JPH0486574A - Charge potential measuring apparatus for object to be conveyed - Google Patents

Abstract

PURPOSE:To enable the measuring of a surface charge potential of an object to be conveyed by arranging an auxiliary electrode shielded from an external electric field together with a detection electrode disposed at a position facing the object to be conveyed to eliminate effect of pollution of a carrier. CONSTITUTION:When a semiconductor substrate 2 as object to be conveyed on a rotary disc 1 is irradiated with an ion beam, the substrate 2 is charged electrically. As the substrate 2 passes in front of a detection electrode 12 with a switching means 14 connected to the electrode 12, the electrode 12 is charged with electricity opposite in polarity corresponding to a surface potential of the substrate 2 as caused by electrostatic induction and a voltage corresponding to a variation of the electricity is applied to a gate of a field effect transistor 15 to be outputted from an amplifier 17. So, when a switch 14 is switched over to an auxiliary electrode 13 by a time shorter than a time constant determined by the electrode 12 and a ground to ground insulation resistance synchronizing the rotation of the disc 1, the gate of the transistor 15 is zero in charge. Thus, with a zero potential obtained as reference, a charge potential of the substrate 2 can be measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a charged potential measuring device for a transported object, and more particularly, to a means for accurately detecting the charged potential of a transported object such as a semiconductor substrate.

(Prior Art) FIG. 6 shows a conventional charged potential measuring device for an ion implanter, in which a detection electrode 1 is placed inside a case 101.
02, a field effect transistor 103, an amplifier 104, and the like. An opening 105 is formed in the front surface of the detection electrode 102, and by moving the semiconductor substrate 107 on the rotating disk 106 into which ions have been implanted in front of the opening 105, the detection electrode 102 is opened.
A charge is induced in the semiconductor substrate 107, the gate electric field of the field effect transistor 103 is changed by this charge, an output corresponding to the change in the amount of charge is obtained, and the charged potential of the semiconductor substrate 107 is measured.

(Problem to be Solved by the Invention) Since the above measurement means sets the surface potential of the rotating disk 106 on which the semiconductor substrate 107 is placed to zero potential, when the rotating disk 106 passes in front of the detection electrode 102, The charged potential of the semiconductor substrate 107 was determined by setting the detected value of the voltage to zero potential.

However, there are cases where the surface of the rotating disk 106 is dirty and the surface potential is not zero due to the coating, which causes the problem that the potential of the semiconductor substrate 107 cannot be measured accurately.

Therefore, an object of the present invention is to provide an apparatus for measuring the charged potential of a transported object, which eliminates the problems of the conventional means as described above.

(Means for Solving the Problems) The present invention includes a detection electrode disposed at a position facing a transported object transported by a transport carrier, an auxiliary electrode shielded from an external electric field, and a gate electric field that is changed. A charged potential measuring device is constituted by a field effect transistor that outputs an output according to a change in the amount of charge, and a switch means for switching the connection between the detection electrode and the auxiliary electrode and the gate of the field effect transistor. .

(Function) In the above configuration, when the transported object 2 passes in front of the detection electrode 12, a charge is induced in the detection electrode 12, and the gate electric field of the field effect transistor 15 changes depending on the amount of charge, and the amount of charge changes. The corresponding output is extracted.

Further, by switching the switch means 14 to the auxiliary electrode 13, zero potential can be detected, so the charged potential of the transported object 2 can be accurately measured.

(Example 1) Next, the present invention will be described in detail with reference to the drawings, taking as an example an apparatus for measuring the charged potential of a semiconductor substrate in an ion implantation process.

FIG. 1 shows an ion implantation apparatus for a semiconductor substrate. Reference numeral 1 denotes a rotary disk serving as a transport carrier that rotates at a constant speed, and a plurality of semiconductor substrates 2 as objects to be transported are disposed on the surface of the rotary disk along the circumferential direction. Reference numeral 3 denotes an ion beam generator, from which an ion beam is injected into the semiconductor substrate 2. Reference numeral 4 denotes a charge detector disposed at a position facing the semiconductor substrate 2, and is connected to the display device 5.

The rotating disk 1 is mounted perpendicularly to its rotating shaft 7, and even when the rotating disk 1 rotates, the distance between the semiconductor substrate 2 and the charge detector 4 does not change and remains constant.

Next, the charge detector 4 will be explained with reference to FIG.

Reference numeral 10 denotes a case that houses an electric circuit, and is made of an electrostatic and electromagnetic shielding material. 11 is case 1
0, in which a detection electrode 12, an auxiliary electrode 13, and a switch means 14 for switching between them are arranged. This detection electrode 12
is arranged on the rotating disk 1 at a position facing the semiconductor substrate 2. Further, the auxiliary electrode 13 is completely electrostatically shielded and is disposed at a position where it is not affected by external electric fields. The electrical circuit has a source follower circuit consisting of field effect transistors 15,16. The gate of the field effect transistor 15 is connected to the detection electrode 12 and the auxiliary electrode 13 via the switch means 14,
Further, its output side is connected to an amplifier 17.

The switch means 14 has a variable contact a on the field effect transistor 15 side, a fixed contact on the detection electrode 12, and a fixed contact C on the auxiliary electrode 13 side. Therefore, with the variable contact a connected to the fixed contact a, the detection electrode 12
When the semiconductor substrate 2 passes through the front surface of the field effect transistor 15, charges are induced and the change in the amount of charges causes the field effect transistor 15 to
The gate electric field changes and a corresponding output is obtained.

Further, when variable contact a is connected to fixed contact C, zero potential is detected.

This device has the above-mentioned configuration, and its operation will be explained next. When the semiconductor substrate 2 is irradiated with an ion beam from the ion beam generator 3 while rotating the rotary disk 1, the semiconductor substrate 2 is charged. When the semiconductor substrate 2 passes in front of the detection electrode 12 with the variable contact a connected to the fixed contact A, a charge of opposite polarity corresponding to the surface potential of the semiconductor substrate 2 is generated in the detection electrode 12 by electrostatic induction. A voltage corresponding to the change in the amount of charge is applied to the gate of the field effect transistor 15, and as a result, the detection electrode 12
An output corresponding to a change in the amount of charge is taken out from the output terminal of the amplifier 17.

The output waveform is a continuous mountain-shaped waveform as shown in FIG. 3, and the valley portions indicate the output from the surface of the rotating disk 1. Therefore, in synchronization with the rotation of the rotating disk 1,
By switching the switch means 14 from the detection electrode 12 to the auxiliary electrode 13 for a time shorter than the time constant determined by the insulation resistance between the detection electrode 12 and the ground, the gate of the field effect transistor 15 becomes in a state of zero charge, as shown in FIG. As shown in FIG. 3, zero potential can be detected during the ta waiting time. Therefore, the charged potential of the semiconductor substrate 2 can be accurately monitored based on the zero potential obtained thereby, and neutralization measures can be taken more effectively.

(Example 2) FIG. 5 shows another example of the present invention. The case 10 is housed inside an outer case 20. The outer case 20 also has an opening 21 in its front face, and a shield electrode 22 is disposed between the opening 11 and the opening 21 .

24 is a switch means, which has a variable contact a connected to the shielding electrode 22, a floating contact, and a ground contact C.
have.

Therefore, when the variable contact a is connected to the floating contact A, the potential of the semiconductor substrate 2 is measured. Furthermore, when variable contact a is connected to ground contact C, zero potential is measured.

Note that the present invention can be used not only as a means for measuring the charged potential of a semiconductor substrate in an ion implantation process, but also as a means for measuring the charged potential of a transported object.

(Effects of the Invention) As explained above, according to the present invention, it is possible to eliminate the influence of dirt on the transport carrier, detect the zero potential of the transport carrier, and accurately measure the surface charge potential of the transported object. can.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is an overall view of the ion implantation device, Fig. 2 is a cross-sectional view of the main parts, Figs. 3 and 4 are output waveform diagrams, and Fig. 5 is a diagram of the output waveform. 6 is a sectional view of a main part of another embodiment, and FIG. 6 is a sectional view of a conventional means. 1... Transport carrier 2... Transported object 12... Detection electrode 13... Auxiliary electrode 14.24... Switch means 15... Field effect transistor 22... Shielding electrode Applicant Corporation Tokyo Cathode Institute Representative Patent Attorney Toshiyuki Takamatsu

Claims (2)

[Claims] (1) A charging potential measuring device for a transported object transported by a transport carrier, comprising a detection electrode disposed at a position facing the transported object;
An auxiliary electrode shielded from an external electric field, a field effect transistor that changes the gate electric field to take out an output according to a change in the amount of charge, and a connection between the detection electrode and auxiliary electrode and the gate of this field effect transistor. 1. A charged potential measuring device for a conveyed object, comprising a switch means for switching. (2) A charging potential measuring device for a transported object transported by a transport carrier, a detection electrode disposed at a position facing the transported object;
A field effect transistor whose gate is connected to the detection electrode and which outputs an output according to a change in the amount of charge by changing the gate electric field, and a shielding electrode arranged between the object to be transported and the detection electrode. and a switch means for switching between grounding and non-grounding of the shield electrode.