Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
2002-04-25
2003-04-15
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
C250S251000
Reexamination Certificate
active
06548381
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ion beam irradiation apparatus for carrying out a process of implanting ions into a substrate by irradiating the substrate with an ion beam, and a method of operating the ion beam irradiation apparatus. The invention also relates to a method of manufacturing semiconductor devices by implanting ion beams into a semiconductor substrate in a manner that the substrate is irradiated with an ion beam, and more particularly to means for suppressing the accumulatively charging (charge-up) in the surface of the substrate when it is irradiated with the ion beam.
2. Description of the Related Art
When manufacturing semiconductor devices by ion implantation, it is important to suppress the charge-up of the substrate surface when it is irradiated with an ion beam. A charge-up suppressing technique has been proposed in the related art. In the proposed technique, plasma generated by a plasma generator is supplied to an upstream region of the substrate. Electrons contained in the plasma are used for neutralizing the positive charge of the substrate produced by the ion beam irradiation. The proposed technique supplies electrons of lower energy to the substrate, when compared with the technique of utilizing primary electrons emitted from a filament or secondary electrons emitted from an object when the object is irradiated with the primary electrons emitted from the filament. Accordingly, the proposed technique has an advantage of reducing the negative charge in the substrate.
A plasma generator of a radio frequency discharge type is known which generates a plasma by ionizing, using radio frequency discharge, a plasma generating gas that is led into a plasma production chamber. This type of plasma generator is advantageous over the plasma generator of the type which uses the filament for the discharge in the following points: a) the plasma has a long lifetime, and b) it is operable at low gas pressure, and hence the vacuum within a process chamber can be maintained while the plasma is being generated.
One of the problems involved in the plasma generator of the radio frequency (RF) discharge type which utilizes radio frequency discharging for the plasma generation, resides in the plasma ignition.
The plasma generator of the RF discharge type usually includes an electrode (capacitively coupling), e.g., an antenna, or a coil (inductively coupling) for introducing a radio frequency wave into a plasma production chamber. Usually, a magnetic field for generating a plasma and maintaining the generated plasma is applied into the plasma production chamber.
In this case, to ignite a plasma, at least one electron must exist within the plasma production chamber. The electron, accelerated by a high RF electric field, hits an atom or a molecule to ionize them. Then, the electrons emitted as a result of the ionization successively ionize other atoms or molecules. Thus, a plasma is suddenly generated at a certain time point, or in other words, a plasma is ignited.
It is generally considered that the first electron is produced in such a way that high-energy particle beams coming from outer space ionize a gas. The number of electrons that high energy particle beams produce by hitting a gas is much smaller than the number of thermions (usually, several mA) emitted by the filament, for example. Accordingly, it is difficult to reliably ignite a plasma by merely introducing an RF wave into the plasma production chamber.
To reliably ignite an RF plasma, the following methods are employed in the related art.
1) A discharge gap is formed in the plasma production chamber. A high voltage is applied across the gap to cause a discharge, and in turn, the discharge generates a great number of electrons.
2) Laser light of high energy density is introduced into the plasma production chamber. A plasma is ignited by thermally ionizing a plasma generating gas using direct laser light.
In method 1) above, at least one discharge gap electrode having an exposed metal part must be provided within the plasma production chamber. Further, a high voltage source for applying a high voltage to the electrode must also be provided. As a result, the device used for method 1) has complex construction which increases its costs.
After the plasma ignition, the discharge gap electrode is exposed to the plasma and sputtered. Then, the sputtered particles (metal particles) reach the substrate. This results in metal contamination of the substrate.
Further, the discharge causes a surge voltage. Accordingly, there is a danger that the surge voltage adversely affects components of the device, such as for example, the control devices of low voltage in an ion beam irradiation apparatus.
Method 2) requires a laser light source and a laser light transmission window for introducing a laser light emitted from the laser light source into the plasma production chamber. Again, like in method 1), the device used for method 2) has complex construction which increases its costs.
In addition, material deposited during the plasma generation accumulatively attaches to the laser light transmission window. If the amount of the deposited material grows to interrupt the laser light, the plasma ignition becomes impossible. In this case, maintenance is frequently carried out to clean the deposited material, which can become cumbersome.
SUMMARY OF THE INVENTION
Accordingly, a principal object of the present invention is to provide a method and apparatus which are capable of reliably and simply igniting a plasma without creating problems such as metal contamination, in a plasma generator of the RF discharge type for the substrate charge-up suppression as mentioned above.
According to one aspect of the present invention, there is provided a method of operating an ion beam irradiation apparatus. In the operating method, when a plasma is ignited in the plasma generator, the ion beam travels beside or in the vicinity of the plasma generator, and in this state a voltage, positive with respective to ground, is applied to the plasma production chamber. Further, secondary electrons, which are generated when the ion beam collides with the plasma generating gas which flows out of the plasma production chamber into a path of the ion beam, are led into the plasma production chamber by the positive voltage, and in the plasma production chamber a plasma ignition is triggered with the secondary electrons led into the plasma production chamber.
In the operating method, an amount of secondary electrons, which is high enough to reliably ignite the plasma, may be led into the plasma production chamber. Accordingly, a plasma may be reliably ignited in the plasma production chamber.
The operating method advantageously utilizes the ion beam, which is originally present for the processing of the substrate, for generating secondary electrons and in turn, the plasma ignition. The plasma may be ignited by the utilization of the ion beam and by applying a positive voltage to the plasma production chamber. Accordingly, the plasma ignition operation is very simple, and complicated means are not needed for the plasma ignition. Further, the operating method does not cause the problems of metal contamination, surge voltage generation, or complicated maintenance.
According to another aspect of the invention, there is provided an ion beam irradiation apparatus which is characterized by a DC power source which applies a voltage, positive with respective to ground, to the plasma production chamber, and leads secondary electrons, which are generated when the ion beam collides with the plasma generating gas which flows out of the plasma production chamber into a path of the ion beam, into the plasma production chamber by the positive voltage, and triggers a plasma ignition with the secondary electrons led into the plasma production chamber, in the plasma production chamber.
In the ion beam irradiation apparatus, an amount of secondary electrons, which is high enough to reliably ignite the plasma, may be led into the plasma
Chaudhuri Olik
Finnegan Henderson Farabow Garrett & Dunner LLP
Nissin Electric Co. Ltd.
Trinh Hoa B.
LandOfFree
Ion beam irradiation apparatus and method of igniting a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ion beam irradiation apparatus and method of igniting a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ion beam irradiation apparatus and method of igniting a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3073340