process by frequently changing the HNA solution. However, the number of etching wafers that the HNA solution can support in one acid change cycle is limited, and each time a new acid change cycle is entered, a new warm-up sheet is consumed to complete the warm-up operation and a new control sheet is used to monitor the etching rate. Therefore, with the increase in the frequency of acid change and the shortening of the acid change cycle, the time and raw materials consumed by the entire back thinning process will increase, which will lead to a decrease in product production capacity and an increase in process costs.

[0039] Exemplary Application Scenarios

[0040] In view of this, the disclosed embodiment provides a wafer thinning solution, which establishes an etching solution recovery channel through a solution recovery pool, a first recovery pipeline, and a second recovery pipeline, and can recycle and reuse the used HNA solution, reduce the number of acid changes, and extend the acid change cycle. In addition, the particle separation device on the second recovery pipeline filters out the silicon particles formed by etching, which can ensure the cleanliness of the HNA solution used during etching, avoid silicon particles from contaminating the wafer, ensure the etching effect, and reduce the number of times the HNA solution is replaced due to contamination, thereby reducing the consumables loss of the entire process and reducing the process cost.

[0041] Figure 1 An exemplary structural diagram of an apparatus for thinning a wafer according to some embodiments of the present disclosure is shown, Figure 1 As shown, the device is provided with a wafer etching chamber 10 and a solution recovery pool 20, wherein the wafer etching chamber 10 is used to place a wafer 11 and etch the wafer using an etching solution. After the etching solution put into the wafer etching chamber 10 etches the wafer, the residue removed by etching is mixed into the etching solution to form a dirty etching solution. In order to recover the etching solution, the device of the disclosed embodiment is provided with a solution recovery pool 20 to collect the dirty etching solution.

[0042] In the BSI backside thinning process, the etching solution used is a HNA solution composed of hydrofluoric acid, nitric acid and acetic acid. The principle of wet etching of wafers with HNA solution can be expressed by the following overall reaction formula:

[0043] ;

[0044] Specifically, in the above chemical reaction process, the reaction process of each effective etching component in the HNA solution and the wafer material includes: first, nitric acid is decomposed to generate , the reaction equation at this time is ;then, It reacts with the silicon on the back of the wafer to form silicon dioxide. The reaction equation is: ; Finally, hydrofluoric acid etching removes silicon dioxide, and the reaction formula is It should be noted that the above reaction formula is that excess hydrofluoric acid reacts with silicon dioxide to generate fluorosilicic acid, that is, .

[0045] In an acidic solution, fluorosilicic acid can be ionized to generate fluorosilicate ions, which are negatively charged. Under acidic conditions, fluorosilicate ions can be adsorbed onto the surface of particles to form negatively charged particles. In the existing BSI backside thinning process, these particles are mixed in the HNA solution, affecting the cleanliness of the HNA solution and may also contaminate the wafers that subsequently enter the wafer etching chamber.

[0046] In order to collect the dirty etching solution, that is, the HNA solution mixed with fluorosilicic acid and its adsorbed particles, the device of the embodiment of the present disclosure is provided as follows: Figure 1 The solution recovery tank shown is provided with corresponding pipelines to connect the solution recovery tank and the wafer etching solution, so as to recover the dirty etching solution and filter and reuse it.

[0047] In the device for thinning a wafer provided in the embodiment of the present disclosure, the pipeline can be roughly divided into two parts: one is a recovery pipeline for recovering dirty etching liquid, and the other is a liquid infusion pipeline for delivering clean etching liquid.

[0048] First, the recovery pipeline in the equipment is described in detail, such as Figure 1As shown, the recovery pipeline may include: a first recovery pipeline 30 and a second recovery pipeline 40. One end of the first recovery pipeline 30 is connected to the wafer etching chamber 10, and the other end is connected to the solution recovery tank 20. The function of the first recovery pipeline 30 is to collect the dirty etching solution formed by etching the wafer from the wafer etching chamber 10, and then transport it to the solution recovery tank 20 for storage. One end of the second recovery pipeline 40 is connected to the solution recovery tank 20, and a particle separation device 41 is arranged on the second recovery pipeline 40, and the particle separation device 41 includes a positive electrode plate and a negative electrode plate arranged opposite to each other.

[0049] In the BSI backside thinning process, the particles mixed in the dirty etching solution have a negative potential due to the adsorption of fluorosilicate ions, that is, the dirty etching solution contains negatively charged residues. Therefore, the positive electrode plate in the particle separation device can adsorb the negatively charged residues to purify the dirty etching solution.

[0050] exist Figure 1 In the device shown, the positive electrode plates and the negative electrode plates are arranged on both sides of the conveying direction of the second recovery pipeline. After the dirty etching liquid stored in the solution recovery pool is drawn into the second recovery pipeline, when the dirty etching liquid flows along the second recovery pipeline and passes between the positive electrode plates and the negative electrode plates on both sides, the positive electrode plates adsorb the negatively charged residues and filter them out from the dirty etching liquid, so that the second recovery pipeline outputs clean etching liquid.

[0051] Furthermore, in order to store clean etching liquid, a solution holding tank 50 can also be provided in the device, which can be used to hold the etching liquid initially put in, and can also receive the etching liquid formed by filtering the dirty etching liquid. In some embodiments, the end to which the conveying direction of the second recovery pipeline 40 points is connected to the solution holding tank 50, and the clean etching liquid formed by filtering by the particle separation device 41 on the second recovery pipeline 40 is mixed with the etching liquid originally stored in the solution holding tank 50, and continues to be used for wet etching on the back side of the wafer. Through this recovery pipeline, the dirty etching liquid formed by etching can filter out the residues that affect the etching effect, thereby purifying it into an etching liquid that can be put back into use, thereby delaying the acid replacement cycle of the BSI back thinning process, and can also prevent the residues from contaminating the wafers in the wafer etching chamber.

[0052] Furthermore, in order to facilitate extraction of dirty etching solution from the solution recovery tank 20, a water pump 43 may be further provided on the second recovery pipeline 40 to assist the second recovery pipeline 40 in extracting the dirty etching solution and conveying it to the particle separation device 41. In some embodiments, the water pump 43 and the particle separation device 41 may be arranged in sequence along the conveying direction of the second recovery pipeline 40. It should be noted that the arrangement positions of the water pump 43 and the particle separation device 41 may also be swapped, and no excessive restrictions are imposed here.

[0053] In some embodiments, the positive electrode plate can be replaced manually according to a preset cycle or according to the actual dirtiness to ensure its ability to adsorb residues. In other embodiments, the particle separation device may also be equipped with a drive mechanism for automatically replacing the electrode plate, for example, a turntable with multiple electrode plates arranged circumferentially, and the turntable rotates with its central axis as the rotation axis to achieve the replacement of the electrode plate. It should be noted that the drive mechanism for automatically replacing the electrode plate described above is only an example, and other drive mechanisms that can realize automatic replacement of motor plates are also applicable to the present disclosure, and no excessive elaboration will be made here.

[0054] The above introduces the structure of the recovery pipeline. Figure 1 The infusion pipeline used to deliver clean etching liquid in the equipment is described in detail. Figure 1 As shown, the device is also provided with a liquid delivery pipeline 60, one end of the liquid delivery pipeline 60 is connected to the solution holding tank 50, and the other end is connected to the wafer etching chamber 10. The etching liquid stored in the solution holding tank 50 can be transported to the wafer etching chamber 10 through the liquid delivery pipeline 60, so as to be used for wet etching of the wafer 11 in the wafer etching chamber 10.

[0055] Furthermore, in actual application, the solution holding tank 50 can be connected to the solution recovery tank 20. As an example, the wall of the solution holding tank 50 can be attached to the wall of the solution recovery tank 20, and the top of the solution holding tank 50 is higher than the top of the solution recovery tank 20, so that the etching solution in the solution holding tank 50 can overflow from the solution holding tank 50 to the solution recovery tank 20. As another example, a connecting pipeline can also be set between the solution holding tank 50 and the solution recovery tank 20, and the connecting pipeline only allows the etching solution in the solution holding tank to flow into the solution recovery tank by setting a one-way valve or adjusting the liquid level line. This connecting structure provides an additional flow channel for the etching solution in the solution holding tank, and the flow channel is shorter than the circulation channel formed by the recovery pipeline and the delivery pipeline, thereby avoiding the accumulation of pollution caused by the etching solution in the solution holding tank being in a "dead water" state for a long time and affecting the operation safety of the equipment.

[0056] Based on the device provided in the above embodiments, the present disclosure also provides a method for thinning a wafer. Figure 2 An exemplary flow chart of a method 200 for thinning a wafer according to some embodiments of the present disclosure is shown.

[0057] like Figure 2As shown, in step S201, the dirty etching solution formed by etching the wafer is recovered to the solution recovery tank. In this step, the wafer is placed in the wafer etching chamber, and the residue formed after the etching solution etches the wafer is mixed in the etching solution, thereby forming a dirty etching solution. Since the BSI back thinning process uses HNA solution, it reacts with the silicon on the back of the wafer to form fluorosilicic acid, which can be ionized to form fluorosilicate ions. The fluorosilicate ions are negatively charged, which are further adsorbed on the particles to form negatively charged residues.

[0058] The device in this embodiment provides a first recovery pipeline, one end of which is connected to the wafer etching chamber, and the other end of which is connected to the solution recovery tank. The dirty etching solution can be recovered to the solution recovery tank through the first recovery pipeline.

[0059] In step S202, the dirty etching liquid is transported to the particle separation device through the second recovery pipeline. In this embodiment, one end of the second recovery pipeline is connected to the solution recovery tank, and the particle separation device is provided on the second recovery pipeline. The dirty etching liquid can be extracted from the solution recovery tank and transported to the particle separation device by means of the second recovery pipeline.

[0060] In step S203, the residue is adsorbed by the positive electrode plate in the particle separation device to obtain the filtered etching solution. In the particle separation device, a positive electrode plate and a negative electrode plate are respectively provided on both sides of the conveying direction of the second recovery pipeline. Since the residue is negatively charged, after the dirty etching solution is conveyed to the particle separation device along the second recovery pipeline, the residue can be adsorbed by the positive electrode plate, so the etching solution output from the particle separation device is purified into a clean etching solution.

[0061] In step S204, the etching solution is delivered to the wafer etching chamber to etch the wafer. In some embodiments, the pipeline of the equipment for thinning the wafer can be roughly divided into a recovery pipeline and an infusion pipeline. The other end of the second recovery pipeline in the recovery pipeline is connected to the solution holding tank, and the infusion pipeline includes a liquid delivery pipeline connecting the solution holding tank and the wafer etching chamber. When executing step S204, the filtered etching solution can be delivered to the solution holding tank for storage through the second recovery pipeline, and then the etching solution in the solution holding tank can be delivered to the wafer etching chamber through the infusion pipeline to etch the wafer in the wafer etching chamber.

[0062] Combination Figure 1 The equipment shown and Figure 2In the method shown, the etching liquid invested at the beginning of the process can be poured into a solution holding tank for storage, and reaches the wafer etching chamber through a liquid delivery pipeline for use in etching. The dirty etching liquid formed after use is collected into the solution recovery tank through a first recovery pipeline. During the transportation along the second recovery pipeline, the residue in the dirty etching liquid is adsorbed and filtered, thereby forming a clean etching liquid to be recovered to the solution holding tank, mixed with the etching liquid invested at the beginning of the process and reused.

[0063] It should be noted that the device and method described in the above embodiments can filter out negatively charged residues in the dirty etching solution, thereby completing the purification of the dirty etching solution. In actual applications, the used etching solution may also contain other waste particles with non-negative potentials, such as particles mixed in during transportation due to dirty pipelines and impurities caused by microbial growth.

[0064] In order to filter out the above waste particles, some embodiments of the present disclosure further provide a device for thinning a wafer, which is based on the device described in any of the above embodiments and further includes a filtering device 42. Figure 3 An exemplary structural diagram of an apparatus for thinning a wafer according to some embodiments of the present disclosure is shown.

[0065] like Figure 3 As shown, the filter device 42 is arranged on the second recovery pipeline 40, and it can filter out waste particles in the dirty etching solution whose particle size is larger than the filter size. On the second recovery pipeline 40, the particle separation device 41 uses the electrical properties of the particles in the dirty etching solution as the filtering basis, and the filter device 42 uses the particle size as the filtering basis.

[0066] In some embodiments, considering that the filtering size of the filtering device 42 is limited to a certain range, since the particle size of the negatively charged residue and waste particles is relatively small, a filtering size that is too large will lead to a poor filtering effect. Also, since the etching liquid has a certain viscosity, a filtering size that is too small will easily cause the filtering device to be subjected to excessive pressure and be damaged. Therefore, in actual application, the particle separation device 41 and the filtering device 42 can be selected to be arranged in sequence on the second recovery pipeline 40 along the conveying direction of the second recovery pipeline 40.

[0067] Through this arrangement design, the particle separation device 41 can first absorb and filter out some particles, thereby reducing the viscosity of the dirty etching liquid delivered to the filter device 42, thereby alleviating the pressure on selecting the filter size of the filter device 42, and also reducing the replacement frequency of the filter device 42.

[0068] Based on the previous Figure 3 The device shown, some embodiments of the present disclosure also provide a method for thinning a wafer, Figure 4An exemplary flow chart of a method 400 for thinning a wafer according to some embodiments of the present disclosure is shown.

[0069] like Figure 4 As shown, in step S401, the dirty etching solution formed by etching the wafer is recovered to the solution recovery tank. In this embodiment, step S401 is consistent with step S201 in the above embodiment, and will not be described in detail here.

[0070] In step S402, the dirty etching liquid is transported to the particle separation device through the second recovery pipeline. In this embodiment, step S402 is consistent with step S202 in the above embodiment, and will not be described in detail here.

[0071] In step S403, the residue in the dirty etching solution is filtered out by using the positive electrode plate in the particle separation device. In this embodiment, step S403 is consistent with step S203 in the above embodiment, and will not be described in detail here.

[0072] In step S404, the dirty etching liquid is transported to the filter device through the second recovery pipeline. In this embodiment, the filter device can use the pore structure of the filter medium to intercept particles larger than the pore size by physical filtration, which can specifically include screening, inertial collision, diffusion and interception. The pore size here can be understood as the filtration size of the filter device.

[0073] In step S405, waste particles in the dirty etching solution are filtered out by a filter device. In this embodiment, steps S404 and S405 can also be performed before steps S402 and S403, that is, the dirty etching solution in the second recovery pipeline can first enter the filter device and then enter the particle separation device.

[0074] In step S406, the filtered etching solution is transported to the wafer etching chamber to etch the wafer. In this embodiment, step S406 is consistent with step S204 in the above embodiment, and will not be described in detail here.

[0075] In practical applications, it is taken into account that the filtering size of the filtering device is limited to a certain range. Since the particle size of the negatively charged residue and waste particles is relatively small, an excessively large filtering size will lead to a poor filtering effect. Moreover, since the etching liquid has a certain viscosity, an excessively small filtering size will easily cause the filtering device to be damaged due to excessive pressure. Therefore, in some embodiments, the particle separation device and the filtering device are arranged in sequence along the conveying direction of the second recovery pipeline, so that after the dirty etching liquid enters the second recovery pipeline, it first enters the particle separation device and then enters the filtering device.

[0076] Based on the above considerations, some embodiments of the present disclosure provide a Figure 5The method shown is to thin the wafer, Figure 5 An exemplary flow chart of a method 500 for thinning a wafer according to yet other embodiments of the present disclosure is shown.

[0077] like Figure 5 As shown, in step S501, the dirty etching solution formed by etching the wafer is recovered to the solution recovery tank. In this embodiment, step S501 is consistent with step S201 in the above embodiment, and will not be described in detail here.

[0078] In step S502, the dirty etching liquid is transported to the particle separation device through the second recovery pipeline. In this embodiment, step S502 is consistent with step S202 in the above embodiment, and will not be described in detail here.

[0079] In step S503, the positive electrode plate in the particle separation device is used to adsorb the residue to obtain a filtered etching solution with reduced viscosity. In this embodiment, the dirty etching solution delivered to the particle separation device contains residue and waste particles, and the negatively charged residue can be filtered out through the adsorption effect of the positive electrode plate, thereby reducing the impurity content in the dirty etching solution and further reducing its viscosity.

[0080] In step S504, the filtered etching liquid is transported to the filter device through the second recovery pipeline. In this embodiment, the viscosity of the etching liquid will affect the selection of the filter size of the filter device. The etching liquid with higher viscosity will bring greater pressure when passing through the filter device with smaller filter size, which is easy to cause damage to the filter device. After reducing some impurities through the particle separation device, a filtered etching liquid with reduced viscosity can be obtained, which is conducive to selecting a filter device with a smaller filter size, achieving better filtering effect, and reducing the replacement frequency of the filter device.

[0081] In step S505, the filter device is used to filter out waste particles in the filtered etching solution to obtain etching solution. In this embodiment, the filter device uses the pore structure of the filter medium to filter out waste particles with a particle size larger than the filter size, further purifies the filtered etching solution, and obtains clean etching solution.

[0082] In step S506, the etching solution is transported to the wafer etching chamber to etch the wafer. In this embodiment, step S506 is consistent with step S204 in the above embodiment, and will not be described in detail here.

[0083] The above describes the equipment and method for recycling and reusing the dirty etching solution using the recycling pipeline and the particle separation device. Through the equipment and method shown in the above embodiments, silicon-containing particles can be separated from the recycled etching solution to form a clean etching solution for thinning the wafer, thereby effectively preventing the residues of the etching process from contaminating the wafer and ensuring the etching effect. In addition, by recycling, filtering and reusing the etching solution, the frequency of acid replacement is greatly reduced, the acid replacement cycle is extended, thereby reducing the loss of consumables and reducing the process cost.

[0084] In the actual BSI backside thinning process, in addition to the accumulation of dirt that will shorten the acid replacement cycle, the continuous consumption of effective etching components in the etching solution will lead to a decrease in the etching rate, which will also shorten the acid replacement cycle. In order to maintain the stability of the etching rate during the process, an additional acid replenishment mechanism can be introduced to micro-replenish the effective etching components. However, the etching rate and acid replenishment concentration are difficult to achieve precise control. Insufficient acid replenishment cannot solve the problem of etching stability, and excessive acid replenishment will also affect the consistency of the etching rate at the beginning and end of the process.

[0085] In order to solve the problems of shortened acid replacement cycle and unstable etching rate caused by the consumption of effective etching components, some embodiments of the present disclosure, based on the previous embodiments, provide a device and method for thinning wafers, which stabilize the etching rate and extend the acid replacement cycle by adding an acid replenishment mechanism.

[0086] In order to better understand the additional acid replenishment mechanism provided by this embodiment, the reaction principle of the BSI backside thinning process is first described below.

[0087] In the BSI backside thinning process, the etching solution used is a HNA solution composed of hydrofluoric acid, nitric acid and acetic acid. The principle of wet etching of wafers with HNA solution can be expressed by the following overall reaction formula:

[0088] ;

[0089] Specifically, in the above chemical reaction process, the reaction process of each effective etching component in the HNA solution and the wafer material includes: first, nitric acid is decomposed to generate , the reaction equation at this time is ;then, It reacts with the silicon on the back of the wafer to form silicon dioxide. The reaction equation is: ; Finally, hydrofluoric acid etching removes silicon dioxide, and the reaction formula is It should be noted that the above reaction formula is that excess hydrofluoric acid reacts with silicon dioxide to generate fluorosilicic acid, that is, .

[0090] According to the above chemical reaction process, the decomposition of nitric acid will generate colored nitrogen dioxide, and the concentration of nitrogen dioxide in the etching solution can reflect the degree of decomposition of nitric acid. According to Lambert-Beer's law, the concentration of reactants is positively correlated with the color depth, that is, the concentration of nitrogen dioxide is positively correlated with the color of the etching solution. Therefore, the concentration of nitrogen dioxide can be inferred from the color information of the etching solution, thereby reflecting the decomposition of nitric acid, and then reflecting the degree of consumption of effective etching components in the HNA solution.

[0091] Based on this, some embodiments of the present disclosure provide a device for thinning a wafer. Figure 6 An exemplary structural diagram of an apparatus for thinning a wafer according to some other embodiments of the present disclosure is shown, Figure 6 As shown, the device includes, in addition to the wafer etching chamber 10, the solution recovery tank 20, the solution holding tank 50, the recovery pipeline and the delivery pipeline, a liquid replenishing device 70, a light detection device 80 and a control device 90. Among them, the light detection device 80 is arranged inside the solution holding tank 50, and it can collect the spectral information of the etching solution in the solution holding tank, thereby reflecting the concentration information of nitrogen dioxide, so as to calculate the decomposition of nitric acid, and then reflect the consumption degree of effective etching components in the HNA solution. As an example, the light detection device can be a spectrometer, a spectrometer, an optical wavelength meter and other devices, which are not limited here.

[0092] The light detection device 80 is communicatively connected to the control device 90. The spectral information collected by the light detection device 80 will be sent to the control device 90 for calculation by the control device 90. The control device 90 is also communicatively connected to the liquid replenishing device 70. Under the control of the control device 90, the liquid replenishing device 70 replenishes the etching liquid in the solution holding tank 50 with corresponding effective etching components according to the consumption of the effective etching components.

[0093] It should be noted that, in some embodiments, the light detection device 80 and / or the liquid replenishing device 70 itself may have a computing functional unit for executing partial information processing. As an example, the computing functional unit of the light detection device 80 itself may directly process the collected spectral information, calculate the concentration information of nitrogen dioxide, and then send the concentration information to the control device. As another example, the computing functional unit of the liquid replenishing device itself may be used to parse the instructions sent by the control device, so as to identify the replenishment amount of the effective etching component that needs to be replenished.

[0094] It should be further explained that, since the adjustment range of the additional acid replenishment mechanism is very fine, high requirements are placed on the accuracy of the spectral information collected by the optical detection device. However, impurities in the etching solution, such as waste particles and residues, can easily affect the color of the etching solution, thereby affecting the reliability of the spectral information collected by the optical detection device. Therefore, the purpose of using the particle separation device on the second recovery pipeline to filter out the residues is not only to prevent them from contaminating the wafer and the etching solution, but also to ensure the accuracy of the spectral information collected by the optical detection device, thereby ensuring the reliable operation of the additional acid replenishment mechanism.

[0095] based on Figure 6 The device shown, some embodiments of the present disclosure also provide a method for implementing an additional acid replenishment mechanism, Figure 7 An exemplary flow chart of a method 700 for executing an additional acid replenishment mechanism according to some embodiments of the present disclosure is shown.

[0096] like Figure 7 As shown, in step S701, the spectral information of the etching solution in the solution holding tank is collected by using a light detection device. In this embodiment, the spectral information can reflect the color depth of the etching solution, thereby reflecting the concentration of nitrogen dioxide, and further reflecting the degree of decomposition of nitric acid. Nitric acid is one of the effective components in the HNA solution, and its decomposition as the first round of chemical reaction of wet etching can reflect the consumption of effective etching components.

[0097] In step S702, the control device is used to analyze the spectral information to obtain the concentration information of the effective etching components in the etching solution. In this embodiment, the controller can calculate the concentration of nitrogen dioxide through the spectral information, and further calculate the decomposition amount of nitric acid, so as to calculate the concentration information of the remaining effective etching components in the etching solution based on the concentration information of the original HNA solution. It should be noted that in some embodiments, the light detection device itself can have a calculation function unit, that is, a control unit can be provided inside the light detection device to analyze the concentration information of the effective etching components in the etching solution according to the spectral information, and then send the concentration information to the external control device.

[0098] In step S703, the concentration information is compared with the concentration reference information by using a control device. In this embodiment, a numerical range can be pre-set as the concentration reference information of the effective etching component. When the concentration information of the effective etching component in the etching solution is lower than the lower limit of the concentration reference information, it means that the effective etching component is consumed excessively, which will affect the etching rate and acid replenishment is required. As an example, in order to stabilize the etching rate of the P-type heavily doped area at 10.01±1.4μm / min and the etching rate of the P-type lightly doped area at 0.14±0.07μm / min, the concentration reference information of nitric acid can be set to 17.5%-18%. It should be noted that this numerical range is only an example, and the concentration reference information can be adjusted according to the actual etching rate requirements.

[0099] According to the reaction principle of HNA solution wet etching wafer, the main factors affecting the etching rate are Therefore, when replenishing the effective etching components, you can either replenish nitric acid or directly replenish , no restriction is made here.

[0100] In step S704, the control device is used to control the liquid replenishing device to replenish the effective etching component into the solution containing pool according to the comparison result. In this embodiment, the control device is in communication connection with the liquid replenishing device, and under the control of the control device, the liquid replenishing device replenishes the effective etching component into the solution containing pool according to the difference information between the concentration information and the concentration reference information.

[0101] It needs to be further explained that Figure 7 The execution method of the additional acid replenishment mechanism shown can be combined with the method for thinning a wafer shown in any of the previous embodiments to form a new method for thinning a wafer. While the recovery pipeline transports the recovered and filtered etching solution to the solution holding tank and the delivery pipeline transports the etching solution in the solution holding tank to the wafer etching chamber, the light detection device in the solution holding tank can detect the etching solution in the solution holding tank in real time and monitor the concentration of the effective etching components therein, and then the control device and the liquid replenishment device are combined to perform acid replenishment. In other words, Figure 7 The steps shown can be combined with the previous Figure 2 , Figure 4 or Figure 5 The steps described are executed simultaneously. While the frequency of acid change is reduced by recycling and filtering the dirty etching solution, an additional acid replenishment mechanism is used to stabilize the etching rate and delay the acid change cycle, thereby reducing the time and raw materials consumed by frequent acid changes, greatly increasing the number of wafers that can be processed in a single acid change cycle, and reducing process costs.

[0102] In summary, the disclosed embodiment provides a device for thinning wafers, which recycles the used etching solution in the wafer etching chamber through the first recovery pipeline and stores it in the solution recovery pool, and filters the dirty etching solution stored in the solution recovery pool through the particle separation device on the second recovery pipeline, purifies it into clean etching solution and reuses it, thereby effectively preventing the residues of the etching process from contaminating the wafer. At the same time, the acid replacement frequency is greatly reduced through recycling, filtering and reuse, and the acid replacement cycle is extended, thereby reducing the loss of consumables and reducing process costs.

[0103] In addition, some embodiments of the present disclosure also provide a device for thinning a wafer, which combines a filtering device and a particle separation device to filter different impurities in the dirty etching solution according to different filtering mechanisms. Furthermore, by designing the filtering device and the particle separation device to be arranged in a specific order on the second recovery pipeline, the selection pressure of the filtering device is reduced, and the purification effect of the dirty etching solution is optimized.

[0104] Furthermore, some embodiments of the present disclosure also provide a device for thinning wafers, which is additionally provided with a light detection device, a liquid replenishing device, and a control device to realize an additional acid replenishing mechanism. While reducing the frequency of acid replacement by recycling and filtering the dirty etching liquid, the additional acid replenishing mechanism is used to stabilize the etching rate and delay the acid replacement cycle, thereby reducing the time and raw materials consumed by frequent acid replacement, greatly increasing the number of wafers that can be processed in a single acid replacement cycle, and reducing process costs. In addition, the filtering function of the particle separation device can effectively avoid the influence of residues on the reliability of the detection results of the light detection device, thereby optimizing the execution effect of the additional acid replenishing mechanism and ensuring the stability of the etching rate.

[0105] In order to implement the method steps described in the foregoing text of this disclosure in conjunction with the accompanying drawings at the software and hardware level, the present disclosure also provides the following Figure 8 The electronic device shown. Specifically, Figure 8 An exemplary structural block diagram of an electronic device 800 according to an embodiment of the present disclosure is shown.

[0106] like Figure 8 As shown, the electronic device 800 disclosed herein may include a processor 810 and a memory 820. Specifically, the memory 820 stores executable program instructions. When the program instructions are executed by the processor 810, the electronic device implements the above-mentioned Figure 2 , Figure 4 , Figure 5 and Figure 7 The method steps are described.

[0107] It is understood that in order to clearly illustrate the solution of the present disclosure and avoid confusion with the prior art, Figure 8The electronic device 800 only shows the components related to the embodiment of the present disclosure, and omits those components that may be necessary for implementing the embodiment of the present disclosure but belong to the scope of the prior art. Therefore, based on the content disclosed in the present disclosure, a person skilled in the art can clearly understand that the electronic device 800 of the present disclosure may also include components related to the embodiment of the present disclosure. Figure 8 The constituent elements shown in are different from the common constituent elements.

[0108] In an exemplary implementation scenario, the above-mentioned processor 810 can control the overall operation of the electronic device 800. For example, the processor 810 can control the operation of the electronic device 800 by executing the program stored in the memory 820. In terms of implementation, the processor 810 of the present disclosure can be implemented by a central processing unit (CPU), an application processor (Application Processor, AP), an artificial intelligence processor chip (Intelligent Processing Unit, IPU), etc. provided in the electronic device 800. Further, the processor 810 of the present disclosure can also be implemented in any appropriate manner. For example, the processor 810 can take the form of a computer-readable medium, a logic gate, a switch, an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), a programmable logic controller, and an embedded microcontroller, etc., such as a microprocessor or a processor and a computer-readable program code (such as software or firmware) that can be executed by the (micro) processor.

[0109] In terms of storage content, the memory 820 can be used to store hardware of various data and instructions processed in the electronic device 800. For example, the memory 820 can store processed data and data to be processed in the electronic device 800. The memory 820 can store data sets that have been processed or to be processed by the processor 810. In addition, the memory 820 can store applications, drivers, etc. to be driven by the electronic device 800. For example: the memory 820 can store various programs to be executed by the processor 810. The memory 820 can be a DRAM, but the present disclosure is not limited to this. In terms of type, the memory 820 may include at least one of a volatile memory or a non-volatile memory. The non-volatile memory may include a read-only memory (ROM), a programmable ROM (PROM), an electrically programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a flash memory, a phase change RAM (PRAM), a magnetic RAM (MRAM), a resistive RAM (RRAM), a ferroelectric RAM (FRAM), etc. The volatile memory may include dynamic RAM (DRAM), static RAM (SRAM), synchronous DRAM (SDRAM), PRAM, MRAM, RRAM, ferroelectric RAM (FeRAM), etc. In an embodiment, the memory 820 may include at least one of a hard disk drive (HDD), a solid state drive (SSD), a high-density flash memory (CF), a secure digital (SD) card, a micro secure digital (Micro-SD) card, a mini secure digital (Mini-SD) card, an extreme digital (xD) card, caches, or a memory stick.

[0110] In summary, the specific functions implemented by the memory 820 and the processor 810 of the electronic device 800 provided in the embodiments of this specification can be explained in comparison with the aforementioned embodiments in this specification, and can achieve the technical effects of the aforementioned embodiments, and will not be repeated here.

[0111] Additionally or optionally, the present disclosure may also be implemented as a non-temporary machine-readable storage medium (or computer-readable storage medium, or machine-readable storage medium) on which computer program instructions (or computer program, or computer instruction code) are stored. When the computer program instructions (or computer program, or computer instruction code) are executed by a processor of an electronic device (or electronic device, server, etc.), the processor executes part or all of the steps of the above-mentioned method according to the present disclosure.

[0112] Although multiple embodiments of the present disclosure have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art may think of many changes, modifications, and alternatives without departing from the thought and spirit of the present disclosure. It should be understood that in the process of practicing the present disclosure, various alternatives to the embodiments of the present disclosure described herein may be adopted. The attached claims are intended to define the scope of protection of the present disclosure, and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A device for thinning a wafer, characterized in that: include: A wafer etching chamber (10), used for placing a wafer and etching the wafer using an etching solution; A solution recovery pool (20) for containing dirty etching solution formed by etching the wafer, wherein the dirty etching solution contains negatively charged residues; A first recovery pipeline (30), one end of which is connected to the wafer etching chamber (10) and the other end of which is connected to the solution recovery tank (20), so as to transport the dirty etching solution from the wafer etching chamber (10) to the solution recovery tank (20); as well as A second recovery pipeline (40) has one end connected to the solution recovery tank (20) so as to extract the dirty etching liquid from the solution recovery tank (20); a particle separation device (41) is provided on the second recovery pipeline (40); in the particle separation device (41), a positive electrode plate and a negative electrode plate are respectively provided on both sides of the conveying direction of the second recovery pipeline (40); the positive electrode plate is used to absorb the residue so as to filter the dirty etching liquid into the etching liquid.

2. The device according to claim 1, characterized in that Also includes: A solution containing tank (50), connected to the other end of the second recovery pipeline (40), and used for receiving the etching solution formed by filtering the dirty etching solution; as well as A liquid delivery pipeline (60) has one end connected to the solution containing tank (50) and the other end connected to the wafer etching chamber (10) so as to deliver the etching solution in the solution containing tank (50) to the wafer etching chamber (10).

3. The device according to claim 2, characterized in that Also includes: Fluid refilling device (70); A light detection device (80), which is arranged inside the solution containing tank (50) and is used to collect spectral information of the etching solution; as well as A control device (90) is respectively connected to the light detection device (80) and the liquid replenishing device (70) for communication, so as to control the liquid replenishing device (70) to replenish effective etching components into the etching solution in the solution containing tank (50) according to the spectral information.

4. The device according to claim 1, characterized in that Also includes: Filtering device (42); The filtering device (42) is arranged on the second recovery pipeline (40) and is used to filter out waste particles in the dirty etching liquid whose particle size is larger than the filtering size.

5. The device according to claim 4, characterized in that The particle separation device (41) and the filtering device (42) are arranged in sequence on the second recovery pipeline (40) along the conveying direction of the second recovery pipeline (40).

6. A method for thinning a wafer, characterized in that: include: Recovering the dirty etching solution formed by etching the wafer in the wafer etching chamber to the solution recovery tank through a first recovery pipeline, wherein one end of the first recovery pipeline is connected to the wafer etching chamber, and the other end is connected to the solution recovery tank, and the dirty etching solution contains negatively charged residues; The dirty etching solution in the solution recovery tank is transported to the particle separation device through a second recovery pipeline, wherein one end of the second recovery pipeline is connected to the solution recovery tank, the particle separation device is arranged on the second recovery pipeline, and in the particle separation device, a positive electrode plate and a negative electrode plate are respectively arranged on both sides of the transport direction of the second recovery pipeline; Adsorbing the residue using the positive electrode plate to obtain a filtered etching solution; and The etching solution is transported to the wafer etching chamber through the second recovery pipeline to etch the wafer.

7. The method according to claim 6, characterized in that The method of conveying the etching solution to the wafer etching chamber through the second recovery pipeline to etch the wafer comprises: delivering the filtered etching solution to a solution containing tank through the second recovery pipeline, wherein the other end of the second recovery pipeline is connected to the solution containing tank; and The etching liquid in the solution containing tank is transported to the wafer etching chamber through a liquid delivery pipeline to etch the wafer in the wafer etching chamber, wherein one end of the liquid delivery pipeline is connected to the solution containing tank, and the other end is connected to the wafer etching chamber.

8. The method according to claim 7, characterized in that A light detection device is provided in the solution containing tank, the light detection device is in communication connection with the control device, and the control device is also in communication connection with the liquid replenishing device, and the method further comprises: Using the light detection device to collect spectrum information of the etching solution in the solution containing tank; Analyzing the spectral information using the control device to obtain concentration information of effective etching components in the etching solution; comparing the concentration information with concentration reference information using the control device; and The control device is used to control the liquid replenishing device to replenish effective etching components into the solution containing pool according to the comparison result.

9. The method according to claim 6, characterized in that The second recovery pipeline is further provided with a filtering device, wherein after the dirty etching solution formed by etching the wafer in the wafer etching chamber is recovered to the solution recovery pool through the first recovery pipeline, the method further comprises: delivering the dirty etching liquid to the filtering device through the second recovery pipeline; and The filter device is used to filter out waste particles in the dirty etching solution whose particle size is larger than the filter size.

10. The method according to claim 6, characterized in that On the second recovery pipeline, a particle separation device and a filtering device are sequentially arranged along the conveying direction of the second recovery pipeline, wherein the positive electrode plate is used to adsorb the residue to obtain the filtered etching solution, which includes: Adsorbing the residue using the positive electrode plate to obtain a filtered etching solution with reduced viscosity; delivering the filtered etching liquid to the filtering device through the second recovery pipeline; and The filtering device is used to filter out waste particles with a particle size larger than the filtering size in the filtered etching liquid to obtain the etching liquid.

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