JPH0567667A - Potential measuring device for ion implanter - Google Patents

Abstract

PURPOSE:To enable the surface potential of a wafer of an ion implanter to be accurately measured. CONSTITUTION:A measuring unit 6 equipped with an electrometer sensor is arranged on a disk 4 mounted with semiconductor wafers 2 adjacent to them. Dielectric plates 8 adequate in capacitance and nearly proximate to the surface state of the wafer 2 are arranged over the length close to the diameter of the wafer 2. Electrometer sensors 10 are arranged confronting the rears of the dielectric plates 8. A metal coating film is formed on the ion implantation surface of the dielectric plate 8 so as to protect it against change in quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric potential measuring apparatus for measuring an electric charge on a wafer in an ion implantation machine for implanting ions in a wafer in a manufacturing process of a semiconductor integrated circuit device.

[0002]

2. Description of the Related Art When ion-implanting a wafer, especially by charging with an ion beam during high-current ion implantation,
The gate of the MOS transistor may be destroyed.
Therefore, it is necessary to detect the surface potential of the wafer at the time of implantation and determine the ion implantation conditions that reduce the surface potential. In the ion implanter, as shown in FIGS. 4 and 5, a disk 24 on which a semiconductor wafer 22 to be ion-implanted is mounted is attached to the ion implanter in a chamber 32 so as to be rotatable and vertically movable. .. 36 is a motor for rotating the disk 24. Reference numeral 28 denotes an ion implantation position where the ion beam 34 is incident and implantation is performed, and ions are uniformly implanted into the wafer 22 by rotation of the disk 24 and vertical movement.

In order to detect the charged potential of the wafer 22,
A potential measuring device called a charge monitor is commercially available (for example, MYZ-0 manufactured by Tokyo Cathode Laboratory Co., Ltd.).
1 etc.). The surface potential of the wafer can be measured by disposing the electrometer sensor of such an electric potential measuring device so as to face the wafer 22. However, not only the surface potential of the wafer but also the positive potential and the electron by the ion beam can be measured near the ion implantation position. Since there is a negative potential due to the shower,
It is not possible to measure only the wafer surface potential. Therefore, the electrometer sensor 30 is located at approximately 1 from the ion implantation position 28.
It is often placed at the 80 degree position.

[0004]

If the electrometer sensor 30 is placed away from the ion implantation position 28, the wafer surface potential in the implanted state cannot be accurately measured.
Therefore, an object of the present invention is to provide a potential measuring device capable of accurately measuring the wafer surface potential of an ion implanter.

[0005]

According to the present invention, a dielectric plate is arranged on the surface of a disk on which a wafer to be ion-implanted by an ion-implanter is mounted, and an electrometer sensor is provided facing the back surface of the dielectric plate. Install. In a preferred example, a metal film is provided on the surface of the dielectric plate on the ion implantation side as a protective film for preventing alteration. In another preferred example, a plurality of dielectric plates are arranged according to the ion beam shape, and electrometer sensors are also arranged corresponding to the respective dielectric plates, and the in-plane of the ion beam is determined from the outputs of those electrometer sensors. Be able to measure the current density distribution. In still another preferred example, the connection between the electrometer sensor output terminal provided on the disk on which the wafer is mounted and the input terminal on the measuring instrument side that captures and amplifies the output of the electrometer sensor to obtain a measurement value, Use a non-contact type connection terminal. In still another preferred example, a control device is provided which controls ion implantation operation such as changing ion implantation conditions or stopping implantation based on an electrometer sensor output signal.

[0006]

1 is a schematic plan view showing the arrangement of a measuring unit of an electrometer sensor according to an embodiment, and FIG. 2 is a schematic sectional view of a measuring unit portion in the embodiment. FIG. 1 shows a semiconductor wafer 2 to be ion-implanted by an ion-implanter.
1 shows a state in which a potential measuring device for detecting a substance close to the surface potential of the wafer is arranged on the disk 4 mounted with. A measuring unit 6 including an electrometer sensor is arranged near the wafer 4. In the measurement unit 6, a dielectric plate 8 having an appropriate capacitance close to the surface state of the wafer is arranged over a length close to the diameter of the wafer 2. In this example, five dielectric plates 8 are arranged in a row in the radial direction of the disk 4. An electrometer sensor 10 is arranged so as to face the back surface of each dielectric plate 8.

Ions are implanted into the surface of the dielectric plate 8 under the same conditions as the ion implantation into the wafer 2, and the dielectric plate 8 is charged. The electric charge of the dielectric plate 8 is detected by the electrometer sensor 10 arranged so as to face the back surface thereof. Each electrometer sensor 10 is connected to the amplifier 16 by connecting the connection terminals 12 and 14, and a detection signal is output. Although the amplifiers 16 are collectively shown in the figure, one amplifier 16 is assigned to each electrometer sensor 10.
Since ions continue to be injected by the ion beam on the surface of the dielectric plate 8 on the ion implantation side, a metal film having a low impurity contamination property is formed for the purpose of preventing alteration of the surface of the dielectric plate 8.

The connection between the output terminal 12 of the electrometer sensor 10 provided on the disk 4 and the input terminal 14 on the chamber side connected to the amplifier 16 is mechanical because the disk 4 rotates and moves vertically. You can make a connection with a different brush. Further, the connection may be a non-contact connection such as a capacitance or an optical signal transmission method. The contactless connection improves the accuracy of the signal value.

FIG. 3 shows an example of a signal processing system of the electrometer sensor 10. The dielectric 8 is charged by the ion beam, and its potential is taken out as a potential signal by the electrometer sensor 10. Each electrometer sensor 10 is amplified by the amplifier 16 and sent to the meter or oscilloscope 18. The in-plane current density distribution of the ion beam can be measured by individually extracting the detection signal of each electrometer sensor 10 and measuring the charging potentials at a plurality of positions. Further, when the detection signals of all the electrometer sensors 10 are amplified and overlapped and the result is out of the set range, for example, an interlock signal is generated to stop the ion implantation operation,
It is also possible to provide a control device so as to interlock with the operation of the ion implanter, such as generating a feedback signal so as to change the implantation condition and return it within the set range. in this case,
The control device includes, for example, an interlock signal generation circuit and a feedback signal generation circuit.

[0010]

According to the first aspect of the present invention, it is possible to detect the charge amount close to the surface potential of the state of being injected into the wafer. According to the second aspect of the present invention, it is possible to prevent deterioration caused by alteration of the dielectric plate due to ion implantation. According to the present invention of claim 3, the in-plane distribution of the ion beam can be measured. According to the present invention of claim 4, since the connection between the detection signal output terminal on the rotating disk side and the fixed detection signal input terminal on the chamber side is performed in a non-contact manner, the detection accuracy is improved. According to the invention of claim 5,
Anomalies in ion implantation can be prevented by linking the ion implantation operation with the surface potential of the wafer.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an arrangement of measurement units of an electrometer sensor according to an embodiment.

FIG. 2 is a schematic cross-sectional view of a measurement unit section in one embodiment.

FIG. 3 is a schematic block diagram showing a signal processing system of an embodiment.

FIG. 4 is a cross-sectional view of the vicinity of an ion implanter chamber showing a conventional surface potential measuring method.

FIG. 5 is a schematic plan view showing a positional relationship between an ion implantation position and an electrometer sensor in a conventional surface potential measuring method.

[Explanation of symbols]

 2 semiconductor wafer 4 disk 6 measuring unit 8 dielectric plate 10 electrometer sensor 12 output terminal of electrometer sensor 14 input terminal connected to amplifier 16 amplifier 18 meter or oscilloscope

Claims (5)

[Claims] 1. A potential measuring device in which a dielectric plate is arranged on the surface of a disk on which a wafer to be ion-implanted by an ion implanter is mounted, and an electrometer sensor is attached so as to face the back surface of the dielectric plate. 2. The potential measuring device according to claim 1, wherein the surface of the dielectric plate on the side of ion implantation has a metal film as a protective film for preventing alteration. 3. A plurality of said dielectric plates are arranged in accordance with the shape of the ion beam, said electrometer sensors are also arranged corresponding to each dielectric plate, and the surface of the ion beam is determined from the outputs of these electrometer sensors. The potential measuring device according to claim 1, wherein the internal current density distribution can be measured. 4. A non-contact connection between an electrometer sensor output terminal provided on a disk on which a wafer is mounted and an input terminal on a measuring instrument side which captures and amplifies an output of the electrometer sensor to obtain a measurement value. The electric potential measuring device according to claim 1, wherein the electric potential measuring device is performed with a connection terminal. 5. The potential measuring device according to claim 1, further comprising a control device that controls ion implantation operation such as changing ion implantation conditions or stopping implantation based on an electrometer sensor output signal.