Method for manufacturing multi-pixel gas microsensor with multiple sensing capabilities

Abstract

The present invention relates to a method for manufacturing a multi-pixel gas microsensor, wherein each multi-pixel gas microsensor includes at least a first pixel group having a first sensing material and a second pixel group having a second sensing material different from the first material. The method includes a first step of providing a wafer substrate and processing the wafer substrate to construct a plurality of multi-pixel microsensors having a first pixel group and a second pixel group, a second step of selecting a sensing material for each pixel group, and a third step of activating the first pixel group and the second pixel group by coating an electrode pair of the first pixel group and the second pixel group with the selected corresponding sensing material.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a multi-pixel microsensor with multiple sensing capabilities. More specifically, the present invention also relates to a multi-pixel microsensor for detecting gases and / or volatile organic compounds. Background Art

[0002] Seeking smart environmental monitoring solutions, process control, security or healthcare service applications, low-power and low-cost sensors are needed, especially sensors for detecting the presence / absence and concentration of specific harmful gases or disease markers (e.g., volatile compounds).

[0003] Examples of known environmental sensors are solid-state semiconductor sensors that utilize metal oxide surfaces to detect gases. However, these metal oxide gas sensors require high operating temperatures (typically above 200 to 500°C) to activate the surface reaction between the material and the gas to be detected. Therefore, these types of sensors are not very suitable considering their power consumption.

[0004] Alternative sensors are those that use polymer- and nanocomposite-based sensor materials. These materials react at room temperature or below 60°C, thus significantly reducing the power consumption of the sensor.

[0005] However, current sensors using these polymer- and nanocomposite-based sensor materials are not manufactured according to mass production processes and are therefore not always produced in a cost-effective manner. In addition, depending on the type of gas or environmental parameter to be detected, various sensors need to be manufactured and assembled together to form a selective sensor array. This further increases manufacturing costs.

[0006] Thus, there is room for improvement in methods for fabricating sensors having multiple sensing capabilities, particularly for sensing gases and volatile compounds. Summary of the invention

[0007] The object of the present invention is to provide a method for manufacturing a multi-pixel microsensor with multiple sensing capabilities, in particular for sensing gases and volatile compounds. Another object is to provide a cost-effective manufacturing method by reducing the number of manufacturing steps. More specifically, the method aims to manufacture low-power microsensors compatible with "smart sensors" and IoT communication protocols, in particular microsensors for long-life or battery-free autonomous applications.

[0008] The invention is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims.

[0009] According to a first aspect of the present invention, a method for manufacturing a plurality of multi-pixel gas microsensors is provided, wherein each multi-pixel gas microsensor comprises at least one or more pixels having a first sensing material and one or more pixels having a second sensing material different from the first material.

[0010] The method comprises the following steps:

[0011] A) providing a wafer substrate including an insulating layer, and processing the wafer substrate for constructing a plurality of multi-pixel microsensors, the processing comprising at least the following steps:

[0012] A1) Create a photolithography mask defined for each of the plurality of microsensors:

[0013] i) one or more first electrode pairs form a first pixel group, and each of the first electrode pairs comprises a first electrode and a second electrode,

[0014] ii) one or more pairs of second electrode pairs form a second pixel group, and wherein each pair of second electrode pairs includes a third electrode and a fourth electrode,

[0015] iii) a first electrical connection line is connected to each of the first electrodes of the first electrode pair, and a second electrical connection line is connected to each of the second electrodes of the first electrode pair,

[0016] A2) applying a metallization process to the insulating layer according to a photolithography mask to form a first electrode pair, a second electrode pair, a first electrical connection line, and a second electrical connection line, and wherein the metallization process comprises depositing one or more layers of metal on the substrate,

[0017] A3) depositing a protective mask onto the substrate, the protective mask preferably being made of nitride or oxide,

[0018] B) selecting a first sensing material and a second sensing material, and wherein the first sensing material is a first polymer suitable for electropolymerization,

[0019] C) performing on-wafer activation or on-die activation of the first pixel group and the second pixel group, the on-wafer activation or on-die activation comprising at least the following steps:

[0020] C1) locally removing a portion of the protection mask covering the first electrode pair of the first pixel group,

[0021] C2) applying a first electropolymerization process to simultaneously coat each of the first electrode pairs of the first pixel group (G1) with a first sensing material, and wherein the first electrical connection line and the second electrical connection line serve as electrical connections in the first electropolymerization process for applying a first voltage to the first electrode and the second electrode or for applying a first voltage difference between the first electrode and the second electrode,

[0022] C3) locally removing a portion of the protection mask covering the second electrode pair of the second pixel group,

[0023] C4) Coating a second electrode pair of a second pixel group with a second sensing material.

[0024] Advantageously, by performing pixel activation as a separate step (i.e., a back-end step) after wafer substrate processing that defines the set of electrode pairs, the selection of the sensing material is independent of the wafer substrate processing. Thus, a variety of sensing materials can be selected after wafer substrate processing. This allows for the manufacture of inexpensive customized sensor arrays. In fact, with the method according to the invention, "on-demand" activation of pixels is performed by covering the electrode pairs with the specific sensing material required for a given application.

[0025] Advantageously, by using an electropolymerization process for polymer pixel activation, a technique for easily and inexpensively depositing polymers on the electrode pairs used to form the pixels is implemented. In fact, each of the pixels requiring the same sensing material (i.e. belonging to the same pixel group) can be coated simultaneously.

[0026] Advantageously, by defining electrical connections for the first electrode pair and using these interconnections to apply a first voltage or a first voltage difference during electropolymerization, only the first electrode pair receives the first voltage and thus polymerization proceeds in a selective manner.

[0027] Advantageously, with the method according to the invention, a compact and inexpensive single-chip detector for detecting a variety of different gases is obtained.

[0028] Advantageously, using the method according to the invention, some pixel groups can be coated with a polymer to sense gas, while other pixel groups can be coated with other materials suitable for measuring, for example, temperature and / or humidity on the chip. This allows compensation of parasitic effects of the detected signal, such as drift or aging.

[0029] The method according to the invention is not limited to a specific order of steps identified by a sequence of letters such as A), B) and C) or by other symbol sequences. For example, in an embodiment, both steps C1) and C3) are performed before steps C2) and C4). In other embodiments, step B) is performed, for example, before step A).

[0030] In an embodiment, the first sensing material and / or the second sensing material is any one of the following polymers: polypyrrole, polyaniline, polythiophene or polysilane compound. In other embodiments, the first sensing material and / or the second sensing material is a molecular imprinting polymer.

[0031] In an embodiment, the method comprises the additional step of cutting the first and second electrical connecting lines after the first electropolymerization process such that each first electrode pair of the first set becomes isolated from other first electrode pairs of the first set.

[0032] In an embodiment, the first electrical connection line and the second electrical connection line form a common connection line, or wherein the first electrical connection line and the second electrical connection line are interconnected to short-circuit the first electrode and the second electrode, so that during the first electropolymerization process the first voltage is a single common voltage for the first electrode and the second electrode, and wherein after the first electropolymerization process, the method includes a further step of cutting the first electrical connection line and the second electrical connection line or cutting the common connection line so that an open circuit is formed between the first electrode and the second electrode of each pair of first electrode pairs.

[0033] In an embodiment, after the first electropolymerization process, the method according to the invention comprises the additional step of cutting off said first electrical connection line and said second electrical connection line for each microsensor so that each first electrode pair of the first group becomes isolated from other first electrode pairs of the first group.

[0034] In an embodiment, for each multi-pixel gas microsensor, the number of pixels having the first sensing material is equal to or greater than two. Advantageously, for a detector having multiple pixels with the same sensing material, more reliable sensing can be performed by, for example, taking an average or by accumulating data from various sensors having the same sensing material.

[0035] Generally speaking, the signal-to-noise ratio can be improved.

[0036] In an embodiment according to the invention, the second sensing material is a second polymer suitable for electropolymerization, and wherein the step A1) of providing a photolithographic mask further defines: iv) a third electrical connection line connected to each of the third electrodes of the second electrode pair, and a fourth electrical connection line connected to each of the fourth electrodes of the second electrode pair (E2), and wherein the step A2) of metallization further forms the third electrical connection line and the fourth electrical connection line, and wherein the step C4) comprises applying a second electropolymerization process to simultaneously coat each pair of the second electrode pairs of the second group with the second sensing material, and wherein the third connection line and the fourth connection line serve as electrical connections in the second electropolymerization process for applying a second voltage to the third electrode and the fourth electrode or applying a second voltage difference between the third electrode and the fourth electrode.

[0037] In a further embodiment, the third electrical connection line and the fourth electrical connection line also form an additional common connection line, or the third connection line and the fourth connection line are interconnected to short-circuit the third electrode and the fourth electrode, so that during the second electropolymerization process, a second voltage is applied to the third electrode and the fourth electrode, and wherein, after the second electropolymerization process, the method includes the further step of cutting off the third electrical connection line and the fourth electrical connection line or cutting off the additional common connection line, so that an open circuit is formed between the third electrode and the fourth electrode of each pair of the second electrode pairs.

[0038] In a further embodiment, after the second electropolymerization process, the method comprises an additional step of severing the third and fourth electrical connection lines such that each second electrode pair of the second group becomes isolated from other second electrode pairs of the second group.

[0039] The microsensor obtainable with the method according to the invention is not limited to the first and second pixel groups and in embodiments more than two pixel groups are provided by applying the method steps as defined for the first pixel group and / or the second pixel group to additional pixel groups.

[0040] According to a second aspect of the present invention, there is provided a multi-pixel microsensor for detecting gases and volatile organic compounds, the multi-pixel microsensor being manufactured according to the method defined in the accompanying claims.

[0041] Advantageously, combining several sensing materials (such as molecularly imprinted polymers and non-imprinted polymers) on a single device improves sensitivity and selectivity and enables gas discrimination.

[0042] Advantageously, the multi-pixel microsensor according to the invention operates at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] These and further aspects of the invention will be explained in more detail by way of example and with reference to the accompanying drawings, in which:

[0044] Figure 1 A flow chart showing an embodiment of a method according to the present invention;

[0045] Figure 2 A top view of a wafer substrate and an enlarged view of a portion of the wafer substrate showing an embodiment of a pixel array produced according to the method of the present invention are shown;

[0046] Figure 3 schematically shows a cross-sectional view of an embodiment of a pixel according to the present invention before activation of the pixel;

[0047] Figure 4 Schematically shows Figure 2 A cross-sectional view of an embodiment of a pixel is shown after activation of the pixel;

[0048] Figure 5 A cross-sectional view schematically showing another embodiment of a pixel of a microsensor according to the present invention;

[0049] Figure 6 A readout device for a microsensor according to the present invention is schematically shown.

[0050] The figures are not drawn to scale. Generally, identical components are indicated by identical reference numerals in the figures. DETAILED DESCRIPTION

[0051] The present disclosure will be described according to specific embodiments, which are illustrative of the present disclosure and should not be construed as limiting. It will be understood by those skilled in the art that the present disclosure is not limited by what has been specifically shown and / or described, and that alternative or modified embodiments may be developed based on the overall teachings of the present disclosure. The accompanying drawings described are only schematic and non-limiting.

[0052] Use of the verb "comprise", and its conjugations, does not exclude the presence of elements other than those stated.

[0053] Use of the article "a", "an" or "the" preceding an element does not exclude the presence of a plurality of such elements.

[0054] In addition, the terms first, second, etc. in the description and claims are used to distinguish between similar elements and are not necessarily used to describe a sequence in time, space, order or any other manner. It should be understood that the terms so used are interchangeable under appropriate circumstances, and the embodiments of the present disclosure described herein are capable of operating in other sequences than those described or illustrated herein.

[0055] General manufacturing method

[0056] According to a first aspect of the present invention, a method for large-scale production of a multi-pixel gas microsensor having multiple sensing capabilities is provided.

[0057] A multi-pixel microsensor has to be understood as a sensor array comprising a plurality of pixels and wherein at least a first pixel group has different sensing capabilities when compared to a second pixel group of the sensor array. Pixels are sometimes also referred to as transducers. The different sensing capabilities are obtained by using different sensing materials for the pixels. In this way, the microsensor behaves like an "environmental camera", wherein, for example, a first pixel group is able to detect a first specific gas, while a second pixel group is able to measure temperature and / or humidity or a second specific gas different from the first gas. The multi-pixel microsensor is not limited to the number of different sensing materials used. For example, a third pixel group may comprise a sensing material for detecting a further specific gas. For practical reasons, the number of different sensing materials within a microsensor is preferably limited to 25.

[0058] The pixel groups of a multi-pixel microsensor must be interpreted as groupings of one or more pixels of the microsensor having the same sensing material. For example, in an embodiment of the microsensor, a first pixel group may include three pixels having a first sensing material, and a second pixel group may include one pixel having a second sensing material. In other words, in an embodiment, some of the pixel groups may also include one pixel.

[0059] Each of the multi-pixel gas microsensors manufactured according to the method of the present invention includes at least a first pixel group G1 having a first sensing material and a second pixel group G2 having a second sensing material different from the first material.

[0060] Methods for manufacturing multi-pixel microsensors include: Figure 1 Three main steps are schematically shown: a first step 100 of providing a wafer substrate and processing the wafer substrate to construct a plurality of multi-pixel microsensors having a first pixel group G1 and a second pixel group G2, a second step 200 of selecting a sensing material for each pixel group, and a third step 300 of activating the first pixel group and the second pixel group with the selected sensing material.

[0061] The first step 100 of the method according to the present invention provides a wafer substrate, wherein an insulating layer is formed on the outer surface, and then the wafer substrate is processed to construct a plurality of multi-pixel microsensors. Various examples of wafer substrates suitable for applying the present method will be further discussed below. The processing of the wafer substrate includes at least a sub-step A1 of creating a photolithography mask). A photolithography mask is defined for each of the plurality of microsensors: i) one or more pairs of first electrode pairs E1 form a first pixel group G1, and wherein each pair of first electrode pairs includes a first electrode and a second electrode, ii) one or more pairs of second electrode pairs E2 form a second pixel group G2, and wherein each pair of second electrode pairs includes a third electrode and a fourth electrode, and iii) a first electrical connection line is connected to each of the first electrodes of the first electrode pair E1, and a second electrical connection line is connected to each of the second electrodes of the first electrode pair E1. These first electrical connection lines and second electrical connection lines are also generally referred to as interconnect wiring.

[0062] The invention is not limited to a specific lithography technique for applying the lithography mask. In embodiments, the lithography mask is a light field mask such as obtained by photolithography, and in other embodiments, electron beam lithography or any other suitable lithography technique for applying the mask is applied.

[0063] In an embodiment, the first electrode of the first electrode pair and the third electrode of the second electrode pair are positive electrodes, and the second electrode of the first electrode pair and the fourth electrode of the second electrode pair are negative electrodes.

[0064] Note that the number of electrode pairs in each group is not necessarily the same for each group, for example, the first group may have four pairs of first electrode pairs, and the second group may have two pairs of second electrode pairs.

[0065] In sub-step A2), the insulating layer of the wafer substrate is subjected to a metallization process according to the created photolithography mask to form a first electrode pair, a second electrode pair, and a first electrical connection line and a second electrical connection line. This metallization process includes depositing at least one or more layers of metal on the wafer substrate. The metallization process based on photolithography is a known process and is commonly used in the back end of the production line of the IC manufacturing process. Figure 2 , a top view of a wafer substrate 10 showing an embodiment of a pixel array produced by processing steps A1) and A2) and an enlarged view of a portion of the wafer substrate are shown. In this example, the pixel array forming the microsensor includes five groups of pixels P1, P2, P3, P4, and P5. In this example, the total number of pixels Pi in the pixel array is equal to twenty. Group P1 includes four electrode pairs E1, and group P2 includes four electrode pairs E2. Group P3 includes eight electrode pairs E3. Group G4 includes two electrode pairs E4, and group P5 also includes two electrode pairs. As will be discussed further below, those electrode pairs E1 to E5 may be the same or different.

[0066] To further illustrate the manufacturing process, Figure 3 In the figure, a cross-sectional view of an embodiment of a pixel produced by processing steps A1) and A2) is shown. The cross-sectional view shows a first electrode E1 of a pixel constructed on a wafer substrate 10, and in this embodiment, the electrode pair E1 is formed by two interdigitated electrodes. In this exemplary embodiment, the electrical connection lines of the pixel group are realized using three metallization layers 20a, 20b and 20c, which are connected to through holes 21a, 21b. The number of required metallization layers depends on the number of defined pixel groups. If the microsensor to be manufactured only requires two different sensing materials, two layers of metal are usually sufficient. If more different sensing materials are required, more metal layers are provided.

[0067] After the metallization process, in a third sub-step A3), a protective mask is deposited onto the substrate. In an embodiment, the protective mask is made of nitride or oxide.

[0068] In the second step 200, a first sensing material for the first pixel group and a second sensing material for the second pixel group are selected. The first sensing material is a first polymer suitable for electropolymerization. The second step 200 can be interpreted as a custom decision making step and can be performed before or after the first step 100.

[0069] In the third step 300, on-wafer activation or on-die activation is performed on the first pixel group and the second pixel group. Such on-wafer activation or on-die activation includes at least the following four steps:

[0070] C1) locally removing a portion of the protection mask covering the plurality of first electrode pairs of the first pixel group,

[0071] C2) applying a first electropolymerization process to simultaneously coat each of the first electrode pairs of the first pixel group with a first sensing material, and wherein the first electrical connection line and the second electrical connection line serve as electrical connections for applying a first voltage to the first electrode pairs during the first electropolymerization process,

[0072] C3) locally removing a portion of the protection mask covering the second electrode pair of the second pixel group,

[0073] C4) Coating a second electrode pair of a second pixel group with a second sensing material.

[0074] exist Figure 4 , a cross-sectional view of an embodiment of a pixel resulting from process steps C1) and C2) is shown. The cross-sectional view illustrates that the first electrode E1 is covered by a polymer 40.

[0075] In an embodiment, steps C1) and C3) are performed before steps C2) and C4). In practice, the inventors have observed that locally removing a portion of the protective mask for all electrode pairs and subsequently coating the pixel groups with their appropriate sensing material does not affect the coating process for each individual pixel group. Advantageously, this reduces the time required to perform the activation of each of the pixel groups.

[0076] In an alternative embodiment, only step C3) is performed after completing steps C1) and C2).

[0077] As described above, the microsensor may include different sensing materials for sensing different gases. In these embodiments, the second sensing material is a second polymer such as suitable for electropolymerization. Then, the sub-step A1) of providing a photolithography mask further defines: iv) a third electrical connection line and a fourth electrical connection line respectively connected to the third electrode and the fourth electrode of the second electrode pair, and then the step A2) of metallization further forms the third electrical connection line and the fourth electrical connection line. Step C4) further includes applying a second electropolymerization process for simultaneously applying the second sensing material to each pair of the second electrode pairs of the second sensing group. The third electrical connection line and the fourth electrical connection line are used here as electrical connections for applying a second voltage to the second electrode pair during the second electropolymerization process.

[0078] It is understood that those skilled in the art can extend the present method to fabricate microsensors having more than two different polymers as sensor materials.

[0079] In some embodiments, after the activation process, the protective mask applied in step A3) is completely removed (e.g. by an etching process), while in other embodiments the protective mask remains. Figure 5 , an example in which the protective mask 50 is retained is shown.

[0080] Wafer Substrate

[0081] A wafer substrate provided for carrying out the method according to the invention has to be interpreted as any substrate suitable for applying method steps A1) to A3).

[0082] In an embodiment, Figure 3 As shown, the wafer substrate 10 comprises at least a first layer 11 made of a semiconductor material such as Si or Ge or a metal such as Al, Au, Ag, Pt, etc. and a second layer 12 made of an insulating material. The second insulating layer forms the outer surface of the substrate wafer and is a starting layer for performing the above-mentioned processing step 100.

[0083] Typically, the insulating layer 12 of the wafer substrate is formed by any of the following methods: oxidation process, nitridation process, oxide deposition or nitride deposition.

[0084] In other embodiments, the wafer substrate comprises a layer made of an insulating material such as glass or quartz. In an embodiment, the entire wafer substrate is made of glass or quartz.

[0085] In a particular embodiment, the wafer substrate provided for performing the method according to the invention is a wafer substrate resulting from an initial front-end-of-line (FEOL) process. For example, the wafer substrate may include transistors configured to read out the signals generated by the electrode pairs of the microsensor. In the case of on-die activation of the pixel, these transistors may also be used as switches to control the aggregate voltage supplied to the electrode pairs.

[0086] Sensing Materials

[0087] Various materials can be used as sensing materials for pixels, such as conductive polymers such as molecularly imprinted polymers (MIPs) and non-imprinted polymers (NIPs), and nanocomposites based on materials such as carbon nanotubes or graphene.

[0088] The microsensor obtained according to the manufacturing method of the present invention comprises at least one polymer as a first sensing material. In an embodiment, the sensing material is any one of the following polymers: polypyrrole, polyaniline, polythiophene or polysilane compound.

[0089] In an embodiment, the microsensor comprises a combination of sensor materials, wherein a first sensor material is a molecularly imprinted polymer (MIP) and a second sensor material is a non-imprinted polymer (NIP).

[0090] In some embodiments, one or more pixel groups may have a film as the sensing material, for example a film made of graphene. In other embodiments, the sensing material is made of a resistive or semiconductor material.

[0091] As described above, the microsensor manufactured according to the present invention includes at least a first pixel group having a polymer as a sensor material, and the sensor material is deposited on a first electrode pair by a first electropolymerization process.

[0092] If the microsensor comprises a second pixel group having, for example, carbon nanotubes, graphene or a nanocomposite material as sensing material, then in step C4) of the method according to the invention, the sensing material is deposited using one of the following processes: spraying, drop coating or inkjet printing. These processes are known in the technical field of applying coatings.

[0093] In some embodiments, one or more electrode pairs are not coated, ie no sensing material is added between the electrodes of the electrode pair. These electrode pairs are used, for example, for resistance measurements without any coating present, for example for temperature measurement purposes.

[0094] electrode

[0095] In an embodiment, the first electrode pair and / or the second electrode pair are formed by two interdigitated electrodes. In an alternative embodiment, the first electrode pair or the second electrode pair are formed by two opposing electrical contacts. Each pair in the electrode pair includes a positive electrode and a negative electrode. For example, the electrode is made of copper.

[0096] In some embodiments, the first pixel group includes an electrode pair formed by two interdigitated electrodes, and the second pixel group includes an electrode pair formed by two opposing electrical contacts. In other words, the electrode pairs may differ from pixel group to pixel group.

[0097] In some embodiments, a conductive element (e.g. a mesh made of graphene) is placed between two opposing electrical contacts forming an electrode pair. This allows increasing the distance between the electrical contacts and facilitates the polymerization process. For these embodiments, the method includes a further step as part of the pixel activation step 300 to couple such a conductive element between the electrodes of the electrode pair.

[0098] In embodiments using interdigitated electrodes, when coated with a polymer, the thickness of the polymer applied to the electrode pair is approximately 1 to 2 μm to completely cover both electrodes of the electrode pair and form an ohmic contact.

[0099] In other embodiments, the distance between electrodes of an electrode pair may be less than 1 μm, such as several hundred nanometers. Generally, smaller distances are more efficient for the electropolymerization process.

[0100] The interdigitated electrode comprises a plurality of fingers, and the number of fingers is optimized according to the required resistance between the electrodes of the electrode pair. For example, in an embodiment, the required resistance may be in the range between 100 kilo-ohms and 1 megohm.

[0101] Electrical connection wire

[0102] An electrical connection line has to be interpreted as a conductor or a part of a conductor for interconnecting electrodes of an electrode pair having the same sensing material. For example, the electrical connection line is made of copper.

[0103] In an embodiment, the first electrical connection line and the second electrical connection line of the first pixel group are connected to each other, that is, the first electrode and the second electrode of the electrode pair of the first pixel group form a short circuit. In this way, during the first electropolymerization process, a first single voltage can be applied to the first electrode and the second electrode of the first electrode pair of the first group. This means that, for example, the positive electrode and the negative electrode are at the same voltage during the electropolymerization process.

[0104] In some embodiments, the first electrical connection line and the second electrical connection line form a common connection line, so that the first electrode and the second electrode of the first electrode pair are short-circuited by default.

[0105] Therefore, for embodiments in which the first electrode pair is short-circuited as described above, after the first electropolymerization process, the method according to the present invention includes a further step of cutting the first electrical connection line and the second electrical connection line or cutting the common connection line so that an open circuit is formed between the first electrode and the second electrode of each pair in the first electrode pair.

[0106] Similarly, for example, if the second sensing material is a second polymer, the third electrical connection line and the fourth electrical connection line are connected to each other and form a further short circuit. In this way, during the second electropolymerization process, a second single voltage can be applied to the third electrode and the fourth electrode of all second electrode pairs. Therefore, during the second electropolymerization process, the positive electrode and the negative electrode are also at the same voltage.

[0107] More generally, in some embodiments where the microsensor includes multiple groups of pixel groups using multiple polymers as sensing materials, each of the electrical conductors of an electrode pair in each of the pixel groups is configured to short-circuit the electrode pair.

[0108] In other embodiments, the first electrical connection line and the second electrical connection line form two separate electrical conductors, i.e., for example, a first electrical conductor connecting the positive electrodes of all first electrode pairs and a second electrical conductor connecting the negative electrodes of all first electrode pairs. In this way, during the electropolymerization process, the first electrical connection line and the second electrical connection line can be used to apply a first voltage to all positive electrodes of the first electrode pairs and a second voltage to all negative electrodes of the first electrode pairs. In other words, a first voltage difference can be applied between the first electrode and the second electrode.

[0109] When the electrode pair is short-circuited by using a common connection line or by interconnecting the first electrical connection line and the second electrical connection line as described above, the number of metallization layers that need to be applied during the metallization process is reduced. In this case, using one metallization layer, two different sensor materials can be covered. For example, four different sensor materials can be covered using two metallization layers. On the other hand, if the first electrode and the second electrode are maintained separated by using dedicated first electrical connection lines and second electrical connection lines connected to the first electrode and the second electrode, respectively, more metallization layers are required for each sensor material. Then typically one metallization layer is required for each sensing material.

[0110] On-wafer activation of pixels

[0111] The activation of the pixels can be performed at the wafer level (ie, "on-wafer"), or at the die level (ie, "on-die" after the wafer has been diced).

[0112] In an embodiment in which activation of the first pixel group and the second pixel group is performed on a wafer, a sub-step C2 of applying a first electropolymerization process is simultaneously performed for each first pixel group of a plurality of multi-pixel microsensors supported by the wafer substrate). After the processing of steps A1) to A3), simultaneous electropolymerization on the wafer is performed by placing the wafer substrate in a first electrolyte solution and applying a first voltage to the first electrode pair and the second electrode pair if the first electrode and the second electrode are short-circuited, or applying a voltage difference between the first and second electrodes if the first electrode and the second electrode are not short-circuited. As described above, the first electrical connection line and the second electrical connection line serve as electrical connections for applying voltage to the electrodes.

[0113] When activation of pixels is to be performed on the wafer, before performing processing steps A1) to A3), the wafer substrate is provided with global electrical contacts GC1, GC2 at the edge of the wafer, allowing the connection of a voltage source providing the voltage for performing the polymerization process. In these embodiments, as part of the metallization step A2), the first electrical connection line and the second electrical connection line of each of the microsensors are connected to one or two global electrical contacts at the edge of the wafer. If the multi-pixel sensor to be manufactured comprises a plurality of groups, each with a different polymer sensing material, one or two global electrical contacts are provided at the edge of the wafer for each pixel group requiring a polymer sensing material.

[0114] exist Figure 2 In the embodiment shown, five global contacts GC1 to GC5 are shown on the wafer substrate, which allow the five pixel groups G1 to G5 to be coated with different polymer sensing materials. The number of global contacts required on the wafer substrate depends on the number of pixel groups that require polymer as sensing material. Figure 2 In the example shown, only groups G1 to G3 need to be coated by the polymerization process, and three global contacts on the wafer are then sufficient.

[0115] In some embodiments, as part of the metallization process, multiple first electrical connection lines of multiple microsensors are connected to each other, and multiple second electrical connection lines of these multiple microsensors are also connected to each other. These connected first electrical connection lines and connected second electrical connection lines are then connected to a single global contact or a pair of global contacts at the edge of the wafer. In this way, the total number of global contacts at the edge of the wafer for each sensing material can be greatly reduced. In some embodiments, only one or a few global contacts are required for each sensing material.

[0116] As described above, for each microsensor, the first electrodes of the first electrode pairs E1 of the first group G1 are interconnected by first electrical connection lines, and the second electrodes of the first electrode pairs E1 of the first group G1 are interconnected by second electrical connection lines. Therefore, for an embodiment in which activation is performed on a wafer, after the first electropolymerization process, the method includes an additional step of cutting off the first electrical connection line and the second electrical connection line, for example by an etching process, so that each first electrode pair E1 of the first group G1 becomes isolated from the other first electrode pairs of the first group G1. In fact, each electrode pair and its sensor material form an independent pixel sensor. When the microsensor is in operation, each pixel sensor will acquire a signal and transmit the signal to a reading device independently of any signal detected in another pixel sensor.

[0117] Pixel on-die activation

[0118] For embodiments where activation of the first pixel group and the second pixel group is performed on-die, the method comprises an additional step of dicing the wafer before performing step C), ie performing on-die activation of the first pixel group and the second pixel group.

[0119] For those embodiments in which pixel activation is performed on die, the wafer substrate provided in step A) results from an initial front-end process. As part of the front-end process, a pair of transistors is provided for each first electrode pair of the first pixel group. Advantageously, these transistors of the first electrode pair act as switches allowing control of the first voltage during the first electropolymerization process. For example, those transistors 15 are NMOS transistors or PMOS transistors. Figure 5 In FIG. 1 , a cross-sectional view of a pixel is shown, wherein a wafer substrate 10 is produced by an initial front-end production line process, wherein a pair of transistors is provided for each electrode pair. Figure 5 In FIG. 1 , transistor 15 is shown together with electrical connections 20 a to 20 d .

[0120] In an embodiment, the die is packaged and the resulting chip comprises a plurality of peripheral connection pads. Some of these pads are electrically connected to the transistor pairs of the first pixel group and allow the first voltage to be controlled during the first polymerization process.

[0121] When the activation of the first electrode pair is performed on the die, the polymerization process used in step C2) is a droplet polymerization process or a dedicated microfluidic process. Using the droplet polymerization process, droplets containing a polymerization liquid are supplied to the top of the pixel where the protective mask is partially removed. When a microfluidic system is used, for example, a fluid circulates through a chamber above the pixel, so that the pixel where the protective mask is partially removed is in contact with the fluid.

[0122] Multi-pixel micro sensor

[0123] According to a second aspect of the present invention, there is provided a multi-pixel microsensor for detecting gases and / or volatile organic compounds. The multi-pixel microsensor according to the present invention is obtained by the manufacturing method as described above, the method comprising: Figure 1 The manufacturing step 100 , the manufacturing step 200 and the manufacturing step 300 are schematically shown.

[0124] The die corresponding to a single microsensor may have an overall surface size that may vary from embodiment to embodiment. For example, in an embodiment, the die corresponding to a single microsensor has a 1x1 mm 2 or 0.5x0.5 mm 2 Or smaller typical overall surface size. In other embodiments, the size can be larger and have up to, for example, 3x3 mm 2 The surface size of a single pixel of the microsensor may vary from embodiment to embodiment. In some embodiments, for example, the pixel size is 10x10 μm 2 In other embodiments, the pixel size can be much larger, for example, if a larger area microsensor is to be used, the pixel size of such a microsensor can even be 1x1 mm. 2 .

[0125] In embodiments where a pair of transistors for each first electrode pair of the first pixel group is provided as part of the initial front-end processing of the wafer substrate, the transistors may also be used to control the readout process of the detector. For example, the applied readout process is performed by multiplexing in a similar manner as in known CMOS cameras, followed by readout of resistance and / or capacitance.

[0126] exist Figure 6 In the figure, an embodiment is shown, wherein a multiplexer is coupled to a microsensor according to the invention, wherein a readout can be performed for each pixel and wherein during the manufacturing process of the microsensor, coating of electrode pairs by electropolymerization can also be selectively performed. Figure 6 The system shown comprises a column decoder 81 and a row decoder 82. The row decoder is coupled to a control box 86 which allows activating one of the rows of the row decoder, e.g. Figure 6 One of the rows L1, L2, L3, L4 shown. Figure 6As shown schematically, each of these rows is coupled to a plurality of gates of a transistor pair associated with a pixel. A write control device 84 and a read control device 85 are coupled to the column decoder 81. The write control device 84 is used to selectively apply voltages to pixels that require electropolymerization during the electropolymerization process. For example, if row L1 is activated by the control box 86, the write control device 84 can set a voltage for columns Cl and Cl', which is sufficient for the electropolymerization process if the pixels located on row L1 and columns Cl / Cl' require electropolymerization. In this way, the electropolymerization process of each pixel can be selectively applied and controlled. Depending on the type of electropolymerization process used, the voltages applied to columns such as Cl and Cl' can be equal or different.

[0127] As described above, when the activation of the pixels of the microsensor is completed and the microsensor starts to work, then Figure 6 The column decoders and row decoders shown and associated controls can be used to selectively read data from each pixel, such as through resistors and / or capacitors. For example, if row L1 is activated, data from pixels located on row L1 and columns Cl / Cl' can be read out by read control device 85 through column connections Cl and Cl'.

Claims

1. A method for manufacturing a plurality of multi-pixel gas microsensors, wherein: Each multi-pixel gas microsensor includes at least one or more pixels having a first sensing material and one or more pixels having a second sensing material different from the first material, and the method includes: A) providing a wafer substrate (10) comprising an insulating layer (12), and processing the wafer substrate to construct a plurality of multi-pixel gas microsensors, wherein the processing comprises at least the following steps: A1) Creating a photolithographic mask defined for each of the plurality of microsensors: i) one or more first electrode pairs (E1) form a first pixel group (G1), wherein each first electrode pair comprises a first electrode and a second electrode, ii) one or more second electrode pairs (E2) form a second pixel group (G2), wherein each second electrode pair comprises a third electrode and a fourth electrode, iii) a first electrical connection line is connected to each of the first electrodes of the first electrode pair (E1), and a second electrical connection line is connected to each of the second electrodes of the first electrode pair (E1), A2) applying a metallization process to the insulating layer according to the photolithography mask to form the first electrode pair, the second electrode pair, the first electrical connection line and the second electrical connection line for each of the plurality of microsensors, wherein the metallization process comprises depositing one or more layers of metal on the substrate, A3) depositing a protective mask onto the substrate, B) selecting the first sensing material and the second sensing material, wherein the first sensing material is a first polymer suitable for electropolymerization, C) performing on-wafer activation or on-die activation of the first pixel group (G1) and the second pixel group (G2), wherein the on-wafer activation or the on-die activation comprises at least the following steps: C1) locally removing a portion of the protection mask covering the first electrode pair (E1) of the first pixel group (G1), C2) applying a first electropolymerization process to simultaneously coat each of the first electrode pairs (E1) of the first pixel group (G1) with the first sensing material, wherein the first electrical connection line and the second electrical connection line serve as electrical connections in the first electropolymerization process for applying a first voltage to the first electrode and the second electrode or for applying a first voltage difference between the first electrode and the second electrode, C3) locally removing a portion of the protection mask covering the second electrode pair (E2) of the second pixel group (G2), C4) Coating the second electrode pair (E2) of the second pixel group with the second sensing material.

2. The method according to claim 1, characterized in that The wafer substrate at least comprises: i) a first layer (11) made of a semiconductor material or made of a metal, and ii) forming a second layer of the insulating layer (12), wherein the insulating layer (12) is formed by any one of the following methods: oxidation process, nitridation process, oxide deposition or nitride deposition.

3. The method according to claim 1, characterized in that The wafer substrate includes a layer made of an insulating material.

4. The method according to any one of claims 1 to 3, characterized in that Steps C1) and C3) are performed before steps C2) and C4).

5. The method according to any one of claims 1 to 3, characterized in that For each of the microsensors, the first electrical connection line and the second electrical connection line form a common connection line, or wherein the first connection line and the second connection line are interconnected to short-circuit the first electrode and the second electrode, so that during the first electropolymerization process the first voltage is a single common voltage for the first electrode and the second electrode, wherein, after the first electropolymerization process, the method includes a further step of cutting off the first electrical connection line and the second electrical connection line or cutting off the common connection line, so that an open circuit is formed between the first electrode and the second electrode of each pair of the first electrode pairs.

6. The method according to any one of claims 1 to 3, characterized in that Activation of the first pixel group and the second pixel group is performed on the wafer, and sub-step C2 of applying a first electropolymerization process is simultaneously performed on each first pixel group of the plurality of multi-pixel gas microsensors by placing the wafer substrate in a first electrolyte solution).

7. The method according to claim 6, comprising an additional step of cutting off the first electrical connection line and the second electrical connection line after the first electropolymerization process, so that each first electrode pair (E1) of the first pixel group (G1) becomes isolated from other first electrode pairs of the first pixel group (G1).

8. The method according to any one of claims 1 to 3, characterized in that Activation of the first pixel group and the second pixel group is performed on-die, and the method comprises an additional step of dicing the wafer before performing the on-die activation of the first pixel group and the second pixel group, and the wafer substrate provided in step A) is produced by an initial front-end production line process comprising the step of forming a pair of transistors (15) for each first electrode pair (E1) of the first pixel group, and wherein the transistors of the first electrode pair are used as switches allowing control of the first voltage or the first voltage difference during the first electropolymerization process.

9. The method according to any one of claims 1 to 3, characterized in that The first sensing material is any one of the following polymers: polypyrrole, polyaniline, polythiophene or polysilane compound, or the first sensing material is a molecular imprinting polymer.

10. The method according to any one of claims 1 to 3, characterized in that The second sensing material is made of any one or any combination of the following: carbon nanotubes, graphene or nanocomposite materials.

11. The method according to any one of claims 1 to 3, characterized in that The second sensing material is made of a resistor or a semiconductor material.

12. The method according to any one of claims 1 to 3, characterized in that The second sensing material is coated on the second electrode pair by using a spray coating, a drop coating or an inkjet printing process.

13. The method according to any one of claims 1 to 3, characterized in that The second sensing material is a second polymer suitable for electropolymerization, and wherein the step A1) of providing a photolithographic mask further defines: iv) a third electrical connection line connected to each of the third electrodes of the second electrode pair (E2), and a fourth electrical connection line connected to each of the fourth electrodes of the second electrode pair (E2), The metallization step A2) further forms the third electrical connection line and the fourth electrical connection line, wherein said step C4) comprises applying a second electropolymerization process to simultaneously coat each of the second electrode pairs (E2) of the second pixel group (G2) with the second sensing material, And wherein the third electrical connection line and the fourth electrical connection line are used as electrical connections during the second electropolymerization process to apply a second voltage to the third electrode and the fourth electrode or to apply a second voltage difference between the third electrode and the fourth electrode.

14. The method according to any one of claims 1 to 3, characterized in that The first electrode pair and / or the second electrode pair are formed by interdigitated electrodes or by two opposing electrical contacts.

15. A multi-pixel gas microsensor for detecting gases and / or volatile organic compounds, obtained by the manufacturing method according to any one of claims 1 to 3.

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