Visible light imaging-assisted method for precise removal of bonding adhesive

Abstract

Disclosed in the present invention is a visible light imaging-assisted method for precise removal of a bonding adhesive, comprising: providing, between a bonding adhesive layer and a wafer, a transparent layer which is composed of a fluorescent material and overlaps with the bonding adhesive layer, and delineating at least one fixed-point region within the transparent layer; performing a laser debonding operation on the bonding adhesive layer; directing an ultraviolet light beam from the side where the bonding adhesive layer is located to irradiate the transparent layer, so that the fluorescent material within the transparent layer is excited by ultraviolet light to emit visible light; and acquiring a luminance value of visible light generated in each fixed-point region, and establishing a luminance histogram on the basis of the obtained luminance value; on the basis of the luminance histogram, determining whether any portion of the bonding adhesive layer remains unremoved during the operation of step S2; and according to the determining result, if any portion of the bonding adhesive layer remains unremoved, on the basis of the luminance histogram, determining operational parameters for reperforming the laser debonding process, to ablate and remove the unremoved portion of the bonding adhesive layer, so as to ensure complete debonding between the wafer and a glass substrate.

Description

A method for precise removal of bonding adhesive based on visible light imaging Technical Field

[0001] The present invention relates to the field of semiconductor process technology, and in particular to a method for accurately removing bonding glue based on visible light imaging assistance. Background Art

[0002] During semiconductor manufacturing, to prevent the wafer from being subjected to stress during processing, which could lead to breakage or bending, it is usually necessary to temporarily bond the wafer to a glass substrate using bonding adhesive before undergoing other processing steps such as wafer thinning and circuit fabrication. Furthermore, after the process is completed, a laser debonding operation (i.e., allowing a laser to penetrate the glass substrate and illuminate the bonding adhesive to ablate it) is performed to render the bonding adhesive ineffective, allowing the wafer to be successfully separated from the glass substrate.

[0003] However, this processing method has certain defects in actual operation: 1) Since the wafer and glass substrate are easily affected by external factors during temporary bonding, the bonding adhesive between the two is unevenly distributed. After the laser debonding operation, some bonding adhesive still remains, making it difficult for the wafer to be smoothly separated from the glass substrate due to the adhesion of the residual bonding adhesive. Among them, if the wafer is forcibly separated from the glass substrate by manual peeling, the quality of the wafer will be greatly damaged; 2) The distribution position and residual amount of the residual bonding adhesive are irregular, making it difficult to determine the laser irradiation position and required laser amount when performing the laser debonding operation again, which is very inconvenient. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for accurately removing bonding glue based on visible light imaging. By setting a transparent layer, it is possible to accurately locate and quantify the residual bonding glue that was not removed in the first laser debonding operation, and then effectively determine the operating parameters required for the laser debonding operation again, while ensuring that the wafer and the glass substrate can be completely debonded while avoiding damage to the wafer quality as much as possible.

[0005] To achieve the above-mentioned objectives, the present invention provides a method for precisely removing bonding adhesive based on visible light imaging, comprising a wafer, a glass substrate, and a bonding adhesive layer for temporary bonding between the wafer and the glass substrate. The method comprises the following steps:

[0006] Step S1: Disposing a transparent layer composed of a fluorescent material between the bonding layer and the wafer and overlapping the bonding layer, and dividing and establishing at least one fixed area in the transparent layer, wherein each fixed area can represent a portion of a spatial area defined in the bonding layer;

[0007] Step S2: performing a laser debonding operation on the bonding adhesive layer;

[0008] Step S3: irradiating the transparent layer with an ultraviolet light beam from the side provided with the bonding adhesive layer. The fluorescent material in the transparent layer is excited by the ultraviolet light to generate visible light. Then, the brightness value of the visible light generated in each of the fixed point areas is obtained and a brightness statistical graph is created based on the obtained brightness values.

[0009] Step S4: judging whether there is a portion of the bonding layer that has not been cleared in step S2 based on the brightness statistical graph;

[0010] Step S5: If there is a portion of the bonding layer that has not been cleared, determine the operating parameters for performing the laser debonding operation again based on the brightness statistical graph to ablate and clear the portion of the bonding layer that has not been cleared, wherein the operating parameters at least include the irradiation intensity and scanning path of the laser beam.

[0011] Furthermore, dividing and establishing at least one fixed point area in the transparent layer includes: dividing the transparent layer into a number of areas with the same volume, wherein each equally divided area serves as a fixed point area.

[0012] Furthermore, a brightness statistical graph is established based on the acquired brightness values, including: sorting the acquired brightness values ​​in order from small to large / from large to small, and constructing a brightness statistical graph with the brightness value as the vertical axis and the fixed point area as the horizontal axis.

[0013] Further, in step S4, it is determined based on the brightness statistical graph whether there is a partial bonding layer that has not been cleared in the operation of step S2, including: step S4.1: pre-establishing a corresponding relationship between the brightness value and the volume value of the partial bonding layer that has not been cleared, wherein the brightness value and the volume value of the partial bonding layer that has not been cleared are negatively correlated; step S4.2: determining the volume value of the partial bonding layer that has not been cleared corresponding to each brightness value in the brightness statistical graph, wherein if the volume value of the partial bonding layer that has not been cleared corresponding to the brightness value is zero, it indicates that there is no partial bonding layer that has not been cleared.

[0014] Furthermore, in step S4, if there is no portion of the bonding adhesive layer that has not been removed, step S5 is not performed.

[0015] Further, in step S5, the operating parameters for performing the laser debonding operation again are determined based on the brightness statistical graph to ablate and remove the uncleared portion of the bonding adhesive layer, including: step S5.1: obtaining the volume value of the uncleared portion of the bonding adhesive layer and the thickness value of the glass substrate corresponding to each brightness value in the brightness statistical graph; step S5.2: determining the irradiation intensity and scanning path of the laser beam according to the volume value and thickness value to perform the laser debonding operation again to ablate and remove the uncleared portion of the bonding adhesive layer.

[0016] The present invention adopts the above-mentioned scheme, and its beneficial effect is that by setting a transparent layer, it can accurately locate and quantify the residual bonding glue that was not removed in the first laser debonding operation, and then effectively determine the operating parameters required for the laser debonding operation again. While ensuring that the wafer and the glass substrate can be completely debonded, it avoids damaging the wafer quality as much as possible, and there is no need for manual peeling, which is convenient and quick. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a flow chart of a method for accurately removing bonding adhesive based on visible light imaging assistance in this embodiment.

[0018] FIG2 is a schematic diagram showing the arrangement of the transparent layer in one embodiment of the present application.

[0019] FIG3 is a detailed flowchart of determining whether there is a portion of the bonding adhesive layer that has not been cleared in step S2 based on the brightness statistical graph in step S4.

[0020] FIG4 is a detailed flow chart of determining the operating parameters for performing the laser debonding operation again based on the brightness statistical graph in step S5 to ablate and remove the remaining bonding adhesive layer.

[0021] Among them, 1-glass substrate, 2-bonding layer, 3-transparent layer, 4-wafer. DETAILED DESCRIPTION

[0022] To facilitate understanding of the present invention, the present invention is described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided solely to provide a more thorough and comprehensive understanding of the present disclosure.

[0023] The following describes in detail the implementation details of the technical solution of the embodiment of the present invention:

[0024] 1 and 2 , in this embodiment, a wafer 4, a glass substrate 1, and a bonding adhesive layer 2 for temporary bonding between the wafer 4 and the glass substrate 1 are included. Based on the above components, the method for precise bonding adhesive removal based on visible light imaging in an embodiment of the present invention is further explained.

[0025] Step S1: A transparent layer 3 composed of a fluorescent material and overlapping with the bonding layer 2 is set between the bonding layer 2 and the wafer 4, and at least one fixed area is divided and established in the transparent layer 3, wherein each fixed area can represent a portion of the spatial area demarcated in the bonding layer 2.

[0026] In this embodiment, the transparent layer 3 is divided into several equal regions of uniform volume, each of which serves as a fixed point region. Specifically, referring to FIG2 , in this embodiment, a glass substrate 1 is positioned above a wafer 4. A bonding layer 2 and a transparent layer 3 are provided between the glass substrate 1 and the wafer 4 for temporary bonding between the wafer 4 and the glass substrate 1. The transparent layer 3 is positioned between the bonding layer 2 and the wafer 4, and the shapes and sizes of the bonding layer 2, the transparent layer 3, and the wafer 4 coincide with each other. More specifically, the transparent layer 3 is formed from a transparent adhesive. The adhesive is uniformly distributed with a plurality of inorganic ultraviolet fluorescent particles of uniform diameter. Each inorganic ultraviolet fluorescent particle serves as a fixed point region of the transparent layer 3. Since the transparent layer 3 and the bonding layer 2 overlap, each inorganic ultraviolet fluorescent particle also serves as a fixed point region of the bonding layer 2, representing a defined portion of the spatial region within the bonding layer 2.

[0027] Step S2: performing a laser debonding operation on the bonding adhesive layer 2 .

[0028] In this embodiment, a laser debonding operation is performed on the bonding adhesive layer 2. Specifically, a laser beam is emitted from a laser emitter or other emitting device, which scans through the glass substrate 1 and irradiates the bonding adhesive layer 2 to ablate the bonding adhesive layer 2, rendering the bonding adhesive layer 2 inoperable. Once the bonding adhesive layer 2 is completely ablated and inoperable, the wafer 4 can be successfully separated from the glass substrate 1. However, in actual production operations, external influences such as external forces impacting the glass substrate 1 and uneven surfaces of the glass substrate 1 can cause uneven distribution of the bonding adhesive between the wafer 4 and the glass substrate 1 during temporary bonding. As a result, portions of the bonding adhesive layer 2 may remain unremoved after the initial laser debonding operation. This portion of the bonding adhesive layer 2 may remain between the wafer 4 and the glass substrate 1, preventing the wafer 4 from being successfully separated from the glass substrate 1 due to adhesion. Therefore, in this embodiment, the following operation is performed to determine whether portions of the bonding adhesive layer 2 between the wafer 4 and the glass substrate 1 remain unremoved (i.e., whether complete debonding has been achieved between the wafer 4 and the glass substrate 1).

[0029] Step S3: An ultraviolet light beam is directed to the transparent layer 3 from the side where the bonding adhesive layer 2 is provided. The fluorescent material in the transparent layer 3 is excited by the ultraviolet light to generate visible light. Subsequently, the brightness value of the visible light generated in each fixed point area is obtained and a brightness statistical graph is created based on the obtained brightness values.

[0030] Step S4: judging whether there is a portion of the bonding adhesive layer 2 that has not been cleared in step S2 based on the brightness statistical graph.

[0031] In this embodiment, a fluorescent camera positioned on one side of the bonding layer 2 emits an ultraviolet beam that illuminates the transparent layer 3. The camera also captures a fluorescent image of the fluorescent material within the transparent layer 3, which is excited by the ultraviolet light and produces visible light. This fluorescent image is then analyzed to determine the brightness of the visible light within each fixed area. The acquired brightness values ​​are then sorted in ascending order and vice versa. A brightness statistical graph is constructed with the brightness value on the vertical axis and the fixed area on the horizontal axis to visually display the brightness corresponding to each fixed area.

[0032] Specifically, because the ultraviolet light beam irradiates the transparent layer 3 from the side where the bonding layer 2 is located, if a portion of the bonding layer 2 is not removed, the intensity of the ultraviolet light beam will be weakened when passing through this portion of the bonding layer 2. This results in a low intensity of ultraviolet light received by the transparent layer 3 in the local area facing this portion of the bonding layer 2, and the ultraviolet fluorescent material particles in the transparent layer 3 in this area are excited by the ultraviolet light and produce low brightness of visible light. Furthermore, as the volume (i.e., the residual amount) of the uncleaned portion of the bonding layer 2 increases, the ultraviolet light intensity received by the transparent layer 3 in the local area facing this portion of the bonding layer 2 decreases, and the brightness of the visible light produced by the ultraviolet fluorescent material particles in the transparent layer 3 in this area is lower. In other words, the volume value and brightness value of the uncleaned portion of the bonding layer 2 are negatively correlated.

[0033] More specifically, referring to FIG. 3 , judging whether there is a portion of the bonding adhesive layer 2 that has not been removed in step S2 based on the brightness statistical graph can be performed according to the steps shown in FIG. 3 , including steps S4.1 to S4.2:

[0034] Step S4.1 : pre-establishing a corresponding relationship between the brightness value and the volume value of the uncleared portion of the bonding adhesive layer 2 , wherein the brightness value and the volume value of the uncleared portion of the bonding adhesive layer 2 are negatively correlated.

[0035] Step S4.2, determining the volume value of the uncleared portion of the bonding layer 2 corresponding to each brightness value in the brightness statistical graph, wherein if the volume value of the uncleared portion of the bonding layer 2 corresponding to the brightness value is zero, it means that there is no uncleared portion of the bonding layer 2.

[0036] In this embodiment, first, the brightness values ​​are pre-divided into several brightness ranges, and the volume value of the partially uncleaned bonding layer 2 corresponding to each brightness range is set. Then, the volume value of the partially uncleaned bonding layer 2 corresponding to each brightness range in the brightness statistical graph is determined. The higher the brightness value, the lower the volume value of the partially uncleaned bonding layer 2. When the volume value of the partially uncleaned bonding layer 2 corresponding to the brightness value is zero, it indicates that there are no partially uncleaned bonding layers 2, and the bonding layers 2 have been completely uncleaned during the first laser debonding operation. Therefore, if the judgment result is that there are no partially uncleaned bonding layers 2, step S5 is not performed.

[0037] Furthermore, when the judgment result is that there is a part of the bonding layer 2 that has not been cleared, in this embodiment, step S5 is used to accurately locate and quantify this part of the bonding layer 2 that has not been cleared, thereby effectively determining the operating parameters required for performing the laser debonding operation again to avoid damaging the quality of the wafer 4.

[0038] Step S5: If there is a portion of the bonding layer 2 that has not been cleared, determine the operating parameters for performing the laser debonding operation again based on the brightness statistical diagram to ablate and clear the portion of the bonding layer 2 that has not been cleared, wherein the operating parameters at least include the irradiation intensity and scanning path of the laser beam.

[0039] Furthermore, referring to FIG. 4 , the operating parameters for performing the laser debonding operation again are determined based on the brightness statistical graph to ablate and remove the remaining portion of the bonding adhesive layer 2 , including:

[0040] Step S5.1, obtaining the volume value of the unremoved portion of the bonding layer 2 and the thickness value of the glass substrate 1 corresponding to each brightness value in the brightness statistical graph; effectively improving the reliability of laser debonding

[0041] Step S5.2: Determine the irradiation intensity and scanning path of the laser beam according to the volume value and the thickness value, and perform the laser debonding operation again to ablate and remove the remaining portion of the bonding adhesive layer 2.

[0042] In this embodiment, the laser beam passes through the glass substrate 1 before acting on the bonding layer 2. Glass substrates 1 of varying thicknesses have different transmission characteristics for the laser beam, and bonding layers 2 made of varying materials have different absorption characteristics for the laser beam. Therefore, to enhance operational stability and reliability, this embodiment utilizes a single-shot pulse laser for laser debonding. The energy of a single-shot pulse laser is a fixed value. The required number of single-shot laser pulses (i.e., the irradiation intensity of the laser beam) is calculated by calculating the sum of the volume of the remaining bonding layer 2 (i.e., the residual volume) and the energy required to pass through the glass substrate 1. This sum is then divided by the single-shot laser energy value to determine the required number of single-shot laser pulses (i.e., the irradiation intensity of the laser beam). The laser beam scanning path is then determined by marking the fixed point area corresponding to the brightness value of the residual volume in a brightness statistical graph. This significantly improves the reliability and accuracy of subsequent laser debonding operations.

[0043] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any person skilled in the art who, without departing from the scope of the technical solution of the present invention, utilizes the technical content disclosed above to make more possible changes and modifications to the technical solution of the present invention, or modifications are all equivalent embodiments of the present invention. Therefore, any equivalent and equivalent changes made in accordance with the ideas of the present invention without departing from the content of the technical solution of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for accurately removing bonding adhesive based on visible light imaging, comprising a wafer (4), a glass substrate (1), and a bonding adhesive layer (2) for temporary bonding between the wafer (4) and the glass substrate (1), characterized in that: The method comprises the following steps: Step S1: a transparent layer (3) composed of a fluorescent material and overlapping with the bonding layer (2) is provided between the bonding layer (2) and the wafer (4), and at least one fixed point area is divided and established in the transparent layer (3), wherein each fixed point area can represent a portion of a spatial area demarcated in the bonding layer (2); Step S2: performing a laser debonding operation on the bonding adhesive layer (2); Step S3: allowing an ultraviolet light beam to irradiate the transparent layer (3) from the side where the bonding adhesive layer (2) is provided, and at this time, the fluorescent material in the transparent layer (3) is excited by the ultraviolet light to generate visible light; then, obtaining the brightness value of the visible light generated in each of the fixed point areas and establishing a brightness statistical graph based on the obtained brightness values; Step S4: judging whether there is a portion of the bonding layer (2) that has not been cleared in the operation of step S2 based on the brightness statistical graph; Step S5: If there is a portion of the bonding adhesive layer (2) that has not been cleared, then based on the brightness statistical graph, determine the operating parameters for performing the laser debonding operation again to ablate and clear the portion of the bonding adhesive layer (2) that has not been cleared, wherein the operating parameters at least include the irradiation intensity and scanning path of the laser beam.

2. The method for accurately removing bonding adhesive based on visible light imaging according to claim 1, characterized in that: At least one fixed point area is divided and established in the transparent layer (3), comprising: dividing the transparent layer (3) into a plurality of areas of uniform volume, wherein each equally divided area serves as a fixed point area.

3. The method for accurately removing bonding adhesive based on visible light imaging according to claim 1, characterized in that: A brightness statistical graph is established based on the acquired brightness values, including: sorting the acquired brightness values ​​in order of small to large / large to small, and constructing a brightness statistical graph with the brightness values ​​as the vertical axis and the fixed point area as the horizontal axis.

4. The method for accurately removing bonding adhesive based on visible light imaging according to claim 1, characterized in that: In step S4, judging whether there is a portion of the bonding adhesive layer (2) that has not been cleared in step S2 based on the brightness statistical graph includes: Step S4.1: pre-establishing a corresponding relationship between the brightness value and the volume value of the portion of the bonding adhesive layer (2) that has not been cleared, wherein the brightness value and the volume value of the portion of the bonding adhesive layer (2) that has not been cleared are negatively correlated; Step S4.2: Determine the volume value of the uncleared portion of the bonding layer (2) corresponding to each brightness value in the brightness statistical graph, wherein if the volume value of the uncleared portion of the bonding layer (2) corresponding to the brightness value is zero, it indicates that there is no uncleared portion of the bonding layer (2).

5. The method for accurately removing bonding adhesive based on visible light imaging according to claim 1, characterized in that: In step S4, if there is no part of the bonding adhesive layer (2) that has not been removed, step S5 is not performed.

6. The method for accurately removing bonding adhesive based on visible light imaging according to claim 1, characterized in that: In step S5, based on the brightness statistical graph, the operating parameters for performing the laser debonding operation again are determined to ablate and remove the portion of the bonding adhesive layer (2) that has not been removed, including: Step S5.1: obtaining the volume value of the uncleared portion of the bonding layer (2) and the thickness value of the glass substrate (1) corresponding to each brightness value in the brightness statistical graph; Step S5.2: determining the irradiation intensity and scanning path of the laser beam according to the volume value and the thickness value, and performing the laser debonding operation again to ablate and remove the portion of the bonding adhesive layer (2) that has not been removed.

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