Patent Application
20240410849
The present invention relates to a manufacturing method and a structure of a micro heating and sensing device, especially to a manufacturing method and a structure of a micro heating and sensing device using conductive oxides or conductive nitrides to partially or fully replace metal electrode.
Along with commercialization and industrialization of modern society, more and more inner space is built and vehicles are used for people to take breaks, work and commute. However, when people stay in the closed inner space, harmful gases often accumulate in the space due to poor air circulation. The harmful gases at least affect people's quality of life, and worst of all, they become toxic and dangerous to human bodies. Generally, the indoor CO2 levels under 1000 ppm are considered normal with good circulation in indoor environments. When the indoor CO2 levels are increased to 1,000 ppm˜2,000 p, insufficient oxygen makes people feel tired and irritable. When the indoor CO2 levels are further raised to 2,000 ppm˜5,000 ppm, people feel uncomfortable including headaches, sleepiness, poor concentration, loos of attention, increased heart rate and slight nausea. Once the indoor CO2 levels are over 5,000 ppm, exposure may lead to serious oxygen deprivation, resulting in permanent brain damage, coma, even death. While measuring the indoor CO2 levels in our daily lives, the value of the indoor CO2 level measured reaches about 2,000 ppm˜3,000 ppm due to poor indoors air circulation or too many people in certain space. People start to get sleepy and feel a bit discomfort. If no measure is taken to control the indoor CO2 levels, the indoor CO2 levels may keep increasing and people in the space are exposed to hazards.
Owing to the rise of Internet of Things (IoT) and progress in environmental sensing technology, demand for gas sensing technology is growing. The gas sensing technology can be applied to monitoring different environments including home environment, offices, factories, medical institutions, etc.
The conventional gas sensors have wide applications, not matter in industry or at home. The resistance-type gas sensor uses metal electrodes to heat heating plates made of metal oxides. When oxygen in air is in contact with the metal oxides (such as tin(IV) oxide), the oxygen takes electrons away from the metal oxides so that electrical resistance raises. When gas in air users intend to detect (such as flammable gas) are getting closer, it reacts with oxygen around the sensor and the electrons are returned to the metal oxides so that electrical resistance decreases. Now users learn that there is the gas users intend to detect. In such sensing way, the gas users intend to detect directly reacts with the oxygen surrounding the sensor instead of the metal oxides. Thereby stability of the gas sensor after long term use is improved. Later the development of the gas sensor is nothing more than better heating materials or additives while there is no significant change in basic principles.
In recent years, the environmental sensors integrated with multiple functions are developed. For compact design, most of gas sensors are produced using MEMS (Micro Electro Mechanical Systems) technology.
The MEMS is a process technology developed by combination of microelectronics with mechanical engineering and used to create tiny devices with sizes ranging from micrometer (μm) to millimeter (mm). Generally, MEMS is a tiny device formed by integration of mechanical parts, electronic circuit, sensors and actuators onto a substrate and produced using similar processes as those used in the fabrication of semiconductor.
Wherein, the micro heating and sensing device is a tiny temperature control unit including at least two metal electrodes to heat a resistance material at a center thereof. Thus, resistivity changes due to the temperature changes, or the resistance material reacts with substances outside. The micro heating and sensing device are not only applied to gas sensors and temperature sensors but also temperature sensing and control units in components and microreactors.
In conventional micro heating and sensing devices, extremely thin metal electrodes are used in order to prevent heat conduction during fabrication of the electrodes. At the same time, a surface of the electrode is covered with a passivation layer made of insulation materials to reduce poisoning of the electrode caused by contact with external gases for protection of the electrode.
In order to coating the passivation layer on the surface of the electrode, surface treatment is carried out after a plurality of times of deposition of the insulation materials and metal sputtering or evaporation during manufacturing process. Yet the complicated manufacturing process leads to significantly increased cost and production time.
The arrangement of the passivation layer(s) is easy to make a heating layer used for sensing/temperature control and the extremely-thin metal electrode have level difference between them and further cause poor contact.
Thus, there is room for improvement and there is a need to provide a novel improved manufacturing process of the surface of the heating electrode with temperature control capability.
Therefore, a primary object of the present invention is to provide a manufacturing method of a micro heating and sensing device, in which additional conductive substances are adopted as a circuit connection between two metal heating electrodes and both ends of a conductive layer for sensing or temperature-control. Thereby, the structure of the heating electrodes is improved and the heating electrodes have both high electrical conductivity and low thermal conductivity. At the same time, abilities of measurement, temperature control and thermal insulation for the heating electrode are also maintained.
A secondary object of the present invention is to provide a structure for a micro heating and sensing device in which heating electrodes are produced by conductive oxides or conductive nitrides. By replacement of the whole metal electrodes with the electrodes made of conductive oxides or conductive nitrides, the manufacturing process is simplified.
Another primary object of the present invention is to provide a micro heating and sensing device in which additional conductive substances are used for circuit connection between two metal heating electrodes and one end of a sensing or temperature-control conductive layer in contact with the electrodes. Thereby structure of the heating electrodes is improved and the heating electrodes have both high electrical conductivity and low thermal conductivity. At the same time, measurement ability, temperature control ability and thermal insulation ability of the heating electrode are also maintained.
It is another secondary object of the present invention to provide a micro heating and sensing device in which insulation materials covering an outer surface of metal electrodes and conductive layers are used as passivation layers to reduce poisoning of the electrode caused by effects of gas on the metal electrodes and the conductive layer while performing gas sensing.
In order to achieve the above primary objects, a method of manufacturing a micro heating and sensing device according to the present invention includes the following steps. First disposing a sacrificial layer on a substrate. Then etching the sacrificial layer to form a first hole and a second hole spaced apart from each other and both penetrating the sacrificial layer to an upper surface of the substrate. Disposing a first passivation layer on the sacrificial layer, removing the first passivation layer on a bottom of the first hole and a bottom of the second hole by etching, and disposing a first electrode layer and a second electrode layer respectively on the first hole and the second hole. Next covering the first electrode layer and the second electrode layer with a second passivation layer. Then mounting a conductive layer over an interval space between the first electrode layer and the second electrode layer and the conductive layer located on the first passivation layer. Later covering the conductive layer with a third passivation layer. Removing a part of the third passivation layer on the conductive layer by etching to form a first port and a second port. Also removing a part of the second passivation layer on the first electrode layer and the second electrode layer respectively by etching to form a third port and a fourth port. Then disposing a first connection electrode layer and a second connection electrode layer on both the second passivation layer and the third passivation layer and the first connection electrode layer and the second connection electrode layer are spaced apart from each other. The first connection electrode layer is coupled to the conductive layer and the first electrode layer respectively through the first port and the third port. The second connection electrode layer is coupled to the conductive layer and the second electrode layer respectively through the second port and the fourth port. Lastly, removing the sacrificial layer, the first passivation layer located outside the first hole and covering the sacrificial layer, and the first passivation layer located outside the second hole and covering the sacrificial layer by etching.
Preferably, after the step of removing the first passivation layer on a bottom of the first hole and a bottom of the second hole by etching and disposing a first electrode layer and a second electrode layer respectively on the first hole and the second hole, the method further includes a step of etching the first electrode layer and the second electrode layer respectively to form a first recess and a second recess.
Preferably, the first connection electrode layer and the second connection electrode layer are made of a material selected from the group consisting of indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), aluminum (Al), titanium (Ti), and a combination thereof.
In order to achieve the above secondary objects of the present invention, a material for both the first electrode layer and the second electrode layer is selected from the group consisting of gold (Ag), silver (Au), platinum (Pt), aluminum (Al), titanium (Ti), tantalum (Ta), indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), and a combination thereof.
In order to achieve another primary object of the present invention, a micro heating and sensing device according to the present invention includes a substrate, a first electrode layer, a first connection electrode layer, a conductive layer, a second connection electrode layer, and a second electrode layer. The first electrode layer is disposed on the substrate and the first connection electrode layer is disposed on and coupled to the first electrode layer. The first connection electrode layer is extending horizontally. The conductive layer is disposed under and coupled to the first connection electrode layer. The conductive layer and the first electrode layer are spaced apart from each other and an air layer is formed between the conductive layer and the substrate. The second connection electrode layer is disposed on and coupled to the conductive layer. The first connection electrode layer and the second connection electrode layer are spaced apart from each other while the second electrode layer is mounted on the substrate and coupled under the second connection electrode layer. During electrical conduction process, a current is flowing from the first electrode layer to the first connection electrode layer, then through the conductive layer, the second connection electrode layer, and the second electrode layer in sequence, and finally flowing to the substrate.
Preferably, the first connection electrode layer and the second connection electrode layer are made of a material selected from the group consisting of indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), aluminum (Al), titanium (Ti), and a combination thereof.
Preferably, a material for both the first electrode layer and the second electrode layer is selected from the group consisting of gold (Ag), silver (Au), platinum (Pt), aluminum (Al), titanium (Ti), tantalum (Ta), indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), and a combination thereof.
In order to achieve the another secondary object of the present invention, the micro heating and sensing device further includes at least one passivation layer which is an insulation material covering the first electrode layer, the second electrode layer, and the conductive layer. The first passivation layer is made of materials selected from the group consisting of aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon dioxide (SiO2), titanium dioxide (TiO2), and a combination thereof.
Preferably, a lower part of the first electrode layer is extending horizontally toward a first side and then extending upward while a lower part of the second electrode layer is extending horizontally toward a second side and then extending upward.
In order to learn features and functions of the present invention more clearly and completely, please refer to the following embodiments and related detailed descriptions.
In the method and structure of a micro heaters and sensor available now, a passivation layer covering its surface is used to prevent electrode poisoning caused by direct contact between metal electrodes and gases outside. However, cost is increased and production time is extended due to multiple times of deposition for coating of the metal electrodes during semiconductor process.
In a micro heating and sensing device of the present invention, additional conductive substances are used for circuit connection between two metal heating electrodes and one end of a sensing or temperature-control conductive layer in contact with the electrodes. Thereby structure of the heating electrodes is improved and the heating electrodes have both high electrical conductivity and low thermal conductivity. At the same time, measurement ability, temperature control ability and thermal insulation ability of the heating electrode are also maintained.
In the following descriptions, a plurality of embodiments is used to describe the present invention in detail, not intended to limit the present invention.
Refer to
Refer to
As shown in
A material for the substrate 10 is selected from the group consisting of silicon (Si), silicon dioxide (SiO2), silicon nitride (Si3N4), and a combination thereof. The above materials are all silicon-based materials with low thermal conductivity.
The sacrificial layer 20 is made of phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), photoresists, or high molecular weight polymer. An ideal material for the sacrificial layer 20 must meet the following requirements. First a thickness of the sacrificial layer 20 must be controlled within an acceptable tolerance because that non-uniform deposition leads to a rough or uneven surface of mechanical parts. While releasing parts of a structural layer, the sacrificial layer 20 should be removed clearly. Moreover, the sacrificial layer 20 must have high etch selectivity and etch rate so that other parts of the structure will not get damaged significantly during etching of the sacrificial layer 20. PSG or BPSG with loose structure can be removed clearly in hydrofluoric acid (HF) at a faster etching rate, without causing other damages to the structure. In a preferred embodiment, the photoresists and high molecular weight polymers can be removed using oxygen plasma etching which will not cause other damages to the structure due to its low etching efficiency for conductive metal oxides and metal nitrides.
Refer to
As shown in
The first passivation layer 30 is made of a material selected from the group consisting of aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon dioxide (SiO2), and titanium dioxide (TiO2), and a combination thereof, which are all electrical insulation materials.
In the step S16, as shown in
The first electrode layer 40 and the second electrode layer 50 both are made of a material selected from the group consisting of gold (Ag), silver (Au), platinum (Pt), aluminum (Al), titanium (Ti), tantalum (Ta), indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), and a combination thereof.
In the step S18, as shown in
As shown in
A material for the conductive layer 70 is selected from the group consisting of gold (Au), aluminum (Al), titanium (Ti), vanadium (V), nickel (Ni), Tungsten (W), titanium nitride (TiN), tantalum nitride (TaN), polyacetylene (PA), graphene, polycrystalline silicon, and a combination thereof.
Refer to
Refer to
As shown in
In the step S28, as shown in
Both the first connection electrode layer 92 and the second connection electrode layer 94 are made of a material selected from the groups consisting of indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), aluminum (Al), titanium (Ti), and a combination thereof.
In the above embodiment, one end of the metal electrode is replaced by conductive oxides or conductive nitrides. Thus damages or modifications of metals of the metal electrode caused by use of semiconductor processes including deposition, wet etching, plasma ion bombardment, etc. can be solved. Both difficulties of manufacturing processes and production time are reduced. There is no need to dispose a passivation layer at a surface of the conductive oxides or conductive nitrides. The structural design of the heating electrode is further simplified to reduce the difficulties of the manufacturing processes.
As shown in
Refer to
In short, in a first embodiment of a method of manufacturing a micro heating and sensing device according to the present invention, one end of the metal electrode or the whole metal electrode is replaced by conductive oxides or conductive nitrides instead of a heating electrode made of signal precious metals in conventional manufacturing process. Thereby difficulties of manufacturing processes of the electrode are minimized and production time is reduced. There is no need to dispose the passivation layer on the surface of the conductive oxides or nitrides so that sputtering process required is reduced and the difficulties of the manufacturing processes are further reduced.
The metal electrode itself is a good conductor. In order to reduce effects of heat loss caused by the metal electrode on the micro heating and sensing device, a further embodiment which is formed based on the first embodiment and shown in
Step S162: etching the first electrode layer and the second electrode layer respectively to form a first recess and a second recess.
Also refer to
Refer to
Refer to
In a second embodiment of a method of manufacturing a micro heating and sensing device, recesses are further disposed on the electrodes to reduce heat loss caused by the metal electrode on the micro heating and sensing device 1 and further increase temperature control capability of the micro heating and sensing device 1, besides the replacement of one end of the electrode or the whole electrode with conductive oxides or nitrides to reduce difficulties of manufacturing processes of the electrode and production time in the first embodiment.
Refer to
Still refer to
In the third embodiment, input and output positions of the current I of the micro heating and sensing device are positioned on a surface of the substrate 10 by the printed circuit technique. Then deposit or coat a sacrificial layer and form holes on the sacrificial layer to correspond to the input and output positions. Next form the first electrode layer 40 and the second electrode layer 50 both made of metal by sputtering or evaporation. Or form the first electrode layer 40 and the second electrode layer 50 both made of conductive oxides or conductive nitrides by deposition. The metal electrodes provide better electrical and thermal conductivities. Although the metal electrodes are unable to be deposited by semiconductor processes, gas sensors have better performance during detection of their resistance due to their excellent electrical properties. The electrodes made of conductive oxides or conductive nitrides is easier to be produced. The manufacturing tolerance and time are both reduced when the electrode layer is produced by deposition. During sensing of gases, the conductive oxides or nitrides are not easily affected by the gases and no significant electrode poisoning occurs. Electrode poisoning is the reduction of efficiency on the electrode surface due to deposition of reactants. A surface of the electrode is contaminated or covered with oxide or nitrides during electrochemical process so that electrode activity is lowered and the electrode efficiency is reduced. Thereby the electrochemical reaction is affected.
Next the conductive layer 70 is formed between and spaced apart from the first electrode layer 40 and the second electrode layer 50 by deposition. The conductive layer 70 is disposed on the sacrificial layer between the two electrodes and a conductive path of the current I is mounted on the conductive layer 70 by the printed circuit technique. Then the first connection electrode layer 92 and the second connection electrode layer 94 are disposed thereover. Use conductive oxides or conductive nitrides as a rear end of the metal electrode can reduce reaction probability of metal with gases. That means probability of occurrence of the electrode poisoning mentioned above is reduced. The rear end of the electrode made of the conductive oxides or conductive nitrides can reduce extra heat caused by defects generated by connection of two different materials during the electrical conduction process. The extra heat affects accuracy of the temperature control. Lastly, remove the sacrificial layer to complete production of the micro heating and sensing device 1. The conductive layer 70 is suspended in the air to form an air layer 22 which provides good thermal insulation effect and increase contact area between the conductive layer 70 and air outside to improve sensor accuracy while being applied to gas sensors.
Refer to
A material for both the first electrode layer 40 and the second electrode layer 50 is selected from the group consisting of gold (Ag), silver (Au), platinum (Pt), aluminum (Al), titanium (Ti), tantalum (Ta), indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), and a combination thereof.
Both the first connection electrode layer 92 and the second connection electrode layer 94 are made of a material selected from the groups consisting of indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), aluminum gallium oxide (AGO), aluminum-doped zinc oxide (AZO), titanium nitride (TiN), tantalum nitride (TaN), aluminum (Al), titanium (Ti), and a combination thereof.
Therefore, the third embodiment of the present invention provides a micro heating and sensing device in which one end of the electrode or the whole electrode is made of conductive oxides or conductive nitrides instead of metal to reduce difficulties of manufacturing processes, production time required, and sputtering processes needed.
In order to prevent the electrode layer from being affected by external air and impurities, refer to
Still refer to
A material for the passivation layer 110 is selected from the group consisting of aluminum oxide (Al2O3), silicon nitride (Si3N4), silicon dioxide (SiO2), titanium dioxide (TiO2), and a combination thereof.
In conventional micro heating and sensing device, an outer surface of the metal electrode is covered with insulation passivation layer made of insulation nitrides or oxides which are difficult to react with air and impurities outside and having lower thermal conductivity. These materials protect the electrodes and further address the electrode poisoning issue.
The same as the third embodiment, one end of the metal electrode or the whole metal electrode is replaced by conductive oxides or conductive nitrides in the fourth embodiment. Thereby the process to deposit passivation layers on the metal electrode on the surface of the micro heating and sensing device for protection can be omitted.
The metal electrode itself is a good thermal conductor. In order to reduce effects of heat loss of the metal electrode on the micro heating and sensing device, sectional views of a fifth embodiment formed based on the third and the fourth embodiments and shown in
Refer to
Compared with the third and the fourth embodiments in which one end of the metal electrode or the whole metal electrode is replaced by conductive oxides or conductive nitrides and covering with the passivation layers, the fifth embodiment is further provided with the recesses on the electrodes to reduce heat loss caused by the conductive electrode and further reduce effects of the heat loss on the micro heating and sensing device. Thus, the micro heating and sensing device's ability of temperature control and thermal retention is improved.
In summary, the present invention uses conductive oxides or conductive nitrides to replace metals on one end of the metal electrodes or the whole metal electrodes. Thereby not only the problem of the micro heating and sensing device available now that the passivation layer must be disposed on the rear end of the electrodes can be solved, process cost and production time are also both reduced. Poor contact between the electrode and the conductive layer can be reduced by using different electrode structures. The temperature control ability and thermal insulation effect are improved. The passivation layers are used to prevent interactions between the electrode and external gases or impurities.
The present invention meets requirements for patentability including novelty, non-obviousness and usefulness.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalent.
| Number | Date | Country | Kind |
|---|---|---|---|
| 112121139 | Jun 2023 | TW | national |
