MTJ read head with sidewall spacers
AssigneesHeadway Technologies, Inc., Applied Spintronics, Inc.
InventorLin Yang
Life of this patent
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Abstract
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.
Claims18
A process to manufacture a magnetic tunnel junction stack that is free of shorting problems that arise from MTJ cap protrusion after CMP, comprising:
- forming a magnetic tunnel junction stack, having sidewalls and a cap layer, on a substrate;
- using a first conformal deposition method, depositing a layer of silicon nitride on said stack and on said substrate;
- anisotropically etching said layer of silicon nitride until said cap layer is fully exposed, thereby forming spacers on said MTJ sidewalls;
- using a second conformal deposition method, depositing a layer of silicon oxide, having a surface, on all exposed surfaces to form a structure;
- and
- by means of a CMP process that selectively removes silicon oxide at a faster rate than silicon nitride and tantalum, planarizing said structure until said cap layer and spacers protrude above said silicon oxide surface.
A process to manufacture a magnetic tunnel junction stack that is free of shorting problems that arise from MTJ cap protrusion after CMP, comprising:
- forming a magnetic tunnel junction stack, having sidewalls and a cap layer, on a substrate;
- using a first conformal deposition method, depositing a layer of silicon nitride on said stack and on said substrate;
- using a second conformal deposition method, depositing a first layer of silicon oxide on said layer of silicon nitride;
- anisotropically etching said first layer of silicon oxide until said layer of silicon nitride is reached, thereby forming spacers on vertical portions of said layer of silicon nitride;
- then, using said silicon oxide spacers as a hard mask, selectively removing all exposed silicon nitride thereby forming said silicon nitride layer into opposing L-shaped spacers on said MTJ sidewalls;
- using said second conformal deposition method, depositing a second layer of silicon oxide, having a surface, on all exposed surfaces to form a structure;
- and
- by means of a CMP process that selectively removes silicon oxide at a faster rate than silicon nitride and tantalum, planarizing said structure until said cap layer and L-shaped spacers protrude above said silicon oxide surface.
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 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 spacers being in contact with both the cap and the silicon oxide;
- said 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.
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 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 spacers being in contact with all of said sidewalls and with the silicon oxide;
- said 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.
Dependencies are inferred from the claim text.