JP2990126B2 - Ion implantation apparatus and ion beam measurement method - 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 implantation apparatus and an ion beam measurement method, and more particularly to an ion implantation apparatus and an ion beam measurement method for controlling the amount and energy of ions implanted into a semiconductor wafer as a sample. About.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, it is important to control the amount of implanted ions and the depth of implantation of ions in an ion implantation apparatus in order to secure the operation performance as the miniaturization progresses.

In recent years, high-energy ion implantation with an acceleration voltage exceeding 1 MeV has been demanded in many cases. However, as the energy becomes higher, the structure of the ion implantation apparatus becomes more complicated, and a measurement error of the implantation amount and the acceleration voltage is more likely to occur, thereby lowering the control accuracy.

FIG. 3 shows a prior art method for measuring the amount of ion implantation. In the method shown in FIG. 1, an ion beam 10 is extracted from an ion source 1 by an extraction electrode 2 and emitted. The ion beam 10 obtains implantation energy by an accelerator 3 and is selected by a magnet 4 to select only specific ions. Is injected into the sample stage 12 including the sample 11,
The current flowing from the sample stage to the ground due to the potential fluctuation of the sample stage 12 is measured by the ammeter 13 and calculated by the ion counting system 8 to obtain the injection amount.

[0005] The accuracy of measuring the injection amount by this method is determined by the correction of the change in the valence of ions caused by the collision with the floating gas and the state of being cut off from the outside of the Faraday system.

FIG. 4A shows another prior art method for measuring the amount of ion implantation, which utilizes X-rays (indicated by dotted lines). In this method, the sample stage 12
Characteristic X-ray (indicated by a dotted line) generated when the ion beam 10 moves up and down while rotating so that ions are implanted evenly and hits the target 15 when the ion beam 10 comes off the sample stage.
Is detected by the X-ray measurement sensor 16, and the intensity is proportional to the ion beam 10.
Japanese Patent Application Laid-Open No. Hei 5-
This is described in JP-A-326437. The injection amount can be obtained by averaging the injection amount in one cycle from the characteristic X-ray intensity emitted when the ion beam 10 collides with the target 15.

[0007] The measurement accuracy of this method is determined by the stability of the ion beam current during the measurement period. Further, FIG.
As shown in FIG. 4 (B), by changing the method described above, assuming a method of constantly measuring X-rays (indicated by a dotted line) generated from the sample stage, the stability of the X-ray intensity measurement indicates the measurement accuracy. Can be determined.

FIG. 5 shows a prior art method for measuring implantation energy. In this method, the implantation energy is measured by X-rays in an ion implantation apparatus.
A dedicated target 15 for measuring the injection energy and an X-ray measurement sensor 16 are set around the area 2 to measure the shortest wavelength of the X-ray (indicated by a dotted line). This is described in Japanese Patent Publication No.

As other methods, there are a SIMS method in which a surface of a Si wafer is dug to measure a profile of an impurity concentration and a method in which surface damage of a Si wafer is measured. Further, a method of measuring by using a change in electric resistance of a Si wafer is disclosed in Japanese Patent Application Laid-Open No. 63-128541.

[0010]

In the method of measuring the amount of ion implantation using the charge of ions as shown in FIG.
A change in the valence of the ion beam due to the degree of vacuum of the beam line lowers the measurement accuracy. In particular, in the manufacture of semiconductor devices, in recent years, photoresists made of organic materials have become common as mask materials for ion implantation, and outgas generated when an ion beam hits a mask changes the charge of the ion beam, leading to a disorder in the amount of implantation. Cause.

[0011] High energy ion implantation exceeding 300 keV generates more outgas, and low energy implantation causes only neutron neutralization to change valence. The increase in valence due to electron peeling is added, and the factors that disturb the injection amount are complicated. For these reasons, the ion implantation dose is 10
% Or more.

Here, when the correction by pressure is performed to suppress the influence of the injection amount due to the change in the valence of the ion beam, the measurement accuracy can be improved and the deviation can be reduced to 1% or less. Requires a lot of man-hours.

[0013] In addition, in the implantation by the batch method, the dependency on the number of wafers with photoresist must be included in the correction method, and when changing the material of the photoresist, it is necessary to read all of these conditions.

Further, in the measurement using electric charge, as the structure of the ion implantation apparatus becomes larger and more complicated, it becomes more difficult to completely shut off the Faraday system for measuring the implantation amount from the outside.
There is a problem that the measurement accuracy of the inflow amount due to the electric leak is apt to decrease.

In the method of measuring the ion implantation amount by the characteristic X-ray as shown in FIG. 4A, the ion implantation amount is not affected by the valence fluctuation of the ion beam.
If the ion beam fluctuates during the measurement cycle, the measurement accuracy of the implantation dose will be reduced.

On the other hand, X by the method shown in FIG.
In the measurement of the line, the X obtained by the sample table and the clamper that holds the sample and not having a flat surface structure, the mixture of various materials, and the change in the number of samples in the batch method, etc. are obtained. The measured intensity of the line is less reliable, which makes the conversion of the injection volume difficult and impractical.

As shown in FIG. 5, the method using a dedicated target for measuring the implantation energy can be measured only at the time of set-up. Therefore, when the energy shift or fluctuation occurs during the ion implantation, the ion implantation apparatus needs to be installed. Measurement results cannot be reflected.

Further, in the method of indirectly measuring the implantation energy on the Si wafer, the time until the result is obtained becomes long, and the result cannot be reflected on the ion implantation apparatus during the ion implantation.

[0019]

SUMMARY OF THE INVENTION The present invention is characterized in that an ion beam extracted from an ion source is accelerated, selected, and injected into a sample surface by means of irradiating the ion beam with X-rays. , An ion implantation apparatus provided with means for measuring transmitted X-rays and scattered X-rays. Here, the transmission X-ray measurement means may include a first X-ray measurement sensor and an ion count control system. In this case, it is preferable to control the amount of ions to be implanted into the sample surface by sending a control signal from the ion count control system to the Faraday. The scattering X
The radiation measuring means may include a second X-ray measurement sensor and an energy control system. In this case, the control signal from the energy control system is sent to an accelerator for accelerating the ion beam to control the ion energy, or the control signal from the energy control system is sent to the flag Faraday to transmit the ion beam. Preferably, an interruption operation is performed.

Another feature of the present invention is that an ion beam traveling toward the surface of a sample is irradiated with X-rays and transmitted therethrough.
An ion beam measuring method for measuring and calculating the ion amount of the ion beam by detecting a line. Or,
An ion beam measuring method for measuring and calculating the ion energy of the ion beam by irradiating the ion beam traveling toward the sample surface with X-rays and detecting scattered X-rays. Alternatively, an X-ray generating means and a scattered X-ray are provided on one side of the ion beam traveling toward the sample surface.
X-ray measuring means is provided on the other side of the ion beam, and X-rays are emitted from the X-ray generating means toward the ion beam. Detecting the transmission intensity of the X-ray transmitted across the beam, measuring and calculating the ion amount of the ion beam, detecting the reflection wavelength of the X-ray scattered from the ion beam by the scattered X-ray measuring means, An ion beam measurement method for measuring and calculating an ion energy amount of an ion beam.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a batch type ion implantation apparatus according to an embodiment of the present invention. The ion implantation apparatus includes an ion source 1 for generating ions of an ion beam 10, an extraction electrode 2, an accelerator 3 for imparting implantation energy to the ion beam, a magnet 4 for mass analysis for selecting the ion beam, Sample table 12 on which sample 11 is placed
An X-ray generator 5 for generating X-rays and controlling the irradiation direction, a first X-ray measurement sensor 6 for measuring the transmission intensity of the X-rays, and a second X-ray for measuring the reflection wavelength of the X-rays It mainly includes a measurement sensor 7, a flag Faraday 14 for adjusting the amount of implanted ions by comparing an ion beam and X-ray transmission intensity, an ion count control system 8, and an energy control system 9. . In addition, the accelerator 3 and the mass spectrometer 4
The order of and may be reversed.

The ion beam extracted from the ion source 1 by the extraction electrode 2 obtains implantation energy by the accelerator 3 and is selected by the magnet 4 for mass analysis, and travels in one direction (one horizontal direction in the figure). The liquid is injected into the sample 11 on the rotating sample stage 12 connected to the ground potential. In the manufacture of the semiconductor device, the sample 11 is a semiconductor wafer, and this ion implantation is performed, for example, to form a predetermined impurity region.

The X-ray generator 5 and the second X-ray measuring sensor 7 are located on one side (lower side in the figure) of the ion beam 10 traveling in one direction, and the first X-ray measuring sensor 6 is on the other side. (Upper side in the figure).

The X-rays 2 are directed from the X-ray generator 5 to the first X-ray measurement sensor 6 so as to traverse the entire ion beam.
1, the first X-ray measurement sensor 6 measures the transmitted X-ray intensity of the X-rays 22 transmitted through the ion beam 10, and the 21st X-ray measurement sensor 7 scatters the The reflection wavelength of the reflected X-ray 23 reflected from the beam is measured.

At this time, the X-ray generator 5, the first X-ray measurement sensor 6, the second X-ray measurement sensor 7, etc.
The line unit is installed after the ion beam has the implantation energy and is selected by mass spectrometry, and after the sample stage 12
There is no particular limitation as long as it is between the above and a magnet for confirming the final injection energy may be placed in front of the X-ray unit.

Further, the system of the apparatus is configured by the ion count control system 8 and the energy control system 9 so that the measurement result is reflected on the ion implantation apparatus.

First, the measurement of the amount of ions in the ion beam and the control of the amount of implanted ions will be described.

When the ion beam current is i, the valence of the ion is n, the charge is e, the intensity of the X-ray is I, and the average value of the probability that the X-ray collides with the ion when crossing the ion beam is η. The number of collisions per time is n = iη / ne
Then, assuming that the probability of the further colliding X-rays reaching the first X-ray measurement sensor 6 is ξ, the average transmission intensity I ′ is given by the first equation.

I ′ = {1−iη (1-ξ) / ne｝ I (1) Expression 1 is obtained by averaging the transmission intensities of X-rays received over the entire area of the first X-ray measurement sensor 6, A signal 31 is sent to the ion count control system 8. In the ion count control system 8, a measurement system based on a calibration curve is registered for each ion beam, and the correlation between the ion beam current and the transmitted X-ray is stored by the flag friday 14 before every injection. Since the measurement of the injection amount based on the intensity of the transmitted X-ray is not affected by the change in the valence of the ion beam, stable measurement with a measurement error of less than 1% can be performed.

That is, the transmitted X-ray intensity is detected by the first X-ray measuring sensor 6, and a detection signal 31 based on the detected intensity is sent to the ion count control system 8, and the ion amount is measured and calculated. The information signal 32 relating to the ion amount of the ion beam from the ion count control system 8 interrupts the ion beam flowing constantly to control the start / end of implantation and to the flag Faraday 14 having the function of setting up the beam current. Then, the amount of implanted ions (dose amount) is controlled.

Next, the energy of the ion beam (implantation energy) and its control will be described.

When the X-ray energy is made smaller than the ion energy and the irradiation is performed perpendicularly, the shortest scattering wavelength λ′min due to the Compton effect is given by the following equation (2). λ'm
Since in depends on the velocity and mass of the ions, the implantation energy can be determined from this. Here, the angle between the ion beam and the incident X-ray or the angle θ between the scattered X-ray and the ion beam is not particularly limited as long as it does not coincide with the traveling direction of the ion beam.

[0034]

Here, m ₀ is the mass of the ion (static mass), v is the velocity of the ion, λ ′ is the wavelength of the reflected X-ray, ν is the frequency before the collision of the X-ray, and θ is the scattered X-ray and the ion. The angle formed by the beams, h is Planck's constant, and c is the speed of light.

FIG. 2 shows an image in which ions collide with X-rays. The velocity of the ions changes from v to v 'due to the incident X-rays of wavelength λ, and the angle from the traveling direction is φ.
(Not shown), indicating that reflected X-rays of wavelength λ ′ are generated at an angle θ. It should be noted that the change in ion velocity and the occurrence of angle due to X-ray collision are negligibly small, but these are used in a logical expression for deriving the second expression as described later. Since the mass of the ions is much smaller than the speed of light, the mass does not change with the speed, and the mass m _{0 in the} stationary state is used in the second equation and FIG.

A part of the X-rays 21 irradiated by the ion beam becomes scattered X-rays 23 by collision with the ions, and can be detected by the second X-ray measurement sensor 7. Is sent to the energy control system 9 to measure and calculate the energy.

At this time, since the minimum wavelength λ'min of the scattered X-ray is determined only by the mass and energy of the ions, the energy at the time of injection can be measured and calculated by registering a measurement system using a calibration curve.

The control signal 34 from the energy control system 9 is sent to the accelerator 3 to correct the energy fluctuation of the ion beam. Also, a control signal 35 from the energy control system 9 is sent to the flag Faraday 14,
Perform the interruption operation when a large amount of energy occurs,
You can also control the restart.

The principle of measuring the energy will be described in more detail.

When the X-ray collides with the ion beam, the energy and the path of the X-ray are determined by the law of conservation of energy and momentum. Decided.

When the incident angle and the scattering angle of the X-ray are determined in advance and the sensor is installed, the scattered X-ray enters with a certain energy width.

At this time, the scattered X-ray which receives energy from the ion beam most efficiently is λ'min. That is, the larger the energy of the X-ray, the shorter the wavelength and the higher the frequency. (If the frequency after the X-ray collision is ν ′, ν ′ becomes max, and from c / ν ′ = λ ′, λ ′ Becomes λ′min).

By monitoring this threshold value, the energy of the ion beam can be measured.

It should be noted that the wavelength of the X-ray is not directly measured, but is obtained by measuring and calculating its energy. That is, the energy of X-rays is determined by the magnitude of hν (h: Planck constant, ν: frequency), and the X-ray sensor detects the energy and converts it into an electric signal corresponding to the energy. Thus, the magnitude of the X-ray energy can be measured and measured.

Finally, a logical expression for deriving the second expression is briefly shown.

X-rays traveling straight in the y direction collide with ion particles traveling straight in the x direction, and the wavelength of reflected X-rays traveling in the θ direction is determined as follows.

Here, the momentum before the collision of the particles is p, the momentum after the collision of the particles is p ′, the mass before the collision of the particles is m, the mass after the collision of the particles is m ′, and the mass of the particles in the stationary state is m. m ₀ ,
The traveling direction of the particle after collision is φ (the angle changes by φ from before the collision), the frequency ν before the X-ray collision, the frequency ν ′ after the X-ray collision, before the X-ray collision Wavelength λ, wavelength frequency λ ′ after X-ray collision, light velocity c, Planck constant h, velocity before particle collision v, velocity after particle collision v ′, particle collision before Is the kinetic energy of E, and the kinetic energy of the particle after collision is E '.

The third and fourth equations are obtained from the law of conservation of momentum, and the fifth equation is obtained from the law of conservation of energy.

[0050]

Here, the speed of the ions to be implanted for the purpose of manufacturing a semiconductor device is at most 10 ⁶ km / sec.
c], the velocity of the particles before and after the collision is given by the following equation (6).

[0052]

Therefore, the fifth equation becomes the seventh equation, and the ninth and tenth equations are obtained from the seventh and eighth equations.

[0054]

By squaring the two sides of the ninth and tenth equations and adding them together, φ is eliminated, v ′ is substituted from the seventh equation, and the wavelength is tied to obtain the second equation shown above. Can be

[0056]

As described above, in the present invention, the ion amount and the energy of the ion beam are measured by irradiating the X-ray during the traveling of the ion beam. Absent. In addition, measurement can be performed at all times during the ion implantation operation.

Therefore, according to the present invention, the target
Even if the degree of vacuum deteriorates due to the collision of ions with the sample, it is not affected by the change in the valence of the ion beam. And the injection amount correction by the degree of vacuum is not required.

Further, according to the present invention, since the energy of the ion beam itself during the implantation is measured and the determination as to whether or not the implantation is possible can be self-controlled, highly reliable ion implantation is possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing an image of collision between ions and X-rays.

FIG. 3 is a diagram showing a configuration of a conventional technique.

FIG. 4 is a diagram showing a configuration of another conventional technique.

FIG. 5 is a diagram showing a configuration of another conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion source 2 Extraction electrode 3 Accelerator 4 Magnet 5 X-ray generator 6 First X-ray measurement sensor 7 Second X-ray measurement sensor 8 Ion count control system 9 Energy control system 10 Ion beam 11 Sample 12 Sample stand 13 Current 14 Flag Faraday 15 Target 16 X-ray measurement sensor 21,22,23 X-ray 31,32,33,34,35 Signal

Claims (9)

(57) [Claims] 1. An ion implantation apparatus for accelerating and selecting an ion beam extracted from an ion source, implanting the ion beam on a sample surface, irradiating the ion beam with X-rays, and measuring transmitted X-rays and scattered X-rays. An ion implantation apparatus characterized by comprising means. 2. The ion implantation apparatus according to claim 1, wherein said transmission X-ray measuring means has a first X-ray measurement sensor and an ion count control system. 3. The ion implantation apparatus according to claim 2, wherein a control signal from said ion count control system is sent to a flag Faraday to control the amount of ions to be implanted into the sample surface. 4. The ion implantation apparatus according to claim 1, wherein said scattered X-ray measuring means includes a second X-ray measurement sensor and an energy control system. 5. The ion implantation apparatus according to claim 4, wherein the ion energy is controlled by sending a control signal from the energy control system to an accelerator for accelerating the ion beam. 6. The ion implantation apparatus according to claim 4, wherein the operation of interrupting the ion beam is performed by sending a control signal from the energy control system to a flag Faraday. 7. An ion beam measuring method, comprising irradiating an ion beam traveling toward a sample surface with X-rays and detecting transmitted X-rays to measure the amount of ions in the ion beam. 8. An ion beam measuring method, comprising irradiating an ion beam traveling toward a sample surface with X-rays and detecting scattered X-rays to measure the ion energy of the ion beam. 9. An X-ray generating means and a scattered X-ray measuring means are provided on one side of an ion beam traveling toward a sample surface, and a transmitted X-ray measuring means is provided on the other side of said ion beam. X-rays are emitted from the X-ray generation means toward the ion beam, and the transmitted X-ray measurement means detects the transmission intensity of the X-ray transmitted across the ion beam and measures the ion amount of the ion beam. An ion beam measuring method, wherein the scattered X-ray measuring means detects the reflection wavelength of X-rays scattered from the ion beam and measures the ion energy amount of the ion beam.