Method for etching reliable small contact holes with improved profiles for semiconductor integrated circuits using a carbon doped hard mask
First Claim
1. A method for fabricating improved contact holes in an interlevel dielectric (ILD) layer on a semiconductor substrate for integrated circuits, comprising the steps of:
- providing a semiconductor substrate having partially completed device structures including a patterned electrically conducting layer;
depositing said interlevel dielectric (ILD) layer on said electrically conducting layer;
depositing a polysilicon layer on said interlevel dielectric (ILD) layer;
ion implanting carbon in said polysilicon layer to form a carbon doped polysilicon layer;
forming a patterned photoresist layer having openings on said carbon doped polysilicon layer for said contact holes;
anisotropic plasma etching openings in said carbon doped polysilicon layer to said interlevel dielectric (ILD) layer in said openings of said photoresist;
anisotropically plasma etching using said carbon doped polysilicon layer as a hard mask to etch said contact openings in said interlevel dielectric layer to said electrically conducting layer, whereby said carbon atoms released from said carbon doped polysilicon layer during said etching, minimizes contamination buildup in said contact openings and increases the etch rate of said interlevel dielectric layer;
removing said photoresist layer;
annealing in an oxidizing atmosphere and converting said polysilicon hard mask to a silicon oxide layer;
blanket anisotropic plasma etching to remove any oxide formed on said conductive layer exposed in said contact holes;
cleaning any residual carbon atoms from the surface of said silicon oxide layer by wet etching, and completing said interlevel dielectric (ILD) layer having said improved contact holes.
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Accused Products
Abstract
A method is achieved for fabricating small contact holes in an interlevel dielectric (ILD) layer for integrated circuits. The method increases the ILD etch rate while reducing residue build-up on the contact hole sidewall. This provides a very desirable process for making contact holes small than 0.25 um in width. After depositing the ILD layer over the partially completed integrated circuit which includes patterned doped first polysilicon layers, a second polysilicon layer is deposited and doped with carbon by ion implantation. A photoresist mask is used to etch openings in the carbon doped polysilicon layer to form a hard mask. The photoresist is removed, and the contact holes are plasma etched in the ILD layer while free carbon released from the hard mask, during etching, reduces the free oxygen in the plasma. This results in an enhanced fluorine (F+) etch rate for the contact holes in the ILD layer and reduces the residue build-up on the sidewalls of the contact holes. The hard mask is anneal in O2 to form an oxide layer and any surface carbon is removed in a wet etch. Reliable metal plugs can now be formed by depositing a barrier layer, such as titanium (Ti) or titanium nitride (TiN) and a metal such as tungsten (W) and etching back or chemical/mechanical polishing back to the oxide layer.
101 Citations
22 Claims
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1. A method for fabricating improved contact holes in an interlevel dielectric (ILD) layer on a semiconductor substrate for integrated circuits, comprising the steps of:
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providing a semiconductor substrate having partially completed device structures including a patterned electrically conducting layer; depositing said interlevel dielectric (ILD) layer on said electrically conducting layer; depositing a polysilicon layer on said interlevel dielectric (ILD) layer; ion implanting carbon in said polysilicon layer to form a carbon doped polysilicon layer; forming a patterned photoresist layer having openings on said carbon doped polysilicon layer for said contact holes; anisotropic plasma etching openings in said carbon doped polysilicon layer to said interlevel dielectric (ILD) layer in said openings of said photoresist; anisotropically plasma etching using said carbon doped polysilicon layer as a hard mask to etch said contact openings in said interlevel dielectric layer to said electrically conducting layer, whereby said carbon atoms released from said carbon doped polysilicon layer during said etching, minimizes contamination buildup in said contact openings and increases the etch rate of said interlevel dielectric layer; removing said photoresist layer; annealing in an oxidizing atmosphere and converting said polysilicon hard mask to a silicon oxide layer; blanket anisotropic plasma etching to remove any oxide formed on said conductive layer exposed in said contact holes; cleaning any residual carbon atoms from the surface of said silicon oxide layer by wet etching, and completing said interlevel dielectric (ILD) layer having said improved contact holes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for fabricating an interlevel dielectric (ILD) layer having improved metal plug contacts on a semiconductor substrate for integrated circuits, comprising the steps of:
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providing a semiconductor substrate having partially completed device structures including a patterned electrically conducting layer; depositing said interlevel dielectric (ILD) layer on said electrically conducting layer; depositing a polysilicon layer on said interlevel dielectric (ILD) layer; ion implanting carbon in said polysilicon layer to form a carbon doped polysilicon layer; forming a patterned photoresist layer having openings on said carbon doped polysilicon layer for said contact holes; anisotropic plasma etching openings in said carbon doped polysilicon layer to said interlevel dielectric (ILD) layer in said openings of said photoresist; anisotropically plasma etching using said carbon doped polysilicon layer as a hard mask to etch said contact openings in said interlevel dielectric layer to said electrically conducting layer, whereby said carbon released from said carbon doped polysilicon layer, during said etching, minimizes contamination buildup in said contact openings and increases the etch rate of said insulating layer; removing said photoresist layer; annealing in an oxidizing atmosphere and converting said polysilicon hard mask to a silicon oxide layer; blanket anisotropic plasma etching to remove any oxide formed on said conductive layer exposed in said contact holes; cleaning any residual carbon atoms from the surface of said silicon oxide layer by wet etching; depositing a barrier layer over and in said contact openings; forming metal plug contacts in said contact openings. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification