Microlens Array Fabrication by Chemical Mechanical Polishing

Chemical mechanical polishing (CMP) is widely accepted as the best planarization technique for fabricating nanoscale devices. A soft CMP pad that can enable higher oxide removal rates (RRs) and good planarity has been proposed for oxide CMP applications. In this study, three pads namely, Pad-1 (hard), Pad-2 (soft), and a commercial pad (hard) were used to polish blanket oxide, and STI patterned wafers. The Pad-2 demonstrated significantly higher RRs and better planarization than the hard pads. Post-polish pad texture analysis on Pad-2 showed a uniform surface asperity distribution. This is due to the novel method of pad manufacturing, which enables precise material placement and consistent pore construction.

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confidence: 99%

Soft Chemical Mechanical Polishing Pad for Oxide CMP Applications

Kenchappa

Popuri

Chockkalingam

et al. 2021

“…CMP has also been applied for surface texture engineering applications such as fabrication of microlens arrays for light-emitting diodes (LEDs). [1][2][3] The integration schemes for ICs are becoming increasingly complex with the advances in consumable electronics and emerging applications thereof. ITRS has reported strict requirements for dishing, within-wafer non-uniformity (WIWNU), wafer-to-wafer non-uniformity (WTWNU), within-die non-uniformity (WIDNU) and defectivity for CMP process.…”

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confidence: 99%

Investigation of the Impact of Pad Surface Texture from Different Pad Conditioners on the CMP Performance

Khanna

Yamamura

Kakireddy

et al. 2020

Chemical mechanical polishing (CMP) is a common method for planarization/polishing materials during integrated circuits (IC) fabrication. Pad conditioning is a critical component of a CMP process. Herein, the impact of surface textures created by different types of pad conditioners (PC) such as coarse, mid-coarse, and fine PC on the solid pads are studied. Additional surface texture parameters such as surface height distribution, skewness, Dale Void Volume are used to determine an optimum surface texture that gives desired CMP performance such as material removal rate and within-wafer non-uniformity. It was determined that an optimum surface texture on a solid CMP pad can be obtained with a mid-coarse disk. It is further demonstrated that by the addition of porosity to the pads, it is possible to recreate an optimum surface texture and desired CMP performance, similar to that obtained with a mid-coarse disk and a solid pad. Tribological mechanisms of the different pad and PC combinations are presented using the coefficient of friction. It is concluded that porous pad and fine PC pairing can tackle the issues of slurry transport limitations, lack of asperity contact, and process stability over pad life.

“…CMP has been demonstrated to have applications beyond IC fabrication such as in the fabrication of microlens arrays to improve light-out extraction from LEDs. [1][2][3] International Technology Road Map for Semiconductors (ITRS) has reported strict requirements for advanced technology nodes for CMP performance parameters such as within-wafer non-uniformity (WIWNU), wafer-to-wafer non-uniformity (WTWNU), and withindie non-uniformity (WIDNU) due to complex process technologies and device structures. [4][5][6] Several CMP process knobs such as platen & head rpm, wafer pressure, slurry flow, and pad conditioning to name a few are used to improve the CMP performance in the industry.…”

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confidence: 99%

High-Performance Pad Conditioning (HPPC) Arm for Augmenting CMP Performance

Khanna

Kakireddy

Fung

et al. 2020

Pad conditioning (PC) is one of the key aspects of a chemical mechanical polishing (CMP) process. PC is known to impact the material removal rates (MRR), within-wafer non-uniformity (WIWNU) of material removal rates, planarization, defects, and the overall cost of ownership of the CMP process. Herein, changes in the aggressiveness of a pad conditioning disk with usage and exposure to the slurry are determined using the novel high-performance pad conditioning (HPPC) arm. The changes in the PC sweep torque was correlated to the change in the aggressiveness of the PC disk with usage. Thereafter, the rate of drop in the PC torque was used to characterize a PC disk into different regimes such as stable and unstable regimes. The stable regime of a PC disk is defined as the one in which the rate of drop in the PC sweep torque i.e. change in the disk aggressiveness with usage is not significant. Further, it is demonstrated that it is possible to maintain stable MRR, WIWNU over a large number of wafers by using a PC disk in its stable regime, which in turn augments the stability of a CMP process.