Molybdenum etching using an SF₆, BCl₃ and Ar based recipe for high aspect ratio MEMS device fabrication

Abstract

This paper presents the development of a dry etch recipe for molybdenum (Mo), based on SF6, BCl3 and Ar gases for high-topography MEMS device fabrication. The recipe was optimized for a high Mo etch rate, a low Mo by-product generation and a low Mo undercut using photoresist (PR) masks. The presented optimized recipe is very effective in Mo etching using a PR mask. The Mo by-product generated during the Mo etch can be easily removed using the ACT NE-14 etch residue remover. This optimized recipe was also used for etching Mo electrodes using oxide, PR or composite oxide-PR masks to select the better mask and selectivity. It was observed in this study that Mo has a better selectivity when using an oxide hard mask. However, it has the serious drawback of generating by-products which are difficult to clean later on. On the other hand, Mo has a poor selectivity with PR masks compared with oxide masks but there was no issue of by-product cleaning. At the same time, no extra mask layer deposition is required for Mo etching. The optimized recipe was also used for Mo electrode etching using PR and PR-oxide composite masks for the demonstration of working film bulk acoustic wave resonators and actuator microelectromechanical system devices.

Integration of AlN with molybdenum electrodes and sacrificial amorphous silicon release using XeF2

“…Other metals like Pt, Ti, Cr and Mo are hard enough to act as a stop layer for AlN dry-etch. While it is difficult to dry etch Pt, Ti and Cr, Mo is comparatively easy to dry etch [28]. It should be noted here that Mo also etched by Cl 2 /BCl 3 /Ar-based recipe.…”

Bulk molybdenum field emitters by inductively coupled plasma etching

“…Various reports have also shown that the Mo etch rate is dominated by low energetic, yet highly chemically active species [21,22]. More recently, deep reactive ion etching of Mo using SF6 was reported for high aspect ratio structures, 3 with mesa larger than 10 µm produced [23,24]. In the case of Mo, it was shown that reduced undercutting and high selectivity over SiO2 were achieved when SF6 was mixed with BCl3 and Ar.…”

“…21,22 More recently, deep reactive ion etching of Mo using SF 6 was reported for high aspect ratio structures, with mesa larger than 10 mm produced. 23,24 In the case of Mo, it was shown that reduced undercutting and high selectivity over SiO 2 were achieved when SF 6 was mixed with BCl 3 in an Ar ballast. Upon mixing of SF 6 with O 2 , a less volatile MoOF 4 product was generated.…”

Dry Etching of Metal Inserted Poly-Si Stack for Dual High-k and Dual Metal Gate Integration

“…6 However, dry etching of n/pMOS MIPS with different gate stacks is expected to be one of the challenges for the DHDMG integration. Some studies have already been performed on TaN, 7 Mo metal gate 8 and MIPS structure etching. 9 However, to our knowledge, dry etching of two different thickness and composition gate stacks for n/pMOS at the same time have never been explored before.…”