A rework method for CIS wafers

Abstract

This invention discloses a reprocessing method for CIS wafers. First, a fluoroalcohol compound solution is used to pre-treat the exposed photoresist layer on the surface of the CIS wafer to be reprocessed. This effectively prevents the formation of a dense carbonization layer on the photoresist layer surface during subsequent ashing, which is beneficial for improving etching efficiency and effect. Then, the pre-treated exposed photoresist layer is sequentially ashed, soaked, peeled off, and cleaned. This method can quickly and completely remove the exposed photoresist layer from the CIS wafer surface, and effectively remove contaminants generated during the process while effectively protecting the CIS wafer. It has advantages such as simple process, convenient operation, low cost, high removal efficiency, good removal effect, and minimal damage to the CIS wafer. It is beneficial for improving the reprocessing efficiency and effect of CIS wafers, reducing product defects, increasing yield, lowering costs, and enhancing the market competitiveness of products. It has high practical value and good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of CIS wafer surface treatment technology, and relates to a rework method for CIS wafers. Background Technology

[0002] In a CMOS image sensor (CIS), the color filter array (CFA) achieves color imaging through red (R) / green (G) / blue (B) filters. The core structure of the CFA includes microlenses and color filters. However, if minute defects (such as color shifts or uneven coating) are found in the CFA photoresist layer (e.g., a Bayer array) before the CMOS image sensor manufacturing process is completed or before wafer testing, the defective areas need to be selectively removed and recoated. In other words, the CFA must be completely removed before rework.

[0003] Currently, there are two main methods commonly used for selectively removing CFA from the surface of CIS wafers: the first method is the PH rework process, such as... Figure 1 As shown, the first method involves wet stripping of the photoresist. This means that after defects are detected in the photoresist before exposure, it is removed using a developer (such as TMAH) or a photoresist stripper (such as NMP / DMSO-based), followed by cleaning of the CIS wafer surface with an acidic solution. The second method is a non-pharmaceutical rework process, such as... Figure 2 As shown, this is a method combining plasma ashering and wet cleaning. Specifically, for CIS wafers with defects found after photoresist exposure, plasma ashering is first used to asher the exposed photoresist layer on the surface of the CIS wafer, and then wet cleaning is used to clean the surface of the CIS wafer. However, this method still has the following defects: (1) As shown Figure 3As shown, since the CFA's Color Filter is heavily doped with a small amount of metal elements, during the ashing process, these metal elements will agglomerate with the organic materials in the photoresist layer and form residues, which will cause new contamination and damage to the wafer. Moreover, these residues are difficult to remove effectively by subsequent wet cleaning processes, which leads to a decrease in rework efficiency; (2) Plasma ashing processes usually require very high energy and temperature, such as temperatures as high as 250°C or above. This will cause the carbon chains on the photoresist surface to undergo cross-linking reactions (the ratio of CC / C=C bonds increases), causing carbonization on the photoresist layer surface and forming a dense carbonized layer. The resistivity of the carbonized layer is very high, which will hinder the penetration of O free radicals into the photoresist layer, thus leading to a decrease in rework efficiency; in addition, if the temperature of the plasma ashing process is reduced, it will be difficult to form high-temperature, high-energy, and high-density O plasma, which will make it difficult to effectively remove CFA and will also be detrimental to improving rework efficiency; (3) During the ashing process, the surface chemical bonds will be destroyed, making the polymer surface inert. At this time, the surface lacks polar groups, the surface energy is insufficient, and the adhesion decreases, which will make it difficult for new CFA to be uniformly and stably attached to the CIS wafer surface, making it difficult to achieve rework. At the same time, with the increase in process complexity, such as the more advanced process / smaller pixel process of CFA, higher requirements are put forward for the cleaning process. It is necessary not only to improve the removal efficiency and removal effect, but also to prevent the risk of cross-contamination of residual by-products to ensure the smooth completion of rework.

[0004] Therefore, overcoming the technical problems existing in the above-mentioned rework methods for CIS wafers with defects after photoresist exposure, and obtaining a method for selectively removing CIS wafer surface defects that is simple in process, convenient in operation, low in cost, high in removal efficiency, good in removal effect, and minimally damaging to CIS wafers, is of great significance for reducing defects, improving yield, reducing costs, and enhancing product market competitiveness. Summary of the Invention

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

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A reworking method for CIS wafers includes the following steps: pre-treating the exposed photoresist layer on the surface of the CIS wafer to be reworked using a fluoroalcohol compound solution.

[0008] In a further improvement to the above-mentioned reprocessing method, the concentration of the fluoroalcohol compound solution is 0.5 wt% to 2 wt%.

[0009] In a further improvement to the above-mentioned heavy-duty method, the fluorohydrin solution is prepared by dissolving the fluorohydrin in water.

[0010] In a further improvement to the above-mentioned heavy-duty method, the fluoroethanol compound includes one or more combinations of hexafluoroisopropanol, 2-fluoroethanol, 1,3-difluoro-2-propanol, 2,2-difluoroethanol, and 2,2,2-trifluoroethanol.

[0011] In a further improvement to the above-mentioned reprocessing method, the pretreatment involves immersing the CIS wafer to be reprocessed in a fluoroalcohol compound solution for 2 to 5 minutes.

[0012] The above-described rework method, in a further improvement, includes the following processing after the preprocessing is completed:

[0013] (1) The exposed photoresist layer on the surface of the pretreated CIS wafer is aerated using a plasma ashing process;

[0014] (2) Immerse the CIS wafer obtained by ashing in step (1) in the stripping solution;

[0015] (3) Peel off and clean the CIS wafer obtained after soaking in step (2) to remove the exposed photoresist layer and contaminants on the surface of the CIS wafer.

[0016] (4) Repeat steps (1) to (3) until the surface quality of the CIS wafer meets the requirements for rework.

[0017] In a further improvement to the above-mentioned rework method, in step (1), the plasma ashing process uses an ashing device to ashing the exposed photoresist layer on the surface of the pre-treated CIS wafer; the ashing device includes a reaction chamber, and a number of permanent magnets are respectively provided on the top and sides of the reaction chamber; the permanent magnets are symmetrically arranged on the top of the reaction chamber; the permanent magnets are symmetrically arranged on the sides of the reaction chamber.

[0018] The above-mentioned rework method is further improved in step (1), in the first ashing process, the thickness of the exposed photoresist layer on the CIS wafer surface is retained to be 10% to 20% of the initial thickness.

[0019] In a further improvement to the above-mentioned reprocessing method, in step (1), the ashing treatment is carried out at a temperature of 100℃~160℃.

[0020] In a further improvement to the above-mentioned reprocessing method, in step (2), the stripping liquid is EKC265; and the soaking time is 10 min to 15 min.

[0021] Further improvements to the aforementioned reprocessing method include the following treatments:

[0022] (5) Surface repair treatment is performed on CIS wafers whose surface quality meets the requirements for heavy-duty applications.

[0023] The above-mentioned rework method is further improved by using pulsed plasma to perform surface repair treatment on CIS wafers whose surface quality meets the rework 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 carried out at a temperature <80℃.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] (1) In view of the problems of low etching efficiency and poor etching effect caused by the formation of a dense carbon layer on the surface of the photoresist layer in the existing reworking method, the present invention creatively provides a reworking method for CIS wafers. The method uses a fluoroalcohol compound solution to pre-treat the exposed photoresist layer on the surface of the CIS wafer to be reworked. The unexpected technical effect is that during the pre-treatment process of the fluoroalcohol compound solution, CF chemical bonds can be formed on the exposed photoresist layer on the surface of the CIS wafer. This can effectively prevent the formation of a dense carbon layer on the surface of the photoresist layer during the subsequent ashing process, thereby improving the etching efficiency and etching effect of the plasma on the photoresist layer. Specifically, the polarity of the fluoroalcohol compound and the photoresist layer are matched. Therefore, the F atoms in the fluoroalcohol compound can replace the H in the CH / C=C bond of the photoresist surface layer through nucleophilic substitution reaction to form CF chemical bonds. This not only reduces the stability of the carbon network structure, but also promotes the formation of F* free radicals during the subsequent ashing process. For example, the FO* transition state intermediate can reduce the CC fracture activation energy and generate volatile CF. x O y The product can optimize the surface energy of CIS wafers, thereby promoting the formation of a microcracked carbonized layer on the surface of the photoresist layer during the ashing process. This, in turn, increases the porosity of the carbonized layer, promotes the penetration depth of the plasma, and significantly improves the etching efficiency and effect of the plasma on the photoresist layer.

[0026] (2) In view of the problems that existing reprocessing methods are difficult to effectively remove residues on the surface of CIS wafers and are prone to damage to CIS wafers, the present invention optimizes the processing of CIS wafers to be reprocessed, and the unexpected technical effect is: firstly, a fluoroalcohol compound solution is used to pre-treat the exposed photoresist layer on the surface of the CIS wafer to be reprocessed, which can effectively prevent the formation of a dense carbonization layer on the surface of the photoresist layer. On this basis, the surface of the CIS wafer is sequentially ashed, soaked, peeled and cleaned. Under the combined action of plasma and stripping solution, the exposed photoresist layer on the surface of the CIS wafer can be removed quickly and completely. More importantly, the CIS wafer is preserved during the first ashing process. The thickness of the exposed photoresist layer is 10% to 20% of the initial thickness. At this time, the detached metal particles will be captured in the photoresist residue layer due to surface adsorption energy. Byproducts, practical particles, and residues generated during the ashing process will also remain on the photoresist layer. Thus, the protective effect of the photoresist residue layer can be used to prevent the above-mentioned contaminants from damaging the CIS wafer. While avoiding the decrease in the adhesion of the CIS wafer surface, it can also improve the reusability of the CIS wafer, which is conducive to reducing production costs. Furthermore, contaminants on the surface of the CIS wafer can be effectively removed by simple peeling and cleaning.

[0027] (3) In this invention, the ashing equipment includes a reaction chamber, with several permanent magnets respectively arranged at the top and bottom of the reaction chamber. These permanent magnets are symmetrically arranged at the top and sides of the reaction chamber, thereby constructing a stronger magnetic field outside the reaction chamber of the ashing equipment. The unexpected technical effects are: (a) Adding an axial magnetic field can confine electrons, improve ionization efficiency, increase O radical concentration, enhance etching efficiency, and guide ions to move towards the wafer direction. The axial magnetic field makes electrons spiral around the magnetic field lines, enhancing directionality and reducing lateral diffusion; (b) A permanent magnet pair structure is set at the top (upper part) of the reaction chamber. Through the action of the permanent magnets, plasma dissociation can be enhanced, and density can be increased. When a static magnetic field is applied, electrons spiral in the magnetic field, and their cyclotron frequency is similar to the microwave frequency (2.45). (c) When the magnetic field matches the GHz signal, resonance occurs, the electron kinetic energy increases sharply, the mean free path of the electron is extended by the magnetic field, and the ionization efficiency is improved; (d) Several permanent magnets are provided on the side of the reaction chamber. Through the installation of magnetic rings on the outside, the magnetic field direction is perpendicular to the particle motion direction. Charged particles are deflected by the Lorentz force, allowing only neutral free radicals to pass through, improving directionality. In addition, low-energy ions can be selectively filtered by adjusting the magnetic field gradient, reducing damage to the CIS wafer; (e) A strengthening magnetic field is constructed outside the reaction chamber (top and bottom). This can significantly reduce the plasma ashing process temperature while enhancing plasma dissociation efficiency and directionality. Thus, the etching rate and etching effect can be improved at lower temperatures. This allows for rapid and complete removal of the exposed photoresist layer on the CIS wafer surface while significantly reducing processing costs. In addition, ashing the exposed photoresist layer on the CIS wafer surface at lower temperatures can 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. It can also effectively reduce metal residue and polymer residue. The formation of residues is beneficial to further improve the remanufacturing efficiency and effect of CIS wafers.

[0028] (4) In this invention, after processing the CIS wafer to be reworked by combining plasma ashing and wet stripping, the invention further includes: performing surface repair treatment on the CIS wafer whose surface quality meets the requirements for rework. Specifically, pulsed plasma is used to perform surface repair treatment on the CIS wafer whose surface quality meets the requirements for rework. The unexpected technical effect is that it can effectively repair the surface defects of the CIS wafer, which is beneficial to improving the use effect of the CIS wafer in the subsequent rework process.

[0029] As can be seen, the reprocessing method for CIS wafers of this invention brings unexpected technical effects: it can not only quickly and completely remove the exposed photoresist layer on the surface of CIS wafers, but also quickly and effectively remove residual contaminants on the surface of CIS wafers while effectively protecting them. It has the advantages of simple process, convenient operation, low cost, high removal efficiency, good removal effect, and minimal damage to CIS wafers. It is conducive to improving the reprocessing efficiency and effect of CIS wafers, reducing product defects, improving yield, and reducing costs, while also enhancing the market competitiveness of products. It has high use value and good application prospects. Attached Figure Description

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the conventional PH rework process.

[0032] Figure 2 This is a schematic diagram of the conventional NON-PH rework process.

[0033] Figure 3 This is a surface SEM image of a CIS wafer obtained after reworking using a conventional NON-PH rework process.

[0034] Figure 4 This is a schematic diagram of the rework process of CIS wafers in Embodiment 1 of the present invention.

[0035] Figure 5 This is a schematic diagram of the pretreatment process in Embodiment 1 of the present invention.

[0036] Figure 6 This is a surface SEM image of the CIS wafer to be reworked in Embodiment 1 of the present invention.

[0037] Figure 7 This is a schematic diagram of the ashing equipment in Embodiment 1 of the present invention.

[0038] Figure 8 This is a magnetic flux density distribution diagram of the reaction chamber in Embodiment 1 of the present invention.

[0039] Figure 9 This is a surface SEM image of the CIS wafer after reprocessing in Embodiment 1 of the present invention.

[0040] Figure 10 This is a diagram showing the surface defects of the CIS wafer after reprocessing in Embodiment 1 of the present invention.

[0041] Figure 11The image shows the surface SEM image of the CIS wafer after reprocessing in Comparative Example 1.

[0042] Figure 12 This is a diagram showing the surface defects of the CIS wafer after reprocessing in Comparative Example 1.

[0043] Legend:

[0044] 1. Reaction chamber; 2. Permanent magnet. Detailed Implementation

[0045] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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 complete.

[0046] Example 1

[0047] A rework method for CIS wafers, such as Figure 4 As shown, it includes the following steps:

[0048] S1. A fluoroalcohol compound solution is used to pretreat the exposed photoresist layer on the surface of the CIS wafer to be remanufactured, specifically as follows:

[0049] CIS wafers with defects after photoresist exposure were used as CIS wafers to be reworked. The CIS wafers to be reworked were immersed in a 1.5 wt% hexafluoroisopropanol solution for 3 minutes.

[0050] The reaction that occurs in this step is: C x H y O z (Photoresist backbone) + (CF3)2CHOH → C a H b O c F d + Byproducts. In this reaction equation, x, y, z, a, b, c, and d represent the number of atoms of each element. For example, when the photoresist backbone in the exposed photoresist layer can be C6H... 10 O2, but not limited to this.

[0051] At the same time, such as Figure 5 As shown, fluorine was introduced into the surface of the exposed photoresist layer after pretreatment.

[0052] In this step, the surface morphology of the CIS wafer to be reworked is as follows: Figure 6 As shown. Figure 6 In the image, the left image shows a color filter, and the right image shows a micro lens. Figure 6It can be seen that the photoresist layer on the surface of the CIS wafer of the heavy industry has obvious defects after the photoresist is exposed.

[0053] In step S1 of other embodiments, the concentration of the fluoroalcohol compound solution 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%, or 2 wt%, but is not limited thereto. However, when the concentration of the fluoroalcohol compound solution is below 0.5 wt%, the fluorination layer coverage is insufficient and the fluorination effect is poor. When the concentration of the fluoroalcohol compound solution is above 2.0 wt%, it will cause the photoresist layer to swell and lead to the fluoroalcohol compound solution penetrating to the bottom of the photoresist layer, which can easily damage the wafer.

[0054] In this embodiment, the hexafluoroisopropanol solution used is prepared by dissolving hexafluoroisopropanol in water.

[0055] In step S1 of other embodiments, the fluoroethanol compound used may also be 2-fluoroethanol, 1,3-difluoro-2-propanol, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, and combinations thereof, but is not limited thereto. However, apart from fluoroethanol compounds, other fluorinated compounds cannot be used to process CIS wafers. For example, fluoroether compounds lack active groups and cannot form CF bonds with the photoresist layer; fluoroketone compounds, due to the presence of carbonyl groups, have strong oxidizing properties, easily causing over-corrosion, and are highly polar, easily causing excessive swelling of the photoresist, and have low boiling points and high volatility, making them unstable and unusable.

[0056] 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, or 5 min, but is not limited to these. However, when the soaking time is short, the thickness of the fluorinated layer formed is relatively low, and the effect of inhibiting carbonization is poor. On the other hand, if the soaking time is too long, the fluorinated alcohol compound solution can easily penetrate into the bottom layer of the photoresist layer, which can damage the wafer.

[0057] In this invention, before ashing the exposed photoresist layer on the surface of the CIS wafer to be manufactured, a fluoroalcohol compound solution is used to pre-treat the exposed photoresist layer on the surface of the CIS wafer to be manufactured. This pre-treatment can form CF chemical bonds on the exposed photoresist layer on the CIS wafer surface, thereby effectively preventing the formation of a dense carbonization layer on the surface of the photoresist layer during the subsequent ashing process. This is beneficial to improving the etching efficiency and etching effect of the plasma on the photoresist layer during the subsequent ashing process.

[0058] S2. The exposed photoresist layer on the surface of the CIS wafer after pretreatment in step S1 is ashed using a plasma ashing process, specifically as follows:

[0059] The pretreated CIS wafer surface is ashed using an ashing device (e.g., a plasma asher). During the ashing process, plasma can be generated using the ashing device, and the plasma (e.g., O2 plasma, whose main active species are O radicals and O2 radicals) is then ashed. + Under the action of ions, the exposed photoresist layer on the surface of the CIS wafer is quickly and completely removed, including the microlens and color filter.

[0060] In step S2, during the initial ashing process, the thickness of the exposed photoresist layer on the CIS wafer surface is retained to be 20% of the initial thickness. Specifically, if the original thickness of the photoresist layer on the CIS wafer surface is 1μm to 2μm, then after the initial ashing process, the thickness of the exposed photoresist layer retained on the CIS wafer surface is 0.2μm to 0.4μm. In this invention, by retaining a certain thickness of photoresist layer on the CIS wafer surface, detached metal particles are captured in the photoresist residue layer due to surface adsorption energy. Byproducts, practical particles, and residues generated during the ashing process also remain on the photoresist layer. This protects the CIS wafer from damage caused by these contaminants, preventing a decrease in adhesion on the CIS wafer surface and improving the reusability of the CIS wafer, thus reducing production costs.

[0061] In step S2, such as Figure 7 As shown, the ashing equipment includes a reaction chamber 1. Several permanent magnets 2 are arranged on the top and sides of the reaction chamber 1. Specifically, four permanent magnets are arranged symmetrically on the top of the reaction chamber 1; two permanent magnets are arranged symmetrically opposite each other on the sides of the reaction chamber 1. The surface magnetic flux density of the permanent magnets ranges from 0.8 to 1.5 T (8000-15000 Gauss). It can be seen that a reinforced magnetic field is formed outside the reaction chamber 1 of the ashing equipment, and this is further illustrated by the magnetic flux density distribution diagram of the reaction chamber 1 (see...). Figure 8It can be seen that the unexpected technical effects are: (a) Adding an axial magnetic field can confine electrons, improve ionization efficiency, increase O radical concentration, enhance etching efficiency, and guide ions to move towards the wafer. The axial magnetic field makes electrons spiral around the magnetic field lines, enhancing directionality and reducing lateral diffusion; (b) Setting a permanent magnet pair structure at the top (upper part) of the reaction chamber can enhance plasma dissociation and increase density through the action of the permanent magnet. When a static magnetic field is applied, electrons spiral in the magnetic field, and their cyclotron frequency is similar to the microwave frequency (2.45). (c) When the GHz) matching occurs, resonance occurs, the electron kinetic energy increases sharply, the electron mean free path is extended by the magnetic field, and the ionization efficiency is improved; (d) Several permanent magnets are provided on the side of the reaction chamber. Through the installation of magnetic rings on the outside, the magnetic field direction is perpendicular to the particle motion direction. Charged particles are deflected by the Lorentz force, allowing only neutral free radicals to pass through, improving directionality. Low-energy ions can be selectively filtered by adjusting the magnetic field gradient, reducing damage to the CIS wafer; (e) A strengthening magnetic field is constructed outside the reaction chamber (top and bottom), which can significantly reduce the plasma ashing process temperature while enhancing plasma dissociation efficiency and directionality.

[0062] In step S2, the ashing process is carried out at a temperature of 120°C.

[0063] In step S2 of other embodiments, the temperature of the ashing treatment can also be 100°C, 110°C, 115°C, 125°C, 130°C, 140°C, 150°C, or 160°C.

[0064] Compared to conventional plasma ashing processes, the plasma ashing process used in this invention can improve the etching rate and etching effect at lower temperatures. It can quickly and completely remove the exposed photoresist layer on the surface of CIS wafers while significantly reducing processing costs. In addition, ashing the exposed photoresist layer on the surface of CIS wafers at lower temperatures can effectively avoid the adverse effects of high temperature and high energy on CIS wafers, which helps to reduce the damage caused by high temperature and high energy to CIS wafers. At the same time, it can also effectively reduce the generation of metal residue and polymer residue, which is conducive to further improving the remanufacturing efficiency and remanufacturing effect of CIS wafers.

[0065] In step S2, the plasma ashing process includes: (1) stabilizing the chamber state (ventilation, voltage stabilization); (2) introducing O2, applying radio frequency, generating plasma, and performing RIE (reactive ion etching); (3) stopping ventilation and ending the process.

[0066] S3. Immerse the CIS wafer obtained after ashing in step S2 in the stripping solution, specifically as follows:

[0067] The ashing-treated CIS wafers were immersed in EKC265 (hydroxylamine / ethanolamine) for 12 minutes, allowing the chelating agent EKC265 to form a stable complex with the metal particles. EKC265 also reduces interfacial tension, improving the capture effect of the residual photoresist layer on contaminants such as metal particles while reducing the adsorption force of the photoresist layer on the CIS wafer, thus effectively reducing the difficulty of photoresist layer peeling. Simultaneously, EKC265 can also etch a small amount of photoresist layer and metal, further enhancing the removal of contaminants.

[0068] In step S3 of other embodiments, the immersion time of the CIS wafer in the stripping solution (EKC265) can also be 10 min, 11 min, 13 min, 14 min, or 15 min, but is not limited to these. However, if the immersion time is too short, the photoresist layer cannot be effectively removed, while if the immersion time is too long, the Al-Cu pads will be damaged, resulting in damage to the substrate.

[0069] S4. The CIS wafer obtained after soaking in step S3 is peeled off to remove the residual photoresist layer on the surface of the CIS wafer, and the surface of the CIS wafer is cleaned with deionized water to remove contaminants from the surface of the CIS wafer.

[0070] S5. Repeat steps S2 to S4 until the surface quality of the CIS wafer meets the requirements for rework.

[0071] In step S5, a cycle consists of ashing, soaking, peeling, and cleaning. After each cycle, the surface defects of the CIS wafer are inspected until the surface quality of the CIS wafer meets the requirements for rework.

[0072] S6. Perform surface repair treatment on CIS wafers whose surface quality meets the requirements for rework, specifically:

[0073] The CIS wafers obtained in step S5 with surface quality meeting the requirements for rework are surface repaired using pulsed plasma. Specifically, Ar / N2 is introduced at low energy in an etching machine (e.g., a plasma etching machine) to form Ar / N2 plasma for surface repair of the CIS wafers. The surface repair process is carried out at a temperature of 20°C to 40°C to repair surface defects of the CIS wafers, which is beneficial to improving the performance of the CIS wafers in subsequent rework processes.

[0074] The surface morphology and surface defects of the CIS wafer after step S6 in Example 1 were inspected, and the results are as follows: Figure 9 and Figure 10 As shown.

[0075] Depend on Figure 9It can be seen that after processing by the method of the present invention, the exposed photoresist layer on the surface of the CIS wafer has been effectively removed, that is, the CFA has been completely removed from the surface of the CIS wafer. Simultaneously, combined with... Figure 10 As can be seen, after processing by the method of the present invention, there are very few defects on the surface of the CIS wafer (very few red dots in the figure), which indicates that the method of the present invention will basically not cause damage to the CIS wafer.

[0076] Comparative Example 1

[0077] A rework method for CIS wafers is basically the same as that in Example 1, except that in Comparative Example 1, a fluorinated alcohol compound solution is not used to pre-treat the exposed photoresist layer on the surface of the CIS wafer.

[0078] The surface morphology and surface defects of the CIS wafer after treatment in Comparative Example 1 were inspected, and the results are as follows: Figure 11 and Figure 12 As shown.

[0079] Depend on Figure 11 It is known that without treating the CIS wafer with a fluorohydrin solution, under the same conditions, the exposed photoresist layer on the CIS wafer surface cannot be effectively removed, making it difficult to effectively remove the CFA on the CIS wafer surface. Simultaneously, combined with... Figure 12 As can be seen, after processing using the method in Comparative Example 1, the CIS wafer surface has a large number of defects (many red dots in the figure), and cannot be used for rework.

[0080] The results above show that, compared with conventional reprocessing methods, the reprocessing method for CIS wafers of this invention, by using a fluoroalcohol compound solution for pretreatment of the exposed photoresist layer on the surface of the CIS wafer to be reprocessed, and by optimizing the processing, brings unexpected technical effects: it can not only quickly and completely remove the exposed photoresist layer on the surface of the CIS wafer, but also quickly and effectively remove residual contaminants on the surface of the CIS wafer while effectively protecting the CIS wafer. It has the advantages of simple process, convenient operation, low cost, high removal efficiency, good removal effect, and minimal damage to the CIS wafer. It is beneficial to improve the reprocessing efficiency and effect of CIS wafers, reduce product defects, improve yield, reduce costs, and enhance the market competitiveness of products. It has high use value and good application prospects.

[0081] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A reprocessing method for CIS wafers, characterized in that, Before ashing the exposed photoresist layer on the surface of the CIS wafer of the heavy industry, a fluoroalcohol compound solution is used to pretreat the exposed photoresist layer on the surface of the heavy industry CIS wafer.

2. The reprocessing method according to claim 1, characterized in that, The concentration of the fluoroalcohol compound solution is 0.5 wt% to 2 wt%.

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

4. The reprocessing method according to claim 3, characterized in that, The pretreatment involves immersing the CIS wafer to be reworked in a fluoroalcohol compound solution for 2 to 5 minutes.

5. The reprocessing method according to any one of claims 1 to 4, characterized in that, After the preprocessing is completed, the following processing is also included: (1) The exposed photoresist layer on the surface of the pretreated CIS wafer is aerated using a plasma ashing process; (2) Immerse the CIS wafer obtained by ashing in step (1) in the stripping solution; (3) Peel off and clean 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 requirements for rework.

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

7. The reprocessing 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 CIS wafer surface is retained to be 10% to 20% of the initial thickness; the ashing process is carried out at a temperature of 100℃ to 160℃.

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

9. The reprocessing method according to claim 5, characterized in that, It also includes the following processing: (5) Surface repair treatment is performed on CIS wafers whose surface quality meets the requirements for heavy-duty applications.

10. The reprocessing method according to claim 9, characterized in that, Pulsed plasma is used to perform surface repair treatment on CIS wafers whose surface quality meets the requirements for heavy industry; 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 carried out at a temperature <80℃.

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