MTJ read head with sidewall spacers
View Patent ↗Following CMP, a magnetic tunnel junction stack may protrude through the oxide that surrounds it, making it susceptible to possible shorting to its sidewalls. The present invention overcomes this problem by depositing silicon nitride spacers on these sidewalls prior to oxide deposition and CMP. So, even though the stack may protrude through the top surface of the oxide after CMP, the spacers serve to prevent possible later shorting to the stack.
1. A magnetic tunnel junction stack having a cap with sidewalls and a top surface, comprising:
a layer of silicon oxide, having a top surface, surrounding said magnetic tunnel junction stack;
said cap protruding a distance above said silicon oxide top surface;
silicon nitride spacers that surround said cap, located between said sidewalls and said silicon oxide layer, said silicon nitride spacers being in contact with both the cap and the silicon oxide;
said silicon nitride spacers having a thickness that increases from zero at said cap top surface to a maximum of about 0.1 microns where it is below said silicon oxide top surface; and
whereby said silicon nitride spacers prevent shorting to said cap layer during operation of said magnetic tunnel junction stack.
2. The magnetic tunnel junction stack described in claim 1 wherein said layer of silicon oxide has a thickness between about 600 and 1,000 Angstroms.
3. The magnetic tunnel junction stack described in claim 1 wherein said cap top surface is between about 200 and 400 Angstroms above said silicon oxide top surface.
4. A magnetic tunnel junction stack having a cap with sidewalls and a top surface, comprising:
a layer of silicon oxide, having a top surface, surrounding said magnetic tunnel junction stack;
said cap protruding a distance above said silicon oxide top surface;
silicon nitride spacers that surround said cap, located between said sidewalls and said silicon oxide layer, said silicon nitride spacers being in contact with all of said sidewalls and with the silicon oxide;
said silicon nitride spacers having a uniform thickness of between about 500 and 1,000 Angstroms; and
whereby said silicon nitride spacers prevent shorting to said cap layer during operation of said magnetic tunnel junction stack.
5. The magnetic tunnel junction stack described in claim 4 wherein said layer of silicon oxide has a thickness between about 600 and 1,000 Angstroms.
6. The magnetic tunnel junction stack described in claim 4 wherein said cap top surface is between about 200 and 400 Angstroms above said silicon oxide top surface.