Method for making tungsten metal plugs in a polymer low-K intermetal dielectric layer using an improved two-step chemical/mechanical polishing process
First Claim
1. A method for making metal plugs in an intermetal dielectric layer comprising the steps of:
- providing a semiconductor substrate having semiconductor devices and a planar insulating layer on surface of said substrate;
depositing a conducting layer on said planar insulating layer;
patterning said conducting layer to form electrical interconnections for said semiconductor devices;
depositing a planar intermetal dielectric layer over said electrical interconnections;
depositing a hard mask layer on said intermetal dielectric layer;
etching contact openings in said hard mask layer and said intermetal dielectric layer to said electrical interconnections;
depositing a conformal barrier layer on said hard mask layer and in said contact openings;
depositing a metal layer sufficiently thick to fill said contact openings and to form an planar surface;
forming metal plugs in said contact openings by a first chemical/mechanical polishing of said metal layer and said barrier layer selectively to said hard mask;
using a second chemical/mechanical polishing to remove said hard mask layer and polishing said metal plugs at a comparable polishing rate and thereby minimizing electrical shorts between adjacent said metal plugs.
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Accused Products
Abstract
A novel two-step chem/mech polishing process is described for making tungsten metal plugs in a low-k polymer intermetal dielectric (IMD) layer for ULSI circuits. Since the etch selectivity between the polymer and photoresist is low, a hard mask (SiO2) is used over the low-k IMD layer to allow contact openings to be etched in the low-k polymer. A tungsten metal is deposited and a first polishing step, having a high polishing selectivity of tungsten to SiO2, is used to form tungsten plugs. However, during the etching of the contact openings, erosion of the hard mask at the periphery of the openings is damaged and degrades the IMD, and causes residual metal between the plugs to cause intralevel shorts. To eliminate this problem, a second shorter polishing step, having a low polishing selectivity of tungsten to SiO2, is then used to remove the hard mask and remove any residual metal between adjacent metal plugs.
62 Citations
20 Claims
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1. A method for making metal plugs in an intermetal dielectric layer comprising the steps of:
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providing a semiconductor substrate having semiconductor devices and a planar insulating layer on surface of said substrate;
depositing a conducting layer on said planar insulating layer;
patterning said conducting layer to form electrical interconnections for said semiconductor devices;
depositing a planar intermetal dielectric layer over said electrical interconnections;
depositing a hard mask layer on said intermetal dielectric layer;
etching contact openings in said hard mask layer and said intermetal dielectric layer to said electrical interconnections;
depositing a conformal barrier layer on said hard mask layer and in said contact openings;
depositing a metal layer sufficiently thick to fill said contact openings and to form an planar surface;
forming metal plugs in said contact openings by a first chemical/mechanical polishing of said metal layer and said barrier layer selectively to said hard mask;
using a second chemical/mechanical polishing to remove said hard mask layer and polishing said metal plugs at a comparable polishing rate and thereby minimizing electrical shorts between adjacent said metal plugs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 20)
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11. A method for making metal plugs in an intermetal dielectric layer comprising the steps of:
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providing a semiconductor substrate having semiconductor devices and a planar insulating layer on surface of said substrate;
depositing a conducting layer on said planar insulating layer;
patterning said conducting layer to form electrical interconnections for said semiconductor devices;
depositing a planar intermetal dielectric layer composed of polymer over said electrical interconnections;
depositing a hard mask layer on said intermetal dielectric layer;
etching contact openings in said hard mask layer and said intermetal dielectric,layer to said electrical interconnections;
depositing a conformal barrier layer on said hard mask layer and in said contact openings;
depositing a tungsten metal layer sufficiently thick to fill said contact openings and to form an planar surface;
forming tungsten metal plugs in said contact openings by a first chemical/mechanical polishing of said tungsten metal layer and said barrier layer selectively to said hard mask;
using a second chemical/mechanical polishing to remove said hard mask layer and polishing said tungsten metal plugs at a comparable polishing rate and thereby minimizing electrical shorts between adjacent said metal plugs. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification