Wafer cutting method and die
By attaching inner and outer ring cutting tapes to the wafer surface and pressing an extension film on the back side, the problem of poor cutting stability of wafers with a thickness of less than 100um was solved, achieving high-quality wafer dicing and a simplified cutting process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANTONG FUJITSU MICROELECTRONICS
- Filing Date
- 2023-05-19
- Publication Date
- 2026-06-23
Smart Images
Figure CN116544106B_ABST
Abstract
Description
Technical Field
[0001] This disclosure pertains to the field of semiconductor technology, specifically relating to a wafer dicing method and a die. Background Technology
[0002] For wafers with through-silicon vias (TSVs), since solder balls (PADs) need to be formed on the back side of the ground wafer, the wafers are often thinned to the target thickness and have a wafer ring when they arrive after packaging. If the remaining thickness is still relatively thick, traditional blade dicing or other processes can be used. However, for memory stacked chips, the wafer thickness after thinning is very thin, often only 50-60 μm or even thinner. In this case, the traditional blade dicing process (Dicing After Grinding, DAG) will inevitably have chipping problems. Stealth Dicing Before Grinding (SDBG) requires dicing tape on the back side of the wafer, i.e., stealth dicing via tape.
[0003] Through tape (SDTT) process; this process is more difficult and has relatively poor stability due to the influence of the cutting film. Summary of the Invention
[0004] The embodiments disclosed herein aim to at least solve one of the technical problems existing in the prior art, and provide a wafer cutting method and a die.
[0005] One aspect of this disclosure provides a method for dicing a wafer.
[0006] The law includes:
[0007] Provide thinned wafers for dicing;
[0008] Inner ring cutting tape and outer ring cutting tape are respectively attached to the central area and the edge area of the first surface of the wafer, and the outer ring cutting tape is disposed at the bottom of the wafer frame;
[0009] An extended film is laminated onto the second surface of the wafer;
[0010] Remove the inner ring cutting tape;
[0011] The first surface of the wafer is invisibly cut;
[0012] The wafer after stealth dicing is expanded using the expanded film to divide the wafer into multiple grains.
[0013] Optionally, there is a gap between the edges of the inner ring cutting tape and the outer ring cutting tape, and after applying the inner ring cutting tape, the method further includes:
[0014] The edge of the inner ring cutting tape is intermittently cut to form a tear.
[0015] Optionally, the edges of the inner ring cutting tape and the outer ring cutting tape overlap, and the inner ring cutting tape is disposed on the side of the outer ring cutting tape away from the wafer frame at the overlapping portion.
[0016] Optionally, the extended film includes a non-conductive film and a protective film; the process of laminating the extended film onto the second surface of the wafer includes:
[0017] The non-conductive film is pressed onto the second surface of the wafer;
[0018] The protective film is attached to the surface of the non-conductive film facing away from the wafer; wherein the diameter of the protective film is larger than the diameter of the wafer, and the edge of the protective film is bonded to the outer ring cutting tape.
[0019] Optionally, the protective film is made of a material with elasticity.
[0020] Optionally, the step of using the extended film to perform a film expansion process on the stealth-diced wafer, dividing the wafer into multiple grains, includes:
[0021] The second surface of the wafer is fixed to the support platform by the extended film;
[0022] The wafer is divided into multiple grains by performing a film expansion process on the extended film.
[0023] Optionally, the stealth cutting of the first surface of the wafer includes: stealth cutting the first surface of the wafer using a laser stealth cutting method.
[0024] Optionally, removing the inner ring cutting tape includes:
[0025] The central region of the first surface of the wafer is irradiated with ultraviolet light;
[0026] The inner ring cutting tape is peeled off from the first surface of the wafer.
[0027] Optionally, the wafer has multiple through-silicon vias.
[0028] Another aspect of this disclosure provides a grain obtained by cutting using the method described above.
[0029] In the wafer dicing method of this disclosure embodiment, the thinned wafer is diced. An inner ring dicing tape is pasted in the central region of the first surface of the wafer, and an outer ring dicing tape is pasted in the edge region. Before dicing, the inner ring dicing tape is removed, and the first surface of the wafer is diced. This avoids dicing through the dicing film, eliminates the instability of through-film dicing, thereby improving the wafer dicing quality and enhancing product reliability. This dicing process is simple and easy to operate. Attached Figure Description
[0030] Figure 1 This is a schematic flowchart of a wafer dicing method according to an embodiment of the present disclosure;
[0031] Figures 2 to 8 This is a schematic diagram of the process flow of a wafer dicing method according to an embodiment of the present disclosure.
[0032] In the picture:
[0033] 100. Wafer; 200. Inner ring dicing tape; 300. Outer ring dicing tape; 400. Wafer frame; 500. Extended film; 510. Non-conductive film; 520. Protective film; 600. Die. Detailed Implementation
[0034] To enable those skilled in the art to better understand the technical solutions of the embodiments of this disclosure, the embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0035] The inventors of this disclosure have discovered that in the prior art, for wafers with a thickness of less than 100um, stealth dicing is often used for dicing. In the process of stealth dicing from the back of the wafer, the laser needs to pass through the dicing tape, which makes the dicing process difficult and the stability poor. Even with relevant improved processes, where the laser acts directly on the back of the wafer, the process is still relatively complex and the stability cannot be guaranteed.
[0036] Based on this, this disclosure proposes a method for dicing a wafer 100. This involves attaching an inner ring dicing tape 200 and an outer ring dicing tape 300 to the central and edge regions of the first surface of the wafer 100, respectively, and fixing them to the bottom of a wafer frame 400. An expansion film 500 is then pressed onto the second surface of the wafer 100 to stabilize it. Before dicing, the inner ring dicing tape 200 is removed, and the first surface of the wafer 100 is diced to divide the wafer 100 into independent dies 600. This dicing process is simple and improves the stability of the wafer dicing process.
[0037] like Figure 1 As shown, a wafer dicing method, the method S100 includes:
[0038] S110, provides a thinned wafer 100 to be diced.
[0039] Specifically, in step S110, the wafer 100 can be a silicon wafer, supplied after packaging, and can be supplied via a backside via (BVR) or through-hole via (backside via-reveal). The wafer 100 has undergone thinning treatment, and its thickness is less than 100 μm; for example, the wafer thickness range can be 50 μm to 60 μm. The size of the wafer can be an 8-inch diameter wafer, a 12-inch diameter wafer, etc., and is not limited here. The wafer contains multiple dies, and the specific number is also not limited here.
[0040] S120. Inner ring cutting tape 200 and outer ring cutting tape 300 are respectively attached to the central area and edge area of the first surface of the wafer 100, and the outer ring cutting tape 300 is disposed at the bottom of the wafer frame 400.
[0041] Specifically, in step S120, such as Figure 2 As shown, the first surface of wafer 100 can refer to the back surface of wafer 100. Unlike previous methods where a single sheet of dicing adhesive film was applied to the back surface of wafer 100 after thinning, this embodiment of the present disclosure applies inner and outer double-ring dicing tapes to the first surface of wafer 100. The inner ring dicing tape 200 is applied to the central region of the first surface of wafer 100, and the outer ring dicing tape 300 is applied to the edge region of the first surface of wafer 100, serving to support and protect the wafer. The outer edge of the outer ring dicing tape is positioned at the bottom of the wafer frame, which increases the stability of the wafer. The centers of the inner ring dicing tape 200 and the outer ring dicing tape 300 coincide.
[0042] To facilitate subsequent processes of tearing off the inner ring cutting tape, this disclosure provides two methods for applying inner and outer cutting tapes, as follows:
[0043] As a specific example of a wafer cutting method, there is a gap between the edges of the inner ring cutting tape 200 and the outer ring cutting tape 300. After the inner ring cutting tape 200 is pasted, the method further includes: intermittently cutting the edges of the inner ring cutting tape 200 to form a tear.
[0044] In this embodiment, there is a gap between the inner ring cutting tape and the outer ring cutting tape, providing space for manual tearing. The edge of the inner ring cutting tape is intermittently cut to form a tear, which allows the inner ring cutting tape to be easily torn apart and separated from the wafer. The shape of the tear can be serrated or similar.
[0045] As a specific example of a wafer dicing method, such as Figure 2 and Figure 3 As shown, the edges of the inner ring cutting tape 200 and the outer ring cutting tape 300 overlap, and the inner ring cutting tape 200 is disposed on the side of the outer ring cutting tape 300 away from the wafer frame 400 in the overlapping part.
[0046] In this embodiment of the present disclosure, the edge of the inner ring cutting tape is located on the side of the outer ring cutting tape away from the wafer frame, which facilitates the removal of the inner ring cutting tape.
[0047] S130, an extended film 500 is pressed onto the second surface of the wafer 100.
[0048] Specifically, in step S130, the second surface of the wafer 100 can refer to the front surface of the wafer 100, which has a redistribution layer or pads. After the wafer enters the subsequent packaging process, a vacuum lamination method is used to attach an extension film to the second surface of the wafer for secondary support, which supports the central part of the wafer. At this time, the first and second surfaces of the wafer are fixed and protected by inner and outer cutting tapes and extension films, respectively.
[0049] As a specific example of a wafer dicing method, such as Figure 4 As shown, the extended film 500 includes a non-conductive film 510 and a protective film 520. The process of pressing the extended film 500 onto the second surface of the wafer 100 includes:
[0050] S131, The non-conductive film 510 is pressed onto the second surface of the wafer 100.
[0051] Specifically, in step S131, the non-conductive NCF film is pressed onto the second surface of the wafer using an existing vacuum lamination method. Vacuum lamination allows the non-conductive NCF film to be completely adhered to the second surface of the wafer.
[0052] The non-conductive NCF film is disposed on the second surface of the wafer. The NCF film is made of modified epoxy resin, which has high fluidity at 80–95°C, allowing for pore-free lamination at this temperature. The high transparency and pore-free nature of the material facilitate the detection of alignment marks on the wafer surface. The NCF film has good adhesion and mechanical properties to the front side of the wafer, supporting the wafer and preventing damage to the NCF during dicing. During thermoforming, the NCF substrate can quickly soften, flow, and wet.
[0053] S132, the protective film 520 is attached to the surface of the non-conductive film 510 facing away from the wafer 100; wherein the diameter of the protective film 520 is larger than the diameter of the wafer 100, and the edge of the protective film is adhered to the outer ring cutting tape 300.
[0054] Specifically, such as Figure 4 As shown, the diameter of the protective film is larger than the diameter of the wafer to ensure a firm bond between the protective film and the outer ring cutting tape, and to ensure that the protective film has sufficient strength for subsequent film expansion. The protective film, which is the base film of the NCF, is made of a material with good ductility.
[0055] Specifically, the protective film 520 is made of polyethylene (poly). It should be noted that the poly material is commonly used as a die-attach film (DAF) material.
[0056] S140, Remove the inner ring cutting tape 200.
[0057] In this embodiment of the disclosure, in order to protect the wafer before subsequent cutting, an extension film is first attached to the second surface of the wafer to cover the entire wafer.
[0058] As a specific example of a wafer dicing method, such as Figure 5 and Figure 6 As shown, removing the inner ring cutting tape 200 includes:
[0059] S141. Irradiate the central region of the first surface of the wafer 100 with ultraviolet light.
[0060] It should be noted that an inner ring cutting tape 200 is adhered to the central area of the first surface of the wafer 100, such as... Figure 5 As shown, the inner ring cutting tape firmly grips the wafer with its super strong adhesion, and its adhesion can be reduced by irradiating with an appropriate amount of ultraviolet light.
[0061] S142. The inner ring cutting tape 200 is peeled off from the first surface of the wafer 100.
[0062] In other words, such as Figure 6 As shown, after appropriate ultraviolet irradiation, the adhesion of the inner ring cutting tape is reduced, allowing it to be easily removed for subsequent wafer cutting. Removing the inner ring cutting tape also reduces the space occupied, while the remaining outer ring cutting tape secures the wafer edges and improves wafer stability.
[0063] S150, perform stealth cutting on the first surface of the wafer 100.
[0064] Specifically, in step S150, after peeling off the inner ring cutting tape, as follows: Figure 7 As shown, the first surface of the wafer is invisibly cut to divide the wafer into individual grains without passing through the cutting tape, thus eliminating the instability factors of through-film cutting, improving cutting quality, and enhancing product reliability.
[0065] As a specific example of a wafer cutting method, the stealth cutting of the first surface of the wafer includes: stealth cutting the first surface of the wafer 100 using a laser stealth cutting method.
[0066] It should be noted that for wafers with a thickness of less than 100µm, laser stealth dicing is more suitable. During the laser stealth dicing process, the laser acts directly on the first surface of the wafer, thereby avoiding through-film dicing and eliminating the instability factors of through-film dicing.
[0067] S160. The wafer 100 is divided into multiple grains 600 by using the extended film to perform an expanded film process on the wafer after stealth cutting.
[0068] As a specific example of a wafer dicing method, such as Figure 8 As shown, the process of using the extended film to expand the wafer after stealth dicing, dividing the wafer into multiple grains, includes:
[0069] S161. The second surface of the wafer is fixed to the support platform by the extended film.
[0070] Specifically, the wafer frame is fixed to the fixing part of the support platform. The wafer frame and the outer ring cutting tape can more stably fix the wafer to the support platform. At this time, the second surface of the wafer is facing down, and the extended film is fixed to the moving part of the support platform.
[0071] S162. Perform a film expansion process on the extended film; divide the wafer 100 into multiple grains 600.
[0072] Specifically, after the wafer is fixed on the support platform, the moving part of the support platform rises, thereby lifting the center of the expansion film and fixing the outer ring cutting tape, thus expanding the expansion film. During the expansion process, the protective film is subjected to a tensile force pointing outwards. Since the wafer is bonded to the non-conductive NCF film, the non-conductive NCF film is also subjected to a tensile force pointing outwards, thereby separating the die.
[0073] As a specific example of a wafer dicing method, the wafer 100 has a plurality of through-silicon vias.
[0074] Thus, the chip cut using the wafer cutting method of this embodiment is attached to the NCF bottom mold with its front side facing down. During the thermal compression bonding (TCB) process, the cut chip, i.e. the die, is directly picked up and bonded by the bonding head, without the need for flipping, which facilitates subsequent packaging.
[0075] Another aspect of this disclosure provides a grain obtained by cutting using the method described above.
[0076] Specifically, the dies prepared using the wafer dicing method of this disclosure have high reliability and guaranteed quality. During the wafer dicing process, the inner ring dicing tape in the central region of the first surface of the wafer is removed, thus avoiding through-film dicing when the first surface of the wafer is diced, eliminating the instability factors of through-film dicing, and therefore improving the reliability of the product.
[0077] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the embodiments of this disclosure, and the embodiments of this disclosure are not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the embodiments of this disclosure, and these modifications and improvements are also considered to be within the protection scope of the embodiments of this disclosure.
Claims
1. A method for dicing a wafer, characterized in that, The method includes: Provide thinned wafers for dicing; Inner ring cutting tape and outer ring cutting tape are respectively attached to the central area and the edge area of the first surface of the wafer, and the outer ring cutting tape is disposed at the bottom of the wafer frame; An extended film is laminated onto the second surface of the wafer; Remove the inner ring cutting tape; The first surface of the wafer is invisibly cut; The wafer after stealth dicing is expanded using the expanded film to divide the wafer into multiple grains.
2. The method according to claim 1, characterized in that, There is a gap between the edges of the inner ring cutting tape and the outer ring cutting tape. After applying the inner ring cutting tape, the method further includes: The edge of the inner ring cutting tape is intermittently cut to form a tear.
3. The method according to claim 1, characterized in that, The edges of the inner ring cutting tape and the outer ring cutting tape overlap, and in the overlapping portion, the inner ring cutting tape is disposed on the side of the outer ring cutting tape away from the wafer frame.
4. The method according to any one of claims 1 to 3, characterized in that, The extended film includes a non-conductive film and a protective film. The process of laminating the extended film onto the second surface of the wafer includes: The non-conductive film is pressed onto the second surface of the wafer; The protective film is attached to the surface of the non-conductive film facing away from the wafer; wherein the diameter of the protective film is larger than the diameter of the wafer, and the edge of the protective film is bonded to the outer ring cutting tape.
5. The method according to claim 4, characterized in that, The protective film is made of a stretchable material.
6. The method according to any one of claims 1 to 3, characterized in that, The process of using the extended film to expand the wafer after stealth dicing, dividing the wafer into multiple grains, includes: The second surface of the wafer is fixed to the support platform by the extended film; The wafer is divided into multiple grains by performing a film expansion process on the extended film.
7. The method according to any one of claims 1 to 3, characterized in that, The stealth dicing of the first surface of the wafer includes: The first surface of the wafer is invisibly cut using a laser stealth cutting method.
8. The method according to any one of claims 1 to 3, characterized in that, The removal of the inner ring cutting tape includes: The central region of the first surface of the wafer is irradiated with ultraviolet light; The inner ring cutting tape is peeled off from the first surface of the wafer.
9. The method according to any one of claims 1 to 3, characterized in that, The wafer has multiple through-silicon vias.
10. A type of grain, characterized in that, It is obtained by cutting using the method described in any one of claims 1 to 9.