JPH0381946A - Ion mass spectrometer - Google Patents

Abstract

PURPOSE:To enhance the reliability in ion analysis to a great extent by performing proper judgement in compliance with the field mag. current value at the time of mass spectrometry through provision of a plurality of reference values when judgement is to be made to know eventual occurrence of mismeasurement, etc., by a mag. flux density sensing means. CONSTITUTION:For a plurality of field mag. current values, the ratio of each field mag. current value to its corresponding output from a mag. flux density sensing means is stored in a memory means 21 as a reference value. At the time of mass spectrometry, a control means 11 calculates the ratio of the actual field mag. current value to the output from sensing means to be fed to this control means 11, and the ratio obtained is compared with the appropriate reference value corresponding to the actual field mag. current value. If the result from comparison says that the ratio lies within the specified range in the neighborhood of the corresponding reference value, it is judged that the ion analysis is being performed correctly. If there is fear that ion analysis may not be performed properly, this can be sensed in good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion mass spectrometer suitably implemented in an ion implanter or the like.

[Conventional technology]

In the manufacture of semiconductor devices, ion implantation equipment has been used for adding impurities, and its basic configuration is shown in FIG. The ion beam 3 accelerated and extracted from the ion source 1 by the extraction voltage applied from the extraction power supply 2 is guided to, for example, a substantially fan-shaped analysis electromagnet 4, and is influenced by its acceleration energy and the strength of the magnetic field formed by the analysis electromagnet 4. receive a corresponding deflection. The ion beam 3 that has undergone this deflection is further analyzed by an analysis slit 5. Since the ions constituting the ion beam 3 are given substantially uniform acceleration energy by the extraction voltage from the extraction power source 2, the amount of deflection depends on their mass. Therefore, only ions of a certain type, subjected to a certain deflection, can pass through the analysis slit 5. Ion beam 3 after being analyzed in this way
After being accelerated in the acceleration tube 6, a is further injected into a target 7 such as a semiconductor wafer.

The extraction voltage value of the extraction power source 2 is given from a telemeter 8 to a mass controller 11 via a light guide 9 and a telemeter 10 . This mass controller 11
sets the mass of ions to be implanted into target 7,
It also controls the analysis electromagnet 4 so that the desired ion species can be analyzed well. That is, the mass controller 11 transmits the output of the magnetic flux density detection element 12 that measures the magnetic flux density B of the analysis electromagnet 4 to the telemeter 8. It is received via the light guide 12 and the telemeter 10, and based on the thus obtained magnetic flux density B and the above-mentioned extraction voltage value, the analysis electromagnet power supply 14 is sent from the telemeter 10 to the light guide 13 and then to the telemeter 8. A control signal is given to the analysis electromagnet 4, thereby controlling the magnetic flux density B of the analysis electromagnet 4 to a value for analyzing desired ions. mass controller 11
Also, the ion beam 3a is implanted into the target 7.
The output of a beam ammeter 15 that measures the beam current is given, and the maximum injection efficiency is obtained by finely adjusting the strength of the magnetic field of the analysis electromagnet 4 so that the beam current takes a maximum value. ing.

The mass number (mass value) of ions analyzed by the analysis electromagnet 4 and the analysis slit 5 is determined by the magnetic flux density B of the analysis electromagnet 4.
It is proportional to the square of , and inversely proportional to the extraction voltage from the extraction power source 2. Therefore, by keeping the extraction voltage constant and setting the magnetic flux density B to a value corresponding to the mass number of ions to be implanted, desired ions can be analyzed. This magnetic flux density B is approximately proportional to the field current i given to the analysis electromagnet 4 from the analysis electromagnet power supply 14, and therefore, the field current i such that a predetermined magnetic flux density B is obtained in the magnetic detection element 12 is set in the analysis electromagnet. If the analysis electromagnet power supply 14 is controlled by the mass controller 11 as given in FIG. 4, desired ions can be analyzed.

By controlling the field current 5 based on the magnetic flux density B detected by the magnetic detection element 12 in this way, desired ions can be analyzed.
If an accurate value of the magnetic flux density B cannot be given to the mass controller 11 due to a failure of the magnetic flux density B or the telemeter system, etc., ion analysis cannot be performed satisfactorily. For this reason, conventionally, using the fact that the magnetic flux density B is approximately proportional to the field type mr, a constant k such that i = -B... Magnetic flux density information B input manually in 9. ,.

The value iogs = -Bows - (2) calculated by is given by i5up- for the field current j suP actually given to the analysis electromagnet 4 from the analysis electromagnet power supply 14.
α≦ioms≦L sup+α (3) where α is a positive constant.

I am trying to check whether the following relationship is satisfied.

If the above formula (3) is not satisfied, a display to that effect (not shown) is displayed to inform the operator of the ion implanter that the ion analysis may not be performed correctly. I'm trying to let you know something. As a result, even greater precision in ion analysis is expected during ion implantation.

[Problem to be solved by the invention]

The proportionality constant in the above equation (1) is usually determined by the manufacturer of the ion implantation device as follows: k=1o/BO... (4) It is determined as follows and is written in, for example, a FROM (programmable read-only memory) (not shown) in the mass controller 11. However, as mentioned above, the field current i is only approximately proportional to the magnetic flux density B, and therefore, the above-mentioned prior art applies the determination based on the above equation (3) to any magnetic flux density B. So,
Confirmation processing regarding erroneous measurements of the magnetic flux density B cannot be performed with high precision. In other words, strictly speaking, the determination using the proportionality constant k is based on a field current with a value near the predetermined field current i0. It is only valid for other VA
In the above-mentioned prior art in which the determination according to the above equation (3) is applied uniformly to the ini flow i using the proportionality constant k,
Highly accurate judgment cannot be expected.

Furthermore, since the proportionality constant is a value stored in the PROM and cannot be rewritten, there is a problem in that it is difficult to deal with changes over time in a telemeter system, etc. That is, as the telemeter system changes over time, complicated maintenance is required, such as recalculating the proportionality constant k and attaching the FROM in which the new proportionality constant k is written to the mass controller roller 11.

An object of the present invention is to provide an ion mass spectrometer that solves the above-mentioned technical problems and significantly improves the reliability of ion analysis.

[Means to solve the problem]

The ion mass spectrometer according to claim (1) includes: an analysis electromagnet power supply that applies a field current to an analysis electromagnet; a magnetic flux density detection means that measures a magnetic flux density within the analysis electromagnet; and regarding the plurality of values of the field current. , storage means storing each ratio of the output of the magnetic flux density detection means corresponding to each field fR current value and each field electric fL value as a reference value; and controlling the analysis electromagnet power supply based on the output of the magnetic flux density detection means; Calculate the ratio between the value of the field current given to the analysis electromagnet by the analysis electromagnet power source and the output of the magnetic flux density detection means, and set the reference value corresponding to this ratio and the value of the field current given to the analysis electromagnet. and a control means for determining that the ion analysis is being performed correctly when the calculated ratio is within a predetermined range in the vicinity of the reference value. In the ion mass spectrometer of 2), when storing the reference value in the storage means, the control means controls the analysis electromagnet power supply to change the field current and samples the output of the magnetic flux density detection means. The reference value is calculated from the sampled output of the magnetic flux density detection means and the field current value 1 at the time of sampling, and the calculated reference value is written in the storage means.

[Effect]

According to the ion mass spectrometer of claim (1), for a plurality of field current values, each ratio between each field current value and the output of the magnetic flux density detection means corresponding to each field current value is stored as a reference value. stored in the means. Then, during mass analysis, the control means calculates the ratio between the actual field current value and the output of the magnetic flux density detection means inputted to the control means, and corresponds to the calculated ratio and the actual field current value. Compare the above reference value. As a result of this comparison, if the calculated ratio is within a predetermined range near the corresponding reference value, it is determined that the ion analysis has been performed correctly. In this way? ! By preparing the reference values corresponding to different numbers of field current values and using the reference values corresponding to the field current values during 1Tit analysis as appropriate, a detection error occurs in the output of the magnetic flux density detection means. Therefore, if there is a possibility that ion analysis may not be performed satisfactorily, this can be detected with high accuracy.

According to the ion mass spectrometer of claim (2), the control means changes the field current value given to the analysis electromagnet from the analysis electromagnet power supply, samples the output of the magnetic flux density detection means in accordance with this, and satisfies the above-mentioned standard. Since the value is calculated and written to the storage means, for example, when there is a change over time in the transmission system of the output signal of the magnetic flux density detection means to the control means, the reference value in the storage means can be easily stored. Updates can be made to easily accommodate changes over time.

This makes it possible to make the above-mentioned determination with high accuracy regardless of changes over time, and since the reference value can be easily updated, maintenance is significantly reduced.

[Embodiment] FIG. 1 is a conceptual diagram showing the basic configuration of an ion implantation apparatus to which an ion mass spectrometer according to an embodiment of the present invention is applied. In FIG. 1, parts corresponding to those shown in FIG. 7 described above are designated by the same reference numerals. In this embodiment, a mass controller 11 functioning as a control means is provided with a readable/writable storage means 21.

This storage means 21 can be composed of, for example, EEFROM (electrically writeable/writable ROM) or RAM (random access memory).

The storage means 21 stores each field current value and a magnetic flux density detection means obtained corresponding to each field current value regarding a plurality of values of the field current i given to the analysis electromagnet 4 by the analysis electromagnet power source 14. Each part of the output of the magnetic detection element 12 is stored as a reference value.

The process of writing this reference value into the storage means 21 is shown in FIG. In this embodiment, the reference value is written to the mass controller 11 by an operator of the ion implantation apparatus or the like inputting a corresponding instruction from a control panel (not shown).
This is realized through program processing at, for example, during periodic inspections. In step nl, an instruction input operation for writing the reference value is awaited, and when the instruction is input, data is collected in step n2. This data collection can be performed using, for example, a mass controller II.
control signal given to the analysis electromagnet power supply 14 (analysis electromagnet 4
corresponds to the field M1 current i given to . ) is monotonically increased, and the output of the magnetic detection element 12 is sampled accordingly. That is, regarding a plurality of values of the field current i, data represented by a pair of a control signal corresponding to each field current value and an output of the magnetic detection element 12 corresponding to each field current value is collected.

In step n3, each part of the control signal and the output of the magnetic detection element 12 for the plurality of values of the field current i is calculated and set as a reference value, and this calculated reference value is stored in the storage means 21 in step n4. written.

FIG. 3 is a diagram for explaining the data collection process. The control signal and the output signal of the magnetic detection element 12 are transmitted using, for example, a frequency modulated signal. For example, the voltage value representing the field current i corresponds to the control signal 1(f) expressed in frequency, and when the field current i increases, the control signal 1(f) also increases. Further, the output signal of the magnetic detection element 12 is expressed as B(f) by a frequency signal corresponding to the magnetic flux density B of the analysis electromagnet 4, and it is assumed that as the magnetic flux density B increases, the output signal B(f) also increases.

As the control signal 1(f) increases, the output signal B(f) of the magnetic detection element 12 increases almost linearly.

This corresponds to the fact that the field current i is approximately proportional to the magnetic flux density B. At the time of collecting the above data, the control signal 1(f) and the output signal B(f) are, for example, a plurality of control signals 1(f) indicated by reference numeral ll-1* in FIG.
f) is sampled (step n2 in FIG. 2). Then, there are sampled data pairs i (f),, B (f).

For (m=1.2, 3...,k), the reference value x
,=i(f)−/B(r). is calculated (
Step n3 in FIG. 2). The reference value X 1 ”
are stored in the storage means 21 in association with (step n4 in FIG. 2).

FIG. 4 is a flowchart showing the processing in the mass controller 11. In step p1, the mass controller 11 gives a control signal i (f) to the analysis electromagnet power supply 14 based on the output signal B (f) from the magnetic detection element 12, and controls the field current i to obtain a desired value! ! Analyze ions with a number. Then, a control signal i is used to adjust the field current i so that the output of the beam ammeter 15 is maximized.
(As D changes, the beam current ■ changes as shown in Fig. 5, but by setting the control signal i (f) pEAx where the beam current ! injection efficiency is maximized.

In step p2, it is determined whether or not the above analysis process has been completed, and if it has not been completed, the process returns to step p1.

When the ion analysis process is completed in this way, in step p3, the reference value X associated with the control signal i (f)H closest to the control signal value i (f)riAg is determined. (=i(f)+i/B(f)N) is searched and read from the storage means 21. Each flight i (f)
rtAK.

The relationship between i (f)N and B(f)++ is shown in FIG.

In step p4, the output signal B (
f) is read. Then, in step p5, the value i (f)riAg of the control signal and the read output signal B
(f) ratio X P! IIJ is calculated. Then, in step p6, XPEAII XNl≦β − (6) where β is a positive constant.

It is determined whether or not the above formula (6) is satisfied, the process is terminated and the process returns to the normal control process, and if it is not satisfied, the process proceeds to step p7, and the analysis of the ion species is performed normally. Do error handling as it may not be possible. This error processing is, for example, a process of displaying and outputting a message on a display device provided on a control panel or the like to call the operator's attention.

Due to such processing, if the output signal B (f) of the magnetic sensing element 12 is not properly obtained due to, for example, an incorrect measurement of the magnetic sensing element 12 or a malfunction of the telemeter system, the operator can can be quickly known, and it is possible to prevent ions other than desired ions from being implanted into the target 7. Moreover, in this embodiment, as described above, a plurality of different control signals i (f
) is recorded in the storage means 21, and the control signal i (f) at the time of mass spectrometry is
The value of the control signal closest to the value i (f) pcm of i (f
) The reference value X8 corresponding to s is used to determine the presence or absence of malfunction of the magnetic measurement element 12, etc., so that a uniform value can be obtained for all the values of the control signal i (f). Compared to the conventional configuration in which determination is made using k, it becomes possible to perform determination with much higher accuracy.

Furthermore, in this embodiment, the reference values X, ~X, in the storage means 21 can be easily updated by the operator inputting instructions from the control panel, so that the telemeter system signal can be easily updated due to changes over time. Even if there is a shift in transmission, by updating the reference values X, ~Xk, the user can easily respond and make judgments with the same accuracy as at the beginning of use. Therefore, maintenance is significantly reduced.

〔Effect of the invention〕

According to the ion mass spectrometer of claim (1), in determining whether or not there is an erroneous measurement of the magnetic flux density detection means, a uniform method is used for any given field current as in the conventional method. Instead of making a judgment, multiple reference values are set to make an appropriate judgment corresponding to the field current value during mass spectrometry, so the judgment can be made with high accuracy. As a result, the reliability of ion analysis can be significantly improved.

Further, according to the ion mass spectrometer of claim (2), the reference value used for the determination can be easily updated, and can be easily adjusted to change over time, for example, in the transmission path of the output signal of the magnetic flux density detection means to the control means. Since we will be able to respond to
The accuracy of the determination can be maintained at a high level regardless of the above-mentioned changes over time, and the reference value can be easily updated, so that maintenance can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the basic configuration of an ion implantation apparatus to which an ion mass spectrometer according to an embodiment of the present invention is applied, and FIG. 3 is a diagram for explaining the data collection process for calculating the reference value, FIG. 4 is a flowchart for explaining the process in the mass controller 11, and FIG. 5 is a diagram for explaining the process of collecting data for calculating the reference value. f) and beam current■
FIG. 6 is a diagram for explaining the comparison process between the reference value and measured data, and FIG. 7 is a conceptual diagram showing the basic configuration of the prior art. 3...Ion beam, 4...Analysis electromagnet, 11...
・Mass controller (control means), 14... Analyzing electromagnet power supply diagram (Figure 1(f)-(f)-1)

Claims (2)

[Claims] (1) In an ion mass spectrometer configured to analyze ions of a predetermined mass by guiding accelerated ions to a magnetic field formed by an analysis electromagnet and deflecting them, an analysis electromagnet power source that supplies a field current to the analysis electromagnet; A magnetic flux density detection means for measuring the magnetic flux density within the analysis electromagnet; and regarding the plurality of values of the field current, each ratio of each field current value and the output of the magnetic flux density detection means corresponding to each field current value is set as a reference value. controlling the analysis electromagnet power supply based on the output of the magnetic flux density detection means, and calculating a ratio between the value of the field current given by the analysis electromagnet power supply to the analysis electromagnet and the output of the magnetic flux density detection means; Then, this ratio is compared with the reference value corresponding to the value of the field current given to the analysis electromagnet, and when the calculated ratio is within a predetermined range near the reference value, the ion An ion mass spectrometer comprising: a control means for determining that analysis is being performed correctly. (2) In storing the reference value in the storage means, the control means controls the analysis electromagnet power supply to change the field current and samples the output of the magnetic flux density detection means, and the sampled magnetic flux 2. The ion mass spectrometer according to claim 1, wherein the reference value is calculated from the density detection means output and the field current value at the time of sampling, and the calculated reference value is written in the storage means.