A method for scribing ultra-small size grains in an ultra-thin wafer

Abstract

The application discloses a kind of ultra-thin wafer in ultra-small size grain's scribe processing method, double-layer film, step scribe scheme is adopted, first wafer is cut into several small pieces and is in the mode of front film coating and baking, effectively increase the contact area of grain and adhesive film in scribe process, reduce the jitter offset of grain in scribe process, greatly reduce the probability of grain flying piece, improve wafer yield, and eliminate reduce the internal stress of wafer, effectively improve the problem that wafer is broken when ultra-high speed blade is ground due to that ultra-thin wafer is not pasted in place in scribe process, adhesive film, further improve the jitter offset of grain caused by CH2 direction when ultra-small size grain is scribed due to and adhesive layer adhesion area reduction, no wafer internal connection, and by improving the scribe speed of CH1 direction, improve scribe efficiency, greatly reduce the problem of edge collapse, corner defect in wafer scribe process.

Description

Technical Field

[0001] This invention relates to the field of semiconductor die manufacturing technology, and in particular to a method for dicing ultra-small dies in ultra-thin wafers. Background Technology

[0002] With the continuous development of the semiconductor wafer manufacturing industry and the increasing demands of applications, wafer thickness is constantly decreasing, and die size is also continuously evolving towards ultra-small dimensions and ultra-high concentration. However, the continuous thinning of wafers and the shrinking of die size have made them extremely fragile. Front-end thinning processes and back-end metallization processes cause the internal stress value of the wafer to increase continuously, and the ultra-small die size makes the requirements for the adhesive film increasingly stringent. This puts enormous pressure on the back-end wafer dicing process, causing wafer fragmentation, flyaways, edge chipping, and other phenomena during the dicing process, reducing the yield of die production. Summary of the Invention

[0003] The purpose of this invention is to provide a method for dicing ultra-small-sized grains in ultra-thin wafers, so as to improve the phenomena of wafer fragmentation, flyaway, and edge chipping during the dicing process and increase the yield of grain production.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] This invention provides a method for scribing ultra-small grains in ultrathin wafers, comprising the following steps:

[0006] (1) Apply adhesive film to the slicing ring, attach the bottom surface of the wafer to the adhesive film and remove air bubbles, bake in an oven at 70-75℃ for 10-30 minutes, apply adhesive film to the top of the wafer and remove air bubbles, bake in an oven at 70-75℃ for 5-10 minutes.

[0007] (2) Select the dicing blade according to the wafer thickness and subsequent process requirements and install it on the dicing machine spindle to complete the initialization, height measurement, blade repair and height measurement processes.

[0008] (3) Remove the baked dicing ring, let it cool naturally to room temperature, place it on the dicing machine work tray and turn on the vacuum;

[0009] (4) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-50mm / s, and the stepping distance of n*a0 to dice the wafer in the CH1 direction, and cut the wafer into multiple square pieces in the horizontal direction, where a0 represents the width of the die and n≥2.

[0010] (5) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-30mm / s, and the stepping distance of n*b0 to dice the wafer in the CH2 direction, and cut the wafer into multiple square pieces in the longitudinal direction, where b0 represents the length of the die and n≥2;

[0011] (6) Remove the slicing ring and bake it in an oven at 70-75℃ for 5-10 minutes;

[0012] (7) Remove the baked dicing ring, let it cool naturally to room temperature, place it on the dicing machine work tray and turn on the vacuum;

[0013] (8) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-50mm / s, and the step pitch of a0 to dice the wafer in the CH1 direction; according to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 2-30mm / s, and the step pitch of b0 to dice the wafer in the CH2 direction; until the wafer is diced to the target core size a0×b0.

[0014] Preferably, the film is a blue film, a white film, a UV film, a resin solid film, or an adhesive transparent film.

[0015] Preferably, the dicing water and cooling water are kept on throughout the dicing process. The dicing water cools the wafer, and the cooling water cools the dicing blade. Wafer cleaning fluid is added to the dicing water.

[0016] Preferably, the directions of CH1 and CH2 are perpendicular to each other.

[0017] Preferably, each dicing is performed in two cuts. The depth of the first cut is controlled to be 1 / 2 to 2 / 3 of the total wafer thickness, and the depth of the second cut is the wafer thickness + 0.02 to 0.07 mm.

[0018] Preferably, in step (4), when dicing the wafer in the CH1 direction, the number of dicing cuts is 2(A+1), where A represents the number of square pieces obtained by dicing in the horizontal direction; in step (5), when dicing the wafer in the CH2 direction, the number of dicing cuts is 2(B+1), where B represents the number of square pieces obtained by dicing in the vertical direction.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] (1) The present invention adopts a double-layer coating and step-by-step dicing scheme. The wafer is first cut into several small pieces and coated and baked on the front side. This effectively increases the contact area between the grain and the adhesive film during the dicing process, reduces the grain shaking and displacement during the dicing process, thereby greatly reducing the probability of grain flying and improving the wafer yield.

[0021] (2) The present invention proposes a method for cutting wafers into several small pieces by cutting them in the horizontal and vertical directions, and eliminating and reducing the internal stress of the wafers by coating and baking the front side. This effectively improves the problem that the wafers are prone to displacement and vibration during the cutting process due to the inadequate adhesion of the adhesive film, which leads to the wafers breaking when the ultra-high speed blades are grinding.

[0022] (3) The present invention adopts a double-layer coating and step-by-step dicing scheme. First, the wafer is cut into several small pieces and coated and baked on the front side. This effectively increases the contact area between the die and the adhesive layer during the dicing process and reduces the jitter and offset of the die during the dicing process. At the same time, the present invention further improves the die jitter and offset caused by the reduced adhesion area with the adhesive layer and the lack of internal wafer connection when dicing ultra-small die by reducing the dicing speed in the CH2 direction. Furthermore, by increasing the dicing speed in the CH1 direction, the dicing efficiency is improved, which greatly reduces the problems of edge chipping and corner missing during the wafer dicing process. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart illustrating the dicing process for ultra-small grains in an ultrathin wafer provided by this invention;

[0025] Figure 2 This is a schematic diagram of the structure of the dicing ring, adhesive film, and wafer of the present invention;

[0026] Figure 3 Electron micrographs of the wafer bottom surface dicing process to improve its appearance;

[0027] Figure 4 Electron micrographs of the wafer bottom surface after dicing to improve its appearance.

[0028] In the diagram: 1-Scrubbing ring, 2-Film, 3-Wafer. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The purpose of this invention is to provide a method for dicing ultra-small-sized grains in ultra-thin wafers, so as to improve the phenomenon of wafer fragments, flyaways, and edge breakage during the dicing process.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figures 1-2 As shown, this embodiment provides a method for scribing ultra-small size grains in an ultrathin wafer, including the following steps:

[0033] (1) Attach adhesive film 2 to the slicing ring 1, attach the bottom surface of the wafer 3 to the adhesive film 2 and remove the air bubbles, bake in an oven at 70-75℃ for 10-30 minutes, preferably 15 minutes, attach adhesive film to the wafer 3 and remove the air bubbles, bake in an oven at 70-75℃ for 5-10 minutes, preferably 5 minutes.

[0034] (2) Select the dicing blade according to the wafer thickness and subsequent process requirements, install it on the dicing machine spindle, and complete the initialization, height measurement, blade repair and height measurement processes.

[0035] (3) Remove the baked dicing ring 1, let it cool naturally to room temperature, place it on the dicing machine work plate and turn on the vacuum;

[0036] (4) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-50mm / s, and the stepping distance of n*a0 to dice the wafer in the CH1 direction, and cut the wafer 3 into multiple square pieces in the horizontal direction, where a0 represents the width of the grain, and n≥2 (n=2, 3, 4……).

[0037] (5) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-30mm / s, and the stepping distance of n*b0 to dice the wafer in the CH2 direction, and cut the wafer 3 into multiple square pieces in the longitudinal direction, where b0 represents the length of the die and n≥2 (n=2, 3, 4……);

[0038] (6) Take out the slicing ring 1 and bake it in an oven at 70-75℃ for 5-10 minutes, preferably 5 minutes;

[0039] (7) Remove the baked dicing ring 1, let it cool naturally to room temperature, place it on the dicing machine work plate and turn on the vacuum;

[0040] (8) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-50mm / s, and the step pitch of a0 to dice the wafer in the CH1 direction; according to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 2-30mm / s, and the step pitch of b0 to dice the wafer in the CH2 direction; until the wafer 3 is diced to the core target size a0×b0.

[0041] The adhesive film 2 used is a blue film, white film, UV film, resin solid film, or a sticky transparent coating. During the dicing process, the dicing water and cooling water are kept on throughout. The dicing water cools the wafer 3 and washes away the grinding chips, while the cooling water cools the dicing blade. Wafer cleaning fluid is added to the dicing water.

[0042] During the dicing process, CH1 and CH2 are perpendicular to each other. If other conditions arise, the directions can be adjusted as required.

[0043] Each dicing operation is performed in two cuts. The depth of the first cut is controlled to be 1 / 2 to 2 / 3 of the total thickness of wafer 3, and the depth of the second cut is wafer 3 thickness + 0.02 to 0.07 mm.

[0044] like Figure 3 The image shown is an electron microscope image of the dicing on the bottom surface of the wafer before improvement. Figure 4 The image shown is an electron microscope image of the improved wafer bottom surface scribing obtained by the present invention. The comparison shows that the scribing effect is significantly improved after adopting the present invention.

[0045] By using a step-by-step dicing method, the entire wafer 3 is divided into several small pieces. After baking, the fragmentation of the ultrathin wafer during the dicing process is effectively eliminated. By using a front-side coating method, the fly crystal rate is reduced to less than 0.5‰ for ultra-small grain fly crystals.

[0046] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for dicing ultra-small grains in an ultrathin wafer, characterized in that, Includes the following steps: (1) Apply adhesive film to the slicing ring, attach the bottom surface of the wafer to the adhesive film and remove air bubbles, bake in an oven at 70-75℃ for 10-30 minutes, apply adhesive film to the top of the wafer and remove air bubbles, bake in an oven at 70-75℃ for 5-10 minutes. (2) Select the dicing blade according to the wafer thickness and subsequent process requirements and install it on the dicing machine spindle to complete the initialization, height measurement, blade repair and height measurement processes. (3) Remove the baked dicing ring, let it cool naturally to room temperature, place it on the dicing machine work tray and turn on the vacuum; (4) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-50mm / s, and the stepping distance of n*a0 to dice the wafer in the CH1 direction, and cut the wafer into multiple square pieces in the horizontal direction, where a0 represents the width of the die and n≥2. (5) According to the wafer material and dicing requirements, use the spindle speed of 25000-35000rpm, the feed speed of 3-30mm / s, and the stepping distance of n*b0 to dice the wafer in the CH2 direction, and cut the wafer into multiple square pieces in the longitudinal direction, where b0 represents the length of the die and n≥2; (6) Remove the slicing ring and bake it in an oven at 70-75℃ for 5-10 minutes; (7) Remove the baked dicing ring, let it cool naturally to room temperature, place it on the dicing machine work tray and turn on the vacuum; (8) According to the wafer material and dicing requirements, use the process parameters of 25000-35000rpm spindle speed, 3-50mm / s feed speed and a0 step spacing to dice the wafer in the CH1 direction; Based on the wafer material and dicing requirements, the wafer is diced in the CH2 direction using process parameters of 25000-35000rpm spindle speed, 2-30mm / s feed speed, and b0 step pitch until the wafer is diced to the target core size a0×b0.

2. The method for dicing ultra-small grains in an ultrathin wafer according to claim 1, characterized in that: The film can be blue film, white film, UV film, resin solid film, or adhesive transparent film.

3. The method for dicing ultra-small grains in an ultrathin wafer according to claim 1, characterized in that: The dicing water and cooling water are kept running throughout the dicing process. The dicing water cools the wafer, and the cooling water cools the dicing blade. Wafer cleaning fluid is added to the dicing water.

4. The method for dicing ultra-small grains in an ultrathin wafer according to claim 1, characterized in that: CH1 and CH2 are perpendicular to each other.

5. The method for dicing ultra-small grains in an ultrathin wafer according to claim 1, characterized in that: Each dicing operation is performed in two cuts. The depth of the first cut is controlled to be 1 / 2 to 2 / 3 of the total wafer thickness, and the depth of the second cut is the wafer thickness + 0.02 to 0.07 mm.

6. The method for dicing ultra-small grains in an ultrathin wafer according to claim 5, characterized in that: In step (4), when the wafer is diced in the CH1 direction, the number of dicing cuts is 2(A+1), where A represents the number of square pieces obtained by dicing in the horizontal direction; in step (5), when the wafer is diced in the CH2 direction, the number of dicing cuts is 2(B+1), where B represents the number of square pieces obtained by dicing in the vertical direction.

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