Comparison of etch characteristics of KOH, TMAH and EDP for bulk micromachining of silicon (110)

Dutta, Shankar; Imran,; Kumar, Prem; Pal, R.; Datta, P.; Chatterjee, Ratnamala

doi:10.1007/s00542-011-1351-6

Cited by 52 publications

(30 citation statements)

References 15 publications

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“…In general, a 10 • C increase in the temperature possibly will double the etch rate. 26 This indicates that the polish temperature can directly affect the polish rate and for Case 2 higher polish rates were observed at higher pH values.…”

Section: Resultsmentioning

confidence: 94%

The Effect of Slurry Properties on the CMP Removal Rate of Boron Doped Polysilicon

Pirayesh

Cadien

2016

ECS J. Solid State Sci. Technol.

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Doped polysilicon is used as a via fill material for through silicon via technology. Boron doping is used to reduce the polysilicon resistivity but boron doping significantly decreases the polish removal rate. Here the influence of slurry characteristics, chemistry and abrasive properties, on the chemical mechanical polishing of heavily boron-doped polysilicon is investigated. The effect of slurry pH on silica abrasive size and colloidal stability is examined as well as the influence of these effects on the polish rate. The optimum abrasive concentration is ∼6 wt% and higher concentrations did not improve the polish rate due to the saturation of slurry particles on the wafer surface. Smaller abrasive particles, with 10 times higher surface area per unit weight improved the polish rate ∼20%. Finally, polish conditions with mechanical and chemical dominance are compared.Integrated circuit fabrication includes many depostion manufacturing steps which leave undesired topographies on wafer surfaces. These include copper electroplate for damascene copper interconnects and Si chemical vapor deposition (CVD) for through silicon via (TSV) fill. 1,2 These technologies have been enabled by the use of chemical mechanical polish (CMP) which has high removal rate and the ability to planarize and minimize damage of the polished surface. 3,4 During the CMP process a rotating wafer is pushed (with down force F) into a polymeric rotating pad while slurry is spread over the pad to provide chemistry and abrasives to the wafer surface. The polished surface quality and the polish rate depend strongly on the polish properties such as polish pressure, velocity and the slurry chemistry and abrasives which are specific to the type of material being polished. The presence of oxidizers is essential to improve the polish behavior for metals while for semiconductors an etchant is used to weaken the wafer surface chemical bonds. 3,5 The pH of the solution, chemical additives and abrasive shape, type and size are some of the slurry factors which can influence the polish rate significantly.Doped polysilicon is used as both a p-type and n-type semiconductor in field effect transistors and as a fill material for TSV used for the front end of line and 3D packaging processes. 6 CMP is an enabling IC fabrication process and the CMP of doped polysilicon has been studied. 7-9 Improving the polish rate of doped polysilicon can significantly improve the manufacturing cost and time. Enhancement of polish rate can be achieved by optimizing the polish properties such as pressure, flow rate and velocity, as has been shown in our prior publications. 10,11 Polish rate can also be improved by enhancing the slurry chemistry and by understanding the basic properties of the slurry.Pietsch et al. studied the influence of slurry pH and found that the maximum etch and polish rate of single crystal silicon (n-type Si (100) and (111) wafers with 150 cm resistivity) occurs at pH∼11. 8,[12][13][14] They showed that the presence of hydroxyl anions plays a major role in th...

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Section: Resultsmentioning

confidence: 94%

The Effect of Slurry Properties on the CMP Removal Rate of Boron Doped Polysilicon

Pirayesh

Cadien

2016

ECS J. Solid State Sci. Technol.

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“…It is a low cost technique and suitable for batch process. Potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) are the two main etchants used for wet anisotropic etching-based silicon bulk micromachining [6][7][8][9][10][11][12]. These etchants are thoroughly investigated under various etching conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Each method has its own benefits and drawbacks. Maximum etch rate of Si{100} and Si{110} is obtained in KOH with a concentration range from 15 to 25 wt% [8][9][10][11]. Different kinds of additives (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of the wafer with {110} surface, two slanted planes making an angle of 35.5° with wafer surface and four vertical planes with respect to wafer surface appear along ⟨110⟩ and ⟨112⟩ directions, respectively. Therefore, in order to fabricate microstructures with vertical sidewalls {110} wafer is a most appropriate choice [10,[28][29][30][31][32][33][34]. It can be used to fabricate deep channels/cavities with vertical sidewall.…”

Section: Introductionmentioning

confidence: 99%

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Etching characteristics of Si{110} in 20 wt% KOH with addition of hydroxylamine for the fabrication of bulk micromachined MEMS

Rao

Swarnalatha

Pal

2017

Micro and Nano Syst Lett

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Anisotropic wet etching is a most widely employed for the fabrication of MEMS/NEMS structures using silicon bulk micromachining. The use of Si{110} in MEMS is inevitable when a microstructure with vertical sidewall is to be fabricated using wet anisotropic etching. In most commonly employed etchants (i.e. TMAH and KOH), potassium hydroxide (KOH) exhibits higher etch rate and provides improved anisotropy between Si{111} and Si{110} planes. In the manufacturing company, high etch rate is demanded to increase the productivity that eventually reduces the cost of end product. In order to modify the etching characteristics of KOH for the micromachining of Si{110}, we have investigated the effect of hydroxylamine (NH 2 OH) in 20 wt% KOH solution. The concentration of NH 2 OH is varied from 0 to 20% and the etching is carried out at 75 °C. The etching characteristics which are studied in this work includes the etch rates of Si{110} and silicon dioxide, etched surface morphology, and undercutting at convex corners. The etch rate of Si{110} in 20 wt% KOH + 15% NH 2 OH solution is measured to be four times more than that of pure 20 wt% KOH. Moreover, the addition of NH 2 OH increases the undercutting at convex corners and enhances the etch selectivity between Si and SiO 2 .

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“…Common silicon wet isotropic etchants are mixture of HF, HNO 3 and CH 3 COOH [29,30], while potassium hydroxide (KOH) [2,7,[31][32][33][34][35][36][37][38][39][40][41][42][43] and tetramethylammonium hydroxide (TMAH) [1,5,35, etchants are most extensively used for wet anisotropic etching. There are some other alkaline solutions which have been investigated for silicon wet anisotropic etching such as ethylenediamine pyrocatechol water (EDP or EPW) [4,35,41,[65][66][67], hydrazine [31,68,69], ammonium hydroxide [70], and cesium hydroxide (CsOH) [71]. In wet anisotropic etching, {111} planes are the slowest etch rate planes in all types of anisotropic etchants.…”

Section: Introductionmentioning

confidence: 99%

Determination of precise crystallographic directions for mask alignment in wet bulk micromachining for MEMS

Singh

Pal

Pandey

et al. 2016

Micro and Nano Syst Lett

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In wet bulk micromachining, the etching characteristics are orientation dependent. As a result, prolonged etching of mask openings of any geometric shape on both Si{100} and Si{110} wafers results in a structure defined by the slowest etching planes. In order to fabricate microstructures with high dimensional accuracy, it is vital to align the mask edges along the crystal directions comprising of these slowest etching planes. Thus, precise alignment of mask edges is important in micro/nano fabrication. As a result, the determination of accurate crystal directions is of utmost importance and is in fact the first step to ensure dimensionally accurate microstructures for improved performance. In this review article, we have presented a comprehensive analysis of different techniques to precisely determine the crystallographic directions. We have covered various techniques proposed in the span of more than two decades to determine the crystallographic directions on both Si{100} and Si{110} wafers. Apart from a detailed discussion of each technique along with their design and implementation, we have provided a critical analysis of the associated constraints, benefits and shortcomings. We have also summed up the critical aspects of each technique and presented in a tabular format for easy reference for readers. This review article comprises of an exhaustive discussion and is a handy reference for researchers who are new in the field of wet anisotropic etching or who want to get abreast with the techniques of determination of crystal directions.

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Comparison of etch characteristics of KOH, TMAH and EDP for bulk micromachining of silicon (110)

Cited by 52 publications

References 15 publications

The Effect of Slurry Properties on the CMP Removal Rate of Boron Doped Polysilicon

The Effect of Slurry Properties on the CMP Removal Rate of Boron Doped Polysilicon

Etching characteristics of Si{110} in 20 wt% KOH with addition of hydroxylamine for the fabrication of bulk micromachined MEMS

Determination of precise crystallographic directions for mask alignment in wet bulk micromachining for MEMS

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