A comparison of new thick photoresists for solder bumping

Flack, Warren W.; Nguyen, Ha-Ai; Neisser, Mark; Sison, Ernesto S.; Lu, Ping Hung; Plass, Bob; Makii, Toshimichi; Murakami, Yoshio

doi:10.1117/12.598469

Cited by 4 publications

(6 citation statements)

References 6 publications

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“…Process times up to 6min and temperatures of 50°C are necessary for the negative type Acrylic and PHS resists. These resists show a higher crosslinking compared to positive tone type A and E, which leads to increased stripping times also with traditional solvent stripping where process times of 50min are necessary [8]. Most stripping complexity is observed for the epoxy type resist which is in good agreement with the expectations from literature [9,10].…”

Section: Semiconductor Compatibilitysupporting

confidence: 76%

Introduction of an innovative water based photoresist stripping process using intelligent fluids

Rudolph

Thrun

Schümann³

et al. 2014

SPIE Proceedings

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The usage of phasefluid based stripping agents to remove photoresists from silicon substrates was studied. Due to their highly dynamic inner structure phasefluids offer a new working principle, they are penetrating layers through smallest openings and lift off the material from the surface. These non-aggressive stripping fluids were investigated regarding their cleaning efficiency as well as contamination behavior to enable usage in semiconductor and MEMS manufacturing. A general proof of concept for the usage of phasefluids in resist stripping processes is shown on silicon coupons and BKM’s are given for different resist types. In addition a baseline process on 12inch wafers has been developed and characterized in terms of metallic and ionic impurities and defect level

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Section: Semiconductor Compatibilitysupporting

confidence: 76%

Introduction of an innovative water based photoresist stripping process using intelligent fluids

Rudolph

Thrun

Schümann³

et al. 2014

SPIE Proceedings

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“…Flack et.al. [1] noted resist strip times of 5 minutes for two positive resists used in their experiments vs. 50 minutes for the AZ-100nXT negative tone resist, using AZ400T at 80 o C. Long strip times or special stripping requirements are also noted on the data sheets of the other major suppliers of negative resists. A similar issue is seen with the chemically amplified positive tone resists as well, vs. non-chemically amplified positive resists.…”

Section: Introductionmentioning

confidence: 98%

“…Thick, negative tone resists are more transparent to exposure light wavelengths than standard Novolak positive tone resists and can be exposed by the lithography process much faster (~1 x 10 4 cross-linking chemical events are driven by 1 photochemical event vs. 100 -1000 chemically amplified resists, or 1:1 for traditional positive tone resists) [1]. Therefore exposure times can be shorter, post-exposure bake steps can be shorter, and delays before or after exposure is not necessary, saving photolithography time and CoO.…”

Section: Introductionmentioning

confidence: 99%

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Wet Chemical Processing with Megasonics Assist for the Removal of Bumping Process Photomasks

Seong¹,

Tracy²

2014

Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT)

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A new generation of negative tone resists by TOK, JSR, and Dow Chemical is gaining momentum in advanced packaging applications. Resist thickness requirements are actually increasing to the 50-100 um range as Cu pillars are adopted to accommodate the tighter pitches required in advanced packaging. In order to form pillars the resist must be thicker to contain the entire bump structure. Thick, negative tone resists are more transparent to exposure light wavelengths than positive tone resists and can be exposed by the lithography process much faster (~1 x 104 cross-linking chemical events are driven by 1 photochemical event vs. 100 – 1000 for positive tone resist).1 Therefore exposure times can be shorter, post-exposure bake steps can be shorter, and delay before or after exposure is not necessary, saving photolithography time and CoO. And, due to more complete cross-linking throughout the resist, the resist mask profiles are truer (from Flack et.al, “A Comparison of New Thick Photoresists for Solder Bumping”, SPIE 2005).1 The major drawback to negative tone resists is that the solvent strip times of the highly cross-linked resist masks are much longer than for positive tone. Flack et.al. noted resist strip times of 5 minutes for two positive resists used in their experiments vs. 50 minutes for the AZ-100nXT negative tone resist, using AZ400T at 80°C (most likely in an immersion tool). Long strip times or special stripping requirements are noted on the data sheets of the other majority suppliers of negative resists as well. Akrion engineers have developed a novel, single-wafer, negative PR strip processes using organic solvents plus Goldfinger megasonics, to provide 30 - 70% reductions in process times and the associated chemical consumption when compared to processes that do not utilize a megasonics assist. The multi-step process can be accomplished in a single process chamber, with each step optimized for time and temperature based on the resist thickness and solvent stripping chemistry used. In the Akrion process, a period of solvent exposure at low wafer spin speed is used initially to begin swelling and dissolving the thick photoresist layer. This is followed by a second solvent exposure step using aggressive frontside megasonic energy to promote polymer chain scission throughout the bulk of the photoresist layer. Following this step A DI water rinse and spin dry step are sufficient to completely remove the solvent, dissolved photoresist and any polymer residues. This paper reviews the development of the Akrion process and several examples of improvement in stripping time and results from work with customers.

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“…The stripping and removal of thick photoresist (PR) of 20µm thickness or more has traditionally been problematic [1]. The problem is compounded when the PR is of the highly cross-linked negative tone or chemically amplified positive tone variety [2]. Typically performed in tanks through wafer immersion, a variety of wet bench designs have been employed for PR removal.…”

Section: Introductionmentioning

confidence: 99%

Cost-of-Ownership Comparison of Single-Wafer Processes for Stripping Copper Pillar Bump Photomasks

Sohn¹,

Hua²,

Liu

et al. 2014

SSP

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A new generation of negative tone and chemically amplified positive tone photoresists by TOK, JSR, Dow Chemical and others has gained momentum for advanced packaging applications. Resist thickness requirements are increasing to the 40-100 μm range as Cu pillars and micro-bumps are adopted, to accommodate the tighter pitches required in the newest multi-chip package designs. In order to form the pillars, the resist mask must be thicker than the height of the pillars to contain the entire bump structure.

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A comparison of new thick photoresists for solder bumping

Cited by 4 publications

References 6 publications

Introduction of an innovative water based photoresist stripping process using intelligent fluids

Introduction of an innovative water based photoresist stripping process using intelligent fluids

Wet Chemical Processing with Megasonics Assist for the Removal of Bumping Process Photomasks

Cost-of-Ownership Comparison of Single-Wafer Processes for Stripping Copper Pillar Bump Photomasks

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