JP5824262B2 - Sample observation method and pressure measurement holder - Google Patents

Description

  The present invention relates to a sample observation method using an electron microscope capable of observing a sample in a gas atmosphere, a pressure measurement holder used in the sample observation method, and an electron microscope.

  In an electron microscope, it is necessary to place a sample in an atmospheric gas and observe the reaction process between the sample and the atmospheric gas dynamically in that state (this type of observation is called “in-situ observation”). May be.

  FIG. 1 shows a schematic example of an electron microscope capable of in-situ observation.

  In the figure, reference numeral 1 denotes an electron gun, and 2 denotes a focusing lens that focuses an electron beam EB emitted from the electron gun.

  An objective lens 3 includes an upper magnetic pole 3A and a lower magnetic pole 3B, and a gas atmosphere sample storage block 4 is disposed between both magnetic poles. An electron beam EB is applied to a sample set in the gas atmosphere sample storage block. The light is squeezed finely. A space between the upper magnetic pole 3A and the lower magnetic pole 3B of the objective lens 3 in which the gas atmosphere sample storage block 4 is disposed is referred to as a sample chamber 5.

  Reference numerals 6 and 7 denote an intermediate lens 6 for transmitting the sample set in the gas atmosphere sample storage block 4 and enlarging and projecting the electron beam focused by the objective lens 3 on the fluorescent plate 8 as a transmission image of the sample. This is the lens 7.

  Reference numeral 9 denotes a camera (for example, a CCD camera) installed below the fluorescent plate 8 so that an enlarged image can be detected by retracting the fluorescent plate from the optical axis of the electron beam by a fluorescent plate retracting means (not shown). It has become.

  Reference numeral 10 denotes a control device to which an output signal from the camera 9 is sent via the AD converter 11, and performs control of various means constituting the electron microscope, various arithmetic processes, and the like.

  In the figure, reference numeral 12 denotes a display device that displays a sample image or the like on the screen based on a command from the control device 10, and 13 denotes an input device such as a mouse or a keyboard.

  FIG. 2 shows details of the gas atmosphere sample storage block 4 and a peripheral portion connected to the gas atmosphere sample storage block.

  In FIG. 2, reference numeral 14 denotes a cylindrical goniometer support attached to a part of the lens barrel C so as to support the goniometer 15, and the goniometer support includes an exhaust pipe connected to the tip end side space Sa of the goniometer support. 16 is connected.

  A vacuum pump 17 is connected to the end of the exhaust pipe, and a pressure gauge G1 and an opening / closing valve V1 are attached to an intermediate part of the exhaust pipe.

  Reference numeral 18 denotes a sample holder having a sample holder 19 attached to the tip thereof. The sample holder 18 is attached to the goniometer 15. Although not shown in detail, the sample S set on the sample holder 19 is printed on the paper surface by the goniometer. Can be rotated (tilted) around the XZ direction parallel to the Y direction, the Y direction perpendicular to the paper surface, and the X axis. A ring-shaped groove is cut on the outer periphery of the intermediate portion of the sample holder, and an O-ring 20 is fitted in the groove.

  Reference numeral 21 denotes a bottomed cylindrical gas atmosphere container in which a portion corresponding to the front end surface is blown out. 14 is in a state of being fitted into the tip portion. A ring-shaped groove is formed on the outer peripheral portion of the front end of the gas atmosphere container, and an O-ring 22 is fitted in the groove.

  Electron beam passage holes Ha and Hb are formed in the center portion of the upper wall OW and the center portion of the bottom wall BW of the gas atmosphere container so that the centers thereof coincide with the electron optical axis O.

  Further, an exhaust pipe 23a is connected to the electron beam passage hole Ha at one end inside the upper wall OW of the gas atmosphere container, and an exhaust pipe 23a is connected to the exhaust pipe 23c provided at the side wall SW. An exhaust pipe 23b connected to the beam passage hole Hb and the other end connected to an exhaust pipe 23c provided on the side wall SW is provided. Note that an open / close valve V3 and a vacuum pump 25 are connected to the exhaust pipe 23c through an exhaust pipe 24.

  Further, orifice plates Oa and Ob are respectively attached in parallel to the upper and lower portions in the electron beam passage hole Ha on the upper wall OW of the gas atmosphere container, and the upper portion in the electron beam passage hole Hb on the lower wall BW of the gas atmosphere container. Orifice plates Oc and Od are attached to the lower part in parallel. By adopting such a configuration, space portions Da and Db (hereinafter referred to as these spaces) for isolating the space in the sample chamber 5 and the space in the gas atmosphere vessel 21 in the electron beam passages Ha and Hb in a pressure manner. Are referred to as differential pressure spaces).

  Furthermore, a gas supply pipe 26 is attached to the gas atmosphere container side wall SW so as to penetrate the lens barrel C and the gas atmosphere container side wall.

  A nozzle N is attached to one side (gas atmosphere container 21 side) of the gas supply pipe so that the tip of the gas supply pipe faces the sample S. On the other side of the gas supply pipe 26, an open / close valve V2 and a gas flow rate adjusting device are provided. 28 and the gas cylinder 29 are connected in this order, and the flow rate of the reaction gas from the gas cylinder 29 is adjusted by the gas adjusting device 28 and discharged from the tip of the nozzle N via the open / close valve V2. In addition, a pressure gauge G2 is attached to the gas supply pipe 26 around an intermediate portion between the opening / closing valve V2 and the nozzle N.

  In FIG. 2, G3 is a pressure gauge for detecting the pressure in the sample chamber 5.

  In the electron microscope apparatus having such a configuration, the sample S is set on the sample holder 19, and the sample holder 18 supporting the sample holder is attached to the goniometer 14.

  Then, the goniometer is operated to move the sample S in the X, Y, and Z axis directions and rotate around the X axis so that the sample can be observed in a predetermined manner.

  Next, the sample chamber 5 is evacuated by a vacuum pump (not shown) until a predetermined high degree of vacuum is reached.

  At the same time, the valve V1 is opened, the inside of the gas atmosphere container 21 is opened by the vacuum pump 17, the valve V3 is opened, and the differential pressure spaces Da and Db are exhausted by the vacuum pump 25 until a predetermined pressure is reached.

  In this state, an electron beam EB is generated from the electron gun 1. The electron beam EB emitted from the electron gun is focused by the focusing lens 2, narrowed down by the objective lens 3, and passes through the differential pressure space Da in the electron beam passage hole Ha on the upper wall portion of the gas atmosphere container 21. The position of Sp on S is irradiated.

  And the electron which permeate | transmitted the sample passes the differential pressure space Db in the electron beam passage hole Hb of the gas atmosphere container 21 lower wall part, and on the fluorescent plate 8 or the camera 9 by the intermediate lens 6 and the projection lens 7. An enlarged projection image of the sample is projected onto the sample.

  When observing the reaction process between the sample and the reaction gas, the open / close valve V2 is opened, the reaction gas flow rate from the gas cylinder 29 is adjusted by the gas amount adjusting device 28, and the gas is sent to the nozzle N through the gas supply pipe 26. .

  Then, when the reaction gas is sprayed from the nozzle tip to the sample S arranged in the gas atmosphere container 21, the reaction between the sample and the reaction gas starts.

  At this time, the pressure in the gas atmosphere container 21 rises due to the supply of the reaction gas and becomes a low vacuum state, but the space in the gas atmosphere container 21 and the space in the sample chamber 5 in the high vacuum state have a differential pressure space Da, Due to the formation of Db, the reaction gas in the gas atmosphere container 21 does not leak into the sample chamber 5.

  In this state, the electron beam EB from the electron gun 1 is passed through the differential pressure space Da in the electron beam passage hole Ha on the upper wall portion of the gas atmosphere container 21 to irradiate the sample S that has reacted with the reaction gas. The electrons that have passed through the sample S are allowed to pass through the differential pressure space Db in the electron beam passage hole Hb in the lower wall portion of the gas atmosphere container 21, and the sample is placed on the fluorescent plate 8 or the camera 9 by the intermediate lens 6 and the projection lens 7. A transmission image of is projected.

  Although not specifically described, normally, in order to promote the reaction between the sample S and the reaction gas, a sample heating means is separately provided to heat the sample.

JP 2009-259760 A

When observing the reaction process between the sample and the reaction gas, the gas pressure in the sample observation device when the reaction occurs is an important parameter.
Conventionally, it is assumed that the pressure in the gas atmosphere container 21 is equal to the gas pressure at the sample observation position, and the measured value by the pressure gauge G1 is adopted as the pressure of the gas atmosphere container 21.

  However, when a large amount of reaction gas continues to flow into the gas atmosphere container 21, the above process is established because the pressure in the container becomes uniform. However, a small amount of gas is supplied to the sample from a nozzle arranged close to the sample. It is considered that it does not hold when spraying on the observation position.

  That is, the gas ejected from the nozzle proceeds toward the sample observation position, but immediately expands due to a pressure difference and diffuses.

  From this, even if it is 5 mm or 10 mm away from the sample observation position, the pressure at that location becomes a value significantly lower than the pressure at the sample observation position. Moreover, the pressure measurement value in the gas atmosphere container 21 is It must be far from the pressure at the sample observation position.

  In addition, the pressure gauge G1 is provided in the middle of the exhaust pipe 16 communicating with the inside of the gas atmosphere container 21 and the tip space Sa of the goniometer support 14, and is not directly attached to the gas atmosphere container 21. Therefore, neither the pressure value of the pressure gauge G1 nor the pressure value in the gas atmosphere container 21 is accurately represented.

The present invention has been made to solve such problems, and an object thereof is to provide a novel sample observation method and pressure measurement Hol da.

An electron beam passage hole is formed on the electron optical axis, a gas atmosphere container in which gas is supplied from a gas supply system, a sample is held at the tip, and the sample is removed from the vacuum from the gas atmosphere container. a sample observation method in an electron microscope equipped with a sample holder for introducing within, the sample holder prior to introduction into the gas atmosphere in the container, the pressure measurement holder for pressure measurement element are only attached The gas flow rate when the gas supply system is adjusted by the gas supply system so that the pressure in the gas atmosphere container introduced into the gas atmosphere container and the pressure in the gas atmosphere container detected by the pressure measuring element becomes a predetermined pressure. Record the set value, then introduce the sample holder into the gas atmosphere container instead of the pressure measurement holder, and adjust the pressure in the gas atmosphere container based on the recorded gas flow rate set value and, Irradiating an electron beam from a child beam generating means to said sample, was set to obtain a sample image based on electron beam transmitted through the sample.

  According to the present invention, since the gas pressure at the sample observation position can be set to the target gas pressure, it is possible to perform sample observation in a state where the gas pressure at the sample observation position is set to a desired pressure.

An example of an electron microscope capable of in-situ observation is shown. FIG. 2 shows a part of the details of FIG. An example of an apparatus for carrying out the sample observation method of the present invention is shown. It is a figure which shows the example which used the thermocouple type pressure gauge as a pressure sensor.

FIG. 3 shows an example of an apparatus for carrying out the sample observation method of the present invention. The basic configuration is the same as that shown in FIG. 2, and the pressure measurement holder 30 is replaced with the goniometer 15 instead of the sample holder 18. It shows the state of wearing.

  The pressure measurement holder 30 shown in FIG. 3 has a structure in which a pressure sensor chip 31 is attached to the tip of a normal sample holder via a lead wire 33.

  The lead wire 33 is connected to a lead wire 35 taken out to the outside of the pressure measurement holder 30 through a hermetic seal 34 for hermetically sealing and maintaining the pressure between the vacuum and the atmosphere. Is connected to a pressure gauge 36.

  A ring-shaped groove is cut in the outer periphery of the intermediate portion of the pressure measurement holder 30 main body, and an O-ring 20 for vacuum sealing is fitted in this groove.

In describing the embodiment of the present invention, the sample observation method of the embodiment will be described below in steps.
(Step 1)
First, the gas atmosphere container 21 and the sample chamber 5 are leaked, and the pressure measurement holder 30 is attached to the goniometer 15 as shown in FIG.
By mounting the pressure measuring holder 30, the pressure measuring element 31 attached to the tip of the pressure measuring holder 30 is positioned at the position Sp where the sample in FIG. That is, at the time of observation, the sample is placed at a position where the electron beam is irradiated.
(Step 2)
Next, with the pressure measurement holder 30 attached, after the gas atmosphere container 21 is evacuated and the pressure is stabilized, the pressure at the position where the sample in the gas atmosphere container should be placed using the pressure measurement element 31. While detecting (sample observation position pressure), an operation is performed to adjust the gas flow rate of the gas supply system so that the sample position pressure becomes the target pressure.
That is, the sample chamber 5 is evacuated from the atmospheric pressure by a vacuum pump (not shown), and at the same time, the open / close valves V1 and V3 are opened, and the vacuum pump 17 in the gas atmosphere container 21 by the vacuum pump 17 is opened. Exhaust of the differential pressure spaces Da and Db is started.
Then, each vacuum pump is evacuated until the pressure in the sample chamber 5, the gas atmosphere container 21, and the differential pressure spaces Da and Db becomes stable. For example, in a stable state before gas introduction, the pressure value of the pressure gauge G3 disposed in the sample chamber 5 is P3a, the pressure value of the pressure gauge G1 installed between the gas atmosphere container 21 and V1 is P1a, the sample and electron beam light It is assumed that the pressure value of the pressure measuring element 31 installed at the position Sp where the axes intersect each indicates Psa.
Next, the opening / closing valve V2 is opened, the gas flow rate from the gas cylinder 29 is adjusted by the gas amount adjusting device 28, and the gas is sent to the nozzle N through the gas supply pipe 26.
At this time, if the target value of the sample observation position pressure is Psb, the operator adjusts the gas flow rate while checking the pressure with the pressure measuring element 31 so that the pressure value detected by the pressure measuring element 31 becomes Psb. The gas amount of the device 28 is adjusted.
(Step 3)
When the flow rate is adjusted by the gas flow rate adjusting device 28 and the pressure value measured by the pressure measuring element 31 is stably maintained at the value of Psb, the pressure value P3b of the pressure gauge G3 connected to the sample chamber 5; A pressure value P1b of a pressure gauge G1 provided in an exhaust pipe connected to a vacuum pump for exhausting the gas atmosphere container 21 and a gas supply pipe connected to a gas supply system for supplying gas into the gas atmosphere container. Record (store) the flow rate set value F1 of the flowmeter.

  Normally, P3b and P1b are higher by the amount of gas introduced than the values P3a and P1a before the gas introduction.

Through the above steps 1 to 3, the condition setting for setting the sample observation position pressure to the target pressure value is completed.
(Step 4)
Next, the pressure measurement holder is removed in the following procedure, and the sample holder on which the sample to be observed is set is attached to the goniometer.
The on-off valves V1, V2, and V3 are closed, and then the gas atmosphere container 21 leaks from the sample chamber 5, and after the pressure in the gas atmosphere container 21 reaches atmospheric pressure, the pressure measurement holder 30 is removed from the goniometer 15. Instead, the sample holder 18 on which the sample S to be observed is set is mounted on the goniometer 15 (the state shown in FIG. 2).
(Step 5)
Next, the inside of the gas atmosphere container is evacuated by the following procedure, and the gas supply valve is opened to make a gas atmosphere state in which the sample is observed.
After mounting the sample holder 18, the sample chamber 5 is started to be evacuated from a state of atmospheric pressure by a vacuum pump (not shown), and at the same time, the open / close valves V 1 and V 3 are opened and the inside of the gas atmosphere container 21 is opened by the vacuum pump 17. Then, the vacuum pump 25 starts exhausting the differential pressure spaces Da and Db.
Then, as in step 2, the vacuum pumps are evacuated until the vacuum pressure in the sample chamber 5, the gas atmosphere container 21, and the differential pressure spaces Da and Db is stabilized. That is, each exhaust pump exhausts until the pressure value of the pressure gauge G3 arranged in the sample chamber 5 reaches P3a and the pressure value of the pressure gauge G1 installed between the gas atmosphere container 21 and V1 reaches P1a.

  Next, the on-off valve V2 is opened, and the reaction gas is sent to the nozzle N through the gas supply pipe 26 while the flow rate setting value F1 adjusted last time by the gas amount adjusting device 28 for adjusting the gas flow rate from the gas cylinder 29 is maintained.

The positional relationship between the tip of the nozzle N and the observation position of the sample is the same as the positional relationship between the nozzle N and the pressure measuring element 31 in step 3, and the reaction gas is applied to the sample at the set value F1 that has been previously adjusted. The pressure at the observation position of the sample is the same Psb as set in step 3.
(Step 6)
Since the sample observation position pressure is set to Psb as described above, sample observation is performed. That is, the electron beam EB from the electron gun 1 is passed through the differential pressure space Da in the electron beam passage hole Ha in the upper wall portion of the gas atmosphere container 21 to irradiate the sample S that is reacting with the gas. Is transmitted through the differential pressure space Db in the electron beam passage hole Hb in the lower wall portion of the gas atmosphere container 21, and the transmission image of the sample is transferred onto the fluorescent screen 8 or the camera 9 by the intermediate lens 6 and the projection lens 7. Project.

  By the above procedure, the sample observation position pressure is set to the target value Psb, and the process in which the sample S reacts with the reaction gas can be observed.

  The timing at which the introduction of the reaction gas at the flow rate F1 in Step 5 is started and the observation is shifted to the observation in Step 6 may be set to an appropriate waiting time, but the measured value of the pressure gauge G1 is stored in Step 3 first. It may be a point in time when the pressure value P1b coincides with or substantially equals.

  Further, the measured value of the pressure gauge G3 may be referred to and the measured values of the pressure gauges G1 and G3 may be regarded as reaching the stored pressure values of P1b and P3b.

  By the way, in the said example, as a pressure measurement element used for a pressure measurement, you may employ | adopt the thermocouple type pressure gauge using the heat conduction phenomenon of a gas molecule, for example.

This thermocouple type pressure gauge is based on the fact that the temperature of the heater wire heated at a constant current changes due to the thermal conduction of gas molecules, and the temperature of the heater wire is measured with a thermocouple connected to the heater wire. The pressure value is measured by converting the temperature of the wire into a pressure value.
FIG. 4 shows a pressure measurement holder 38 incorporating such a thermocouple pressure gauge. The pressure measurement holder 38 is positioned between the terminals 41a and 41b on the support 39a at the tip of the pressure measurement holder main body 39b at the position (sample observation position) Sp where the sample and the electron beam optical axis intersect when the sample holder is inserted as shown in FIG. The heater wire 40 stretched between the thermocouples 43 a and 43 b is connected to the heater wire 40. The lead wires connected to the terminals 41a and 42b and the thermocouples 42a and 42b are connected to the lead wires 45a, 45b, 46a and 46b connected to the inside of the pressure measurement holder main body 39b via the hermetic seal 44. . The lead wires 45 a and 45 b are connected to a constant current supply power source 47, and the lead wires 46 a and 46 b are connected to a voltmeter 48.
With such a configuration, the temperature of the heater wire 40 is such that a constant current is supplied to the heater wire 40 so that the amount of heat generated by the heater wire 40 is kept constant, and the amount of heat taken by the surrounding gas depends on the ambient pressure. It changes with.
Then, the temperature of the heater wire 40 is detected by a thermocouple, the electromotive force of the thermocouple is detected by a voltmeter 48, and the pressure value is converted into a pressure value by a pressure indicator 49 to display a pressure value near the heater wire 40. To do.
Thus, the pressure sensor system is not limited as long as the pressure sensor attached to the pressure measurement holder is of a size that can measure the pressure at the sample observation position and can be disposed at the tip of the pressure holder.

1: electron gun, EB: electron beam, 2: focusing lens, 3: objective lens, 3A: upper magnetic pole, 3B: lower magnetic pole, 4: gas atmosphere sample storage block, 5: sample chamber, 6: intermediate lens, 7: Projection lens, 8: fluorescent screen, 9: camera, 10: control device, 11: AD converter, 12: display device, 13: input device, 14: goniometer,
15: Goniometer support, Sa: space, 16: exhaust pipe,
17: vacuum pump, 18: sample holder, C: lens barrel, S: sample, 19: sample holder, 20: O-ring, 21: gas atmosphere container,
22: O-ring, 23a, 23b, 23c: exhaust pipe,
24: Exhaust pipe, 25: Vacuum pump, OW: Upper wall, BW: Lower wall, SW: Side wall, O: Electron optical axis, Ha, Hb: Electron beam passage hole, Oa, Ob, Oc, Od: Orifice plate, Da, Db: differential pressure space, 26: gas introduction pipe, 28: gas flow rate adjusting device, 29: gas cylinder,
V1, V2, V3: Open / close valve, N: Nozzle,
G1, G2, G3: pressure gauge, 30: pressure measurement holder,
31, pressure measuring element 33, 35: lead wire,
34: Hermetic seal, 36: Pressure gauge, 38: Pressure measurement holder, 40: Heater, 43a, 43b: Thermocouple, 47: Constant current supply source, 48: Voltmeter, 49: Pressure indicator

Claims (3)

An electron beam passage hole is formed on the electron optical axis, a gas atmosphere container in which gas is supplied from a gas supply system, a sample is held at the tip, and the sample is removed from the vacuum from the gas atmosphere container. a sample observation method in an electron microscope equipped with a sample holder for introducing within, the sample holder prior to introduction into the gas atmosphere in the container, the pressure measurement holder for pressure measurement element are only attached The gas flow rate when the gas supply system is adjusted by the gas supply system so that the pressure in the gas atmosphere container introduced into the gas atmosphere container and the pressure in the gas atmosphere container detected by the pressure measuring element becomes a predetermined pressure. Record the set value, then introduce the sample holder into the gas atmosphere container instead of the pressure measurement holder, and adjust the pressure in the gas atmosphere container based on the recorded gas flow rate set value and, Child beam was irradiated with an electron beam from the generator means to the sample, the sample observation method was as observing a sample image based on the electron beam transmitted through the sample. Stores a pressure value measured by a pressure gauge provided in an exhaust pipe connected to a vacuum pump for exhausting the inside of the gas atmosphere container, and then replaces the pressure measuring holder with the sample holder as the gas atmosphere container. The sample observation method according to claim 1, wherein the observation is performed after the pressure gauge is introduced and the pressure gauge is confirmed to have reached the stored pressure value.   This is a pressure measurement holder that can be inserted into the sample chamber by replacing the sample holder that holds the sample, and when inserted, the pressure sensor is held at the tip so that it is located at approximately the same position as the sample is placed. Holder for pressure measurement.

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