TW200534447A - Bump and the fabricating method thereof - Google Patents

Abstract

A bump for a chip is described. The composition of the bump comprises tin(Sn), lead(Pb), and copper(Cu). The weight percent of the Sn, Pb, and Cu are about 61.5%-62.5%, 35.5%-36.5%, and 1.5%-2.5%, respectively. Compared with the 63% Sn 37% Pb bumps, the bump provided above has better reliability and the reflow temperature is similar to the 63% Sn 37% Pb bumps.

Description

200534447 V. Description of the invention (1) Field of the invention The present invention relates to a bump and a manufacturing method thereof, and more particularly to a tin-lead bump and a manufacturing method thereof. Prior art In the technical field of integrated circuit (IC) packaging, the first level package (First Level Package) is mainly used to connect a chip to a carrier (ca ri er), there are roughly three types of packaging , Respectively, wire bonding technology, tape automatic bonding technology (TAB) and flip chip bonding technology (F / C). Among them, whether it is tape automatic bonding technology (TAB) or flip-chip bonding technology (F / C) 'During the bonding process of the die and the carrier, it must be on the wafer pad (pad) The bumps are fabricated on the substrate, and the bumps are used as a medium for the electrical connection between the die and the carrier. There are many types of bumps that are known. There are four kinds of solder bumps: Solder Bump, Gold Bump, Conductive Polymer Bump, and Polymer Bump. Among them, the tin bump is the most widely used. At present, the common manufacturing method of tin-lead bumps is above the solder pads of the wafer. First, a ball-bottom metal layer is formed at a predetermined position by means of evaporation, sputter, or plating. (Under Ball Metallurgy, UBM). After that, a thick photoresist is formed on the wafer, and the thick photoresist layer is exposed and developed, and multiple openings are formed in the thick photoresist layer.

12632TWF.PTD Page 5 200534447 V. Description of the invention (2) Exposed through these openings. Then, using a manufacturing method such as eVaporatif, plating, or printing, a tin-lead solder (solder paste) is filled into the opening, and a reflow process is performed. After re-soldering, tin-lead bumps with a ball-like appearance were formed on the ball-bottom metal layer. As mentioned above, the ball bottom metal layer can generally be divided into an adhesion layer, a barrier layer, and a wetting layer. The material of the adhesion layer is usually titanium (Ti) and barrier. The material of the layer is usually nickel-vanadium alloy (Niv), and the material of the kick layer is usually copper (Cu). The soldering layer is connected to the tin-lead bump, and the subsequent layer is connected to the circuit layer of the wafer. As for tin-lead bumps, when the tin-bumps are exposed to high temperature for a long time, copper-tin intermetallic compounds (IMC) are likely to be produced at the interface between the tin-bumps and the ball-bottom metal layer. For example, Cu3Sn and Cu6Sn5, or Sn-Ni-Cu IMC. Since most of the copper metal and nickel metal in the intermetallic compound come from the ball bottom metal layer, when the tin-lead bump is operated under high temperature and / or high current density, the problem of the ball bottom metal layer consumption will occur. In other words, when the nickel or copper metal of the ball bottom metal layer is consumed, the tin metal in the bumps may invade the inside of the wafer, thereby causing the wafer to fail. In addition, the electromigration effect generated under the surface temperature and / or south current operation often causes micro voids (v oid) inside the bumps. When the micro voids gather, it may cause electrical voids. Sexual connection was interrupted. Both of the above reasons are caused by tin-lead bumps and wafers

200534447 V. Description of the invention (3) In the electrical connection Summary of the invention In view of improving the problem of intermetallics. In addition, the method to improve the weight percentage based on its suitable configuration and copper is based on its suitable configuration and copper, and the copper percentage is based on its suitable configuration and copper, and its weight percentage is based on The above method is one of the reasons why the bumps are broken on a solder pad. Therefore, the object of the present invention is to provide a bump. The reliability caused by the compound (re 1 iabi 1 ity) is asked. Another object of the present invention is to provide a reliability problem caused by the production of a bump-shaped metal compound. . For the stated purpose or other purposes, the present invention proposes a bump on a wafer, and the material of the bump, for example, includes tin, and the weight percentage of tin is between 61.5% -6 2.5%, the percentage It is between 35.5% -36.5%, and the weight of copper is between 1.5% -2.5%. The purpose or other purposes, the present invention proposes a bump on a wafer, and the material of the bump, for example, includes tin, lead, tin, lead, the weight percentage is between 9 7. 5% -98. 5% by weight The percentage is between 1.5% and 2.5%. For the stated purpose or other purposes, the present invention proposes a bump on a wafer, and the material of the bump includes, for example, tin, misintermediate tin, and lead in a weight percentage of not less than 98%, and a copper content of not more than 2% . For the stated purpose or other purposes, the present invention provides a bump system suitable for manufacturing a plurality of bumps on a plurality of bonding pads of a wafer. The method includes the following steps, for example. First, a solder paste is formed on each wafer, and the material of the solder is

12632TWF.I Page 7 200534447 V. Description of the Invention (4) Including tin, lead and copper, where the weight percentage of tin is between 6 1.5%-6 2.5%, and the weight percentage of lead is referred to Between 35.5% and 36.5%, and the weight percentage of copper is between 1.5% and 2.5%. These solders are then re-soldered. According to the bump manufacturing method according to the preferred embodiment of the present invention, the above-mentioned solder forming method is, for example, printing (P r i n t i n g). Based on the foregoing or other objectives, the present invention provides a bump manufacturing method, which is suitable for manufacturing a plurality of bumps on a plurality of pads of a wafer, and the bump manufacturing method includes the following steps. First, a solder is formed on each pad of the wafer, and the material of the solder includes tin, lead, and copper, wherein the weight percentage of tin and copper is between 97.5% -98.5%, and the weight percentage of copper It is between 1.5% and 2.5%. These solders are then re-soldered. According to the bump manufacturing method described in the preferred embodiment of the present invention, the above-mentioned method for forming the solder is, for example, printing. Based on the foregoing or other objectives, the present invention provides a bump manufacturing method, which is suitable for manufacturing a plurality of bumps on a plurality of bonding pads of a wafer, and the bump manufacturing method includes the following steps. First, a solder is printed on each solder pad of the wafer, and the material of the solder includes tin, lead, and copper. The weight percentage of tin and copper is not less than 98%, and the weight percentage of copper is not more than 2%. These solders are then re-soldered. According to the bump manufacturing method described in the preferred embodiment of the present invention, the above-mentioned solder forming method is, for example, printing. Based on the above, the bump component of the present invention can slow down the ball-bottom metal layer

12632TWF.PTD Page 8 200534447 V. Explanation of the invention (5) ----- The rate of elimination of ^ to improve the reliability of the bonding between the bump and the wafer. It ’s easy to see, the following is a better practice. "Features: and advantages can be explained in more detail as follows. Γ Example, and in conjunction with the attached drawings, make Embodiment 37. / Λ 于 ΛΛ 技术 W convex block composition The composition is mainly tin with m and & / ° 1f 二 = # pt. The bumps of the composition cannot meet the requirements of U Λ at high temperature, because the tin bottom bump is the metal layer on the bottom of the ball. Intermediate reactions will generate ΐ ΐίί + i ff the bottom metal layer is gradually depleted and loses its function. Therefore, my brother chooses two ghosts i2 ^ b37) at middle age at high temperature and / or high current density The generation of 1: leads to tin-lead bumps and crystals. In the present invention, the bump component = 1 is positive for the above-mentioned phenomenon, so as to improve the problems of gradual consumption and holes of the bottom metal layer. 63% tin 37% lead bump reliability test 'and evaluate the impact of current strength and bump temperature on the reliability of the bump-to-chip connection. Please refer to Figure 1' The weight percentages listed in the table are Reliability experimental data chart of 6 3% tin 3 7% lead bumps. First The content is explained. The first failure represents the time of the first failure sample in the experimental matrix sample, and 6 3 · 20% represents the time required for the cumulative failure sample to account for 63 · 20% of the experimental matrix sample. When the test is performed at an operating current of 160 mA and an operating temperature of 150 C, the first failure time is 3 9 〇

12632TWF.PTD Page 9 200534447 V. Description of the invention (6) hours, and the time to reach 6 3 · 20% failure rate is 506 hours. When the sample is tested at an operating current of 160 m A and an operating temperature of 160 ° C, the first failure time is reduced to 2 2 7 hours, and the time to reach 63. 20% failure rate is only For 3 0 7 hours. When the sample is tested at an operating current of 32 0mA and an operating temperature of 150 ° C, the time to first failure is reduced to 2 16 hours, and the time to reach 6 3 · 2 0% failure rate is 3 0 7 hours. From the above experimental data, it can be inferred that, for the bumps of 63% tin and 37% lead, no matter whether the operating temperature is increased or the current density is increased, the life of the bumps will be shortened and the reliability will be reduced. As mentioned above, a preferred embodiment of the present invention provides a bump that is suitable for being disposed on a wafer. The material of the bump includes, for example, tin, lead, and copper. The weight percentage of tin and lead is between 9 and 9. 7. 5% -98. 5%, and the weight percentage of copper is between 丨 · 5 2 · 5%. However, the preferred weight percentage of tin is between 61.5% -6 2 · 5%, and the weight percentage of lead is between 35 · 5% -3 6 · 5%. In the following, experiments will be performed on the tin-lead bumps of this embodiment and other tin-lead bumps with different tin-lead ratios, and the reliability evaluations of the bumps of various compositions will be performed respectively. Please refer to Figure 2 for a table of reliability test data of various tin weight bumps with different weight percentages. When the samples were tested at an operating current of 32 〇mA and an operating temperature of 150 ° C, 95% lead 5% tin bumps, 90% lead 10% tin bumps, and 6 For 3% tin, 37% lead bumps, the first failure time is 3 150 hours, 17 2 8 hours, and 2 16 hours, and the time to reach 6 3 · 2% failure rate is 3 9 2 9 hours, 1 9 7 0 hours

12632TWF.PTD Page 10 200534447 V. Description of invention (7) and 307 hours. It is clear from Figure 2 that the high-lead bumps have better reliability and are more suitable for high temperature and / or high current density operations. It is worth noting that although the higher the weight percentage of lead in the bumps, the higher the reliability life, but the high temperature of reflow soldering of high lead bumps, and those familiar with this technology can understand the reflow A higher temperature will cause a series of thermal problems, so the current trend is that the lower the reflow temperature, the better. Please refer to Figure 2 again. For 62% lead, 36% tin, 2% copper bumps, and 63% tin, 37% lead bumps, the first failure times are 7 5 2 hours and 2 1 6 hours, and the time to reach 63.2% failure rate was 139 hours and 307 hours. Therefore, the present invention can significantly improve the reliability life by using copper of 1.5% to 2.5%. In addition, since the composition of the bumps of the present invention is similar to that of 63% lead and 37% tin, the reflow temperature of the two bumps is similar. In addition, the method of making the bumps proposed by the present invention will be described in detail later. The invention provides a bump manufacturing method, which is suitable for manufacturing a plurality of bumps on a plurality of bonding pads of a wafer, and the bump manufacturing method includes the following steps. First, a solder is formed on each pad of the wafer, and the material of the solder includes tin, copper, and copper, wherein the weight percentage of tin and copper is between 97.5% -98.5%, and copper The weight percentage is between 1.5% and 2.5%. 5% -36. 5% 的。 It is worth noting that the above-mentioned content of tin and lead is preferably between 61.5% -62.5% by weight of tin, and the wrong weight percentage is between 35.5% -36.5% Meanwhile, the content of tin and lead may be other ratios. Alternatively, the weight percentage of tin and lead is not less than 98%, and the weight percentage of copper is not more than 2%. Subsequently, the solder

12632TWF.PTD Page 11 200534447 V. Description of the invention (8) Reflow soldering, and the method of forming solder is, for example, printing. It is worth mentioning that, compared with the conventional method for forming solder by using the evaporation or electroplating process, the solder forming method of this embodiment is printing, so the bump manufacturing method of the present invention has a cost advantage. In summary, the bumps of the present invention and the manufacturing method thereof have the following advantages: First, in addition to tin and lead, the bumps of the present invention have a weight percentage between 1.5%-2.5%. Copper metal, so compared with the conventional 63% tin 37% lead bumps, the bumps of the present invention have better reliability. Second, the bumps of the present invention have a weight percentage of copper metal between 1.5.2.5% and a wrong weight percentage of between 35.5% -36.5%, so the temperature of reflow Similar to the conventional 6 3% tin 3 7% lead bump. 3. Compared with the conventional bump manufacturing method, the bump manufacturing method of the present invention has a cost advantage in forming solder by printing. Although the present invention has been disclosed in the preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and retouching without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be determined by the scope of the attached patent application.

12632TWF.PTD Page 12 200534447 Brief description of the diagram The first chart shows the reliability test data of the bumps with a weight percentage of 63% tin and 37% lead. Figure 2 shows the reliability test data of tin-lead bumps with different weight percentages.

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Claims (1)

200534447 VI. Application for patent scope 1. A bump suitable for disposing on a wafer. The material of the bump includes tin, lead and copper, wherein the weight percentage of tin is between 61.5% -6 2.5% Between, the weight percentage of lead is between 35.5% to 36.5%, and the weight percentage of copper is between 1.5% to 2.5%. 2. —A kind of bump, suitable for disposing on a wafer. The material of the bump includes tin, copper and copper. The weight percentage of tin and copper is between 9 7.5% -98.5%, and copper The weight percentage is between 1.5% and 2.5%. 3—A kind of bump is suitable to be arranged on a wafer. The material of the bump includes tin, lead and copper, wherein the weight percentage of tin and lead is not less than 98%, and the weight percentage of copper is not more than 2%. 4. A bump manufacturing method suitable for manufacturing a plurality of bumps on a plurality of bonding pads of a wafer. The bump manufacturing method includes the following steps: forming a solder on each of the bonding pads of the wafer, each The materials of these solders include tin, copper and copper, wherein the weight percentage of tin is between 6 1.5% -6 2.5%, and the weight percentage of lead is between 35.5.5%-3 6 5%, and the weight percentage of copper is between 1.5%-2.5%; and reflow of these solders. 5. The bump manufacturing method according to item 4 of the scope of patent application, wherein the method of forming the solders includes printing. 6-A bump manufacturing method suitable for manufacturing a plurality of bumps on a plurality of pads of a wafer, the bump manufacturing method includes the following steps: forming a solder on each of the pads of the wafer, Every one 12632TWF.PTD Page 14 200534447 VI. Scope of patent application Solder materials include tin, lead and copper, where the weight percentage of tin and lead is between 97.5% -9 8.5%, and the weight percentage of copper Is between 1.50 / 〇-2. 5%; and reflow of these solders. 7. The bump manufacturing method according to item 6 of the scope of patent application, wherein the method of forming the solders includes printing. 8. A bump manufacturing method suitable for manufacturing a plurality of bumps on a plurality of bonding pads of a wafer, the bump manufacturing method includes the following steps: forming a solder on each of the bonding pads of the wafer by printing The material of each of these solders includes tin, lead, and copper, wherein the weight percentage of tin and lead is not less than 98%, and the weight percentage of copper is not more than 2%; and the solder is reflowed. 9. The bump manufacturing method according to item 8 of the scope of patent application, wherein the method for forming the solders includes printing. 12632TWF.PTD Page 15