TW507337B - Method of forming high flip chip solder bump - Google Patents

Abstract

This invention provides a bumping method to form high bump height, which utilizes non-electrical plating technique to further plate a layer of bump material on the bump formed by electroplating and thus results in the bump with greater height after reflow. It consists of the following steps: forming sequentially a metal pad, a passivation layer, an under bump metallurgy (UBM) layer on a chip; using photoresist to define position of the UBM; forming the solder bump on the position of the UBM; using flux and hard bake process to remove oxide on the surface of the solder bump; then forming an extra plated layer through non-electrical plating method; removing the photoresist; removing the exposed UBM; and performing reflow process to form solder balls.

Description

507337

V. Description of the invention (1) Field of the invention: The present invention relates to a bumping process of an integrated circuit, and more particularly to a bumping process that can increase the bump height. ^ Long background of the invention: Chip packaging is an indispensable step in the current integrated circuit manufacturing process. With the demand for high integration of semiconductor components, how to increase the number of IC chips to 5 ^ package and how to make the packaged chip become Thinner, will become more important. The main functions of the CV package include: protecting the 1C and providing an interface for information transmission between the chip and external system devices. Therefore, the development of the IC process and the functionality of the system products are the main reasons that affect the development of the IC packaging technology. ^ The requirements for electronic products are light, thin and short, and there must be a technology to reduce the size of the crystal grains. The miniaturization of the IC process has resulted in an increase in the number of logic circuits contained in the crystal grains. The number of I / O pins of the 1C package connected to the outside is not only increasing and denser, which has led to many different new-generation packaging methods, such as · baii grid array (BGA), Advanced technologies such as chip size package (CSP), multi-chip module (MCM), and flip chip have come into being. Flip-chip packaging has better electrical characteristics because it reduces the path distance for information transmission between the chip and external system devices. It is the next generation packaging technology that has attracted much attention. "

507337 V. Description of the invention (2) ir flip-chip packaging technology uses conductor bumps as input / output. In the process of forming a conductive solder bump, the protective layer is usually etched on the aluminum metal pad using a face-etching process to expose the solder pad. A combination layer of a barrier layer and a conductive layer is deposited thereon, and the general composition includes Cr / Cu and Ti / Cu. After that, a photoresist is applied and patterned using a lithography process to form a window 1 on the pad, and tin is formed by electroplating. The next step is to use solder bumps as =, then

The barrier layer and the conductive layer are completed to form a J-mask to remove the uncovered combination layer of the barrier layer and the conductive layer, which is called: $ process, the resistance left by metallurgy (UBM). Under bump metal (under bump) The bump height is relatively reliable for subsequent packaging steps. The success or failure and whether the bump height in the block process can be expanded can be achieved. Convex increase, but still, it will be unstable due to the size of the final convex metal. In addition, the metal under the convex is limited, and the performance of the two adjacent metal under the convex expands after each other. , May cause defects in contact and contact.

At present, the main method of long bumps is (plating), which can increase the increase of bump high-frequency, (print) and electroplating methods. The increase in photoresistance is limited. If the photoresistance is too high, it is difficult to handle it. It may cause problems on adjacent shirts. More plating, one bump is connected to each other

507337

V. Description of the invention (3) Short circuit defect. Therefore, how to provide a method to increase the height of the bumps while avoiding the above problems is a major effort in the industry. OBJECTS AND SUMMARY OF THE INVENTION The object of the present invention is to provide a bump formation method to obtain a sufficient bump height, with a sound yield and reliability. The present invention provides a bump forming method, which includes the following steps: Provide a wafer 'wherein the wafer has completed the integrated circuit manufacturing process and has metal pads on the wafer. A protective layer is formed on the wafer and etched to expose the surface of the metal pad. Next, a metal layer under the bump is formed on the protective layer and the metal pad, and then a photoresist is used to define the position of the metal under the bump, and then a solder bump is formed on the metal position under the bump, and then a flux (f 丨ux) and hard bake to remove the oxide on the surface of the solder bumps, and then use the helmet electroplating method to form an additional plating layer, then remove the photoresist, remove the exposed metal layer under the bumps, and finally reflow solder Bumps to form solder balls. Detailed description of the invention: The object of the present invention is to provide a bump height formed by bumps, with a sound yield and a reliable production method:

The height of the bumps is too special, and it will increase the Θ two stages to form the welding Λ 形成 M t 4 ..., the method of plating into bumps, or the screen-printed ancient a / ^, f j f, and clever bumps. First, the original solder bumps are formed in the form of 1 2 P, and then the bumps are reported to Dan. From the electroless plating method, a new layer of welding material is formed on it 疋, a new bump (new bumi

507337

The description is not intended to limit the invention. Referring to FIG. 1, there is a metal pad 2 on the wafer 100. The wafer 100 and the surface of the metal pad 2 form a passivation layer 4. The photoresist is used to define the location of the pad. Area, the protective layer j is eroded by the etching process.:!: 于 垫 2. The composition of the protective layer 4 described above may include polyimide (polyimide), yimjde (Pl), BCB (benzo, Cyclbutene), or nitride. Next, the thickness of the bump will be thick. Several metal, the role of _: connected to the lower metal -13, the surface, usually contains a barrier layer and a conductive layer, with a metal structure containing titanium or a road: first form a barrier ,: You can choose to include copper or copper alloys. You can first :: 'Electric layer on it' conductive layer-sublayer (seedlng Uyer), and then a copper seed that is good for copper plating, and then use the plating method to open the surface The recording is performed by the electric / electric mining method, and then can be calculated; the squareness is about 2 to 4 microns. The above copper seed layer is formed on the barrier layer by gas bonding.

Ti / Cu. The description of the materials mentioned here is ur / Lu: ¾, but it is not used to limit the essence of the present invention and the degree of god son 3 only as an embodiment to describe the replacement of functional materials. Therefore, the scope of the present invention includes equality

The cloth-photoresist layer 8 is formed on the photoresist by the metal film process under this bump. The layer 6 structure is then determined by lithography. Then τ = defines the area where the solder bumps are formed. Next, the formation of the solder core micro Π:] ;: way: the solution containing lead (1 ead) and tin (ti η) in the exposed λ and Γ2 in the cathode under the bump as the key bond is generally combined on the disk. The metal bump 6 has solder bumps 10 formed on the surface. Proportion; Integrate the two convex projections: doped lead at times, and set the oblique m of the mixture according to the needs. He, as a solder bump material, still has a mixture. Alloys with different compositions of metals such as bismuth, bismuth, or indium, etc. See different melting points and fatigue resistance levels for matching. After coating, it is removed / resisted, as shown in Fig. 4, and then flux 12 is applied on the solder bumps. The function of the flux 12 is to clean the surface tension between the solder bump and the substrate to improve the wettability. For proper soldering, foaming, volatility and viscosity, to facilitate soldering. get on. The composition of the flux 12 includes activators, carriers, solvents and other special functional additives. The higher the flux activity, the better the cleaning effect. The oxide coating on the surface of the solder bump 10 is removed by the flux coating of the flux 12 to facilitate subsequent electroless plating and soldering. The hard bake is then removed to remove the flux and oxides. Next, 'immersion solder bump 10 is immersed in electroless plating solution 2000 (as shown in Fig. 5)' and perform electroless mining 'to form a new bump layer 14 on the surface of solder bump 10. Composition and welding of this newly plated bump layer ι4

Page 9 507337 V. Description of the invention (6) The bump 10 has the same choice, such as ship tin alloy. The electroless plating bath makes the metal to be plated on the surface of the object to be plated by the difference of the redox potential. The electroless plating solution must contain water-soluble salts of the metal to be plated, such as water-soluble tin salts, water-soluble lead salts, water-soluble bismuth salts, water-soluble indium salts, etc. Organic sulfonic acid, phosphoric acid, fluoboric acid, condensed phosphoric acid, hydrochloric acid and pyrophosphoric acid or a mixture of two or more of these acids ^, such as oxalic acid, tartaric acid, citric acid, ethylenediaminetetraacetic acid (EDTA) & its salts , Sulfur [CX8A68], sulfur [CX8A68] derivatives and triethanolamine or a mixture of two or more of these complexing agents. Finally, as shown in FIG. 7, after pre-bake, pre-flow, and reflow, the solder bumps are produced due to cohesive forces and the like due to the f-ball structure. The solder ball 301 was used as a mask to remove the exposed metal layer under the bump. The solder ball 3 0 〇 is a material with no bonding material and the volume of the bump layer is converted into a ball height. Therefore, the thickness of the new bump layer is sufficient to ship the new bump layer 14. The height of the solder ball formed by the heat also becomes a ball. The volume can be achieved by adding solder balls as needed. The results obtained after the flow are lower. The added tin can be used to estimate the increased tin height. After the electroless plating is completed, the above photo is taken. The removal of the photoresist 8 can also form a new bump layer η-a new solder bump ㈣. Bump layer

507337 V. Description of the invention (7) The wafers may be bent, so that the degree of immersion in the electroless plating solution 2000 is different, and the height of the solder balls added at the end is different. The present invention has been described above with reference to the preferred embodiments, and those skilled in the art can make some modifications and modifications without departing from the spirit of the present invention. Field-specific.

Page 507337 Brief description of the diagram Using the following description and the cooperation of the following diagrams, the contents and advantages of the present invention can be more clearly understood, where: The first diagram shows a schematic cross-sectional view of a bump formed according to an embodiment of the present invention First, a metal pad, a protective layer, and a metal layer under the bump are sequentially formed on the wafer. The second figure shows the use of a photoresist definition to define the position of the metal under the bump according to one embodiment of the present invention. The third figure shows a cross-section of a bump formed according to an embodiment of the present invention, which is not intended. The fourth figure is a schematic cross-sectional view of applying a flux on a bump and removing photoresist according to an embodiment of the present invention. The fifth figure shows that the bumps are immersed in an electroless plating solution according to an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of a bump formed according to an embodiment of the present invention, which includes forming another layer of solder material on the bump. FIG. 7 is a schematic cross-sectional view of a spherical bump formed by heat flow according to an embodiment of the present invention.

Claims (1)

507337 VI. Scope of patent application1. A method for long convex, this party provides a wafer to form a plurality of welding to form a protective layer under the protective layer block gold patterning to form a convex pad; use light to form overlaid; remove light The coating assists the hard formation of a hot reflow solder ball. The method of increasing the bump height in the bumping process includes at least the following steps: the wafer has completed the integrated circuit circuit process; pad on the wafer; the wafer and On the plurality of bonding pads; exposing the upper surface of the plurality of bonding pads; a layer on the protective layer and connecting the exposed plurality of solder resistances to define a plurality of solder resistances; the flux on the baking removal layer newly protrudes the plurality ; And a plurality of patterns to form a plurality of areas of the solder bumps; the bumps on the metal layer under the bumps that are not covered by the photoresist on the plurality of solder bumps; the plurality of solder bumps may be The generated oxide material; new bumps on the surface of the plurality of solder bumps; the solder bumps and the new bumps thereon to form a plurality of metal layer solder balls as a cover etch Engraving and removing the gold under exposed bumps = Method for adding bumps to long bumps as described in item 请 i of the patent claim, wherein the protective layer is composed of polyimide (PI: 3). As claimed, adding bumps to the long bump process as described in item 丄 of the monthly patent scope Page 13 507337 VI. Method of patent application Height, wherein the protective layer is composed of BCB. 4. The method for increasing the height of a bump in a long bump process as described in item 1 of the scope of the patent application, wherein the protective layer is composed of silicon nitride. 5. The method for increasing the height of a bump in a long bump process as described in item 1 of the scope of the patent application, wherein the metal layer under the bump includes at least a barrier layer below and a conductive layer on the barrier layer. 6. The method for increasing the bump height in a long bump process as described in item 5 of the scope of the patent application, wherein the barrier layer includes at least a titanium composition, a chromium composition, or a copper composition. 7. The method for increasing the height of a bump in a long bump process as described in item 5 of the scope of the patent application, wherein the conductive layer has a copper composition and a nickel composition. 8. The method for increasing the height of a bump in a long bump process as described in item 1 of the scope of patent application, wherein said forming a new bump includes at least an electroless plating method, and this electroless plating method includes welding bumps The step of immersing the block in an electroless plating solution. 9. The method for increasing the height of a bump in a long bump process as described in item 8 of the scope of the patent application, wherein the electroless plating solution contains at least the water-soluble salts of the metal to be plated, Acid liquid and complexing agent group 507337 VI. Scope of patent application. 10. The method for increasing the height of a bump in a long bump process according to item 9 of the scope of the patent application, wherein the water-soluble salt comprises at least a water-soluble tin salt. 11. The method for increasing the height of a bump in a long bump process according to item 9 of the scope of the patent application, wherein the water-soluble salt contains at least a water-soluble lead salt. 1 2. The method for increasing the height of a bump in a long bump process according to item 9 of the scope of the patent application, wherein the water-soluble salt contains at least a water-soluble bismuth salt. 1 3. The method for increasing the height of a bump in a long bump process according to item 9 of the scope of the patent application, wherein the water-soluble salt comprises at least a water-soluble indium salt. 1 4. The method for increasing the height of a bump in a long bump process according to item 9 of the scope of the patent application, wherein the acid solution contains at least perchloric acid, organic sulfonic acid, phosphoric acid, fluoboric acid, condensed phosphoric acid, and hydrochloric acid. And pyrophosphate. 15. The method for increasing the height of a bump in a long bump process according to item 9 of the scope of the patent application, wherein the complexing agent comprises at least oxalic acid, tartaric acid, citric acid, ethylenediaminetetraacetic acid (EDTA) and Salt, sulfur [CX8A68], sulfur Page 15 507337 [CX8A6 8] Derivative and triethanolamine. 16 · —A method added in a bumping process. The method includes at least the following steps. ^ A bump height is provided for a wafer, which has completed the integrated circuit circuit manufacturing process; forming a plurality of solders Pad on the wafer; 'form a layer on the wafer and the plurality of pads; pattern the protective layer' to expose the upper surface of the pads; use photoresist to define the number of solder bumps to be formed A plurality of solder bumps are formed in the area on the surface that is not covered by the photoresistor; the metal layer substance under the bumps; the surface; Forming a plurality of solder bumps on the metal layer under the bump; applying a flux on the plurality of solder bumps; performing hard baking to remove the oxygen that may be generated on the plurality of solder bumps to form a new bump ( new bump) to remove the photoresist in the plurality of solders; # u H ΐ back to the plurality of solder bumps and the new bumps thereon to form tin, and use the plurality of solder balls as a mask to etch the exposed bumps to remove the exposed bumps. The method for increasing the southness of the bumps in the long bump process as described in item 16 of the patent scope of Shenyan Patent, wherein the protective layer is polyimide (PI). composition. Circle Page 16 507337 VI. Scope of Patent Application 1 8 · The method for increasing the height of bumps in the process of long bumps as described in item 16 of the scope of patent application, wherein the protective layer is composed of BCB. 19. The method for increasing the height of a bump in a long bump process as described in item 16 of the scope of patent application, wherein the protective layer is composed of silicon nitride. 20. The method for increasing the height of a bump in a long bump process as described in item 16 of the scope of the patent application, wherein the metal layer under the bump includes at least a barrier layer below and a conductivity on the barrier layer Floor. 2 1. The method for increasing the height of a bump in a long bump process as described in item 20 of the scope of patent application, wherein the barrier layer includes at least a titanium composition, a chromium composition, or a copper composition. 2 2. The method for increasing the height of a bump in a long bump process as described in item 20 of the scope of patent application, wherein the conductive layer is composed of copper and nickel. 2 3. The method for increasing the height of a bump in a long bump process as described in item 16 of the scope of patent application, wherein said forming a new bump includes at least an electroless plating method, and this electroless plating method includes The step of immersing the solder bump in the electroless plating solution. 2 4. The method for increasing the height of a bump in a long bump process as described in item 23 of the scope of patent application, wherein the electroless plating solution contains at least the metal to be plated. Page 17 507337 6. Scope of patent application Water-soluble salts, acid solution and dissolving agent which can dissolve the water-soluble salts mentioned above. 25. The method for increasing the height of a bump in a long bump process as described in item 24 of the scope of the patent application, wherein the water-soluble salt comprises at least a water-soluble tin salt. 2 6 · The method for increasing the height of a bump in a long bump process as described in item 24 of the scope of patent application, wherein the water-soluble salt contains at least water-soluble lead m 〇 JSL · 2 7. The method for increasing the height of a bump in a long bump process as described in item 24 of the scope of the patent application, wherein the water-soluble salt contains at least a water-soluble grade salt. 2 8. The method for increasing the height of a bump in a long bump process as described in item 24 of the scope of patent application, wherein the water-soluble salt contains at least a water-soluble indium salt composition. 2 9. The method for increasing the height of a bump in a long bump process as described in item 24 of the scope of patent application, wherein the acid solution contains at least perchloric acid, organic sulfonic acid, phosphoric acid, fluoboric acid, condensed phosphoric acid, Composition of hydrochloric acid and pyrophosphate. 30. Add bumps to the long bump process as described in item 24 of the scope of patent application Page 18, 507337 VI. Method for applying the same degree of patent scope, wherein the complexing agent contains at least oxalic acid, tartaric acid, citric acid, ethylenediaminetetraacetic acid (EDTA) and its salts, sulfur [CX8A68], sulfur [CX8A6 8 ] Derivatives and triethanolamine. 31 · —A method for increasing the height of a bump in a bumping process, the method includes at least the following steps: providing a wafer, the wafer has completed the integrated circuit circuit manufacturing process; forming a plurality of bonding pads on the wafer Forming a protective layer on the wafer and the plurality of pads; patterning the protective layer to expose the upper surface of the plurality of pads; forming a subordinate layer of the bump on the protective layer and connecting the exposed layer The plurality of solder pads; forming a plurality of solder bumps on the metal layer under the bumps; applying a flux to the plurality of solder bumps; performing a hard roast to remove oxide substances that may be generated on the plurality of solder bumps Forming a layer of new bumps on the surfaces of the plurality of solder bumps; reflowing the plurality of solder bumps and the new bumps thereon to form a plurality of solder balls; and using the plurality of solder balls The exposed under-bump metal layer is removed for mask etching. 3 2 · The method for increasing the height of a bump in a long bump process as described in item 31 of the scope of patent application, wherein the method of forming a solder bump is a print. Page 19, 507337 6. Application scope 33. The method for increasing the height of a bump in a long bump process as described in item 31 of the scope of patent application, wherein the protective layer is composed of polyimide (PI) . 34. The method for increasing the height of a bump in a long bump process as described in item 31 of the scope of the patent application, wherein the protective layer is composed of BCB. 3 5. The method for increasing the height of a bump in a long bump process as described in item 31 of the scope of patent application, wherein the protective layer is composed of silicon nitride. 3 6. The method for increasing the height of a bump in a long bump process as described in item 31 of the scope of patent application, wherein the metal layer under the bump includes at least a barrier layer below and a conductive layer on the barrier layer Floor. 37. The method for increasing the height of a bump in a long bump process according to item 36 of the scope of patent application, wherein the barrier layer includes at least a titanium composition, a chromium composition, or a copper composition. 3 8. The method for increasing the height of a bump in a long bump process as described in item 36 of the scope of patent application, wherein the conductive layer has a copper composition and a nickel composition. 39. The method for increasing the height of a bump in a long bump process as described in item 31 of the scope of patent application, wherein said forming a new bump (newbum ρ) includes at least an electroless plating method, and this electroless plating method includes Solder bump immersed in electroless plating Page 20 507337 VI. Patent Application Procedures. 40. The method for increasing the height of a bump in a long bump process as described in item 39 of the scope of the patent application, wherein the electroless plating solution contains at least the water-soluble salts of the metal to be plated and can dissolve the water-soluble salts. It is composed of similar acid solution and complexing agent. 41. The method for increasing the height of a bump in a long bump process as described in item 40 of the scope of the patent application, wherein the water-soluble salt comprises at least a water-soluble tin salt. 4 2. The method for increasing the height of a bump in a long bump process as described in item 40 of the scope of patent application, wherein the water-soluble salt contains at least a water-soluble lead salt. 4 3. The method for increasing the height of a bump in a long bump process as described in item 40 of the scope of patent application, wherein the water-soluble salt contains at least a water-soluble bismuth salt. 44. The method for increasing the height of a bump in a long bump process according to item 40 of the scope of patent application, wherein the water-soluble salt comprises at least a water-soluble indium salt composition. 4 5. Add bumps to the long bump process as described in item 40 of the scope of patent application 507337 6. Scope of patent application Block height method, wherein the acid solution contains at least peracid acid, organic sulfonic acid, phosphoric acid, fluoboric acid, condensed phosphoric acid, hydrochloric acid and pyrophosphoric acid. 4 6. The method for increasing the height of a bump in a long bump process as described in item 40 of the scope of patent application, wherein the complexing agent contains at least oxalic acid, tartaric acid, citric acid, ethylenediaminetetraacetic acid (EDTA) And its salts, sulfur [CX8A68], sulfur [CX8A6 8] derivatives and triethanolamine. Page 22