Reworking method of CIS wafer

Abstract

The invention discloses a reworking method of a CIS wafer, and the method comprises the steps: firstly carrying out the pretreatment of an exposed photoresist layer on the surface of the to-be-reworked CIS wafer through employing a fluoroalcohol compound solution, can effectively prevent the surface of the photoresist layer from forming a compact carbonization layer in a subsequent ashing process, and facilitates the improvement of the etching efficiency and the etching effect; and then the pre-treated exposed photoresist layer is sequentially ashed, soaked, stripped and cleaned, so that the exposed photoresist layer on the surface of the CIS wafer can be quickly and completely removed, and pollutants generated in the treatment process can be effectively removed while the CIS wafer is effectively protected. The method has the advantages of being simple in process, convenient to operate, low in cost, high in removal efficiency, good in removal effect, small in damage to the CIS wafer and the like, improvement of the remanufacturing efficiency and the remanufacturing effect of the CIS wafer is facilitated, market competitiveness of products can be improved while product defects are reduced, the yield is increased and the cost is reduced, and the method is high in use value and good in application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of CIS wafer surface treatment and relates to a CIS wafer reprocessing method. Background Art

[0002] The color filter array (CFA) in a CMOS image sensor (CIS) achieves color imaging through red (R), green (G), and blue (B) filters. The core structure of the CFA includes a microlens and a color filter layer. Furthermore, before the end of the CMOS image sensor manufacturing process or wafer testing, if minor defects (such as color shift or uneven coating) are discovered in the CFA photoresist layer (e.g., Bayer array), the defective areas must be selectively removed and re-coated. This means that the CFA must be completely dismantled before rework.

[0003] Currently, there are two common methods for selectively removing CFA on the surface of CIS wafers: the first method is the PH rework process, such as Figure 1 As shown, the specific method is wet stripping of photoresist, that is, after the defects are found before the photoresist is exposed, the photoresist is removed using a developer (such as TMAH) or a photoresist stripper (such as NMP / DMSO based), and then the CIS wafer surface is cleaned using an acidic solution. The second method is the NON-PH rework process, such as Figure 2 As shown in FIG, this is a method that combines a plasma ashing process with a wet cleaning process. Specifically, for CIS wafers with defects found after photoresist exposure, a plasma ashing process is first used to ash the exposed photoresist layer on the CIS wafer surface, and then a wet cleaning process is used to clean the CIS wafer surface. However, this method still has the following defects: (1) Figure 3As shown, due to the heavy doping of a small amount of metal elements in the Color Filter of the CFA, during the ashing process, these metal elements will agglomerate with the organic material in the photoresist layer and form residues, which will cause new contamination and damage to the wafer, and these residues are difficult to be effectively removed by subsequent wet cleaning process, thereby causing the efficiency of rework to be poor; (2) The plasma ashing process usually requires very high energy and temperature, such as a temperature as high as 250°C or more, which will cause the cross-linking reaction of the carbon chain on the surface of the photoresist (the proportion of C-C / C=C bond increases), so that the surface of the photoresist layer is carbonized and a dense carbonized layer is formed, and the resistivity of the carbonized layer is very high, which will hinder the penetration of O free radicals into the photoresist layer, thereby causing the efficiency of rework to be poor; in addition, if the temperature of the plasma ashing process is reduced, it is difficult to form high-temperature, high-energy, and high-density O plasma, thereby making it difficult to effectively remove the CFA and not conducive to improving the efficiency of rework; (3) During the ashing process, the surface chemical bonds are destroyed, so that the surface of the polymer is inert, at this time the surface lacks polar groups, the surface energy is insufficient, and the adhesion is decreased, thereby causing the new CFA to be difficult to uniformly and stably adhere to the surface of the CIS wafer, and it is difficult to achieve rework. At the same time, with the increase of process complexity, such as more advanced processes of CFA and smaller pixel processes, higher requirements are put forward for the cleaning process. Not only the removal efficiency and removal effect need to be improved, but also the cross-contamination risk of residual by-products needs to be prevented to ensure the smooth completion of rework.

[0004] Therefore, how to overcome the technical problems existing in the above-mentioned rework method for CIS wafers with defects after photoresist exposure, and obtain a method for selectively removing surface defects of CIS wafers with simple process, convenient operation, low cost, high removal efficiency, good removal effect, and small damage to CIS wafers, has important promoting significance for reducing defects, improving yield, reducing cost, and improving product market competitiveness. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a rework method for CIS wafers with simple process, convenient operation, low cost, high removal efficiency, good removal effect, and small damage to CIS wafers.

[0006] To solve the above technical problems, the present application adopts the following technical solutions: A rework method for a CIS wafer, comprising the following steps: using a fluorine alcohol compound solution to pretreat an exposed photoresist layer on the surface of a CIS wafer to be reworked.

[0007] The rework method described above is further improved, and the concentration of the fluorine alcohol compound solution is 0.5 wt% to 2 wt%.

[0008] The reworking method, further improved, wherein the fluoroalcohol compound solution is prepared by dissolving the fluoroalcohol compound in water.

[0009] The reworking method, further improved, wherein the fluoroalcohol compound includes one or a combination of hexafluoroisopropanol, 2-fluoroethanol, 1,3-difluoro-2-propanol, 2,2-difluoroethanol, and 2,2,2-trifluoroethanol.

[0010] The reworking method, further improved, wherein the pretreatment is soaking the CIS wafer to be reworked in the fluoroalcohol compound solution; and the soaking time is 2-5 minutes.

[0011] The reworking method, further improved, wherein after the pretreatment, the method further includes the following processing: (1) using a plasma ashing process to ash the exposed photoresist layer on the surface of the pretreated CIS wafer; (2) soaking the CIS wafer ashed in step (1) in a stripping solution; (3) stripping, cleaning, and removing the exposed photoresist layer and contaminants on the surface of the CIS wafer obtained after soaking in step (2); (4) repeating the operations in steps (1)-(3) until the surface quality of the CIS wafer meets the reworking requirements.

[0012] The reworking method, further improved, wherein in step (1), the ashing equipment is used to ash the exposed photoresist layer on the surface of the pretreated CIS wafer in the plasma ashing process; the ashing equipment includes a reaction chamber, and a plurality of permanent magnets are symmetrically arranged on the top and side of the reaction chamber.

[0013] The reworking method, further improved, wherein in step (1), the thickness of the exposed photoresist layer on the surface of the CIS wafer is retained to be 10-20% of the initial thickness during the first ashing process.

[0014] The reworking method, further improved, wherein in step (1), the ashing process is performed at a temperature of 100-160°C.

[0015] The reworking method, further improved, wherein in step (2), the stripping solution is EKC265; and the soaking time is 10-15 minutes.

[0016] The reworking method, further improved, further including the following processing: (5) the CIS wafer with surface quality meeting the heavy-duty requirement is subjected to surface repair treatment.

[0017] The heavy-duty method is further improved, and pulse plasma is used to perform surface repair treatment on the CIS wafer with surface quality meeting the heavy-duty requirement; at least one of Ar / N2 and He / N2 is used as a reaction gas in the surface repair treatment; and the surface repair treatment is performed at a temperature < 80 DEG C.

[0018] Compared with the prior art, the present application has the following advantages: (1) In view of the problem of low etching efficiency and poor etching effect caused by the formation of a dense carbonized layer on the surface of the photoresist layer in the prior art heavy-duty method, the present application provides a heavy-duty method for a CIS wafer, in which a fluorine alcohol compound solution is used to pretreat the exposed photoresist layer on the surface of the CIS wafer to be subjected to heavy-duty treatment, and the unexpected technical effect is that a C-F chemical bond can be formed on the exposed photoresist layer on the surface of the CIS wafer in the pretreatment process of the fluorine alcohol compound solution, which can effectively prevent the formation of a dense carbonized layer on the surface of the photoresist layer in the subsequent ashing process, thereby improving the etching efficiency and etching effect of the plasma on the photoresist layer; specifically, the fluorine alcohol compound is polar matched with the photoresist layer, so that the F atom in the fluorine alcohol compound can replace the H in the C-H / C=C bond on the surface of the photoresist layer through a nucleophilic substitution reaction to form a C-F chemical bond, which not only reduces the stability of the carbon network structure, but also promotes the formation of F* free radicals in the subsequent ashing process, such as F-O* transition state intermediates, which can reduce the C-C breaking activation energy to generate volatile CF x O y products, and at the same time, the surface energy of the CIS wafer can be optimized, thereby promoting the formation of a carbonized layer with micro-cracks on the surface of the photoresist layer in the ashing process, and further improving the porosity of the carbonized layer to promote the penetration depth of the plasma, and significantly improving the etching efficiency and etching effect of the plasma on the photoresist layer. (2) In view of the problems that the existing heavy-duty method is difficult to effectively remove the residues on the surface of the CIS wafer and is easy to cause damage to the CIS wafer, the processing procedure of the CIS wafer to be reworked is optimized in the present application, and the unexpected technical effects are: first, a fluorine alcohol compound solution is used to pretreat the exposed photoresist layer on the surface of the CIS wafer to be reworked, which can effectively prevent the formation of a dense carbonized layer on the surface of the photoresist layer, and then the surface of the CIS wafer is sequentially subjected to ashing, soaking, peeling and cleaning, under the combined action of plasma and peeling liquid, the exposed photoresist layer on the surface of the CIS wafer can be quickly and completely removed, and more importantly, the thickness of the exposed photoresist layer on the surface of the CIS wafer is 10% to 20% of the initial thickness during the first ashing process, at this time, the metal particles that fall off will be captured in the photoresist residual layer due to surface adsorption energy, and byproducts, particles and residues generated during the ashing process will also remain on the photoresist layer, thereby the protective effect of the photoresist residual layer can be used to avoid the damage of the above-mentioned pollutants to the CIS wafer, the adhesion of the surface of the CIS wafer is prevented from being reduced, and the reuse effect of the CIS wafer is improved, which is beneficial to reduce the production cost, and then the pollutants on the surface of the CIS wafer can be effectively removed through simple peeling and cleaning.

[0019] (3) In the application, the ashing equipment comprises a reaction chamber, a plurality of permanent magnets are arranged on the top and bottom of the reaction chamber respectively, and the permanent magnets are symmetrically arranged on the top and side of the reaction chamber, so that a strengthened magnetic field can be constructed outside the reaction chamber of the ashing equipment, and the unexpected technical effects are: (a) the addition of the axial magnetic field can constrain electrons, improve ionization efficiency, increase the concentration of O free radicals, strengthen etching efficiency, guide ions to move in the direction of the wafer, make electrons revolve around the magnetic field line by the axial magnetic field, enhance directionality, and reduce lateral diffusion; (b) the permanent magnet pair structure is arranged on the top (upper part) of the reaction chamber, and the plasma dissociation and density can be enhanced by the action of the permanent magnet; when a static magnetic field is applied, the electron does spiral motion in the magnetic field, and when the cyclotron frequency matches the microwave frequency (2.45 GHz), resonance occurs, the electron kinetic energy increases sharply, the electron mean free path is lengthened by the magnetic field, and the ionization efficiency is improved; (c) a plurality of permanent magnets are arranged on the side of the reaction chamber, a magnetic ring is installed outside, the magnetic field direction is perpendicular to the particle motion direction, the charged particles are deflected by the Lorentz force, only neutral free radicals are allowed to pass through, the directionality is improved, and low-energy ions can be selectively filtered by adjusting the magnetic field gradient, thereby reducing the damage to the CIS wafer; (d) the strengthened magnetic field is constructed outside (top and bottom) of the reaction chamber, the plasma dissociation efficiency and directionality can be enhanced, and the plasma ashing process temperature can be significantly reduced, so that the etching rate and etching effect can be improved at a lower temperature, thereby the exposed photoresist layer on the surface of the CIS wafer can be removed quickly and completely, the processing cost can be significantly reduced, and the adverse effects of high temperature and high energy on the CIS wafer can be effectively avoided, which is beneficial to reducing the damage of high temperature and high energy to the CIS wafer, and can effectively reduce the generation of metal residues (Metal residue) and polymer residues (PR residue), and is beneficial to further improving the remanufacturing efficiency and effect of the CIS wafer.

[0020] (4) In the application, after the CIS wafer to be remanufactured is treated by combining plasma ashing and wet stripping, the CIS wafer with surface quality meeting the remanufacturing requirements is subjected to surface repair treatment, and the unexpected technical effects are: the surface defects of the CIS wafer can be effectively repaired, and the use effect of the CIS wafer in the subsequent remanufacturing process can be improved.

[0021] It can be seen that the unexpected technical effects brought by the CIS wafer rework method of the application are that not only the exposed photoresist layer on the surface of the CIS wafer can be quickly and completely removed, but also the residual contaminants on the surface of the CIS wafer can be quickly and effectively removed under the premise of effectively protecting the CIS wafer, and the CIS wafer rework method has the advantages of simple process, convenient operation, low cost, high removal efficiency, good removal effect, small damage to the CIS wafer and the like, and is beneficial to improving the rework efficiency and rework effect of the CIS wafer, reducing product defects, improving yield, reducing cost, improving market competitiveness of the product, and has high use value and good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application.

[0023] Figure 1 It is a flowchart of a conventional PH rework process.

[0024] Figure 2 It is a flowchart of a conventional NON-PH rework process.

[0025] Figure 3 It is a surface SEM image of a CIS wafer obtained after the conventional NON-PH rework process.

[0026] Figure 4 It is a rework flowchart of a CIS wafer in Embodiment 1 of the application.

[0027] Figure 5 It is a process flowchart of pretreatment in Embodiment 1 of the application.

[0028] Figure 6 It is a surface SEM image of a CIS wafer to be reworked in Embodiment 1 of the application.

[0029] Figure 7 It is a structural schematic diagram of an ashing device in Embodiment 1 of the application.

[0030] Figure 8 It is a magnetic flux density distribution diagram of a reaction chamber in Embodiment 1 of the application.

[0031] Figure 9 It is a surface SEM image of a CIS wafer after rework in Embodiment 1 of the application.

[0032] Figure 10 It is a surface defect effect diagram of a CIS wafer after rework in Embodiment 1 of the application.

[0033] Figure 11This is the surface SEM image of the CIS wafer after reprocessing in Comparative Example 1.

[0034] Figure 12 This is a diagram showing the surface defects of the CIS wafer after reprocessing in Comparative Example 1.

[0035] Legend: 1. Reaction chamber; 2. Permanent magnet. DETAILED DESCRIPTION

[0036] The technical solutions of the present invention are described below in detail and in full detail with reference to the accompanying drawings. It should be understood that the embodiments described herein are only a portion of the embodiments of the present invention, rather than all of them. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0037] Example 1 A CIS wafer reprocessing method, such as Figure 4 As shown, the following steps are included: S1. Pre-treating the exposed photoresist layer on the surface of the CIS wafer to be reworked using a fluoroalcohol compound solution, specifically: A CIS wafer with defects after photoresist exposure is used as a CIS wafer to be reworked, and the CIS wafer to be reworked is immersed in a hexafluoroisopropanol solution with a mass concentration of 1.5wt% for 3 minutes.

[0038] In this step, the reaction that occurs is: C x H y O z (Photoresistance main chain) + (CF3)2CHOH → C a H b O c F d + by-products, in this reaction formula, x, y, z, a, b, c, d represent the atomic number of each element. For example, when the photoresist backbone in the exposed photoresist layer can be C6H 10 O2, but not limited to it.

[0039] At the same time, if Figure 5 As shown, fluorine element is introduced into the surface of the exposed photoresist layer after pretreatment.

[0040] In this step, the surface morphology of the CIS wafer to be reworked is as follows: Figure 6 shown. Figure 6 In the middle, the left picture is the color filter, and the right picture is the Micro lens. Figure 6 It can be seen that there are obvious defects in the photoresist layer on the surface of the CIS wafer to be reworked after the photoresist is exposed.

[0041] In step S1 of other embodiments, the concentration of the fluorinated alcohol compound solution used can also be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, but not limited to this. However, when the concentration of the fluorinated alcohol compound solution is less than 0.5 wt%, the fluorination layer coverage is insufficient, and the fluorination effect is not good, and when the concentration of the fluorinated alcohol compound solution is higher than 2.0 wt%, it will cause the photoresist layer to swell, and the fluorinated alcohol compound solution will penetrate into the bottom of the photoresist layer, which is easy to cause damage to the wafer.

[0042] In this embodiment, the hexafluoroisopropanol solution is prepared by dissolving hexafluoroisopropanol in water.

[0043] In step S1 of other embodiments, the fluorinated alcohol compound used can also be 2-fluoroethanol, 1,3-difluoro-2-propanol, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, and combinations thereof, but not limited to this. However, other fluorine-containing compounds cannot be used to process the CIS wafer in addition to the fluorinated alcohol compound, for example, in fluorinated ether compounds, there is no active group, which cannot form a C-F bond with the photoresist layer; in fluorinated ketone compounds, due to the presence of carbonyl groups, they are highly oxidizing and easy to cause over-etching, and they are highly polar and easy to over-swelling photoresist, and have low boiling point, high volatility, resulting in instability and cannot be used.

[0044] In step S1 of other embodiments, the soaking time can also be 2 min, 2.5 min, 3.5 min, 4 min, 4.5 min, 5 min, but not limited to this. However, when the soaking time is short, the thickness of the fluorinated layer formed is low, and the inhibition effect on carbonization is poor, and when the soaking time is too long, the fluorinated alcohol compound solution will penetrate into the bottom layer of the photoresist layer, which will cause damage to the wafer.

[0045] In the present application, before the exposed photoresist layer on the surface of the CIS wafer to be reworked is subjected to ashing treatment, the exposed photoresist layer on the surface of the CIS wafer to be reworked is pretreated with a fluorinated alcohol compound solution, which can form a C-F chemical bond on the exposed photoresist layer on the surface of the CIS wafer, thereby effectively preventing the formation of a dense carbonized layer on the surface of the photoresist layer during the subsequent ashing process, thereby facilitating the etching efficiency and etching effect of the plasma on the photoresist layer during the subsequent ashing process.

[0046] S2, using a plasma ashing process to ash the exposed photoresist layer on the surface of the CIS wafer pretreated in step S1, specifically: The pretreated CIS wafer surface is ashed by an ashing device (for example, a plasma stripper, Plasma Asher). During the ashing process, the ashing device forms a plasma, and under the action of the plasma (for example, O2 plasma, the main active species of which is O radical and O + ion), the exposed photoresist layer on the CIS wafer surface, including the micro lens (Micro Lens) and the color filter (Color Filter), is quickly and completely removed.

[0047] In the first ashing process in step S2, the thickness of the exposed photoresist layer remaining on the CIS wafer surface is 20% of the initial thickness. Specifically, the original thickness of the photoresist layer on the CIS wafer surface is 1 μm to 2 μm, and after the first ashing process, the thickness of the exposed photoresist layer remaining on the CIS wafer surface is 0.2 μm to 0.4 μm. In the present application, by retaining a certain thickness of the photoresist layer on the CIS wafer surface, the detached metal particles can be captured in the photoresist residual layer due to surface adsorption, and byproducts, particles, residues, etc. generated during the ashing process will also remain on the photoresist layer. Thus, the protective effect of the photoresist residual layer can be used to avoid damage to the CIS wafer caused by the above-mentioned pollutants, thereby avoiding the decrease in the adhesion of the CIS wafer surface and improving the reuse effect of the CIS wafer, which is beneficial to reducing production costs.

[0048] As shown in Figure 7 , the ashing device used in step S2 includes a reaction chamber 1, and a plurality of permanent magnets 2 are arranged on the top and side of the reaction chamber 1. Specifically, four permanent magnets are arranged on the top of the reaction chamber 1, and the permanent magnets are arranged in a central symmetry. Two permanent magnets are arranged on the side of the reaction chamber 1, and the permanent magnets are arranged in a symmetry on the side of the reaction chamber 1. The surface magnetic flux density of the permanent magnets ranges from 0.8 to 1.5 T (8000 to 15000 Gauss). As can be seen, a strengthened magnetic field is formed outside the reaction chamber 1 of the ashing device, and the magnetic flux density distribution of the magnetic field of the reaction chamber 1 is shown in Figure 8It can be known that the unexpected technical effects brought are: (a) adding an axial magnetic field can constrain electrons, improve ionization efficiency, increase O radical concentration, strengthen etching efficiency, and guide ions to move towards the wafer direction, utilize the axial magnetic field to make electrons spiral around the magnetic field lines, enhance directionality, and reduce lateral diffusion; (b) a permanent magnet pair structure is arranged at the top (upper part) of the reaction chamber, and the plasma dissociation and density can be enhanced by the action of the permanent magnet; when a static magnetic field is applied, electrons spiral in the magnetic field, and when the cyclotron frequency matches the microwave frequency (2.45 GHz), resonance occurs, the electron kinetic energy increases sharply, the electron mean free path is lengthened by the magnetic field, and the ionization efficiency is improved; (c) a plurality of permanent magnets are arranged on the side of the reaction chamber, and a magnetic ring is installed outside, the magnetic field direction is perpendicular to the particle motion direction, the charged particles are deflected by the Lorentz force, only the neutral radicals are allowed to pass through, the directionality is improved, and low-energy ions can be selectively filtered by adjusting the magnetic field gradient to reduce damage to the CIS wafer; (d) a strengthened magnetic field is constructed outside (top and bottom) of the reaction chamber, which can significantly reduce the plasma ashing process temperature under the premise of enhancing the plasma dissociation efficiency and directionality.

[0049] In this step S2, the ashing treatment is performed at a temperature of 120℃.

[0050] In other embodiments, the temperature of the ashing treatment in step S2 can also be 100℃, 110℃, 115℃, 125℃, 130℃, 140℃, 150℃, 160℃.

[0051] Compared with the conventional plasma ashing process, the plasma ashing process adopted by the present application can improve the etching rate and etching effect at a lower temperature, significantly reduce the processing cost while rapidly and completely removing the exposed photoresist layer on the CIS wafer surface, and effectively avoid the adverse effects of high temperature and high energy on the CIS wafer, which is beneficial to reducing the damage caused by high temperature and high energy to the CIS wafer, and also effectively reduces the generation of metal residues (Matel residue) and polymer residues (PR residue), which is beneficial to further improving the remanufacturing efficiency and remanufacturing effect of the CIS wafer.

[0052] In this step S2, the steps of the plasma ashing process include: (1) stable chamber state (ventilation, stable pressure); (2) O2 is introduced, radio frequency is applied, plasma is generated, and RIE (reactive ion etching) is performed; (3) stop ventilation, end process.

[0053] S3, immerse the CIS wafer obtained after the ashing treatment in step S2 in a stripping solution, specifically: The graying treated CIS wafer is soaked in EKC265 (hydroxylamine / ethanol amine group) for 12 minutes. The chelating agent EKC265 forms a stable complex with the metal particles, and EKC265 can reduce the interfacial tension. The EKC265 can improve the capture effect of the residual photoresist layer on the metal particles and other pollutants, and can also reduce the adsorption of the photoresist layer on the CIS wafer, thereby effectively reducing the peeling difficulty of the photoresist layer. At the same time, the EKC265 used can also etch a small amount of photoresist layer and metal, and can also enhance the removal effect of pollutants.

[0054] In step S3 of other embodiments, the soaking time of the CIS wafer in the stripping liquid (EKC265) can also be 10 minutes, 11 minutes, 13 minutes, 14 minutes, 15 minutes, but is not limited thereto. However, if the soaking time is too short, the photoresist layer cannot be effectively removed, and if the soaking time is too long, the Al-Cu pad will be damaged, which will damage the substrate.

[0055] S4, stripping the CIS wafer obtained after soaking in step S3 to remove the residual photoresist layer on the surface of the CIS wafer, and cleaning the surface of the CIS wafer with deionized water to remove the pollutants on the surface of the CIS wafer.

[0056] S5, repeating the operations in steps S2 to S4 until the surface quality of the CIS wafer meets the rework requirements.

[0057] In step S5, graying, soaking, stripping, and cleaning are a cycle period. After each cycle, the surface defects of the CIS wafer are detected until the surface quality of the CIS wafer meets the rework requirements.

[0058] S6, surface repair treatment is performed on the CIS wafer whose surface quality meets the rework requirements, specifically: The surface quality of the CIS wafer obtained in step S5 meets the rework requirements, and the surface repair treatment is performed on the CIS wafer by using pulsed plasma. Specifically, in an etching machine (for example, it can be a plasma etching machine), Ar / N2 is introduced to form Ar / N2 plasma to repair the surface of the CIS wafer at a low energy, and the surface repair treatment is performed at a temperature of 20°C to 40°C. The surface repair treatment is used to repair the surface defects of the CIS wafer, which is beneficial to improve the use effect of the CIS wafer in the subsequent rework process.

[0059] The surface morphology and surface defects of the CIS wafer treated in step S6 in Example 1 are detected, and the results are shown in Figure 9 and Figure 10 .

[0060] from Figure 9It can be seen that the exposed photoresist layer on the surface of the CIS wafer has been effectively removed after the method of the present application, that is, the CFA has been completely removed from the surface of the CIS wafer. At the same time, combining with the surface morphology of the CIS wafer after the method of the present application, it can be seen that the surface of the CIS wafer is very clean, and the CFA has been completely removed from the surface of the CIS wafer. Figure 10 It can be seen that the defects on the surface of the CIS wafer after the method of the present application are very few (very few red dots in the figure), which indicates that the method of the present application basically does not cause damage to the CIS wafer.

[0061] Comparative Example 1 A rework method of a CIS wafer is basically the same as Example 1, the only difference is that in Comparative Example 1, the fluorine alcohol compound solution is not used to pretreat the exposed photoresist layer on the surface of the CIS wafer.

[0062] The surface morphology and surface defects of the CIS wafer after treatment in Comparative Example 1 were detected, and the results are shown in Figure 11 and Figure 12 .

[0063] It can be seen from Figure 11 that when the CIS wafer is not treated with a fluorine alcohol compound solution, the exposed photoresist layer on the surface of the CIS wafer cannot be effectively removed under the same conditions, and it is difficult to effectively remove the CFA on the surface of the CIS wafer. At the same time, combining with the surface morphology of the CIS wafer after the method of the present application, Figure 12 it can be seen that after the method in Comparative Example 1, there are a large number of defects on the surface of the CIS wafer (a large number of red dots in the figure), which cannot be used for rework.

[0064] From the above results, compared with the conventional rework method, the rework method of the CIS wafer of the present application, by pretreating the exposed photoresist layer on the surface of the CIS wafer to be reworked with a fluorine alcohol compound solution, and by optimizing the treatment process, the unexpected technical effects are: not only can the exposed photoresist layer on the surface of the CIS wafer be quickly and completely removed, but also the residual contaminants on the surface of the CIS wafer can be quickly and effectively removed under the premise of effectively protecting the CIS wafer, which has the advantages of simple process, convenient operation, low cost, high removal efficiency, good removal effect, small damage to the CIS wafer, etc., which is conducive to improving the rework efficiency and rework effect of the CIS wafer, reducing product defects, improving yield, reducing cost, and improving the market competitiveness of the product, and has high use value and good application prospect.

[0065] The above examples are only preferred embodiments of the present application, and the protection scope of the present application is not limited to the above examples. Any technical solution falling within the scope of the present application is within the protection scope of the present application. It should be pointed out that improvements and refinements made by ordinary skilled persons in the art without departing from the principles of the present application should also be considered within the protection scope of the present application.

Claims

1. A CIS wafer reprocessing method, characterized in that: The following steps are involved: A fluoroalcohol compound solution is used to pretreat the exposed photoresist layer on the surface of the CIS wafer to be reworked.

2. The reworking method according to claim 1, wherein: The concentration of the fluoroalcohol compound solution is 0.5 wt % to 2 wt %.

3. The reworking method according to claim 2, characterized in that: The fluoroalcohol compound solution is prepared by dissolving a fluoroalcohol compound in water; the fluoroalcohol compound includes one or more combinations of hexafluoroisopropanol, 2-fluoroethanol, 1,3-difluoro-2-propanol, 2,2-difluoroethanol, and 2,2,2-trifluoroethanol.

4. The reworking method according to claim 3, characterized in that: The pretreatment is to immerse the CIS wafer to be reworked in a fluoroalcohol compound solution; the immersion time is 2 minutes to 5 minutes.

5. The reworking method according to any one of claims 1 to 4, characterized in that: After the pre-processing is completed, the following processing is also included: (1) Using plasma ashing process to ash the exposed photoresist layer on the surface of the CIS wafer after pretreatment; (2) immersing the CIS wafer obtained by ashing in step (1) in a stripping solution; (3) peeling and cleaning the CIS wafer obtained after soaking in step (2) to remove the exposed photoresist layer and contaminants on the surface of the CIS wafer; (4) Repeat steps (1) to (3) until the surface quality of the CIS wafer meets the rework requirements.

6. The reworking method according to claim 5, characterized in that: In step (1), in the plasma ashing process, an ashing device is used to ash the exposed photoresist layer on the surface of the pre-treated CIS wafer; the ashing device includes a reaction chamber, and a plurality of permanent magnets are respectively provided on the top and side of the reaction chamber; the permanent magnets are symmetrically arranged on the top of the reaction chamber; and the permanent magnets are symmetrically arranged on the side of the reaction chamber.

7. The reworking method according to claim 6, characterized in that: In step (2), during the first ashing process, the thickness of the exposed photoresist layer on the surface of the CIS wafer is retained to be 10% to 20% of the initial thickness; the ashing process is performed at a temperature of 100° C. to 160° C.

8. The reworking method according to claim 5, characterized in that: In step (2), the stripping liquid is EKC265; and the soaking time is 10 min to 15 min.

9. The reworking method according to claim 5, characterized in that: The following processing is also included: (5) Perform surface repair on CIS wafers whose surface quality meets the rework requirements.

10. The reworking method according to claim 9, characterized in that: Pulsed plasma is used to perform surface repair treatment on CIS wafers whose surface quality meets heavy industry requirements; the reaction gas used in the surface repair treatment process is at least one of Ar / N2 and He / N2; the surface repair treatment is performed at a temperature of less than 80°C.

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