Pan Pacific Symposium Conference Proceedings

Thin Wafer Processing for 3D Integration: Status and Update

Authors: Markus Wimplinger, Jürgen Burggraf, Harald Wiesbauer, Thomas Uhrmann, Thorsten Matthias, Garrett Oakes, and Masaya Kawano
Company: EV Group
Date Published: 2/11/2014   Conference: Pan Pacific Symposium

Abstract: With end applications in the high performance server, mobile computing and smart phone space demanding ever higher performance of microelectronic devices while reducing power consumption and package size, the industry is preparing for the market introduction of 3D stacked devices based on TSV technology. The ability to reliably handle and process wafers with a thickness significantly less than 100µm plays a key role in enabling low cost, high volume manufacturing of TSVs with acceptable yield. Consensus has developed on the use of Temporary Bonding/ Debonding Technology as the solution of choice for reliably handling thin wafers through backside processing steps. While the majority of the device manufacturing steps on the front side of the wafer will be completed with the wafer still at full thickness, it will be temporarily mounted onto a carrier before thinning and processing of the features on its backside. Once the wafer reaches the temporary bonding step, it already represents a significant value, as it has already gone through numerous processing steps. This fact further underlines the need for a temporary carrier technology that provides for high yield at low cost. A widely shared perception in the semiconductor industry views temporary bonding and debonding technology as "immature", "expensive", posing "yield problems", having "low throughput" and being expensive.

The first part of this paper reviews the recent history of thin wafer processing solutions and issues seen with different process technology and material options. Based on that technological background, an analysis is attempted aimed at explaining the user experience related to temporary bonding/debonding solutions and the perception that is resulting from the collective experiences. The second part of the paper focuses on the current state of thin wafer handling solutions from a technical perspective, supply chain aspects and technological trends observed today.

Finally, the paper concludes with reporting latest achievements in equipment and process technology development aimed at addressing some of the key deficiencies hindering implementation of the technology in high volume manufacturing (HVM). This is illustrated by a review of advances made with respect to in-line metrology solutions aimed at monitoring key quality aspects of temporary bonding / debonding process solutions. Furthermore, novel material solutions schemes are presented and reviewed as well as latest advances related to equipment throughput, cost of ownership and process performance.

Key Words: 

Temporary Bonding, Debonding, in-line metrology, crosslinking adhesive, thermoplastic adhesive, mechanical debonding, laser debonding

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