Etching a substrate: processes – Forming or treating material useful in a capacitor
Reexamination Certificate
2000-07-28
2001-09-04
Markoff, Alexander (Department: 1746)
Etching a substrate: processes
Forming or treating material useful in a capacitor
C216S013000, C216S067000, C216S075000
Reexamination Certificate
active
06284146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gas for fabricating a semiconductor device and a fabrication method using the same, and more particularly, to an etching gas mixture for a transition metal thin film and a method for etching the transition metal thin film using the same.
2. Description of the Related Art
In general, with high integration of semiconductor devices, patterns becomes smaller greatly. Thus, the importance of an etching process directly related to formation of a fine pattern has increased. Also, an etching target has been diversified to improve the characteristics of semiconductor devices, including a transition metal as well as conventional materials such as monosilicon, polysilicon, silicon oxide and aluminum.
Generally, the transition metal thin film is widely used as an electrode material for a capacitor. The transition metal thin film is mainly etched by a reactive ion etching and a low-pressure high-density plasma etching. When etching the transition metal thin film by the reactive ion etching, a product of a chemical reaction between an etching gas and the transition metal thin film, e.g., metal halide, exists in a solid state with a high boiling point, so that a physical etching mainly occurs by collision with accelerated ions. Thus, there is a problem in that an etching by-product, dislodged by the physical ion sputtering, is redeposited on the sidewalls of the pattern. If the etching by-product is redeposited on the sidewalls of the pattern, the profile of the pattern becomes inferior. Thus, when the transition metal thin film is used as an electrode of a capacitor, the electrode may not be totally insulated. Also, the pattern is formed in a trapezoid shape, so that the degree of accuracy of the pattern is decreased. Accordingly, it is impossible to form a fine pattern.
When patterning the transition metal thin film by low -pressure high-density plasma etching, the low pressure gives the effect of lowering the boiling point of a product formed by the reaction of a reaction gas with the transition metal. However, the low-pressure high-density plasma etching method gives only limited improvement of the volatility of an etching product, so that the etching product is still redeposited on the sidewalls of the pattern. Thus, it is impossible to form a fine pattern of a critical dimension or less.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an etching gas mixture for a transition metal thin film, which is capable of forming an etching reaction product having a high volatility, through a reaction with a transition metal thin film.
It is another object of the present invention to provide a method for etching a transition metal thin film, which is capable of forming a fine pattern of a transition metal thin film having few defects.
Accordingly, to achieve the above first object, there is provided an etching gas mixture for a transition metal thin film, comprising: a first gas which is one selected from the group consisting of halogen gas, halide gas, halogen gas mixture, halide gas mixture and gas mixture of halogen and halide; and a second gas which is one selected from the group consisting of carbon oxide gas, hydrocarbon gas, nitrogen oxide gas and nitrogen-containing gas. The etching gas mixture converts the transition metal thin film into a volatile metal halide, and the volatile metal halide comprises one selected from the group consisting of metal carbonyl halide, organic metal halide, metal amine halide and metal nitrosohalide. Here, preferably, the mixing ratio of the first gas to the second gas is 1:0.01~1:100.
To achieve the second object, there is provided a method for etching the transition metal thin film, comprising the steps of loading a semiconductor substrate having the transition metal thin film in a reaction chamber. Then, an etching gas mixture composed of a first gas which is one selected from the group consisting of halogen gas, halide gas, halogen gas mixture, halide gas mixture and gas mixture of halogen and halide, and a second gas which is one selected from the group consisting of carbon oxide gas, hydrocarbon gas, nitrogen oxide gas and nitrogen-containing gas, is injecting into the reaction chamber to form a volatile metal halide through a reaction between the transition metal thin film and the etching gas mixture, thereby etching the transition metal thin film.
Preferably, the mixing ratio of the first gas to the second gas is 1:0.01~1:100, and the mixing ratio of the first gas and the second gas may be controlled to multiple levels.
Here, the step of etching the transition metal thin film in the method comprises the sub-steps of: injecting the etching gas mixture to the reaction chamber under a predetermined pressure. Then, a plasma is formed in the reaction chamber, and then the etching gas mixture is activated in the plasma. The activated etching gas mixture is reacted with the transition metal thin film to form the volatile metal halide. Finally, the volatile metal halide is volatilized. Preferably, the semiconductor substrate is is loaded onto an electrode in the reaction chamber and radio frequency power is applied to the electrode to perform a reactive ion etching.
Also, there is provided a method for etching the transition metal thin film comprising the steps of loading a semiconductor substrate having the transition metal thin film into a reaction chamber. Then, a first gas which is one selected from the group consisting of halogen gas, halide gas, halogen gas mixture, halide gas mixture and gas mixture of halogen and halide, is injected to react with the transition metal thin film, thereby forming a metal halide. Subsequently, a second gas which is one selected from the group consisting of carbon oxide gas, hydrocarbon gas, nitrogen oxide gas and nitrogen-containing gas, is injected to react with the metal halide, thereby forming a volatile metal halide.
Here, the step of forming the metal halide comprises the sub-steps of injecting the first gas into the reaction chamber under a predetermined pressure. Then, radio frequency power is applied to an electrode in the reaction chamber to form a plasma. Then, the first gas is activated in the plasma. Finally, the activated first gas is reacted with the transition metal thin film to form the metal halide.
Also, the step of forming the volatile metal halide comprises the sub-steps of stopping the injection of the first gas. Then, the second gas is injected into the reaction chamber, to react with the metal halide, thereby forming the volatile metal halide. Here, preferably, in the step of forming the volatile metal halide by injecting the second gas, the radio frequency power is not applied to the electrode of the reaction chamber, such that the plasma is not formed and a reaction between the second gas and the surface of the metal halide occurs. Also, it is preferable to repeatedly perform the steps of forming the metal halide and the volatile metal halide in sequence.
In the present invention, preferably, the transition metal thin film comprises one selected from the group consisting of tungsten (w), molybdenum (Mo), ruthenium (Ru), iron (Fe), iridium (Ir), rhodium (Rh), platinum (Pt), nickel (Ni), copper (Cu) and gold (Au). The halogen gas may comprise one selected from the group consisting of chlorine (Cl
2
), fluorine (F
2
), bromine (Br
2
) and iodine (I
2
), and the halide gas may comprise one selected from the group consisting of chloride gas, fluoride gas, bromide gas and iodide gas. The carbon oxide gas may comprise one selected from the group consisting of carbon monoxide (CO), carbon dioxide (CO
2
) and carbonyl compound. The hydrocarbon gas may comprise one selected from the group consisting of benzene, cyclopentadiene, toluene and butadiene. The nitrogen-containing gas may be ammonia (NH
3
). The nitrogen oxide gas may comprise one selected from the group consisting of nitrogen monoxide (NO) and nitrogen dioxide (NO
2
).
Preferably, the temperature of t
Kim Jin-Hong
Woo Seong-Ihl
Markoff Alexander
Myers Bigel Sibley & Sajovec P.A.
Olsen Allan
Samsung Electronics Co,. Ltd.
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