JPH03167745A - Device and method for irradiating ion beam - Google Patents

Abstract

PURPOSE:To restrain changes in device characteristics with time so as to enhance the reliability of the process of device characteristics by generating oxygen plasma on the inner wall of a Faraday cup or both the inner wall of the Faraday cup and the surface of an ion beam irradiated target. CONSTITUTION:Oxygen plasma is generated on the inner wall of a Faraday cup 13 or both the inner wall of the Faraday cup 13 and the surface of an ion beam irradiated target 12 by an oxygen plasma generating means 21 so that a thin insulating film of metal oxides is formed on the inner wall or both the inner wall and the surface of the target 12. Potential distribution inside the Faraday cup 1 therefore becomes a predetermined one from the beginning and the efficiency of the arrival of secondary electrons l2 to the target is enhanced immediately after cleaning, etc., and the chargeup resistance of a device is maintained from the beginning. The efficiency of the arrival of the secondary electrons l2 to the target is thus enhanced without being affected by changes in device characteristics with time, and the service conditions of the device are prevented from shifting or becoming unstable, thereby enhancing the reliability of the process.

Description

[Detailed Description of the Invention] 1 Overview] Regarding the ion beam irradiation device and the ion beam irradiation method, even if it is applied immediately after cleaning the inner wall of the Faraday force knob, the efficiency of reaching the target of secondary electrons is improved, and the change over time is improved. The purpose of this invention is to provide an ion beam irradiation device and an ion beam irradiation method that can improve the process reliability of device characteristics by suppressing them and maintain the charge-up characteristics of the device. a Faraday force knob arranged to face the target, an electron supply means provided inside the Faraday cannob, and a supply means for supplying a gas containing oxygen to the vicinity of the Faradaycannob; The device is equipped with an oxygen plasma generating means for generating oxygen plasma on the inner wall of the Faraday cup or Faraday force, and on the inner wall of the Faraday cup and the surface of the ion beam irradiation target, and also supplies gas containing oxygen near the Faraday cup. In this method, a discharge voltage is applied in the vacuum container to oxidize the inner wall of the Faraday cup or the inner wall of the Faraday cup and the ion beam irradiation target, and then the target is irradiated with the ion beam.

[Industrial Application Field] The present invention relates to an ion beam irradiation device, and more particularly to an ion beam irradiation device and an ion beam irradiation device equipped with an electron charge neutralization device and capable of reducing charge anopia generated on the surface of an insulating film of a target during ion beam irradiation. This invention relates to an ion beam irradiation method.

In recent years, the use of ion implantation techniques in the high dose region has increased, and these implantation techniques can implant high doses in a short time; Practical use of the current ion ion device is progressing. However, in these high-current ion implanters, the amount of charge supplied to the target surface per unit time increases (of course), so the surface of the semiconductor wafer etc. is coated with an insulator such as an oxide or resist film. If there is a film, there is a problem that a charge knob is generated in the insulating film on the wafer, leading to breakdown of the insulating film due to the potential difference between the wafer and the surface of the insulating film. On the other hand, even on the device side where ions are implanted, there is an increasing tendency for the oxide film thickness to decrease δ and the contact window with the wafer to decrease as devices become smaller. This is decreasing and exacerbating the aforementioned problems.

(Prior art: This method is used to solve problems, for example,
There is a honeycomb as shown in the figure. FIG. 5 shows the conventional Io＞” ”−L ′! This is a scientific diagram explaining the inside of the irradiation device. In the figure, the ion beam irradiation target 11 is the target, and the ion beam irradiation target 11 is the target disk rotating up and down, and also; It is a known device that moves left and right, and a semiconductor wafer 2 is placed on its surface. 3. A Faraday force knob is formed from aluminum or the like, and the Faraday cup 3 is composed of a filament 4 as a primary electron generating section, an electron supply means composed of a secondary electron generating section 5, etc., and a cylindrical cylindrical section. 6, and is interposed between the ion beam irradiation target l and the sublenosa 7. 8: It is a Mamenosh-like drawing spirit pole. Here, the reason why the secondary electron generating part 5 is formed slightly backward from the inner surface of the cylindrical part 6 of the Faraday force knob 3 is because
The primary cage e1 emitted from the filament 4 is accelerated by the extraction electrode 8 and collides with the secondary electron generating section 5, and in addition to the low-energy secondary electrons e2, high-electron recoil electrons eI' are emitted by the ion beam. This is to prevent direct incidence on the target 1. When this recoil electron e1' enters the electron beam 1, the surface of the semiconductor wafer 2 is negatively charged, as shown in the figure. ．． The device will be destroyed in the same way as when it is positively charged by ions irradiated from a non-1' ion source.

In this ion beam irradiation apparatus, positively charged As ions (As), for example 5, are generated from an ion beam generation source, and high energy is applied to and accelerated to generate an ion beam a, which can be used to fertilize semiconductor wafers. 2 to perform ion implantation.

On the semiconductor wafer 2, a device such as a MOS-IC is formed, and there is a layer of an insulating material such as an oxide or a resist film, and the surface thereof is charged with positive charges. .

On the other hand, primary electrons e1 generated from the filament biased at -100 to -300V are accelerated by the extraction electrode 8 at the ground potential, and are irradiated across the ion beam a to the opposing secondary electron generation section 5. Therefore, low energy secondary electrons e2 are emitted from the secondary electron generating section 5,
A part of the ions reaches the semiconductor wafer 2 and cancels out (neutralizes) the positive charges caused by the ions, thereby reducing charge-up.

[Problems to be Solved by the Invention] However, in such a conventional ion beam irradiation device, recoil electrons can be removed and the charge amplifier can be reduced.
Immediately after cleaning, when the metal surface of the inner wall of the cylindrical portion 6 of the Faraday cup 3 is exposed, there is a problem that the efficiency with which the low-energy secondary electrons e2 reach the ion beam irradiation target 1 deteriorates. .

The reason why the arrival efficiency deteriorates in this way is that the secondary electrons e2 generated in the secondary electron generating section 5 are absorbed by the surface 6a on one side of the Faraday cassob 3. This point is specifically shown in FIG. FIG. 3 is a diagram showing the potential distribution of the ion beam a and the secondary electrons e2 inside the Faraday cup 3 when the metal surface of the cylindrical part 6 of the Faraday cup 3 is exposed, and shows the potential inside the Faraday cup 3. It is shown along the axis perpendicular to the ion beam. As shown in the figure, the secondary electron generating section 5 of the Faraday cup 3
Since the secondary electrons ez generated in the ion beam have an energy of several to tens of volts with respect to the ground potential using the farade canopy 3 as the ground, they reach the surface 6a on one side before being incident on the ion beam irradiation target l. Therefore, it is absorbed by the surface 6a on one side.

However, on the other hand, the arrival efficiency of the secondary electrons e2 improves with the passage of time. In other words, in ion implantation of semiconductor devices, a resist film is often used as a material, so this resist is removed during ion irradiation, and the cylindrical part 6 of the Faraday cassop 3 is
It adheres to the surface and forms an insulating resist film over time. Then, recoil electrons e1', secondary electrons e2, etc. adhere to the surface of the resist film, and the resist film becomes electrically charged. Therefore, the potential distribution of the ion beam a in the Faraday cup 3 is negatively charged on one side 6a as shown in FIG. e2 is not absorbed by the surface 6a on one side and bounces back. Therefore, the secondary electron e2
can easily reach the ion beam irradiation target l, improving the efficiency of reaching the ion beam irradiation target l.

However, since this represents changes in equipment characteristics over time, although the achieved efficiency increases, it not only causes a shift or instability in the usage conditions of the equipment, deteriorating the reliability of the process, but also impairs practical use. There is a problem in that it takes a long time for enough ions to reach the ion beam irradiation target 1, and during this time the charge-up resistance of the device is impaired.

Therefore, the present invention improves the efficiency of secondary electrons reaching the target even immediately after cleaning, and also prevents shifts or instability in the usage conditions of the equipment due to changes over time, thereby improving process reliability and improving equipment maintenance. It is an object of the present invention to provide an ion beam irradiation device and an ion beam irradiation method that can maintain charge-up characteristics.

[Means for Solving the Problems] In order to achieve the above object, the ion beam irradiation device according to the first invention includes an ion beam irradiation target housed in a vacuum container and an ion beam irradiation target arranged to face the target. a Faraday cup, an electron supply means provided inside the Faraday cup, a supply means for supplying a gas containing oxygen to the vicinity of the Faraday cannob, and an ion beam irradiation of the inner wall of the Faraday cumbe or the inner wall of the Faraday force knob. It is characterized by comprising an oxygen plasma generating means for generating oxygen plasma on the surface of the Yuichi Genoto, and the generating means is placed between the Faraday cup electrode and the ion beam irradiation target or between the Faraday force knob electrode and the vacuum. It may be provided between the container or between the ion beam irradiation target and the vacuum container. Further, the Faraday cup may be divided into two parts, the first cup and the second cup, and the generating means may be provided between the first cup and the second cup.

In order to achieve the above-mentioned object, the ion beam irradiation method according to the second invention applies a discharge voltage in the vacuum container while supplying oxygen-containing gas near the Faraday force knob, and applies a discharge voltage to the inner wall of the Faraday cup or the inner wall of the Faraday force knob. The ion beam irradiation target is oxidized and then the target is irradiated with the ion beam.

[Effect] In the present invention, oxygen plasma is generated by the oxygen plasma generation means on the inner wall of the Faraday cup or on the surface of the Faraday cup inner wall and the ion beam irradiation target, and a thin insulating film made of metal oxide is formed on the inner wall or on the inner wall and the target surface. Formally imposing.

Therefore, the potential distribution inside the Faraday cup is initially 5
The potential distribution becomes as shown in FIG. 4, the efficiency of secondary electrons reaching the target is improved immediately after cleaning, and the resistance of the device to the charge amplifier is maintained from the beginning. Also,
The target arrival rate of secondary electrons is improved because it is not affected by changes in device characteristics over time, and the operating conditions of the device are prevented from shifting or becoming unstable, thereby improving the reliability of the process.

:Example;· Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a diagram showing an embodiment of an ion beam irradiation apparatus applied to an ion beam irradiation apparatus and an ion beam irradiation method according to the present invention.

First, the structure will be explained. In the figure, 11 is a vacuum container, and the ion beam irradiation target 12, the Faraday cup 13, and the sublenosa 14 are housed in the vacuum container 11. The ion beam irradiation target 12 is composed of a target disk rotated by a disk rotation motor 16 via a motor shaft 15. Also,
The target 12 is made of aluminum alloy or the like, and a semiconductor wafer 17 is attached to its surface as an ion implantation substrate. Faraday Power Nop 1
3: It has an S-shaped structure made of aluminum, etc., and is arranged so as to face the target disk 12, and has a filament 18 inside as a primary electron generating section, and the generated primary electrons collide to generate secondary electrons e2. It is composed of a secondary electron generating section 19 as a generating means and cylindrical metal electrodes 13a and 13b (Faraday cup electrodes).

A gas supply means 20 is attached to the vacuum container 11,
The gas supply means 20 supplies a gas containing oxygen to approximately Q, l Tor.
The ion beam irradiation target 12 is designed to supply about 100 yen of the ion beam to the vicinity of the ion beam irradiation target 12. Furthermore, a high frequency power source 21 is provided as an oxygen plasma generating means between the metal electrode 13a of the ion beam irradiation target l2 and the motor shaft l6 connected to the ion beam irradiation target l2. A high frequency discharge voltage of IKV is applied between the ion beam irradiation target 12 and the metal electrode 13a. Note that 22 is a rotary pump provided with 18 vacuum vessels, and discharges the gas inside the vacuum vessel 11 to the outside.

Next, the effect will be explained.

First, immediately after cleaning the inner wall of the Faraday knob 3, a gas containing oxygen is supplied to the vicinity of the Faraday knob 13 by the gas supply means 20 at a rate of approximately Q. A discharge voltage of IKV is applied between the ion beam irradiation target 12 and the metal electrode 13a of the Faraday cup 13 by the high frequency power source 21 while supplying approximately 1 Torr. Therefore, the inner wall of the Faraday cassop 13 and the ion beam irradiation target l-
Oxygen plasma is generated near the surface of the Faraday cassop 13, and the inner wall surface of the Faraday cassop 13 and the surface of the target disk 16 are alumite-treated (oxidized) to form a thin alumina insulating film. Then, the surface of the semiconductor wafer 17 is irradiated with an ion beam and secondary electrons e2 are supplied.

In this embodiment, the insulating film shaped by oxygen plasma corresponds to the insulating film that is super-soldered from the target by ion beam irradiation, and the insulating film that is super-soldered as in the conventional case changes over time to form the inner wall surface of the Faraday cassop 13. It is possible to foretell in advance the situation in which the object is attached to the surface. Therefore, the potential distribution inside the Faraday cup 13 can be set to the state shown in FIG. 4 from the beginning, so that the target arrival rate of secondary electrons can be improved immediately after cleaning, and the resistance of the device to the charge anop can be improved from the beginning. can be sufficiently maintained.

As the ion beam continues to irradiate the semiconductor wafer 17, the insulating film from the semiconductor wafer 17 is deposited on the inner wall of the metal electrode 13b of the Faraday cassop 13, and the negative charge on the surface of the metal electrode 13b further increases. However, the device characteristics due to the change in potential distribution at this time are caused by shifting the potential distribution inside the Faraday cassock 13 from the potential distribution shown in FIG. 3 to the potential distribution shown in FIG. It has been confirmed that the change in characteristics is small compared to the change in characteristics.

Further, in this embodiment, the high frequency power source 21 is provided between the metal electrode 13b of the Faraday cup 13 and the ion beam irradiation target l2, but the present invention is not limited to this.
It may be provided between the ion beam irradiation target 12 and the vacuum vessel 11 or between the ion beam irradiation target 12 and the vacuum vessel 11. because,
The point is that the inner wall of the Faraday cup 13 or the inner wall of the Faraday cup 13 and the surface of the ion beam irradiation target 12 can be oxidized by applying a discharge voltage in the vacuum container 11. Furthermore, as shown in FIG.
A high frequency power source 2I may be provided between the first canopy A and the second canopy B as a two-divided structure consisting of a cup B. In this case, the distance between cups AB is IIIIII1
Setting the value to 5 marks is preferable in order to prevent the secondary electrons e2 from leaking to the outside.

[Effects of the Invention] According to the present invention, the target arrival rate of secondary electrons can be improved immediately after cleaning the inner wall of the Faraday cup, and the resistance of the device to the charge anop can be sufficiently maintained from the beginning.

In addition, since the target arrival rate of secondary electrons is not affected by changes over time, it is possible to prevent the operating conditions of the device from shifting or becoming unstable, improving the reliability of the process. can.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the ion beam irradiation device according to the present invention, and Fig. 2 is a schematic diagram of the Nafaraday cup showing another embodiment of the ion beam irradiation device according to the present invention. , Figure 3 is a diagram explaining the Faraday force and potential distribution inside the Faraday cup when the inner surface of the knob is clean, and Figure 4 is a diagram explaining the potential distribution inside the Faraday cup when an insulating material is deposited on the inside of the Faraday cup. FIG. 5 is a diagram showing a conventional ion beam irradiation device. 1l...Vacuum container, l2...Ion beam irradiation target area 13...
...Faraday force knob, 13b...Metal electrode (Faraday 20...
...Gas supply means, 2l...High frequency lightning source. Figure 2 Electron button/J+R number 7 Radical knob inner surface is strange A diagram explaining the internal potential distribution during Mfi Figure 3 ◆ A diagram explaining the internal potential distribution when a material is deposited on the inner surface of a Faraday cup. Diagram for explanation: Figure 5

Claims (6)

[Claims] (1) An ion beam irradiation target housed in a vacuum container, a Faraday cup arranged to face the target, an electron supply means provided inside the Faraday cup, and oxygen near the Faraday cup. 1. An ion beam irradiation device comprising: a supply means for supplying a gas containing the above; and an oxygen plasma generation means for generating oxygen plasma on an inner wall of a Faraday cup, or on an inner wall of a Faraday cup and a surface of an ion beam irradiation target. (2) The ion beam irradiation apparatus according to claim 1, wherein the generating means is provided between a Faraday cup electrode and an ion beam irradiation target. (3) The ion beam irradiation apparatus according to claim 1, wherein the generating means is provided between a Faraday cup electrode and a vacuum vessel. (4) Claim 1, wherein the generating means is provided between the ion beam irradiation target and the vacuum container.
The ion beam irradiation device described. (5) Claim 1 characterized in that the Faraday cup has a two-part structure consisting of a first cup and a second cup, and the generating means is provided between the first cup and the second cup.
The ion beam irradiation device described. (6) Applying a discharge voltage in the vacuum chamber while supplying oxygen-containing gas near the Faraday cup to oxidize the inner wall of the Faraday cup or the inner wall of the Faraday cup and the ion beam irradiation target, and then ionize the target. An ion beam irradiation method characterized by irradiating a beam.