JPH02304842A - Method and apparatus for generating ion - Google Patents

Abstract

PURPOSE:To reduce stagnation in starting ionization of source gas by a method wherein prior to ionization of the source gas auxiliary gas which can become plasma more easily than the source gas is made to be plasma by an ion source to start ionization of the source gas by the plasma. CONSTITUTION:An ion source 10 is easily subjected to arc discharge with supply of auxiliary gas so that current flows to an arc current meter 25 while the auxiliary gas becomes plasma at the same time. A system 30 closes an auxiliary gas valve 24 by this arc current to open a source gas valve 23. Source gas is supplied to the ion source 10 while the auxiliary gas is made to be plasma so that ionization of the source gas is immediately started, and the ion source 10 with the supply of the auxiliary gas stopped generates only ions of the source gas. Therefore by using this ion generating apparatus, stagnation in starting ionization of ion gas can be eliminated. Thus stagnation in starting ionization of the source gas can be reduced.

Description

[Detailed Description of the Invention] [Summary] An ion generation method and method for generating ions of a source gas using an ion source that ionizes gas into plasma, which reduces the delay in starting ionization of the source gas. The purpose of the method is to provide an ion generator that performs this, and in the method, when generating source gas ions using an ion source that ionizes gas into plasma, the ion source generates ions from the source gas before ionizing the source gas. The apparatus is configured to convert an auxiliary gas that easily turns into plasma into plasma, and to start ionizing the source gas with the plasma, and the apparatus includes an ion source that turns the supplied gas into plasma and ionizes it, and a source gas that is supplied to the ion source. means for supplying the ion source with an auxiliary gas that is more easily converted into plasma than the source gas; and means for detecting that the gas supplied to the ion source has turned into plasma and stopping the supply of the auxiliary gas. Configure it so that it can be used.

[Industrial application field]

The present invention relates to an ion generation method in an ion implanter or the like, and an ion generation apparatus for performing the same.

Ion implantation equipment uses an ion source to ionize a source gas and irradiates the target object with the ions.It is used throughout the manufacturing of semiconductor devices, and the ionization ( It is desired to start ion generation immediately.

[Conventional technology]

A commonly used method for generating ions in an ion implantation apparatus is to arc discharge a source gas in an arc chamber to turn it into plasma.

FIG. 3 is a block diagram of an example of an ion source that does this.

In FIG. 3, this ion source 10 is called a Freeman type, and generates ions by a mechanism explained below.

That is, the thermoelectrons E generated from the filament 11 are drawn out by the arc voltage applied to the arc chamber 12, and are rotated within the chamber 12 by the magnetic field from the magnet 13. When gas is supplied in this state, an arc discharge occurs in which gas molecules M become plasma due to collisions with electrons E, and gas ions are generated. The generated ions are extracted to the outside through the slit 14. The pressure inside chamber I2 when gas is supplied is 3 xio-5
~IXl0-'Torr.

In addition to the above-mentioned Freeman type, such ion sources include an RF type that uses high frequencies, and all of them generate ions by converting supplied gas into plasma.

In the manufacture of semiconductor devices, the source gas used for ion implantation is gas such as BF:l, PH3, AsH3, etc., so in order to perform ion implantation, the ionization of the source gas (ion Conventionally, the source gas is directly supplied to the ion source when starting the ion source.

[Problem to be solved by the invention]

However, in reality, it is often difficult to cause arc discharge, and it may take a lot of time to adjust the device before ion generation starts. This stagnation poses a problem that reduces the throughput of ion implantation in the case of an ion implanter.

SUMMARY OF THE INVENTION Therefore, the present invention provides an ion generation method and an ion generation apparatus that reduces the delay in starting the ionization of the source gas when generating source gas ions using an ion source that ionizes gas into plasma. The purpose is to provide.

[Means to solve the problem]

The above purpose is to generate source gas ions using an ion source that ionizes gas into plasma.
The problem is solved by the ion generation method of the present invention, in which an auxiliary gas that is more easily turned into plasma than the source gas is turned into plasma by the ion source before ionizing the source gas, and the ionization of the source gas is started by the plasma. An ion source that converts into plasma and ionizes it, a means for supplying a source gas to the ion source, a means for supplying an auxiliary gas that is more easily converted into plasma than the source gas to the ion source, and a method for converting the gas supplied to the ion source into plasma. This problem is solved by the ion generator of the present invention, which includes means for detecting the auxiliary gas and stopping the supply of the auxiliary gas.

[For production]

The aforementioned delay before the start of ionization is due to the inexperience of the operator who adjusts the apparatus, but is also due to the fact that the source gas itself is not ionized.

The present invention focuses on this point and utilizes the following in order to reduce the above-mentioned stagnation.

This is a phenomenon in which if a plasma exists in advance, even a gas that is somewhat difficult to ionize will be immediately ionized, and the plasma may be of another gas. This phenomenon is a knowledge that the present inventor has learned from experience through operation of an ion implantation apparatus.

That is, even if the source gas itself is difficult to ionize, it is ionized by the plasma of the auxiliary gas, so there is no delay in starting ionization. Since the auxiliary gas is easier to turn into plasma than the source gas, it does not require much effort to turn it into plasma. As a result, the delay until the ionization of the source gas starts is significantly reduced.

Then, if the supply of the auxiliary gas is stopped when the auxiliary gas becomes plasma to ionize the source gas,
When the auxiliary gas in the ion source disappears, only the ions of the source gas are generated.

Since the above-mentioned ion generator includes the above-mentioned means for stopping the supply of auxiliary gas in its configuration, the supply of auxiliary gas is automatically stopped in a timely manner, thereby eliminating the stagnation in the rise of source gas ion generation. becomes effective, and also makes the operation for that purpose simple.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. Figure 1 is a configuration diagram of an embodiment of the ion generator,
FIG. 2 is a circuit diagram of the gas control system of this embodiment, and the ion generation method should be understood through an explanation of the operation of this ion generator.

In FIG. 1, 10 is the ion source explained in FIG.
1 is a source gas cylinder, 22 is an auxiliary gas cylinder, 23 is a source gas pulp, 24 is an auxiliary gas valve, 25 is an arc ammeter, 30 is a gas control system, 40 is an operator operation panel, 41 is a source gas switch, 42 is an auxiliary gas switch , is.

The source gas pulp 23 opens and closes the supply of source gas from the cylinder 21 to the ion source 10, and the auxiliary gas valve 24
opens and closes the supply of auxiliary gas from the cylinder 22 to the ion source 10 . The arc current meter 25 indicates the current of the arc discharge in which the gas in the ion source 10 becomes a plasma state.

The gas control system 30 is a circuit that opens and closes the source gas pulp 22 and the auxiliary gas valve 24 by inputting the current of the arc ammeter 25 and the signals of the source gas switch 41 and the auxiliary gas switch 42. As shown in Figure 2.

In FIG. 2, 31 is a switch connected to the arc ammeter 25, 32 is a switch connected to the source gas switch 41, and 33 is a switch connected to the auxiliary gas switch 42. This system 30 includes a source gas switch 4
When 1 is turned on, switches 31 and 32 are turned on,
The auxiliary gas valve 24 is kept open until the ion source 10 generates an arc discharge, and when the arc discharge occurs, the auxiliary gas valve 2 is opened by the arc current signal flowing through the ammeter 25.
4 is closed and the source gas pulp 23 is opened. Further, when the auxiliary gas switch 42 is turned on, the switch 33 is turned on and the auxiliary gas valve 24 is opened. Note that 34 is an amplifier, 35 is an N07 circuit, 36 is an AND circuit, 37 is an OR circuit, 38 is an operational amplifier, and 39 is a diode.

Therefore, the means for supplying the source gas, the means for supplying the auxiliary gas, and the means for stopping the supply of the auxiliary gas are the cylinder 21 + the valve 23 + the system 30, respectively.
, cylinder 22 + valve 24 + system 30, and arc current signal child valve 24 + system 30 of ammeter 25.

The auxiliary gas used is one that is more easily converted into plasma by the ion source 1o than the source gas.

Based on the above, the operation of this ion generator is as follows.

■ The operator turns on the source gas switch 41 on the operator panel 40.

(2) This signal causes the gas control system 30 to open the auxiliary gas valve 24, and auxiliary gas is supplied to the ion source 10.

(2) The ion source 10 easily causes arc discharge by supplying auxiliary gas, and current flows through the arc ammeter 25. At the same time, the auxiliary gas enters a plasma state.

(2) This arc current causes the system 30 to close the auxiliary gas valve 24 and open the source gas pulp 23.

(2) In the ion source 10, the source gas is supplied to the part where the auxiliary gas is in a plasma state, and the source gas immediately starts to be ionized.

(2) The ion source 10 whose supply of auxiliary gas has been stopped in accordance with (1) above gradually loses the auxiliary gas and comes to generate only source gas ions.

Therefore, if this ion generator is used, the stagnation in the rise of source gas ion generation is eliminated, and the operation for this purpose is simple because only the ON operation of the source gas switch 41 is required.

Here, B F 3 , PH 3 , ASH 3, etc. are used as source gases for ion implantation in semiconductor device manufacturing, but it has been empirically found that among these, A5H:l is most easily converted into plasma. B F s, PH
When No. 3 is used as a source gas, AsH is used as an auxiliary gas.

For example, when implanting p-type impurities using BF as a source gas, AsHz becomes the source gas for n-type impurities.
Even if the auxiliary gas is used as the auxiliary gas, the above-mentioned operation (2) will not cause any problems in ion implantation.

Although the above explanation is based on one type of source gas, for example, if you want to select one type of source gas from among multiple types of source gas and generate ions using one ion implanter, In FIG. 1, a plurality of sets of source gas cylinders 21, source gas valves 23, and source gas switches 41 are arranged in parallel, and selection of the source gas switches 41 is
A circuit in which the corresponding source gas valve 23 is selected by N may be added to the circuit shown in FIG. 2.

Note that the auxiliary gas may be selected based on the source gas, and is not limited to the above-mentioned ASH3.

Furthermore, in the above embodiment, the supply of the auxiliary gas and the supply of the source gas are switched at the same time when the ions a10 cause arc discharge, but at this point the supply of the auxiliary gas and the supply of the source gas are temporarily overlapped. You can let me. However, when starting the supply of source gas before causing arc discharge, it is necessary to take into account that if the gas pressure within the ion source 10 becomes excessive, it becomes difficult to cause arc discharge.

Furthermore, although the above embodiment deals with the case where the ion source 10.6 is <Freeman type, the same can be applied even if the ion source is the RF type described above.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in generating source gas ions using an ion source that ionizes gas by turning it into plasma, ion generation is performed to reduce the delay in starting ionization of the source gas. A method and an ion generator capable of performing the same with a simple operation are provided, which has the effect of preventing a decrease in ion implantation throughput in, for example, an ion implanter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an ion generator, FIG. 2 is a circuit diagram of a gas control system of the embodiment, and FIG. 3 is a block diagram of an example of an ion source. In the figure, 10 is an ion source, 21 is a source gas cylinder, 22 is an auxiliary gas cylinder, 23 is a source gas valve, 24 is an auxiliary gas valve, 25 is an arc ammeter, 30 is a gas control system, 40 is an operator operation panel, 41 is a source gas The switch 42 is an auxiliary gas switch. 22 Drunkenness, assistance 7J, - public 23. Source przuharu 7゛24, it is durable ■ or i"kuroha"°lf 40 O l+ Ion-free grass cover! No. 7 examples 0 Kozue Boshu Part I - Kube

Claims (1)

[Claims] 1) When generating source gas ions using an ion source that ionizes gas by turning it into plasma, before ionizing the source gas, the ion source turns an auxiliary gas that is easier to turn into plasma than the source gas into plasma. 1. A method for generating ions, comprising: ionizing a source gas, and causing the plasma to start ionizing a source gas. 2) an ion source that converts the supplied gas into plasma and ionizes it; a means for supplying a source gas to the ion source; a means for supplying an auxiliary gas that is more easily turned into plasma than the source gas; An ion generator comprising means for detecting that the auxiliary gas has turned into plasma and stopping the supply of the auxiliary gas.