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US 2015/0084108 A1Published application
Transistor structure and method with an epitaxial layer over multiple halo implants
OwnerSamar Sahainventor
Life of this patent
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Abstract
A transistor structure having an epitaxial layer deposited over an implanted substrate in order to reduce process variability. The epitaxial layer is able to be deposited doped, un-doped or lightly doped via up-diffusion from the implanted substrate, and used to form the channel for the transistor structure. As a result, this use of un-doped epitaxial layer provides the benefit of reducing process variability (e.g. random dopant fluctuation) and thus the transistor performance variability despite the small physical size of the transistors.
Claims25
A transistor structure comprising:
- a first control gate;
- a semiconductor substrate doped to a first conductivity type;
- a first shallow halo implant region of the first conductivity type at a first depth in a portion of the substrate that at least partially extends under the first control gate;
- a first deep halo implant region of the first conductivity type at a second depth in a portion of the substrate that at least partially extends under the first control gate, wherein the second depth is greater than the first depth;
- an epitaxial layer formed on top of the substrate and below the first control gate;
- and
- a first source region and a first drain region both of a second conductivity type and formed in the epitaxial layer over the first shallow halo implant and the first deep halo implant and to the sides of the first control gate.
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A method of providing a transistor, the method comprising:
- forming a gate mask on a substrate having a vertical location aligned with that of a transistor control gate;
- implanting first conductivity type dopants with the gate mask as an implant mask to form a first shallow halo region;
- implanting first conductivity type dopants with at least the gate mask as an implant mask to form a first deep halo region;
- forming an epitaxial layer on top of the substrate;
- forming a control gate structure on the epitaxial layer;
- and
- forming a source region and a drain region both of a second conductivity type over the first shallow halo region and the first deep halo region.
4 more elements
Dependencies are inferred from the claim text.