JPH08195184A - Ion implanting device and ion implanting method - Google Patents

Abstract

PURPOSE: To provide an ion implanting device capable of implanting ions of target impurities into a sample without electrifying the surface of the sample. CONSTITUTION: This ion implanting device is provided with an accelerating tube 4 accelerating the ion beam 2 of the target impurities generated by an ion source 1 to the prescribed energy, a sample holder 5 holding a sample on the orbit of the ion beam 2 accelerated by the accelerating tube 4, and an electron beam generation section 7 feeding an electron beam 6 in the middle of the orbit of the ion beam 2 and capable of controlling the acceleration energy of the electron beam 6 at the time of incidence.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus and an ion implantation method used in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art When impurities are implanted into a wafer during a semiconductor device manufacturing process, an ion beam composed of cations of target impurities is accelerated to a predetermined energy and the accelerated ion beam is applied to the wafer. FIG. 5 is a schematic diagram showing the basic configuration of a conventional ion implantation apparatus. In FIG. 5, cations of target impurities (eg, As ⁺ , B ⁺
Etc.) are generated by the ion source 31, and the ion beam 32 extracted from the ion source 31 with a predetermined extraction voltage is bent into a fan shape by an analysis electromagnet (analyzer magnet) 33. Further, the ion beam whose trajectory is bent in this way is accelerated to a predetermined energy by the accelerating tube 34, and the accelerated ion beam is applied to the wafer (not shown) attached to the substrate holder 35.

[0003]

However, in the conventional ion implantation apparatus, since the wafer to be the sample is irradiated with the cations of the target impurities, there is a so-called charge-up phenomenon in which the wafer surface is charged with positive charges. This may occur, and this may cause dielectric breakdown. Therefore, as a general means for preventing such dielectric breakdown, as shown in FIG. 6, for example, thermoelectrons are provided on the orbit of the ion beam 32 between the acceleration tube 34 and the wafer 36 (usually in the vicinity of the wafer 36). There is known one provided with a filament 37 which is a generation source of. This is because the primary electrons (electron shower) generated from the filament 37 collide with the tube wall surface (target) facing the primary electrons to form secondary electrons, and an electron cloud composed of an assembly of the secondary electrons is formed on the wafer 36. It is formed in the vicinity, and is intended to neutralize the beam itself by irradiating the wafer 36 with the ion beam 32 through this electron cloud.

However, when the apparatus configuration shown in FIG. 6 is adopted, the ion beam 32 is incident on the electron cloud in a substantially floating state.
However, only the peripheral portion of the ion beam 32 was neutralized (neutralized), and the satisfactory effect was not obtained.

The present invention has been made to solve the above problems, and an object thereof is an ion implantation apparatus and an ion implantation method capable of implanting ions of a target impurity into a sample without charging the sample surface. To provide.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and an accelerating tube for accelerating an ion beam of target impurities generated by an ion source to a predetermined energy, and this accelerating tube. In an ion implantation apparatus equipped with a sample holder that holds a sample on the trajectory of an ion beam accelerated by a tube, an electron beam is injected in the trajectory of the ion beam, and the acceleration energy of the electron beam at the time of incidence is A structure including a controllable electron beam generator is adopted.

[0007]

In the ion implanter of the present invention, the ion beam and the electron beam join on the same orbit by injecting the electron beam from the electron beam generator into the orbit of the ion beam extracted from the ion source. In addition, by giving the electron beam the same acceleration energy as that of the ion beam at the time of incidence, the electrons can efficiently enter the inside of the ion beam, which promotes neutralization of the ion beam and the electron beam, which It becomes possible to irradiate the sample with a neutral beam that is almost completely neutralized.

[0008]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a first embodiment of an ion implantation apparatus according to the present invention. The illustrated ion implantation apparatus has, as its basic constituent elements, an ion source 1 serving as an ion generation source of target impurities, and this ion source 1
An analysis electromagnet 3 for bending the ion beam 2 extracted from the sample in a predetermined direction, an accelerating tube 4 for accelerating the ion beam 2 bent by the analysis electromagnet 3 to a predetermined energy, and a wafer (not shown) serving as a sample. The sample holder 5 holds the ion beam 2 on its orbit.

The ion source 1 is for extracting the ions of target impurities from the gas sent from a gas source (not shown) into high density plasma by using, for example, high frequency or microwave, and extracting the ions of the target impurities from the plasma. Are accelerated by a high voltage to form an ion beam 2. The analyzing electromagnet 3 is
This is for extracting only the ion species of the target impurity from the various ions contained in the ion beam 2, which bends the ion beam 2 so as to draw a circle by a fan-shaped magnetic field.
Here, by adjusting the strength of the magnetic field, the heavy element is bent with a large radius and the light element is bent with a small radius and separated, so that only the ions of the target impurity are sent to the acceleration tube 4. .

The accelerating tube 4 is for giving a predetermined ion energy to the ions extracted from the ion source 1 as described above, and usually has a multistage structure composed of an insulator and an electrode. In this accelerating tube 4, an accelerating voltage is divided and applied to each electrode, and ions are accelerated by an electric field formed between the electrodes. The sample holder 5 holds a wafer to be a sample as described above, and in this embodiment, a wafer disk to which a large number of wafers can be attached is used. A prescribed number of wafers are mounted on the sample holder 5 on a concentric circle at predetermined intervals.

Here, in the device configuration of the first embodiment, in addition to the above-mentioned basic components, an electron beam generator 7 for injecting an electron beam 6 in the middle of the trajectory of the ion beam 2 is provided. ing. The electron beam generator 7 is
Although not shown, for example, a filament serving as a source of thermoelectrons and an accelerating tube (accelerating electrode) that gives a predetermined accelerating energy to the electron beam 6 extracted from the filament are provided as main components of the accelerating device. The acceleration energy of the electron beam can be controlled by adjusting the voltage applied to the tube.

A shutter mechanism 8 that can be opened and closed is provided in the path of the electron beam 6. The shutter mechanism 8 is for controlling the incidence of the electron beam 6 on the trajectory of the ion beam 2. Further, an ion beam deflection magnetic field 9 is formed at the confluence of the ion beam 2 and the electron beam 6, and the ion beam 2 deflected by this is applied to the wafer mounted on the sample holder 5. ing. On the other hand, the electron beam 6 accelerated to a predetermined energy by an unillustrated accelerating tube
Is set to follow the trajectory of the ion beam 2 after passing through the ion beam deflection magnetic field 9 and its incident direction is set.

Next, the ion implantation method according to the first embodiment will be described. First, the ion beam 2 of the target impurity extracted from the ion source 1 is bent by a fan-shaped magnetic field in the analyzing electromagnet 3 and further accelerated by the accelerating tube 3 to a predetermined energy (implantation energy). Next, the ion beam 2 thus accelerated is incident on the ion beam deflection magnetic field 9, where the beam trajectory is deflected.

On the other hand, in the electron beam generator 7, the electron beam 6 extracted from a filament (not shown) is accelerated by an accelerating tube (for electron beam) to an acceleration energy equivalent to that of the ion beam 2, and the accelerated electron beam is generated. 6 follows the trajectory of the deflected ion beam 2 and is incident midway on the trajectory. That is, the electron beam 6 is incident on the same orbit as the ion beam 2 after deflection.

As a result, the ions of the target impurity extracted from the ion source 1 and the electrons extracted from the electron beam generator 7 are relatively stationary, so that they are attracted to each other by the Coulomb force. Therefore, if the same amount of electrons as the positive ions in the ion beam 2 are made to enter from the electron beam generating unit 7, the positively charged ions and the negatively charged electrons in the combined beam will be. It is possible to mix and evenly.

To explain this schematically, the electron beam 6
Immediately before incidence on the beam, as shown in FIG. 2A, a beam is formed only by the ions (+) of the target impurities. However, when the electron beam 6 is incident on the same orbit as the ion beam 2, ions (+) and electrons (e) are mixed in the beam, as shown in FIG. The ion beam 2 is neutralized, and the electrically stable neutral beam 10 (see FIG. 1) is obtained.
Therefore, the neutral beam 10 obtained by the incidence of the electron beam 6 on the wafer held by the sample holder 5 on the trajectory of the ion beam 2 (on the end station side).
Is irradiated.

As described above, in the first embodiment, the electron beam 6 having the same acceleration energy as that of the ion beam 2 extracted from the ion source 1 is injected from the electron beam generator 7. Since the ion beam 2 is neutralized and the neutralized neutral beam 10 is applied to the wafer 11, the charge (charge-up) on the wafer 1 by cations can be significantly reduced. . Further, by neutralizing the ion beam 2 with the electron beam 6, the spread of the beam due to the space charge effect can be effectively suppressed.

By the way, in general, when measuring the ion implantation amount (dose amount) to the wafer 11, as shown in FIG. 3A, one position on the concentric circle with the mounting position of the sample holder 5 on the wafer 11 is measured. A dose is measured by providing a Faraday cup 12 in the portion and detecting the current amount of the ion beam 2 taken into the Faraday cup 12. However, when the target wafer 11 is irradiated with the electrically neutralized neutral beam 10 as in the above embodiment, the Faraday cup 12 is adopted when the above measurement system is adopted.
Since both ions and electrons are taken in, accurate dose measurement becomes impossible.

Therefore, in this embodiment, as shown in FIG. 3B, a Faraday cup 12 is provided at a position deviating from the mounting position of the wafer 11 on the sample holder 5, and the beam width is set to the beam width when measuring the dose amount. When the sample holder 5 is also moved, the beam is scanned (overscanned) to the opening position of the Faraday cup 12, and when the beam spot deviates from the wafer 11, the shutter mechanism 8 is closed to stop the incidence of the electron beam 6. I was allowed to. As a result, when the beam spot irradiates the Faraday cup 12, only the ions intervene in the beam, so that only the ions of the target impurity can be taken into the Faraday cup 12 and the neutral beam 10 is applied to the wafer 11. The dose amount can be accurately measured even when the irradiation is performed.

In FIG. 3B, the wafer 11
The Faraday cups 12 are provided on the outer circumference side and the inner circumference side of the array circle, respectively. This is done by averaging the measurement data obtained by each Faraday cup 12 to measure the dose more accurately. In particular, if the same level of measurement accuracy as before is required, there is no problem even if the Faraday cup 12 is provided at any one position.

FIG. 4 is a schematic view showing a second embodiment of the ion implantation apparatus according to the present invention. In the ion implantation apparatus shown in FIG. 4, 1 is an ion source, 3 is an analyzing electromagnet, 4 is an acceleration tube, 5 is a sample holder, 7 is an electron beam generator, and 8 is a shutter mechanism. The function is the same as that of the first embodiment. Book 2 here
In the embodiment, an electron beam deflection magnetic field 13 is formed on the orbit of the electron beam 6 on the upstream side of the point of time when the ion beam 2 and the electron beam 6 merge, and the electron beam deflection magnetic field 13 is formed.
The orbit of the electron beam 6 is deflected. That is, in the first embodiment described above, the device configuration is adopted in which the trajectory of the ion beam 2 is deflected by the ion beam deflection magnetic field 9 and the electron beam 6 is incident on the trajectory after deflection.
In the case of the second embodiment, the electron beam 6 side is deflected by the electron beam deflection magnetic field 13 without deflecting the ion beam 2, and the deflected electron beam 6 is incident along the trajectory of the ion beam 2. The device configuration is adopted.

As a result, also in the second embodiment, the electron beam 6 having the same acceleration energy as that of the ion beam 2 extracted from the ion source 1 is injected from the electron beam generator 7. Since the ion beam 2 is neutralized and the neutralized neutral beam 10 can be applied to the wafer 11, it is possible to significantly reduce charging (charge-up) due to positive ions on the wafer 1. At the same time, by neutralizing the ion beam 2 with the electron beam 6, it is possible to effectively suppress the spread of the beam due to the space charge effect.

Further, when measuring the dose amount, the Faraday cup 12 is placed at the position deviated from the mounting position of the wafer 11 on the sample holder 5, as shown in FIG. 3B, by the same means as in the first embodiment. By providing and controlling the opening / closing timing of the shutter mechanism 8 as appropriate, the beam can be overscanned to the opening position of the Faraday cup 12 for accurate measurement.

[0024]

As described above, according to the present invention,
In the middle of the orbit of the ion beam extracted from the ion source,
By injecting an electron beam having an acceleration energy equivalent to that of the ion beam from the electron beam generator, the ion beam is efficiently neutralized, and the neutral beam obtained by this is applied to the sample, It is possible to effectively suppress the charging (charge-up) on the sample surface. As a result, various problems such as dielectric breakdown due to charging are solved especially in the semiconductor manufacturing process, so that the process yield at the time of ion implantation can be improved. Further, since the ion beam is more certainly neutralized, the spread of the beam due to the space charge effect is also effectively suppressed, which leads to the improvement of the implantation uniformity between the samples (wafers).

[Brief description of drawings]

FIG. 1 is a schematic view showing a first embodiment of an ion implantation apparatus according to the present invention.

FIG. 2 is a schematic diagram illustrating the principle of the present invention.

FIG. 3 is a comparative view of a sample holder.

FIG. 4 is a schematic view showing a second embodiment of the ion implantation apparatus according to the present invention.

FIG. 5 is a schematic view showing a conventional ion implantation device.

FIG. 6 is a schematic view showing another conventional device configuration.

[Explanation of symbols]

 1 Ion Source 2 Ion Beam 4 Accelerator 5 Sample Holder 6 Electron Beam 7 Electron Beam Generator 10 Neutral Beam

Claims (2)

[Claims] 1. An accelerating tube for accelerating an ion beam of a target impurity generated by an ion source to a predetermined energy, and a sample holder for holding a sample on an orbit of the ion beam accelerated by the accelerating tube. An ion implantation apparatus comprising: an ion implantation apparatus, comprising an electron beam generation unit capable of injecting an electron beam in the course of the ion beam and controlling acceleration energy of the electron beam at the time of incidence. 2. In an ion implantation method for implanting ions of a target impurity into a sample, an electron beam having an acceleration energy equivalent to that of the ion beam is injected midway along the trajectory of the ion beam accelerated to a predetermined energy. This neutralizes the ion beam,
An ion implantation method comprising irradiating the sample with the neutralized neutral beam.