JPH0563897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion implantation method for implanting ions into a sample by deflecting and scanning an ion beam.

[Conventional technology]

In an ion implanter that uses medium current or less, in order to uniformly implant ions into the sample, the ion beam is deflected by a deflection scanning electrode installed in front of the sample disk that holds the sample, and the ions are placed on the surface of the sample to be implanted. Ion implantation methods using electrostatic scanning of a beam have been well known in the art. However, with conventional ion implantation methods,
When the ion beam is scanned, the depth of the implanted layer changes because the angle between the ion beam and the sample is different between the center and the edge of the implanted sample. Therefore, the depth of the implanted layer changes over the entire sample. There was a drawback that it was difficult to form an injection layer with a certain depth [Publication: Solid State Technology.November
(197861))]. This drawback becomes more pronounced as the sample size increases. A detailed description will be given below with reference to the drawings.

FIG. 3 shows an example of the configuration of an electrostatic scanning portion of an ion implanter used in a conventional ion implantation method. As shown in FIG. 3, ions are extracted from the ion source 10 by an electric field lens 11, subjected to mass analysis by a mass spectrometer 12, and accelerated by an accelerator 13.
Ion beam 15 shaped by electrostatic lens 14
are + and - configured parallel to the plane of the paper and facing each other.
It is deflected when passing through the Y scanning electrode 16 consisting of electrodes. The reference triangular wave a generated by the Y sweep generator 17 is converted into a triangular wave with the positive and negative polarities reversed by the negative converter 18 for application to the - electrode of the Y scanning electrode 16, and then the ion beam 15 is transferred to the sample disk. In order to obtain a voltage sufficient to scan in the Y-axis direction of 28, the voltage is converted into a high voltage triangular wave by an amplifier 19 and applied to one electrode of the Y-scanning electrode 16. On the other hand, regarding the triangular wave applied to the + electrode of the Y-scanning electrode 16, the triangular wave a generated by the Y-sweep generator 17 is immediately converted into a high-voltage triangular wave by the amplifier 20, parallel to and facing the - electrode of the Y-scanning electrode 16. + applied to the electrode.

The ion beam 21 deflected by the Y-scan electrode 16 so as to scan in the Y-axis direction enters the X-scan electrode 22 to scan in the X-axis direction, and is further deflected. The reference triangular wave b generated by the X sweep generator 23 in the same way as the Y scan electrode 16 is applied to the negative converter 2 of the X scan electrode 22.
4, the ion beam 21 is converted into a triangular wave with the positive and negative polarities reversed, and then converted into a high voltage triangular wave by an amplifier 25 to generate a voltage sufficient to allow the ion beam 21 to scan the sample disk 28 in the X-axis direction. 22 - electrode. On the other hand, regarding the triangular wave applied to the + electrode of the X scan electrode 22, the X sweep generator 2
The triangular wave b generated in step 3 is immediately turned into a high voltage triangular wave by the amplifier 26 and applied to the + electrode opposite to the - electrode of the X scanning electrode 22.

In order to remove neutral ions, the ion beam is offset by about 7 degrees by applying a DC bias voltage to a deflection scanning electrode (generally the X scanning electrode 22) (not shown).

[Problem that the invention seeks to solve]

According to the ion implantation apparatus used in the conventional ion implantation method described above, the Y scan electrode 16,
Ion beam 27 deflected to scan with the X scanning electrode 22 [In FIG. 3, the central ion beam in the X direction is shown as 27a, and the ion beams deflected to the maximum in the X direction (deflection angle θ) are shown as 27b and 27c] is scanned in the Y-axis direction and the X-axis direction by the area required for injection on the sample disk 28,
There is a drawback that the angle formed between the sample disk 28 and the ion beam 27 always changes depending on the position of the ion beam 27 on the sample disk 28, and as mentioned above, the depth distribution of the implanted impurity changes depending on the implantation location. A problem had arisen.

An object of the present invention is to provide an improved ion implantation method that consistently forms a uniform ion implantation layer.

[Means for solving problems]

The present invention provides an ion implantation method in which ions are implanted into a sample by deflection scanning an ion beam, in which a second deflection scan is performed after a first deflection scan of the ion beam, and The deflection signal applied to the second deflection scanning electrode is
From the deflection signal applied to the first deflection scanning electrode for deflection scanning of charge, v is the accelerating voltage,
This method is characterized in that the ion beam is always made incident on the sample as a parallel beam by delaying the time t given by m (the mass of the ion).

[Effect]

According to the ion implantation method of the present invention, the inclination angle between the normal to the implanted surface of the sample and the ion beam remains constant even when the ion beam is deflected and scanned, that is, the ion beam incident on the sample becomes a parallel beam. After the ion beam is deflected and scanned, the ion beam is deflected and scanned again. Note that the first deflection scan is referred to as the first deflection scan,
The second deflection scan will be referred to as a second deflection scan.

In such an ion implantation method, the deflection signal applied to the deflection scanning electrode for causing the ion beam to perform the second deflection scan is applied to the deflection signal applied to the deflection scanning electrode for causing the ion beam to perform the second deflection scan. By delaying the deflection scanning electrode for the deflection scanning of the ion beam by the time it takes for the ion beam to pass, the inclination angle between the normal to the implanted surface of the sample and the ion beam is always constant, and the ion implantation layer The depth is made uniform.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of an ion implanter used in an embodiment of the present invention. As shown in FIG. The ion beam 15, which has been accelerated by the accelerator 13 and shaped by the electrostatic lens 14, is deflected when passing through the Y scanning electrode 16, which consists of + and - electrodes arranged parallel to the paper and facing each other. be done. The reference triangular wave generated by the Y sweep generator 17 is converted into a triangular wave with the sign reversed by the negative converter 18 for application to the - electrode of the Y scanning electrode 16, and then the ion beam 15 is transferred to the sample disk 28.
In order to make the voltage high enough to scan in the Y-axis direction, the amplifier 19 converts the voltage into a high-voltage triangular wave and applies it to the negative electrode of the Y-scanning electrode 16. On the other hand, regarding the triangular wave applied to the + electrode of the Y scanning electrode 16,
The reference triangular wave generated by the sweep generator 17 is immediately converted into a high voltage triangular wave by the amplifier 20 and applied to the + electrode parallel to and opposite to the - electrode of the Y scan electrode 16.

The ion beam 21 deflected by the Y-scan electrode 16 so as to scan in the Y-axis direction enters the X-scan electrode 22 to scan in the X-axis direction, and is further deflected. Similarly to the Y-scan electrode 16, the reference triangular wave generated by the X-sweep generator 23 is connected to the X-scan electrode 2.
After the ion beam 21 is converted into a triangular wave whose positive and negative polarities are inverted in order to be applied to the - electrode of 2, an amplifier 25 is applied to the voltage to enable the ion beam 21 to scan the sample disk 28 in the X-axis direction. The voltage is converted into a high voltage triangular wave and applied to the negative electrode of the X scanning electrode 22. On the other hand, regarding the triangular wave to be applied to the + electrode of the X-scanning electrode 22, the reference triangular wave generated by the Apply to.

In order to remove neutral ions, the ion beam is offset by about 7 degrees (not shown) by applying a DC bias voltage to the deflection scanning electrode (generally the X scanning electrode 22). , is the same as the conventional ion implantation method, but in the present invention, Y
Ion beam 1 is generated by scanning electrode 16 and X scanning electrode 22.
5 scans the sample disk 28 in the Y-axis direction and the X-axis direction, respectively, and then the ion beam 28 is deflected again by the re-deflection Y scan electrode 29 and the re-deflection X scan electrode 30 to scan the sample disk 28. The ion beam 31 is deflected again (in FIG. 1, the central ion beam in the X direction is shown as 31a, and the ion beams that are maximally deflected in the X direction are shown as 31b and 31c).
From the deflection signals applied to the re-deflection scanning electrodes 29 and 30 and the deflection signals applied to the deflection scanning electrodes 16 and 22, the formula t=l/√
2qv/m (where l is the distance between the scanning electrode for the first deflection scan and the scanning electrode for the second deflection scan, q is the charge of the ion, v is the accelerating voltage, and m is the mass of the ion) The signal is applied after being delayed by the time t given by .

This process will be explained in detail using FIGS. 1 and 2.

Figure 2 shows the ion beam and the scan electrodes for the first and second deflection scans (both X scan electrodes 2
2 and 30 are shown) and a deflection signal. X scan electrode 22 and X scan electrode 30
Let the distance between the two be _lX .

In FIG. 2, the ion beam 27 that has entered the X scanning electrode 22 at a velocity v ₀ is converted into an
Scan in the direction. Since the triangular wave c for deflection scanning at time _t0 has the maximum negative voltage, the ion beam
This is the position 27b that is most drawn to the scanning electrode 22.
On the other hand, at the re-deflection X-scan electrode 30 that is a distance _lX away from the X-scan electrode 22 at time _t0 , the ion beam 32 that was deflected and scanned by the X-scan electrode 22 a time _tX before is present. For comparison, if the deflection signal applied to the _re -deflection The trajectory is no longer parallel to the ion beam trajectory 34 when the sample disk 28 and the ion beam are not scanned. In order to solve these problems, according to the present invention, the triangular wave applied to the re-deflection X scanning electrode 30 _is
= l _X / v ₀ (where, l _X is the distance between the deflection X scanning electrode 22 and _the re-deflection The ion beam 32 entering the X-scanning electrode 30 becomes an ion beam 31 shown by a solid line, which is parallel to the ion beam 34.

The ion velocity v ₀ is expressed by the formula v ₀ =√2 (however,
Since q is given by the charge of the ion, v is the acceleration voltage, and m is the mass of the ion, it is necessary to change the delay time when the acceleration voltage and ion mass change, so it is necessary to use the method described below. be. In FIG. 1, the accelerating voltage is determined by measuring the voltage of the power source 35 for applying to the electric field lens 11 with a voltage measuring device 36, and measuring the voltage of the power source 37 for applying to the accelerator 13 with a voltage measuring device 38. value and adder 3
It is added by 9. On the other hand, the mass of the ion m
The radius of the ion beam orbit of the mass analyzer 12 is expressed by the formula r=√2 _E ² (where m is the mass of the ion, v _E
is given by the extraction voltage, the charge of the q ions, and B is the magnetic flux), so it can be calculated using the method described below.

Since the ion beam orbit radius r is determined by the mass analyzer 12 in FIG. A mass calculation unit 42 calculates the mass m of the ion using a value obtained by squaring the magnetic flux measured by a multiplier 41 . After calculating the mass m of the ion, the ion speed calculator 43 calculates the ion speed v ₀ .

_The delay time _t Ion velocity determined by
The reference triangular wave generated by the X sweep generator 23 is delayed by a time _tX in the delay device 50, and then applied to the re _- deflected X scanning electrode 30. In this case, a high voltage triangular wave is applied to the - electrode of the X-scanning electrode 30 by an amplifier 51, and a triangular wave whose positive and negative sides are inverted is applied to the + electrode of the X-scanning electrode 30 by a negative converter 52. 53, a high voltage triangular wave is applied.

The above has explained the triangular wave applied to the reorganized X scan electrode 30, but similarly, the reorganized Y scan electrode 2
The delay time t _Y of the triangular wave applied to the Y deflection delay time calculator 44 is determined by the ion velocity determined by the ion velocity calculator 43 using the electrode interval l _Y between the deflection Y scan electrode 16 and the re-deflection Y scan electrode 29. The reference triangular wave generated by the Y sweep generator 17 is delayed by the time t _Y in the delay device 45, and then re _- deflected Y
The voltage is applied to the scanning electrode 29. In this case, a high voltage triangular wave is applied to the negative electrode of the Y-scanning electrode 29 or the amplifier 46, and the polarity is inverted by the negative converter 47 to the positive electrode of the Y-scanning electrode 29 to form a triangular wave. 48, a high voltage triangular wave is applied.

Although the above embodiments have been described with respect to an electrostatic scanning method, the present invention can also be applied to a magnetic field scanning method.

〔Effect of the invention〕

As is clear from the above, when the ion beam is deflected and scanned to implant ions into a sample, the ion beam is deflected after the first deflection scan, and then the second deflection scan is performed, and the deflection electrode for performing the second deflection scan is used. From the deflection signal applied to the deflection electrode for performing the first deflection scan, the formula t=l/√2
By applying a deflection signal delayed by the time t given by , the inclination angle between the normal to the implanted surface of the sample and the ion-on beam is always constant, and a uniform ion-implanted layer can be formed at all times. effective.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIG. 2 shows the deflection X-scanning electrode and re-deflection X-scanning electrode shown in FIG. 1, the ion beam incident on the sample disk, and the deflection signal. FIG. 3 is a diagram for explaining the conventional ion implantation method. 10...Ion source, 11...Electric field lens, 12
... Mass spectrometer, 13 ... Accelerator, 14 ... Electrostatic lens, 15, 21, 27, 31, 32 ... Ion beam, 16 ... Y scanning electrode, 17 ... Y sweep generator, 18, 24 , 47, 52...Negative converter, 19, 20, 25, 26, 46,
48, 51, 53...Amplifier, 22...X scanning electrode, 23...X sweep generator, 28...Sample disk, 29...Redeflection Y scanning electrode, 30...Redeflection 37...Power supply, 36, 38...
... Voltage measuring device, 39 ... Adder, 40 ... Magnetic flux measuring device, 41 ... Multiplier, 42 ... Mass calculator, 4
3...Ion velocity calculator, 44...Y deflection delay time calculator, 45, 50...Delay unit, 49...X
Delay time calculator for deflection.

Claims (1)

[Claims] 1 In an ion implantation method in which ions are implanted into a sample by deflection-scanning an ion beam, a second deflection scan is performed on the ion beam after a first deflection scan; From the equation t=l/√2 (where l is the first deflection scan electrode), the deflection signal applied to the first deflection scan electrode is
the distance between the deflection scanning electrode and the second deflection scanning electrode,
An ion implantation method characterized by making the ion beam always enter the sample as a parallel beam by delaying it by a time t given by: q is the charge of the ion, v is the accelerating voltage, and m is the mass of the ion.