Method for detecting contamination in air, corresponding device, clean room, and use

Abstract

The invention relates to a method (100, 200) for detecting contamination in air, in particular in room air, comprising the following step: providing (102, 202) a wafer (22), in particular a semiconductor wafer (22), which has a collecting surface (24), in particular a polished collecting surface (24), for receiving particles from the air. According to the invention, it is proposed for the method (100) to be further characterized by the following steps: cleaning (104) the collecting surface (24) of the wafer (22); supplying (108) the air to be analyzed to the collecting surface (24) for a supply time such that particles from the air settle on the collecting surface (24) and form a particle layer on the collecting surface (24); detecting (110) a thickness of the particle layer using an electro-optical device (8), wherein the electro-optical device (8) is designed and configured to resolve a layer thickness in a measurement range of less than 250 picometers, in particular less than 50 picometers; determining (112) the air contamination on the basis of the thickness of the particle layer. The invention further relates to a corresponding detection device, a room, and a use.

Description

[0001] Method for detecting contamination in air, device in question, clean room and use

[0002] The invention relates to a method for detecting contamination in air, in particular in room air, comprising the step of: providing a wafer, in particular a semiconductor wafer, which has a collecting surface, in particular a polished collecting surface, for collecting particles from the air.

[0003] Such methods for detecting air contamination are typically used in clean rooms or operating rooms, or generally in environments where monitoring air contamination is of paramount importance. In clean rooms in particular, it is common practice to lay out wafers, especially semiconductor wafers. Particles deposit on the wafers, which can be examined microscopically after a certain exposure time, allowing surface contamination to be determined. Surface contamination, in turn, is a measure of the air contamination in the room in question.

[0004] A disadvantage, however, is that the resolution of the detectable particle sizes in existing evaluation systems is very limited and is typically 0.3 micrometers laterally. Smaller particles cannot be reliably detected with existing systems. Another disadvantage of this method is that the particle concentration in the air cannot be monitored in real time or near real time, but only with some time delay. The evaluation of the results can therefore only be carried out with a time delay. This makes the method unsuitable for dynamic measurement applications in which information on air contamination must be available in real time or near real time. In addition, particle counters are known from the state of the art that are designed to detect particles in a size range between 0.3 micrometers and 25 micrometers.Smaller particles typically cannot be detected with such particle counters.

[0005] Another state-of-the-art method is known as TOC analysis, which, however, only allows the detection of carbon components. Particles that are not made of carbon cannot be reliably detected with this method. Another known state-of-the-art method is the Tenax method. In this method, air is drawn into a container and then chemically analyzed. However, due to the limited volume of the container, only a small volume can be analyzed.

[0006] Furthermore, the so-called vapor phase decomposition (VPD) process is known from the prior art. In this process, thermal, chemical, or native oxides are etched onto silicon wafers. During the process, the oxide dissolves. Any impurities located on or in such a SiO2 layer can then be collected by scanning the surface with a droplet, known as droplet surface etching (DSE). This rolling process is feasible because the silicon surface exhibits hydrophobic properties after etching in the VPD reactor. The etching process makes the process more complex.

[0007] Against this background, the object of the invention was to further develop a method for detecting contamination in air of the type described above in such a way that the disadvantages found in the prior art are eliminated as far as possible. In particular, a method was to be provided in which contamination in air can be detected automatically or as largely automatically as possible and which is also suitable for small particle sizes.

[0008] According to the invention, the object is achieved in a method of the type mentioned at the outset in that the method comprises the steps of: cleaning the collection surface of the wafer, supplying the air to be analyzed to the collection surface for a supply time such that particles from the air settle on the collection surface and form a particle layer on the collection surface, detecting a thickness of the particle layer by means of an electro-optical device, wherein the electro-optical device is designed and configured to resolve a layer thickness in a measuring range of less than 250 picometers, in particular less than 50 picometers, determining the air contamination on the basis of the thickness of the particle layer.

[0009] The invention makes use of the knowledge that by cleaning the collection surface of the wafer, subsequently supplying the air to be analyzed to the collection surface and detecting a thickness of the particle layer with an electro-optical device, a possibility is provided for detecting contamination in air. By specifically selecting the electro-optical device, a layer thickness in a measuring range of less than 250 picometers, in particular less than 50 picometers, can be resolved and thus molecular contamination or dust contamination can be detected. By cleaning the collection surface, it is ruled out that contamination of the collection surface of the wafer will reduce the quality of the measurement result. The supply of the air to be analyzed to the collection surface can be done either passively, in such a way that the collection surface is simply exposed to the surrounding air, or actively, e.g.by a fan or similar device. Using a fan can increase the detected contamination. In this case, it often takes more than an hour for an equilibrium to be established between the contamination in the room and the layer thickness on the wafer. The air contamination is then finally determined based on the thickness of the particle layer.

[0010] The wafer is preferably moistened with benzine using a cleaning wipe (e.g., Viscot C445) and rubbed clean. The wafer is then preferably wiped dry with a cleaning wipe (e.g., Viscot C445) until no liquid remains on the wafer. If the wafer has already been pre-cleaned, this step can be omitted. The wafer is then preferably wiped dry with a precision cleaning wipe (e.g., Microweb DU-G). The goal here is to make the wafer so clean that the contamination in the air settles on the wafer. The described cleaning process can also be fully or partially automated.

[0011] According to one embodiment, after cleaning the collection surface of the wafer, the method comprises the step of detecting a thickness of a particle layer on the collection surface using the electro-optical device as part of a reference measurement, wherein the thickness of the particle layer of the reference measurement is used as a reference value when determining the thickness of the particle layer of a measurement. Should minor contamination remain on the collection surface of the wafer after the cleaning process, the reference measurement can be used to ensure that this contamination is taken into account later in the actual measurements of the thickness of the particle layer. For example, the layer thickness of the contamination can be subtracted from the thickness of the particle layer determined as part of the regular measurement.

[0012] According to one embodiment, the step of detecting a thickness of the particle layer using the electro-optical device is repeated after a predetermined or definable time, in particular repeated multiple times over time. Depending on the repetition interval of the detection step, this allows a detailed analysis of the layer thickness growth of the particle layer over time. Furthermore, the multiple detections can determine a state in which further supply of the air to be analyzed to the collection surface no longer leads to a further increase in the measured layer thickness, which can be used as an indication of saturation of the wafer's collection surface.

[0013] According to one embodiment, the supply time of the air to be analyzed to the collection surface is at least 30 minutes. This period has proven to be effective, as an equilibrium between the contamination in the ambient air and the layer on the wafer often develops within this period.

[0014] According to one embodiment, the electro-optical device is designed as a complete or incomplete ellipsometer, in particular as a picometer ellipsometer, a zero ellipsometer, or a submonolayer ellipsometer. A submonolayer ellipsometer is commercially available, for example, from DRE - Dr. Riss Ellipsometerbau GmbH. These ellipsometers are designed and configured to determine the thickness of the particle layer within a measuring range of less than 250 picometers and to resolve corresponding layer thicknesses. The measuring range of less than 250 picometers is also referred to as the submonolayer measuring range. This sensitivity is sufficient to measure molecular and particle contamination in the air. A picometer ellipsometer is commercially available, for example, from Beaglehole. The measuring range of such electro-optical devices is typically in the range of 0 - 2500 picometers.

[0015] According to one embodiment, the wafer, in particular a semiconductor wafer, used for the method comprises a metal carrier configured to prevent or reduce electrostatic charging. The use of such a metal carrier prevents electrostatic charges from influencing the deposition of the particles on the collection surface of the wafer.

[0016] According to one embodiment, the contamination is molecular contamination or dust contamination. Molecular contamination occurs, for example, as outgassing from acids, bases, solvents, or silicones. These gaseous contaminants typically have a size of up to 0.1 micrometers. Dust contamination is understood to mean contamination by dust particles, which typically have a size of 0.1 micrometers to 5 micrometers.

[0017] According to a second aspect of the invention or according to an advantageous development of the invention according to the first aspect, it is proposed that the method is a method for detecting a specific molecular contamination and comprises the steps of: coating the collection surface of the wafer with a capture antibody, in particular a molecular capture antibody, such that a coating with a layer thickness is formed, detecting the layer thickness of the coating with the electro-optical device, moistening the collection surface and supplying the air to be analyzed to the collection surface for a supply time such that ligands contained in the air couple to the capture antibodies, evaporating the moisture of the collection surface, and again detecting a thickness of the coating with the electro-optical device.

[0018] The method according to the second aspect of the invention, or according to an advantageous development of the invention according to the first aspect, utilizes the finding that specific molecular contamination can be determined through the use of capture antibodies. This is achieved by coupling the ligands present in the air to the specifically selected capture antibodies, thus allowing not only a general contamination measurement in the air, but also detecting specific molecular contamination. Humidification can promote the coupling process between the ligands and the capture antibodies in the humid environment, and at the same time, the effect of moisture on the layer thickness can be reduced or avoided through subsequent evaporation.

[0019] The invention has been described above with reference to a method. In a further aspect, the invention relates to a detection device for detecting contamination in air, in particular in ambient air, comprising a receptacle for receiving a wafer, in particular a semiconductor wafer, a supply device configured to supply air, in particular ambient air, to a wafer inserted into the receptacle in the region of a collecting surface of the wafer, in particular by means of a fan, and an electro-optical device. A fan is preferably arranged in a suction-type manner so that its outgassing does not influence the measurement result.

[0020] The invention achieves the object described above with regard to the detection device in that the electro-optical device is designed and configured to resolve and determine a layer thickness in a measuring range of less than 250 picometers, in particular less than 50 picometers.

[0021] The detection device utilizes the same advantages and preferred embodiments as the method according to the invention, and vice versa. In this regard, reference is made to the above explanations, and their content is incorporated herein. The feed device preferably has a fan. This can increase the detected contamination. This means that an equilibrium between the contamination in the space and the layer thickness on the wafer is established only at a later point in time compared to passive layer deposition without a fan.

[0022] According to one embodiment, the electro-optical device comprises an irradiation device which is configured to irradiate a wafer accommodated in the holder with light in the region of its collecting surface, a first polarization device which is configured to polarize the light emitted onto the collecting surface, a second polarization device which is configured to polarize the light emitted by the collecting surface, a measuring device, in particular with a photodiode, which is configured to receive and evaluate the polarized light emitted by the collecting surface.

[0023] The electro-optical device takes advantage of the fact that the emitted light has a different polarization direction than the polarization of the incident light. The intensity of this changed polarization is evaluated using a measuring device, in particular a photodiode. The irradiation device preferably comprises a laser or is designed as a laser.

[0024] Alternatively, a picometer ellipsometer, e.g., one from Beaglehole, a zero ellipsometer, or a submonolayer ellipsometer from DRE - Dr. Riss Ellipsometerbau GmbH can be used. This electro-optical device allows for the measurement of so-called submonolayer layers. Submonolayer layers are those smaller than a molecular monolayer. The measuring range of these devices is typically 0–2500 picometers.

[0025] According to one embodiment, the detection device further comprises a cleaning unit configured to clean the collection surface of the wafer, in particular in an automated or semi-automated manner. In this way, the cleaning process can be carried out at least partially, in particular completely, by the detection device. This reduces the manual effort that would otherwise be required for manual cleaning.

[0026] According to one embodiment, the detection device comprises a control device configured and designed to carry out the method according to one of the preceding embodiments. In this way, complete or partial automation of the method can be achieved.

[0027] In a further aspect, the invention relates to a room, in particular a clean room or operating room. The invention achieves the object defined above with respect to the room by having at least one, in particular a plurality of, detection devices according to one of the preceding embodiments. The room utilizes the same advantages and preferred embodiments as the detection device according to the invention, and vice versa. In this regard, reference is made to the above statements, and their content is hereby incorporated. Preferably, a plurality of detection devices according to the invention are arranged in the room, for example at particularly critical points, such as in the area of ​​a manufacturing facility arranged in the clean room, or the like.

[0028] In a further aspect, the invention relates to the use of a detection device according to one of the preceding claims for detecting contamination in air, in particular room air, preferably in a clean room or an operating room. This use also utilizes the same advantages and preferred embodiments as the detection device according to the invention, and vice versa. In this regard, reference is made to the above statements, and their content is incorporated herein. Further features and advantages of the invention emerge from the appended claims and the following description, in which exemplary embodiments are explained in detail with reference to schematic drawings.

[0029] In detail:

[0030] Fig. 1 is a block diagram of the method according to the invention;

[0031] Fig. 2 shows an alternative representation of a block diagram of the method according to the invention;

[0032] Fig. 3 shows an alternative embodiment of a method according to the invention in a block diagram;

[0033] Fig. 4 shows an embodiment of a detection device according to the invention in a schematic representation;

[0034] Fig. 5 is a schematic representation of a clean room according to the invention with detection devices according to the invention in a schematic representation;

[0035] Fig. 6a is a first diagram in which the layer thickness is plotted against the feed time; and

[0036] Fig. 6b shows a second diagram in which the layer thickness is also plotted against the feed time.

[0037] Figure 1 shows a method 100 for detecting contamination in air, in particular in room air. The method comprises the steps of: providing 102 a wafer 22, which is shown in Figure 4, in particular a semiconductor wafer 22. The provided wafer 22 has a collecting surface 24, in particular a polished collecting surface 24, for collecting particles from the air. The method 100 further comprises the steps of: cleaning 104 the collecting surface 24 of the wafer 22, supplying 108 the air to be analyzed to the collecting surface 24 for a supply time such that particles from the air settle on the collecting surface 24 and form a particle layer on the collecting surface 24.The method 100 further comprises the step of detecting 110 a thickness of the particle layer by means of an electro-optical device 8, wherein the electro-optical device 8, which is shown by way of example in Figure 4, is configured and designed to resolve a layer thickness in a measuring range of less than 250 picometers, in particular less than 50 picometers, and determining 112 the air contamination based on the thickness of the particle layer. Preferably, the wafer 22 is wetted with cleaning solvent using a cleaning cloth and rubbed clean. If the wafer is already clean, this step can be omitted. The wafer 22 is preferably then wiped dry with a cleaning cloth until no more liquid remains on the wafer 22. According to a preferred embodiment, the wafer 22 is wiped dry with a precision cleaning cloth.This ensures that the wafer 22 is so clean that the contamination in the air settles on the wafer 22.

[0038] The method 100 further comprises, after the step of cleaning 104 the collection surface 24 of the wafer 22, the step of detecting 110 a thickness of the particle layer on the collection surface 24 with the electro-optical device as part of a reference measurement, wherein the thickness of the particle layer of the reference measurement is used as a reference value when determining the thickness of the particle layer of a measurement. In this way, effects attributable to residual contamination on the collection surface 24 can be taken into account when determining the thickness of the particle layer, in particular, they can be subtracted from the thickness of the particle layer, thus avoiding falsification of the measurement results due to possible contamination on the collection surface 24.

[0039] As can be seen in particular from Figure 2, which shows an alternative representation of the method shown in Figure 1, after a definable time, the step of detecting 110 a thickness of the particle layer by means of the electro-optical device 8 is repeated within the scope of a further number of measurements 114. This makes it possible to determine how the thickness of the particle layer changes over time. This also reveals saturation effects, such that after a certain time has elapsed, an equilibrium typically arises between the contamination in the space around the layer and the layer on the wafer 22, as is also shown in Figures 6a and 6b. For example, the feed time is at least 60 minutes.The electro-optical device 8 used in the method 100 is preferably designed as a complete or incomplete ellipsometer, in particular as a picometer ellipsometer, a null ellipsometer, or a submonolayer ellipsometer. Preferably, the wafer used for the method 100, as shown in Figure 4, has a metal carrier 26 configured to prevent or reduce electrostatic charging. The contamination measurable with the method 100 is preferably molecular contamination or dust contamination.

[0040] Figure 3 shows an alternative embodiment of a method 200 for detecting specific molecular contamination. The method 200 can also be a further development of the method 100 shown in Figures 1 and 2. The method 200 for detecting specific molecular contamination comprises the steps of: providing 202 a wafer 22, in particular a semiconductor wafer 22, which has a collecting surface 24, in particular a polished collecting surface 24, for collecting particles from the air.The method 200 is further characterized by the steps: coating 204 the collection surface 24 of the wafer 22 with a capture antibody, in particular a molecular capture antibody, such that a coating with a layer thickness is formed, detecting 206 the layer thickness of the coating with the electro-optical device 8, moistening 208 the collection surface 24 and supplying the air to be analyzed to the collection surface 24 for a supply time such that ligands contained in the air couple to the capture antibodies, evaporating 210 the moisture of the collection surface 24, and again detecting 212 a thickness of the coating with the electro-optical device. In particular, the method 200 achieves that a specific molecular contamination can be determined, since only specific ligands couple to the capture antibodies and thus a specific molecular contamination is detectable.

[0041] Figure 4 shows an embodiment of a detection device 2 for detecting contamination in air, in particular in room air. The detection device 2 has a receptacle 4 for receiving a wafer 22, in particular a semiconductor wafer 22. The receptacle 4 primarily serves to align and / or fix the wafer 22 relative to an electro-optical device 8. The detection device 2 has a supply device 6, which is configured to supply air, in particular room air, to a wafer 22 inserted into the receptacle 4 in the region of the collection surface 24 of the wafer 22. This is the air, in particular room air, whose contamination is to be determined. The supply device 6 can be configured to supply the air to the collection surface 24 passively, for example in such a way that only the air, in particular room air, is in contact with the collection surface 24.In addition, active feeding to the collecting surface 24 can also be achieved by means of the feeding device 6, in particular by means of a fan. The detection device 2 further comprises an electro-optical device 8. The electro-optical device 8 is designed and configured to determine a thickness of a particle layer on the collecting surface 24 in a measuring range of less than 250 picometers. The electro-optical device 8 has an irradiation device 10. The irradiation device 10 can, for example, comprise or be formed from a laser. The irradiation device 10 is configured to irradiate a wafer 22 held in the holder 4 with light in the region of its collecting surface 24. Before the light from the irradiation device 10 strikes the collecting surface 24, it passes through a first polarization device 12, in which the light emitted in the direction of the collecting surface 24 is polarized.

[0042] The electro-optical device 8 further comprises a second polarization device 14, which is configured to polarize the light emitted by the collecting surface 24. The electro-optical device 8 further comprises a measuring device 16, which in particular comprises or is formed from a photodiode, and which is configured to receive and evaluate the polarized light emitted by the collecting surface 24. This is done based on the knowledge that the deposition of particles from the air on the wafer 22 has an effect on the polarization of the reflected light. This changes, for example, the current produced by a photodiode of the measuring device 16. Based on the change in current, the layer thickness of the deposited particle layer can be determined, which in turn is a measure of the contamination of the air.The electro-optical device 8 further comprises a control device 20 which is configured and designed to carry out the method 100, 200.

[0043] The electro-optical device 8 can alternatively be designed as at least one of the following: a picometer ellipsometer, a zero ellipsometer, or a submonolayer ellipsometer. Optionally, the detection device 8 further comprises a cleaning device 18. The cleaning device 18 is configured to clean the collection surface 24 of the wafer 22, in particular in an automated or semi-automated manner. The cleaning device 18 can comprise suitable cleaning agents for this purpose, such as rotationally driven cleaning agents or the like. Furthermore, the cleaning device 18 can also comprise spray nozzles for applying a cleaning fluid to the collection surface 24 of the wafer 22. The cleaning steps can be carried out in an automated or semi-automated manner.The detection device 2 optionally also has a control device 20, which is set up and designed to carry out the method 100, 200 described in Figures 1 to 3. Figure 5 schematically shows a room 30, in particular a clean room 30 or an operating room. The room 30 has a total of four detection devices 2 according to Figure 4. In the exemplary illustration in Figure 5, the detection devices 2 are each arranged adjacent to the corners of the room 30. In this way, a high quality of the measurement result can be ensured, in particular by carrying out several contamination measurements, or specific measurements can be carried out in individual areas of the room 30. This is, for example,This is particularly preferable if a specific production facility is located adjacent to such a detection device 2 and particularly precise monitoring of the contamination of the room air is required in this area.

[0044] Figure 6a shows the layer thickness in picometers establishing itself on the collection surface 24 of a wafer 22 over the feed time in minutes. For this purpose, a large number of measurements were carried out using the method 100 according to the invention, with the measuring interval being approximately one minute. The room air was passively fed to the collection surface 24 of the wafer, i.e., the collection surface 24 was exposed to the room air without any active supply of air to the collection surface 24, e.g., with a fan. The diagram shows that after approximately 60 minutes, an equilibrium was formed between the contamination in the room air and the layer on the wafer. In other words, after a feed time of approximately 60 minutes or more, the layer thickness only increases slightly or reaches a plateau.

[0045] In the diagram according to Figure 6b, the layer thickness in picometers was also plotted against the feed time in minutes. However, the ambient air was not passively supplied to the collection surface 24 of the wafer 22, but actively using a fan. This can increase the overall detected contamination. While the maximum detected contamination in Figure 6a is in the range of approximately 225 picometers, the active supply of air via the fan can achieve a maximum detected contamination in the range of approximately 1100 picometers and more. However, in the diagram shown in Figure 6b, an equilibrium between the contamination in the ambient air and the layer thickness on the wafer only develops after more than one hour.

[0046] 2 Detection device

[0047] 4 Holder for holding a wafer

[0048] 6 Feeding device

[0049] 8 electro-optical device

[0050] 10 Irradiation facility

[0051] 12 first polarization device

[0052] 14 second polarization device

[0053] 16 Measuring device

[0054] 18 Cleaning device

[0055] 20 Control device

[0056] 22 wafers / semiconductor wafers

[0057] 24 Wafer collection area

[0058] 26 metal supports

[0059] 30 cleanroom

[0060] 100 procedures

[0061] 102 Providing a wafer

[0062] 104 Cleaning a wafer collection surface

[0063] 106 Reference measurement

[0064] 108 Supplying the air to be analyzed to the collecting surface

[0065] 110 Detecting a thickness of the particle layer

[0066] 112 Determining air contamination from the thickness of the particle layer

[0067] 114 Number of measurements

[0068] 200 procedures

[0069] 202 Providing a wafer

[0070] 204 Coating the collection surface of the semiconductor wafer with a capture antibody

[0071] 206 Detecting the coating thickness

[0072] 208 Humidifying the collecting surface and supplying the air to be analyzed

[0073] 210 Evaporation of moisture from the collecting surface

[0074] 212 Re-detecting a coating thickness

Claims

Claims 1. A method (100, 200) for detecting contamination in air, in particular in room air, comprising the step of: providing (102, 202) a wafer (22), in particular a semiconductor wafer (22), which has a collecting surface (24), in particular a polished collecting surface (24), for receiving particles from the air, the method (100) further being characterized by the steps of: Cleaning (104) the collection surface (24) of the wafer (22), Supplying (108) the air to be analyzed to the collecting surface (24) for a supply time such that particles from the air settle on the collecting surface (24) and form a particle layer on the collecting surface (24), Detecting (110) a thickness of the particle layer by means of an electro-optical device (8), wherein the electro-optical device (8) is designed and configured to resolve a layer thickness in a measuring range of less than 250 picometers, in particular less than 50 picometers, Determining (112) the air contamination based on the thickness of the particle layer.

2. The method (100) of claim 1, wherein the method (100) comprises, after cleaning (104) the collection surface (24) of the wafer (22), the step of: Detecting (110) a thickness of a particle layer on the collecting surface (24) with the electro-optical device (8) as part of a reference measurement, wherein the thickness of the particle layer of the reference measurement is used as a reference variable when determining the thickness of the particle layer of a measurement.

3. Method (100) according to one of the preceding claims, wherein after a definable time, the step of detecting (110) a thickness of the particle layer by means of the electro-optical device (8) is repeated, in particular repeated several times over time.

4. The method (100) according to any one of the preceding claims, wherein the feeding time is at least 30 minutes.

5. Method (100) according to one of the preceding claims, wherein the electro-optical device (8) is designed as a complete ellipsometer, which is set up and designed to resolve layer thicknesses in the picometer range, or as an incomplete ellipsometer, and / or wherein the electro-optical Device is designed in particular as a picometer ellipsometer, zero ellipsometer or as a submonlayer ellipsometer.

6. Method (100) according to one of the preceding claims, wherein the wafer (22), in particular semiconductor wafer (22), has a metal carrier (26) which is designed to prevent or reduce electrostatic charging.

7. The method (100) according to any one of the preceding claims, wherein the contamination is a molecular contamination or a dust contamination.

8. Method (100, 200) according to the preamble of claim 1 or according to any one of the preceding claims, wherein the method (100, 200) is a method for detecting a specific molecular contamination and comprises the steps: Coating (204) the collecting surface (24) of the wafer (22) with a capture antibody, in particular a molecular capture antibody, such that a coating with a layer thickness is formed, Detecting (206) the layer thickness of the coating with the electro-optical device (8), Moistening (208) the collecting surface (24) and supplying the air to be analyzed to the collecting surface (24) for a supply time such that ligands contained in the air couple to the capture antibodies, Evaporation (210) of the moisture of the collecting surface (24), Detecting (212) a thickness of the coating again with the electro-optical device.

9. Detection device (2) for detecting contamination in air, in particular room air, comprising: a holder (4) for holding a wafer (22), in particular a semiconductor wafer (22), a feed device (6) which is designed to supply air, in particular room air, to a wafer (22) inserted into the holder in the region of a collecting surface (24) of the wafer (22), in particular by means of a fan, an electro-optical device (8), characterized in that the electro-optical device (8) is designed and set up to resolve and determine a layer thickness in a measuring range of less than 250 picometers, in particular less than 50 picometers.

10. Detection device (2) according to claim 9, wherein the electro-optical device (8) comprises: an irradiation device (10) which is configured to irradiate a wafer (22) accommodated in the holder (4) with light in the region of its collecting surface (24), a first polarization device (12) which is configured to polarize the light emitted onto the collecting surface (24), a second polarization device (14) which is configured to polarize the light emitted by the collecting surface (24), a measuring device (16), in particular with a photodiode, which is configured to receive and evaluate the polarized light emitted by the collecting surface (24).

11. Detection device (2) according to claim 9 or 10, wherein the electro-optical device (8) is designed as at least one of the following: Complete ellipsometer, which is designed to resolve layer thicknesses in the picometer range, incomplete ellipsometer, Picometer Ellipsometer, zero ellipsometer, Submonlayer ellipsometer.

12. Detection device (2) according to one of claims 9-11, wherein the detection device (8) further comprises a cleaning device (18) which is designed to clean the collecting surface (24) of the wafer (22), in particular in an automated or semi-automated manner.

13. Detection device (2) according to one of claims 9-12, with a control device (20) which is set up and designed to carry out the method (100, 200) according to one of the preceding claims.

14. Room (30), in particular clean room (30) or operating room, with at least one, in particular several detection devices (2) according to one of claims 9-13.

15. Use of a detection device (2) according to one of claims 9-13 for detecting contamination in air, in particular room air, preferably in a clean room (30) or an operating room.

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