WO2016066003A1

WO2016066003A1 - Silicon heater-based mems methane sensor, manufacturing method for same, and applications thereof

Info

Publication number: WO2016066003A1
Application number: PCT/CN2015/091133
Authority: WO
Inventors: 马洪宇; 丁恩杰
Original assignee: 中国矿业大学
Priority date: 2014-10-31
Filing date: 2015-09-29
Publication date: 2016-05-06
Also published as: CN104316576B; CN104316576A

Abstract

A silicon heater-based microelectromechanical systems (MEMS) methane sensor and a manufacturing method therefor, related to methane sensors and manufacturing methods therefor, and specifically related to a methane sensor employing a MEMS processing technique, a manufacturing method for the sensor, and a methane detection method therefor. The methane sensor employs a common monocrystalline silicon wafer to process a silicon heater (1011). The silicon heater (1011) also serves as a methane-sensitive component and obviates the need for a catalyst carrier and a catalyst material. A processing process for the methane sensor is compatible with a CMOS process, provides the advantage of being inexpensive if produced by mass, and allows batch calibration. The methane sensor has the characteristics of having a low power consumption, high sensitivity, and fast response rate, preventing methane detection from being affected when oxygen is deficient, and being free from effects brought forth by a catalyst, such as carbon deposition and poisoning.

Description

基于硅加热器的MEMS甲烷传感器及其制备方法与应用Silicon heater based MEMS methane sensor and preparation method and application thereof

技术领域Technical field

本发明涉及传感器及其制备方法与应用，特别是一种工矿企业中对瓦斯防治时使用的基于硅加热器的MEMS甲烷传感器及其制备方法与应用。The invention relates to a sensor and a preparation method and application thereof, in particular to a silicon heater-based MEMS methane sensor used for gas prevention and control in an industrial and mining enterprise, and a preparation method and application thereof.

背景技术Background technique

随着物联网的发展，当前的甲烷传感器无法满足数量庞大的个人移动监测装备等对低功耗、长寿命、低成本的检测低浓度甲烷的高性能甲烷传感器的需求。目前基于传统铂丝加热的催化燃烧式甲烷传感器仍在煤矿井下广泛应用，其原理是基于甲烷气体的催化燃烧反应释热效应，其功耗较大，且由于使用催化剂存在诸多无法克服的缺点。如调校周期短、积碳、中毒、激活、性能不稳定、测量结果受氧气浓度的影响等从根本上是源于使用催化剂及催化剂载体。现有催化燃烧式甲烷传感器采用铂丝等贵金属绕制的线圈作为加热元件，难以批量化生产、且一致性较差，且功耗较大。因此，不能很好的满足物联网对甲烷传感器的应用需求。而红外甲烷传感器价格高、传感元件受粉尘与水汽严重影响，也不能很好的满足物联网对低功耗高性能甲烷传感器的应用需求。现有热导式甲烷传感器在煤矿井下用于检测高浓度的以甲烷为主的甲烷气体，对于低浓度(0～4％)的以甲烷为主的甲烷气体由于灵敏度太低则无法用于检测报警。本发明提供一种不使用催化剂的可检测低浓度(0～5％)甲烷的新型微型甲烷传感器。With the development of the Internet of Things, current methane sensors cannot meet the demand for high-performance methane sensors with low power consumption, long-life, and low-cost detection of low-concentration methane, such as a large number of personal mobile monitoring equipment. At present, the catalytic combustion type methane sensor based on traditional platinum wire heating is still widely used in coal mines. The principle is based on the catalytic combustion reaction heat release effect of methane gas, and its power consumption is large, and there are many insurmountable shortcomings due to the use of catalyst. For example, the short calibration cycle, carbon deposition, poisoning, activation, unstable performance, and the influence of the oxygen concentration on the measurement result are fundamentally derived from the use of the catalyst and the catalyst carrier. The existing catalytic combustion type methane sensor uses a coil wound with a noble metal such as platinum wire as a heating element, which is difficult to mass-produce, has poor consistency, and has a large power consumption. Therefore, the application requirements of the Internet of Things for methane sensors cannot be well met. The price of infrared methane sensor is high, and the sensing element is seriously affected by dust and water vapor, which can not meet the application requirements of low-power high-performance methane sensor. Existing thermal conductivity methane sensors are used in coal mines to detect high concentrations of methane-based methane gas. For low concentrations (0 to 4%) of methane-based methane gas, the sensitivity is too low to be used for detection. Call the police. The present invention provides a novel micromethane sensor that can detect low concentrations (0 to 5%) of methane without using a catalyst.

发明内容Summary of the invention

技术问题：针对上述技术的不足之处，提供一种结构简单，低浓度甲烷(0～4％)具有灵敏度高，该甲烷传感器以普通低成本硅圆片为衬底进行加工，可采用CMOS兼容的MEMS工艺批量化生产，成本低，且不使用传感器的基于硅加热器的MEMS甲烷传感器及其制备方法与应用。Technical problem: In view of the deficiencies of the above technologies, a simple structure is provided, and low-concentration methane (0 to 4%) has high sensitivity. The methane sensor is processed by using a common low-cost silicon wafer as a substrate, and can be CMOS-compatible. MEMS process mass production, low cost, and silicon heater-free MEMS methane sensor without sensor and its preparation method and application.

技术方案：为实现上述技术目的，本发明的基于硅加热器的MEMS甲烷传感器以P型硅为衬底，在所述P型硅衬底上形成N型硅；以所述P型硅衬底上的N型硅加工制备硅加热元件；所述硅加热元件包括两个固定端、硅加热器、两个硅悬臂；所述单个硅悬臂长度至少300um；所述单个的硅悬臂的一端与硅加热器相连，另一端与一个固定端相连，为硅加热器提供电连接；所述两个硅悬臂平行并排设置、与硅加热器整体构成U形悬臂结构将硅加热器悬于空气中；所述硅加热元件的硅加热器及硅悬臂的外表面设有钝化保护层；所述固定端设在P型硅衬底上，所述固定端包括N型硅、N型硅上的氧化硅层及用作电引出焊盘Pad的金属，所述电引出焊盘金属Pad设在N型硅之上的氧化硅层上，且电引出焊盘金属Pad通过氧化硅层的窗口与其下面的N型硅直接接触构成欧姆接触，电引出焊盘金属Pad与其下的N型硅层接触部分没有氧化硅层；Technical Solution: To achieve the above technical object, a silicon heater-based MEMS methane sensor of the present invention uses P-type silicon as a substrate to form N-type silicon on the P-type silicon substrate; and the P-type silicon substrate Forming a silicon heating element on the N-type silicon; the silicon heating element comprises two fixed ends, a silicon heater, two silicon cantilevers; the single silicon cantilever is at least 300 um in length; one end of the single silicon cantilever is silicon The heater is connected and the other end is connected to a fixed end to provide an electrical connection for the silicon heater; the two silicon cantilevers are parallel and Arranging, integrally forming a U-shaped cantilever structure with the silicon heater to suspend the silicon heater in the air; the silicon heater of the silicon heating element and the outer surface of the silicon cantilever are provided with a passivation protective layer; On the P-type silicon substrate, the fixed end includes N-type silicon, a silicon oxide layer on the N-type silicon, and a metal serving as an electrical extraction pad Pad, and the electrical extraction pad metal pad is disposed on the N-type silicon. On the silicon oxide layer, and electrically drawing the pad metal pad directly through the window of the silicon oxide layer to form an ohmic contact with the underlying N-type silicon, the contact portion of the pad metal pad and the underlying N-type silicon layer has no silicon oxide layer. ;

在所述硅加热元件的固定端周围设置有去除掉N型硅的隔离沟槽，所述隔离沟槽使所述硅加热元件及其固定端的N型硅与P型硅衬底上的其余N型硅之间为高阻状态，尤其是使设在P型硅衬底上的硅加热元件的两个固定端之间除了由硅悬臂和硅加热器构成的电通路之外无其它电路通路。An isolation trench with N-type silicon removed is disposed around the fixed end of the silicon heating element, the isolation trench such that the silicon heating element and its fixed end N-type silicon and the remaining N on the P-type silicon substrate The type of silicon is in a high resistance state, in particular, there is no circuit path between the two fixed ends of the silicon heating element provided on the P-type silicon substrate except for the electrical path formed by the silicon cantilever and the silicon heater.

一种基于硅加热器的MEMS甲烷传感器的应用方法：使用两个基于硅加热器的MEMS甲烷传感器，其中一个基于硅加热器的MEMS甲烷传感器的硅加热元件与环境空气接触，另一个基于硅加热器的MEMS甲烷传感器的硅加热元件为气密性封装、封装内的密封空气与环境空气隔绝，这两个基于硅加热器的MEMS甲烷传感器的硅加热元件构成惠斯通电桥检测桥臂；在基于硅加热器的MEMS甲烷传感器的硅加热元件的两个固定端上施加电压或电流，使硅加热元件的工作点位于电流-电压特性曲线中的转折点左侧的工作点区域，使硅加热元件的硅加热器发热，其特征在于加热温度在500摄氏度以上；所述转折点为电阻随电流或电压增大而出现的电阻最大点，当电流或电压继续增大时，电阻不再继续增大反而减小；当有甲烷气体出现时，与环境空气接触的硅加热器的温度降低、使硅加热元件电阻发生变化，通过由所述基于硅加热器的MEMS甲烷传感器构成的惠斯通电桥实现甲烷浓度的检测。A silicon heater-based MEMS methane sensor application method: using two silicon heater-based MEMS methane sensors, one of which is based on a silicon heater-based MEMS methane sensor, the silicon heating element is in contact with ambient air, and the other is based on silicon heating. The silicon heating element of the MEMS methane sensor is hermetically sealed, and the sealed air inside the package is isolated from the ambient air. The silicon heating elements of the two silicon heater-based MEMS methane sensors constitute the Wheatstone bridge detection bridge arm; Applying a voltage or current to the two fixed ends of the silicon heating element of the silicon heater-based MEMS methane sensor, so that the operating point of the silicon heating element is located in the operating point region to the left of the turning point in the current-voltage characteristic curve, so that the silicon heating element The silicon heater generates heat, characterized in that the heating temperature is above 500 degrees Celsius; the turning point is the maximum point of resistance that occurs when the resistance increases with current or voltage, and when the current or voltage continues to increase, the resistance does not continue to increase. Decrease; when methane gas is present, the temperature of the silicon heater in contact with the ambient air is lowered, so that silicon is added The resistance of the thermal element changes, and the detection of methane concentration is achieved by a Wheatstone bridge composed of the silicon heater-based MEMS methane sensor.

基于硅加热器的MEMS甲烷传感器的两种制备方法为：Two preparation methods for MEMS methane sensors based on silicon heaters are:

制备方法(一)的步骤为：The steps of the preparation method (1) are as follows:

第一步，在晶向(100)的P型硅衬底的正面经掺杂或扩散制备N型硅，N型硅厚度为3至30um；In the first step, N-type silicon is prepared by doping or diffusion on the front side of the crystal orientation (100) P-type silicon substrate, and the thickness of the N-type silicon is 3 to 30 um;

第二步，热氧化生成氧化硅层，厚度0.5至1um；The second step, thermal oxidation to form a silicon oxide layer, thickness of 0.5 to 1 um;

第三步，在P型硅衬底的正面制备光刻胶，光刻后形成硅加热元件、硅加热元件的固定端周围设置的隔离沟槽及正面刻蚀窗口的图形，随后采用RIE(Reactive Ion Etching，反应离子刻蚀)方法干法刻蚀露出的氧化硅层及其下面的硅，刻蚀深度大于N型硅与氧化硅层厚度之和，去除光刻胶；In the third step, a photoresist is prepared on the front side of the P-type silicon substrate, and after lithography, a silicon heating element, an isolation trench disposed around the fixed end of the silicon heating element, and a pattern of the front etching window are formed, and then RIE (Reactive) is adopted. Ion Etching, reactive ion etching) dry etching of the exposed silicon oxide layer and the underlying silicon, deep etching The degree is greater than the sum of the thicknesses of the N-type silicon and the silicon oxide layer, and the photoresist is removed;

第四步，在P型硅衬底的正面光刻第二步生成的氧化硅层，形成金属接触孔图形；In the fourth step, the silicon oxide layer formed in the second step is photolithographically formed on the front side of the P-type silicon substrate to form a metal contact hole pattern;

第五步，在P型硅衬底的正面溅射或淀积或蒸发形成金属层，金属层的材料可以是金或铝，并退火，金属层与P型硅衬底上的露出的N型硅形成欧姆接触；In the fifth step, a metal layer is formed by sputtering or depositing or evaporating on the front side of the P-type silicon substrate. The material of the metal layer may be gold or aluminum, and annealed, and the exposed N-type on the metal layer and the P-type silicon substrate. Silicon forms an ohmic contact;

第六步，在金属层上光刻，刻蚀金属层后形成电引出焊盘金属Pad、金属连接线及总金属连接端，所形成的每个硅加热元件的电引出焊盘金属Pad与金属连接线通过金属层相连通，金属连接线与总金属连接端通过金属层相连通，所述总金属连接端设在P型硅衬底的边缘，当在总金属连接端施加电势时，整个硅圆片上的所有硅加热元件的N型硅形成良好电连接并具有与总连接端相同的电势，所述金属连接线设在划片槽内；In the sixth step, the metal layer is photolithographically etched to form an electrical extraction pad metal pad, a metal connection line and a total metal connection end, and the electrical extraction pad metal pad and metal of each silicon heating element are formed. The connecting wires are connected by a metal layer, and the metal connecting wires are connected to the total metal connecting end through a metal layer, and the total metal connecting end is disposed at an edge of the P-type silicon substrate, and when a potential is applied at the total metal connecting end, the whole silicon is The N-type silicon of all the silicon heating elements on the wafer form a good electrical connection and have the same potential as the total connection end, the metal connection line being disposed in the scribe groove;

第七步，在P型硅衬底的正面制备光刻胶，光刻后形成正面刻蚀窗口图形，采用RIE方法干法刻蚀所形成的正面刻蚀窗口图形所露出的P型硅，刻蚀深度大于20um，形成正面湿法硅刻蚀的刻蚀窗口，去除光刻胶；硅加热元件的硅加热器的投影位于刻蚀窗口的中心位置；In the seventh step, a photoresist is prepared on the front surface of the P-type silicon substrate, and a front etching window pattern is formed by photolithography, and the P-type silicon exposed by the front etching window pattern formed by dry etching by the RIE method is engraved. The etching depth is greater than 20um, forming an etching window of the front wet silicon etching to remove the photoresist; the projection of the silicon heater of the silicon heating element is located at the center of the etching window;

第八步，在P型硅衬底的正面制备刻蚀保护层，采用耐四甲基氢氧化铵溶液或氢氧化钾溶液的光刻胶作为刻蚀保护层；图形化所述刻蚀保护层后露出总金属连接端及第七步制备的正面湿法硅刻蚀的刻蚀窗口；In the eighth step, an etch protection layer is prepared on the front side of the P-type silicon substrate, and a photoresist resistant to tetramethylammonium hydroxide solution or potassium hydroxide solution is used as an etch protection layer; the etch protection layer is patterned After exposing the total metal connection end and the front side wet silicon etching etching window prepared in the seventh step;

第九步，将上述制备好的硅片置于四甲基氢氧化铵溶液或氢氧化钾溶液中对P型硅进行正面湿法刻蚀，即硅刻蚀从P型硅衬底的正面开始，刻蚀时通过总金属连接端给P型硅衬底上的N型硅施加正电压，所述正电压高于PN结自停止刻蚀的钝化电势，以使P型硅衬底与N型硅所形成的PN结处于反偏状态；在PN结自停止刻蚀的作用下，硅加热元件的N型硅不被刻蚀，由P型硅正面刻蚀的深度至少100um以完全释放出硅加热元件，优选刻穿硅片形成通孔；硅加热元件的硅加热器的投影位于通孔中心位置，且外形尺寸远小于通孔的尺寸；In the ninth step, the prepared silicon wafer is placed in a tetramethylammonium hydroxide solution or a potassium hydroxide solution to perform a front side wet etching of the P-type silicon, that is, the silicon etching starts from the front side of the P-type silicon substrate. Applying a positive voltage to the N-type silicon on the P-type silicon substrate through the total metal connection end during etching, the positive voltage being higher than the passivation potential of the PN junction from the stop etching, so that the P-type silicon substrate and the N-type The PN junction formed by the silicon is in a reverse bias state; the N-type silicon of the silicon heating element is not etched by the PN junction self-stop etching, and the depth of the front surface of the P-type silicon is at least 100 um to be completely released. a silicon heating element, preferably penetrating the silicon wafer to form a through hole; a projection of the silicon heater of the silicon heating element is located at a center of the through hole, and the outer dimension is much smaller than the size of the through hole;

第十步，去除第八步制备的刻蚀保护层，干燥后采用氢氟酸溶液或氢氟酸气雾去除第二步生成的硅加热元件表面的氧化硅；In the tenth step, the etching protection layer prepared in the eighth step is removed, and after drying, the silicon oxide on the surface of the silicon heating element generated in the second step is removed by using a hydrofluoric acid solution or a hydrofluoric acid gas mist;

第十一步，氧化硅加热元件外表面露出的硅，形成厚度均匀的薄层氧化硅，其厚度为十数nm至100nm，作为钝化保护层；In the eleventh step, the silicon exposed on the outer surface of the silicon oxide heating element forms a thin layer of silicon oxide having a uniform thickness, the thickness of which is from ten to 100 nm, as a passivation protective layer;

第十二步，沿划线槽划片，并切断电引出焊盘金属Pad与设置的金属连接线的连接，切断后每一个硅加热元件的两个电引出焊盘金属Pad之间不存在金属连接；裂片后得到数量众多的本发明所述的基于硅加热器的MEMS甲烷传感器；The twelfth step, dicing along the scribe groove, and cutting off the electrical lead pad metal pad and the set metal connection line Connection, there is no metal connection between the two electrical extraction pad metal Pads of each silicon heating element after cutting; after the cleavage, a plurality of silicon heater-based MEMS methane sensors according to the present invention are obtained;

或制备方法(二)的步骤为：Or the steps of the preparation method (2) are:

第一步，在(100)晶向的P型硅衬底的正面经掺杂或扩散制备N型硅，N型硅厚度为3至30um；In the first step, N-type silicon is prepared by doping or diffusion on the front side of the (100) crystal orientation P-type silicon substrate, and the thickness of the N-type silicon is 3 to 30 um;

第三步，在P型硅衬底正面的氧化硅层上制备光刻胶，光刻后形成硅加热元件、硅加热元件的固定端周围设置的隔离沟槽及正面刻蚀窗口的图形，并采用RIE方法干法刻蚀露出的氧化硅层及其下面的硅，刻蚀深度大于N型硅与第二步生成的氧化硅层厚度之和，去除光刻胶；In the third step, a photoresist is prepared on the silicon oxide layer on the front surface of the P-type silicon substrate, and after lithography, a silicon heating element, an isolation trench disposed around the fixed end of the silicon heating element, and a front etching window are formed, and Drying the exposed silicon oxide layer and the underlying silicon by RIE, the etching depth is greater than the sum of the thickness of the N-type silicon and the silicon oxide layer formed in the second step, and removing the photoresist;

第四步，在P型硅衬底的正面光刻第二步生成的氧化硅层，形成金属接触孔；In the fourth step, the silicon oxide layer formed in the second step is photolithographically formed on the front side of the P-type silicon substrate to form a metal contact hole;

第五步，在P型硅衬底的正面溅射或淀积或蒸发形成金属层，金属层的材料为铝，并退火，金属层与P型硅衬底上的露出的N型硅形成欧姆接触；In the fifth step, a metal layer is formed by sputtering or depositing or evaporating on the front side of the P-type silicon substrate. The material of the metal layer is aluminum and annealed, and the metal layer forms an ohmic with the exposed N-type silicon on the P-type silicon substrate. contact;

第六步，在P型硅衬底的正面溅射或淀积或蒸发形成金属层，金属层的材料为铝，厚度2至5um；In the sixth step, a metal layer is formed by sputtering or depositing or evaporating on the front side of the P-type silicon substrate, the material of the metal layer is aluminum, and the thickness is 2 to 5 um;

第七步，在金属层上制备光刻胶，光刻后形成正面刻蚀窗口的图形，去除所述正面刻蚀窗口的图形所对应的金属层，随后采用RIE干法刻蚀所露出的P型硅，刻蚀深度30um，形成正面湿法刻蚀窗口；硅加热元件的硅加热器的投影位于刻蚀窗口的中心位置；In the seventh step, a photoresist is prepared on the metal layer, and a pattern of the front etching window is formed by photolithography, and the metal layer corresponding to the pattern of the front etching window is removed, and then the exposed P is etched by RIE dry etching. Type silicon, etching depth 30um, forming a front wet etching window; the projection of the silicon heater of the silicon heating element is located at the center of the etching window;

第八步，将上述制备好的硅片置于四甲基氢氧化铵溶液，采用PN结自停止刻蚀从P型硅衬底的正面开始湿法刻蚀，刻蚀时通过第七步制备的P型硅衬底边缘上的金属给P型硅衬底上的N型硅施加正电压，所述正电压高于PN结自停止刻蚀的钝化电势，以使P型硅衬底与N型硅所形成的PN结处于反偏状态；在PN结自停止刻蚀的作用下硅加热元件的N型硅不被刻蚀，由P型硅正面刻蚀深度至少100um以完全释放出硅加热元件，优选刻穿硅片形成通孔；硅加热元件的硅加热器的投影位于通孔中心位置，且外形尺寸远小于通孔的尺寸；In the eighth step, the prepared silicon wafer is placed in a tetramethylammonium hydroxide solution, and a wet etching is started from the front surface of the P-type silicon substrate by stop etching using a PN junction, and is prepared by the seventh step during etching. The metal on the edge of the P-type silicon substrate applies a positive voltage to the N-type silicon on the P-type silicon substrate, the positive voltage being higher than the passivation potential of the PN junction from the stop etching, so that the P-type silicon substrate and The PN junction formed by the N-type silicon is in a reverse bias state; the N-type silicon of the silicon heating element is not etched under the action of stopping the etching of the PN junction, and the front side etching depth of the P-type silicon is at least 100 μm to completely release the silicon. The heating element preferably etches through the silicon wafer to form a through hole; the projection of the silicon heater of the silicon heating element is located at the center of the through hole, and the outer dimension is much smaller than the size of the through hole;

第九步，在硅加热元件的固定端上制备光刻胶，烘干，刻蚀去除掉除硅加热元件的固定端上的电引出焊盘金属Pad以外的金属；In the ninth step, a photoresist is prepared on the fixed end of the silicon heating element, dried, and etched to remove metal other than the electrical lead pad metal pad on the fixed end of the silicon heating element;

第十步，采用氢氟酸溶液或氢氟酸气雾去除第二步生成的硅加热元件表面的氧化硅，去除第九步的光刻胶； In the tenth step, the silicon oxide on the surface of the silicon heating element generated in the second step is removed by using a hydrofluoric acid solution or a hydrofluoric acid gas mist to remove the photoresist of the ninth step;

第十一步，氧化硅加热元件外表面露出的硅，形成厚度均匀的薄层氧化硅，其厚度十多nm至100nm，作为钝化保护层；In the eleventh step, the silicon exposed on the outer surface of the silicon oxide heating element forms a thin layer of silicon oxide having a uniform thickness of more than ten nm to 100 nm as a passivation protective layer;

第十二步，划片、裂片，得到数量众多的本发明所述的基于硅加热器的MEMS甲烷传感器。In the twelfth step, dicing, splitting, and obtaining a large number of silicon heater-based MEMS methane sensors according to the present invention.

有益效果：Beneficial effects:

1.本发明的基于硅加热器的MEMS甲烷传感器采用价格低廉的普通P型硅片为衬底，而不是高价格的SOI硅片，这使得原料成本大幅降低；且加工工艺简单，可与CMOS工艺兼容、易于批量化生产；硅刻蚀工艺采用湿法硅刻蚀工艺，使用低廉的化学溶液即可完成本发明器件的释放，与干法刻蚀相比，不需使用昂贵的干法刻蚀设备及加工费用，因此加工成本更低；因此本发明的甲烷传感器具有加工成本低廉的优势；1. The silicon heater-based MEMS methane sensor of the present invention uses a low-cost ordinary P-type silicon wafer as a substrate instead of a high-priced SOI silicon wafer, which greatly reduces the cost of raw materials; and has a simple processing process and can be combined with CMOS. The process is compatible and easy to mass-produce; the silicon etching process adopts a wet silicon etching process, and the release of the device of the invention can be completed by using a low-cost chemical solution, and the expensive dry etching is not required compared with the dry etching. Corrosion equipment and processing costs, so the processing cost is lower; therefore, the methane sensor of the present invention has the advantage of low processing cost;

2.本发明的甲烷传感器的硅加热器悬在空气中远离硅衬底、距离大于300um以上，很好的降低了通过硅片损失的热量，因此可较低的功率即可将硅加热器加热到500℃以上的高温，具有功耗低的优势，单个硅加热元件工作时的功耗约80～90mW；2. The silicon heater of the methane sensor of the invention is suspended in the air away from the silicon substrate, and the distance is more than 300 um, which greatly reduces the heat lost through the silicon wafer, so that the silicon heater can be heated at a lower power. Up to 500 ° C high temperature, has the advantage of low power consumption, the power consumption of a single silicon heating element is about 80 ~ 90mW;

3.本发明的甲烷传感器不使用催化剂与催化载体，因此，传感器的性能不受催化剂的影响，不存在催化剂活性降低导致的灵敏度降低、中毒、激活及其导致的不可预测的零点漂移等问题；同时，本发明的甲烷传感器对甲烷的检测无需氧气参与，因此不受空气中氧气的影响；3. The methane sensor of the present invention does not use a catalyst and a catalytic carrier, and therefore, the performance of the sensor is not affected by the catalyst, and there is no problem of sensitivity reduction, poisoning, activation, and unpredictable zero drift caused by a decrease in catalyst activity; At the same time, the methane sensor of the present invention does not require oxygen to participate in the detection of methane, and thus is not affected by oxygen in the air;

4.本发明的MEMS甲烷传感器以硅加热元件为加热元件和甲烷检测元件，不使用催化剂便可实现对低浓度甲烷气体(0～4％)的高灵敏度的检测；采用硅加热元件对甲烷检测，硅加热器的结构为多个硅加热条的并联形式，具有较大的与空气接触的高温表面积，有助于灵敏度的提高；本发明的MEMS甲烷传感器的灵敏度可达10mV/CH₄％，可以直接推动仪表，达到了国家标准的要求。4. The MEMS methane sensor of the present invention uses a silicon heating element as a heating element and a methane detecting element, and can realize high sensitivity detection of low concentration methane gas (0 to 4%) without using a catalyst; detection of methane by using a silicon heating element The structure of the silicon heater is a parallel form of a plurality of silicon heating strips, and has a high temperature surface area in contact with air, which contributes to the improvement of sensitivity; the sensitivity of the MEMS methane sensor of the present invention can reach 10 mV/CH ₄ %, It can directly push the instrument and meet the requirements of national standards.

5.本发明的甲烷传感器可采用CMOS工艺批量生产，可具有良好的一致性，因此还可批量校准，因此能进一步提高传感器性能并降低传感器的校准环节成本；5. The methane sensor of the present invention can be mass-produced in a CMOS process, and has good consistency, so that it can be batch-calibrated, thereby further improving sensor performance and reducing the cost of calibration of the sensor;

6.本发明的甲烷传感器尺寸小，传感器功耗低，灵敏度高，而且响应速度快、响应速度可达40ms左右，输出信号线性度好，寿命长。6. The methane sensor of the invention has small size, low power consumption, high sensitivity, fast response speed, response speed of about 40 ms, good linearity of output signal and long service life.

7.本发明的硅加热元件的材料为单晶硅，在高温下性能稳定，这使本发明的甲烷传感器在高温工作状态下具有良好的稳定性与长的寿命。这是因为单晶硅不存在铂、钨等金属加热材料在500摄氏度以上的高温容易挥发、迁移等缺点、也不存在多晶硅电阻在高温下晶界电阻易于变化、无法掌控的缺点。同时，在本发明的硅加热元件的外表面设置的钝化层也降低了外界环境对上述元器件的影响，从而进一步提高了本发明的甲烷传感器性能的稳定性。7. The material of the silicon heating element of the present invention is monocrystalline silicon, which is stable at high temperatures, which makes the methane sensor of the present invention have good stability and long life under high temperature operation. This is because monocrystalline silicon is not There are disadvantages such as rapid heating and migration of metal heating materials such as platinum and tungsten at a high temperature of 500 degrees Celsius or higher, and there is no disadvantage that the grain boundary resistance of the polysilicon resistor is easily changed at a high temperature and cannot be controlled. At the same time, the passivation layer provided on the outer surface of the silicon heating element of the present invention also reduces the influence of the external environment on the above components, thereby further improving the stability of the performance of the methane sensor of the present invention.

8.本发明的甲烷传感器可采用CMOS工艺批量生产，可具有良好的一致性，因此还可批量校准，因此能进一步提高传感器性能并降低传感器校准环节的成本。8. The methane sensor of the present invention can be mass-produced in a CMOS process, and has good consistency, so that it can be batch-calibrated, thereby further improving sensor performance and reducing the cost of sensor calibration.

附图说明DRAWINGS

图1为本发明的基于硅加热器的MEMS甲烷传感器的俯视示意图。1 is a top plan view of a silicon heater based MEMS methane sensor of the present invention.

图2为本发明图1中A-A截面剖视图。Figure 2 is a cross-sectional view taken along line A-A of Figure 1 of the present invention.

图3为本发明的硅加热器的一种结构示意图。Fig. 3 is a schematic view showing the structure of a silicon heater of the present invention.

图4为本发明的基于硅加热器的MEMS甲烷传感器在硅圆片上的金属连接线与部分划片槽的示意图。4 is a schematic view showing a metal connecting wire and a partial dicing groove of a silicon heater-based MEMS methane sensor on a silicon wafer according to the present invention.

图5为本发明的基于硅加热器的MEMS甲烷传感器的硅加热元件的电流-电阻特性曲线。5 is a current-resistance characteristic curve of a silicon heating element of a silicon heater-based MEMS methane sensor of the present invention.

图中：01-P型硅衬底，02-N型硅，20-氧化硅层，21-电引出焊盘金属Pad，22-钝化保护层，23-氧化硅，31-金属连接线，32-总金属连接端，40-划片槽，101-硅加热元件，102-固定端，103-隔离沟槽，104-正面刻蚀窗口，105-背面面刻蚀窗口，1011-硅加热器，1012-硅悬臂，1013-硅加热条。In the figure: 01-P type silicon substrate, 02-N type silicon, 20-silicon oxide layer, 21-electric lead pad metal pad, 22-passivation protective layer, 23-silicon oxide, 31-metal connecting line, 32-total metal connection, 40-scriber slot, 101-silicon heating element, 102-fixed end, 103-isolation trench, 104-front etch window, 105-back side etch window, 1011-silicon heater , 1012-silicon cantilever, 1013-silicon heating strip.

具体实施方式detailed description

下面结合附图对本发明的实施例作进一步的描述：The embodiments of the present invention are further described below with reference to the accompanying drawings:

实施例：在图1、图2、图3、图4中，以P型硅衬底01，所述P型硅衬底01经掺杂或扩散后形成N型硅02；以所述P型硅衬底01上的N型硅02加工制备硅加热元件101；所述硅加热元件101包括两个固定端102、硅加热器1011、两个硅悬臂1012；所述单个的硅悬臂1012长度至少300um；所述单个的硅悬臂1012的一端与硅加热器1011相连，另一端与一个固定端102相连，为硅加热器1011提供电连接；所述两个硅悬臂1012平行并排设置、与硅加热器1011整体构成U形悬臂结构，将硅加热器1011悬于空气中；所述硅加热元件101的硅加热器1011及硅悬臂1012外表面设有钝化保护层22；所述固定端102设在P型硅衬底01上，包括N型硅02、N型硅02上的氧化硅层20及用作电引出焊盘Pad的金属21，所述电引出焊盘金属Pad 21设在N型硅02之上的氧化硅层20上，且电引出焊盘金属Pad 21通过氧化硅层20的窗口与其下面的N型硅02直接接触构成欧姆接触，电引出焊盘金属Pad 21与其下的N型硅层02接触部分没有氧化硅层20。Embodiments: In FIG. 1, FIG. 2, FIG. 3, FIG. 4, a P-type silicon substrate 01 is formed, and the P-type silicon substrate 01 is doped or diffused to form an N-type silicon 02; A silicon heating element 101 is fabricated by N-type silicon 02 on a silicon substrate 01; the silicon heating element 101 includes two fixed ends 102, a silicon heater 1011, and two silicon cantilevers 1012; the single silicon cantilever 1012 is at least at least 300 um; one end of the single silicon cantilever 1012 is connected to the silicon heater 1011, and the other end is connected to a fixed end 102 to provide electrical connection for the silicon heater 1011; the two silicon cantilevers 1012 are arranged side by side in parallel with silicon heating The device 1011 integrally forms a U-shaped cantilever structure, and suspends the silicon heater 1011 in the air; the silicon heater 1011 of the silicon heating element 101 and the outer surface of the silicon cantilever 1012 are provided with a passivation protective layer 22; On the P-type silicon substrate 01, including a silicon oxide layer 20 on the N-type silicon 02, the N-type silicon 02, and a metal 21 serving as an electric extraction pad Pad, The electric extraction pad metal pad 21 is disposed on the silicon oxide layer 20 over the N-type silicon 02, and the electrically-extracted pad metal pad 21 is directly in contact with the underlying N-type silicon 02 through the window of the silicon oxide layer 20 to form an ohmic contact. The portion of the electric lead pad metal pad 21 that is in contact with the underlying N-type silicon layer 02 has no silicon oxide layer 20.

在所述硅加热元件101及其固定端102周围设置有去除掉N型硅的隔离沟槽103，所述隔离沟槽103使所述硅加热元件101及其固定端102的N型硅与P型硅衬底01上的其余N型硅之间为高阻状态，尤其是设在P型硅衬底01上的硅加热元件101的两个固定端102之间除了由硅悬臂1012和硅加热器1011构成的电通路之外无其它电路通路。An isolation trench 103 from which N-type silicon is removed is disposed around the silicon heating element 101 and its fixed end 102, and the isolation trench 103 makes the silicon heating element 101 and its fixed end 102 N-type silicon and P The remaining N-type silicon on the type silicon substrate 01 is in a high resistance state, in particular, between the two fixed ends 102 of the silicon heating element 101 disposed on the P-type silicon substrate 01, except for being heated by the silicon cantilever 1012 and silicon. There is no other circuit path beyond the electrical path formed by the device 1011.

图3是硅加热器的一种结构示意图，图中所示的多个硅加热条1013的并联硅加热器可增加与空气中甲烷相接触的高温表面积，硅加热器还可以是圆环形。3 is a schematic view of a structure of a silicon heater in which a plurality of parallel silicon heaters of the silicon heating strip 1013 can increase the high temperature surface area in contact with methane in the air, and the silicon heater can also be annular.

图4是本发明的基于硅加热器的MEMS甲烷传感器的硅圆片上的金属连接线与部分划片槽的示意图。沿示意的部分划片槽40划片后不仅可使基于硅加热器的MEMS甲烷传感器从硅圆片上分离出来，还使每一个硅加热元件101的两个电引出焊盘金属Pad 21之间不再有金属连接。在图1、图2、图3中未示出金属连接线31。4 is a schematic view of a metal connecting line and a partial dicing groove on a silicon wafer of a silicon heater-based MEMS methane sensor of the present invention. After dicing along the illustrated partial dicing grooves 40, not only can the silicon heater-based MEMS methane sensor be separated from the silicon wafer, but also the two electrical extraction pad metal pads 21 of each silicon heating element 101 are not There is a metal connection. The metal connecting wires 31 are not shown in Figs. 1, 2, and 3.

一种基于硅加热器的MEMS甲烷传感器的甲烷检测应用方法：其使用两个基于硅加热器的MEMS甲烷传感器，其中一个基于硅加热器的MEMS甲烷传感器的硅加热元件101与环境空气接触，另一个基于硅加热器的MEMS甲烷传感器的硅加热元件101则为气密性封装、封装内的密封空气与环境空气隔绝，这两个基于硅加热器的MEMS甲烷传感器的硅加热元件101构成惠斯通电桥检测桥臂；在基于硅加热器的MEMS甲烷传感器的硅加热元件101的两个固定端102上施加电压或电流，使硅加热元件101的工作点位于如图5所示的电流-电阻特性曲线中的转折点左侧的工作点区域，使硅加热元件101的硅加热器1011发热，其特征在于加热温度在500摄氏度以上；所述转折点为电阻随电流或电压增大而出现的电阻最大点，当电流或电压继续增大时，电阻不再继续增大反而减小；单个硅加热元件工作时的功耗约80～90mW；当有甲烷气体出现时，与环境空气接触的硅加热器1011的温度降低、使硅加热元件101电阻发生变化，通过由所述基于硅加热器的MEMS甲烷传感器构成的惠斯通电桥实现低浓度甲烷的检测；对低浓度甲烷气体(0～4％)的检测灵敏度可达10mV/CH₄％，响应时间可达40ms左右。A silicon heater-based MEMS methane sensor for methane detection: it uses two silicon heater-based MEMS methane sensors, one of which is based on a silicon heater-based MEMS methane sensor. The silicon heating element 101 is in contact with ambient air. A silicon heater-based MEMS methane sensor silicon heating element 101 is hermetically sealed, and the sealed air inside the package is isolated from ambient air. The silicon heating elements 101 of the two silicon heater-based MEMS methane sensors constitute Whist. The power bridge detects the bridge arm; a voltage or current is applied to the two fixed ends 102 of the silicon heating element 101 of the silicon heater based MEMS methane sensor, such that the operating point of the silicon heating element 101 is at the current-resistance as shown in FIG. The working point region on the left side of the turning point in the characteristic curve causes the silicon heater 1011 of the silicon heating element 101 to generate heat, which is characterized in that the heating temperature is above 500 degrees Celsius; the turning point is the maximum resistance that occurs when the resistance increases with current or voltage. Point, when the current or voltage continues to increase, the resistance no longer continues to increase but decreases; when a single silicon heating element is operating It consumes about 80-90 mW; when methane gas is present, the temperature of the silicon heater 1011 in contact with the ambient air is lowered, and the resistance of the silicon heating element 101 is changed, and the MEMS methane sensor based on the silicon heater is formed. The Stone Bridge realizes the detection of low concentration methane; the detection sensitivity of low concentration methane gas (0~4%) can reach 10mV/CH ₄ %, and the response time can reach 40ms.

全硅MEMS甲烷传感器的两种制备方法如下： The two preparation methods of the all-silicon MEMS methane sensor are as follows:

第一步，在(100)晶向的P型硅衬底01的正面经掺杂或扩散制备N型硅02，N型硅02厚度为3至30um；In the first step, N-type silicon 02 is prepared by doping or diffusion on the front side of the (100) crystal orientation P-type silicon substrate 01, and the thickness of the N-type silicon 02 is 3 to 30 um;

第三步，在P型硅衬底01的正面制备光刻胶，光刻后形成硅加热元件101、硅加热元件的固定端周围设置的隔离沟槽103及正面刻蚀窗口104的图形，并采用RIE干法刻蚀露出的氧化硅层及其下面的硅，刻蚀深度大于N型硅02与第二步生成的氧化硅层厚度之和，去除光刻胶；In the third step, a photoresist is prepared on the front surface of the P-type silicon substrate 01, and after lithography, a pattern of the silicon heating element 101, the isolation trench 103 disposed around the fixed end of the silicon heating element, and the front etching window 104 is formed. Etching the exposed silicon oxide layer and the underlying silicon by RIE, the etching depth is greater than the sum of the thickness of the N-type silicon 02 and the silicon oxide layer formed in the second step, and removing the photoresist;

第四步，在P型硅衬底01的正面光刻第二步生成的氧化硅层，形成金属接触孔；In the fourth step, the silicon oxide layer formed in the second step is photolithographically formed on the front side of the P-type silicon substrate 01 to form a metal contact hole;

第五步，在P型硅衬底01的正面溅射或淀积或蒸发形成金属层，金属层的材料可以是金或铝，并退火，金属层与P型硅衬底01上的露出的N型硅02形成欧姆接触；In the fifth step, a metal layer is formed by sputtering or deposition or evaporation on the front surface of the P-type silicon substrate 01. The material of the metal layer may be gold or aluminum and annealed, and the exposed metal layer and the P-type silicon substrate 01 are exposed. N-type silicon 02 forms an ohmic contact;

第六步，在金属层上光刻，刻蚀金属层后形成电引出焊盘金属Pad 21、金属连接线31及总金属连接端32，所形成的每个硅加热元件101的电引出焊盘金属Pad 21与金属连接线31通过金属层相连通，金属连接线31与总金属连接端32通过金属层相连通；所述总金属连接端32设在P型硅衬底的边缘，当在总金属连接端32施加电势时，整个硅圆片上的所有硅加热元件101的N型硅形成良好电连接并具有与总金属连接端32相同的电势，所述金属连接线31设在划片槽内40；In the sixth step, the metal layer is photolithographically etched to form an electrical extraction pad metal pad 21, a metal connection line 31 and a total metal connection end 32, and the electrical extraction pads of each of the silicon heating elements 101 are formed. The metal pad 21 is connected to the metal connection line 31 through a metal layer, and the metal connection line 31 is connected to the total metal connection end 32 through a metal layer; the total metal connection end 32 is provided at the edge of the P-type silicon substrate, when When the metal connection end 32 applies an electric potential, the N-type silicon of all the silicon heating elements 101 on the entire silicon wafer forms a good electrical connection and has the same potential as the total metal connection end 32, and the metal connection line 31 is disposed in the dicing groove. 40;

第七步，在P型硅衬底01的正面制备光刻胶，光刻后形成正面刻蚀窗口104图形，采用RIE方法干法刻蚀所形成的正面刻蚀窗口104图形所露出的P型硅，刻蚀深度大于20um，形成正面湿法硅刻蚀的刻蚀窗口104，去除光刻胶；硅加热元件101的硅加热器1011的投影位于刻蚀窗口104的中心位置；In the seventh step, a photoresist is prepared on the front surface of the P-type silicon substrate 01, and a pattern of the front etching window 104 is formed by photolithography, and the P-type exposed by the pattern of the front etching window 104 formed by dry etching by the RIE method is performed. Silicon, the etching depth is greater than 20 um, forming an etch window 104 of the front wet silicon etch, removing the photoresist; the projection of the silicon heater 1011 of the silicon heating element 101 is located at the center of the etch window 104;

第八步，在P型硅衬底01的正面制备刻蚀保护层，采用耐四甲基氢氧化铵溶液或氢氧化钾溶液的光刻胶作为刻蚀保护层；图形化所述刻蚀保护层后露出总金属连接端32及第七步制备的正面湿法硅刻蚀的刻蚀窗口104；In the eighth step, an etching protection layer is prepared on the front surface of the P-type silicon substrate 01, and a photoresist resistant to tetramethylammonium hydroxide solution or potassium hydroxide solution is used as an etching protection layer; the etching protection is patterned After the layer, the total metal connection end 32 and the front side wet silicon etched etching window 104 prepared in the seventh step are exposed;

第九步，将上述制备好的硅片置于四甲基氢氧化铵溶液或氢氧化钾溶液中对P型硅进行正面湿法刻蚀，即硅刻蚀从P型硅衬底01正面的刻蚀窗口104开始，刻蚀时通过总金属连接端32给P型硅衬底01上的N型硅02施加正电压，所述正电压高于PN结自停止刻蚀的钝化电势，以使P型硅衬底01与N型硅02所形成的 PN结处于反偏状态在PN结自停止刻蚀的作用下，硅加热元件101的N型硅02不被刻蚀，由P型硅正面刻蚀的深度至少100um以完全释放出硅加热元件101，优选刻穿硅片形成通孔105；硅加热元件101的硅加热器1011的投影位于通孔105中心位置，且外形尺寸远小于通孔105的尺寸；In the ninth step, the prepared silicon wafer is placed in a tetramethylammonium hydroxide solution or a potassium hydroxide solution to perform a front side wet etching of the P-type silicon, that is, the silicon etching is performed from the front side of the P-type silicon substrate 01. The etching window 104 starts, and a positive voltage is applied to the N-type silicon 02 on the P-type silicon substrate 01 through the total metal connection end 32 during etching, which is higher than the passivation potential of the PN junction from the stop etching, Forming a P-type silicon substrate 01 and an N-type silicon 02 The PN junction is in a reverse bias state. Under the action of the PN junction self-stop etching, the N-type silicon 02 of the silicon heating element 101 is not etched, and the depth of the front surface of the P-type silicon is etched by at least 100 um to completely release the silicon heating element 101. Preferably, the through hole 105 is formed through the silicon wafer; the projection of the silicon heater 1011 of the silicon heating element 101 is located at the center of the through hole 105, and the outer dimension is much smaller than the size of the through hole 105;

第十步，去除第八步制备的刻蚀保护层，干燥后采用氢氟酸溶液或氢氟酸气雾去除第二步生成的硅加热元件101表面的氧化硅；In the tenth step, the etching protection layer prepared in the eighth step is removed, and after drying, the silicon oxide on the surface of the silicon heating element 101 generated in the second step is removed by using a hydrofluoric acid solution or a hydrofluoric acid gas mist;

第十一步，氧化硅加热元件101外表面露出的硅，形成厚度均匀的薄层氧化硅，其厚度为十数nm至100nm，作为钝化保护层22；The eleventh step, the silicon exposed to the outer surface of the silicon oxide heating element 101, forming a thin layer of silicon oxide having a thickness of ten to 100 nm, as a passivation protective layer 22;

第十二步，沿图4中所示部分划线槽40的示意划片，切断电引出焊盘金属Pad21与设置的金属连接线31的连接，使每一个硅加热元件101的两个电引出焊盘金属Pad 21之间不存在金属连接；裂片后得到数量众多的本发明所述的基于硅加热器的MEMS甲烷传感器；In the twelfth step, along the schematic dicing of the partial scribe groove 40 shown in FIG. 4, the connection of the electrical extraction pad metal Pad 21 and the disposed metal connection line 31 is cut off, so that two electric leads of each silicon heating element 101 are taken out. There is no metal connection between the pad metal Pad 21; after the split, a large number of silicon heater-based MEMS methane sensors according to the present invention are obtained;

制备方法二的步骤为：The steps of the second preparation method are as follows:

第三步，在P型硅衬底01正面的氧化硅层上制备光刻胶，光刻后形成硅加热元件101、硅加热元件的固定端周围设置的隔离沟槽103及正面刻蚀窗口104的图形，并采用RIE刻蚀露出的氧化硅层及其下面的硅，刻蚀深度大于N型硅02与第二步生成的氧化硅层厚度之和，去除光刻胶；In the third step, a photoresist is prepared on the silicon oxide layer on the front surface of the P-type silicon substrate 01, and a silicon heating element 101, an isolation trench 103 disposed around the fixed end of the silicon heating element, and a front etching window 104 are formed after photolithography. a pattern, and RIE etching the exposed silicon oxide layer and the underlying silicon, the etching depth is greater than the sum of the thickness of the N-type silicon 02 and the silicon oxide layer formed in the second step, and removing the photoresist;

第五步，在P型硅衬底01的正面溅射或淀积或蒸发形成金属层，金属层的材料为铝，并退火，金属层与P型硅衬底01上的露出的N型硅02形成欧姆接触；In the fifth step, a metal layer is formed by sputtering or deposition or evaporation on the front surface of the P-type silicon substrate 01. The material of the metal layer is aluminum, and the metal layer and the exposed N-type silicon on the P-type silicon substrate 01 are exposed. 02 forming an ohmic contact;

第六步，在P型硅衬底01的正面溅射或淀积或蒸发形成金属层，金属层的材料为铝，厚度2至5um；In the sixth step, a metal layer is formed by sputtering or depositing or evaporating on the front surface of the P-type silicon substrate 01, the material of the metal layer is aluminum, and the thickness is 2 to 5 um;

第七步，在金属层上制备光刻胶，光刻后形成正面刻蚀窗口104的图形，去除所述正面刻蚀窗口104的图形所对应的金属层，随后采用RIE干法刻蚀所露出的P型硅，刻蚀深度30um，形成正面湿法刻蚀窗口104；硅加热元件101的硅加热器1011的投影位于刻蚀窗口104的中心位置； In the seventh step, a photoresist is prepared on the metal layer, and a pattern of the front etching window 104 is formed by photolithography, and the metal layer corresponding to the pattern of the front etching window 104 is removed, and then exposed by RIE dry etching. P-type silicon, etching depth 30 um, forming a front wet etch window 104; the projection of the silicon heater 1011 of the silicon heating element 101 is located at the center of the etch window 104;

第八步，将上述制备好的硅片置于四甲基氢氧化铵溶液，采用PN结自停止刻蚀从P型硅衬底01正面的刻蚀窗口104开始湿法刻蚀，刻蚀时通过第七步制备的P型硅衬底01边缘上的金属给P型硅衬底01上的N型硅02施加正电压，所述正电压高于PN结自停止刻蚀的钝化电势，以使P型硅衬底01与N型硅02所形成的PN结处于反偏状态；在PN结自停止刻蚀的作用下硅加热元件101的N型硅02不被刻蚀，由P型硅正面刻蚀的深度至少达100um以完全释放出硅加热元件101，优选刻穿硅片形成通孔105；硅加热元件101的硅加热器1011的投影位于通孔105中心位置，且外形尺寸远小于通孔105的尺寸；In the eighth step, the prepared silicon wafer is placed in a tetramethylammonium hydroxide solution, and the wet etching is started from the etching window 104 on the front surface of the P-type silicon substrate 01 by the PN junction self-stop etching. The metal on the edge of the P-type silicon substrate 01 prepared by the seventh step applies a positive voltage to the N-type silicon 02 on the P-type silicon substrate 01, which is higher than the passivation potential of the PN junction from the stop etching, The PN junction formed by the P-type silicon substrate 01 and the N-type silicon 02 is in a reverse bias state; the N-type silicon 02 of the silicon heating element 101 is not etched by the PN junction self-stop etching, and the P-type is The front surface of the silicon is etched to a depth of at least 100 um to completely release the silicon heating element 101, preferably through the silicon wafer to form the via 105; the projection of the silicon heater 1011 of the silicon heating element 101 is located at the center of the via 105 and has a large outer dimension Less than the size of the through hole 105;

第九步，在硅加热元件101的固定端102上制备光刻胶，烘干，刻蚀去除掉除硅加热元件101的固定端102上的电引出焊盘金属Pad 21以外的金属；In the ninth step, a photoresist is prepared on the fixed end 102 of the silicon heating element 101, dried, and etched to remove metal other than the electrical extraction pad metal Pad 21 on the fixed end 102 of the silicon heating element 101;

第十步，采用氢氟酸溶液或氢氟酸气雾去除第二步生成的硅加热元件101表面的氧化硅23，去除第九步的光刻胶；In the tenth step, the silicon oxide 23 on the surface of the silicon heating element 101 generated in the second step is removed by using a hydrofluoric acid solution or a hydrofluoric acid gas mist to remove the photoresist of the ninth step;

第十一步，氧化硅加热元件101外表面露出的硅，形成厚度均匀的薄层氧化硅，其厚度十多nm至100nm，作为钝化保护层22；The eleventh step, the silicon exposed to the outer surface of the silicon oxide heating element 101, forming a thin layer of silicon oxide having a thickness of more than ten nm to 100 nm, as a passivation protective layer 22;

第十二步，划片、裂片，得到数量众多的本发明所述的基于硅加热器的MEMS甲烷传感器。 In the twelfth step, dicing, splitting, and obtaining a large number of silicon heater-based MEMS methane sensors according to the present invention.

Claims

一种基于硅加热器的MEMS甲烷传感器，其特征在于：它包括P型硅衬底(01)，P型硅衬底(01)上设有N型硅(02)；以所述P型硅衬底(01)上的N型硅(02)加工制备硅加热元件(101)；所述硅加热元件(101)包括两个固定端(102)、硅加热器(1011)、两个硅悬臂(1012)；所述单个的硅悬臂(1012)长度至少300um；所述单个的硅悬臂(1012)的一端与硅加热器(1011)相连，另一端与一个固定端(102)相连，为硅加热器(1011)提供电连接；所述两个硅悬臂(1012)平行并排设置、与硅加热器(1011)整体构成U形悬臂结构，将硅加热器(1011)悬于空气中；所述硅加热元件(101)的硅加热器(1011)及硅悬臂(1012)的外表面设有钝化保护层(22)；所述固定端(102)设在P型硅衬底(01)上，包括N型硅(02)、N型硅(02)上的氧化硅层(20)及用作电引出焊盘金属Pad(21)，所述电引出焊盘金属Pad(21)设在N型硅(02)之上的氧化硅层(20)上，且电引出焊盘金属Pad(21)通过氧化硅层(20)的窗口与其下面的N型硅(02)直接接触构成欧姆接触，电引出焊盘金属Pad(21)与其下的N型硅层(02)接触部分没有氧化硅层(20)；A MEMS methane sensor based on a silicon heater, characterized in that it comprises a P-type silicon substrate (01), a P-type silicon substrate (01) is provided with N-type silicon (02); and the P-type silicon is used A silicon heating element (101) is fabricated by N-type silicon (02) on the substrate (01); the silicon heating element (101) includes two fixed ends (102), a silicon heater (1011), and two silicon cantilevers (1012); the single silicon cantilever (1012) is at least 300 um in length; the single silicon cantilever (1012) has one end connected to the silicon heater (1011) and the other end connected to a fixed end (102), which is silicon. The heater (1011) provides an electrical connection; the two silicon cantilevers (1012) are arranged side by side in parallel, form a U-shaped cantilever structure integrally with the silicon heater (1011), and suspend the silicon heater (1011) in the air; The outer surface of the silicon heater (1011) and the silicon cantilever (1012) of the silicon heating element (101) is provided with a passivation protective layer (22); the fixed end (102) is disposed on the P-type silicon substrate (01) , comprising a silicon oxide layer (20) on N-type silicon (02), N-type silicon (02), and a metal pad (21) serving as an electrical extraction pad, the metal pad Pad (21) being disposed at N On the silicon oxide layer (20) over the silicon (02), and electrically lead the pad The Pad (21) forms an ohmic contact by directly contacting the window of the silicon oxide layer (20) with the underlying N-type silicon (02), and electrically extracts the contact portion between the pad metal Pad (21) and the underlying N-type silicon layer (02). No silicon oxide layer (20);

在所述硅加热元件(101)的固定端(102)周围设置有去除掉N型硅的隔离沟槽(103)，所述隔离沟槽(103)使所述硅加热元件(101)及其固定端(102)的N型硅与P型硅衬底(01)上的其余N型硅之间为高阻状态，尤其是使设在P型硅衬底(01)上的硅加热元件(101)的两个固定端(102)之间除了由硅悬臂(1012)和硅加热器(1011)构成的电通路之外无其它电路通路。An isolation trench (103) with N-type silicon removed is disposed around the fixed end (102) of the silicon heating element (101), the isolation trench (103) causing the silicon heating element (101) and The N-type silicon of the fixed end (102) is in a high resistance state with the remaining N-type silicon on the P-type silicon substrate (01), especially the silicon heating element provided on the P-type silicon substrate (01) ( There is no circuit path between the two fixed ends (102) of 101) except for the electrical path formed by the silicon cantilever (1012) and the silicon heater (1011).
一种基于硅加热器的MEMS甲烷传感器的应用，其特征在于：使用两个基于硅加热器的MEMS甲烷传感器，其中一个基于硅加热器的MEMS甲烷传感器的硅加热元件(101)与环境空气接触，另一个基于硅加热器的MEMS甲烷传感器的硅加热元件(101)为气密性封装、封装内的密封空气与环境空气隔绝，这两个基于硅加热器的MEMS甲烷传感器的硅加热元件(101)构成惠斯通电桥检测桥臂；在基于硅加热器的MEMS甲烷传感器的硅加热元件(101)的两个固定端(102)上施加电压或电流，使硅加热元件(101)的工作点位于电流-电阻特性曲线中的转折点左侧的工作点区域，使硅加热元件(101)的硅加热器(1011)发热，其特征在于加热温度在500摄氏度以上；所述转折点为电阻随电流或电压增大而出现的电阻最大点，当电流或电压继续增大时，电阻不再继续增大反而减小；当有甲烷气体出现时，与环境空气接触的硅加热器(1011)的温度降低、使硅加热元件(101)电阻发生变化，通过由所述基于硅加热器的MEMS甲烷传感器构成的惠斯通电桥实现甲烷浓度的检测。A silicon heater based MEMS methane sensor is characterized by the use of two silicon heater based MEMS methane sensors, one of which is a silicon heater based MEMS methane sensor silicon heating element (101) in contact with ambient air Another silicon heater-based MEMS methane sensor silicon heating element (101) is hermetic package, sealed air in the package is isolated from ambient air, and silicon heating elements of two silicon heater-based MEMS methane sensors ( 101) constituting a Wheatstone bridge detection bridge arm; applying a voltage or current to the two fixed ends (102) of the silicon heating element (101) of the silicon heater-based MEMS methane sensor to operate the silicon heating element (101) The point is located in the working point region on the left side of the turning point in the current-resistance characteristic curve, causing the silicon heater (1011) of the silicon heating element (101) to generate heat, characterized in that the heating temperature is above 500 degrees Celsius; the turning point is the resistance with current Or the voltage increases The maximum point of resistance appears. When the current or voltage continues to increase, the resistance does not continue to increase but decreases. When methane gas is present, the temperature of the silicon heater (1011) in contact with the ambient air is lowered, and the silicon is heated. The resistance of the element (101) changes, and the detection of methane concentration is achieved by a Wheatstone bridge composed of the silicon heater-based MEMS methane sensor.
如权利要求1所述的基于硅加热器的MEMS甲烷传感器的制备方法，包括两种制备方法，其特征在于：A method of fabricating a silicon heater-based MEMS methane sensor according to claim 1, comprising two preparation methods, characterized in that:

制备方法(一)的步骤为：The steps of the preparation method (1) are as follows:

第一步，在(100)晶向的P型硅衬底(01)的正面经掺杂或扩散制备N型硅(02)，N型硅(02)厚度为3至30um；In the first step, N-type silicon (02) is prepared by doping or diffusing the front side of the (100) crystal orientation P-type silicon substrate (01), and the N-type silicon (02) has a thickness of 3 to 30 um;

第二步，热氧化生成氧化硅层，厚度0.5至1um；The second step, thermal oxidation to form a silicon oxide layer, thickness of 0.5 to 1 um;

第三步，在P型硅衬底(01)的正面制备光刻胶，光刻后形成硅加热元件(101)、硅加热元件的固定端周围设置的隔离沟槽(103)及正面刻蚀窗口(104)的图形，并采用RIE(Reactive Ion Etching，反应离子刻蚀)方法干法刻蚀露出的氧化硅层及其下面的硅，刻蚀深度大于N型硅(02)与第二步生成的氧化硅层厚度之和，去除光刻胶；In the third step, a photoresist is prepared on the front side of the P-type silicon substrate (01), and a silicon heating element (101) is formed after photolithography, an isolation trench (103) disposed around the fixed end of the silicon heating element, and a front side etching are formed. a pattern of the window (104), and dry etching the exposed silicon oxide layer and the underlying silicon by RIE (Reactive Ion Etching) method, the etching depth is greater than that of the N-type silicon (02) and the second step The sum of the thicknesses of the generated silicon oxide layers to remove the photoresist;

第四步，在P型硅衬底(01)的正面光刻第二步生成的氧化硅层，形成金属接触孔；In the fourth step, the silicon oxide layer formed in the second step is photolithographically formed on the front side of the P-type silicon substrate (01) to form a metal contact hole;

第五步，在P型硅衬底(01)的正面溅射或淀积或蒸发形成金属层，金属层的材料可以是金或铝，并退火，金属层与P型硅衬底(01)上的露出的N型硅(02)形成欧姆接触；In the fifth step, a metal layer is formed by sputtering or depositing or evaporating on the front surface of the P-type silicon substrate (01). The material of the metal layer may be gold or aluminum, and annealed, metal layer and P-type silicon substrate (01) The exposed N-type silicon (02) on the upper surface forms an ohmic contact;

第六步，在金属层上光刻，刻蚀金属层后形成电引出焊盘金属Pad(21)、金属连接线(31)及总金属连接端(32)，所形成的每个硅加热元件(101)的电引出焊盘金属Pad(21)与金属连接线(31)通过金属层相连通，金属连接线(31)与总金属连接端(32)通过金属层相连通；所述总金属连接端(32)设在P型硅衬底的边缘，当在总金属连接端(32)施加电势时，整个硅圆片上的所有硅加热元件(101)的N型硅形成良好电连接并具有与总金属连接端(32)相同的电势，所述金属连接线(31)设在划片槽内(40)；In the sixth step, photolithography is performed on the metal layer to form an electrical extraction pad metal pad (21), a metal connection line (31) and a total metal connection end (32), and each silicon heating element is formed. The electrical extraction pad metal Pad (21) of (101) is in communication with the metal connection line (31) through a metal layer, and the metal connection line (31) is connected to the total metal connection end (32) through a metal layer; the total metal The connection end (32) is provided at the edge of the P-type silicon substrate, and when a potential is applied at the total metal connection end (32), the N-type silicon of all the silicon heating elements (101) on the entire silicon wafer forms a good electrical connection and has The same potential as the total metal connection end (32), the metal connection line (31) is disposed in the scribe groove (40);

第七步，在P型硅衬底(01)的正面制备光刻胶，光刻后形成正面刻蚀窗口(104)图形，采用RIE方法干法刻蚀所形成的正面刻蚀窗口(104)图形所露出的P型硅，刻蚀深度大于20um，形成正面湿法硅刻蚀的刻蚀窗口(104)，去除光刻胶；硅加热元件(101)的硅加热器(1011)的投影位于刻蚀窗口(104)的中心位置；In the seventh step, a photoresist is prepared on the front surface of the P-type silicon substrate (01), and a front etching window (104) pattern is formed by photolithography, and the front etching window formed by dry etching by the RIE method is used (104). The figure is exposed P-type silicon, etching depth greater than 20um, forming an etch window (104) for front wet silicon etching, removing the photoresist; projection of the silicon heater (1011) of the silicon heating element (101) is located at the etch window The central location of (104);

第八步，在P型硅衬底(01)的正面制备刻蚀保护层，图形化所述刻蚀保护层后露出总金属连接端(32)及第七步制备的正面湿法硅刻蚀的刻蚀窗口(104)；In the eighth step, an etch protection layer is prepared on the front side of the P-type silicon substrate (01), and the etch protection layer is patterned to expose the total metal connection end (32) and the front side wet silicon etch prepared in the seventh step. Etching window (104);

第九步，将上述制备好的硅片置于四甲基氢氧化铵溶液或氢氧化钾溶液中对P型硅进行正面湿法刻蚀，即硅刻蚀从P型硅衬底(01)的正面开始，刻蚀时通过总金属连接端(32)给P型硅衬底(01)上的N型硅(02)施加正电压，所述正电压高于PN结自停止刻蚀的钝化电势，以使P型硅衬底(01)与N型硅(02)所形成的PN结处于反偏状态；在PN结自停止刻蚀的作用下，硅加热元件(101)的N型硅(02)不被刻蚀，由P型硅正面刻蚀的深度至少100um以完全释放出硅加热元件(101)，优选刻穿硅片形成通孔(105)；硅加热元件(101)的硅加热器(1011)的投影位于通孔(105)中心位置，且外形尺寸远小于通孔(105)的尺寸；In the ninth step, the prepared silicon wafer is placed in a tetramethylammonium hydroxide solution or a potassium hydroxide solution to perform front side wet etching of the P-type silicon, that is, silicon etching from the P-type silicon substrate (01) Starting from the front side, a positive voltage is applied to the N-type silicon (02) on the P-type silicon substrate (01) through the total metal connection end (32) during etching, which is higher than the blunt PN junction self-stop etching The potential is such that the PN junction formed by the P-type silicon substrate (01) and the N-type silicon (02) is in a reverse bias state; under the action of stopping the etching of the PN junction, the N-type of the silicon heating element (101) Silicon (02) is not etched, the front side of the P-type silicon is etched to a depth of at least 100 um to completely release the silicon heating element (101), preferably through the silicon wafer to form the via (105); the silicon heating element (101) The projection of the silicon heater (1011) is located at the center of the through hole (105), and the outer dimension is much smaller than the size of the through hole (105);

第十步，去除第八步制备的刻蚀保护层，干燥后采用氢氟酸溶液或氢氟酸气雾去除第二步生成的硅加热元件(101)表面的氧化硅；In the tenth step, the etching protection layer prepared in the eighth step is removed, and after drying, the silicon oxide on the surface of the silicon heating element (101) generated in the second step is removed by using a hydrofluoric acid solution or a hydrofluoric acid gas mist;

第十一步，氧化硅加热元件(101)外表面露出的硅，形成厚度均匀的薄层氧化硅，其厚度为十数nm至100nm，作为钝化保护层(22)；In the eleventh step, the silicon exposed on the outer surface of the silicon oxide heating element (101) forms a thin layer of thin silicon oxide having a thickness of ten to 100 nm as a passivation protective layer (22);

第十二步，沿划线槽(40)划片，并切断电引出焊盘金属Pad(21)与设置的金属连接线(31)的连接，切断后每一个硅加热元件(101)的两个电引出焊盘金属Pad(21)之间不存在金属连接；裂片后得到数量众多的本发明所述的基于硅加热器的MEMS甲烷传感器；In the twelfth step, dicing along the scribe groove (40), and cutting off the connection of the electrical lead pad metal Pad (21) and the set metal connection line (31), and cutting off each of the two silicon heating elements (101) There is no metal connection between the electrical lead pad metal Pads (21); after the split, a large number of silicon heater-based MEMS methane sensors according to the present invention are obtained;

或制备方法(二)的步骤为：Or the steps of the preparation method (2) are:

第一步，在(100)晶向的P型硅衬底(01)的正面经掺杂或扩散制备N型硅(02)，N型硅(02)厚度为3至30um；In the first step, N-type silicon (02) is prepared by doping or diffusing the front side of the (100) crystal orientation P-type silicon substrate (01), and the N-type silicon (02) has a thickness of 3 to 30 um;

第二步，热氧化生成氧化硅层，厚度0.5至1um；The second step, thermal oxidation to form a silicon oxide layer, thickness of 0.5 to 1 um;

第三步，在P型硅衬底(01)正面的氧化硅层上制备光刻胶，光刻后形成硅加热元件(101)、硅加热元件的固定端周围设置的隔离沟槽(103)及正面刻蚀窗口(104)的图形，并采用RIE(Reactive Ion Etching，反应离子刻蚀)方法干法刻蚀露出的氧化硅层及其下面的硅，刻蚀深度大于N型硅(02)与第二步生成的氧化硅层厚度之和，去除光刻胶；In the third step, a photoresist is prepared on the silicon oxide layer on the front surface of the P-type silicon substrate (01), and a silicon heating element (101) is formed after photolithography, and an isolation trench (103) disposed around the fixed end of the silicon heating element is formed. And a pattern of the front etching window (104), and dry etching the exposed silicon oxide layer and the underlying silicon by RIE (Reactive Ion Etching), the etching depth is greater than that of the N-type silicon (02) Oxygen generated with the second step The sum of the thicknesses of the silicon layers to remove the photoresist;

第四步，在P型硅衬底(01)的正面光刻第二步生成的氧化硅层，形成金属接触孔；In the fourth step, the silicon oxide layer formed in the second step is photolithographically formed on the front side of the P-type silicon substrate (01) to form a metal contact hole;

第五步，在P型硅衬底(01)的正面溅射或淀积或蒸发形成金属层，金属层的材料为铝，并退火，金属层与P型硅衬底(01)上的露出的N型硅(02)形成欧姆接触；In the fifth step, a metal layer is formed by sputtering or depositing or evaporating on the front side of the P-type silicon substrate (01). The material of the metal layer is aluminum and annealed, and the metal layer is exposed on the P-type silicon substrate (01). N-type silicon (02) forms an ohmic contact;

第六步，在P型硅衬底(01)的正面溅射或淀积或蒸发形成金属层，金属层的材料为铝，厚度2至5um；In the sixth step, a metal layer is formed by sputtering or depositing or evaporating on the front side of the P-type silicon substrate (01), the material of the metal layer is aluminum, and the thickness is 2 to 5 um;

第七步，在金属层上制备光刻胶，光刻后形成正面刻蚀窗口(104)的图形，去除所述正面刻蚀窗口的图形所对应的金属层，随后采用RIE干法刻蚀所露出的P型硅，刻蚀深度30um，形成正面湿法刻蚀窗口(104)；硅加热元件(101)的硅加热器(1011)的投影位于刻蚀窗口(104)的中心位置；In the seventh step, a photoresist is prepared on the metal layer, and a pattern of the front etching window (104) is formed by photolithography, and the metal layer corresponding to the pattern of the front etching window is removed, and then the RIE dry etching method is used. The exposed P-type silicon has an etching depth of 30 μm to form a front wet etching window (104); the projection of the silicon heater (1011) of the silicon heating element (101) is located at a center position of the etching window (104);

第八步，将上述制备好的硅片置于四甲基氢氧化铵溶液，采用PN结自停止刻蚀从P型硅衬底(01)的正面开始湿法刻蚀，刻蚀时通过第七步制备的P型硅衬底(01)边缘上的金属给P型硅衬底(01)上的N型硅(02)施加正电压，所述正电压高于PN结自停止刻蚀的钝化电势，以使P型硅衬底(01)与N型硅(02)所形成的PN结处于反偏状态；在PN结自停止刻蚀的作用下硅加热元件(101)的N型硅(02)不被刻蚀，由P型硅正面刻蚀深度至少100um以完全释放出硅加热元件(101)，优选刻穿硅片形成通孔(105)；硅加热元件(101)的硅加热器(1011)的投影位于通孔(105)中心位置，且外形尺寸远小于通孔(105)的尺寸；In the eighth step, the prepared silicon wafer is placed in a tetramethylammonium hydroxide solution, and a wet etching is started from the front surface of the P-type silicon substrate (01) by a PN junction self-stop etching, and the etching is performed. The metal on the edge of the P-type silicon substrate (01) prepared in seven steps applies a positive voltage to the N-type silicon (02) on the P-type silicon substrate (01), which is higher than the PN junction self-stop etching Passivating the potential so that the PN junction formed by the P-type silicon substrate (01) and the N-type silicon (02) is in a reverse bias state; the N-type of the silicon heating element (101) under the action of stopping the etching of the PN junction Silicon (02) is not etched, the front side of the P-type silicon is etched to a depth of at least 100 um to completely release the silicon heating element (101), preferably through the silicon wafer to form vias (105); silicon of the silicon heating element (101) The projection of the heater (1011) is located at the center of the through hole (105), and the outer dimension is much smaller than the size of the through hole (105);

第九步，在硅加热元件(101)的固定端(102)上制备光刻胶，烘干，刻蚀去除掉除硅加热元件(101)的固定端(102)上的电引出焊盘金属Pad(21)以外的金属；In the ninth step, a photoresist is prepared on the fixed end (102) of the silicon heating element (101), dried, and etched to remove the electrical lead-out pad metal on the fixed end (102) of the silicon heating element (101). a metal other than Pad (21);

第十步，采用氢氟酸溶液或氢氟酸气雾去除第二步生成的硅加热元件(101)表面的氧化硅(23)，去除第九步的光刻胶；In the tenth step, the silicon oxide (23) on the surface of the silicon heating element (101) generated in the second step is removed by using a hydrofluoric acid solution or a hydrofluoric acid gas mist to remove the photoresist of the ninth step;

第十一步，氧化硅加热元件(101)外表面露出的硅，形成厚度均匀的薄层氧化硅，其厚度十多nm至100nm，作为钝化保护层(22)；In the eleventh step, the silicon exposed on the outer surface of the silicon oxide heating element (101) forms a thin layer of silicon oxide having a uniform thickness of more than ten nm to 100 nm as a passivation protective layer (22);

第十二步，划片、裂片，得到数量众多的本发明所述的基于硅加热器的MEMS甲烷传感器。 In the twelfth step, dicing, splitting, and obtaining a large number of silicon heater-based MEMS methane sensors according to the present invention.