TW418470B - Method for forming solder bumps on flip chips and devices formed - Google Patents

Abstract

A method for forming solder bumps on flip chips and a structure thereof is disclosed. According to the bonding technology of flip chips, the present invention provides a method for forming solder bumps on flip chips with minute clearance, and discloses a method of forming solder bumps with minute clearance by using a double photolithography technique together with a double photoresist layer; in which the first photolithography technique uses a thin photoresist to define a BLM layer to a required location, and the second photolithography technique uses a thick photoresist to open an aperture desired to grow a solder bump and define the height of the solder bump grown; in which the thickness of the thin photoresist used in the first photolithography technique is very thin, the alignment there has a high precision. Therefore, a minute location of the solder bump to be grown can be accurately defined. Furthermore, even though the thickness of the photoresist used in the second photolithography is thicker and its alignment accuracy is poorer, the self-alignment process of the solder bump per se can fully follow the location of the solder bump defined in the first photolithography technique to grow into a solder bump with a minute clearance.

Description

4184 70 V. Description of the invention (1) [Scope of the invention] The present invention relates to a method and a structure for manufacturing a polycrystalline solder ball, and particularly relates to a first photoresist using a double-layer photoresist. The layer is used to define on the BLM (Bali-Limitting-Metallurgy) layer-to the desired position, and its second thick photoresist layer is used to define the desired openings of the solder bumps and the solder they grow into. The height of the bumps is used to form the structure of the fine-pitch flip-chip solder ball by the double photoresist layer and the manufacturing method thereof. [Background of the Invention] In the current semiconductor element manufacturing technology, most of the semiconductor elements are obtained by increasing the circuit density of the semiconductor element or reducing the size of the element to obtain a high-density semiconductor element. _, Leading to increasingly stringent requirements for the reliability of packaging technology and interconnecting technology. One of the methods used to package chips is the Flip-Chip Attachment Method. The crystal bonding technology is to replace the lead frame with a metal conductor, that is, a technology that connects the bare crystal with the substrate in a face-down manner. The metal conductor can be metal bumps, tape bonding ( Tape-Automated Bonding), Anisotropic Conductive Adhesives, polymer bumps, etc. 'Among them, metal bumps are the mainstream of flip-chip bonding technology, and the material of metal bumps is Tin-lead alloy is the main component. Therefore, metal bumps made of tin-lead alloy are also called tin-lead bumps. A first solder bumps formed in the joint surface of the semiconductor die, and then by melting solder bumps your aluminum pads of the wafer (A1 Bonding Pad) bonded to the substrate and the line End

4 184 TO Five 'invention description (2) t-assembly, in which the above-mentioned tin-lead bump contacts are arranged in a surface matrix (' Area Array) on the surface of the die, which can improve the wafer's I / 0 ratio, and currently Methods for making tin-lead bumps include evaporation, electroplating, printing, electrodeposition, or other methods. The electrodeposition method is a new technology that has only been developed in recent years. In addition to the above technologies, there are other technologies that can grow tin-lead bumps on various substrates, such as one of the solder paste printing technologies (Solder-Paste Screening M ethod) commonly used in 8 11-inch wafer packaging. ) 'However, with the reduction in component size and the reduction of the pitch of tin-lead bumps, solder paste printing becomes impractical due to the following reasons. The first point is when used This solder paste printing technology is often bonded by the emperor compound when bonding tin-lead bumps to the substrate. This is because the solder paste (S ο 1 der Paste) is made of a flowable (F 1 u X) material and The solder (S ο 1 der) alloy particles are formed, so it is very difficult to control the concentration and uniformity of the solder paste compound when the volume of tin-lead bumps is reduced. For this reason, the conventional method has disclosed Fine particles with uniform particle size can improve the disadvantages mentioned above, but this will inevitably increase the production cost. The second point is that when using this solder paste printing technology to manufacture high-density semiconductor components, two tin-lead bumps will be produced. Of The space between them becomes very limited. This is because the volume of the tin will be greatly reduced when the tin changes from a flowing state to a solid state, making the solder paste screen holes (Screen Holes) ____straight .. As a result of the large tin fault & block coming, the significant reduction in the volume of the aforementioned tin fault bumps will also cause difficulties in solder paste printing technology in manufacturing high density components. Other technologies that can produce tin-lead bumps are C4 technology (Controlled

4 184T j_ V. Description of invention ¢ 3)

Col lapse Chip Connection Technique and Thin Film Electrodeposition Technique have also been applied to the manufacture of semiconductor components in recent years. Among them, the C4 technology is limited to the use of molybdeum masks in the manufacturing process. By definition-The pattern size of the BLM layer and the tin-lead bumps is not precise because of the alignment of the molybdenum mask. Therefore, the fine pitch (that is, the pitch < 150 μm) of tin / lead must be manufactured by C 4 technology. Bumps are difficult. Similarly, the thin film deposition technology is also limited to the need to deposit a BL LM layer and coat a thick photoresistor on the process, because the thick photoresistor has poor accuracy in alignment, so it also has the same unmanufacturability as C4. Disadvantages of forming fine-pitch tin-lead bumps' The manufacturing flow chart of conventionally using thin-film deposition technology to manufacture tin-lead balls is shown in "Figure 1A ~ 1F". One of the conventional semiconductor structures 10 is shown in FIG. 1A. This semiconductor structure 10 is built on a silicon substrate 12, and its manufacturing method is to first form a soldering pad on the top surface 16 of the substrate. (Bonding Pad) 14 is used as an electrical connection between the silicon substrate 12 and the outer substrate circuit. This pad 14 is made of a conductive metal material (such as aluminum 'A1), and then a protective layer 20 is deposited on the silicon. The substrate 1 2 ′ is used to protect the bonding pads 14. The protective layer 20 is made of an insulating material such as oxide, nitride, or organic material, and then the photolithography technology is used on the protective layer 20. A window 2 2 is opened to be electrically connected, and then a welding metal pad layer (BLM) can be deposited on the top surface 24 of the protective layer 20 and the exposed top surface 18 of the pad 14 (BLM can also be called Is UBM, Under Bump Metallurgy ') layer 26 (as shown in Figure IB), this blM layer 26 is made of a glue

4184T0 V. Description of the invention (4) An anti-diffusion layer (Adhe. Ion diffusion barrier layer) 30 and a wetting layer (also known as a tin layer) 28 are formed, wherein the adhesion. The anti-diffusion layer 30 may be Titanium (Ti), titanium nitride (TiN), Cr (Cr) or other metal materials, and the wet layer 28 can be bitten by copper (Cu). Nickel (Ni) and other materials The BLM layer 26 is mainly used to improve the adhesion relationship between the tin-lead ball to be formed and the top surface 18 of the pad 14. As shown in FIG. 1C, in this step, a thick photoresist layer 34 is deposited on the surface of the BLM layer 26, and then the exposure and development methods are used to define the window opening 38 of the tin-lead ball to be θ long. Then, a hole is formed in this window by electroplating ^ to form a tin-lead bump 40. The thickness of the aforementioned photoresist layer 34 is generally maintained between 30 μm and 4 0 // m, preferably Maintained at about 3 5 # m, this—the thickness of the photoresist layer 34 is related to whether or not a fine-pitch tin bump 4 can be made. The thicker the photoresist layer 34 is, the more it is aligned. The worse the accuracy, the more difficult it is to make ^ fine-pitch tin-lead bumps 40, but because the thickness of the photoresist layer 34 is directly proportional to the height of the tin-lead bumps 40, the photoresist layer 3 4 must be There is a certain degree of corpse, so the thickness of the photoresist layer 34 must be carefully selected. In this step, a sufficiently thin photoresist layer 34 is used to make a mushroom-shaped tin-lead bump 40, such as 圊As shown in FIG. 1D, as shown in FIG. 1E, after the formation of the tin-lead bump 40, ~ 1 UΊ is a photoresist cutting process (Wet Stripping proceSs) to remove the photoresist layer 34. tin The bumps 40 and the 81 ^ layer 26 are maintained in their original state. 'Next: Step, as shown in Figure 1 F.' In this step, a tin-lead convex soul U mask is used, and the excess Bu layer is wet-etched using a wet etching process. 2 6 Etching clean, then, ',

4184 70 V. Description of the invention (5) Using a heavy-flow process (R ef 1 〇w P r cess) to heat the tin-lead bump 40 at a temperature higher than the melting point of the tin-block β block 4 0 to make tin-lead The bump 40 changes from a solid state to a liquid state. Finally, during the cooling process, the tin-lead bump 40 forms a spherical tin-lead ball 42 due to its cohesion. At this step, the manufacture of the tin-lead ball 42 is completed, as shown in FIG. 1 F. However, the above-mentioned method of manufacturing tin-lead bumps by electroplating technology has several disadvantages, as follows: The first point is that the volume of the conventional mushroom-shaped tin-lead bumps limits the miniaturization process, among which fine-pitch tin-lead The meaning of the bump is that the distance between the two tin-lead bumps must be at least less than 150 μm, and preferably less than 1 2 0 // m. However, according to the above manufacturing method, the tin bumps are formed first, and then The BL Μ layer deposited under the tin-lead bump is removed by a wet etching process. Therefore, when the fine tin-lead bump is formed in the opening of the window to be left by the BL Μ layer, due to the The pitch is very small, so it is very difficult to completely remove the BLM layer in such a small pitch. To achieve this purpose, most of the time is increased by the time of the last name to completely remove the BL Μ layer, but in this case, it is possible It will etch to the tin-lead bumps or cause severe oxidation of the tin-lead bumps due to the long etching time; the second point is that the thick photoresist layer has poor alignment accuracy, which may cause the aluminum gasket to be exposed Which affects the reliability of tin-lead bumps, The fatigue life of a point is directly proportional to the height of the tin bump (greater than the power of 1). Therefore, the height of the tin bump is increased when the tin-lead bump is manufactured to increase the contact of the tin-lead bump. Fatigue life, but in this case, it is necessary to increase the thickness of the photoresist layer, but the alignment accuracy of the thick photoresist layer is poor, and it may etch into the aluminum gasket, leaving the aluminum gasket exposed. Affects the quality and reliability of tin-lead bumps.

f 418470 V. Description of the invention (6) [Objective and summary of the invention] In view of this, the main purpose of the present invention is to provide a method for manufacturing flip-chip solder balls to improve the fine pitch that cannot be made by conventional manufacturing methods. Problems such as misalignment of the solder ball and the thick photoresist layer, and oxidation of the solder ball. Another object of the present invention is to provide a method for manufacturing a fine-pitch flip-chip solder ball using lithography at least twice. Another object of the present invention is to provide a method for manufacturing a fine-pitch flip-chip solder ball having a fine pitch aligned with the BLM layer before the solder ball is established. Another object of the present invention is to provide a manufacturing method capable of making the pitch of solder balls with a fine pitch smaller than 120 m between them. Another object of the present invention is to provide a method for manufacturing a fine-pitch flip-chip solder ball using two lithography techniques. The first lithography technique uses a thin photoresist to define a BL Μ layer to a desired position, and The second lithography technique uses a thick photoresist to open the openings of the solder bumps to be grown. Another object of the present invention is to provide a method for manufacturing a micro-pitch flip-chip solder ball using dual lithography technology, in which a BLM layer is first coated on a solder pad to be formed, and then the wet etching process is used to accurately The BL M layer was removed. Another object of the present invention is to provide a method for manufacturing a fine-pitch flip-chip solder ball using dual lithography technology, in which a non-leachable metal layer (such as copper, Cu, or chromium, Cr) is finally It is deposited on top of the engraved BLM layer and used as an electrode in electroplating. Another object of the present invention is to provide a flip chip welding with a fine pitch.

Page 10

4184 TO V. Description of the Invention (7) A method for manufacturing a ball, wherein the solder ball is connected to the BLM layer through an interface containing non-meltable metal ions (such as Cu or Cr). In order to achieve the above-mentioned object, the present invention discloses a method for manufacturing a flip-chip solder ball, which includes at least the following steps: providing a substrate with a metal pad formed on the top thereof, wherein all parts of the pad except the top are exposed are buried; On an insulating layer; depositing a BLM layer on the surface of the substrate; coating a first photoresist layer on the surface of the BLM layer, wherein the first photoresist layer has a first thickness, the first thickness must be very thin, So that the exposure accuracy is at least ± 2 // m; etch away the wet layer deposited in the BLM layer outside the pad; apply a second photoresist layer on the top surface of the etched BLM layer, where the first The two photoresist layers have a second thickness, the second thickness is greater than the first thickness, an opening is formed in the second photoresist layer, and a solder is injected into the opening to form a columnar solder bump; and The second photoresist layer is removed and the columnar solder bumps are formed into a spherical solder ball due to the cohesive force of the columnar solder bump through a heavy-flow process. At this step, the manufacture of the solder ball is completed. The solder ball may be made of tin-lead alloy or other solder alloys, and the manufacturing steps disclosed in the present invention may further include a metal deposition process, which means that before the second photoresist layer is coated, A non-leachable metal layer (None-Leachable Metal Layer) is deposited on the surface of the etched BLM layer. This non-meltable metal layer is formed of a metal that will not be melted by solder bumps. It is made of conductive material, such as Cu or Ni, and its thickness cannot exceed 1 / zm, it is generally between 0.01 / zm ~ lym, preferably between 0.05 μm. The BLM layer mentioned above is composed of 2 ~ 3 layers of different metals, which are

Page U

4184 TO V. Description of Invention (8) Adhesion Diffusion Barrier Layer This layer has two functions. One is to act as a diffusion prevention layer to prevent the diffusion of solder (such as tin and lead). It is used as an adhesion layer to form strong adhesion with aluminum pads and solders. The adhesion prevention diffusion layer can be made of metals such as C r or Τ ί; and a wet layer (B ο nd 1 ng 〇r W e 11 ing Layer), which can be made of metals such as Cu, Pd, Pt, or Ni; and the thickness of the above-mentioned first photoresist layer is preferably not more than 10Vm, and of course, the best is between 2 " m ~ 5 # m, and the second photoresist layer is used to open the opening of the long ball and provide the height required for the solder ball. In order to increase the reliability of the solder ball, it will be used in the manufacturing process by Increasing the thickness of this photoresist layer to increase the height of the solder ball, so the thickness of the second photoresist layer is preferably not less than 50 # m, and the step of injecting solder into the opening to form the solder ball is performed by electroplating Way to form. Although what is disclosed above is a method for manufacturing flip-chip solder balls, this method can also be applied to a method for manufacturing fine-pitch solder bumps on a silicon wafer, including at least the following steps: providing a plurality of top portions Silicon wafers with metal pads; a BLM layer is deposited on the top surfaces of the metal pads, and a first photoresist layer is coated on the surface of the BL M layer, and the pattern to be formed is defined in the first photoresist Agent layer, wherein the coating thickness of the first photoresist layer is less than 10 V m; defining and forming a plurality of openings on the second photoresist layer; injecting a solder into the openings to form a plurality of tans Material bumps; and removing the second photoresist layer, so far this step completes the manufacture of the fine-pitch silicon wafer solder bumps. After that, the solder bump is subjected to a heavy-flow process to make the solder bump due to its internal

Page 12. A184TQ_ Five 'Description of the Invention (9) Converge to form a spherical solder ball, and the solder can be made of tin-lead alloy or other solder alloys, and the above process can also include a metal deposition process, It means that before the second photoresist layer is applied, a non-meltable metal layer is deposited on the surface of the BL BL layer being etched. This non-melt metal layer is made of a highly conductive material , Such as Cu or Ni, and its thickness cannot exceed lym, generally between 0.01 / zm ~ l / 2m, and most preferably between 0.05 // m ~ 0 · 3 ym. The BL LM layer disclosed above is composed of an adhesion prevention diffusion layer and a wetting layer. The BLM layer can be selectively made of Ti / Cu, TiN / Cu, Cr / Ni, A1 / Ni-V / Cu or Cr / CrCu / Cu / Au, and the material of the solder ball is composed of S η and P d. In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is given below in conjunction with the accompanying drawings for detailed description as follows: [Simple description of the formula] Section 1 A ~ Figure 1 F is a flow chart of the conventional manufacturing process of tin-lead balls using thin film deposition technology; Figure 2 is a block flow chart of the tin-lead ball manufacturing process of the present invention; Figures 3 A to 3 I are manufacturing processes of the present invention A cross-sectional view of each manufacturing step of the tin-lead ball; and FIGS. 4A to 4I are cross-sectional views of each manufacturing step of the tin-lead ball manufacturing method of the present invention. In the method of manufacturing crystal solder balls,

Page 13 A184T0 V. Description of the Invention (（) A unique and novel double lithography technology combined with a double photoresist layer to achieve the purpose of making fine solder balls. In the first lithography technology, it was first in the BLM A thin photoresist is coated on the layer, and the positions of the tin-lead bumps to be grown are defined by the way of exposure and development, and then the thin photoresist is removed together with the wet layer of the BL Μ layer located outside the pad-; In the lithography technology, a thick photoresist is applied on the BLM layer, and the exposure and development methods are used to define the openings of the solder bumps and the height of the solder bumps. Generally speaking, the first The thickness of the photoresist layer is preferably not more than 10 / zm, and of course the best is between 2 # m ~ 5 // m, the reason is that when using a thick photoresist (that is, the thickness is greater than 5 0 // m ), It is often accompanied by problems such as exposure / focus, which makes the alignment accuracy worse. Therefore, the present invention uses a thin photoresist as the first photoresist layer, which can avoid the problems of exposure / focus and so on. Be polite to make fine pitch tin Ball. The thick photoresist used in the second lithography technology is used to open the openings for the solder bumps and provide the height required for the solder bumps. Generally, the thickness of the thick photoresist used is more than 50 // m. As mentioned earlier, the manufacturing steps of the present invention may further include a metal deposition process, which is to deposit a non-meltable metal layer between the BL MM layer and the solder ball, which is used as an electrode during electroplating. The thickness of a non-fusible metal layer is very thin, about less than 1 # m, and it is generally between 0.01 μm and 1 μm, and preferably between 0.05 / zm and 0.3 // in. The BUi layer disclosed in the present invention is composed of 2 to 3 layers of different metals, which are an adhesion prevention diffusion layer, a wetting layer, and a protective layer, respectively. The BLM layer can be made of Ti / Cu, TiN / Cu, and Cr.

Page 14 4184 70 V. Description of the invention (11) / Ni, A1 / Ni-V / Cu, Cr / CrCu / Cu / Au or other metals, in which in the present invention a bond extinction process is used in A BLM layer is deposited on the substrate surface, and the BLM layer located outside the pads is removed in a subsequent process. Please refer to the block flow chart shown in "Figure 2" and the cross-sectional view of each manufacturing step shown in "Figures 3 Α ~ 3 I" to explain the method for manufacturing the fine tin lead ball of the present invention. In the embodiment disclosed in the present invention, solder bumps and solder balls made of tin-lead alloy are used. Therefore, in the following related description, tin-lead bumps and tin-lead balls are used instead. First, refer to the first figure in FIG. 2 Step 5 2 and “3A” illustrate the first manufacturing step. The wafer 70 includes an aluminum bond pad 72 formed on the top surface 74 of the wafer 70 and a protective layer 76. Wherein, the surface of the aluminum pad 72 has at least an exposed area for the tin-lead bump to grow, whereby the tin-lead bump is electrically connected so that the aluminum pad 72 can be bonded to the substrate circuit. Please continue to cooperate with the second step 54 in Figure 2 and "Figure 3B" to explain the second manufacturing step. In this step, the protective layer 76 and the aluminum pad 7 2 are exposed .. Exposed above the outer area A BLM layer 80 is deposited. The BLM layer 80 includes different layers of metal, which are an adhesion prevention diffusion layer, a wetting layer (also called a tin dip layer), and a protective layer (the user can choose whether to deposit this layer according to the circumstances) ), And the BL M layer 80 used in this embodiment only includes an adhesion prevention diffusion layer 82 and a wetting layer 84, and is deposited on the top surface of the protective layer 76 and the aluminum pad 72 is exposed on The outer top surface, of course, as mentioned above, the BLM layer 80 may also include a protective layer (not labeled), but this is only required under the premise of using some metals, such as when the adhesion prevention diffusion layer 8 When the material of 2 is made of C r or T i and the wet layer 8 4 is made of C u, P d, P t or Ni

Page 15 41847 05. Description of the invention (12) At this time, there is a concern that the surface layer of the wet layer 8 4 will be oxidized before the tin-lead bump is plated. Therefore, the wet layer 8 4 is generally finished after plating. After that, a protective layer is plated to prevent the wet layer 84 from being oxidized. The above protective layer is made of precious metals (, such as Au, Pt). -Please continue to cooperate with the third step 5 of Figure 2 and "3C" to explain the third manufacturing step. In this step, a first photoresist is formed on the BLM layer 80 by deposition or coating. Agent layer 90, the thickness of the first photoresist layer 90 is preferably not more than 10 / im, it is preferably between 2 / zm ~ 5 / zm, because the first photoresist layer 90 can Allows highly accurate development technology on the BL Μ layer 80, that is, the first photoresist layer 90 can make the alignment very accurate, so it can accurately determine the position of the tin-lead bump to be grown. And this position is near the center point of the aluminum pad 72, where the above-mentioned method of photolithography is to correctly determine the position of the tin-lead bump by a photomask 92, that is, here A mask 92 is covered above the position. The pattern on the mask 92 is transferred to the BLM layer 80 by exposure and development under UV Light, and then the wet layer that is not covered by the mask 9 2 is wet-etched or dry-etched. 8 4 is removed, this step is the fourth step 5 8 in FIG. 2, and the sectional view is as shown in FIG. 3 D, but in this step That need special attention, i.e. when B L Μ layer 80 is etched, etching only the upper layer and the underlying retention, because the bottom layer material or is C r T i, the electroplating process may be used as an electrode in a subsequent. Please continue to cooperate with the fifth step 60 in FIG. 2 and the “FIG. 3E” to explain the fifth manufacturing step. In this step, a second photoresist layer 1 0 0 is deposited on the wafer 70, where The height of the second photoresist layer 100 and the formed

Page 16 4104 70 V. Description of the invention (13) The height of the tin-lead bump is related to the reliability of the tin-lead bump. Therefore, in order to obtain higher reliability, it is necessary to add a second The height of the photoresist layer 100 is to form a high tin-lead bump, and the thickness of the second photoresist layer 100 generally used is more than 50 μηι; after the fifth step is completed, it is then reused. The second photomask 1 02 defines the opening 110 of the tin-lead bump to be grown, as shown in the sixth step 62 and "3F figure" of FIG. 2. Next, a solder composed of Sn and Pd is injected into the above-mentioned openings 1 10 by electroplating to form a columnar tin-lead bump 1 2 0, as shown in the seventh step 64 of FIG. 2 and “3G diagram”. ", And then remove the second photoresist layer 100, and then heat the tin-lead bump 1 2 0 by a reflow process at a temperature higher than the melting point of the tin bump 1 120, The tin-lead bump 1 2 0 is changed from a solid state to a liquid state, and the columnar tin-lead bump 1 2 0 is formed into a spherical tin-lead ball 1 3 0 due to its cohesion during the cooling process, as shown in FIG. 2 The eighth step 68 and "Figure 3H" are shown. Finally, please continue to cooperate with the ninth step 6 of FIG. 2 and the “3rd I” to explain the ninth manufacturing step. In this step, an etching process (which can be wet or dry etching) is used to remove other excess The adhesion prevention diffusion layer 8 2 is removed, and thus the fabrication of the flip-chip tin lead ball is completed. In the method disclosed in the present invention, the eighth step 68 heavy-flow solder and the ninth step 66 etch the BL Μ layer. It can be reversed, that is, the adhesion prevention diffusion layer 8 2 can be removed by an etching process first, and then a spherical tin-lead ball 130 can be formed through a heavy-flow process, which can also achieve the purpose of making a fine-pitch tin-lead ball. In the process disclosed above, in the fourth step 5 8 the BLM layer is etched. In the 8 step, only the wet layer 8 4 is etched. The adhesion prevention diffusion layer is not etched.

Page 17 4184 70 V. Description of the invention (14) 8 2 As shown in "3D drawing", in another embodiment disclosed in the present invention, the BLM layer 80 (including the wet layer 84 and The adhesion prevention diffusion layer 82) is completely etched (as shown in "Figure 4D"), but in this embodiment, a metal deposition step must be inserted between the fourth step and the fifth step. Before the two photoresist layers 100, a non-fusible metal layer 96 is deposited on the top surface of the etched BL M layer 80. The non-fusible metal layer 96 is made of tin and lead. The bump 1 2 0 is formed of melted metal, and is generally made of a highly conductive material, such as Cu or Ni. The thickness is generally between 0.01 / zm and 1, preferably 0. 0 5 # m Between 0.3 m and 0.3 m, but it should be noted that after adding the step of depositing the metal layer, an etching step must be performed in the subsequent steps to remove the rest of the area except above the aluminum pad 7 2 The non-fusible metal layer 9 6 is removed, and then a reflow process is performed to form a tin-lead ball 1 3 0. A cross-sectional view of the entire manufacturing process is shown in FIG. 4A-41. It is shown that, except for the above steps, the remaining steps are similar to the manufacturing steps of "Figures 3A to 3I", which will not be described in detail here. The present invention uses the first photoresist layer 90 to define the positions of the tin-lead bumps 120 on the BLM layer 80. Since the thickness of the first photoresist layer 90 is very thin, The alignment can be very accurate, although when the second photoresist layer 1 0 0 is used to define the opening of the tin-lead bump 1 2 0 and the height of the tin-lead bump 1 2 0, the The second photoresist layer 100 is thick and causes misalignment. However, in the subsequent heavy-flow process, it will be self-aligned due to the combination effect of the tin-lead bump 1 2 0 and the wetting layer 84 ( Sel f-Al lgment), that is, in the reflow process, when the solder is molten, the offset solder is pulled back to the aluminum pad 72, that is, the tin that was previously defined in the first photoresist layer 90 is pulled back. Lead bump

Page 18 418470 V. Description of the invention (15) 1 2 0 position, so long as the position of the tin-lead bump 1 2 0 to be long can be accurately defined in the first photoresist layer 90, it can be ensured that A finely pitched tin-lead ball 1 3 0. [Effect of the invention] In the present invention, the first layer of thin photoresist is used to define the position of the solder ball on the BLM layer, and then the second layer of thick photoresist is used to define the opening and height of the solder ball. Among them, because the thickness of the first thin photoresist is very thin, the accuracy of the alignment is high, that is, the position of the solder ball to be grown can be accurately defined, and the solder bump formed by the present invention is a columnar solder. The bumps can improve the fine-pitch manufacturing process, and because the BL M layer is etched first, it can avoid the solder bumps being etched or severely oxidized due to long-term etching. Therefore, the technology disclosed in the present invention can make Form fine-chip flip-chip solder balls. [Explanation of Schematic Symbols] 10 .............................. ............... ff body 'knot only 12 ............... ................... Shi Xi substrate 14 .............. ........................................ ..... ¥ t 16 ..................................... ........ Top surface 18 ............. ............... Dingle Table®

2 0 ................................................ ......... 4 Silent Words I 22 ............... ..................... window 24 .............. .................................................top Surface 26 ... ......... BLM layer 28 ............ ............... wet layer

Page 19 ^ 8470 V. Description of the invention ¢ 16) 3 0 ................................... ...... adhesion preventing diffusion layer 3 4 ............ tIg) ¾ Μ 38 ............ ................................... f? catty 1 1 40 ............... Wj ^ FREE ^-42 ............ ......... m ^ 52 ......... .................................. $- ^ ^ 54 ............................... .............% ^% 5 6 ... ............ $ ^ 58 ......... ...............% n ^ 60 ..... ........................................ ..... $ Έ. Ψ ^ 62 ............... ........... g Six steps

64 ....................................... ........... $ -t ^ W 66 ............. .......; ...... 9th step 6 8 ........ ................. $ y \ ^ 7 0 .. ........................................ .............. wafer 72 ............. ................... is ^ ^ 7 4 ............... ............................................................................. 7 6. ........................................ ............ fi > f 78 ............ ........................ Surface 80 .............. ....................... BLM ^ 82 ................................................ ... adhesion preventing diffusion layer ... ........... wet 'moisture layer 9 0 ......... ............... First photoresist layer 92 ......... ........................................ .... Xiange

Page 20 4 184 70 V. Description of the invention (17) 10 0 ......... ...... Second photoresist layer 102 ............... .......................... ft ^ 110 ........... ........................................ ..Opening 120 .................... ............ m ^ a it 130 ............. ................. Pin Shot _ Painting Off Page 21

Claims (1)

4 184 7j VI. Application for patent scope. 1 'A method for manufacturing flip-chip solder balls, including at least the following steps: Provide a substrate with a metal pad formed on the top, wherein all parts of the pad except the top are exposed. Buried in an insulating layer; depositing a BLM layer on the surface of the substrate; coating a first photoresist layer on the surface of the BL M layer 'wherein the first photoresist layer has a first thickness, the first The thickness must be very thin so that the exposure accuracy is at least ± 2 / zm; etch away one of the wet layers of the BLM layer deposited in the area outside the pad; apply a second photoresist layer to the etched The top surface of the BLM layer, wherein the second photoresist layer has a second thickness, the second thickness is greater than the first thickness, an opening is formed in the second photoresist layer, and a solder is injected into the Opening holes to form a columnar solder bump; and removing the second photoresist layer and subjecting the columnar solder bump to a spherical solder ball due to its cohesive force through a heavy-flow process. 2. The method for manufacturing a flip-chip solder ball according to item 1 of the scope of the patent application, wherein before the second photoresist layer is coated, if the BL M layer is completely etched, it is further included in the etched A non-meltable metal layer is deposited on the top surface of the BL M layer. The non-meltable metal layer is formed of a metal that will not be melted by the solder bump. 3. The method for manufacturing a flip-chip solder ball as described in item 2 of the scope of patent application, wherein the non-meltable metal layer is made of a highly conductive metal material. 4 As described in item 2 of the scope of patent application Manufacturing method of flip chip solder ball Page 22 4 \ 8470 6. Scope of patent application Where the non-meltable metal layer is deposited from one of copper or nickel. 0 5 Fabrication of flip-chip solder balls as described in item 2 of the patent Capricorn Method> wherein the thickness of the non-fusible metal layer deposited is less than 1 m Ό 6, the method for manufacturing a flip-chip solder ball as described in item 2 of the patent scope, wherein the thickness of the non-fusible metal layer is 0 0 1 β m to 1 β m 0 7% The manufacturing method of the flip-chip solder ball as described in item 2 of the patented ArfT target enclosure > wherein the thickness of the non-meltable metal layer is preferably less than 0 · 05 β m and 0.3! Fi m 〇8, as described in the patent application of the scope of the first method of manufacturing flip-chip solder balls, wherein the BLM layer includes--adhesion prevention diffusion layer and-- Wet layer 9, as patented / rfc target enclosure No. 8 The manufacturing method of the flip-chip solder ball described above, wherein the adhesion prevention diffusion layer is made of one of metal materials such as chromium or titanium, and the wet layer is made of metal material such as copper> 1 white or nickel 0, The method for manufacturing a flip-chip solder ball according to item 8 of the patent application, wherein the BL Μ layer is still f-protective layer '1 1, as described in the item 10 of the patent application A-Λτ Chapter 巳Method for manufacturing flip-chip solder ball, wherein the protective layer is made of one of precious metals such as gold or platinum Fang Jinfang Welding balls made of composite materials Welding materials whose welding crystals are crystal-coated or covered with gold Description of the items listed in the lead and tin items I—I Page 23 VI. Patent Application Scope Law Wherein the first thickness of the first photoresist layer is less than 1 0 // m. 14. The method for manufacturing a flip-chip solder ball according to item 1 of the scope of patent application, wherein the first thickness of the first photoresist layer is preferably between 2 μm and 5 μm. 15. The method for manufacturing a flip-chip solder ball according to item 1 of the scope of the patent application, which makes the second thickness of the second photoresist layer slightly smaller than the opening growth in the second photoresist layer. The height of the solder bump = 1 6. The manufacturing method of a flip-chip solder ball as described in item 1 of the scope of patent application, wherein the second thickness of the second photoresist layer must not be less than 5 0 // m . 17. The method for manufacturing a flip-chip solder ball as described in item 1 of the scope of patent application, wherein a solder bump can be grown in the opening by electroplating. 18. A manufacturing method for growing fine-pitch solder bumps on a silicon wafer, comprising at least the following steps: providing a silicon wafer with a plurality of metal pads formed on top; and depositing a BLM layer on the metal pads A top photoresist layer is coated on the surface of the BL M layer, and a pattern to be formed is defined in the first photoresist layer, wherein the coating thickness of the first photoresist layer is less than 1 0 "m; define and form a plurality of openings in the second photoresist layer; inject a solder into the openings to form a plurality of solder bumps; and remove the second photoresist layer. 19. Develop microchips on Shixi wafers as described in item 18 of the scope of patent application A184 * T ° ^, patent application scope The method for manufacturing fine-pitch solder bumps further includes subjecting the solder bumps to a multiple flow process to form a plurality of spherical solder balls. 20. The manufacturing method of growing fine-pitch solder bumps on a shixi wafer as described in item 18 of the scope of patent application, wherein before the second photoresist layer is coated, it is further included in the etched A non-fusible metal layer is deposited on the top surface of the BL M layer, and the non-fusible metal layer is formed of a metal that will not be melted by the solder bump. 2 1. The method for manufacturing a fine-pitch solder bump on a silicon wafer as described in item 20 of the scope of the patent application, wherein the non-fusible metal layer is deposited by copper and one of the electrodes. 2 2. The method for manufacturing a fine-pitch solder bump on a silicon wafer as described in item 20 of the scope of patent application, wherein the thickness of the non-meltable metal layer is between 0.01 and 1. 23. The method for manufacturing a fine-pitch solder bump on a silicon wafer as described in item 18 of the scope of patent application, wherein the solder can be made of tin-lead alloy or other solder alloys. 24. A structure of a silicon wafer solder ball, comprising: a silicon wafer having a top surface after pretreatment; a welding finish formed on the top surface of the Shi Xi wafer; and a deposition on the surface of the solder pad A BLM layer; and a solder ball growing above the BLM layer, wherein the solder ball and the BLM layer have an interface, which is formed by depositing one of non-meltable metals such as copper or copper ° 2 5 The junction of the silicon wafer solder ball as described in the scope of patent application No. 24 Page 25 6. The structure of the patent application, wherein the BL M layer includes a structure of a silicon wafer solder ball as described in item 24 of the patent application scope, including an adhesion prevention diffusion layer and a wetting layer 0 2 6. The BLM layer can be made of one of Ti / Cu, TiN / Cu, Cr / Ni, A1 / Ni-V / Cu or Cr / CrCu / Cu / Au. 27. According to the structure of the silicon wafer solder ball described in item 24 of the scope of the patent application, the coal pellets can be made of tin alloy or other solder alloys. II Page 26