Method for gradually stripping chip from UV film

Abstract

The invention belongs to the field of semiconductor integrated circuit package testing, and discloses a method for gradually stripping chips from a UV film, and the method achieves the precise shielding of the UV film through the arrangement that an opaque steel mesh outer ring groove is aligned with a wafer scribing channel, enables the UV film on each chip to be divided into a shielding region and a non-shielding region, and enables the shielding regions and the non-shielding regions to be arranged in a staggered manner. In the first UV solution treatment, only the UV film in the non-shielding area is exposed, and the viscosity of the UV film in the non-shielding area is weakened; and after the second UV solution treatment, the viscosity of the UV film in the shielding area is weakened, and at the moment, the viscosity of the UV film in the non-shielding area is thoroughly lost, so that the chip is more easily separated from the UV film in the subsequent stripping operation. Through two times of UV solution treatment, the UV film is adhered to the back surface of the chip and is symmetrically distributed, the stress distribution in the stripping process is controlled, meanwhile, the action time of pressure concentration of the ejector pin on the chip in the stripping process is shortened, the chip jacking crack risk caused by long-time pressure concentration is greatly reduced, and the damage to the chip is avoided.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit packaging and testing, and in particular relates to a method for gradually peeling a chip from a UV film. Background Art

[0002] Peeling the chip off the UV film is a mechanical action of the die bonding machine. It is the process of the die bonding machine using the cooperation of the wafer expansion device, ejector cap, ejector pin and vacuum nozzle to make a single chip leave the UV film. Chip peeling is an important process in the die bonding process. Whether the peeling process is safe greatly determines whether the chip is safe during the die bonding process.

[0003] The current process for peeling chips from UV film in the industry is mainly as follows: (1) The thinned and diced wafer is debonded by a UV glue dissolving machine to reduce the viscosity of the UV film; (2) The wafer is placed in a special wafer bonding machine, and the wafer expansion ring rises from the bottom of the UV film to lift the UV film to make the UV film tight. At this time, the distance between the chips adhered to the film becomes larger to realize the crystal expansion process; (3) The ejector cap lifts the UV film to keep the chip to be peeled stable; (4) The ejector pin lifts the chip to gradually separate it from the UV film; (5) The vacuum nozzle adsorbs the chip surface from above the chip and takes the chip away, completing the process of peeling the chip from the UV film. The above-mentioned existing chip peeling method is prone to the risk of chip cracking. The main reasons are: First, the stress is relatively large during the peeling process: in the process of peeling the UV film from the four sides of the chip to the center, the chip is subjected to the continuous downward pulling force of the film on the four sides. The chip resists the pulling force with its own rigidity. At this time, the contact point of the ejector pin is used as a fulcrum, and the stress inside the chip is concentrated, which can easily damage the chip; second, the pressure is concentrated at the ejector pin and the action time is relatively long: in order to ensure that the vacuum nozzle can take away the chip, the ejector pin needs to rise to a sufficient height to separate the chip from the film. In this process, the pressure is concentrated on the back of the chip for a long time, which may crack the chip; third, there are risks in the picking process: in the process of the vacuum nozzle adsorbing the chip and pulling it off the UV film, the vacuum nozzle and the film exert force on the chip in opposite directions. When the adhesion of the film to the chip is large, there is a risk of chip cracking.

[0004] It can be seen that with the existing chip stripping measures, the chip is subjected to greater stress during the stripping process, the pressure at the ejector pin is concentrated and the action time is longer, and there are risks in the picking process, which can easily lead to chip damage. Summary of the invention

[0005] The purpose of the present invention is to provide a method for gradually peeling a chip from a UV film, so as to solve the technical problems that the chip is subjected to large stress during the peeling process, the pressure at the ejector pin is concentrated and the action time is long, and there are risks in the picking process, which can easily lead to chip damage.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: A method for gradually peeling a chip from a UV film, comprising: An opaque steel mesh is used to block the UV film; wherein, the outer ring of the opaque steel mesh is grooved to align with the wafer dicing road, so that the corresponding UV film on each chip is divided into multiple blocking areas and multiple non-blocking areas, and the blocking areas and non-blocking areas are arranged in a staggered manner; Carry out the first UV treatment on the UV film under the cover of the opaque steel mesh; Remove the opaque steel mesh and perform a second UV treatment on the UV film; The chip is peeled off from the UV film by using the combination of ejector pin and vacuum nozzle.

[0007] Furthermore, the multiple shielding areas of the corresponding UV film on each chip are arranged symmetrically between the two sides, and the multiple non-shielding areas are arranged symmetrically between the two sides.

[0008] Furthermore, the plurality of shielding areas are bilaterally symmetrical with respect to the diameter of the wafer in a vertical direction as an axis, and the plurality of non-shielding areas are bilaterally symmetrical with respect to the diameter of the wafer in a vertical direction as an axis.

[0009] Furthermore, before using an opaque steel mesh to block the UV film, the wafer is first thinned, UV filmed, and diced.

[0010] Furthermore, during the thinning process, the wafer is thinned to 70-120 μm.

[0011] Further, the UV film under the opaque steel mesh is subjected to a first UV treatment, wherein the irradiation dose of the first UV treatment is 4200-4400 mj / cm 2 ; Irradiation time is 1.8~2.2 s.

[0012] Further, the opaque steel mesh is removed, and the UV film is subjected to a second UV treatment, wherein the irradiation dose of the second UV treatment is 4200-4400 mj / cm 2 ; Irradiation time is 1.8~2.2 s.

[0013] Furthermore, the specific steps of peeling the chip from the UV film by using the cooperation of the ejector pin and the vacuum nozzle are as follows: After the second UV treatment, the wafer with UV film is placed in the die bonding machine; Use a vacuum nozzle of model R3-40 or R3-41, and use a multi-pin assembly to lift the chip from the UV film and then adsorb it, so that the chip can be peeled off the UV film.

[0014] Furthermore, after the chip is peeled off from the UV film, the chip is subjected to a chip bonding process.

[0015] Furthermore, after the die bonding process, the bonded chips are inspected and transferred to subsequent processes for processing.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention provides a method for gradually peeling a chip from a UV film. The method realizes accurate shielding of the UV film by aligning the arrangement of wafer scribing lanes with the outer ring of an opaque steel mesh through slots, so that the UV film on each chip is divided into a shielding area and a non-shielding area, and the UV films are arranged in a staggered manner; during the first UV stripping treatment, only the UV film in the non-shielding area is exposed, the viscosity of the UV film in the non-shielding area is weakened, and the adhesion of the film is no longer concentrated on the entire chip area that is stripped at one time, but is dispersed in smaller areas that are stripped multiple times, thereby effectively reducing the risk of chip damage caused by excessive stress during the stripping process; through two UV stripping treatments, the stress distribution during the stripping process is further controlled; after the first UV stripping treatment, the viscosity of the UV film in the non-shielding area is weakened, and after the second UV stripping treatment, the UV film in the non-shielding area completely loses its viscosity, and in subsequent stripping operations, the chip is more easily separated from the UV film, and at the same time, the pressure concentration and action time of the ejector pin on the chip during the stripping process are reduced, thereby greatly reducing the risk of chip top cracking caused by long-term pressure concentration, and avoiding damage to the chip during the stripping process.

[0017] Preferably, in the present invention, the shielding area and the non-shielding area are arranged bilaterally symmetrically, thereby ensuring the uniformity of the UV film during UV treatment and further reducing the risk of chip damage caused by uneven stress distribution.

[0018] Further preferably, in the present invention, a left-right symmetrical design is performed with the diameter of the wafer in the vertical direction as the axis, thereby ensuring a more reasonable layout of the shielding area and the non-shielding area, which is conducive to achieving a more uniform UV desolvation effect and improving the stripping quality.

[0019] Preferably, in the present invention, wafer thinning, UV film application and dicing are first performed before using the opaque steel mesh for shielding, which provides a good foundation for the subsequent step-by-step stripping and ensures the smooth progress of the stripping process.

[0020] Preferably, in the present invention, the irradiation dose and irradiation time of the first UV treatment are controlled within a certain range, thereby ensuring the UV treatment effect of the UV film in the shielding area and providing favorable conditions for subsequent peeling.

[0021] Preferably, in the present invention, the irradiation dose and irradiation time of the second UV stripping treatment are the same as those of the first, ensuring that the UV stripping effect of the UV film in the non-shielded area is consistent with that in the shielded area, further improving the uniformity and success rate of stripping.

[0022] Preferably, in the present invention, the peeled chip is subjected to a chip bonding process, which provides a good foundation for subsequent packaging, testing and other processes and ensures the reliability and stability of the chip.

[0023] Preferably, in the present invention, the chip after bonding is inspected, so that potential defects and problems can be discovered and handled in time, ensuring product quality; at the same time, the chip is transferred to the subsequent process for processing, which is conducive to achieving continuity and efficiency in chip production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the film viscosity distribution on the chip after two UV treatments provided by an embodiment of the present invention; Figure 2 A schematic diagram of a UV protective film and a wafer after dicing provided by an embodiment of the present invention; Figure 3 Schematic diagram of an opaque steel mesh shielding a wafer provided by an embodiment of the present invention; Figure 4 Schematic diagram for comparing chip peeling provided in an embodiment of the present invention, wherein the upper figure is a schematic diagram for double UV peeling provided in this embodiment, and the lower figure is a schematic diagram for conventional single UV peeling; Figure 5 A flow chart of a method for gradually peeling a chip from a UV film provided in an embodiment of the present invention.

[0025] The accompanying drawings are marked as follows: 1. First shielding area; 2. First non-shielding area; 3. Second shielding area; 4. Second non-shielding area; 5. Chip; 6. Slicing road; 7. Opaque steel mesh. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiment.

[0028] Example 1 As described in the background technology, the current chip stripping method has the following disadvantages: First, the stress is high during the peeling process: When the UV film is peeled from the periphery of the chip to the center, the chip is subjected to continuous downward pulling force from the film. The chip resists the pulling force with its own rigidity. At this time, the contact point of the ejector pin is used as a fulcrum, and the stress inside the chip accumulates, which can easily damage the chip.

[0029] Second, the pressure at the ejector pin is concentrated and lasts for a long time: To ensure that the vacuum nozzle can take away the chip, the ejector pin needs to rise high enough to separate the chip from the membrane. During this process, the pressure is concentrated on the back of the chip for a long time, which may crack the chip.

[0030] Third, there are risks in the picking process: when the vacuum nozzle adsorbs the chip and pulls it off the UV film, the vacuum nozzle and the film exert forces on the chip in opposite directions. When the film has a strong adhesion to the chip, there is a risk of chip splitting.

[0031] Therefore, in order to solve the problem of chip damage caused by high stress during the peeling process, concentrated pressure at the ejector pin and long action time, and risks in the picking process, a two-step UV stripping method using an opaque steel mesh is used during the UV stripping process to gradually strip the chip from the UV film, which can reduce the overall stress on the chip and prevent the problem of excessive local stress, thereby improving the quality of chip bonding and yield rate.

[0032] The inventive concept of this embodiment is specifically embodied in the following aspects: First, a method for gradually peeling a wafer is provided. After the secondary UV treatment, the viscosity distribution of the UV film on the chip is as follows: Figure 1 As shown; Figure 1 In the figure, the dark part is the part that is UV-removed once, and the white part is the part that is UV-removed twice. When the wafer is placed in the bonding machine for core loading, the first step is to peel off the UV film in the first shielding area 1 during the process of the ejector pin lifting the chip. Since the UV film in the first non-shielding area 2 is not sticky, the chip falls off directly from the UV at part 2. The second step is to peel off the second shielding area 3 and the second non-shielding area 4, which is the same as the first step. By gradually peeling off the adhesive force in different areas, the overall force on the chip is reduced to prevent excessive local stress.

[0033] (2) Provide a method to reduce the ejector action time In the conventional chip loading process, the ejector pin must be raised to a sufficient height so that the UV film and the chip can be sufficiently separated. At this time, the film has a small adhesion to the chip, allowing the vacuum nozzle to safely take the chip away. In this embodiment, since the first non-shielding area 2 and the second non-shielding area 4 have been UV-treated twice, the two parts of the film have almost no stickiness at this time. Figure 4As shown, the height of the ejector pin rises only to separate part of the chip from the film in the first shielding area 1, which can ensure that the vacuum nozzle can safely take away the chip. Compared with the conventional core loading method, the height of the ejector pin rises significantly, and the contact time between the ejector pin and the chip is reduced, which can well protect the chip.

[0034] (3) Provide an alignment method for an opaque steel mesh like Figure 3 As shown, after slicing, clear slicing marks can be seen on the surface of the UV film, and the slicing marks correspond to each slicing road on the wafer. As shown in FIG. 3, the symmetry of UV deslicing of each chip 5 is achieved by slotting the circumference of the opaque steel mesh 7 and aligning the slots with the slicing roads 6.

[0035] This embodiment provides a method for gradually peeling a chip from a UV film, comprising: When the chip is UV stripped after thinning and dicing, first use an opaque steel mesh 7 of customized size to place it above the UV film, and align the middle shielding piece of the opaque steel mesh 7 with the center dicing road 6 of the wafer to ensure that the UV film of the chip 5 is symmetrical when UV stripping; put the opaque steel mesh 7 and the wafer into a UV glue dissolving machine for one UV stripping to reduce the viscosity of the UV film in the unshielded area; then take away the opaque steel mesh 7, and then perform a second UV stripping to reduce the viscosity of the entire UV film; after two UV strippings, the entire UV film is divided into two parts with greater viscosity and almost no viscosity, and the two parts are symmetrical about the diameter of the wafer in the vertical direction as the axis; put the wafer after the second UV stripping into the bonding machine for core mounting operation.

[0036] like Figure 5 As shown, in this embodiment, the specific steps of the method for gradually peeling the chip from the UV film are as follows: An opaque steel mesh 7 is used to shield the UV film; wherein the outer ring of the opaque steel mesh 7 is grooved and aligned with the wafer dicing road 6, so that the corresponding UV film on each chip 5 is divided into a plurality of shielding areas and a plurality of non-shielding areas, and the shielding areas and the non-shielding areas are arranged in a staggered manner; The UV film under the cover of the opaque steel mesh 7 is subjected to the first UV treatment; Remove the opaque steel mesh 7 and perform a second UV treatment on the UV film; The chip 5 is peeled off from the UV film by using the cooperation of the ejector pin and the vacuum nozzle.

[0037] In this embodiment, Figure 2 As shown, a wafer with a UV protective film on the front side is diced by a diamond knife according to a dicing path 6 using a dicing machine. After dicing, the UV protective film and the wafer are cut into separate units, each of which is composed of a chip and the UV protective film on its surface.

[0038] like Figure 4As shown, the two stripping methods are respectively the twice UV film stripping method designed in this embodiment and the one time UV film stripping method commonly used in production. When the designed pin rise height is consistent, the method of gradually stripping the chip from the UV film provided in this embodiment has a higher degree of stripping than the commonly used production method.

[0039] It can be seen that the method realizes precise shielding of the UV film by aligning the arrangement of the wafer dicing lanes with the slots on the outer ring of the opaque steel mesh, so that the UV film on each chip is divided into a shielding area and a non-shielding area, and the UV film is arranged in a staggered manner; during the first UV stripping treatment, only the UV film in the non-shielding area is exposed, the viscosity of the UV film in the non-shielding area is weakened, and the adhesion of the film is no longer concentrated on the entire chip area that is peeled off at one time, but is dispersed in smaller areas that are peeled off multiple times, effectively reducing the risk of chip damage caused by excessive stress during the peeling process; through two UV stripping treatments, the stress distribution during the peeling process is further controlled; after the first UV stripping treatment, the viscosity of the UV film in the non-shielding area is weakened, and after the second UV stripping treatment, the UV film in the non-shielding area completely loses its viscosity. In the subsequent peeling operation, the chip is easier to separate from the UV film, and at the same time, the pressure concentration and action time of the ejector pin on the chip during the peeling process are reduced, which greatly reduces the risk of chip cracking due to long-term pressure concentration and avoids damage to the chip during the peeling process.

[0040] Example 2 This embodiment provides a method for gradually peeling off a chip from a UV film. For an 8-inch wafer diamond knife scribing process, the initial thickness of the wafer is 670um, the chip size is 6.5mm×11mm, and the scribing road width is 67um. The specific implementation steps are as follows: Step 1: Use a wafer thinning machine to thin the wafer to 120μm; Step 2: Remove the front protective film, apply UV protective film on the back and then perform the scribing operation; Step 3: Use the method of aligning the dicing road with the outer ring of the steel mesh to cover the wafer after dicing, and put the steel mesh and wafer into the UV disintegrator together, with an irradiation dose of 4300mj / cm 2 , time 2s; Step 4: Take out the shielding steel mesh and continue to UV-expose the wafer with a dose of 4300mj / cm 2 , time 2s; Step 5: Place the wafer after two UV treatments into the die bonding machine, select the R3-40 nozzle, select the 250mic multi-ejector, set the ejector rise height to 200μm, and use the above fixture and parameters to perform the die bonding process; Step 6: Inspect the chip after bonding and transfer it to the next process.

[0041] Example 3 This embodiment provides a method for gradually peeling off a chip from a UV film. For a 12-inch wafer diamond knife scribing process, the initial thickness of the wafer is 670um, the chip size is 6.5mm×11mm, and the scribing road width is 67um. The specific implementation steps are as follows: Step 1: Use a wafer thinning machine to thin the wafer to 70μm; Step 2: Remove the front protective film, apply UV protective film on the back and then perform the scribing operation; Step 3: Use the method of aligning the dicing road with the outer ring of the steel mesh to cover the wafer after dicing, and put the steel mesh and wafer into the UV disintegrator together, with an irradiation dose of 4300mj / cm 2 , time 2s; Step 4: Take out the shielding steel mesh and continue to UV-expose the wafer with a dose of 4300mj / cm 2 , time 2s; Step 5: Place the wafer after two UV treatments into the die bonding machine, select the R3-41 nozzle, select a 250mic multi-ejector set, set the ejector rise height to 150μm, and use the above fixtures and parameters to perform the die bonding process; Step 6: Inspect the chip after bonding and transfer it to the next process.

[0042] In summary, this embodiment provides a method for gradually peeling a chip from a UV film, which has the following advantages compared to the existing chip peeling process: This method uses an external steel mesh to block ultraviolet rays. After the UV film passes through two UV de-UV treatments, the UV film is adhesively divided into several symmetrical parts on a single chip. In the process of peeling a single chip, it is actually peeled off step by step in different areas. The advantages of this peeling method are mainly: First, the action of peeling the chip from the UV film is divided into several areas, which reduces the overall stress on the chip and prevents excessive local stress.

[0043] Second, due to the existence of the non-sticky area inside, the chip only needs to be peeled off a small part before it can be safely taken away by the vacuum nozzle, which reduces the rising height of the ejector pin and reduces the risk during the picking process; at the same time, it also improves the peeling efficiency.

[0044] Third, the reduction of the ejector pin height means a reduction in chip peeling time, which improves the efficiency of the chip bonding process.

[0045] In summary, the present invention provides a method for gradually peeling a chip from a UV film. During the UV removal process, a two-step UV removal method is performed through an opaque steel mesh, thereby realizing a process of gradually peeling the chip from the UV film. This can effectively avoid the overall stress on the chip and prevent the problem of excessive local stress, thereby improving the bonding quality and yield rate.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0047] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and the disclosed concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0048] The further detailed description made in the disclosure cannot be used to determine that the specific implementation modes of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention determined by the submitted claims.

Claims

1. A method for gradually peeling a chip from a UV film, characterized in that: include: An opaque steel mesh is used to block the UV film; wherein, the outer ring of the opaque steel mesh is grooved to align with the wafer dicing road, so that the corresponding UV film on each chip is divided into multiple blocking areas and multiple non-blocking areas, and the blocking areas and non-blocking areas are arranged in a staggered manner; Carry out the first UV treatment on the UV film under the cover of the opaque steel mesh; Remove the opaque steel mesh and perform a second UV treatment on the UV film; The chip is peeled off from the UV film by using the combination of ejector pin and vacuum nozzle.

2. The method for gradually peeling off a chip from a UV film according to claim 1, characterized in that: The multiple shielding areas of the UV film corresponding to each chip are arranged symmetrically between the two sides, and the multiple non-shielding areas are arranged symmetrically between the two sides.

3. The method for gradually peeling off a chip from a UV film according to claim 2, characterized in that: The plurality of shielding areas are bilaterally symmetrical with the diameter of the wafer in the vertical direction as an axis, and the plurality of non-shielding areas are bilaterally symmetrical with the diameter of the wafer in the vertical direction as an axis.

4. The method for gradually peeling off a chip from a UV film according to claim 1, characterized in that: Before using an opaque steel mesh to block the UV film, the wafer is first thinned, UV filmed, and diced.

5. The method for gradually peeling a chip from a UV film according to claim 4, characterized in that: During the thinning process, the wafer is thinned to 70-120 μm.

6. The method for gradually peeling a chip from a UV film according to claim 1, characterized in that: The UV film under the opaque steel mesh is subjected to the first UV treatment, wherein the irradiation dose of the first UV treatment is 4200-4400mj / cm 2 ; Irradiation time is 1.8~2.2 s.

7. The method for gradually peeling a chip from a UV film according to claim 1, characterized in that: Remove the opaque steel mesh and perform a second UV treatment on the UV film. The irradiation dose of the second UV treatment is 4200-4400 mj / cm 2 ; Irradiation time is 1.8~2.2 s.

8. The method for gradually peeling a chip from a UV film according to claim 1, characterized in that: The specific steps of peeling the chip from the UV film by using the cooperation of the ejector pin and the vacuum nozzle are as follows: After the second UV treatment, the wafer with UV film is placed in the die bonding machine; Use a vacuum nozzle of model R3-40 or R3-41, and use a multi-pin assembly to lift the chip from the UV film and then adsorb it, so that the chip can be peeled off the UV film.

9. The method for gradually peeling off a chip from a UV film according to claim 1, characterized in that: After the chip is peeled off from the UV film, the chip is bonded.

10. The method for gradually peeling off a chip from a UV film according to claim 9, characterized in that: After the die bonding process, the bonded chips are inspected and transferred to subsequent processes for processing.

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