JP5081174B2 - Sensor and flow sensor - Google Patents

Description

  The present invention relates to a sensor and a flow sensor suitable for measuring a minute flow rate of gas or the like used in a semiconductor manufacturing apparatus, for example.

  As a structure for sealing the semiconductor element, a cap wafer is bonded and integrated through a glass frit to the upper surface of the base wafer on which the semiconductor element and a signal lead line of the semiconductor element are formed, and the glass frit of the lead lines is integrated. An intermediate layer that is in close contact with the lead wire and the glass frit is formed on at least the upper surface of a portion that intersects with the glass frit, and the glass frit is in close contact with the lead wire through the intermediate layer, and the semiconductor device is hermetically sealed by the cab wafer. Has been proposed (see, for example, Patent Document 1).

In the semiconductor sealing structure, an insulating material such as Pyrex (registered trademark) glass is used as a base wafer and a cab wafer, and a glass frit is formed on the entire lower surface of the cab wafer by screen printing. Are heated and pressed to integrate them.
Japanese Unexamined Patent Publication No. 2000-307018 (page 3, FIG. 1)

  In the sealing structure, a semiconductor element is packaged, and lead lines for taking out signals from the semiconductor element are hermetically sealed with a cap wafer through a glass frit. However, in this structure, the bonding strength of the glass frit is weak and it is difficult to give the semiconductor element a pressure-resistant structure. Further, if the bonding temperature of the glass frit is kept low, for example, to 400 ° C. or less, the glass frit has a sufficient adhesive strength that matches the thermal expansion coefficient (3.2 × 10 −6 / ° C.) of the Pyrex (registered trademark) glass. There is no low melting glass. For this reason, it is difficult to apply a low melting point glass having a thermal expansion coefficient matching that of the base wafer and the cab wafer without causing thermal damage to the semiconductor element.

In the present invention, it is preferable to apply an adhesive material having a thermal expansion coefficient close to that of the member to be bonded. (Described in paragraph 0032 of the original application). In order to solve the above-described problem, the invention according to claim 1 is a flow sensor configured by joining a sensor chip and a glass cover member, and the sensor chip includes a flow rate detection unit on a substrate. A signal extraction wiring portion extending on both sides of the detection portion is formed, and the fluid to be measured is placed on the flow rate detection portion along the longitudinal direction in the center of the surface joined to the sensor chip on the cover member. In the flow sensor in which a flow path for flow and a cutout portion are formed in each of the side walls located in the orthogonal direction of the flow path, one end and the other end of the signal extraction wiring portion are formed in respective extending directions. A groove is formed in the cover member along the extending direction of the signal extraction wiring portion in the previous period, and the signal extraction wiring portion is inserted through the groove, Clearance between the groove and the detection of the signal lead-out wires of the wood are filled by the low-melting glass, the flow sensor, wherein the junction region the other are joined by anodic bonding.

Since the center part of the both side walls of the cover member is notched to be a notch part, the joining area can be reduced (described in paragraph 0022 of the original application).

Hereinafter, a sensor and a flow sensor according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a flow sensor of the present invention. The flow sensor 1 has a rectangular parallelepiped shape that is long in the left-right direction in the figure, and a cover member in which a sensor chip 2 and a lower surface are joined to the upper surface of the sensor chip 2. As a glass chip 3, a flow rate detection unit 10 formed on the upper surface of the sensor chip 2, and the like. The glass chip 3 is made of transparent glass and the inside is seen through. Therefore, the flow rate detection unit 10 is also drawn through.

As shown in FIG. 2, the sensor chip 2 has, for example, a silicon nitride or silicon dioxide insulating film (thin film) 5 formed in the center of the upper surface 4a of the silicon substrate 4 in the width direction. A heater 6 as a heating element made of, for example, a platinum (Pt) thin film at a central position, and a temperature measuring element 7 as a resistance element made of, for example, a platinum thin film at equal intervals on the upstream and downstream sides of the heater 6 and a temperature measurement. An element 8 is formed.

Lead patterns 6a, 6b, 7a, 7b, 8a, and 8b as signal extraction wirings for the heater 6 and the temperature measuring elements 7 and 8 extend to the vicinity of the tip of the insulating film 5 on both sides. The heater 6, the temperature measuring elements 7 and 8, and the lead patterns 6a, 6b, 7a, 7b, 8a, and 8b are arranged at regular intervals in a band shape as shown in FIG. The heater 6, the temperature measuring elements 7, 8 and the lead patterns 6a, 6b, 7a, 7b, 8a, 8b are composed of an insulating film (thin film) 9 of silicon nitride or silicon dioxide as shown in FIGS. The whole is covered by.

As shown in FIG. 4, the heater 6, the temperature measuring elements 7, 8 and their lead patterns are formed on the insulating film 5 with a thickness of about 0.1 to 0.5 μm. The insulating film 9 is formed to have a thickness of about 5 to 1.0 μm. Therefore, the upper surface of the insulating film 9 forms a step (concave portion) 9a according to these thicknesses. Further, as shown in FIG. 3, electrode pads 9b for connection are formed in the insulating film 9 in the vicinity of the tips of the respective lead patterns. A flow rate detection unit 10 is formed by the heater 6 and the temperature measuring elements 7 and 8.

In the flow rate detection unit 10, the leading ends of the lead patterns 6a, 7a, 8a and 6b, 7b, 8b are connected to an external measurement circuit (not shown) or the like by wire bonding through the electrode pads 9b. As shown in FIG. 3, the portions of the lead patterns 6a, 7a, 8a and 6b, 7b, 8b extending on both sides of the flow rate detection unit 10 are referred to as signal extraction wiring units 10a.

A recess 4b is formed on the upper surface 4a of the silicon substrate 4 at a position below the flow rate detection unit 10 as shown by a dotted line in FIGS. 2 to 4, and a portion covering the recess 4b of the insulating film 5 is a diaphragm. . Thereby, the flow volume detection part 10 and the silicon substrate 4 are thermally interrupted. The recess 4b is formed by forming a large number of slits at the location of the insulating film 5 by photolithography and etching, and applying anisotropic etching to the silicon substrate 4 through the slits.

The glass chip 3 is formed of a transparent glass, for example, borosilicate glass, which is substantially the same size as the silicon substrate 4, and as shown in FIGS. 1, 5, and 6, the sensor chip 2 extends along the longitudinal direction at the center of the lower surface 3b. A flow path (groove) 11 for flowing a fluid such as a gas is formed on the flow rate detection unit 10 formed in the above. Both ends 11a and 11b of the flow path 11 are open to the upper surface 3a of the glass chip 3, and the flow rate detection unit 10 formed on the sensor chip 2 is, for example, from the temperature measuring element 7 side to the temperature measuring element 8 side. The fluid is made to flow toward it. Therefore, the glass chip 3 has a function as a flow path forming member for flowing a fluid such as the gas.

The flow path 11 may be processed by a processing method such as a process surface, that is, an inner wall surface that is smooth, for example, melt molding or hydrofluoric acid etching, or may be dried after the flow path 11 is formed by an end mill, sandblasting, or the like. Or you may process so that an inner wall surface may become smooth using wet etching together. Thus, it becomes easy to observe the flow volume detection part 10 and the flow path 11 from the outer side of the glass chip 3 by making the inner wall surface of the flow path 11 into a smooth surface. In addition, when it is not necessary to observe the flow rate detection part 10 and the flow path 11 from the outer side of the glass chip 3, it may be processed by an end mill, a sand blast, or the like.

As shown in FIGS. 1 and 5, the glass chip 3 is formed with a notch 3 c formed in a substantially semi-circular shape at the center of both side walls, and the flow path 11 and the center of these notches 3 c are formed. A groove 3d having a substantially rectangular shape when viewed from the end surface is formed along a direction orthogonal to each other, that is, along the extending direction of the signal extraction wiring portion 10a of the flow rate detection unit 10. The groove 3d is an insertion part for taking out the signal extraction wiring part 10a of the flow rate detection part 10 to both sides of the glass chip 3, and is shallower than the flow path 11 as shown in FIG. 6 and the signal as shown in FIG. It is formed slightly larger than the extraction wiring portion 10a. The groove 3d may be processed by melt molding, hydrofluoric acid etching, or the like, or may be formed by an end mill, sand blast, or the like.

Further, as shown in FIG. 5, the glass chip 3 is cut away from the center of both side walls to form a notch 3 c, so that the length of the groove 3 d, that is, from the opening end on the flow channel 11 side of the groove 3 d. The distance to the open end on the notch 3c side is shortened, and the junction area between the signal extraction wiring portion 10a of the flow rate detection portion 10 and the inner wall surface of the groove 3d can be reduced.

Incidentally, the size of the sensor chip 2 is about 1.5 mm × 6.0 mm to 6.0 mm × 12.0 mm / thickness 0.5 mm to 1.0 mm, and the size of the glass chip 3 is 1.5 mm × 6. It is about 0.0 mm to 6.0 mm × 12.0 mm / thickness 0.5 mm to 2.0 mm. The size of the flow path (groove) 11 of the glass chip 3 is about 0.2 mm to 2.0 mm in width / 0.2 mm to 1.0 mm in depth.

The size of the signal extraction wiring portion 10a of the flow rate detection unit 10 is as follows: width 0.7 mm to 1.5 mm / thickness 1 μm to 2 μm / length 0.5 mm to 2.5 mm (from the end of the flow path 11 to the sensor chip 2 And the size of the groove 3d is about 0.7 mm to 1.5 mm wide / 20 μm to 50 μm deep / 0.2 mm to 1.5 mm long.

The glass used for the glass chip 3 needs to have ion conductivity in order to perform anodic bonding, and preferably has a coefficient of thermal expansion close to that of the substrate (silicon) of the sensor chip 2. Borosilicate glass is suitable. Examples of borosilicate glass include glass called Pyrex (registered trademark) glass or Tempax glass. In this embodiment, the glass chip 3 uses Pyrex (registered trademark) glass. When silicon is used as the substrate of the sensor chip 2, the thermal expansion coefficient of silicon (2.3 × 10 ⁻⁶ / ° C.) and the thermal expansion coefficient of Pyrex (registered trademark) glass (3.2 × 10 ⁻⁶ / ° C.) Therefore, the distortion caused by the thermal stress at these joints can be reduced. Note that Pyrex (registered trademark) and Tempax have almost the same characteristics including the coefficient of thermal expansion, and either one may be used.

In addition, since anodic bonding is generally possible between metal (material having electrical conductivity) and glass (material having ion conductivity), the substrate of the sensor chip 2 is not limited to silicon but may be metal or the like. good.

Below, each joining structure and procedure of the sensor chip 2 and the glass chip 3 having the above-described configuration, and the groove 3d of the glass chip 3 and the signal extraction wiring portion 10a of the flow rate detection unit 10 will be described.

First, the groove 3d of the glass chip 3 is opened upward as shown in FIG. 7A, and the low melting point glass 12 is applied to the inner wall surface of the groove 3d as shown in FIG. Baking (hardening by volatilizing solvent etc.). The low melting point glass 12 can be applied by patterning the inner wall surface as the bonding surface of the groove 3d by, for example, screen printing or a dispenser. An appropriate amount of low-melting glass may be applied to the groove 3d and temporarily fired. An example of the low melting point glass is a frit glass. In this embodiment, the frit glass is used as the low melting point glass 12. The frit glass used in this example has a thermal expansion coefficient of 7.0 (˜16.0) × 10 ⁻⁶ / ° C. and a melting point of about 350 ° C. to 450 ° C.

Next, as shown in FIGS. 1 and 9, the glass chip 3 is placed on the silicon substrate 4 with the flow path 11 above the flow rate detection unit 10 and the arrangement direction of the temperature measuring element 7, the heater 6, and the temperature measuring element 8 (FIG. 3) and the signal extraction wiring portion 10a is extended from the lower side of the low melting point glass 12 in the groove 3d to the side of the cutout portion 3c, and the lower surface 3b is brought into contact with the upper surface 4a of the silicon substrate 4. Touch.

Next, as shown in FIGS. 8 to 10, the lower surface 3b of the glass chip 3 and the upper surface 4a of the silicon substrate 4 are bonded together by anodic bonding, and at the same time, the heat applied during the anodic bonding (about 350 ° C. to 420 ° C.). The low-melting glass 12 is melted to form a paste, and the gap between the groove 3d of the glass chip 3 and the signal extraction wiring portion 10a is filled and reliably adhered. In FIG. 8, the anodic bonding portion 13 is indicated by a bold line, and in FIG. 9, the anodic bonding region is indicated by A, and the adhesion region of the low melting point glass 12 is indicated by B.

Since the low melting point glass 12 is melted in a paste form and closely adheres to the step (concave portion) 9a of the insulating film 9 existing on the silicon substrate 4 as shown in FIG. 7C and FIG. Airtightness between 3d and the signal extraction wiring portion 10a of the flow rate detection unit 10 is ensured. In FIG. 7C, the anodic bonding portion 13 is indicated by a thick line. In this way, the flow sensor 1 is formed.

As a material of the low melting point glass 12, it is preferable to apply a material whose thermal expansion coefficient is close to that of the silicon chip 4 and the glass chip 3 formed of Pyrex (registered trademark) glass. For example, a material such as frit glass having a thermal expansion coefficient separated to some extent is used between the signal extraction wiring portion 10a of the flow rate detection portion 10 and the groove 3d, as long as it is used for a local and extremely small bonding area. However, the influence is extremely small, and the mismatch of thermal expansion coefficients can be alleviated.

In this way, airtightness can be secured by adhering a minute gap between the signal extraction wiring portion 10a of the flow rate detection portion 10 and the groove 3d with the low melting point glass 12, and other bonding, that is, FIG. The bonding strength of the entire flow sensor can be ensured by bonding the upper surface of the silicon substrate 4 and the lower surface of the glass chip 3 indicated by the bonding region A by anodic bonding.

Further, if the low melting point glass 12 is used as an adhesive for bonding the inner wall surface of the groove 3d of the glass chip 3 and the signal extraction wiring portion 10a of the flow rate detection unit 10, it becomes glass after curing. Generation of measurement errors due to degassing and contamination of the measurement fluid can be prevented.

The flow sensor 1 causes a fluid such as a gas to flow on the flow rate detection unit 10 from the end 11a toward the end 11b, for example, in the flow path 11 of the glass chip 3 shown in FIGS. Energize the heater 6. The heater 6 is heated by a certain temperature higher than the fluid temperature measured by an ambient temperature sensor (not shown) provided on the silicon substrate 4 by the heater control circuit, and heats the gas flowing through the flow rate detection unit 10 and the flow path 11. When there is no flow, a uniform temperature distribution is formed on the upstream / downstream side of the heater 6, and the upstream temperature measuring element 7 and the downstream temperature measuring element 8 have resistance values corresponding to substantially equal temperatures. Indicates. On the other hand, when there is a flow, the uniform temperature distribution on the upstream / downstream side of the heater 6 is broken, the temperature on the upstream side becomes low, and the temperature on the downstream side becomes high.

Although not described in detail here, the upstream temperature measuring element 7 and the downstream temperature measuring element 8 are connected by a Wheatstone bridge circuit constituted by the upstream temperature measuring element 7 and the downstream temperature measuring element 8. A resistance value difference, that is, a temperature difference is detected, and the flow rate of the gas flowing in the flow path 11 is measured.

The flow sensor 1 includes a glass chip 3 made of transparent glass and a flow path 1.
Since the inner wall surface of 1 is a smooth surface, the flow rate detection unit 10 can be easily observed from the outside of the glass chip 3. For example, fine dust of about 100 μm enters the flow path 11 mixed with gas. Even if it adheres to the flow rate detection unit 10, it can be directly observed from the outside. Thereby, it becomes possible to detect the abnormality of the flow sensor 1 quickly.

Subsequently, a modified example of the above-described embodiment will be described. FIG. 11 shows a modification of the flow sensor according to the present invention. The flow sensor 1 has a length of the low melting point glass 12 that bonds the groove 3d of the glass chip 3 and the signal extraction wiring portion 10a of the flow rate detection unit 10. The bonding area is reduced by shortening the length of the groove 3d. Thereby, the adhesion region C by the low melting point glass 12 can be made smaller than the adhesion region B shown in FIG. 10, and accordingly, the thermal expansion coefficients of the glass chip 3, the silicon substrate 4 and the low melting point glass 12 are inconsistent. Can be further relaxed.

In the above embodiment, the case where the indirectly heated flow rate detection unit 10 is configured by one heater (heating element) 6 and two temperature measuring elements 7 and 8 arranged on both sides of the heater 6 is described. However, the present invention is not limited to this, and one heating element / temperature measuring element, that is, one heater may constitute a self-heating type flow rate detection unit, or two heating elements / temperature measuring elements, That is, a self-heating type flow rate detection unit may be configured by two heaters.

The structure of the flow rate detection unit 10 may be a diaphragm structure in which the insulating films 5 and 9 cover the concave portion 4b of the silicon substrate 4 as in the above embodiment, or the insulating films 5 and 9 are concave portions 4b of the silicon substrate 4. A bridge structure that covers at least a part of the structure may be used.

It is a perspective view concerning one embodiment of a flow sensor of the present invention. It is a top view of the sensor chip of the flow sensor shown in FIG. 1, and is a top view of the state which formed the insulating film and the flow volume detection part on the upper surface of the silicon substrate. It is a top view which shows the state which formed and coat | covered the insulating film on the insulating film and flow-rate detection part which were shown in FIG. FIG. 4 is a cross-sectional view of the sensor chip shown in FIG. 3 taken along an arrow IV-IV. It is a bottom view of the glass chip of the flow sensor shown in FIG. It is sectional drawing which follows the arrow line VI-VI of the glass chip | tip shown in FIG. It is explanatory drawing of the bonding process of the groove | channel of a glass chip, and the signal extraction wiring part of a flow volume detection part of the sensor chip and glass chip of the flow sensor shown in FIG. It is sectional drawing which follows the arrow VIII-VIII of the flow sensor shown in FIG. It is sectional drawing which follows the arrow IX-IX of the flow sensor shown in FIG. It is sectional drawing which follows the arrow XX of the flow sensor shown in FIG. It is explanatory drawing which shows the modification of the flow sensor which concerns on this invention, and shows the junction part of a sensor chip and a glass chip, and the adhesion part of the signal extraction wiring part of a flow volume detection part, and the groove | channel of a glass chip.

DESCRIPTION OF SYMBOLS 1 Flow sensor 2 Sensor chip 3 Glass chip (cover member) 3a Upper surface 3b Lower surface 3c Notch 3d Groove 4 Silicon substrate 4a Upper surface 4b Recessed part 5 Insulating film 6 Heater (heating element) 7, 8 Temperature measuring element 6a, 6b, 7a, 7b, 8a, 8b Lead pattern 9 Insulating film 9a Step 9b Electrode pad 10 Flow rate detection part 10a Signal extraction wiring part 11 Flow path 11a, 11b End part 12 Low melting point glass 13 Anode joining part A Anode joining area B, C Low melting point glass Bonding area

Claims (1)

It is a flow sensor configured by joining a sensor chip and a glass cover member,
The sensor chip is a substrate in which a flow rate detection unit and signal extraction wiring units extending on both sides of the flow rate detection unit are formed,
The cover member is notched in each of a flow path for flowing a fluid to be measured on the flow rate detection unit along a longitudinal direction in the center of a surface to be joined to the sensor chip, and a side wall located in an orthogonal direction of the flow path. In the flow sensor in which the part is formed,
One end of the signal extraction wiring portion and the other end are located in the cutout portion formed in the extending direction, respectively.
A groove is formed in the cover member along the extending direction of the signal extraction wiring portion,
The signal extraction wiring portion is inserted through the groove,
The gap between the groove of the cover member and the signal extraction wiring of the detection unit is filled with low melting point glass,
A flow sensor characterized in that other bonding regions are bonded by anodic bonding.