Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2001-01-18
2003-05-20
Zarabian, Amir (Department: 2822)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S770000, C438S773000, C438S787000
Reexamination Certificate
active
06566199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a film, a system for forming a film, a semiconductor device, and a fabrication method thereof.
2. Related Background Art
Thermal treatment systems being one of semiconductor equipment have been used heretofore as systems for forming a thin film of oxide on a substrate to be treated, such as a semiconductor substrate or the like. Such thermal treatment systems include, for example, systems for oxidizing the surface of the substrate by heating the substrate while supplying oxygen dried under almost ordinary pressure, to the substrate of semiconductor wafer supported on a substrate support member in a chamber (dry oxidation such as RTO; Rapid Thermal Oxidation, or the like), or systems for oxidizing the surface of the substrate by heating the substrate in an oxidizing atmosphere containing water generated by preliminary combustion of oxygen and hydrogen (wet oxidation by external combustion method). There are also attempts to employ a method of oxidizing the surface by exposing the substrate to radical oxygen (or oxygen radicals) generated by ultraviolet irradiation or the like.
SUMMARY OF THE INVENTION
Incidentally, with increase in integration density of such semiconductor devices as VLSI devices, there is the recently increasing desire of further thinning the film while maintaining reliability, for the devices with a thin film of gate oxide or the like. In fabrication of such semiconductor devices, there is always the earnest desire for further enhancement of productivity.
Against such needs, the film formation by conventional dry oxidation such as RTO was superior in repeatability and uniformity of thickness of the film formed, but there was such a tendency that film-forming rates (deposition rates) were not always adequately large. On the other hand, the film formation by wet oxidation in the external combustion method failed to provide adequate controllability of film-forming reaction because of the use of external combustion and thus involved the risk of degrading the repeatability and uniformity of thickness. In addition, it required a torch unit for externally burning oxygen and hydrogen. Meanwhile, the film formation by radical oxygen had the problem that it was necessary to use a unit such as an ultraviolet irradiating unit, a plasma generator, or an ozonator for generating radicals and the system became complicated.
Therefore, the present invention has been accomplished under such circumstances and an object of the invention is to provide a film-forming method and a film-forming system capable of achieving satisfactory repeatability and uniformity of thickness and adequately large deposition rates in the film formation of a thin film on the substrate and simplifying the system configuration.
In order to solve the above problems, the inventors have been conducted intensive and extensive research and found a film-forming pattern demonstrating different behavior from the conventional dry oxidation or wet oxidation on the occasion of forming an oxide film on a silicon (Si) substrate. The inventors continued the research about the reaction mechanism of oxidation in this film formation, discovered that chemically active oxidizing factors (chemically active species) were involved in the reaction, and found preferred film-forming conditions, thus completing the present invention.
Specifically, a film-forming method according to the present invention is a method for forming a thin film on a substrate to be treated, which comprises a pressure reducing step of reducing pressure around the substrate, a heating step of heating the substrate, and a reactant gas supply step of supplying a first gas and a second gas, said second gas being capable of releasing energy by reaction with the first gas, so as to mix the first gas and the second gas, onto the substrate. These pressure reducing step, heating step, and reactant gas supply step do not have to be simultaneously started and stopped, but it is desirable to first carry out the pressure reducing step to reduce the pressure around the substrate and thereafter continuously perform the reactant gas supply step of supplying the gases onto the substrate to maintain the pressure of the reactant gases at a predetermined pressure, while heating the substrate.
In this film-forming method, the first and second gases supplied so as to mix onto the substrate can react with each other above the vicinity of the substrate by the heating of the substrate. This results in generating a variety of chemically active reaction species (chemically active species) immediately above the substrate, so that the surface of the substrate is exposed to these chemically active species. The chemically active species are considered to reach the interface (outermost surface) of the substrate and exert their energy on the constituents of the interface to promote reactions such as decomposition, dissociation, and the like of the constituents and reactions thereof with the chemically active species themselves.
Such reactions gradually proceed from the interface to the interior of the substrate, whereby a thin film of reaction products is formed in a predetermined thickness on the surface of the substrate. It was then verified that the reactivity of the film formation was able to be enhanced by carrying out this film-forming method under a reduced pressure condition.
The film-forming method is preferably one further comprising a substrate setting step of bringing the substrate into a chamber having a support section on which the substrate is set to be supported and a heating section opposed to the substrate and functioning to heat the substrate, and setting the substrate on the support section, wherein the pressure reducing step comprises a step of reducing the pressure around the substrate by reducing pressure in the chamber housing the substrate, wherein the heating step comprises a step of heating the substrate supported on the support section, by the heating section, and wherein the reactant gas supply step comprises a step of supplying the first gas and the second gas so as to mix the first and second gases, to between the heating section and the substrate supported on the support section. This makes it easier to maintain the reduced pressure state around the substrate, i.e., to maintain the first and second gases in predetermined concentrations. Since the first gas and the second gas exist between the substrate and the heating section, reaction efficiency between them is increased.
Further, it is desirable that in the pressure reducing step and the reactant gas supply step, the pressure around the substrate or the pressure in the chamber is regulated to 0.5 to 2 kPa (about 4 to 15 Torr). When the pressure inside the chamber is controlled in this range, the film-forming rate becomes satisfactorily high and an extremely thin film can be formed with excellent uniformity and repeatability of thickness.
Yet further, it is also useful that the reactant gas supply step comprises a step of varying a mixture ratio of the first gas and the second gas or a step of varying a feed of at least either one of the first gas and the second gas. Execution of the former step will result in varying concentrations and the composition of the chemically active species evolved from the reaction between the two gases, while the latter step is suitable for pressure control (concentration control) at a constant mixture ratio of the two gases and can substantially also serve as the former step.
Yet further, the reactant gas supply step is preferably a step using a gas having hydrogen atoms in molecules, as the first gas and using an oxygen gas as the second gas. In this case, the first gas is oxidized to bring about so-called combustion reaction and there is a tendency to facilitate attainment of high reaction energy. As a result, it is feasible to increase the concentrations and energy of the chemically active species evolved from the reaction between the two gases.
Specifically, the
Hashimoto Masayuki
Maeda Yuji
Tokai Nobuo
Applied Materials Inc.
Blakely & Sokoloff, Taylor & Zafman
Brophy Jamie L.
Zarabian Amir
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