Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-10-13
2001-07-03
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C204S22400M, C204S225000, C204S298310
Reexamination Certificate
active
06254719
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates broadly to microelectronics, micromachinery or optics and, in particular, to a geometrically controlled catalytic method wherein removal of material from a solid substrate is carried out without the need of using conventional photolithographic processes The geometrically controlled catalytic removal method of the present invention is particularly useful in providing a pattern such as a deep trench capacitor and a shallow trench isolation region to a semiconductor substrate in a single processing step. In prior art processes, multiple photolithographic and etching steps are required to produce such a pattern in a semiconductor substrate. Additionally, complex shapes may be formed, possibly providing design advantages over the simple geometries of current photolithography/etch processes.
BACKGROUND OF THE INVENTION
In the field of semiconductor manufacturing, it is well known that a pattern can be formed in a surface of a solid substrate by utilizing conventional photolithographic techniques. Conventional photolithographic processes include the steps of providing a photoresist or mask to predetermined areas of a solid substrate, patterning said photoresist or mask, etching the exposed areas of the solid substrate and stripping of the photoresist or mask. In such prior art processes, etching of the solid substrate is generally achieved by employing either a wet etch or a dry etch.
Wet etching is carried out using a chemical etchant which is highly selective for the particular solid substrate being etched. A major problem with wet etching is that an undercut often times develops on each edge of the photoresist. This property of undercutting the photoresist makes it impossible to achieve sub-tenth micrometer geometry reproducibly. Moreover, in order to etch a pattern into a solid substrate having multiple depths, repeated wet etching steps are required.
In the case of dry etching, ion beam etching (IBE) and reactive ion etching (RIE) are known in the art. These dry etching techniques are both line-of-sight etching processes and are able to produce higher resolution patterns with tighter dimensional control. Despite this, each of these dry etching techniques suffer from unique problems.
A major problem associated with IBE is that the edges of all features of the photoresist are etched at a faster rate due to a high flux of incident ions. This phenomenon is caused by the reflection of bombarding ions off the side walls of the photoresist. The above property associated with IBE is referred to in the art as “trenching” and it typically causes roughening at the edges of the etched features.
The problem generally encountered using RIE is the formation of tall, narrow pedestals of unetched material at the bottom of the pattern feature. This phenomenon which is referred to in the art as “grassing” is caused by localized masking of the photoresist during RIE. Such pedestals may be removed by utilizing a wet etch process.
In view of the drawbacks mentioned hereinabove, prior art etching processes (dry and wet etching alike) are incapable of providing geometrically controlled removal of material from a solid substrate. Moreover, multiple etching steps are generally required to produce a pattern in a solid substrate that has varying depths. Additionally, many complex geometries, such as curved or angled surfaces, are difficult or even impossible to create using existing prior art methods. Thus, there remains a need for developing a method for providing geometrically controlled removal of material from a solid substrate whereby patterning of the solid substrate is achieved without using prior art photolithographic processes. Moreover, there is also a need for developing a method wherein a pattern having different depths is produced in a solid substrate utilizing a single step replacing the multiple photolithographic steps required by the prior art to obtain the same pattern.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a method of selectively removing material from a solid substrate wherein a pattern or planarized surface is produced.
Another object of the present invention is to provide a geometrically controlled removal method that is a replacement for prior art etching or planarization methods and which overcomes all of the aforementioned problems associated with such prior art techniques.
A further object of the present is to provide a catalytically induced method which is highly effective in removing material from a solid substrate to form a desired three-dimensional or planar pattern in the solid substrate.
These as well as other objects are achieved by the method of the present invention wherein a geometrically controlled pattern is formed in a solid substrate utilizing a catalyst material and a reactant. Specifically, the method of the present invention comprises contacting a surface of a solid substrate with a catalyst material in the presence of a reactant under conditions effective to remove material from those areas of said solid substrate in contact with said catalyst material and said reactant, wherein at least one of said catalyst material or said reactant is a solid.
In accordance with a preferred embodiment of the present invention, silicon or SiO
2
represent the solid substrate, W is the catalyst material and fluorine atoms represent the reactant.
As stated above, the instant invention utilizes a catalyst material and a reactant to effectively and selectively remove material from a solid substrate. Generally, the catalyst material is a solid and the product of the reaction between the reactant and the solid substrate is mobile, i.e. gas or liquid, thereby facilitating the removal of areas of said solid substrate in contact with said catalyst material and said reactant. It is noted that since two of the species in the catalytic reaction are solids, the catalytic reaction of the present invention occurs only in those areas wherein the two solids are in contact. No sufficient removal of material from the solid substrate occurs in areas which do not contain either the reactant or catalyst material. A reaction between the reactant and solid substrate may proceed without the catalyst material, but it is slow and thus would not result in any significant removal of material from the solid substrate using the conditions employed in the present invention.
Another aspect of the present invention relates to an apparatus for the controlled removal of material from a solid substrate. In accordance with this aspect of the present invention, the apparatus comprises: a catalyst material; a reactant; a solid substrate; and a means for contacting said catalyst material with said solid substrate in the presence of said reactant.
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Amirov, et al., “Catalytic Etching of Silicon In a Plasma Containing Fluorine,” Soviet Tech. Phys. Lett., vol. 17, No. 2, pp. 151-152 (Feb. 1991).
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Goudreau George
International Business Machines - Corporation
Mills Gregory
Scully Scott Murphy & Presser
Shkurko Eugene I.
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