JP2003185605A - Sample inspection device and method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample inspection device capable of accurately detecting the current flowing through a sample, and an inspection method using the same. <P>SOLUTION: The sample inspection device is constituted so that the surface of the sample held to the sample moving mechanism arranged in a sample chamber in an insulated state is irradiated with a primary beam, the current flowing through the sample as a result is detected, and the sample is inspected on the basis of the obtained detection signal. This apparatus is equipped with a differential amplifier for differentially amplifying the signal obtained by detecting the current flowing through the sample, and the signal from the conductive partition member inserted in the gap between the sample and the sample moving mechanism so as to partition both of them in a state insulated from them. The output of the differential amplifier is measured to calculate the difference between the measured value at the on-time of the primary beam and the measured value at the off-time thereof. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample inspection apparatus for irradiating a sample with a primary beam such as an electron beam for inspection, and particularly to a sample inspection apparatus and method capable of detecting a minute current flowing through the sample. It is about.

[0002]

2. Description of the Related Art A scanning electron microscope irradiates and scans a sample with a finely focused electron beam, detects secondary electrons or backscattered electrons generated from the sample, and sends the resulting detection signal to a display device to sample the sample. To obtain a secondary electron image or a backscattered electron image. Further, it is also performed that electrons absorbed by the sample in the irradiated electron beam are detected as a sample current (absorption current), and the obtained detection signal is sent to a display device to display a current image.

As described above, when the sample current is detected, the current of the electron beam with which the sample is irradiated is usually as small as pico-ampere order, and therefore a further minute current must be detected. Therefore, it is necessary to eliminate the influence of electromagnetic waves from the surroundings, and the sample is placed in the sample chamber having an electromagnetic shielding function.

[0004]

However, although the influence of electromagnetic waves from the surroundings can be eliminated by the sample chamber having an electromagnetic shielding function, the moving mechanism arranged in the sample chamber for moving the sample is a driving motor. Are sources of electromagnetic waves. Due to the influence, it becomes difficult to accurately amplify the sample current with a high amplification factor. In particular, when the sample becomes large, the moving mechanism also inevitably becomes large, and the generated electromagnetic wave also has a large strength, so that the influence thereof becomes large.

The present invention has been made in view of this point, and an object thereof is to provide a sample inspection apparatus capable of accurately detecting a sample current.

[0006]

To achieve this object, a first aspect of the present invention relates to a focused energy beam irradiation system for intermittently irradiating a desired portion of a sample with a focused energy beam, and said sample. A conductive member electrically insulated from the sample moving mechanism, a terminal provided on the conductive member for extracting an electrical signal from the conductive member, and the sample are electrically insulated from each other. A terminal that is mounted and provided so as to come into contact with the sample in order to extract an electrical signal from the sample, a sample chamber that houses the sample and the sample moving mechanism, and a difference that differentially amplifies signals from the two terminals. A dynamic amplifier,
A measuring system for measuring an output signal of the differential amplifier as at least two data with a predetermined time difference from the intermittent beam of the focused energy beam, and performing a predetermined calculation based on the data. .

The second aspect of the present invention electrically insulates the focused energy beam irradiation system for intermittently irradiating a desired portion of the sample with the focused energy beam and the sample and the sample moving mechanism. And a conductive member that is arranged,
A terminal provided on the conductive member for taking out an electrical signal from the conductive member, and a terminal provided so as to electrically insulate and mount the sample and to come into contact with the sample for taking out an electrical signal from the sample A sample chamber containing the sample and the sample moving mechanism; a differential amplifier for differentially amplifying the signals from the two terminals; and an output signal of the differential amplifier to obtain data by measuring the data. In a sample inspection device equipped with a measurement system for performing a predetermined calculation based on, the output signal of the differential amplifier is measured as at least two or more data at a predetermined time difference with the intermittent of the focused energy beam, It is characterized in that a predetermined calculation is performed based on the data.

The third aspect of the present invention electrically insulates the focused energy beam irradiation system for intermittently irradiating a desired portion of the sample with the focused energy beam, and the sample and the sample moving mechanism. And a conductive member that is arranged,
A terminal provided on the conductive member for taking out an electrical signal from the conductive member, and a terminal provided so as to electrically insulate and mount the sample and to come into contact with the sample for taking out an electrical signal from the sample A sample chamber containing the sample and the sample moving mechanism; a differential amplifier for differentially amplifying the signals from the two terminals; and an output signal of the differential amplifier to obtain data by measuring the data. Based on the measurement system for performing a predetermined calculation, a function for generating a first trigger signal for controlling the measurement system, and a second trigger signal for controlling the focused energy beam irradiation system. In a sample inspection apparatus having a control system having a function, the step of driving the sample moving mechanism while lowering the two terminals to the ground potential, and the measurement system including the step of driving the sample moving mechanism. First
And the second trigger signal delayed by a predetermined time from the first trigger signal, the first measurement is terminated, and the focused energy beam irradiation system irradiates the energy beam. And a step of performing a second measurement from a lapse of a predetermined time from the second trigger signal to a lapse of a predetermined time from the second trigger signal, and calculating a difference between the first measurement value and the second measurement value. And a step of outputting.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of a scanning electron microscope embodying the present invention. FIG. 2 is an enlarged view of the portion in FIG.

In FIG. 1, the electron beam EB generated from the electron gun 1 is finely focused on the sample S by the focusing lens 2 and is two-dimensionally scanned on the sample by the deflector 3. 101 turns on the electron beam EB at high speed (o
n) / a blanking device for turning off. Four
Is an electron gun 1, a blanking device 101, a focusing lens 2
And an electron optical system controller for controlling the deflector 3.

The sample S is placed on the sample moving mechanism 5 and has a sample chamber made to have an electromagnetic shield (electrostatic shield and magnetic shield) function to prevent the entry of an illegal electric field and magnetic field from the outside. It is housed in 6. On the upper surface of the sample moving mechanism 5, a conductive sample holder 10 is placed on the insulating material 7. The sample S is supported by a plurality of pins 30 so as to be substantially horizontal, and for example, 2 to 4 pressing rollers 3 provided so as to sandwich the sample therebetween.
The peripheral portion is regulated by 1 and is fixed to the sample holder 10. The pin 30 and the pressing roller 31 are attached to the sample holder 10 in an insulating manner by the insulator 9. A wire 32 for detecting a current flowing through the sample is connected to each pin 30 and each pressing roller 31 that come into contact with the sample, and a lead wire 12 for guiding the current to the differential amplifier 22 is connected to the wire 32. ing.

Conductive wires (coaxial lines) 12 and 13 are connected to the sample S and the sample holder 10, respectively, and a terminal 14 for taking out a signal to the outside through the conductive wires is attached to the wall of the sample chamber 6. There is. As shown in FIG. 2, the terminal 14 includes a conductive substrate 15 directly attached to the sample chamber wall (conductor) and insulators 16 and 17 penetrating the substrate 15.
And core wires 18 and 19 penetrating each insulator. The conductors 20 and 21 connected to each core wire are connected to the differential input terminals of the differential amplifier 22, respectively. The outer conductors of the conductors 12 and 13 are connected to the substrate 15.

A conductive wire 24 is also connected between the substrate 15 and the reference input terminal (REF terminal) of the differential amplifier 22. This reference input terminal is grounded, and the grounding point is the grounding point of the acceleration power supply which serves as a reference point for generating an electron beam in the electron gun 1. Furthermore, 33, 34
Is a switch for grounding the input terminal of the differential amplifier 22, and is simultaneously turned on / off by a command signal from the control device 26 via the control signal line 35. Switch 3
The operations related to Nos. 3 and 34 should be called "static elimination operation of sample". Details will be described later.

The differential output signal obtained from the differential amplifier 22 is converted into an optical signal by the voltage optical converter 102,
It is sent to the measurement system 104 through the optical cable 103. The measurement system 104 is provided with a photovoltage converter 105, an analog-digital converter 106, and an arithmetic circuit 107. The optical signal is converted into an electric signal again by the optical voltage converter 105,
The electric signal is converted and measured as digital data by the analog-digital converter 106. The measured value that is digital data is taken into the arithmetic circuit 107 and subjected to necessary arithmetic processing. Here, the output signal from the differential amplifier 22 is sent to the measurement system 104 through the optical cable 103 because the main body side device including the electron optical system including the electron gun 1 and the sample chamber 6 and the like. This is to prevent the transmission of noise components by electrically insulating the signal line with the control measurement system side device configured by the measurement system 104, the control device 26 and the like.

In this way, the signal is taken out of the sample chamber 6 through the terminal 14, but outside the sample chamber 6, it is directly attached to the outer wall of the sample chamber 6 and has electrostatic and magnetic shield functions. Is provided, and each member up to the voltage light converter 102 is housed in the signal extraction chamber 110.

Reference numeral 26 is a control device provided with a memory and a monitor 25 which are constituted by a PC or the like. The measurement value obtained by the measurement system 104 is sent to the control device 26 and stored in the memory. The control device 26 controls the electron optical system control device 4, the measurement system 104, and the like in accordance with an instruction of a device operator or a program incorporated in the control device 26.

The control device 26 includes the following control functions. (1) The control device 26 controls the switches 33 and 34 via the control signal line 35 to ground the input terminal side of the differential amplifier 22 and perform control for the static elimination operation of the sample. (2) The control device 26 generates a trigger signal and sends it to the electron optical system control device 4, and in response to this, the electron optical system control device 4 controls the blanking device 101 to control the electron beam EB.
To turn on or off. (3) The controller 26 generates a trigger signal and sends it to the electron optical system controller 4, and in response to this, the electron optical system controller 4 controls the deflector 3 so that the electron beam EB is two-dimensionally formed on the sample. To scan. (4) The control device 26 generates a trigger signal to measure the measurement system 1
04, and in response to this, the measurement system 104 samples and measures the signal at a predetermined timing, performs arithmetic processing by a predetermined method using the arithmetic circuit 107 based on the measured result, and sends the arithmetic result to the control device 26. . (5) The measurement result is stored in the memory in the control device 26 and displayed on the monitor 25.

Further, a signal indicating the irradiation position of the electron beam on the sample S is sent from the electron optical system controller 4 to the controller 26, and the controller 26 is based on this signal.
Is the electron beam irradiation position on the sample
It is stored in association with (data acquisition position).

The operation principle and the like in the above configuration will be described. (1) In regard to obtaining the difference between the currents from the sample S and the sample holder 10 by the differential amplifier 22, the sample moving mechanism 5 is generated between the sample moving mechanism 5 and the sample chamber 6 in the above configuration. An electric current caused by an electromagnetic field flows,
A change occurs in the potential of the sample moving mechanism 5. In the conventional device, since the potential of the sample S also varies due to the influence of the variation in the potential of the sample moving mechanism 5, the amplifier set to a high amplification factor for detecting the sample current (absorption current) is The output fluctuates due to the influence, and it is difficult to accurately amplify the sample current (absorption current).

In this embodiment, the sample S and the sample holder 10 are
Since the difference in the current from the sample current is obtained by the differential amplifier 22, it is arranged close to the sample S even if a noise component is mixed in the sample current due to the influence of the electromagnetic wave from the sample moving mechanism 5 or the like. The current signal from the sample holder 10 in which almost the same noise component is mixed is subtracted by the differential amplifier 22, and as the output of the differential amplifier 22, a signal of an accurate sample current (absorption current) from which such noise component is removed. Can be obtained. (2) (Regarding the operations of the switches 33 and 34 for grounding the input terminals of the differential amplifier 22 and the "static elimination operation of the sample")
The structure of this embodiment is effective not only when the sample S is attached and detached, but also when the sample S is moved by using the sample moving mechanism 5 and the current flowing through the sample is measured at different points on the sample one after another. is there. This point will be described below.

FIG. 3A shows the result of repeating the measurement for the assumed lattice points on the sample by moving the sample by the sample moving mechanism 5 at regular intervals. In FIG. 3A, the horizontal axis represents the grid point number and the vertical axis represents the sample current value at each grid point. As the sample, a standard sample having the same sample current value over the entire surface of the sample, for example, a so-called bare wafer,
That is, a wafer in a mirror surface state before pattern exposure or the like is used. Therefore, the sample current values measured at all the lattice points should be equal, but the actual measurement results are different at each lattice point as shown in FIG. 3 (a).

This measurement result shows that, when the sample S is moved, the charge charged in the sample holder 10 is changed due to the change of the stray capacitance in the sample chamber and the influence of noise as the sample holder 10 and the sample S are moved. However, it is considered that the sample current to be measured changes after the stationary state.

Therefore, in this embodiment, the switches 33 and 3 are
4 is provided so that the input terminal of the differential amplifier 22, that is, the sample holder 10 and the sample S can be switched between a grounded state and a non-grounded state. Then, the control device 26
Are switches 33, 34 during movement by the sample moving mechanism 5.
Is turned on to ground the input terminal of the differential amplifier 22, and when the sample current is measured by irradiating the electron beam in a stationary state after the movement, the switches 33 and 34 are controlled to be turned off. FIG. 4 is a flowchart showing a procedure of measurement based on such control. As an initial setting in step 1,
The switches 33 and 34 are turned on (measurement off). In step 2, a wafer, which is a sample, is loaded into the sample chamber and set in the holder 10. In step 3,
The alignment is performed so that the wafer is placed in the initial position. In step 4, measurement conditions such as the irradiation time and timing of the electron beam and the gain of the differential amplifier are set. In step 5, the sample moving mechanism 5 moves the first measurement point of the sample to the electron beam irradiation position. In step 6, when stopped, the switches 33 and 34 are turned off, and in step 7, the electron beam EB is irradiated and the sample current is measured. And
When the measurement is completed, switch 3
3, 34 are turned on (measurement is off), and the process returns to step 5 so that the next measurement point is moved to the electron beam irradiation position. Steps 5-8 are repeated for a predetermined number of measurement points, and finally, in step 9, the wafer after measurement is unloaded from the sample chamber.

In FIG. 3B, while performing such control,
Similar to FIG. 3A, the measurement result of the bare wafer is shown. From this figure, the switches 33 and 34 are turned on and the input terminal of the differential amplifier 22 is grounded during the movement by the sample moving mechanism 5, so that the sample current value at each lattice point accompanying the movement appearing in FIG. It can be seen that the fluctuation of is suppressed. (3) (Regarding the measurement system 104 controlled by the controller 26) Further, in the present embodiment, a more accurate sample current (absorption current) is obtained.
In order to obtain the signal of, it has the following functions. Figure 5
This will be described in detail with reference to (a), FIGS. 6 and 7. Figure 5
(a) and FIG. 6 are schematic diagrams for explaining the principle of the measurement, and FIG. 7 is a flow chart diagram for explaining the flow of the measurement.

In FIG. 5A, the horizontal axis represents time and the vertical axis represents the signal intensity of the sample current (absorption current). When the electron beam EB is turned on at a certain point in time, the signal intensity of the sample current (absorption current) rises rapidly, but depending on the nature of the sample, there are regions where the signal intensity is unstable due to charging or the like. After that, a relatively stable area appears. Therefore, it is necessary to measure the signal strength in this relatively stable region. The specific measuring method will be described below.

In FIG. 6, the horizontal axis represents time and the vertical axis represents the signal intensity of the sample current (absorption current). First, prior to the start of measurement, the control device 26 controls the blanking device 101 via the electron optical system control device 4 to control the electron beam EB.
Is turned off (step 21). In such a state, the control device 26 makes the first
Generates a trigger signal (step 22) and sends it to the measurement system 104, and the measurement system 104 receives the sample signal (absorption current).
The first measurement of the signal is started (step 23). At this time, the measurement is performed many times at a predetermined timing to obtain many pieces of data.

Then, at time t2 when T1 has elapsed from time t1, the control device 26 generates a second trigger signal (step 24) and sends it to the measurement system 104 and the electron optical system control device 4, and receives it. Then, the measurement system 104 completes the first measurement. Then, the measured value of T1 time from t1 to t2 (correctly, the average value of many measured values) is obtained (step 24). This will be referred to as "amplifier offset current value". At the same time, the electron optical system controller 4 controls the blanking device 101 to turn on the electron beam EB.
(Step 25).

Then, when the electron beam EB is turned on, the sample current (absorption current) increases as shown in FIG. 6, and at a time point t3 after elapse of a predetermined time T2 from t2.
After that, it shows a stable value (step 26). Therefore, the control device 26 generates a third trigger signal (step 27) and sends it to the measurement system 104 and the electron optical system control device 4, and in response to this, the measurement system 104 starts the second measurement from t3. (Step 28).

Next, at a time point t4 after a lapse of a predetermined time T3 from the time point t3, the control device 26 generates a fourth trigger signal (step 29) to cause the measurement system 104 and the electron optical system control device 4 to operate. send. In response to this, the measurement system 104 completes the second measurement. And T3 from t3 to t4
Take a measurement of time (more precisely, the average of many measurements).
This is called a "stable current value". at the same time,
In response to the fourth trigger signal, the electron optical system controller 4 controls the blanking device 101 to turn off the electron beam EB (o
ff) (step 30).

By subtracting the "amplifier offset current value" from the "stable region current value" thus obtained, a more accurate signal value of the sample current (absorption current) is obtained (step 31). be able to.

Hereinafter, such measurement is performed by the sample moving mechanism 5
Is driven to change the measurement position on the sample S one after another (step 32).

Although it has been described above that sampling for measuring the signal of the sample current (absorption current) is performed at a predetermined timing, specifically, it is synchronized with the commercial power supply frequency supplied to the apparatus. Is good. The reason is that the detection condition of the floating noise component from the commercial power supply can be made constant in each sampling. Further, many points on the sample S are measured one after another, but at that time, the electron beam EB is repeatedly turned on and off at each measurement point. By doing this, as described above, not only can the offset current value of the amplifier be measured and the current value in the stable region can be corrected using this, but the amount of time for which the electron beam EB is off is also reduced. , Helps to reduce the charge of the sample S. The correction performed in this manner will be referred to as an amplifier offset correction.

Further, T1, T2, T3 such as measurement time are
Generally speaking, the longer the better the measured value, the shorter the total time required for the measurement. Actually, some examples in consideration of the acceleration voltage of the electron beam EB, the irradiation current value, the property of the wafer, etc. are experimentally obtained in advance, and the numerical values of T1, T2, T3, etc. are tabulated and controlled. It is advisable to store it in the memory of the device 36 and call up the numerical values in the table as appropriate for measurement. (4) (Regarding determination of measurement result) First, referring to FIG. 5A, after the electron beam EB is turned on, a region where the signal intensity of the sample current (absorption current) is relatively stable is found after a while. Since it appears, it is necessary to measure the signal strength in this relatively stable region. However, even in such a case, for example, the signal intensity of the sample current (absorption current) is shown in FIG.
In the case of (b), a relatively stable region does not appear, and accurate measurement of the signal intensity of the sample current (absorption current) may fail. Therefore, it becomes necessary to make a judgment as to whether or not the measurement has failed. The method is performed as follows, for example.

In the case of FIG. 5B, from time t3 to time t4
Since a large number of data are obtained by sampling a large number of times up to, the standard deviation value for these large numbers of data is obtained, and if this standard deviation value exceeds the separately determined judgment reference value, the It can be judged as "failure". Then, the result is recorded and stored in the memory of the control system 26 along with the measurement result, and is displayed on the monitor 25 as necessary. (5) (Regarding Overall Flow of Measurement) FIG. 8 is a diagram showing an overall flow of measurement according to the present embodiment.

A sample S (wafer) is transferred into the sample chamber 6 via a sample exchange chamber (not shown) and placed on the sample moving mechanism 5. At this time, the electron beam EB is turned off by the blanking device 101 (step 4).
1). Further, the electron beam EB is in a state of being two-dimensionally scanned by the deflector 3 as needed.

The electron beam EB is two-dimensionally scanned in the following cases. When a sufficiently narrowed electron beam EB is applied to one point on the sample, a charging phenomenon may occur at the irradiation point depending on the property of the sample. In such a case, the charging phenomenon can be suppressed by reducing the irradiation current of the electron beam EB or by increasing the diameter of the electron beam EB while keeping the irradiation current constant. The two-dimensional scanning with the electron beam EB has the same meaning as increasing the diameter of the electron beam EB. However, when scanning two-dimensionally for this purpose, the scanning speed must be sufficiently faster than the measurement time. In addition, when the diameter of the electron beam EB is increased or when the electron beam EB is scanned two-dimensionally, the measurement result is naturally within the range.
It is an average value in (area of diameter size or area of two-dimensional scanning).

Device operator or controller 26
When the measurement is started in accordance with the instruction of the program incorporated in (step 42), the first measurement position on the sample S placed on the sample moving mechanism 5 is driven so as to be located immediately below the electron beam EB. (Step 44). During this period, the control device 26 generates a command signal via the control signal line 35,
The switches 33 and 34 in the signal extraction chamber 110 are driven to switch on (on), and the input terminal of the differential amplifier 22 is grounded (step 43). By grounding the input terminal of the differential amplifier 22, the sample S and the sample holder 10 are grounded, and the "static elimination operation of the sample" is performed.

The predetermined measurement position on the sample S is the electron beam E.
When it is located immediately below B, the control device 26 drives the switches 33 and 34 in the signal extraction chamber 110 to switch off.
Then, the input terminal of the differential amplifier 22 is changed from the ground side to the open side (step 45). The controller 26 then generates a first trigger signal (step 46) to the measurement system 104.
In response to this, the measurement system 104 starts measuring the offset current value of the amplifier (step 47). After a predetermined T1 time (= t2-t1) from the first trigger signal, the control device 26 generates a second trigger signal (step 48) and sends it to the measurement system 104 and the electron optical system control device 4. In response to this, the measurement system 104 completes the measurement of the offset current value of the amplifier, and similarly, the electron optical system controller 4 drives the blanking device 101 to turn on the electron beam EB.
(Step 49). At this time, the electron beam EB is in a two-dimensionally scanned state, if necessary. Further, the control device 26 receives a predetermined T2 time (=
After t3-t2), a third trigger signal is generated (step 50) and sent to the measurement system 104, and the measurement system 10 receives it.
4 starts measuring the current value in the stable region (step 5).
1). Furthermore, the control device 26 generates a fourth trigger signal after a predetermined time T3 (= t4−t3) from the third trigger signal (step 52), and causes the measurement system 104 and the electron optical system control device 4 to operate. In response to this, the measurement system 104 completes the measurement of the current value in the stable region, and similarly, the electron optical system controller 4 drives the blanking device 101 to turn off the electron beam EB. (Step 53).

Further, the measurement system 104 calculates the average value of the offset current value of the amplifier and the average value of the current value in the stable region, subtracts the former from the latter, and calculates the standard deviation of the measured values of the former and the latter. Then, the quality of the measurement is judged from these standard deviation values (step 54), and these results are stored in the memory of the control device 26 (step 55). On the other hand, the control device 26
Drives the switches 33 and 34 in the signal extraction chamber 110 to switch them on (turns on), sets the input terminal of the differential amplifier 22 to the ground side, and moves the sample moving mechanism 5 to the next measurement position on the sample S in the electronic state. It is driven so as to be located directly below the beam EB (step 56).

The above is repeated until the measurement at the final measurement position is completed. Then, the control device 26 appropriately displays the final measurement result on the monitor 25, or the like.

In this embodiment, it is convenient to measure the offset value of the analog-digital converter 106. FIG. 9 is a diagram in the vicinity of the analog-digital converter 106 in the measurement system 104, and is a schematic diagram for explaining the principle of the measurement.

In FIG. 9, reference numeral 36 denotes a switch provided on the input side of the analog-digital converter 106, which can drop the input-side terminal of the analog-digital converter 106 to the ground potential. Switch 36 on (on) off (off)
Is controlled by a control signal from the controller 26 via a control line 37. The output of the analog-digital converter 106 when the input side terminal of the analog-digital converter 106 is dropped to the ground potential is measured as the offset value of the analog-digital converter and stored in the memory of the control device 26.
It may be appropriately used as a correction of the offset of the analog-digital converter. The offset correction of the analog-digital converter is useful when the reproducibility of measured values is a problem.

Further, the present invention is not limited to the above-mentioned scanning electron microscope, but may be applied to the case where the current flowing through the sample is measured by a laser microscope, an electron probe microanalyzer (EPMA) or any other sample analyzer using a charged particle beam. It is possible to apply.

[0044]

As described in detail above, according to the present invention,
A sample inspection apparatus capable of accurately amplifying a minute current flowing through a sample by irradiating a primary beam is realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a scanning electron microscope embodying the present invention.

FIG. 2 is a diagram for explaining the vicinity of a terminal 14 of FIG.

FIG. 3 is a diagram showing how the sample current changes as the sample moves when a bare wafer is used as a sample.

FIG. 4 is a flowchart for explaining a measurement procedure for correcting a change in sample current due to sample movement.

FIG. 5: Sample current when electron beam EB is turned on
It is a figure for demonstrating the change of the measurement intensity of (absorption current).

FIG. 6 is a diagram for explaining an on / off state of an electron beam EB and a method of measuring a sample current (absorption current).

7 is a flowchart for explaining a measurement procedure of measurement using the measurement principle of FIG.

FIG. 8 is a flow chart for explaining a measurement procedure in a scanning electron microscope embodying the present invention.

FIG. 9 is a diagram illustrating a method of measuring an offset value of an analog-digital converter.

[Explanation of symbols]

1: electron gun, 2: focusing lens, 3: deflector, S: sample,
4: Electro-optical system control device, 5: Sample moving mechanism, 6: Sample chamber, 7: Insulating material, 10: Sample holder, 12, 13: Conductor
(Coaxial line), 14: Terminal, 15: Substrate, 16, 17: Insulator, 18, 19: Core wire, 20, 21, 24: Conductor wire, 2
2: differential amplifier, 25: monitor, 26: control device 30:
Pin, 31: roller, 32: wire, 33, 34, 3
6: switch, 35, 37: control signal line, 101: blanking device, 102: voltage optical converter, 103: optical cable, 104: measurement system, 105: optical voltage converter, 10
6: analog-digital converter, 107: arithmetic circuit, 11
0: Signal extraction room

Continued front page    F term (reference) 2G001 AA03 BA07 CA03 FA03 FA06                       FA09 GA03 GA04 GA06 GA11                       HA13 JA01 JA07 JA11 JA16                       LA11 MA05 PA02 PA07 PA11                 2G132 AA00 AD01 AE04 AE16 AE18                       AE22 AF12 AF13 AG08                 4M106 AA01 BA02 BA04 CA04 DE30                 5C001 AA03                 5C033 UU03 UU04 UU08

Claims (18)

[Claims] 1. A focused energy beam irradiation system for intermittently irradiating a desired portion of a sample with a focused energy beam, and a conductive member electrically insulated from the sample and the sample moving mechanism. A member, a terminal provided on the conductive member for extracting an electrical signal from the conductive member, and an electrically insulating and mounting the sample and contacting the sample for extracting an electrical signal from the sample A terminal provided, a sample chamber accommodating the sample and the sample moving mechanism, a differential amplifier for differentially amplifying signals from the two terminals, and an output signal of the differential amplifier for connecting and disconnecting the focused energy beam. And a measurement system that measures at least two or more data with a predetermined time difference and performs a predetermined calculation based on the data, a sample inspection apparatus. 2. The sample inspection according to claim 1, wherein the focused energy beam irradiation system scans the focused energy beam at a high scanning speed to irradiate a desired area on the sample. apparatus. 3. The sample moving mechanism is configured to irradiate a large number of portions on the sample with a focused energy beam one after another.
The focused energy beam irradiation system is configured to drive a sample, and the focused energy beam irradiation system is configured to irradiate a focused energy beam to a portion of the driven sample in synchronization with the driving of the sample moving mechanism, and the measurement system includes 3. The sample inspection apparatus according to claim 1, wherein a portion of the driven sample is measured in synchronization with the driving of the sample moving mechanism. 4. The sample inspection apparatus according to claim 1, wherein the two terminals can be set to the ground potential when the sample moving mechanism is driven. 5. The sample inspection apparatus according to claim 1, wherein the sample chamber is an electromagnetically shielded sample chamber. 6. The differential amplifier according to claim 5, wherein the differential amplifier is housed in a sample chamber or is housed in a case which is electromagnetically shielded and directly connected to the sample chamber. The sample inspection device described. 7. The sample according to claim 1, wherein the output signal of the differential amplifier is converted into an optical signal and input to the measurement system via an optical cable. Inspection device. 8. A first trigger signal for controlling the measurement system to start measurement and a second trigger signal for controlling the focused energy beam irradiation system to start irradiation of an energy beam. The sample inspection apparatus according to any one of claims 1 to 7, further comprising a control system configured to generate. 9. The sample inspection apparatus according to claim 8, wherein the second trigger signal is generated after a predetermined time delay from the first trigger signal. 10. The measurement system comprises: a first measurement value from the first trigger signal to the second trigger signal; and a predetermined time after a predetermined time has elapsed from the second trigger signal. 10. The sample inspection apparatus according to claim 9, wherein the second measurement value up to the subsequent step is measured and the difference between the values of the first and second measurement values is output. 11. The measurement system is configured to obtain a large number of data by sampling the output signal of the differential amplifier a number of times in synchronization with a commercial power supply frequency. 10. The sample inspection device according to any one of 10. 12. A focused energy beam irradiation system for intermittently irradiating a desired portion of a sample with a focused energy beam, and a conductive member electrically insulated from the sample and the sample moving mechanism. A member, a terminal provided on the conductive member for extracting an electrical signal from the conductive member, and an electrically insulating and mounting the sample and contacting the sample for extracting an electrical signal from the sample Data are obtained by measuring the output terminals of the differential amplifier that differentially amplifies the signals from the two terminals, the sample chamber in which the terminals are provided, the sample chamber in which the sample and the sample moving mechanism are housed. And a measurement system for performing a predetermined calculation based on the data, the output signal of the differential amplifier is measured as at least two or more data at a predetermined time difference from the intermittent beam of the focused energy beam. Shi , Specimen inspection method characterized by performing a predetermined calculation based on said data. 13. When driving the sample moving mechanism, the
13. The sample inspection method according to claim 12, further comprising the step of dropping one of the terminals to the ground potential. 14. A control system for generating first and second trigger signals is provided, and when the control system generates a first trigger signal and sends it to the measurement system, the measurement system starts measurement. And a step of, when the control system generates a second trigger signal and sends the second trigger signal to the focused energy beam irradiation system with a predetermined time delay, the focused energy beam irradiation system starts irradiation of an energy beam. The sample inspection method according to any one of claims 12 to 13, wherein 15. A first measurement value from the first trigger signal to the second trigger signal in the measurement system,
And a step of measuring a second measurement value after a predetermined time has elapsed from the second trigger signal until a predetermined time has elapsed, and outputting a difference between the first and second measurement values. 15. The sample inspection method according to claim 14, further comprising a step. 16. The measurement according to claim 12, wherein the output signal of the differential amplifier is sampled many times in synchronization with a commercial power supply frequency to obtain a large number of data. The sample inspection method according to any one. 17. A focused energy beam irradiation system for intermittently irradiating a desired portion of a sample with a focused energy beam, and a conductive material electrically isolated between the sample and the sample moving mechanism. A member, a terminal provided on the conductive member for extracting an electrical signal from the conductive member, and an electrically insulating and mounting the sample and contacting the sample for extracting an electrical signal from the sample Data are obtained by measuring the output terminals of the differential amplifier that differentially amplifies the signals from the two terminals, the sample chamber in which the terminals are provided, the sample chamber in which the sample and the sample moving mechanism are housed. And a function for generating a first trigger signal for controlling the measurement system, and a second trigger signal for controlling the focused energy beam irradiation system. And the ability to generate In the sample inspection apparatus and a control system for, (1) while dropping the two terminals to the ground potential, and performing driving of the sample moving mechanism, (2)
The measurement system starts the first measurement with the first trigger signal, and (3) the second trigger signal with a predetermined time delay from the first trigger signal, 1, the focused energy beam irradiation system starts irradiation of the energy beam upon completion of the measurement of 1.
(4) A step of performing a second measurement from a lapse of a predetermined time from the second trigger signal to a lapse of a predetermined time.
(5) A method for inspecting a sample, comprising the step of outputting the difference between the first measurement value and the second measurement value. 18. The sample according to claim 17, wherein in the measurement, the output signal of the differential amplifier is sampled many times in synchronization with the commercial power supply frequency to obtain a large number of data. Inspection method.