TWI227534B - Method for inspecting surface of UBM - Google Patents

Abstract

A method for inspecting surface of UBM (under bump metallurgy) is performed prior to a bumping step of wafer manufacturing process. An UBM is formed on an active surface of a provided wafer. The UBM includes at least a test pad. A melting solder is wetted onto the test pad by solder dipping. The wetting state of solder on the test pad is inspected to determine the bump bonding property of UBM.

Description

1227534 __, V. Description of the invention (1) ~ ~ [Technical field to which the invention belongs] The present invention relates to a method for detecting the surface of a metal layer under a bump of an integrated circuit wafer before making a bump, and particularly relates to Regarding a method for detecting the contamination of a metal layer under a bump of a wafer by an organic material. [Previous technology] It is known that before a bump is formed on an integrated circuit wafer, an under bump metal layer (UBM, Under Bump Metal lurgy) and an organic passivation layer are formed on one of the wafers. On the front side, the metal layer under the bumps provides bonding to the bumps and prevents the metal components in the bumps from diffusing to the internal circuits of the wafer. The organic protective layer can be polyimide or phenylcyclobutene. Ene [BCB], which is provided on the wafer passivation layer of a wafer such as phosphate rock glass [PS G] and the metal layer under the bump to disperse the stress of the bump. The organic protective layer may remain on the metal layer under the bump, and contamination of organic particles may remain on the exposed surface of the metal layer under the bump, resulting in the subsequent failure of the bump formed on the metal layer under the bump. Bonded to the exposed surface of the metal layer under the bump. A conventional method for detecting the exposed surface of a metal layer under a bump is to use contact water droplet detection and analysis. Water droplets need to be dripped on the metal layer under the bump on the wafer, and then water droplets are observed on the metal layer under the bump. The formed shape is used to detect the contamination of the metal layer under the bump on the exposed surface, but the shape of the water drop is not easy to visually observe the surface contamination, and the wetness of the water drop cannot be compared with the actual bump bonding. Strength, lack of specific and objective judgments.

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TECH μ «A conventional method for producing and testing the exposed surface of the metal layer under the bump is to use non-contact optical analysis, which requires a $ detection method ^ C opt ica f faltpe " ^ ^ ^ The energy and intensity of the bumps in Si Through spectrum analysis, detection = influence on the bump bonding of the convex and lower metal layers, and the detection method is suitable for synchronous detection control in the manufacturing process. -The door car is not long [Content of the invention] The main purpose of the present invention is to provide a surface-surface detection method for the metal layer under the bump, using a dipping method to attach molten solder to the metal layer under the bump of a wafer [UBM, Under Bump Metallurgy] Detection 塾, = 4 The degree of adhesion of the detection pad to the molten solder can quickly detect whether the surface of the gold layer under the bump has improper contaminants, so as to ensure that the bump in the subsequent bump manufacturing steps The bump bonding of the metal layer under the block is good, so as to achieve low cost detection before the bump process. The surface inspection method for a metal layer under a bump according to the present invention is used to inspect the surface of a metal layer under a bump (UBM) on a wafer before a bump manufacturing step in a wafer process. The detection method includes The steps include: providing a wafer with a front surface and a corresponding back surface. The front surface is formed with a metal layer under the bump, and the metal layer under the bump includes at least one exposed detection pad. Preferably, the detection pad is provided 'on the periphery' of the front side of the wafer to provide a melt in a solder dipping manner.

1227534 · ~ ...-. V. Description of the invention (3) The detection pad of fused material on the metal layer under the bump, and the degree of adhesion of the molten solder to the test pad to detect whether the metal layer under the bump is Residual contaminants affect the bump bonding of the metal layer under the bump. [Embodiment] With reference to the drawings, the present invention will be described by the following embodiments. According to the surface inspection method of the metal layer under the bump according to the present invention, it is used to detect the surface of the metal layer under the bump (UBM, Under Bump Metal lurgy) on a wafer before making the bump. Please refer to FIG. 1, First, a wafer 10 is provided. The wafer 10 can be a wafer with integrated circuit function or a dummy wafer. The wafer 10 has a front surface 11 and a correspondence. On the back surface 12, the front surface 11 is formed with a plurality of pads 13 [| 3〇11 (1 Pad) and exposed on a wafer passivation layer η, such as phosphorous silicon glass [psG] or silicon nitride The surface of the wafer protective layer 14 on the front surface 11 of the wafer is formed by a sputtering under metal layer 20, such as Ti-Ni / V-Cu, A1-Ni / V-Cu, Ti-Cu Cr—Cu or Cr-Cr / Cu-Cu and other composite metal layers, and the metal layer 20 under the bump includes a plurality of exposed bump bonding pads 2 2 and at least one exposed detection pad 2 1 ′ The method for forming the metal layer 20 under the bumps can be made by referring to the technology disclosed by the applicant in Chinese Patent Publication No. 5 2 91 4 3, and the bumps are bonded. 2 2 is electrically connected to the corresponding solder pad 1 3, or connected by a redistribution circuit [Figure_not shown]. In this embodiment, the detection pad 2 丨 is disposed on the front surface 11 of the wafer. The periphery may be a sheet-like cushion layer. Preferably, the wafer is preset with a dummy chip for setting the detection pad 21. In this embodiment, the wafer 10 is Is a wafer-level package structure.

1227534

V. Description of the invention (4) The circular η surface 11 is further covered with an organic protective layer 3〇 [anic passivation layer], such as δ butene [BCB], and the organic amine 1 [amine] [benzene] or benzene Ring 32 to reveal the detection respectively. The second layer has a plurality of openings 31, and the hole 31 can define the detection 塾 = block bonding pad 22, and the opening ii, see Figures 2 and 3, provide- The molten solder 40 is applied to the bump 2 layer 20 test pad 21, which is immersed in a molten 2 material by solder dipping method. : Valley trough 50 ′ The bath 50 stores molten solder 40, of which the molten fresh material 40 ”warm um tin tin material is better, the bath 5. Keep the two, η: solder 40 is in a molten state, after , Pull away and shake the = A: I # with 1, excess molten solder 4 〇, with the degree of adhesion of the molten solder 40 to Huanju 21, to detect whether the metal layer 20 under the bump is caused by Improper contaminants affect the bonding of the bumps on the metal layer under the bumps. As shown in Figure 3, it can be easily observed visually whether the detection pad 21 is fully immersed. There is a molten solder 40. When the detection pad 21 of the metal layer 20 under the bump has no improper contaminants remaining, the molten solder 40 can fully adhere to the entire exposed surface of the detection pad 21 during the dipping process. Therefore, it can be judged that the bump bonding pad 22 of the wafer 10 has good bump bonding, that is, the metal layer 20 under the bump of the wafer has good bump bonding, and can be well bonded in subsequent bump steps. The bumps (not shown in the figure), so the wafer can be made again or the entire batch of other a-circle bump manufacturing processes. When the & as shown in the figure, the metal layer 2 under the bump 4 of the test pad 2 1 can not fully adhere to the molten solder 4 d in the dipping process, and it can be judged that the bump bonding pad 22 of the wafer 1 0 has enough to affect the bump junction.

Page 8 1227534 V. Description of the invention (5) Contaminant photoresist or organic particles and other pollutants 60, making the bump bonding pad 22 of the metal layer 20 under the bump have poor bump bonding, and subsequent formation The bumps of the metal layer 20 under the bumps may be poorly bonded or dropped. The wafer i 0 or other wafers in the entire batch should be cleaned or etched again before the bump manufacturing process can be performed. Therefore, the present invention provides a low-cost and real-time in-process method for detecting the exposed surface of the metal layer under the bump (UBM), so as to quickly learn the appearance of the metal layer under the bump = Residue of dyes leads to the deterioration of the bonding property of the bumps. Furthermore, the bonding property of the metal layer under the bumps is confirmed, and the metal drawer under the bumps ([UBM]) is replaced by the water drop detection or non-contact optical analysis. No expensive optical analysis equipment is needed, the exposed surface of the metal layer under the bumps is against the bumps] Correct judgment: Except for the second measurement of the wafer before the bumps are made = the layer 3 is exposed, whichever is familiar with this technology Any changes and modifications [such as copper pads or Ming pads, etc.] made within the scope of the surface inspection of phase contamination-round welding. The scope of protection of the present invention shall be regarded as the protection of the present invention. Τ is familiar with this museum ": Spirit of Ming: 4 Scope 1227534_; _ Brief Description of the Drawings [Simplified Description of the Drawings] Figure 1: Partial cross-section of the wafer provided by the surface inspection method of the metal layer under the bump according to the present invention Schematic Figure 2 · The surface inspection method of the metal layer under the bump according to the present invention, the wafer is immersed in a molten solder bath. Figure 3 is the surface inspection method of the metal layer under the bump according to the present invention. Schematic diagram of partial cross section of a well-wet wafer and Figure 4 Schematic diagram of partial cross-section of a wafer with poorly wetted solder according to the method for detecting the surface of a metal layer under a bump according to the present invention 〇 Simple explanation of component symbols 10 Wafer 11 Front 12 Back 13 Welding pads 14 Wafer protection layer 20 Under bump metal layer 21 Detection pad 22 Bump bonding pad 30 Organic protective layer 31 Opening hole 32 Opening hole 40 Fresh material 50 Bath 60 Contamination

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Claims (1)

1227534, ^ 7 'scope of patent application ~ " Ⅰ ~' ·---- ^ [Patent scope of application] 1 step 7 kinds of surface inspection methods of the metal layer under the bump, which includes the following steps: 7 wafers 'The wafer has-a front surface and a corresponding back surface, ^ surface = a metal layer under the bump [_] is formed, the metal layer under the bump includes at least one exposed detection pad; and a molten solder is provided on the The detection pad of the metal layer under the bump uses the adhesion of the melting solder to the detection pad to detect the bump bonding of the metal layer under the bump. 2, such as the scope of patent application! The method for inspecting the surface of the metal under the bump according to the above item, wherein the detection pad of the metal layer under the bump of the wafer in the step of providing molten solder is immersed in a molten solder bath. When the wafer is taken out, the wafer is shaken to discharge excess molten solder. 3. The surface inspection method for the metal layer under the bump as described in item 1 of the scope of the patent application, wherein an additional organic passivation layer is formed on the front side of the wafer to define the detection of the metal layer under the bump. private school. 4. The method for detecting the surface of a metal layer under a bump as described in item 1 of the scope of the patent application, wherein the metal layer under the bump includes a plurality of bump joints. 5. As described in item 1 of the scope of the patent application The surface inspection method of the metal layer under the bump, wherein the wafer is a dummy wafer. 6. Surface inspection of the metal layer under the bump as described in item 1 of the scope of patent application Test method on page 11, where the wafer contains-dummy wafer [duln for the detection pad for setting the gold lip layer under the bump, lp7: a wafer surface inspection method, which includes A wafer, the wafer has a front surface. The front surface is formed with a plurality of pad pairs j on the back surface, and a molten solder is provided for detection and execution. The extent to which solder is second in the inspection? The method for detecting the surface of a wafer is immersed in a melting and melting bond ::::: The detection of the wafer is based on the HI, M Φ π Γ groove, and when the wafer is taken out, Shake the circle a to f to discharge excess molten solder. 9. As stated in the patent claim, where the wafer is the surface inspection method of the wafer described in item f7, ^ Dong Dong Shi Riyuan [dummy wafer]. 0. The method for surface inspection of a wafer as described in item 7 of the Fan patent, wherein the wafer includes ~ dummy chips for setting the detection layer of the metal layer under the bump.