Cleaning and liquid contact with solids – Apparatus – With plural means for supplying or applying different fluids...
Reexamination Certificate
2002-03-13
2003-05-27
Coe, Philip (Department: 1746)
Cleaning and liquid contact with solids
Apparatus
With plural means for supplying or applying different fluids...
C134S095300, C134S099100, C134S144000, C134S902000
Reexamination Certificate
active
06568408
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to an apparatus and a method of removing a liquid from a rotating substrate. This liquid can be any wet processing liquid, as e.g. a wet etching liquid or a cleaning liquid. It can also be a rinsing liquid. The invention is applicable for a number of wet processing steps which are frequently used in the fabrication process of integrated circuits or liquid crystal displays.
BACKGROUND OF THE INVENTION
The complete and efficient removal of a liquid from a surface of a substrate is a multiply repeated step in e.g. the fabrication process of integrated circuits. Such a step can be performed after a wet etching step or a wet cleaning step or a wet rinsing step or any other step used in said fabrication process wherein said substrate is treated or exposed or immersed in a liquid. Said substrate can be a semiconductor wafer or a part thereof or a glass slice or any other slice of an insulating or conductive material.
The manufacturing of integrated circuits evolves towards processing of each substrate individually rather than in batches of several substrates. In state of the art IC manufacturing, most processing steps as e.g. implantation steps, deposition steps are already performed in a single substrate mode. On the other hand, wet processing steps such as e.g. cleaning steps and subsequent liquid removal steps are typically performed in a batch mode because of lack of appropriate alternatives. Therefore, differences in waiting times are created for each individual substrate between a wet processing step, performed in a batch mode and another processing step, performed in a single substrate mode. Such variability is undesirable with regard to process control. Moreover this mixed batch and single substrate processing increases the cycle time, which is also undesirable. Therefore, there is a general interest in the development of competitive single substrate wet processing steps. Particularly, one of the major challenges regarding single wafer wet processing is a method for removing a liquid from both sides of a substrate. There are two major requirements to be fulfilled for such a method. At first the method should work sufficiently fast. Knowing that in state of the art production lines a substrate is processed typically every 2 to 3 minutes, ideally, in order to avoid equipment duplication, the process step and the liquid removal step should be completed in about such a time frame. Another requirement is related to the preferred substrate orientation. State of the art processing equipment and transportation tools are developed to handle substrates in a horizontal position. Therefore in order to avoid additional substrate handling it would be desirable to perform the wet processing steps using horizontally positioned substrates.
In the European Patent EP 0 385 536 B1, a method is disclosed of drying substrates after treatment in a liquid by pulling said substrate slowly out of said liquid. However, this known method, which is based on the Marangoni principle, requires that the substrates are pulled out of the liquid in an upright position, i.e. a surface of said substrate is about perpendicular to the surface of the liquid bath as can be seen in
FIGS. 1
to
6
of the European Patent EP 0 385 536 B1. This handling is incompatible with the majority of the other process steps where the equipment and transportation tools are developed to handle horizontal positioned substrates.
In the U.S. Pat. No. 5,271,774 a spin-drying technique is disclosed which is able to handle horizontal positioned substrates. In fact several small liquid islands are formed being removed from the substrate by a rotary movement. It is known that such a spin-drying technique leaves undesirable residues, often referred to as drying marks, on the substrate surface, particularly on surfaces having mixed hydrophilic and hydrophobic regions.
In the U.S. Pat. No. 5,660,642 a liquid removal technique is disclosed wherein a liquid film present on a surface of a substrate can be removed by applying rinsewater together with a surface tension reducing vapor. Particularly, a disadvantage is that regardless of the precise nature of the liquid, during the liquid removal process always rinsewater is supplied. Furthermore, the surface tension reducing vapor is passively applied, e.g. by natural evaporation, which makes it difficult to locally, i.e. at moving zone, have a good and efficient control on the vapor supply or to direct the vapor. Moreover U.S. Pat. No. 5,660,642 does not disclose how to remove a liquid film substantially simultaneously from two opposite surfaces, i.e. top and bottomside, of a horizontally positioned substrate. Neither does U.S. Pat. No. 5,660,642 disclose how to remove efficiently a liquid from the topside of a horizontally positioned substrate.
SUMMARY OF THE INVENTION
In an aspect of the invention a method of removing a liquid from at least one surface of at least one substrate is disclosed, said method comprising the steps of:
supplying a liquid on at least a part of said surface of said substrate;
supplying a gaseous substance to said surface of said substrate, said gaseous substance being at least partially miscible with said liquid and when mixed with said liquid yielding a mixture having a surface tension being lower than that of said liquid; and
subjecting said substrate to a rotary movement. Said gaseous substance can comprise a vaporised substance which is miscible with said liquid and when mixed with said liquid yields a mixture having a surface tension being lower than that of said liquid. Said gaseous substance can comprise a gas which is miscible with said liquid and when mixed with said liquid yields a mixture having a surface tension being lower than that of said liquid. Said gaseous substance can comprise a mixture of a vaporised substance and a gas, like e.g. helium, argon or nitrogen, said mixture being at least partially miscible with said liquid and when mixed with said liquid yielding a mixture having a surface tension being lower than that of said liquid. Particularly, by supplying said liquid and said gaseous substance on said surface of said substrate, at least locally a sharply defined boundary is created between the liquid and the gaseous substance, i.e. a so-called liquid-vapor boundary.
In an embodiment of the invention, said rotary movement is performed at a speed to guide said liquid-vapor boundary over said substrate. Preferably this boundary is a curved boundary. The configuration is such that the liquid is kept at the outerside of the curved boundary, i.e. at the liquid side of the liquid-vapor boundary. In an embodiment of the invention the substrate can spin around its own axis. Alternatively said substrate can also be subjected to a rotary movement where said substrate no longer spins around its own centre.
In another embodiment of the invention, a method of removing a liquid from at least one surface of at least one substrate is disclosed, comprising the steps of:
subjecting said substrate to a rotary movement
supplying a liquid to at least a part of said surface of said substrate; and
supplying a gaseous substance to said surface of said substrate while supplying said liquid, said gaseous substance being at least partially miscible with said liquid and when mixed with said liquid yielding a mixture having a surface tension being lower than that of said liquid. Particularly on at least a part of the surface of the substrate, fresh liquid is sprayed continuously. The entire surface at the liquid side of the liquid-vapor boundary can be covered, as e.g. for hydrophilic surfaces, with a continuous film of the liquid. The speed of the rotary movement is chosen such that the flow of said sprayed liquid on at least one side of the wafer is transported outwards due to the centrifugal forces. Moreover, said gaseous substance, when mixed with said liquid yields a mixture having a surface tension being lower than that of said liquid. The resulting surface tension reduction of said liquid facilitates the movement of
Heyns Marc
Mertens Paul
Meuris Mark
Coe Philip
Interuniversitair Microelektronica Centrum (IMEC vzw)
McDonnell & Boehnen Hulbert & Berghoff
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