JPH02172152A - Ion implantation apparatus - Google Patents

Abstract

PURPOSE:To obtain a stable ion implantation current by automatically operating a carrier gas supply system not including implanted ions in such a manner that sample gas of a predetermined value or more is supplied to a plasma generator during operation of an ion source. CONSTITUTION:A microwave 11 generated in a microwave generator 1 is introduced into a plasma generator 4 through waveguides 2a, 2b, 2c and a microwave guiding flange 3. A specific magnetic field is applied in the vicinity of the plasma generator 4 by a solenoid coil 12. At this stage, a sample gas flow rate control valve 7 is opened so as to introduce sample gas into the plasma generator 4, and generate plasma so that an ion beam 31 is drawn out from the plasma by ion beam drawing electrode systems 11a, 11b, 11c. A carrier gas flow rate control valve 9 is controlled by a valve control power source 10 using vacuum measured by the vacuum gage 14 of an ion source as an input signal. Therefore, it is possible to obtain a stable ion implantation current.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation device for introducing impurities into semiconductor wafers, and particularly to an device capable of controlling the implantation amount over a wide range of IQ of 11 to 1018 K/d. .

[Conventional technology]

The conventional ion source for ion implantation equipment is disclosed in Japanese Patent Application Laid-Open No. 62-5
As described in No. 8556, one or two sample gas supply systems were connected to the plasma generation section, and in principle, one system had one type of gas. Furthermore, the purpose of connecting multiple sample gas supply systems was to control the distribution of gas species within the plasma generation section to operate the ion source stably for a long time.

[Problem to be solved by the invention]

In general, ion sources that use microwave discharge in a magnetic field (hereinafter referred to as microwave ion sources) do not have a source of electrons such as a filament, and maintain plasma using the electrons generated by microwave discharge. There is. Therefore, when the amount of sample gas supplied decreases, the amount of electrons generated also decreases, making it difficult to maintain plasma at low gas pressures. On the other hand, with ion implantation equipment, the implantation amount is IQ.
l When performing implantation of 1 to 1012 q/d, an implantation ion current of 10μ8 or less is required to ensure implant uniformity, and for implantation of 1013 to 1018 q/a, it is required to ensure productivity. Therefore, an implantation current of about 10 mA is required. Although the microwave ion source according to the above-mentioned conventional technology has the advantage of being able to easily draw out a large current ion beam in the mA class, it does not take into account stable operation under low gas pressure, and ions of 10μ8 or less are not considered. There was a problem that it was difficult to pull out the beam.

An object of the present invention is to realize an ion implantation device that can easily and stably obtain an implantation current of 1 μA to 10 mA.

[Means to solve the problem]

The above purpose is to create a configuration in which a sample gas containing implanted ion species and a carrier gas not containing implanted ion species can be supplied to the plasma generation section at the same time or as a mixed gas. This is achieved by employing a system that automatically controls the amount of supply.

[Effect]

The minimum sample gas pressure for stable operation of a microwave ion source varies slightly depending on the device configuration, but it is assumed to be 3 x 10"-3 Pa in the part where the degree of vacuum in the ion source is determined. Generally, it is 100 μA ~ Since the sample gas pressure to obtain implanted ions of 10 mA is required to be at least 3 x 10-3 Pa, the supply amount of carrier gas is set to zero at this time.Then, the sample gas is supplied in order to make the implanted ion current less than 100 μ8. Reduce the amount and reduce the vacuum level of the ion source to 3 x 10-
If the pressure is less than 3P a, the carrier gas is automatically supplied to ensure 3×10-”Pa.This allows the implantation to continue even if the sample gas supply amount is reduced to reduce the implantation ion current. Since the gas pressure in the plasma generation section can be ensured by replenishing carrier gas unrelated to ions, a stable ion implantation current can be obtained without extinguishing the plasma.

It is necessary that the carrier gas has no reactivity with the sample gas or the materials constituting the ion source, and that the ions generated by the discharge are completely separated from the implanted ions after mass separation.

In the case of ion implantation equipment for silicon semiconductors,
Ar and N2 are good.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 2 is a diagram showing the overall configuration of the ion implantation apparatus, and FIG. 1 is a diagram showing details of the ion source section therein.

First, the overall configuration of the ion implantation apparatus will be explained with reference to FIG. The ion implantation device basically consists of an ion source 21.
．． Mass separator 22, driving chamber 23. beam line 24,
25° vacuum exhaust system 26. It is composed of a power supply control system 27.

The ion beam 31 extracted from the ion source 21 passes through the beam line 24 , and only the ions 32 implanted by the mass separator 22 pass through the beam line 25 after changing the angle of the various chambers and enter the implant chamber 23 . It reaches and is implanted into a semiconductor wafer or the like. The evacuation system 26 is for evacuating the area through which ions pass, and the power supply control system 27 is for controlling the operation of each component such as the ion source 21 and the implantation chamber 23. The ion source shown in FIG. 1 is a microwave ion source. The microwave ion source according to this embodiment includes a microwave generator 1. Waveguide 2a.

2b, 2e, microwave introduction flange 3. Plazk generation part 4. Sample gas introduction pipe 5. Sample gas cylinder 6, sample gas flow rate control valve 7, carrier gas cylinder 8. Carrier gas flow control valve9. Valve control power supply 10. It is composed of an ion beam extraction electrode system 11a, Llb, llc, a solenoid coil 12°, and an insulator 13. In the figure, the microwave 11 generated by the microwave generator 1 is
The guided waves 'ff 2 a , 2 b , 2 c are introduced into the plasma generation section 4 through the microwave introduction flange 3 . Furthermore, a magnetic field of about 0.06 to 0.1 T is applied near the plasma generating section 4 by a solenoid coil 12. If the sample gas flow rate control valve 7 is opened in this state and the sample gas is introduced into the plasma generation section 4, plasma is generated due to the interaction between the microwave electric field and the magnetic field formed within the plasma generation section 4, and ions are generated. An ion beam 31 is extracted from the plasma by beam extraction electrode systems 11a, llb, and llc. The valve control power supply 10 controls the carrier gas flow rate control valve 9 using the degree of vacuum measured by the vacuum gauge 14 of the ion source as a human signal.

That is, the carrier gas flow rate control valve 9 is operated so that the degree of vacuum in the ion source does not fall below 3×10″3 Pa. When the degree of vacuum is 3XLO-''Pa or more, the carrier gas flow rate control valve 9 is fully closed. In this embodiment, the sample gas is BF3.PHa.

One of AsHa, etc., and Ar is used as the carrier gas.

According to this embodiment, it is possible to maintain the gas pressure in the plasma generation section during the operation of the ion source in a state where the plasma can be maintained stably at all times.

〔Effect of the invention〕

According to the present invention, when the supply amount of sample gas is drastically reduced in order to lower the implantation ion current, carrier gas is automatically supplied to keep the ion source stable, and conversely, a large amount of sample gas is introduced. When the implantation ion current is increased by increasing the implantation ion current, the carrier gas supply can be automatically stopped and the acquisition efficiency of implantation ions can be increased, resulting in an ion implantation device that can easily and stably obtain an implantation ion current of 1μA to 10mA. There is an effect that can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing details of the ion source section in an embodiment of the present invention;
FIG. 2 is a diagram showing the overall configuration of the present invention. DESCRIPTION OF SYMBOLS 1... Microwave generation part, 2a, 2b, 2c... Waveguide, 3... Microwave introduction flange, 4... Plasma generation part, S... Sample gas introduction pipe, 6...・Sample gas cylinder, 7...Sample gas flow rate control valve, 8.
... Carrier gas cylinder, 9 ... Carrier gas flow rate control valve, 10 ... Valve control power supply, 11 a,
l l b. 11c...Ion beam extraction electrode system, 12...Solenoid coil, 13...Insulator, 14...Ion source vacuum gauge, 21...Ion source, 22...Mass separator, 23... Impression chamber, 24.25... Beam line, 26... Vacuum exhaust system, 27... Power control system,
31゜32...Ion beam. Figure 1

Claims (1)

[Claims] 1. An ion source that discharges a gaseous sample to create plasma and extracts only ions from the plasma, and a mass separator that selects ions to be implanted from among the various extracted ions; In an ion implantation apparatus equipped with an implantation chamber for implanting selected ions into a semiconductor wafer or the like, in addition to a sample gas supply system containing implanted ion species, the ion implantation apparatus has a carrier gas supply system that does not contain implanted ion species, An ion implantation apparatus characterized in that, when the ion source is operated, the carrier gas supply system is automatically operated so that the amount of sample gas supplied to the plasma generation section does not fall below a certain set value. 2. The ion implantation apparatus according to claim 1, wherein the ion source uses microwave discharge in a magnetic field.