JP2001356063A - Production method of capacity type pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the deflection of a diaphragm generated in a production process. SOLUTION: The temperature of a wafer 2 with a plurality of mobile electrodes 2a formed thereon is raised higher than the temperature of a wafer 1 with a plurality of fixed electrodes 1 thereon. Then, the wafers 1 and 2 are joined together and the joined wafers 1 and 2 are cut off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method of manufacturing a capacitive pressure sensor.

[0002]

2. Description of the Related Art In a capacitive pressure sensor, a fixed electrode formed on a base and a movable electrode formed on a diaphragm include:
A capacitance is formed by opposing each other, and a change in pressure is detected based on the change in capacitance. In addition, sapphire may be used for a diaphragm or a base because of its excellent corrosion resistance and the like.

FIG. 3A is a plan view showing a general capacitive pressure sensor, and FIG. 3B is a sectional view taken along line AA '. As shown in these figures, the pressure sensor 110 includes a base 101 having a fixed electrode 101a provided in a recess, a movable electrode 102a, a reference electrode 102b, and a pad 102.
diaphragm 10 provided with c, 102d, 102e
2 and lead wires 103a and 103b connected to each pad and formed by solder, and the lead wire from the pad 102c is hidden. Note that the reference electrode 102b is used to obtain a reference capacitance. Also,
The pad 102f is a dummy, and a lead wire made of solder is not taken out.

[0004] The pressure sensor 110 thus configured
The diaphragm 102 bends according to the pressure difference between the outside of the sensor and the capacitance chamber, and the capacitance changes due to the change in the distance between the movable electrode 102a and the fixed electrode 101a, and the pressure is measured.

Here, a conventional manufacturing process of the pressure sensor 110 will be described. First, two sapphire wafers are prepared, a base is formed on one wafer, and a diaphragm is formed on the other wafer. That is, one of the sapphire wafers is machined, laser-processed or ultrasonically processed to open through holes for forming the lead wires 103a and 103b for each sensor chip.
Next, a recess is formed for each sensor chip by dry etching, and then the fixed electrode 101a is formed by vapor deposition or the like. As a result, a plurality of fixed electrodes are formed on the sapphire wafer.

On the other hand, a plurality of movable electrodes 102a,
The reference electrode 102b and the pads 102c to 102f are formed. Then, these two wafers are placed in each fixed electrode 1.
After the alignment is performed so that the movable electrode 01a and the movable electrode 102a face each other, direct bonding is performed under a predetermined heating atmosphere.
After the direct bonding, the sapphire wafer on the base 101 side is turned to the upper surface, and then a granular solid solder is placed in the through hole, melted by heating, and the lead wire 103a is melted by the molten solder flowing into the through hole. , 103b
Is formed and connected to the pads 2d and 2f. Finally, by dicing the sapphire wafer, the sensor
A chip is completed.

[0007] Through the above steps, a sapphire capacitive pressure sensor excellent in corrosion resistance can be easily mass-produced conventionally.

[0008]

However, in a so-called micro-pressure sensor, the diaphragm tends to be made thinner (for example, about 50 μm) in order to improve the measurement sensitivity. However, there is a problem that it is bent. on the other hand,
In order to increase the capacity, the area of each electrode (the fixed electrode 101a and the movable electrode 102a) tends to be large and the interval between the electrodes tends to be narrow (several μm). Therefore, even if the diaphragm is slightly bent, the electrodes are short-circuited to each other, which causes a decrease in the yield of the sensor. If the deflection is slight, it is possible to correct the measurement result at the signal processing stage.However, in the state where the deflection has occurred, the point of zero pressure has already been shifted, so when the diaphragm receives pressure, There is a problem in that there is no allowance for bending and the range of measurable pressure is narrowed. Further, in such a sensor, the point of zero pressure shifts due to the secular change of the degree of bending, and the quality is deteriorated.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a method of manufacturing a capacitive pressure sensor capable of easily suppressing the deflection of a diaphragm caused during manufacturing.

[0010]

In order to achieve the above object, a method of manufacturing a capacitive pressure sensor according to the present invention comprises: a pressure receiving diaphragm having a movable electrode; a fixed electrode; In the capacitive pressure sensor having a base joined to the diaphragm, the temperature of the first wafer on which the plurality of movable electrodes are formed is higher than the temperature of the second wafer on which the plurality of fixed electrodes are formed. After that, the first and second wafers are joined, and the joined wafers are cut.

Further, the present invention includes the following configuration as another embodiment. That is, a first reference point is provided on the first wafer, a plurality of movable electrodes are laid out on the first wafer based on the first reference point, and a second reference point is provided on the second wafer. And laying out a plurality of fixed electrodes on a second wafer based on the second reference point, wherein the layout includes a movable electrode on the first wafer that has been thermally expanded, and a layout on the second wafer. This is carried out so as to prevent a displacement during bonding with the fixed electrode. The wafer is made of sapphire, silicon, glass or diamond. Further, the first and second
The temperature difference between the wafers is 50 ° C. or more and 150 ° C. or less.

Therefore, according to the present invention, since the diaphragm that has been thermally expanded contracts after joining, it is possible to prevent the diaphragm from being bent. In addition, by laying out the movable electrode and the fixed electrode in consideration of thermal expansion, it is possible to prevent a displacement that occurs at the time of bonding.

[0013]

Next, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram for explaining a method of manufacturing a capacitive pressure sensor according to one embodiment of the present invention. As shown in the drawing, the manufacturing method according to the present embodiment includes a wafer holding mechanism 3 provided with a heater 3a, a temperature control means 5 for controlling the temperature of heat generated by the heater 3a, and a wafer holding mechanism provided with a heater 4a. 4
And temperature control means 6 for controlling the temperature of heat generated by the heater 4a. The wafer holding mechanisms 3 and 4
Both are provided with an electrostatic chuck, a vacuum chuck or the like, and can temporarily fix and hold the placed wafers 1 and 2, and can move the placed wafers and bond them to each other.

The wafer holding mechanisms 3 and 4 include a heater 3
a, 4a and temperature sensors 3b, 4b.
The temperature of the wafers 1 and 2 can be controlled to a desired temperature by generating heat from the a and 4a. That is, the temperature controllers 5 and 6 increase the temperature of the wafers 3a and 4a by energizing the heaters 3a and 4a, measure the temperatures of the wafers 1 and 2 using the temperature sensors 3b and 4b, and obtain the desired temperature. Then, the power supply to the heaters 3a and 4a is cut off. By this repetition, the temperature control means 5 and 6 control the temperature of the wafers 1 and 2 to be a temperature desired by the user.

Here, the manufacturing procedure according to the present embodiment will be described. First, as shown in FIG. 1A, a sapphire wafer 1 on the base side is placed on the wafer holding mechanism 3 and a sapphire wafer 2 on the diaphragm side is placed on the wafer holding mechanism 4. Then, the movable electrode 2a and the fixed electrode 1 previously formed on both wafers by a conventional method.
a is directly joined after facing each other. Direct bonding is performed only by overlapping mirror-polished wafers 1 and 2 by an intermolecular force, and can be firmly bonded by heating.

At the time of direct bonding, the heat generation of the heaters 3a and 4a is adjusted by the temperature control means 5 and 6, and the temperature of the wafer 2 on the diaphragm side is higher than the temperature of the wafer 1 on the base side (however, the temperature difference). Is controlled to be 50 ° C. or more and 150 ° C. or less). The reason for setting the temperature difference to 150 ° C. or less is that
This is to prevent the wafer bonded by heat shock from breaking, and the temperature is set to 50 ° C. or higher to sufficiently expand the wafer 2 on the diaphragm side. Alternatively, the temperature difference between both wafers may be controlled as described above after raising the temperature of both wafers to several hundred degrees, or the temperature of wafer 2 may be kept at room temperature without heating wafer 1. May be controlled.

As a result, the wafer 2 is directly bonded to the wafer 1 in a thermally expanded state, and after being removed from the wafer holding mechanism, the expanded wafer 2 contracts, as shown in FIG. The wafer 2 is bonded to the wafer 1 while maintaining a slight tension. Therefore, it is possible to prevent the wafer 2 from being bent. Thereafter, if the directly bonded wafer is diced, the pressure sensor 1
0 is completed.

Next, the layout of the movable electrode and the fixed electrode will be described. In the present invention, since the temperature of the wafer 2 on the diaphragm side is higher than that of the wafer 1 on the base side, the wafer 2 slightly expands more thermally than the wafer 1. Therefore, if multiple electrodes are laid out on each wafer,
If the layout is performed at the same interval, the positions of the electrodes may be shifted when they are laminated. Therefore, such a problem can be solved by laying out the electrodes in consideration of thermal expansion.

FIG. 2A is a plan view showing a wafer on which a plurality of movable electrodes and reference electrodes are formed, and FIG. 2B is a plan view showing a wafer on which a plurality of recesses and fixed electrodes are formed. The wafer 1 has a plurality of fixed electrodes 1a formed on the front side of the figure, and the wafer 2 has a plurality of movable electrodes 2a formed on the back side of the figure.
Are formed.

First, movable electrodes 2a are formed at equal intervals on the wafer 2 on the diaphragm side. On the other hand, if the wafers 1 on the base side are formed at equal intervals, when the wafers 2 are directly bonded, the fixed electrodes 1a and the movable electrodes 2a of the expanded wafers 2 are displaced. Then, the layout is performed by shifting the position of the fixed electrode 1a in advance. That is, the layout of the fixed electrode 1a is adjusted according to the distance from the reference point in the drawing and the coefficient of thermal expansion of the wafer 2, and the positional deviation increases as the distance from the reference point increases. Increase the electrode spacing (horizontal and vertical). Expressing this relationship as an equation,
x1 <x2 <x3 <x4 <x5 <x6 <x7 <x8, y8 <y7 <y6 <y5 <y4 <y3 <y2 <y1
Becomes

After that, the reference points in the figure and other alignment marks (not shown)
2 are directly bonded, and the directly bonded wafers are diced to complete a sensor chip. In addition,
Obviously, instead of increasing the distance between the fixed electrodes laid out on the wafer 1 on the base side as described above, the distance between the movable electrodes 2a laid out on the wafer 2 on the diaphragm side may be narrowed. . Further, the position at which the reference point is provided is not limited to the position shown in FIG. 2. For example, if the reference point is provided at the center of the wafer, the amount of displacement during layout can be minimized. Further, in the above, only the position of the electrode is shifted, and the size of the electrode is not changed. However, the size of each electrode may be changed in consideration of thermal expansion.

In the above, the case where sapphire is used as the material of the diaphragm and the base has been described, but the present invention is not limited to this. For example, a single crystal material such as silicon, glass, or diamond may be used. Further, the reference electrode is not an essential component, and may be added as needed. Therefore, the present invention includes a configuration using only the movable electrode and the fixed electrode.

[0023]

As described above, according to the present invention, the temperature of the first wafer for forming the pressure receiving diaphragm is made higher than the temperature of the second wafer for forming the base. Therefore, since the first and second wafers are joined, the diaphragm that has been thermally expanded after the joining contracts, so that it is possible to prevent the diaphragm from being bent. In addition, by laying out the movable electrode and the fixed electrode in consideration of thermal expansion, it is possible to prevent a displacement that occurs at the time of bonding.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a method of manufacturing a capacitive pressure sensor according to one embodiment of the present invention.

FIG. 2A is a plan view showing a wafer on which a plurality of movable electrodes and reference electrodes are formed (each electrode is formed on the back surface of the wafer); FIG. 3 is a plan view showing the wafer (each electrode is formed on the surface of the wafer).

3A is a plan view illustrating a general capacitive pressure sensor, and FIG. 3B is a cross-sectional view taken along line AA ′.

FIG. 4 is a cross-sectional view showing a pressure sensor (in a state where no pressure is applied) manufactured by a conventional manufacturing method.

[Explanation of symbols]

1, 2,... Wafer, 3, 4,... Wafer holding mechanism, 3a, 4a
.. Heater, 3b, 4b temperature sensor, 5, 6 temperature control means, 10 pressure sensor.

Claims (4)

[Claims] 1. A capacitive pressure sensor having a pressure receiving diaphragm on which a movable electrode is formed, and a base on which a fixed electrode is formed and joined to the diaphragm, wherein a first electrode on which a plurality of the movable electrodes are formed is provided. Wafer temperature,
A temperature sensor that is heated to a temperature higher than a temperature of a second wafer on which the plurality of fixed electrodes are formed, and then joins the first and second wafers and cuts the joined wafers. Manufacturing method. 2. The method according to claim 1, wherein a first reference point is provided on the first wafer, and a plurality of movable electrodes are laid out on the first wafer based on the first reference point. A second reference point is provided on the wafer, and a plurality of fixed electrodes are laid out on the second wafer based on the second reference point. The layout includes a movable electrode on the first wafer that has been thermally expanded. And a method for preventing displacement during bonding with the fixed electrode on the second wafer. 3. The method according to claim 1, wherein the wafer is made of sapphire, silicon, glass, or diamond. 4. The method according to claim 1, wherein the temperature difference between the first and second wafers is 50 ° C. or more and 15 ° C.
A method for manufacturing a capacitive pressure sensor, wherein the temperature is set to 0 ° C. or lower.