Large-area femtosecond laser ablation of Silicon to create membrane with high performance CMOS-SOI RF functions

Bhaskar, Arun; Philippe, Jean‐Marc; Berthomé, Matthieu; Okada, Étienne; Robillard, J.F.; Gloria, D.; Gaquière, C.; Dubois, Emmanuel

doi:10.1109/estc.2018.8546407

Cited by 8 publications

(16 citation statements)

References 19 publications

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“…By using an etch mask to protect the unablated regions, membranes are obtained in the ablated areas after the completion of XeF2 etch step leaving rest of the die intact. The process has been described in detail in previous works where mm sized membranes have been demonstrated with material removal rates of up to 8.5x10 6 μm 3 s -1 [16], [17]. At the end of the process, silicon is removed completely under the inductor area (ABCD in Fig.…”

Section: Flame Processmentioning

confidence: 99%

“…A local handler substrate removal method enables suspension of RF circuits freely on the BOX and substrate related losses can be brought to a minimum. In this context, we have developed the Femtosecond Laser Assisted Micromachining and Etch (FLAME) process to fabricate membranes of RF circuits [16], [17]. Substrate removal has already been studied in numerous works as a means of improving Q-factor [18]- [22].…”

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confidence: 99%

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Substrate Engineering of Inductors on SOI for Improvement of Q-Factor and Application in LNA

Bhaskar

Philippe

Avramovic

et al. 2020

IEEE J. Electron Devices Soc.

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High Q-factor inductors are critical in designing high performance RF/microwave circuits on SOI technology. Substrate losses is a key limiting factor when designing inductors with high Q-factors. In this context, we report a substrate engineering method that enables improvement of quality factors of already fabricated inductors on SOI. A novel femtosecond laser milling process is utilized for the fabrication of locally suspended membranes of inductors with handler silicon completely etched. Such flexible membranes suspended freely on the BOX show up to 92 % improvement in Q-factor for single turn inductor. The improvement in Q-factor is reported on large sized inductors due to reduced parallel capacitance which allows enhanced operation of inductors at high frequencies. A compact model extraction methodology has been developed to model inductor membranes. These membranes have been utilized for the improvement of noise performance of LNA working in the 4.9-5.9 GHz range. A 0.1 dB improvement in noise figure has been reported by taking an existing design and suspending the input side inductors of the LNA circuit. The substrate engineering method reported in this work is not only applicable to inductors but also to active circuits, making it a powerful tool for enhancement of RF devices.

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Section: Flame Processmentioning

confidence: 99%

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confidence: 99%

Substrate Engineering of Inductors on SOI for Improvement of Q-Factor and Application in LNA

Bhaskar

Philippe

Avramovic

et al. 2020

IEEE J. Electron Devices Soc.

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“…To control the ON/OFF state of the different branches, the switch contains two DC bias pins. The body and gate are driven by these bias pins through a high series resistance for DC isolation [29].…”

Section: Sp9t Switch Designmentioning

confidence: 99%

“…The measurement is performed at a fundamental input frequency of 1.22 GHz while the 2 nd and 3 rd harmonics (H2/H3) are measured at the output at frequencies of 2.44 and 3.66 GHz, respectively. A low noise-floor setup as described in [29] is used for the measurement. The input power is swept at the fundamental frequency and the 2 nd and 3 rd harmonic power is recorded as shown in Fig.…”

Section: Large Signal Harmonic Distortion Measurementmentioning

confidence: 99%

Mitigation of substrate coupling effects in RF switch by localized substrate removal using laser processing

Bhaskar¹,

Philippe²,

Okada³

et al. 2020

Preprint

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“…The study of trenches scribed in silicon is useful to determine the optimal conditions for performing laser milling. In our previous study, we had described the scribing of trenches for the 1030 nm source 16 . In this publication, the scribing of trenches is discussed for both the 343 nm and 1030 nm source.…”

Section: Study Of Trenches Scribed In Siliconmentioning

confidence: 99%

Femtosecond laser micromachining of crystalline silicon for ablation of deep macro-sized cavities for silicon-on-insulator applications

Bhaskar¹,

Philippe²,

Braud³

et al. 2019

Laser-Based Micro- And Nanoprocessing XIII

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We demonstrate the use of femtosecond laser micromachining for ablating macro-sized cavities in crystalline silicon. The method employed is laser milling in which the focused laser beam is raster scanned over the area to be removed. We report the achievement of very high volume ablation rates for the cavity of up to 8.48x10 6 µm 3 s -1 . To achieve such high rates, we make use of a high average power fiber laser source of 1030 nm wavelength and variable per pulse energy of up to 100 µJ. By carefully controlling the process variables such as pulse energy, repetition rate and scanner speed, the tradeoffs between micromachining quality and ablation rate are quantified. The developed process is applied on Siliconon-Insulator (SOI) wafers for improving performance of RF devices. By making use of laser removal and an additional step of selective silicon etch using XeF2, handler silicon is removed completely under RF circuits such as SP9T switch. The local removal of silicon under such circuits completely eliminates the losses and non-linearities caused by the coupling of RF signals to the semi-conducting substrate. Small-signal and large-signal RF measurements are performed before and after substrate removal to quantify the performance gain. The obtained performance after substrate removal is better than specialized RF-SOI substrates such as trap-rich SOI. This is of practical significance for next generation wireless technologies like 5G which operate at higher frequencies with stringent specifications. The proposed method is also potentially useful for fabricating membrane based devices in SOI technology such as pressure sensors.

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Large-area femtosecond laser ablation of Silicon to create membrane with high performance CMOS-SOI RF functions

Cited by 8 publications

References 19 publications

Substrate Engineering of Inductors on SOI for Improvement of Q-Factor and Application in LNA

Substrate Engineering of Inductors on SOI for Improvement of Q-Factor and Application in LNA

Mitigation of substrate coupling effects in RF switch by localized substrate removal using laser processing

Femtosecond laser micromachining of crystalline silicon for ablation of deep macro-sized cavities for silicon-on-insulator applications

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