Method of fabrication of high spatial resolution and fast sensors on a CMOS platform

Abstract

The present invention is in the field of a measuring system, in particular a sensor, for measuring physicochemical properties comprising a plurality of semiconductor or other solid-state components formed in or on a common substrate, a method of producing such a system, and an integrated circuit comprising said measuring system.

Description

[0001] METHOD OF FABRICATION OF HIGH SPATIAL RESOLUTION AND FAST SENSORS ON A CMOS PLATFORM FIELD OF THE INVENTION

[0002] The present invention is in the field of a measuring system, in particular a sensor, for measuring physicochemical properties comprising a plurality of semiconductor or other solid-state components formed in or on a common substrate, a method of producing such a system, and an integrated circuit comprising said measuring system.

[0003] RELATED APPLICATIONS

[0004] The present application claims the benefit of priority from Dutch Patent Application NL2039690, filed on January 27, 2025, in the name of Technische Universiteit Delft, The Netherlands.

[0005] The entire contents of the above-referenced applications and of all priority documents referenced in the Application Data Sheet filed herewith are hereby incorporated by reference for all purposes.

[0006] BACKGROUND OF THE INVENTION

[0007] Humidity relates to the concentration of water vapor in air. Humidity is considered to depend on both temperature and pressure in air, and likewise any system of interest. Three primary measurements of humidity are widely employed: absolute, relative, and specific. Absolute humidity is expressed as either mass of water vapor per volume of moist air (in grams per cubic meter) or as mass of water vapor per mass of dry air (usually in grams per kilogram). Relative humidity, often expressed as a percentage, indicates a present state of absolute humidity relative to a maximum humidity given at the same temperature. Specific humidity is the ratio of water vapor mass to total moist air mass.

[0008] Optical radiation relates to a part of the electromagnetic spectrum. Wavelengths of optical radiation are typically between 100 nm and 1 mm. This range includes visible light, infrared light, and part of the ultraviolet spectrum. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400-700 nanometers (nm), corresponding to frequencies of 750-420 terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively optical radiation. The infrared spectral band is generally understood to include wavelengths from around 750 nm (400 THz) to 1 mm (300 GHz). Ultraviolet (UV) light is electromagnetic radiation of wavelengths of 10-400 nanometers, which is longer than that of X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun. It is also produced by electric arcs, Cherenkov radiation, and specialized lights, such as mer-cury-vapor lamps, tanning lamps, and black lights. The electromagnetic spectrum relates to a range of electromagnetic radiation, organized by frequency or wavelength. The spectrum may be divided into separate bands, with different names for the electromagnetic waves within each band.

[0009] A sensor relates to a device that produces an output signal for the purpose of detecting aphysical phenomenon input signal. Therefore, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends the information to other components of the sensor, such as electronics, and frequently also a computer processor is used therein for processing input signals. Sensors, such as optical sensors, typically have a resolution, such as in the order of the wavelength of the optical spectrum. Advanced techniques, such as phase-contrast, may increase the resolution significantly.

[0010] Semiconductor technology is widely used. A semiconductor is a material that conducts an electrical current in between a conductor and an insulator. In many cases their conducting properties may be altered by introducing dopants into the crystal structure of the semiconducting materials, typically silicon. Two differently doped and adjacent regions form a semiconductor junction. The behavior of charge carriers, which include electrons, ions, and electron holes, at these junctions is the basis of diodes, transistors, and most modem electronics. There is a combination of processes required to prepare semiconducting materials, such as for ICs. Formation of dielectric material and conducting metal material are important processes. Typically, a critical process is photolithography. Light of a suitable wavelength is used along with a photoresist layer to create a chemical change that generates the patterns for the circuit to be formed. In view of the sensitivity of many processes for environmental influence most or all of these processes are performed in a clean room for obtaining high purity conditions. Complementary metal-oxide semiconductor (CMOS) technology is used in developing a majority of the present-day integrated circuits. CMOS sensors are fabricated by dedicated deposition techniques inside a Cleanroom environment which confines their integration with future smart systems capable to sense a wide variety of stimuli from their surroundings. Clean room space is however very expensive.

[0011] Widdershoven et al. (DOI:10.1007 / 978-3-031-71559-4_2) recite pixelated capacitive sensors. They describe Pixelated Capacitive Sensors (PCS) for Embedded Multi-Sensing, wherein a generic low-cost, low-area, and low-power scalable true complementary metal-oxide-semiconductor (CMOS)-compatible multi-sensing approach is used that allows late definition and implementation of sensor functions with minimal integration effort. The pixelated capacitive sensor (PCS) technology provides a massively parallel, physical multi-sensing interface at the surface of a pre-fabricated CMOS chip onto which multiple sensing functions can be implemented next to each other with inkjet printing. The PCS measurement principle, and two example applications thereof (a PCS biosensor chip and a PCS multi-sensing chip functionalized for detecting ethanol vapor), are given.

[0012] The present invention relates to an improved sensor, in particular a semiconductor sensor, which overcomes one or more of the above disadvantages, without jeopardizing functionality and advantages.

[0013] SUMMARY OF THE INVENTION

[0014] The present invention relates in a first aspect to a capacitive sensor comprising a semiconductor circuit, such as a Complementary Metal Oxide Semiconductor (CMOS) circuit, for determining capacitive changes, on the semiconductor circuit a two-dimensional array of pixels for sensing capacitive changes independently in between at least two pixels by saidsemiconductor circuit, and in between the pixels a space, that is, a physical 3 -dimensional space wherein pixels extend in a vertical direction with respect to the semiconductor circuit, wherein 1-90% of the space between pixels comprises a space filling material, and wherein the space filing material comprising a physicochemical active layer, in particular wherein 10-80% of the space between pixels comprises the physicochemical active material, more in particular 20-75%, even more in particular 30-50%. The present pixel may be regarded as a column type element, extending away from the CMOS circuit surface, and having specific dimensions in terms of height, width and length. So it relates to a small discrete element that together with other pixels may constitute an image or the like. It does not relate to e.g. optical pixels which relate more to electronic components sensitive to light typically embedded in the semiconductor circuit. Typically, a space between two pixels is filled with the physicochemical active layer, or is empty(see e.g. fig. 2). As a result of filling some of the space between pixels may be partly filled. Functionally such a partly filled space typically does not contribute to the capacitive properties of the present sensor. The present sensor provides a three order higher resolution in spatial humidity compared to prior art sensors. A typical prior art X-Y resolution ~ 10 mm, whereas the present sensor provides a spatial resolution of ~ 10 pm. The present sensor also provides a faster response and a faster recovery speed, typically 2-3 orders (100-1000) faster. The present device is also relatively easy to integrate, such as in a CMOS process or in an electronic read out circuit. The present sensor also operates without significant deviation under temperature variations, typically within a few %. Some aspects of the present sensor are amongst others: The sensors may be fabricated on pixelated capacitive sensor array by depositing (via inkjet printing, drop -casting), such as carbon black droplets as a sensing material; The volume of the ink droplets for inkjet printing can be very small (few pL, for instance 3-10 pL). The inkjet printing process minimizes the waste of materials; The amount of particles in the ink composition was typically 2-20 wt.%, such as 7 wt.% weight; The viscosity of the used ink was typically 1-10 mPa.s, such as 2.5 mPa.s, and the surface tension was typically 10-100 mN / m such as 34 mN / m; The average hydrodynamic radius of the carbon black ink was 300-700 nm, such as 522 nm; The capacitance of the humidity sensors increases with increased relative humidity (0-87 %RH); The sensors demonstrated fast response and recovery characteristics; The sensors showed low hysteresis; The sensors can be used to monitor human breath cycles; The sensors showed high-resolution spatial sensing; The sensors can monitor spatial -temporal processes involving changes in capacitance e.g. due to humidity in real time, that is with response times of 10-1000 msec, such as 100-820 msec; The sensors can be used to monitor leaf-sto-mata. CMOS-based sensors are usually fabricated by dedicated deposition techniques inside a Cleanroom environment which confines their integration with smart systems. Tn the present invention, the sensors can be made in a normal laboratory environment using the inkjet printing method or by simply drop-casting carbon black ink on top of pixelated capacitive sensor arrays. The inkjet printing method can also aid the scalable production of high-qualityhumidity sensors. The inkjet printing method not only saves the waste of excess materials but also improves the sensing speed owing to the minimal surface area for water molecules to adsorb. The PCS arrays operating at the high-frequency range (40 MHz) can accurately detect these small capacitance changes (in the range of several aF (10-18F) to thousands of aF). The method of fabrication of the multispectral UV detectors typically involves depositing, such as by inkjet printing, drop-casting, or spin coating metal-oxides in the form of nanoparticles (ZnO, SnO2, and Ga2O3) on top of the PCS array and keeping them in ambient overnight before testing their performance with exposure under different wavelengths of light. ZnO, SnO2, and Ga2O3start absorbing light below 400, 320, and 280 nm, respectively. Accordingly, ZnO mainly responds to wavelengths below 400 nm (UVA), SnO2 mainly responds to wavelengths below 320 nm (UVB) and Ga2O3responds to wavelengths below 280 nm (UVC). Below these particular wavelengths, the conductivity of these metal -oxide nanoparticles increases, and thus the capacitance of the functionalized electrodes increases. Thus, the fabrication method described in the present invention combining inkjet printing of carbon black on PCS array is indeed advantageous. Further, the concept of pixelated sensing is new for humidity sensors and it enables spatial resolution. The present invention allows combining the pixelated sensor elements (1024 sensors each in 3 matrices) and ensures simultaneous and fast data acquisition from them. The pixelated sensor arrays exhibit high spatial resolution (~2-l 5 pm) humidity sensing, which is most probably the highest resolution for the electrical signal-based humidity sensors. The electrical signal-based spatial humidity sensors lack both sensing speed and spatial resolution. Although fluorescence -based humidity sensors provide similar spatial resolution to the present invention, they suffer from slow sensing speed, poor stability, and difficulty in integrating with smart devices / phones. The present UV-sensors provide use of metal oxide nanoparticles / ink that can change their dielectric constant and conductance when illuminated by UV light. These particles are deposited on top of a pixelated capacitive sensor array. The PCS array has an in-built electronic circuit that detects changes in capacitance for each pixel. Different metal particles with different optical absorption spectra / bandgaps are deposited onto a single device. These particles selectively change their dielectric constant for light of different UV wavelengths, as a result, different pixels have a different spectral response. Enabling wavelength selective imaging by combining the pixel array with an optical system that projects an image on the sensor surface. Likewise, different sensitivities can be obtained, as well as different response times to equilibrium and recovery times to equilibrium. For instance, a humidity sensor with pixels more sensitive to a low humidity, to a medium humidity, and to a high humidity may be provided; more in particular, some pixels may be sensitive in a humidity range of 0-1% RH, some further in a range of 1-10 % RH, and even some further in a range of 10-100% RH. The materials deposition on the pixelated capacitive sensor (PCS) array can be performed without using dedicated deposition techniques and without the need for a cleanroom. Theinkjet printing method minimizes materials wastage without compromising device performance. The present invention using CMOS technology scores well in all these aspects

[0015] In a second aspect the present invention relates to a method of producing a semiconductor capacitive sensor comprising providing a semiconductor circuit for determining capacitive changes, on the semiconductor circuit, providing a two-dimensional array of pixels for sensing capacitive changes independently in between at least two pixels by said semiconductor circuit, and Inkjet printing a space filling material filling 1-90% of the space between pixels, wherein the space filing material comprising a physicochemical active material, in particular printing inkjet droplets of the space filling material, wherein space fdling material is selected from inkjet printable material, selected from an ink selected from a carbon black comprising ink, from a comprising graphene ink, from a carbon nanotubes comprising ink, and from a diamond comprising ink, from a spin coating material, from a hygroscopic material, from a metal oxide, in particular from ZnO, from MgO, from SnO2and from Ga2O3, from metal nitrides, such as BN, GaN, and AIN, from metal carbides, such as SiC, from optically active materials, from fluorescent molecules, from phosphorescent molecules, from IR material, from PbS, from InAs, from Fe3N, and combinations thereof,. An important advantage is that the provision of the space filing material can be performed outside strictly controlled environments, such as a clean room, and still yield reliable and reproducible results.

[0016] In a third aspect the present invention relates to an integrated circuit comprising the capacitive sensor according to the invention.

[0017] The present invention also relates to a method of measuring physicochemical changes in an object (e.g. fig. 12) comprising Providing the capacitive sensor according to the invention, Directing a field of vision of the capacitive sensor towards the object to be measured, and optionally adjusting a distance between the capacitive sensor and the object to be measured, Measuring capacitive changes between the pixels of the capacitive sensor, and Converting said capacitive changes into quantities representing said physicochemical changes.

[0018] Thereby the present invention provides a solution to one or more of the above-mentioned problems.

[0019] Advantages of the present description are detailed throughout the description. References to the figures are not limiting, and are only intended to guide the person skilled in the art through details of the present invention.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention relates in a first aspect to the sensor according to claim 1.

[0022] In an exemplary embodiment the present sensor is configured to measure one of (relative) humidity, and multispectral UV radiation.

[0023] In an exemplary embodiment the present sensor comprises at least one sensor electrode configured for providing a sense voltage, a read node R capacitively coupled to said at least one sensor electrode, in between the at least one sensor electrode and the read node R at least one first switch St, coupled to the read node and at least one first switch and a ground at least one second switch Sd, inparticular wherein at least one first switch St and at least one first switch St are configured to switch at a switching frequency / «, more in particular wherein is in a range of 10-100 MHz, in particular 20-50 MHz, and wherein the semiconductor capacitive sensor is configured to provide a voltage to the array of pixels, in particular to each pixel in the array of pixels individually. The read node R is configured to measure a current or change in charge that is related to the capacitance between the electrodes.

[0024] In an exemplary embodiment of the present sensor the semiconductor circuit is configured to provide a ground to a first pixel, and is configured to provide a voltage to a second pixel adjacent to the first pixel, and is configured to provide a ground to a third pixel adjacent to the second pixel.

[0025] In an exemplary embodiment of the present sensor the space filling material is obtained by inkjet printing.

[0026] In the present sensor the space filling material is selected from inkjet printable material, in particular selected from an ink, such as a carbon black ink, from graphene and diamond, from a spin coating material, from a hygroscopic material, from a metal oxide, in particular a ZnO, a MgO, a SnO2, a Ga2O3, from metal nitrides, such as BN, GaN, and AIN, from metal carbides, such as SiC, from optically active materials, in particular selected from molecules, in particular from fluorescent molecules, and from phosphorescent molecules, from IR material, PbS, InAs, Fe3O4, and combinations thereof. Therewith a large variety of phytochemical changes can be measured, wherein the physicochemical changes are caused by typically environmental input to the sensor, such as humidity, light, etc.

[0027] In an exemplary embodiment the present sensor the space filling material is configured to sense radiation in a wavelength range of 120-400 nm, in particular in a sub-range selected from 120-200 nm, 200-280 nm, 280 nm-320 nm, and 320-400 nm.

[0028] These different inks either have a difference in sensitivity range or different wavelength sensitivity range / spectrum (UV, VIS, IR), some of them being configured to capture high humidity values, or high wavelength UV light values, while others being more sensitive for low humidities or small wavelengths. By combining the capacitance values measured by the pixels from the different inks, the lateral distribution of humidity / light intensity can be determined. Alternatively, the combination can be used to realize a humidity sensor with larger sensitivity range, or realizing a spectrometer that determines the intensity of light per wavelength range.

[0029] In an exemplary embodiment the present sensor the amount of material is 1-10 wt.%, e.g. in the to be deposited space filling material, and the remainder is solvent.

[0030] In an exemplary embodiment the present sensor the pixel has a width of 1-100 pm, in particular a width of 2-40 pm, wherein the pixel has a length of 1-100 pm, in particular a length of 2-40 pm, and wherein the pixel has a height of 1-100 pm, in particular a height of 2-40 pm, whereas a space filling material has a height of 1 -100 pm, in particular a height of 2-40 pm, that is, substantially as high as the pixel, e.g. 50-100% of the height thereof, such as 75-95% of said height. It is found that such a relatively thin layer of space filling material provides a swift response time of the capacitivesensor, and a swift recovery time, whereas the sensitivity of the material for a specific physicochemical species is still good. The space filling material may be somewhat porous, e.g. with a porosity of 1-30% volume / volume, such as 5-20% vol. / vol.. The porosity is found to contribute positively to the properties of the space filling material, e.g. response time, sensitivity, and recovery time.

[0031] In an exemplary embodiment the present sensor the array comprises n*m pixels, wherein n is selected from 2-214, in particular from 26-210, more in particular from 27-29, and wherein m is selected from 2-214, in particular from 26-210, more in particular from 27-29.

[0032] In an exemplary embodiment the present sensor pixels occupy 2-50% of a space on the semiconductor circuit.

[0033] In an exemplary embodiment the present sensor the pixels are spaced apart, in particular wherein a first space in a vertical direction between pixels is 1-100 pm, in particular 2-40 pm, and wherein a second space in a horizontal direction is 1-100 pm, in particular 2-40 pm.

[0034] In an exemplary embodiment the present sensor the capacitive sensor comprises 2-512 arrays.

[0035] In an exemplary embodiment the present sensor the capacitive sensor has a spatial resolution of 1 nm-300 pm, in particular 100 nm-200 pm, more in particular 1 pm -100 pm.

[0036] In an exemplary embodiment the present sensor the capacitive sensor has a response time to equilibrium of 1 -800 msec, in particular 10-250 msec, more in particular 50-200 msec.

[0037] In an exemplary embodiment the present sensor the capacitive sensor has a recovery time to equilibrium of 1 -800 msec, in particular 10-250 msec, more in particular 50-200 msec.

[0038] In an exemplary embodiment the present sensor the capacitive sensor is configured to detect capacitive changes from 1-3300 aF, such as from 10-800 aF.

[0039] In an exemplary embodiment the present sensor the capacitive sensor has a sensitivity of 1 -100 kPa water vapor pressure, in particular 2-10 kPa, more in particular 5-8 kPa, in particular a relative water vapor pressure.

[0040] In an exemplary embodiment the present sensor the array is covered with a layer of protecting material, such as silicon nitride, and silicon carbide, in particular wherein said protecting layer has a thickness of 1 -50 um.

[0041] In an exemplary embodiment the present sensor a conducting pixel comprises at least one metal, such as Al.

[0042] In an exemplary embodiment the present sensor a ground pixel comprises a dielectric material, such as Silicon oxide.

[0043] In an exemplary embodiment the present sensor the space filling material is partly covered with a shadow mask, in particular wherein the shadow mask cover 5-95% of a surface area of the space filling material, more in particular 10-90%, even more in particular 30-70 %, such as 40-60%.

[0044] In an exemplary embodiment the present method of producing a semiconductor capacitive sensor the inkjet printing is performed outside a cleanroom. Such is considered a relative advantage, e.g. in terms of costs, practical considerations such as ease of work, etc. In an exemplary embodiment the present method of producing a semiconductor capacitive sensor a viscosity of the ink is 2-3 mPa.s at a shear rate of 10* 103 / s [using a Rheometer MCR 302, Anton Paar], In an exemplary embodiment the present method of producing a semiconductor capacitive sensor the ink comprises particles of the physicochemical active material.

[0045] In an exemplary embodiment the present method of producing a semiconductor capacitive sensor particles have an average size of 300-700 nm and a standard deviation of 30-100 nm (using dynamic light scattering Malvern Mastersizer 3000]

[0046] In an exemplary embodiment the present method of producing a semiconductor capacitive sensor the ink has a surface tension of 10-50 mN / m (droplet volume 11 µl, using a goniome-ter type OCA 25 of DataPhysics).

[0047] In an exemplary embodiment the present method of producing a semiconductor capacitive sensor the ink has a dielectric constant of 2-3, such as 2.5.

[0048] In an exemplary embodiment the present method of producing a semiconductor capacitive sensor the space fdling material is cured at an elevated temperature during a curing time, in particular wherein the elevated temperature is from 80-250 C, such as 100-200 C, and / or in particular wherein the curing time is from 2-20 minutes, such as 8-12 minutes.

[0049] The invention is further detailed by the accompanying figures and examples, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art, it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

[0050] SUMMARY OF FIGURES

[0051] Figures la-d, 2a-i, 3a-h, 4a-e, 5a-c, 6a-b, 7a-c, 8, 9a-b and lOa-b show details of the present invention.

[0052] DETAILED DESCRIPTION OF FIGURES

[0053] Figure 1. (a) An optical microscopic image of the CMOS-based pixelated capacitive sensor array, (b) Schematics showing the dimensions of the electrodes and spacing between them in the three matrices, (c) Tilted SEM image of the marked section of the PCS array (see fig. a), (d) The cross-section image of a sensor electrode (see fig. c) after FIB etching.

[0054] Figure 2. (a) An optical microscopic image of the 3><3 grid of the carbon black ink droplets (~ 10 pL, 200 pm spacing between the ink droplets) inkjet printed on the pixelated capacitive sensor array, (b) The zoomed-in image of (a). (c),(d) show the optical profilometry of the droplets 1, and 2. (e), (f) show the height profiles of lines AB and CD as depicted in (c), and (d) respectively. The thickness of the ink at C2 and C3 pixels are shown inside (e) and (f). (g) Cross-section schematic of the PCS array with one side coated with black ink. (h) The equivalent circuit for monitoring the capacitance of the sensors in PCS array, (i) The change in capacitance values for the CO, Cl, C2 and C3 pixels after printing.

[0055] Measurement of a viscosity of a typical carbon black ink used for inkjet printing showed an almost constant viscosity of ~2.5 mPa.s at a shear rate of 0-27 *1031 / sec.

[0056] Measurement of surface tension of a typical carbon black ink droplet of about 12 pl used for inkjet printing showed surface tension of 34.17 mN / m using a goniometer and a pendant dropmethod.

[0057] In an exemplary embodiment a carbon black particle size distribution showed a 50% peak at about 300 nm (296.7), an average size of 522 nm, and a standard deviation of 62.5 nm, measured with dynamic light scattering.

[0058] Figure 3. (a-c) The optical microscopic image of the 3x3 grid of the carbon black ink droplets (~ 3 pL) inkjet printed on the pixelated capacitive sensor array on matrices 1 -3 as indicated on top of each figure, (d-f) The 2D capacitance map of the matrices 1 -3 respectively, (g) The change in capacitance and (h) the number of functionalized electrodes in each matrix with 3pL carbon black ink droplet. Humidity sensing performance tests. A 3x3 black ink drops on PCS array was used. The real-time 2D capacitance map of the PCS array consisting 1024 pixels at (b) 68% and (c) 87% relative humidity values was monitored. Mainly, the ink coated pixels show a response to changes in humidity. Four specific positions pixels are used, two inside the same array, one inside a second array, and one outside the arrays. The change in capacitance values of these pixels responded well at different relative humidity values (5-87%), apart from the pixel outside the array, which inherently could not show a change in capacitance. The dynamic response of these pixels when switched from 0 to 80%RH and again switched back to 0% RH was very good, well within a second. The response and recovery times are in the order of 750 ms and 820 ms, respectively. The change in capacitance when exposed under exhaled breath air was reproducible and consistent. Breathing cycles could be followed with the present sensor. Typical capacitance levels were in the order of 2-50 aF (aF=10-18F).

[0059] Figure 4. Monitoring stomata using the spatial humidity sensor. The optical image of an umbrella plant (Schefflera arboricola). (b),(d) Optical microscopic image of the stomata on the back side of the leaves when the plant is kept under light and at dark. To mimic the structure of stomata a transparent nail-polish was coated on the leaves and left for drying. After drying the nail polish was then transferred onto a slide using a transparent tape. Then the it was monitored via optical microscope to observe the stomata. At light, the stomata are open and guard cells are turgid (swollen). At dark, the stomata are closed and the guard cells are flaccid (deflated), (c), (e) The 2D capacitance map of a portion of the plant leaf kept in close proximity of the PCS array. We can see the presence of stomata in the 2D capacitance map (low capacitance regions). Inset shows the higher resolution view of an individual stomata using PCS sensors of matrix 3 ( in (c) it is open, in (e) it is closed). The scale bars of insets of (c) and (e) are 10 pm. It is found that for the present humidity sensor, e.g. with carbon black ink on CMOS, the response and recovery time are in the order of hundreds of msecs.

[0060] Figure 5. (a) 2D capacitance map of the matrix 1 exposed under UV A (365 nm), (b) UV B (310 nm). Under UVA only ZnO functionalized pixels (top box) show response. With UV B both ZnO and SnO2(lower box) functionalized pixels show response. Fig. 5c shows a schematic example of the present semiconductor capacitive sensor comprising a two-dimensional array of pixels, wherein each individual pixel is selected from.a first pixel with a first physicochemical material, from a second pixel with a second physicochemical material, and optionally from at least one third pixel with at leastone third physicochemical material, such as an UV A sensitive material, an UV B sensitive material, and an UV C sensitive material. Likewise arrays may be provided, wherein each individual array is selected from.a first array with a first physicochemical material, from a second array with a second physicochemical material, and optionally from at least one third array with at least one third physicochemical material.

[0061] Figure 6. (a) The optical microscopic image of the PCS array inkjet coated with SnO2 nanoparticles mimicking letters TUD. (b) 2D capacitance map of the matrix 1 exposed under UV B (310 nm). The functionalized pixels with TUD expression show high response with UVB.

[0062] Figure 7 (a-c). The UV (365 nm) responses of ZnO functionalized devices cured at different temperatures as indicated on top of each figure. The response and recovery times of the devices are shown inside. Fig. 7a shows the photo response (365 nm) of ZnO film on CMOS cured at room temperature, which has somewhat slow characteristics (namely,, a response time of 4.21 sec and a recovery time of 300 sec). However, if the present sensor is cured at higher temperature (e.g. 100 °C), the response and recovery time improve to 0.44 s and 2.45 s, respectively.

[0063] Figure 8. The UV (365 nm) response of ZnO functionalized pixels at different frequencies (25-100 MHz). The device response improves with decreasing frequency.

[0064] Figs. 9a-b show a present UV-sensor with Ga2O3functionalized pixels, cured at room temperature, exposed for 5 sec under UV C (255 nm), with a normalized response (fig. 9a) and an enlarged section showing a response time of 0.32 sec and a recovery time of 0.25 sec.

[0065] Figs. lOa-b show a present humidity-sensor with black inkjet droplets functionalized pixels, exposed to 80% RH, with showing a response time of 0.5 sec and a recovery time of 0.6 sec. All PCS C1-C4 perform substantially equally well.

[0066] The figures are further detailed in the description of the experiments below.

[0067] EXAMPLES / EXPERTMENTS

[0068] An exemplary sensor was designed. Therein complementary metal-oxide semiconductor (CMOS) technology is used. CMOS sensors are fabricated by dedicated deposition techniques inside a Cleanroom environment which confines their integration with future smart systems capable to sense a wide variety of stimuli from their surroundings. Humidity monitoring for instance is of great importance in our daily life and industrial process. Humidity sensors are widely used in domestic applications, environmental protection, automobiles, food processing and storage, wastewater applications, agricultural applications, health monitoring, human -machine interface, and many other aspects. Inventors provide the fabrication of high spatial resolution and fast (humidity) sensors made via depositing, such as with carbon black, typically using inkjet printing / drop-casting on pixelated capacitive sensor (PCS) arrays supported by CMOS technology (see Figures 1,2). The construction of the PCS arrays is described in Figure 1. As an example, it comprises three sensor matrices, each having 1024 sensors that can monitor changes in capacitance in their vicinity. The dimensions of the sensors in different matrices are of 4-5 pm electrode width and 5-10 pm spacings between adjacent electrodes as shownin Figure lb. The sensors can accommodate sensing material inside the gap between the electrodes (see Figure 1c). An exemplary composition of a single electrode is shown in Figure Id. Humidity sensors on the PCS array are typically made by inkjet printing carbon black ink droplets (3x3 grid, with spacing of 200 pm between the droplets) of volume several picoliters (~ 10 pL) as shown in Figure 2. Carbon black (partially) fills the valley between the electrodes (see Figure 2a-g). A sense capacitor is selected by toggling the potential of its active electrode and grounding adjacent electrodes (see Figure 2g). Groups of sense electrodes are functionalized by filling their surrounding passivation layer valleys with carbon black ink (see Figure 2g). Figure 2h illustrates the measurement principle using the PCS arrays. The read node R is connected to the sense electrode. Ccrepresents the coupling capacitor through the protective layer over this sense electrode. Cprepresents the parasitic capacitor. CM and R represent the material in the passivation layer valleys, which can e.g. be either sensing ink (here carbon black) or air (RM = <» for air). Switches ST and SD toggle the read voltage V between the charge transfer voltage V and ground with a repetition frequency / R. In each cycle an amount of charge Q is transferred from the charge transfer node T to the ground.

[0069] The average charge transfer current is lT.av= RQ. For R» 1 / (2 n R CM), where the current through RM can be neglected, the transferred charge per charge / discharge cycle is Q = FT (CR + Cp) where CR = Cc CM / ( Cc + CM) is the read path capacitance (CM in series with Cc). Here, we measured the change in capacitance (AC) by deducting the current of the electrodes (no ink-filled) from electrodes (which are filled with carbon black) (see Figure 2i). Therefore, the value of the measured current can be written as AImeasured = / R * AC * Vr. In this work, we used f= 40 MHz, VT = 0.9 V. The deposition of carbon black ink can increase the capacitance as shown in Figure 2i. Capacitance can be improved with increasing the thickness of the deposited ink. Carbon black ink used here is comprised of 7% (weight%) carbon black particles and 5% glycerol, all inside the water (solvent). After the ink deposition, we keep the device at ambient for a day to remove excess water and glycerol. The viscosity of the carbon black ink used here was 2.5 mPa.s, and the surface tension was 34.17 mN / tn. The average hydrodynamic size of the carbon black particles was 522 nm.

[0070] Characterization as a humidity sensor:

[0071] The relative humidity (RH) around the PCS array was controlled (from 5% to 87% RH) by placing the device in a closed enclosure, and the RH was increased by adding water droplets inside the enclosure. The RH values inside the enclosure was calibrated using a commercial humidity sensor. The capacitance of the functionalized pixels increases with increasing humidity. The number of water molecules around the PCS array increases with increased humidity. Adsorption of this water molecules occurs mainly onto the carbon black functionalized sensor pixels. As the dielectric constant of water (~ 80) is much higher than the carbon black (~2-3), the adsorption of water molecules results in capacitance increment. The highest capacitance was observed around 470 aF for changing the relative humidity from 5 to 87%. Further, the capacitance increase of a specific sensor pixel with humidity was also analogousto the thickness of the carbon black around the valley of that sensor pixel. The unfunctionalized pixels do not show any changes and can be used as reference sensors. We also measure the dynamic response of the sensor pixels when switched from 0 to 80%RH and again switched back to 0% RH. The response and recovery times are in the order of 750 ms and 820 ms, respectively, and these values fit quite well amongst the fast responsive CMOS -based humidity sensors. The change in capacitance of a pixel for continuous increasing and decreasing cycles relative humidity levels demonstrated low hysteresis, which is considered an important feature for decent humidity sensors.

[0072] Applications:

[0073] Human exhaled breath contains high amount of water molecules. The human breathing cycles can be monitored using the present humidity sensor fabricated in this work. Owing to the quick responsive characteristics of the present invention, different nature of human breathing (fast, normal breathing, exhale-inhale cycles) can be easily distinguished. The present invention can be used to monitor different diseases related to abnormal human breath pattern and other disorders. Abnormal breathing patterns include Kussmaul breathing, Biot's respiration and Cheyne-Stokes respiration. Other breathing disorders include shortness of breath (dyspnea), stridor, apnea, sleep apnea (most commonly obstructive sleep apnea), mouth breathing, and snoring. The sensors can be used to determine the height of an object from the PCS array. To demonstrate this, we have placed a water droplet (volume ~1 pL) on top of the fabricated humidity sensor and then changed the height of the water drop (0.5 to 1.2 mm) from the PCS array. The capacitance of the functionalized sensors exhibited much higher values when the water drop is closer to the sensors, with increasing the height the capacitance decreases. Due to the presence of water droplet, local humidity around the PCS array increases which leads to increased capacitance of the functionalized pixels. The sensors can be used to monitor temporal changes with humidity as well. To demonstrate this, we have placed a water droplet (volume~l pL) on top of the fabricated humidity sensor at a height of 0.5 mm. The water droplet starts evaporating in ambient with time as evident from the decreasing size of the droplet. The functionalized sensors pixels exhibited decreasing values of capacitance with time, letting us to monitor the evaporation.

[0074] The sensors can be used in high resolution spatial humidity sensing. To demonstrate this, we have placed a wet tip in close proximity of the carbon black functionalized-matrix 1 of the PCS array. The height of the wet tip from the PCS array was kept fixed at ~ 20 pm. Then we moved the tip position on top of the respective droplets as mentioned in Figure 1 lb. Higher capacitance change was observed only in the functionalized pixels with particular droplet positions when the tip was exactly on top of them. We can also monitor the movement (motion) of the wet tip. This feature can be used in examining many microscopic processes and mobile micro-objects owing to the high resolution (~10 pm) of the sensors in the PCS array with their fast responsive nature.

[0075] The sensors can be used to monitor the stomata present on a leaf surface (see Figure 12).Stomata are small pores on leaf surfaces formed by a pair of flanking guard cells that swell or deflate in response to turgor pressure, which is regulated through ionic fluxes via ion channels anchored at the plasma membrane. Stomatai opening and closure help in the gaseous exchange between the plant and surrounding. Stomata facilitate carbon dioxide uptake and release of oxygen during the process of photosynthesis. Stomata also help in transpiration and removal of excess water in the form of water vapor. Stomata are open at daytime (in presence of light) and closed at night. Stomata maintain the moisture balance in plants according to weather by opening and closing. Thus, monitoring the stomata can provide important information of plant health. To monitor the stomata, we have placed lower surface of the umbrella plant (Schefflera arboricola) leaves in close proximity of PCS array functionalized with carbon black. Here, we drop casted the carbon black ink for uniform functionalization of all the sensor pixels. At light, the stomata are open and guard cells are turgid (swollen) and it resulted in higher change in capacitance around the adjacent sensors due to low local humidity. At dark, the stomata are closed and the guard cells are flaccid (deflated), and this results in lower change in capacitance near to stomata region (see Figure 4 c,e). The higher resolution features of the stomata can be monitored by matrix 3 as it has lower gap between the adjacent electrodes. The present invention could be the first observation of microscopic stomatai features using electrical sensors.

[0076] UV sensor

[0077] The deposition of the metal oxides (ZnO, SnO2, and Ga2O3) can be made by different methods: e.g. drop-casting, inkjet printing, and spin-coating. For drop-casting, metal-oxide nanoparticles (diameter ~ 30 - 400 nm) are dispersed in suitable solvents (with a low-boiling point below 150 C: water, ethanol, isopropanol, butanol, etc.) with 2-5 weight% of nanoparticles in the solvent. The nanoparticle dispersion was achieved by ultrasonicating the mixture for 10 minutes. A small volume (~ 1-2 pL) of dispersed nanoparticles was then drop-casted onto the PCS array to make these UV photodetectors. For inkjet printing, metal-oxide nanoparticles (diameter ~ 100 nm) were similarly dispersed in a mixture of water (90%) and ethanol (10%). The amount of nanoparticles in the mixture was 5-10 weight %. We also added a small amount (0.1 -0.5 weight %) of surfactant molecules (here SDS) to increase the stability of the nanoparticle dispersion. To make the nanoparticle ink suitable for inkjet printing, we ultrasonicated the mixture for 4 hours and then stirred it for 4 days. Further, the dispersion was kept undisturbed for a day for bigger particles to settle at the bottom. We used the upper part of the dispersion as nanoparticle ink. The viscosity and surface tensions of these inks were in the range of 1 -2 mPa-s and 30-40 tnN-m’1, respectively. Both these values are suitable for inkjet printing. The average hydrodynamic radius of the nanoparticles in the inks was ~ 300-350 nm. We then inkjet printed small amounts (droplet volume ~ 10 pL) of this metal-oxide (ZnO, SnO2, Ga2O3) inks onto the PCS array to make the UV detectors. The device performance can be improved by increasing the number of inkjet -printed droplets and bychoosing a low frequency. The response and recovery times of the ZnO and SnO2 functionalized pixels can be improved by annealing the devices at a higher temperature (100-200 °C for 10 minutes). The GazCh functionalized pixels demonstrate much faster responses without the high-temperature curing, typically in the order of 100-300 ms. For spin-coating, metal-oxide nanoparticles (diameter ~ 30 - 400 nm) were similarly dispersed as stated for drop-casting. Small volumes (~ 1-2 pL) of dispersed nanoparticles were then spin-coated (here we followed 2500 rpm for 40 s) onto the PCS array to fabricate UV photodetectors with uniform metal-oxide film thickness. These spin-coated devices can be used as UV-imagers.

[0078] Applications

[0079] The present invention can be utilized as a UV detector in various applications. Further, the present invention can be used as a multispectral and band-selective detection, such as for UV detection and humidity sensing, e.g. by combining different metal oxides provided in different matrices or in the same matrix device which is rather unique compared to the state-of-the-art devices used in UV detection. The present invention can also be utilized to fabricate band-selective UV-imagers. The present invention can be used to deliver coded messages that can only be read by exposure to a specific UV band. Multispectral sensing captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, such as the present pixels, including light from frequencies beyond the visible light range (i.e. infrared and ultraviolet).

[0080] The present method may utilize UV-responsive metal oxides and ease of using multiple active materials which improves the device response at UV and opens up the possibility to detect multispectral signals.

[0081] The present UV sensors provide a wide bandwidth selectivity and fast device response, a high stability, at low cost, and less complicated device fabrication methods. In view of UV A wavelengths:

[0082] 365 nm, UV B: 310 nm, and UV C: 255 nm; The sensor pixel coated with ZnO nanoparticles show response covering all UV A, B, C wavelengths; SnO2 nanoparticles show response with UV B, C wavelengths (fig. 5b and 6a, b); Ga2O3 nanoparticles show response with only UV C wavelengths.

[0083] The responses of the present sensors typically increase with the number of (metal oxide) drops used, e.g. by increasing a number of droplets of 10 pL from 1 -25 the capacitive response increases by a factor 2-5.

[0084] After curing a response time of the present UC-sensor may decrease by 10-40%, compared to before / without curing.

[0085] Response times are typically in the order of 50-500 ms.

[0086] Spin-coating, such as for spin-coated SnO2nanoparticles, is typically performed at 500-4000 rpm, such as 2500 rpm, for a spin coating time of 5-120 seconds, e.g. 40s, resulting in a thickness of 50-500 nm, such as 148-338 nm.The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying figures.

[0087] It should be appreciated that for commercial application it may be preferable to use one or more variations of the present system, which would be similar to the ones disclosed in the present application and are within the spirit of the invention.

Claims

AMENDED CLAIMSreceived by the International Bureau on 27 May 2026 (27.05.2026)1. A semiconductor capacitive sensor, in particular a Complementary metal Oxide Semiconductor (CMOS) capacitive sensor, comprisingA semiconductor circuit for determining capacitive changes,On the semiconductor circuit a two-dimensional array of pixels for sensing capacitive changes independently in between at least two pixels by said semiconductor circuit, Wherein 1-90% of the space between pixels comprises a space filling material, and wherein the space filing material comprising a physicochemical active layer, wherein space filling material is selected from inkjet printable material, selected from an ink selected from a carbon black comprising ink, from a comprising graphene ink, from a carbon nanotubes comprising ink, and from a diamond comprising ink, from a spin coating material, from a hygroscopic material, from a metal oxide, in particular from ZnO, from MgO, from SnO2, and from Ga20s, from metal nitrides, such as BN, GaN, and AIN, from metal carbides, such as SiC, from optically active materials, from fluorescent molecules, from phosphorescent molecules, from IR material, from PbS, from InAs, from FesOi, and combinations thereof,in particular wherein 10-80% of the space between pixels comprises the physicochemical material, more in particular 20-75%, even more in particular 30-50%,wherein the capacitive sensor has a spatial resolution of 1 nm-300 pm, in particular 100 nm-200 pm, more in particular 1 pm -100 pm, wherein the sensor is configured to measure at least one of (relative) humidity, and multispectral UV radiation.

2. The capacitive sensor according to claim 2 wherein the relative humidity is measured by pixels coated with carbon black ink on CMOS, and multispectral UV radiation is measured by pixels functionalized with UV-responsive metal oxides, in particular UV-responsive metal oxides selected from any or a combination of of ZnO, SnO2 and Ga2O3.

3. The capacitive sensor according to any of claims 1-2, comprising at least one sensor electrode configured for providing a sense voltage, a read node R capacitively coupled to said at least one sensor electrode, in between the at least one sensor electrode and the read node R at least one first switch St, coupled to the read node and at least one first switch and a ground at least one second switch Sd, in particular wherein at least one first switch St and at least one first switch St are configured to switch at a switching frequency fR, more in particular wherein fR is in a range of 10- 100 MHz, andwherein the semiconductor capacitive sensor is configured to provide a voltage to the array of pixels, in particular to each pixel in the array of pixels individually.

4. The capacitive sensor according to any of claims 1-3, wherein the semiconductor circuit is configured to provide a ground to a first pixel, and is configured to provide a voltage to a second pixel adjacent to the first pixel, and is configured to provide a ground to a third pixel adjacent to the second pixel.

5. The capacitive sensor according to any of claims 1-4, wherein the space filling material is obtained by inkjet printing.

6. The capacitive sensor according to any of claims 1-5,Wherein the space filling material is configured to sense radiation in a wavelength range of 120-400 nm, in particular in a sub-range selected from 120-200 nm, 200-280 nm, 280 nm-320 nm, and 320-400 nm, and / orwherein the amount of material is 1-10 wt.%, and the remainder is solvent.

7. The capacitive sensor according to any of claims 1-6, wherein the pixel has a width of 1-100 pm, in particular a width of 2-40 pm, wherein the pixel has a length of 1-100 pm, in particular a length of 2-40 pm, and wherein the pixel has a height of 1-100 pm, in particular a height of 2-40 pm, and / orWherein the array comprises n*m pixels, wherein n is selected from 2-214, in particular from 26-210, more in particular from 27-29, and wherein m is selected from 2-214, in particular from 26-210, more in particular from 27-29, and / orWherein pixels occupy 2-50% of a space on the semiconductor circuit, and / orwherein the pixels are spaced apart, in particular wherein a first space in a vertical direction between pixels is 1-100 pm, in particular 2-40 pm, and wherein a second space in a horizontal direction is 1-100 pm, in particular 2-40 pm, and / orWherein the capacitive sensor comprises 2-512 arrays, and / orwherein each individual pixel is selected from a first pixel with a first physicochemical material, from a second pixel with a second physicochemical material, and optionally from at least one third pixel with at least one third physicochemical material, and / orwherein each individual array is selected from a first array with a first physicochemical material, from a second array with a second physicochemical material, and optionally from at least one third array with at least one third physicochemical material.

8. The capacitive sensor according to any of claims 1-7,Wherein the capacitive sensor has a response time to equilibrium of 1-800 msec, in particular 10-250 msec, more in particular 50-200 msec, and / orWherein the capacitive sensor has a recovery time to equilibrium of 1-800 msec, in particular 10-250 msec, more in particular 50-200 msec, and / orWherein the capacitive sensor is configured to detect capacitive changes from 1-3300 aF, such as from 10-800 aF, and / orWherein the capacitive sensor has a sensitivity of 1-100 kPa water vapor pressure, in particular 2-10 kPa, more in particular 5-8 kPa.

9. The capacitive sensor according to any of claims 1-8, wherein the array is covered with a layer of protecting material, such as silicon nitride, and silicon carbide, in particular wherein said protecting layer has a thickness of 1-50 um, and / orWherein a conducting pixel comprises at least one metal, such as Al, and / orWherein a ground pixel comprises a dielectric material, such as Silicon oxide.

10. The capacitive sensor according to any of claims 1-9, wherein the space filling material ispartly covered with a shadow mask, in particular wherein the shadow mask cover 5-95% of a surface area of the space filling material, more in particular 10-90%, even more in particular 30-70 %, such as 40-60%.

11. A method of producing a semiconductor capacitive sensor comprisingProviding a semiconductor circuit for determining capacitive changes,On the semiconductor circuit, providing a two-dimensional array of pixels for sensing capacitive changes independently in between at least two pixels by said semiconductor circuit, and Inkjet printing a space filling material filling 1-90% of the space between pixels, wherein the space filing material comprising a physicochemical active material, in particular printing inkjet droplets of the space filling material, wherein space filling material is selected from inkjet printable material, selected from an ink selected from a carbon black comprising ink, from a comprising graphene ink, from a carbon nanotubes comprising ink, and from a diamond comprising ink, from a spin coating material, from a hygroscopic material, from a metal oxide, in particular from ZnO, from MgO, from SnO2, and from Ga2O3, from metal nitrides, such as BN, GaN, and AIN, from metal carbides, such as SiC, from optically active materials, from fluorescent molecules, from phosphorescent molecules, from IR material, from PbS, from InAs, from Fe3O4, and combinations thereof.

12. The method according to claim 11, wherein the inkjet printing is performed outside a cleanroom.

13. The method according to any of claims 11-12,Wherein a viscosity of the ink is 2-3 mPa.s at a shear rate of 10*103 / s [using a Rheometer], and / orWherein the ink comprises particles of the physicochemical active material, and / or Wherein particles have an average size of 300-700 nm and a standard deviation of 30-100 nm (us-ing dynamic light scattering Malvern Mastersizer 3000], and / orWherein the ink has a surface tension of 10-50 mN / m (droplet volume 11 µl, using a goniome-ter), and / orWherein the ink has a dielectric constant of 2-3, such as 2.5, and / orWherein the space filling material is cured at an elevated temperature during a curing time, in particular wherein the elevated temperature is from 80-250 °C, such as 100-200 °C, and / or in par-ticular wherein the curing time is from 2-20 minutes, such as 8-12 minutes.

14. An integrated circuit comprising the capacitive sensor according to any of claims 1-10.

15. A method of measuring physicochemical changes in an object comprisingProviding the capacitive sensor according to any of claims 1-10,Directing a field of vision of the capacitive sensor towards the object to be measured, and optionally adjusting a distance between the capacitive sensor and the object to be measured, Measuring capacitive changes between the pixels of the capacitive sensor, and Converting said capacitive changes into quantities representing said physicochemical changes.wherein the space-filling material is obtained by inkjet printing of ink droplets having a volume of 3-10 pL, andwherein the ink comprises nanoparticles having an average hydrodynamic radius of 300-700 nm, a viscosity of 1-10 mPa.s, and a surface tension of 10-100 mN / m

Images