Wafer film sticking and peeling method

Abstract

The application discloses a wafer sticking and peeling film method, which utilizes the adsorption principle characteristics of static electricity, does not need to use manual and external force pressing appliances to press and smooth the wafer, can make the wafer gradually and smoothly flatten from the circumferential center of the wafer to the outside in a natural environment without external force intervention, so that the safety factor of the wafer in the wafer sticking and peeling film process can be greatly improved; the temperature of the temperature heater is increased to slightly soften the wafer structure, so that the wafer stress strength can be reduced, the wafer is softer and safer in the static adsorption smoothing process, wafer breakage is avoided, the adhesive film can be more firmly pasted on the wafer, and the air bubbles formed by air residues between the adhesive film and the wafer are reduced or decreased, and the problem of flying pieces in the cutting and slicing process is effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of semiconductor wafer manufacturing, and in particular to a wafer film peeling method. Background Technology

[0002] The primary purpose of wafer grinding in traditional semiconductor packaging processes is to reduce the wafer thickness from approximately 750µm to the required thickness for the package shape or product characteristics, such as 200µm, 150µm, 100µm, 75µm, 50µm, or 30µm. After grinding, when the wafer is released from the vacuum jig, uneven stress occurs due to factors such as the difference in expansion coefficients between the front and back metal layers, the number of front metal layers, the uniformity of line thickness and spacing, differences in the surface roughness of the back surface, and the temperature environment during grinding. This stress imbalance leads to warping or curling of the wafer after grinding, especially noticeable in the thinner wafer. Figure 1 (as shown);

[0003] If wafer warping or curling occurs after wafer thinning and grinding, it will cause many problems or even scrapping in subsequent production processes (wafer film removal, wafer film application, wafer dicing), such as wafer breakage, wafer dicing misalignment, chip flying, chip microcracks, reliability and safety issues.

[0004] In the traditional wafer lamination process before dicing, the front side of the wafer, containing the metal circuit layer, is placed in the vacuum suction cup positioning groove of the vacuum lamination equipment (front side down, back side up) for wafer orientation. An adhesive lamination material is then used to bond the wafer to the non-metal circuit layer surface on the back side. This placement of the wafer in the positioning groove relies on the negative pressure within the vacuum suction cup to firmly hold it in place. During normal wafer lamination, if the wafer itself is not warped or curled, there are no issues with wafer orientation and lamination adhesion within the positioning groove (e.g., ...). Figure 2 and Figure 3 (As shown); However, during normal wafer lamination, if the wafer has warped or curled, the vacuum suction cup negative pressure in the wafer orientation positioning groove of the wafer lamination equipment will leak due to the wafer warping or curling, failing to meet the required negative pressure, commonly known as vacuum breaking (e.g. Figure 4 (Schematic diagram of wafer warping and vacuum breaking in orientation slots);

[0005] When a vacuum leak occurs between the wafer positioning groove and the film on the back of the wafer, if the wafer warpage is not severe (approximately ≤1.0mm; however, the actual wafer warpage height varies depending on the wafer thickness and stress intensity / hardness; that is, the stronger the stress intensity / hardness, the lower the tolerable wafer warpage height), the simplest method available is to manually flatten the warped wafer using flattening tools, allowing the negative pressure in the vacuum chuck to be re-established. This allows for a somewhat safer completion of the film application process for warped wafers before film application. However, if the wafer is already severely warped before film application, if manual flattening using pressure tools (such as...) is employed... Figure 6 (The diagram shows the fragmentation phenomenon caused by using external force to flatten the wafer). The warped wafer is prone to internal microcracks, breakage, fragmentation and other damage of varying degrees, and may even lead to the scrapping of the entire wafer, affecting the safety and reliability of the subsequent chip packaging yield. It also causes inaccurate wafer alignment and safety hazards in wafer cutting and dicing.

[0006] This undoubtedly increases the difficulty for the global semiconductor chip packaging technology and applications to develop towards high density, high capacity, high precision, high reliability, low latency, low power consumption, and low cost. It is also an important issue that the semiconductor chip packaging industry urgently needs to find solutions and tackle. Summary of the Invention

[0007] This invention provides a wafer bonding and removal method that can solve the problem in the prior art where the wafer cannot be effectively adsorbed and fixed due to the use of vacuum adsorption alone during the bonding, removal, and mold flipping processes.

[0008] A wafer bonding and peeling method includes the following steps:

[0009] Input wafers: Remove the wafers from the wafer storage cassette and transport them to the wafer placement area;

[0010] Place the wafer: Place the wafer in the work tray;

[0011] Wafer fixing: Use at least one of the vacuum generation unit and electrostatic generation unit of the worktable to fix the wafer;

[0012] Adhesive film application / removal: Apply adhesive film to the wafer surface and cut the adhesive film along the outer perimeter of the wafer / remove the adhesive film;

[0013] De-fixing: Release the wafer from its fixation.

[0014] Output wafer: Remove the wafer.

[0015] The method for fixing the wafer in step two is as follows:

[0016] The electrostatic generation unit of the working disk is activated to smooth out warped or curled wafers. After the electrostatic generation unit completes the smoothing and adsorption of the wafers, the vacuum generation unit is activated and the electrostatic generation unit is turned off to achieve the purpose of fixing the wafers.

[0017] Before inputting the wafer in step one, the temperature heater is activated to reduce air bubbles between the wafer and the adhesive film during the film application process.

[0018] The method for releasing the fixation in step five is to shut down the electrostatic generation unit or the vacuum generation unit.

[0019] The following steps are also included when applying a film before wafer dicing:

[0020] Scan alignment: Scanning and positioning the coordinate position and orientation of the semiconductor wafer;

[0021] Placement of the plate ring: Place the plate ring on the adhesive mold;

[0022] The scanning alignment step is performed after the wafer input step and before the wafer placement step.

[0023] The step of placing the wafer ring is performed after the step of fixing the wafer and before the step of applying the adhesive film.

[0024] Compared with the prior art, the beneficial effects of the present invention are: the present invention utilizes the adsorption principle of electrostatics, eliminating the need for manual labor and flattening tools to apply external force to flatten the wafer. The wafer can be flattened gradually and smoothly from the center of the wafer's circumference outwards in a natural environment without external intervention. Therefore, the safety factor of the wafer can be greatly improved during the application or removal of the film.

[0025] By increasing the temperature using a temperature heater, the wafer structure becomes slightly softer, which reduces the intensity of wafer stress and makes it more flexible. During the electrostatic adsorption smoothing process, the wafer becomes more flexible and safer, preventing wafer breakage. It also makes the adhesive film adhere more firmly to the wafer and reduces or eliminates air bubbles formed by air residue between the adhesive film and the wafer, effectively preventing the problem of wafer flying during the dicing process. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of wafer warpage.

[0027] Figure 2 This is a schematic diagram showing the placement of warp-free wafers on a work tray during the grinding process.

[0028] Figure 3 A schematic diagram showing the placement of warp-free wafers in a work tray during the dicing and slicing process;

[0029] Figure 4 A schematic diagram showing a warped wafer placed in a work tray;

[0030] Figure 5 This is a schematic diagram of the deformation of an ultrathin wafer under vacuum adsorption.

[0031] Figure 6 A schematic diagram illustrating the application of external force to flatten a warped wafer;

[0032] Figure 7 This diagram shows the state changes of a warped wafer under electrostatic influence.

[0033] Figure 8 This is a schematic diagram of a wafer being placed on a work tray during the wafer grinding process.

[0034] Figure 9 A schematic diagram of wafer placement on a work tray during the wafer dicing process;

[0035] Figure 10 Flowchart for applying and removing film from wafers.

[0036] Figure reference numerals: 1-Wafer, 2-Glue mold, 3-Plate ring, 4-Vacuum generating unit, 5-Electrostatic generating unit, 6-Temperature heater. Detailed Implementation

[0037] The following detailed description of a specific embodiment of the present invention is provided in conjunction with the accompanying drawings. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiment.

[0038] Example 1

[0039] like Figures 7 to 10 As shown in the figure, an embodiment of the present invention provides a wafer film application and removal method for wafer grinding before and after grinding, comprising the following steps:

[0040] Wafer grinding pre-coating process: Start heating → Input wafer → Place wafer → Fix wafer (establish static electricity / establish vacuum) → Apply adhesive film → Cut adhesive film → Release fixation (dissipate static electricity / dissipate vacuum) → Output wafer;

[0041] Wafer grinding and film removal: Start heating → Input wafer → Place wafer → Fix wafer (establish static electricity / establish vacuum) → Remove adhesive film → Release fixation (dissipate static electricity / dissipate vacuum) → Output wafer;

[0042] Traditional process technologies all employ vacuum adsorption of wafers, but this traditional technical approach has the following drawbacks:

[0043] Because of the warping or curling of wafer 1, it cannot be flattened in the wafer positioning fixture, causing vacuum leakage. This prevents the use of vacuum negative pressure to adsorb and fix wafer 1. Generally, manual and tool force is used to flatten the wafer and place it flat on the work tray to establish the vacuum negative pressure adsorption function. Since the process of flattening wafer 1 by external force is a manual intervention, the flattening force is applied from the outer periphery to the inner edge of the periphery. Therefore, the instability of the magnitude and position of the applied force can easily cause internal microcracks, internal fragmentation, or even external cracks in wafer 1 during the intervention of external force. This results in the semiconductor chip not being able to guarantee a certain level of safe quality or reliability during the packaging process and after packaging. In very careful operation, the damage or breakage rate of wafer 1 is about 1.5%. If not handled carefully, the damage or breakage rate of wafer 1 is even more difficult to estimate.

[0044] To solve the above-mentioned technical problems, the wafer pre-grinding film application method in this embodiment is as follows:

[0045] Start heating: Start the temperature heater 6 to increase the adhesion of the adhesive film 2 by adjusting the temperature and time. It can also slightly relieve wafer stress, which is conducive to the more stable and safer bonding of wafer 1 to the adhesive film 2.

[0046] Input wafer: Remove wafer 1 from the wafer storage box and transport it to the wafer placement area (the transportation method can be automated operation by a robotic arm or manual operation).

[0047] Place the wafer: Place wafer 1 in the work tray;

[0048] Fixing the wafer: At least one of the vacuum generation unit 4 and the electrostatic generation unit 5 of the worktable is used to fix the wafer;

[0049] Adhesive film: The adhesive film is attached to the surface of wafer 1 and the adhesive film is cut along the outer perimeter of wafer 1;

[0050] Release fixation: Release the fixation on wafer 1;

[0051] Output wafer: Remove wafer 1;

[0052] In the step of fixing wafer 1, for wafer 1 that has already warped, an electrostatic generation unit 5 can be used to smooth wafer 1. The electrostatic generation unit 5 can use the magnitude of voltage to adjust the magnitude of electrostatic adsorption energy to adsorb wafers 1 of different thicknesses or different areas.

[0053] Correspondingly, the way to release the fixation is to shut down the vacuum generating unit 4 or the electrostatic generating unit 5;

[0054] For wafer 1 that has not warped, vacuum generation unit 4 can be used to adsorb and fix wafer 1;

[0055] That is, different adsorption mechanisms are selected according to the degree of warpage of wafer 1. No manual force or flattening equipment is needed to flatten wafer 1. Wafer 1 can be smoothly and gradually flattened outwards from its circumference in a natural environment without external intervention (e.g., ...). Figure 7 As shown in the figure, the safety factor of wafer 1 can be greatly improved during the process of attaching or peeling the film on wafer 1.

[0056] The specific method for peeling off the film after grinding wafer 1 in this embodiment is as follows:

[0057] Start heating: Start the temperature heater 6 to increase the adhesion of the adhesive film 2 by adjusting the temperature and time. It can also slightly relieve wafer stress, which is conducive to the more stable and safer bonding of wafer 1 to the adhesive film 2.

[0058] Input wafer: Remove wafer 1 from the wafer storage box and transport it to the wafer placement area (the transportation method can be automated operation by a robotic arm or manual operation).

[0059] Place the wafer: Place the wafer in the work tray;

[0060] Fixing the wafer: Use at least one of the vacuum generation unit 4 and the electrostatic generation unit 5 of the work disk to fix the wafer 1;

[0061] Peel off the adhesive film: Peel off and remove the adhesive film 2;

[0062] Release fixation: Release the fixation on wafer 1;

[0063] Output wafer: Remove wafer 1;

[0064] The steps for fixing wafer 1 and unfixing are the same as above, so they will not be repeated here.

[0065] Example 2

[0066] This embodiment provides a wafer film application and removal method for wafer dicing and re-film application before dicing and wafer flipping after dicing, comprising the following steps:

[0067] Wafer dicing and pre-die bonding: Start heating → Input wafer → Scan alignment → Place wafer → Fix wafer → Place wafer ring → Apply adhesive film → Cut adhesive film → Release fixation → Output wafer;

[0068] Specifically as follows:

[0069] Start heating: Start the temperature heater 6 to increase the adhesion of the adhesive film by adjusting the temperature and time. It can also slightly relieve wafer stress, which is conducive to the more stable and safer bonding of wafer 1 to adhesive film 2.

[0070] Input wafers: Remove the wafers from the wafer storage box and transport them to the wafer placement area (the transportation method can be automated operation by a robotic arm or manual operation).

[0071] Scan alignment: Scanning and positioning the coordinate position and orientation of the semiconductor wafer;

[0072] Place the wafer: Place the wafer in the work tray;

[0073] Fixing the wafer: At least one of the vacuum generation unit 4 and the electrostatic generation unit 5 of the worktable is used to fix the wafer;

[0074] Placement of the ring: Place the ring 3 on the adhesive mold;

[0075] Adhesive film application: The adhesive film is applied to the wafer surface and cut along the outer perimeter of the wafer;

[0076] De-fixing: Release the wafer from its fixation.

[0077] Output wafer: Remove the wafer;

[0078] Wafer dicing and die flipping: Start heating → Input wafer → Scan alignment → Place wafer → Fix wafer → Peel off adhesive film → Place wafer ring → Apply adhesive film → Cut adhesive film → Release fixation → Output wafer;

[0079] Specifically as follows:

[0080] Start heating: Start the temperature heater 6 to increase the adhesion of the adhesive film by adjusting the temperature and time. It can also slightly relieve wafer stress, which is conducive to the more stable and safer bonding of the wafer to the adhesive film.

[0081] Input wafers: Remove the wafers from the wafer storage box and transport them to the wafer placement area (the transportation method can be automated operation by a robotic arm or manual operation).

[0082] Scan alignment: Scanning and positioning the coordinate position and orientation of the semiconductor wafer;

[0083] Place the wafer: Place the wafer in the work tray;

[0084] Fixing the wafer: At least one of the vacuum generation unit 4 and the electrostatic generation unit 5 of the worktable is used to fix the wafer;

[0085] Remove the adhesive film: peel off and remove the adhesive film;

[0086] Placement of the plate ring: Place the plate ring on the adhesive mold;

[0087] Adhesive film application: The adhesive film is applied to the wafer surface and cut along the outer perimeter of the wafer;

[0088] De-fixing: Release the wafer from its fixation.

[0089] Output wafer: Remove the wafer;

[0090] The steps of fixing and unfixing the wafer in the wafer dicing and dicing followed by film flipping and the wafer dicing and dicing followed by film application are the same as those in Example 1, and therefore will not be repeated here.

[0091] The following is a detailed explanation of some of the steps:

[0092] Heating starts: The heating function mainly serves two purposes: (1) to enhance the adhesion of the blue tape after it is bonded to the semiconductor wafer 1, and (2) to reduce the tiny air bubbles between the semiconductor wafer 1 and the blue tape.

[0093] When the blue adhesive film 2 is applied to a small wafer 1, due to its small area, the small wafer 1 is not easily adhered to by the blue adhesive film. During the dicing process of the packaging process, the wafer will fly off and detach from the blue adhesive film 2 (especially if there are air bubbles left between the wafer and the blue adhesive film after the film is applied, the problem will be more serious).

[0094] The film is applied to wafer 1 in a heated environment. After leaving the heated film application environment, wafer 1 will gradually cool down. If there are tiny air bubbles between wafer 1 and the blue adhesive film, they will become smaller or be eliminated due to the principle of thermal expansion and contraction during the cooling process.

[0095] Input wafer: This generally refers to the transportation of semiconductor wafers. The process of taking semiconductor wafers out of the wafer carrier storage box and into the wafer placement area is mostly carried out by automated equipment robotic arms or by manual arms.

[0096] Wafer placement: The wafer placement area is equipped with a work tray (Chuck table), and below the wafer placement tray is a temperature heater 6 / vacuum generator / static generator; depending on the size, thickness and warpage of the semiconductor wafer, a single heating function, vacuum function, static electricity function or dual function or multiple functions can be used simultaneously;

[0097] Scanning and alignment: After the semiconductor wafer is placed on the work tray, the coordinate position and orientation of the semiconductor wafer can be scanned and positioned. The automatic film application equipment is equipped with a PR device to record the angle and coordinate position of the semiconductor wafer, providing correction and compensation for subsequent operations.

[0098] Establishing electrostatic attraction for wafer fixation: After the scanning and positioning process is completed, the electrostatic generator set on the worktable can automatically generate electrostatic attraction, so that the electrostatic function set on the semiconductor wafer worktable forms electrostatic attraction, thereby firmly adsorbing and fixing the semiconductor wafer in the worktable.

[0099] Establishing a vacuum: After the scanning and positioning process is completed, the vacuum generating unit 4 set on the working disk can automatically generate a vacuum negative pressure through the vacuum hole, thereby firmly adsorbing and fixing the semiconductor wafer in the working disk;

[0100] Placement of wafer ring: The function of wafer ring 3 is to connect the adhesive film to wafer ring 3 and wafer 1. The purpose is to directly fix the relevant positions of wafer 1 and wafer ring 3 through the relationship between wafer ring 3 and adhesive film 2, and then use the relative position of wafer ring 3 to fix other packaging process equipment, so as to achieve the accuracy of fixing the orientation and position of semiconductor wafer 1.

[0101] Adhesive film: The main function of adhesive film is to protect the circuitry on the wafer surface and to adhere and fix the wafer or chip. In the semiconductor chip packaging process, adhesive film is mainly used in wafer back-side grinding and thinning, wafer dicing, chip mounting, and molding compound cutting.

[0102] Cutting the adhesive film: Originally, the adhesive film 2 was rolled up. After the adhesive film was used to attach the metal ring and the semiconductor wafer, it was necessary to use a cutting action to cut and separate the metal ring 3 from the rolled adhesive film 2 (the equipment used to cut the adhesive film uses the existing equipment structure and will not be described in detail here).

[0103] Release the fixed vacuum: Vacuum dissipation: After semiconductor wafer grinding and thinning, wafer dicing, chip mounting, and molding compound cutting, the vacuum adsorption function that was originally turned on needs to be turned off and the vacuum dissipated so that the wafer, chip or molding compound can be easily and stably removed from the work tray.

[0104] Static electricity dissipation: After semiconductor wafer grinding and thinning, wafer dicing, chip mounting, and molding compound cutting, the previously activated electrostatic adsorption function needs to be turned off and static electricity dissipated so that the wafer, chip, or molding compound can be easily and securely removed from the work tray.

[0105] Removing the adhesive film: After wafer grinding and thinning or / and film flipping processes, the original adhesive film needs to be removed. In order to avoid vibration, movement or shaking of the wafer or chip during the film removal process, the fixing function of vacuum adsorption and / or electrostatic adsorption is very important.

[0106] Stop heating: After the film application, removal, and flipping processes are completed, turn off the temperature heater 6;

[0107] Example 3

[0108] This invention provides a wafer bonding and peeling method for fixing wafers, as detailed below:

[0109] When fixing wafer 1, the electrostatic generation unit 5 of the working disk is activated first to smooth out the warped or curled wafer 1. After the electrostatic generation unit 5 completes the smoothing and adsorption of wafer 1, the vacuum generation unit 4 is activated and the electrostatic generation unit 5 is turned off to achieve the purpose of fixing wafer 1.

[0110] That is, the electrostatic generation unit 5 and the vacuum generation unit 4 are used in sequence. The main purpose of the electrostatic generation unit 5 is to smooth out the warped and curled wafers. The heating environment provided by the temperature heater 6 can help the wafer 1 to return to a flat state. After the wafer is returned to a flat state, it is adsorbed by the vacuum generation unit 4, which has a better fixing effect.

[0111] Example 4

[0112] This invention provides a wafer bonding and removal device for implementing the bonding and removal method described in the above embodiments, comprising a work tray, wherein the work tray is provided with:

[0113] Electrostatic generation unit 5 is used to smooth out warped or curled wafers;

[0114] Temperature heater 6 is used to increase the adhesion of the adhesive mold and relieve wafer stress; and vacuum generation unit 4 is used to adsorb the wafer;

[0115] The electrostatic generating unit 5, temperature heater 6, and vacuum generating unit 4 are all existing structures, and therefore will not be described in detail here. Furthermore, since the main components of the electrostatic generating unit 5, temperature heater 6, and vacuum generating unit 4 are not shown in the accompanying drawings, the reference numerals are placed on the corresponding working holes of the units. For example, the reference numeral for the vacuum generating unit is placed on the vacuum hole. The distribution of the working holes of the electrostatic generating unit 5, temperature heater 6, and vacuum generating unit 4 is as follows: Figure 8 or Figure 9 As shown;

[0116] The working disc in this embodiment can be used in both the grinding process and the cutting and dicing process. Depending on the equipment used, the connecting parts can be selected to connect with the equipment. This is an existing solution, so it will not be described in detail here.

[0117] If using ultra-thin wafers (approximately 75µm thick or less), a worktable equipped with a vacuum generation unit is less suitable, as the negative pressure of the vacuum can actually deform or even break the ultra-thin semiconductor wafer (e.g., ...). Figure 5(See the schematic diagram of wafer adsorption deformation); Therefore, the working disk in this embodiment is made of ceramic. The ceramic working disk utilizes the capillary pore characteristics of ceramic to allow the vacuum generator's vacuum to pass through the ceramic capillary working disk to adsorb and position the semiconductor wafer. However, the cost of the ceramic working disk is at least 4 times higher than that of the former, so the ceramic working disk will not be used unless ultra-thin semiconductor wafers are encountered.

[0118] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit and essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0119] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A wafer bonding and peeling method, characterized in that, Includes the following steps: Input wafers: Remove the wafers from the wafer storage cassette and transport them to the wafer placement area; Place the wafer: Place the wafer in the work tray; Wafer fixing: Use at least one of the vacuum generation unit and electrostatic generation unit of the worktable to fix the wafer; Adhesive film application / removal: Apply adhesive film to the wafer surface and cut the adhesive film along the outer perimeter of the wafer / remove the adhesive film; De-fixing: Release the wafer from its fixation. Output wafer: Remove the wafer; The method for fixing the wafer is as follows: The electrostatic generation unit of the working disk is activated to smooth out the warped or curled wafer. After the electrostatic generation unit completes the smoothing and adsorption of the wafer, the vacuum generation unit is activated and the electrostatic generation unit is turned off to achieve the purpose of fixing the wafer. Before the wafer is fed in, the temperature heater is activated to apply the film to the wafer in a heated environment. After leaving the heated film-applying environment, the wafer will gradually cool down. The tiny air bubbles remaining between the wafer and the blue adhesive film will become smaller or disappear due to the principle of thermal expansion and contraction during the cooling process.

2. The wafer bonding and peeling method as described in claim 1, characterized in that, The method for releasing the fixation is to shut down the electrostatic generation unit or the vacuum generation unit.

3. The wafer bonding and peeling method as described in claim 1, characterized in that, The following steps are also included when applying a film before wafer dicing: Scan alignment: Scanning and positioning the coordinate position and orientation of the semiconductor wafer; Placement of the plate ring: Place the plate ring on the adhesive mold; The scanning alignment step is performed after the wafer input step and before the wafer placement step. The step of placing the wafer ring is performed after the step of fixing the wafer and before the step of applying the adhesive film.

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