Method for fabricating a semiconductor device with a high-K dielectric
Method for fabricating semiconductor devices with high-K materials without the presence of undesired formations of the high-K material. A preferred embodiment comprises forming a layer of material over a layer of a high-K material, etching the layer of material to expose a portion of the high-K material, performing a CDE (Chemical Downstream Etch) to remove any residual material formed during the etching, and etching the layer of the high-K material into alignment with remaining portions of the layer of material. The removal of the residual material results in a predictable trimming of the high-K material so that the semiconductor device has predictable and consistent performance, which is not possible if the high-K material has unpredictable dimensions.
1 . A method for fabricating a semiconductor device, the method comprising:
forming a layer of material over a layer of a high-K material;
etching the layer of material to expose a portion of the high-K material;
performing a chemical downstream etch thereby removing any residual material formed during the etching; and
etching the layer of the high-K material in alignment with remaining portions of the layer of material.
2 . The method of claim 1 , wherein the etching the layer of material comprises etching a polysilicon layer using a reactive ion etch.
3 . The method of claim 1 , wherein the chemical downstream etch comprises a plasma etch utilizing a combination gas comprised of oxygen and at least one gas selected from the group consisting of tetrafluoromethane (CF 4 ), octafluorocyclobutane (C 4 F 8 ), and trifluoromethane (CHF 3 ).
4 . The method of claim 3 , wherein the combination gas is injected in an oxygen-to-tetrafluoromethane gas ratio of approximately 13.5 at a pressure of about 28 Pa and a gas-to-plasma energizing power source of approximately 700 Watts for about 180 seconds.
5 . The method of claim 1 , wherein the chemical downstream etch comprises a plasma etch utilizing a gas including oxygen (O 2 ) and tetrafluoromethane (CF 4 ).
6 . The method of claim 5 , wherein the gas is injected in an oxygen-to-tetrafluoromethane gas ratio ranging from about 10 to about 30.
7 . The method of claim 6 , wherein the chemical downstream etch is performed at a temperature in the range of about 50 to about 70 degrees Celsius.
8 . The method of claim 6 , wherein the chemical downstream etch is performed for a duration that is greater than about 60 seconds.
9 . The method of claim 6 , wherein a microwave power source is used to energize the gas into the plasma, and wherein the power source is greater than about 200 Watts.
10 . The method of claim 1 , wherein etching the layer of the high-K material comprises performing a diluted hydrofluoric acid clean.
11 . The method of claim 10 , wherein forming a layer of material comprises depositing a layer of polysilicon.
12 . A method of forming a transistor device, the method comprising:
forming a gate dielectric over a semiconductor body, an upper surface of the gate dielectric layer comprising a high-K dielectric material;
forming a conductive layer over the gate dielectric;
performing a first etch to pattern the conductive layer into a gate electrode;
performing a second etch to remove any residual material formed along sidewalls of the gate electrode during the etching; and
performing a third etch to pattern the gate dielectric layer in alignment with the gate electrode, wherein the first etch, the second etch and the third etch comprise separate etching processes.
13 . The method of claim 12 , wherein the second etch comprises a chemical downstream etch that is performed with a plasma.
14 . The method of claim 13 , wherein the second etch uses a combination gas comprised of oxygen (O 2 ) and tetrafluoromethane (CF 4 ).
15 . The method of claim 12 , wherein forming a gate dielectric layer comprises forming an oxide layer over the semiconductor body and forming a high-K dielectric layer over the oxide layer.
16 . The method of claim 15 , wherein the high-K dielectric layer comprises NO x or HfO 2 .
17 . A method of making a transistor device, the method comprising:
forming a gate dielectric over a semiconductor body;
forming a conductive layer over the gate dielectric;
etching the conductive layer to form a gate electrode;
performing a chemical downstream etch to remove any residual material formed along sidewalls of the gate electrode during the etching; and
etching the gate dielectric layer in alignment with the gate electrode, the etching of the gate dielectric layer being performed in a separate process than the chemical downstream etch.
18 . The method of claim 17 , wherein the gate dielectric comprises a high-K dielectric.
19 . The method of claim 18 , wherein performing a chemical downstream etch comprises performing a plasma etch using a combination gas comprised of oxygen (O 2 ) and tetrafluoromethane (CF 4 ).
20 . The method of claim 18 , further comprising forming source/drain regions in the semiconductor body adjacent to edges of the gate electrode.