Etching a substrate: processes – Nongaseous phase etching of substrate – Projecting etchant against a moving substrate or controlling...
Reexamination Certificate
2000-04-20
2002-06-04
Stinson, Frankie L. (Department: 1746)
Etching a substrate: processes
Nongaseous phase etching of substrate
Projecting etchant against a moving substrate or controlling...
C134S002000, C134S031000, C134S033000, C134S036000, C134S037000, C134S902000
Reexamination Certificate
active
06398975
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to a method of localized liquid treatment of the surface of a substrate, like cleaning or etching. The invention is also related to an apparatus used to perform said treatment. Application of the invention is possible in a number of wet processing steps which are frequently used, e.g. in the fabrication of integrated circuits or liquid crystal displays.
BACKGROUND OF THE INVENTION
In the fabrication of micro-electronic devices such as integrated circuits or liquid crystal displays, a substrate has to go through a number of fabrication steps, including wet etching, wet cleaning or rinsing.
In the documents U.S. Pat. No. 5,271,774 and Japanese Patent JP-A-07211686, methods are described to remove a liquid from the surface of a substrate by applying a gaseous substance to the substrate, which, when mixed with the liquid, reduces the surface tension of the liquid, so that it can be easily removed from the surface by a centrifugal force, i.e. by subjecting the substrate to a rotary movement. However, these methods are only applicable to the substrate a whole, and cannot be used for local treatment of the substrate. Document EP-A-817246 is describing an apparatus and method for wet cleaning or etching of flat substrate surfaces, whereby a substrate is moved through a stationary amount of liquid. This method is also related to a treatment of the substrate as a whole, not of a local zone of said substrate.
During some processing steps, an annular edge area of the substrate is treated, for example for the removal of certain layers, like a resist or a metal film (e.g. Cu). Sometimes, it is only the outer rim of the substrate which is treated, while the top and bottom surfaces of the substrate must remain untouched.
Techniques exist whereby a beam of liquid is directed to the edge area or the rim of a rotating substrate in order to perform these process steps. However these existing techniques offer a poor protection of the substrate surface against the cleaning liquid. It would therefore be advantageous to find a way of protecting the substrate surface while treating said annular edge area or its outer rim with a liquid. Another disadvantage of existing techniques is that the rotational speed of the substrate during processing must be relatively high, which is particularly problematic for large substrates.
Some processing steps require the removal of larger sized features from the substrate surface, e.g. for revealing underlying zero markers, which are used for the accurate lateral positioning during processing, e.g., during photographic exposure. Although the definition of the zero markers themselves requires high accuracy, the accuracy requirements of the window for removing a layer on top of the zero markers can be fairly relaxed. So far in the state of the art, the use of a photo resist step is mostly used to accomplish these areas. By using a photo resist step, a patterned protective resist layer is obtained on the substrate surface. The pattern is such that the areas to be etched are not covered with resist. After this, the substrate is etched and the photo resist layer is removed. This is however an expensive and time-consuming effort.
An alternative way of producing such larger sized areas which are free of film, consists of a local shielding by shielding plates during film deposition. However, this technique leads to an increased risk of particle contamination and scratch formation on the substrate. Furthermore, this shielding technique is not generally applicable. It requires compatibility of the shielding plates with the deposition process of interest. To produce these larger sized features, it would therefore be advantageous to find a method that allows less accuracy but lower cost and higher processing speed, without creating any particle contamination.
Document JP-A-11166882 describes a pre-concentration or collection technique, used in contamination measurements for semi-conductors. It is a technique, whereby a droplet is moved over the substrate surface, in order to collect contaminants and subsequently analyze their concentrations. Currently, this technique is mainly used on silicon surfaces, by rendering the surface hydrophobic by way of an HF-treatment. This way, the water-based droplet is contained. The technique is however not confined to silicon surfaces. In some cases, it has been observed that the contact angle between the droplet and the substrate surface is insufficient. Furthermore, it would be advantageous to find a method whereby, in the case of silicon surfaces, the extra processing step of providing an HF-treatment would become unnecessary.
Document U.S. Pat. No. 5,492,566 describes a way of holding a substrate to a flat surface by way of the Bernoulli effect. By supplying a gas at a high speed between said substrate and said surface through an annular nozzle, a pressure drop will result, under said substrate, thus holding said substrate to said surface. Substrates held in this way can be subjected to various wet treatment steps, like cleaning or etching. However, a danger exists of liquid attaching itself to the rim or the backside of the substrate.
SUMMARY OF THE INVENTION
The present invention relates to a method of dispensing liquid on a part of a substrate for processing of the substrate, e.g. for cleaning or etching purposes, while another part of said substrate is prevented from contacting said liquid, said method comprising the steps of:
supplying a liquid on a part of said substrate; and
simultaneously with said step of supplying a liquid, supplying a gaseous tensio-active substance to a surface, said gaseous substance being at least partially miscible with said liquid and when mixed with said liquid yielding a mixture having a surface tension lower than that of said liquid.
A first embodiment of the invention is a method wherein said substrate is circular shaped,
wherein the step of supplying a liquid on a part of said substrate includes supplying at least one stream of a liquid so that said stream hits a flat surface of said substrate in an area of said surface, said area being adjacent to an outer rim of said substrate,
wherein the step of supplying a gaseous tensio-active substance to said surface includes supplying at least one stream of a gaseous tensio-active substance to the flat surface of said substrate so that said stream hits said surface in an area which is adjacent to the area hit by said liquid stream, and closer to the center of rotation, and
further comprising the step of:
rotating the circular shaped substrate about an axis of rotation, preferably in a horizontal plane, the axis being perpendicular to the substrate surface and through a center of gravity said substrate.
An additional stream of liquid may be supplied to the opposite surface of said substrate, in order to treat the whole of said opposite surface.
According to another embodiment of the invention, a stream of liquid may be directed at the outer rim of the substrate, while the flat surfaces are protected from said liquid by a stream of a gaseous tensio-active substance.
Another embodiment of the invention is a method wherein the substrate is circular shaped and has two sides, a first side consisting of an annular edge area and a central area,
the method further comprising the step of holding the circular shaped substrate,
wherein the step of supplying a liquid on a part of said substrate includes supplying a stream of liquid to the entire annular edge area of the first side of the substrate, and
wherein the step of supplying a stream of a gaseous tensio-active substance includes supplying a stream of a gaseous tensio-active substance to the central area of the surface.
In this method, the substrate may be subjected to a rotational movement, the axis of rotation being perpendicular to the substrate surface and comprising the center of said substrate.
An additional stream of liquid may be supplied to a surface which is opposite to a surface of which the annular edge area is treated, in order to treat the whole of
Heyns Marc
Mertens Paul
Meuris Marc
Ahmed Shamim
Interuniversitair Microelektronica Centrum (IMEC)
McDonnell & Boehnen Hulbert & Berghoff
Stinson Frankie L.
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