High Breakdown-Voltage GaN-Based HEMTs on Silicon With Ti/Al/Ni/Ti Ohmic Contacts

Gao, Sheng; Liu, Xiaoyi; Chen, Jingxiong; Xie, Zijing; Zhou, Quanbin; Wang, Hong

doi:10.1109/led.2021.3058659

Cited by 14 publications

(11 citation statements)

References 24 publications

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“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Consequently, TiW diffusion barriers are now being widely implemented in next-generation SiC-based power semiconductor technologies with copper metallisation schemes, [20][21][22] and more recently within electrodes for GaAs photoconductive semiconductor switches (PCSSs), [23] and gate metal stacks in GaN-based high electron mobility transistor (HEMT) devices. [24] Diffusion barriers are needed as Cu and Si readily react at relatively low temperatures to form intermetallic copper-silicide compounds at the interface, which seriously hamper the performance and reliability of devices. [18,[25][26][27][28][29] Studies have shown that TiW films are capable of retarding and limiting this interdiffusion and subsequent reaction.…”

Section: Introductionmentioning

confidence: 99%

Capturing the dynamics of Ti diffusion across Ti$_x$W$_{1-x}$/Cu heterostructures using X-ray photoelectron spectroscopy

Kalha¹,

Thakur²,

Lee³

et al. 2023

Preprint

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Interdiffusion phenomena between adjacent materials are highly prevalent in semiconductor device architectures and can present a major reliability challenge for the industry. To fully capture these phenomena, experimental approaches must go beyond static and post-mortem studies to include in-situ and in-operando setups. Here, soft and hard X-ray photoelectron spectroscopy (SXPS and HAXPES) is used to monitor diffusion in real-time across a proxy device. The device consists of a Si/SiO2/TixW1−x(300 nm)/Cu(25 nm) thin film material stack, with the TixW1−x film acting as a diffusion barrier between Si and Cu. The diffusion is monitored through the continuous collection of spectra whilst in-situ annealing to 673 K. Ti within the TiW is found to be highly mobile during annealing, diffusing out of the barrier and accumulating at the Cu surface. Increasing the Ti concentration within the TixW1−x film increases the quantity of accumulated Ti, and Ti is first detected at the Cu surface at temperatures as low as 550 K. Surprisingly, at low Ti concentrations (x = 0.054), W is also mobile and diffuses alongside Ti. These results provide crucial evidence for the importance of diffusion barrier composition on their efficacy during device application, delivering insights into the mechanisms underlying their effectiveness and limitations.

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Section: Introductionmentioning

confidence: 99%

Capturing the dynamics of Ti diffusion across Ti$_x$W$_{1-x}$/Cu heterostructures using X-ray photoelectron spectroscopy

Kalha¹,

Thakur²,

Lee³

et al. 2023

Preprint

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“…[ 4–19 ] Consequently, TiW diffusion barriers are now being widely implemented in next‐generation SiC‐based power semiconductor technologies with copper metallisation schemes, [ 20–22 ] and more recently within electrodes for GaAs photoconductive semiconductor switches (PCSSs), [ 23 ] and gate metal stacks in GaN‐based high electron mobility transistor (HEMT) devices. [ 24 ]…”

Section: Introductionmentioning

confidence: 99%

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Consequently, TiW diffusion barriers are now being widely implemented in nextgeneration SiC-based power semiconductor technologies with copper metallisation schemes, [20][21][22] and more recently within electrodes for GaAs photoconductive semiconductor switches (PCSSs), [23] and gate metal stacks in GaN-based high electron mobility transistor (HEMT) devices. [24] Diffusion barriers are needed as Cu and Si readily react at relatively low temperatures to form intermetallic coppersilicide compounds at the interface. The presence of such compounds can induce a number of failure routes, including the degradation of the interlayer dielectric, resulting in the creation of short circuit pathways and thermal runaways, the generation of deep trap levels within the semiconductor, and volume expansion at the interface which can cause the delamination between adjacent layers.…”

Section: Introductionmentioning

confidence: 99%

Capturing the Dynamics of Ti Diffusion Across Ti_xW_1−x/Cu Heterostructures using X‐Ray Photoelectron Spectroscopy

Kalha

Thakur

Lee

et al. 2023

Advanced Physics Research

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Interdiffusion phenomena between adjacent materials are highly prevalent in semiconductor device architectures and can present a major reliability challenge for the industry. To fully capture these phenomena, experimental approaches must go beyond static and post‐mortem studies to include in situ and in‐operando setups. Here, soft and hard X‐ray photoelectron spectroscopy (SXPS and HAXPES) is used to monitor diffusion in real‐time across a proxy device. The device consists of a Si/SiO2/TixW1−x(300 nm)/Cu(25 nm) thin film material stack, with the TixW1−x film (x = 0.054, 0.115, 0.148) acting as a diffusion barrier between Si and Cu. The interdiffusion is monitored through the continuous collection of spectra whilst in situ annealing to 673 K. Ti within the TiW is found to be highly mobile during annealing, diffusing out of the barrier and accumulating at the Cu surface. Increasing the Ti concentration within the TixW1−x film increases the quantity of accumulated Ti, and Ti is first detected at the Cu surface at temperatures as low as 550 K. Surprisingly, at low Ti concentrations (x = 0.054), W is also mobile and diffuses alongside Ti. By monitoring the Ti 1s core level with HAXPES, the surface‐accumulated Ti was observed to undergo oxidation even under ultra‐high vacuum conditions, highlighting the reactivity of Ti in this system. These results provide crucial evidence for the importance of diffusion barrier composition on their efficacy during device application, delivering insights into the mechanisms underlying their effectiveness and limitations.

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“…The crystal quality of GaN thin film grown on SiC substrate is quite excellent. However, the cost of the SiC substrate is high, and the wafer size is small (3 to 4 inches), which are obstacles to the industrialization of the GaN HEMT device [6,7]. Compared with SiC substrate, Si substrate has a low price and a large wafer size (≥6 inches), which means that a GaN HEMT device based on Si substrate has some advantage in industrialization.…”

Section: Introductionmentioning

confidence: 99%

Reduction in RF Loss Based on AlGaN Back-Barrier Structure Changes

et al. 2022

Self Cite

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We designed a high electron mobility transistor (HEMT) epitaxial structure based on an AlGaN/GaN heterojunction, utilizing Silvaco TCAD, and selected AlGaN with an aluminum composition of 0.1 as the back-barrier of the AlGaN/GaN heterojunction. We enhanced the confinement of the two-dimensional electron gas (2DEG) by optimizing the structural parameters of the back barrier, so that the leakage current of the buffer layer is reduced. Through these optimization methods, a lower drain leakage current and a good radio frequency performance were obtained. The device has a cut-off frequency of 48.9 GHz, a maximum oscillation frequency of 73.20 GHz, and a radio frequency loss of 0.239 dB/mm (at 6 GHz). This work provides a basis for the preparation of radio frequency devices with excellent frequency characteristics and low RF loss.

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High Breakdown-Voltage GaN-Based HEMTs on Silicon With Ti/Al/Ni/Ti Ohmic Contacts

Cited by 14 publications

References 24 publications

Capturing the dynamics of Ti diffusion across Ti$_x$W$_{1-x}$/Cu heterostructures using X-ray photoelectron spectroscopy

Capturing the dynamics of Ti diffusion across Ti$_x$W$_{1-x}$/Cu heterostructures using X-ray photoelectron spectroscopy

Capturing the Dynamics of Ti Diffusion Across Ti_xW_1−x/Cu Heterostructures using X‐Ray Photoelectron Spectroscopy

Reduction in RF Loss Based on AlGaN Back-Barrier Structure Changes

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High Breakdown-Voltage GaN-Based HEMTs on Silicon With Ti/Al/Ni/Ti Ohmic Contacts

Cited by 14 publications

References 24 publications

Capturing the dynamics of Ti diffusion across Ti$_x$W$_{1-x}$/Cu heterostructures using X-ray photoelectron spectroscopy

Capturing the dynamics of Ti diffusion across Ti$_x$W$_{1-x}$/Cu heterostructures using X-ray photoelectron spectroscopy

Capturing the Dynamics of Ti Diffusion Across TixW1−x/Cu Heterostructures using X‐Ray Photoelectron Spectroscopy

Reduction in RF Loss Based on AlGaN Back-Barrier Structure Changes

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Capturing the Dynamics of Ti Diffusion Across Ti_xW_1−x/Cu Heterostructures using X‐Ray Photoelectron Spectroscopy