JP2882188B2 - Ion beam processing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam processing method and apparatus, and more particularly to an ion beam processing method and apparatus for generating an ion beam based on gas discharge and processing a sample with the generated ion beam.

[0002]

2. Description of the Related Art An ion beam generator of the type that generates an ion beam based on gas discharge has a long life and is suitable for cleanliness because it is filamentless. Therefore, an ion implantation apparatus and an etching apparatus are required. Etc. are widely used in various semiconductor manufacturing apparatuses.

[0003] In this type of ion generator, an electric field and a magnetic field are formed in an ionization chamber, a gas is caused to flow in the ionization chamber in that state, plasma is generated by discharge, and an ion beam is extracted from the plasma. In starting the discharge, the strength of the electric field, the strength of the magnetic field, and the flow rate of the gas are generally set manually. However, these values often differ over time depending on the type of ion, and therefore the type of gas, and since they are not always clear, these values are often set too high in practice.

[0004]

However, if those values are set too large, the following problems occur.

(1) As the sample processing conditions after the start of discharge, the plasma density is excessive and the plasma becomes unstable. Therefore, it is necessary to correct the excessive set value to a value suitable for the sample processing. It is.

(2) There is a problem of contamination of the apparatus due to an excessive gas flow rate and destruction of the apparatus due to abnormal discharge, which lowers the reliability of the entire apparatus.

An object of the present invention is to provide an ion beam processing method and apparatus suitable for appropriately starting discharge.

[0008]

According to the present invention, a discharge starting condition corresponding to the type of gas to be introduced into the ionization chamber is determined in advance, and in response to the specification of the type of gas, the discharge start condition is designated. The discharge is started by introducing a designated gas into the ionization chamber under a discharge start condition determined in advance corresponding to the type of the gas.

[0009]

According to this, it is possible to set the necessary minimum discharge start condition according to the type of gas, so that excessive discharge is prevented and proper discharge start is performed. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS To explain the ion implantation apparatus shown in FIG. 6, an ion beam emitted from an ion source 11 is mass-separated by a magnetic field 13, and an ion beam of a specific ion species obtained by the ion beam is slit. Go through 14,
It is driven into a sample 16 which is a semiconductor wafer placed in the driving chamber 15.

The details of the ion source 11 will be described with reference to FIG. 1. The microwave 3 generated by the microwave generator 20 passes through the waveguide 4, passes through the dielectric vacuum seal 5 and enters the ionization chamber 1. Be guided. As a result, a microwave electric field is formed in the ionization chamber 1. The solenoid coil device 6 generates a magnetic field in the ionization chamber 1 so as to be orthogonal to the microwave electric field. When a gas is introduced into the ionization chamber 1 in this state, microwave discharge occurs therein to generate plasma, and an ion beam is extracted from the plasma.

The gas source 21 stores a plurality of types of gases to be used, for example, arsine gas, argon gas, nitrogen gas, boron trifluoride, phosphine, and the like. The selected gas is introduced into the ionization chamber 1 through the mass flow controller 2, the storage pipe 22, and the stop valve 7. The amount of gas stored in the storage pipe 22 is determined by closing the stop valve 7 and the mass flow meter 2.
Is determined by the time from when the gas flows to the storage tube 22 via the mass flow meter 2 in the state where the flow rate is regulated until the stop valve 7 is opened.

The selection and setting of the gas type, the opening and closing of the mass flow controller 2 and the stop valve 7, and the selection and setting of the microwave power, that is, the strength of the microwave electric field and magnetic field, are performed based on instructions from the computer 23 by the drive and / or control unit 26. Done by Processing conditions, discharge start conditions, and the like are stored in the storage device 24 of the computer 23 in advance.

FIG. 2 shows that when the magnetic field strength B is 0.08 T and the microwave power is 200 W, the discharge necessary for the gas flow (CC / M) to be set in the normal processing step is required to start the discharge. The relationship between the gas amount (accumulated amount) (CC) is shown for each type of gas. The triangular curve is the curve for hydrogen-containing arsine gas, the circle is the curve for argon gas, and the square is the curve for nitrogen gas. From this figure, if the type and flow rate of the gas are determined, the optimum gas accumulation amount necessary for starting the discharge can be found.

FIG. 3 shows that when the magnetic field strength B is 0.08 T and the microwave power is 200 W, the discharge required for the start of the discharge with respect to the nitrogen gas flow rate (CC / M) to be set in the normal processing step. The relationship of the gas accumulation time (S) is shown. In this figure, the upper side of the curve is the discharge area, and the lower side is the non-discharge area. Once the nitrogen gas flow rate has been determined, it is appropriate to select a slightly curved value within the discharge region as the gas accumulation time to prevent excessive plasma generation.

FIG. 4 shows the relationship between the microwave power (W) when the magnetic field strength is 0.08 T and the nitrogen gas flow rate is 2.0 CC / M, and the gas accumulation time required for starting the discharge. The upper side of the curve is a discharge area, and the lower side is a non-discharge area. Once the microwave power is determined, it is important to select a gas accumulation time that is slightly below the curve in the discharge region in order to prevent excessive plasma generation.

FIG. 5 shows the magnetic field strength (T) when the microwave power is 300 W and the nitrogen gas flow rate is 3 CC / M.
The relationship between the gas accumulation time (S) required for starting the discharge with respect to is shown. Lower power translates the curve up.
When the nitrogen gas flow rate is 2 CC / M, the curve is further translated up by 1.5 times.

The storage device 24 of the computer 23 stores in advance the type of gas (and therefore the ion type) required for sample processing, the flow rate of the gas, the microwave power, the strength of the microwave electric field and the strength of the magnetic field. Have been. Further, a gas amount table for each gas type required for starting discharge is stored. This table may be a gas quantity for each magnetic field strength and electric field strength.

In order to explain the operation, the conditions for sample processing from the input / output device 25 include the type of gas (ion type), the flow rate of the gas, the microwave power, the intensity of the microwave electric field,
The strength of the magnetic field is keyed in (FIG. 7A). By this key-in, gas is selected and corresponding
The optimal gas amount for starting the discharge is read from the storage device 24 (FIG. 7B). Based on this, the computer 23 calculates the optimal accumulation time for starting the discharge (FIG. 7C). The drive and / or control device 26 controls the opening and closing of the stop valve 7 and the mass flow controller 2 so that the gas is introduced into the storage tube 22 for the calculated time and stored in an amount optimal for the start of discharge in response to a command from the computer 23. (Figure 7
D). The computer 23 opens the stop valve 7 after the accumulation time, whereby the accumulated gas is introduced into the ionization chamber 1 (FIG. 7E) and the discharge is started (FIG. 7F). After the start of the discharge, the gas enters a steady state, and first, a gas having a flow rate set by the key-in is continuously introduced into the ionization chamber 1,
Sample processing is performed (FIG. 7G). FIG. 8 shows another embodiment according to the present invention. The gas introduced into the ionization chamber 1 is controlled by a mass flow controller 2.
A waveguide 4 and a vacuum seal plate 5 are provided for forming a microwave electric field in the ionization chamber 1. Reference numeral 6 denotes a solenoid coil 6 for forming a magnetic field. As a means for instantaneously increasing the gas pressure in the ionization chamber 1, two gas pipes 8, 9 introduced into the ionization chamber 1 are used. It is realized by opening only for hours. After ignition, the valve 7 of the pipe 9 is closed, and the gas flow rate matching the sample processing conditions is controlled by the mass flow controller 2 of the pipe 8.

[0020]

According to the present invention, there is provided an ion beam processing method and apparatus suitable for appropriately starting discharge.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a part of a main part of an ion beam processing apparatus according to an embodiment of the present invention.

FIG. 2 is a data showing a relationship between a gas flow rate and a gas amount to assist understanding of the present invention.

FIG. 3 is a diagram showing a relationship between a nitrogen gas flow rate and a gas accumulation time to assist understanding of the present invention.

FIG. 4 is a diagram showing a relationship between a microwave power and a gas accumulation amount to assist understanding of the present invention.

FIG. 5 is a diagram showing the relationship between the strength of a magnetic field and the amount of accumulated gas to assist the understanding of the present invention.

FIG. 6 is a conceptual diagram of an ion beam processing apparatus showing one embodiment according to the present invention.

FIG. 7 is a flowchart for explaining the operation of the present invention.

FIG. 8 is a sectional view of a main part of an ion beam processing apparatus according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ionization room, 2 ... Mass flow controller, 4 ... Waveguide, 5 ... Dielectric vacuum seal, 6 ... Solenoid coil device, 7 ... Stop valve, 8, 9 ... Pipe, 13 ... Mass separator (magnetic field), 16 ... sample, 21 ... gas source, 22 ... storage tube, 23 ... computer, 24 ... storage device, 25 ... input / output device, 26 ... drive and / or control device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 27/00-27/26 H01J 37/08

Claims (11)

(57) [Claims] An ion beam processing apparatus for introducing a gas into an ionization chamber, generating plasma of the gas by discharge, extracting an ion beam from the generated plasma, and processing a sample with the extracted ion beam. Means for preliminarily storing a gas introduction amount in accordance with the type of gas to be introduced into the ionization chamber; storage means for accumulating the gas to be introduced; and introduction to the ionization chamber. Means for specifying the type of gas to be produced,
In response to the designation, a gas introduction amount stored corresponding to the designated gas type is read from the storage means, and the read gas introduction amount is stored in the storage means, An ion beam processing apparatus, wherein gas accumulated at the time of starting the discharge is introduced into the ionization chamber. 2. An ion beam generating means, and means for processing a sample with the generated ion beam, wherein the ion beam generating means includes an ionization chamber and a type of gas to be introduced into the ionization chamber. Means for preliminarily storing the corresponding gas introduction amount, means for specifying the type of gas to be introduced into the ionization chamber, means for storing the gas to be introduced, and means for specifying In response to the designation, a gas introduction amount stored corresponding to the designated gas type is read out from the storage means, and the read gas introduction amount is stored in the storage means, and the ionization chamber is stored. Means for generating a plasma of the specified gas by introducing the gas into the ionization chamber at the start of the discharge in the plasma, and extracting the ion beam from the generated plasma. Ion beam processing apparatus are. 3. An ion beam processing apparatus according to claim 1, further comprising means for forming an electric field and a magnetic field in said ionization chamber. 4. An ion beam processing apparatus according to claim 1, wherein said storage means includes a first valve, a second valve for defining a flow rate, and a storage tube interposed between said valves. apparatus. 5. The storage means stores the gas introduction amount into the storage pipe through the second valve with the first valve closed and the flow rate regulated by the second valve. The ion beam processing apparatus according to claim 4, wherein the ion beam processing apparatus is controlled so as to be determined based on a time until the first valve is opened after flowing. 6. An ionization chamber and a gas introduced into the ionization chamber.
Store the gas introduction amount according to the type of gas to be stored in advance.
Means and the type of gas to be introduced into the ionization chamber
Means for specifying the
The gas introduction amount stored corresponding to the type of gas is
Read from the storage means, and read the read gas introduction amount
Accumulating means for accumulating, and starting discharge in the ionization chamber
The gas from the storage means to the ionization chamber.
To generate a plasma of the specified gas,
Means for extracting an ion beam from the formed plasma.
Ion beam generator provided. 7. An electric field and a magnetic field are formed in the ionization chamber.
7. The method according to claim 6, further comprising:
Ion beam generator. 8. The storage means defines a first valve and a flow rate.
A second valve and an intervening valve between them
7. The ion beam according to claim 6, including a storage tube.
Generator. 9. The storage means stores the gas introduction amount in the
The first valve is closed, and the flow rate is regulated by the second valve.
In this state, gas is supplied to the storage tube through the second valve.
Depending on the time it takes to open the first valve after flushing
9. The method according to claim 8, wherein the control is performed so as to determine.
An ion beam processing apparatus as described. 10. A gas is introduced into an ionization chamber, and an electric field and a magnetic field are introduced.
Discharge of the gas in the ionization chamber in the presence of a field
Generates a plasma and draws an ion beam from the plasma
And process the sample with the extracted ion beam.
An ion beam processing method, comprising:
Flow rate and the strength of the electric and magnetic fields.
Gas suitable for starting the discharge for each processing condition of the sample
The storage amount is stored in a storage device in advance, and the
In response to the specified processing condition
The amount of gas suitable for starting the discharge is stored in the storage device.
From the specified gas and read the amount of gas read out from the specified gas.
Gas specified by the accumulation time obtained by dividing by the gas flow rate.
Gas in the storage device and the accumulated gas
And discharge under the specified processing conditions
Starting the ion beam processing. 11. A method for generating an ion beam based on a discharge.
Step and means for treating the sample with the generated ion beam
Wherein the ion beam generating means comprises an ionization chamber,
Means for forming an electric and magnetic field in the ionization chamber;
Means for accumulating gas and the type and flow rate of the gas
The test is determined by the strength of the electric and magnetic fields.
The amount of gas suitable for starting the discharge is predicted for each material treatment condition.
Means for storing and means for specifying the processing conditions
Corresponding to the specified processing condition in response to the specified
Gas amount suitable for the start of the discharge stored in advance
From the storage means, and the read gas amount
Is divided by the specified gas flow rate to obtain the accumulation time.
The specified gas for the storage time
Accumulate in the stage and conduct the accumulated gas to the ionization chamber.
And start the discharge under the designated processing conditions
And an ion beam processing apparatus.