JPH04124266A - Detector for electrostatic charge quantity of wafer - Google Patents

Abstract

PURPOSE:To correctly detect the electrostatic charge quantity of a wafer by providing an electrode or magnetic pole for preventing the inflow of an electric charge around a probe for detecting the electrostatic charge quantity of the electrostatic charge quantity for wafers. CONSTITUTION:The wafer 4 is subjected to irradiation of an ion beam 1 in a certain place of Faraday 2 and is simultaneously subjected to the supply of electrons from an electron neutralizing device 5. The wafer 4 suppressed in electrostatic charge comes under the detecting probe 9 as a disk 7 rotates. The electric charge corresponding to the electrostatic charge quantity of the wafer 4 is induced in the detecting probe 9 at this time. This electric charge is taken out as the surface potential V0 of the wafer 4 through an amplifier 10. The annular electrode 11 is provided around the above-mentioned detecting probe 9. The electrons from the above-mentioned electron neutralizing device 5 are energized in the direction parting from the detecting probe 9 and the inflow thereof to the detecting probe 9 is obviated. Then, the above-mentioned surface potential V0 is correctly detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wafer charge amount detection device for detecting a wafer charge amount during, for example, ion implantation processing.

[Conventional technology]

An ion implanter generates plasma containing desired ions in the ion source, extracts it using an electric field, accelerates it, and passes it through an analysis magnet to guide only the desired ions into the implantation chamber, where the ion beam is delivered to the wafer. irradiate.

Ion implantation is used in many processes as a means of introducing impurities into wafers. Among these, there is a tendency to increase the beam current in order to improve throughput in processes that require a large amount of implantation, such as source/drain implantation of MOS transistors. Along with this, the resist and thick oxide film on the surface of the wafer, which is the target, are becoming more and more charged.

On the other hand, devices are becoming more susceptible to charging as wafers become larger in diameter and patterns become finer.

These synergistic effects cause the problem of electrostatic discharge damage to the gate oxide film.

Since the frequency of electrostatic breakdown of the gate oxide film changes depending on the amount of charge on the wafer, it is necessary to accurately detect the amount of charge on the wafer. FIG. 4 is a diagram showing the configuration of an ion implanter having a conventional wafer charge amount detection device for detecting the wafer charge amount.

In the figure, 1 is an ion beam, 2 is a Faraday that measures the current value of the ion beam 1, 3 is a beam current radiation that displays the current value measured by the Faraday 2, 4 is a wafer that is irradiated with the ion beam 1, and 5 is a is an electron neutralizer for supplying electrons to the wafer 4 in order to suppress charging of the wafer 4. The electron neutralizer 5 consists of a neutralizing power source 5a and a filament 5b. Reference numeral 6 denotes an electrode for preventing electrons generated in the Faraday 2 from going back to an ion source (not shown) as well as preventing electrons from flowing into the Faraday 2 from the outside, and 7 a wafer 4 is attached. disk,
8 is a disk ammeter for measuring the current value flowing through the disk 7; 9 is a detection probe for detecting the amount of charge on the wafer 4; and 10 is an amplifier for amplifying the amount of charge detected by the detection probe 9. be.

Figure 5 shows the ion beam], Faraday 2. Wafer 4. 2 is a diagram showing the positional relationship between the disk 7 and the detection probe 9 as viewed from the ion beam supply side. FIG.

Next, the operation will be explained. The ion beam 1 passes through the Faraday 2 and reaches the wafer 4 . Wafer 4 is disk 7
Usually about 10 pieces are attached to the top.

The disk 7 is rotated at approximately 1000 rp in the direction of the arrow shown in FIG.
Ion implantation into all wafers 4 is performed while rotating at high speed at m. Focusing on only one rotation of the disk 7, the wafer 4 is irradiated with the ion beam 1 at a location where the Faraday 2 is located, and at the same time, the wafer 4, which is suppressed from being charged by being supplied with electrons from the electron neutralizer 5, is placed on the disk 7. is rotated so that it comes under the detection probe 9.

The mechanism of electron supply from the electron neutralizer 5 will be explained. A current is applied to the filament 5b by the neutralizing power source 5a to generate thermoelectrons (-secondary electrons), which are applied to the Faraday 2 to generate secondary electrons. These secondary electrons are supplied to the wafer 4 to suppress positive charging. At this time, if the wafer is positively charged by ion implantation, a charge corresponding to the amount of charge (+Q) of the wafer 4 is induced in the detection probe 9. This is passed through the amplifier 10 to the surface potential V of the wafer 4.
. Close and remove.

The disk 7 further rotates, the wafer 4 is irradiated with ions again, the disk 7 further rotates, and the detection probe 9
The surface potential is V. is detected. This is repeated until the injection amount reaches the desired value.

FIG. 6 shows the changes in the surface potential VO of the wafer 4 detected by the detection probe 9 when ion implantation was performed under the conditions that the ions of the ion beam 1 had an As'' energy of 35 Kev and an ion current of 5 mA. The figure shows one rotation of the disk 7.One of the ten or so wafers 4 placed on the disk 7 has a resist coated on its surface with a thickness of 1 μm to make it easier to detect the amount of wafer charge. , the remaining wafer 4 is an untreated one with no resist applied to its surface.The untreated wafer 4 (usually a Si wafer) has high conductivity, so the surface of the wafer 4 will not be charged during ion implantation.Therefore, The surface potential Vo is approximately O, but since the resist is an insulator on the wafer 4 coated with resist, positive charges accumulate on the surface of the wafer 4 during ion implantation, and the surface potential V becomes a positive value. At this time, the energy of ion implantation is relatively large, so As+
is completely fixed to the wafer 4. Detection when the wafer 4 has a positive potential is performed accurately as shown in FIG.

FIG. 7 shows a case where electrons are excessively supplied to the wafer 4 using an electron neutralizer 5 that suppresses charging of the wafer 4 in an ion implantation process under the same ion implantation conditions as described above.
Surface potential V of the wafer 4 detected by the detection probe 9
The change in o is shown for one rotation of the disk 7.

Note that, by supplying electrons from the electron neutralizer 5, a current of 15 mA is applied to the disk 7 so that the surface potential Vo of the wafer 4 coated with the resist becomes negative. In Figure 7,
The surface potential Vo of the untreated wafer 4 is approximately O, but the surface potential Vo of the wafer 4 coated with resist is detected to be negative due to excessive electrons from the electron neutralizer 5. Although the detection of this negative potential itself is correct, the subsequent detected surface potential V of the unprocessed wafer 4. is not 0 and is not detected correctly. This is because the electrons from the electron neutralizer 5 are supplied onto the wafer 4 with relatively low energy, so some electrons are fixed on the wafer 4 and others are not completely fixed. No electrons detected by probe 9
This is because it jumps directly into.

[Problem to be solved by the invention]

The conventional wafer charge amount detection device is configured as described above, but has the problem that charges such as electrons directly enter the detection probe 9, making it impossible to accurately detect the charge amount of the wafer.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a wafer charge amount detection device that can accurately detect the charge amount of a wafer.

[Means to solve the problem]

The present invention is applied to a wafer charge amount detection device having a charge amount detection probe that faces a wafer and detects the amount of charge on the wafer.

The wafer charge amount detection device according to the present invention is characterized in that an electrode or magnetic pole is provided around the charge amount detection probe for preventing charge from flowing into the charge amount detection probe.

[Effect]

Since the electrodes or magnetic poles in this invention are provided around the charge amount detection probe, electric charge is prevented from flowing into the charge amount detection probe.

〔Example〕

FIG. 1 is a block diagram of an ion implantation apparatus equipped with an embodiment of a wafer suspension charge amount detection device according to the present invention. In the figure, the difference from the conventional device shown in FIG. 4 is that a ring-shaped electrode 11 is newly provided around the detection probe 9. The other configurations are the same as the conventional device.

The operation of rotating the disk 7, performing ion implantation, suppressing the charging of the wafer 4 by the electron neutralizer 5, and then detecting the amount of charging of the wafer 4 by the detection probe 9 is the same as in the conventional method.

Now, as in the case described above, one of the ten or so wafers 4 placed on the disk 7 has a 1 μm resist coated on its surface, and the other wafers 4 are untreated with no resist coated on their surfaces. Suppose there is.

Then, the ions, energy, and beam current of the ion beam 1 are set to the same conditions as described above, and a potential of, for example, -100V to -200V (7) is applied to the electrode]1.

When ions are implanted onto the wafer 4, the change in the surface potential Vo of the wafer 4 detected by the detection probe 9 during one revolution of the disk 7 is similar to the above-described case shown in FIG.

Next, a description will be given of changes in the surface potential Vo of the wafer 4 of one revolution of the disk 7 detected by the detection probe 9 when excessive electrons are supplied to the wafer 4 from the electron neutralizer 5 during ion implantation. do.

The electrons from the electron neutralizer 5 have relatively low energy;
Therefore, even if it is supplied to the wafer 4 coated with resist,
There are some electrons that are not completely fixed on the wafer 4. However, in the embodiment shown in FIG. 1, an annular electrode 11 to which a negative potential is applied is provided around the detection probe 9, so that the electrons are urged in a direction away from the detection probe 9. There will be no inflow into. Therefore, when the detection probe 9 detects the amount of charge on the untreated wafer 4 after the resist-coated wafer 4, erroneous detection is not performed as in the conventional case, and the surface potential V is increased as shown in FIG.

is correctly detected as approximately 0. As described above, according to this embodiment, even if the wafer 4 is charged to a negative potential, the surface potential can be accurately detected.

In the above embodiment, a case where a negative potential is applied to the electrode 11- has been described, but a positive potential may be applied to the electrode 11-. In this case, the electrons trying to flow into the detection probe 9 are
．． , and does not flow into the detection probe 9, and the same effect as in the above embodiment can be obtained.

Further, in the above embodiment, a case has been described in which the electrodes 11 are provided so as to completely surround the detection probe 9, but it is not necessary to completely surround the detection probe 9, and for example, the electrodes 11 may be provided so as to surround the detection probe 9 at regular intervals.

Further, in the above embodiment, the electrode 11 was provided to prevent electrons from flowing into the detection probe 9 by an electric field, but instead of the electrode 11, for example, a ring-shaped semicircle is a south pole, and another semicircle or a magnetic pole is a north pole. It is also possible to provide a magnetic field to prevent electrons from flowing into the detection probe 9.

Further, in the above embodiment, a wafer charge amount detection device for detecting the charge amount of wafer during ion implantation was described, but the present invention is not limited to this and can be applied to all cases of detecting the charge amount of a wafer. .

Further, in the above embodiment, the case where the inflow of electrons into the detection probe 9 is prevented has been explained, but the present invention can be applied to all cases where the inflow of positive or negative charges is prevented.

〔Effect of the invention〕

As described above, according to the present invention, since the electrode or magnetic pole is provided around the probe for detecting the amount of charge, it is possible to prevent the charge from flowing into the probe for detecting the amount of charge, and as a result, the amount of charge on the wafer can be accurately detected. This has the effect that it can be detected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an ion implantation device using an embodiment of the wafer charge amount detection device according to the present invention, FIG. 2 is a diagram of the device shown in FIG. 1 viewed from the ion beam irradiation direction, and FIG. The figures are diagrams for explaining the operation of the device shown in Figure 1, and Figure 4.
The figure shows an ion implantation device equipped with a conventional wafer charge amount detection device, FIG. 5 is a view of the device shown in FIG. It is a diagram for explaining the operation of the device shown in the figure. In the figure, 4 is a probe, 9 is a detection probe, and 1 is an electrode. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] (1) In a wafer charge amount detection device having a charge amount detection probe that faces the wafer and detects the charge amount of the wafer, the charge amount detection device is configured to prevent charge from flowing into the charge amount detection probe around the charge amount detection probe. A wafer charge amount detection device characterized by being provided with an electrode or a magnetic pole for prevention.