SOI wafer fabricated with a diamond BOX layer using surface activated bonding at room temperature

Abstract

We propose a fabrication process for a silicon on insulator (SOI) wafer with a diamond buried oxide (BOX) layer by combining nanodiamondseeding deposition and a surface-activated bonding technique for high-frequency and power device applications. The diamond layer was deposited on a base wafer by the spin-coating of nanodiamonds and microwave-plasma-enhanced chemical vapor deposition. The thermal conductivity of this deposited diamond layer was three times that of a conventional SiO 2 layer. A silicon wafer was then bonded to the diamond layer at room temperature in ultrahigh vacuum without forming any voids. Additionally, this SOI wafer was used to fabricate devices at 1000 °C. Therefore, we believe that this SOI wafer with a diamond BOX layer and its fabrication process are important for the realization of self-heating devices such as next-generation high-frequency and power devices.

Laminated wafer with conductive diamond layer formed by surface-activated bonding at room temperature for micro-electro mechanical system sensors

“…In the SAB process, when argon ions are irradiated on the surfaces of a bonding (silicon) wafer and a diamond layer to activate them with dangling bonds for bonding the bonding wafer to the diamond layer, the irradiated argon ions transform the silicon and nondoped diamond crystals to an amorphous layer at the surface of the crystal layer. 39) Therefore, we concluded that a bonding (silicon) wafer can also be bonded to the boron-doped diamond layer deposited on the base wafer without voids of more than 2 nm.…”

“…The base wafer was seeded with nanometer-size diamonds (nanodiamonds) at more than 1 × 10 6 cm −2 by spin-coating nanodiamonds dissolved in water and then baked at 80 °C. 39) A diamond layer was next deposited on the nanodiamondseeded base wafer by flowing methane, trimethoxyborane, and hydrogen gasses at 1000 °C by MW-CVD [Nihon Koshuha Co., Ltd., MDD-2016; step (a-2) in Fig. 2].…”

“…On the other hand, since the diamond layer irradiated with argon ions remains its sp 3 structure, 39,58) the doped boron remains at the substitution position and is activated, and the diamond layer doped with boron must have a resistance of at least less than 1 × 10 3 Ω cm. R Al2 from Eq.…”

Room-temperature bonded silicon on insulator wafers with a dense buried oxide layer formed by annealing a deposited silicon oxidation layer and surface-activated bonding

“…In our previous study, we found that the parasitic resistances in a silicon layer and a base wafer were much smaller than those in the BOX layer and could be ignored. 23) This measurement method thus enables us to evaluate the breakdown electric field of a BOX layer between a silicon layer and a base wafer. The electric field of a BOX layer as an evaluated parameter is defined as the input voltage divided by the BOX layer thickness.…”

“…In previous studies, we fabricated the SOI wafers with a carbonbased film (diamond, SiC) alternated a silicon oxide as a BOX layer to have a characteristic of heat dissipation for power or high-frequency devices. 23,24) When these wafers are used for MEMS devices, it is necessary to etch selectively this film against a silicon crystal, and its etching might be more difficult than silicon oxide.…”