Methods of forming SOI substrates are disclosed. In some embodiments, an epitaxial layer and an oxide layer are formed on a sacrificial substrate. An etch stop layer is formed in the epitaxial layer. The sacrificial substrate is bonded to a handle substrate at the oxide layer. The sacrificial substrate is removed. The epitaxial layer is partially removed until the etch stop layer is exposed.

A bonding wafer structure includes a support substrate, a bonding layer, and a silicon carbide (SiC) layer. The bonding layer is formed on a surface of the support substrate, and the SiC layer is bonded onto the bonding layer, in which a carbon surface of the SiC layer is in direct contact with the bonding layer. The SiC layer has a basal plane dislocation (BPD) of 1,000 ea/cm.sup.2 to 20,000 ea/cm.sup.2, a total thickness variation (TTV) greater than that of the support substrate, and a diameter equal to or less than that of the support substrate. The bonding wafer structure has a TTV of less than 10 μm, a bow of less than 30 μm, and a warp of less than 60 μm.

Various embodiments of the present application are directed to a method for forming a semiconductor-on-insulator (SOI) substrate without bond interface voids and/or without delamination between layers. In some embodiments, a first high κ bonding structure is formed over a handle substrate. A device layer is formed over a sacrificial substrate. Outer most sidewalls of the device layer are between outer most sidewalls of the sacrificial substrate. A second high κ bonding structure is formed over the device layer. The first high κ bonding structure is bonded to the second high κ bonding structure, such that the device layer is between the sacrificial substrate and the handle substrate. A first removal process is performed to remove the sacrificial substrate. The first removal process comprises performing a first etch into the sacrificial substrate until the device layer is reached.

Method for producing a JFET transistor, comprising: a) producing, on a first substrate, a stack comprising a first layer comprising a first semiconductor doped according to a first conductivity type and a second layer comprising a second semiconductor doped according to a second conductivity type, the first layer being disposed between the first substrate and the second substrate, then b) securing the stack against a second substrate such that the stack is disposed between the first substrate and the second substrate, then c) removing the first substrate, then d) etching the first layer such that a remaining portion of the first layer forms a front gate of the first JFET transistor, then e) etching the second layer such that a remaining portion of the second layer is disposed below the front gate of the first JFET transistor and forms the channel, the source and the drain of the JFET transistor.

A bonding wafer structure includes a support substrate, a bonding layer, and a silicon carbide (SiC) layer. The bonding layer is formed on a surface of the support substrate, and the SiC layer is bonded onto the bonding layer, in which a carbon surface of the SiC layer is in direct contact with the bonding layer. The SiC layer has a basal plane dislocation (BPD) of 1,000 ea/cm.sup.2 to 20,000 ea/cm.sup.2, a total thickness variation (TTV) greater than that of the support substrate, and a diameter equal to or less than that of the support substrate. The bonding wafer structure has a TTV of less than 10 μm, a bow of less than 30 μm, and a warp of less than 60 μm.

The present application provides a process of surface treatment of a silicon-on-insulator (SOI) wafer comprising: providing a SOI wafer comprising a back substrate, a top silicon layer and an insulating buried layer, wherein the insulating buried layer is located between the back substrate and the top silicon layer, and the top silicon layer has a surface roughness of larger than 10 Å; conducting a first planarization to a surface of the top silicon layer by conducting a batch annealing process at a first target temperature, and conducting a second planarization to a surface of the top silicon layer by conducting a rapid thermal annealing process at a second target temperature. The present application combines the batch annealing process and the rapid thermal annealing process to optimize the SOI wafer, especially the surface roughness of the SOI wafer. The SOI wafer planarized by the two thermal annealing processes has a good surface roughness of the top silicon layer which satisfies process requirements.

Embodiments herein describe techniques for a semiconductor device including a carrier wafer, and an integrated circuit (IC) formed on a device wafer bonded to the carrier wafer. The IC includes a front end layer having one or more transistors at front end of the device wafer, and a back end layer having a metal interconnect coupled to the one or more transistors. One or more gaps may be formed by removing components of the one or more transistors. Furthermore, the IC includes a capping layer at backside of the device wafer next to the front end layer of the device wafer, filling at least partially the one or more gaps of the front end layer. Moreover, the IC includes one or more air gaps formed within the one or more gaps, and between the capping layer and the back end layer. Other embodiments may be described and/or claimed.

Methods of forming SOI substrates are disclosed. In some embodiments, an epitaxial layer and an oxide layer are formed on a sacrificial substrate. An etch stop layer is formed in the epitaxial layer. The sacrificial substrate is bonded to a handle substrate at the oxide layer. The sacrificial substrate is removed. The epitaxial layer is partially removed until the etch stop layer is exposed.

A manufacturing method of a semiconductor device includes at least the following steps. A sacrificial substrate is provided. An epitaxial layer is formed on the sacrificial substrate. An etch stop layer is formed on the epitaxial layer. Carbon atoms are implanted into the etch stop layer. A capping layer and a device layer are formed on the etch stop layer. A handle substrate is bonded to the device layer. The sacrificial substrate, the epitaxial layer, and the etch stop layer having the carbon atoms are removed from the handle substrate.

Various embodiments of the present application are directed towards a method for forming a semiconductor-on-insulator (SOI) substrate with a thick device layer and a thick insulator layer. In some embodiments, the method includes forming an insulator layer covering a handle substrate, and epitaxially forming a device layer on a sacrificial substrate. The sacrificial substrate is bonded to a handle substrate, such that the device layer and the insulator layer are between the sacrificial and handle substrates, and the sacrificial substrate is removed. The removal includes performing an etch into the sacrificial substrate until the device layer is reached. Because the device layer is formed by epitaxy and transferred to the handle substrate, the device layer may be formed with a large thickness. Further, because the epitaxy is not affected by the thickness of the insulator layer, the insulator layer may be formed with a large thickness.