Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2002-04-26
2004-03-09
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C156S345420
Reexamination Certificate
active
06703316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a substrate processing method and a substrate processing system applicable to production of such substrates as semiconductor wafers, glass substrates for liquid crystal display panels and plasma display panels (PDPs), printed circuit boards and the like, and more particularly to a substrate processing method and system in which development, deposition, washing, etching, rinsing, and replacement, etc., are performed using liquid or in the so-call wet processing way, and the substrates are dried utilizing a supercritical fluid.
2. Description of the Related Art
As well known, in the field of manufacturing semiconductor substrates, formation of fine patterns or microstructure on a semiconductor substrate has been rapidly developed. Ten years ago, the size of a wiring in a semiconductor substrate is about 1 &mgr;m. Nowadays, the size of a wiring has been reduced to about 0.18 &mgr;m, and even semiconductor devices having a wiring size of 0.13 &mgr;m have almost come into practical use. Further, researches and developments to manufacture semiconductor devices having a wiring size from 0.10 &mgr;m to 0.07 &mgr;m or even of 0.05 &mgr;m have been started.
As production of semiconductor devices having fine patterns has been developed, a capillary force that has not been considered in the production of semiconductor devices having no fine patterns must be considered as a factor in the production of semiconductor substrates having fine patterns. Generally, in producing semiconductor substrates or devices, a number of kinds of liquid are supplied to a substrate one after another prior to washing with deionized water and drying. Since the size or width of a wiring on a substrate is very small to form a fine pattern, it is likely to occur that resists are attracted to each other owing to a capillary force caused by a boundary tension of a liquid between a gas and a liquid after development, resulting in collapse of resists.
Such a phenomenon is also likely to occur in producing electromechanical devices such as a micro electromechanical system having a small rigidity such as a micro cantilever. More specifically, it is a general practice in production of such a device to remove a layer or layers by etching with an aqueous solution containing hydrofluoric acid, potassium hydroxide (KOH) or the like to obtain a certain configuration, followed by washing with a rinsing liquid and drying. In the process, however, it is likely to occur that cantilevers adhere to each other or a cantilever adheres to a base layer mounting the cantilever.
Similar problems are likely to occur in formation of porous insulating layers having a low dielectric constant. The dielectric constant of such an insulating layer is lowered by raising the porosity. Specifically, a liquid film is formed by spin coating, and gelled. After liquid replacement and other processing, drying is performed. In this drying processing, a porous structure in the insulating film is likely to collapse owing to a capillary force caused by the porous structure itself.
It can be conceived that the influence by a capillary force accompanied by production of semiconductor substrates having a microstructure, namely, falling and collapse of the microstructure, has caused and will cause the serious problem in the present and future technology of producing semiconductor substrates having microstructures.
There have been proposed several methods in attempt to solve these problems. Among the proposed methods, supercritical drying technique of drying with supercritical carbon dioxide or supercritical fluid has been regarded as having some advantages, and gained public attention recently. A brief description of the supercritical drying technique is made as follows. As shown in the phase diagram of
FIG. 6
concerning phase changes in association with pressure and temperature, in the ordinary drying manner that is performed merely by raising the temperature or Liquid A changes to Gas D, Liquid A inevitably passes an equilibrium line between a gas phase and a liquid phase. Accordingly, in the course of Liquid A to Gas D in this drying manner, a capillary force occurs in a gas-liquid interface when Liquid A passes the equilibrium line. In the supercritical drying manner that is performed by changing a liquid phase to a gas phase via a supercritical state or Liquid A→Liquid B under a high pressure→Supercritical fluid C→Gas D, on the other arm, Liquid A does not pass the equilibrium line in the process of changing into Gas D. In view of this, the supercritical drying is advantageous in drying semiconductor substrates because of no capillary force.
For example, J. Vac. Sci. Technol. B18(6), November/December 2000, “Supercritical drying for water-rinsed resist systems” in p 3308, and “Aqueous-based photoresist drying using supercritical carbon dioxide to prevent pattern collapse” in p 3313 refers to a problem of resist collapse in drying, and advantages of the supercritical drying as means for solving the problem.
Japanese Unexamined Patent Publication No. (HEI) 8-250464 recites a problem that parts of MEMS are likely to adhere to each other at the time of drying, and advantages of the supercritical drying as means for solving the problem. This publication shows a method and system in which a series of processings are all carried out in a common high-pressure vessel or chamber, that is, the so-called “one-bath” processing way.
In this method and system, a series of steps including placing a substrate in a high-pressure vessel of a supercritical processing apparatus, etching it with a liquid of strong acid, rising it with deionized water, and replacing the deionized water with an alcohol are carried out. Thereafter, liquefied carbon dioxide is introduced in the high-pressure vessel to replace the alcohol, and the carbon dioxide is brought into a supercritical state by raising the temperature of the vessel for supercritical drying. Thereafter, the high-pressure vessel is depressurized.
The above method and system are promising in concept, but involves many problems in practice. It is difficult to put the above method and system into practice for the following reasons.
In the wet processing way, liquids of strong acid or strong alkali are used. Such liquids are liable to corrode an inner surface of members constituting the high-pressure vessel. Accordingly, introduction of these liquids into the high-pressure vessel is not desirable in the aspect of safety. Namely, the above-mentioned method and system utilizing the one-bath processing way remarkably restricts the kind of usable liquid, thereby hindering use of a wide variety of liquids. There is an idea of coating the inner surface of the vessel with a fluoroethylene resin to provide resistance against corrosion. The coating is effective for a short-term use. However, it is difficult to keep the corrosion resistance effective for a long term under a high pressure. Further, even if the inner surface of the vessel is coated with fluoroethylene resin, it is practically difficult to coat the entire inner surfaces of all the parts connected with the vessel, such as the inner surface of small-diametrical pipes, joints, high-pressure valves and the like with such a corrosion resistive agent. Consequently, this idea is also not practical.
Further, in the abovementioned method and system utilizing the one-bath processing way, the high-pressure vessel is subjected to a high pressure. Accordingly, the diameter of pipes and the like connected to the high-pressure vessel cannot be made to be as large as those connected to an ordinary vessel used in the wet processing way. This will take a long time to supply and discharge a liquid in and out of the vessel through such small-diametrical pipes, which consequently obstructs the productivity. Furthermore, the high-pressure vessel is used in even a processing which does not practically require such high-pressure vessel. This is economically undesirable. Thus, the one-bath processing way
Inoue Yoichi
Ishii Takahiko
Iwata Tomomi
Kawakami Nobuyuki
Kitakado Ryuji
Kabushiki Kaisha Kobe Seiko Sho
Luk Olivia T
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