Coating processes – Direct application of electrical – magnetic – wave – or... – Pretreatment of substrate or post-treatment of coated substrate
Reexamination Certificate
1999-03-31
2001-03-06
Beck, Shrive (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Pretreatment of substrate or post-treatment of coated substrate
C427S535000, C427S488000, C427S064000, C216S104000, C216S049000
Reexamination Certificate
active
06197388
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of electronic devices. More particularly, the present invention relates to improved techniques for preventing the corrosion of an aluminum neodymium-containing layer during the manufacture of electronic devices.
In the manufacture of certain types of electro nic devices such as flat panel displays and the like, an aluminum neodymium-containing layer may be employed. Aluminum neodymium is the material of choice for manufacturing these devices due to its superior chemical and physical properties. But as with all aluminum alloys, corrosion remains a significant problem in the processing of aluminum neodymium in spite of its superior material characteristics.
Aluminum neodymium is generally etched with chlorine which results in residual chlorine adhering to the etch surface. When this etch surface comes in contact with the atmosphere, the residual chlorine reacts with moisture in the air to form hydrochloric acid. This hydrochloric acid eats away at the metal, which results in corrosion of that metal. The fundamental approach to resolving this problem is to remove the residual chlorine to prevent the formation of corrosive substances such as hydrochloric acid. Conventionally, this is accomplished by the use of a gas chemistry having CF
4
and oxygen. However, when CF
4
and O
2
are applied to prevent corrosion of aluminum neodymium, the high chlorine content in conjunction with the high ion energy required for the processing of this sturdy material requires a high ion energy level during removal of the residual chlorine. This in turn results in severe damage to the photoresist layer, which is an undesired side effect of the corrosion prevention process. Photoresist damage usually translates into hardened photoresist fragments on the substrate surface, which is harder to strip off in the later step of the manufacturing process. It is believed that high ion energy is necessary to remove the residual chlorine because high ion energy is used in the main etch, which results in the chlorine ions being embedded further in the etched surface than a conventional process where lower ion energy is used.
FIG. 1
illustrates the corrosion problem occurring in an exemplary layer stack
100
. Layer stack
100
has an aluminum neodymium-containing layer
102
disposed above a substrate
104
, which may be, by way of example, glass. It should also be noted that the devices of the figures shown herein are depicted in a simplified format for illustration purposes only. There may be present other additional layers above, below, or in between the layers shown. Further, not all of the shown layers need necessarily be present and some or all may be substituted by other different layers. The layers of the devices shown and discussed herein are readily recognizable to those skilled in the art and may be formed using any of a number of suitable and known deposition processes, including chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and a physical vapor deposition (PVD), such as sputtering.
An optional molybdenum layer
106
is disposed above aluminum neodymium-containing layer
102
and below a photoresist layer
108
. Molybdenum layer
106
is not essential to the invention, but is included to show an example of a corrosion problem where an aluminum neodymium-containing layer is contained within a sandwich structure. A sandwich structure, for example, an aluminum neodymium-containing layer encapsulated in refractory metals such as molybdenum, is typically used to prevent hillock formation that might occur during processing steps and device operation. A refractory metal is a metal having an extremely high melting point, for example, tungsten, molybdenum, tantalum, niobium, and chromium, vanadium, and rhenium. In a broad sense, this term refers to metals having melting points above the range for iron, cobalt, and nickel. However, sandwich structures are often very prone to corrosion, in fact, the severity of corrosion problems in a sandwich structure is greater by orders of magnitude compared to the corrosion problem of an aluminum neodymium-containing layer that is not within a sandwich structure.
The chlorine component in the etchant gas chemistry adheres to the etched surface
110
and forms hydrochloric acid when it comes in contact with moisture in the air. The hydrochloric acid reacts with the aluminum neodymium-containing layer to cause corrosion as shown in exposed portion
112
of aluminum neodymium-containing layer
102
.
FIG. 2
illustrates the situation where an exemplary layer stack
200
having an aluminum neodymium-containing layer
202
disposed below an optional molybdenum layer
204
and above a substrate
206
is treated by the traditional method of using CF
4
and O
2
to prevent corrosion. While corrosion is successfully prevented, the process has the unfortunate side effect of severely degrading the photoresist layer
208
. Severe degradation of photoresist layer
208
may cause unwanted hardening of the photoresist material, which makes subsequent removal of photoresist layer
208
very difficult. Moreover, some of the hardened resist may deposit on sidewalls and other areas, masking certain regions that were designated to be unmasked for the purpose of etching, which causes the formation of jagged sidewalls
210
along aluminum neodymium-containing layer
202
and molybdenum layer
204
as well as severe residue problems.
In view of the foregoing, what are desired are improved methods for preventing corrosion in an aluminum neodymium-containing layer. These improved techniques preferably would prevent corrosion along the etched surface of the aluminum neodymium-containing layer while avoiding problems such as severe degradation of the photoresist layer which might lead to other serious problems.
SUMMARY OF THE INVENTION
The invention relates, in one embodiment, to a method for preventing post-etch corrosion in an etch surface of an aluminum neodymium-containing layer. The method includes providing a first gas chemistry having HBr and SF
6
which supplies the fluorine ions, forming a first plasma with the first gas chemistry, and passivating the etch surface of the aluminum neodymium-containing layer with the first plasma to cause at least some of the fluorine ions to replace at least some of the residual chlorine proximate to the etch surface. The method further includes providing a second gas chemistry having hydrofluorocarbon, forming a second plasma with the second gas chemistry; and depositing a polymer material using the second plasma to coat the etch surface of the aluminum neodymium-containing layer.
In another embodiment, the invention relates to a method of processing a substrate having an aluminum neodymium-containing layer having residual chlorine proximate to an etch surface of the aluminum neodymium-containing layer. The method includes providing a first gas chemistry including HBr and SF
6
which supplies a first plurality of fluorine ions, forming a first plasma from said first gas chemistry, passivating the etch surface of the aluminum neodymium-containing layer with the first plasma to cause a second plurality of fluorine ions to replace a first portion of the residual chlorine. This second plurality of fluorine ions is a subset of the first plurality of fluorine ions. The method further includes providing a second gas chemistry having hydrofluorocarbon and oxygen which provides a third plurality of fluorine ions, forming a second plasma with the second gas chemistry, bombarding the etch surface of the aluminum neodymium-containing layer with the second plasma, causing a fourth plurality of fluorine ions to replace a second portion of the residual chlorine. This fourth plurality of fluorine ions is a subset of the third plurality of fluorine ions. The method additionally includes depositing a polymer material using a third plasma formed from a hydrofluorocarbon gas chemistry to coat the etch surface of the aluminum neodymium-containing layer.
In yet ano
Choi Thomas S.
Holland John P.
Tran Nancy
Beck Shrive
Beyer Weaver & Thomas LLP
Chen Bret
Lam Research Corporation
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