FR3002082A1 - Capacitive electrostatic chuck for use in manufacturing e.g. semiconductor, has gas distribution network on one of ceramic plates, and sealing layer detachably and durably securing ceramic plates for sealing gas distribution network - Google Patents

Abstract

The chuck (105) has a heater (140) provided on a ceramic plate (120) or another ceramic plate (145), and coated with a dielectric layer (135). A gas distribution network (124) is provided on one of the ceramic plates. A sealing layer (130) is made of a material with a melting temperature lower than that of the dielectric layer, so as to allow electrical contacting of conductors reaching a rear face of the former ceramic plate and a front face of the latter ceramic plate. The sealing layer detachably and durably secures the ceramic plates for sealing the gas distribution network.

Description

FIELD OF THE INVENTION Field of the Invention The present invention relates to a temperature-controlled wafer support device, or chuck, equipped with a thermal coupling gas distribution system. It applies, in particular, capacitive type electrostatic chucks for supporting wafers of semiconductor materials such as silicon, insulators, for example sapphire, or silica-based compounds. TECHNOLOGICAL BACKGROUND The manufacturing operations of semiconductors, photovoltaic cells, MEMS (acronym for Micro ElectroMechanical System, for micro electromechanical system), etc., are, as a rule, on platelets, or "substrates" , semiconductor materials, such as silicon, or insulators, such as sapphire or SiO2-based compounds or others. These platelets have the general shape of a disk, a square or a rectangle, of low thickness.

These manufacturing operations must often be conducted in specific reactors consisting of chambers in which the physicochemical conditions of temperature, pressure, positioning, etc.. must be controlled very precisely. These operations are generally performed on one side of the wafer called "active face". Very frequently, one encounters operations (etching, deposition, ion implantation, ...) that must be performed in vacuum chambers more or less pushed, and this, at a controlled temperature to a few degrees near, or more precisely, both in absolute value from one plate to another, in uniformity over the entire surface of the wafer. The absolute values of these temperatures can range from cryogenic values up to very high values of several hundred degrees Celsius. The present invention aims in particular at controlling the temperature, over a range extending from -100 ° C. to + 550 ° C. according to a first embodiment, or over a range extending from 200 ° C. to + 550 ° C. according to second embodiment, a vacuum substrate, positioned on a "hot" ceramic, itself installed on a "cold" table, that is to say less than 80 ° C. Controlling the temperature of an object to be treated under vacuum, with great precision, requires that this object be in intimate thermal contact with a part of the chamber that can be controlled, that is to say, namely the support mandrel of the object. This mandrel which maintains the "non-active" face of the substrate must itself be at a perfectly controlled temperature. The thermal contact between this mandrel and the wafer must be effective over its entire surface and at every moment.

The temperature exchange can be, of course, in both directions: - cooling of the wafer when the operation produces heat and warms the wafer or - on the contrary, warming the wafer, when the conditions are that the wafer has insufficient temperature.

Technically, for this heat exchange to be effected efficiently, there must be conducto-convection contact between the wafer and the mandrel which is in relative contradiction with the "vacuum" environment of the reactor. Practically, this thermal contact is achieved by the presence of a gas as good a thermal conductor as possible and as neutral physico-chemically as possible between the wafer and the support mandrel, such as Helium (He), Argon (Ar ) or Nitrogen (N2). The present invention thus relates in particular to a mandrel equipped with thermal coupling gas. In order not to disturb the vacuum conditions of the chamber, this gas (known as "BSG" for "back side gas") must remain contained in the volume delimited by the wafer and the mandrel. It is thus necessary for this mandrel to firmly hold the non-active surface of the plated wafer against its own surface. Technological evolution has led to the use of electrostatic pressure as a principle for maintaining platelets on mandrels. Indeed, the electrostatic phenomenon produces a homogeneous force per unit area, called "coulomb force" or "clamping pressure", unlike the mechanical clamping solutions around the periphery of the platelets initially used. This coulombic force distributed over the entire surface makes it possible to prevent the wafer from being raised relative to the upper face of the substrate holder under the effect of the pressure of the thermal coupling gas, in particular in the center of the wafer. This point is even more true that the dimensions of the wafers to be treated are large. However, from a certain distance, the efficiency of the thermal coupling is greatly reduced. Reference can be made to US Pat. No. 5,822,172 in this regard. The present invention thus relates in particular to a mandrel of the electrostatic type.

Many electrostatic chucks (or "ESC" for "electrostatic chuck"), also called "chucks", were made to meet specific needs. They consist of a support generally made of insulating material on which is deposited a system of electrodes of conductive material. This system can be powered by a single voltage (ESC called "monopolar") or by several voltages supplying electrodes independent of each other system (ESC called "bipolar", "quadrupole", "hexapolar", ...). These electrodes are covered: in the case of so-called capacitive electrostatic chucks, by a thin layer (preferably less than 150 μm thick), consisting of a material with a high resistivity (preferably greater than 1014 ohm.cm under the conditions normal temperature, more generally greater than 1010 ohm.cm substrate substrate processing temperature, or even 108 ohm.cm for particular temperatures, such as in the case of clamping said "hexapole" described in US Patent 5,452,177), a dielectric constant c as high as possible (typically, c> 8) and very high dielectric strength (typically greater than 15 MV / m and preferably 30 MV / m) and - in the case of Johnson-Rahbeck electrostatic chucks ( "JR"), by a layer of the order of 1 mm very weakly conductive. Johnson-Rahbeck type electrostatic chucks offer the advantage of providing a higher clamping pressure for a lower clamping voltage compared to capacitive type chucks. Conversely, the Johnson-Rahbeck type electrostatic chucks are very sensitive to the resistivity of the dielectric layer, which varies greatly with temperature and de facto limits the temperature range in which the electrostatic chuck can be used. The patent application US2007 / 0215840 provides a detailed and quantified explanation of this phenomenon. Furthermore, the Johnson-Rahbeck type clamping induces relatively long clamping and unclamping times (several seconds), and penalizes de facto the efficiency of the equipment receiving this type of electrostatic chuck, in particular for short processes, such as some implant operations that last about ten seconds, and some deposition processes whose duration is of the order of one minute. The risk of sticking of the wafer on the substrate holder during the unclamping, and the risk resulting from degradation or even destruction of the wafer, are major drawbacks of the Johnson-Rahbeck type electrostatic chucks well known to the human being. art. The reader will be able to refer to the numerous patents relating to the subject to better appreciate the criticality of this point (for example, US 5,117,121, US 5,325,261 and US 2010 / 208,409).

The present invention thus relates in particular to an electrostatic mandrel of the capacitive type. It is noted that despite all the efforts made to confine the coupling gas in the volume delimited by the upper face of the mandrel, on the one hand, and the underside of the wafer to be treated, on the other hand, and in particular despite the fact that in place of sealing ring ("seal ring" in English) well known to those skilled in the art, the leakage to the vacuum of the chamber is never completely eliminated. This results in a pressure gradient of the thermal coupling gas between its or its points of introduction and the limits of the volume receiving this gas. These limits are located on the outer periphery of this volume and in each place where there is a direct passage of this coupling gas to the chamber, and in particular the holes arranged in the mandrel for the passage of the lifting rods or rods the land of the wafer. However, the thermal conduction of the coupling gas is linearly proportional to the pressure of the gas, in the pressure range considered (1 to 30 Torr). A pressure gradient therefore induces a thermal conduction gradient and consequently a non-uniformity of the temperature of the wafer. The person skilled in the art then seeks to position the injection points of the coupling gas as close as possible to the various boundaries of the volume to be filled. For more details on this point, reference may be made by way of example to US Pat. No. 5,822,172. Finally, in some applications, the mandrel may be equipped with independent gas zones, generally concentric, and separated from each other by a sealing ring. This device makes it possible to optimize the temperature uniformity of the wafer to be treated by regulating the pressure of the thermal coupling gas in the various zones thus formed.

The present invention thus relates in particular to a capacitive type electrostatic mandrel having a topography on its upper face for receiving and confining a thermal coupling gas, and equipped with a gas supply network of this cavity.

US Pat. No. 5,280,156 clearly shows the advantage of having a heating element embedded in the electrostatic mandrel. It discloses a wafer carrier in which heating elements are made from resistive pastes which are pressed and fired together with the ceramic, deposited on a hardened ceramic plate and finished after firing.

EP 1 764 829 discloses the limitations associated with the method of manufacturing a heating electrostatic mandrel as described in US Pat. No. 5,280,156. EP 1 764 829 discloses a platelet support provided with a heating element incorporating an electrostatic mandrel. The heating element differs from the heating elements consisting of spirals or resistive wires included inside the ceramics before pressing and sintering as described in US Patent 5,280,156. This technique avoids the problems of non-reproducibility of the thermal characteristics of one electrostatic chuck to another because of the difficulties of reproducibility of the positioning of the resistive elements or with a low manufacturing efficiency due to breaks in these heating elements during pressing. firings. Patent EP 1 764 829 can therefore be considered as describing the state of the art in the production of a heating pad support. The structure it describes is as follows: "Ceramic / bonding layer / conductive layer / ceramic" or preferably "protective layer / conductive layer / ceramic" because of the relative deformation problems of the two ceramics used in the first solution that can introduce "voids" in the tie layer leading to manufacturing losses. In this preferred way, it is also possible to produce conductive and protective layers symmetrically with respect to the plane of the ceramic. These conductive layers may be the electrostatic electrode, the heating element (s), etc. However, this patent has a number of weaknesses or shadows.

The conductive parts have portions that meet the periphery of the support ceramic so as to constitute the electrical contacts with the various power supplies. The way in which these contacts are electrically isolated is not specified, as is the protection of these contacts against attack by chemical species used in the processes. The protective layers deposited on the conductive surfaces are formed by PVD ("vapor deposition" for vapor deposition), CVD ("chemical vapor deposition" for chemical vapor deposition) or thermal spraying of AIN or A1203 material. Furthermore, it is mentioned in this document that the electrostatic holding effect of the wafer is of the order of 200 mbar for a voltage of 150 V. The thickness of these protective layers is not specified but can be deduced technologies used to deposit them and the relatively low voltage generating the Coulomb force that is referred to a Johnson-Rahbeck type electrostatic chuck, with the limitations discussed above in terms of operating temperature range and in terms of speed of clamping and unclamping. If this patent referred to a capacitive type electrostatic chuck, the dielectric thickness would be a few micrometers. This small thickness makes these layers very fragile, and therefore the non-industrial product. Moreover, such a layer thickness is not compatible with a polishing flatness reduction of the order of 50 μm, which de facto assumes a reduction of the order of 50 μm of this dielectric layer. The lack of flatness of the order of 100 pm could therefore not be corrected, making the product incompatible with the needs of the semiconductor industry and related industries. Moreover, even after polishing, the lack of flatness is of the order of 50 pm at rest, that is to say at room temperature and without heat flow through the assembly. Knowing that, under the effect of the heat flow through the wafer and substrate holder assembly, the substrate holder will tend to deform further, the final flatness defect can lead to the destruction of the wafer. A flatness of the order of 10 pm maximum at rest is more than desirable Finally, the thermal coupling between the wafer and the heating support is direct without any transfer agent type BSG. As a first approach, the implementation of a thermal coupling gas distribution system might seem obvious to those skilled in the art, but as soon as we get into the details, the subject appears in all its complexity. For example, gas channels could be provided on the top surface, as in US Patent 6,028,762. But this is not compatible with the notion of independent multizones, nor with capacitive-type clamping since the dielectric thickness is not sufficient to accommodate channels, the only solution being to reduce the surface area of the electrodes. clamping and therefore the electrostatic clamping pressure, ie the efficiency of the thermal coupling between the substrate and the substrate holder. In addition, this technology does not approach the boundaries of the cavity receiving the gas, and therefore to have a uniform pressure of the coupling gas over the entire surface of the substrate holder.

Another example is to arrange gas distribution channels at the interface between the upper ceramic, which carries the clamping electrodes and the lower ceramic, and to arrange holes ("vias") through the upper ceramic to allow the passage of thermal coupling gas from these gas channels to the active face supporting the substrate to be treated. EP 1 764 829 is not compatible with this concept, because the glass serving as a binder between the upper ceramic and the lower ceramic can not, at the same time, serve as electrical insulation: either this glass is present opposite gorges arranged for the distribution of gas, and this glass will block these channels, rendering them useless; either these channels are spared during assembly, which assumes that the tracks of the heating element are not electrically insulated. However, the person skilled in the art knows that for a pressure of the order 10 Torr, the usual pressure of the thermal coupling gases, an electric arc occurs and is maintained between two electrodes separated by 1 mm and having a potential difference of 100 Volt order, according to Paschen's law. Consequently, since the heating elements are usually supplied with 108 V or 240 V, there is a risk of arcing between two adjacent tracks and destruction of the heating track. To remedy this by further discarding the tracks of the heating elements would be detrimental to the uniformity of temperature of the assembly thus produced, as detailed with precision in example 20 of this same patent. Another example would be to develop this gas distribution network in a third ceramic, also glued by the same method. However, it will be understood that the latter example is not interesting from an economic point of view, and aggravates the problem related to the lack of flatness of the substrate carrier thus manufactured.

BRIEF DESCRIPTION OF THE INVENTION The present invention aims to remedy all or part of these disadvantages. For this purpose, the present invention is directed to an electrostatic mandrel of the capacitive type, which comprises: a first ceramic, whose front face is intended to support a substrate to be treated and comprising at least one electrostatic holding electrode on the front face, comprising, on each said electrostatic holding electrode, a dielectric layer having a thickness of less than 200 μm and having an electrical resistivity greater than 108 ohm.cm over a temperature range of 100 ° C. to + 550 ° C., holes for the passage of gas from its rear face to its front face; - A second ceramic, the front face is facing the rear face of the first ceramic, equipped with at least one through hole for the passage of gas from its rear face to its front face; - At least one heating element on the first or second ceramics, respectively, produced after sintering of the ceramic carrying said heating element, coated with a dielectric layer sparing each gas passage hole; a gas distribution network on, respectively, the second or the first ceramic, ranging from each gas passage hole of the second ceramic to each gas passage hole of the first ceramic; a sealing layer, consisting of a material different from the constituent material of each dielectric layer whose melting temperature is lower than the melting temperature of each dielectric layer, between the first and the second ceramic, configured to leave the network empty; dispensing gas and leaving electrically conductive conductors reaching the rear face of the first ceramic and the front face of the second ceramic, said sealing layer being configured to: solidariser the ceramics durably and dismountably and ensure the sealing of the gas distribution network.

Thanks to these arrangements, the electrostatic capacitive-type mandrel object of the present invention can have a flatness of less than 10 μm, is repairable by melting or delamination of the sealing glass layer and has integrated heating elements and electrically isolated from a coupling gas distribution network capable of operating in a temperature range of -100 ° C to + 550 ° C. In embodiments, the heating element is made after sintering the ceramic that carries it. Thanks to these arrangements, the flatness of the mandrel, the sealing and the thermal and mechanical couplings are improved. In embodiments, at least one dielectric layer comprises an aluminosilicate baked at a temperature greater than 820 ° C. In embodiments, the material constituting the sealing layer is a fired glass at a temperature between 600 ° C and 700 ° C. In embodiments, the sealing layer covers the entire surface forming the interface between the upper ceramic plate and the lower ceramic plate, in order to optimize heat exchange between the two plates, while sparing the gas distribution network. BSG, so as not to seal it during the sealing operation. In embodiments, the sealing layer completely surrounds the gas distribution network to prevent leakage of the BSG gas to the process chamber at the interface between the upper and lower ceramics. In embodiments, each heating element is provided with at least two electrical contacts made by brazing an insert at a temperature between 770 ° C and 810 ° C.

In embodiments, the dielectric layer of the front face of the first ceramic has a topography adapted to receive and to contain a thermal coupling gas passing through the gas passage holes.

In embodiments, each heating element is located on the front face of the second ceramic and the gas distribution network is arranged on the rear face of the first ceramic. In embodiments, the first ceramic has a dielectric layer on its back side. The deformation of the first ceramic is thus counteracted during the manufacture of the dielectric layer on the front face of the first ceramic, and a flatness of less than 10 μm is obtained on its front and rear faces, with the exception of the specific topographies arranged on each face.

In embodiments, the second ceramic has a dielectric layer on its back side. The deformation of the second ceramic is thus counteracted during the implantation of the heating elements and the associated dielectric layer in order to obtain a flatness of less than 10 μm on its front and rear faces, disregarding the specific topographies arranged on each face. In addition, any conductive tracks providing electrical continuity between the electrical connection points and temperature sensors or heating elements are isolated. In embodiments, the second ceramic has a dielectric layer on its front face. In embodiments, each heating element is located on the rear face of the first ceramic and the gas distribution network is arranged on the front face of the second ceramic. In embodiments, the first plate, carrying at least one electrode, and the second plate, each have a thickness of less than five millimeters, and are formed of alumina A1203 or AlN by isostatic pressing and then sintering. This minimizes the effects of bimetal when the plates are then joined, for example by bonding with a connecting glass. Since the heat flux passing through the ceramics varies according to the steps of the manufacturing process (process in progress or stopped, etching process or deposition process, etc.), it is less a question of limiting the deformation of the assembly in a case considered to limit the amplitude of deformation during the different stages of a given process, and the resulting mechanical stresses that can be considered as fatigue stresses.

BRIEF DESCRIPTION OF THE DRAWINGS Other advantages, aims and features of the present invention will emerge from the description which follows, given for explanatory and non-limiting purposes, with reference to the accompanying drawings, in which: FIG. 1 represents, schematically and in section, a mandrel which is the subject of the present invention, surmounted by a wafer; FIG. 2 schematically represents steps for manufacturing a mandrel which is the subject of the present invention; FIG. the upper face of the first plate of the electrostatic mandrel shown diagrammatically in FIG. 1; FIG. 4 represents, in sectional view, from above, electrodes of the upper face of a hexapolar electrostatic mandrel carried on a first plate of the mandrel schematized in FIG. FIG. 5 shows, in bottom view, the lower face of the first plate of the electrostatic mandrel shown diagrammatically in FIG. 1; FIG. FIG. 7 represents, in section, the upper face of a third plate, cooled, of the mandrel shown diagrammatically in FIG. 1, in which is shown in plan view the heating tracks of a second mandrel plate schematized in FIG. an embodiment comprising a so-called "differential vacuum" system in which a groove connected directly to a vacuum pump limits the leakage of GLC gas directly into the chamber where the mandrel is located; FIG. 8 represents, in section, and above, the cooling ducts of the third plate of the mandrel schematized in FIG. 1; FIG. 9 represents, in bottom view, the lower face of the third plate of the mandrel shown schematically in FIG. 1; FIG. first axial section, the mandrel schematized in FIG. 1; FIG. 11 shows, in a second axial section, the mandrel schematized in FIG. 1; FIG. 12 represents an enlarged portion of the first FIG. 13 shows an enlarged part of the first axial section of the mandrel, given in FIG. 10, according to a second embodiment, FIG. 14 represents, in axial section, a system of thermal insulation and sealing of the cavity containing the GLC gas for lifting rods of a plate carried by the mandrel shown schematically in Figure 1, according to the first embodiment, - the FIG. 15 represents, in axial section, a thermal insulation system for lifting rods of a plate carried by the mandrel schematized in FIG. 1, according to the second embodiment; FIG. 16 represents, in axial section, a thermal insulation system, sealing the cavity containing the GLC gas and guiding for grounding rods of a wafer carried by the chuck schematically in Figure 1, according to the first embodiment 17 shows, in axial section, a thermal insulation and guiding system for grounding rods of a wafer carried by the mandrel schematized in FIG. 1, according to the second embodiment; FIG. 18 represents, in axial section, a thermal insulation and sealing system between the conduit supplying the cavity containing the gas BSG and the cavity receiving the GLC, according to the first embodiment; FIG. 19 represents, in axial section, a thermal insulation and sealing system between the cavity containing the gas BSG and the chamber in which the mandrel is located for a supply of gas BSG, according to the second embodiment, - Figure 20 represents, in axial section, a thermal insulation and clamping force limiting system for holding screws of the first and second plates on the third plate, according to the first embodiment, and a system of first and second plates relatively to the third plate. FIG. 21 represents, in axial section, a system of thermal insulation and limitation of the clamping force for holding screws of the first and second plates on the third plate, according to the second embodiment, FIG. 22 shows, in axial section, an alternative thermal insulation system for lifting rods and sealing the cavity containing the GLC gas of a wafer carried by the mandrel shown schematically in Figure 1, according to the first embodiment FIG. 23 represents, in axial section, a variant of the thermal insulation and gastightness system described in FIG. 14 (lifting rod) or FIG. 16 (grounding rod) or FIGS. 18 and 19 (FIG. introduction of the gas BSG), - Figure 24 shows, in axial section, another variant of the thermal insulation and gas sealing system described Figure 14 (lifting rod) or Figure 16 (grounding rod) or Figures 18 and 19 (i In FIGS. 25 and 26, bimetals used to separate, at high temperature, a cooled plate and a mandrel, and FIG. 27 represents deflection forces and bimetal movements, of the temperature. DESCRIPTION OF EMBODIMENTS OF THE INVENTION It should be noted that the figures are not to scale, thicknesses of a few tens of microns being able to be represented in the same way as thicknesses of several millimeters. Throughout the description, is called axial section, a section which has the axis of at least one component and which is parallel to the main axis of the mandrel.

FIG. 1 shows schematically a first embodiment of the electrostatic mandrel 105 which is the subject of the present invention. This first preferred embodiment is distinguished from the second embodiment by the use of a gas for cooling (GLC) in a low cavity located between a cooled plate and the second plate. In the second embodiment, this gas is replaced by a heat shield and the vacuum of the chamber surrounding the mandrel, as explained at the end of the description of FIG. 9. As illustrated in FIG. 1, the electrostatic mandrel 105 (or "chuck") ") Supports a wafer 110, also called substrate or wafer, via a peripheral ring 115, also called" seal ring ". The purpose of the "seal ring" is to provide a cavity as tight as possible between the substrate 110 and the electrostatic mandrel 105, cavity for receiving the thermal coupling gas BSG for the thermal coupling of the substrate with the electrostatic mandrel. In the configuration illustrated in FIG. 1, grounding rods 170 pass through the mandrel 105 and rest on the wafer 110. Lifting rods 175 ("lift pins"), or uprising, which pass through the mandrel 105, allow to lift the wafer 110 outside the processing steps of the wafer 110, for its placement on the peripheral ring 115, before treatment, or its removal from the mandrel 105, after treatment. The lifting rods 175 are set in motion by motor means not shown. Chuck 105 comprises successively, from top to bottom, a first plate, also called ceramic, 120, a glass bond 130, a second plate, also called ceramic, 145 and a cooling plate 160, or "table". The first plate 120, upper, called "ESC" ("electrostatic chuck") comprises: - on the upper face, one or more electrodes, here six electrodes 114 which ensure the maintenance (or "clamping") electrostatic of the wafer 110, on the lower face, a network of channels 124, which distributes the front thermal coupling gas 112, or "BSG", from a gas inlet 165 to vias 190 which pass through the first plate 120, as well as the electrical contacts six electrodes (not shown in Figure 1). The second plate 145, lower, called "heater", comprises: - on its upper face, secured to the underside of the first plate by the gluing of glass 130, two heating tracks 140, one in outer edge and the other central, - on its underside, four resistive temperature sensors 118, called "RTD" or "PT100", and (not shown in Figure 1) three connectors and - between its two faces, a BSG 165 gas inlet, which communicates with a gas inlet 166 provided in the cooling plate, and which does not communicate with the cavity 126. The cooling plate 160 comprises the gas inlet BSG 180 (not shown in FIG. 1), an inlet 195 of GLC thermal cooling coupling gas and a cooling water circuit 116. Between the second plate 145 and the cooling plate 160 is a space 126 filled with GLC gas, delimited by a peripheral ring 155, or "seal ring ".

Layers of dielectric material 122, and 135 cover the clamping electrodes 114 and the heating tracks 140. It is observed that, in alternative embodiments, a layer of dielectric material 125 is installed on the underside of the plate 120 serving to preserve the flatness, and to ensure a good hanging of the glass. In another variant, a layer of dielectric material 150 is installed on the lower face of the plate 145 serving to maintain the flatness of the plate 145 before sealing on the plate 120, and for electrically isolating electrically conductive tracks making it possible to connect the electrical contacts of the heating resistors, arranged in the cooled plate, at the ends of the electrical contacts arranged in the plate 145 and which lead to the heating resistors located at the interface between the plates 120 and 145. Electrical contacts (not shown in FIG. 1) connect the base of the cooling plate 160 to the electrodes 114, on the one hand, to the heating electrodes 140, on the other hand, and to the temperature sensors 118, on the other hand.

The base of the cooling plate 160 thus comprises three connectors: - a connector for supplying the heating electrodes 140, having two phase contacts and two neutral contacts, - a connector for the temperature sensors, ie ten contacts as exposed below, and - a connector for the high voltage of the six electrostatic holding electrodes 114, six contacts. With regard to the temperature sensors, there are two primary sensors for two heating zones, internal and external, and two secondary sensors, which double the primary sensors and serve to detect a failure of the primary sensors. Temperature sensors are RTD ("Resistive Thermal Device") sensors whose resistance changes with temperature. It is therefore by measuring their resistance that the temperature is measured. Each sensor is a three-point sensor in which a first loop is used to measure the resistance and a second loop is used to measure the resistance of the connection cables. This second loop makes it possible to correct the temperature measurement by removing the resistance of the connection cables. Secondary temperature sensors do not have a second loop. They are therefore two-point sensors. There are thus ten contacts on the connector of the temperature sensors.

FIG. 2 diagrammatically represents the steps of manufacturing a mandrel 205 similar to the mandrel 105 illustrated in FIG. 1. The first, initially raw plate 210 is then printed at 215, at about 850 ° C., to form the holding electrodes. electrostatic of the wafer to be treated, the dielectric layer covering these electrodes, the topography adapted to receive and confine the thermal coupling gas BSG, and optionally the dielectric layer on the rear face. At this stage, the functionality of this first ceramic can be tested before continuing the manufacturing process.

The second, initially raw plate 220 is then printed at 225 to 850 ° C., to form the heating electrodes, the heating electrode supply tracks, the contact tracks of the temperature sensors, the dielectric layers covering the heating electrodes and the various feed tracks, then soldered at about 780 ° C at 230 to form the feed contacts of the heating electrodes 140. At this point, the functionality of this second ceramic can be controlled before continuing the manufacturing process. The first and second plates are then assembled by gluing with glass at 600 ° C-650 ° C and give the assembly 235.

It should be noted that each of the ceramics 120 and 145 can be produced, tested and repaired independently, which reduces the manufacturing, retouching and repair costs. On its side, the raw cooling plate 240 is provided, at 260, with heating electrode contacts 245, contacts of the holding electrodes 250 and temperature sensor contacts 255. Finally, the assembly 235 and the cooling plate 260 are assembled at 205, bringing into contact the different power supply contacts of the heating electrodes. FIG. 3 shows the upper face of the first plate 120, above the dielectric layer 122. On the periphery of this plate 120, openings 335 form the entrances of the vias 190, through which part of the BSG gas is injected between the first plate 120 and the wafer 110. Apertures 340 serve for the passage of the lifting rods 175. Openings 306 serve for the passage of the ground rods 170. A central opening 302 and openings 303, 304 and 308 , located near the openings 340 and 306, are also used for the injection of BSG gas. Seal ring rings 312 are formed on the surface of the first plate around each zone where there is a risk of gas leakage, that is to say around openings 340 and 306. Their height is equal to that of the peripheral ring 115. Combined with the openings 303, 304 and 308, positioned outside these rings 312, they reduce the risk of local depression and, consequently, of reducing the amount of heat transmitted to the wafer 110. In FIG. 4, the electrodes 114, referenced 305, 310, 315, 320, 325 and wafer 110. As illustrated in FIG. 4, except for the central part, the six electrodes 305 to 330 are identical and superposable by rotation of 60 degrees around the center of the upper face of the mandrel 105. Their geometry is adapted to a minimum the separation distance 300 between two successive electrodes and the uniformity of distribution of these separation lines. Thus, no point of the upper face of the upper ceramic is more than a predetermined limit distance of an electrode. The electrostatic force exerted on the wafer 110 is thus maximized and very uniform. It is also noted that these electrodes extend as close as possible to the periphery of the plate 120, and more particularly beyond the circumference on which are located the gas injection vias 190 BSG, in order to generate an electrostatic clamping pressure. outside this circumference, and thus limit the leakage of gas BSG to the process chamber. FIG. 5 shows an eccentric BSG gas inlet 660 leading through a groove 655 at the center of a star with three radial grooves 665. Each groove 665 ends in a fork, each branch 670 of which reaches a first circular groove 675 Three other radial grooves 680 connect the first circular groove 675 to a second circular groove 685. The eccentric BSG gas inlet makes it possible to release a central space for functions which require a symmetry of revolution, for example a mechanism for actuating lifting rods 175 ("lift pins"). The groove 655, which brings the BSG gas to the center of the lower surface of the first plate, allows a symmetry of revolution of the other grooves, so that the pressure uniformity of the gas is optimized. The branches 670 of the forks ending the radial grooves 665 make it possible to bypass the lifting rod passages 175. The vias 190, 302, 303, 304 and 308, which pass through the first plate 120, start from the grooves shown in FIG. two vias 303 and 304 frame each upright rod passage 340 and that a via 308 is near each passage 306 grounding rod 170. The other gas passage vias, 190, are on the periphery of the mandrel 105 and open into the second circular groove 685. Thus, the gas is distributed near each potential gas leakage zone. FIG. 6 shows the heating electrodes positioned below a layer of dielectric material on the upper face of the second plate 145. Two of the contacts 405 supply, in parallel, two electrodes 410 and 415, called "interior" electrodes. because they are close to the center. Two of the contacts 405 supply, in parallel, two electrodes 420 and 425, called "outer" because they are close to the periphery. As is understood, the geometry of the electrodes aims to generate as uniform a heat as possible on the substrate 110 to be treated while bypassing the passages of rods and vias. Thus, in the present case having two independent heating zones, one outside and the other inside, the amount of heat per unit area is greater on the outer zone. Thus, from the point of view of the operator, the indicator of the power consumed on each zone, which appears as a percentage of the power of each zone, will be substantially identical for each zone. In the case of a design with a single heating element, the outer zones have a higher power density. An opening 430 passes the electrostatic holding electrode contacts of the wafer 110. Apertures 435 receive free mounted tapped inserts, trapped between the upper plate 120 and the lower wafer 145. The housings are non-axi-symmetrical in shape (oblong ), as well as the inserts themselves (not shown), so that these inserts are locked in rotation when tightening the screws for the passage of threaded rods solidarisant the cooled plate 160 under the second plate 145. In variants, it is brazed inserts or threads made in the ceramic. However, the version illustrated in the figures with an oblong nut locked in rotation limits the introduction of unnecessary mechanical stresses. The shapes and sections of the electrodes 410 to 425 are adapted to ensure a heat release as uniform as possible on the surface of the upper face of the second plate 145 while leaving free zones for passage of the lifting rods, contact contacts to the earth, the supply of gas BSG and contacts for the electrical supply of the electrostatic holding electrodes 114. There is seen in FIG. 7 an optional system, called a "differential vacuum" system having a groove 440 directly connected to a vacuum pump (not shown) limits the leakage of the GLC gas directly into the chamber where the mandrel 105 is located (international application W02012 / 094139). FIG. 8 shows a representation of the cooling circuit 116 with respect to the elements carried by the lower face of the third plate 160. As can be seen, the cooling circuit 116 follows concentric circles regularly spaced between an inlet water 132 and a water outlet 134, positioned near the center of the third plate 160. The shape of the cooling circuit 116 is optimized so that any point of the third plate 160 is not at a distance greater than one predetermined limit distance, so that the temperature of the third plate is as uniform as possible. In addition, in this case, the cooling circuit 116 is cross-flow, which limits the impact of the temperature gradient of the cooling liquid between the inlet and the outlet on the temperature uniformity of the assembly. FIG. 8 shows the upper face of the cooled plate 160, the through holes for the contacts of the connectors 605, 610 and 615 detailed with reference to FIG. 9. The size of these through holes is reduced to a minimum, to protect the maximum radiation from the hot part, located in the upper part, the elements below (in the rear of the cooled plate 160) of the device. In the embodiment, the four-axis rotational head of the chamber housing the chuck, which also contains electrical connections, water and gas circuits, and atmosphere and high vacuum sealing devices, is protected. FIG. 9 shows the lower face of the cooled plate 160 comprising: - the connector 605 for supplying the heating electrodes 140, having two phase contacts and two neutral contacts, - the connector 610 for the temperature sensors 10 contacts as discussed below, the connector 615 for the high voltage of the six electrostatic holding electrodes 114, six contacts, the three grounding rods 170, the three lifting rods - The six fixing screws 580 of the electrostatic chuck on the cooled plate 120 - three screws 505 holding in position three planar springs 510 (see Figure 17). FIG. 10 shows a cross-section of the mandrel 105 passing through a lifting rod 175 and via the connector 615. The cooling water circuit 116 formed by a recess in the cooled plate 160 and closed by lids is observed 465. There is, in FIG. 10, the first plate 120, the second plate 145 and the third plate 160 as well as the connector 605. FIG. 11 shows a cross section of the mandrel 105 passing through two fixing screws 580. 11, the first plate 120, the second plate 145 and the third plate 160 and the connector 615. Housing 616 are intended to receive, each, a positioning pin (not shown). FIG. 12 shows a partial cross-section of mandrel 105 according to the first embodiment. In FIG. 12, on the lower face of the second plate 145, there is a channel 127 serving to standardize the pressure distribution of the thermal coupling gas GLC between the plate 145 and the plate 160.

On the upper face of the plate 160, there is also a passage channel 128 for the "differential vacuum" system illustrated in FIG. 7. It can be seen that a lid 362 for closing the cooling circuit 116 is on the lower face. of the third plate 160. FIG. 13 shows a partial cross-section of the mandrel 105 according to the second embodiment. FIG. 13 shows, between the second plate 145 and the third plate 160, the heat shield 352, provided with bosses 351 and 354 intended to limit the contact surface between the heat shield and the lower ceramic 145 of a part, and the cooling plate 160 on the other hand. It can be observed that a lid 364 for closing the cooling circuit 116 is located on the upper face of the third plate 160. FIGS. 14 and 15 show the insulation and sealing elements of the lifting rod passages 175 These passages are subjected to several constraints, on the one hand, thermal (low thermal conductivity limiting conduction losses) to ensure the uniformity of heating of the wafer avoiding gas losses and a long service life of the joints ( low thermal conductivity to limit their temperature at the contact with the joint) and, secondly, mechanical, to allow different expansions between the different plates when they are brought to different temperatures while preserving the tightness of the lower cavity that receives GLC gas. Thus, according to the second embodiment, these elements 470 and the seal 460 are not essential. FIGS. 14 and 15 show the first plate 120, through which the vias 190, 303, 304 and 308 pass, the second plate 145 and the cooled plate 160 traversed by the cooling circuit 116. The glass bonding 130 secures the The first plate 120 on the second plate 145. In the first embodiment, illustrated in FIG. 14, an elastomeric O-ring 460 is inserted into the cooled plate 160. In the second embodiment, illustrated in FIG. Thermal 352 separates the second plate 145 and the cooled plate 160. An insulating ceramic sheath 470 is fitted and glued into the second plate 145. It is noted that the sheath 470 can be brazed. The sealing of the connection between the sleeve 470 and the ceramic 145 can also be improved by adding a ceramic cement around the connection. The sheath 470 has a clearance 475 in the cooled plate 160. The O-ring 460 seals this game, in the first embodiment. In the cooled plate 160, the cooling circuit 116 takes the form of a recess closed by a cover 465, here welded, in which cold water circulates. In FIGS. 16 and 17, the insulation and sealing elements of the grounding rod passages 530 ("grounding") of the wafer 110 are observed. Like the lifting rod passages 175, the passages of Grounding rods 530 are subjected to several constraints, on the one hand, thermal in order to guarantee the uniformity of heating of the wafer, avoiding gas losses and a long service life of the seals, and on the other hand , mechanical, to allow different expansions between the different plates when they are brought to different temperatures. FIGS. 16 and 17 show the first plate 120, the second plate 145 and the cooled plate 160. In the first embodiment, illustrated in FIG. 16, an elastomeric O-ring 525 is inserted into the cooled plate 160. In the second embodiment, illustrated in FIG. 17, the heat shield 352 separates the second plate 145 and the cooled plate 160.

An insulating ceramic sheath 520, adjusted and glued in the second plate 145, has a clearance 535 in the cooled plate 160. It is noted that the sheath 520 can be brazed. Tightness of the bond can also be improved by adding a ceramic cement around the bond. The O-ring 525 seals this clearance in the first embodiment illustrated in FIG. 16. The grounding rod 530 takes the form of a point having a shoulder which bears on the underside of the housing. the first plate 120 in the absence of wafer 110 and deviates from the lower face of the first plate 120 in the presence of the wafer 110. The shank 530 bears, in its lower part, on a plane spring 510 fixed on the face lower part of the cooled plate 160 by a screw 505. FIGS. 18 and 19 show the thermal insulation elements of the gas inlet BSG 190 up to the gas inlet 660 shown in FIG. in Figures 18 and 19, the first plate 120, the second plate 145 and the chilled plate 160. In each of the embodiments, an elastomeric O-ring 555 is inserted into the chilled plate 160. In the second embodiment, illustrated in FIG. Figure 19, the heat shield e 352 separates the second plate 145 and the cooled plate 160. An insulating ceramic sheath 560, adjusted and glued in the second plate 145, has a clearance 565 in the cooled plate 160. It is noted that the sheath 560 can be brazed . Tightness of the bond can also be improved by adding a ceramic cement around the bond. The O-ring 555 seals the gas inlet in all the positions of the sheath 560 inside this set. FIGS. 20 and 21 show a restraint force-holding system for the second set. plate 145 on the cooled plate 160. There is also, in FIGS. 20 and 21, the first plate 120. In the first embodiment, illustrated in FIG. 20, the layer 126 of the cooling thermal coupling gas GLC separates the second and third plates 145 and 160. In the second embodiment, illustrated in Figure 21, the heat shield 352 and the vacuum of the chamber, separate the second plate 145 and the cooled plate 160. The heat shield 352 is preferably made of a material having a good reflectivity, such as aluminum, even polished aluminum. In one embodiment, the heat shield 352 is provided with bosses judiciously distributed over its surface, and oriented either towards the ceramic plate 145 or towards the metal plate 160, so as to limit the possible contact between the heat shield 352 and the metal plates 160 and ceramic 145, due to the deformation, for example of the web, of the heat shield 352 resulting from its heating.

The vacuum is present between the heat shield 352 and the plate 160 on the one hand, and between the heat shield 352 and the plate 145 on the other hand, because the heat shield 352 is separated from these plates 145 and 160 by spacers. These spacers are preferably constructed of a thermally insulating material, such as zirconia, and located at the points of attachment of the ceramic plates 120 and 145 to the metal plate 160. The force for holding the plate 145 on the plate 160 is introduced by the spring 584 trapped between the plate 160 on its upper part, and the spacer 588 on its lower part. The spacer 588 is secured to the plate 145 by means of the screw 580. The coil spring assembly 584 and spacer 588 constitute a system for limiting the clamping force of the plate 145 on the table 160, whatever the tightening torque applied to the clamping screw 580. Typically, the force introduced by each spring is 60 N, compared to the force of 1000 N introduced by a M6 screw tightened to 1 Nm Similarly, the stiffness of the spring is 15 N / mm compared to a screw M6 free length 10 mm, for which the stiffness is of the order of 400 000 N / mm. In embodiments, the spacer 588 is made of a weakly thermally conductive material, such as quartz or zirconia. The screw 580 is preferably a hollow screw, to limit the thermal conduction and to allow the evacuation of the gas trapped at the end of the thread during assembly, produced in the atmosphere, which is screwed into a partially free nut 582, whose cross section of the head is oblong. This head of the nut 582 is inserted in the second plate 145 in an oblong opening whose smaller dimension is smaller than the largest dimension of this cross section so as to prevent the complete rotation of the nut 582 in the oblong opening. It should be noted that a lateral clearance 590 is provided between the sleeves 586 and 588 to absorb the thermal expansion differences of the second and third plates of the mandrel 105. In FIG. 20, the presence of a plug 587, glued to the cooled plate 160 sealingly, so as to prevent leakage of GLC gas to the process chamber. According to the second embodiment, no GLC gas is present, the cap 587 is no longer necessary and is not installed, as illustrated in FIG. 21. It is noted in FIG. 20 the presence of a bimetal element. 805 mounted tight on the plate 145 through the screw 580 and the spacer 588. The operation of this bimetal is described further with reference to Figures 25, 26 and 27. The clamping of the bimetallic strip 805 on the plate 145 ensures good thermal conduction between the bimetallic strip 805 and the plate 145. Note also in Figure 20 the presence of a stroke limiter 586 having a shoulder resting on a thermally insulating ceramic sleeve 588 surrounding the threaded portion of the screw 580. The piece 586 is free at its upper end and serves to limit the vertical stroke of the screw 580 when the bimetal enters into action under the effect of heat and tends to move the plate 145 away from the plate 160. According to the second embodiment, bimetallic is no longer needed area and is not installed. Likewise, the race limiter is no longer necessary. It remains present in Figure 21 because in this embodiment, it has not been removed for reasons of standardization of the manufacturing process of the assembly. FIG. 23 shows a partial section of a third embodiment of the mandrel 105 comprising, in the path of the injection of gas BSG from the gas inlet 180 to the central via 302 illustrated in FIG. 3, a bellows 136 shown in detail in FIG. 22. In embodiments, an insulation of the gas between a GLC gas cavity and an external part of the cooled plate 160 is provided by a bellows 850 (see FIG. flat surfaces at its ends, these flat surfaces itself bearing on flat surfaces on both the metal plate 160 and the ceramic plate 145. In another embodiment, the bellows 850 is brazed in the ceramic plate 145. In another embodiment, in the case of cooled metal plates 160, the seal between the bellows 850 and the metal plate 160 is formed by an O-ring. FIGS. 22 to 24 show other embodiments of the sealing of the upper gas inlet BSG, or the passage of the support rods. Indeed, the bellows 850 ensure: - a "thermal seal" due to the conduction length vis-à-vis the passage section, - a gas seal and - a free vertical and horizontal movement of hot parts 120 and 145 vis-à-vis the plate or cold table 160. Concerning the gas tightness, with the elements illustrated in Figure 23, we obtain a high pressure drop and therefore a small leak compared to the gas pressures introduced - 20 Torr approx. With the elements illustrated in FIG. 24, a solder seal in the hot part and an O-ring seal 855 in the cold part are obtained. This embodiment is thus more effective than those presented above, but it has a larger footprint and can not be implanted in small spaces. As illustrated in FIG. 25, in embodiments, bimetallic members 805 are inserted between the metal plate 160 and the ceramic 145. Each member 805 has a strain force. From a certain temperature, typically of the order of 200 ° C., this deformation force is greater than the clamping force introduced by the springs 584 of the device for fixing ceramics 120 and 145 to the metal plate 160. From this temperature, the deformation force of the bimetallic strips 805 disengages the lower face of the ceramic 145 from the upper face of the metal plate 160, so as to limit the contact surface between the ceramic 145 and the metal plate 160, as illustrated in FIG. 26. The thermal exchanges are thus limited by conduction, and a good penetration of the vacuum of the process chamber between the metal plate 160 and the ceramic 145 is ensured. In embodiments, these bimetallic elements 805 are inserted at the points of attachment of the ceramics 120 and 145 to the metal plate 160, so as to limit the bending moments introduced into the ceramics 120 and 145 because of the distribution of the fixing points of the ceramics 120 and 145 on the metal plate 160 and bimetallic strips 805. In embodiments, these bimetallic elements 805 are clamped on the ceramic plate 145 in order to provide a connection recess, and thus optimize the thermal contact between the ceramic 145 and the bimetallic strip 805 facing the thermal contact of this bimetallic strip 805 with the metal plate 160, point contact, with a lower contact force. In embodiments, the bimetallic elements 805 consist of a so-called "passive" element in FeNi36 (Invar) and a so-called "active" element in Ni (nickel).

Other pairs of materials are available on the market, such as Fe Ni20 Mn6 with Fe Ni42. In the case of rectangular bimetallic strips 805 embedded at one end, the deflection D in the free state is given, in millimeters, by the following formula: 2 D = aLAT e Formula in which a is the specific deflection in ° Ki, L is the free length of the bimetallic strip in mm, e is the thickness of the bimetallic strip in mm and AT is the temperature difference in ° K between the considered temperature of the resting temperature, at room temperature. In the embodiment shown, bimetallic strip 805 has a rectangular shape of half length L = 6.5 mm, width 10 mm and thickness 6 mm. This bimetallic strip 805 is installed with a clearance of 0.5 mm with respect to the metal plate 160. When the bimetallic strip 805 heats up to 150.degree. C., the deformation of the bimetal strip 805 reaches the value of the clearance, for example 0.5 mm, and the bimetallic strip 805 comes into contact with the metal plate 160. At a temperature of 200 ° C., the force developed by the bimetallic strip 805 is 290 N. The clamping force introduced by the spring 584 being 60 N , the ceramic plates 120 and 145 are raised relative to the metal plate 160. In a preferred embodiment, the compression of the fixing spring 584 under the effect of the force introduced by the bimetal 805, is limited by a mechanical stop clear, for example the abutment 586 of Figure 20. The permissible compression being 0.5 mm, and the stiffness of the spring being 15 N / mm, the mechanical stopper goes into action when the temperature of the bimetal has increased 160 ° C. Figure 27 illustrates these movements. FIG. 27 shows a free deflection curve 905 and a developed stress curve 910 as a function of temperature.

Claims (10)

1 electrostatic chuck capacitive type (105), characterized in that it comprises: - a first ceramic (120), whose front face is intended to support a substrate (110) to be treated and ^ ^ comprising at least one electrode ( 114) having, on each said electrostatic holding electrode, a dielectric layer (122) having a thickness of less than 200 μm and having an electrical resistivity greater than 108 ohm.cm over a temperature range. from -100 ° C to + 550 ° C, piercing holes (190) for the passage of gas from its rear face to its front face; - A second ceramic (145), the front face is facing the rear face of the first ceramic, equipped with at least one hole (165) passing through the gas passage from its rear face to its front face; - at least one heating element (140) on the first or second ceramics, respectively, produced after sintering of the ceramic carrying said heating element, coated with a dielectric layer (135) sparing each gas passage hole; - a gas distribution network (124) on respectively the second or the first ceramic, from each gas passage hole of the second ceramic to each gas passage hole of the first ceramic; a sealing layer consisting of a material different from the constituent material of each dielectric layer, whose melting temperature is lower than the melting temperature of each dielectric layer, between the first and the second ceramic, configured for leaving the gas distribution network empty and leaving electrically conductive conductors reaching the rear face of the first ceramic and the front face of the second ceramic, said sealing layer being configured to: solidarize the ceramics in a durable and removable manner and ^ ensure the tightness of the gas distribution network. 2. mandrel (105) according to claim 1, wherein at least one dielectric layer comprises an aluminosilicate baked at a temperature greater than 820 ° C. 3. mandrel (105) according to one of claims 1 or 2, wherein the material constituting the sealing layer is a fired glass at a temperature between 600 ° C and 700 ° C. 4. mandrel (105) according to one of claims 1 to 3, wherein each heating element is provided with at least two electrical contacts made by brazing an insert at a temperature between 770 ° C and 810 ° C. 5. Chuck (105) according to one of claims 1 to 4, wherein the dielectric layer of the front face of the first ceramic (120) has a topography adapted to receive and to contain a thermal coupling gas passing through the gas passage holes. 6. mandrel (105) according to one of claims 1 to 5, wherein each heating element is located on the front face of the second ceramic (145) and the gas distribution network is arranged on the rear face of the first ceramic. 7. mandrel (105) according to one of claims 1 to 5, wherein each heating element is located on the rear face of the first ceramic (120) and the gas distribution network is arranged on the front face of the second ceramic (145). 8. mandrel (105) according to one of claims 6 or 7, wherein the first ceramic (120) has a dielectric layer on its rear face. 9. Mandrel according to one of claims 6 to 8, wherein the second ceramic (145) has a dielectric layer on its rear face. 10. Chuck according to one of claims 7 to 9, wherein the second ceramic (145) has a dielectric layer on its front face.