TWI227528B - Method for forming bumps on a wafer and plating tool for performing the method - Google Patents

Abstract

A method for forming bumps on a wafer is disclosed. A wafer is provided. An under bump metallurgy layer (UBM) is formed on an active surface of the wafer and is further extended onto lateral of the wafer. A photoresist layer covers partial of the UBM layer on the active surface of the wafer. Then a wafer plating tool having a seal ring and at least a contact pin on its annular internal wall clamps the wafer. The seal ring seals the lateral of the wafer without covering the active surface of the wafer to prevent the UBM layer on lateral of the wafer, back surface of the wafer and the contact pin from being exposed. The contact pin contacts the UBM layer on the lateral of the wafer for completely plating bumps on the active surface of the wafer.

Description

1227528 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a method for forming bumps on a wafer, and in particular, to a method for fully plating bumps on a wafer and a plating fixture used therefor. . ° [Prior technology] The conventional method for forming bumps on wafers can be divided into Electroplating, Evaporation, and Printing (Screen

Printing or Stud Bumping, etc. The method of forming bumps on a wafer by electroplating is a method for mass production. However, the plating fixture used to fix the wafer during the plating process will seriously affect ·· Wafer yield with good bumps. In the process of forming bump keys on a wafer, please refer to FIG. 1. A wafer 10 has a front surface 11 and a back surface 2. The wafer 10 has a protective layer 13 on the front surface 11. And a plurality of bonding pads 14, 14a, an under bump metallurgy (UBM) 20 is formed on the front surface 11 of the wafer 10, and covers and bonds the bonding pads 14, and then forms a photoresist A layer 30 is on the metal layer 20 under the bump on the front side 11 of the wafer 10. The photoresist layer 30 has a plurality of openings 31 after exposure, and the openings 31 are used to expose the pads 14 The upper part of the bump is under the metal layer 20, and the photoresist layer 30 does not cover the peripheral pads 4a to the front surface 11 of the wafer 10, and is electrically connected to the crystal during power plating. The front side of the circle 〇 丨 丨 The surrounding metal layer 20 under the bump which is not covered by the photoresist layer 30. Before plating, the wafer 10 is placed on a conventional plating fixture 50. The 50 series is composed of a wafer carrier 51 and a clamping ring 52. The clamping ring 52 is formed to extend horizontally and inwardly.

Page 5 1227528 V. Description of the invention (2) 2 plate portion 53, a seal 2 "and a contact pin 55 are installed on the inner surface of the extension plate portion 53, when the wafer 10 is positioned on the wafer carrier tray 51. The sealing ring 54 of Ershuang holding ring 52 is in sealing contact with the photoresist layer 30 to clamp the circle 10, and the contact pin 55 of the holding ring 52 is in electrical contact with the front side of the wafer The peripheral metal layer 20 under the bump which is not covered by the photoresist layer 30 at the periphery of 11 is used to provide cathode potential to 7 lower metal layers 20. It is known that the contact pin 55 is located at the edge of the front side 11 of the circle 10 At a distance of about 2.5 mm from the side of the wafer, and to prevent the contact pin 55 from being exposed and contaminated by the plating solution, the sealing ring 54 should cover the front side of the wafer. The edge is away from the wafer. The side is about 3 ~ 5 mm, so that the peripheral pads located on the front side of the wafer 丨 0 are often sealed by the sealing ring 54, which leads to the peripheral edges of the wafer 丨 0

Surface * 塾 14a cannot form bumps 40 ′ by electric keys, so that after wafer dicing, good wafers can only be scrapped, reducing the generation rate of wafers with bumps. In addition, such as China Patent Publication No. 461 0 1 5 "Wafer plating fixture" According to the disclosure, another wafer plating fixture has an upper cover (ie, a clamping ring). The opening of the upper cover is used to expose the plating area of the wafer. However, the upper cover covers the wafer. The periphery of the front side of the circle prevents the front side periphery of the wafer from electrically bonding to form bumps, thereby reducing the efficiency of wafers with bumps. [Summary of the Invention] The main purpose of the present invention is to provide a bump forming method for a wafer. In the wafer fixing step, a sealing ring of a wafer electroplating jig is used to closely contact a side surface of a wafer. The contact pins of the circular electroplating jig are in electrical contact with the metal layer under the bump (Under Bump Metallurgy,

1227528

(ϋΒΜ), so that the front surface of the wafer has a good bump crystal to improve the second time of the present invention_ 日 日 尨 + # h is used for-wafer power supply keying, which can be provided with a seal The circle and at least touch "Hai; circle: =: pass between the bumps on the side of the clamping wafer; when the circle is fixed, the tail metal layer is electrically contacted, so that the welding lane on the front edge of the wafer can be plated. 'Bump formation' to improve wafer yield with good bumps. According to the present invention, a bump formation method for a wafer, first & mention a wafer, which has a front surface, a back surface and a wafer. A plurality of bonding pads are formed on the side surface between the front surface and the back surface; an under bump metallurgy (UBM) is formed on the front side of the wafer; and the under bump metal layer is extended To the side of the wafer; ♦ After that, a photoresist layer is formed on the front side of the wafer, the photoresist layer covers the metal layer under the bump on the front side of the wafer, and the photoresist layer has A plurality of openings for exposing the metal layer under the bumps on the pads; An electric mining fixture fixes the wafer, the wafer key fixture has a plurality of, the clamping ring system is provided with a dense friction and at least one contact pin, and the sealing ring system seals the face of the wafer. The contact pins are in electrical contact with the metal layer under the bumps on the side of the sealed wafer. During the electroplating process, a number of bumps are formed in the openings. Therefore, the openings in the photoresist layer are not required. Affected by the cover of the wafer electrical and mining jig, it can be designed to form bumps with electrical keys at any position on the front side of the wafer (including the periphery of the front side), and increase the number of wafers with bumps after cutting the wafer. .

Page 7 1227528 ____ V. Description of the invention (4) [Embodiment] Referring to the attached drawings, the present invention will be enumerated with the following examples. According to the bump forming method of the wafer according to the present invention, first referring to FIG. 2A, a wafer 110 is provided. The wafer 110 has a front surface 111, a back surface 112, and a front surface 111 and a back surface 11. The ring-shaped side surface 11 3 between two, the front surface 111 is formed with a protective layer 11 4 [passivation layer] and a plurality of pads 1 1 5 exposed in the protective layer 11 4, wherein the pads 11 5 include at least A peripheral pad 11 5 a, preferably, the distance between the peripheral pads 115 a and the side surface 113 of the wafer 110 is not greater than 5.Omni. Referring again to FIG. 2B, a & Under Bump Metallurgy (UBM) 120 is formed on the front surface 111 of the wafer by using sputtering or vapor evaporation technology. The metal layer 120 under the bump extends to the side 11 3 of the wafer 110, and in this step, the metal layer 120 under the bump completely covers the protective layer 114 and the protective layer 114 on the front side 111 of the wafer. Those soldering pads 115. Please refer to FIG. 2C again. For example, a photoresist layer 1 30 is formed on the front surface 111 of the wafer 111 by a dry film attachment method or a wet photoresist spin coating or printing method. 2 0, and after exposure and development, the photoresist layer 1 30 is formed with a plurality of openings 1 31, the openings 1 31 are exposed under the bump metal layer 120 on the solder 114, the openings 131 includes at least one trimming opening 131a, which corresponds to the peripheral pad 115a described above, and the distance from the side surface 113 of the wafer 110 is not greater than 5.0 mm. In this embodiment, the photoresist layer The 1 30 series completely covers the front surface 111 of the wafer 110, and the photoresist layer 130 does not cover the side 11 3 of the wafer π 0.

Mil IRH Page 8 1227528 V. Description of the invention (5) Please refer to Figure 2D. A wafer plating fixture 200 is used to fix the wafer 110. The wafer plating fixture 200 includes a wafer. Carrier disk 2 and a clamp ring 220 'The wafer carrier disk 210 has a carrier surface 211 for carrying the wafer 110, and the clamp ring 220 is combined with the wafer carrier disk 21 for clamping. It is assumed that the wafer 110 is fixed, the clamping ring 22o has an annular internal wall 221, and the annular inner wall 221 of the clamping ring 220 is joined with a soft sealing ring 230 and at least one contact pin 24o, The Φ seal ring 2 3 0 is located on the outer edge of the annular inner wall 2 21 and is used to contact the side surface 11 3 of the wafer 11 0 or / and the vertical side of the photoresist layer 丨 3 〇, the contact pin 240 series is provided between the sealing ring 230 and the wafer carrier 21 0. When the crystal circle 110 is fixed by the wafer plating jig 200, the back surface of the wafer 110 is 1 j 2 series Attached to the bearing surface 211 of the wafer carrier disk 21 〇, the sealing ring 2 3 0 is closely adhered to the side surface 11 3 of the wafer 110 and does not cover the front surface of the wafer 11 丨n, the contact pin 24 is electrically contacted with the metal layer 1 2 under the bump of the sealed wafer side 3, so the wafer plating fixture 2 is used; 〇〇 can be fixed The photoresist layer 130 on the front surface 111 of the wafer 110 is completely exposed, and the peripheral opening 131a of the photoresist layer 13 is of course not affected by the cover of the wafer plating fixture 200 for full plating. Referring to FIG. 2E, the fixed wafer 110 is immersed in a plating bath (not shown in the figure). Since the metal layer 120 under the bump is electrically connected to the cathode with the contact pin 24, a cathode is formed. A plurality of bumps 140 are formed on the openings 131 (including peripheral openings 131a) of the photoresist layer 130 by electroplating. The bumps 14 are bonded to the metal layer 120 under the bumps 115 on the solder pads 115. In the embodiment, the bumps 140 are tin-lead alloys formed by electroplating. Since the wafer 1227528 V. Description of the Invention (6) ----- 110, the peripheral edge of the front surface 111 is not covered by the sealing ring 23o. During the electroplating process, all the openings 131 (including the peripheral openings 131a) of the photoresist layer 13 can be fully plated, so that a bump 14 can be bonded to a pad 115 on the wafer front lu. There will not be any problem of scrapping the peripheral wafers around the wafer due to the phenomenon of covering plating, so that the entire wafer can be cut into more wafers with good bumps. Please refer to FIG. 3, after the bumps 140 are formed by electroplating, the wafer key bond fixture 200 is removed and the photoresist layer 13 is removed, and the bumps 140 are used as anti-button recording covers. # 刻Remove the metal layer under the bump 1 2 0, so that the metal layer 120 under the bump under the bump 丨 4 is retained. 'If necessary, the process is performed by Re Uqw to make the bumps. Block 1 40 is spherical. The protection scope of the present invention shall be determined by the scope of the appended patent application. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention. .

Page 10 1227528 Simple description of the pattern [simple figure 1 figure 2A to 2E figure 3 figure description]: Known in wafer electroplating • According to the hair in the bump shape: according to the hair with the bump circle The process of forming the crystal-clear wafer with the bumper fixture fixed is the process of the local plating of the wafer-clear wafer. The local cross-section of the bump is formed. The local cross-section shows the cross-section of the bump formation square, and the crystal plane is known. ; Law, a wafer intention; and law, the drawing. Simple description of the component symbols: 10 wafer 11 front 12 13 protective layer 14 back of solder pads 20 metal layer under bump 14a peripheral pad 30 photoresist layer 31 opening 40 50 wafer plating fixture bump 51 wafer carrier tray 52 Clamping ring 53 Extension plate portion 54 Sealing ring 55 Contact pin 110 Wafer 111 Front surface 112 Back surface 113 Side surface 114 Protective layer 115 Solder pad 115a Peripheral pad 120 Under bump metal layer 130 Photoresist layer 131 Opening 131a Peripheral opening D 140 Bump 200 wafer plating jig 210 wafer carrier tray 211 bearing surface

1227528 Schematic illustration 220 Clamping ring 221 Ring inner wall 230 Sealing ring 240 Contact pin

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Claims (1)

1227528 — [Scope of patent application] 1. A bump forming method for a wafer, including: & for a wafer, the wafer having a front surface, a back surface, and a side surface between the front surface and the back surface, the A plurality of bonding pads are formed on the front surface; an under bump metallurgy (UBM) is formed on the front side of the wafer, and the under metal bump layer extends from the front side of the wafer to the side of the wafer Forming a photoresist layer on the front side of the wafer, the photoresist layer covering the metal layer under the bump on the front side of the circle B, and the photoresist layer having a plurality of openings, the openings are It is used to expose the metal layer under the bumps on the solder pads; the wafer is fixed on a wafer; the wafer electroplating jig has a clamping ring, and the clamping ring is provided with a sealing ring and At least one contact pin, the sealing ring seals the front surface of the wafer, the contact pin electrically contacts the metal layer under the bump on the side of the sealed wafer; and electroplating forms a plurality of bumps at the openings. 2. The bump formation method for a wafer as described in item 1 of the scope of the patent application, wherein in the step of forming a photoresist layer, the photoresist layer completely covers the front side of the wafer. 3. The bump forming method for a wafer as described in the first item of the scope of the patent application, wherein the photoresist layer has at least one peripheral opening, and the peripheral opening is provided on the front side of the wafer and connected to the wafer. The distance on the side is not greater than 5.0 mm. The bump forming method of the wafer as described in item 3 of the scope of patent application. __ The scope of the application for patents includes a crystal sealing ring covering i, a crystal system formed with UBM) and one side of a wafer and a clamping circle, which cools at least the wafer ~ enter the sealing ring and the side circle of the wafer Electroplating a bump photoresist layer 'The crystal bears the disk ring, its holding ring system ring, and the side and contacts the pins of the wafer in the step of plating the plating fixture, the lower metal, which is a circular plating, is used for the installation The photoresist layer has a metal opening under the cover, and the peripheral opening of the photoresist layer is not opened by the block at the peripheral. It is used to fix a wafer, and the front layer of the wafer (Under Bump Metallurgy, the metal layer under the bump extends to the wafer fixture system includes: carrying the wafer; on the wafer carrier disk, for Fix the inner ring-shaped inner wall of the crystal; 环形 The inner ring-shaped inner wall of the clamping ring is used to seal the front side of the wafer; and it is arranged on the clip: between: & _, = the inner ring-shaped wall and in this layer. 乂 Electrical contact Should be sealed Hi Page 14