Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
2000-05-05
2001-03-06
Dang, Thi (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C118S7230ER, C204S298370
Reexamination Certificate
active
06197151
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus and a plasma processing method, and more particularly relates to a plasma processing apparatus and a plasma processing method suitable for forming a fine pattern in a semiconductor device manufacturing process.
The need for improving the fine pattern manufacturing capability and the processing speed in plasma processing is growing further as integration of semiconductor devices become higher. In order to respond to this need, it is required to decrease the pressure of the processing gas and to increase the plasma density.
In regard to plasma processing apparatuses aiming to decrease the pressure of the processing gas and to increase the plasma density, there presently are: (1) a method which utilizes the electron cyclotron resonance phenomena (hereinafter referred to as ECR) of a microwave (e.g., 2.45 GHz electromagnetic field with a static magnetic field (e.g., 875 G); and (2) a method which utilizes induction coupling processing (hereinafter referred to as ICP) in which a plasma is generated by generating an induced electromagnetic field by exciting a coil using an RF frequency power source.
In a case where a film of the oxide film group is etched using a gas of fluorocarbons, when either of the methods of the ECR described in the above item (1) or the ICP described in the item (2) is employed, it is difficult to increase selectivity of an oxide-film to a base material, for example, Si or SiN since dissociation of the gas progresses excessively.
On the other hand, in a conventional method of generating a plasma by applying an RF frequency voltage between a pair of parallel flat plates, it is difficult to stably discharge under a pressure condition below 10 Pa.
As a countermeasure, there are: (3) a two-frequency exciting method in which a plasma is generated using a high frequency voltage above several tens MHz and bias control of a sample is performed using a low frequency voltage below several MHz, which is disclosed in Japanese Patent Application Laid-Open No. 7-297175 or Japanese Patent Application Laid-Open No. 3-204925; and (4) a magnetron RIE (hereinafter referred to as M-RIE) method which utilizes an action of confining electrons by Lorentz force of electrons by applying a magnetic field B in a direction intersection with a self-bias electron field (E) induced on the surface of the sample, which is disclosed in Japanese Patent Application Laid-Open No. 2-312231.
Further, a method of increasing plasma density under a low pressure condition is described in Japanese Patent Application Laid-Open No. 56-13480. This method obtains a high plasma density under a low pressure condition of 0.1 Pa to 1 Pa by utilizing an electron cyclotron resonance (ECR) effect induced by a microwave of electromagnetic waves (e.g., 2.45 GHz) and a static magnetic field (e.g., 875 gauss).
On the other hand, in the technical field of performing etching processing or film forming processing of a semiconductor material using a plasma, an apparatus is employed having a high frequency power source for accelerating ions in a plasma to a sample table for mounting an object to be processed (for example, a semiconductor wafer substrate, hereinafter referred to as the sample) and an electrostatic attracting film for holding the sample on the sample table by an electrostatic attracting force.
For example, in an apparatus disclosed in the specification of U.S. Pat. No. 5,320,982, a plasma is generated by microwaves and a sample is held on a sample table by an electrostatic force, and using a high frequency power source output having a sinusoidal waveform as a bias electric source, the ion energy incident on the sample is controlled by connecting the power source to the sample table while the temperature of the sample is being controlled by introducing a heat transfer gas between the sample and the sample table.
Further, Japanese Patent Application Laid-Open No. 62 280378 discloses that a distribution of the ion energy incident to the sample can be narrowed by applying a pulse-shaped ion control bias voltage to a sample table for maintaining the electric field intensity between a plasma and an electrode at a constant value. Thereby, it is possible to improve the dimensional accuracy of plasma etching processing and the etching rate ratio of a processed film to a base material by several times.
Furthermore, Japanese Patent Application Laid-Open No. 6-61182 discloses that it is possible to prevent the occurrence of notches by generating a plasma utilizing electron cyclotron resonance and applying a pulse bias having a width of pulse duty of 0.1% or more to a sample.
An example of increasing a plasma density by generating cyclotron resonance using an electromagnetic wave of VHF band and a static magnetic field is described in the Journal of Applied Physics, Japan, Vol. 28, No. 10. However, in this example, by applying a high frequency voltage of 144 MHz to a coaxial central conductor and adding a magnetic field of 51 gauss in parallel to the central conductor, cyclotron resonance is formed to generate a high density plasma, and a grounded sample table is arranged in a position downstream of the plasma generating portion.
In the plasma generating methods described in Japanese Patent Application Laid-Open No. 7-288195 or Japanese Patent Application Laid-Open No. 7-297175 among the above-mentioned conventional technologies, a plasma is generated by a high frequency source of 13.56 MHz or several tens MHz. It is possible to generate a plasma appropriate for etching an oxide film under a gas pressure of several tens Pa to 5 Pa (Pascal). However, as a pattern dimension becomes as small as nearly 0.2 &mgr;m or smaller, verticality in a processed shape is strongly required and consequently it is inevitable that the gas pressure decreases.
However, in the two-frequency exciting method or the M-RIE method described above, it is difficult to stably produce a plasma having a desired density higher than nearly 5×10
10
cm
−3
under a pressure condition lower than 4 Pa (0.4 to 4 Pa). For example, in the two-frequency exciting method described above, even if the plasma exciting frequency is increased up to a frequency around 50 MHz, the plasma density cannot be increased but, on the contrary, it decreases. Therefore, it is difficult to produce a plasma having a desired density higher than nearly 5×10
−10
cm
−3
under a pressure condition of 0.4 to 4 Pa.
Further, in the M-RIE method, the density distribution of a plasma generated by an action of confining electrons by Lorentz force of electrons produced on a surface of a sample must be uniform all over the surface of the sample. However, there is a disadvantage in that an inclination of the plasma density generally occurs over the surface of the sample due to drift of E×B. The inclination of the plasma density formed by the action of confining electrons cannot be corrected by any method such as diffusion or the like since the inclination occurs near the sheath in the vicinity of the sample where intensity of the magnetic field is strong.
Japanese Patent Application Laid-Open No. 7-288195 discloses a method of solving this problem in which it is possible to obtain a uniform plasma without inclination by arranging magnets so that the magnetic field intensity is weakened in a direction of electron drift due to the drift of E×B. even when a magnetic field with a maximum value as high as 200 gauss is applied in parallel to a sample. However, there is a disadvantage with this method in that it is difficult to follow a change in a processing condition since a condition for maintaining the plasma uniform is limited to a specified narrow range once the distribution of magnetic field intensity is fixed. In particular, in a case of a large sized sample having a diameter larger than 300 mm, when a distance between the electrodes is as narrow as 20 mm or less, pressure above the central portion of the sample becomes 10% or more greater than pressure above t
Kaji Tetsunori
Mitani Katsuhiko
Otsubo Toru
Tachi Shinichi
Tanaka Junichi
Antonelli Terry Stout & Kraus LLP
Dang Thi
Hitachi , Ltd.
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