Flash memory cell with drain and source formed by diffusion of a dopant from a silicide
View Patent ↗The present invention is a flash memory manufacturing process that facilitates efficient fabrication of a flash memory cell. In one embodiment, a silicide (e.g., CoSi) is utilized as a diffusion source. A layer of silicide is deposited over a source area and drain area. The dopant is implanted into the CoSi and diffuse out conformably along CoSi-Si interface at a relatively low temperature. The low temperature diffusion facilitates fabrication of a Flash core cell with a very shallow source/drain junction, and as a result a robust DIBL. The present invention also facilitates fabrication of memory cells with smaller spacers and shorter gate length.
1. A memory cell comprising:
a control gate component having a capacity to receive a charge;
an oxide region having electrical charge insulation characteristics and electrical charge penetration characteristics, said oxide region coupled to said control gate;
a floating gate having a charge trapping region, said floating gate coupled to said oxide region;
a well component having a charge doping characteristic, said well coupled to said floating gate component;
a source component having opposite charge doping characteristics formed by implantation of a dopant and diffusion of said dopant from a silicide in a source metal contact region, said source component coupled to said well component; and
a drain component having similar doping charge characteristics to said source component and formed by implantation of a dopant and diffusion of said dopant from said silicide in a drain metal contact region, said drain component coupled to said well component.
2. The memory cell of claim 1 wherein said source and drain form shallow junctions.
3. The memory cell of claim 1 wherein some of said dopant is trapped in said silicide layer during an implantation of dopants in said source and drain areas.
4. The memory cell of claim 1 wherein said diffusion is performed in a temperature range of about 600 to 800 Celsius.
5. The memory cell of claim 1 wherein said silicide includes cobalt silicide.
6. The memory cell of claim 1 wherein said dopant includes arsenic.
7. The memory cell of claim 1 further comprising sidewall spacers that have a thickness of about 50 Å to about 800 Å, wherein said silicide is deposited between a pair of said sidewall spacers.