WO2010049186A1

WO2010049186A1 - Precursor disposal

Info

Publication number: WO2010049186A1
Application number: PCT/EP2009/059227
Authority: WO
Inventors: Philipp Hotz; Stefan Schneider; Benjamin Vogler; Peter Probst
Original assignee: Oerlikon Solar Ip Ag, Trübbach
Priority date: 2008-10-31
Filing date: 2009-07-17
Publication date: 2010-05-06
Also published as: TW201017793A

Abstract

The present invention provides a system for the disposal of waste of substrate treatment systems which comprises at least one process module connected to at least one reservoir and at least one abatement system, wherein the reservoir collects the waste produced by the process module and wherein the waste collected in the reservoir is transferred to the abatement system and wherein the waste comprises a substance selected from the group consisting of pyrophoric metalorganic chemicals, phosphine, diborane, silane, dimethylzinc and/or diethylzinc. Thus, the production of waste by the substrate treatment system is decoupled from the disposal of the waste by the abatement system. This has the advantage that the abatement system can be designed to be capable of handling an average waste load from the substrate treatment system, whereby no unused overcapacities of the abatement system need to be accepted.

Description

Precursor disposal

FIELD OF THE INVENTION

The present invention relates to the field of substrate treatment systems. Particularly, the present invention discloses a method and apparatus for the handling and abatement of residuals resulting from production and/or cleaning of substrate treatment systems such as coating or deposition systems.

BACKGROUND OF THE INVENTION

Photovoltaic devices, photoelectric conversion devices or solar cells are devices which convert light, especially sunlight into direct current electrical power. For low-cost mass production thin film solar cells are being of interest since they allow using glass, glass ceramics or other rigid or flexible substrates as a base material, i.e. a substrate, instead of crystalline or poly crystalline silicon. The solar cell structure, i.e. the layer sequence responsible for or capable of the photovoltaic effect is being deposited in thin layers. This deposition may take place under atmospheric or vacuum conditions. Deposition techniques are widely known in the art, such as PVD, CVD, PECVD, APCVD, or MOCVD all being used in semiconductor technol- ogy. Pyrophoric metalorganic chemicals such as dimethylzinc and diethylzinc can be used as precursor for the deposition of ZnO in thin film deposition application as used for solar cell manufacturing. Commonly liquid precursors are employed, which are evaporated in a first process step to form a vapor, which is then used for the process of coating objects.

The pyrophoric metalorganic chemicals and further substances such as phosphine, diborane and silane, which are commonly used in the deposition processes are mostly toxic, flammable, and/or a health hazard. Thus, special precautions have to be taken handling them.

Generally, an abatement system has to be installed to take care of treating said pyrophoric metalorganic chemicals and further substances and to dispose them in a way not to harm the environment. Abatement systems based on burning these substances, washing, transforming them with a liquid process, or a combination thereof into less or non hazardous material are commonly used and installed with the main system, i.e. the coating, treatment or deposition system, using these precursors.

In general, the abatement systems have to cope with two situations:

Firstly, they have to handle the waste amount of the pyrophoric metalorganic chemicals and further substances during normal operating conditions of the main system. This is due to the fact that every system using precursors, like pyrophoric metalorganic chemicals, is typically characterized by a utilization rate of less than 100 %, for example 80 %. Thus, the remaining 20 % of the precursor that is not deposited during the process is usually exhausted from the main system and then transferred to the abatement system for disposal.

Secondly, for handling the liquid precursors and evaporating them, storage tanks, pipes, and/or evaporators are used, which have to be cleaned periodically. During such cleaning cycles drained liquids are produced that need to be disposed of, too. Furthermore, after a cleaning cycle of the whole system will have to be flushed with the precursor substances, i.e. the pyrophoric metalorganic chemicals and further substances, in order to reestablish an equi- librium in the system. During this procedure the utilization rate is 0 %, i.e. all of the precursor substances that are used to flush the system have to be disposed of.

The toxic, flammable and/or hazardous waste generated during cleaning and/or flushing of the system may be collected and shipped to an external facility for disposal. However, such pro- ceedings are restricted by local and international law, are difficult and, in turn, very costly. These drained liquids may thus additionally be transferred to the abatement system but will generate peak loads. If abatement systems are used for the disposal of such peak loads, the systems have to be able to handle such peak flows of gases and/or liquids. Thus, under normal operating conditions where only average flows have to be handled, such abatement systems have a considerable overcapacity. However, particularly in industrial large-scale systems, such unused overcapaci- ties have to be avoided since they entail high unnecessary expenses. Furthermore, since the abatement system will be operated in at least two different modes, i.e. one mode for the disposal of an average amount of waste during normal operation, and another mode for the disposal of a peak load of waste after cleaning and/or flushing of the system, a process optimization of the abatement system is difficult to carry out. Thus, such abatement systems do not operate at optimal conditions at all times, which eventually will produce unnecessary expenses, too.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system for the disposal of waste resulting from production and/or cleaning of substrate treatment systems, wherein no overcapacities of an abatement system have to be accepted and wherein a process optimization of the abatement system can be carried out.

This object is achieved by a system according to claim 1. In particular, the system for the disposal of waste of substrate treatment systems comprises at least one process module connected to at least one reservoir and at least one abatement system, wherein the reservoir collects the waste produced by the process module, wherein the waste collected in the reservoir is transferred to the abatement system and wherein the waste comprises a substance selected from the group consisting of pyrophoric metalorganic chemicals, phosphine, diborane, silane, dimethylzinc and/or diethylzinc. Thus, the waste generated by the processing module is buffered by the reservoir and not directly transferred to the abatement system. In turn, the buffered waste is then fed from the reservoir to the abatement system. - A -

Accordingly, it is an essential idea of the invention to decouple the production of waste by the substrate treatment system from the disposal of the waste by the abatement system. This has the advantage that the abatement system can be designed to be capable of handling an average waste load from the substrate treatment system, whereby no unused overcapacities of the abatement system need to be accepted. In other words, the throughput of the abatement system needs not to be designed for peak flows of waste, but can be configured to cope with an average flow. System cost, operating conditions and capacity utilization will therefore improve. Another advantage is that the abatement system can preferably be run in an optimized and/or continuous mode, further improving its performance and consequently reducing costs, too. Finally, another advantage of the present invention is that the abatement system can be run during downtime of the substrate treatment system, e.g. during cleaning, maintenance, service, loading and/or unloading.

The substrate treatment system can be any system using a precursor substance to treat a substrate. In one embodiment the substrate treatment system is a coating and/or deposition system. In a further embodiment the substrate treatment system is used for the production of photovoltaic devices, photoelectric conversion devices, solar cells, and/or semiconductors. In a further embodiment the substrate treatment system is used for the deposition of thin layers. In a preferred embodiment, the substrate treatment system is a large-scale and/or industrial size substrate treatment system as such systems of bigger size produce greater amounts of waste and are highly dependent on the proper disposal of such waste. Furthermore, with such systems of bigger size even the smallest unused overcapacities of the abatement system and/or suboptimal process control generate extremely high costs.

The process module may be any module of the substrate treatment system that is in contact with a precursor substance used in the substrate treatment process. In one embodiment of the invention the process module is a vapor deposition module. The deposition may take place under atmospheric or vacuum conditions. Preferably the process module is a chemical vapor deposition (CVD) or physical vapor deposition (PVD) module. More preferably, the process module is a plasma enhanced CVD (PECVD), an atmospheric pressure CVD (APCVD) and/or a metal-organic CVD (MOCVD) module. In another preferred embodiment the process module is used for thin film deposition, more preferably for ZnO thin film deposition. In another embodiment of the invention the substrate treatment system contains > 1 process module.

The reservoir can be any container that is suitable to store the waste produced by the substrate treatment system, preferably by the processing module. In one embodiment the reservoir is dimensioned to contain at least the amount of waste produced during normal operation of the substrate treatment system. Preferably, the reservoir is dimensioned to contain at least a peak load of waste, i.e. at least the amount of waste generated during cleaning and/or flushing of the substrate treatment system. This has the advantage that the packaging, transport, shipping and subsequent external disposal of the waste created during cleaning and/or flushing of the substrate system, i.e. of storage tanks, pipes, process modules and/or evaporators, or a combination thereof is eliminated as the produced waste can be disposed of by the abatement system. In another embodiment of the invention the substrate treatment system contains > 1 reservoir. In a further embodiment the container is a cylinder with a volume of 20 liters.

The waste preferably comprises a precursor chemical used by the substrate treatment system. Such waste further preferably comprises any liquid, solid material or gas that is toxic, flammable, and/or a health hazard. In a more preferred embodiment the liquid, solid material or gas comprises pyrophoric metalorganic chemicals, phosphine, diborane and/or silane. Even more preferably, the liquid, solid material or gas comprises dimethylzinc (DMZ) and/or diethylzinc (DEZ). In another preferred embodiment the waste is produced during normal operation of the substrate treatment system, preferably when the utilization rate of the precursor is less than 100 %. In a further preferred embodiment the waste is produced during cleaning and/or flush- ing of the substrate treatment system, for example during cleaning of the storage tanks, pipes, process modules and/or evaporators used for the handling and evaporating of the precursors or during flushing of the system with the precursors in order to reestablish an equilibrium in the substrate treatment system, i.e. when the utilization rate is 0 %.

The abatement system can be any kind of abatement system known in the art. In one embodiment the abatement system is based on burning the waste, washing the waste and/or transforming the waste with a liquid process into less or non hazardous material. Preferably, the abatement system is based on burning the waste. In another embodiment of the invention the substrate treatment system contains > 1 abatement system.

In a preferred embodiment the abatement system is designed to dispose an average amount of waste produced by the substrate treatment system. For example, the substrate treatment system produces 100 % of waste during cleaning and/or flushing of the system and produces 20 % of waste during normal operation of the system. Then the abatement system may be designed to be capable to dispose 30 % of the waste or even less, depending on the size of the reservoir. In a preferred embodiment the abatement system is operated continuously, with fixed process parameters and/or with a fixed rate or turnover. This has the advantage that the abatement system can be fine tuned, i.e. a process optimization of the abatement system can be carried out such that said system operates at an optimal and most efficient level. For example, with a conventional abatement system that is based on burning of the waste the flame used for the burning will have to be adjusted to the amount of waste that is currently fed into the abatement system. This entails suboptimal results as the efficiency and completeness of the burning process is dependent on, e.g., the temperature of the flame which changes if the flame has to be adapted to cope with a larger amount of waste fed into the abatement system. In contrast, as the abatement system of the present invention can be continuously run with optimized and fixed process parameters the flame can be set to the optimal temperature for the most efficient burning of the waste. In a further preferred embodiment the abatement system is run with 100 % or close to 100 % of the capacity it is designed for, thus no unused overcapacities will result. It will be understood that if more than one abatement system is present then these abatement systems are preferably run with 100 % or close to 100 % of their total capacity.

The waste collection in the reservoir and the transfer to the abatement system may achieved by several means known to the skilled person. Preferred examples for such means are connecting pipes/conduits, pumps and/or overpressure that are used to move and/or transfer the waste. Preferably, the process module is connected to the reservoir by at least one pipe and the reservoir is connected to the abatement system by at least one pipe. Transfer of the waste within the pipes, i.e. from process module to reservoir and/or from reservoir to abatement system is affected by means of pumps and or overpressure. In another preferred embodiment the waste is initially transformed into the gas phase, preferably by means of evaporation, for example by reduction of the pressure by a vacuum pump, and then transferred to or from the reservoir. Thus, in a preferred embodiment the system of the present invention furthermore comprises at least one pipe connecting the process module to the reservoir, at least one pipe connecting the reservoir to the abatement system, at least one pump, at least one means to produce an overpressure and/or at least one means for the evaporation of the waste.

In a further preferred embodiment the system of the present invention further comprises at least one means for flow restriction and/or flow control that is arranged between the reservoir and the abatement system and/or between the reservoir and the process module. Preferably, said means is arranged between the reservoir and the abatement system to ensure that the capacity of the abatement system is not exceeded. The means for flow restriction and/or flow control can consist of a sensor, preferably an optical, sonic or pressure sensor, measuring the amount of waste passing through the piping connecting reservoir and abatement system and a controller, e.g. a microprocessor, connected to the sensor. Said controller can then be utilized to control a valve that is arranged within the piping connecting the reservoir and the abate- ment system and/or to control the pump, means for generating an overpressure and/or means for evaporation comprised by the system of the present invention.

As the control of the material flow has not to be very precise, also robust instruments and ma- terial flow control means can be employed.

As stated above the system according to the present invention can comprise more than a single process module, more than a single reservoir and/or more than a single abatement system. In a preferred embodiment of the invention the system comprises more than one process module. This has the advantage that the number of abatement systems of the system may be reduced and/or that only a single abatement system is comprised by the system of the present invention. Thus, preferably, a number of p_ process modules are connected to a number of a abatement systems via a series of r reservoirs, wherein a < p and/or r < p and/or a < r. Thus, the system preferably comprises less abatement systems than process modules, a smaller or the same number of reservoirs than process modules and/or a smaller or the same number of abatement systems than reservoirs. Most preferably a < p and r < p and a < r.

In another aspect, the present invention is directed to a method of operating the system according to the invention and/or a method for the disposal of waste of a substrate treatment system, i.e. waste produced by a substrate treatment system. Particularly, the method for the disposal of waste of a substrate treatment system comprises the steps of: a) Collecting the waste produced by the substrate treatment system in at least one reservoir; and b) Transferring the waste collected in the reservoir to at least one abatement system, wherein the waste comprises a substance selected from the group consisting of pyrophoric metalorganic chemicals, phosphine, diborane, silane, dimethylzinc and/or diethylzinc.

As has been described above, the waste generated by the processing module is thus initially buffered by the reservoir and not directly transferred to the abatement system. In turn, the buffered waste is then fed from the reservoir to the abatement system. Thus, the production of waste by the substrate treatment system is decoupled from the disposal of the waste by the abatement system. Advantageously, the throughput of the abatement system needs not to be designed for peak flows of waste, but can be configured to cope with an average flow. Thus, by employing the method of the invention system cost, operating conditions and capacity utilization will therefore improve.

The preferred embodiments and advantages of the method according to the invention correspond to those described for the system of the invention above. Particularly, the abatement system can preferably be run in an optimized and/or continuous mode, further improving its performance and consequently reducing costs, too. Furthermore, the abatement system can preferably be run during downtime of the substrate treatment system, e.g. during cleaning, maintenance, service, loading and/or unloading.

In particularly preferred embodiments of the invention the abatement system is operated continuously, with fixed process parameters and/or with a fixed rate or turnover. In further particularly preferred embodiments of the invention the abatement system is operated with 100 % or close to 100 % of the capacity it is designed for.

Further advantageous embodiments of the present invention are given in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings: Fig. 1 shows a schematic representation of the system according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows a system for the disposal of waste of an industrial size substrate treatment system 1 according to the present invention comprising four LPCVD process modules for the deposition of ZnO 2 connected to two reservoirs 3 and a single abatement system 4. Thus, a number of p_ process modules are connected to a number of a abatement systems via a series of r reservoirs, wherein a < p and r < p and a < r. The reservoir collects the waste produced by the process module during normal operation of the substrate treatment system and during cleaning and/or flushing of the substrate treatment system. Said waste is consequently fed to the abatement system.

The reservoirs 3 are dimensioned such that they can contain 150 % of the peak load of waste produced by each of the respective process modules connected to them.

The abatement system 4 is an abatement system that is based on burning of the waste and it is designed to dispose the average amount of waste produced by the four process modules 2. The abatement system is operated continuously, with fixed process parameters for an optimal burning of the waste and is operated with about 100 % of the capacity it is designed for.

The waste is initially transferred from the process modules 2 to the reservoirs 3 by means of the connecting pipes 5, 6, 7, 8. The waste collected by the reservoirs is then further transferred to the abatement system 4 by means of the connecting pipes 9, 10. The transfer is achieved by pumps. Connecting pipes 8, 9, 10 further comprise a flow control 11 consisting of a sensor measuring the amount of waste passing through the piping and a controller controlling a valve. The flow control ensures that the capacity of the abatement system and the reservoir is not exceeded.

During operation of the system 1, deposition of ZnO takes place within the process modules for a time of 5 minutes followed by an unloading of the deposited substrate and reloading of new substrate to be processed. The unloading/reloading procedure takes 2 minutes, during which no precursor, e.g. DEZ, is fed into the process modules and thus no waste is produced.

However, during these 2 min waste is fed from the reservoirs 3 into the abatement system 4 and consequently disposed. During the whole cycle of 7 minutes, the abatement system is operated continuously with fixed process parameters for an optimal burning of the waste and with about 100 % of the capacity it is designed for.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.

Claims

1. A system for the disposal of waste of a substrate treatment system (1) comprising at least one process module (2) connected to at least one reservoir (3) and at least one abatement system (4), wherein the reservoir collects the waste produced by the process module, wherein the waste collected in the reservoir is transferred to the abatement system and wherein the waste comprises a substance selected from the group consisting of pyrophor- ic metalorganic chemicals, phosphine, diborane, silane, dimethylzinc and/or diethylzinc.

2. The system according to claim 1, wherein the process module is selected from the group consisting of a CVD module, a PVD module, a PECVD module, an APCVD module and/or an MOCVD module.

3. The system according to claim 1, wherein the reservoir is dimensioned to contain at least a peak load of waste produced by the substrate treatment system.

4. The system according to claim 1, wherein the waste is produced during normal operation of the substrate treatment system and/or during cleaning and/or flushing of the substrate treatment system.

5. The system according to claim 1, wherein the abatement system is designed to dispose an average amount of waste produced by the substrate treatment system.

6. The system according to claim 1, wherein the abatement system is operated continuously, with fixed process parameters and/or with a fixed rate or turnover.

7. The system according to claim 1, further comprising at least one pipe (5, 6, 7, 8) connecting the process module to the reservoir, at least one pipe connecting the reservoir to the abatement system (9, 10), at least one pump, at least one means to produce an overpressure and/or at least one means for the evaporation of the waste.

8. The system according to claim 1, further comprising at least one means for flow restric- tion and/or flow control (11) that is arranged between the reservoir and the abatement system and/or between the reservoir and the process module.

9. The system according to claim 1, wherein a number of p process modules are connected to a number of abatement systems via a series of r reservoirs, wherein a < p and/or r < p and/or a < r.

10. Method for the disposal of waste of a substrate treatment system, comprising the steps of: a) Collecting the waste produced by the substrate treatment system in at least one reservoir (3); and b) Transferring the waste collected in the reservoir to at least one abatement system

(4), wherein the waste comprises a substance selected from the group consisting of pyrophor- ic metalorganic chemicals, phosphine, diborane, silane, dimethylzinc and/or diethylzinc.

11. The method according to claim 10, wherein the abatement system is run during downtime of the substrate treatment system.

12. The method according to claim 10, wherein the flow of transfer of the waste from the reservoir to the abatement system is monitored by a sensor and/or controlled by a control- ler connected to the sensor.