Sensor semiconductor device

Abstract

A sensor semiconductor device comprises a transducer which comprises a capacitor with at least two electrodes. The transducer further comprises a polymer which is arranged between at least two electrodes of the capacitor, and a top surface of the transducer. The polymer is able to absorb water and the top surface is arranged such that it is exposed to the environment of the sensor semiconductor device. Furthermore, at least a part of the top surface is superhydrophobic and the sensor semiconductor device is capable of measuring the humidity of the environment of the sensor semiconductor device.

Claims

1. A sensor semiconductor device comprising: a transducer comprising: a capacitor with at least two electrodes, a polymer arranged between the at least two electrodes of the capacitor, and a top layer of the transducer with a top surface, wherein the polymer is able to absorb water, wherein the top surface is arranged such that it is exposed to an environment of the sensor semiconductor device, wherein at least a part of the top surface is superhydrophobic as a result of structures extending into the top layer, wherein a size of the structures is at least 1 μm and at most 100 μm in lateral directions which are parallel to a main plane of extension of the transducer, wherein an angle between the top surface and the structures at the top surface is less than 90°, wherein the structures have an undercut as a result of the angle of less than 90°, and wherein the sensor semiconductor device is capable of measuring humidity of the environment of the sensor semiconductor device.

2. The sensor semiconductor device according to claim 1, wherein the capacitor is a plate capacitor.

3. The sensor semiconductor device according to claim 1, wherein the capacitor is a fringe capacitor.

4. The sensor semiconductor device according to claim 1, wherein a trench is arranged around the transducer, the trench configured to provide drainage of a liquid from the top surface.

5. The sensor semiconductor device according to claim 1, wherein structures are patterned within the top surface by photolithography, and wherein the size of the structures is at least 1 nm and at most 1 μm in vertical direction, which is perpendicular to the main plane of extension of the transducer.

6. The sensor semiconductor device according to claim 1, wherein the top surface is a surface of the polymer.

7. A method for producing a sensor semiconductor device, the method comprising: forming a transducer comprising a capacitor with at least two electrodes; arranging a polymer between the at least two electrodes of the capacitor; and structuring a top layer of the transducer such that a top surface of the top layer is at least partially superhydrophobic as a result of structures extending into the top layer, wherein the polymer is able to absorb water, wherein the top surface is arranged such that it is exposed to an environment of the sensor semiconductor device, wherein a size of the structures is at least 1 nm and at most 100 μm in lateral directions which are parallel to a main plane of extension of the transducer, wherein an angle between the top surface and the structures at the top surface is less than 90°, wherein the structures have an undercut as a result of the angle of less than 90°, and wherein the sensor semiconductor device is capable of measuring humidity of the environment of the sensor semiconductor device.

8. The method according to claim 7, wherein the top layer is comprised by the polymer.

9. The method according to claim 7, wherein an electrode of the capacitor comprises the top layer.

10. The method according to claim 7, wherein the top layer is comprised neither by the polymer nor by an electrode of the capacitor.

11. The method according to claim 7, wherein the capacitor is a plate capacitor.

12. The method according to claim 7, wherein the capacitor is a fringe capacitor.

13. The method according to claim 7, wherein a trench is arranged around the transducer, the trench providing drainage of a liquid from the top surface.

14. The method according to claim 7, wherein structuring the top layer comprises patterning.

15. The method according to claim 7, wherein the top surface is a surface of the polymer.

16. The method according to claim 7, wherein structuring the top layer comprises roughening.

17. The method according to claim 7, wherein structuring the top layer comprises providing a chemical treatment.

18. The method according to claim 7, wherein structuring the top layer comprises etching.

19. The method according to claim 7, wherein structuring the top layer comprises providing ultra violet light exposure.

20. The method according to claim 7, wherein structuring the top layer comprises growing nanostructured metal layers.

21. The method according to claim 7, wherein, prior to structuring, the top layer is a homogenous non-fiber layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The following description of figures may further illustrate and explain exemplary embodiments. Components that are functionally identical or have an identical effect are denoted by identical references. Identical or effectively identical components might be described only with respect to the figures where they occur first. Their description is not necessarily repeated in successive figures.

(2) FIG. 1A shows a cutaway view of an exemplary embodiment of a sensor semiconductor device.

(3) FIG. 1B shows a top view of the exemplary embodiment of the sensor semiconductor device of FIG. 1A.

(4) With FIGS. 2A, 2B, 3A, 3B, 4A and 4B further exemplary embodiments of the sensor semiconductor device are shown.

(5) FIG. 5 shows a cutaway view of another exemplary embodiment of the sensor semiconductor device.

(6) With FIG. 6A a method for forming an exemplary embodiment of the sensor semiconductor device is described.

(7) In FIG. 6B another method for forming an exemplary embodiment of the sensor semiconductor device is shown.

(8) In FIGS. 7A, 7B, 7C and 7D further exemplary embodiments of the sensor semiconductor device with a structured top surface are shown.

(9) In FIGS. 8A and 8B a top view and a cutaway view on a structured top surface of the sensor semiconductor device are shown.

(10) In FIG. 9 a randomly structured top surface of a sensor semiconductor device is shown.

DETAILED DESCRIPTION

(11) In FIG. 1A a cutaway view of an exemplary embodiment of a sensor semiconductor device 10 is shown. The sensor semiconductor device 10 comprises a transducer 11 which comprises a capacitor 12. In this embodiment the capacitor 12 is a parallel plate capacitor. The capacitor 12 comprises two electrodes 13 which are arranged at a distance from each other. The two electrodes 13 are arranged parallel to each other and they are arranged on top of each other in vertical direction z which is perpendicular to the main plane of extension of the transducer 11. A polymer 14 is arranged between the two electrodes 13. The polymer 14 has a larger extent in a lateral direction x than the two electrodes 13. The lateral direction x is perpendicular to the vertical direction z. The dashed line marks the extent of the transducer 11.

(12) The polymer 14 is able to absorb water. The polymer 14 can reversibly collect or absorb water from the air in the environment of the sensor semiconductor device 10 and the dielectric constant of the polymer 14 depends on the amount of collected water or moisture.

(13) The transducer 11 further comprises a top surface 15. In this embodiment the top surface 15 is comprised by the upper electrode 13. The top surface 15 is arranged such that it is exposed to the environment of the sensor semiconductor device 10 and at least a part of the top surface 15 is superhydrophobic.

(14) FIG. 1B shows a top view of the exemplary embodiment of the sensor semiconductor device 10 of FIG. 1A. The upper electrode 13 is shown from the top and the polymer 14 has a larger lateral extent than the electrodes 13 of the capacitor 12.

(15) In FIG. 2A a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 is shown. In this embodiment the capacitor 12 is a fringe capacitor. This means, the two electrodes 13 of the capacitor 12 are arranged as combs. The polymer 14 is arranged between and above the electrodes 13 of the capacitor 12. The dashed line again marks the extent of the transducer 11.

(16) FIG. 2B shows a top view of the exemplary embodiment of the sensor semiconductor device 10 of FIG. 2A. The two electrodes 13 are arranged as combs and the polymer 14 is arranged between and above the two electrodes 13.

(17) In FIG. 3A a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 is shown. The capacitor 12 is a parallel plate capacitor. In addition to the embodiment shown in FIG. 1A the sensor semiconductor device 10 further comprises a trench 17 which is arranged around the transducer 11 and it provides drainage of a liquid from the top surface 15. The trench 17 is arranged within the polymer 14 and it optionally completely surrounds the transducer 11. This means, the trench 17 is arranged at a lower vertical position than the top surface 15 such that water droplets repelled by the top surface 15 roll off towards the trench 17. Advantageously, the trench 17 collects the liquid or the water droplets from the top surface 15 such that no other places of the transducer 11 or the sensor semiconductor device 10 are wetted by the liquid or the water droplets.

(18) FIG. 3B shows a top view of the exemplary embodiment of the sensor semiconductor device 10 of FIG. 3A. The trench 17 surrounds the transducer 11 at all lateral sides.

(19) In FIG. 4A a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 is shown. The capacitor 12 is a fringe capacitor. In addition to the embodiment shown in FIG. 2A the sensor semiconductor device 10 further comprises a trench 17 which is arranged around the transducer 11 and it provides drainage of a liquid from the top surface 15. The top surface 15 is comprised by the polymer 14.

(20) FIG. 4B shows a top view of the exemplary embodiment of the sensor semiconductor device 10 of FIG. 4A. The trench 17 surrounds the transducer 11 at all lateral sides.

(21) FIG. 5 shows a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10. The capacitor 12 is a parallel plate capacitor. In difference to the embodiment shown in FIG. 1A the capacitor 12 consists of two capacitors in series and comprises in total three electrodes 13. Two electrodes 13 are arranged next to each other in a plane which is parallel to the main plane of extension of the polymer 14. The third electrode 13 is arranged above the two other electrodes 13 in vertical direction z. The two electrodes 13 arranged next to each other form the bottom electrodes of the two capacitors 12 connected in series. These capacitors 12 share the third top electrode 13.

(22) With FIG. 6A a method for forming an exemplary embodiment of the sensor semiconductor device 10 is described. In a first step S1 the polymer 14 is provided. The polymer 14 is arranged between and above the two electrodes 13 of the capacitor 12. The polymer 14 comprises a top layer 16 which is structured in the following steps.

(23) In a second step S2 a masking layer 19 is deposited on top of the polymer 14. The masking layer 19 can be a photoresist layer or a hard mask layer which comprises for example silicon oxide, a nitride or a metal.

(24) In the third step S3 the masking layer 19 is patterned by lithographic methods such that the masking layer 19 is removed from the polymer 14 in places. In this embodiment a regular pattern in the masking layer 19 is formed on top of the polymer 14.

(25) In the fourth step S4 the top layer 16 of the polymer 14 is etched by wet chemical etching or by reactive ion etching through the masking layer 19. This means, the top layer 16 is only etched in the areas where the masking layer 19 is removed from the top layer 16. In this way, structures 18 are formed in the top layer 16. The lateral size of the structures 18 is at least 1 nm and at most 100 μm. However, the lateral size of the structures 18 is limited by the lithographic methods. The top layer 16 is laterally etched such that the angle between the top surface 15 and the structures 18 at the top surface 15 is less than 90°. In this way, the top surface 15 is made superhydrophobic. The depth of the etching and therefore the vertical height of the structures 18 can be tuned by the duration of the etching process. The height of the structures 18 in vertical direction z can be at least 1 nm and at most 1 μm.

(26) In the fifth step S5 the masking layer 19 is removed. Regularly arranged structures 18 are formed within the top layer 16 of the polymer 14 such that the top surface 15 is superhydrophobic.

(27) Alternatively, in the fourth step S4 the top layer 16 is laterally etched such that the masking layer 19 creates an overhang (not shown in FIG. 6A). In this case the fifth step S5 should be omitted.

(28) In FIG. 6B another method for forming an exemplary embodiment of the sensor semiconductor device 10 is shown. In a first step S1 the polymer 14 is provided. The polymer 14 is arranged between and above the two electrodes 13 of the capacitor 12.

(29) In a second step S2 an additional top layer 16 is deposited on top of the polymer 14. It can be advantageous to deposit an additional top layer 16 which is structured if the top layer 16 comprises a material which can be more easily structured than the polymer 14.

(30) In a third step S3 a masking layer 19 is deposited on top of the top layer 16.

(31) In a fourth step S4 the masking layer 19 is patterned by lithographic methods such that the masking layer 19 is removed from the top layer 16 in places. A regular pattern in the masking layer 19 is formed on top of the top layer 16.

(32) In a fifth step S5 the top layer 16 is etched by wet chemical etching or by reactive ion etching through the patterned masking layer 19. Thus, structures 18 are formed in the top layer 16. The top layer 16 is laterally etched such that the angle between the top surface 15 and the structures 18 at the top surface 15 is less than 90°. In this way, the top surface 15 is made superhydrophobic. In this case the depth of the etching can also be tuned by the thickness of the top layer 16.

(33) In a sixth step S6 the masking layer 19 is removed. Regularly arranged structures 18 are formed within the top layer 16 such that the top surface 15 is superhydrophobic.

(34) In FIG. 7A a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 with a structured top surface 15 is shown. The capacitor 12 is a parallel plate capacitor. The surface of the upper electrode 13 is structured with a regular pattern such that the top surface 15 of the transducer 11 is superhydrophobic.

(35) In FIG. 7B a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 with a structured top surface 15 is shown. The capacitor 12 is a fringe capacitor. The polymer 14 is arranged between and above the two electrodes 13 of the capacitor 12. The surface of the polymer 14 is structured with a regular pattern such that the top surface 15 of the transducer 11 is superhydrophobic.

(36) In FIG. 7C a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 with a structured top surface 15 is shown. The capacitor 12 is a parallel plate capacitor. On top of the upper electrode 13 an additional top layer 16 is arranged. The top layer 16 is structured with a regular pattern such that the top surface 15 of the transducer 11 is superhydrophobic.

(37) In FIG. 7D a cutaway view of a further exemplary embodiment of the sensor semiconductor device 10 with a structured top surface 15 is shown. The capacitor 12 is a fringe capacitor. On top of the polymer 14 an additional top layer 16 is arranged. The top layer 16 is structured with a regular pattern such that the top surface 15 of the transducer 11 is superhydrophobic.

(38) In FIG. 8A a top view on a structured top surface 15 of a sensor semiconductor device 10 is shown. The square-shaped structures 18 are arranged on top of the top layer 16 of the transducer 11. This means the top layer 16 can be an electrode 13, the polymer 14 or an additional top layer 16. The square-shaped structures 18 are formed on or within the top layer 16 and are arranged in a regular pattern.

(39) If water droplets condense on the structured top surface 15 the contact angle θ.sub.W of the water droplets is given by:
cos θ.sub.W=r cos θ,
where θ is the contact angle on a flat, not structured surface, θ.sub.W is the contact angle on a structured surface and r is the ratio between the real surface area A.sub.r and the projected surface area A.sub.p. The contact angle θ.sub.W is a measure for the hydrophobicity of a surface.

(40) The real surface area A.sub.r is given by:
A.sub.r=(x.sub.st+x.sub.sp)*(y.sub.st+y.sub.sp)+2*x.sub.st*z.sub.st+2*y.sub.st*z.sub.st,
where x.sub.st gives the size of one structure 18 in x-direction, y.sub.st gives the size of one structure 18 in y-direction and z.sub.st gives the size of one structure 18 in z-direction. x.sub.sp gives the distance between two neighboring structures 18 in x-direction and y.sub.sp gives the distance between two neighboring structures 18 in y-direction.

(41) The projected surface area A.sub.p is given by:
A.sub.p=(x.sub.st+x.sub.sp)*(y.sub.st+y.sub.sp).

(42) Therefore, structures 18 that are large in x- and y-direction are giving low r-values for a constant z-value and are less effective in increasing the contact angle θ.sub.W of water droplets. Thus, the lateral size of the structures 18 is at least 1 nm and at most 100 μm, whereas the size of the structures 18 in vertical direction z can be at least 1 nm and at most 1 μm.

(43) In FIG. 8B a cutaway view of a structured top surface 15 of the sensor semiconductor device 10 is shown. The square-shaped structures 18 are arranged on top of or in the top layer 16 of the transducer 11.

(44) In FIG. 9 a randomly structured top surface 15 of a sensor semiconductor device 10 is shown. The picture is obtained by scanning electron microscopy. It is shown that a top layer 16 is structured by reactive ion etching such that the top surface 15 of the transducer 11 is structured in a random pattern. The top surface 15 is roughened by exposure to a plasma of N.sub.2, O.sub.2 and CF.sub.4.