WO2013064737A2

WO2013064737A2 - Apparatus and method for processing substrate

Info

Publication number: WO2013064737A2
Application number: PCT/FI2012/051050
Authority: WO
Inventors: Jarmo Maula
Original assignee: Beneq Oy
Priority date: 2011-11-01
Filing date: 2012-10-31
Publication date: 2013-05-10
Also published as: WO2013064737A3; TW201339354A

Abstract

The present invention relates to an apparatus and a method for subjecting a surface of a substrate (5) to successive surface reactions of at least a first precursor (A) and a second precursor (B). The apparatus comprises a reaction space (7) and a precursor system (6) for supplying the at least first and second precursors (A, B) to the reaction space (7).The precursor system (6) comprises a precursor vessel (10, 12), a precursor supply line (16, 18, 30) for supplying the precursor (A, B) from precursor vessel (10, 12) to the reaction space (2) and a dosing valve (22, 24, 32) provided to the precursor supply line (16, 18, 30). The apparatus further comprises a temperature sensor (8, 9, 11, 13, 15, 17, 19) arranged to the precursor system (6) in free gas space (16, 18, 30, 38) upstream of the dosing valve (22, 24, 32).

Description

Apparatus and method for processing substrate

Field of the invention

The present invention relates to an apparatus for processing a substrate and especially to an apparatus as defined in the preamble of independent claim 1 . The present invention further relates to a method for processing a substrate and more particularly to a method as defined in the preamble of independent claim 8.

Background of the invention

The present invention relates to processes where substrates are processed by subjecting a surface of the substrate to successive surface reactions of two or more vapour phase or gas phase precursors. Processing of a precursor refers generally to coating a surface of the substrate with a coating layer or doping a surface layer with a doping agent. One generally known method for processing a surface of the substrate by subjecting a surface of the substrate to successive surface reactions of two or more vapour phase or gas phase precursors is atomic layer deposition (ALD). During processing two or more precursors are successively supplied to the surface of the substrate via precursor system.

The dosages of the precursors supplied during one processing cycle used in the processing are generally small. The coating or doping process works properly if the precursors are supplied at designed order and a designed minimum amount of the precursors is supplied. Therefore it is essential to track or detect the precursor supply for monitoring and controlling the processing of the substrate. Prior art methods and systems for detecting supply of the precursors are based on pressure measurements. Conventionally these prior art detection systems have been used to track pressure changes in flow channels before and after a reaction chamber in which the substrates are processed.

The problem with prior art detection systems utilizing pressure measurement devices, manometers, is that they are unable to provide exact information and information from the precursor vessel. Furthermore, manometers have to be at the same temperature as the precursor for avoiding condensation to the manometer. This makes the constructions in connection with manometer very complex or even impossible due to the high process and precursor temperatures used in atomic layer deposition. Additionally highly reactive precursors may deteriorate or even prevent the operation of the manometers. The manometers may also provide very small signals making the detection or tracking difficult. Brief description of the invention

The object of the present invention is to provide an apparatus and a method so as to overcome or at least alleviate the prior art disadvantages. The objects of the present invention are achieved with an apparatus according to the characterizing portion of claim 1 . The objects of the present invention are further achieved with a method according to the characterizing portion of claim 8.

The preferred embodiments of the invention are disclosed in the dependent claims.

The present invention is based on the idea of monitoring supply of vapour phase materials by temperature measurement with a temperature sensor inside an apparatus for processing a substrate by subjecting a surface of the substrate to successive surface reactions of at least a first precursor and a second precursor, the apparatus comprising a precursor system for supplying the at least first and second precursors. According to the present invention the temperature sensor may be arranged to detect supply of at least one of the precursors in vapor phase. When precursors are contained in a precursor vessel there is a certain vapor pressure of precursor in the free gas space in the precursor vessel when the precursor vessel is closed. Due to the mentioned vapor pressure of the precursor all the surface in the free gas space will be exposed to the vapor phase precursor. Thus the precursor will be attached to or in contact with surfaces in the free gas space of the precursor vessel. When the precursor vessel or a conduit connected to it is opened the vapor pressure in the free gas space inside the precursor vessel will decrease as the gaseous precursor flows out of the precursor vessel. The decreased vapor pressure causes precursor to leave or vaporize from the surfaces of the free gas space of the precursor vessel. Leaving or vaporization of the precursor from a surface will cause temperature decrease on the surface as the vaporization takes thermal energy from the surface. In some embodiments, when a liquid or solid precursor material evaporates and goes through a phase transition it absorbs energy from the environment. This absorbed energy provides a temperature variation by decreasing the temperature of the environment. In a method for processing a substrate by subjecting a surface of the substrate to successive surface reactions of at least a first precursor and a second precursor, the evaporation of at least one precursor takes place during a dosing state when the dosing valve is opened. Therefore a temperature sensor can detect temperature variations during evaporation of a precursor or during dosing. A corresponding temperature decrease will occur when molecules of a precursor material leaves from a surface. Therefore the present invention provides an apparatus comprising a reaction space in which the substrate is processed and a precursor system for supplying the at least first and second precursors to the reaction space. The precursor system comprises a precursor vessel for a precursor, a precursor supply conduit for supplying the precursor from precursor vessel to the reaction space and a dosing valve provided between the precursor vessel and the reaction space for supplying a dose of the precursor to the reaction space by opening and closing the dosing valve. According to the present invention the apparatus further comprises a temperature sensor arranged to the precursor system in free gas space upstream of the dosing valve for detecting supply of one or more gaseous precursors to the reaction space. The present invention also provides a method for processing a substrate in a reaction space by subjecting a surface of the substrate to successive surface reactions of at least a first gaseous precursor and a second gaseous precursor, the method comprising supplying a dose of the precursors from a precursor vessel to the reaction space via a precursor supply conduit by opening and closing a dosing valve provided between precursor vessel and the reaction space. According to the present invention the method further comprises detecting the supply of a precursor by temperature measurement with a temperature sensor provided in free gas space upstream of the dosing valve.

The present invention has the advantage that it provides a simple and accurate way for monitoring dosing of precursor and other vapor phase materials when a substrate is processing in an apparatus by subjecting it to successive surface reactions of precursors. The present invention further provides a reliable measurement solution which is not sensitive to reactive precursors.

Brief description of the figures In the following the invention will be described in greater detail, in connection with preferred embodiments, with reference to the attached drawings, in which

Figure 1 is a schematic view of an atomic layer deposition apparatus according to one embodiment of the present invention;

Figure 2 shows a schematic view of precursor vessel of a precursor system of an atomic layer deposition apparatus according to one embodiment of the present invention; and

Figure 3 shows a schematic view of another precursor vessel of a precursor system of an atomic layer deposition apparatus according to one embodiment of the present invention. Detailed description of the invention

The figure 1 shows one exemplary embodiment of an atomic layer (ALD) apparatus. Atomic layer deposition is generally known technique for coating and doping substrates by subjecting the surface to successive surface reactions of at least two precursors. The precursors are supplied to a reaction chamber in gaseous form. After the surface reactions of one precursor is carried out the reaction chamber is evacuated and then purge gas is supplied may be supplied to the reaction chamber. After the purge gas pulse the reaction chamber is again evacuated and then another precursor material is supplied to the reaction chamber. In some applications the evacuation and/or supply of purge gas may be omitted. Usually ALD is operated with two separate precursor materials, but it may also be operated with more than two separate precursor materials. A full ALD cycle is completed when all precursors are supplied once to the reaction chamber. The precursor materials may be in gaseous, liquid or in solid form in precursor vessels and during supply of the precursors to the reaction chamber they are vaporized.

The ALD apparatus of figure 1 comprises a chamber 4 and a reaction chamber 2 inside the chamber 4. The reaction chamber 2 defines inside a reaction space 7. It should be noted that in another embodiment the chamber 4 may be omitted and the reaction chamber 2 may function also as a chamber. The pressure in the chamber 4 may have any desired value. Although ALD process commonly use vacuum during the deposition, the use of vacuum is not requirement for the ALD. However, vacuum often provides the most efficient deposition environment and thus the chamber 4 may be a vacuum chamber. In a yet alternative embodiment the ALD apparatus may comprise a nozzle head (not shown) for supplying precursors on the surface of a substrate such that no separate reaction chamber is provided. In that case the reaction chamber may be form between the surface or the substrate and the nozzle head. As shown in figure 1 a substrate 5 is placed in the reaction space 7 inside the reaction chamber 2. In this embodiment only one substrate 5 is processed at a time but in an alternative embodiment several substrates may be processed at the same time in the reaction chamber 2. The substrates 5 may be placed on a substrate holder (not shown) for loading into the reaction chamber 2, processing inside the reaction chamber 2 and unloading from the reaction chamber 2. The ALD apparatus further comprises a precursor system 6 for supplying precursors to the reaction chamber 2 and for exhausting precursors from the reaction chamber 2. The precursor system 6 comprising a precursor vessels 10, 12 for precursors A, B, precursor supply conduits 16, 18 for supplying the precursors A, B from precursor vessels 10, 12 to the reaction space 7, respectively, and dosing valves 22, 24 provided between the precursor vessels 10, 12 and the reaction space (7) for supplying a dose of the precursors A, B to the reaction space 7 by opening and closing the dosing valves 22, 24, respectively.

The embodiment of figure 1 comprises a first precursor vessel 10 having first precursor A, a second precursor vessel 12 having second precursor B and a purge gas vessel 14 having purge gas C. The precursors A, B and the purge gas are supplied to the reaction chamber 2 via a supply conduit 30. The supply conduit 30 is provided with a supply valve 32 for opening and closing the supply conduit 30 and/or for controlling the supply of the precursors A, B and purge gas C. In another embodiment the supply valve may be omitted. The first precursor vessel 10 is connected to the supply conduit 30 with a first precursor conduit 16. The first precursor conduit 16 is provided with a first dosing valve 22 for carrying out supply of the first precursor A from the first precursor vessel 10. The second precursor vessel 12 is connected to the supply conduit 30 with a second precursor conduit 18. The second precursor conduit 18 is provided with a second dosing valve 24 for carrying out supply of the second precursor B from the second precursor vessel 12. The purge gas vessel 14 is connected to the supply conduit 30 with a purge gas conduit 20. The purge gas conduit 20 is provided with a purge gas dosing valve 26 for carrying out supply of the purge gas C from the purge gas vessel 14. As shown in figure 1 the first precursor conduit 16, the second precursor conduit 18 and the purge gas conduit 20 are all connected to the supply conduit 30 at a branch point 28. This means that in this embodiment the supply conduit 30 is common for all the precursors A, B and the purge gas C. Alternatively the first and second precursor conduit 16, 18 and the purge gas conduit 20 may be separate and extend directly to the reaction chamber 2. It is also possible that two or more of the precursor conduits 16, 1 8 and the purge gas conduit 20 have a common supply conduit 30. In the case of common supply conduit, as in figure 1 , the supply valve 32 may also be formed or it may operate as a dosing valve. The dosing valves 22, 24, 26 may also be provided to or in connection with the precursor vessels 10, 12 or purge gas vessel 14 instead of precursor conduits 16, 18 and purge gas conduit 20. Also alternatively the dosing valves may be provided to or in connection with the reaction chamber 2, especially when the separate precursor conduits extend directly to the reaction chamber 2.

Some ALD systems use continuous N₂ flow through the deposition system and the purge gas dosing valve 26 is replaced by gas mass flow controller. The precursor system 6 comprises also an evacuation conduit 34 via which the precursors A, B and the purge gas C may be evacuated from the reaction chamber 2. The evacuation conduit 34 may be provided with suction by using a suction pump or the like (not shown). The evacuation conduit 34 may also be provided with evacuation valve 36 for opening and closing the evacuation conduit 34 and/or controlling the evacuation from the reaction chamber 2. In the precursor vessels 10, 12 the precursors A, B is normally in liquid or solid form, but it may also be in gaseous from. During the non-dosing state of the precursor A, B the dosing valve 22, 24 are closed and during a dosing state the dosing valve 22, 24 is opened for short time to supply a dosing pulse of precursor A, B to the reaction chamber 2. In the same manner during a purge state the purge gas dosing valve 26 is opened for supplying purge gas C to the reaction chamber 2 and during non-purge state the purge gas dosing valve 26 is closed. Each dosing valve 22, 24, 26 is opened at a time for supplying the precursors A, B and the purge gas C separately to the reaction chamber 2. Thus the dosing valves 22, 24 are or may be arranged for supplying a desired dose of the precursor A, B to the substrate 5 by opening and closing the dosing valve 22, 24.

The precursor A, B is kept on specified conditions in the precursor vessel 10, 12. Therefore, there is a specified pressure and temperature inside the precursor vessels 10, 12. When the dosing valve 22, 24 is opened the precursor vapor or gas in the vessel flows through the dosing valve 22, 24 to the reaction chamber 2. Liquid or solid precursors A, B are vaporized or sublimated during and/or between the supply doses. In a case of gaseous precursor A, B or purge gas C no vaporization occurs, but the precursor A, B or purge gas C will flow through the dosing valve 22, 24, 26 to the reaction chamber 2. The precursor A, B may be heated in the precursor vessel 10, 12 to keep in a desired temperature. The heating may be carried out with a radiant heater, conductive heater or convective heater (not shown). Figure 1 shows one embodiment of the present invention in which the ALD apparatus is provided with temperature sensors 9, 1 1 and 19. The temperature 9, 1 1 , 19 sensors are positioned to the precursor conduits 16, 18 and supply conduit 30 of the precursor system 6, respectively, and upstream of the dosing valves 16, 18 and supply valve 32. The temperature sensors 9, 1 1 , 19 are arranged to detect supply of at least one of the precursors A, B in vapor phase to the reaction chamber 2. The temperature sensor 9, 1 1 , 19 may be any known type of temperature sensor such as a resistance temperature detector, resistive thermal device (RTD), a thermistor, a semiconducting sensor, a thermocouple, a thermo element, an infrared thermometer, or a Coulomb Blockade thermometer. Also expensive systems detecting gas/vapor molecule temperature directly or indirectly can be used. Alternatively the temperature sensor 9, 1 1 , 19 may comprise any kind of thermo element arranged to the supply conduit 30 or the precursor conduits 16, 18. The mass of the thermo element is preferably small such that it may detect also very small temperature changes. In this kind of arrangement the temperature sensor 9, 1 1 , 19 may be arranged to monitor the temperature changes of the thermo element provided to the supply conduit 30. As shown in figure 1 the first precursor vessel 10 is connected to the supply conduit 30 with the first precursor conduit 16 provided with the first dosing valve 22. The second precursor vessel 12 is connected to the supply conduit 30 with the second precursor conduit 18 provided with the second dosing valve 22. In a non-dosing state the dosing valves 22, 24 are closed and when a dose of precursor A or B is supplied to the reaction chamber 2 the respective dosing valve 22, 24 is opened for short time. In a non-dosing state of the dosing valve 22, 24 the dosing valve 22, 24 prevents precursor A, B from flowing to the reaction chamber 2. When gaseous, liquid or solid precursor A, B is used, there is a certain vapor pressure of precursor A, B in the free gas space of the precursor vessel 10, 12. The free gas space means the space in the vessel 10, 12 not occupied by the precursor A, B up to the dosing valve 22, 24 in a case of liquid or solid precursors. When gaseous precursor is used the free gas space means the whole space of the vessel 10, 12 up to the dosing valve 22, 24. Thus the free gas space comprises space in the precursor vessel 10, 12 not occupied by the precursor A, B and space inside the precursor conduit up to the dosing valve 22, 24 or in some cases up to the supply valve 30. According to the above mentioned the temperature sensors 9, 1 1 , 19 may be arranged in a free gas space in fluid connection with the interior of the precursor vessel 10, 12 or in fluid connection with the precursor A, B in the precursor vessel 10, 12. The temperature sensors are arranged to the precursor system and in the free gas space upstream of the dosing valve. Accordingly, precursor material is supplied from the precursor vessel via the precursor conduit to the reaction space and the dosing valve is provided between the precursor vessel and the reaction space. Therefore, arranging the temperature sensor to free gas space upstream of the dosing valve means that the temperature sensor is placed to free gas space in fluid connection with the precursor or inner volume of the precursor vessel when the dosing valve is closed. In other words the temperature sensor is arranged in the free gas space in the precursor vessel or between the precursor vessel and the dosing valve.

Thus all the surfaces of the free gas space are exposed to the vapor phase precursor A, B. In the dosing state of the precursor A, B the respective dosing valve 22, 24 is opened causing leaving of the precursor A, B from the volume of the free gas space and also from the surfaces of the free gas space. The leaving of the precursors A, B may occur due evaporation, flowing or sublimation of the precursor A, B. The leaving of the precursor A, B from surfaces of the free gas space consumes energy and thus the temperature of the surface will temporarily decreased. The consumed energy for the precursor A, B to leave from the surface is at least partly taken directly from the material of the surface as thermal energy. In the embodiment of figure 1 there is a first temperature sensor 9 provided to the free gas space of the first precursor vessel 10 upstream of the first dosing valve 22 provided to the first precursor conduit 16. A second temperature sensor 1 1 is provided to the free gas space the second precursor vessel 12 upstream of the second dosing valve 24 provided to the second precursor conduit 18. The temperature sensors 9, 1 1 may be located to the free space gas inside the precursor vessel 10, 12 or in the precursor conduit 16, 18 upstream of the dosing valve 22, 24. In a non-dosing state the temperature sensors 9, 1 1 are also exposed to the precursor vapor and the precursor vapor will attach to or be in contact with the surfaces of the temperature sensor 9, 1 1 such that the temperature of the temperature sensors 9, 1 1 reach the temperature of the precursor vapor during long enough exposure. When the dosing valve 22, 24 is opened the pressure inside the precursor vessel 10, 12 and the free gas space upstream of the dosing valve 22, 24 decreases and precursor A, B will flow out of the precursor vessel 10, 12 to the reaction chamber 2 such that precursor A, B will leave from the surface of the temperature sensor 9, 1 1 . The leaving of the precursor A, B from the surface of the temperature sensor 9, 1 1 decreases the temperature of the temperature sensor 9, 1 1 . In some embodiments the precursor A, B is evaporated from the surface of the temperature sensor 9, 1 1 . The evaporation causes the temperature of the temperature sensor 9, 1 1 to decrease as the evaporation takes energy. Accordingly the temperature sensor 9, 1 1 may monitor and detect the leaving or evaporation of the precursor A, B and thus the supply of the precursor A, B to the reaction chamber during the dosing state when the dosing valve 22, 24 is opened. Figure 2 shows an alternative embodiment in which a floating temperature sensor 15 is arranged inside the precursor vessel 10 comprising liquid precursor A and specifically to the free gas space 38 inside the precursor vessel 10. As shown in figure 2 at least part of the floating temperature sensor 15 remains above the surface level of the liquid precursor A in the free space 38 of the precursor vessel 10. This may be carried out such that a thermo element of the floating temperature sensor remains above the surface of the liquid precursor A. The precursor vessel 10 is connected to the precursor conduit 16 having a dosing valve 22. In a non-dosing state the floating temperature sensor 15 is at least partly exposed to the precursor vapor in the free space 38. When the dosing valve 22 is opened the pressure inside the precursor vessel 10 and the free gas space 38 decreases and liquid precursor A evaporates. The evaporation occurs also on the surfaces of the floating temperature sensor 15 above the surface level of the liquid precursor A and thus temperature of the floating evaporation temperature sensor 15 decreases as the evaporation takes energy. Accordingly the floating temperature sensor 15 may monitor and detect the evaporation of the precursor A and thus the supply of the precursor A to the reaction chamber 2 during the dosing state when the dosing valve 22 is open. Furthermore, the floating temperature sensor 15 may be arranged to monitor surface level of the liquid precursor A in the precursor vessel 10 or the position or inclination of the precursor vessel 10. Thus the temperature sensor 15 may be arranged inside the precursor vessel 10, 12 as a level sensor for detecting surface level of a liquid precursor A, B in the precursor vessel 10, 12 or the position of the precursor vessel 10, 12. The floating temperature sensor 15 may be connected to a control system 42, such a computer system, through a signal line 40 for controlling the operation of the ALD apparatus and for controlling the supply of the precursor A to the reaction chamber 2. The floating temperature sensor 15 may be a resistance temperature detector, resistive thermal device (RTD), a thermistor, a semiconducting sensor, a thermocouple, a thermo element, an infrared thermometer, or a Coulomb Blockade thermometer.

Figure 3 shows yet another embodiment of the present invention in which several temperature sensors 17 are arranged to the precursor vessel 10. The temperature sensors 17 are positioned sequentially from the bottom of the precursor vessel 10 to the upper part of the precursor vessel 10 such that when the surface level of the liquid precursor A lowers the temperature sensors 17 are revealed from liquid precursor A. The temperature sensors 17 may be attached to the inner side wall the precursor vessel 10. This kind of arrangement may comprise one or more temperature sensors 17 functioning as level sensors in the precursor vessel 10. When the ALD apparatus is used a portion of the precursor A is evaporated during each dose and supplied to the reaction chamber for processing a substrate. Thus the amount of precursor A in the precursor vessel 10 decreases and the surface level of the precursor A lowers. When a temperature sensor 17 is revealed above the surface level of the liquid precursor A it is in the free space 38 of the precursor vessel and it may detect the evaporation of the precursor A during dosing state, as mentioned above. All the evaporation temperature sensors 17 may be connected to a control system 42, such as a computer system 42, via signal line. The arrangement of figure 3 may be used for monitoring and detecting the evaporation of the precursor A and thus the supply of the precursor A to the reaction chamber 2 during the dosing state. Furthermore, the temperature sensors 17 may be arranged to monitor surface level of the liquid precursor A in the precursor vessel 10 or the position or inclination of the precursor vessel 10. This is achieved by monitoring which of the temperature sensors 17 detect the temperature change caused by evaporation of the precursor A during a dosing state. The temperature sensors 17 which do not detect precursor A evaporation are below the surface level of the liquid precursor A. The temperature sensor 17 may be a resistance temperature detector, resistive thermal device (RTD), a thermistor, a semiconducting sensor, a thermocouple, a thermo element, an infrared thermometer, or a Coulomb Blockade thermometer.

According to the above described the present invention provides an ALD apparatus in which one or more temperature sensors are used for monitoring or detect supply of precursor A, B and/or purge gas to a reaction chamber in a process for subjecting a surface of a substrate 5 to successive surface reactions of at least a first gaseous precursor A and a second gaseous precursor B. Furthermore, the present invention may provide an ALD apparatus in which one or more temperature sensors may be used for monitoring surface level of a liquid precursor A, B in a precursor vessel 10, 12 in a process for subjecting a surface of the substrate 5 to successive surface reactions of at least a first precursor A and a second precursor B. Generally the present invention provides an apparatus and method for monitoring or detecting precursor supply to the reaction chamber or reaction space by temperature measurement. In the present invention temperature sensors may be arranged in the precursor vessel or in the free space upstream of the dosing valve to detect evaporation of precursors during dosing state through the temperature change caused by the evaporation. Thus these temperature sensors are always located in fluid connection with the liquid or solid precursor in a non-dosing state in which the dosing valve is closed. It should be noticed that the ALD apparatus may comprise one or more of the above described temperature sensors and the measurement results of the temperature sensors may be further used for controlling or adjusting the precursors supply and evacuation or other operating features.

The present invention provides a method for detecting the supply of a precursor A, B by measuring temperature with the temperature sensor 9, 1 1 , 15, 17, 19 arranged in a free gas space 16, 18, 30, 38 in fluid connection with the interior of the precursor vessel 10, 12 or in fluid connection with the precursor A, B in the precursor vessel 10, 12. The method may detect vaporization of a liquid or solid precursor A, B in the free gas space 16, 18, 30, 38 by measuring temperature with the temperature sensor 9, 1 1 , 15, 17, 19 during supply of the precursor A, B. The method is based on detecting precursor supply by measuring temperature comprises detecting a temperature change of a thermo element of the temperature sensor 9, 1 1 , 15, 17, 19 during the supply of the precursor A, B or measuring temperature change with the temperature sensor 9, 1 1 , 15, 17, 19 caused by evaporation of the precursor A, B in the free gas space 16, 18, 30, 38 when the dosing valve is opened. The present invention furthermore provides use of a temperature sensor 8, 9, 1 1 , 13, 15, 17, 19 for detecting supply of a gaseous precursor A, B from a precursor vessel 10, 12 to a reaction space 7 via a precursor supply line 16, 18, 30 by opening and closing a dosing valve 22, 24, 32 provided to the precursor supply line 16, 18, 30 in a process for subjecting a surface of the substrate 5 to successive surface reactions of at least a first precursor A and a second precursor B by measuring temperature change with the temperature sensor 9, 1 1 , 15, 17, 19 with the temperature sensor 9, 1 1 , 15, 17, 19 in free gas space 16, 18, 30, 38 between the precursor A, B and the dosing valve 22, 24, 32 during supply of the precursor A, B. The invention also provides se of a temperature sensor 17 for detecting surface level of one or more liquid precursors A, B in a precursor vessel 10, 12 in a process for subjecting a surface of the substrate 5 to successive surface reactions of at least a first precursor A and a second precursor B.

It is apparent to a person skilled in the art that as technology advanced, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

Claims

1 . An apparatus for processing a substrate (5) by subjecting a surface of the substrate (5) to successive surface reactions of at least a first gaseous precursor (A) and a second gaseous precursor (B), the apparatus comprising: - a reaction space (2) in which the substrate (5) is processed; and

- a precursor system (6) for supplying the at least first and second precursors (A, B) to the reaction space (7), the precursor system (6) comprising:

- a precursor vessel (10, 12) for a precursor (A, B); - a precursor supply conduit (16, 18, 30) for supplying the precursor (A, B) from precursor vessel (10, 12) to the reaction space (7); and

- a dosing valve (22, 24, 32) provided between the precursor vessel (10, 12) and the reaction space (7) for supplying a dose of the precursor (A, B) to the reaction space (7) by opening and closing the dosing valve (22, 24, 32), characterized in that the apparatus further comprises a temperature sensor (9, 1 1 , 15, 17, 19) arranged to the precursor system (6) in free gas space (16, 18, 30, 38) upstream of the dosing valve (22, 24, 32) for detecting supply of one or more gaseous precursors (A, B) to the reaction space (2).

2. An apparatus according to claim 1 , characterized in that the temperature sensor (9, 1 1 , 15, 17, 19) is arranged in a free gas space (16, 18, 30, 38) in fluid connection with the interior of the precursor vessel (10, 12) or in fluid connection with the precursor (A, B) in the precursor vessel (10, 12).

3. An apparatus according to claim 1 or 2, characterized in that the dosing valve (22, 24, 32) is provided to the precursor supply conduit (16, 18, 30) between the precursor vessel (10, 12) and the reaction space (7) or to the precursor vessel (10, 12).

4. An apparatus according to any one of claims 1 to 3, characterized in that the temperature sensor (15, 17) is arranged to the free gas space (38) inside the precursor vessel (10, 12) outside of the liquid or solid precursor (A, B).

5. An apparatus according claim 4, characterized in that the at least one temperature sensor (9, 1 1 , 15, 17) is arranged inside the precursor vessel (10, 12) as a level sensor for detecting surface level of a liquid precursor (A, B) in the precursor vessel (10, 12) or the position of the precursor vessel (10, 12).

6. An apparatus according claim 3, characterized in that the temperature sensor (9, 1 1 , 19) is arranged in the precursor supply conduit (16, 18, 30) upstream of the dosing valve (22, 24, 32) for detecting supply of the precursor (A, B) or for detecting vaporization of the precursor (A, B).

7. An apparatus according any one of claims 1 to 5, characterized in that the temperature sensor (9, 1 1 , 15, 17, 19) a resistance temperature detector, resistive thermal device (RTD), a thermistor, a semiconducting sensor, a thermocouple, a thermo element, an infrared thermometer, or a Coulomb Blockade thermometer.

8. A method for processing a substrate (5) in a reaction space (7) by subjecting a surface of the substrate (5) to successive surface reactions of at least a first gaseous precursor (A) and a second gaseous precursor (B), the method comprising supplying a dose of the precursors (A, B) from a precursor vessel (10, 12) to the reaction space (7) via a precursor supply conduit (16, 18, 30) by opening and closing a dosing valve (22, 24, 32) provided between precursor vessel (10, 12) and the reaction space (7), characterized in that the method further comprises detecting the supply of a precursor (A, B) by temperature measurement with a temperature sensor (9, 1 1 , 15, 17, 19) provided in free gas space (16, 18, 30, 38) upstream of the dosing valve (22, 24, 32).

9. A method according to the claim 8, characterized in that detecting the supply of a precursor (A, B) by measuring temperature with the temperature sensor (9, 1 1 , 15,

17, 19) arranged in a free gas space (16, 18, 30, 38) in fluid connection with the interior of the precursor vessel (10, 12) or in fluid connection with the precursor (A,

B) in the precursor vessel (10, 12).

10. A method according to claim 8 or 9, characterized in that the method comprises detecting vaporization of a liquid or solid precursor (A, B) in the free gas space (16,

18, 30, 38) by measuring temperature with the temperature sensor (9, 1 1 , 15, 17, 19) during supply of the precursor (A, B).

1 1 . A method according to any one of claims 8 or 10, characterized in that detecting precursor supply by measuring temperature comprises detecting a temperature change of a thermo element of the temperature sensor (9, 1 1 , 15, 17, 19) during the supply of the precursor (A, B).

12. A method according to claim any one of claims 8 to 1 1 , characterized in that the method comprises measuring temperature change with the temperature sensor (9, 1 1 , 15, 17, 1 9) caused by evaporation of the precursor (A, B) in the free gas space (16, 18, 30, 38) when the dosing valve is opened.

13. A method according to claim any one of claims 8 to 12, characterized in that the method comprises measuring temperature with the temperature sensor (9, 1 1 , 15,

17, 19) inside the precursor vessel (10, 12) or in the precursor supply conduit (16,

18, 30) upstream of the dosing valve (22, 24, 32) during supply of the precursor (A, B).

14. A method according to any one of claims 8 to 13, characterized in that the method comprises detecting surface level of a liquid precursor (A, B) in a precursor vessel (10, 12) by monitoring supply of gaseous precursor (A, B) by temperature measurement with the temperature sensor (15, 17).

15. A method according to any one of claims 8 to 14, characterized in that the temperature measurement is carried out by a resistance temperature detector, resistive thermal device (RTD), a thermistor, a semiconducting sensor, a thermocouple, a thermo element, an infrared thermometer, or a Coulomb Blockade thermometer.

16. A method according to any one of claims 8 to 15, characterized by adjusting the precursor (A, B) supply based on the temperature measurement results or by adjusting opening and closing of the dosing valve based on the temperature measurement results.

17. Use of a temperature sensor (8, 9, 1 1 , 13, 15, 17, 19) for detecting supply of a gaseous precursor (A, B) from a precursor vessel (10, 12) to a reaction space (7) via a precursor supply line (16, 18, 30) by opening and closing a dosing valve (22, 24, 32) provided to the precursor supply line (16, 18, 30) in a process for subjecting a surface of the substrate (5) to successive surface reactions of at least a first precursor (A) and a second precursor (B) by measuring temperature change with the temperature sensor (9, 1 1 , 15, 17, 19) with the temperature sensor (9, 1 1 , 15, 17, 19) in free gas space (16, 18, 30, 38) between the precursor (A, B) and the dosing valve (22, 24, 32) during supply of the precursor (A, B).

18. Use of a temperature sensor (17) for detecting surface level of one or more liquid precursors (A, B) in a precursor vessel (10, 12) in a process for subjecting a surface of the substrate (5) to successive surface reactions of at least a first precursor (A) and a second precursor (B).