SELECTIVE ETCH OF HIGH-K DIELECTRIC MATERIAL

• US 20090258502A1
• Filed: 04/10/2009
• Published: 10/15/2009
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: LIU, Shenjian, FU, Qian, LEE, Wonchul, BAE, In Deog
• Granted Patent: US 8,124,538 B2
• Time in Patent Office: Days
• US Class Current: 438/719
• CPC Class Codes: H01L 21/31122 of layers not containing Si, e.g. PZT, Al2O3

Abstract

A method for selectively etching a high-k dielectric layer with respect to a polysilicon material is provided. The high-k dielectric layer is partially removed by Ar sputtering, and then the high-k dielectric layer is etched using an etching gas comprising BCl₃. The high-k dielectric layer and the polysilicon material may be formed on a substrate. In order to partially remove the high-k dielectric layer, a sputtering gas containing Ar is provided into an etch chamber in which the substrate is placed, a plasma is generated from the sputtering gas, and then the sputtering gas is stopped. In order to etch the high-k dielectric layer, the etching gas is provided into the etch chamber, a plasma is generated from the etching gas, and then the etching gas is stopped.

Claims

1. A method for selectively etching a high-k dielectric layer with respect to a polysilicon material, comprising:

partially removing the high-k dielectric layer by Ar sputtering; and

etching the high-k dielectric layer using an etching gas comprising BCl₃.

2. The method as recited in claim 1, wherein the high-k dielectric layer and the polysilicon material are formed on a substrate, the partially removing comprising:

providing a sputtering gas into an etch chamber in which the substrate is placed, the sputtering gas comprising Ar;

generating a plasma from the sputtering gas to partially remove the high-k dielectric layer; and

stopping the sputtering gas.

3. The method as recited in claim 2, wherein the etching the high-k dielectric layer comprises:

providing the etching gas into the etch chamber;

generating a plasma from the etching gas to etch the high-k dielectric layer; and

stopping the etching gas.

4. The method as recited in claim 2, wherein the sputtering gas is free of chemical etch gases,

5. The method as recited in claim 2, wherein the sputtering gas is free of Cl, HBr, and F.

6. The method as recited claims 2, wherein the sputtering gas is pure Ar.

7. The method as recited in claim 1, wherein the partially removing the high-k dielectric layer by Ar sputtering provides a high selectivity of the high-k dielectric to the polysilicon material of about 2 to 20.

8. The method as recited in claim 7, wherein the partially removing the high-k dielectric layer by Ar sputtering provides a high selectivity of the high-k dielectric to the polysilicon material of about 5 to 20.

9. The method as recited in claims 1, wherein the high-k dielectric layer is a metal oxide layer.

10. The method as recited in claim 1, wherein the high-k dielectric layer is formed over a patterned polysilicon layer, a second polysilicon layer being formed over the high-k dielectric layer, the method further comprising:

exposing the high-k dielectric layer to be etched by etching the second polysilicon layer.

11. A method for selectively etching a high-k dielectric layer in a stack of layers with respect to a polysilicon material, the stack including a patterned first polysilicon layer formed on a substrate, the high-k dielectric layer formed over the first polysilicon layer, and a second polysilicon layer formed over the high-k dielectric layer, the method comprising:

etching the second polysilicon layer through a mask with mask features having a dense area and an isolated area; and

selectively etching, through the mask, the high-k dielectric layer with respect to the patterned polysilicon layer, including;

partially removing the high-k dielectric layer by Ar sputtering; and

further etching the high-k dielectric layer using an etching gas comprising BCl₃,

wherein combination of the partially removing by Ar sputtering and the further etching using the etch gas reduces micro loading with respect to the dense area and the isolated area.

12. The method as recited in claim 11, wherein the stack of layers further includes a contact layer formed on the second polysilicon layer, the mask being formed on the contact layer.

13. The method as recited in claim 11, wherein the first polysilicon layer is also removed through the mask features during the selectively etching of the high-k dielectric layer.

14. The method as recited in claim 13, wherein an oxide layer is formed on the substrate below the first polysilicon layer, the selectively etching of the high-k dielectric layer removing the first polysilicon layer through the mask features and leaving the oxide layer on the substrate.

15. An apparatus for selectively etching a high-k dielectric layer with respect to a polysilicon material, comprising:

a plasma processing chamber, comprising;

a chamber wall forming a plasma processing chamber enclosure;

a substrate support for supporting a substrate within the plasma processing chamber enclosure;

a pressure regulator for regulating the pressure in the plasma processing chamber enclosure;

at least one electrode for providing power to the plasma processing chamber enclosure for sustaining a plasma;

a gas inlet for providing gas into the plasma processing chamber enclosure; and

a gas outlet for exhausting gas from the plasma processing chamber enclosure;

a gas source in fluid connection with the gas inlet, comprising;

a sputtering gas source; and

a high-k dielectric etching gas source;

a controller controllably connected to the gas source and the at least one electrode, comprising;

at least one processor; and

computer readable media comprising;

computer readable code for selectively etching the high-k dielectric layer with respect to the polysilicon material, comprising;

computer readable code for providing an Ar sputtering gas from the sputtering gas source;

computer readable code for generating a plasma from the sputtering gas to partially remove the high-k dielectric layer;

computer readable code for stopping the sputtering gas;

computer readable code for providing an etching gas from the high-k dielectric etching gas source;

computer readable code for generating a plasma from the etching gas to etch the high-k dielectric layer; and

computer readable code for stopping the etching gas.