CN108728800B - Multifunctional processing device used in vacuum environment - Google Patents

Abstract

The present invention relates to a multifunctional processing device for use in a vacuum environment. According to an embodiment, a multi-function processing device may include: a metal platform comprising a cylindrical sidewall and a platform layer covering one end of the cylindrical sidewall, the platform layer having an opening at a central portion for receiving a sample holder, the metal platform having a first electrode thereon for applying a voltage to the metal platform; the insulating cylinder is arranged on the lower side of the metal platform; the water cooling cylinder is arranged at the lower side of the insulating cylinder and physically connects the metal platform and the water cooling cylinder together in an insulating way; and a filament disposed in a cylindrical space defined by the metal platform, the insulating cylinder, and the water-cooling cylinder and facing the opening, both ends of the filament being connected to two screw electrodes, respectively, the two screw electrodes being mounted on an insulating plate fixed to a lower side of the water-cooling cylinder.

Description

Multifunctional processing device used in vacuum environment

Technical Field

The present invention relates generally to the field of sample processing and, more particularly, to a multi-functional processing device for use in a vacuum environment that can be used to perform various types of thermal processes on various different samples and even to deposit low evaporation temperature materials. The multifunctional treatment device has the advantages of simple operation, easy replacement and the like.

Background

In a vacuum environment, in order to realize the heating treatment of a sample, a target material and other vacuum components, methods such as thermal radiation heating, electron beam bombardment heating, direct current heating and the like are mainly adopted. Thermal radiant heating relies primarily on radiation to transfer heat to the components to be heated. For example, tungsten wire generates a large amount of heat when an electric current is passed through it, and this heat is transferred to a low-temperature component in a radiation manner, thereby achieving a heating process for the component. For electron beam bombardment heating, positive high voltage is required to be added to a part to be heated, and appropriate current is introduced into the tungsten filament, so that the tungsten filament generates heat to radiate electron beams outwards, and the electron beams bombard the part with the positive high voltage under the action of an electric field and transfer energy to the part, thereby realizing the function of electron beam bombardment heating. For the mode of directly heating the current, the current directly flows through the semiconductor sample, and because the resistance of the semiconductor sample is relatively large, a large amount of heat can be generated when the current passes through the semiconductor sample, so that the temperature of the semiconductor sample is increased, and the aim of directly heating the semiconductor material by the current is fulfilled.

The method plays an important role in the heat treatment of the sample, the target material and the corresponding vacuum part in a vacuum environment. The substrate with the grown material is first heat treated, so that not only the impurities on the surface can be removed to obtain a clean substrate surface, but also the atoms on the surface can obtain enough kinetic energy to be reconstructed to form a new surface structure. Secondly, during the material deposition process, resistive or electron beam bombardment evaporation sources are often used to heat the target materials to the respective temperatures so that they can be deposited on the respective substrates. Meanwhile, during or after the material deposition process, the substrate is subjected to heat treatment, so that samples on the surface of the substrate can obtain enough kinetic energy, and the samples can form a stable structure by means of self interaction. In addition, in vacuum systems, there may be other components that require heat treatment. For example, a needle tip in an ultrahigh vacuum scanning tunneling microscope system needs to be heated before use, so that the needle tip can have a stable and good state and clear and reliable data can be obtained.

However, there is no processing apparatus capable of implementing the above-described various processing methods. In addition, when implementing various processes in a vacuum environment, not only needs for various functions need to be satisfied, but also many other problems need to be considered, such as compact structure, cooling water circulation, current conduction, high-voltage safe transmission, avoidance of short circuit, temperature monitoring, and the like. These problems present difficulties in the design and implementation of a multi-purpose processing device for use in a vacuum environment.

Disclosure of Invention

In view of the above, the present invention provides a multi-functional processing unit under vacuum environment. It has the advantages of simple structure, complete functions and small volume. Firstly, the processing unit can be compatible with a universal flat-plate type sample rack in a laboratory and can well meet the requirements of the laboratory. Secondly, a large amount of space is saved for the system due to the simple structure and compact design of the processing unit, which is convenient to install in a narrow space.

According to an exemplary embodiment, a multi-function processing device may include: a metal platform comprising a cylindrical sidewall and a platform layer covering one end of the cylindrical sidewall, the platform layer having an opening at a central portion for receiving a sample holder, the metal platform having a first electrode thereon for applying a voltage to the metal platform; the insulating cylinder is arranged on the lower side of the metal platform; the water cooling cylinder is arranged at the lower side of the insulating cylinder and physically connects the metal platform and the water cooling cylinder together in an insulating way; and a filament disposed in a cylindrical space defined by the metal platform, the insulating cylinder, and the water-cooling cylinder and facing the opening, both ends of the filament being connected to two screw electrodes, respectively, the two screw electrodes being mounted on an insulating plate fixed to a lower side of the water-cooling cylinder.

In some examples, the platform layer has a recess around the opening for receiving a sample holder.

In some examples, a portion of the platform layer and the cylindrical side wall adjacent thereto are cut away to expose one side of the opening, and the platform layer has a slot (18) formed in a portion at an edge of the opening so that a sample holder can be inserted into the opening within the slot.

In some examples, the metal platform further comprises: a metal dome mounted on the metal platform and electrically insulated from the metal platform; and a second electrode disposed on the metal elastic sheet so as to enable direct current heating of a sample by the first electrode and the second electrode.

In some examples, the filament is used for thermal radiation heating of the sample. The first electrode is used for applying a preset positive voltage to the metal platform, so that electrons emitted by the filament are accelerated towards the metal platform, and electron beam bombardment heating is realized.

In some examples, the multi-function processing apparatus further comprises: a sample holder having a plate-like body portion for mounting into an opening of the metal platform.

In some examples, the sample holder is a semiconductor sample holder comprising a first support portion for supporting one end of a semiconductor sample on the body portion and a second support portion for supporting the other end of the semiconductor sample on the body portion, the first support portion also electrically connecting one end of the semiconductor sample to the body portion, the second support portion being in physical contact with but electrically insulated from the body portion, and the second support portion electrically connecting the other end of the semiconductor sample to the metal dome.

In some examples, the sample holder is a crucible sample holder used as an evaporation source, and includes a cylindrical crucible body formed integrally with or mounted on the body portion and a crucible cover covering the crucible body, the crucible cover having a through hole therein.

In some examples, the crucible cover has a cylindrical shape, and mating threads are formed on an inner wall of the crucible cover and an outer wall of the crucible body for securing the crucible cover to the crucible body.

In some examples, the multi-function processing apparatus further comprises: a third electrode disposed on the metal platform for performing temperature monitoring by a thermocouple.

The multifunctional processing device can be used for heating common samples (metal, semiconductor and insulator) in a heat radiation type and an electron beam bombardment type, can be used for additionally heating semiconductor samples in a direct current manner, can also be used for carrying out heat treatment on special parts in a vacuum environment, such as a needle point in a scanning tunnel microscope system, and can even be used for depositing materials with low evaporation temperature, including organic molecules, low-temperature metal, semiconductor and other solid materials.

Drawings

FIG. 1 is a schematic diagram of a multi-function processing apparatus that can be used in a vacuum environment, according to one embodiment of the present invention;

FIG. 2 is a partial cross-sectional view of the multi-purpose processing device of FIG. 1;

FIG. 3A is a schematic view of a conventional sample being heated by thermal radiation and electron beam bombardment with the multi-function processing apparatus of FIG. 1;

FIG. 3B is a schematic view of a generic sample holder;

FIG. 4A is a schematic illustration of the direct current heating of a semiconductor sample with the multi-function processing device of FIG. 1;

FIG. 4B is a schematic view of a semiconductor sample holder;

FIG. 5A is a schematic view of a heat treatment of a needle tip with the multi-function treatment apparatus of FIG. 1;

FIG. 5B is a schematic view of a tip sample holder;

FIG. 6A is a schematic view when the multi-functional processing apparatus of FIG. 1 is used as an evaporation source;

FIG. 6B is a schematic view of the structure of the crucible holder;

FIG. 6C is a partial cross-sectional view of the crucible holder;

fig. 7 is a schematic view of material deposition using the multi-functional processing apparatus of fig. 1 in cooperation with an evaporation source while heating a sample.

Detailed Description

Exemplary embodiments of the present invention are described below with reference to the accompanying drawings.

Fig. 1 illustrates a schematic structural view of a multi-functional processing apparatus 100 that can be used in a vacuum environment according to an embodiment of the present invention, and fig. 2 illustrates a partial sectional view of the multi-functional processing apparatus 100 of fig. 1. As shown in fig. 1 and 2, the multifunctional processing apparatus 100 may include a metal stage 10, an insulating cylinder 30, and a water-cooled cylinder 50.

The metal platen 10 may include a cylindrical sidewall 12 and a platen layer 14 covering one end of the cylindrical sidewall 12, which may have an integral structure or may be assembled from separate elements. The central portion of the platform layer 14 may have an opening 16, such as a rectangular or square opening, to expose the interior of the cylinder 12. A portion of the terrace layer 14 and the cylindrical side wall 12 adjacent thereto are cut away, and the cut-out communicates with the opening 16 so that one side of the opening 16 is exposed. In other words, the opening 16 is an open, rather than a closed, opening. Slots 18 may be formed in the platform layer 14 at the edges of the opening 16 so that sample holders (described in detail later) may be inserted into the opening 16 from the open side of the opening 16. The slit may also facilitate evacuation of gas from the cylinder, thus facilitating use of the device 100 in a vacuum environment.

It should be understood that the sample holder may be placed onto the platform layer 14 in other ways as well. For example, the platform layer 14 around the opening 16 has a recess in which a sample holder can be placed. In this embodiment, the opening 16 may be closed without exposing one side of the opening 16 by cutting.

The metal stage 10 may be formed of a material resistant to high temperature and having excellent conductivity, such as molybdenum, tungsten, and the like. Molybdenum is described below as an example, but it should be understood that the components described herein as molybdenum may be replaced by other materials that are resistant to high temperatures and have excellent electrical conductivity, such as tungsten and the like.

With continued reference to fig. 1, one or more electrodes, such as a high voltage electrode 20, a temperature sensing electrode 22, etc., may be disposed on the platform layer 14 of the metal platform 10. The high voltage electrode 20 may be used to apply a high voltage to the metal platform 10, which will be described in further detail below. The thermometric electrode 22 may be used to effect a thermocouple temperature measurement. A metal dome 24 may also be provided above the platform layer 14, which may be used to electrically connect to the samples on the sample holders. The metal dome 24 is mounted to the mesa layer 14 by an insulating ceramic tube 26 and electrically insulated from the mesa layer 14. The heating electrode 28 is disposed on the metal dome 24.

The insulation cylinder 30 is disposed at the lower side of the metal platform 10 and insulates and connects the metal platform 10 to the water cooling cylinder 50. As shown in the cross-sectional view of fig. 2, a portion of the side wall 12 of the metal platform 10 may extend to the inside of the insulation tube 30 so that the two may be tightly joined together. Similarly, a portion of the inner wall of the water-cooled cylinder 50 may extend to the inside of the insulation cylinder 30 so that the two can be tightly joined together. The outer side walls of the metal platform 10, the insulating cylinder 30 and the water cooling cylinder 50 may be flush to achieve an aesthetically pleasing, compact structure.

The water-cooling cartridge 50, which may be formed of a metallic material having good thermal conductivity such as stainless steel, includes a water circulation passage 52 having a ring shape, and the water circulation passage 52 is connected to a water inlet pipe 54 and a water outlet pipe 56, thereby achieving water circulation. The circulating water may cool the processing device 100 to control the temperature of the sample in conjunction with the heating element.

As shown in fig. 2, the treatment apparatus 100 further includes a filament 60, which may be, for example, a spiral tungsten filament, disposed in the cylindrical space formed by the metal stage 10, the insulating cylinder 30, and the water cooling cylinder 50. The filament 60 may be substantially opposite the opening 16 and connected to screw electrodes 62 and 64 so that power may be applied to the filament 60. The screw electrodes 62 and 64 may be secured to an insulator plate 66. An insulating plate such as a ceramic plate 66 may be fixed to the lower side of the water-cooled cylinder 50.

Having described an exemplary structure of the multifunction processing device 100, use of the processing device 100 will be described below in conjunction with various sample holders.

Fig. 3A is a schematic view of a general sample being heated by thermal radiation type heating and electron beam bombardment type heating using the multi-function processing apparatus 100 of fig. 1, and fig. 3B is a schematic view of a general sample holder 110.

As shown in fig. 3A and 3B, the sample holder 110 may be inserted into the opening 16 of the multi-function processing device 100. In the example shown in fig. 3B, the general sample holder 110 includes a molybdenum sheet a for fixing a sample, a sample B, and a sample holder body c. The sample holder body c may also be formed of molybdenum, generally in the form of a flat plate, and in order to be able to be inserted into the slot 18 of the metal platform 10, the widest part of the molybdenum sample holder c is smaller than the width of the slot 18, but larger than the width of the opening 16. Preferably, in order to facilitate the insertion and removal of the molybdenum sample holder a, a protruding handle may be further provided at one end of the molybdenum sample holder a not entering the slot 18; of course, the handle may also be omitted for simplicity. A group of molybdenum sheets a can be arranged in the middle of the plane of the sample holder body c, and the group of molybdenum sheets a are spaced at a certain distance and are respectively symmetrically provided with clamping grooves for fixing the sample b.

As shown in fig. 3A, a general sample holder 110 is inserted into the insertion slot 18 of the metal platform 10, wherein a molybdenum sample holder c is in contact with the insertion slot 18, and a sample b is supported by the molybdenum sample holder c above the filament 60. During the process, current is applied to the screw electrodes 62 and 64 to heat the filament 60, so that the heat radiation heating can be performed on the stack sample b. In addition, a positive high voltage is applied to the high voltage electrode 20, so that electrons emitted from the filament 60 are accelerated toward the metal platform 10 under the action of the electric field, and then bombard the sample b, thereby performing electron beam bombardment type heating. Temperature monitoring can also be achieved by using the temperature measuring electrode 22 during heating. Of course, temperature monitoring may also be accomplished using an infrared device disposed externally to the device.

Fig. 4A is a schematic view of the multi-function processing apparatus 100 of fig. 1 for performing current direct heating of a semiconductor sample, and fig. 4B is a schematic view of the semiconductor sample holder 120. Portions similar to those of the previously described sample holder will be omitted and the description will not be repeated.

As shown in fig. 4B, the semiconductor sample holder 120 includes a first molybdenum sheet a, a second molybdenum sheet c, an insulating sheet f, a molybdenum sample holder body e, a molybdenum screw B, an insulating tube g, and a semiconductor sample d, wherein the molybdenum sample holder body e is a flat plate similar to that shown in fig. 3B, which is not described herein again, and a plurality of through holes are further disposed on the molybdenum sample holder body e for passing through the molybdenum screw B, and in this embodiment, four through holes capable of forming four vertices of a quadrilateral are disposed for passing through the four molybdenum screws B1-B4, but it should be understood that the number of the through holes is not limited to 4, and can be set to be less than or greater than 4 as required. The molybdenum screws b1 and b2 are fixed by molybdenum nuts provided on the front and back sides of the flat plate portion of the molybdenum sample holder body e, and the molybdenum screws b3 and b4 are also fixed by molybdenum nuts provided on the front and back sides of the flat plate portion of the molybdenum sample holder body e, but an insulating tube g is provided between the molybdenum nuts and the molybdenum sample holder body e. In this way, the molybdenum screws b1 and b2 are electrically connected to the molybdenum body e, but the molybdenum screws b3 and b4 may be electrically insulated from the molybdenum body e. The insulation sheet f1 passes through the molybdenum screws b1 and b2 to be lapped on the molybdenum nuts, the insulation sheet f2 passes through the molybdenum screws b3 and b4 to be lapped on the molybdenum nuts, and the insulation sheets f1 and f2 are at the same height, and the height can be adjusted by increasing or decreasing the number of the molybdenum nuts. The insulating sheets f1 and f2 can be provided with semiconductor samples d, and the upper surfaces of the semiconductor samples d are fixed on the insulating sheets f through molybdenum sheets a and c by molybdenum nuts. Specifically, a first molybdenum sheet a is pressed on one side of the semiconductor sample d through molybdenum screws b1 and b2 and is fastened through molybdenum nuts arranged thereon, and a second molybdenum sheet c is pressed on the other side of the semiconductor sample d through molybdenum screws b3 and b4 and is fastened through molybdenum nuts arranged thereon, wherein the second molybdenum sheet c may have an L-shaped cross section, and when the semiconductor sample holder 120 is placed in the slot 18, the second molybdenum sheet c may be overlapped with the metal dome 24 for conducting current.

As shown in fig. 4A, the semiconductor sample holder 120 is inserted into the slot 18 of the metal stage 10, wherein the sample d is located just above the filament 60. In addition to the electron beam bombardment for the deposition process and the heat radiation for the heat treatment of the substrate, the present embodiment can also perform direct heating by electric current. Specifically, when the semiconductor sample holder 120 is inserted into the slot 18, the second molybdenum sheet c is in close contact with the metal spring sheet 24, and at this time, a conductive path is formed from the heater electrode 28 through the spring sheet 24, the second molybdenum sheet c, the semiconductor sample d, the first molybdenum sheet a, the molybdenum screws b1 and b2, the molybdenum sample holder body e, the metal platform 10, and the hv electrode 20. Note that the molybdenum screws b3 and b4 are electrically insulated from the sample holder body e. By applying appropriate voltages to the high voltage electrode 20 and the heating electrode 28, current flows through the semiconductor sample d, and because the semiconductor resistance is relatively large, a large amount of heat can be generated, so that the temperature of the semiconductor sample d is increased, and the purpose of directly heating the semiconductor material by the current is achieved. Although a part of the sample holder 120 is also in the circuit, its resistance is much smaller than that of the semiconductor material, and thus the amount of heat generation is small, so that the heating efficiency of the semiconductor material is high.

Fig. 5A is a schematic view of the heat treatment of the needle tip using the multi-functional processing device 100 of fig. 1, and fig. 5B is a schematic view of the needle tip sample holder 130.

As shown in fig. 5B, the tip sample holder 130 includes a tip sample a, a molybdenum tip holder B and a tip seat c, the molybdenum tip holder B is a flat plate similar to that shown in fig. 3B, and is not described herein again, in addition, the tip seat c is disposed at the center of the molybdenum tip holder B, and the tip seat is provided with a groove on the axis for placing the tip sample a.

As shown in fig. 5A, the tip sample holder 130 is inserted into the slot 18 of the metal stage 10, wherein the tip a faces the filament 60 side. Similar to fig. 3A, heat treatment of the tip may be accomplished by thermal and electron beam bombardment to remove impurities from the surface of the tip, thereby obtaining a sharp image with the tip.

Fig. 6A is a schematic view when the multi-function processing apparatus 100 of fig. 1 is used as an evaporation source, fig. 6B is a schematic view of a structure of a crucible holder 140, and fig. 6C is a partial sectional view of the crucible holder 140.

As shown in fig. 6B, the crucible holder 140 includes a body portion a similar to the previous sample holder, and a crucible located at the center of the body portion a. Referring to fig. 6C, the crucible includes a cylindrical lower portion d and a cover portion b. The lower portion may be formed integrally with the body portion a or may be seated in an opening in the center of the body portion a. The cover part b may also be cylindrical, but with an inner diameter slightly larger than the outer diameter of the cylindrical lower part d, so that the cover part b can be snapped back onto the lower cylinder d. In some embodiments, mating threads may also be formed on the inner wall of the cover portion b and the outer wall of the lower cylinder d to achieve a tight connection therebetween. The lower cylinder d may contain therein a material to be evaporated, and the cover portion b may have formed therein a through hole c for facilitating evaporation of the material to be evaporated after being heated, and then for material deposition. For lower evaporation temperature materials, thermal radiative heating deposition can be achieved by heating the tungsten filament 60 by passing an electric current through molybdenum screw electrodes 62, 64 of the processing unit. For the material with higher evaporation temperature, the molybdenum screw electrodes 62 and 64 and the high-voltage electrode 20 of the processing unit need to be respectively electrified and heated by high voltage electron beam bombardment. The temperature measuring electrode 22 can realize the monitoring of the evaporation temperature of the material.

Fig. 7 is a schematic view of the multifunctional processing apparatus of fig. 1 cooperating with an evaporation source to perform material deposition while heating a sample, which can use the general sample holder 110 shown in fig. 3B. As shown in fig. 7, a substrate on which a sample is to be deposited is placed in the opening 16 of the processing apparatus through the sample holder 110 while the substrate is heated by the processing unit, which may be any one of the aforementioned manners. The evaporation source 150 may be a commercial plate evaporation source, or the evaporation source apparatus shown in fig. 6A may be used. During the material deposition process, the substrate is heated, so that atoms or molecules deposited on the surface can obtain enough energy, and a stable structure is formed by the support of mutual acting force. And different structures may be formed by different regulation of the substrate temperature. The temperature detection has two modes of infrared temperature measurement and thermocouple temperature measurement. Wherein thermocouple thermometry is effected by means of thermometric electrodes 22.

Although some examples of sample holders are described above, it will be appreciated that the multi-function processing device of the present invention may also be adapted for use with sample holders of various other designs to meet various needs.

The processing device has small volume, easy adjustment and strong function, can meet the requirements of heating different samples and parts in various modes, and can be used as an evaporation source for material deposition. Because this processing unit still has the circulating water cooling function, can realize sample, target and heating device's rapid cooling and accurate temperature control. The processing device can be compatible with a universal flat plate type sample rack in a laboratory, and can well meet the requirements of the laboratory. Secondly, a large amount of space is saved for the system due to the simple structure and compact design of the processing unit, which is convenient to install in a narrow space.

The foregoing description has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit embodiments of the application to the form disclosed herein. While a number of example aspects and embodiments have been discussed above, those of skill in the art will recognize certain variations, modifications, alterations, additions and sub-combinations thereof. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims (10)

1. A multifunction processing device, comprising:

a metal platform (10) comprising a cylindrical side wall (12) and a platform layer (14) covering one end of the cylindrical side wall, the platform layer having an opening (16) at a central portion for receiving a plate-type sample holder, the metal platform having a first electrode (20) thereon for applying a voltage to the metal platform;

an insulating cylinder (30) disposed under the metal stage;

a water-cooled cylinder (50) disposed at a lower side of the insulating cylinder, the insulating cylinder physically connecting the metal platform and the water-cooled cylinder to each other in an insulated manner; and

and a filament (60) disposed in a cylindrical space defined by the metal stage, the insulating cylinder, and the water-cooled cylinder and facing the opening, both ends of the filament being connected to two screw electrodes (62, 64), respectively, the two screw electrodes being mounted on an insulating plate fixed to a lower side of the water-cooled cylinder.

2. The multi-function processing device of claim 1, wherein the platform layer has recesses around the opening for receiving the plate-like sample holders.

3. A multi-function processing device according to claim 1, wherein a portion of the stage layer and a cylindrical side wall adjacent thereto are cut away to expose one side of the opening, and a slot (18) is formed in a portion of the stage layer at an edge of the opening so that the plate-type sample holder can be inserted into the opening within the slot.

4. A multifunction processing device as in claim 1, wherein said metal platform further comprises:

a metal dome (24) mounted on the metal platform (10) and electrically insulated from the metal platform; and

a second electrode (28) disposed on the metal tab to enable direct galvanic heating of a sample by the first and second electrodes.

5. A multifunctional processing apparatus as claimed in claim 1, wherein said filament is used for thermal radiation heating of a sample, and

the first electrode is used for applying a preset positive voltage to the metal platform, so that electrons emitted by the filament are accelerated towards the metal platform, and electron beam bombardment heating is realized.

6. A multifunction processing device as in claim 1, further comprising:

the plate-shaped sample holder has a plate-shaped body portion for fitting into an opening of the metal platform.

7. The multi-function processing device of claim 6, wherein the plate-type sample holder is a semiconductor sample holder, comprising a first support portion for supporting one end of a semiconductor sample on the body portion and a second support portion for supporting the other end of the semiconductor sample on the body portion, the first support portion further electrically connecting one end of the semiconductor sample to the body portion, the second support portion being in physical contact with but electrically insulated from the body portion, and the second support portion electrically connecting the other end of the semiconductor sample to the metal dome.

8. The multi-functional processing apparatus according to claim 6, wherein the plate-type sample holder is a crucible sample holder serving as an evaporation source, and includes a cylindrical crucible body formed integrally with or mounted to the body portion and a crucible cover covering the crucible body, the crucible cover having a through hole therein.

9. A multi-functional processing apparatus as defined in claim 8, wherein the crucible cover has a cylindrical shape, and mating threads are formed on an inner wall of the crucible cover and an outer wall of the crucible body for fastening the crucible cover to the crucible body.

10. A multifunction processing device as in claim 1, further comprising:

a third electrode (22) disposed on the metal platform for performing temperature monitoring by thermocouple.