Copper pillar bump structure capable of preventing lateral corrosion and manufacturing method of copper pillar bump structure

Abstract

The invention discloses a copper pillar bump structure for preventing lateral corrosion and a manufacturing method thereof. The method comprises the following steps: depositing a metal seed layer on the surface of a wafer; spin-coating photoresist on the seed layer; photoetching for the first time, and patterning the photoresist to form a first pattern; growing copper in the first pattern area to form a copper column with a required height; growing a metal barrier layer on the surface of the copper column to form a metal barrier layer with a required height; growing a solder on the surface of the metal barrier layer to form a solder with a required height; photoresist is spin-coated on the solder; photoetching for the second time, and patterning the photoresist to form a second pattern; growing a metal protection layer on the side surface of the copper column to form a metal protection layer with the same height as the barrier layer; cleaning and removing the photoresist; etching the metal seed layer, and patterning the metal seed layer to form a required pattern; and heating at high temperature to melt the solder to form smooth salient points, and then cooling and solidifying. Lateral corrosion of the copper pillar bump structure can be avoided, and the interconnection reliability of the copper pillar bumps is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chip manufacturing, and in particular relates to a copper column bump structure for preventing lateral corrosion and a manufacturing method thereof. Background Art

[0002] Copper pillar bump interconnect is a wafer-level advanced packaging technology with advantages such as fine pitch, micro size, and ultra-high I / O density. It can be used for direct connection between silicon chips and substrates on flip-chip packages. At present, with the continuous growth in demand for high-density chip packaging, the interconnect pitch based on copper pillar bumps is constantly shrinking, and its service reliability under stress conditions such as high temperature and current has attracted widespread attention in the industry.

[0003] At present, the copper pillar bump manufacturing process often grows a 1um~5um thick Ni barrier layer between the copper pillar and the solder to slow down the metal compound reaction between the copper pillar and the solder, thereby achieving the purpose of improving the reliability of the interconnection structure. However, during the high-temperature welding process, the solder will melt into a liquid state and bypass the Ni layer from the side to make a small amount of contact with the copper pillar, and a Cu-Sn metal compound reaction will occur, which will corrode the copper pillar structure and reduce the reliability of the copper pillar bump interconnection. As the service life of the interconnection structure increases, this corrosion phenomenon will intensify. Therefore, the industry is in urgent need of a technical method that can effectively prevent lateral corrosion of copper pillar micro-bumps. Summary of the invention

[0004] The purpose of the present invention is to provide a copper pillar bump structure that prevents lateral corrosion and a method for making the same, in order to address the problem in the prior art that during the high-temperature welding process of copper pillar bumps, the solder melts into a liquid state and bypasses the Ni layer from the side to make a small amount of contact with the copper pillar, thus causing corrosion to the copper pillar structure. The present invention can avoid lateral corrosion of the copper pillar bump structure and improve the interconnection reliability of the copper pillar bumps.

[0005] In order to achieve the above object, one aspect of the present invention provides a method for manufacturing a copper pillar bump structure for preventing lateral corrosion, comprising: Depositing a metal seed layer on the surface of the wafer; Spin coating photoresist on the metal seed layer for the first time; Performing a first photolithography to pattern the photoresist to form a circular first pattern, wherein the radius of the circle corresponds to the radius of the desired copper column; Growing copper in the region of the first pattern to form a copper column of a desired height; Growing a metal barrier layer on the surface of the copper column to form a metal barrier layer of required height; growing solder on the surface of the metal barrier layer to form solder of a desired height; Spin-coating photoresist on the metal seed layer for a second time, wherein the spin-coating height exceeds the height of the solder; Performing a second photolithography to pattern the photoresist to form a second ring-shaped pattern, wherein the width of the ring corresponds to the required thickness of the metal protection layer; Growing a metal protection layer on the side of the copper pillar to form a metal protection layer with the same height as the metal barrier layer; Cleaning and removing photoresist; Etching the metal seed layer to retain the metal seed layer under the copper pillar; The solder is melted by high temperature heating, forming smooth bumps and then cooled to solidify.

[0006] Preferably, the material of the metal seed layer includes Ti, Cu and Cr, the material of the metal barrier layer includes Ni, Ta, Ti and Pd, and the solder includes Sn-based lead-free solder and lead-containing solder.

[0007] Another aspect of the present invention provides a copper pillar bump structure for preventing lateral corrosion, which is manufactured using the above method and includes a metal seed layer on a wafer, a copper pillar, a metal barrier layer, a metal protective layer and solder.

[0008] The copper pillar bump structure for preventing lateral corrosion and the manufacturing method thereof according to the above aspects of the present invention can avoid lateral corrosion of the copper pillar bump structure and improve the interconnection reliability of the copper pillar bump. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work: Figure 1 It is a flow chart of a method for manufacturing a copper pillar bump structure for preventing lateral corrosion according to an embodiment of the present invention; Figure 2 is a schematic diagram of depositing a metal seed layer on a wafer surface according to an embodiment of the present invention; Figure 3 is a schematic diagram of first spin coating of photoresist on a metal seed layer according to an embodiment of the present invention; Figure 4 is a schematic diagram of performing the first photolithography according to an embodiment of the present invention; Figure 5 is a schematic structural diagram of a photomask required for the first photolithography according to an embodiment of the present invention; Figure 6 is a schematic diagram of growing a copper pillar in a region of a first graphic according to an embodiment of the present invention; Figure 7 is a schematic diagram of growing a metal barrier layer on the surface of a copper pillar according to an embodiment of the present invention; Figure 8 is a schematic diagram of growing solder on the surface of a metal barrier layer according to an embodiment of the present invention; Fig. 9 is a schematic diagram of secondary spin coating of photoresist on solder according to an embodiment of the present invention; Fig.10 is a schematic diagram of performing a second photolithography according to an embodiment of the present invention; Fig.11 is a schematic structural diagram of a photomask required for the second photolithography according to an embodiment of the present invention; Fig.12 is a schematic diagram of growing a metal protective layer on the side of a copper column according to an embodiment of the present invention; Fig.13 is a schematic diagram of cleaning and removing photoresist according to an embodiment of the present invention; Fig.14 is a schematic diagram of etching a metal seed layer according to an embodiment of the present invention; Fig.15 It is a schematic diagram of forming a copper pillar bump structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0011] One embodiment of the present invention provides a method for manufacturing a copper pillar bump structure that prevents lateral corrosion, such as Figure 1 As shown, the method of the embodiment of the present invention includes steps S1 to S12.

[0012] (1) Step S1: Figure 2 As shown, a metal seed layer 201 is deposited on the surface of the wafer 101. The material of the metal seed layer 201 includes but is not limited to Ti, Cu, Cr and other materials. Figure 2 In the figure, the wafer 101 includes a three-layer structure, the bottom layer is a silicon wafer, the upper layer is a metal pad, and a polyester amide buffer layer is arranged on the metal pad.

[0013] (2) Step S2: Figure 3 As shown, photoresist 202 is first spin-coated on the metal seed layer 201 .

[0014] (3) Step S3: Figure 4As shown, the first photolithography is performed to pattern the photoresist 202 to form a circular first pattern 203, and the radius of the first pattern 203 corresponds to the radius of the required copper column. The photomask structure required for the first photolithography is as follows: Figure 5 As shown, in the white circular area, the radius of the circle is the radius of the required copper column structure, for example, 2um to 20um, and the distance between the two circle centers is the distance (pitch) between the copper columns, and the copper column pitch is, for example, 10um to 100um.

[0015] (4) Step S4: Figure 6 As shown, copper is grown in the region of the first pattern 203 to form a copper pillar 204 of a desired height. The height of the copper pillar 204 is determined according to actual needs and can be adjusted by the time of electroplating, sputtering and other processes in the growth process.

[0016] (5) Step S5: Figure 7 As shown, a metal barrier layer is grown on the surface of the copper pillar 204 to form a metal barrier layer 205 of a desired height. The material of the metal barrier layer 205 includes but is not limited to Ni, Ta, Ti, Pd, etc. The height of the metal barrier layer 205 is determined according to actual needs.

[0017] (6) Step S6: Figure 8 As shown, solder is grown on the surface of the metal barrier layer 205 to form solder 206 of a desired height, and the solder 206 includes but is not limited to Sn-based lead-free solder and lead-containing solder, etc. The height of the solder 206 is determined according to actual needs.

[0018] (7) Step S7: Fig. 9 As shown, a second photoresist 202 is spun on the metal seed layer 201. The height of the second spun photoresist 202 exceeds the height of the solder 206, and the spun coating height exceeds the height of the solder, thereby covering the solder 206, the metal barrier layer 205, the copper pillar 204, and the metal seed layer 201 below.

[0019] (8) Step S8: Fig.10 As shown, a second photolithography is performed to pattern the photoresist to form a second annular pattern 207, the width of which corresponds to the required thickness of the metal protective layer. The photomask structure required for the second photolithography is as follows: Fig.11 As shown, the overall size is the same as the photomask of the first photolithography, the middle black circular area corresponds to the copper column 204, and the width of the white ring area is the thickness of the metal protection layer, for example, 1um to 5um.

[0020] (9) Step S9: Fig.12 As shown, a metal protection layer is grown on the side of the copper pillar 204 to form a metal protection layer 208 having the same height as the metal barrier layer 205. The material of the metal protection layer 208 includes but is not limited to Ni, Ta, Ti, Pd and other materials; (10) Step S10: Fig.13 As shown, the photoresist 202 is removed by cleaning.

[0021] (11) Step S11: Fig.14 As shown, the metal seed layer 201 is etched to remove the metal seed layer 201 in the area other than below the copper pillar 204, and only the metal seed layer 201 below the copper pillar 204 is retained to achieve conductive connection.

[0022] (12) Step S12: Fig.15 As shown, reflow is performed, where the solder 206 is melted by high temperature heating to form smooth bumps and then cooled and solidified.

[0023] Through the above manufacturing steps, the copper pillar bump structure for preventing lateral corrosion according to the embodiment of the present invention is obtained. Fig.15 As shown, the copper pillar bump structure for preventing lateral corrosion according to the embodiment of the present invention includes a metal seed layer 201 , a copper pillar 204 , a metal barrier layer 205 , a metal protection layer 208 , and a solder 206 on a wafer 101 .

[0024] According to the copper pillar bump structure and its manufacturing method for preventing lateral corrosion of the embodiment of the present invention, by optimizing the copper pillar bump manufacturing process, a metal protective layer is grown on the side of the copper pillar, and a barrier layer is grown on the top of the copper pillar to form a complete protection for the copper pillar structure, which effectively prevents the solder from melting into liquid during the high-temperature welding process, bypassing the barrier layer from the side and directly contacting the copper pillar, and causing a Cu-Sn metal compound reaction. This technical invention successfully solves the lateral corrosion problem of the copper pillar bump structure, and achieves the purpose of improving the interconnection reliability of the copper pillar bump.

[0025] The application of the present invention will help to further popularize the application of copper pillar bump interconnection technology in high-density packaging technology. With the widespread application of high-density packaging chips in new energy vehicles, consumer electronics, 5G communications and other fields, the present invention will present good engineering application value and huge economic and social benefits. The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for manufacturing a copper pillar bump structure for preventing lateral corrosion, characterized in that: include: Depositing a metal seed layer on the surface of the wafer; Spin coating photoresist on the metal seed layer for the first time; Performing a first photolithography to pattern the photoresist to form a circular first pattern, wherein the radius of the circle corresponds to the radius of the desired copper column; Growing copper in the region of the first pattern to form a copper column of a desired height; Growing a metal barrier layer on the surface of the copper column to form a metal barrier layer of required height; growing solder on the surface of the metal barrier layer to form solder of a desired height; Spin-coating photoresist on the metal seed layer for a second time, wherein the spin-coating height exceeds the height of the solder; Performing a second photolithography to pattern the photoresist to form a second ring-shaped pattern, wherein the width of the ring corresponds to the required thickness of the metal protection layer; Growing a metal protection layer on the side of the copper pillar to form a metal protection layer with the same height as the metal barrier layer; Cleaning and removing photoresist; Etching the metal seed layer to retain the metal seed layer under the copper pillar; The solder is melted by high temperature heating, forming smooth bumps and then cooled to solidify.

2. The method according to claim 1, characterized in that The materials of the metal seed layer include Ti, Cu and Cr, the materials of the metal barrier layer include Ni, Ta, Ti and Pd, and the solder includes Sn-based lead-free and lead-containing solders.

3. A copper pillar bump structure for preventing lateral corrosion, characterized in that: The method according to claim 1 or 2 is used to manufacture the wafer, and the wafer comprises a metal seed layer, a copper pillar, a metal barrier layer, a metal protective layer and solder.

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