TW477047B - Method for forming bumps by using copper as solder pads - Google Patents

Abstract

The method comprises: forming a copper pad on a wafer, and depositing a passivation layer on the copper pad, wherein the passivation layer is stacked by two or more individual layers; next, etching the passivation layer without exposing the metal pad, and forming an under bump metallurgy layer by sputtering deposition before performing the sputtering deposition of the in-situ ion milling on the under bump metallurgy layer and after exposing the copper pad; next, forming a photoresist pattern with an opening on the copper pad and under bump metallurgy layer by photolithography process; plating tin and removing the photoresist pattern to form a tin bump; using the tin bump as an etching mask to etch the exposed under bump metallurgy layer; then, performing a reflow to form a ball structure due to the surface tension of the tin bump, thereby completing the manufacture of the tin bump.

Description

477047

V. Description of the invention (1) Field of the invention: The present invention relates to an integrated circuit manufacturing process, and particularly relates to a variety of applications. Copper is a method for bonding pads in a bumping process. BACKGROUND OF THE INVENTION: In the ultra-large integrated circuit (ULSI) trend, the size of semiconductor components is constantly shrinking to continuously increase the accumulation of components on wafers. With the reduction of the component size, there are two battles in the manufacturing process of integrated circuits. awai ’Because of the rapid development of computer and communication technology, the following: = What we need is more electronic components of different types and applications. For example, ^ operating computer interface or other communication interface needs to allow: 1 2 different types of semiconductor components. … The trend of integrated circuits will develop towards a high degree of integration, but ’in recent years 3 still:

The development and advanced guidance Z is not only more and more dense, but also more and more ancient: the number of π ic + conductors J / 0 is increasing, and the speed is longer. The number of pins of 70 pieces is increasing. The larger the size, the faster the increase of the package J, leading to component power consumption before the package is getting smaller and smaller. @ Package is also accompanied by the development of the ball matrix array to seal the 3 m high number of I / O BGA packages) technology development * 1 grid array; I / 0 pins for short are more spherical than the structure of the wire rod A It is' negative and not easy to be damaged and deformed. I seal shoes /, the length of the 70-piece slender pins and the short transmission distance are short. 4 // U4 /

Flip chip packaging is also dying when it can meet the needs of current and future digital systems. This technology is a trend that uses lead-in / new-generation packaging technology to produce lean tin bumps. In / Out. For the formation of the conductive process Hilt different! Welding metal welding first, use your layer of the user in the welding pad. After depositing the barrier layer and conductive separately, use! The general composition includes Cr / Cu, Ti / Cu. ^ ^ On the aluminum pad, forming a pattern, forming a photoresist pattern conductive acoustic contact M ′, 电镀 a plating method to form tin in the window opening to contact the isoelectric layer '', and then removing the photoresist pattern to form a tin bump One: Use = block as an etching mask to remove the unshielded 'electricity ,,', and then make a tin bump. After that, the tin bump undergoes a thermal manifold.]; Electricity ::... The various limitations of aluminum materials, the scale of components: breakthrough. In order to meet the needs of various components in the process to 0.13 microns and millet [because & the current use of copper instead of ㈣ has become a trend in interconnects. This is derived from Copper metal itself has various inherent advantages in electrical properties, such as (丨) low-resistance characteristics, (2) two electron mobility (ant i-electr〇ffligrat i〇n), four numbers higher than aluminum The third level (3) has good anti-stress induced void formation properties, which can give the device better characteristics such as faster speed, can reduce cr 0 ssta 1 k, and has a smaller RC time constant. 〃 χ ”But copper has better electrical properties Performance, such as low resistance, has the disadvantages of being difficult to etch and easy to oxidize and silicify. Due to the shortcomings of copper, 477047 V. Description of the invention (3) Before the 1C process is completed, it is difficult to control the surface condition of the copper substrate before the bump forming process is performed. Especially in the South Wen J clothing environment, the copper metal oxidizes very quickly, unlike aluminum, it may stop oxidizing at a thickness of hundreds of angstroms; and the copper metal surface is obviously not conducive to its use as a wire or other electrical properties. This is because the oxide film, in addition to causing the poor bumping of the under bump metal lurgy (UBM) and the metal pad, also increases the resistance value. How to overcome the difficulty of copper metal in process application is one of the goals of the industry. Purpose of the invention: a bump shape with copper as the solder pad

The main object of the present invention is to provide a method. Another object of the present invention is to solve the queue time issue of copper pads. Generally, the queue time is controlled by a private station, and it cannot be left for too long. It is invented that because there is a nitride layer on the copper pad, the 5 pad will encounter an oxide layer. The nitride layer should be removed before the bumps are made. 'Copper is protected'. Yet another object of the present invention is to make the mask etching process outside the process. ° Simplified support technology, no amount required The present invention provides a method for using copper as a soldering pad. The method includes: forming a copper metal pad on a wafer, taking Wanling, and using the method on the pad. Next, remove the yttrium deposited protective layer on the copper pad to the first opening of the copper metal, but the copper pad is not separated from the first opening to form a protective layer, and then form a bump, and then form a bump.

477047 V. Description of the invention (4) Remove the remaining protective layer in the first opening before lowering the metal layer to expose the copper pad. Then, a metal layer under the bump is formed in the first opening without filling the first opening, and a photoresist pattern having a second opening is formed so that the metal layer under the bump in the first opening is exposed from the second opening. Forming a tin bump in the first and first openings' followed by removing the photoresist pattern and reflowing the tin bump with heat. Detailed description of the invention:

The present invention discloses a new manufacturing method, which uses copper as a solder pad in a conductive bump manufacturing process. The detailed description is as follows. The described preferred embodiments are only used for illustration and are not intended to limit the present invention. Referring to FIG. 1, a semiconductor substrate 2 that completes the 1C front-end process is first provided.

A metal pad 4 is formed on the semiconductor substrate 2, and then a first protective layer 6 'is deposited. A chemical vapor deposition (CVD) method, such as an electro-enhanced chemical vapor deposition method (PEC VD), may be used as a deposition method. The material of the first protective layer 6 can be selected from any material with excellent barrier properties such as silicon nitride and silicon carbide; in a preferred embodiment, the thickness of the nitrided stone is about 400-600 angstroms by using the P EC V D method. Deposit the first protective layer 8 on the first protective layer 6. The deposition method can be chemical vapor deposition. The material selection of the first protective layer 8 should be different from that of the first protective layer 6 in order to obtain a car. Properties, such as silicon dioxide, spin-on glass SOG; in a better embodiment, PECVD is used to deposit silicon dioxide. After that, the second layer 10 is deposited on the second protective layer 8. The deposition method can be deposited using chemical gas, and the thickness is about 3000-4000 angstroms. The material of the third protective layer 10 is more non-yang, and it is better to choose a material different from the second protective layer 8; in a better implementation ^

477047 V. Description of the invention (5) The silicon nitride is deposited by PECVD with a thickness of about 5 0 0-6 0 0 0 Angstroms. The above thicknesses are merely examples, and are not intended to limit the present invention. Referring to FIG. 2, a photoresist is used to expose a photoresist to a photoresist pattern (not shown) by using a photolithography process. The photoresist pattern is used as an etching mask, and the third protective layer 10 and the second protective layer 8 are used. Until the first protective layer 6 is left, the first ^ layer is retained; continue to be used as a protective layer to avoid exposing the copper pad 4. The above-mentioned reserved first protective layer prevents the wafer from θ when transferring the processing station or waiting for the next process, and avoids the oxidation of the bottom layer with the same material 4 due to exposure to the atmosphere. 1 Please refer to FIG. 3. The next step is to form an under bump metallurgy (UBM), which is used by / ,, (sputtering). Before base plating, the first protective layer 6 on the copper pad 4 is ion-milled in-situ. Secondly, it facilitates subsequent sputter plating of the UB on the copper pad 4 as a nickel layer. The third protective layer Π of the copper pad 4 is removed from the road. The above-mentioned materials / = process also uses the formula: as an embodiment to illustrate the 'not to limit this two = product T, so the scope of the present invention includes replacement of equal functional materials. 1 中 疋 Referring to Figure 4, a lithography process is used to form a metal 1 with the bump under the bump 12. The conventional method is: = light: pattern " Yu Cheng, and a tin or tin bump can be formed using printing or electroplating. Use electricity mining method. After that, the photoresist pattern 14 is removed to form tin. This embodiment is shown in FIG. -Generally used when making tin bumps) 丄 6 ’as shown in Figure 5 ^ ^ j to doped lead, according to

Page 10 477047

V. Description of the invention (6) The mixing ratio is required to adjust the melting point. Next, the tin bump 16 is used as a mask for money engraving, and the exposed BM metal layer 12 is removed. After the flux coating and heat flow (refiow), the solder bumps 16 are formed into spherical structures due to cohesion and other factors to complete the production of solder balls, as shown in Figure 6. In the process of making a tin bump, the opening is generally directed to the metal pad 4. The advantages of the present invention are as follows: I. It is a method for replacing the aluminum pad with copper as the pad, and controlling the oxidation of copper makes the process too complicated. In the painful and slightly old method, the time required for the soldering process is as early as ^: layer ', which can reduce the number of mask etchings, shorten the waiting time, and achieve the purpose of efficient energy production. Half of the integrated upper body? The structure should be: ui in the substrate: the structure contains: copper metal 塾, formed on-the steel metal I on the first protective layer; $ two protective layers, in the shape of 'the first protective layer from the opening Protect! Containing openings formed in the copper metal to prevent oxygen oxidation, the other protective layer mentioned above may be the second protective layer package: the second protective layer is a multi-layer structure, in which a layer is formed. 3Emulsified layer and nitrided layer. The first protective layer includes nitrided in the main channel μ ^ 'substrate after the bump is completed; the second conductor structure includes: copper metal 形成 formed on the bottom layer' on the copper metal pad; the second protective layer, shaped 477047 V. Description of the invention (7) On the first protective layer, wherein the first protective layer and the second protective layer include an opening formed therein; a metal layer under the bump is formed in the opening but does not fill the opening; tin A bump is formed in the opening. The above description uses a preferred embodiment to describe the present invention in detail, but not to limit the scope of the present invention, and those skilled in the art will understand that appropriate changes and adjustments will still be made without departing from the spirit of the present invention. It does not depart from the spirit and scope of the present invention.

Page 477047 Brief description of the drawings Brief description of the drawings: The preferred embodiment of the present invention will be described in more detail with the following figures in the following explanatory text: Figure 1 shows the semiconductor deposited by the coating of the present invention Wafer cross section. FIG. 2 is a cross-sectional view of a semiconductor wafer before a bump is formed after the protective layer is etched according to the present invention. FIG. 3 is a cross-sectional view of a semiconductor wafer in which a metal layer under the bump is formed by a sputtering method according to the present invention. FIG. 4 is a cross-sectional view of a semiconductor wafer in which conductive tin bumps are formed by electroplating according to the present invention. FIG. 5 is a cross-sectional view of a semiconductor wafer with an under-bump metal layer according to the present invention. FIG. 6 is a cross-sectional view of a semiconductor wafer forming a solder ball according to the present invention. Description of drawing number: substrate 2 copper pad 4 first protective layer 6 'second protective layer 8 third protective layer 1 0 metal under bump 12 photoresist pattern 1 4 tin bump 1 6

Claims (1)

477047 VI. Scope of patent application Patent scope: 1. A bump forming method using copper as a fresh pad, the method includes: forming a copper metal pad on a wafer; depositing a protective layer on the copper metal pad Part of the protective layer on the copper pad is removed to form a first opening, but the copper cymbal is not exposed from the first opening; before the metal layer under the bump is formed, the remaining part of the first opening remains The protective layer is removed to expose the copper pad; a metal layer under the bump is formed in the first opening but does not fill the first opening; a photoresist pattern having a second opening is formed so that the bump in the first opening is formed A lower metal layer is exposed from the second opening; a tin bump is formed in the first and second openings; the photoresist pattern is removed; and the tin bump is reflowed with heat. 2. The method for forming a bump using copper as a solder pad as described in item 1 of the application, wherein the metal layer under the bump is formed by sputtering. '3. For example, the method for forming bumps using copper as a bonding pad in item 1 of the scope of the patent application, wherein the protective layer remaining in the first opening is removed by a synchronous ion beam. 4. The method for forming a bump using copper as a solder pad according to item 1 of the scope of the patent application, wherein the protective layer includes at least a first insulating layer and a second insulating layer. 477047 6. Scope of patent application 5. For the method for forming bumps using copper as a solder pad in item 4 of the scope of patent application, wherein the protective layer remaining in the first opening is a first insulating layer on the copper pad. 6. The method for forming bumps using copper as a solder pad as described in item 4 of the scope of patent application, wherein the first insulating layer includes a silicon nitride layer and the second insulating layer includes an oxide ^ 〇7.—A kind of fresh copper A bump forming method, the method comprising: forming a copper metal pad on a wafer; forming a first protective layer on the copper metal pad; forming a second protective layer on the first protective layer; A portion of the second protective layer on the copper pad is removed to form a first opening, but the first protective layer is exposed from the first opening; the first opening in the first opening is formed in the first opening before the metal layer under the bump is formed. The protective layer is removed to expose the copper pad; a metal layer under the bump is formed in the first opening but does not fill the first opening; a photoresist pattern having a second opening is formed so that the bump under the first opening is under the bump A metal layer is exposed from the second opening; a tin bump is formed in the first and second openings; the photoresist pattern is removed; and the tin bump is reflowed with heat. 477047 VI. Scope of patent application 8. For the bump formation method using copper as a solder pad in item 7 of the scope of patent application, the second protective layer is a multi-layer structure. 9. The method for forming bumps using copper as a solder pad according to item 8 of the scope of patent application, wherein the second protective layer includes an oxide layer and a nitride layer. 10. The method for forming bumps using copper as a bonding pad according to item 7 of the scope of the patent application, wherein the first protective layer includes a nitride layer. 11. The method for forming a bump using copper as a bonding pad according to item 7 of the scope of the patent application, wherein the metal layer under the bump is formed by sputtering. 1 2. A method for forming a bump using copper as a bonding pad as described in item 7 of the scope of the patent application, wherein before the metal layer under the bump is formed by sputtering, the first protective layer is removed by a synchronous ion beam to expose The copper metal pad. 1 3. —A semiconductor structure that facilitates the production of bumps using copper as a solder pad. The semiconductor structure includes: a copper metal pad formed in a substrate; a first protective layer formed on the copper metal pad; a second A protective layer formed on the first protective layer, wherein the first protective layer includes an opening formed therein, and the first protective layer is exposed from the opening; wherein the first protective layer described above can prevent the copper metal pad from being oxidized . 1 4. If item 13 of the scope of patent application is beneficial to the production of bumps with copper as the solder pad Page 16 477047 6. Scope of patent application Semiconductor structure, wherein the second protective layer is a multi-layer structure. 1 5. According to item 14 of the scope of the patent application, a semiconductor structure which is advantageous for making bumps by using copper as a bonding pad, wherein the second protective layer includes an oxide layer and a nitride layer. 16. According to claim 13 of the scope of the patent application, a semiconductor structure is advantageous for making bumps by using copper as a bonding pad, wherein the first protective layer includes a nitride layer. 1 7. —A semiconductor structure that facilitates the production of bumps using copper as a solder pad. The semiconductor structure includes: a copper metal pad formed in a substrate; a first protective layer formed on the copper metal pad; a second protective layer Layer formed on the first protective layer, wherein the first protective layer and the second protective layer include openings formed therein; a metal layer under the bump is formed in the opening but does not fill the opening; A block is formed in the opening. 1 8. According to claim 17 of the scope of patent application, a semiconductor structure made of copper as a bonding pad is advantageous for the semiconductor structure, wherein the second protective layer is a multi-layer structure. 1 9. According to claim 18 of the scope of the patent application, a semiconductor structure which is advantageous for making bumps by using copper as a bonding pad, wherein the second protective layer includes an oxide layer and a nitride layer. 2 0. If item 17 of the scope of patent application is beneficial to the production of bumps with copper as the pad 477047 6. Scope of patent application Semiconductor structure, wherein the first protective layer includes a nitride layer 1 ^ · page 18