Etching a substrate: processes – Gas phase etching of substrate – Application of energy to the gaseous etchant or to the...
Reexamination Certificate
1999-02-17
2002-04-09
Gulakowski, Randy (Department: 1746)
Etching a substrate: processes
Gas phase etching of substrate
Application of energy to the gaseous etchant or to the...
C216S069000, C438S720000, C438S738000, C438S742000
Reexamination Certificate
active
06368517
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention provides a method for post-etch treating a dielectric layer on a substrate in order to prevent subsequent corrosion of the dielectric layer. More specifically, the present invention provides a method for removing or inactivating corrosion-forming etch residues remaining on a dielectric layer after etching a metal layer in order to prevent subsequent corrosion of the dielectric layer.
2. Description of the Prior Art
The implementation of digital information storage and retrieval is a common application of modern digital electronics. Memory size and access time serve as a measure of progress in computer technology. Quite often storage capacitors are employed as memory array elements. As the state of the art has advanced, small-feature-size high density dynamic random access memory (DRAM) devices require storage capacitors of larger capacitance having high dielectric constant materials. High dielectric constant materials are made primarily of sintered metal oxide and are becoming attractive to provide the necessary capacitance within a limited space.
Another type of dielectric material or ferroelectric material has perovskite structures to demonstrate a hyteresis loop as voltage is applied. These ferroelectric materials such as strontium bismuth tantalate SrBi
2
Ta
2
O
9
(SBT) or lead zirconate titanate, Pb(Zr
1−x
Ti
x
)O
3
(PZT) have been used in non-volatile random access memory (NVPRAM) devices application such as RF-ID Card to fabricate a ferroelectric capacitor.
Among the available high dielectric constant materials or ferroelectric materials, the combination of the compounds barium titanate (BaTiO
3
) and strontium titanate (SrTiO
3
) (collectively typically referred to as barium strontium titanate “BST”) has been widely studied as one of the more promising high dielectric constant material. To fabricate BST capacitors, a bottom conductive layer, such as platinum, is disposed on a substrate and etched in a pattern to form bottom electrodes. Subsequently a BST layer is deposited on top of the bottom electrodes. A top conductive layer, such as platinum and/or TiN, is subsequently deposited on top of the BST layer and etched in a plasma of an etchant gas to form top electrodes. Because the etchant gas which forms the plasma for etching the top conductive layer contains halogen gases (e.g. Cl
2
, etc.) and/or halogen-based gases (e.g., BCl
3
etc), etching of the top conductive layer leaves halogen-containing residues (e.g., chlorine-containing residues) on the BST layer.
If such halogen-containing residues (regardless of their source) are not removed or inactivated from the BST layer, they will cause corrosion of the BST layer underlying the top electrodes. The BST layer possesses sufficient porosity and permeability such that halogen-containing residue on the BST layer extrudes or permeates into the BST layer from the surface thereof to cause bridging between the bottom and top electrodes. Also, halogen-containing residues may react with moisture to form an acid (e.g., hydrochloric acid) which would attack the surface of the BST layer.
Therefore, what is needed and what has been invented is a method for removing or inactivating corrosion-forming etch residues remaining on the surface of a dielectric material after etching a metal layer which is supported by the dielectric material. What is further needed and what has been invented is a method of preventing corrosion of a dielectric layer disposed on a substrate, especially after etching a contiguous metal layer in a plasma of an etchant gas containing at least one corrosive gas, such as chlorine.
SUMMARY OF THE INVENTION
The present invention provides a method of preventing corrosion of a dielectric layer disposed on a substrate comprising the steps of:
a) providing a substrate supporting a dielectric layer having a corrosive residue on a surface thereof; and
b) treating the surface of the dielectric layer of step (a) to remove the corrosive residue and prevent corrosion of the dielectric layer.
The present invention also provides a method of preventing corrosion of a dielectric layer disposed on a substrate comprising the steps of:
a) providing a substrate supporting a dielectric layer and metal layer (e.g., a platinum layer) on the dielectric layer;
b) etching the metal layer of step (a) in a plasma of an etchant gas containing at least one corrosive gas to expose a surface of the dielectric layer and cause the formation of a corrosive residue on the surface of the dielectric layer; and
c) post-etch treating the surface of the dielectric layer of step (b) to remove the corrosive residue and prevent corrosion of the dielectric layer.
The present invention further provides a method of preventing corrosion of a dielectric layer disposed on a substrate comprising the steps of:
a) providing a substrate supporting a patterned conductive layer;
b) depositing a dielectric layer on the patterned conductive layer of step (a);
c) depositing a conductive layer on the dielectric layer of step (b);
d) forming a patterned layer on the conductive layer of step (c) such as to expose part of the conductive layer;
e) etching the exposed part of the conductive layer with an etchant gas containing at least one corrosive gas to expose a surface of the dielectric layer and cause a corrosive residue to be deposited on the surface of the dielectric layer; and
f) post-etch treating the surface of the dielectric layer of step (e) to remove the corrosive residue and prevent corrosion of the dielectric layer.
The post-etched treating of the surface of the dielectric layer comprises contacting the surface of the dielectric layer with a plasma of a gas, such as a hydrogen-containing gas (e.g., water vapor (H
2
O), NH
3
, H
2
, CH
4
, H
2
O
2
and mixtures thereof). Preferably, post-etch treating of the surface of the dielectric layer includes disposing in a reactor chamber under a vacuum the substrate including the dielectric layer having the surface supporting the corrosive residue and contacting the corrosive residue on the surface of the dielectric layer with a microwave downstream hydrogen-containing gas plasma under the following process conditions:
Process
Parameters
Gas flow
50 to 10,000 sccm
Pressure, milliToor
50 to 100,000 milliToor
Microwave Power (watts)
100 to 5000 watts
Temperature
20° C. to 500° C.
Time
30 to 600 secs.
The dielectric layer comprises a ceramic or ferroelectric material, such as barium titanate (BaTiO
3
) and/or strontium bismuth tantalate (SrBi
2
Ta
2
O
9
, SBT). The dielectric layer may also include strontium titanate (SrTiO
3
) or a combination of barium titanate (BaTiO
3
) and strontium titanate (SrTiO
3
) (i.e. BST) and/or strontium bismuth tantalate (SrBi
2
Ta
2
O
9
, SBT) and/or lead zirconium titanate (Pb(Zr
1−x
Ti
x
)O
3
, PZT).
The foregoing provisions along with various ancillary provisions and features which will become apparent to those skilled in the art as the following description proceeds, are attained by the practice of the present invention, a preferred embodiment thereof shown with reference to the accompanying drawings, by way of example only, wherein:
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patent: 5269878 (1993-12-01), Page et al.
patent: 5397432 (1995-03-01), Konno et al.
patent: 5556714 (1996-09-01), Fukuyama et al.
patent: 5599424 (1997-02-01), Matsumoto et al.
patent: 5700740 (1997-12-01), Chen et al.
patent: 5744402 (1998-04-01), Fukazawa et al.
patent: 5990018 (1999-11-01), Ho et al.
patent: 6153530 (2000-11-01), Ye et al.
patent: 6162733 (2000-12-01), Obeng
patent: WO 9711482 (1997-03-01), None
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Copy of International Search Report in corresponding PCT Application No. PCT/US00/04019, mailed Aug. 29, 2000.
Chiang Kang-Lie
Hwang Jeng H.
Jin Guangxiang
Ahmed Shamim
Applied Materials Inc.
Bean Kathi
Church Shirley
Gulakowski Randy
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