TW201341571A - Method for removing deposits performed with varying parameters - Google Patents

Abstract

A method for removing deposits from the surface of a solid body inside a plasma chamber and especially from the inner surface of a tube of a LPCVD system is described. During treatment of the deposits with an etching gas, especially F2, the pressure is varied, especially from a higher pressure level to a lower pressure level. This allows the removal of deposits from areas close to the etching gas inlet to areas more remote from the etching gas inlet. It is especially possible to remove deposits from the inner surface of tubes over the whole length, even of tubes having a length of more than 1 m, e.g. 2 m tubes. Remote microwave sources are preferred sources to irradiate the etching gas (cleaning gas).

Description

Method for removing deposits with varying parameters

The present invention claims the benefit of the European Patent Application No. 11195326.1 filed on Dec. 22, 2011, the entire content of which is incorporated herein in its entirety.

The present invention relates to a method for removing deposits which is particularly useful as a process for cleaning a processing chamber, particularly for large plasma chambers.

Processing chambers are used in the semiconductor and photovoltaic industry to fabricate semiconductors, flat panel displays, or photovoltaic devices. The fabrication generally includes a plurality of operations, such as etching using an etching gas, or chemical vapor deposition using a CVD gas to form a treated substrate, which is typically disposed in the process during processing. On the support inside the chamber. In other chambers, such as low pressure chemical vapor deposition chambers (LPCVD), the wafer is introduced into a chamber that is arranged on a support. Typically, they are assembled back to back such that only the other side is in contact with the deposition gas. After deposition, the support carrying the processed wafers is removed from the chamber and another support is introduced into the chamber. These wafers typically have diameters from 200 mm up to 400 mm and a tendency to process even larger wafers is observed.

In these manufacturing steps, particularly in the chemical vapor deposition step, The material is not only typically deposited on the substrate but is also deposited on a plurality of internal parts of the chamber, such as the chamber walls.

EP-A-1138802 discloses that amorphous germanium deposited on internal parts of a processing chamber can be thermally cleaned using fluorine as a purge gas. This reference also teaches that yttrium oxide or tantalum nitride cannot be removed by this method.

WO 2011/051410 discloses the removal of ruthenium hydride from the surface of a solid body.

In large LPCVD chambers, the inner walls can be composed of a plurality of large tubes that are up to 2 m long and possibly even longer, and which are suitable for processing up to 500 mm in diameter and even larger up to 500 mm. Wafer. At one end, a line is connected to a vacuum tube and the other end includes a line for introducing the process gas. The plasma within the tube can be obtained by a coil located on the exterior surface of the chamber. Since the deposits formed on the walls must be removed after several deposition steps to prevent damage to the wafer, it is customary to remove the tubes from the chamber and in a wet process Washing is carried out, for example, by contacting them with hydrofluoric acid. This is time consuming and, particularly annoying, because the deposition process is very sensitive in view of the process conditions, and the process conditions must be finely adjusted for each cleaned tube (especially for the deposition process). Obtain an optimal temperature curve). It usually takes a full working day to clean the tubes. It is not very desirable that the alternatives discard them.

The invention now makes, in particular, one for the processing chamber and in particular An efficient process for cleaning the tubes of large LPCVD systems is available. As indicated by the term "LP" CVD, the deposition in such systems is carried out in a vacuum.

Accordingly, the present invention is directed to a method for removing deposits from a surface of a solid body within a plasma chamber, the method comprising treating the deposits with an etching gas, the method comprising at least one step wherein The slurry activates the etching gas, and wherein the pressure within the plasma chamber is varied, at least in part during the performing the at least one processing step, and the etching gas comprises F ₂ or COF ₂ or by F ₂ or COF ₂ Composition. This change in pressure is used to imply a different gas velocity for the etching gas; as a result, the etching gas will pass through a shorter or longer spacing in an activated state and thus can act closer to or away from the A deposit of an inlet of a plasma activated etching gas in a chamber or tube. It is worth noting that, as mentioned above, tubes having a length of 2 m or longer are used in the LPCVD process.

A typical method of producing the plasma includes exposing the etching gas to a high frequency electric field.

In a first aspect of the first embodiment, the generated field has a frequency from 10 MHz to 15 MHz. A typical frequency is 13.56 MHz.

In a second aspect of the first embodiment, the generated field has a frequency from 40 MHz to 100 MHz, preferably from 40 MHz to 80 MHz. A typical frequency is selected from 40 MHz and 60 MHz.

In a third aspect of the invention, applied in the higher MHz range The frequency, for example, has a frequency greater than 500 MHz. Preferably, frequencies in the range from 1 GHz to 5 GHz are applied. The 2.45 GHz microwave frequency is especially suitable, which is also the frequency used in microwave ovens. The microwave source is a remote source connected to the inlet of the processing chamber. In the vicinity of the microwave source, the purge gas becomes dissociated. The reactive species are passed into the processing chamber and the cleaning is performed. These free radicals are assumed to be constantly maintained for a reactivity of approximately 0.5 seconds to 0.7 seconds.

This pressure change can be linear or non-linear.

The term "surface of a solid solid within a plasma chamber" preferably refers to the surface of a plurality of parts within the chamber, and it particularly refers to the walls of the chamber. A plurality of parts within the chamber, for example, structural material and a plurality of lines within the chamber, and a plurality of pump conduits. In a preferred embodiment, the method of the present invention involves the removal of deposits within the tubes of the LPCVD apparatus. In view of this preferred embodiment, the invention will be described in detail.

Preferred tubes are those described above which have at least one line for introducing an etching gas (also referred to as "cleaning gas" in the context of the present invention) and at least one line for connection to a On the vacuum pump. Preferably, the lines are separated from each other, such as the one or the lines for introducing an etching gas at or near one end of the tube, and the line for connecting to the vacuum pump or the other line at the other end of the tube .

Generally, in the case of a PECVD apparatus, the etching gas is converted into a plasma by a coil or a plurality of plates (which provide electromagnetic frequencies) surrounding the outer wall of the tube. This is especially suitable for "lower" frequencies, for example equal to or Below 100 MHz.

According to a preferred embodiment of the present invention, in the cleaning of the LPCVD apparatus with a tube, as described above, the microwave frequency is generated by a microwave source having a frequency equal to or greater than 500 MHz, which is in the cleaning Free radicals are provided in the gas. The purge gas is then transferred to the tube to be cleaned. Preferably, the microwave source is a remote microwave source.

In contrast to other cleaning processes, it is not necessary to remove the tube from the LPCVD apparatus.

At least one inlet for the etching gas is connected to a source of the gas, and the other at least one line is connected to a vacuum pump or remains attached thereto.

The vacuum pump is started to run and the line or lines for supplying etching gas into the tube are opened. Depending on the pump power and the supply of etching gas per unit time, any desired pressure can be generated within the tube to be cleaned.

As noted above, the pressure is varied during at least a portion of the processing step; the plasma remains activated during at least a portion of the pressure change. To achieve this increase in pressure, the pump power can be reduced and/or the supply of the etching gas can be increased. In order to achieve a reduction in pressure, the pump power can be increased and/or the supply of the etching gas can be reduced.

The pressure varies between a minimum pressure and a maximum pressure. The minimum pressure and maximum pressure may depend on the type of tube to be treated, for example depending on the inner diameter and length of the tube. The inner diameter of the tube makes it possible to process wafers of the desired size, for example crystals having a diameter of 200 mm to 400 mm Round, and currently uncommon wafers up to 500 mm in diameter. The length of the tube can vary, but typically the tubes have a length of 2 meters and even greater.

Usually, during the cleaning process, especially during the cleaning process of the tube, the minimum pressure is equal to or greater than 0.05 mbar, and preferably equal to or greater than 0.1 mbar. Preferably, in some cases, the minimum pressure is equal to or greater than 0.2 mbar. Usually, during the cleaning process, especially during the cleaning process of the tube, the maximum pressure is equal to or lower than 100 mbar, preferably equal to or lower than 30 mbar, and very preferably, It is equal to or lower than 5 mbar. More preferably, the maximum pressure is equal to or lower than 3 mbar, and most preferably, it is equal to or lower than 2.5 mbar, and particularly preferably, it is equal to or lower than 2 mbar.

Preferably, the ratio of the higher degree to the lower degree of a pressure change is equal to or greater than 1.5, and more preferably equal to or greater than 2. This ratio can be very high; it depends on the plasma device and the tools used to produce lower and higher pressures. Typically, the ratio of a higher degree to a lower degree of pressure change is equal to or less than 50. For example, the pressure can vary from a minimum pressure of 0.1 mbar to a maximum pressure of 3 mbar, or from 0.2 mbar to 2 mbar.

In a preferred alternative, the initial pressure in the tube to be cleaned is equal to or greater than 1.5 mbar. Especially good is 2 mbar. Under such a pressure, the cleaning gas removes deposits in the tube over a length of up to 50 cm from the inlet of the cleaning gas. By reducing the pressure The force can clean the areas of the tubes that are further away from the purge gas inlet. Here, a pressure equal to or lower than 0.2 mbar is particularly suitable. In another preferred alternative, the initial pressure is relatively low, for example equal to or lower than 0.2 mbar, in order to clean the area of the tube that is at a greater distance from the purge gas inlet, and then, to allow the pressure to be raised For example, up to 2 mbar, in order to clean the area closer to the gas inlet, especially those areas having a distance of between 50 cm and 1 m.

Therefore, the pressure change can be made such that the pressure changes from a lower degree to a higher degree. Alternatively, the pressure can vary from a higher level to a lower level.

In a particularly preferred embodiment, the chamber is an LPCVD chamber, the plasma source being a remote microwave source, and the electromagnetic frequency is equal to or greater than 500 MHz.

It is preferred to start from a higher pressure level and then gradually proceed to a lower level. In this way, after the plasma is activated, the surface near the inlet of the etching gas is cleaned. As the pressure is gradually reduced, the plasma activated etching gas front moves to a surface further from the etching gas inlet. This pressure is then reduced to cause all of the inner surfaces to contact the plasma activated etching gas.

If desired, the process can be carried out by changing the pressure from a higher degree to a lower degree at least twice, and between them, changing from a lower degree to a higher degree at least once, Or vice versa.

Usually, this is enough to introduce the etching gas into the tube, creating a hope The pressure, the plasma is activated and the pressure is varied from a higher level to a lower level.

Preferably, the pressure is adjusted by adjusting the power of a vacuum pump and/or adjusting the flow rate of the etching gas.

The processing time depends, for example, on the thickness and nature of the deposits, the desired level of cleaning, the power of the plasma, the gas pressure, and the nature of the etching gas. Whether or not the processing time is sufficient can be easily determined by optically controlling the inner surfaces of the tubes after cleaning. The duration of a drop in pressure (or, correspondingly, a rising change) is very flexible. For example, the time interval from the beginning of the higher or lower degree of change to correspondingly reaching the lower or higher degree may be from 1 second to 60 seconds; if desired, it may be even longer, up to 10 Minutes or longer. This change can be achieved by operating a vacuum pump to vary the pressure downward, or by opening a valve to supply the etching gas and thereby raising the pressure.

This pressure change can be repeated until the desired degree of deposit removal is achieved.

According to the process of the present invention, it is possible to clean a 2 m tube over the entire length in one hour.

The etching gas includes at least one of F ₂ and COF ₂ , or it is composed of F ₂ , COF ₂ or a mixture thereof. Such gases and gas mixtures include, but are not limited to, F ₂ , COF ₂ ; F ₂ or COF ₂ , further comprising at least one additional etching gas selected from the group consisting of NF ₃ , SF _6. Perfluoroalkanes and perfluoroolefins such as CF ₄ , C ₂ F ₆ , C ₃ F ₈ , C ₃ F ₆ , C ₄ F ₈ , C ₄ F ₆ , hydrofluoroalkanes and hydrofluoroolefins , such as CHF ₃ , C ₂ H ₂ F ₄ , C ₂ HF ₅ , or C ₃ H ₂ F ₄ , any mixture comprising or consisting of two or more thereof, and comprising at least one inert gas (eg A mixture of at least one inert gas selected from the group consisting of N ₂ and Ar).

Preferably, pure COF ₂ is applied.

F ₂ can be applied in pure form or preferably in a mixture with at least one of N ₂ and Ar, and is preferably applied in the form of a mixture comprising F ₂ , N ₂ and Ar.

Molecular fluorine (F ₂ ) is particularly effective for removing deposits from the surface of the tube. Fluorine gases do not have global warming potential and can be used, for example, with relatively low energy consumption compared to conventionally used NF ₃ purge gases, while effectively removing such deposits. Generally used is F ₂ diluted with N ₂ , Ar or both. In the binary mixture with N ₂ or Ar, the content of F ₂ is preferably from equal to or more than 10% by volume to equal to or less than 95% by volume; N ₂ or Ar constitutes a difference of up to 100% by volume. Generally, in the ternary mixture, the content of F ₂ is equal to or more than 10% by volume and equal to or less than 30% by volume, the content of N ₂ is equal to or greater than 55 % by volume and equal to or less than 80% by volume, and the content of Ar is equal to or It is more than 5% by volume and equal to or less than 15% by volume, and the contents of F ₂ , N ₂ and Ar are 100% by volume in total. In a preferred ternary mixture, the content of F ₂ is equal to or greater than 10% by volume and equal to or less than 25% by volume, and the content of N ₂ is equal to or greater than 60% by volume and equal to or less than 80% by volume, and the content of Ar is equal to Or more than 5% by volume and equal to or less than 15% by volume, and the contents of F ₂ , N ₂ and Ar total 100% by volume. A particularly suitable mixture consists of approximately 20% by volume of F ₂ , approximately 70% by volume of N ₂ , and approximately 10% by volume of Ar. Here, the term "substantially" preferably means a range of 20% by volume ± 1% by volume for F ₂ , a range of 70 % by volume ± 1% by volume for N ₂ and 10% by volume for Ar Range of ±1% by volume.

The deposits that can be removed by the process of the present invention can be organic deposits or inorganic deposits.

For example, organic deposits are formed, for example, in a plasma-assisted anisotropic etching process when a molecule with a CF bond is applied as an etchant, or when an organic compound is applied as a precursor to a polymer coating. For example, as described in WO 2010/007064, unsaturated hydrofluorocarbon molecules are suitable for this purpose. In anisotropic etching, it is desirable to form a polymeric coating in certain areas of the article to be treated to protect the coated regions from etching. In this case, or when a molecule having a CF bond is applied as an etchant, deposits from the fluorinated polymer are formed not only in the desired range of the article to be processed but also in the plasma chamber. On the surface and inside the tube. By application of the process of the present invention, F ₂ (if desired, or diluted Ar N ₂ and / or use) it is suitable for removing organic deposits.

The method of the invention is equally suitable for removing inorganic deposits within the tube. If the etchant forms a volatile reaction product with the deposit, the inorganic deposit can be removed. For example, Si deposits, SiO ₂ deposits or W deposits form gaseous SiF ₄ or gaseous WF ₆ corresponding to F ₂ as an etchant. Prominent examples of inorganic deposits that can be removed in accordance with the process of the present invention are SiON, amorphous, microcrystalline, and crystalline Si, SiO ₂ , amorphous, microcrystalline, and crystalline Si hydrides, TiN, TaN Or W.

The removal of Si is a major area in which this process is applied. In order to give an example, reference is made to EP-A-1138802, which discloses a plasma CVD process for forming an amorphous germanium layer using germane and hydrogen.

In the present invention, molecular fluorine (F ₂ ) is used as a preferred etchant for the etching gas.

The molecular fluorine used in the present invention can be produced, for example, by heating a suitable fluorometalate such as fluoronickate or manganese tetrafluoride. Preferably, the molecular fluorine is produced by electrolysis of a molten salt electrolyte, specifically a potassium fluoride/hydrogen fluoride electrolyte, preferably KF. 2HF.

Preferably, purified molecular fluorine is used in the present invention. Purification operations suitable for obtaining purified molecular fluorine for use in the present invention include removal of particles (e.g., by filtration or absorption) and removal of the starting material (particularly HF) (e.g., by absorption) and impurities (such as specifically CF ₄ and O ₂ ). Typically, the molecular fluorine used in the present invention has an HF content of less than 10 ppm moule. Typically, the fluorine used in the present invention contains at least 0.1 mole ppm of HF.

In a preferred embodiment, the purified molecular fluorine used in the present invention is obtained by one of the following methods: (a) electrolysis of a molten salt (specifically as described above) to provide HF-containing particles. And crude molecular fluorine which is free of impurities; (b) an operation for reducing the HF content relative to the HF content of the crude molecular fluorine, the operation including, for example, adsorption on sodium fluoride and preferably fractionation The HF content in the fluorine is reduced to the value mentioned above; (c) an operation of reducing the content of the particulate relative to the particulate content of the crude molecular fluorine, the operation comprising, for example, passing a fluorine-containing stream containing particles A solid absorbent such as, for example, sodium fluoride.

The molecular fluorine, in particular produced and purified as previously explained, can be supplied to the process according to the invention, for example in a transportable container. This method of supply is preferred when a mixture of fluorine gas and an inert gas as specifically described above is used in the process according to the invention.

Alternatively, the molecular fluorine can be supplied directly from its manufacture and freely purified to the process according to the invention, for example by a gas which is both attached to the ruthenium hydride removal step and to the fluorine production and/or purification. Conveyor system. This embodiment is particularly advantageous if the gas used in the process according to the invention consists of or consists essentially of molecular fluorine.

In the method according to the invention, the solid body generally comprises or consists of a conductive material, such as, for example, aluminum, or an aluminum alloy, in particular an aluminum/magnesium alloy, stainless steel, or a ceramic such as SiC, quartz or Al. ₂ O ₃ ) or consist of it. The preferred LPCVD tube system according to the present invention is made of ceramic, especially quartz.

The microwave source can be mounted to a flange having the same geometry as the front door through which the tube is loaded. A flange that can be secured to a suspension post, crane or a lifting device may have weight compensation and can be pressed onto the inlet of the pipe rather than the front door. The vacuum provided acts as a secure connection to the tube.

The invention also relates to a method for manufacturing a product, wherein At least one processing step of making the product is performed in a processing chamber, and deposits are formed on internal parts of the processing chamber, the process comprising cleaning the interior of the chamber by the method of the present invention Components. These tubes are described above.

Typically, the manufacture of the product includes at least one chemical vapor deposition step, for example, to form SiON, amorphous Si, microcrystalline, and crystalline Si, SiO ₂ , amorphous, microcrystalline, and crystalline Si hydrides. , TiN, TaN or W, or a step of forming a polymer coating, especially as described above, forming a fluorine-substituted polymer on a substrate. A typical product is selected from the group consisting of a semiconductor, a flat panel display, and a photovoltaic device such as a solar panel; preferably, a tube of a CVD apparatus, particularly a tube for a PLCVD apparatus for fabricating photovoltaic elements, is cleaned.

In the event that any disclosure of patents, patent applications, and publications incorporated by reference is inconsistent with the present disclosure, and the extent of such conflicts renders the term unclear, the present description should be preferred.

The following examples are intended to illustrate and not to limit the invention.

Instance Example 1: Cleaning the LPCVD tube with F ₂

In the manufacture of a solar panel, a chemical vapor deposition step using decane gas and H ₂ and a dopant gas containing PH ₃ is performed to deposit a layer on a plurality of planar substrates mounted on a support member. The crucible layer; the support member is automatically introduced into the quartz tube of an LPCVD processing chamber. The tube is suitable for processing 400 mm wafers and has a length of 2 m. A plurality of coils arranged around the tube are used to create a plasma within the tube. A deposition gas is introduced into the tube by a line at one end of the tube. Depending on the deposition conditions and the concentration of the reagent, it is observed that after the LPCVD step, microcrystalline or amorphous Si deposits appear on the inner wall of the tube, and the deposits may further include some hydrogen. After the planar substrates and their supports are removed from the tube, a line for transporting the deposition gas is connected to a line for transporting F ₂ as an etching gas (cleaning gas). Starting the vacuum pump (which is connected to the tube by a line on the opposite end of the inlet of the etching gas), supplies F ₂ , activates the plasma and adjusts the vacuum pump power and the F ₂ supply amount so that the tube The pressure inside is approximately 2 mbar. The inner surface of the quartz tube near the inlet of the etching gas is cleaned. Slowly, the pressure is reduced to approximately 0.2 mbar. The deposits are now washed step by step until the deposit over the entire length of the 2 m tube is removed. After less than an hour, the LPCVD process can be started again. There is no need to fine tune the temperature program.

Example 2: Plasma cleaning with F ₂ mixed with an inert gas

Repeat example 1. After removing the planar substrate from the chamber, a gas mixture consisting of molecular fluorine (20%), nitrogen (70%), and Ar (10%) is introduced into the chamber to activate the vacuum pump and will The pressure is adjusted to approximately 2 mbar. Start the plasma again. Slowly and gradually adjust the pressure At a minimum pressure of 0.2 mbar, the entire length of the 2 m tube is cleaned during this process.

Example 3: In-situ plasma cleaning with COF ₂

Example 1 was repeated using COF ₂ as a purge gas. Preferably, pure COF _{2 is used} .

Example 4: Cleaning the LPCVD tube with F ₂

In the manufacture of a solar panel, a chemical vapor deposition step using decane gas and H ₂ and a dopant gas containing PH ₃ is performed to deposit a layer on a plurality of planar substrates mounted on a support member. The ruthenium layer; the support is automatically introduced into the quartz tube of the LPCVD processing chamber. The tube is suitable for processing 400 mm wafers and has a length of 2 m. A deposition gas is introduced into the tube through a line on one end of the tube. Depending on the deposition conditions and the concentration of the reagent, it is observed that after the LPCVD step, microcrystalline or amorphous Si deposits appear on the inner wall of the tube, and the deposits may further include some hydrogen. After removing the planar substrates and their supports from the tube, a microwave source radiating at 2.45 GHz on a flange mated with the open gate of the LPCVD tube is arranged to cover the plasma. The front door of the tube. The microwave source is connected to a line for transporting F ₂ as an etching gas (cleaning gas), and the etching gas passes through the microwave source. Activating the vacuum pump (which is connected to the tube through a line at the opposite end of the inlet of the etching gas), supplies F ₂ , activates the microwave plasma and adjusts the vacuum pump power and the F ₂ supply amount so that the tube is inside the tube The pressure is roughly 2 mbar. The inner surface of the quartz tube near the inlet of the etching gas (up to about 50 cm to 1 m) is cleaned by F radicals generated by the microwave source and delivered to the tube. Slowly, the pressure is reduced to approximately 0.2 mbar. The deposits are now washed step by step, even at a distance greater than about 1 m from the purge gas inlet, until the deposit over the entire length of the 2 m tube is removed. After less than an hour, the LPCVD process can be started again. There is no need to fine tune the temperature program.

Claims (15)

A method for removing deposits from a surface of a solid body inside a plasma chamber, the method comprising treating the deposits with an etching gas, the method comprising at least one step, wherein the etching gas is activated by a plasma, And wherein at least in part during the performing the at least one processing step, the pressure within the plasma chamber is varied, and wherein the etching gas comprises F ₂ or COF ₂ or consists of F ₂ or COF ₂ . The method of claim 1, wherein the etching gas is activated by a plasma. The method of claim 1, wherein the method is for removing deposits from an inner surface of a tube of an LPCVD chamber. The method of claim 3, wherein the LPCVD chamber is used to produce a substrate having a diameter of up to 200 mm, preferably up to 400 mm. The method of claim 3, wherein the tube has a length equal to or greater than 1 m and equal to or less than 3 m. The method of claim 2, wherein the pressure changes downward from a higher degree to a lower level. The method of claim 1, wherein the etching gas consists of pure COF ₂ . The method of claim 1, wherein the etching gas system F ₂ is a mixture of at least one inert gas selected from the group consisting of nitrogen and argon. The method of claim 8, wherein the etching gas system is a mixture of F ₂ , N ₂ and Ar, and wherein the etching gas has an F ₂ content of from equal to or more than 10% by volume to equal to or less than 30% by volume, The N ₂ content is from equal to or more than 55 vol% to equal to or less than 80 vol%, and the Ar content is from equal to or more than 5 vol% to equal to or less than 15 vol%. The method of claim 1, wherein the pressure is from equal to or greater than 0.1 mbar to equal to or less than 2.5 mbar. The method of claim 1, wherein the chamber is an LPCVD chamber, the plasma source being a remote microwave source, and the electromagnetic frequency is equal to or greater than 500 MHz. The method of claim 3, wherein the tube is used to make a portion of a processing chamber of a photovoltaic element. The method of claim 1, wherein the method further comprises providing F ₂ by electrolysis of a molten salt electrolyte for use in the method. The method of claim 1, wherein the plasma source is a remote microwave source. A method for making a product, preferably a solar panel, wherein at least one processing step for making the product is performed in a processing chamber in which an organic or inorganic deposit is deposited in the processing chamber The method of the present invention includes cleaning the inner part by the method of any one of claims 1 to 14.