JP2003142444A - Washing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove a Cu ion adhering onto the back of, especially, a wafer W or the like in a brush scriber. SOLUTION: In a brush scriber (washing apparatus) for carrying out washing treatment after chemical mechanical polishing treatment, a first jetting nozzle 30 for jetting first washing liquid that has weak acidity and is deionized water or the like to a front W1 of the erected wafer W is arranged, a second jetting nozzle 40 for jetting second washing liquid that has relatively strong Cu removal capability such as HF to a back W2 is arranged, and different washing liquid is jetted to the front W1 and back W2, thus protecting a film formed on the front W1, and at the same time efficiently washing both the front and back.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning apparatus for cleaning a front surface and a back surface of a wafer, and more particularly to a cleaning apparatus for cleaning a front surface and a back surface after a chemical mechanical polishing process.

[0002]

2. Description of the Related Art Generally, chemical mechanical polishing (CMP) is used to flatten the surface of a wafer that has been subjected to various film forming processes.
A treatment (hereinafter, simply referred to as a polishing treatment) is performed. In this polishing treatment, since the surface is chemically and mechanically polished using an abrasive, many particles and the like are generated. Therefore, it is necessary to completely remove these particles in order to transfer the wafer after the polishing process to the next step. In order to perform this removal process, conventionally, a series of cleaning steps such as ultrasonic cleaning, a two-step brush scrubber, a jet scrubber, etc. are sequentially passed to clean the front and back surfaces of the wafer. Has been processed.

As shown in FIG. 8, this brush scrubber holds a wafer W vertically and rotates it, and also arranges spray nozzles 1 so as to face the front surface W1 and the back surface W2, respectively. The rotating brush 2 is arranged so as to come into contact with the back surface W2, and the rotating brush 2 is rotated while the weakly acidic chemical liquid or deionized water filled in the cleaning liquid tank 3 is sprayed from the spray nozzle 1, so that the front surface W1 and the back surface W1.
2 is washed at the same time.

Cu formed for Cu wiring and the like
After polishing the film (eg, Cu damascene), Cu ions adhere to the back surface of the wafer. Since contamination by Cu has a great influence on the performance as a semiconductor, even if it is attached to the back surface W2, it must be reliably removed. On the other hand, it is difficult to remove the Cu ions by a cleaning process using only a cleaning solution such as weakly acidic or deionized water, like the cleaning process using the brush scrubber. In the case of performing the cleaning process, separately from the above-described series of cleaning processes, the cleaning process was performed in a separate step using a cleaning device dedicated to the back surface.

[0005]

By the way, in the conventional cleaning process as described above, a separate cleaning device for cleaning the back surface of the wafer is required, and since it is not a in-line process but a separate process, the work is performed. The number of man-hours increases and the process becomes complicated, and it takes a long time until the series of cleaning processes is completed, which leads to a decrease in productivity, an increase in equipment cost, and an increase in production cost. Further, it is difficult to completely remove the Cu component (Cu ion) even with a separate cleaning device.

The present invention has been made in view of the above points, and an object thereof is to efficiently perform, for example, when a Cu component or the like adheres to the back surface in a series of cleaning treatments. Another object of the present invention is to provide a cleaning device that can be surely cleaned (removed), the complexity of the cleaning process can be eliminated, the time required for the cleaning process can be shortened, the equipment cost can be reduced, and the productivity can be improved.

[0007]

A cleaning device of the present invention is a cleaning device for cleaning a front surface and a back surface after a chemical mechanical polishing process is performed on a film formed on a front surface of a wafer. For injecting a first cleaning liquid to clean the first
It has a spray nozzle and a second spray nozzle that sprays a second cleaning liquid to clean the back surface. According to this configuration, on the surface on which the film is formed, a cleaning liquid having a relatively small effect on the film (for example, a weakly acidic chemical liquid or deionized water) is jetted from the first jet nozzle as the first washing liquid. On the other hand, on the back surface, the back surface can be cleaned by injecting a cleaning liquid (for example, HF) having a relatively high cleaning power as the second cleaning liquid from the second injection nozzle. That is, by cleaning the front surface and the back surface with different cleaning liquids, it is possible to efficiently clean each surface.

In the above structure, the support roller for rotating the wafer in an upright state, and the rotating brush for rotating and contacting the front surface and the back surface of the wafer, respectively, and the first jet nozzle face the front surface. It is possible to adopt a configuration in which the second injection nozzle is arranged so as to face the back surface. According to this configuration, the wafer is vertically erected and rotated, and when cleaning the front surface and the back surface while the rotating brush rotates, the first cleaning liquid efficiently cleans the front surface and the second cleaning liquid efficiently cleans the back surface. You can

In the above structure, the second injection nozzle has
A configuration can be adopted in which a switching system for switching between the second cleaning liquid and the first cleaning liquid and ejecting the liquid is provided.
According to this configuration, by performing the switching operation in the switching system, for example, after cleaning the front surface with the first cleaning liquid and the back surface with the second cleaning liquid, the first cleaning liquid is also sprayed from the second spray nozzle. The front surface and the back surface can be cleaned with the first cleaning liquid.

In the above structure, a second cleaning liquid supply line for supplying a second cleaning liquid is connected to the second injection nozzle, and a first cleaning liquid is supplied to the first injection nozzle.
A cleaning liquid supply line is connected, and in the switching system, the connection line connecting the first cleaning liquid supply line to the second cleaning liquid supply line and the line communicating with the second injection nozzle are either the first cleaning liquid supply line or the connection line. A configuration having a switching valve for switching to can be adopted. With this configuration, the switching system can be configured with a simple structure. In addition, even in the existing cleaning system,
The configuration of the present invention can be easily provided by some modifications.

In the above structure, the third jet nozzle for jetting the first cleaning liquid is arranged on the side facing the back surface,
It is possible to adopt a configuration in which a supply line for supplying the first cleaning liquid to the third injection nozzle when the first cleaning liquid is injected from the second injection nozzle by the switching system is provided in the third injection nozzle. According to this configuration, for example, when the injection amount from the second injection nozzle is smaller than the injection amount from the first injection nozzle, by providing the third injection nozzle,
The injection amount of the first cleaning liquid can be set equal on the back surface side and the front surface side.

In the above structure, the first cleaning liquid is deionized water or a weakly acidic chemical liquid, and the second cleaning liquid is at least C
A composition that is a chemical liquid capable of removing the u component can be adopted.
According to this configuration, after the Cu film is polished,
When the wafer cleaning process is performed, the Cu component on the back surface can be efficiently removed while suppressing the effect of the cleaning on the front surface.

In the above structure, it is possible to adopt a structure in which the respective spraying amounts of the first spraying nozzle and the second spraying nozzle are adjusted so that the second cleaning liquid sprayed on the back surface does not go around to the front surface. With this configuration, even when the second cleaning liquid is a chemical liquid that affects the film on the front surface, the second cleaning liquid does not wrap around to the front surface side, so that the back surface can be reliably cleaned while protecting the front surface. .

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4
1 shows an embodiment of a cleaning apparatus according to the present invention, FIG. 1 is an overall configuration diagram of a chemical mechanical polishing apparatus to which the cleaning apparatus is applied, and FIG. 2 is a plan view showing a series of cleaning lines in the apparatus. 3 is a side sectional view showing a two-stage cleaning device (brush scrubber) including the cleaning device of the present invention, and FIG. 4 is a schematic view showing the cleaning device of the present invention.

As shown in FIG. 1, the chemical mechanical polishing apparatus comprises:
A dry-in / dry-out system that includes a buffer station A, a polishing station B, a cleaning station C, and the like, and performs a polishing process, a cleaning process, and a drying process on a wafer W loaded into the apparatus in a dry state, and takes out in a dry state. It was adopted.

As shown in FIGS. 1 and 2, the cleaning station C includes a wet bench C1, an ultrasonic cleaning device C2,
A cleaning device (brush scrubber) C3 according to the present invention, a second cleaning device (brush scrubber) C4, a cleaning device (jet scrubber) C5, a transfer mechanism C6 for sequentially transferring the wafer W, and the like.

The wet bench C1 is intended to prevent the waiting wafer W from drying with pure water or the like, and the front and back surfaces of the wafer W may be washed with a chemical solution such as a weak acid or a weak alkali. Cleaning such as RCA cleaning may be performed. The ultrasonic cleaning device C2 puts the wafer W in a cleaning liquid such as pure water or aqueous ammonia, applies ultrasonic waves to the cleaning liquid, and cavitation and vibration acceleration of the liquid contaminate particles such as particles attached to the front surface and the back surface. It removes things.

Second cleaning device (brush scrubber) C4
As shown in FIGS. 3 and 8, while rotating the wafer W upright by the supporting roller 4, the rotating brush 2 is brought into contact with the front surface W1 and the back surface W2, and the deionized water filled in the cleaning liquid tank 3 or The cleaning is performed by spraying a weakly acidic chemical liquid or the like from the spray nozzle 1. The cleaning liquid supply line 5 that connects the injection nozzle 1 and the cleaning liquid tank 3 is provided with a valve 6 that opens and closes a passage. That is, in this cleaning step, the same cleaning liquid is sprayed on the front surface W1 and the back surface W2 of the wafer W to remove contaminants. The cleaning device (jet scrubber) C5 applies a pressure to a cleaning liquid such as water with respect to the spun wafer W and ejects the cleaning liquid at a high speed from a nozzle to remove contaminants such as particles attached by the impact force.
It is dehydrated and dried by centrifugal force.

The cleaning device (brush scrubber) C3 is shown in FIG.
And, as shown in FIG. 4, the three support rollers 10 for rotating the wafer W in the upright state, the front surface W of the wafer W
1 and the back surface W2, respectively, to rotate the rotary brush 20, above the rotary brush 20, three first jet nozzles 30 arranged to face the front surface W1 of the wafer W, above the rotary brush 20. It is provided with one second injection nozzle 40 and the like arranged so as to face the back surface W2 of the wafer W.

A first cleaning liquid supply line 31 is connected to the first injection nozzle 30, and a valve 32 for opening and closing a passage and a first tank 33 filled with the first cleaning liquid are connected upstream of the first cleaning liquid supply line 31. There is. Here, as the first cleaning liquid,
A weakly acidic chemical solution, deionized water, or the like that can be washed to the extent that it does not affect the film on the surface W1 is used. Meanwhile, the second
A second cleaning liquid supply line 42 is connected to the injection nozzle 40, and upstream of the second cleaning liquid supply line 42, a valve 42 for opening and closing a passage, and a second
The second tank 43 filled with the cleaning liquid is connected.
Here, as the second cleaning liquid, a relatively strong chemical liquid effective for removing Cu components (Cu ions), for example, H 2
F or the like is used.

By the way, in the above structure, the number of the first jet nozzles 30 is three, but the number of the second jet nozzles 40 is one, and the jet amount of the first washing liquid is the same as that of the second washing liquid as a whole. It is set to be larger than the injection amount. Therefore, even if the second cleaning liquid sprayed on the back surface W2 tries to wrap around to the front surface W1, the rush of the first cleaning liquid is strong, so that the wraparound is reliably prevented. This prevents the second cleaning liquid having a relatively strong cleaning ability from damaging the laminated film or the like for the electronic circuit formed on the surface W1. In particular, the second injection nozzle 40
Is directed obliquely downward near the center of the back surface W2, and thus the jetted second cleaning liquid flows downward along the back surface W2 due to gravity while being affected by centrifugal force. Therefore, the second cleaning liquid is prevented from wrapping around to the front surface W1 side as much as possible.

Next, the processing in the cleaning station including the above cleaning device will be described. First, the wafer W that has undergone the polishing process is brought into the cleaning station by the transfer mechanism. Then, the wafer W that has undergone the cleaning process in the wet bench C1 and the ultrasonic cleaning device C2 is transferred by the transfer mechanism C.
6 is brought to the cleaning device C3.

In this cleaning process, the wafer W is
The support roller 10 is supported in an upright state and rotated. Further, the rotating brush 20 is rotated while being in contact with the front surface W1 and the back surface W2. In this state, a first cleaning liquid (for example, a weakly acidic chemical liquid, deionized water) is sprayed from the first spray nozzle 30, and the rotary brush 20
The surface W1 is cleaned by the interaction with. On the other hand, the second cleaning liquid (for example, HF) is sprayed from the second spray nozzle 40 and interacts with the rotary brush 20, so that the back surface W is formed.
2 are washed.

Thus, the front surface W1 and the back surface W2 are
Since different cleaning liquids are sprayed, contaminants such as Cu components (Cu ions) adhering to the back surface W2 are reliably removed while protecting the film on the front surface W1, and the cleaning process is efficiently performed as a whole.

Subsequently, the wafer W is carried into the cleaning device C4. In this cleaning step, brush cleaning is similarly performed. That is, the wafer W is rotated while being supported by the support roller 4, and the same cleaning liquid (for example, weakly acidic chemical liquid, deionized water) is sprayed onto the front surface W1 and the back surface W2 while rotating the rotating brush 2. Then, the front surface W1 and the back surface W2 are cleaned by the interaction with the rotating brush 2.

Subsequently, the wafer W is carried into the jet scrubber C5 and washed with high-pressure water or the like, and after the series of washing steps described above is finished, it is dehydrated and dried by a centrifugal force (drying step). It

As described above, the cleaning process by the cleaning device C3 is incorporated into a series of cleaning processes (in-line).
Since it is a system, compared to the case of cleaning separately using a dedicated cleaning device at another station,
The complexity of the cleaning process is eliminated, the time required for the entire cleaning process can be shortened, and as a result, the productivity can be improved. The order of the cleaning process performed by the cleaning device C3 and the cleaning process performed by the cleaning device C4 may be reversed.

FIG. 5 is a schematic configuration diagram showing another embodiment of the cleaning apparatus according to the present invention. This embodiment is the same as the embodiment shown in FIG. 4 described above except that a switching system is provided, and therefore, the same components are designated by the same reference numerals and the description thereof will be omitted. In this cleaning device, a connection line 51 is provided between the first cleaning liquid supply line 31 and the second cleaning liquid supply line 41 to connect the two passages. And the connection line 51
A valve 52 for avoiding the passage is disposed in the middle of the path.

Therefore, from the second injection nozzle 40 to the second
When injecting the cleaning liquid, the valve 52 is closed to block the inflow of the first cleaning liquid and the valve 42 is opened to supply the second cleaning liquid in the second tank 43 toward the second injection nozzle 40. On the other hand, when injecting the first cleaning liquid from the second injection nozzle 40, the valve 42 is closed to cut off the supply of the second cleaning liquid, the valve 52 is opened, and the first line in the first tank 33 is connected through the connection line 51. The cleaning liquid is supplied toward the second injection nozzle 40.

That is, in the above structure, the valve 5
A switching valve that switches the line communicating with the second injection nozzle 40 to either the first cleaning liquid supply line 41 or the connection line 51 is formed by the valve 2 and the valve 42. A switching system 50 for switching and injecting the cleaning liquid supplied to the two-injection nozzle 40 is formed. As described above, in the cleaning device C3, by adopting the switching system 50, the back surface W is changed according to the contamination state of the wafer W.
The cleaning liquid to be sprayed on the second side can be selected.

Alternatively, the back surface W2 may be subjected to the cleaning treatment with the second cleaning liquid and then the cleaning treatment with the first cleaning liquid. Therefore, the next cleaning device C
Since the same processing as the cleaning step in 4 can be performed, a further cleaning effect can be obtained.

On the other hand, when the cleaning up to that point is not necessary, by partially modifying the apparatus and performing the cleaning step by the cleaning apparatus C4 by the cleaning apparatus C3, the cleaning step by the cleaning apparatus C4 can be omitted. The cleaning device C4 can be eliminated, and therefore the time for transferring the wafer W to the cleaning device C4 can be saved. As a result, it is possible to reduce the time required for the entire cleaning process, reduce the cost of equipment, and the like.

6 and 7 are schematic configuration diagrams showing another embodiment of the cleaning apparatus according to the present invention. This embodiment is the same as the above-described embodiment shown in FIG. 5 except that a supply system for separately supplying the first cleaning liquid is provided in addition to the switching system. Therefore, the same components are designated by the same reference numerals and the description thereof is omitted.

In this cleaning apparatus, two third injection nozzles 60 are arranged so as to face the back surface W2 of the wafer W. The third ejection nozzles 60 are arranged so as to sandwich the second ejection nozzle 40. Therefore, the second
3 in total consisting of the injection nozzle 30 and the third injection nozzle 60
The individual injection nozzles have the same arrangement configuration as the three first injection nozzles 30 arranged so as to face the surface W1.

A connecting line 51 is provided between the first cleaning liquid supply line 31 and the second cleaning liquid supply line 41 to connect the passages of the two, and a valve 52 for opening and closing the passage is provided in the middle of the connecting line 51. Are arranged. Further, a supply line 71 that can supply the first cleaning liquid to the third injection nozzle 60 is connected to the downstream side of the valve 52, and a valve 72 that opens and closes a passage is arranged in the middle of the supply line 71.

Therefore, from the second injection nozzle 40 to the second
When spraying only the cleaning liquid, as shown in FIG. 6, the valve 52 and the valve 72 are closed to block the inflow of the first cleaning liquid, and the valve 42 is opened to supply the second cleaning liquid in the second tank 43 to the second cleaning liquid. Supply toward the injection nozzle 40. On the other hand, when injecting the first cleaning liquid from a total of three injection nozzles of the second injection nozzle 40 and the third injection nozzle 60, as shown in FIG. 7, the valve 42 is closed to stop the supply of the second cleaning liquid. The valve 52 and the valve 72 are opened, and the first cleaning liquid in the first tank 33 is supplied toward the second injection nozzle 40 and the third injection nozzle 60 via the connection line 51 and the supply line 72.

That is, in the above configuration, the valve 7
2 and the supply line 71, when the switching system 50 injects the first cleaning liquid from the second injection nozzle 40,
The first cleaning liquid is supplied to the third injection nozzle 60. As described above, in the cleaning device C3, by adopting the third spray nozzle 60, the supply line 71, and the valve 72 in addition to the switching system 50, the cleaning liquid sprayed to the back surface W2 side according to the contamination state of the wafer W. Can be selected, and when the first cleaning liquid is sprayed onto the back surface W2, the first cleaning liquid can be sprayed with an injection amount equivalent to that on the front surface W1.

Therefore, the completely same process as the cleaning process in the next cleaning device C4 can be performed,
Further cleaning effect can be obtained. On the other hand, when the cleaning up to that point is not required, the apparatus is partially modified and the cleaning process by the cleaning apparatus C4 is performed in the same manner as described above.
By performing the process in Step 3, the cleaning process in the cleaning device C4 can be omitted, that is, the cleaning device C4 can be eliminated, and therefore the time for transferring the wafer W to the cleaning device C4 can be saved. As a result, it is possible to reduce the time required for the entire cleaning process, reduce the cost of equipment, and the like.

In the above embodiment, the first jet nozzle 30 has three nozzles, and the second jet nozzle 40 has one nozzle.
Although two nozzles are shown as the one nozzle and the third injection nozzle 60, the number is not limited to this, and the number can be appropriately changed. In this case, the second injection nozzle 40
It is preferable to set the injection amount of the first cleaning liquid ejected from the first injection nozzle 30 to be larger than the injection amount of the second cleaning liquid ejected from the. By setting in this way, it is possible to prevent the second cleaning liquid from wrapping around the front surface W1 of the wafer W as much as possible.

In the above embodiment, the valve 32 on the first cleaning liquid supply line 31, the valve 42 on the second cleaning liquid supply line 41, the valve 52 on the connection line 51, and the valve 72 on the supply line 71 are the same as those of the entire apparatus. A switching control of the switching system 50 is performed by centrally controlling the opening and closing operations thereof by a control device that controls the control.
The cleaning of the front surface W1 or the back surface W2 of the wafer W with the cleaning liquid and the cleaning of the back surface W2 of the wafer W with the second cleaning liquid may be performed efficiently.

[0041]

As described above, according to the cleaning apparatus of the present invention, in the cleaning apparatus for cleaning the front surface and the back surface of the wafer after the chemical mechanical polishing treatment, the first cleaning liquid is sprayed to clean the front surface. By providing a first spray nozzle for spraying and a second spray nozzle for spraying a second cleaning liquid to clean the back surface so that different cleaning liquids can be supplied to the front surface and the back surface, the film formed on the front surface is protected. However, each surface can be cleaned efficiently. In particular, C
When the wafer cleaning process is performed after the u film is subjected to the polishing process, it is possible to efficiently remove the Cu component (Cu ions) on the back surface while suppressing the effect of the cleaning on the front surface. As a result, it is possible to shorten the time required for the cleaning process and improve the productivity.

Further, by providing a switching system for switching the cleaning liquid supplied to the second injection nozzle, for example,
After cleaning the front surface with the first cleaning liquid and the back surface with the second cleaning liquid, respectively, the first cleaning liquid can be sprayed from the second spray nozzle to clean the front surface and the back surface with the first cleaning liquid. According to this, even in the existing cleaning system, the present invention can be easily applied by a partial change or the like.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a chemical mechanical polishing apparatus to which a cleaning apparatus according to the present invention is applied.

FIG. 2 is a plan view showing a cleaning station included in the apparatus shown in FIG.

3 is a side view showing a schematic configuration of a cleaning apparatus according to the present invention and a cleaning apparatus in a next step included in the cleaning station shown in FIG.

FIG. 4 is a perspective view showing an embodiment of a cleaning apparatus according to the present invention.

FIG. 5 is a perspective view showing another embodiment of the cleaning apparatus according to the present invention.

FIG. 6 is a perspective view showing still another embodiment of the cleaning apparatus according to the present invention.

7 is a perspective view showing another operation mode of the cleaning apparatus shown in FIG.

FIG. 8 is a perspective view showing a schematic configuration of a conventional cleaning device.

[Explanation of symbols]

C cleaning station C3, C4 cleaning device W wafer W1 surface W2 back side 10 Support roller 20 rotating brush 30 First injection nozzle 31 First cleaning liquid supply line 32 valves 33 First tank 40 Second injection nozzle 41 Second cleaning liquid supply line 42 valves (switching valve) 43 Second tank 50 switching system 51 connection line 52 valve (switching valve) 60 Third injection nozzle 71 supply line 72 valves (switching valve)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Megumi Taoka             14-3 Shinizumi, Narita City, Chiba Prefecture Nogedaira Industrial Park             Uchi Applied Materials Japan Co., Ltd.             In the company

Claims (7)

[Claims] 1. A cleaning device for cleaning a front surface and a back surface after a chemical mechanical polishing process is performed on a film formed on a front surface of a wafer, the method comprising spraying a first cleaning liquid to clean the front surface. A cleaning device comprising: one spray nozzle; and a second spray nozzle that sprays a second cleaning liquid to clean the back surface. 2. A support roller that rotates the wafer in an upright state, and a rotating brush that comes into contact with the front surface and the back surface of the wafer while rotating, respectively. The cleaning device according to claim 1, wherein the cleaning device is arranged so as to face a front surface, and the second injection nozzle is arranged so as to face the back surface. 3. The switching system for switching and ejecting the second cleaning liquid and the first cleaning liquid is provided in the second injection nozzle, and the switching system is provided. Cleaning equipment. 4. A second cleaning liquid supply line for supplying the second cleaning liquid is connected to the second injection nozzle, and a first cleaning liquid supply line for supplying the first cleaning liquid is connected to the first injection nozzle. The switching system is connected to either the first cleaning liquid supply line or the connection line that connects the first cleaning liquid supply line to the second cleaning liquid supply line and the line that communicates with the second injection nozzle. 4. The cleaning apparatus according to claim 3, further comprising a switching valve for switching between the two. 5. A third jet nozzle for jetting the first cleaning liquid is arranged on a side facing the back surface, and the third jet nozzle is arranged from the second jet nozzle to the first jet nozzle by the switching system. When the cleaning liquid is sprayed,
The cleaning device according to claim 3 or 4, wherein a supply line that supplies the first cleaning liquid to the third injection nozzle is provided. 6. The first cleaning solution is deionized water or a weakly acidic chemical solution, and the second cleaning solution is a chemical solution capable of removing at least Cu components. The cleaning device according to any one of claims. 7. The respective spray amounts of the first spray nozzle and the second spray nozzle are adjusted so that the second cleaning liquid sprayed on the back surface does not go around to the front surface.
The cleaning device according to any one of claims 1 to 6, wherein the cleaning device is a cleaning device.