JPH02295051A - Ion implanting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure ion implantation amount precisely by radiating deflected and modulated laser light to a substrate and installing an ellipsometer to detect reflected laser light in photo receipt region. CONSTITUTION:An ellipsometer is comprised of a light emitting part 3 consisting of a polarizer 12, a modulator 13 installed in the tip of a He.Ne laser 11 and a photoreciept part 4 consisting of an analyzer 14 to detect reflected light from a substrate 1 and a photo receiptor 15. Light absorption index of the substrate 1 is obtained by computing a detected signal from the photo receiptor 15 by a computer. The difference of the light absorption indexes before and after ion implantation is directly proportional to the amount of injected ions and thus the amount of ions injected into the substrate 1 is calculated by those computing processes. Consequently, ion implantation amount can be measured precisely without effects of the degree of vacuum and current leakage.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an ion implanter.

[Conventional technology]

In conventional ion implanters, the method of monitoring the implantation amount is to measure the beam current using a Faraday measurement system and convert it into the implantation amount. This will be explained below using FIG.

The ion beam extracted from the ion source 7 is passed through the analysis tube 6,
After passing through the acceleration tube 5, it is injected into the substrate 1, which is the material to be injected. The heel current received by the substrate 1 and the substrate support 2 was amplified and integrated by a current amplifier 18, and was measured as the amount of ion implantation. Actual ion implantation amount control is performed by driving the beam shutter 17.

After performing a predetermined adjustment with the beam shutter 17 upright, the beam shutter 17 is brought down and ion implantation into the substrate 1 is started. This operation causes the ion beam to reach the substrate 1. When the implantation amount obtained by the aforementioned measurement means reaches the target implantation amount, the beam shutter 1-7 is raised to prevent the ion beam from reaching the substrate. This series of operations controlled the injection amount.

[Problem to be solved by the invention]

Generally, when the degree of vacuum in a vacuum chamber in which ions are implanted becomes worse than usual, the proportion of ions that become neutral increases. Neutralized ions are not measured as a beam current even though they are implanted into the substrate, so they are not measured as an ion implantation amount. Conversely, if leakage current from the ion source or the presser flows into the heem current measurement system,
Even though no ions are implanted into the substrate, the leakage current is measured as the ion implantation amount.

As described above, monitoring the amount of ion implantation by measuring the heel current in the conventional ion implantation apparatus has the drawback of large errors.

[Means to solve the problem]

The ion implanter of the present invention separates and accelerates ions from an ion source and implants them into a substrate held in a vacuum chamber. The device is equipped with an ellipsometer configured to irradiate the substrate with the laser beam and detect the unreflected laser beam with a light receiving section consisting of an analyzer and a light receiver.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a plan view of a first embodiment of the invention.

The ion beam extracted from the ion source 7 is passed through the analysis tube 6
After passing through the acceleration tube 5, the holder 2 in the vacuum chamber 9
The substrate 1 is injected perpendicularly to the substrate 1, which is held at an angle. and a light emitting unit 3 that irradiates the substrate 1 with a laser beam obliquely;
An ellipsometer including a light receiving section 4 that receives reflected light from the substrate 1 is provided.

As shown in Figure 2, this ellipsometer is a He-Ne
A polarizer 12 and a modulator 13 are provided at the tip of the laser 11, and there is a light emitting unit 3 that irradiates the substrate 1 with a polarized and modulated laser beam, and an analyzer 14 that detects the reflected light from the substrate 1.
and a light receiving section 4 consisting of a light receiver 15 and a light receiver 15.

The detection signal from the light receiver 15 is processed by a computer 16 to determine the light absorption coefficient of the substrate 1. Since the difference in optical absorption coefficient before and after ion implantation is proportional to the amount of ions implanted, the amount of ions implanted into the substrate 1 can be determined by these operations. In other words, by measuring the optical absorption coefficient with an ellipsometer on the substrate 1 during ion implantation, the true amount of ions to be implanted can be immediately determined.

Actual injection amount control is performed by raising and lowering the beam shutter 17 using an air cylinder (not shown).

Ions are implanted into the substrate 1 by closing down the beam shutter 17 at the start of implantation. When the injection volume obtained by measuring the optical absorption coefficient with an ellipsometer reaches the target injection volume,
The computer 16 issues an injection end signal and the beam shutter 1
Put up 7. The substrate 1 is taken in and taken out through the preliminary vacuum chamber 8.

Furthermore, in the first embodiment, the surface of the substrate is perpendicular to the beam line, but if the substrate 1 is tilted to an arbitrary injection angle, the position of the laser receiving part 4 may be
There is no problem if you install it in a position where it can receive the reflected light.

FIG. 3 is a plan view of a second embodiment of the invention.

Ion source, 7 analysis tube 6, acceleration tube 5. The light emitting part 3 and the light receiving part 4 have the same oval shape as in the first embodiment. In this second embodiment, the heel current applied to the substrate 1 and the holder 2 is further measured by a current amplifier 18. This current amplifier 1
A comparator 19 is provided to compare the ion implantation amount measured in step 8 with the implantation amount measured by the ellipsometer, and an alarm buzzer 2 is provided to issue an alarm when a difference is detected by the comparator 19.
0 is set.

According to the second embodiment configured in this manner, there is an advantage that troubles in the apparatus, such as leaks in the vacuum chamber, can be discovered at an early stage.

〔Effect of the invention〕

As explained above, the present invention irradiates a substrate in a vacuum chamber where ions are implanted with a polarized and modulated laser beam, and is equipped with an ellipsometer that receives the reflected laser beam, thereby adjusting the degree of vacuum and leakage current. This has the effect of being able to accurately measure the amount of ion implantation without being influenced.

[Brief explanation of drawings]

FIG. 1 is a plan view of the first embodiment of the present invention, and FIG. 2 is a plan view of the first embodiment of the present invention.
FIG. 3 is a plan view of a second embodiment of the present invention, and FIG. 4 is a plan view of a conventional ion implantation apparatus.

Claims (1)

[Claims] In an ion implantation device that separates and accelerates ions from an ion source and implants them into a substrate held in a vacuum chamber, the light emitting part consists of a laser, a polarizer, and a modulator, and the laser beam that has been polarized and modulated is directed into the substrate. An ion implantation device comprising an ellipsometer configured to detect emitted and reflected laser light with a light receiving section consisting of an analyzer and a light receiver.