Method for etching of metal
A method of etching a metal includes performing at least two cycles of an etch process. A cycle of the etch process includes: performing a surface modification on an exposed surface of a metal layer over a substrate, performing a hydrogen treatment on the metal layer, and performing a cleaning treatment on the metal layer. The hydrogen treatment forms a layer of reaction products on the metal layer. The cleaning treatment removes the layer of reaction products.
1 . A method of etching a metal, the method comprising:
performing at least two cycles of an etch process, wherein each cycle comprises:
performing a surface modification on an exposed surface of a metal layer of a substrate, the metal layer and a dielectric layer of the substrate having a coplanar top surface;
performing a hydrogen treatment on the metal layer, wherein the hydrogen treatment forms a layer of reaction products on the metal layer; and
performing a cleaning treatment on the metal layer, wherein the cleaning treatment removes the layer of reaction products.
2 . The method of claim 1 , wherein the surface modification comprises oxidizing the exposed surface of the metal layer.
3 . The method of claim 1 , wherein the hydrogen treatment comprises exposing the metal layer to a plasma-excited H 2 gas.
4 . The method of claim 1 , wherein the cleaning treatment comprises exposing the metal layer to a plasma-excited noble gas.
5 . The method of claim 1 , wherein a first cycle of the etch process removes a thickness of 3 Å to 4 Å of the metal layer.
6 . A method of smoothing a surface, the method comprising:
providing a substrate, the substrate being planarized and containing a metal layer and a dielectric layer in the same horizontal plane, the metal layer having a rough or oxidized surface; and
performing one or more cycles of a smoothing process, wherein each cycle comprises:
exposing the rough or oxidized surface to a plasma-excited H 2 gas, wherein the plasma-excited H 2 gas chemically reduces the oxidized surface of the metal layer and forms a layer of reaction products on the metal layer; and
exposing the rough or oxidized surface to a plasma-excited Ar gas, wherein the plasma-excited Ar gas removes the layer of reaction products overlying the metal layer, wherein kinetic energy of the plasma-excited Ar gas is at or below a sputtering threshold for removing metal from the metal layer.
7 . The method of claim 6 , further comprising:
forming a mask over the metal layer, the mask exposing the rough or oxidized surface; and
after performing the one or more cycles of the smoothing process, removing the mask.
8 . The method of claim 6 , further comprising performing an etch process before performing the smoothing process, wherein a cycle of the etch process comprises:
exposing the metal layer to an oxidizing gas;
exposing the metal layer to the plasma-excited H 2 gas; and
exposing the metal layer to the plasma-excited Ar gas.
9 . The method of claim 6 , wherein the metal layer is selectively etched relative to the dielectric layer.
10 . The method of claim 9 , wherein the dielectric layer comprises SiO 2 or a high-k material.
11 . The method of claim 6 , wherein the smoothing process utilizes an inductively coupled plasma (ICP) system.
12 . The method of claim 6 , wherein the kinetic energy of the plasma-excited Ar gas is controlled by applying an RF or pulsed DC bias voltage to the substrate.
13 . The method of claim 6 , wherein the metal layer comprises copper.
14 . A method of etching a metal, the method comprising:
exposing a metal layer of a substrate to a surface modifying gas, the substrate being planarized and containing the metal layer and a dielectric layer in a same horizontal plane, the surface modifying gas oxidizing a surface of the metal layer;
exposing the metal layer to a plasma-excited H 2 gas, the plasma-excited H 2 gas chemically reducing the oxidized surface of the metal layer and forming a layer of metal-containing reaction products on the metal layer; and
exposing the metal layer to a plasma-excited Ar gas, the plasma-excited Ar gas removing the layer of metal-containing reaction products overlying the metal layer.
15 . The method of claim 14 , wherein kinetic energy of the plasma-excited Ar gas is at or below a sputtering threshold for removing metal from the metal layer.
16 . The method of claim 14 , wherein the surface modifying gas comprises a plasma-excited O 2 gas.
17 . The method of claim 16 , wherein kinetic energy of the plasma-excited O 2 gas is at or below a sputtering threshold for removing metal from the metal layer.
18 . The method of claim 14 , wherein the metal layer is selectively etched relative to the dielectric layer.
19 . The method of claim 6 , wherein the smoothing process utilizes a rotating DC magnetic field system.
20 . The method of claim 14 , wherein the metal layer is a copper (Cu) metal layer.