A method for back-side film application before Taiko wafer plating

Abstract

This invention provides a method for back-side film application on a Taiko ring wafer before electroplating. The method includes fixing the back-side-film-applied wafer on a base, pre-cutting a long section of square protective film and placing it at the edge of the Taiko ring on the wafer; moving a three-segment film application roller to the edge of the Taiko ring on the wafer for application, the three-segment film application roller comprising film application roller one, film application roller two, and film application roller three, with both ends of film application roller two movably connected to film application roller one and film application roller three respectively; rotating the base one full turn to remove excess protective film; opening the bottom air curtain, with the bottom air curtain facing the side of the wafer, to support the unapplied protective film; rotating the base while simultaneously moving the three-segment film application roller to roll and apply the film along the edge of the Taiko ring; continuing to move the three-segment film application roller to roll and apply the film along the side of the Taiko ring; closing the bottom air curtain and removing the three-segment film application roller. This invention, by employing a segmented film application method, ensures that protective film is also applied to the edge and side of the Taiko ring on the wafer, reducing the risk of metal plating peeling off the wafer edge during electroplating.

Description

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[0001] The present invention relates to the technical field of semiconductor manufacturing, and particularly relates to a method for backside film pasting before Taiko wafering plating. Background Art

[0002] With the development of semiconductor products towards being light, thin, short, and small, Flip chip (flip chip packaging technology) has been increasingly widely used. The key of Filp chip lies in using the plating process to fabricate the welded metal layer UBM (UnderBumping Metallization). The UBM fabricated in this way is widely used because of its low cost and good performance.

[0003] In the production process of some high-end power chips such as IGBTs, wafer thinning needs to be carried out first and then the front-side nickel-palladium-gold plating process. Before the plating process, in order to protect the process state already completed on the backside of the wafer, a protective film needs to be pasted first for protection. However, in the current mature Taiko wafer backside film pasting process, as Figure 1 shown, the protective film cannot be pasted on the edge and side positions of the wafer; as Figure 2 shown, during the plating operation, the plating metal nickel-palladium-gold will be deposited on the edge and side positions of the wafer; as <着 Figure 3 shown, it will cause peeling during the subsequent operation process, and further cause contamination. Summary of the Invention

[0004] In view of this, the present invention provides a method for backside film pasting before Taiko wafering plating, so as to solve the problem that the existing film pasting process insufficiently protects the edge and side positions of Taiko wafers, and easily causes the peeling of the edge plating of the wafers.

[0005] The present invention provides a method for backside film pasting before Taiko wafering plating, including the following steps:

[0006] Step 1: Thinning the backside of the wafer by using the Taiko thinning process;

[0007] Step 2: Performing a backside film pasting process on the wafer;

[0008] Step 3: Fixing the wafer with the backside film pasted on a base, pre-cutting a relatively long square protective film and placing it at the Taiko ring edge of the wafer;

[0009] Step 4: Moving a three-stage film pasting roller to the Taiko ring edge of the wafer for pasting. The three-stage film pasting roller includes a film pasting roller 1, a film pasting roller 2, and a film pasting roller 3. The two ends of the film pasting roller 2 are respectively movably connected to the film pasting roller 1 and the film pasting roller 3;

[0010] Step 5: Rotate the base one full turn to remove the excess protective film;

[0011] Step 6: Activate the bottom air curtain, which faces the side of the wafer to support the unattached protective film;

[0012] Step 7: Rotate the base while moving the three-section film-applying roller to perform Taiko ring edge rolling film application;

[0013] Step 8: Continue moving the three-section film-applying roller to perform Taiko ring side rolling film application;

[0014] Step 9: Close the bottom air curtain and remove the three-section film-applying roller.

[0015] Preferably, in step one, the back side of the wafer is thinned to form a Taiko ring.

[0016] Preferably, the protective film formed by the back-side film application process in step two does not cover the edges and sides of the Taiko ring.

[0017] Preferably, the pre-cut, longer section of the square protective film described in step three is sufficient to cover the edges and sides of the Taiko ring.

[0018] Preferably, the width of the protective film in step three is 2.0 mm to 5.0 mm.

[0019] Preferably, the film-applying rollers one, two, and three described in step four have the same shape and structure.

[0020] Preferably, the moving three-section film-applying roller mentioned in steps seven and eight specifically refers to moving the movable connection position of the three-section film-applying roller.

[0021] In the wafer back-side film application process before electroless plating, this invention, in addition to the traditional wafer back-side film application process, also incorporates a three-section film application roller at the wafer edge. By continuously adjusting the rolling position of the three-section film application roller, the protective film is sequentially applied to the edge of the Taiko wafer, the upper side, and the bottom side. This solves the problem of insufficient protection for the edges and sides of the Taiko wafer in existing film application processes, which easily leads to the peeling of the wafer edge plating. It reduces the risk of wafer edge plating peeling during electroless plating and avoids wafer fragments or machine contamination. Attached Figure Description

[0022] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0023] Figures 1-3 This is a schematic diagram of Taiko's current wafer back-side lamination process;

[0024] Figure 4 The flowchart shown is a method for applying a back-side film to a Taiko wafer before plating according to an embodiment of the present invention.

[0025] Figures 5-11 The diagram shows the structural schematics of each step in the Taiko wafer back-side film application method before plating, as described in an embodiment of the present invention. Detailed Implementation

[0026] The present invention is described below based on embodiments, but the invention is not limited to these embodiments. In the detailed description of the invention below, certain specific details are described in detail. Those skilled in the art will fully understand the invention even without these details. To avoid obscuring the essence of the invention, well-known methods, processes, flows, elements, and circuits are not described in detail.

[0027] Furthermore, those skilled in the art should understand that the accompanying drawings provided herein are for illustrative purposes only and are not necessarily drawn to scale.

[0028] Unless the context explicitly requires it, words such as "including" or "contains" throughout the application should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to".

[0029] In the description of this invention, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0030] Due to increasingly stringent requirements for IGBT chips, chemical plating can be used to deposit metal onto the front side of the wafer to enhance its thickness and hardness. However, in practice, chemical plating can result in metal adhering to the uneven and unprotected Taiko rings, easily leading to metal detachment from the Taiko rings and even wafer fragmentation and equipment contamination. Therefore, this invention proposes a method for fabricating semiconductor power devices. The technical solution of this invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Figure 4 The flowchart shown is a method for applying a back-side film to a Taiko wafer before plating according to an embodiment of the present invention. Figures 5-9 The diagram shows the structural schematics of each step in the Taiko wafer plating back-side film application method according to an embodiment of the present invention. Figure 4 As shown, the back-side film application method before Taiko wafer plating in this embodiment of the invention includes the following steps:

[0032] Step 1: Thinning the backside of the wafer using the Taiko thinning process.

[0033] The Taiko thinning process is a new technology for wafer backside grinding. This technology is different from the previous backside grinding. When grinding the wafer, the edge part around the wafer (about 3 mm) will be retained, and only the inside of the circle will be ground and thinned. By leaving a margin around the wafer, wafer warping is reduced and the wafer strength is increased. 12-inch wafers usually use the Taiko thinning process for backside thinning. After thinning, a Taiko ring is formed at the backside edge of the wafer. In the embodiments of the present invention, the constituent material of the wafer can be undoped single-crystalline silicon, single-crystalline silicon doped with impurities, silicon-on-insulator (SOI), etc. Before performing Taiko thinning on the backside of the wafer, the front-side process of the wafer is carried out, which will not be described in detail here. According to the thickness requirements and packaging conditions of the power device, after thinning the backside of the wafer to form a Taiko ring, the thickness of the wafer is reduced.

[0034] Step 2: Performing a backside film pasting process on the wafer.

[0035] As Figure 5 shown, use the suction cup in the upper cavity to adsorb the protective film, and the base in the lower cavity to carry the Taiko wafer. Close the upper and lower cavities, and use the backpressure gas supply to perform the backside film pasting process on the wafer. The edge and side positions of the Taiko ring cannot be pasted with the protective film. As shown in the circle in the figure, the protective film does not cover the edge and side positions of the Taiko ring.

[0036] Step 3: Fix the wafer with the backside film pasted on the base, pre-cut a relatively long square protective film and place it at the edge of the Taiko ring of the wafer.

[0037] Specifically, as Figure 6 shown, fix the wafer with the backside film pasted on the base. As Figure 7 shown, the base moves horizontally to the film pasting operation station, and pre-cut a square protective film with a suitable width according to the process requirements. In the embodiments of the present invention, pre-cut a relatively long square protective film that can sufficiently cover the edge and side positions of the Taiko ring. The width of the protective film is 2.0 mm to 5.0 mm. As Figure 8 shown, the base rises vertically to the operation station and place the protective film at the edge of the Taiko ring of the wafer.

[0038] Step 4: Move the three-stage film pasting roller to the edge of the Taiko ring of the wafer for pasting. The three-stage film pasting roller includes film pasting roller 1, film pasting roller 2, and film pasting roller 3. The two ends of film pasting roller 2 are respectively movably connected to film pasting roller 1 and film pasting roller 3.

[0039] As Figure 9As shown, the three-section laminating roller of this embodiment includes laminating roller one, laminating roller two, and laminating roller three. Both ends of laminating roller two are movably connected to laminating roller one and laminating roller three, respectively. Laminating roller one, laminating roller two, and laminating roller three have the same shape and structure. The three-section laminating roller moves to the initial working position, at the edge of the Taiko ring on the wafer.

[0040] Step 5: Rotate the base one full turn to remove the excess protective film.

[0041] In this embodiment of the invention, the base is rotated one revolution to measure the length of the protective film required to complete the adhesion of the protective film at the edge and side positions of the Taiko ring, and the longer protective film pre-cut in step three is removed.

[0042] Step 6: Activate the bottom air curtain.

[0043] Step 7: Rotate the base while moving the three-section film-applying roller to apply the film to the edge of the Taiko ring.

[0044] like Figure 10 As shown in the embodiment of the invention, the bottom air curtain faces the side of the wafer, supporting the unattached protective film. The movable three-section film-applying roller specifically refers to the movable connection position of the three-section film-applying roller, as shown in the figure, which moves along the Z1 and Z2 directions. In this embodiment of the invention, by rotating the base and simultaneously moving the three-section film-applying roller, Taiko ring edge rolling film application is performed.

[0045] Step 8: Continue moving the three-section film-applying roller to apply the film by rolling it onto the side of the Taiko ring.

[0046] like Figure 11 As shown, continue moving the three-section film-applying roller to roll and apply film to the sides of the Taiko ring, thereby completing the coverage of the protective film on the edges and sides of the Taiko ring.

[0047] This invention provides a complete protective film on the back side of the wafer, covering the back side, edges, and sides. This film protects the Taiko ring from subsequent chemical plating processes, isolating the Taiko ring from the chemical agents and preventing metal deposition on the Taiko ring, thus reducing the risk of metal plating peeling off.

[0048] Step 9: Close the bottom air curtain and remove the three-section film-applying roller.

[0049] The back-side film application method for Taiko wafers before electroplating in this invention employs a segmented film application scheme on the back of the wafer before the electroplating process. Building upon traditional wafer back-side film application processes, a three-segment film application roller is added at the wafer edge. By continuously adjusting the rolling position of the three-segment film application roller, the protective film is sequentially applied to the Taiko circumferential edge, the upper side, and the bottom side. This completes the edge film application process for the circular wafer (including the back, edge, and side), ensuring the back of the wafer is protected by a protective film. This prevents the back-side metal from peeling off during subsequent electroplating, solving the problem of insufficient protection for the edges and sides of Taiko wafers in existing film application processes, which easily leads to wafer edge plating peeling. This reduces the risk of wafer edge plating peeling during electroplating, avoiding wafer fragmentation or equipment contamination.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for back-side film application before Taiko wafer plating, characterized in that, Includes the following steps: Step 1: Thin the back side of the wafer using the Taiko thinning process; Step 2: Perform a back-side lamination process on the wafer; Step 3: Fix the wafer with the back film applied onto the base, pre-cut a long square protective film and place it at the edge of the Taiko ring of the wafer; Step 4: Move the three-section film-applying roller to the edge of the Taiko ring on the wafer and apply the film. The three-section film-applying roller includes film-applying roller 1, film-applying roller 2 and film-applying roller 3. The two ends of film-applying roller 2 are movably connected to film-applying roller 1 and film-applying roller 3, respectively. Step 5: Rotate the base one full turn to remove the excess protective film; Step 6: Activate the bottom air curtain, which faces the side of the wafer to support the unattached protective film; Step 7: Rotate the base while moving the three-section film-applying roller to perform Taiko ring edge rolling film application; Step 8: Continue moving the three-section film-applying roller to perform Taiko ring side rolling film application; Step 9: Close the bottom air curtain and remove the three-section film-applying roller.

2. The method for back-side film application before Taiko wafer plating according to claim 1, characterized in that, In step one, the back side of the wafer is thinned to form a Taiko ring.

3. The method for back-side film application before Taiko wafer plating according to claim 2, characterized in that, The protective film formed by the back-mounting process described in step two does not cover the edges and sides of the Taiko ring.

4. The method for back-side film application before Taiko wafer plating according to claim 2, characterized in that, The pre-cut, longer square protective film described in step three is sufficient to cover the edges and sides of the Taiko ring.

5. The method for back-side film application before Taiko wafer plating according to claim 1, characterized in that, The width of the protective film mentioned in step three is 2.0mm to 5.0mm.

6. The method for back-side film application before Taiko wafer plating according to claim 1, characterized in that, The film-applying rollers 1, 2, and 3 described in step 4 have the same shape and structure.

7. The method for back-side film application before Taiko wafer plating according to claim 1, characterized in that, The moving of the three-section film-applying roller in steps seven and eight specifically refers to moving the movable connection position of the three-section film-applying roller.

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