Pad roughness evolution during break-in and its abrasion due to the pad-wafer contact in oxide CMP

Vasilev, Boris; Bott, Sascha; Rzehak, Roland; Bartha, Johann W.

doi:10.1016/j.mee.2013.04.027

Cited by 23 publications

(34 citation statements)

References 14 publications

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“…Moreover, longer break-in times have been generally shunned since they reduce pad life, tool availability, and the overall wafer throughput in high-volume IC manufacturing environments. Several other groups of researchers have reported similar 30-min experimental conditions where a stable pad micro-texture has been achieved only after 30 min of break-in [4,7,8]. Therefore, pad break-in is performed for 5, 20 and 30 min with UPW flowing onto the centre of the rotating pad.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 90%

Feasibility of a Real-Time Method in Determine the Extent of Pad Break-In During Copper Chemical Mechanical Planarization

2016

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Material removal rate, shear force and variance of shear force during copper polishing are studied as a function of pad break-in time. Results show that copper removal rate and variance of shear force increase within 30 min of pad break-in. Spectral analysis of raw shear force data is employed to help elucidate the fundamental physical phenomena during copper chemical mechanical planarization. Fast Fourier transform is performed to convert the shear force data from time domain to frequency domain. The energy distribution of copper polishing is quantified which sheds light on the effect of pad break-in time. Spectral analysis indicates that as pad break-in progresses, newly formed pad asperities dominate the interaction with the wafer and therefore shifting the spectral amplitudes to the higher frequency peaks (i.e. 101-108 Hz). Further spectral analysis also confirms that such increases in the high-frequency range dominate the distribution of energies. This study shows that a combination of unique spectral fingerprinting and analysis of force variance can be used to monitor the progress of pad break-in in real-time. This work underscores the importance of real-time detection and non-destructive method in chemical mechanical planarization process to quantify the extent of pad break-in.

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Section: Experimental Apparatus and Proceduresmentioning

confidence: 90%

Feasibility of a Real-Time Method in Determine the Extent of Pad Break-In During Copper Chemical Mechanical Planarization

2016

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“…Extensive research has shown that pad surface micro-texture plays an important role in CMP and is affected by several factors such as conditioner type, conditioning downforce, and pad break-in time [2,3,4,5,6,7,8,9,10]. In addition, laser scanning confocal microscopy has been successfully used to analyze pad surface micro-texture and has led to a better understanding of how it affects CMP performance [2,3,4,5,6,7,8,9,10]. Sun et al studied the effect of conditioner type and conditioning downforce on pad topography and found that the surface becomes more abrupt and copper removal rates decrease with increasing conditioning downforce [2].…”

Section: Introductionmentioning

confidence: 99%

Effect of Conditioner Type and Downforce, and Pad Surface Micro-Texture on SiO2 Chemical Mechanical Planarization Performance

et al. 2019

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Based on a previous work where we investigated the effect of conditioner type and downforce on the evolution of pad surface micro-texture during break-in, we have chosen certain break-in conditions to carry out subsequent blanket SiO2 wafer polishing studies. Two different conditioner discs were used in conjunction with up to two different conditioning downforces. For each disc-downforce combination, mini-marathons were run using SiO2 wafers. Prior to polishing, each pad was broken-in for 30 min with one of the conditioner-downforce combinations. The goal of this study was to polish wafers after this break-in to see how the polishing process behaved immediately after break-in. One of the discs used in this study produced similar micro-texture results at both downforces, which echoed the results seen in the mini-marathon. When comparing the different polishing results obtained from breaking-in the pad with the different discs used in this study, the coefficient of friction (COF) and SiO2 removal rate (RR) were uncorrelated in all cases. However, the use of different discs resulted in different COF and RR trends. The uncorrelated COF and RR, as well as the differing trends, were explained by pad micro-texture results (i.e. the differing amount of fractured, poorly supported pad asperity summits).

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“…Concurrently, however, process complexity in terms of the number of CMP steps and uniqueness of each step has also increased by orders of magnitude [1][2][3][4]. The CMP process has evolved through multiple generations, dated back to 1969 [5,6], employing a large pad and a single wafer carrier that rotated about their respective axes.…”

Section: Introductionmentioning

confidence: 99%

“…As an industrial process, CMP is expensive both in terms of capital cost, and cost of operation. Recently, with shrinking feature size (currently <15 nm), CMP has also been mired by defectivity (e.g., scratch and film delamination) [2][3][4] at a multiplicity of length-scales ranging from within wafer nonuniformity at wafer scale, within die nonuniformity at die scale to defectivity concerns at feature or nano-scale.…”

Section: Introductionmentioning

confidence: 99%

Performance and modeling of paired polishing process

Asplund

Bastawros

et al. 2016

International Journal of Machine Tools and Manufacture

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Paired polishing process (PPP) is a variant of the chemical mechanical polishing process which facilitates defect mitigation via minimization of maximum force as well as effective planarization via profile driven determination of force gradient. The present embodiment of PPP machine employs two polishing wheels, radially spanning the wafer surface on a counter-gimbaled base. The PPP machine is deployed to experimentally investigate the role of the process parameters on the surface roughness evolution, and the effective material removal rate. Two sets of copper and aluminum blanket layers were polished under a range of applied down force, polishing wheel speed and transverse feed rate to examine the scalability of the process parameters for different material constants. The experimental measurements along with the topological details of the polishing pad have been utilized to develop a mechanistic model of the process. The model employs the soft wheel-workpiece macroscopic contact, the polishing wheel roughness and its amplification to the local contact pressure, the kinematics of abrasive grits at the local scale, and the collective contribution of these individual micro-events to induce an effective material removal rate at the macroscale. The model shows the dependence of the material removal on the ratio of wheel rotational to feed speed for the PPP process, in a form of an asymptote that is scaled by the surface hardness of each material. The PPP machine exploits this insight and utilizes an oblique grinding technique that obviates the traditional trade-off between MRR and planarization efficiency.

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Pad roughness evolution during break-in and its abrasion due to the pad-wafer contact in oxide CMP

Cited by 23 publications

References 14 publications

Feasibility of a Real-Time Method in Determine the Extent of Pad Break-In During Copper Chemical Mechanical Planarization

Feasibility of a Real-Time Method in Determine the Extent of Pad Break-In During Copper Chemical Mechanical Planarization

Effect of Conditioner Type and Downforce, and Pad Surface Micro-Texture on SiO2 Chemical Mechanical Planarization Performance

Performance and modeling of paired polishing process

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