Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
2000-06-29
2002-04-09
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C216S037000, C216S077000, C438S720000, C438S742000
Reexamination Certificate
active
06368977
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device manufacturing method and, more particularly, a semiconductor device plasma processing method. Also, the present invention relates to a gas introducing method of capable of preventing the falling of particles onto a wafer before and after a plasma process.
2. Description of the Related Art
Such a substrate processing method is widely employed in the current semiconductor manufacturing steps that a processed substrate such as a wafer is placed in a reaction chamber, then plasma is generated by introducing a reaction gas and then applying a high frequency power to an electrode, a coil, or the like, and then a film is deposited on the processed substrate, a film deposited on the processed substrate is etched, and so forth. For example, according to a plasma CVD (Chemical Vapor Deposition) method, since the reaction gas introduced in the reaction chamber is activated by the plasma, a desired film can be formed on a surface of the processed substrate. Also, according to a dry etching method such as a CDE (Chemical Dry Etching) method, since the reaction gas activated by the plasma is coupled with film material which is subjected to the etching, reaction product having a high vapor pressure can be formed.
In these substrate processing methods using the plasma, the process of the substrate is not proceeded until the reaction gas is introduced into the low pressure reaction chamber and then the plasma is generated to activate the reaction gas. In other words, introduction of the reaction gas, control of a gas flow rate and a pressure in the reaction chamber up to desired values, and stable generation of the plasma are needed to execute the desired substrate process. Also, if generation of the plasma is stopped by stopping the application of the high frequency power, the process of the substrate is stopped. Therefore, normally the introduction of the reaction gas is stopped at the same time when application of the high frequency power is stopped. According to circumstances, in some cases, after the desired substrate process by the plasma is finished, the high frequency power that is applied to the electrode arranged in the reaction chamber is reduced once, then supply of the direct current voltage supplied to an electrostatic chuck is stopped, and then application of the high frequency power is stopped. In this case, the introduction of the reaction gas is also stopped at the same time when application of the high frequency power is stopped. In addition, in order to control the flow rate of the reaction gas introduced into the reaction chamber and the pressure in the reaction chamber during the process of the substrate, a mass flow controller is connected to gas introducing ports and also a variable valve whose opening can be adjusted is arranged between the reaction chamber and the vacuum pump.
However, the mass flow controller needs a minute time until it can operate stably immediately after the introduction of the reaction gas is started, and thus an increasing rate of the gas flow rate cannot be controlled during this time period. Therefore, a large amount of reaction gas exceeding the predetermined flow rate is introduced abruptly into the reaction chamber immediately after the introduction of the reaction gas is started. Also, under the pressure in the reaction chamber in which the substrate process is performed, behaviors of the particles existing in the reaction chamber is affected mostly by the flow of the reaction gas. Therefore, since the flow rate and the flow speed of the gas are changed abruptly if a large quantity of reaction gas is introduced suddenly, in some cases the particles existing in the reaction chamber are blown up and then fallen down on the processed substrate. In addition, normally the variable valve starts to operate together with the start of the gas introduction. Since the variable valve operates so as to restore the increase in pressure by the suddenly introduced reaction gas into the predetermined pressure in a short time, controllability of the variable valve becomes worse immediately after the introduction of the reaction gas is started. Accordingly, since the flow rate, the flow speed, and the pressure are changed irregularly in the reaction chamber immediately after the introduction of the reaction gas is started, there is a possibility that the particles existing in the reaction chamber are blown up and then fallen down on the processed substrate. If the substrate process is performed in the situation that the particles are still present on the processed substrate, abnormality of shapes of the film to be deposited or abnormality of shapes of the film to be etched is caused, and thus it is difficult to manufacture the semiconductor device with good yield.
Moreover, based on various experiments, it can be understood that, while the generation of the plasma is being maintained, the particles are charged into the minus and repelled by the sheath as the negative potential area, so that such particles are floating over the sheath and seldom fallen down on the substrate. However, when the sheath disappears by stopping the generation of the plasma, the particles lose a repulsion force against the sheath and thus they are fallen down onto the wafer. It is needless to say that, if the succeeding processes are performed while the particles still exist on the processed substrate as they are, such particles are not preferable for the semiconductor manufacturing steps.
SUMMARY OF THE INVENTION
The present invention has been made to overcome such problems, and it is an object of the present invention to provide a semiconductor device manufacturing method capable of reducing the particles that fall down onto a processed wafer before and after a plasma process to thus reduce generation of abnormality of shapes due to the particles.
It is another object of the present invention to provide a semiconductor device manufacturing method capable of achieving high production yield.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a semiconductor device manufacturing method which comprises at least a first step of loading a processed substrate in a reaction chamber; a second step of introducing a reaction gas into the reaction chamber at a predetermined flow rate; a third step of maintaining an interior of the reaction chamber at a predetermined pressure; a fourth step of starting generation of plasma by supplying a high frequency power to an electrode arranged in the reaction chamber; a fifth step of applying a predetermined process to the processed substrate; and a sixth step of stopping generation of the plasma by stopping supply of the high frequency power while introducing continuously a gas at the predetermined flow rate after the predetermined process is completed. Here, the “predetermined process”are a process of depositing a film on the processed substrate, a process of etching the film deposited on the processed substrate, etc. The “predetermined flow rate”is a flow rate at which the predetermined process can be performed by generating the plasma. The “predetermined pressure” is a pressure in the reaction chamber, by which the predetermined process can be performed by generating the plasma.
According to the first aspect of the present invention, since the gas is still introduced continuously at the predetermined flow rate when the generation of the plasma is stopped, the particles that are floating over the sheath can be exhausted together with the gas introduced continuously, to prevent their falling onto the wafer.
In the first aspect of the present invention, in the sixth step, preferably the flow rate of the gas introduced continuously is larger than the predetermined flow rate. By introducing continuously the gas larger than the predetermined flow rate, the particles being floating over the sheath can be exhausted more effectively to together with the introduced gas without falling on the p
Aoki Katsuaki
Fujita Hiroshi
Kaji Naruhiko
Matsui Isao
Narita Masaki
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Powell William A.
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