Stage

Abstract

[Problem] To provide a stage capable of being easily energized, and the like. [Solution] This stage comprises: a stage body; a sample platform on which a sample is mounted; a cooling unit; and an electrode unit. The stage is characterized in that the stage body is provided with an attachment mounting device. Moreover, this stage, in a preferred embodiment, is characterized by including an attachment. Furthermore, the stage in the preferred embodiment is characterized in that the attachment is provided with a sample platform mounting device.

Description

Stage

[0001] The present invention relates to a stage, and more particularly to a stage capable of being energized and cooled.

[0002] In recent years, high-resolution analysis in electron microscopes such as transmission electron microscopes (TEMs) and scanning transmission electron microscopes (STEMs) has advanced. For example, high-resolution analysis from the nano-order to the pico-order has been demanded. Recently, "in-situ observation" in which cooling (or heating, electric field application, magnetic field application, rotation, etc.) is performed while observing a sample in an electron microscope has attracted attention. In particular, sample cooling is considered effective for reducing damage to a sample by an electron beam, and sample cooling from this perspective has also been attempted.

[0003] Also, although the magnification of SEM is lower than that of TEM, since there are fewer restrictions on the size of the observation sample, a large sample can be observed, and it is easier to use than TEM, so the difficulty of observation analysis is lower than that of TEM. Therefore, electron microscope manufacturers are developing products that can observe various objects.

[0004] In addition, research on lithium-ion secondary batteries has become active, and an electron microscope observation method combined with sample transportation without exposure to air has attracted attention. Not limited to lithium-ion secondary batteries, SEM observation and FIB processing under cooling have been attempted to reduce the influence of electron beam irradiation damage. There are several cooling methods, and a method of cooling a sample by using liquid nitrogen prepared outside the SEM chamber or gasifying liquid nitrogen outside the chamber and sending cold air to the sample pedestal portion in the SEM chamber is common.

[0005] For example, as an apparatus having a cooling means, a cooling stage for installing a sample from which moisture has been sublimated in a sample chamber of a scanning electron microscope, and a manipulator that extends on this cooling stage and cuts out necessary components of the sample under the observation of the scanning electron microscope are provided. A sample processing apparatus using a scanning electron microscope is known (Patent Document 1).

[0006] Japanese Unexamined Patent Publication No. 62-85840

[0007] Given this need for cooling, conventional technologies, including the aforementioned Patent Document 1, only use the method of attaching the sample to the upper surface of the sample base of the existing cooling stage, and cooling is limited to the lower surface of the sample.

[0008] Furthermore, conventional technology enables sample observation by transferring the sample to an externally cooled SEM stage under vacuum. That is, a method is employed in which a cartridge containing the sample is inserted into the SEM using a rod or similar device. However, because this transfer is done from outside the electron microscope, it is physically impossible to bring electrical wiring and other components into the vacuum. For this reason, many researchers are eagerly awaiting an SEM stage that can observe the sample while simultaneously cooling it and supplying power.

[0009] As mentioned above, given the need for both airtightness and cooling, combining airtightness and cooling within the SEM was relatively easy and feasible until now. However, to add functions such as power supply and voltage application, it was necessary to manufacture a transfer shuttle with a cooling function. At this time, however, a transfer shuttle with a cooling function had the problem of requiring the SEM chamber, which had been evacuated, to be returned to atmospheric pressure, the door to be opened, the shuttle to be set in the SEM goniometer, connections of various power cables and tubes for supplying refrigerant water to be made, the chamber to be closed, and then the chamber to be evacuated again. Furthermore, in addition to being opened to the atmosphere once, bringing cables and tubes into the chamber doubled the vacuuming time, resulting in a significant decrease in work efficiency.

[0010] Therefore, the present invention aims to provide a stage that allows for easy power supply and other operations.

[0011] In order to achieve the above objective, the inventors diligently studied the mechanism of the stage and, as a result, came to discover the present invention.

[0012] In other words, the stage of the present invention is a stage having a stage body, a sample base for mounting a sample, a cooling unit, and an electrode unit, wherein the stage body is equipped with an attachment mounting device.

[0013] Furthermore, a preferred embodiment of the stage of the present invention is characterized by further having an attachment.

[0014] Furthermore, in a preferred embodiment of the stage of the present invention, the attachment is characterized by comprising the sample base mounting device.

[0015] Furthermore, in a preferred embodiment of the stage of the present invention, the sample base mounting device is characterized in that it can be used in conjunction with the electrode section.

[0016] Furthermore, in a preferred embodiment of the stage of the present invention, the sample base is detachable from the stage body via the attachment.

[0017] Furthermore, in a preferred embodiment of the stage of the present invention, it is further characterized by having a sample fixing portion that covers the sample.

[0018] Furthermore, in a preferred embodiment of the stage of the present invention, the electrode portion is characterized by being composed of an electrode electrically insulated from the attachment.

[0019] Furthermore, in a preferred embodiment of the stage of the present invention, the electrode is characterized in that it has a structure that holds the sample in place by an elastic member.

[0020] Furthermore, in a preferred embodiment of the stage of the present invention, the electrode portion is further characterized in that it is composed of an electrode electrically insulated from the sample base.

[0021] Furthermore, in a preferred embodiment of the stage of the present invention, the attachment mounting device is characterized by a screw hole and a clamp.

[0022] Furthermore, a preferred embodiment of the stage of the present invention is characterized by further having a thermoelectric element installed in close proximity to the cooling section.

[0023] Furthermore, in a preferred embodiment of the stage of the present invention, the thermoelectric element is characterized by being a thermoelectric element that utilizes an effect selected from at least one of the Peltier effect or the Thomson effect.

[0024] Furthermore, in a preferred embodiment of the stage of the present invention, the heat dissipation side of the thermoelectric element is in contact with the cooling section.

[0025] Furthermore, in a preferred embodiment of the stage of the present invention, the cooling unit is characterized by comprising at least one of a solid refrigerant, a liquid refrigerant, or a gaseous refrigerant.

[0026] Furthermore, in a preferred embodiment of the stage of the present invention, the sample base and the thermoelectric element are in contact.

[0027] The stage of the present invention offers the advantageous effect of enabling observation of the sample while applying power in a simple manner. Furthermore, according to another embodiment of the stage of the present invention, it offers the advantageous effect of enabling observation of the sample while cooling and / or applying power without exposure to the atmosphere.

[0028] Figure 1 shows a conceptual diagram of a stage in one embodiment of the present invention. Figure 1(a) shows a perspective view of the stage. Figure 1(b) shows a top view of the stage. Figure 1(c) shows a side view of the stage as seen from the side in the longitudinal direction of the resin tube, from the side in which the sample is inserted into the stage body. Figure 1(d) shows a side view of the stage as seen from the side opposite to the side in which the resin tube is installed. Figure 2 shows one embodiment of a thermoelectric element applicable to the present invention. Figure 2(a) shows a cross-sectional view of the Peltier element, and Figure 2(b) shows a schematic diagram of the principle of the Peltier element. Figure 3 shows a perspective view of a stage in one embodiment of the present invention. This figure shows the process of attaching the sample base to the stage body. This figure shows an embodiment having a sample fixing part that covers the sample. In this figure, the sample fixing part that covers the sample at the top of the sample is transparent, allowing the inside to be seen. Figure 4 shows a perspective view of a stage in one embodiment of the present invention. This figure shows the process of attaching the sample base to the stage body. This figure shows an embodiment in which the sample fixing part covers the sample at the top of the sample. Figure 5 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show an embodiment in which only terminals are attached to the sample and there are no electrodes on the sample base. They also show the state just before the sample is attached to the stage body. Figure 5(a) shows a top view of the stage. Figure 5(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 5(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. Figure 6 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show an embodiment in which there are electrodes on the sample base. They also show the state just before the sample is attached to the stage body. Furthermore, for understanding the contents, the electrodes are shown in an exposed state. Figure 6(a) shows a top view of the stage. Figure 6(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 6(c) shows a side view of the stage, seen from the opposite side of the resin tube, in a direction perpendicular to the direction in which the sample is inserted into the stage body. Figure 7 shows a conceptual diagram of the stage in one embodiment of the present invention.These figures show the configuration when the sample base has electrodes. They also show the state immediately before the sample is attached to the stage body. Figure 7(a) shows a top view of the stage. Figure 7(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 7(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. Figure 8 shows a conceptual diagram of the stage in one embodiment of the present invention. These figures show the configuration when the sample base has electrodes. They also show the state in which the sample is attached to the stage body. Figure 8(a) shows a top view of the stage. Figure 8(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 8(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. Figure 9 shows a conceptual diagram of the stage in one embodiment of the present invention. These figures show the configuration when the sample base has electrodes. They also show the state in which the sample is mounted on the stage body. Furthermore, for clarity, they show the state in which the electrodes are exposed. Figure 9(a) shows a top view of the stage. Figure 9(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 9(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. Figure 10 shows a perspective view of the stage in one embodiment of the present invention. Figure 11 shows the state in which the stage in one embodiment of the present invention is set on an electron microscope such as an SEM.

[0029] The present invention provides a stage comprising a stage body, a sample base (part) for mounting a sample, a cooling unit, and an electrode unit, wherein the stage body is equipped with an attachment mounting device. In the present invention, the sample base for mounting a sample is not particularly limited in shape, structure, etc., as long as it is capable of mounting a sample to be observed in an electron microscope. Furthermore, in the present invention, one or more electrode units can be set. In the present invention, it is possible to attach electrode shapes desired by the user. This makes it possible to customize the method of applying electricity as desired by researchers. In a preferred embodiment of the stage of the present invention, the stage further comprises a sample fixing unit that covers the sample. In an embodiment where an attachment is also provided on the upper part of the sample, as described later, the attachment can also be attached via the fixing unit.

[0030] Furthermore, a preferred embodiment of the stage of the present invention is characterized by having an attachment. By using this attachment, it becomes possible to add new functions to the stage, such as a cooling stage.

[0031] Furthermore, in a preferred embodiment of the stage of the present invention, the attachment is characterized by comprising the sample base mounting device. That is, the stage body is equipped with an attachment mounting device, and the attachment can be mounted via the attachment mounting device. Moreover, as will be described later, the attachment can be equipped with a sample base mounting device. In this case, the sample base can be installed via the sample base mounting device.

[0032] Furthermore, in this invention, the sample base (part) can be detached from the attachment and, consequently, from the stage body. This allows for sample transport from the load lock.

[0033] Furthermore, in a preferred embodiment of the stage of the present invention, the sample base mounting device is also capable of being used in conjunction with the electrode section. In addition, in a preferred embodiment of the stage of the present invention, the electrode is characterized in that it has a structure that holds the sample in place with an elastic member. That is, as described above, since the attachment is equipped with a sample base mounting device, it is possible to install the sample base via the sample base mounting device, and at this time, the electrode provided on the attachment can be held in place using an elastic member such as a torsion spring or a leaf spring. The electrode provided on the attachment can also hold (fix) the sample base, and by extension the sample.

[0034] Furthermore, in a preferred embodiment of the stage of the present invention, the electrode portion is characterized by being composed of an electrode electrically insulated from the attachment.

[0035] In this invention, by providing electrodes to the attachment, it is possible to receive signals from the outside while avoiding exposure to the atmosphere, thereby enabling the conduction of electricity.

[0036] Furthermore, in a preferred embodiment of the stage of the present invention, the sample base is detachable from the stage body via the attachment, with the viewpoint of also accommodating sample transport from the load lock.

[0037] The sample transfer from the load lock is described as follows: A small chamber can be optionally attached to the main chamber of the SEM. After evacuating the small chamber, the door to the chamber can be opened to transfer the sample to the main chamber. The vacuum level in the small chamber is not as high as in the main chamber, but it is designed to not significantly affect the vacuum level of the main chamber. The present invention is applicable in such cases as well.

[0038] Furthermore, in a preferred embodiment of the stage of the present invention, the electrode portion is further characterized in that it is composed of an electrode electrically insulated from the sample base. That is, in the present invention, the sample base can be provided with an electrode. In an embodiment in which both the sample base and the attachment have electrodes, when the sample base and the attachment are connected, the electrodes are also connected to each other, making it possible to conduct electricity or apply voltage.

[0039] In this invention, the method of making an electrical connection with the sample is not particularly limited, but two methods can be listed below: 1. A method of directly bringing the electrodes of the attachment into contact with the sample, and 2. A method of indirectly bringing the electrodes of the attachment into contact with the sample.

[0040] In the case described in 1 above, electrically insulated electrodes can be prepared on the attachment, and the electrodes can be structured to press the sample downwards using springs or the like. As the sample and sample stage are inserted from the load lock, the sample stage and sample are inserted in a way that pushes the electrodes upwards, and when the electrodes reach the position of the sample, electrical contact can be formed with the sample.

[0041] In the case of option 2 above, electrodes can also be embedded in the sample stage, leaving both ends of the electrodes open. One electrode on the sample stage can be electrically connected to the sample outside the SEM chamber beforehand, and after insertion from the load lock, the electrode on the attachment side can be connected to the other electrode on the sample stage side.

[0042] Further, in a preferred embodiment of the stage of the present invention, it further has a feed-through portion. In the conventional air non-exposure, the sample is placed on the cartridge and transferred in vacuum from the outside of the electron microscope, so the design is such that a voltage cannot be applied. To allow the flow of electricity, a feed-through, which blocks the vacuum from the wiring, is required. A feed-through can be defined as a vacuum component attached to a vacuum wall that separates the vacuum state from the atmosphere in order to transport and control electrical signals, physical movements, fluids, etc. into the interior of a device that maintains a vacuum state. In the present invention, the field-through portion enables, for example, sample observation while applying a voltage.

[0043] In a preferred embodiment of the stage of the present invention, the sample pedestal may further include an attachment mounting device. That is, in an embodiment including the attachment mounting device of the present invention, it becomes possible to easily attach and remove the attachment, and various attachments can be exchanged. The position where the attachment mounting device is provided may be the position of the above-described electrode, or it may be provided separately from the electrode.

[0044] Further, in a preferred embodiment of the stage of the present invention, it further has a cooling portion. In the present invention, the cooling portion is not particularly limited as long as it can cool the sample observed within the electron microscope, including its shape, structure, etc.

[0045] Although the sample pedestal portion can be cooled by the cooling portion or a Peltier element, since the portions other than the cooling portion are at a higher temperature, when an attachment is connected and fixed to a portion outside the periphery of the cooling portion (outside the cooling system), the attachment will heat up by receiving heat from outside the cooling system. In this case, when the attachment heats up, heat also transfers to the sample, so the sample that has been cooled warms up, resulting in a reduced cooling effect. In an embodiment where the sample pedestal of the present invention includes an attachment mounting device, the attachment exists within the cooling system via the attachment mounting device, and thus it becomes possible to cool the sample while minimizing heat loss.

[0046] Also, in a preferred embodiment of the stage of the present invention, from the viewpoint that the attachment can be firmly and reproducibly fixed, the attachment mounting device is characterized by being a screw hole or a clamp. In the present invention, since the attachment mounting device includes, for example, a screw portion or the like, it is easy to replace the attachment according to the purpose. Double-sided tapes and adhesives are difficult to remove after fixing the attachment and are not assumed to be reused. Also, each time the attachment is replaced, the thermal contact condition between the attachment and the sample pedestal changes, or it is difficult to control the posture of the attachment. In contrast, in the present invention, by attaching the attachment mounting device, the attachment or the like can be reproducibly replaced, so it has the advantage of being able to flexibly respond to various applications.

[0047] Further, the attachment is not particularly limited as long as it can be attached. In a preferred embodiment of the stage of the present invention, the attachment is characterized by being at least one selected from a grid holding attachment for FIB, a sample fixing attachment, and a current-carrying attachment. That is, for the present invention as well, it is possible to remove an attachment (provisional name: load lock attachment) for receiving a load lock-compatible sample stage and attach another attachment. Also, another attachment (second attachment) may be set on the upper part of the sample pedestal without removing it. That is, in the present invention, it is also possible to add a grid holding function for FIB to the sample stage on the load lock attachment.

[0048] Also, in addition to the grid holding attachment for FIB and the upper surface fixing attachment, when observing the sample with the clamping direction horizontal, if cooling is performed from the clamped portion, a temperature gradient can be created from that portion to the free end portion. In the present invention, an attachment capable of imparting such a temperature gradient can also be installed. An attachment having a cold trap function for preventing contamination by arranging a cooling member near the upper surface of the sample is also conceivable.

[0049] Here, when the term "cold trap" is used, it can be understood as a device that cools and captures trace amounts of suspended matter (gases: hydrocarbons, etc.) in a vacuum. In other words, if there is gas in the vacuum, it is expected that it will be struck against the sample when irradiated with an electron beam and accumulate on top of the sample. As in the present invention, when a cooling member is placed near the top surface, it is possible to create a mechanism that surrounds the vicinity of the sample with a cooled metal member (cooling member) in a range that does not obstruct electron beam irradiation, etc., thereby creating a region with a locally high vacuum. This makes it possible to construct a mechanism that cools and condenses the released gas in order to collect it, and consequently makes it possible to prevent gas present in the vacuum within the electron microscope from adhering to the sample.

[0050] Furthermore, when considering applications that involve not only cooling but also simultaneously applying current to the sample, the influence of external temperature can be reduced by fixing electrodes and sample holders using (via) attachment devices such as screw parts, or by fixing and applying current to the sample on an extended platform fixed with an attachment device. Such attachments can also be attached in this invention.

[0051] Furthermore, in a preferred embodiment of the stage of the present invention, the attachment mounting device is characterized by being made of a thermally conductive material. Examples of materials with high thermal conductivity include copper and copper alloys, aluminum and aluminum alloys, silver, and gold. In the present invention, for example, an attachment mounting device, such as screw holes, is integrally arranged on the sample base portion of the stage for cooling a sample in a scanning electron microscope (SEM), making it possible to attach attachments of shapes and forms according to the purpose. As a result, the attachment is also incorporated into the cooling system, reducing the influence of external heat and enabling various cooling methods.

[0052] Furthermore, in a preferred embodiment of the stage of the present invention, the cooling unit is characterized by comprising at least one of a solid refrigerant, a liquid refrigerant, or a gaseous refrigerant. In the cooling unit, the refrigerant can be appropriately set depending on the application and is not particularly limited. From the viewpoint of versatility, a liquid can be mentioned as a preferred medium. If a liquid (such as water) is used, the temperature can be adjusted using a general-purpose device (cooling chiller), but because it is a fluid, it can become a source of vibration. Liquid nitrogen or liquid helium can also be used as the liquid.

[0053] Furthermore, in this invention, the cooling unit may be a solid refrigerant, as it is possible to reduce the effects of vibrations caused by water flow and pulsation to virtually zero compared to water cooling. That is, in this invention, the heat dissipation surface of a Peltier element or the like can be cooled with a solid refrigerant such as dry ice. This makes it possible to reduce the effects of vibrations caused by water flow and pulsation to virtually zero compared to water cooling. In the case of a solid, the difficulty in adjusting the temperature of the cooling unit can be addressed by using a thermoelectric element as described later.

[0054] On the other hand, when the cooling gas is flowed at a minute flow rate, the effect of vibration is minimal, so these methods can also be used in the present invention. Examples of cooling gases include those extracted by gasifying liquid nitrogen. This makes it possible to cool the sample effectively. In the present invention, the cooling gas is not limited to liquid nitrogen. If the gas is simply passed weakly through the heat dissipation surface, the effect of vibration is almost negligible, and it is considered to be practical. Therefore, in the present invention, as described above, even when a solid refrigerant is actually used as the cooling unit, it is sufficient to apply the cold air with a gap rather than pressing it against the heat dissipation surface. Similarly, when using liquid nitrogen gas, observation is possible without being affected by vibration by passing the cooling gas through the heat dissipation surface. The difficulty in adjusting the temperature of the cooling unit can be controlled using a thermoelectric element as described later.

[0055] Furthermore, in a preferred embodiment of the stage of the present invention, it is further characterized by having a thermoelectric element installed in close proximity to the cooling section. In the present invention, the placement position of the thermoelectric element is not particularly limited, as long as it is installed in close proximity to the cooling section. The thermoelectric element makes it possible to efficiently set the temperature required for the sample, i.e., to control the temperature. In the embodiment using a thermoelectric element, the cooling and heating response is good, and the effects of thermal drift can be minimized. Also, because the cooling and heating response is good, precise temperature control is possible. In the embodiment using a thermoelectric element, cooling and heating can be achieved with a single element simply by reversing the direction of current flow, and at the same time, because the cooling and heating response is fast, it is easy to change to a predetermined temperature. Furthermore, precise temperature control is possible by adjusting the output of the input power, so precise temperature control is possible, and the effects of thermal drift can be minimized.

[0056] Furthermore, in a preferred embodiment of the stage of the present invention, the heat dissipation side of the thermoelectric element and the cooling section are in contact. That is, in the present invention, the thermoelectric element only needs to be positioned close to the cooling section. For example, it may be a structure in which the cooling section, such as a solid refrigerant, is pressed against the heat dissipation side (heat dissipation surface side), or a structure in which cold air is applied with a gap. When applying cold air, natural convection or forced convection using a fan may be used, but if forced convection generates vibration, natural convection is preferable, depending on the degree of forced convection. Even in the case of natural convection, since the solid refrigerant has a sufficiently low temperature, there is a large temperature gradient between the heat dissipation surface side and the cold air of the cooling section such as the solid refrigerant, so it is thought that sufficient heat transfer occurs and the heat dissipation surface can be appropriately cooled. It should be noted that heat dissipation by forced convection is more effective than natural convection, and by water cooling is more effective than air cooling.

[0057] Furthermore, in a preferred embodiment of the stage of the present invention, the thermoelectric element is characterized by being a thermoelectric element that utilizes an effect selected from at least one of the Peltier effect or the Thomson effect. The Peltier effect (also called the Peltier effect) is an effect that converts electrical energy into thermal energy, and is a phenomenon in which a temperature difference is generated at both ends when an electric current is passed through two dissimilar metals (or semiconductors) connected at both ends. It is particularly called a Peltier element and is used for cooling precision instruments and wine cellars. The Thomson effect, on the other hand, is an effect that occurs when an electric current is passed through a uniform metal (or dissimilar metals) with a temperature gradient, resulting in the generation of heat other than Joule heat (heat absorption when the current is reversed). Both can generate or absorb heat.

[0058] Furthermore, a heat dissipation member may be installed between the thermoelectric element and the cooling unit, etc., from the viewpoint of efficiently dissipating heat from the thermoelectric element.

[0059] Furthermore, in a preferred embodiment of the stage of the present invention, the thermoelectric element is characterized by being a Peltier element, from the viewpoint of having good cooling and heating response and minimizing the effects of thermal drift. A Peltier element is also called a Peltier element (thermo-module), and this is a general term for elements that utilize the Peltier effect. The structure currently considered to be the most popular and performant is called the "π type," which has the structure shown in Figure 2. By passing an electric current through a PN junction using a P-type semiconductor and an N-type semiconductor, heat can be dissipated between the PN and heat absorbed between the NP.

[0060] The principle is as follows. Figure 2 shows one embodiment of a thermoelectric element applicable to the present invention. Figure 2(a) shows a cross-sectional view of a Peltier element, and Figure 2(b) shows a schematic diagram of the principle of the Peltier element. In Figure 2(a), 21 is the hot side metal (mainly Cu), 22 is the ceramic substrate (mainly alumina), 23 is the heat dissipation surface, 24 is the N-type semiconductor, 25 is the P-type semiconductor, 26 is the wire, 27 is the power supply, 28 is the heat absorption, 29 is the conduction band of the N-type semiconductor, 30 is the heat dissipation, 31 is the positive side, 32 is the heat absorption side, 33 is the valence band, 34 is the heat dissipation side, 35 is the negative side, 36 is the cold side metal (mainly Cu), 37 is the cold side metal (mainly Cu), 38 is the electron, 39 is the hole, and 40 is the conduction band of the P-type semiconductor.

[0061] In Figure 2(a), the negative electrode is connected to the metal 36 on the N-type semiconductor 24 side. Therefore, the voltage pushes electrons from the conduction band of the metal 36 to the conduction band 29 of the N-type semiconductor 24. At this time, because there is an energy gap between the conduction band of the metal 36 and the conduction band 29 of the N-type semiconductor 24, the electrons absorb thermal energy from the metal 36, thereby cooling it. Subsequently, the electrons flow and fall from the conduction band 29 of the N-type semiconductor 24 to the conduction band of the metal 21. Due to the energy gap between the two bands, the electrons release thermal energy. In this way, the hot-side metal 21 is heated. Furthermore, the flowing electrons fall from the conduction band of the metal 21 into holes 39 that have flowed through the P-type semiconductor 25, releasing thermal energy and heating the hot-side metal 21. In the P-type semiconductor 25, holes 39 are produced by the voltage and flow from the cold side 37 to the hot side 21. The electrons generated at that time are pushed up to the conduction band of the metal on the cold side by the voltage, and absorb thermal energy corresponding to the energy gap, cooling the metal 37 on the cold side. In this way, heat is carried from the cold side to the hot side of the Peltier module by the flow of current. In addition to the thermal energy carried by the current, there is also thermal energy carried by heat conduction, but since the direction of heat conduction is reversed, the less thermal energy carried by heat conduction there is, the better the performance of the Peltier module will be. In other words, removing the thermal energy from the hot side as quickly as possible with a heat sink or the like will allow the Peltier module to perform well. Simply put, electrons carry (or remove) heat.

[0062] While there are no particular limitations on semiconductor materials, and any of them can be applied, Bi-Te semiconductors are considered to have the best performance and are therefore the mainstream.

[0063] The performance of a Peltier cooler can generally be considered in terms of how much temperature difference ΔT can be created relative to the temperature Th of the heat-dissipating side, when the temperature of the heat-dissipating side is kept constant. For example, for Th = 75, 50, 25 (°C), ΔT = 93, 85, 75. If the heat-dissipating surface is simply cooled to, for example, the temperature of liquid nitrogen (-196°C), the heat-absorbing surface is thought to exceed minus 200 degrees Celsius. However, in reality, due to the properties of the material, ΔT is assumed to be around 10°C near liquid nitrogen. This is thought to be because the lower the temperature, the less heat is available to excite electrons, thus reducing the Peltier cooling capacity. Also, at lower temperatures, the electrical resistance of the semiconductor part increases, resulting in self-heating due to the current, which reduces the overall cooling capacity.

[0064] Furthermore, in a preferred embodiment of the present invention, the heat-dissipating side of the thermoelectric element is cooled, which allows for setting a lower temperature. The heat-dissipating side of the thermoelectric element is in contact with the cooling section. In the following embodiments, the case of cooling is mainly described, but in the present invention, heating is also possible using the thermoelectric element. During heating, the lower surface of the thermoelectric element cools down, so it is necessary to heat the cooling section before use (to process at a higher temperature than the lower surface). In this case, the cooling section can function as a heating section rather than a cooling section.

[0065] In the case of heating, the phenomenon is simply the reverse of that in the case of cooling, but the practicality also changes depending on the shape of the thermoelectric element (whether it is multi-stage or not), such as a Peltier element. Basically, when aiming for the lowest possible temperature, a multi-stage thermoelectric element, such as a Peltier element, can be used. In this case, a pyramidal structure can be made in which the area of ​​the heat-absorbing surface (upper stage) is small and the area increases towards the heat-dissipating surface. The reason for this structure is that, basically, a larger area absorbs more heat, so the heat absorbed by the small area upper stage is dissipated by the larger area lower stage element. When using it for heating by reversing the polarity of the current, it is not simple, and there is a tendency for heat from the larger area lower stage to flow rapidly into the small area upper stage. If the upper stage cannot absorb that heat, the heat accumulates in the middle stage and tends to become hotter than the upper stage. For this reason, even when using Peltier elements for heating, the temperature is thought to be around +100°C (the temperature at which the solder at the junction does not deteriorate). Peltier elements create heat-absorbing and heat-dissipating surfaces through electron movement, and by controlling the amount of current flowing through the Peltier element, it is theoretically possible to precisely control the temperature from near room temperature to below freezing. These effects enable stable, high-resolution observation.

[0066] Furthermore, in a preferred embodiment of the stage of the present invention, the sample base and the thermoelectric element are in contact, from the viewpoint of cooling the sample base portion and beyond.

[0067] The following describes a stage in one embodiment of the present invention with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, it goes without saying that the present invention can be modified as appropriate without departing from its spirit.

[0068] Figure 1 shows a conceptual diagram of a stage in one embodiment of the present invention. Figure 1(a) shows a perspective view of the stage. Figure 1(b) shows a top view of the stage. Figure 1(c) shows a side view of the stage as seen from the side in the longitudinal direction of the resin tube, from the side in which the sample is inserted into the stage body. Figure 1(d) shows a side view of the stage as seen from the side opposite to the side in which the resin tube is installed. In Figure 1, 1 is the sample base (sample base section, sample stage, or transfer cartridge) (with a cooling section (if present) below), 2 is the attachment, 3 is the attachment mounting device, 4 is the stage body, 5 is the sample (MEMS chip), 6 is the terminal, 7 is the electrode and electrical insulating member, 8 is the resin tube, 9 is the torsion spring, and 10 is the cooling section. The resin tube 8 can be used as a flow path for a refrigerant to cool the heat dissipation on the heat dissipation side of the Peltier element. The torsion spring 9 can also be used to hold (fix) the electrode in place. Additionally, attachment 2 allows the sample base to be received from the load lock.

[0069] Referring to the figures, the roles of each component and the connections between them in the sample base of the stage in one embodiment of the present invention will be explained as follows. First, there is the stage body, which in Figure 1 has a cooling section 5. However, in the case of heating as described above, the lower surface of the thermoelectric element cools down during heating, so it is necessary to heat the cooling section before use (to process at a temperature higher than the lower surface). In this case, it can be used as a heating section instead of a cooling section. Although not shown, a thermoelectric element is also used in this example (the thermoelectric element can be installed between the sample base and the cooling section). In embodiments that do not use a thermoelectric element, the thermoelectric element can be omitted. In this example, a thermoelectric element is used, so although not shown, a heat dissipation member may be provided between the cooling section and the thermoelectric element as needed. Also, in this example, the attachment mounting device 3 is specifically a screw hole, but as mentioned above, it may be a clamp or the like, and is not particularly limited as long as the attachment can be attached and detached. The attachment mounting device 3 is preferably made of a thermally conductive material. This makes it possible to further reduce heat loss.

[0070] Furthermore, the Peltier element and the sample base can be positioned directly above or with a lateral offset, as long as they are in thermal contact. The attachment mounting holes or electrodes may be integrated with the sample base, and the mounting holes or electrodes may be machined as a single piece, or the screw holes may be manufactured separately and then press-fitted or bonded later.

[0071] Furthermore, using Peltier cooling enables an overwhelmingly high throughput. Cooling with liquid nitrogen requires a significant amount of time before and after observation: one hour to cool the temperature, another hour for the temperature to stabilize, and another hour to return to room temperature after observation. However, Peltier cooling simply involves passing an electric current, allowing for extremely responsive cooling: -100 degrees Celsius in 3 minutes and room temperature in 1 minute, dramatically increasing the speed of research. The reason why liquid nitrogen was used conventionally is that conventional Peltier cooling stages could only cool down to -50 degrees Celsius. At -50 degrees Celsius, it is not possible to reduce damage from electron beams or focused ion beams, and cooling to -80 to -100 degrees Celsius is necessary. Therefore, even if one wanted to use Peltier cooling, the only option was to use the liquid nitrogen type. However, surprisingly, this invention makes it possible to achieve -100 degrees Celsius with the Peltier cooling method.

[0072] Although not shown in the diagram, a FIB grid may also be installed as an attachment. In this case, the FIB grid holder attachment can be attached to the FIB grid holder base using copper screws or the like. It is also possible to fix the FIB sample holder base to the sample base as a cooling attachment. The FIB mesh can be clamped so that it stands vertically in the center of the FIB grid's divisions. This reduces damage from electron beams and ion beams through the cooling effect. If the base is made a little larger, it is also possible to clamp and observe regular samples. A structure that allows the sample to be clamped horizontally may also be used.

[0073] Furthermore, although not shown in the diagram, it is also possible to fix the sample from above as a second attachment. The top surface of the observation sample can be fixed by the sample fixing attachment installed at the top. If the sample is fixed from above as an attachment, and if the attachment is made of a material with thermal conductivity, it is possible to cool the sample from above as well. In this invention, since attachments can be changed with good reproducibility by attaching an attachment mounting device, it has the advantage of being able to flexibly respond to various applications.

[0074] Next, Figure 3 shows a perspective view of a stage in one embodiment of the present invention. This figure shows the process of attaching the sample base to the main body of the stage. This figure shows an embodiment having a sample fixing part that covers the sample. In this figure, the sample fixing part that covers the sample at the top of the sample is transparent, allowing the inside to be seen.

[0075] Figure 4 shows a perspective view of a stage in one embodiment of the present invention. This figure shows the process of attaching the sample base to the main body of the stage. This figure shows an embodiment in which the stage has a sample fixing part that covers the sample at the top of the sample.

[0076] Next, Figure 5 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show an embodiment in which only terminals are attached to the sample and there are no electrodes on the sample base. They also show the state immediately before the sample is attached to the stage body. Figure 5(a) shows a top view of the stage. Figure 5(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 5(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. In Figure 5, 1 is the sample base (sample base section, sample stage, or transfer cartridge) (the bottom is the cooling section (if present)), 3 is the attachment mounting device, 4 is the stage body, 5 is the sample, 6 is the terminals, 7 is the electrodes and electrical insulating members, 8 is the resin tube, 10 is the cooling section, and 50 is the transfer rod.

[0077] An attachment 2 for receiving the sample base 1 is attached to the stage, and electrodes are connected to the attachment via a cable 63, insulated from other components. Two methods for making an electrical connection with the sample can be given, for example: 1) a method of directly contacting the electrodes of the attachment with the sample, and 2) a method of indirectly contacting the electrodes of the attachment with the sample.

[0078] Figure 5 shows an example of the embodiment described in 1) above. In the case of 1), electrically insulated electrodes are prepared on the attachment, and the electrodes are structured to press the sample downwards with a spring or the like. As the sample and sample stage are inserted from the load lock, the sample stage and sample are inserted in such a way that they push the electrodes upwards, and when the electrodes reach the position of the sample, electrical contact can be formed with the sample.

[0079] The sample base (transfer cartridge) can be docked to the chamber inside the SEM from the outside using the transfer rod 50.

[0080] Next, Figure 6 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show the configuration when the sample base has electrodes. They also show the state immediately before the sample is attached to the stage body. Furthermore, for clarity, the exposed state of the electrodes is shown. Figure 6(a) shows a top view of the stage. Figure 6(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 6(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. In Figure 6, 1 is the sample base (sample base section, sample stage, or transfer cartridge) (the bottom is the cooling section (if present)), 5 is the sample, 50 is the transfer rod, 60 is the electrode on the sample base side, 61 is the electrode on the attachment side, 62 is the sample seating surface, 63 is the cable, and 64 is the leaf spring.

[0081] Figure 6 shows an example of the embodiment of 2) above. That is, 2) is a method of indirectly bringing the sample and the electrodes of the attachment into contact as a method of making an electrical connection with the sample. In the case of 2) above, electrodes are also embedded on the sample stage side, and both ends of the electrodes are left open. One electrode of the sample stage and the sample are electrically connected in advance outside the SEM chamber, and after insertion from the load lock, the electrode on the attachment side and the other electrode on the sample stage side can be connected. The present invention can accommodate sample replacement from the load lock, and this point will be explained as follows. Normally, sample replacement from the load lock involves an extra step. The sample is first placed in a capsule in a glove box or similar and transported to the load lock. The capsule can be in either a vacuum or an inert gas atmosphere. After the load lock is evacuated, the capsule is released. Then, the sample is transported into the chamber using a transfer rod. As the name suggests, the transfer rod is rod-shaped and often has a threaded tip. A rod is screwed into the sample stage to secure it, and after transport, the screw is loosened and the rod is pulled out, leaving the sample and sample stage in the desired position. With this method, vacuum transfer or inert gas transfer is possible even without a shutter.

[0082] Although not shown in the figures, a feedthrough section may be provided in any of the embodiments. The position of the feedthrough section is not particularly limited.

[0083] Next, Figure 7 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show the configuration when the sample base has electrodes. They also show the state immediately before the sample is attached to the stage body. Figure 7(a) shows a top view of the stage. Figure 7(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 7(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. In Figure 7, 70 indicates a connector (with electrodes on the back). For other parts, refer to the examples described above.

[0084] Figure 6 shows the circuit and other components for easier understanding, while Figure 7 shows the circuit and other components covered by a cover, connectors, etc.

[0085] The sample stage has electrodes embedded in it, and the electrodes on the sample stage and the sample (MEMS chip) are pre-connected. When the sample stage is inserted into the attachment, power can be supplied.

[0086] Next, Figure 8 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show the case where the sample base has electrodes. They also show the state in which the sample is mounted on the stage body. Figure 8(a) shows a top view of the stage. Figure 8(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 8(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body.

[0087] Next, Figure 9 shows a conceptual diagram of a stage in one embodiment of the present invention. These figures show the case where the sample base has electrodes. They also show the state in which the sample is mounted on the stage body. Furthermore, for clarity, they show the state in which the electrodes are exposed. Figure 9(a) shows a top view of the stage. Figure 9(b) shows a side view of the stage as seen from the electrode side of the attachment in the direction in which the sample is inserted into the stage body. Figure 9(c) shows a side view of the stage as seen from the opposite side of the resin tube in a direction perpendicular to the direction in which the sample is inserted into the stage body. Figure 10 shows a perspective view of a stage in one embodiment of the present invention.

[0088] Next, Figure 11 shows the stage in one embodiment of the present invention set on an electron microscope such as an SEM. In Figure 11, 1 is the sample base (transfer cartridge), 2 is the attachment, 4 is the stage, 50 is the transfer rod, 100 is the transfer chamber, 101 is the SEM (scanning electron microscope), and 102 is the FIB (focused ion beam). For example, taking the embodiment of 2) above as an example, by using an attachment with electrodes, electrodes are pre-installed on the (cooled) stage body and docked to the sample base (cartridge), and electrodes are also installed on the cartridge side, making it possible to supply electricity to the sample. Alternatively, electrodes can be attached to the sample base (cartridge) to supply current to the sample. The Peltier attachment also has electrodes, and by connecting them, it is possible to receive signals from the outside while avoiding exposure to the atmosphere, and to supply current.

[0089] Furthermore, the sample base can be docked to the chamber located within the SEM using the transfer rod 50. Conventionally, it was considered impossible to apply power in this state, but surprisingly, it has been found that the present invention makes it possible to achieve airtightness while also enabling cooling and power application.

[0090] As described above, the present invention has been shown to enable a powered and cooled stage for sample exchange from a loading lock for a scanning electron microscope. In other words, the present invention makes it possible to perform scanning electron microscope observation while power is supplied to a (Peltier cooled) stage that is compatible with sample exchange from a loading lock of a FIB-SEM. This is achieved by combining an attachment that enables sample exchange from the stage and the loading lock, and electrodes for power supply. A sample stage that enables sample exchange to the stage via the loading lock and an attachment component that receives and fixes the sample stage are prepared. Power can be supplied by pressing down on the sample from above with a plate with electrodes prepared on the attachment side, or by connecting electrodes prepared on the shuttle side to the sample in advance and then connecting the sample stage to the attachment to enable power supply. In addition, non-exposure transfer shuttles for performing observation without exposure to air via the loading lock are sold by microscope manufacturers and third parties. By combining these, it is possible to transport the sample into the FIB-SEM chamber without exposing it to the air, and then perform FIB processing and SEM observation while cooling, as well as observation while power is supplied.

[0091] Furthermore, in the present invention, the cooling method may be liquid nitrogen cooling or nitrogen gas cooling, or a cooling method using Peltier cooling or other refrigerants, but Peltier cooling is preferred.

[0092] The reasons why Peltier cooling is preferable are as follows: When processing a sample using FIB in a FIB-SEM, there is a process to form a protective film by gasifying compounds such as carbon or tungsten and bombarding them onto the sample surface with an ion beam or electron beam (called carbon deposit or tungsten deposit; "deposit" means deposition) to protect the surface of the processed area from ion beams, etc. At this time, if the sample surface is cooled, the cold trap effect will be strong before the gas is bombarded by the beam, resulting not only in the formation of a protective film in the intended location but also in the formation of an uneven protective film across the entire sample surface. Similarly, when preparing a TEM sample using FIB, the probe is brought as close as possible to the sample, and the probe and the cut sample are joined using carbon deposit, etc. After separation, the TEM sample is prepared by joining them again to a microgrid with deposit. At this time as well, if the cooling effect is strong, it will not be possible to join them in the intended location and the entire sample will be contaminated.

[0093] The advantages of using Peltier cooling for these phenomena are: 1. By adjusting the amount of current supplied to the element, the temperature can be raised or lowered much faster than with other methods. Also, after changing the temperature, the temperature can be controlled by the current, so temperature stabilization is quick, and the effects of temperature drift can be minimized in a short time. 2. In the case of Peltier cooling, the heat dissipation side of the Peltier needs to be treated with a coolant for heat dissipation, but it is possible to use a flexible resin tube, which has the advantage of allowing the SEM gonioscope stage to move relatively freely. In the case of liquid nitrogen cooling, the resin tube hardens and cannot be moved due to the extremely low temperature. Similarly, if metal piping (bellows) is used, it does not have the same flexibility as a resin tube. In the case of liquid nitrogen cooling, it is necessary to combine it with another mechanism to enable flexible gonioscope stage movement, which has many limitations. 3. In the case of Peltier cooling, installation and removal are relatively easy compared to liquid nitrogen cooling systems, so it is also an advantage that it can be easily removed from the chamber when the cooling function is not being used, which leads to an improvement in productivity.

[0094] In-situ observation is possible even under conditions of electrical current and cooling, without exposure to the atmosphere, and it is applicable in a wide range of technical fields.

[0095] 1 Sample base (sample base section, sample stage, or transfer cartridge) (below is the cooling section (if present)) 2 Attachment 3 Attachment mounting device 4 Stage body 5 Sample 6 Terminals 7 Electrodes and electrical insulating material 8 Resin tube 9 Torsion spring 10 Cooling section 21 Hot side metal (mainly Cu) 22 Ceramic substrate (mainly alumina) 23 Heat dissipation surface 24 N-type semiconductor 25 P-type semiconductor 26 Electric wire 27 Power supply 28 Heat absorption 29 Conduction band of N-type semiconductor 30 Heat dissipation 31 Positive side 32 Heat absorption side 33 Valence band 34 Heat dissipation side 35 Negative side 36 Cold side metal (mainly Cu) 37 Cold side metal (mainly Cu) 38 Electron 39 Hole 40 Conduction band of P-type semiconductor 50 Transfer rod 60 Electrode on the sample base side 61 Electrode on the attachment side 62 Sample seating surface 63 Cable 64 Leaf spring 70 Connector (with electrodes on the back) 100 Transfer chamber 101 SEM 102 FIB

Claims

1. A stage comprising a stage body, a sample base for mounting a sample, a cooling unit, and an electrode unit, wherein the stage body is equipped with an attachment mounting device.

2. The stage according to claim 1, further characterized by having an attachment.

3. The stage according to claim 2, characterized in that the attachment is provided with the sample base mounting device.

4. The stage according to claim 3, characterized in that the sample base mounting device can be used in conjunction with the electrode section.

5. The stage according to claim 1 or 2, characterized in that the sample base is detachable from the stage body via the attachment.

6. The stage according to claim 1, further characterized by having a sample fixing portion that covers the sample.

7. The stage according to claim 1 or 2, wherein the electrode portion is composed of an electrode electrically insulated from the attachment.

8. The stage according to claim 7, characterized in that the electrode has a structure that holds the sample in place by an elastic member.

9. Furthermore, the stage according to claim 1, characterized in that the electrode portion is composed of an electrode electrically insulated from the sample base.

10. The stage according to claim 1, characterized in that the attachment mounting device is a screw hole or a clamp.

11. The stage according to claim 1, further characterized by having a thermoelectric element installed in close proximity to the cooling section.

12. The stage according to claim 11, characterized in that the thermoelectric element is a thermoelectric element that utilizes an effect selected from at least one of the Peltier effect or the Thomson effect.

13. The stage according to claim 11, characterized in that the heat dissipation side of the thermoelectric element and the cooling section are in contact.

14. The stage according to claim 1, characterized in that the cooling unit consists of at least one of a solid refrigerant, a liquid refrigerant, or a gaseous refrigerant.

15. The stage according to claim 11, characterized in that the sample base and the thermoelectric element are in contact.

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