JP3971920B2 - Flow characteristic measuring element and manufacturing method thereof - Google Patents

Description

表中「＊」は本発明の範囲外であることを示す。
【００５２】
【表２】

表中「＊」は本発明の範囲外であることを示す。
【００５３】
表１及び表２の結果より、Ｘの値が０．０１を超える実験例３の素子においては、表２における誤差率が１．１％となり、誤差率を１．０％以下に抑えることができないことが分かる。これに対して、実験例１及び実験例２のように、Ｘの値が０．０１以下となる素子においては、表２における誤差率を１．０％以下に抑えることができることが分かる。即ち、誤差率が１．０％以下のより正確な流れ特性を測定することができることが分かる。
【図面の簡単な説明】
【図１】本発明の流れ特性測定用素子の一例の模式的な断面図である。
【図２】本発明の流れ特性測定用素子の他例の模式的な断面図である。
【図３】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図４】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図５】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図６】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図７】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図８】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図９】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図１０】実施例における本発明の流れ特性測定用素子の作製過程を表す説明図である。
【図１１】実験例１として作製した本発明の流れ特性測定用素子の各種パターンの形状を模式的に表す説明図である。
【図１２】実験例１として作製した本発明の流れ特性測定用素子とこれに接続された外部回路とを併せた回路図である。
【図１３】従来の流れ特性測定用素子の一例の模式的な断面図である。
【符号の説明】
１；流れ特性測定用素子、１１；基板、１２；空間部、１３；絶縁膜、１３１；絶縁膜隔離部、１４１；ヒータパターン、１４１１；昇温部、１４１２；リード部、１４１’；リード部上層、１４２；ヒータパターン上流温度測定用パターン、１４３；ヒータパターン下流温度測定用パターン、１４４；温度補償用パターン、１５；ボンディングワイヤ接続位置、１６；層間層、１７；保護層、１８；析出膜、２；ボンディングワイヤ、３；ボンディングパッド、４；隔壁。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow characteristic measuring element capable of measuring a flow rate, a flow rate (mass flow rate), a temperature, a flow direction, and the like of a fluid (measurement atmosphere) and a manufacturing method thereof. More specifically, the present invention relates to an element for measuring flow characteristics in which the resistance of a lead portion of a heater pattern is reduced, measurement accuracy is high, and power consumption is reduced, and a manufacturing method thereof.
The element for measuring flow characteristics of the present invention can be used for measuring the above-described characteristics of any fluid. Especially, it is suitable for the measurement of the flow velocity and / or mass flow rate of the gas, and can be used for the measurement of the intake air amount of the internal combustion engine, for example.
[0002]
[Prior art]
Conventionally, a part of an insulating film formed on a substrate is thermally isolated from the substrate by using a micromachining technique (this thermally isolated portion is simply referred to as an “insulating film isolating portion” hereinafter). There is known a flow characteristic measuring element (1) in which a heater pattern is arranged on the insulating film isolation part. For example, it is disclosed in JP-A-58-72059, JP-A-60-142268, JP-A-6-50783, JP-A-11-201792, and the like. Such a flow characteristic measuring element (hereinafter also simply referred to as “element”) has a voltage and electric power required to keep the temperature constant when the heat-generating element that has generated heat is cooled by the flow of the measurement atmosphere. The flow characteristics (flow velocity, etc.) are calculated from the above.
[0003]
In the element as described in the above (1), the temperature rising portion of the heater pattern, which is the part of the heating element that actually increases the temperature, and the substrate are thermally isolated, so that the heat of the temperature rising portion is applied to the substrate. Less power is consumed, and less power is required to raise the temperature to a predetermined temperature (power consumption is one to two orders of magnitude smaller than conventional thin film type flow rate sensors or hot wire type flow rate sensors). Further, since the heat of the temperature raising portion is not easily taken away by the substrate, the temperature rise of the substrate itself can be suppressed, and the temperature of the substrate can be regarded as the same as the temperature of the measurement atmosphere. For this reason, it becomes possible to keep the temperature of the temperature raising part at a constant value with respect to the temperature of the substrate regarded as the temperature of the measurement atmosphere, and it is possible to accurately measure the flow characteristics.
[0004]
Among the elements described above, the element disclosed in Japanese Patent Laid-Open No. 6-50783 is an element in which only a portion related to substantial measurement is exposed in the flow path of the measurement atmosphere and the other part is disposed outside the flow path ( 2). For this reason, unlike conventional devices where the entire device is exposed to the measurement atmosphere, disconnection of bonding wires due to flying foreign matter, and short-circuiting of circuits (for example, between bonding pads) due to conductive foreign matter are prevented. It can be done.
[0005]
[Problems to be solved by the invention]
However, in the element as in (1), the heat of the temperature rising portion of the heater pattern is actually conducted slightly through the insulating film to the substrate, and a voltage is applied to the temperature rising portion of the heater pattern. The lead part, which is a part for this purpose, also generates heat. For this reason, the temperature of the substrate is slightly higher than the temperature of the measurement atmosphere. Therefore, when the measurement is performed by regarding the temperature of the substrate as the temperature of the measurement atmosphere, it is strictly difficult to keep the temperature of the temperature rising portion at a constant value with respect to the temperature of the measurement atmosphere.
[0006]
Further, the element as in (2) inevitably becomes longer. Along with this, the length of the lead portion becomes longer, the resistance value of the lead portion increases, and the amount of heat generated in the lead portion itself may not be negligible. In addition, an increase in the resistance value of the lead portion increases the power consumption, which is not preferable. For this reason, until now, attempts have been made to solve this problem by forming the lead pattern as thick as possible on the device. However, the thickness of the pattern of the lead part is limited depending on the size of the element. For example, in an element provided with two or more heaters, the wiring width of the lead part may be hardly expanded.
[0007]
The present invention has been made in view of the above problems, and by reducing the resistance of the lead portion of the heater pattern, measurement errors due to the resistance of the lead portion of the heater pattern are smaller than before, and measurement is performed with higher accuracy. It is another object of the present invention to provide a flow characteristic measuring element with reduced power consumption and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
An element for measuring flow characteristics according to the present invention includes a substrate having a space formed of at least one of a cavity, a notch, and a recess, an insulating film formed on the substrate so as to cover at least the space, and A heater pattern formed on the insulating film, and the heater pattern includes a heating portion where the space portion is located below, and a lead portion for electrical connection between the outside and the heating portion In a flow characteristic measuring element comprising:
(1) When the heater pattern is not energized, the bonding wire that connects the outside and the lead portion is connected to the lead wire portion at a position higher than the bonding wire connecting position where the bonding wire is connected to the lead portion. The ratio of the resistance value to the resistance value of the entire heater pattern is α, and (2) the resistance of the heater pattern measured between the bonding wire connection positions of the heater pattern to which a predetermined voltage is applied in a state where the measurement atmosphere does not flow. The difference between the heater pattern average temperature calculated from the value and the measured atmosphere temperature is ΔTa, and (3) the substrate average temperature when the predetermined voltage is applied to the heater pattern in a state where the measured atmosphere does not flow, and the measured atmosphere When the difference from the temperature is ΔTb, the value X represented by the following formula [1] is 0.01 or less.
X = {α / (1-α)} × (ΔTb / ΔTa) [1]
[0009]
In the element for measuring flow characteristics of the present invention, the lead portion may be multi-layered over at least 1 mm from the bonding wire connecting position toward the temperature raising portion. Furthermore, the lead portion may be covered with an insulating protective film except for a region for connecting the bonding wire to the lead portion. The temperature raising portion is disposed on the measurement atmosphere side of the partition wall separating the measurement atmosphere and the non-measurement atmosphere, the bonding wire connection position is disposed on the non-measurement atmosphere side, and the surface of the partition wall on the non-measurement atmosphere side It can be arranged so that the distance from the bonding wire connection position to 0.2 mm or less.
[0010]
The flow characteristic measuring element manufacturing method of the present invention includes a multi-layering step of multi-layering a conductive layer serving as the lead portion on the substrate having insulating films formed on the front and back surfaces, and In the layering step, when the method includes an interlayer layer forming step for forming an interlayer layer that forms a deposited film on the outermost surface of the lead portion by heating between the layers of the conductive layer, the deposited film removal for removing the deposited film A process is provided.
[0011]
【The invention's effect】
According to the element for measuring flow characteristics of the present invention, it is possible to perform more accurate measurement in the measurement of various characteristics related to the flow, and further, it is possible to reduce power consumption in the heater pattern. In addition, by forming a multilayer in the direction from the bonding wire connection position of the lead portion to the temperature rising portion, the resistance value of the lead portion (between the bonding wire connection position and the temperature rising portion) with respect to the entire heater pattern is reduced. The ratio (hereinafter, also simply referred to as “resistance contribution ratio”) can be reduced, more accurate measurement can be performed as compared with the prior art, and power consumption in the heater pattern can be reduced. Furthermore, since the lead portion is covered with the insulating protective film except for the vicinity of the bonding wire connection position, it is possible to effectively prevent a short circuit and disconnection of the heater pattern and the like. Also, by setting the distance from the non-measurement target atmosphere side surface of the partition wall to the bonding wire connection position to be 0.2 mm or less, the resistance contribution ratio of the lead portion can be reduced as a result, and the measurement is more accurate than before. Further, power consumption in the heater pattern can be reduced.
Moreover, according to the manufacturing method of the element for measuring flow characteristics of the present invention, the element for measuring flow characteristics as described above can be obtained with certainty.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the flow characteristic measuring element of the present invention will be described in detail.
The “cavity” is a defect of the substrate opened on both the front and back surfaces of the substrate, for example, a hole such as a through hole and a communication hole. The “notch” is a defect of the substrate opened to at least one of the front and back surfaces of the substrate and opened to any one of the side surfaces of the substrate. The “recess” is a defect of the substrate opened on one of the front and back surfaces of the substrate.
[0013]
The “space part” is a part in which a part of the substrate consisting of at least one of these cavities, notches and recesses is missing, and the opening shape (including the open shape) and the internal shape are particularly It is not limited. However, the opening shape is usually a simple shape, such as a rectangle or a circle. Also, the size of the space is not particularly limited, but normally, an opening area that opens to one side of the front and back direction with respect to the substrate having one space (open area that opens to one side of the front and back in the notch) ) Is 0.25-4mm ² Degree (especially, □ 0.5 to □ 2 mm is preferable). Any number of spaces may be provided on the substrate, and the number is not particularly limited.
[0014]
A method for forming such a space is not particularly limited, but the space can be formed by removing a part of a substrate described later by etching. The etching method used at this time is not particularly limited, and any of a wet etching method and a dry etching method (including anisotropic etching and isotropic etching, respectively) may be used. In particular, a wet etching method using an anisotropic etching solution is generally used for forming the cavity.
[0015]
The “substrate” is a portion that becomes a base of the element of the present invention. Although the material which comprises this base | substrate is not specifically limited, Usually, a semiconductor material is used. Of these, silicon substrates are frequently used. Although the shape of this board | substrate is not specifically limited, For example, it can be set as a rectangle or a circle. Moreover, the size is not limited.
[0016]
The “insulating film” is a thin film formed on the substrate so as to cover at least the space. This insulating film has a function of electrically and thermally insulating a heater pattern, which will be described later, and the substrate.
The method for forming the insulating film is not particularly limited, and can be obtained by modifying the surface of the substrate by, for example, a thermal oxidation method. Alternatively, a component that becomes an insulating film can be deposited and deposited on the surface of the substrate (can be formed by vapor deposition, sputtering, ion plating, vapor deposition, or the like). In addition, an insulating film formed in advance on the surface of the substrate can be attached.
[0017]
This insulating film may be made of any material and is not particularly limited. ₂ , Si _Three N _Four And SiO _x N _y It can comprise from silicon compounds etc., such as. Further, the shape, size, thickness, and the like of the insulating film are not particularly limited, and may be a single layer film or a multilayer film. However, the insulating film isolating portion (see FIG. 11, 131 is the insulating film isolating portion in FIG. 11) located on the space portion of the insulating film usually has an area of 0.25 to 4 mm. ² (In particular, □ 0.5 to □ 2 mm is preferable), and the thickness is about 0.5 to 2 μm.
[0018]
The “heater pattern” includes a temperature raising portion that generates heat when a voltage is applied and actually raises the temperature, and a lead portion that conducts from the outside to the temperature raising portion (see FIGS. 1 and 2). In FIG. 1 and FIG. 2, 1411 is a temperature raising portion and 1412 is a lead portion).
The method for forming the heater pattern is not particularly limited, but a predetermined material is deposited on the insulating film (can be deposited by vapor deposition, sputtering, ion plating, vapor deposition, etc.), and then It can be obtained by removing unnecessary portions by various etching methods similar to those exemplified in the method for forming the space. Although the material which comprises a heater pattern will not be specifically limited if it has electroconductivity, For example, a platinum single-piece | unit, a platinum alloy, a nickel alloy, a chromium alloy etc. can be used. Among them, it is preferable to use platinum alone or a nickel-chromium alloy because the resistance temperature coefficient is large and the resistance value and the resistance temperature coefficient hardly change even after repeated use over a long period of time.
[0019]
The “temperature raising part” is a part of the heater pattern in which the space part is located below, regardless of the pattern shape of the heater pattern, and regardless of whether heat is generated by applying a voltage, It is a part where the temperature can be actually increased by applying voltage {even if the pattern of the heater pattern is difficult to generate heat (for example, the line width is wide, etc.) because it is located on the insulating film isolation part The portion where there is almost no heat conduction to the substrate and the temperature can actually be raised is the temperature raising portion}.
[0020]
The “lead part” is a part of a heater pattern in which no space part is positioned below and the outside (outside the element) and the temperature raising part are electrically connected to each other (however, a bonding wire described later leads to the outside). Between the part). Regardless of the pattern shape of the heater pattern (for example, even if the lead portion has a shape suitable for heat generation, for example, part of the lead portion is narrowed) The part that is difficult to increase due to heat conduction or does not increase in temperature is included in the lead part), and is not related to whether or not heat is generated due to the application of voltage (even if it generates heat, on the insulating film isolation part) (There is no temperature rise due to heat conduction to the substrate.) In the following description, the portion of the lead portion that is actually involved in conduction from the bonding wire connecting position to the temperature raising portion is referred to as “real conduction lead portion”.
[0021]
As the resistance contribution ratio of the actual conductive lead portion is as small as possible, a highly accurate measurement can be performed. For this reason, it is preferable to make the wiring width of the lead portion as wide as possible. However, there is a limit to increasing the wiring width in the plane direction on the substrate. For this reason, the lead portion (which may be only the actual conductive lead portion) may be a single layer, but the resistance contribution ratio can also be reduced by making it into multiple layers. In particular, it is more preferable to form the wiring width as wide as possible and to form a multilayer.
[0022]
Multiple layers may be formed at any position of the actual conductive lead portion {see FIGS. 1 and 2}. Moreover, it may be multi-layered in any number of layers, and is not particularly limited. In addition, the length to be multilayered is not particularly limited, but in particular, at least 1 mm or more (more preferably 2 mm or more, or even the whole) is multilayered from the bonding wire connection position toward the temperature rising portion. Is preferred. If the thickness is less than 1 mm, it is difficult to sufficiently exert the effect of the multilayering. In addition, each of the multilayered layers may be made of the same material, but may be a layer made of a different material. In particular, it is not necessary to use the metal exemplified as the heater pattern because a part of the layer that is the upper layer of the actual conductive lead portion does not need to generate heat as in the temperature rising portion, rather, highly conductive gold, It is preferably composed of gold alloy, aluminum, aluminum alloy, silver, silver alloy, copper, copper alloy or the like. Thereby, the resistance value of the actual conduction lead portion can be effectively reduced.
[0023]
In addition, it is preferable that the lead portion is covered with a protective layer in a region located in the measurement atmosphere {see FIG. 1 and FIG. 2], and further, the protective layer is excluded except for a region for connecting a bonding wire. Is preferably covered by {see FIG. 1}. Thereby, disconnection of the lead part by the foreign material which flies from measurement atmosphere, and the short circuit of the lead parts by the conductive foreign material which flies can be prevented.
[0024]
The “protective layer” is an insulating layer. The components constituting this protective layer are not particularly limited, but for example, SiO ₂ , Si ₃ N ₄ , SiO _x N _y , Al ₂ O ₃ And Ta ₂ O ₅ Etc. Moreover, the thickness, shape, etc. of a protective layer are not specifically limited. Further, the method for forming this protective layer is not particularly limited, but it is unnecessary, for example, by various etching methods similar to those exemplified in the above-described method for forming the space after depositing and depositing similarly to the formation of the heater pattern. It can be obtained by removing the various parts. It can also be obtained by baking after applying a component to be an insulating film.
[0025]
The “bonding wire” is a thin line {2 in FIGS. 1 and 2] for conducting between the lead portion and the outside when the element of the present invention is actually used for measurement of flow characteristics. However, it is not a component of the element). The length, thickness, shape and material of the bonding wire are not particularly limited (usually gold or aluminum is used as the material).
The “region for connection” is a region necessary for bonding the bonding wire to the lead portion. The area and shape of the region are not particularly limited, but are usually regions that are similar to the cross-section of the bonding wire to be connected and that have a cross-sectional area that is four times the cross-section of the bonding wire.
[0026]
In addition, in the heater pattern of the element of the present invention, for example, when the heater pattern is formed in a U-shape from a portion that is not the insulating film isolation portion to a portion that straddles the insulating film isolation portion and is not the insulating film isolation portion, The part located on the membrane isolation part is the temperature raising part, and the part extending from the two ends of the U-shaped system to this temperature raising part is the lead part. Further, the portion corresponding to the U-shaped bottom portion that is not located on the insulating film isolation portion generated by straddling the insulating film isolation portion is attributed to the lead portion.
[0027]
The “α” is the ratio of the resistance value of the actual conduction lead portion to the resistance value of the entire heater pattern when the heater pattern is not energized. This α is preferably small, but the value is not particularly limited, and X given by the above formula [1] may be 0.01 or less.
The “heater pattern average temperature” is obtained by applying a predetermined voltage to the heater pattern in a state where the measurement atmosphere does not flow, measuring the resistance value between the bonding wire connection positions, and obtaining the resistance value R ₁ And resistance value R between bonding wire connection positions at 0 ° C. ₀ , And c, which is the resistance temperature coefficient of the heater pattern, is a calculated value calculated by the following equation [2].
T = (R ₁ / R ₀ -1) / c [2]
[0028]
The “measurement atmosphere temperature” is the temperature of the atmosphere to be measured. The measurement method of this measurement atmosphere temperature is not specifically limited, For example, it can measure using a radiation (infrared ray) thermometer etc. Usually, the element itself is provided with a resistor pattern for temperature measurement (pattern for atmospheric temperature measurement, temperature compensation pattern for substrate average temperature measurement, etc.), so that no voltage is applied to the heater pattern. The resistance value of this resistor pattern is measured, and the measured ambient temperature can be calculated from this resistance value.
[0029]
The “substrate average temperature” is an average temperature of the substrate in a state where the heater pattern is energized. The measurement method of this board | substrate average temperature is not specifically limited, For example, it can measure using a radiation | emission (infrared ray) thermometer etc. Usually, the substrate average temperature can be calculated from the resistance value of a temperature measurement resistor pattern (a substrate average temperature measurement pattern, a temperature compensation pattern also used for atmospheric temperature measurement, etc.) provided in the element itself.
[0030]
The “X” is not particularly limited as long as it is 0.01 or less. If X exceeds 0.01, it is not preferable because a measurement error caused by the heat generated in the actual conductive lead portion increases. That is, for example, when the measurement atmosphere temperature is 25 ° C. and the element is controlled using a bridge circuit that attempts to maintain the heater pattern average temperature at 200 ° C., the heater pattern average temperature and measurement in a state where the measurement atmosphere does not flow ΔT is the difference from the ambient temperature _h0 The difference between the average temperature of the heater pattern and the measured ambient temperature in a state where the measured atmosphere is flowed and controlled by the bridge circuit is ΔT _h1 T _h0 T against _h1 Is the error rate of {(T _h1 -T _h0 ) / T _h0 } The ratio represented by × 100 exceeds 1%, which is not preferable (see Examples).
[0031]
When measuring the flow characteristics using the element of the present invention, as described above, the temperature raising portion is disposed on the measurement atmosphere side, the bonding wire connection position is disposed on the non-measurement atmosphere side, and It is preferable that the distance from the surface on the non-measurement atmosphere side of the partition wall to the bonding wire connection position is 0.2 mm or less (more preferably 0.1 mm or less, still more preferably 0.05 mm or less). Thereby, the length of a lead part becomes short and the resistance contribution rate of a lead part can be reduced.
[0032]
In addition to the heater pattern described above, the element of the present invention includes a temperature measurement pattern {for atmospheric temperature measurement, substrate average temperature measurement, heater pattern upstream temperature measurement, heater pattern downstream temperature measurement, temperature One or more resistor patterns such as for compensation resistance (used for measuring atmospheric temperature and average substrate temperature)} can be provided. Although the formation method of these patterns is not specifically limited, It can obtain by the method similar to the said heater pattern. Moreover, the material which comprises these patterns is not specifically limited, The same thing as what was illustrated in the said heater pattern is applicable. Each of these patterns can be formed simultaneously with the formation of the heater pattern on the same layer as the layer on which the heater pattern is formed.
[0033]
In the production of such a flow characteristic measuring element, the method is not particularly limited, but each component can be formed as described above. However, in order to at least make the actual conductive lead part multi-layered, the case where an interlayer layer forming step for forming an interlayer layer that forms a deposited film on the outermost surface of the lead part by heating between the layers of the conductive layer as the lead part is provided. Can be provided with a deposited film removing step of removing the deposited film in a subsequent step.
[0034]
The “interlayer” is a layer having a property that part or all of it is deposited on the outermost surface of the lead portion by heating, and has conductivity. The purpose of forming such a layer is not particularly limited. For example, in order to improve the adhesion strength of the conductive layer when it is difficult to obtain a sufficient adhesion strength between the conductive layer and at least a part of the outermost surface of the substrate on which the conductive layer is to be formed. However, a bonding wire for connection with the outside is connected to any position on the outermost surface of the lead portion. For this reason, if a deposited film is formed, bonding may not be performed normally. Therefore, it is preferable to provide a step of removing the deposited film.
[0035]
There are no particular restrictions on the component that forms the interlayer layer, but since it is formed between the layers of the layers constituting the lead portion, the adhesion between the layers can be sufficiently improved, and furthermore, it has sufficient conductivity. preferable. That is, for example, Cr, Ti, Mo, W, Ta, Nb, etc. can be mentioned. These may be used alone or in combination of two or more. As a component for these interlayer layers, when platinum is used for the lower layer and gold is used for the upper layer, it is preferable to use at least one of Cr, Ti, and Mo, and further, an insulating film and a conductive layer. Cr is particularly preferable because the etching rate ratio (selection ratio) at the time of etching falls within a preferable range and is excellent in chemical durability. The method for forming this interlayer layer is not particularly limited, but for example, it can be formed by depositing and depositing a desired component, as in the case of forming the heater pattern described above. Similarly, if necessary, unnecessary portions can be removed by etching.
[0036]
The purpose of performing the “heating” is not particularly limited, but for example, the entire substrate may be heated when a protective layer for protecting the lead portion from flying foreign matter or the like is formed. Further, the heating temperature and the heating time are not particularly limited. For example, when the above-described Cr, Ti, Mo, W, Ta, Nb, or the like is deposited as an interlayer, it is deposited at about 250 to 300 ° C. Sometimes.
[0037]
The composition or the like of the “deposited film” is not limited, but is, for example, a part or all of the components used as the interlayer. Therefore, when Cr, Ti, Mo, W, Ta, Nb or the like is used as an interlayer as described above, these components (regardless of the presence or absence of reaction with other components) are precipitated. Become.
The method for removing the deposited film is not particularly limited, but can be removed by various etching methods similar to those exemplified in the method for forming the space portion.
[0038]
【Example】
Hereinafter, the present invention will be specifically described by way of examples.
1. Fabrication of flow characteristics measuring element
(1) Formation of insulating film
An insulating thin film 13 was formed on the front and back surfaces of the cleaned silicon substrate 11 (thickness: 400 μm) (see FIG. 3). The back surface of the insulating film is composed of an oxide film having a thickness of 0.1 μm by a thermal oxidation method and a silicon nitride film having a thickness of 0.1 μm by an LP (Low Pressure) CVD method. On the other hand, the surface side is composed of an oxide film having a thickness of 0.1 μm by thermal oxidation, a silicon nitride film having a thickness of 0.1 μm by LPCVD, and a silicon nitride film having a thickness of 0.4 μm by plasma CVD. The oxide film formed by the thermal oxidation method and the silicon nitride film formed by the LPCVD method were formed simultaneously on the front and back surfaces.
[0039]
(2) Formation of first interlayer layer, heater pattern, heater pattern upstream temperature measurement pattern, heater pattern downstream temperature measurement pattern, and ambient temperature measurement pattern
A tantalum layer having a thickness of 20 nm was formed on the entire surface of the insulating film 13 obtained in (1) by sputtering. Thereafter, a platinum layer having a thickness of 0.1 μm was further formed on the tantalum layer by sputtering. Next, after applying a photoresist on the platinum layer, necessary portions were exposed and cured, and then unnecessary portions were removed to form a resist pattern. Next, the platinum layer is etched by wet etching (using aqua regia), and the heater pattern 141 having the shape shown in FIG. 11, the heater pattern upstream temperature measurement pattern 142, the heater pattern downstream temperature measurement 143, and the temperature compensation A pattern 144 was formed. Further, the tantalum layer was etched by a dry etching method to form a first interlayer layer 161. Thereafter, the range pattern was removed with sulfuric acid / hydrogen peroxide (see FIGS. 4 and 11).
[0040]
(3) Formation of second interlayer and upper layer of lead part
A chromium layer having a thickness of 50 nm was formed by sputtering on the entire surface of the substrate on which the insulating film and each pattern were formed. Thereafter, a gold layer having a thickness of 1 μm was further formed on the chromium layer by sputtering. Next, after applying a photoresist on the gold layer, necessary portions were exposed and cured, and then unnecessary portions were removed to form a resist pattern. Next, etching of the gold layer (using aqua regia) was performed by a wet etching method to form a lead portion upper layer 141 ′ (3.5 to 4 mm from the bonding wire connecting position toward the temperature rising portion). Further, the chromium layer was etched by wet etching (using a second cerium ammonium nitrate-based etchant) to form a second interlayer 162 (formed on the entire lower surface of the upper portion of the lead portion). Thereafter, the range pattern was removed with sulfuric acid / hydrogen peroxide (see FIG. 5).
[0041]
(4) Formation of protective layer
A protective layer 17 made of silicon nitride having a thickness of 1 μm was formed on the entire surface of the substrate having each pattern by plasma CVD (the substrate was heated to about 300 ° C. by performing plasma CVD, Chromium constituting at least the second interlayer layer is deposited below the protective layer 17 from below the lead portion upper layer 141 ′ (see FIG. 6). Thereafter, only a portion necessary for bonding (near the end of the lead portion of each pattern) was removed by an etching method using RIE (Reactive Ion Etching), and a hole for bonding was formed in the protective layer (see FIG. 7). .
[0042]
(5) Formation of space
A predetermined region on the surface of the insulating film 13 on the side where the patterns of the substrate obtained up to {circle around (4)} are not formed was removed by an etching method using RIE (see FIG. 8). Next, the silicon substrate 11 that appears on the surface by etching is removed by etching using an anisotropic etchant up to the surface of the insulating film on the surface side where each pattern of the substrate is formed, and the space portion 12 is removed. Formed (see FIG. 9).
[0043]
(6) Removal of deposited film
Since the deposited film 18 was formed on the bottom surface (lead surface outermost surface) of the bonding hole opened in (4), the ceric ammonium nitrate-based etching used for etching the second interlayer layer in (3). Using the liquid, the portion of the deposited film exposed from the bonding hole was removed (see FIG. 10), and the element 1 of Experimental Example 1 was obtained.
▲ 7 ▼ Calculation of element α
Α of the obtained element of Experimental Example 1 was calculated to be α = 0.01.
[0044]
2. Fabrication of elements with different α
(I) Fabrication of device with α = 0.12 (Experimental example 2) (see FIG. 2)
(1) Formation of insulating film, first interlayer layer, heater pattern, etc.
Above 1. (1) to 1 above. After forming an insulating film on the silicon substrate in the same manner as in (2) above, a first interlayer layer is formed on the insulating film, and further a heater pattern and a heater pattern upstream temperature measurement pattern are formed on the first interlayer layer. The heater pattern downstream temperature measurement pattern and the temperature compensation pattern were formed.
Thereafter, the above 1. In the same manner as (3), a chromium layer and a gold layer were formed on the chromium layer by sputtering. Thereafter, a resist pattern is formed, and the above 1. The gold layer was etched by the wet etching method in the same manner as in (3) to form the lead portion upper layer 141 ′. However, the lead layer upper layer is formed from 1 to 2 mm from the bonding wire connecting position toward the temperature rising portion. This is shorter than the lead portion upper layer 141 ′ included in the element of Experimental Example 1 obtained in (1). Thereafter, the above 1. The chromium layer was etched in the same manner as in (3) to form the second interlayer layer 162, and the range pattern was further removed.
[0045]
(2) Formation of protective layer
A protective layer made of silicon nitride having a thickness of 1 μm was formed on the entire surface provided with each pattern formed in (1) above by plasma CVD. Thereafter, etching was performed using RIE so that the entire surface of the lead portion upper layer 141 ′ formed in the above (1) was exposed.
[0046]
(3) Formation of space
A predetermined region on the surface of the insulating film on the side where the respective patterns of the substrate obtained up to the above (2) are not formed is defined in the above 1. A space was formed by etching in the same manner as in (5). Next, the above 1. In the same manner as (6), the deposited film was removed to obtain the device of Experimental Example 2. (4) Calculation of element α
Α of the obtained element of Experimental Example 2 was calculated to be α = 0.12.
[0047]
(Ii) Fabrication of element with α = 0.15 (Experimental Example 3) (see FIG. 13)
2. (I) In (1) above, except that the bonding pad 3 is formed which is only multilayered by 0.2 mm from the bonding wire connection position toward the temperature rising portion when the gold layer is etched. The element of Experimental Example 3 was obtained in the same manner as (i). Α of the obtained element of Experimental Example 3 was α = 0.15.
[0048]
3. Evaluation using elements
(1) Manufacture of flow characteristic measuring instrument
Above 1. And 2. Each element of Experimental Examples 1 to 3 obtained in 1 above is projected to a predetermined position of a diverter pipe for diverting the measurement atmosphere, the temperature rising portion of the element protrudes into the diversion channel (measurement atmosphere side), and 1. The part from which the protective layer and the deposited film were removed was inserted into the partition wall and fixed so as to protrude out of the branch channel (non-measurement atmosphere side). Next, a bonding wire is bonded to the lead portion exposed at the site where the protective layer and the deposited film are removed, and an external circuit is connected so as to obtain the circuit configuration shown in FIG. Got.
[0049]
(2) X measurement
3. above. Using each flow characteristic measuring instrument obtained in (1), a voltage was applied from an external circuit so that the heater pattern average temperature was 175 ° C. in a state where the measurement atmosphere having a temperature of 25 ° C. did not flow. In addition, when the measurement atmosphere having a temperature of 25 ° C. did not flow, the average substrate temperature was measured and found to be as shown in Table 1. The results of calculating X from these are also shown in Table 1.
[0050]
(3) Measurement of error rate of heater pattern average temperature
The measurement atmosphere at 25 ° C. was caused to flow so that the average substrate temperature was 25 ° C. in the branch flow path of each flow characteristic measuring instrument. At this time, the circuit shown in FIG. 12 was controlled so that the difference between the measured ambient temperature and the heater pattern average temperature was 175 ° C. The heater pattern average temperature was calculated based on the voltage applied to the heater pattern. Furthermore, the difference ΔT between the heater pattern average temperature and the measured atmosphere temperature in a state where the measured atmosphere does not flow _h0 Difference ΔT between the heater pattern average temperature and the measured ambient temperature in a state where the measured atmosphere is flowed and controlled by the external circuit _h1 And these ΔT _h0 And ΔT _h1 Difference (ΔT _h1 -ΔT _h0 Are shown in Table 2. Also, “T _h0 "T" _h1 Error rate of { _h1 -T _h0 ) / T _h0 } × 100 was calculated and shown in Table 2.
[0051]
[Table 1]

“*” In the table indicates that it is outside the scope of the present invention.
[0052]
[Table 2]

“*” In the table indicates that it is outside the scope of the present invention.
[0053]
From the results of Tables 1 and 2, in the element of Experimental Example 3 in which the value of X exceeds 0.01, the error rate in Table 2 is 1.1%, and the error rate can be suppressed to 1.0% or less. I understand that I can't. On the other hand, as shown in Experimental Example 1 and Experimental Example 2, it is understood that the error rate in Table 2 can be suppressed to 1.0% or less in the element where the value of X is 0.01 or less. That is, it can be seen that more accurate flow characteristics with an error rate of 1.0% or less can be measured.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an example of a flow characteristic measuring element of the present invention.
FIG. 2 is a schematic cross-sectional view of another example of the flow characteristic measuring element of the present invention.
FIG. 3 is an explanatory diagram showing a manufacturing process of a flow characteristic measuring element of the present invention in an example.
FIG. 4 is an explanatory view showing a process of manufacturing a flow characteristic measuring element of the present invention in an example.
FIG. 5 is an explanatory diagram showing a manufacturing process of a flow characteristic measuring element of the present invention in an example.
FIG. 6 is an explanatory diagram showing a manufacturing process of the flow characteristic measuring element of the present invention in Examples.
FIG. 7 is an explanatory diagram showing a manufacturing process of a flow characteristic measuring element of the present invention in an example.
FIG. 8 is an explanatory diagram showing a manufacturing process of the element for measuring flow characteristics of the present invention in Examples.
FIG. 9 is an explanatory diagram showing a manufacturing process of a flow characteristic measuring element of the present invention in an example.
FIG. 10 is an explanatory diagram showing a manufacturing process of the element for measuring flow characteristics of the present invention in Examples.
11 is an explanatory view schematically showing the shapes of various patterns of the flow characteristic measuring element of the present invention produced as Experimental Example 1. FIG.
12 is a circuit diagram in which a flow characteristic measuring element of the present invention manufactured as Experimental Example 1 and an external circuit connected thereto are combined. FIG.
FIG. 13 is a schematic cross-sectional view of an example of a conventional flow characteristic measuring element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1; Element for flow characteristic measurement, 11; Substrate, 12; Space part, 13; Insulating film, 131; Insulating film isolating part, 141; Heater pattern, 1411; Temperature rising part, 1412; Lead part, 141 '; Upper layer, 142; Heater pattern upstream temperature measurement pattern, 143; Heater pattern downstream temperature measurement pattern, 144; Temperature compensation pattern, 15; Bonding wire connection position, 16; Interlayer, 17; Protective layer, 18; 2; bonding wire, 3; bonding pad, 4;

Claims (5)

A substrate having a space formed of at least one of a cavity, a notch, and a recess; an insulating film formed on the substrate so as to cover at least the space; and a heater pattern formed on the insulating film; And the heater pattern is a flow characteristic measuring element including a temperature rising portion in which the space portion is located below and a lead portion for electrical connection between the outside and the temperature rising portion.
(1) When the heater pattern is not energized, the bonding wire that connects the outside and the lead portion is connected to the lead wire portion at a position higher than the bonding wire connecting position where the bonding wire is connected to the lead portion. The ratio of the resistance value to the resistance value of the entire heater pattern is α, and (2) the resistance of the heater pattern measured between the bonding wire connection positions of the heater pattern to which a predetermined voltage is applied in a state where the measurement atmosphere does not flow. The difference between the heater pattern average temperature calculated from the value and the measured atmosphere temperature is ΔTa, and (3) the substrate average temperature when the predetermined voltage is applied to the heater pattern in a state where the measured atmosphere does not flow, and the measured atmosphere A flow characteristic measuring element, wherein a value X expressed by the following formula [1] is 0.01 or less when a difference from temperature is ΔTb.
X = {α / (1-α)} × (ΔTb / ΔTa) [1] 2. The flow characteristic measuring element according to claim 1, wherein the lead portion is multilayered at least 1 mm from the bonding wire connecting position toward the temperature raising portion. 3. The flow characteristic measuring element according to claim 1, wherein the lead portion is covered with an insulating protective film except for a region for connecting the bonding wire to the lead portion. The temperature raising portion is disposed on the measurement atmosphere side of the partition wall separating the measurement atmosphere and the non-measurement atmosphere, the bonding wire connection position is disposed on the non-measurement atmosphere side, and the partition wall from the non-measurement atmosphere side surface The element for measuring flow characteristics according to any one of claims 1 to 3, wherein the element is arranged so that a distance to a bonding wire connection position is 0.2 mm or less. 5. The method for manufacturing a flow characteristic measuring element according to claim 2, wherein a conductive layer to be the lead portion is formed on the substrate having an insulating film formed on the front and back surfaces. An interlayer forming step of forming an interlayer that includes a multilayering step for layering, and in which the deposited film is formed on the outermost surface of the lead portion by heating between the layers of the conductive layer in the multilayering step; A method for producing a device for measuring flow characteristics, comprising a step of removing a deposited film to remove the deposited film.

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