Etching of quartz crystals in liquid phase environment: A review

Dong, Yide; Zhou, Yike; Huang, Haizhou; Zhang, Bosong; Li, Xihan; Chen, Kaiwen; Sun, Litao; Dou, Guangbin

doi:10.1063/10.0025651

Cited by 2 publications

(2 citation statements)

References 108 publications

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“…This facilitates integrating drive and sensing electrodes within a single resonator, thus minimizing alignment errors common in high-end sensors [ 7 ]. Consequently, quartz is widely used in manufacturing MEMS devices [ 8 , 9 ]. In wet etching, quartz crystals are typically etched using saturated ammonium fluoride (NH 4 HF 2 ) or buffered oxide etchant (BOE), the latter being a blend of NH 4 F:HF.…”

Section: Introductionmentioning

confidence: 99%

Etching Rate Analysis Model Based on Quartz Bond Angle Characteristics

Zhao,

Lv,

Song

et al. 2024

Micromachines

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This paper proposes a method for classifying crystal planes based on the bond angle characteristics of quartz unit cells and constructs an etch rate model for quartz crystal planes at both macro and micro scales. By omitting oxygen atoms from the quartz cell structure, a method based on bond angle characteristics was established to partition the atomic arrangement of the crystal surface. This approach was used to analyze the etching processes of typical quartz crystal planes (R, r, m, and (0001)), approximating the etching process of crystals as a cyclic removal of certain bond angle characteristics on the crystal planes. This led to the development of an etch rate model based on micro-geometric parameters of crystal planes. Additionally, using the proposed bond angle classification method, the common characteristics of atomic configurations on the crystal plane surfaces within the X_cut type were extracted and classified into seven regions, further expanding and applying the etch rate model. The computational results of this model showed good agreement with experimental data, indicating the rationality and feasibility of the proposed method. These also provide a theoretical basis for understanding the microstructural changes during quartz-based MEMS etching processes.

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Section: Introductionmentioning

confidence: 99%

Etching Rate Analysis Model Based on Quartz Bond Angle Characteristics

Zhao,

Lv,

Song

et al. 2024

Micromachines

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“…Since Statek [ 6 ] applied Micro-Electro-Mechanical system (MEMS) process technology to the fabrication of quartz crystal devices for the first time in 1973, quartz MEMSs (QMEMSs) provided a good starting point for all kinds of sensors and actuators, such as gyroscopes [ 7 , 8 , 9 , 10 ], accelerometers [ 11 , 12 , 13 , 14 ] and oscillators [ 15 , 16 , 17 ]. Since then, wet etching in fluoride-based solutions has been one of the most fundamental QMEMS techniques used in the process of fabricating quartz devices [ 18 ].…”

Section: Introductionmentioning

confidence: 99%

Size-Effect-Based Dimension Compensations in Wet Etching for Micromachined Quartz Crystal Microstructures

Dong,

Dou,

Wei

et al. 2024

Micromachines

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Microfabrication technology with quartz crystals is gaining importance as the miniaturization of quartz MEMS devices is essential to ensure the development of portable and wearable electronics. However, until now, there have been no reports of dimension compensation for quartz device fabrication. Therefore, this paper studied the wet etching process of Z-cut quartz crystal substrates for making deep trench patterns using Au/Cr metal hard masks and proposed the first quartz fabrication dimension compensation strategy. The size effect of various sizes of hard mask patterns on the undercut developed in wet etching was experimentally investigated. Quartz wafers masked with initial vias ranging from 3 μm to 80 μm in width were etched in a buffered oxide etch solution (BOE, HF:NH4F = 3:2) at 80 °C for prolonged etching (>95 min). It was found that a larger hard mask width resulted in a smaller undercut, and a 30 μm difference in hard mask width would result in a 17.2% increase in undercut. In particular, the undercuts were mainly formed in the first 5 min of etching with a relatively high etching rate of 0.7 μm/min (max). Then, the etching rate decreased rapidly to 27%. Furthermore, based on the etching width compensation and etching position compensation, new solutions were proposed for quartz crystal device fabrication. And these two kinds of compensation solutions were used in the fabrication of an ultra-small quartz crystal tuning fork with a resonant frequency of 32.768 kHz. With these approaches, the actual etched size of critical parts of the device only deviated from the designed size by 0.7%. And the pattern position symmetry of the secondary lithography etching process was improved by 96.3% compared to the uncompensated one. It demonstrated significant potential for improving the fabrication accuracy of quartz crystal devices.

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Etching of quartz crystals in liquid phase environment: A review

Cited by 2 publications

References 108 publications

Etching Rate Analysis Model Based on Quartz Bond Angle Characteristics

Etching Rate Analysis Model Based on Quartz Bond Angle Characteristics

Size-Effect-Based Dimension Compensations in Wet Etching for Micromachined Quartz Crystal Microstructures

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