TWI437120B - Parallel plate reactor for uniform thin film deposition with reduced tool foot-print - Google Patents

Description

Parallel plate reactor for uniform film deposition with reduced tool footprint

The present invention relates to a capacitively coupled parallel plate plasma enhanced chemical vapor deposition reactor comprising a gas distribution unit integrated in an RF electrode and comprising a gas outlet.

Capacitively coupled plasma enhanced chemical vapor deposition (PECVD) reactors are commonly used to deposit thin films on substrates, such as semiconductor substrates used to fabricate solar cells. It is important to use a high spatial uniformity of the substrate surface for the plasma manufacturing process. That is, a deposition process should be performed such that the deposited material has a uniform thickness and quality at all locations on the surface of the substrate.

The concept of such a parallel plate reactor is characterized by a parallel plate-like electrode arrangement in which the electrodes are arranged in a hermetic, closed, and temperature controlled chamber. This closed chamber is connected to a vacuum pumping system of its own and has its own gas supply. Such parallel plate reactors are also often used in a vacuum chamber that is also equipped with its own pumping system.

Typically, an asymmetric RF voltage is used to provide plasma generated by electrical energy in the parallel plate arrangement. This RF voltage is provided by an RF generator. Typically, the plasma excitation frequency used is in the range of between 13 MHz and about 80 MHz. At least one of the two parallel electrodes, particularly the RF supply electrode, has a gas distribution system to provide a reaction space with the gas in the parallel plate reactor.

The reaction space of a parallel plate reactor is primarily defined by the dimensions and distance between the electrodes and the walls of the reaction chamber. A so-called pumping grid provided on the side of the RF electrode is used to electrically separate the reaction space in the gas discharge direction. The pumping grid is constructed of a conductive material and is gas impermeable. Often, two pumping grids are applied in an opposite arrangement. With this configuration, it is possible to perform mutual symmetrical evacuation of the reaction space. The distance between the electrodes is determined by technical needs and is typically in the range between about 10 mm and 30 mm. The substrate to be processed is usually placed on a ground electrode.

A technical advantage of a parallel plate reactor concept is the presence of a closed, defined reaction space and a small available gas buffer volume of the supplied gas. Thus, the time between the ignition of the plasma and the adjustment of an equilibrium state of the plasma chemical reaction and thus to the adjustment of the steady-state gas composition within the reaction space is very short. This is especially important for the limited deposition of a plurality of very thin layers. A final layer gradient formed by the transient vibrational behavior of the plasma deposition process will thus be strongly reduced.

With a parallel plate reactor, the necessary requirements for cleaning and the special requirements of certain processes can be easily met. By causing the gas space separation between the parallel plate reactor and the vacuum chamber in which the reactor is placed, a pressure differential of several orders of magnitude between the atmosphere and the process pressure is achieved. Therefore, the partial pressure and thus the influence of atmospheric gases on the preparation process can be strongly reduced. Furthermore, the transfer of process gases used to the vacuum chamber and adjacent chambers is prevented.

It is also very advantageous to separately clean the parallel plate reactor independently of the surrounding space of the vacuum chamber. A well-induced, thermally induced separation of the vacuum chamber is possible by a generally tightly packed parallel plate reactor. The wall heater integrated in the reactor is arranged for uniform temperature control of the substrate.

The effectiveness of the surface treatment by a parallel plate reactor is essentially dependent on the possible process parameters and the requirements for the achievable uniformity. Important process parameters are, for example, the plasma excitation frequency, the RF power, the process pressure, the total gas flow rate, and the mixing ratio of the gases used. For plasma enhanced chemical vapor deposition (PECVD), the available layer deposition rates are often very important. This layer deposition rate is primarily affected by the plasma excitation frequency used and the RF power used herein. The higher the excitation frequency, the higher the density of electrons and ions in the plasma. At the same time, the arcing voltage on the electrode arrangement can be reduced, with the ion energy reaching the surface of the substrates decreasing with it. Furthermore, at higher plasma excitation frequencies, the dissociation or fragmentation of the gases used is more dense, whereby a higher deposition rate can be achieved in particular.

Many designs have been developed to improve the spatial uniformity of the plasma manufacturing process. Some designs, such as US Patent Application No. 2009/0159423 A1, focus on forming a uniform plasma density because asymmetry in plasma density is undesirable because it produces a corresponding correspondence in the plasma process performed on the substrate. Asymmetry. It is further necessary to provide a uniform gas distribution in a plasma chamber which can be achieved by means of so-called showerhead electrodes. The showerhead is comprised of one or more gas distribution plates or diffusers having a plurality of apertures that form a plurality of gas outlet passage paths within the showerhead. This showerhead combines the function of an RF electrode with a gas distribution in a unit.

Since the holes in the showerhead electrode plates are dependent on the velocity of the gas flow through the holes and the cross-sectional area of the holes, the gas distribution plates on the layers deposited on the substrate are often present through the showerhead. An "image" of a hole distribution. That is, the deposited layer forms a wavy surface in which the crests are formed directly under the holes.

Furthermore, known reactors are typically subjected to an incomplete shadowing around the reactor, resulting in unnecessarily inserting particles into the reactor chamber.

It is therefore an object of the present invention to provide a capacitively coupled parallel plate plasma enhanced chemical vapor deposition reactor of the type mentioned above, with which a layer having a high thickness uniformity and quality can be produced.

The object is solved by a capacitively coupled parallel plate plasma enhanced vapor deposition reactor comprising a gas distribution unit integrated in the RF electrode and comprising a gas outlet, wherein the gas distribution unit comprises a plurality A stage showerhead constructed in such a manner as to provide an independent adjustment of the gas distribution and gas emission characteristics of the gas distribution unit.

The gas distribution in the deposition zone of a parallel plate reactor depends mainly on the specific conditions of the gas supply of the fresh gas and the specific conditions of the gas outlet of the gas used or the decomposition product of the gas used, which conditions do not contribute to The formation of a layer. As mentioned above, in the known showerheads used in parallel plate reactors, the gas emission characteristic curve is directly dependent on the gas distribution provided by the corresponding gas distribution unit and results in the above The contour of the wavy surface of the deposited layer. In contrast, the invention proposes a gas distribution unit comprising a sprinkler configuration which separates the gas distribution from the formation of the gas emission characteristic and thus enables adjustment of the gas distribution on the one hand and not on the other hand Depend on each other to provide a certain gas emission characteristic curve. This results in a uniform layer deposition, especially in the case of films.

Preferably, the inventive concept can be implemented by a capacitively coupled parallel plate plasma enhanced vapor deposition reactor comprising a gas distribution unit integrated into the RF electrode and comprising a gas outlet, wherein The gas distribution unit includes at least one perforated first gas distribution plate and at least one perforated second gas distribution plate spaced apart from the first gas distribution plate in a gas flow direction through the reactor, in the second The holes in the gas distribution plate are configured to have a larger cross section than the holes in the first gas distribution plate, and wherein a plurality of individual holes or sets of holes in the first gas distribution plate are A plurality of separate gas buffer volumes are provided between the second gas distribution plates, wherein the gas buffer volumes are configured to have a larger cross-section than the holes in the second gas distribution plate.

In the present invention, the requirements necessary for the gas supply to adjust a uniform layer deposition may be by a locally applicable pattern opposite the deposition area and by the individual dimensions of the gas holes in the different plates of the showerhead. achieve. In accordance with the present invention, the size of the gas holes is sized such that the amount of gas flowing through each gas port is defined in dependence on the total gas flow rate necessary for the plasma process. For this reason, a corresponding gas buffer formed by separate gas buffer volumes between the holes of the first and second gas distribution plates within the electrode is used, resulting in the following effects: A separate gas orifice provides a sufficient amount of gas.

The present invention brings the possibility of providing a preferred gas management and thereby adjusting the profile of the layer deposited on the substrate. The first gas distribution plate of the showerhead acts as a plate with a low gas guiding effect due to its smaller aperture, resulting in a relatively small flow of gas escaping from the orifice of the first plate. Flow diameter. If this gas stream impinges directly on the surface of the substrates, the area of the substrate below the gas stream will be deposited at a higher layer thickness than the other regions.

According to the present invention, this gas stream does not directly impinge on the surface of the substrate but flows into the gas buffer volume, which respectively corresponds to each hole of the first gas distribution plate. The gas flow is distributed within the space provided by the corresponding gas buffer volume after each orifice of the first plate, resulting in an increase in the diameter of the gas stream. When the gas buffer volumes connect the apertures of the first and second gas distribution plates, the gas flow thereafter passes through the apertures in the second gas distribution plate of the showerhead. The second gas distribution plate is preferably parallel to the first gas distribution plate and has a greater gas guiding effect than the first gas distribution plate by a larger hole formed in the second gas distribution plate. Thus, this well-distributed gas flows through the holes in the second gas distribution plate with a large spreading angle and high uniformity.

The gas flow from the holes of the second gas distribution plate can be adjusted by appropriately selecting the gas flow guiding action of the first and second gas distribution plates by means of the second gas distribution plate Part of the gas flow that escapes from adjacent holes overlaps and forms a layer having a relatively uniform thickness on the surface of the underlying substrate. By separating the plurality of gas buffer volumes from each other, it is further achieved that the gas flow escaping from the plurality of holes of the first gas distribution plate does not mix with each other.

The principles of the present invention are still effective when more than two showerhead gas distribution plates are used and where several holes of the first and/or second plates are combined to form a plurality of sets of holes.

The reactor of the present invention can be implemented in that the holes in the second plate are configured to have a larger cross-sectional area than the holes in the first plate, and the gas buffer volume is configured to have the same The holes in the second plate have a larger cross-sectional area. In that configuration, the gas buffer volumes have a cylindrical form that can be constructed by drilling. In other embodiments of the invention, the sidewalls of the gas buffer volumes may be inclined such that the gas buffer volumes have a smaller diameter near the first plate and are larger near the second plate. diameter. In any case, the gas buffer volumes are sufficiently large and long enough to allow the gas flow within the gas buffer volume to expand in a balloon and to perform a good gas distribution within the gas buffer volume so that the gas can The high uniformity is guided almost linearly through the large holes in the second plate to the substrate.

The relationship between the hole diameter of the hole in the second gas distribution plate and the hole diameter of the hole in the first gas distribution plate can be easily adapted to the corresponding requirements of the parameters of the reactor and the deposition layers. .

According to another embodiment of the invention, the first gas distribution plate has a guiding effect of the gas flow such that it can cause a gas pressure drop which is necessary to achieve a gas barrier function through the first gas distribution plate. . In order to achieve this, the gas flow directing action of each gas orifice and the total gas flow directing action of all the orifices of the first gas distribution plate are adjusted in such a way as to produce an appropriate reduction in gas pressure on the gas distribution unit. This gas pressure reduction should be adjusted so that the gas blocking effect known in vacuum technology is achieved for each hole.

This gas barrier is also referred to as a blocked flow, which can be observed during air venting in a vacuum box. During the opening of the vent valve, air flows from the environment to the tank at a certain pressure and at a high speed. The magnitude at which the speed can reach its maximum sonic velocity and flow therethrough does not depend on the internal pressure of the tank. In order to achieve the effect of the present invention, it is therefore preferred to configure the pores of the first gas distribution plate to have a cross section such that gas flowing through the pores during operation of the reactor can be achieved Sound speed. Preferably, the size of the gas holes is adjusted in such a way that the gas barrier effect will be maintained over the entire varying region of total gas flow and at processing pressures for all possible processes.

In a preferred embodiment of the invention, in order to achieve this blocking action, the first gas distribution plate comprises a perforated foil having a defined orifice arrangement.

In order to properly secure the apertured foil, in another development of this embodiment, an additional apertured plate can be used. The additional apertured plate can be used as a mask for the apertured foil to achieve independent adjustment of the gas distribution and thereby the overall gas flow directing effect of the selected apertures in the foil.

The first and second gas distribution plates may be formed by two or more separate plates stacked one on another such that not only the gas distribution may be formed by the special configuration of the first and/or second gas distribution plates The holes can also form a gas buffer volume between the holes.

Furthermore, the holes of the second gas distribution plate may be provided with a plurality of countersinks on the gas escape side and/or the gas inlet side. Such countersinks can be used to properly adjust the gas emission profile of the gas distribution unit.

According to another example of the present invention, the hole density of the second gas distribution plate is correspondingly at the edge thereof (in the region of the pumping grid provided adjacent to the side of the RF electrode) corresponding to the second gas distribution The central part of the board is higher. In this way, the air flow is more direct and more intense at the edge of the board. Increasing the flow at the edges helps repay the energy loss due to friction between the gas and the edges, which maintains the harmonic motion of the flow.

Furthermore, it may be useful to provide additional multi-venting distributor plate holes at an outer edge of the gas distribution unit in the gas outlet direction of the reactor.

By optimizing the size adjustment and arrangement of the individual gas orifices, the gas flow rate in the corresponding gas orifices varies depending on the total gas flow rate. This effect has a simultaneous effect on the gas outlet characteristic curve of the gas orifice. Depending on the magnitude of the flow velocity of the gas particles and the distance between the electrodes, inconsistencies in the local layer thickness on the substrate may occur in the gas pore region. In that case, it may be necessary to control other process parameters.

In order to remove the gas used for uniform gas removal from the deposition zone, uniform gas discharge by the pumping grid provided on the side of the RF electrode of the reactor in the gas outlet direction of the reactor is necessary. Typically, this is accomplished by a plurality of gas discharge devices arranged after pumping the grid in the direction of gas flow through the reactor or by a plurality of universal devices that permit flow correction. At high gas flows and low electrode distances, significant pressure reduction can occur in the direction of the pumping grid depending on the corresponding process pressure. It is also possible to reduce the uniformity of the layer thickness that is achievable by the high electrode size and thus the edges of the gas particles to the electrodes and the long path to the gas outlet. In order to reduce this problem, a double-sided gas discharge hole can be used at the discharge gap of the parallel plate arrangement and the gap between the electrodes can be adapted to the corresponding technical requirements.

In a specific embodiment of the invention, the pumping grid provided beside the RF electrode and the gas outlet of the reactor are correspondingly equipped with a plurality of gas evacuation extending in the direction of gas flow through the reactor. aisle. The gas evacuation passages provide a gas pressurization unit after the pumping grids by which a direct gas flow toward one or more gas outlet orifices of the reactor can be avoided. In this way, a new gas flow management can be provided on the back side of the pumping grids, thereby providing the possibility of achieving an almost complete deposition uniformity over the entire deposition area of the parallel plate reactor.

In a variation of this embodiment, the evacuation channels are formed by a plurality of parallel gas deflectors provided after the gas is passed through the reactor in the direction of flow. The gas deflectors push an elongated and straight gas flow toward the gas outlet. The use of a gas deflector is a method for significantly reducing airflow disturbances within the plasma.

Furthermore, it has been shown that in order to reduce the effect of the combined gas flow line on plasma uniformity, the pumping zone should have a certain length. This length is reduced in the present invention by applying a force to the gas stream to achieve a straight flow in the desired direction. In this example of the invention, this force is applied by using the gas deflectors on the gas exit path of the reactor. That is, the gas deflectors do not interfere with the reaction within the processing space of the reactor and the formation of layers. The reduction in the pumping zone results in a reduction in the reactor footprint at a given electrode area.

In an alternative embodiment of the invention, the evacuation channels may be integrated into at least one wall of the reactor to provide a relatively long pumping zone. In this case, it is especially preferred to provide a pumping from the top of the reactor. With such a design, the length of the gas path between the pumping grid and the pumping orifice can be extended while the additional dimensions in the deposition plane of this additional gas path can be minimized. Therefore, the proposed new gas emission design makes it possible to significantly improve the footprint of the reactor at a given deposition area without reducing the length of the long path between the pumping grid and the gas outlet. Excellent deposition uniformity.

In a desirable form of this embodiment of the invention, the gas deflector includes several parallel panels provided after pumping the grid in a direction in which the gas flows through the reactor. The panels may be rectangular panels and are mounted to push the gas to flow in the desired flow direction. The use of a panel-shaped deflector makes it possible to guide the gas flow over a long distance clearly and easily. Thus, the use of a deflector makes it possible to avoid any airflow disturbances in the plasma caused by the combined gas flow lines towards the pumping orifice. When such deflecters are not used, the pumping zone must be long enough to reduce the effect of the combined gas flow lines towards the pumping orifice on plasma uniformity. Thus, the use of a deflector allows for reducing the footprint of the reactor at a given electrode area by avoiding large pumping zones. The realization of highly oriented gas flow depends on the length of the panel. By increasing the length of the panel, a better gas flow orientation can be obtained.

In another option of the invention, at least one additional grid is provided between the pumping grid and the gas outlet of the reactor, the additional grid having a reduced gas compared to the pumping grid Flow guiding role. An additional grid with a smaller gas flow directing effect enables orientation to be maintained and increases the accuracy of gas flow generated by the pumping grid.

Preferably, the additional grid has a total gas flow directing effect that enables the grid to produce a reduction in gas pressure under a predetermined gas flow, the reduction being achieved for achieving the gas barrier system mentioned above necessary. It is further possible to size the pumping grid of the reactor such that the gas barrier is provided by the pumping grid under a predetermined gas flow.

In a preferred form of the invention, the gas outlet orifice of the reactor is provided in a deposition plane or at the top of the reactor. Providing the outlet orifice in a deposition plane is the best way to obtain a certain flow due to a very short distance between the deflector and the outlet orifice. Mounting the outlet orifice at the top provides a very long distance between it and the inlet orifice that will act to redirect the flow at this distance.

In the case of extensive thin layer deposition using a parallel plate reactor, the achievable deposition uniformity is primarily affected by the plasma and gas distribution in the deposition zone between parallel electrode arrangements. This plasma distribution is strongly dependent on a uniform voltage and current distribution at the electrodes. Depending on the size of the electrodes and the plasma excitation frequency used, the uniformity of the plasma former can be primarily adapted to the location of the RF power source, or (where more than one RF source is used) Next) Corresponding requirements for the technical selection of the location of the RF power supply unit. By creating an electrical influence on the grounded sidewall of the RF electrode in the edge region of the electrode arrangement, a uniform electric field can be formed between the RF electrode and the ground electrode, resulting in an uneven surface of the substrate. deal with. This effect can be reduced by variations in the edge geometry of the RF electrode.

To this end, in an embodiment of the invention, the showerhead includes a plurality of elongated, vertical sidewalls that form a vertical perimeter wall of the RF electrode. Such a quasi-local edge rise formed by the elongated vertical or tapered side walls of the showerhead results in the planar portions between the RF electrode plane and the ground electrode plane in the edge region of the parallel plate arrangement Higher symmetry.

In addition to such vertical edge rise, in a more similar variation of the invention, the showerhead can include an elongated tapered sidewall. In doing so, a slanting change-over can be formed from the inner plane of the RF electrode in the direction in which the edge rises. Therefore, the risk of forming a gas vortex (especially in the gas transport direction) can be reduced.

Fig. 1 schematically shows a cross-sectional side view of a capacitively coupled parallel plate reactor 1 in accordance with an embodiment of the present invention. In the example described, the parallel plate reactor 1 is a large area parallel plate reactor for plasma enhanced chemical vapor deposition (PECVD). The reactor 1 is placed in a vacuum chamber 6.

The reactor 1 comprises an RF electrode 2 comprising a gas distribution unit 10. The gas distribution unit 10 is formed as a so-called showerhead and is connected to a single or a plurality of gas connections. According to the invention, the gas distribution unit 10 has a special importance. It significantly affects the uniformity of the plasma process within the reactor 1. The gas distribution unit 10 in the illustrated example consists of a first and a second gas distribution plate 12, 13 arranged in parallel at a very small distance from one another and will be described in more detail with reference to Figures 2 to 4 Description.

The RF electrode 2 has a symmetrical configuration and can be connected to a single or multiple power supplies. The single or multiple power supplies can be used flexibly as a gas inlet, as a cooling or heating connection for the electrode and/or as a mechanical support for the RF electrode 2. The RF electrode 2 includes a plurality of tapered edges 52 in the side view shown. On the other side of the reactor, not shown, the RF electrode 2 is formed to have a plurality of vertically elongated edges. The symmetry of the RF electrode 2 is used to ensure uniform deposition on the side walls of the reactor by reducing or eliminating so-called Telegraph inhomogeneities. The wedge-shaped edge of the RF electrode 2 is used in the pumping direction of the gas through the reactor to effect a non-turbulent gas flow within the plasma of the reactor 1, while the vertically elongated edges of the walls of the RF electrode 2 are preferably On the lateral side, i.e. not in the pumping direction, to avoid any plasma changes to the side walls of the reactor.

At the bottom 51 of the reactor 1, the substrate 5 will be placed to deposit at least one layer thereon. The bottom 51 and the electrode 2 are separated from one another by a spacing S and together with the pumping grids 4a, 4b provided on the side of the electrode 2 limit the plasma space 9. An electrode supply 3 serves as both an RF supply and a gas supply. The electrode supply 3 is electrically insulated and integrated in the reactor 1 and the vacuum chamber 6 in a vacuum sealed manner.

A gas buffer 7 ensures a continuous gas supply to the individual gas orifices of the gas distribution unit 10 without significant pressure differentials within the gas buffer 7. The vacuum chamber 6 includes a pumping orifice 11 for connection to a vacuum pumping system. Further shown pumping orifices 8a, 8b are used for gas venting holes from the process gas used in the plasma space 9. The pumping orifices 8a, 8b are connected to a separate vacuum pumping system and will be provided on the deposition surface as shown in Figure 1 or on top of the reactor as shown in Figure 7 in accordance with the present invention. The gas pressure within the vacuum chamber 6 is typically in the range between about 10 ^-1 Pa and <10 ^-4 Pa. The process pressure in the parallel plate reactor 1 is in the range of from about 1 Pa to about several 100 Pa.

As mentioned above, it is very important to provide fresh gas in a defined manner and to distribute the gas in a defined manner in a PECVD process in a parallel plate reactor (as in reactor 1 of Figure 1). On the other hand, the required distribution of fresh gas is determined by the technical requirements of the plasma space 9 as well as the specific dimensions. These technical requirements include the process conditions necessary for achieving a quality treated substrate, the uniformity of the process, and the process speed requirements. These process conditions are defined by the selection of process parameters. Important process parameters are the number and type of gases used, the gas flow of the individual gases, the total gas flow adjusted with it, the process pressure, and the electrical process parameters. Electrical process parameters include the plasma excitation frequency, the effective electrical work used by the plasma, and specific electrical process conditions, such as if a continuous or pulsed electrical work is used for plasma formation.

Depending on the technical requirements, a necessary adjustment of the gas distribution can advantageously be achieved by the gas distribution unit 10 used in the invention. 2 through 4 schematically illustrate an enlarged cut-away view of several alternative implementations of the region 100 marked in FIG.

Figure 2 shows a variant with two gas distribution plates 12, 13 stacked one on top of the other. The first gas distribution plate 12 has a defined orifice arrangement having a plurality of individual apertures 14 and a plurality of defined gas flow directing values. The first gas distribution plate 12 acts as a gas distribution while simultaneously regulating a defined pressure reduction on this first gas distribution plate 12. Thereby, an overpressure is generated in the gas damper 7 as compared to the process pressure in the plasma space 9. This overpressure depends on the total gas flow through the first gas distribution plate 12.

If this pressure is reduced sufficiently, a so-called gas barrier action occurs. In this case, the amount of gas flowing through each of the holes 14 of the first gas distribution plate 12 is determined only by the initial pressure.

The flow rate of the gas particles within the corresponding holes 14 is varied depending on the gas flow through each of the holes 14, by which the gas emission characteristic curve is also changed. This problem is solved by the second gas distribution plate 13. A plurality of gas buffer volumes 15 are formed in the second gas distribution plate 13. The size of the gas buffer volume 15 is adjusted in such a manner that the cavities of the gas buffer volume 15 are able to positively retain the gas flowing from the holes 14 therein without forming significant back pressure. The gas buffer volumes 15 are sealed against each other such that there is no appreciable gas exchange between the gas buffer volumes 15. By expanding the cross-section of the gas buffer volumes 15 compared to the holes 14, the velocity of the gas particles in the gas buffer volume 15 is strongly reduced.

The second gas distribution plate 13 opposite the substrate 5 includes a plurality of holes 16 connected to the gas buffer volumes 15. These apertures 16 provide an easy adjustment of the gas emission profile. The gas emission characteristic of each orifice 16 can be defined by the length and cross-section of the orifice 16 and by a plurality of additional counterbores of the orifice 16 on the gas escape side and/or the gas inlet side or by continuous Or stepwise variation of the hole diameter to configure.

The gas distribution unit 10 of the present invention is configured to allow for independent adjustment of gas distribution and gas emission characteristics.

The second gas distribution plate 13 may be composed of two or more separate perforated plates or foils. Preferably, each of said plates or foils has a defined porous arrangement having a defined diameter. The thickness of the corresponding plate or foil determines the corresponding hole length.

Figure 3 schematically illustrates a further development of the arrangement of Figure 2. A foil 18, rather than the first gas distribution plate 12, is used in FIG. 3 to limit the gas pressure reduction to provide the gas barrier effect described above. The foil 18 is secured by a perforated plate 17 which provides a defined location of the apertures 20 in the foil 18 and a seal. In addition, the perforated plate 17 may pre-define the gas path through the foil 18 or the number of holes 20 in the foil 18 that are effective for defining the total gas flow directing action of the foil 18. For this purpose, the orifice plate 17 can be used as a mask for the foil 18. The gas can only flow through those holes 20 of the foil 18, on which a plurality of holes 19 of the apertured foil 17 are provided. For this case, it is advantageous for the foil 18 to be formed with a relatively simple and uniform pattern of holes 20 by the same density and size of the holes 20. Therefore, a simple adjustment of the total gas flow guiding action of the first gas distribution plate arrangement independent of the gas distribution is possible.

The second gas distribution plate 13', the gas buffer volume 15', and the hole 16' have the same function as the second gas distribution plate 13, the gas buffer volume 15, and the hole 16 in Fig. 2.

Figure 4 shows schematically a further variant of a gas distribution unit usable in the reactor 1 of the invention. As shown in Figure 3, a foil 22 is used herein together with a perforated plate 21 to regulate this gas barrier. In contrast to Figure 3, each of the apertures 26 of the foil 22 of Figure 4 does not all have a corresponding gas buffer volume. Rather, several apertures 26 of the foil 22 open into a common gas buffer volume 25. This gas buffer volume 25 can be a large hole or a recess of a particular geometry. FIG. 4 exemplarily shows a combination of two holes 26 of the foil 22 that are discharged into a common gas buffer volume 25.

On this side of the substrate 5 in the illustrated example, the gas buffer volume 25 is connected to the three holes 27 of the second gas distribution plate 23. A variant of this gas distribution unit shows the possibility that the copying of the hole arrangement of the first gas distribution plate on the inlet side on the second gas distribution plate on the substrate side is not absolutely necessary in the present invention. Therefore, there is a possibility that the density of the pores is changed independently of the gas barrier action. The number of holes to be joined on the side of the substrate 5 and the specific hole arrangement are produced from the corresponding technical requirements.

Fig. 5 schematically shows a bottom view from the side of the substrate 5 of the second gas distribution plate 13 or a gas distribution unit 10 of an RF electrode 2 correspondingly as shown in Fig. 1. The second gas distribution plate 13 includes a central region 28 having apertures 16 arranged at a relatively low hole density and a peripheral region 29 having a higher aperture density. In the evacuation direction of the gas, additional rows 16 of holes 30a, 30b are provided. As the pore density relative to the selected RF electrode 2 changes, the necessary supply of fresh gas can be adjusted to the requirements of local gas consumption in the plasma treatment. For example, this allows for correction of layer features within the edge regions of the substrate electrodes or for uniformity of deposition within the edge regions.

In addition to the limited supply of fresh gas, the defined emissions of the gases used are very important for the quality and uniformity of the plasma treatment.

Figure 6 is a schematic illustration of a cut through a parallel plate reactor (such as the reactor of Figure 1 or Figure 7), wherein the cutting is parallel to the RF electrode 2, by the plasma chamber, and the pump Part of the grill is completed. Figure 6 shows a pumping grid 31, a pumping orifice 34 and several pumping passages 32 separated by a plurality of walls 33. The distribution of the vented gases over the several pumping passages 32 significantly enhances the uniformity of the gas exiting the plasma chamber because the pumping passages 32 avoid interference with the flow of gases within the plasma. For a uniform pumping result in the region of the pumping grid 31, it is critical to provide the pumping channels 32 with the same gas guiding action before the pumping orifices 34. This gas guiding effect is determined by the cross section and length of the pumping passage 32. A large number of pumping passages 32 promote uniformity of gas emissions to the pumping orifices 34.

Fig. 7 shows schematically another variant of the tight integration of the pumping channels 42a, 42b in the walls 35, 35' of the parallel plate reactor 1' according to the invention. In this variation, the process gas is supplied to a gas buffer 38 of the RF electrode 36 by an electrode supply 37. The gas flows into a processing space 40 by the integrated gas distribution unit 39 of the RF electrode 36. Thereafter, the gases are pumped from the processing space 40 by pumping grids 41a, 41b provided on the sides of the RF electrode 36, respectively. For this purpose, a plurality of pumping orifices provided at the top of the reactor 1&apos; in the illustrated example are connected to a suitable pumping system.

The throughput of the vacuum pump of the pumping system is then directed through the pumping passages 42a, 42b to the pumping grids 41a, 41b. As shown in Figure 6, the pumping passages 42a, 42b are formed by several separate passages. When the gas is discharged by the walls 35, 35' of the parallel plate reactor 1', the pumping passages 42a, 42b can be formed in a very space-saving and tight manner. The direction of gas discharge can be adapted to the particular design of the reactor 1.

In the example depicted in Figure 7, the gas discharge is directed near the center of the RF electrode 36, at the top of the reactor 1'. In other embodiments of the invention not shown, it is also possible to direct the gas onto a region or sidewall of the bottom of the parallel plate reactor. However, the latter alternative has the disadvantage that laborious processing of the pumping channels is required and that the pumping channels must be manufactured to have a certain minimum length.

Figure 8 is a schematic representation of two cross-sectional views of a parallel plate reactor in accordance with the present invention. The top panel shows half of a vertical cut, and the lower view is a top view cut by the plasma space 48 of the reactor. An RF electrode 50, a pumping grid 44 and an additional grid 45 are provided between a bottom 49 and an upper wall 47 of the reactor. The RF electrode 50 and bottom portion 49 form a plasma space 48. The plasma space 48 is separated by a pumping grid 44 in the direction of evacuation of the gas. The additional grid 45 is arranged in the evacuation direction of the gas, which is indicated by the arrow in Fig. 8 directly after the pumping grid 44.

A defined pressure reduction can be achieved on the additional grid 45 by a defined configuration of the additional grid 45 resulting in a defined gas flow directing action of the additional grid 45 and dependence on the total gas flow. small. For example, the grid 45 can be formed from a defined number of suitable holes or slits having a defined gas flow directing effect. In the case where there is such a decrease in pressure on the additional grid 45 to cause a gas barrier, the pumping grid 44 simultaneously causes homogenization of the gas discharge. The material of the additional grid 45 can be adapted to the corresponding mechanical and/or chemical requirements since there is no requirement for the conductivity of the additional grid 45.

In principle, the pumping grid 44 can also assume the function of achieving a gas barrier. However, this is disadvantageous in the process of depositing the plasma, because in such a case, the pumping grid 45 will also be deposited. Thus, a change in the gas guiding action of the pumping grid 45 is produced, resulting in an undefined change in the process parameters. This arrangement is schematically illustrated in Figure 9, wherein similar details of the construction of Figure 9 are similarly referenced to Figure 8. In this configuration, the pumping grid 46 acts as a gas guiding plate which provides a gas barrier as in the other grid 45 of Figure 8, provided that the pumping grid 46 of Figure 9 is constructed of a conductive material. .

Therefore, in the embodiment of the present invention, the gas barrier effect is fully utilized in the fresh gas supply process and in the process in which the used gas is discharged from the treatment space.

The invention makes it possible to deposit a layer having a high thickness uniformity on the substrate, wherein the gas flow at the gas inlet and/or the gas outlet can be well controlled, in particular by gas barrier. The present invention makes it possible to increase the available area for large area deposition and to reduce the gas precursors required for a given throughput. As a result, the source gas consumption, along with the footprint of the deposition tool, can be reduced, resulting in an improvement in cost of ownership.

1. . . reactor

1'. . . reactor

2. . . RF electrode

3. . . Electrode supply

4a, 4b. . . Pumping grille

5. . . Substrate

6. . . Vacuum chamber

7. . . Gas buffer

8a, 8b. . . Pumping orifice

9. . . Plasma space

10. . . Gas distribution unit

11. . . Pumping orifice

12. . . First gas distribution plate

13. . . Second gas distribution plate

13’. . . Second gas distribution plate

14. . . hole

15. . . Gas buffer volume

15’. . . Gas buffer volume

16. . . hole

16’. . . hole

17. . . Perforated board

18. . . Foil

19. . . hole

20. . . hole

twenty one. . . Perforated board

twenty two. . . Foil

twenty three. . . Second gas distribution plate

25. . . Common gas buffer volume

26. . . hole

27. . . hole

28. . . Central area

29. . . Surrounding area

30a, 30b. . . row

31. . . Pumping grille

32. . . Pumping channel

33. . . wall

34. . . Pumping orifice

35,35’. . . wall

36. . . RF electrode

37. . . Electrode supply

38. . . Gas buffer

39. . . Gas distribution unit

40. . . Processing space

41a, 41b. . . Pumping grille

42a, 42b. . . Pumping channel

44. . . Pumping grille

45. . . Grille

47. . . Upper wall

48. . . Plasma space

49. . . bottom

50. . . RF electrode

51. . . bottom

52. . . Wedge edge

100. . . region

Preferred examples of the invention are described in more detail below.

Figure 1 is a schematic cross-sectional side view of a capacitively coupled parallel plate reactor in accordance with an embodiment of the present invention;

2 is a schematic cross-sectional view of a gas distribution unit of a capacitively coupled parallel plate reactor in accordance with an embodiment of the present invention;

Figure 3 is a schematic illustration of another gas distribution unit of a capacitively coupled parallel plate reactor in accordance with a second embodiment of the present invention;

4 is a schematic cross-sectional view showing still another gas distribution unit of a capacitively coupled parallel plate reactor in accordance with a third embodiment of the present invention;

Figure 5 is a schematic plan view showing the pore distribution of a gas distribution plate of a capacitively coupled parallel plate reactor according to another embodiment of the present invention;

Figure 6 is a schematic plan view of a region of a pumping grid of a capacitively coupled parallel plate reactor in accordance with another embodiment of the present invention;

Figure 7 is a schematic cross-sectional side view of a capacitively coupled parallel plate reactor in accordance with yet another embodiment of the present invention;

Figure 8 is a schematic cross-sectional side view showing a region of a pumping grid of a capacitively coupled parallel plate reactor in accordance with another embodiment of the present invention;

Figure 9 is a schematic cross-sectional side view of a region of another pumping grid of a capacitively coupled parallel plate reactor in accordance with another embodiment of the present invention.

1. . . reactor

2. . . RF electrode

3. . . Electrode supply

4a, 4b. . . Pumping grille

5. . . Substrate

6. . . Vacuum chamber

7. . . Gas buffer

8a, 8b. . . Pumping orifice

9. . . Plasma space

10. . . Gas distribution unit

11. . . Pumping orifice

12. . . First gas distribution plate

13. . . Second gas distribution plate

51. . . bottom

52. . . Wedge edge

100. . . region

Claims (12)

A capacitively coupled parallel plate plasma enhanced chemical vapor deposition reactor (1, 1 ') comprising a gas distribution unit integrated in an RF electrode (2, 36, 50, 50') 10) and comprising at least one gas outlet (8a, 8b; 34; 43a, 43b), wherein the gas distribution unit (10) comprises a multi-stage showerhead configured to provide the gas distribution unit ( 10) a gas distribution and an independent adjustment of the gas emission characteristic curve, wherein the gas distribution unit (10) comprises at least one perforated first gas distribution in the gas flow direction through the reactor (1, 1 ') a plate (12) and at least one perforated second gas distribution plate (13, 13', 23) spaced apart from the first gas distribution plate (12), in the second gas distribution plate (13, 13', 23 The holes (16, 16', 27) on the structure are configured to have a larger cross section than the holes (14, 19, 24) in the first gas distribution plate (12), wherein a plurality of individual holes (14, 19, 24) or a plurality of sets of holes (14, 19, 24) of the first gas distribution plate (12) and the second gas distribution plate (13, 13', Between 23) a plurality of separate gas buffer volumes (15, 15', 25) are provided, wherein the gas buffer volumes (15, 15', 25) connect them correspondingly, wherein the gas buffer volumes ( 15,15',25) is configured to be in the second gas distribution plate (13, 13', 23) The holes (16, 16', 27) therein have a larger cross section than the ones. The reactor of claim 1, wherein the first gas distribution plate (12) has a gas flow guiding effect such that it can generate a gas pressure reduction, the reduction being It is necessary for the gas distribution plate (12) to achieve a gas barrier. The reactor of claim 1, wherein the first gas distribution plate comprises a perforated foil (18) having a defined orifice arrangement. The reactor of claim 3, wherein the apertured foil (18) is secured by an additional apertured plate (17). The reactor of claim 1, wherein the holes (16) in the second gas distribution plate (13, 13', 23) are included on the escape side and/or the gas inlet of the gas. Multiple countersinks on the side. The reactor of claim 1, wherein the second gas distribution plate (13, 13', 23) has a pore density at its plurality of edges (29) adjacent to the RF electrode ( In a region of the plurality of pumping grids (4a, 4b) on the side of 2, 36, 50, 50'), correspondingly higher than in the center of the second gas distribution plate (13, 13', 23) Part (28). The reactor of claim 1, wherein the plurality of rows (30a, 30b) of the gas distribution plates (12; 13, 13', 23) are in the reaction. The gas outlet direction (8a, 8b; 34; 43a, 43b) of the device (1, 1') is provided on an outer edge of the gas distribution unit (10). The reactor of claim 1, wherein a plurality of gas evacuation passages (32; 42a; 42b) extending in a gas flow direction through the reactor (1, 1') are correspondingly provided at The pumping grid (31; 41a, 41b) provided on the side of the RF electrode (2, 36) is interposed between the gas outlet (34; 43a, 43b) of the reactor (1). The reactor of claim 8, wherein the gas evacuation passages (32) are in the pumping grid (31) in the direction of gas flow through the reactor (1, 1'). ) formed by a plurality of parallel gas deflecting plates (33) provided thereafter. The reactor of claim 8, wherein the gas evacuation passages (42a, 42b) are integrated in at least one wall (35, 35') of the reactor (1, 1'). The reactor of claim 1, wherein at least one additional grid (45) is correspondingly provided with a plurality of pumpings provided beside the RF electrode (2, 36, 50, 50') Between the grid (44, 46) and the gas outlet of the reactor (1, 1 '), the additional grid (45) has a decrease compared to the pumping grids (44, 46) The gas flow guides. The reactor of claim 11, wherein the pumping grid (46) and/or the additional grid (45) have a guiding effect of gas flow such that the corresponding grid (45, 46) is capable of producing a drop in gas pressure which is necessary to obtain a gas barrier from the grid (45, 46).