Model for a multiple-step deep Si etch process

Rauf, Shahid; Dauksher, William J.; Clemens, Stephen; Smith, Kenneth H.

doi:10.1116/1.1477418

Cited by 50 publications

(30 citation statements)

References 45 publications

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“…Kokkoris et al have performed such modeling. 5,21 The key point to notice in Fig. 5, which shows that molecular flux to the bottom center of a trench as a function of both the trench aspect ratio and the sticking coefficient ("SC" ¼ sticking probability) for the molecule being modeled.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4][5][6] The Bosch process also has some well-known difficulties such as aspect ratio dependent etch rates (ARDE) in vias and trenches, 6-10 mask undercut, 11,12 feature dimension uniformity, 1,3 feature closing (etch stop), 13 imprecise control of sidewall profiles, 6,12 and a fluorocarbon film that remains on feature sidewalls. The process is unique in that it allows one to control the etch profile and rate through manipulation of the process timing as well as plasma parameters.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of the deposition step in time multiplexed deep silicon etches

Saraf¹,

Goeckner²,

Goodlin³

et al. 2012

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The time multiplexed deep silicon etch (TMDSE) process is the etch process of choice to make MEMS devices and through wafer vias. It has been used to produce deep trenches and vias at reasonable throughputs. Significant issues remain for the TMDSE process as well as room for improvement even though it has been both experimentally studied and modeled by a wide variety of researchers. This is because it is a highly complex process. Aspect ratio dependencies, selectivity, and the ability to use photoresist masks (instead of SiO 2 ) are examples of remaining issues. The presently obtainable etch rates do not indicate efficient use of the etchant species. In this article, the authors focus on the deposition step in the TMDSE process. While prior research has generally assumed that the deposition step can be adequately modeled as being controlled by a reactive sticking coefficient, they have experimentally examined the deposition step of the process and found that the film growth is dominantly ion-enhanced. The results shown here were obtained in C 4 F 8 plasmas but are also consistent with results found in CHF 3 and C 4 F 6 plasmas. As a result, the deposited film thickness can be larger at the bottom of a high aspect ratio feature than at the top sidewall, which is exactly the opposite of the desired profile. The very nature of the deposition mechanism leads to mask undercut at the same time as feature closing/etch stop.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics of the deposition step in time multiplexed deep silicon etches

Saraf¹,

Goeckner²,

Goodlin³

et al. 2012

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

View full text Add to dashboard Cite

show abstract

“…12(d). This is a combined effect of a higher polymer sputtering yield 24 and an increased ion-enhanced Si etching yield. 25 For F-based chemistry, the linearity behavior of ER on the bias voltage can be expressed by…”

Section: Reactionmentioning

confidence: 95%

Etching mechanism of the single-step through-silicon-via dry etch using SF6/C4F8 chemistry

Ouyang

Ruzic

Kiehlbauch

et al. 2014

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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A single-step etching method using the SF6/C4F8 chemistry is developed in this study as an alternative through-silicon-via (TSV) etching approach of the traditional Bosch process to realize ultrasmooth and vertical TSV profiles. Experimental results show that there is a profile discontinuity, or a “transition,” on the TSV profile produced by the single-step etching method at high bias voltages and high SF6 flow rates. Comparison between the intensity of the species generated in a pure SF6 or a pure C4F8 plasma and in a SF6/C4F8 plasma is investigated for better understanding interactions between SF6 and C4F8. The densities of all positive ions are reduced in the SF6/C4F8 plasma compared to a pure SF6 plasma and a pure C4F8 plasma at the same partial pressure, indicating a change of plasma chemistry when SF6 and C4F8 fluxes are mixed. The formation mechanism of the transition is proposed as a chemistry discontinuity caused by large-angle ion sputtering at the top part of the sidewalls and the polymer accumulation at the bottom part of the sidewalls. The formation of the transition has found to have an effect of improving the sidewall smoothness below the position where it is formed. Parameter study has shown that a decreased bias voltage and a reduced SF6/C4F8 ratio can help to improve the sidewall smoothness and eliminate the transition on the TSV profiles.

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“…Indeed, low platen power induces lower ion bombardment energy. Fluorocarbon film is assumed to be etched by ion-assisted sputtering and it is known that sputter yield is proportional to the square root of the ion energy at constant ion flux [19]. As coil power applied is only 100 W, one could say that the platen brings power to the plasma and increases the ion flux causing an ''exponential'' etch rates variation.…”

Section: Etch Ratesmentioning

confidence: 99%