JPH11238483A - Charged particle beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the effect of a temp. change in a magnetic field type lens upon a specimen observed. SOLUTION: A charged particle beam device is equipped with a magnetic field type lens cooling means 19 to remove Joule's heat generated by the energizing current flowing in a magnetic field type lens 5 and a heat emission amount detecting means 16 to detect the heat emission amount of Joule's heat from the energizing current of the lens 5, and the lens 5 is cooled in accordance with the result from detection, and the lens temp. is kept at room temp. at all times. This enables keeping constant the lens temp. at all times irrespective of the level of the energizing current of the magnetic field type lens 5, as one sort of the charged particle beam optical lens, and allows minimizing the effect of the temp. change in the lens upon the specimen to be observed. It is also possible to prevent the objective lens from dew condensation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam apparatus for irradiating a sample with a charged particle beam to inspect, analyze, process, and observe the sample.

[0002]

2. Description of the Related Art A charged particle beam apparatus is used for irradiating a sample with a charged particle beam such as an electron beam or an ion beam to inspect, analyze, process, and observe an image of the sample. Charged particle beam devices include electron beam exposure devices used to form patterns on photomasks and wafers in the semiconductor device manufacturing process,
There are a scanning electron microscope used for inspecting the appearance of a pattern formed on a wafer and the like, a transmission electron microscope used for analyzing the inside of a sample, and a charged particle processing apparatus for performing fine processing of the sample.

In these charged particle beam apparatuses, charged particles such as an electron beam emitted from an electron gun and an ion beam emitted from an ion beam source are focused on a sample and irradiated, or transmitted through the sample. In order to form a charged particle beam image, a magnetic field type lens which is a kind of a charged particle beam optical lens is provided. The exciting current of these magnetic lenses is increased or decreased in accordance with a change in observation conditions such as a change in charged particle beam acceleration voltage or a change in image observation magnification. When the operator finishes observing a certain sample, the operator carries in the next sample to be observed from a cassette located at a predetermined distance from the apparatus. At that time, since the sample is often released into the atmosphere of the room, the initial value of the sample temperature is often room temperature. Therefore, the temperature of the sample and the temperature of the magnetic lens often do not always match.

In a conventional charged particle beam apparatus, for example, an electron microscope, only when a large exciting current is required for a magnetic field type lens, a water flow tube which is in thermal contact with the magnetic field type lens,
The cooling water cooled to a constant temperature is circulated to remove Joule heat generated by the magnetic lens.
Therefore, the temperature of the magnetic lens is designed to be within a certain range from the temperature of the cooling water under a certain use condition. However, in practice, the excitation current of the magnetic field type lens is not always used constant.

On the other hand, for example, a scanning electron microscope is required to keep a pattern image in a desired and stable observation state regardless of a change in a magnetic field type lens excitation current amount. In particular, in order to automatically perform a visual inspection or the like and automatically call out a pattern, it is required that the pattern has high positional accuracy on the sample stage. Furthermore, it requires a high processing capacity and a high operation rate.

[0006]

By the way, for example, a sample image observed with a scanning electron microscope is affected by physical properties of the sample and interaction of primary electrons. In other words, a collection of bright spots on the image observation display, which represents the detected amount of secondary electrons or reflected electrons depending on the incident energy of the primary electrons and the intrinsic physical properties of the sample material, is used as the sample image. Therefore, the sample and its observation conditions are not always constant, and the observer changes the acceleration energy of the primary electrons depending on the observation sample.
If the acceleration energy of primary electrons is increased or decreased, the excitation current flowing through a magnetic field type lens, which is a kind of charged particle optical lens, needs to be increased or decreased in order to focus the primary electron beam focal position on the sample. . When the magnetic field type lens exciting current is increased or decreased, the generated Joule heat increases or decreases.

Further, since the height of the sample to be observed (the position in the direction of the electron optical axis is referred to as "height") differs depending on the individual sample, it is necessary to adjust the focal position by changing the observation sample. At that time, it is necessary to increase or decrease the magnetic field type lens exciting current similarly to the above, and at that time, the Joule heat generated from the magnetic type lens fluctuates greatly or smallly. This is because, when the sample to be observed is a pattern on the wafer, the wafer surface height varies depending on the location in the wafer due to the warpage of the wafer, so that the focal position changes every time the pattern to be observed is changed.

As described above, when a change in the primary electron acceleration energy or a change in the sample height occurs, it is necessary to change the magnetic field type lens excitation current, and the Joule heat generated at that time also changes. However, in the conventional electron microscope, since the cooling water for cooling the magnetic lens is controlled to a constant temperature, there is no means for correcting the change in the amount of Joule heat generated.

[0009] indicates the amount of heat q absorbed from magnetic lens by the cooling water, the magnetic field type lens temperature T, the relationship between the coolant temperature T _W by the following equation (1). In the equation, k represents the cooling capacity, and is a coefficient of the temperature difference and the amount of heat absorbed from the magnetic lens.
Here, for simplicity, a simple proportional relationship is assumed.

[0010]

Q = k (T−T _W ) (Equation 1) If the amount of heat generated by the magnetic lens increases, the coefficient k or the temperature difference (T−T _W ) between the magnetic lens and the cooling water increases. There is a need to. However, since k always takes a constant value depending on the cooling device and the fixed use conditions (cooling water flow rate, etc.),
(T−T _W ) needs to be increased. Here, since the cooling water temperature T _W is controlled to be constant, it is necessary to increase the magnetic lens temperature T in order to increase (T−T _W ). Therefore, in the conventional electron microscope, the magnetic field lens temperature is increased or decreased by increasing or decreasing the excitation current of the magnetic field lens.

As described above, when the magnetic field type lens exciting current becomes large or small due to the change of the use condition and the magnetic field type lens temperature becomes high or low, the magnetic field type lens as shown in FIG. In a simple electron microscope, for example, a scanning electron microscope, the sample is affected by the magnetic lens temperature.

That is, when the temperature of the magnetic lens increases, heat is transferred from the magnetic lens to the sample by radiant heat or the like, and the temperature of the sample increases. When the sample is a pattern on a wafer, the heat causes thermal expansion of the wafer, causing a shift phenomenon in which the test pattern moves within the visual field during observation. Conversely, when the temperature of the magnetic lens decreases, heat is transferred from the sample to the magnetic lens, and the temperature of the wafer decreases. When the temperature decreases, the wafer shrinks, and similarly, the pattern to be inspected under observation moves within the visual field. The larger the temperature difference between the initial wafer observation temperature and the magnetic lens temperature, the greater this shift amount. Before observation, the wafer is often stored at room temperature in the atmosphere, so when the magnetic lens temperature matches room temperature, the amount of shift of the pattern on the wafer is minimized.

When the temperature of the magnetic field type lens rises, the adsorption energy when gas molecules in a vacuum occupying the gap between the magnetic field type lens and the sample are adsorbed on the lens surface or the surface of the vacuum vessel is reduced, and the gaseous molecules are transferred to the sample surface. This facilitates the movement of contamination and activates the phenomenon of contamination deposited on the surface of the sample irradiated with the primary electron beam. The amount of contamination increases as the temperature of the magnetic lens increases.

Here, the scanning electron microscope has been described as an example, but the situation in which the sample is affected by a temperature change of the magnetic field type lens facing the sample is the same in other charged particle beam devices. For example, in a charged particle beam processing device,
When the processing conditions are changed, the exciting current of the magnetic field type lens changes, which causes a temperature change of the magnetic field type lens, so that the sample placed opposite to the magnetic field type lens is affected. Further, even in an electron beam exposure apparatus, a change in the exposure condition involves a change in the exciting current of the magnetic field type lens, which changes the temperature of the magnetic field type lens, so that the sample is affected by the temperature change.

Therefore, in the conventional charged particle beam apparatus, when the excitation condition of the magnetic lens, especially the magnetic lens facing the sample is changed by changing the observation conditions, processing conditions, exposure conditions, etc. When the sample was carried in, observation, processing, exposure, and the like had to be interrupted until thermal equilibrium was reached and the device was stabilized. This is the same when the apparatus is turned on. In other words, when the power is turned on to a device which is usually at room temperature, the magnetic lens generates heat due to Joule heat generated by the exciting current, but it takes a relatively long time until it reaches thermal equilibrium with cooling by cooling water. In short, you can't get into full-scale work.

The present invention has been made in view of such problems of the prior art, and changes the observation conditions, processing conditions, exposure conditions, and the like when the apparatus power is turned on or during operation of the apparatus. It is an object of the present invention to provide a charged particle beam apparatus capable of shortening the time required for stabilizing the apparatus and increasing the operation rate when the exciting current of the lens is changed.

[0017]

According to the present invention, the amount of change in the excitation current of a magnetic field type lens, which is a kind of charged particle beam optical lens, is detected to determine the change in Joule heat generation of the magnetic field type lens. The object is achieved by correcting the cooling capacity of the magnetic lens cooling means by the amount of change. Alternatively, the above object is achieved by detecting a temperature change of the magnetic field type lens by a temperature sensor and correcting the cooling ability of the magnetic field type lens cooling means according to the temperature change. It is effective that the magnetic field type lens for correcting the cooling capacity is a magnetic field type lens arranged at a position close to the sample, for example, an objective lens. In addition, the magnetic lens cooling means includes:
It is preferable to keep the temperature of the magnetic lens at a constant temperature near room temperature.

That is, the present invention provides a charged particle beam apparatus including a means for irradiating a sample with a charged particle beam, a charged particle beam optical system including a magnetic field lens, and a cooling means for cooling the magnetic field lens. A heating value detecting means for determining a heat value of the mold lens; and a control means for controlling a cooling capacity of the cooling means, wherein the control means determines the heating value by the heating value detecting means so that the temperature of the magnetic lens is kept substantially constant. The cooling capacity of the cooling means is controlled according to the generated heat value.

The heat generation amount detecting means obtains the heat generation amount of the magnetic field type lens facing the sample, and the control means can control the cooling ability of the cooling means of the magnetic field type lens facing the sample.
The heat generation amount detection means can determine the heat generation amount based on the exciting current amount of the magnetic field type lens or based on the temperature of the magnetic field type lens.

Further, the present invention relates to a charged particle beam apparatus including a means for generating a charged particle beam for irradiating a sample, a charged particle beam optical system including a magnetic lens, and a cooling means for cooling the magnetic lens. And temperature control means for detecting the temperature of the magnetic lens facing the sample, and control means for controlling the cooling capacity of the cooling means, wherein the control means controls the temperature so that the temperature of the magnetic lens is kept substantially constant. The cooling capacity of the cooling means is controlled according to the temperature detected by the detecting means.

Further, the present invention provides a charged particle beam generating means,
Scanning means for scanning the sample with a charged particle beam, an objective lens, cooling means for cooling the objective lens, and charged particle beam focus correction means for controlling the exciting current of the objective lens to focus the charged particle beam on the sample surface A charged particle beam device including a sample signal detector for detecting a sample signal emitted from the sample, and a calorific value detector for detecting a calorific value of the objective lens based on an exciting current of the objective lens; Control means for controlling the cooling capacity of the cooling means based on the detection result of the detection means to keep the objective lens at a substantially constant temperature.

The present invention also provides a charged particle beam generating means,
Scanning means for scanning the sample with a charged particle beam; an objective lens; objective lens cooling means for cooling the objective lens; and a charged particle beam focus for controlling the excitation current of the objective lens to focus the charged particle beam on the sample surface In a charged particle beam device including a correction unit and a sample signal detection unit that detects a sample signal emitted from a sample, a temperature detection unit that detects a temperature of an objective lens, and a cooling unit based on a detection result of the temperature detection unit Control means for controlling the cooling capacity of the objective lens to keep the objective lens at a substantially constant temperature.

When the cooling means is a cooling means using a coolant such as cooling water, cooling oil or cooling air, the control means can control the cooling capacity of the cooling means by changing the temperature or the flow rate of the coolant. . When the cooling means is a cooling means using a heat pump such as a Peltier element, the control means can control the cooling capacity of the refrigerant means by changing the drive voltage of the heat pump.

The cooling means preferably keeps the temperature of the magnetic field type lens, especially the objective lens, at a constant temperature near room temperature. By doing so, the time required for the sample or the magnetic lens to reach thermal equilibrium after the power is turned on or the sample is carried into the apparatus, the thermal time constant τ (= C / C /
k, where C is the heat capacity of the main unit, the unit is [J / ° C],
k is the radiation coefficient of the main unit after cooling, the unit is [W / ° C])
Can be shorter.

According to the present invention, an operation involving a change in the magnetic field type lens exciting current is performed in order to determine the Joule heat generation of the magnetic field type lens and to correct the cooling capacity of the magnetic field type lens cooling means according to the heat generation amount. In addition, the time required for the sample and the magnetic lens (especially the objective lens) to reach thermal equilibrium can be shortened, and observation, inspection, processing, and processing of the sample can be performed while always minimizing the effect of the magnetic lens temperature on the sample. Operations such as exposure can be stably performed. Similarly, when power is supplied to the apparatus or when a sample is carried into the apparatus, the time required for the sample to reach thermal equilibrium is shortened, and observation, inspection, processing, exposure, etc. of the sample are performed stably immediately after power is supplied. be able to.

In particular, when the appearance inspection or the like is performed automatically by a scanning electron microscope, the Joule heat generated by the magnetic field type lens (objective lens) is prevented from being transferred to the wafer by radiation or the like, and the thermal expansion of the wafer is prevented. By suppressing the phenomenon that the observation pattern moves in the visual field, the position of the pattern on the sample stage can be obtained with high accuracy. Further, by minimizing the time required for the thermal transient caused by Joule heat generation in the magnetic field type lens, it is possible to perform a stable appearance inspection at a high operation rate without waiting time.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. Here, a scanning electron microscope will be described as an example.

FIG. 1 is a schematic diagram showing an example of a scanning electron microscope according to the present invention. The primary electron beam emitted from the electron source 1 is accelerated to an arbitrary acceleration energy by a potential difference between the primary electron accelerating electrode 2 and the electron source, and then temporarily converged by the converging lens 3 to exert a lens action on the charged particle beam. The surface of the sample 6 placed on the sample stage 7 is focused by the objective lens 5 which is a kind of a magnetic lens. Secondary electrons generated by the interaction between the primary electrons and the material of the sample 6 are detected by the secondary electron detector 8, the signal is amplified by the amplifier 9, and displayed as bright spots on the display 11 for observation. The brightness of the bright spot indicates the amount of secondary electrons from the surface of the sample 6 irradiated with the primary electron beam. At this time,
The primary electron beam is deflected by the deflection lens 4 driven by the scanning power supply 10 and scans the surface of the sample 6. On the observation display 11 synchronized with the deflection lens 4 by the scanning power supply 10, a secondary electron image of the sample 6 is formed as a collection of bright spots having a one-to-one relationship with the surface of the sample 6 scanned by the primary electron beam. Is displayed.

The operator selects the primary electron acceleration energy suitable for the sample material while observing the secondary electron image, and focuses the primary electron beam on the sample surface while observing the defocus of the secondary electron image. Try to focus.

When the operator performs an operation of increasing or decreasing the primary electron acceleration energy, the changed set value VAS is stored in the primary electron acceleration power supply 20. A voltage VAC generated based on the VAS value by the primary electron acceleration power supply 20 is applied to the primary electron acceleration electrode 2 as a primary electron acceleration voltage. Further, it outputs the stored primary electron acceleration voltage set value signal VAS to the objective lens excitation current drive device 13. The objective lens exciting current driver 13 causes the objective lens exciting current IOB based on the focal position signal FPS sent from the focal position setting unit 12 to flow to the objective lens coil 15. At this time, the correction by the primary electron acceleration voltage VAC is also performed by reading the VAS. The relational expression at this time is shown in the following (Equation 2).

[0031]

(Equation 2)

Here, FPS is the focal position of the objective lens 5, N is the number of turns of the objective lens coil 15, and VAC is the primary electron acceleration voltage. The function f is determined by the material and shape of the flow path forming the objective lens 5. Actually, it is obtained by simulation and actual measurement at the time of setting the objective lens 5. FIG. 2 shows an example of this function f.

The focus position signal FPS and the primary electron acceleration voltage V
When obtaining the objective lens excitation current IOB from AC, as a practical method, N × IOB / VAC for an arbitrary FPS is used.
^{A half} value is discretely obtained by experiment or simulation or the like (indicated by a circle in FIG. 2), and a table TBL_an as shown in FIG.
Create In the objective lens excitation current driver 13, N × IOB / VAC corresponding to the read FPS value f _n
^1/2 value a _n indexing from TBL_an (Figure 3), the objective lens current IO from the winding number N is known and the primary electron acceleration voltage VAC read simultaneously by equation (3) below
Find B.

[0034]

(Equation 3)

In order to focus the secondary electron image, the operator raises or lowers the focal point of the primary electron beam (the axial direction of the electron optical system is set to the “height” direction, the electron source side is set to “high”, Side is the “low” side), the focal position setting unit 12
Stores the value. The focus position setting device 12 outputs a focus position signal FPS to the objective lens excitation current drive device 13. The objective lens excitation current driver 13 generates the objective lens excitation current IOB from the FPS based on the above (Equation 3), and excites the objective lens coil 15 to focus the primary electron beam on the surface of the sample 6. .

The objective lens excitation current signal OBS measured by the ammeter 14 connected in series in the middle of the line through which the objective lens excitation current IOB flows is used as the objective lens heating value detector 1
6 is output. The OBS read by the objective lens heating value detector 16 is converted into an objective lens heating value signal QS. At this time, the relational expression is represented by the following (Equation 4).

[0037]

QS = r × IOB ² (Equation 4) QS is a heat generation amount signal of the objective lens 5, r is a resistance value of the objective lens coil 15, and IOB is a current (signal OBS) flowing through the objective lens coil 15. ). The objective lens calorific value signal QS converted based on (Equation 4) is used as a coolant temperature setting unit 17 for setting the temperature of the coolant, here, the coolant.
Output to

On the other hand, the room temperature is set by the room temperature sensor 32, and the result is output to the computer 28. The computer 28 outputs the set temperature (here, room temperature T ₀ ) to the cooling water temperature setter 17 based on the result. The cooling water temperature setter 17 reads the objective lens heat generation amount signal QS and the set temperature T ₀ and converts them into a cooling water temperature set value signal TWS. FIG. 4 shows the relationship at this time. A or B in FIG. 4 is a curve including a straight line. Here, for simplicity, it is assumed that the straight line is a straight line, and the formula is described below. The straight line A represents the relationship when the cooling water temperature is T _W1 , and the straight line B represents the relationship when the cooling water temperature is T _W2 .

A: q = k ₁ × (T−T _W1 ) B: q = k ₁ × (T−T _W2 ) Now, when the cooling water temperature is set to T _W1 , the objective lens temperature T ₁ becomes room temperature T _{It is} assumed that it has become ₀ (T ₁ = T ₀ ). The heat absorption at this time is the intersection of the straight line A and the temperature T = T ₀ , and the heat absorption q = q ₁
= The amount of heat generated Q _1. Coefficient k ₁ representing this relationship,
(1) The degree of thermal contact between the objective lens coil 15 as a heat source and the objective lens cooling water flow path pipe 19 on the heat absorbing side, (2)
It is determined by the overall cooling capacity including the ability to receive the heat of the refrigerant (in this case, water) and the ability to transport the heat, and (3) the efficiency of heat transfer to the refrigerant in the cooling water producing apparatus.
Actually, it is obtained through experiments.

Here, it is assumed that the calorific value has increased to Q = Q ₂ (Q ₁ <Q ₂ ). The temperature of the objective lens is T = T ₂ (T ₁ <T ₂ ) at the intersection of the straight line A and Q = Q ₂ , and the temperature rises by (T ₂ −T ₁ ).

Therefore, the cooling water set temperature is set to T _W2 (T _W1 > T _W
W2 ). In this case, the objective lens temperature at the intersection of the straight line B and Q = Q _2, coincides with T = T _1, and the room temperature T ₀ is the original temperature. Actually, the room temperature T ₀ obtained by the temperature sensor 32 or the like placed in the room, the QS previously obtained,
The following equation (5) is used to calculate T from k ₁ obtained through experiments and the like.
Find WS.

[0042]

(Equation 5)

The cooling water temperature set value signal TWS obtained in this manner is output to the cooling water producing device 18. The cooling water producing device 18 reads the cooling water temperature set value signal TWS, and cools the outward cooling water W1 to a temperature at which the temperature of the objective lens 5 becomes room temperature based on the signal. That is, the outward cooling water W1 is supplied to the objective lens cooling water flow path pipe 19.
, The objective lens 5 and the objective lens coil 15 are cooled, the Joule heat thereof is deprived, and the cooling water is returned to the cooling water producing device 18 as the return-path cooling water W2. In the cooling water production device 18, the return water cooling water W2 is cooled again to a temperature based on the cooling water temperature set value signal TWS, and circulated as the outward cooling water W1.

Hereinafter, the steps for executing a series of operations for setting the cooling water temperature will be described with reference to FIG.

[Step 100] First, the objective lens exciting current driver 13 reads the focal position signal FPS stored in the focal position setting unit 12. The FPS is a value obtained by adjusting the focal position to the in-focus position before the observer.

[0046] [Step 101] the objective lens current driving device 13, obtains the N × IOB / VAC ^1/2 value a _n corresponding to the FPS value f _n according TBL_an (Figure 3).

[Step 102] Further, the objective lens exciting current driver 13 reads the value of the primary electron acceleration voltage VAC stored in the primary electron acceleration power supply 20 by the signal VAS. The VAC has been previously set to a value appropriate for the sample by the observer.

[0048] [Step 103] the objective lens current driving device 13, the basis of the a _n calculated in step 101, VAC obtained in step 102, and from the known objective lens coil winding number N in the equation (3) Then, the objective lens excitation current IOB is obtained.

[Step 104] Objective lens exciting current I
The ammeter 14 connected in series to the OB measures the IOB and outputs the current value OBS. Objective lens calorific value detector 1
In step 6, the OBS is read, the IOB is obtained, and the objective lens heating value signal QS is obtained based on the above (Equation 4) using the known objective lens coil resistance value r.

[Step 105] Cooling water temperature setting unit 17
Reads the objective lens heating value signal QS and the set temperature T ₀ , and sets the cooling water temperature set value signal T
Find WS.

[Step 106] Cooling water producing apparatus 18
Reads and stores the cooling water temperature set value signal TWS,
After cooling the inbound cooling water W2 to a temperature equivalent to TWS, the cooling water W2 starts to be sent to the objective lens cooling water flow pipe 19 as outward cooling water W1.

[Step 107] The objective lens exciting current driver 13 constantly monitors whether the focal position signal FPS or the primary electron acceleration voltage set value signal VAS is rewritten, and returns to step 100 if a change occurs. Actually, the host computer that controls the entire scanning electron microscope having the features of the present invention always monitors the presence or absence of the operation of the operator, rewrites the FPS or VAS, and executes steps 100 to 1
It is good to control the flow of 07.

By the above series of operations, it is possible to keep the objective lens temperature at a desired state regardless of the change in the objective lens exciting current. This is shown in FIG. And it increased the time t ₁ which is the objective lens coil calorific value Q. The reason for this is that the operator sets the primary electron acceleration voltage V
This is due to raising or lowering the AC or adjusting the focus position FPS. Then, a series of operations of each block shown in FIG. 1 is performed according to the flowchart of FIG. 5, so that the heat absorption amount q from the objective lens 5 has a short time delay Δt _0.
At time t ₂ which put the increases only increase ΔQ equivalent calorific value Q. As a result, the transient phenomenon of the objective lens temperature T causes a time delay Δt _s1 shorter than the time constant τ from the time t ₁ (however,
Thermal time constant τ = C / k of the scanning electron microscope main body, where C is the heat capacity of the main body and the unit is [J / ° C], and k is the radiation coefficient of the main body after cooling and the unit is [W / ° C]). It occurs until the time t _{3 when} it is placed, but converges to the original temperature T ₀ at the time t ₃ .

By minimizing the time from when the increase in the objective lens exciting current IOB is detected to when the temperature of the outward cooling water W1 has been lowered by the cooling water producing device 18, the present invention including the objective lens 5 can be realized. Thermal time constant τ of the body of the scanning electron microscope (τ = C / k, where C is the heat capacity of the apparatus body and the unit is [J / ° C.], k is the heat dissipation coefficient of the apparatus body after cooling and the unit is [W / ° C]) on the time delay Δt _s1 , and the time difference Δt _s1 can be minimized.

Thus, the operator can set the primary electron acceleration voltage V
Even when the AC is raised or lowered or the focal position FPS is readjusted, the influence of the Joule heat generated by the objective lens 5 on the sample 6 is always minimized even if the operator starts observation with little waiting time. Can be kept. Similarly, when power is turned on to the device at the start of observation,
The time required for the sample to reach thermal equilibrium in the apparatus can be reduced, and stable sample observation can be performed immediately after power is turned on. In this way, the operating rate of the scanning electron microscope can be improved.

In the above embodiment, the objective lens exciting current IOB is obtained by the ammeter 14 connected in series, and the current value OBS is output to the objective lens heat generation amount detector 16. However, since the objective lens exciting current driving device 13 obtains the objective lens exciting current IOB value, the signal OBS representing the value may be directly output.

FIG. 7 shows the functional blocks. Similarly to the above embodiment, the objective lens excitation current IO is read from the objective lens excitation current drive device 13 which has read the signals FPS and VAS.
B is output. On the other hand, a signal OBS representing the IOB value
Is output to the objective lens calorific value detector 16. The objective lens calorific value detector 16 obtains the objective lens calorific value signal QS based on the above (Equation 4) and outputs the signal to the cooling water temperature setting device 17. The following is the same as the form of the actual sleep. With this configuration, the ammeter 14 required in the above embodiment can be omitted, and the configuration can be simplified.

Further, in the above embodiment, when the heat value of the objective lens coil 15 rises from Q ₁ to Q ₂ , the temperature of the cooling water is lowered from T _W1 to T _W2 , so that the temperature of the objective lens 5 becomes room temperature. Kept. The situation is as shown in FIG. When the heating value Q = Q _1, the temperature of the objective lens 5 was T = T ₁ from the intersection of the straight line A and Q = Q ₁ , but the heating value of the objective lens coil 15 increased to Q = Q ₂ . ,
From the intersection of the straight line A and Q = Q ₂ , the temperature of the objective lens 5 is T = T
_Rose to _two . Therefore, by lowering the cooling water temperature to T _W2 , the objective lens temperature T = from the intersection of the straight line B and Q = Q ₂
T ₁ = T ₀ , and the temperature of the objective lens 5 could be kept at room temperature.

However, in the above (Equation 1), increasing k representing the cooling capacity by the coefficient of the temperature difference and the amount of heat absorbed from the objective lens has an effect equivalent to increasing the temperature difference (T−T _W ). can get. That is, by increasing the flow velocity v of the refrigerant (in this case, water), the ability to receive heat can be increased, and as a result, the cooling capacity k can be increased. This is shown in FIG. A and C in FIG. 8 are curves including a straight line. As in the case of FIG. 4, for simplicity, it is assumed that the straight lines are used, and the equations are described below. Line A is the flow rate v of the cooling water
Represents the relationship between the time of _1, line C represents the relation when the flow velocity v ₂ of the cooling water.

A: q = k ₁ × (T−T _W1 ) C: q = k ₂ × (T−T _W1 ) q is the amount of heat absorbed from the objective lens, k ₁ and k ₂ are the cooling capacity, The difference and the coefficient of the amount of heat absorbed from the objective lens (k ₁ <
k ₂ ), v ₁ and v ₂ are the flow rates of the cooling water (v ₁ <v ₂ ), T is the objective lens temperature, and T _W1 is the cooling water temperature.

Now, when the cooling water temperature is set to T _W1, it is assumed that the objective lens temperature T ₁ has reached room temperature T ₀ (T ₁ = T ₀ ). The heat absorption at this time is the intersection of the straight line A and the temperature T = T ₀ ,
The amount of heat absorption q = q ₁ = the amount of emitted light Q ₁ . This relationship is determined by the overall cooling capacity as in the case of FIG. actually,
Obtain it by experiment.

Here, the calorific value rose to Q = Q ₂ (Q
₁ <Q ₂ ). The temperature of the objective lens is T = T ₂ (T ₁ <T ₂ ) at the intersection of the straight line A and Q = Q ₂ , and the temperature rises by (T ₂ −T ₁ ). Therefore, increasing the flow rate of the cooling water from v ₁ to v _2. In this case, the objective lens temperature at the intersection of the straight line C and Q = Q _2, coincides with T = T _1, and the room temperature T ₀ is the original temperature.

The cooling water temperature setting unit 17 calculates the following based on the room temperature T ₀ obtained by the room temperature sensor 32 and the like placed in the room, the objective lens heat generation amount signal QS obtained previously, and k ₂ obtained by experiments and the like. The TWS is obtained by (Equation 6).

[0064]

(Equation 6)

As a practical method, a flow rate v of the cooling water with respect to an arbitrary heating value Q of the objective lens coil is obtained by an experiment or the like, and a table TBL_vn as shown in FIG. 9 is created. In the experiment, the calorific value Q of the objective lens coil is actually given, and the flow rate v of the cooling water when the temperature of the objective lens 5 becomes room temperature is obtained.

By the way, in the above embodiment,
This has been realized by circulating cold water as a cooling means for the objective lens. However, there is a Peltier element which is a kind of heat pump as another means for removing heat. FIG. 10 shows a schematic configuration diagram when a Peltier element is used as the objective lens cooling means. Objective lens excitation current driver 13
Output the objective lens excitation current IOB from the output of the objective lens 5 including the objective lens coil 15, and
The operation up to obtaining the objective lens calorific value signal QS from OB is the same as in the above embodiment.

The Joule heat generated by the objective lens coil 15 is led out of the objective lens 5 by a good heat conductor 21 typified by a heat pipe or the like which is brought into thermal contact with the objective lens 5 and the objective lens coil 15. Good thermal conductor 21
The other end of the objective lens coil 15 and the endothermic plate 2
2, the Peltier element 23 and the heat generating plate 24 are fixed in order. The contact surfaces of the heat absorbing plate 22, the Peltier element 23, and the heat generating plate 24 have the minimum surface roughness so as to minimize the thermal contact resistance. Also, if necessary, the thermal contact resistance can be further reduced by applying the heat-conductive cream to the surfaces after contacting each other. On the heat generating plate 24, a radiating fin 25, which is also devised to reduce the thermal contact resistance, is fixed to the contact surface.

The Peltier device driving device 26 that has read QS from the objective lens calorific value detector 16 generates a Peltier device driving voltage VP necessary for the Peltier device 23 to absorb heat equivalent to QS, and applies it to the Peltier device 23. I do. The Peltier element 23 generates the heat absorption Q _p1 by the VP and passes through the heat absorbing plate 22 and the good heat conductor 21 to the objective lens 5.
And absorbs the heat of the objective lens coil 15. Through heating plate 24 from the radiating fins 25, it dissipates Q _p2 including the calorific value of heat absorption amount Q _p1 and the Peltier element 23 itself (Q _p1
<Q _p2 ). Here, when Q _p1 = QS, the objective lens 5 is kept at room temperature. As a practical method, the Peltier device driving voltage V for an arbitrary objective lens coil heating value Q
P is obtained by experiments or the like, and a table TBL as shown in FIG.
Create _VP. In the experiment, the VP at the time when the temperature of the objective lens reaches room temperature is obtained by giving the heat generation amount Q of the objective lens coil.

As described above, in the embodiments described above, the heat generation amount Q of the objective lens 5 is obtained to correct the cooling capacity of the cooling means. However, the cooling capacity may be corrected by a temperature sensor attached to the objective lens 5 so that the temperature of the objective lens 5 is set to room temperature.

FIG. 11 shows an example in that case. When the temperature has the greatest effect on the sample on the surface of the objective lens 5, for example, a temperature signal TWS obtained by the temperature sensor 27 attached to the lower surface of the objective lens is input to the cooling water producing device 18. In the cooling water production device 18, the TWS
Is read, and based on the signal, the outward cooling water W1 is cooled to a temperature at which the temperature of the objective lens 5 becomes room temperature. The circulation of the cooling water and the like are the same as in the case of FIG.

FIG. 12 shows how the temperature changes. And it increased the time t ₁ which is the objective lens coil calorific value Q. The cause is that the operator raises or lowers the primary electron acceleration voltage VAC or adjusts the focus position FPS. Then, the temperature T of the objective lens 5 rises under the influence of the heat radiation coefficient k (unit [W / ° C.]) and the heat capacity C (unit [J / ° C.]) of the cooled scanning microscope main body. The cooling water producing apparatus 18 that has detected the rise in the temperature T by the temperature sensor 27 gradually starts increasing the heat absorption q, and finally converges to a value obtained by increasing the amount of increase ΔQ in the amount of heat generated by the objective lens coil. The objective lens temperature T also converges at substantially the same time. However, the transient phenomenon is strongly affected by the thermal time constant τ of the main body of the scanning electron microscope including the objective lens 5.
As a result, as compared with the convergence time Δt _S1 in the above embodiment, the transient phenomenon converges, requiring a slightly longer Δt _S2 . Thereafter, the temperature of the objective lens 5 is always kept at room temperature.

Thus, the operator can set the primary electron acceleration voltage V
Even if the AC is raised or lowered or the focal position FPS is readjusted, the influence of Joule heat generated by the objective lens 5 can always be kept to a minimum even if the operator starts observation with little waiting time. .

In the embodiment described with reference to FIG. 11, the cooling capacity of the cooling water producing device 18 is corrected so that the temperature of the objective lens 5 obtained by the temperature sensor 27 is always kept constant. However, obtains the time change gradient of the temperature of the objective lens 5 at the initial stage of the transients is measured by a temperature sensor 27, and determined from the slope of the calorific value Q ₂ of after rising from the initial heating value Q ₁ by ΔQ Is also good.

FIG. 13 is a diagram showing the time change of the temperature TO of the objective lens 5 when the cooling capacity of the cooling water producing device 18 is not corrected even after the heat generation amount increases from Q ₁ to Q ₂ . . Until time t _1, a scanning electron microscope main body is in equilibrium temperature T _i with respect to the temperature T _W of the cooling water. It is assumed that the amount of heat generated by the objective lens 5 at time t ₁ has changed from the initial amount of heat Q ₁ to the amount of heat Q ₂ increased by ΔQ. At this time, the temperature TO of the objective lens 5 is raised gradually to reach the temperature T _e which is determined by the radiation coefficients k of the scanning electron microscope main body after cooling a new heating value Q ₂ from the temperature T _i, T _e Converges to Here, the initial temperature gradient tanθ ₀ of this transient phenomenon is obtained by the following (Equation 7).

[0075]

(Equation 7)

Here, Q ₂ is the heat value after the rise, k is the cooling capacity as in the case of (Equation 1), the temperature difference between the cooling water and the objective lens 5, and the heat absorption from the objective lens to the cooling device. Is the coefficient of C represents the heat capacity of the scanning electron microscope main body.

FIG. 14 shows a method for actually determining the gradient tan θ ₀ . Just before the initial heating value Q ₁ time t ₁ was changed to the calorific value Q ₂ to which rises by ΔQ from the temperature TO of the objective lens has a initial equilibrium temperature T _i. From here, Δt
Assume that after a time the rise in temperature difference ΔT ₀ has been measured by a temperature sensor. At this time, the temperature gradient tan θ ₀ can be approximately obtained by the following (Equation 8).

[0078]

(Equation 8)

At this time, the measurement time interval Δt should be smaller than the calculation accuracy of tan θ ₀ in consideration of the time accuracy of Δt and the measurement accuracy of temperature difference ΔT ₀ within a range where the result tan θ ₀ has significance. Is good. By the following equation (9) which is obtained from the equation (7) and (8) above, the gradient approximation [Delta] T ₀ / Delta] t, it is possible to determine the calorific value Q ₂ after rising.

[0080]

(Equation 9)

FIG. 15 shows an example of an apparatus configuration for performing such control. Time interval Δ by temperature sensor 27
The temperature TO of the objective lens 5 obtained at t is stored in the waveform storage device (memory) 29 each time. The temperature difference ΔT ₀ between the time t ₁ and the time Δt after the time t ₁ can be obtained at an arbitrary time by referring to the waveform storage device 29 by the computer 28. Assuming that the values are T (t ₁ ) and T (t ₁ + Δt), the temperature difference ΔT ₀ is obtained immediately after the time t ₁ + Δt from the following equation.

ΔT ₀ = T (t ₁ + Δt) −T (t ₁ ) From the ΔT ₀ obtained as described above, the heat value Q ₂ after the rise is obtained. Here, the heat capacity C and the coefficient k representing the cooling capacity of the main body of the scanning electron microscope are obtained in advance by simulation or experiment. The cooling water temperature T _W is the measurement result T _W1 of the water temperature sensor 30 provided in the middle of the outward cooling water W1, the water temperature sensor 31 provided in the middle of the return cooling water W2 measured results than T _W2 below It is determined by (Equation 10).

[0083]

(Equation 10)

The signal QS indicating the calorific value Q ₂ of the objective lens obtained as described above is output to the cooling water temperature setting device 17. Subsequent operations are the same as those in the embodiment of FIG. Also in the present embodiment, it is possible to shorten the time to reach thermal equilibrium, as shown in FIG.

As described above, in the embodiments described above, for example, dew condensation on the surface of the cooling water channel tube 19 and the surface of the objective lens coil 15 cannot be prevented.

When the surface temperature of the flow path tube 19 and the objective lens coil 15 exposed to the cooling water having the outward cooling water temperature T _W1 or the returning cooling water temperature T _W2 becomes lower than the dew point determined by the surrounding environment, The moisture contained in the surrounding air is condensed and adheres to the surface. It is a flow pipe 1
9 and the surface of a metal material or the like constituting the objective lens coil 15 may cause corrosion.

FIG. 17 is a schematic configuration diagram of an embodiment for preventing this dew condensation. The principle that the objective lens excitation current IOB is output from the objective lens excitation current driving device 13 and the objective lens 5 including the objective lens coil 15 generates heat,
The operation up to the calculation of the objective lens heat generation amount QS is the same as that of the above embodiment.

The signal QS output from the objective lens calorific value detector 16 is output to a cooling water temperature setting device 17 for setting the temperature of the cooling water.

On the other hand, the room temperature is measured by the room temperature sensor 32, and the ambient humidity is measured by the hygrometer 33, and the results are output to the computer 28, respectively. The computer 28 determines the dew point TL based on the results. At this time,
It is known that the dew point can be uniquely determined from room temperature and humidity. In practice, it is preferable that the relationship be obtained for individual conditions, a table TBL_TL (FIG. 18) as shown in FIG. 18 be created and stored in the computer 28. Calculator 2
8, the cooling water temperature setter this dew point TL and the room temperature T ₀ 17
Output to The cooling water temperature setter 17 sets the cooling water set value T
Find WS. At this time, when the cooling water set value TWS obtained by (Equation 5) is a temperature higher than the dew point TL, the TWS obtained by (Equation 5) is output to the cooling water producing device 18 as it is. If TWS is lower than TL, TWS = TL is reset and output to the cooling water producing device 18.

FIG. 19 shows the relationship at this time. A, B, and D in FIG. 19 are curves including straight lines. Here, for the sake of simplicity, the straight lines are assumed, and the equations are described below. The straight line A represents the relationship when the cooling water temperature is T _W1 , the straight line B represents the relationship when the cooling water temperature is T _W2 , and the straight line D represents the relationship when the cooling water temperature is TL.

A: q = k ₁ × (T−T _W1 ) B: q = k ₁ × (T−T _W2 ) D: q = k ₁ × (T−TL) Now, the cooling water temperature is set to T _W1 . At the time of setting, it is assumed that the objective lens temperature T ₁ has reached room temperature T ₀ (T ₁ = T ₀ ). The heat absorption at this time is the intersection of the straight line A and the temperature T = T ₀ , and the heat absorption q = q ₁
= The amount of heat generated Q _1. Coefficient k ₁ representing this relationship is a coefficient representing the entire cooling capacity as in the above embodiment.

Here, it is assumed that the calorific value has increased to Q = Q ₂ (Q ₁ <Q ₂ ). The temperature of the objective lens is T = T ₂ (T ₁ <T ₂ ) at the intersection of the straight line A and Q = Q ₂ , and the temperature rises by (T ₂ −T ₁ ).

Therefore, the cooling water set temperature T _W2 (T _W1 > T _W2 ) which coincides with the room temperature T ₀ which is the original temperature of the objective lens temperature.
Ask for. However, this T _W2 becomes lower than the dew point TL, and there is a possibility that dew condensation occurs. Then, assuming that the set temperature of the cooling water is TL, the temperature of the objective lens is represented by a straight line D and Q = Q
₂ intersections, T = T _3, and the rises from room temperature T ₀ is the original temperature may be a temperature lower than T _2.

The cooling water temperature set value signal TWS obtained in this way is output to the cooling water producing device 18. The subsequent series of operations including the cooling water production device 18 is the same as in the above embodiment.

Hereinafter, the steps for executing a series of operations for setting the cooling water temperature will be described with reference to FIG.

[Step 100] to [Step 104] Same as the above embodiment [Step 108] The computer 28 reads the room temperature T ₀ .

[Step 109] The computer 28 determines the humidity W ₀
Read.

[Step 110] The computer 28 sets the dew point TL
From TBL_TL.

[Step 105] Cooling water temperature setting unit 17
Reads the objective lens heating value signal QS and the set temperature T ₀ , and sets the cooling water temperature set value signal T
Find WS.

[Step 111] The TWS obtained in step 105 is compared with the TL obtained in step 110.

[Step 112] When the temperature becomes lower than the TWS TL, TWS = TL is substituted.

[Step 106] to [Step 107] Same as in the above embodiment. Through the above-described series of operations, the objective lens temperature can be set in a desired state within a condition range where dew condensation does not occur regardless of a change in the objective lens exciting current. Can be maintained.

As described above, the scanning electron microscope according to the present invention always maintains the temperature of the objective lens facing the sample at room temperature, so that the observation condition is changed and the excitation condition of the objective lens is changed, When the power is turned on, the time required for the objective lens and the sample to reach thermal equilibrium can be reduced. Further, the time when the sample temperature reaches an equilibrium state when the sample (wafer) is carried in can be minimized. Therefore, stable sample observation can be started immediately after performing an operation of changing observation conditions, turning on the power to the device, or loading the sample into the device.

Here, the present invention has been described by taking a scanning electron microscope as an example. However, the present invention is not limited to the scanning electron microscope, but may be applied to other types of charged particle beam apparatuses such as a charged particle processing apparatus, a charged particle exposure apparatus such as an electron beam exposure apparatus, a transmission electron microscope, and an ion electron microscope. Can be similarly applied.

[0105]

According to the present invention, the temperature of the magnetic field type lens is maintained at a constant temperature regardless of the intensity of the exciting current of the magnetic field type lens, which is a kind of charged particle beam optical lens, and the temperature change of the magnetic field type lens to the observation sample. Can be minimized. In addition, dew condensation on the objective lens can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a scanning electron microscope according to the present invention.

FIG. 2 is a graph for obtaining an objective lens excitation amount.

FIG. 3 is a table for obtaining an objective lens excitation amount.

FIG. 4 is a graph for obtaining a cooling water set temperature speed.

FIG. 5 is a diagram showing a flow of a series of operations for setting a cooling water temperature.

FIG. 6 is a diagram for explaining a change in a heat generation amount of a magnetic field type lens and a change in a temperature of a magnetic field type lens.

FIG. 7 is a partial block diagram showing another example of the present invention.

FIG. 8 is a graph for obtaining a cooling water flow velocity.

FIG. 9 is a table for determining a cooling water flow velocity.

FIG. 10 is a partial block diagram showing another example of the present invention.

FIG. 11 is a partial block diagram showing another example of the present invention.

FIG. 12 is a diagram illustrating a change in the heat generation amount of the magnetic field type lens and a change in the temperature of the magnetic field type lens.

FIG. 13 is a view for explaining a temperature change of the magnetic field type lens when the cooling capacity is not corrected even after the amount of generated heat increases.

FIG. 14 is a diagram illustrating an initial temperature gradient.

FIG. 15 is a partial block diagram showing another example of the present invention.

FIG. 16 is a table for obtaining a Peltier element driving voltage.

FIG. 17 is a partial block diagram showing another example of the present invention.

FIG. 18 is a table for obtaining a dew point.

FIG. 19 is a graph showing an example of the effect of the present invention.

FIG. 20 is a diagram showing an example of a flow of a series of operations for setting a cooling water temperature.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron source, 2 ... Primary electron acceleration electrode, 3 ... Converging lens,
4 Deflection lens, 5 Objective lens, 6 Sample, 7 Sample stage, 8 Secondary electron detector, 9 Amplifier, 10 Scanning power supply, 11 Display for observation, 12 Focus setting device,
13: Objective lens excitation current drive, 14: Ammeter, 1
5: Objective lens coil, 16: Objective lens calorific value detector, 17: Cooling water temperature setting device, 18: Cooling water producing device,
Reference numeral 19: objective lens cooling water flow path tube, 20: primary electron accelerating power supply, 21: good thermal conductor, 22: heat absorbing plate, 20: Peltier element, 24: heat generating plate, 25: radiating fin,
26: Peltier device driving device, 27: Temperature sensor, 2
8 ... Calculator, 29 ... Waveform storage device (memory), 30 ... Outbound cooling water / water temperature sensor, 31 ... Returning cooling water / water temperature sensor, 32 ... Room temperature sensor, 33 ... Hygrometer, VAC ... Primary electron acceleration voltage, VAS ... Primary electron acceleration voltage setting value, FP
S: Focus position signal, IOB: Objective lens excitation current, OB
S: Objective lens excitation current signal, QS: Objective lens calorific value signal, TO: Objective lens temperature, T _W1 : Incoming path cooling water temperature, T _W2 : Incoming path cooling water temperature, TWS: Cooling water temperature set value signal, W1 ... Inbound cooling water, W2: Inbound cooling water, VP: Peltier element drive voltage.

Claims (15)

[Claims] 1. A charged particle beam apparatus comprising: means for irradiating a sample with a charged particle beam; a charged particle beam optical system including a magnetic lens; and cooling means for cooling the magnetic lens. A heat generation amount detection means for calculating a heat generation amount; and a control means for controlling a cooling capacity of the cooling means, wherein the control means detects the heat generation amount by the heat generation amount detection means such that the temperature of the magnetic lens is maintained substantially constant. A charged particle beam apparatus, wherein the cooling capacity of the cooling means is controlled in accordance with the calorific value obtained. 2. The method according to claim 1, wherein the heating value detecting means determines a heating value of the magnetic field type lens facing the sample, and the control means controls a cooling capacity of a cooling means of the magnetic field type lens facing the sample. The charged particle beam device according to claim 1. 3. The charged particle beam apparatus according to claim 1, wherein said heat generation amount detecting means obtains a heat generation amount based on an excitation current amount of said magnetic field type lens. 4. The charged particle beam apparatus according to claim 1, wherein said heat generation amount detecting means obtains a heat generation amount based on a temperature of said magnetic field type lens. 5. A charged particle beam apparatus comprising: means for generating a charged particle beam for irradiating a sample; a charged particle beam optical system including a magnetic lens; and cooling means for cooling the magnetic lens. Temperature detecting means for detecting the temperature of the opposed magnetic field type lens, and control means for controlling the cooling capacity of the cooling means, wherein the control means is configured to maintain the temperature of the magnetic field type lens substantially constant. A charged particle beam device, wherein the cooling capacity of the cooling means is controlled according to the temperature detected by the temperature detecting means. 6. A charged particle beam generating means, a scanning means for scanning the sample with the charged particle beam, an objective lens, a cooling means for cooling the objective lens, and an exciting current for controlling the exciting current of the objective lens. In a charged particle beam device including charged particle beam focus correction means for adjusting the focus of the charged particle beam to the sample surface, and sample signal detection means for detecting a sample signal emitted from the sample, the excitation current of the objective lens A heating value detecting means for detecting a heating value of the objective lens based on the heating value; a control means for controlling a cooling capacity of the cooling means based on a detection result of the heating value detecting means to keep the objective lens at a substantially constant temperature. A charged particle beam device comprising: 7. A charged particle beam generating means, a scanning means for scanning the sample with the charged particle beam, an objective lens, an objective lens cooling means for cooling the objective lens, and controlling an exciting current of the objective lens. A charged particle beam focus correction means for adjusting the focus of the charged particle beam to the sample surface, and a sample signal detection means for detecting a sample signal emitted from the sample, the temperature of the objective lens A charged particle beam apparatus comprising: a temperature detecting means for detecting; and a control means for controlling a cooling capacity of the cooling means based on a detection result of the temperature detecting means to keep the objective lens at a substantially constant temperature. . 8. When the exciting current of the objective lens changes, the time required for the sample and the objective lens to reach thermal equilibrium is a thermal time constant τ (= C / C /
k, where C is the heat capacity of the main unit, the unit is [J / ° C],
k is the radiation coefficient of the main unit after cooling, the unit is [W / ° C])
The charged particle beam device according to claim 5, wherein the charged particle beam device is shorter. 9. The charged particle beam apparatus according to claim 1, wherein said control means controls the cooling capacity of said cooling means by changing the temperature of the refrigerant. 10. The charged particle beam apparatus according to claim 1, wherein said control means controls the cooling capacity of said cooling means by changing the flow rate of the refrigerant. 11. The charged particle beam apparatus according to claim 1, wherein said cooling means is a heat pump. 12. The charged particle beam apparatus according to claim 1, wherein said substantially constant temperature is room temperature. 13. The charged particle beam apparatus according to claim 1, wherein said charged particle beam apparatus is a scanning electron microscope. 14. After turning on the power or loading the sample into the apparatus, the time required for the sample and the lens to reach thermal equilibrium is the thermal time constant τ (= C / C /
k, where C is the heat capacity of the main unit, the unit is [J / ° C],
k is the radiation coefficient of the main unit after cooling, the unit is [W / ° C])
13. The charged particle beam device according to claim 12, which is shorter. 15. The charged particle beam device according to claim 1, further comprising means for obtaining a dew point, and controlling the cooling capacity of said cooling means based on the result. Charged particle beam equipment.