Backside abrasive tape etching for improved laser cutting
By laser etching the back grinding tape before back grinding, laser cutting defects caused by changes in wafer thickness due to back grinding are solved, and higher manufacturing yields and more uniform wafer thickness are achieved.
Patent Information
- Application Number
- CN202411625687.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-11-30
- Filing Date
- 2024-11-14
- Publication Date
- 2025-05-30
AI Technical Summary
During laser cutting, the wafer thickness changes caused by back grinding can easily cause laser cutting defects and reduce manufacturing yield.
Before back grinding, the back grinding tape is etched using a laser to remove the material opposite to the second side of the tape to make its thickness more uniform, thereby reducing defects during subsequent laser cutting.
By etching the back grinding belt, the thickness uniformity of the back surface of the wafer is achieved, the occurrence of laser cutting defects is reduced, and the manufacturing yield is improved.
Smart Images
Figure CN120072628A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to backgrinding with tape etching for improved laser cutting. Background Art
[0002] Laser cutting is a technique for separating semiconductor die from a processed wafer. A laser is used to create latent damage along a scribe lane between unit regions of the wafer, which initiates and propagates cracks beneath the wafer surface. Multiple laser scans are typically used with a focused laser beam to create preferential fractures at different depths within the wafer material, followed by radially expanding the carrier tape attached to the wafer. Laser energy is controlled based on the desired fracture depth, and the process is customized to the processed wafer thickness dimension. The laser operating settings for a given latent damage depth can result in laser cutting defects and reduced manufacturing yield due to variations in wafer thickness. Such defects can include die non-separation where a given die does not separate from an adjacent unit region, or meandering defects where die cracks propagate into the active region of the separated die. Semiconductor wafers are typically backgrinded prior to laser cutting and radial expansion to remove material from the wafer backside, and the backgrinding operation sets the wafer thickness prior to die singulation. During backgrinding, the wafer is mounted to a carrier tape, which is referred to as a backgrinding tape. The tape is placed on a backgrinding chuck fastener and pulled towards the chuck by a vacuum pressure, which can bend or bow the wafer due to variations in the backgrinding tape thickness, where the wafer edges typically bow downwards towards the chuck fastener. Subsequent backgrinding produces a flat surface on the backside of the wafer in its bowed position. However, flattening the wafer back surface creates a wafer profile with thickness variations, and terminating the vacuum pressure releases the pressure on the wafer, which causes the wafer to return to its natural orientation with non-uniform wafer thickness. Due to the thickness variations of the backgrinded wafer, subsequent laser cutting can result in laser cutting defects. Summary of the Invention
[0003] In one aspect, an electronic device includes a semiconductor die manufactured by attaching a first side of a tape to a first side of a wafer using a laser; flattening an opposite second side of the tape; flattening an opposite second side of the wafer with the first side of the wafer attached to the first side of the tape; and separating the semiconductor die from the wafer after grinding the second side of the wafer.
[0004] In another aspect, a method of manufacturing an electronic device includes attaching a first side of a tape to a first side of a wafer using a laser; flattening an opposite second side of the tape; flattening an opposite second side of the wafer with the first side of the wafer attached to the first side of the tape; and separating the semiconductor die from the wafer after grinding the second side of the wafer.
[0005] In another aspect, a method of fabricating an electronic device includes attaching a first side of a tape to a first side of a wafer; etching an opposite second side of the tape; planarizing an opposite second side of the wafer while the first side of the wafer is attached to the first side of the tape; and separating a semiconductor die from the wafer after grinding the second side of the wafer. BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Figure 1 is a flow chart showing a method for fabricating an electronic device.
[0007] Figure 2 is a partial cross-sectional side view of a wafer having a starting thickness and a top-side conductive metal or solder bumps.
[0008] Figure 3 is a partial cross-sectional side view of a wafer undergoing a tape placement process.
[0009] Figure 3A is a complete cross-sectional side view of a wafer undergoing a tape placement process.
[0010] Figure 4 is a partial cross-sectional side view of a wafer undergoing an etching process using a laser to remove material from an exposed side of the tape.
[0011] Figure 4A is a complete cross-sectional side view of a wafer undergoing a tape etching process.
[0012] Figure 5 is a partial cross-sectional side view of a wafer undergoing a placement process of placing the tape on a wafer chuck.
[0013] Figure 5A is a complete cross-sectional side view of a wafer undergoing a placement process.
[0014] Figure 6 is a partial cross-sectional side view of a wafer undergoing a vacuum activation process of securing the tape to a wafer chuck.
[0015] Figure 6A is a complete cross-sectional side view of a wafer undergoing a vacuum activation process.
[0016] Figure 7 is a partial cross-sectional side view of a wafer undergoing a back grinding process of removing material from the back side of the wafer.
[0017] Figure 7A is a complete cross-sectional side view of a wafer undergoing a back grinding process.
[0018] Figure 8 is a cross-sectional side view of releasing the wafer and the tape from the wafer chuck.
[0019] Figure 9Is a cross-sectional side view of a wafer that has undergone a laser cutting process. Detailed implementation
[0020] In the figures, like reference numerals refer to like elements throughout, and the various features are not necessarily drawn to scale. Additionally, the term "couple" or "couples" includes indirect or direct electrical or mechanical connections or combinations thereof. For example, if a first device is coupled to or couples with a second device, the connection can be by direct electrical connection or by indirect electrical connection via one or more intervening devices and connections. One or more operating characteristics of various circuits, systems, and / or components are described below in the context of functions, which in some cases are produced by the configuration and / or interconnection of various structures when the circuit system is powered on and operating. In the following discussion and claims, the terms "including", "includes", "having", "has", "with" or variations thereof are intended to be inclusive in a manner similar to the term "comprising" and should thus be interpreted to mean "including but not limited to".
[0021] Unless otherwise stated, "about", "substantially" or "generally" in front of a value means + / - 10% of the stated value. One or more operating characteristics of various circuits, systems, and / or components are described below in the context of functions, which in some cases are produced by the configuration and / or interconnection of various structures when the circuit system is powered on and operating. For ease of description in connection with specific figures, one or more structures, features, aspects, components, etc. may be referred to herein as first, second, third, etc., such as first and second terminals, first, second, and third wells, etc., where these should not be construed as limitations on the claims. The various disclosed structures and methods of the present disclosure can be advantageously applied to manufacturing electronic devices such as integrated circuits. Although it may be desirable for such examples to provide various improvements, the present disclosure does not require specific results unless explicitly recited in the specific claims.
[0022] Figure 1 Method 100 for manufacturing an electronic device is shown, and Figures 2 to 9 A starting wafer processed according to method 100 is shown. Method 100 includes back grinding with etching before back grinding the wafer to reduce defects during laser cutting for die singulation.
[0023] Method 100 begins wafer processing at 102, for example, to form one or more electronic components, such as transistors, diodes, resistors, capacitors, etc. (not shown) in corresponding unit areas of the wafer. Figure 2Shown is a starting wafer 200 having a starting thickness TS, such as a silicon wafer, silicon-on-insulator (SOI), gallium arsenide (GaN) wafer, etc. The wafer 200 has a front or first side 201 and a back or second side 202. In one example, the wafer 200 has a plurality of unit regions or die regions 204, which individually correspond to the expected semiconductor dies after die singulation.
[0024] In one embodiment, method 100 includes Figure 1 bumping at 103 in to form conductive metal or solder bumps along one side of the processed wafer. Figure 2 Shown is an example where conductive metal or solder bumps 208 are formed on conductive die pads (not shown) through openings in an insulating layer 206 on the first side 201 of the processed wafer 200. In another embodiment, bumping at 103 is omitted, for example, for applications having die pads for wire bond interconnections for subsequent die singulation of semiconductor dies.
[0025] Method 100 includes Figure 1 tape attachment at 104 in. Figure 3 and 3A Shown is an example where a back grinding tape 300 is attached to the first side 201 of the wafer 200 by a tape placement process 304. The placement process 304 can be a manual operation or can be automated. In one example, the process 304 attaches the first side 301 of the tape 300 to the first side 201 of the wafer 200 and includes covering the conductive metal or solder bumps 208 with the tape 300. In one example, the back grinding tape 300 is UV curable, and the placement process 304 includes attachment and curing steps.
[0026] In this example or another example, the back grinding tape 300 is a MY595 or equivalent tape laminated to the first side 201 of the wafer 200 to prepare for wafer back grinding and subsequent laser cutting. In these examples or another example, the tape 300 can include polyester. In one or more embodiments of method 100, the polyester-based tape can facilitate evaporation during subsequent laser etching for selectively removing material from the second side 302 of the back grinding tape 300.
[0027] As Figure 3 and 3A shown in, the attached back grinding tape 300 has a non-uniform thickness along a third direction Z. As Figure 3AAs best shown, the attached tape 300 has an initial thickness before a subsequent etching process, wherein the tape thickness between the respective first side 301 and second side 302 of the tape 300 varies between a first thickness T1 and a smaller second thickness T2. In the illustrated example, the tape thickness at the center of the tape 300 is approximately the first thickness T1, and the thickness at the outer periphery of the tape 300 is approximately the smaller second thickness T2. The smaller tape thickness T2 at the wafer edge may be due to various reasons, such as edge effects associated with the placement process 304, any included one or more adhesive curing steps, tape trimming around the edge of the wafer 200, etc. Other backgrind tape thickness variation profiles are possible before subsequent tape etching.
[0028] Method 100 continues backgrind tape etching at 106 in Figure 1 to promote background wafer thickness uniformity and subsequent processing steps. Figure 4 and 4A shows an example in which an etching process 400 is performed that removes material from the exposed second side 302 of the backgrind tape 300. In one example, the etching process 400 is a laser etching process performed using a laser 402 that is translated along a path shown as arrow 403. In one example, the power and positioning of the laser 402 and the etching time of the etching process 400 are controlled according to a desired final or third thickness T3 between the respective first side 301 and second side 302 of the tape 300. In one example, the laser etching extends across the entire exposed second side 302 of the tape 300. In another embodiment, the laser etching only etches one or more portions of the second side 302 of the backgrind tape 300.
[0029] In one example, the etching process 400 provides non-contact removal of a selected amount of tape material from all or part of the second side 302 of the tape 300, including evaporating at least a portion of the material on the second side 302 of the tape 300 using the laser 402. This provides advantages compared to alternative methods such as using chemicals to dissolve and / or grind the tape.
[0030] In the illustrated example, the etching process 400 provides a generally flat etched second side 302 of the tape 300 through a non-contact etching process, although not all possible embodiments are strictly required to be so. Performing the etching process 400 with a laser 402 facilitates the evaporation of the material to be removed and allows the processing chamber to be evacuated to remove the etched material. In contrast, contact techniques (e.g., using a grinding wheel or diamond cutter to fly cut or grind the exposed side of the tape to flatten the top surface of the tape) can result in production downtime to clean the discharge port inside the processing chamber. The use of the polyester-based tape 300 can also facilitate the removal of tape material by laser etching. The etching process provides cost savings and improved unit output per hour compared to grinding or fly cutting and eliminates or reduces the downtime for converting the machine to a fly cutting operation and cleaning the tool from a clogged discharge port. Any suitable laser 402 can be used, and the power setting can be adjusted to remove the desired amount of tape material to provide a generally consistent tape thickness T3.
[0031] In the illustrated example, the etching process 400 flattens the second side 302 of the tape 300, although not all possible embodiments are strictly required to be so. In addition to providing a generally flat second side 302, in one example, the laser etching process 400 provides a generally uniform thickness T3 of the tape 300. In one example, the laser 402 is a carbon dioxide (CO 2 ) laser. In another example, the laser 402 is a light emitting diode (LED) laser.
[0032] In the illustrated embodiment, the final or third thickness T3 of the etched tape 300 is less than the first thickness T1 and less than the second thickness T2, and the laser etching process 400 removes tape material from all portions of the second side 302 of the tape 300 to provide a flat etched second side 302. In another example, the third thickness T3 is approximately equal to the second thickness T2, and the etching process 400 does not require the removal of tape material from all surfaces of the top side 302, and the third thickness T3 is less than the first thickness T1.
[0033] Method 100 continues at Figure 1 108 to mount the wafer into the back grinding tool. In one example, at 108, the wafer is mounted with the flattened second side 302 of the back grinding tape 300 engaging the back grinding chuck table. Figure 5 And 5A illustrates an example where a wafer mounting process 500 is performed that mounts the wafer on a wafer chuck 502 for grinding processing.
[0034] In the illustrated example, at Figure 1 110, the vacuum system of the wafer chuck is turned on. Figure 6 And 6AAn example is shown where a vacuum start process 600 is performed that evacuates a vacuum to hold the tape 300 against the top side of the wafer chuck 502. The vacuum start process 600 does not significantly bend or bow the wafer 200 because the back grinding tape 300 has a substantially uniform thickness T3.
[0035] Method 100 continues to planarize the second side 202 of the wafer 200 at 112 in Figure 1 Figure 7 and 7A An example is shown where a back grinding process 700 is performed with the first side 201 of the wafer 200 attached to the first side 301 of the tape 300. The back grinding process 700 in the illustrated example removes material from the second side 202 of the wafer 200, and the process 700 provides a reduced final thickness TF, as Figure 7 and 7A shown.
[0036] At 114 in Figure 1 Method 100 continues wafer release. Figure 8 An example is shown where a wafer chuck release process 800 is performed that releases the back ground wafer 200 and the back grinding tape 300 from the wafer chuck table 502, including stopping the chuck table vacuum.
[0037] At 116 in Figure 1 Method 100 in this example includes separating individual semiconductor die from the processed and back ground wafer 200. Figure 9 An example is shown where a laser cutting process 900 is performed using the laser 402 to selectively create latent damage at a desired depth within the semiconductor wafer 200. In this example, the laser cutting process 900 is performed along the back or second side 202 of the semiconductor wafer 200, where the first side 201 of the wafer 200 remains attached to the first side 301 of the back grinding tape 300.
[0038] The method may include additional processing steps of removing the back grinding tape 300 and / or mounting the wafer 200 to a dicing tape (not shown) and radially expanding the dicing tape to complete separation of the individual semiconductor die from the processed wafer 200 (not shown) using known techniques.
[0039] Other aspects of the present disclosure provide an electronic device having a semiconductor die manufactured by the above-described process, the process including, for example, attaching a first side 301 of a tape 300 to a first side 201 of a wafer 200 using a laser 402, planarizing an opposite second side 302 of the tape 300, etching and / or planarizing an opposite second side 202 of the wafer 200 with the first side 201 of the wafer 200 attached to the first side 301 of the tape 300, and separating the semiconductor die from the wafer 200 after lapping 112 the second side 202 of the wafer 200.
[0040] Within the scope of the claims, modifications to the described examples are possible and other embodiments are possible.
Claims
1. A method for manufacturing an electronic device, the method comprising: attaching a first side of the tape to a first side of the wafer; planarizing an opposing second side of the ribbon using a laser; planarizing an opposing second side of the wafer with the first side of the wafer attached to the first side of the tape; and Semiconductor dies are separated from the wafer after grinding the second side of the wafer. 2 . The method of claim 1 , wherein separating the semiconductor die from the wafer comprises performing a laser cutting process with the first side of the wafer attached to the first side of the tape.
3. The method of claim 2, wherein the tape comprises polyester. 4 . The method of claim 3 , wherein planarizing the second side of the ribbon comprises evaporating at least a portion of material of the second side of the ribbon using a laser. 5 . The method of claim 2 , wherein planarizing the second side of the wafer comprises grinding the second side of the wafer.
6. The method of claim 2, further comprising forming conductive metal or solder bumps along the first side of the wafer, wherein attaching the first side of the tape to the first side of the wafer includes covering the conductive metal or solder bumps with the tape.
7. The method of claim 1, wherein the tape comprises polyester.
8. The method of claim 1, wherein planarizing the second side of the ribbon comprises evaporating at least a portion of the material of the second side of the ribbon using a laser.
9. The method of claim 1 wherein planarizing the second side of the strip comprises performing a laser etching process using the laser.
10. The method of claim 9, wherein the laser is a carbon dioxide laser.
11. The method of claim 9, wherein the laser is a light emitting diode laser.
12. The method according to claim 9, wherein: Prior to performing the laser etching process, the thickness of the tape between the first side and the second side varies between a first thickness and a second, smaller thickness; the laser etching process removes tape material from the second side of the tape to provide a flat etched second side of the tape having a uniform third thickness between the etched second side of the tape and the first side of the wafer; and The third thickness is smaller than the second thickness.
13. The method of claim 12, wherein before performing the laser etching process, the thickness between the first side and the second side of the tape at the center of the tape is approximately the first thickness, and the thickness between the first side and the second side of the tape at the peripheral edge of the tape is approximately the second thickness.
14. The method of claim 9, wherein: Prior to performing the laser etching process, the thickness of the tape between the first side and the second side varies between a first thickness and a second, smaller thickness; the laser etching process removes tape material from at least a portion of the second side of the tape to provide a flat etched second side of the tape having a uniform third thickness between the etched second side of the tape and the first side of the wafer; and The third thickness is substantially equal to the second thickness.
15. The method of claim 14, wherein before performing the laser etching process, the thickness between the first side and the second side of the tape at the center of the tape is approximately the first thickness, and the thickness between the first side and the second side of the tape at the peripheral edge of the tape is approximately the second thickness.
16. The method of claim 1, wherein: Prior to flattening the second side of the tape, a thickness between the first side and the second side of the tape varies between a first thickness and a smaller second thickness; planarizing the second side of the tape removes tape material from at least a portion of the second side of the tape to provide a planar etched second side of the tape having a uniform third thickness between the etched second side of the tape and the first side of the wafer; and The third thickness is smaller than the first thickness.
17. An electronic device comprising a semiconductor die manufactured by: attaching a first side of the tape to a first side of the wafer; planarizing an opposing second side of the ribbon using a laser; planarizing an opposing second side of the wafer with the first side of the wafer attached to the first side of the tape; and The semiconductor dies are separated from the wafer after grinding the second side of the wafer.
18. The electronic device of claim 17, wherein the semiconductor die includes conductive metal or solder bumps along a side of the semiconductor die.
19. A method of manufacturing an electronic device, the method comprising: attaching a first side of the tape to a first side of the wafer; etching an opposing second side of the strip; planarizing an opposing second side of the wafer with the first side of the wafer attached to the first side of the tape; and Semiconductor dies are separated from the wafer after grinding the second side of the wafer.
20. The method of claim 19, wherein etching the second side of the strip comprises performing a laser etching process.