Study of crack formation in high-aspect ratio SU-8 structures on silicon

Svetlana Nikolajevna van Nieuwkasteele-Bystrova, Regina Lüttge, Albert van den Berg

Research output: Contribution to journalArticleAcademicpeer-review

15 Citations (Scopus)

Abstract

Abstract The high-aspect ratio capability of SU-8 photoresist led to the successful use of this epoxy based material in a diversity of microfabricated devices as a construction material as well as for micromolding purposes. Throughout the literature it was noticed that the thermal mismatch of SU-8 and the substrate material silicon generates high film stress in the spin-coated SU-8 causing crack formation in the microstructures. Using baking parameters this crack formation can be minimized but will remain a critical aspect of design. In this study the process was first optimised on non-patterned wafers. Secondly, we transferred this optimised process to a pre-patterned wafer containing deep silicon etch pits to account for a specific application in micromolding. We discuss the behaviour of film stress, number of cracks and crack length. The number of cracks as well as the length of cracks in concave corner designs can be significantly decreased, while round holes resulted even in crack-free microstructures. In the case of pre-patterned wafers no cracks appear around the features, however we observed unsatisfied development within the resist features caused by insufficient solidification in the deep etch pits during Soft Bake. Increased Soft Bake time can overcome these problems but will require more systematic investigations.
Original languageUndefined
Article number10.1016/j.mee.2007.01.091
Pages (from-to)1113-1116
Number of pages4
JournalMicroelectronic engineering
Volume84
Issue numberSINTEF A13
DOIs
Publication statusPublished - May 2007

Keywords

  • Micromolding
  • SU-8
  • Post Exposure Bake control
  • Crack formation
  • METIS-241705
  • IR-61760
  • EWI-10319

Cite this

van Nieuwkasteele-Bystrova, S. N., Lüttge, R., & van den Berg, A. (2007). Study of crack formation in high-aspect ratio SU-8 structures on silicon. Microelectronic engineering, 84(SINTEF A13), 1113-1116. [10.1016/j.mee.2007.01.091]. https://doi.org/10.1016/j.mee.2007.01.091
van Nieuwkasteele-Bystrova, Svetlana Nikolajevna ; Lüttge, Regina ; van den Berg, Albert. / Study of crack formation in high-aspect ratio SU-8 structures on silicon. In: Microelectronic engineering. 2007 ; Vol. 84, No. SINTEF A13. pp. 1113-1116.
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van Nieuwkasteele-Bystrova, SN, Lüttge, R & van den Berg, A 2007, 'Study of crack formation in high-aspect ratio SU-8 structures on silicon' Microelectronic engineering, vol. 84, no. SINTEF A13, 10.1016/j.mee.2007.01.091, pp. 1113-1116. https://doi.org/10.1016/j.mee.2007.01.091

Study of crack formation in high-aspect ratio SU-8 structures on silicon. / van Nieuwkasteele-Bystrova, Svetlana Nikolajevna; Lüttge, Regina; van den Berg, Albert.

In: Microelectronic engineering, Vol. 84, No. SINTEF A13, 10.1016/j.mee.2007.01.091, 05.2007, p. 1113-1116.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Study of crack formation in high-aspect ratio SU-8 structures on silicon

AU - van Nieuwkasteele-Bystrova, Svetlana Nikolajevna

AU - Lüttge, Regina

AU - van den Berg, Albert

N1 - 10.1016/j.mee.2007.01.091

PY - 2007/5

Y1 - 2007/5

N2 - Abstract The high-aspect ratio capability of SU-8 photoresist led to the successful use of this epoxy based material in a diversity of microfabricated devices as a construction material as well as for micromolding purposes. Throughout the literature it was noticed that the thermal mismatch of SU-8 and the substrate material silicon generates high film stress in the spin-coated SU-8 causing crack formation in the microstructures. Using baking parameters this crack formation can be minimized but will remain a critical aspect of design. In this study the process was first optimised on non-patterned wafers. Secondly, we transferred this optimised process to a pre-patterned wafer containing deep silicon etch pits to account for a specific application in micromolding. We discuss the behaviour of film stress, number of cracks and crack length. The number of cracks as well as the length of cracks in concave corner designs can be significantly decreased, while round holes resulted even in crack-free microstructures. In the case of pre-patterned wafers no cracks appear around the features, however we observed unsatisfied development within the resist features caused by insufficient solidification in the deep etch pits during Soft Bake. Increased Soft Bake time can overcome these problems but will require more systematic investigations.

AB - Abstract The high-aspect ratio capability of SU-8 photoresist led to the successful use of this epoxy based material in a diversity of microfabricated devices as a construction material as well as for micromolding purposes. Throughout the literature it was noticed that the thermal mismatch of SU-8 and the substrate material silicon generates high film stress in the spin-coated SU-8 causing crack formation in the microstructures. Using baking parameters this crack formation can be minimized but will remain a critical aspect of design. In this study the process was first optimised on non-patterned wafers. Secondly, we transferred this optimised process to a pre-patterned wafer containing deep silicon etch pits to account for a specific application in micromolding. We discuss the behaviour of film stress, number of cracks and crack length. The number of cracks as well as the length of cracks in concave corner designs can be significantly decreased, while round holes resulted even in crack-free microstructures. In the case of pre-patterned wafers no cracks appear around the features, however we observed unsatisfied development within the resist features caused by insufficient solidification in the deep etch pits during Soft Bake. Increased Soft Bake time can overcome these problems but will require more systematic investigations.

KW - Micromolding

KW - SU-8

KW - Post Exposure Bake control

KW - Crack formation

KW - METIS-241705

KW - IR-61760

KW - EWI-10319

U2 - 10.1016/j.mee.2007.01.091

DO - 10.1016/j.mee.2007.01.091

M3 - Article

VL - 84

SP - 1113

EP - 1116

JO - Microelectronic engineering

JF - Microelectronic engineering

SN - 0167-9317

IS - SINTEF A13

M1 - 10.1016/j.mee.2007.01.091

ER -

van Nieuwkasteele-Bystrova SN, Lüttge R, van den Berg A. Study of crack formation in high-aspect ratio SU-8 structures on silicon. Microelectronic engineering. 2007 May;84(SINTEF A13):1113-1116. 10.1016/j.mee.2007.01.091. https://doi.org/10.1016/j.mee.2007.01.091