EP2459767A1

EP2459767A1 - Cleaning of a process chamber

Info

Publication number: EP2459767A1
Application number: EP10724707A
Authority: EP
Inventors: Rudolf Beckmann; Michael Geisler; Harald Rost
Original assignee: Leybold Optics GmbH
Current assignee: Buehler Alzenau GmbH
Priority date: 2009-07-26
Filing date: 2010-05-28
Publication date: 2012-06-06
Also published as: WO2011012185A1; KR20120054023A; JP2013500595A; CN102597306A; US20120180810A1; TW201126011A

Abstract

The method for cleaning at least one component arranged in the inner region of a plasma process chamber by using a cleaning gas which comprises fluorine gas, the process chamber having at least one electrode and counter-electrode for producing a plasma for the plasma treatment, in particular the CVD or PECVD treatment, of flat substrates with a surface of over 1 m², is distinguished by the fact that the inner region is subjected to gaseous fluorine compounds with a partial pressure of greater than 5 mbar. In a further method V for cleaning at least one component arranged in the inner region of a process chamber by means of a cleaning gas which comprises fluorine gas, the process chamber having at least one electrode and counter-electrode for producing a plasma, in particular for the CVD or PECVD treatment, of flat substrates with a surface of over 1 m², it is provided that the fluorine gas is thermally activated by means of a temperature control medium, the component to be cleaned being at a temperature of < 350°C.

Description

Cleaning a process chamber

The invention relates to a method and a process chamber, each according to the respective preamble of the independent claims.

Substrates for electronic or optoelectronic applications, for example semiconductor elements or even solar cells, are preferably produced by means of PVD, CVD or PECVD processes (PVD: p_hysical yapor deposition CVD: chemical vapor deposition; PECVD: plasma-enhanced chemical vapor deposition)

Prozesskmmern treated, wherein in the process chamber reaction gases are introduced, which are deposited on the substrate.

From WO 2009/0033552 a treatment system for plasma coating of large-area substrates is known, wherein the substrate surface may be in a size of 1 m ² or more. The plasma is generated in a process chamber between an electrode and a counter electrode, between which the substrate to be treated is introduced. A reaction gas is supplied via a gas shower integrated in the electrode. The gas shower comprises a gas shower exit plate with a plurality of outlet openings, with the help of the reaction gas evenly into the

Process chamber is passed.

The coating speed and quality of the plasma deposition depends on several process parameters, in particular pressure, flow and

Composition of reaction gases, power density and frequency of

Plasma excitation, the substrate temperature and the distance between the electrode and the counter electrode or the distance between the substrate surface and the respective counter electrode.

A disadvantage of this coating method is that the reaction gases not only attach to the substrate, and thereby also portions of the process chamber

be coated. The coating of the process chamber can cause particles to dissolve from this coating and contamination of the substrate takes place. If such contamination of the substrate occurs, quality degradation in the coating can be expected.

It is therefore important to clean the process chamber of coatings. For this purpose, a, preferably corrosive, cleaning gas is introduced into the process chamber, which cleans the contaminated surfaces. Since no coating in the vacuum chamber is possible during the cleaning itself and also a certain time after the cleaning, it is desirable to carry out this cleaning as quickly as possible.

Essentially, two cleaning methods are known from the prior art. During in-situ cleaning, a cleaning gas is excited directly in the process chamber, while in remote plasma cleaning excitation of the cleaning gas takes place in an external device and an excited cleaning gas is introduced into the process chamber at low pressure.

The cleaning gas currently used is mainly nitrogen trifluoride NF3. The fluorine species or fluorine radicals provided by the excitation of nitrogen trifluoride can be those used for the coating of solar cells

Silicon compounds, e.g. Dissolve silicon dioxide, silicon oxynitride and / or silicon nitride from the contaminated surfaces. However, nitrogen trifluoride is one

environmentally hazardous gas that acts as a greenhouse gas and an atmospheric one

Has a half-life of several hundred years. In addition, nitrogen trifluoride is very expensive as demand has increased significantly in recent years.

In order to replace nitrogen trifluoride, other fluorine gas mixtures, such as tetrafluoromethane CF 4, have been proposed in the prior art.

Sulfur hexafluoride SF6, or a mixture of argon, nitrogen and fluorine Ar / N ₂ / F2 to use. In particular, it is known from the document EP 1 138 802 A2 to use a cleaning gas with a content of at least 50 vol.% Molecular fluorine, wherein at a chamber pressure between 37OmT and 45OmT the chamber or at least the objects to be cleaned within the chamber on a elevated temperature of about 450 ⁰ C are brought.

The invention is based on the object of cleaning surfaces of a

Component of an interior of a process chamber to provide on the Use of nitrogen trifluoride dispensed, but a fast and effective

Cleaning possible.

The object is solved by the features of the independent claims.

Advantageous embodiments are the subject of the dependent claims.

The method according to the invention for cleaning a surface of at least one component arranged in the inner region of a process chamber by means of

Exposure to a cleaning gas comprising fluorine gas, wherein the process chamber at least one electrode and counter electrode for generating a plasma for plasma treatment of a substrate, characterized by

Acting on the component to be cleaned with fluorine gas and / or gaseous fluorine compounds having a total partial pressure of greater than 5 mbar and / or thermal activation of the fluorine gas and / or gaseous fluorine compounds and

Tempering of the component to be cleaned to a temperature <350 ° C.

In particular, but not necessarily, the process chamber is designed and set up for CVD or PECVD treatment of flat substrates having a surface area greater than 1 m ² . It is preferred if the substrate, electrode and counterelectrode have a flat surface. The surfaces mentioned are preferably planar. It is understood that substrate, electrode and counter electrode can also have concave or convex surfaces.

In the production of amorphous or microcrystalline coatings is a

Process gas pressure between 100 Pa and 2000 Pa, in particular 1300 Pa, and a

Power density between 0.01 W / cm ³ and 5 W / cm ³ , in particular 1 W / cm ^{3 is} preferred. The output power of the HF generator is in a range between 5OW and 5OkW, preferably 1kW. The excitation frequency is in a range between 1 MHz and 150 MHz, preferably 13, 56 MHz. It is proposed according to the invention, fluorine gas, or due to its ease of substitution a fluorine gas mixture to use as a cleaning gas, wherein the total partial pressure in the interior of the chamber is at least in partial areas of the process chamber greater than 5 mbar, preferably greater than 20 mbar. Preferably, molecular fluorine is used, but atomic fluorine can also be used.

Surprisingly, it has been shown that the cleaning rate by the

high partial pressures of the fluorine gas or gaseous according to the invention

Fluorine compounds can be significantly increased. The surface of the component is preferably of a contamination or parasitic coating with in the manufacture of, for example, solar cells used silicon compounds such. Silicon dioxide, silicon nitride and / or silicon nitride cleaned. However, the application to other contaminants is also conceivable.

Particularly advantageous is a total - partial pressure between 20 mbar and 1000 mbar has been found, with very good results can be achieved with a partial pressure of 250-500 mbar. The cleaning gas can be supplied with a partial pressure of fluorine between 20 mbar and 1000 mbar and / or be brought in the process chamber to the mentioned fluorine compound partial pressure between 20 mbar and 1000 mbar.

The cleaning gas can be selected as fluorine gas or as fluorine gas in a carrier gas, for example an inert gas such as nitrogen or argon, with a molar concentration of fluorine of 1%, 10%, 20%, 30% and more in the carrier gas.

According to a further aspect of the invention, a method for cleaning at least one component arranged in the inner region of a process chamber is proposed, which is characterized in that preferably by means of a

Temperature control means, a thermal activation of the fluorine gas takes place, wherein the component to be cleaned has a temperature <350 ⁰ C. In this method, therefore, the component to be cleaned with cleaning gas, which comprises thermally activated fluorine, applied, in contrast to the usual thermal etching, the component to be cleaned or its surface is not heated or only relatively low is, especially compared to the heating of the component during the

Plasma treatment, for example a PECVD or CVD coating.

The component is also according to this aspect of the invention of a contamination or coating with silicon compounds, such as. Silicon dioxide, silicon nitride and / or silicon nitride cleaned. However, in this case, the application to other contaminants is conceivable.

In particular, the component to be purified has a temperature <250 ° C, <200 ° C, <150 ° C, <100 ° C or between 20 ⁰ C and 60 ⁰ C. The thermal activation of the cleaning gas can take place via the contact of the cleaning gas with a heated surface which has a higher temperature than the surface to be cleaned

It is self-evident that a thermal activation can also take place outside the process chamber, for example in a pipe section heated to a temperature of> 350 ° (Remote Thermal Activation).

It is therefore proposed to thermally activate the fluorine gas for cleaning, although, in contrast to conventional thermal etching, the component to be cleaned has relatively low temperatures. Surprisingly, it has been found that such thermal activation of the fluorine makes it possible to

Clean surfaces inside the process chamber and effectively reduce the contamination of the substrate with residuals or parasitic coatings, especially when the component to be cleaned is selected appropriately. Particularly critical areas for parasitic coatings of the process chamber include the electrodes for plasma generation, especially when it has an outlet, for example, an integrated gas shower for reaction gases, which is prone to coating and therefore with a high degree of safety and security

Completeness must be cleaned.

The described method can be combined with thermal etching. By thermal etching is meant here the etching of an object or a surface at elevated temperature of the object or the surface, an increase in the etching rate being exploited as the temperature of the surface to be etched increases. According to a further preferred embodiment, therefore, the cleaning effect can be further increased if parts of the process chamber, In particular, parts of the process chamber which are particularly susceptible to parasitic coatings are heated before or during cleaning.

If at least one component to be cleaned is an electrode, counterelectrode and / or a gas distributor and / or at least one electrode, counterelectrode and / or a gas distributor as temperature control means for thermal activation of the

Fluorine gas is used, the cleaning is done in terms of parasitic

Coating of particularly critical components by spatially obvious

Tempering. It is understood that different components

different temperatures can be brought. For example, an external temperature control can be brought to an elevated temperature, for example to a temperature> 350 ⁰ C, while the electrode is brought to a temperature in the range 20 ° C-80 ° C and the counter electrode to 18O ⁰ C.

If, prior to the application of the cleaning gas by means of a plasma treatment, a substrate is coated with a silicon-containing layer and a residue comprising silicon is formed at least on the component to be cleaned, an integrated coating and cleaning process can thus be provided.

If, during the treatment with the cleaning gas to clean the

Component has a temperature which is at most 1, 8 times the temperature of the component during the plasma treatment, preferably less than 60 ⁰ C, more preferably less than 20 ⁰ C, so that the thermal load of the component to be cleaned and the necessary energy use in the

Cleaning be reduced.

The method can also be used if, prior to the application of the cleaning gas, a substrate having a silicon-containing layer is etched and at least on the component to be cleaned, a silicon-containing residue is formed.

As a surface to be cleaned, at least a portion of the electrode, the

Counter electrode, one of the electrode associated gas distributor, one of

Counter electrode associated substrate support surface or a boiler wall surface of the process chamber is selected and / or during the application of the Cleaning gas, the surface to be cleaned has a temperature which is at most 1, 8 times the temperature of the surface during the plasma treatment, preferably less than 60 ⁰ C, more preferably less than 20 ⁰ C.

By preventing the formation of a residue on a surface region of the electrode, the counter electrode, the gas distributor, the substrate support surface and / or a boiler wall surface of the process chamber, it can be achieved that critical areas are not even contaminated and thus the cleaning by means of the

Cleaning gas can be cost-effectively limited to partial areas. The

Cover can be made by constructive-mechanical covering or constructive-electrical covering means, the latter use that a contamination does not occur when a surface is in the range of a dark space shield in which no plasma can form.

If the substrate is arranged on a support surface during the plasma treatment, the substrate support surface is covered in particular, so that it is not contaminated. In particular, the cover can be effected by the substrate such that the formation of a residue on the substrate support surface is prevented during the plasma treatment. The cover reduces the time required for cleaning and reduces the amount of gas required for cleaning. Furthermore, the preferably large surface bearing surface can be heated or annealed and thus serve as a means for thermal activation of the cleaning gases, in particular the fluorine gas.

In particular, at least partial surfaces of holding means can be selected as the surface to be cleaned, wherein the holding means are assigned to the substrate supporting surface. The holding means serve to hold the

Substrate during plasma treatment. In particular, the holding means may be thermally and / or electrically isolated from the support surface so that, while the support surface is brought to an elevated temperature, for example greater than> 350 ° C, the support means at a temperature of <350 ⁰ C, in particular < 80 ⁰ C or in a range between 20 ⁰ C and 60 ⁰ C.

If, during the application of the cleaning gas between one of the

Electrode associated gas outlet plate of a gas distributor and the counter electrode is set a distance in a range between 2 mm and 100 mm, the Purge gas act on both the area of the electrode and the counter electrode. It is particularly advantageous if the counter electrode is heated while the electrode and / or the gas distributor have a lower temperature, for example a temperature in the range of the temperature during the plasma treatment, in particular the coating. The contact surface can be the counter electrode

be assigned and also, or else heated independently of the counter electrode and thus, as described above allow thermal activation of the cleaning gas particularly simple.

If an inert gas, in particular nitrogen or argon, is used in the cleaning gas in addition to fluorine gas, this facilitates the handling of the method, since such gas mixtures with regard to corrosion of the chamber components and

Management systems are easier to control. Argon also has the advantage that it does not form any compounds with coating constituents, in particular silicon, and therefore no dust contamination is to be expected, as is the case with nitrogen.

If plasma excitation of the cleaning gas occurs inside and / or outside (remote plasma cleaning) of the process chamber to form excited fluorine species, the reactivity of the cleaning gas can be further increased.

The process chamber according to the invention with at least one electrode and

Counter electrode for generating a plasma for plasma treatment of a substrate is arranged and intended to carry out a method according to any one of the preceding claims, wherein

Means for acting on the component to be cleaned with fluorine gas or gaseous fluorine compounds having a total partial pressure of greater than 5 mbar and / or

Means for thermally activating the fluorine gas or gaseous

Fluorine compounds and for tempering the component to be cleaned to a temperature <350 ⁰ C. are provided.

The device according to the invention for the plasma treatment of a substrate comprises in an embodiment

Means for exciting a capacitively coupled having plasma discharge in a region between an electrode and a counter electrode and

Means for transporting a quantity of at least one activatable gas species in a region of the plasma discharge, wherein the substrate between the electrode and the counter electrode between a surface to be treated surface of the substrate and the electrode is arranged or can be arranged.

The plasma discharge takes place in particular at an excitation frequency between 1 MHz and 150 MHz, preferably 13, 56 MHz. Preferably, either the

Electrode or the counter electrode lying or laying at ground potential. However, arrangements with floating electrode and / or counter electrode are also conceivable.

In particular, a control device is provided which controls a pumping device for supplying and removing the cleaning gas as well as the adjustment of the desired fluorine partial pressure.

The means for thermally activating the fluorine gas or gaseous fluorine compounds may comprise at least parts of the electrode, a gas distributor associated with the electrode, the counter electrode, a substrate support surface associated with the counter electrode, and / or a thermal activation device located outside the process chamber.

According to a further advantageous embodiment, the thermal

Excitation of the cleaning gas fluorine species alternatively or additionally carried out by a heating medium or temperature control means arranged externally of the process chamber. It is particularly preferred if the cleaning gas before entering the

Process chamber is passed over a heated surface. The heatable surface may be, inter alia, a heatable filament or a heatable inlet pipe section. In the case of the process chambers to be cleaned, it is taken into account that these are often designed for large-area elements to be coated (> 1m ² ). This means that not only the coating quality but also the quality of cleaning can depend on the distance between the electrode and the counter electrode. For example, it has been found that when the fluorine gas is excited by the electrode or counterelectrode, a small distance of 10 to 20 mm is advantageous. If one

Means is provided, with the electrode and counter electrode are displaceable relative to each other, during the cleaning of electrode and / or

Counter electrode, the distance between the two kept small and then inserted into the then narrow gap activated fluorine gas, so that the one another

facing surfaces of the electrode and counter electrode are exposed to fluorine at a relatively high current density of thermally activated fluorine.

Furthermore, the process chamber is characterized in that a preferably provided with a temperature control gas distributor is provided. Such a

Gas distributor is useful for a homogeneous plasma treatment, such as coating, wherein the temperature control allows the cleaning of the opposite ektrode but also other components. In an advantageous embodiment of the invention, the cleaning gas is passed via a gas distributor integrated in the electrode, for example a gas distributor for coating gas, into the process chamber. To ensure a homogeneous gas supply into the process chamber, the

Gas distributor provided with a gas outlet plate, which comprises a plurality of regularly arranged in a surface gas outlet openings.

The temperature control, for example, the electrode and / or counter electrode

assigned, are advantageously (controlled or regulated) tempered,

for example, with the aid of a circulating in a circulating bath liquid. Heat transfer oils are preferably used, for example, by

outside the process chamber circulating circulators are kept at a temporarily constant temperature.

In the following the invention will be described with reference to one of the figures

Embodiment explained in more detail. Showing: Fig. 1 shows a longitudinal section through an inventively to be cleaned device for plasma treatment of a substrate

2 shows a graph of an etching rate for a thermally activated fluorine / nitrogen mixture at different total partial pressure of the fluorine or fluorine-containing gas components as a function of the temperature of the

Cleaning gas.

Figure 1 shows a schematic representation of a preferred reactor 1 for

Treatment of Flat Substrates 2. The reactor may in particular be designed as a PECVD reactor. The reactor 1 comprises a process chamber 3 with an electrode 4 and a counter electrode 5 for generating a plasma, by means of which a surface of a substrate 2 can be treated, in particular coated. The electrodes 4, 5 are formed as large-area metal plates and can for

Generation of an electric field in the process chamber 3 to a (not shown in Figure 1) voltage source, preferably a high-frequency power source with an excitation frequency between ImHz and 150MHz, preferably 13, 56 MHz, are connected. Preferably, the electrodes and other components are formed from a fluororesistant material (in particular metal) or have a coating of a fluororesistant material.

Reactor 1 is suitable for treating large flat substrates,

for example, with an area of 1 m ² or larger. In particular, the reactor 1 is suitable for carrying out processing steps in the production of highly efficient thin-film solar modules, for example for amorphous or

microcrystalline silicon thin-film solar cells.

As can be seen from FIG. 1, the two electrodes 4, 5 form two opposite walls of the process chamber 3. The process chamber 3 is arranged in a vacuum chamber 7 with an evacuable housing 8, which has an opening 10 for introducing and removing substrates. The chamber opening 10 is through a

Closing device 9 closed vacuum-tight. For sealing the

Vacuum chamber 7 relative to the outer space 12 seals 11 are provided. The seals are preferably formed from a fluororesistant material. The vacuum chamber 7 may have any spatial form and may in particular have a round or rectangular cross-section. The in the Vacuum chamber 7 embedded process chamber 3 may in particular have the shape of a flat cylindrical disk or a flat cuboid. It goes without saying that the invention can also be used with differently configured reactors, in particular with a different process chamber and / or electrode geometry. It is equally understood that embodiments in which the process chamber itself is a vacuum chamber are also encompassed by the invention.

The electrode 4 is arranged in a holding structure 37 in the vacuum chamber 7, which is formed in the embodiment of FIG. 1 of the housing rear wall 19. For this purpose, the electrode 4 is accommodated in a recess 38 of the housing rear wall 19 and separated from it by a dielectric 20.

The counter electrode 5 has on its side facing the electrode 4 a

Device 21 for holding a substrate. The device 21, which is preferably designed as a fixing device, comprises one or more retaining means

Downholder 31, which can press a substrate edge on the surface acting as a substrate - supporting surface 5a of the counter electrode 5. The holding means may be formed finger-like or frame-like. In particular, the

Holding means mechanically connected to the counter electrode 3, but at the same time electrically and / or thermally isolated from this. In particular, at a

Temperature of the counter electrode 3 and the substrate - support surface 5a of> 350 ⁰ C, the temperature of the Halteugsmittel in a range between 20 ° C and 100 ⁰ C.

As can be seen from FIG. 1, the counterelectrode 5 covers the recess 38 of the holding structure 37 during the execution of the treatment in such a way that a gap 25 is formed between the edge region 23 of the counterelectrode 5 and an edge region 24 of the recess 38. The gap 25 has a width of the

Order of magnitude of about 1 mm. The gap width is in such a way

dimensioned, on the one hand while the treatment is being carried out, a plasma can be kept inside the process chamber 3, but on the other hand, no too great pressure gradient is built up between the process chamber 3 and the remaining interior of the vacuum chamber 7.

For coating or etching the substrates, a reactive gas is passed into the process chamber 3. For this purpose, the reactive gas is supplied from a source via a supply channel 13 to a gas distributor 15, from which it flows into the process chamber 3. The gas distributor 15 in the present embodiment comprises a gas chamber 16, which has on the side facing the counter electrode 5, a gas outlet plate 17 with a plurality of outlet openings (not shown) for

Gas passage is provided. On an area of about 1, 0 m ² - 2.0 m ^{2 of} the

Gas outlet plate 17 are typically provided several thousand outlet openings.

Selected surfaces or components can be used during the

Plasma treatment are covered. The cover can be made by constructive mechanical covering or constructive-electrical covering, the latter use that a contamination does not occur when a surface is in the range of a dark space shield in which no plasma can form. For example, no contamination of the gap 25 occurs.

In the device of FIG. 1, the substrate 2 is arranged on a substrate support surface 5a during the plasma treatment. It takes place in particular a

Covering the substrate support surface by the substrate so that it is not contaminated. In particular, the covering by the substrate 2 can take place such that the formation of a residue on the substrate support surface 5a is prevented during the plasma treatment. In an embodiment of the invention deviating from FIG. 1, the counterelectrode 5 has no or only slightly beyond the area of the gas shower extending end region 23, so that in this respect no contamination takes place.

Areas of the vacuum chamber 7, which are arranged outside the process chamber 3, are connected via vacuum lines 26 with a vacuum pump 26 ', so that when operating the vacuum pump 26' due to the larger volume of the vacuum chamber 7 in a simple manner, a high homogeneity of the gas flows from the Process chamber 3 can be achieved via the gap 25 in the vacuum chamber 7.

The process chamber 3 is provided with control means with a pumping device and a control device, which are designed to at least temporarily in the process chamber 3 and in some areas a fluorine-containing cleaning gas having a partial pressure of gaseous fluorine compounds of more than 5 mbar, preferably in a range between 20mbar and 1000 mbar. It is understood that during cleaning, generally no substrate is placed in the process chamber. For cleaning the process chamber 3 or the vacuum chamber 7, the cleaning gas is passed into the process chamber 3. For this purpose, the cleaning gas from a source 14 via a supply channel,

For example, the channel 13 is preferably supplied to the gas distributor 15, from which it flows into the process chamber 3. The source 14 and / or the feed channel are preferably pressure-resistant for a partial fluorine pressure of more than 5 mbar, preferably more than 20 mbar, 100 mbar, 500 mbar or 1000 mbar.

During cleaning, in a variant of the method, the cleaning gas can be pumped out. In another variant, the process chamber 3 is flooded during a time interval of cleaning with the cleaning gas and it takes place a pumping out at a later time.

In order to achieve a particularly good cleaning result, heating or tempering means 27, 29, 30 are provided in the reactor 1. With the aid of these means 27, 29, 30, the thermal energy supply to the electrode 4 and / or the counter electrode 5 or the support surface 5a is controlled or regulated during the cleaning process. It has been found in experiments that it is sufficient to arrange the tempering only at one of the electrodes, for example at the electrode 4 or counter electrode 5. The thermal excitation of the cleaning gas at the temperature-controlled electrode 4 or counter electrode 5 creates a sufficient number of

Fluorine radicals to also clean the opposite (counter) electrode 5, 4.

In the embodiment of Fig. 1 are the electrodes 4, 5 associated

Tempering provided, wherein the temperature control of the counter electrode 5 include a device 29 which is disposed below the counter electrode 5 in the vacuum chamber 7. With the aid of this device 29, the counter electrode 5,

In particular, the substrate support surface 5a are tempered in such a manner that optimum cleaning can be achieved. Advantageously, the substrate support surface 5a has not been contaminated by the applied substrate 2, so that no cleaning of this component took place. By a small distance of the heated to temperatures> 350 ° surface 5a to the electrode 4 and the gas distributor 15 can be a very effective cleaning of electrode 4 and gas distributor 15 done without them during cleaning a higher temperature than zwichen in a range between 2O ⁰ C and 80 ⁰ C must have. A tempering device is in principle also providable for the electrode 4.

Alternatively, an electrode 4 and / or counter electrode 5 may be provided, in which the device 29 is formed integrally with the electrode 4,5.

In order to determine the level of the required temperature control of the devices 27, 29 or 30, measurements can be carried out in which the electrodes 4, 5 are provided on their mutually facing sides with thermal sensors 40, 40 '. With the help of these thermal sensors 40, 40 'can for different RF power,

Gas flows, etc., a local temperature of the electrodes 4.5 as a function of the performance of the temperature control 27, 29, 30 are determined. Based on such measurements, the instantaneous temperature control, if necessary, the geometric

Design of tempering devices 27, 29, 30 are optimized. Furthermore, measured values of the thermal sensors 40, 40 'can be obtained during the cleaning and used for a process-accompanying control of the power of the temperature control devices 27, 29, 30.

In addition to the temperature control devices 27, 29, 30 which are equally usable for one or both electrodes 4, 5, the electrode 4 can also be brought into contact by means of heated gas introduced via the gas distributor 15 or brought to a desired temperature. It is particularly advantageous if the cleaning gas itself is used for this purpose. This can be heated, for example, by means of a feed channel 13 which can be heated by means of a temperature control medium, or be conducted via a heatable surface or a heatable filament.

In addition, the gas outlet plate 17 can be tempered. This can be the

Gas exit plate 17 may be connected by means of webs 35 with the electrode 4, which consist of a material having high thermal conductivity, so that the

Gas outlet plate 17 is thermally connected to the electrode 4. The electrode 4 (and thus also the gas outlet plate 17) can also be tempered during the cleaning by circulating a bath liquid through channels 36 in the electrode 4. The temperature of the electrode 4 can be controlled or regulated. In particular, thermal sensors 40 'may be arranged in the area of the gas outlet plate 17, the measured values of which are used to control the temperature control flow through the electrode 4. In the following, etching rates of the method according to the invention are compared with the etching rates of a conventional method.

In the case of the etching processes to be compared, it is assumed in each case one

Process chamber for the deposition of silicon thin films for photovoltaics, which is coated with 4.5 μm μc silicon or amorphous silicon. The coating can be general from one of the usual used in solar cells

Silicon compounds, e.g. Silicon dioxide, silicon nitride and / or silicon nitride exist. The coating occurs mainly on the electrode 4, the one

Gas distributor includes, on. The electrode is tempered by means of tempering to about 60 ⁰ C; the counter electrode to about 200 ⁰ C. The distance of the electrodes from each other in the coating 14 mm, the surfaces of the electrodes are each about 2 m ² . a) Conventional method (remote plasma, 3 KW, microwave):

A remote plasma device (company R3T, excitation with microwave) is flanged frontally to the reactor. The distance between the two electrodes is increased from 14mm to 180mm and excited NF3 flows through a hole in the process chamber with parallel flow to the electrode surfaces. The gas flow is 2slm (standard liters per minute). The pressure in the chamber during the etching process is 2 mbar. After 45 minutes, the etching is completed. A visual inspection of the reactor shows consistently clean surfaces. The duration of the etching process was determined by the residual gas analysis: as soon as SiF4 was no longer produced, the etching process was completed. b) Method according to the invention:

The electrodes are 14 mm apart. The cleaning gas of 20% F2 in N2 is introduced into the process chamber through the gas shower (gas distributor) integrated into the electrode with a flow of 18 slm - without being excited by any kind of electrical discharge. The valve is the

Process gas pump closed so far that sets after 15 minutes, a constant process chamber pressure of 250 mbar, with a total process chamber volume of 510 liters. For a further 15 minutes, the gas mixture remains with the gas flow of 18 slm in the boiler. Then the flow was set to 0 slm and the kettle pumped out within another 10 minutes. The kettle was then opened and visually inspected for residual silicon coatings. The result was a completely clean kettle. Surprisingly, not only was the 200 ⁰ C hot counter electrode etched clean; It was also completely clean with 60 ⁰ C comparatively cold electrode. According to the invention, the F2 gas at the hot

Excited counter electrode and is then enough excited at the colder electrode enough to etch even here effectively. In this case, a small distance of the electrodes of about 14mm is advantageous.

After a total time of 40 minutes (gas inlet to pump off) in the process b) according to the invention, the 4.5 μm coating on the electrode and on the gas shower was completely removed. Thus, the inventive method is faster than the conventional cleaning with a R3T remote plasma device with 3 KW power and a 2slm NF3 flow.

As mentioned under b), it should be noted that the thermal excitation of the fluorine radicals by the heated counterelectrode is sufficient to advantageously provide fast and complete cleaning results. This is also done by a

Investigation of the etching rate of a fluorine / nitrogen mixture as a function of

Temperature of a surface to be etched occupied.

FIG. 2 shows a graph in which the etching rate during etching of a thermally activated fluorine nitrogen mixture in nm / s (y-axis) is plotted against the temperature in ⁰ C (x-axis). In this case, a fluorine / nitrogen mixture is selected which has a partial pressure of 250 mbar.

The graph 100 shown in Figure 2 shows that the etch rate increases sharply from a temperature of about 100 ⁰ C at a partial pressure of 250mbar when compared to etching at conventional low pressures of at most 1 mbar, wherein a at values above 150 ⁰ C. Etch rate of more than 8 nm / s is achieved. At temperatures at 200 ⁰ C, the etching rate is already tripled.

It is therefore advantageous to bring one of the electrodes to the highest possible temperature, taking into account structural preconditions and restrictions should be taken so as not to shorten the life of the plate reactor or the electrodes or other device. As a good compromise, a temperature of about 200 ⁰ C has proven that shows a considerable etching rate. The other electrode preferably has a lower temperature, for example in a range between 20 ⁰ C and 6O ⁰ C and 100 ⁰ C, preferably at most 15% over the temperature during the plasma treatment, for example, the plasma coating of substrates.

Claims

claims

Method for cleaning a surface of at least one component arranged in the interior region of a process chamber by means of a cleaning gas comprising fluorine gas, the process chamber having at least one electrode and counterelectrode for generating a plasma for plasma treatment of a substrate, in particular for CVD or PECVD Treatment of flat substrates having a surface area of more than 1 m ² , characterized by

Acting on the component to be cleaned with fluorine gas or gaseous fluorine compounds having a total partial pressure of greater than 5 mbar and / or thermal activation of the fluorine gas or gaseous

Fluorine compounds and

Tempering of the component to be cleaned to a temperature <350 ° C.

2. The method according to claim 1, characterized in that the inner region is exposed to fluorine gas or gaseous fluorine compounds having a total partial pressure of greater than 5 mbar.

3. The method according to any one of the preceding claims, characterized in that before the application of the cleaning gas by means of

Plasma treatment a substrate with a preferably silicon or

Coated silicon-containing compounds coated layer and at least on the component to be cleaned preferably a silicon silicon-containing compounds containing residue is formed.

4. The method according to any one of the preceding claims, characterized in that etched prior to exposure to the cleaning gas by means of the plasma treatment, a substrate and at least on the component to be cleaned

Preferably, a silicon or silicon-containing compounds containing residue is formed.

5. The method according to any one of the preceding claims, characterized in that as a surface to be cleaned, at least a portion of the electrode, the counter electrode, a gas distributor associated with the electrode, a substrate support surface associated with the counter electrode or a

Boiler wall surface of the process chamber is selected and / or during the application of the cleaning gas, the surface to be cleaned has a temperature which is at most 1, 8 times the temperature of the surface during the plasma treatment, preferably less than 60 ⁰ C, more preferably less than 20 ⁰ C. is.

6. The method according to claim 5, characterized by preventing the formation of a residue on a surface region of the electrode, the counter electrode, the gas distributor, the substrate support surface and / or a boiler wall surface of the process chamber, in particular by constructive-mechanical or constructive-electrical covering.

7. The method according to claim 6, characterized by covering the substrate

Support surface, preferably by a substrate, such that during the

Plasma treatment, the formation of a residue on the substrate support surface is prevented.

8. The method according to claim 7, characterized in that as a surface to be cleaned at least part surfaces of support means are selected, wherein the support means are associated with the substrate support surface.

9. The method according to any one of the preceding claims, characterized in that are used as a means for thermally activating the fluorine gas and / or the gaseous fluorine compounds at least parts of the electrode and / or one of the electrode associated gas distributor.

10. The method according to any one of the preceding claims, characterized in that as a means for thermally activating the fluorine gas or the gaseous fluorine compounds at least parts of the counter electrode and / or one of the counter electrode associated substrate support surface can be used.

11. The method according to any one of the preceding claims, characterized in that in the cleaning gas in addition to fluorine gas, an inert gas, in particular nitrogen or argon, is used.

12. The method according to any one of the preceding claims, characterized in that a plasma excitation of the cleaning gas inside and / or outside of the process chamber and / or a thermal activation outside of the

Process chamber takes place.

13. The method according to any one of the preceding claims, characterized in that a distance in a range between 2 mm and 100 mm is set during the application of the cleaning gas between an electrode associated gas outlet plate of a gas distributor and the counter electrode associated substrate support surface.

14. Process chamber with at least one electrode and counter electrode for

Producing a plasma for plasma treatment of a substrate, set up and intended to carry out a method according to any one of the preceding claims, wherein

Means for thermally activating the fluorine gas or gaseous

Fluorine compounds and for controlling the temperature of the component to be cleaned to a temperature <350 ⁰ C are provided.

15. Process chamber according to claim 14, characterized in that the means for thermally activating the fluorine gas or gaseous fluorine compounds at least parts of the electrode, one of the electrode associated gas distributor, the counter electrode, one of the counter electrode associated substrate support surface and / or arranged outside the process chamber include thermal activation device.

16. Process chamber according to one of claims 14 or 15, characterized

characterized in that covering means for preventing the formation of a

Residue are provided during a plasma treatment at a surface region of the electrode, the counter electrode, the gas distributor and / or the substrate support surface.

17. Process chamber according to claim 16, characterized in that a counter-electrode associated substrate support surface is provided, which during the plasma treatment of a substrate, preferably by the substrate, can be covered such that during the plasma treatment, the formation of a residue on the substrate support surface is preventable.