WO2013024313A1

WO2013024313A1 - Electrode structure for use in a reaction chamber

Info

Publication number: WO2013024313A1
Application number: PCT/HU2012/000072
Authority: WO
Inventors: Zsolt VADADI; Tamás STRAUSZ
Original assignee: Ecosolifer Ag
Priority date: 2011-08-15
Filing date: 2012-08-14
Publication date: 2013-02-21
Also published as: HUP1100438A2

Abstract

An electrode structure for a reaction chamber wherein in the inner volume of the reaction chamber rectangular substrates are arranged spaced apart from each other and electrodes suitable for providing high-frequency electromagnetic field are disposed between the substrates; the spaces presenting between the substrates provide flow channels for reaction gases; and the opposing electrodes are connected to a high-frequency generator and the inner volume of the body is provided with heating means, wherein the electrodes comprise (i) two parallel, spaced apart lateral sheets which are connected to each other; (ii) a central sheet placed into the space formed between the lateral sheets, the central sheet being aligned parallel to the lateral sheets and being separated from them by insulation and (iii) the lateral sheets of the electrodes are connected to the high-frequency generator, and the central sheet to the power supply of the heating means.˙

Description

Electrode structure for use in a reaction chamber

The present invention refers to an electrode structure for use in a reaction chamber, preferably in a reaction chamber for thin layer deposition. In the reaction chamber deposition of a semiconductor layer or layer structure on a surface of a plurality of substrates in substrate batches is possible, wherein the reaction chamber comprises a body with an inner volume and an upper lid and closing bottom lid, in the inner volume rectangular plate-like substrates are arranged in a spaced apart relationship with each other and electrodes suitable for providing high-frequency electromagnetic field in order to deposit a thin material layer are disposed between the substrates; each electrode is disposed in a spaced-apart relationship adjacent to the surface of the substrate not to be deposited; and each space extending between the surfaces to be deposited forms a flow channel making available the laminar flow of reaction gases between two opposite sides of the chamber; the opposite electrodes are connected to a high-frequency generator and the closed inner volume of the chamber is provided with a heater element.

In case of the most common types of so the called batch-processing equipments - applicable to simultaneously deposit various layers onto a plurality of large substrates - in the reaction chamber various methods are known for heating the substrates to be coated by layer deposition.

According to a first method the substrates are preheated in a heating chamber dedicated to this purpose and are loaded into the reaction chamber while they are warm. According to an alternative method heater elements are disposed inside the reaction chamber, e.g. on the walls of the chamber which elements are operated when the reaction chamber is closed and are suitable to provide in situ warming of the substrates loaded into the reaction chamber. A common drawback of the above methods is that different areas of the substrate surfaces may be heated to different temperatures; which is due to the non-uniform cooling of the substrates in the first case, and due to the non-uniform inflow of thermal energy in between the substrates in the second case. An even further drawback is that a considerable amount of time is needed to obtain a uniform temperature distribution, which is required for the reaction, inside the large volume of the reaction chamber. This extra time lowers the productivity of the process.

Hungarian patent application No. P0700164 discloses an apparatus which has an inner reaction volume, in the reaction volume a plurality of parallel, planar, spaced apart electrode pairs are arranged, and the planar electrodes on their opposite surfaces support a plurality of substrates envisaged to be subject of layer deposition. During normal operation of this apparatus the substrates can be loaded only in the unloaded state of the electrodes from the chamber, and substrates must be placed onto the electrode surfaces one by one outside the reaction chamber, and the electrodes and substrates are loaded together again into the reaction chamber. The loading of electrodes is done individually or in electrode batches.

Object of the present invention is to provide a structure which can overcome the weaknesses of the prior art solutions and wherein surfaces of the substrates can be heated up quickly and uniformly. The electrode structure of the present invention is based on an idea that the electrodes, which are made of metal plates and are suitable to provide a high frequency electromagnetic field, are configured to have a closed, flat inner volume between to plates and in the inner volume heater elements of a specific design are disposed and being insulated from the outer surfaces.

The above goals are achieved according to the invention by an electrode structure for reaction chambers, wherein the reaction chamber is applicable for the deposition of a semiconductor layer or layer structure on a surface of a plurality of substrates in substrate batches, and the reaction chamber comprises a body with an inner volume and an upper lid and closing bottom lid, in the inner volume rectangular plate-like substrates are arranged in a spaced apart relationship with each other and electrodes suitable for providing high-frequency electromagnetic field in order to deposit a thin material layer are disposed between the substrates; each electrode is disposed in a spaced-apart relationship adjacent to the surface of the substrate not to be deposited; and each space extending between the surfaces to be deposited forms a flow channel making available the laminar flow of reaction gases between two opposite sides of the chamber; the opposite electrodes are connected to a high-frequency generator and the closed inner volume of the chamber is provided with a heater element, and according to the invention the electrodes are comprised of (i) two parallel, spaced apart lateral plates which are connected to each other; (ii) a central plate disposed in the inner volume between the lateral plates, and being aligned parallel to and being insulated from the lateral plates; (iii) wherein the electrodes are connected to the high-frequency generator and ends of the central plate are connected to the power supply of the heating current.

A clear advantage of the above structure is that it provides quick and uniform heating and the heater elements do not occupy the inner volume of the reaction chamber.

In the following description an advantageous embodiment of the invention will be described in detail with reference to the attached drawing, wherein in

Fig. 1 a reaction chamber supported by a structure of metal profiles is shown in perspective view, Fig. 2 is a top view of the supporting frames which are placed adjacent to each other and in which the substrates will be inserted, in

Fig. 3 a loading container containing a plurality of adjacent supporting frames is shown in perspective top view, in Fig. 4 is a perspective, partially cut-out sectional view of the reaction chamber, wherein the chamber is rotated by -90° with respect to the view of Fig. 1, in

Fig. 5a to 5d a planar electrode plate is shown in side view (5a) with full view of the lateral side, in side view (5b) from the direction of its edge, in top view (5c) and a cut-out of Fig. 5c is shown in the enlarged view of fig. 5d; in

Fig. 6 a planar electrode plate is depicted in side view where the outer lateral plate of the electrode is removed and the heater element disposed in the inner volume of the electrode is seen;

Fig. 7 is a cross sectional view of a bolt fastening together the two lateral plates of the planar electrode and a planar heater element disposed between the lateral plates.

The reaction chamber 1 in fig. 1 has a framework made of 10a, 10b, 10c consoles. The 10a,

10b, 10c consoles are perpendicular to each other and are arranged along x, y and z directions, respectively. Dimensions and materials of the 10a, 10b, 10c consoles are selected so as to have sufficiently large load bearing capacity for holding the reaction chamber 1 which is very heavy in its loaded state. In the drawing it is not shown, but the walls provide an air tight sealing of the reaction chamber 1 and during operation in the inside of the reaction chamber 1 a background pressure lower than the atmospheric pressure is present, which is necessary for the reaction. The inner volume of the reaction chamber 1 comprises a structure of parallel, spaced apart plates. Said inner structure is partially made up by substrates 2, here substantially rectangular glass plates - depicted in the enlarged partial view of Fig. 2 - and on one surface of the glass plates a semiconductor thin layer or thin layer structure is to be deposited in the reaction chamber 1, for example by a CVD process and finally, on said plates photovoltaic devices are formed. The thin layer structure may comprise layers not made of semiconductor materials; such layers are built in a separate deposition step in the same or in a different reaction chamber 1. Such deposition step may comprise e.g. the formation of a slightly conducting layer on top of the active surface of the glass substrates 2. In Fig. 1 it is schematically shown that the substrates 2 are surrounded and supported along their side edges and along their bottom by supporting frames 3. These frames form an interconnected supporting structure, this structure being attached to the bottom closing lid 6 of the reaction chamber 1. This whole mechanical structure in the form of a loading container 5 can be loaded in a properly guided manner into the reaction chamber 1 from the bottom, upwards along the z direction and when the layers are deposited the loading container can be unloaded. In Fig. 1 the whole structure is shown at the beginning of the loading step.

In the same figure there is shown the upper lid of the reaction chamber 1 with connectors V to which a heater F and a generator G is connected through wiring. The heater F is connected by means of connecting elements which also have a function of 43 threaded rods. A further connecting element 44 protruding from the upper lid of the reaction chamber 1 is used for the connection of the radio frequency ( F) generator G. On the upper lid of the reaction chamber 1 a number of such threaded rods 43 and connecting elements 44 are arranged in a manner to be described later in detail. In this diagrammatic view only three of them are shown in order to schematically represent the connection of the heater F and the generator G.

On the two opposite sidewalls of the reaction chamber 1 perpendicular to the y direction an inlet channel 50 for introducing the reaction gases and an outlet channel 51 for removing the reaction byproducts are arranged. Between the inlet channel 50 and the outlet channel 51 the direction of gas flow is parallel to the plane of substrates 2.

Fig. 2 is a top view of an enlarged section of the supporting frames 3 in which the substrates

2 are inserted. In the inventive batch-processing equipment, which is capable to simultaneously handle a plurality of large 2 substrates, a number of supporting frames 3 are placed adjacent to each other - in Fig. 2 three of them are shown. Each supporting frame 3 comprises three recesses: two recesses 4b of identical shape and thickness, and a third recess 4a formed between said two recesses 4b and being deeper and having larger width than said two recesses 4b. Recesses 4b have a dimension so that substrates 2 /e.g. glass plates used as substrates/ can snugly fit into them. Thickness of the substrates 2 is between about 0.5 mm and 5 mm, preferably 2 mm, thus the width of said two recesses 4b is also in this range. The actual width of recess 4b must be determined in advance, e.g. by etching, according to the actual size of substrates 2 to be used in the apparatus. The supporting frames 3 are made of an electrically insulating and mechanically rigid material, which also have sufficient resistance against compositions participating in the reaction to be carried out in the inner volume of the reaction chamber 1 and can also withstand high pressure and high temperature existing in the chamber. The supporting frames 3 are placed adjacent to each other in a periodic structure. For example in Fig. 2 going from left to right first comes a recess 4b which belongs to a first supporting frame 3, then recess 4a and again recess 4b belonging to the same frame 3 is seen, then we see a very narrow gap 4c dividing the first supporting frame 3 from the next adjacent supporting frame 3, then recess 4b, recess 4a and again recess 4b of the adjacent supporting frame 3 is seen etc.

In Fig. 3 the loading container 5 to be introduced into the reaction chamber 1 is shown in elevational perspective view from above and for the sake of better visibility some details are hidden. For example the substrates 2 which are supported in the recesses 4b are not seen. Each supporting frame 3 consists of two lateral frame parts 3b and a bottom frame part 3a which together are joined to a single, rigid mechanical structure. The supporting frame 3 is open from above, thus it supports the substrates 2 only on the bottom and from the sides. This is particularly important, since the substrates 2 are inserted into the recesses 4b of the supporting frame 3 from the top which is kept open. In the loading container 5 built up by a plurality of supporting frames 3 the following periodic structure is seen - using reference signs of Fig. 2: a recess 4b then a recess 4a and again recess 4b of the same supporting frame 3, then a small gap 4c between two adjacent supporting frames 3 and in the loading container 5 this period is repeated in a finite number. The number of supporting frames 3 is chosen on the basis of practical aspects, their number is preferably 25 to 50. Here the number of substrates 2 to be loaded is twice the number of frames. Each supporting frame 3 in the loading container 5 has the same dimensions. The supporting frames 3 and their recesses can firmly support the large glass plate substrates 2 during loading and unloading operations and the reaction. Lateral frame parts 3b of each supporting frame 3 are slightly longer than the height of the substrates 2; whereas the bottom frame parts 3a of the supporting frames 3 are slightly longer than the width of substrates 2. Size of the substrates 2 corresponds to the size foreseen for the devices to be fabricated and can be set to different values. The most preferred range is between 50 cm x 75 cm and 150 cm x 200 cm; a very frequently used dimension is 100 cm x 150 cm.

The supporting frames 3 which comprise more frame parts are made of an electrically insulating material. Such materials can be chosen among plastics or ceramics, e.g. alumina or Teflon, but for this purpose other electrically insulating materials with high mechanical hardness can also be used i.e. glass, minerals, composite materials etc. It is not excluded to make the supporting frames 3 of metal, however, in this case the metal surface must be covered by an insulation layer.

The bottom of the loading container 5 is fastened to the bottom closing lid 6 which is disposed below the bottom frame parts 3a and is attached to the supporting frames 3 and has a broad rim portion. In order to make the structure more rigid the two outermost supporting frames 3 limiting the loading container 5 in the lateral direction are connected to fastening plates 71 and on the rear side or in the middle of the vertically oriented lateral frame parts 3b apertures are provided through which threaded bolts 72 are guided in the transversal direction, the ends of the bolts are fastened by means of nuts, and these bolts keep all lateral frame parts 3b together. Similarly, on the bottom the bottom frame parts 3a are kept together by threaded bolts 73 and corresponding nuts. The whole structure is held firmly together on the bottom by the bottom closing lid 6.

In Fig. 4 the reaction chamber 1 is shown in a partially cut-out, perspective view, with the loading container 5 being in an intermediate phase of loading. The cut-out is made such that one quarter of the chamber is removed at a one corner of the reaction chamber 1 and the important elements inside are also visible. The reaction chamber 1 is rotated by -90° degree with respect to the view of Fig. 3, which can be observed from the different orientation of the substrates 2. In order to provide better visibility of the change of orientation x, y and z directions are also shown. The x, y, z directions form here as well a right-handed coordinate system, however the x and y axes point to other directions, rotated by -90° degree.

From the upper part of the reaction chamber 1 planar, rectangular, spaced apart, equidistant and parallel electrodes 40 are suspended towards the bottom and during the upwards movement of the frames each electrode along its width reaches into recesses 4a of the supporting frames 3 and the recesses support and guide the electrodes. In this manner an interpositioned, comb-shaped plate structure is formed, in which two substrates 2 always enclose an electrode 40, and on the side of the substrates 2 opposite to the electrodes 40 a volume suitable for gas flow is formed. Due to this advantageous arrangement during introduction into the reaction chamber 1 the substrates 2 line up in a comb-shaped manner between the electrodes 40 which are fixed in their positions in the chamber 1. Between the substrates 2 volume 20 and volume 21 are alternating. The volumes 20 are reaction volumes for reaction gases. Into volumes 21 the electrodes 40 are inserted. Loading is completed when the substrates 2 are all the way slid into the reaction chamber 1 with the electrodes 40 interpositioned between them. In this position the flattened part 41 (rims) of each electrode 40 fits into recess 4a of the respective supporting frame 3 and is firmly supported and guided therein. In each recess 4a the respective electrode 40 is inserted with a small play such that sufficiently large space is left for deformations due to thermal dilatation. Even further, electrode 40 is inserted with a small play into volume 21 between two substrates 2 such that sufficiently large space is left between the substrate 2 and the electrode 40 for deformation due to thermal dilatation. As it has been shown earlier recess 4a is deeper than the two recesses 4b encompassing it. Consequently, in a completely loaded position the electrodes 40 slightly reach over the surfaces of the substrates 2. In this manner we achieve that in the region of the substrate 2 surfaces inhomogeneous plasma conditions and related fluctuations and transient processes of the deposition conditions are suppressed and the quality and thickness of the deposited layer is homogeneous.

Thus, in the fully loaded position the electrodes 40 and the substrates 2 which are completely slid between them form a sandwich structure in which e.g. the following come periodically in a consecutive order: a substrate 2 placed into a recess 4b corresponding to a first supporting frame 3, an electrode 40 placed into recess 4a, again a substrate 2 placed into recess 4b, then the volume 20 between substrates 2 of two adjacent supporting frames 3 (which volume is eventually a broadened extension of the gap 4c between two adjacent supporting frames 3 and extends further between the substrates 2), then a subsequent substrate 2 inserted into recess 4b corresponding to a supporting frame 3 next to the first one, an electrode 40 inserted into recess 4a and again a substrate 2 inserted into recess 4b etc. In the loading container 5 introduced into the reaction chamber 1 this periodic structure is repeated in finite number. ln Fig. 4 it is shown that the bottom of the loading container 5 is fastened to the bottom closing lid 6 which has a broad flange and is disposed below the lower 3a frame parts and is connected to the 3 supporting frames. In order to hold the structure in place the outermost supporting frames 3 limiting the loading container 5 in the lateral direction are connected to fastening plates 71 and on the rear side or in the middle of the vertically oriented lateral frame parts 3b apertures are provided through which threaded bolts 72 are guided in the transversal direction, and these bolts keep all lateral frame parts 3b together. Similarly, on the bottom the bottom frame parts 3a are kept together by threaded bolts 73 and corresponding nuts. The whole structure is held firmly together on the bottom by the bottom closing lid 6.

According to a preferred configuration ribs 8 are attached to the lateral frame parts 3b of the supporting frames 3 by releasable fastening means, e.g. by screws. One single rib 8 is responsible to connect three adjacent supporting frames 3. The ribs 8 may contain cut-outs, e.g. grooves 9, which are positioned so that the grooves 9 overlap with the gaps 4c between the supporting frames 3, when the structure is installed. As a result, during the CVD process the gases enter the reaction chamber 1 by flowing through the grooves 9 of the ribs 8, then flow into the gaps 4c between the supporting frames 3 and flowing further in the direction of the inside of the chamber the gases enter the volumes 20 between two substrates 2. These volumes 20 form reaction spaces for igniting a plasma and to maintain an intended chemical reaction.

A main feature of the reaction chamber 1 is that the electrodes 40 are suspended from the inner side of the upper part of the reaction chamber 1 - using directions of Fig. 4 - and are fixed at the same place in such manner that from the upper part of the reaction chamber 1 planar, rectangular, spaced apart, equidistant and parallel electrodes 40 are extending towards the middle.

The structure of the electrode 40 plate is shown in detail in Figs. 5a to 7. According to Fig. 5a the electrode 40 comprises two threaded bolts 43 which are protruding from the upper part of the electrode 40. Said threaded bolts 43 are introduced into holes provided in the upper lid of the reaction chamber 1 and said threaded bolts 43 are fastened to the lid of the reaction chamber 1 by releasable connecting elements, e.g. by screws. The threaded bolts 43 serve - beyond fastening - as electric connectors for the electric power supply of the heater. At the upper edge of the electrode 40 a further connector element 44 is disposed for connecting the RF generator G. The electrodes 40 are suspended by releasable connecting means, however during normal operation conditions e.g. between two CVD cycles these connections do not need to be disconnected. This means that the heating F cables and the connections of the radio frequency generator G need not to be disconnected, which makes the implementation of the CVD process easier, more reliable and thus, productivity is improved. With the aid of the threaded bolts 43 the electrodes 40 are firmly fixed, and protrude vertically from the upper lid of the reaction chamber 1 towards the inside of the reaction chamber 1; between two edges of the electrodes 40 and the reaction chamber 1 a gap is formed. The lateral frame parts 3b of the supporting frames 3 of the loading container 5, into which the substrates 2 are loaded, can be inserted into this gap. In Fig. 5a reference number 41 indicates the flattened parts along the side and bottom edges of the electrode 40. When the loading container 5 is introduced into the gap between the edges of the electrodes 40 and the reaction chamber 1, the flattened parts 41 along the side and bottom edges slide into the recesses 4a of the lateral frame parts 3b of the supporting frames 3. When the container is fully inserted, the flattened parts 41 of the bottom edge are engaged and supported in recesses 4a of the lower frame parts 3a of the supporting frames 3, and flattened parts 41 along both lateral edges of the electrodes 40 are all the way inserted and kept in place in the recesses 4a of the lateral frame parts 3b of the supporting frames 3. In this manner the flattened parts 41 are responsible to firmly support the electrodes 40 against the substrates and the supporting frames 3. On the lateral plate 40b of the electrode 40 screws 42 are provided.

In the side view of Fig. 5b it is seen that the electrodes 40 are comprised of two lateral plates

40b and a central plate 40a disposed between the lateral plates 40b. Screws 42 extend through the lateral plates 40b and the central plate 40a of the electrode 40. This configuration ensures that the lateral plates 40b and the central plate 40a are aligned parallel to each other. The parallel arrangement of the lateral plates 40b and the central plate 40a ensures that between the plates 40b, 40a no electrical connection is established. In essence, the central plate 40a is provided as a meander shaped resistance heater for heating the electrode 40. The lateral plates 40b and the central plate 40a are made of metal, preferably an acid resistant metal, which can withstand the chemically aggressive environment being present during the CVD reaction.

In Fig. 5c the electrode is shown in top view. Here the most important visible parts are the threaded bolts 43 and the connector element 44. Electrical power supply of the central plate 40a - which plate operates as a heater element - is coupled through the threaded bolt 43. The electric current passes into the central plate 40a on through one threaded bolt 43, as an electrical connector, on a first side and another threaded bolt 43 arranged on the other side works as the terminal electrode for the drain. The two connectors of opposite polarity are arranged on the upper edge of the same electrode 40 but on opposite sides of the edge. Threaded bolts 43 are separated from the lateral plate 40b of the electrode 40 by insulation, so they are electrically not connected. Connector element 44 serves as the electrical connector of the generator G. The generator G is connected to both lateral plate 40b of the electrodes. The central plate 40a can be regarded as a conductor which is placed in a Faraday-cage built up by the lateral plates 40b and being completely intact by the radio frequency field of the generator G. The poles of the RF generator G are connected to the electrodes 40 in such manner that two opposite poles of the generator, i.e. the warm- and the hot spot, is connected to two neighboring electrodes 40. Thus, the electrodes 40 are arranged in a sequence in which during operation one electrode 40 is the hot spot and the neighboring electrode 40 is always the cold spot or ground potential, periodically.

The number of electrodes 40 is determined by practical aspects, their number is preferably 25 to 50, from which during operation 12 to 25 is connected to the hot spot of the generator G and 12 to 25 to the cold spot of the generator G. In the interpositioned, comb-shaped plate structure of Fig. 4 each two substrates 2, which are in contact with an electrode 40 connected to the hot spot, are connected to the same hot spot potential. This electrode 40 is arranged in the volume 21 between said two substrates 2. The other substrate 2 pairs which stay in contact with each second electrode 40 connected to the cold spot, are connected to the same cold spot potential. We have also shown that on the side of the substrates 2 opposite to the electrodes 40 always a volume 20 for gas flow is present. The substrates 2 which are disposed on the other side of the volume 20 for gas flow are on ground potential. Consequently, as the electrodes 40 are arranged in a periodic sequence in which during operation one electrode 40 is the hot spot and the neighboring electrode 40 is always the cold spot or ground potential, accordingly, substrates 2 which are in contact with the hot spot electrodes 40 are also connected to hot spot potential, and substrates 2 which are in contact with the cold spot electrodes 40 are also connected to cold spot or ground potential. The plasma is always formed in volume 20 between substrates 2 which form hot spot - cold spot pairs. In Fig. 5d the region around the threaded bolt 43 of electrode 40 is shown in enlarged view. In this view the lateral plates 40b are well visualized. Width of the lateral plates 40b is smaller than width of the electrode 40 itself. It is also well visualized that between the lateral plates 40b and the central plate 40a a hollow space is formed, thus the electrical circuits of the heater F and the radio frequency generator G are well insulated from each other.

In Fig. 6 an electrode 40 is shown, however, here the lateral plates 40b are removed, and the central plate 40a or heater element in the inside of the electrode 40 is visible. In the inside of the electrode 40 the central plate 40a is wound according to a meander shape. Details of the structure of the heater element can be understood even better with the aid of "A" and "B" cut-outs. The threaded bolt 43 on one side of the upper edge of the electrode 40 is connected to the central plate 40a guided in meander shape in the inside of the electrode 40. The threaded bolt 43 on the other side of the upper edge of the electrode 40 is connected to the other terminal end of the central plate 40a guided in meander shape in the inside of the electrode 40. The heating current flows through a first threaded bolt 43, then through the meander-shape central plate 40a and exits through the other HU I /HU201 2 O U 0 0 7 2 threaded bolt 43 as an output port. The central plate 40a is fixed at several points to the lateral plates 40b by means of screws 42. The screws 42 extend through the lateral plates 40b and the central plate 40a of the electrode as well and the parallel arrangement of the lateral plates 40b and the central plate 40a is thus achieved. The way how fastening is effected with the aid of the screws 42 is shown in detail in Fig. 7 where the electrical insulation of the lateral plates 40b and the central plate 40a can be understood.

In Fig. 7 the lateral plates 40b include an opening 45 at the position of every screw 42. Between the parallel lateral plates 40b and central plate 40a a hollow space 47 is formed (on both sides of the central plate 40a). The spacers 46 made of a suitable ceramic material and surrounding the screws 42 have the function to keep the distance of this hollow space 47. In the figure it is clearly shown that the spacers 46 have a shape which is suitable to maintain an electrical contact between the lateral plates 40b and the screws 42, however, the central plate 40a is insulated both from the lateral plates 40b and the section of the screw 42 extending through the inside of the electrode 40.

With the above electrode structure we achieve that in a batch-type equipment, applicable to simultaneously deposit various layers onto a plurality of large substrates 2, the simultaneous F supply and heating of the electrodes 40 is solved. This implies that heating of the substrates 2 in the reaction chamber 1 can be carried out in situ, i.e. there is no need to have a preliminary preheating step before the substrates 2 are introduced into the reaction chamber 1. Further, due to the large size of the central plate 40a homogeneous heating of the substrates 2, including their entire area, results in a more homogeneous temperature distribution and thus more stable conditions for layer deposition and finally a better layer quality. Even further, with the aid of the in situ heating the conditions of layer deposition can be modified which means that in one chamber more CVD reaction types can be applied.

The proposed heater element provides a quick and evenly distributed heating-up process and as a consequence the cycle time will be shorter and the energy required to heat up the inner volume of the reaction chamber 1 is decreased. For CVD reactions the surface temperature of electrodes 40 is set generally to 200°C.

Claims

1. Electrode structure for reaction chambers (1), wherein the reaction chamber (1) is applicable for the deposition of a semiconductor layer or layer structure on a surface of a plurality of substrates (2) in substrate batches, and the reaction chamber (1) comprises a body with an inner volume and an upper lid and closing bottom lid (6), in the inner volume rectangular plate-like substrates (2) are arranged in a spaced apart relationship with each other and metal electrodes (40) suitable for providing high-frequency electromagnetic field in order to deposit a thin material layer are disposed between the substrates (2); each electrode (40) is disposed in a spaced-apart relationship adjacent to the surface of the substrate (2) not to be deposited; and each space extending between the surfaces to be deposited forms a flow channel making available the laminar flow of reaction gases between two opposite sides of the reaction chamber (1); the opposite electrodes (40) are connected to a high-frequency generator (G) and the closed inner volume of the reaction chamber (1) is provided with a heater (F), characterized in that the electrodes (40) are comprised of

- two parallel, spaced apart lateral plates (40b) which are connected to each other;

- a central plate (40a) disposed in the inner volume between the lateral plates (40b), and being aligned parallel to and being insulated from the lateral plates (40b); wherein

- the lateral plates (40b) are connected to the high-frequency generator (G) and ends of the central plate (40a) are connected to the power supply of the heater (F).

2. Electrode structure according to claim 1, characterized in that each electrode comprises:

- two threaded bolts (43) protruding from the upper edge of the electrode (40) in the neighborhood of the two opposite ends of the edge, respectively;

- a connector element (44) disposed in the central region of the upper edge of the electrode (40); wherein

- the lateral plates (40b) and the central plate (40a) are fixed to each other by means of screws (42);

- the lateral plates (40b) are connected to the RF generator (G) through the connector element (44);

- the central plate (40a) is provided as a meander shaped resistance heater and is connected to the power supply of the heater (F) by the threaded bolts (43); and

- the lateral plates (40b) and the central plate (40a) are aligned parallel to each other in such manner that no electrical contact is formed between them.

3. Electrode structure according to claim 1, characterized in that in order to provide good electrical insulation, in the attachment points provided by screws (42) between the lateral plates (40b) and the central plate (40a) spacers (46) of ceramic material are disposed and by means of said spacers (46) hollow spaces (47) are formed between the lateral plates (40b) and the central plate (40a) and two respective lateral plates (40b) are in contact with each other indirectly through the screw (42) and the central plate (40a) is not in contact with the screw (42).

4. Electrode structure according to claim 1, characterized in that the central plate (40a) has a meander shape.

5. Electrode structure according to claim 1, characterized in that poles of the RF generator (G) are connected to the electrodes (40) in such manner that two opposite poles of the generator, i.e. the warm- and the hot spot, is connected to two neighboring electrodes (40) and in the reaction chamber (1) the electrodes (40) are arranged in a sequence in which during operation one electrode (40) is the hot spot and the neighboring electrode (40) is always the cold spot or ground potential, periodically.