JPH0613017A - Processor and ion implantation device - Google Patents

Abstract

PURPOSE:To suppress the generation of particles from the surface of a bias electrode in an ion implantation device. CONSTITUTION:A Faraday cup 2 is arranged directly before a semiconductor wafer W on a rotational disc 17, and a semiconductor film 6 such as SiC is formed on the surface (the surface of the inside) of a conductor 5 such as carbon, in the side of the Faraday cup 2 into which an ion beam penetrates, while two bias electrodes 3A, 3B(3) are provided. The inner wall surface of each of these electrodes is formed into circle. A bias voltage of -2KV, for example, is applied to the bias electrodes 3 so that no electron jumps out from the outside of the Faraday cup 2. Sputtered grains from the surface of a wafer W are adhered to the surface of the bias electrodes 3, and an insulating film is thus formed. Electric discharge is prevented due to the resistance of a semiconductor, even when positive charges are stored on the surface of the insulating film and exceed the withstand charge amount of the insulating film, and the generation of particles can thus be suppressed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a processing apparatus and an ion implantation apparatus.

[0002]

2. Description of the Related Art The ion implantation technique is a method of accelerating impurity ions generated in an ion source in a high electric field and mechanically introducing impurities into a semiconductor wafer by utilizing the kinetic energy thereof. This is a very effective method in that the total amount of the impurities thus removed can be accurately measured as the charge amount.

Conventionally, such ion implantation is performed by, for example, FIG.
It is performed using the device shown in. That is, gas or solid vapor is turned into plasma in the ion source 9, positive ions in this plasma are extracted with a constant energy by the extraction electrode 91, and then mass analysis is performed on the ion beam by the mass analyzer 92. The desired ions are separated, and further the separation slit 93 completely separates the ions. Then, the separated ion beam of the desired ions is accelerated to the final energy through the accelerating tube 94, and then irradiated onto the wafer W, so that desired impurities are introduced into the surface of the wafer W.

Immediately before the wafer W, in order to accurately measure the ion implantation amount by confining secondary electrons generated when ions are implanted on the surface of the wafer W so as not to flow outside, the Faraday is measured. A cup 95 is provided, and a bias voltage of, for example, −2 KV is applied from the voltage source E to the ion beam intrusion side of the Faraday cup 95 so that the secondary electrons do not go out of the Faraday cup 95. A Faraday bias electrode 96 is arranged. A plasma generating unit 97 is provided outside the Faraday cup 95 to neutralize the positive charges accumulated on the surface of the wafer W by the irradiation of the ion beam.

[0005]

However, since a small amount of residual gas exists in the vacuum atmosphere in the main body of the ion implantation apparatus, the particles of the residual gas are ionized by collision with the particles of the residual gas. As a result, charged particles are generated. Among the generated charged particles, particles having a charge opposite to the potential of the bias electrode 96, that is, particles having a positive charge (positive charged particles) are attracted to the bias electrode 96. Further, some of the positively charged particles in the plasma generated by the plasma generation unit 97 are also attracted to the bias electrode 96.

On the other hand, while using the ion implanter, SiO ₂ , Al ₂ O ₃ , and P ₂ were formed on the surface of the bias electrode 96.
An insulating film such as O ₅ or AS ₂ O ₃ is formed, so that the positively charged particles attracted to the bias electrode 96 are not attracted into the bias electrode 96 but are accumulated on the surface thereof. The left side of FIG. 7 schematically shows such a state and shows an equivalent circuit thereof, where A, C, and V are an insulating film, a capacitance of the insulating film, and a bias voltage, respectively. When the surface of the wafer W is irradiated with the ion beam, the insulating film A is sputtered with a photoresist film or an insulating film formed on the surface, and the sputtered particles are scattered to the surface of the bias electrode 96. It is presumed that it was formed by adhesion and deposition.

However, as described above, the bias electrode 96
When positively charged particles accumulate on the surface of the and the charge increases,
The charge amount exceeds the withstand voltage of the insulating film A and is discharged between the surface of the insulating film A and the bias electrode 96 as shown on the right side of FIG. Since 96 is a conductor, electrons are supplied from the voltage source E side by the amount corresponding to the current, so that the instantaneous thermal energy due to discharge increases, and as a result, the insulating film on the surface of the bias electrode 96 explosively due to the impact of discharge. There is a problem that part of A and the bias electrode 96 scatters and causes generation of particles.

The present invention has been made under such circumstances, and an object thereof is to provide an ion implantation apparatus capable of suppressing the generation of particles.

[0009]

According to a first aspect of the present invention, in a processing apparatus provided with an electrode to which a voltage is applied in a vacuum atmosphere or a gas atmosphere in which an object to be processed is placed, at least the surface of the electrode. The part is made of a semiconductor.

According to a second aspect of the present invention, in the ion implantation apparatus, an electrode to which a bias voltage is applied is provided at a position facing a passage region of an ion beam irradiated for implanting ions into a target object. At least the surface portion of the electrode is made of a semiconductor.

[0011]

When charged particles having a charge opposite to the potential of the electrode are attracted to the electrode, if the insulating film is formed on the surface of the electrode for some reason, the above-mentioned charge, for example, positive charge is accumulated on the surface of the insulating film. . When the amount of charge exceeds the withstand voltage of the insulating film, a current suddenly flows in that portion, but since at least the surface of the electrode is made of a semiconductor, the current is suppressed by the resistance of the semiconductor and the current peaks. The value is smaller than that when only the conductor is used, damage due to discharge is suppressed, and generation of particles is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram showing the entire ion implantation apparatus according to an embodiment of the present invention. The entire apparatus will be briefly described with reference to the same figure. In the figure, reference numeral 1 is an ion source for converting gas sublimated from a solid raw material in a vaporizer 11 into plasma, and the ions in the plasma are extracted electrodes. An ion beam is extracted to the outside by an extraction voltage applied between 12 and the main body of the ion source 1. A mass spectrometer 14 is arranged on the downstream side of the extraction electrode 12 via a slit portion 13, where only desired ions are taken out, and then the slit portion 1 is provided.
Entering into the accelerating tube 16 via 5. The ion is the acceleration tube 1
After passing through the Faraday cup 2 after being accelerated by the acceleration voltage applied to the electrode 16a in 6 inside the object to be processed, for example, the semiconductor wafer W, which is mounted and held on the rotating disk 17 driven by the motor 18. Injected.

The Faraday cup 2 is "prior art".
As described above, the purpose is to accurately measure the ion implantation amount by confining secondary electrons generated at the time of ion implantation so as not to flow out to the outside, and encloses the passage region of the ion beam immediately before the wafer W. Thus, for example, it is configured by a conductive cylinder such as aluminum.

A bias electrode 3 called a Faraday bias electrode is arranged on the ion beam entrance side of the Faraday cup 2 as shown in FIGS. 2 and 3, and further on the ion beam entrance side of the bias electrode 3. Is provided with a ring-shaped ground aperture 4 for focusing the ion beam. Further, the plasma generation chamber 41a is provided outside the Faraday cup 2 to neutralize the positive charges accumulated on the surface of the wafer W by the irradiation of the ion beam.
A plasma generation unit 41 is provided which is configured by providing a filament 41b therein.

The bias electrode 3 will be described below. In this embodiment, two bias electrodes 3A and 3B (collectively referred to as "3") are provided along the ion beam. Each of the voltage sources E1 and E2 is composed of a cylindrical body whose inner wall has a circular cross section.
As a result, a bias voltage of −2 KV is applied to the ground and is maintained at that potential. However, the positive electrode side of the voltage source E2 connected to the bias electrode 3B on the rear side (the bias electrode on the right side in FIG. 2) is connected to the current measurement line from the Faraday cup 2 and the rotating disk 17, and the dose amount (one time It is grounded via a beam current detection unit 42 in the ion implantation process. The bias electrodes 3 (3A, 3B) are formed by forming a semiconductor film 6 made of, for example, SiC to a thickness of 100 μm on the surface of a conductor 5 made of, for example, carbon or aluminum. The material of the semiconductor film is not limited to SiC, but Si or the like may be used. Further, the film is not limited to the semiconductor material, and may be formed of, for example, a mixed material of a conductor and an insulator or another resistor. Good.

Next, the operation of the above embodiment will be described. The ion beam extracted from the ion source 1 and containing ions of impurities such as phosphorus and arsenic is subjected to mass analysis by the mass analyzer 14, further accelerated by the accelerating tube 16, and then passed through the inside of the Faraday cup 2. The wafer W placed and held on the rotating disk 17 is irradiated with the impurities, and the impurities are implanted into the wafer W.

When the wafer W is irradiated with the ion beam IB and its surface energy becomes high, secondary electrons jump out from the surface of the wafer W, and when these secondary electrons jump out of the Faraday cup 2, the positive charge is increased accordingly. Although it is not possible to accurately measure the ion implantation amount due to a large number of counts, the bias electrode 3 (3A, 3B) to which a bias voltage of -2 KV is applied is arranged immediately before the Faraday cup 2, so that electrons are It is repulsed by and the outflow from the Faraday cup is suppressed. On the other hand, ion beam IB
Is not attracted to the bias electrode 3 because of its high velocity, but positively charged particles generated by ionization of the residual gas in the apparatus main body by collision with the ion beam IB and plasma generated in the plasma generation unit 41. The positive charged particles therein are attracted to the bias electrode 3.

As described in the section "Problems to be solved by the invention", the surface of the wafer W is ion beam IB.
When the insulating film is formed on the surface of the bias electrode 3 due to the fact that the sputtered particles are ejected from the insulating film, the photoresist film, etc., the above-mentioned positively charged particles attracted to the bias electrode 3 are generated. It is accumulated on the surface of the insulating film.

FIG. 4 is a diagram schematically showing this state, and at the same time, an equivalent circuit is described correspondingly. C,
R and V represent the capacitance of the insulating film 7, the resistance of the semiconductor film, and the bias voltage, respectively. When the amount of positive charges accumulated on the surface of the insulating film 7 exceeds the withstand voltage charge amount of the insulating film 7, when the insulating film 7 is formed on the conductor as in the conventional case, the withstand voltage charge amount is exceeded. Although a discharge is generated in a portion and a current flows rapidly, in the above-described embodiment, since the insulating film 7 is formed on the semiconductor film 6, the discharge is hard to occur, and even if the discharge occurs, the current is supplied when the initial discharge occurs. The discharge time constant can be lengthened by limiting the applied current.
As a result, it is possible to prevent the explosion due to the instantaneous temperature rise.

A bias electrode in which a SiC film which is a semiconductor film is actually formed on the surface of a conductor made of carbon, and Si
Bias electrodes not having a C film formed thereon were used in the same condition after being incorporated into an ion implantation apparatus, and the surface of the bias electrodes was observed with a microscope. In comparison, the number of holes due to discharge was small and the diameter of the holes was also small. In this experiment, the number of particles of 0.3 μm or more adhering to the surface of the 8-inch wafer W after ion implantation was examined, and when the bias electrode having the SiC film was used, it was 20 to 30 particles. Was,
When a bias electrode that does not form a SiC film is used,
It was about 60 pieces. The reason why there is a difference between a semiconductor film formed on the surface of the conductor of the bias electrode and a semiconductor film not formed is not clear, but because the insulating film and the semiconductor film are joined, there is a semiconductor resistance. It is presumed that the discharge is unlikely to occur, and the peak value of the discharge current is suppressed by the resistance of the semiconductor even if the discharge occurs, so that the instantaneous thermal energy is small, and as a result, the surface portion of the bias electrode is suppressed from being damaged.

The bias electrode 3 is not limited to forming a semiconductor film on the surface of a conductor, and the bias electrode 3 may be entirely made of a semiconductor. FIG. 5 is a diagram showing a state in which the insulating film 7 is formed on the surface of the bias electrode 3 constituted by the semiconductor 8 as described above and positive charges are accumulated on the surface, and the same effect can be obtained in this case as well.

Further, when the inner wall surface (the surface surrounding the passage of the ion beam) is, for example, a square shape, the bias electrode is preferably circular because there are many traces of damage due to discharge at the corners. The reason for this is that since the ion beam is circular, if the inner wall surface of the bias electrode 3 is circular, the inner wall surface is sputtered by the ion beam and the insulating film is peeled off.

As the bias electrode whose surface or the whole is made of a semiconductor as described above, not only the Faraday cup bias electrode for preventing the electrons from jumping out from the Faraday cup, but also the extraction electrode and the acceleration in the accelerating tube. It may be applied to an electrode or the like, and as an ion implantation apparatus which is the object of the present invention, the Faraday cup is arranged on the back side of the rotating disk (the side opposite to the surface irradiated with the ion beam). It may be applied to other types of devices.

The apparatus to which the present invention is applied is not limited to the ion implantation apparatus, but may be any semiconductor processing apparatus in which a bias electrode is provided in a vacuum atmosphere or a gas atmosphere in which a semiconductor is arranged. The body is not limited to a semiconductor, and may be a device that processes an LCD substrate or the like as long as it is necessary to suppress the adhesion of particles.

[0025]

According to the present invention, since at least the surface portion of the electrode to which the bias voltage is applied is made of a semiconductor, an insulating film is formed on the surface of the electrode, and even if charges are accumulated on the surface of the insulating film, The discharge can be suppressed, and therefore, the generation of particles due to the damage of the surface portion can be suppressed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an ion implantation apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of an embodiment of the present invention.

FIG. 3 is a perspective view showing an overview of a main part of the above embodiment.

FIG. 4 is an explanatory diagram for explaining the operation of the above embodiment.

FIG. 5 is an explanatory diagram for explaining the operation of another embodiment of the present invention.

FIG. 6 is a schematic explanatory view showing a conventional ion implantation device.

FIG. 7 is an explanatory diagram showing a state of charge accumulation and discharge of a bias electrode used in a conventional ion implantation apparatus.

[Explanation of symbols]

 1 Ion Source 2 Faraday Cup 3, 3A, 3B Bias Electrode 41 Plasma Generation Section W Wafer 5 Conductor 6 Semiconductor Film 7 Insulating Film

Claims (2)

[Claims] 1. A processing apparatus in which an electrode to which a voltage is applied is provided in a vacuum atmosphere or a gas atmosphere in which an object to be processed is placed, wherein at least a surface portion of the electrode is made of a semiconductor. Processing equipment. 2. An ion implantation apparatus in which an electrode to which a bias voltage is applied is provided at a position facing a passage region of an ion beam irradiated to implant ions into a target object, at least a surface portion of the electrode. An ion implanter characterized by comprising a semiconductor.