Method for forming bumps

专利摘要:
A method of forming bumps on a wafer is provided. A thick photoresist having a plurality of openings is formed on the wafer to expose bonding pads. Solder paste is filled in the openings of the thick photoresist. A stencil having a plurality of openings corresponding to the openings of the photoresist is applied on the wafer. After the stencil is removed, a reflow process is performed to form bumps. The thick photoresist is then removed. The bumps are formed in two steps using thick photoresist and stencil, resulting in increased height and uniformity after reflow.
公开号:KR20020091470A
申请号:KR1020010030160
申请日:2001-05-30
公开日:2002-12-06
发明作者:샤오퉁-리앙
申请人:아펙 테크놀로지스 인코포레이티드；
IPC主号:

专利说明:

Method for forming bumps
[8] The present invention relates to a bump forming method. More specifically, the present invention relates to a bump forming method that is formed in two steps using thick photoresist and stencil, resulting in increased height and uniformity after reflow.
[9] As electronic technology advances, the miniaturization of electronic products is particularly emphasized. This miniaturization results in more complex and integrated electronic products. In the electronics industry, package structures with small dimensions and high densities are required for the packaging of electronic devices. Ball grid array (BGA) packages, chip-scale packages (CSP), flip-chip (F / C) packages, and multi-chip modules Many types of packages have been developed, such as chip module packages.
[10] IC package density represents the number of pins per unit area of the package. In high-density IC packages, short access paths help to increase signal transmission speeds. Thus, bumps are increasingly being used as connections in high-density packages.
[11] In a conventional method of forming bumps, under ball metallurgy (UBM) is formed on a bonding pad on the wafer. A resist having a plurality of openings is applied to the wafer, the openings exposing the bonding pads thereunder. Solder paste is then filled in the openings. A reflow process is performed to form bumps on the bonding pads. Finally, the photoresist is removed. Since the solder paste is filled in the photoresist, the bump formed of the solder paste is limited by the thickness of the photoresist.
[12] One object of the present invention is to provide a bump forming method. In the present invention, a thick photoresist with openings is used to define the location where the solder paste is filled. Stencils with openings corresponding to the openings in the thick photoresist are also additionally used. After the solder paste is filled through the thick photoresist and the stencil, a reflow process is performed to increase the height and uniformity of the bumps thus formed.
[1] 1 to 3 are cross-sectional views schematically illustrating various steps in a wafer bumping process according to an exemplary embodiment of the present invention.
[2] <Brief description of the major symbols in the drawings>
[3] 100. Wafer 102. Bonding pad
[4] 104. Passivation layer 106. Under ball metallurgy
[5] 107. First opening 108. Photoresist
[6] 110..Stencil 112..Second opening
[7] 114 Solder Paste
[13] In order to achieve the above and other objects, the present invention provides a bump forming method. A wafer having a plurality of chips is provided, each chip being provided with a plurality of bonding pads and a passivation layer protecting the chip and exposing the bonding pads.
[14] Each bonding pad is further provided with an under ball metallage (UBM) thereon. A photoresist having a plurality of first openings corresponding to the UBMs is formed on the wafer. Solder paste is filled in the first openings. A stencil having a plurality of second openings is applied on top of the photoresist so that the second openings correspond to the first openings. The solder paste is filled in the second openings. After the stencil is removed, a reflow process is performed. The photoresist is removed.
[15] In the present invention, the bump is formed in two steps using a thick photoresist and a stencil. After reflow, the bumps have the desired height without the limitations of conventional bumps, resulting in increased height and uniformity.
[16] It is to be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further explanation of the invention as claimed.
[17] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, help to explain the principles of the invention.
[18] DETAILED DESCRIPTION The following detailed description of embodiments and embodiments of the invention in connection with the appended drawings is merely illustrative and non-limiting.
[19] 1 to 3 are schematic cross-sectional views for illustrating bump formation according to a preferred embodiment of the present invention.
[20] Referring to FIG. 1, the wafer 100 has a plurality of chips thereon, each chip being provided with a plurality of bonding pads 102 and a passivation layer 104. In addition, under ball metallage UBM 106 is formed on the bonding pads 102, respectively. The UBMs 106 may be made of multilayers of chromium / chromium-copper / copper, for example. A patterned photoresist 108 having a plurality of openings corresponding to the UBMs 106 is formed on top of the wafer 100 to expose the UBMs 106 to the bottom. Solder paste 114 is then filled in the first openings 107 by, for example, printing. Patterned photoresist 108 may be, for example, a liquid photoresist or a dry film.
[21] Since the patterned photoresist 108 has a limited thickness, the solder paste 114 filled in the first opening 107 in the photoresist 108 may not form bumps having a desired height. To overcome this drawback, as shown in FIG. 2, the inventor places a stencil 110 on the patterned photoresist 108 to form bumps with the desired height.
[22] Referring to FIG. 2, a stencil 110 having a plurality of second openings 112 corresponding to the first openings 107 is applied on the patterned photoresist 108. Solder paste 114 is then filled in the first openings 107 and in the second openings 112 by, for example, printing. The solder paste 114 is, for example, a tin-lead paste having various ratios of Sn _x Pb _y . However, the solder paste 114 may also be comprised of other solder components not cited in the specification of the present invention. Referring to FIG. 3, the stencil 110 is then removed. The solder paste 114 is then reflowed to form a plurality of bumps 116. The patterned photoresist 108 is then removed.
[23] If the same content of solder paste is added to the low bumps and the high bumps having the same diameter, the low bumps grow more significantly than the high bumps. In other words, regardless of the amount of solder paste added to the bump, the larger the volume of the bump, the less the bump height increases.
[24] Therefore, by using the patterned photoresist 105 and the stencil 110, the solder paste 114 filled in the first opening 107 and the second opening 112 has a significantly higher bump 116. ) And make a more uniform bump.
[25] From the foregoing, the bump forming method according to the present invention can provide the following advantages.
[26] 1. By using thick photoresist and stencil, bumps after reflow have a desired height, without limitations with conventional bumps.
[27] 2. In the present invention, after reflow, the bumps are formed in two steps, resulting in increased height and uniformity.
[28] It will be apparent to those skilled in the art that various modifications and variations can be made from the configuration of the present invention without departing from the scope or spirit of the invention. As discussed above, if the variations and modifications of the present invention fall within the scope of the following claims and their equivalents, it is meant that the present invention includes the variations and modifications of the present invention.

权利要求:
Claims (6)
[1" claim-type="Currently amended] Providing a wafer having a plurality of chips, wherein a plurality of bonding pads are provided on each chip, each chip having a passivation layer protecting the chip and exposing a bonding pad, wherein each bonding pad has a passivation layer thereon; A wafer providing step of providing further under ball metallurgical (UBM);
Forming a photoresist on the wafer, the photoresist having a plurality of first openings corresponding to the UBMs, respectively;
Filling solder paste into the first openings;
Applying a stencil having a plurality of second openings on top of the photoresist, the second openings corresponding to the first openings;
Filling solder paste into the second openings;
Removing the stencil; And
And performing a reflow process and removing the photoresist.
[2" claim-type="Currently amended] According to claim 1,
And wherein said patterned photoresist is a liquid photoresist or a dry film.
[3" claim-type="Currently amended] According to claim 1,
And the solder paste is a tin lead paste having various ratios.
[4" claim-type="Currently amended] Providing a wafer having a plurality of chips, each chip being provided with a plurality of bonding pads, the passivation layer protecting the chip and exposing a bonding pad, wherein each bonding pad has an under ball metal thereon; A wafer providing step of further providing a UBM;
Forming a photoresist on the wafer, the photoresist having a plurality of first openings corresponding to the UBMs, respectively;
Filling solder paste into the first openings;
Applying a stencil having a plurality of second openings on top of the photoresist, the second openings corresponding to the first openings;
Filling solder paste in the first openings and in the second openings;
Removing the stencil; And
And performing a reflow process and removing the photoresist.
[5" claim-type="Currently amended] The method according to claim 4,
And the photoresist is a liquid photoresist or a dry film.
[6" claim-type="Currently amended] The method according to claim 4,
And the solder paste is a tin lead paste having various ratios.

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同族专利:

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引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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法律状态:
2001-05-30|Application filed by 아펙 테크놀로지스 인코포레이티드

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2001-05-30|Priority to KR1020010030160A

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2002-12-06|Publication of KR20020091470A

优先权:

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申请号 | 申请日 | 专利标题

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KR1020010030160A|KR20020091470A|2001-05-30|2001-05-30|Method for forming bumps|