WO2014037486A1

WO2014037486A1 - A chamber cleaning method using low pressure f2

Info

Publication number: WO2014037486A1
Application number: PCT/EP2013/068439
Authority: WO
Inventors: Oliviero Diana
Original assignee: Solvay SA
Current assignee: Solvay SA
Priority date: 2012-09-10
Filing date: 2013-09-06
Publication date: 2014-03-13
Anticipated expiration: 2015-03-10
Also published as: TW201428821A

Description

A chamber cleaning method using low pressure F?

The invention concerns a chamber cleaning method using F₂ which is supplied at a low pressure.

F₂ (elemental fluorine) is used, i.a., as an etching agent and as a cleaning agent for cleaning of chambers, e.g. CVD or PVD chambers, used in the manufacture of semiconductors, micro-electromechanical devices, solar cells, TFTs (thin film transistors). HF was considered as undesirable component in F₂ intended for etching or chamber cleaning. WO 2012/016997 for example provides a purification process for the manufacture of highly pure F₂, useful as etching agent and chamber cleaning agent, with a content of equal to or less than 10 ppm of HF.

F₂ is often manufactured by the electrolysis of hydrogen fluoride (HF) in the presence of molten/dissolved fluoride salts ; especially adducts of HF and KF having a formula of about KF (1.8 - 2.3)HF are electrolyzed. Often, production of F₂ for chamber cleaning is performed on site, i.e. on the premises of the point of use.

Object of the present invention is to provide a technically and

economically advantageous method of chamber cleaning wherein F₂ is used as chamber cleaning agent.

This object and other objects as apparent from the description and the claims are achieved by the present invention.

Consequently, the present invention concerns a method for the cleaning of at least one chamber using elemental fluorine wherein the fluorine is produced in at least one electrolytic cell, and wherein the pressure of F₂ in the electrolytic cell is equal to or lower than 1.1 bar (abs), and the pressure of the F₂ delivered to the at least one chamber is equal to or lower than 0.85 bar (abs). Preferably, the pressure of the F₂ in the electrolytic cell is equal to or greater than 1 bar (abs). BRIEF DESCRIPTION OF THE DRAWING

Figure 1 shows a scheme for an assembly useful for performing the invention.

Preferably, the pressure of the F₂ in the at least one electrolytic cell is equal to or lower than 1.05 ± 0.02 bar (abs). A pressure range of from 1 to 1.05 ± 0.02 bar (abs) is very suitable. The chambers which can be cleaned are preferably those used in the manufacture of semiconductors, micro-electromechanical devices, solar cells (photovoltaic items), and TFTs (thin film transistors). In such chambers, items are treated according to known processes. For example, layers of Si, Si0₂, silicon nitride, silicon oxynitride, metals, metal oxides or carbon- fluorine polymers are formed on the surface or a part of the surface of the items, e.g. according to plasma enhanced (PECVD) processes, and partially etched away in other treatment steps. During these processes, layers do not only form on the items but also undesirably on parts in the chamber, e.g. construction parts, lines, shower heads or the walls. The method of the invention serves to clean the chambers from such undesired deposits.

The technical parameters of chamber cleaning are known to the expert in the art.

The chamber cleaning method of the present invention can be performed thermally or supported by in-situ plasma and/or by remote plasma.

The temperature during a thermal chamber cleaning is preferably equal to or greater than 400°C. In plasma- supported chamber cleaning, the temperature inside the chamber may often be greater than 100°C.

The plant for F₂ manufacture may preferably be located on site of the plant having chambers of which are to be purified. If desired, however, the F₂ may be produced remote from the point of use and be transported from the location of its manufacture to its point of use.

The expert is aware that F₂ and H₂, when getting into contact, may react in the form of heavy explosions. Thus, the F₂ compartments in an electrolytic cell are separated by so-called "shirts" from the H₂ compartments.

To avoid any risk of contact between F₂ and H₂, it is preferred that the pressure in the electrolytic cell both on the F₂ and H₂ side does not oscillate over a too high range ; often, it is preferred to keep the cell pressure within ± 0.01 to ± 0.05 bar of a preset value.

The F₂ is especially preferably generated in the electrolytic cell at a pressure of approximately 1.05 ± 0.02 bar (abs) and forwarded, via several steps to the point of use as chamber cleaning agent. At the point of use, the F₂ has a pressure below 1 bar (abs), preferably having a pressure in the range from equal to or greater than 0.2 bar (abs) to equal to or lower than 0.85 bar (abs). Often, it is in a pressure of from 0.2 to 0.55 bar (abs). From the electrolytic cell to the point of use in the chamber, the F₂ is not pressurized in the method of the invention. Thus, the pressure of the F₂ is lower after every treatment step due to a pressure drop in each step.

The preferred embodiment of the method of the invention comprises A) a step of electro lytically producing raw F₂ from HF in the presence of KF

B) a step of removing particles entrained in the raw F₂ obtained in step A)

C) a step of filtering any remaining particles out of the F₂ leaving step B)

D) a step of delivering the F₂ to the chamber, optionally via a buffer tank or a storage tank, and

E) cleaning the chamber.

The F₂ is not pressurized neither in any of these steps, nor between any of them. This means that the driving force passing the F₂ from step A) to the final use in step E) is the pressure of approximately 1 to 1.1 bar (abs) in the electrolytic cell compartment in which the raw F₂ is generated.

Preferably, the method of the invention consists of these steps.

The flow of F₂ can be measured, for example, with a flow indicator, for example, a flow indicator operating according the Coriolis type which is very accurate.

Step A) usually is performed by electrolysis of HF in the presence of an electrolyte salt of the approximate formula KF*(1.8-2.3)HF.

Step B) may be performed by contacting the raw F₂ from step B) with liquid HF, e.g. by passing the raw F₂ through liquid HF, in a static scrubber or in a jet scrubber.

The scrubber can be operated in large range of temperatures ; it may be composed of multiple stages ; two or more scrubbers can be arranged in parallel and/or in series ; and each of these scrubbers can be operated at different pressures and/or different temperatures. The temperature of the scrubber or each of the scrubbers, if there are more scrubbers than one, can vary between -200°C and +20°C. Preferably, the temperature of the scrubber or each of scrubbers is equal to or higher than -150°C, and more preferably, it is equal to or higher than -82°C. Preferably, the temperature of the scrubber or each of the scrubbers, if there are more scrubbers than one, is equal to or lower than -50°C. A preferred temperature range for the scrubber or each of the scrubbers, if more than one scrubbers are in use, is from -150°C to -20°C ; an especially preferred range is from -80°C to -50°C. Depending especially on the number, temperature and the pressure of the scrubber or scrubbers, the amount of HF which is removed from the F₂, will vary. For example, at a higher pressure, at a lower temperature in the scrubber or scrubbers, and if several scrubbers are assembled in series, the amount of HF removed can be almost completely, such that only a few ppm are left in the treated F₂. If the temperature is in the upper region of the range given above, at a lower pressure and only one scrubber to be passed, the amount of removed HF is low, and the F₂ after treatment may comprise almost all of the HF entrained. Nevertheless, the advantage of scrubbers, namely to remove solids, still will be achieved.

Step C) may be performed by passing the F₂ withdrawn from step B) through a filter made from suitably resistant material, e.g. made from Monel metal. The pore size may be equal to or smaller than 100 μιη, preferably equal to or smaller than 20 μιη. A suitable pore size range is 1 to 20 μιη. Preferably, the pore size is equal to or greater than 0.001 μιη. A preferred range is from 0.001 to 20 μιη.

According to step D), the F₂ withdrawn from step C) may be passed into a storage tank or in a buffer tank before it is delivered to the point of use in chamber cleaning step E). Preferably, the F₂ is stored in a sufficiently large buffer tank before its delivery to the point of use for the step of chamber cleaning.

In a preferred embodiment of the inventive method, F₂ containing more than 0.1 % by weight and less than 2.5 % by weight of HF is produced in steps A) to D. In this preferred embodiment, the content of HF in the F₂ is preferably equal to or greater than 0.5 % by weight. Preferably, it is equal to or lower than 2 % by weight ; and the pressure of the F₂ in the line to the chamber or chambers to be cleaned, i.e. at the point of use, preferably is 0.2

to 0.55 bar (abs).

To give an impression of the trend of the pressure in the different steps from electrolytic generation of F₂ to the delivery of the point of use for chamber cleaning, the estimated minimal and maximal pressure drop in each step is given in the following table 1. It has to be noted that in the following description, a method is further explained wherein the pressure in the electrolytic cell is 1.05 bar (abs) because this is the preferred embodiment. The absolute pressure (but essentially not the pressure drop) may also be higher if the cell is operated at a higher pressure of the F₂ compartment. Pressure drop in intermediate steps from F₂ generation to the point of

The F₂ is preferably not passed through an adsorbent tower, e.g., an NaF tower, or through a cooled trap, e.g. a trap cooled to a temperature equal to or lower than -90°C. That is because the aim of this invention is to keep the process as simple as possible, because simple means cheap, reliable and safe. However, without a finishing step like NaF adsorption or very cold trap (temperature equal to or lower than -90°C), it may be difficult to reduce the residual HF content into the final F₂ product to very low values, equal or less than about 1 % by weight. While it was found out that is not necessary, such a low HF content for F2 used for chamber cleaning, if it should be desirable to reduce HF values below the above said level, then one or both of the above said finishing steps can be added to the present invention as an option.

If desired, the F₂ can be passed to the point of use via a flow indicator, e.g. a flow indicator operating according to the Coriolis type.

Under the assumption that the F₂ is generated in the electrolytic cell compartment having a pressure of 1.05 bar (abs), and under the assumption that it is desired to deliver the F₂ after its treatment with a pressure of from equal to or greater than 0.2 bar (abs) to equal to or lower than 0.55 bar (abs), and under the assumption that - in the absence of an NaF tower - the minimum pressure drop is 90 mbar, and the maximum pressure drop is 330 mbar, then the F₂ pressure must be reduced using control valves

• from 0.95 bar (abs) to 0.2 bar to 0.55 bar if a minimum pressure drop is observed, or

· from 0.72 bar (abs) to 0.2 bar to 0.55 bar if a maximum pressure drop is observed.

Of course, the actual pressure drop depends on the apparatus used, on the temperature, gas flow and other parameters. Thus, the values given above are only to help the expert to better understand the invention.

Preferred embodiments of step A) : In step A), F₂ is produced electrolytically. Often, salt compositions of the approximate formula KF (1.8 - 2.3)HF are applied. Such compositions have a melting point, depending on the composition, around 80°C or above. Usually, an electrolyzer contains several electrolytic cells. Each cell often contains a multitude of anodes. Often, the cell vessel containing the molten salt serves as cathode, or several separate electrodes are used as cathodes. Fresh HF is supplied continuously or batch wise to the cell to replenish electrolyzed HF.

HF is electrolyzed to form F₂ and H₂ which are collected in separate cell compartments. H₂ may be dumped. The raw F₂ formed contains up to 10 % by weight of HF, and possibly even more ; the raw F₂ further contains entrained particles which are essentially constituted of solidified electrolyte salt.

In step A), the raw F₂ is withdrawn from the respective cell compartment having a pressure of equal to or greater than 1 bar (abs). Usually, the pressure of the raw F₂ in the F₂ compartments is approximately 1.05 ± 0.05 bar (abs).

Preferred embodiments of step B) :

In step B), the raw F₂ is subjected to a purification treatment to separate all or a major part of solid impurities from the raw F₂. Preferably, the solid- removing treatment comprises at least one step of contacting the raw F₂ with cooled liquid HF in a static scrubber.

The liquid HF with which the raw F₂ is contacted has a low temperature and consequently a low vapor pressure. The temperature of the liquid HF during its purifying contact with the fluorine is equal to or higher than the melting point of the HF at the respective pressure in the static scrubber. Preferably, it is equal to or higher than -83°C, more preferably, it is equal to or higher than -82°C. It is preferably equal to or lower than -60°C. The temperature of the liquid HF is preferably in the range between -60°C and -82°C. The HF can be cooled by cooling machines which provide a suitably cooled liquid to heat exchangers to keep the HF at the desired low temperature. In a preferred embodiment, the liquid HF in the scrubber is indirectly cooled by means of liquid N₂ which, when passing from the liquid to the gaseous state, provides the desired cooling effect.

The F₂ can be contacted with technical grade liquid HF. If desired, purified liquid HF can be applied.

Methods to purify HF, mainly to remove phosphorous compounds, sulfur compounds, arsenic compounds, metals, hydrocarbons and water are well known. See for example US patent 5,362,469 and US patent 5,585,085.

According to US patent 5,362,469, water, arsenic compounds, boron compounds, phosphorous compounds and sulfur compounds as well as carbon compounds and metal compounds are removed from HF by contacting liquefied hydrogen fluoride with lithium fluoride and elemental fluorine. The HF is then distilled to provide pure HF. According to US patent 5,585,085, water and hydrocarbons are removed from HF by contacting it with elemental fluorine and subsequent distillation.

The raw F₂ from step A) may preferably be contacted with a purified liquid HF which is essentially free of at least phosphorous compounds, sulfur compounds and arsenic compounds. HF can be purified according to the process of US patent 5,362,469 and then has a content of water of less than 1 ppm.

Often, it is sufficient to perform step B) only once to achieve a desired degree of solids removal. But if desired, the contact between F₂ and liquid HF can be repeated once, or even more often.

The raw F₂ is supplied to the static scrubber to be contacted with liquid HF under the pressure it has in the electrolytic cell compartment. No pump or compressor is used to raise the pressure of the raw F₂ withdrawn from the electrolytic cell compartment. Due to the marginal pressure loss in the line from the electrolytic cell compartment to the scrubber, the raw F₂ enters the scrubber with a pressure corresponding to the pressure in the electrolytic cell, i.e. 1.05 ± 0.02 bar (abs).

Due to the low temperature of the liquid HF during its contact with fluorine, the vapor pressure of HF is very low. Thus, not only the content of entrained solids is reduced, but also entrained HF is removed. The F₂ after the contact with liquid HF contains more than 0.1 % by weight and less than 2.5 % by weight.

The liquid HF which is used in the purification step is preferably circulated or reused, optionally after regeneration, e.g. by a step of distillation, to remove any solids washed out from the raw fluorine as described above. The advantage is that any water initially present in the HF reacts with F₂ to form HF and OF₂ ; after some time, the water is consumed, and the fluorine to be purified will not be consumed by water in a side reaction, and the fluorine will not take up any OF₂ anymore because it is no longer formed.

The F₂ which leaves the static scrubber has a pressure which is, as a rule of thumb, approximately 40 to 80 mbar lower than upon entering the static scrubber. The HF content depends from several conditions, e.g. from the initial HF concentration, from the temperature of the liquid HF and from the contact time. The conditions of contact between the liquid HF and the F₂ are selected such that the HF content is in the range given above, and notably, in the preferred ranges.

Preferred embodiments of step C) :

The F₂ withdrawn from step B) is then treated in step C). Once again, no pump or compressor is used to raise the pressure of the F₂ withdrawn from step B) and forwarded to step C). For solids removal, the F₂ is passed in step C) through one or more particle filters with small pores to remove any residual solids content. The filter or filters may comprise pores in the range of 0.01 to 20 μιη. Pore size denotes the pore diameter. Particle filters with a pore size greater than 20 μιη could be applied but may not be effective enough. The particle filters serve to remove any solid particles before the contact with liquid HF, or to remove solids still entrained after the purifying treatment of the present invention ; the particle filters may be constructed from materials resistant to F₂, especially from steel or Monel metal.

The temperature in the filter should advantageously be lower than the melting point of the solids (which is usually somewhat above 80°C). Preferably, the temperature in the filter is equal to or lower than 50°C. Especially preferably, step C) is performed at ambient pressure.

The F₂ leaving the filter in step C) has a pressure which is approximately

10 to 150 mbar lower than upon entering the filter.

F₂ having passed steps B) and C) is suitably pure to be used as cleaning agent for chambers used for CVD-enhanced deposition of matter on items. It is especially suitable for cleaning of chambers which have been used for deposition and/or etching of layers, like CVD chambers, used in the manufacture of semiconductors, micro-electromechanical devices, solar cells, TFTs (thin film transistors).

Preferred embodiments of step D) :

The F₂ leaving step C) is subjected to step D). In step D), it is delivered, optionally via a buffer tank or a storage tank, to the point of use, i.e. a chamber or a plurality of chambers to be cleaned. No pressurization is performed, thus it is not passed through a pump or a compressor.

Preferably, in step D), the F₂ leaving step C) is stored in a storage tank. In the storage tank, it is preferably stored at the pressure with which it is withdrawn from step C). If desired, a control valve may be applied to reduce the F₂ pressure in the buffer tank. In the buffer tank, the F₂ pressure preferably is in a range from equal to or greater than 0.2 bar (abs) to 0.8 bar (abs). In view of this relatively low pressure, the buffer tank or tanks may require a large internal volume. For example, one or more buffer tanks having an internal volume from 10 to 50 m³ are preferred. Using two or more buffer tanks, e.g. 4 buffer tanks, having an internal volume of 25 m³ provides sufficient capacity to provide a reliable F₂ delivery. To be noted that the F₂ buffer tanks represent usually the major hold-up of F₂ of all the process and of all the plant, and hence are the most hazardous item in the process. Here, in spite of the large volume of the F₂ buffer tank, the safety of the process is significantly increased vs. the standard pressurized process, because any leak of F₂ to the external atmosphere is intrinsically impossible. To further increase the safety, against inlets of air or moisture, the buffer tanks can also be made double walled, with the jacked kept under vacuum or dry Nitrogen blanket. This intrinsic safety applies actually not only to the Buffer tanks, but to all process items, from the electrolytic cells down to the final user CVD chamber.

Preferably, the chamber cleaning method of the invention is performed such that step A) is performed in an electrolyzer, step B) is performed in a static scrubber, step C) is performed using a metallic filter, step D) is performed in a buffer tank or storage tank, and the F₂ leaving step D) is delivered to at least one chamber and used in the chamber in a chamber cleaning step E), wherein the electrolyzer, the static scrubber, the metallic filter, the buffer tank or storage tank and the at least one chamber are operably connected.

Preferrred embodiments of step E) :

It is preferred that the chamber cleaning step E) is performed by applying a remote plasma, an in-situ plasma or both.

As mentioned, the pressure of the F₂ in each of the steps B) to D) and in step E) is lower than the pressure of F₂ in the preceding step. Preferably, the F₂ pressure in step A) is equal to or lower than 1.1 bar (abs), preferably equal to or lower than 1.05 ± 0.02 bar (abs), and preferably, the F₂ is delivered to the chamber in step (II) at a pressure from equal to or greater than 0.2 bar (abs) to equal to or lower than 0.55 bar (abs).

The F₂ provided by the invention often contains HF from 0.1 to 2.5 % by weight, and it is very well suited as chamber cleaning agent. An F₂ containing 1 to 2 % by weight of HF can be manufactured technically easy (only a short contact time in the static scrubber is necessary, for example), no NaF tower is used, no cold trap to remove further HF, and nevertheless the F₂ containing HF is very suitable as chamber cleaning agent.

In a preferred embodiment, steps A) to E) are performed on site. The electrolyzer apparatus, scrubber, filter, storage tank and chamber or chambers are connected through lines in this embodiment.

The method of chamber cleaning has many advantages over the prior art. The method does not make use of steps needed to provide F₂ which is free of HF, and compressors or other means to raise the F₂ pressure are not applied ; contrary to the common belief that highly pure F₂, notably F₂ essentially free of HF, is needed for chamber cleaning, it was found that F₂ containing HF with a content of up to 2.5 % by weight of HF is very suitable for that purpose. Consequently, it is not necessary to subject F₂ to thorough and careful purifying operations to remove even minute amounts of HF. An added advantage is the finding that the purifying steps according to the process of the invention can be performed such that no pump or compressor is needed to subject purified F₂ to pressurization. The combination of both observations - simple purification with low pressure drop, and consequently, no need for pressurization - provides an economic advantage because of less energy consumption and less equipment ; the latter also has technical advantages because less equipment and less treatment steps mean less incidents due to failure of apparatus, less maintenance costs and less downtime. Less apparatus, less treatment steps and a lower F₂ pressure also provide a higher degree of safety.

The invention will now be further explained in view of figure 1.

F₂ is produced electrolytically in an electrolyzer comprising multiple indicated in figure 1 under the reference sign 1. H₂ formed is passed to scrubber 2 where F₂ and HF are removed, e.g. by a caustic aqueous solution. Gases passing scrubber 2 are released to the atmosphere in line 3. Raw F₂ is passed through line 4 (where the pressure of F₂ is approximately 1.05 bar (abs) to a scrubber 5 operated -80°C wherein solids and some HF are removed. F₂ leaves scrubber 5 at a pressure of approximately 0.95 bar (abs) through line 6. It is passed to filter 7 which is operated at 20°C to remove any solids still entrained. Through line 8, F₂ is passed at a pressure of 0.8 bar (abs) to a buffer tank 9. For example, 4 tanks, each with a capacity of 25 m³, can be foreseen as buffer tank assembly. The pressure in the buffer tank 9 corresponds approximately to the pressure in line 8. F₂ is withdrawn through line 10 to be supplied to chamber 11. The pressure of F₂ withdrawn from buffer tank 9 can be reduced by valves to a pressure in a range of from 0.55 to 0.2 bar (abs).

Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.

The following example is intended to explain the invention further without limiting it. It is performed according to the embodiment wherein the pressure in the electrolytic cell is 1.05 bar (abs).

Example 1 : Manufacture of F₂, its purification and its delivery for chamber cleaning

Step A) : manufacture of F₂

An electrolyte salt with a composition of about KF 2HF is filled into an electrolysis cell, heated to about 80 - 120°C and molten therein. A voltage between 8 to 10 V is applied, and current is passed through the composition of electrolyte salt dissolved in the hydrogen fluoride. HF is introduced into the electrolytic cell in an amount corresponding to consumed HF. Raw F₂ under a pressure of about 1.05 bar (abs) and H₂ form in the respective electrode compartments. H₂ is passed through a water scrubber to removed entrained HF and is then released to the atmosphere.

Step B) : Removal of HF and solids

The raw F₂ in the anode compartment of the electrolytic cells contains HF and entrained solids (mainly electrolyte salt) It is withdrawn from the electrolytic cells at a pressure of about 1.05 bar (abs) and contacted in a static scrubber with liquid HF which has a temperature of about -80°C. Most of the solids and the major part of HF entrained in the F₂ are removed in the static scrubber. The F₂ leaving the static scrubber has an HF content of about 1 % by weight, and its pressure is about 0.95 bar (abs).

Step C) : Additional solids removal in a filter

The F₂ leaving step B) is passed through a Monel metal frit with pores having a diameter of approximately 1 μιη to further reduce the solids content. The F₂ leaving the metal frit has a pressure of approximately 0.8 bar (abs) and a very low content of entrained solids. The frits are plugged from time to time by filtered solids. They can be cleaned by a treatment with liquids to dissolve the solids.

Step D) : Delivery to the buffer tank The F₂ leaving the Monel filter frit in step C) still has a content of about 1 % by weight of HF, but a very low solids content. It is passed into a buffer tank having an internal volume of 25 m³ ; four such buffer tanks are assembled. In the buffer tank, the F₂ is stored under a pressure of approximately

0.8 bar (abs). If desired, a control valve can be foreseen between the Monel filter of step C) and the buffer tank ; by means of the control valve, the pressure of the F₂ in the buffer tank can be reduced to a still lower level (e.g., it can be stored at a pressure ranging from 0.2 to 0.55 bar).

Step E) : As soon as F₂ is needed as chamber cleaning agent, it is provided from the buffer tank through a delivery line. It is passed through a control valve which further reduces the pressure, e.g. to 0.5 bar (abs) if the F₂ pressure in the buffer tank is greater than 0.5 bar (abs). The F₂ which finally is delivered to a chamber (used for the manufacture of photovoltaic cells) as cleaning agent has an HF content of 1 % by weight and a pressure of approximately 0.5 bar (abs).

In the chamber, F₂ containing HF is introduced as the cleaning agent, an in- situ plasma is ignited and the cleaning agent, having a pressure of about

0.5 bar (abs), removes deposits, e.g. deposits of Si and Si0₂, from the walls and parts inside the chamber.

Claims

C L A I M S

1. A method for the cleaning of at least one chamber using elemental fluorine wherein the fluorine is produced in at least one electrolytic cell, and wherein the pressure of F₂ in the electrolytic cell is equal to or lower than

1.1 bar (abs), and the pressure of the F₂ delivered to the at least one chamber is equal to or lower than 0.85 bar (abs).

2. The method of claim 1 wherein the pressure of F₂ in the electrolytic cell is equal to or greater than 1 bar (abs) and equal to or lower than 1.05

± 0.02 bar (abs).

3. The method of claim 1 wherein the F₂ contains equal to or more than 1 % by weight of HF, and a content of equal to or less than 2 % by weight of HF.

4. The method of claim 1 or 2 wherein the chamber is a CVD chamber.

5. The method of anyone of claims 1 to 3 wherein the chamber is used during the manufacture of a semiconductor, a micro-electromechanical system, TFT (flat panel display) or a solar cell for depositing at least one layer.

6. The method of anyone of claims 1 to 5 wherein F₂ is applied which was obtained in a process comprising the following steps A) to E)

A) at least one step of electrolytically producing raw F₂ from HF in the

presence of KF

B) at least one step of removing particles entrained in the raw F₂ obtained in step A)

C) at least one step of filtering any remaining particles out of the F₂ leaving step B)

D) an optional step of providing F₂ to a buffer tank or a storage tank ; and

E) a step wherein F₂ is withdrawn from step C) or step D) and delivered to a chamber to perform a t least one step of chamber cleaning.

7. The method of claim 5 wherein F₂ is applied which was obtained in a process comprising the following steps A) to E)

A) at least one step of electrolytically producing raw F₂ from HF in the

presence of KF B) at least one step of removing particles entrained in the raw F₂ obtained in step A)

D) a step of providing F₂ to a buffer tank or a storage tank ; and

E) a step wherein F₂ is withdrawn from step D) and delivered to a chamber to perform a t least one step of chamber cleaning.

8. The method of claim 6 consisting of steps A), B), C) and E).

9. The method of claim 7 consisting of steps A), B), C), D) and E).

10. The method of anyone of claims 6 or 9 wherein the particle filter of step C) comprises pores having a diameter between 0.01 and 20 um.

11. The method of anyone of claims 6 to 10 wherein the steps A) to E) are performed on the site of chamber cleaning.

12. The method of anyone of claims 6 to 11 wherein step A) is performed in an electrolyzer, step B) is performed in a static scrubber, step C) is performed using a metallic filter, step D) is performed in a buffer tank or storage tank, and the F₂ leaving step D) is delivered to at least one chamber and used in the chamber in a chamber cleaning step E), wherein the electrolyzer, the static scrubber, the metallic filter, the buffer tank or storage tank, the buffer tank or storage tank, and the at least one chamber are operably connected.

13. The method of anyone of claims 6 to 12 wherein the pressure of the F₂ in each of the steps B) to E) is lower than the pressure of F₂ in the preceding step.

14. The method of anyone of claims 1 to 13 wherein the F₂ is delivered to the chamber in step (II) at a pressure from equal to or greater than 0.2 bar (abs) to equal to or lower than 0.85 bar (abs).

15. The method of anyone of claims 1 to 14 wherein the F₂ is not subjected to any pressurizing treatment.