Patent Application
20090293810
The invention relates to an arrangement for coating a substrate.
Arrangements for coating a substrate with cadmium sulfide or zinc cadmium sulfide or with OLED substances are already known (U.S. Pat. No. 4,401,052, DE 102 24 908 A1, EP 1 357 200 A1). Herein the materials with which the substrate is to be coated are vaporized in vaporizers.
With these arrangements, however, no materials are vaporized which belong to the group alkali- and/or alkaline earth-metals, because these metals are highly reactive and form compounds with glass and water. Of the alkali- and alkaline earth-metals, lithium is in particular of interest since it is suitable for the production of only extremely slowly discharging batteries and accumulators.
Modern lithium batteries came first on the market in 1991. With them, Li+ ions are exchanged between a graphite (LixC6) anode and a layered oxide (Li1-x TMO2) cathode, TM being a transition metal—cobalt, nickel or occasionally manganese. At an average voltage of 3.8 V the energy density is approximately 180 Whkg−1, which is approximately the fivefold of the considerably older lead-acid battery.
The most recent developments in the field of Li+ batteries involve the use of nanomaterials. Moreover, lithium-oxygen batteries are being investigated, which comprise an oxygen cathode and a lithium anode (M. Armand and J.-M. Tarascon: Building Better Batteries, Nature, Vol. 451, 7 Feb. 2008, pp. 652-657).
Lithium batteries are also produced as thin-layer batteries (WO 02/099910 A1, p. 1, lines 17-20). The application of the thin layers takes place by sputtering. During the sputtering ions, for example of lithium orthophosphate are deposited on a substrate. Through reactive sputtering an electrolyte layer of LixPyONz can be applied.
It is also known to apply thin layers of SiO2 and lithium by means of PECVD (=Plasma Enhanced Chemical Vapor Deposition) onto a substrate (U.S. Pat. No. 6,177,142 B1).
Further known is the coating of a substrate with Li—Co—O, wherein an electron beam vaporizer is being utilized (JP 2003 234 100).
In another known arrangement for the production of thin layers of lithium or lithium alloys on a substrate, lithium, located in a crucible, is vaporized under vacuum (JP 2002 206 160).
The invention addresses the problem of providing an arrangement for coating a substrate, wherein the coating material can also be a member of the group of chemically reactive alkali- and alkaline earth-metals.
The advantage attained with the invention comprises in particular that a vaporizer crucible can readily be replenished or exchanged free of risks. This is of significance in particular for highly reactive materials to be vaporized, for example lithium, since these must not be contacted nor be exposed to normal atmosphere, oxygen or water.
The invention consequently relates to an arrangement for the coating of a substrate by means of a vapor distributor. This vapor distributor is connected with a vaporizer crucible via a feed system. Between the crucible and the feed system at least one valve is disposed. The vaporizer crucible is located in a chamber which can be evacuated or flooded via a vacuum valve by means of a gas supply and a vacuum pump.
Embodiment examples of the invention are shown in the Figures and will be described in further detail in the following. In the drawing depict:
The vapor feed system 1 comprises a vertically oriented vaporizer tube 3, opposite to which is disposed a substrate 4 to be coated. The vaporizer tube 3, which is provided with several, linearly vertically disposed vaporizer nozzles, is connected with an inlet tube 5 which is directed at right angles to the vaporizer tube 3. This vaporizer tube 3, consequently, serves as a vapor distributor. Parallel to the vaporizer tube 3 and perpendicularly to the inlet tube 5 is provided a cylindrical vaporizer crucible 7, which is located in a crucible housing 8. If reactive materials, for example lithium, are vaporized, the crucible 7 is, for example, comprised of stainless steel, titanium or molybdenum. Beneath the vaporizer crucible 7 is located a cylinder 9 with a piston 10. The vaporizer crucible 7, which in
However, since not only the crucible 7 is exposed to the reactive material, it is obvious that the entire vapor feed system must be comprised of a material that is inert relative to these reactive materials.
In this crucible chamber 12 is located a linear guide 31 which contributes to the stabilization of the crucible chamber 12. On this linear guide 31 is disposed a guide element 32 that is connected to the vaporizer crucible 7. By moving the guide element 32 along the linear guide 31 the vaporizer crucible 7 is also moved along the linear guide 31, i.e. in the direction of arrows 33 and 34.
With the aid of a separating valve 13, shown in
Within the crucible chamber 12 is further evident a holding arrangement 36 that is placed onto the piston 10. A thermocouple 44 is wound from a vacuum-tight power feedthrough 50 in a spiral about the holding arrangement 36 and terminates in an indentation 51 located in the bottom of crucible 7. By means of the thermocouple 44 the temperature at the bottom of the vaporizer crucible 7 can be measured. The spiral winding of the thermocouple 44, that, on the one hand, is fastened on the power feedthrough 50 and, on the other hand, on the holding arrangement 36, permits the necessary lift of crucible 7 from a lower into an upper position. This is illustrated in
In
Evident is also a cooling means port 37, in
By 20 is denoted a crucible heating system that encompasses the vaporizer crucible 7. This crucible heating system 20 is connected with a PID controller 21 which, in turn, is connected with a rate acquisition 22. This rate acquisition 22 can be provided with a measuring instrument 23, for example an oscillating crystal or an emission spectroscope. This measuring instrument 23 acquires the vaporization rate of the material which reaches the substrate 4 from the vaporizer tube 3. For this purpose in the vaporizer tube 3 a special nozzle 24 is provided which generates a rate signal that is proportional to the coating rate on the substrate 4. Through this nozzle 24 streams the vapor onto the measuring instrument 23. In this manner, the crucible heating system 20 can be regulated as a function of the coating rate. On the PID controller 21 can also be set a nominal value. Instead of a PID controller, another controller can also be provided. The PID controller involves the general basic type of a controller comprised of the parallel circuit of PD controllers and I controllers, whose properties—early detection of disturbances, rapid correction and elimination of regulation deviation—it combines. If the regulated process contains dead times, the PID controller cannot be utilized due to its D component.
The vapor exiting the vaporizer tube 3 through the perpendicularly linearly disposed holes is shown symbolically by arrows 26. The holes are laid out such that high vaporization rates and uniform coating are attained. For example, they have a diameter of 1 mm to 4 mm and a distance of 5 mm to 30 mm. To compensate the layer thickness decreases in the margin regions of substrate 4, the holes or nozzle bores can here be located more closely to one another and, for example, only have half the distance from one another. Instead of cylindrical holes, elongated holes or other forms of openings are also conceivable.
The housing of the separating valve 27 must be implemented such that it is vacuum tight, however, the gate of the valve only needs to be diffusion-tight against gases. Since after flooding of crucible 7 to atmospheric pressure, no pressure difference with respect to the ambient air exists, the gate of the valve 27 does not need to absorb any vacuum forces.
In the representation of
In the depiction of
It is understood that exchanging the crucible 7 or also filling it is only possible with the valve 27 open. The vaporizer crucible 7 must therefore be encompassed by the glovebox 40 filled with the protective gas.
As is shown in
After filling the crucible 7 with the vaporization material, the separating valve 27 is closed and the crucible chamber 12 is evacuated. Subsequently crucible chamber 12 and vaporizer crucible 7 move along rail 30 back into their rearward position by moving in the direction of arrow 42. After the separating valves 13 and 27 have been connected vacuum-tight with one another and the crucible chamber 12 has been evacuated, the separating valves 13, 27 can be opened. The vaporizer crucible 7 is subsequently brought into the upper position by movement in the direction of arrow 33.
According to a further embodiment example, which is not depicted, the glovebox 40 can be located spaced apart from the coating installation. In this case the crucible 7 under protective gas is removed with the valve 27 closed in the pulled-out position shown in
The above described processes can be utilized for the coating of glass substrates. However, using them, it is also possible to coat silicon wafers of 200 mm or 300 mm diameter, wherein a substrate carrier can be equipped with one or with several wafers. A substrate carrier is, however, not shown in
Moreover, flexible substrates of synthetic material or metal can also be worked in an installation, such as for example depicted in FIG. 3 of EP 1 589 130. In this known installation only the vapor distributor tube and the vapor exit nozzle would need to be disposed horizontally and parallel to the sheeting.
It is understood that, instead of one crucible, several crucibles can also be provided and be interconnected in the manner described in EP 1 357 200 A1.
In conclusion, the present invention provides, among other things, a system and method for coating a substrate. Those skilled in the art can readily recognize that numerous variations and substitutions may be made in the invention, its use and its configuration to achieve substantially the same results as achieved by the embodiments described herein. Accordingly, there is no intention to limit the invention to the disclosed exemplary forms. Many variations, modifications and alternative constructions fall within the scope and spirit of the disclosed invention as expressed in the claims.
