JPH0888154A - Anode-junction device - Google Patents

Abstract

PURPOSE: To reduce a junction interfacial stress, which is generated in the anode junction between a silicon wafer and a glass member. CONSTITUTION: An anode-junction device has a silicon wafer 1, which is heated and is abutted against a glass member 2, the glass member 2, a DC voltage power supply 9 for applying a voltage between a first electrode plate 41 , which is abutted against the wafer 1, and a second electrode plate 5 which is abutted on the back surface to the surface, which is abutted on the wafer 1, of the member 2, a control part 11 comprising a polarity change-over switch 11a for changing over the polarity of a DC voltage which is applied to the electrode plates 4 and 5, a current monitor 10 for monitoring a current between the electrode plates 4 and 5 and an arithmetic part 12 comprising means for calculating the amount of a charge transferred within the member 2. The control part 11 gives an indication to the power supply 9 so as to invert the polarity to apply the voltage between the plates 4 and 5 on the basis of the amount of the charge transferred while the voltage is applied to the plates 4 and 5 using the plate 4 as an anode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anodic bonding apparatus for bonding a silicon wafer and a glass substrate in manufacturing a semiconductor device.

[0002]

2. Description of the Related Art An anodic bonding method in which silicon is used as an anode and glass is used as a cathode and both members are heated to about 400 ° C. and a direct current voltage of several hundred volts is applied to join the contact surfaces of both members The feature is that they can be joined without using an adhesive. Further, since the adhesive does not intervene between the silicon member and the glass substrate, the joining distance between both members can be controlled with high accuracy. Such characteristics are configured such that the silicon member and the glass substrate are opposed to each other, a part of them is bonded by the anodic bonding method, and the other part has electrodes fixed to the respective members and has a predetermined minute gap. It is suitable for a capacitance detection sensor. In this capacitance detection sensor, the silicon member is composed of a beam extending from the frame and a weight provided at the tip thereof, and one electrode (movable electrode) is fixed to this weight portion. Further, the other electrode (fixed electrode) is provided on the surface of the glass substrate so as to face this electrode, and the capacitance detection sensor captures a change in the distance between these electrodes as a change in capacitance. Therefore, it is necessary to control the distance between both electrodes with high accuracy. For this reason, as described above, the anodic bonding method is used to bond the silicon member of the capacitance detection sensor and the glass substrate.

FIG. 9 shows the basic structure of a conventional anodic bonding apparatus. A heater 6 for heating members to be joined, a temperature sensor 7 for detecting the temperature of the heater, a temperature controller 8 for controlling the temperature of the heater 6, and a first electrode plate 4 placed on the heater 6. A second electrode plate 5 arranged so as to face the first electrode plate 4 with a joining member interposed therebetween, a DC voltage power supply 9 for applying a voltage to the joining member, and a current flowing through the joining member when energized. It comprises a current monitor 10 for monitoring. Next, the joining method will be described. Drive the temperature controller 8,
The silicon wafer 1, the glass substrate 2,
The dummy glass 3 is heated to a desired temperature. And the first
Of the silicon wafer 1 by applying a desired DC voltage with the second electrode plate 5 as the cathode and the second electrode plate 5 as the anode.
And the contact surface of the glass substrate 2 are joined. In general, the glass substrate 2 and the dummy glass 3 are made of Pyrex glass whose coefficient of thermal expansion of the silicon wafer is slightly smaller than that of the silicon wafer. Then, after the joining process is completed, the dummy glass 3 is removed.

The dummy glass 3 is used to prevent the zero point variation of the sensor due to deterioration of moisture resistance. In other words, as a result of the temperature and DC voltage application increasing the sodium ion concentration on the glass surface in contact with the cathode electrode, the coefficient of thermal expansion changes and the zero point fluctuation of the sensor caused by absorption of ambient moisture is prevented. It is used to The change in the coefficient of thermal expansion and the absorption of water cause local stress on the glass substrate, resulting in warpage of the chip such as the capacitance detection sensor, which changes the distance between the movable electrode and the fixed electrode. It is known to cause fluctuations.

Between the anodic-bonded members, stress is generated at the bonding interface due to the difference in thermal expansion coefficient between the two members. The mechanism of anodic bonding and the factors that cause the bonding interface stress will be described using the bonding of silicon and Pyrex glass. By applying temperature and DC voltage, sodium ions in the Pyrex glass substrate move to the cathode side, a space charge layer is formed at the junction interface of the Pyrex glass substrate, and a high electric field is generated. This electric field causes electrostatic attraction between the silicon wafer and the Pyrex glass substrate, resulting in close contact. Then, the OH groups on the surface of the silicon wafer and the Pyrex glass substrate are bonded and further dehydrated by heat, and the silicon wafer and the Pyrex glass substrate are bonded by Si—O covalent bonding. The space charge layer is a sodium ion deficient layer, and this layer has a smaller thermal expansion coefficient than the original Pyrex glass base material. Occurs. Therefore, there are two types of stress at the bonding portion of the glass substrate made of Pyrex glass: thermal stress generated by the difference in thermal expansion coefficient of the bonding member and bonding interface stress generated by the movement of sodium ions in the Pyrex glass. Will be applied.

When a silicon wafer on which a structure composed of a diaphragm, a beam and a weight is formed by etching, and a glass substrate on which electrodes and the like are patterned are anodically bonded to manufacture a pressure sensor or an acceleration sensor of capacitance detection type, Deformation of the structure due to the stress of, and the spring constant of the structure changes with the temperature change due to the temperature dependence of the stress,
There was a problem that the sensor characteristics deteriorate. Regarding reduction of thermal stress caused by the difference in thermal expansion coefficient, Japanese Patent Application Laid-Open No. Hei 4-
There is provided a glass material matched to the thermal expansion coefficient of silicon disclosed in Japanese Patent No. 83733. However, since the stress generated at the bonding interface is related to the movement of mobile ions in the glass as described above, even if a glass material matching the thermal expansion coefficient of silicon is used, it is possible to avoid the stress generation. Can not.

[0007]

The anodic bonding of silicon and glass is performed as described above, and in the conventional anodic bonding apparatus, the stress generated at the bonding interface lowers the yield and characteristics of the semiconductor sensor. There was a problem.

The present invention has been made in view of the above problems, and an object thereof is to provide an anodic bonding apparatus which can reduce the bonding interface stress generated during anodic bonding between silicon and glass.

[0009]

The anodic bonding apparatus according to the present invention is a silicon wafer contact surface of a glass member including a first electrode that contacts the silicon wafer and movable ions that contact the silicon wafer. A second electrode in contact with the back surface of the first electrode, a DC voltage power supply for applying a DC voltage to the first and second electrodes, a controller for controlling the output voltage of the DC voltage power supply, the silicon wafer and the glass Heating means for heating a member, a current monitor for monitoring a current flowing between the first and second electrodes, and a mobile charge amount calculating means for calculating a mobile charge amount in the glass member based on an output of the current monitor. And switching means for switching the polarities of the first electrode and the second electrode,
The control unit performs a bonding process of controlling the DC voltage power supply and applying a predetermined voltage for a predetermined time by using the first electrode as an anode, and after the bonding process is completed, the bonding process calculated by the mobile charge amount calculating unit. A stress reducing step of applying a voltage with the first electrode as a cathode is carried out based on the amount of mobile charge therein.

Another anodic bonding apparatus according to the present invention is a silicon wafer contacting device comprising a first electrode contacting a silicon wafer and a first glass member including movable ions contacting the surface of the silicon wafer. A second electrode that abuts the back surface with respect to the surface, a third electrode that abuts the back surface of the second glass member including movable ions that abuts the back surface of the silicon wafer, and abuts the back surface of the silicon wafer, and the first electrode. And a second electrode, and between the first and third electrodes, a DC voltage power supply for applying a DC voltage, a controller for controlling the output voltage of the DC voltage power supply, the silicon wafer, and A heating means for heating the insulating member; a current monitor for monitoring a current flowing between the first and second electrodes; and a current flowing between the first and third electrodes; It has a mobile charge amount calculating means for calculating the mobile charge amount in the first and second glass members, and a switching means for switching the polarities of the first electrode and the second and third electrodes, The control unit performs a bonding step of controlling the DC voltage power source and applying a predetermined voltage for a predetermined time by using the first electrode as an anode, and after the bonding step is completed, during the bonding step calculated by the mobile charge amount calculating means. The stress reducing step of applying a voltage with the first electrode as a cathode is carried out based on the amount of the mobile charges.

Further, in each of the above anodic bonding devices,
The control unit may perform a stress reducing step of moving an electric charge amount that is substantially equal to the electric charge amount that has been calculated by the moving electric charge amount calculation means during the bonding process.

The present invention will be described more specifically. When a silicon wafer and a glass member are brought into contact with each other and these two members are heated and a DC voltage is applied, mobile ions (mainly sodium ions which are cations) in the glass member move to the cathode side. In the bonding step, since the DC voltage is applied so that the silicon wafer serves as the anode, the movable ions move to the second electrode side which is the back surface of the silicon wafer. On the other hand, mobile ions are reduced in the layer near the surface of the glass member that contacts the silicon wafer, and this layer becomes the space charge layer. A high electric field is generated by this space charge layer, an electrostatic attractive force is generated between the silicon wafer and the glass member, and these are brought into close contact with each other. Then, the silicon wafer and the OH group of the glass member are bonded to each other and further dehydrated by heat to form a Si—O covalent bond, thus completing the bonding of the two members.

At this time, as described above, the space charge layer is deficient in mobile ions (mainly, cations, sodium ions). Then, in order to re-supply the movable ions in this portion, in the present invention, after joining both members, the polarities are inverted and the DC voltage is applied again.
As a result, the mobile ions lacking in the space charge layer due to the anodic junction can be supplied to the space charge layer. By supplying mobile ions to the space charge layer, the space charge layer has characteristics that are the same as or close to the initial physical characteristics of the glass member, and the difference in the coefficient of thermal expansion from the silicon wafer is reduced. As a result, it is possible to reduce the compressive residual stress generated at the bonding interface when the temperature is returned to room temperature.

[0014]

According to the present invention, after the anodic bonding of the silicon wafer and the glass member containing the movable ions, the step of reducing the bonding interface stress for applying a DC voltage in the opposite direction to the bonding is performed, and It is possible to control so that the mobile ions are redistributed in the mobile ion deficient layer formed at the bonding interface, and reduce the bonding interface stress generated when cooled to normal temperature after anodic bonding. Therefore, the amount of deformation of the bonding member and the stress applied to the silicon wafer can be reduced, and the yield and characteristics of the semiconductor sensor can be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) A preferred embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows the basic structure of a preferred anodic bonding apparatus according to the present invention. The anodic bonding apparatus of the present invention includes a heater 6 for heating members to be joined, a temperature sensor 7 for detecting the temperature of the heater 6, a temperature controller 8 for controlling the temperature of the heater 6, and the heater 6. A first electrode plate 4 arranged on the upper side, and a second electrode plate 5 mounted so as to face the first electrode plate 4 via a joining member mounted on the first electrode plate 4, A DC voltage power source 9 for applying a voltage to the joining member, a current monitor 10 for monitoring the current flowing through the joining member at the time of joining, driving of the DC voltage power source 9 and the temperature controller 8,
A control unit 11 including a polarity change switch 11a for stopping and switching the polarity of the first electrode plate 4 and the second electrode plate 5 in the voltage application direction, and a calculation unit 12 for calculating the amount of charge in the glass that has moved during bonding. It consists of

The anodic bonding apparatus of the present invention has the above-mentioned structure. Next, a bonding method using this apparatus and a method for reducing stress generated at the bonding interface will be described.

In the apparatus shown in FIG. 1, a silicon wafer 1, a glass substrate 2 as a glass member, and a dummy glass 3 are placed in this order on a first electrode plate 4. At this time, the bonding surfaces of the silicon wafer 1 and the glass substrate 2 are brought into contact with each other. Next, the second electrode plate 5 is placed on the dummy glass 3. After the installation as described above, the polarities of the first and second electrode plates, the heating temperature of the heater 6, the DC voltage value applied to the joining member, the time from the start of heating to the application of the DC voltage, Enter the joining conditions such as voltage energization time. In addition, as the condition of the stress control process performed after the completion of joining,
The polarity of the second electrode plate, the heating temperature and the waiting time until the temperature is reached, the applied voltage in the reverse direction, and the ratio of the charge amount moved in the reverse direction to the charge amount moved at the time of bonding are input. Then, the joining process is started. The temperature controller 8 is driven by a joining process start signal from the control unit 11. The temperature controller 8 controls the heater 6 based on the detection signal of the temperature sensor 7 so as to reach the set temperature. When the preset time for applying the DC voltage is reached, the control unit 11 controls the polarity changeover switch 11a to control the first voltage.
The electrode plate 4 is an anode and the second electrode plate 5 is a cathode. After that, the control unit 11 drives the DC voltage power supply 9,
The set DC voltage is applied to the members to be joined, and electricity is continued for the set time. In this joining process, current monitor 1
The current waveform monitored at 0 is shown in FIG. Immediately after bonding, the mobile ions in the glass substrate 2 rapidly move and a current flows.
The current value decreases as the bonding progresses, and almost no current flows when the bonding is completed. Regarding the size of the joining member and the joining conditions, the time from the start of energization to the completion of joining is obtained in advance and is input to the control unit 11 as described above. The amount of charge transferred in the joining process corresponds to the area A in FIG. This area A is calculated by the calculation unit 12,
Calculate the amount of charge.

The step of reducing the joint interface stress will be described. When the set energization time has elapsed, the control unit 11 stops the DC voltage power supply 9. Next, the control unit 11 transmits a signal to the temperature controller 8 so as to reach the set heating temperature in the stress reducing process. When the set waiting time elapses, the control unit 11 controls the polarity changeover switch 11a so that the first electrode plate 4 becomes the cathode and the second electrode plate 5 becomes the anode, and the set DC voltage is changed to the DC. Voltage power supply 9
Apply by. In the process of reducing the stress at the bonding interface, the calculation unit 12 continues to calculate the charge amount, and when the preset desired charge amount (corresponding to the area B in FIG. 2) is reached, the control unit 11 causes the DC voltage power supply 9 to operate. And the temperature controller 8 are stopped.

Next, a specific joining method and reduction of stress generated at the joining interface when this apparatus is used will be described.

In the anodic bonding apparatus shown in FIG. 1, a silicon wafer 1 having a diameter of 3 inches and a thickness of 0.3 mm is placed on the first electrode plate 4 placed on the heater 6, and the diameter of the silicon wafer 1 is placed on the silicon wafer 1. A Pyrex glass substrate 2 having a thickness of 3 inches and a thickness of 1 mm is stacked so that the joint surfaces of both members come into contact with each other. next,
A dummy glass 3 of Pyrex glass having a diameter of 3 inches and a thickness of 1 mm is placed on the glass substrate 2, and the second electrode plate 5 is placed on the dummy glass 3. Next, the conditions in the joining process and the stress control process are input to the control unit 11.

In this example, the following conditions were applied.
In the joining step, the first electrode plate 4 is used as an anode, the second electrode plate 5 is used as a cathode, the heating temperature is 350 ° C., and the DC voltage value is 6
00 volt, the time to apply DC voltage from the start of heating is 2
The energization time was 0 minutes and the direct current voltage was 20 minutes. In the stress control step, the first electrode plate 4 was used as the cathode and the second electrode plate 5 was used as the anode, and the heating temperature was 350 ° C. Since the heating temperature was the same as in the joining step, the waiting time was zero. The applied voltage value in the reverse direction is 300 V, and the amount of charge moved in the opposite direction is 1/100 of the amount of charge moved at the time of joining.
Was set. Then, the joining process is started. Control unit 11
The temperature controller 11 is driven by the joining process start signal from the. The temperature controller 8 controls the heater 6 based on the detection signal of the temperature sensor 12 so that the set temperature becomes 350 ° C. When the time for applying the DC voltage is reached, the control unit 11 causes the first electrode plate 4 to be the anode and the second electrode plate 5 to be the cathode. After that, the control unit 11 drives the DC voltage power supply 9, applies a DC voltage of 600 V to the members to be joined, and continues energizing for a set time. The current waveform monitored by the current monitor 10 in this joining process is shown in FIG.
Shown in Immediately after joining, sodium ions that are mobile ions in the Pyrex glass substrate 2 move and a current flows rapidly. The current value decreases as the bonding progresses, and almost no current flows when the bonding is completed.

FIG. 3 shows the Pyrex glass substrate 2 at this time.
Show internal behavior. A space charge layer, a so-called sodium ion deficient layer, is formed along with the movement of sodium ions. Since this layer has a smaller coefficient of thermal expansion than the Pyrex glass base material, compressive stress is generated at the bonding interface by returning the temperature to room temperature after bonding the silicon wafer 1 and the Pyrex glass substrate 2. The amount of charge transferred in the joining process corresponds to the area A in FIG. This area A is calculated by the calculation unit 12 to calculate the charge amount. The amount of charge transferred in this example was 2.5 coulombs.

The step of reducing the joint interface stress will be described. When the set energization time has elapsed, the control unit 11 stops the DC voltage power supply 9. Next, the control unit 11 switches the first electrode plate 4 to be the cathode and the second electrode plate 5 to be the anode, and applies a DC voltage of 300 V from the DC voltage power supply 9. In the process of reducing the stress at the bonding interface, the calculation unit 12 continues to calculate the charge amount, and when the amount of charge that has moved in the bonding process reaches 1/100, the control unit 11 drives the DC voltage power supply 9 and the temperature. The driving of the controller 8 is stopped. FIG. 4 shows the behavior inside the Pyrex glass substrate 2 in the stress reduction step. By applying a DC voltage in the direction opposite to that at the time of joining, sodium ions move to the sodium ion deficient layer 20 formed at the junction. The amount of electric charges moved in the opposite direction in the joining interface stress reduction step of this example is 0.025 coulomb.

It was found that a compressive stress of about 30 MPa was generated in the sodium ion deficient layer which was subjected to only the joining step of this example. The stress could be reduced to about 20 MPa by performing the stress reduction process of this example. Only the ratio of the amount of sodium ions moved in the opposite direction to the amount of sodium ions moved at the time of joining is 1/50,
When the stress reducing step was performed by changing the setting, the stress in the sodium ion deficient layer could be reduced to about 15 MPa. Also,
When the applied voltage value in the reverse direction is 600 V and the ratio of the amount of sodium ions moved in the opposite direction to the amount of sodium ions moved in the bonding is 1 and the stress reduction step is performed and the stress reduction step is performed, the sodium ion deficient layer Stress did not become zero, but could be reduced to about 3 MPa. further,
When the ratio of the amount of sodium ions moved in the opposite direction to the amount of sodium ions moved at the time of bonding is set to more than 1, sodium is deposited on the Pyrex glass substrate 2 at the bonding interface between the silicon wafer 1 and the Pyrex glass substrate 2 and cracks occur. There has occurred. From this result, in the step of reducing the bonding interface stress generated by anodic bonding, the ratio of the amount of charge moved in the opposite direction to the amount of charge moved at the time of bonding is desirable to be 1 or less, which can be controlled in the present invention. Understand the usefulness of anodic bonding equipment.

With respect to the joining member of this example, the joining strength of the joining member subjected only to the joining process and the joining member subjected to the stress reduction process were evaluated. As an evaluation method, a joining member was cut into a 10 mm square, and a jig was adhered to the opposite surfaces of the silicon 1 and the Pyrex glass substrate 2 to perform a tensile test. The measured sample has a bonding member that has undergone only the bonding step, and the amount of charge that has been moved in the opposite direction to the amount of charge that has moved during bonding is 1
There are three kinds of 1/00 and 1/50 joint members. The Pyrex glass substrate 2 destroyed the base material in all three types of samples. From this result, it was found that sufficient bonding strength can be obtained even if the stress reducing step is performed.

(Second Embodiment) A second preferred embodiment of the present invention will be described with reference to FIG. The members corresponding to those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted.

The heater 6, the temperature sensor 7, the temperature controller 8, the first electrode plate 25 connected to the silicon wafer, and the second electrode connected to the silicon wafer via an insulating member such as glass. The plate 26 and the third electrode plate 27 are composed of a DC voltage power supply 9, a current monitor 10, a controller 11, and a calculator 12.

Next, the joining method using this apparatus and the reduction of the stress generated at the joining interface will be described.

In the anodic bonding apparatus shown in FIG. 5, a lower dummy glass 3b having a diameter of 3 inches and a thickness of 1 mm is placed on the third electrode plate 27 mounted on the heater 6 and a lower portion having a diameter of 3 inches and a thickness of 1 mm. Pyrex glass substrate 2b, silicon wafer 1 having a diameter of 3 inches and a thickness of 0.3 mm, upper Pyrex glass substrate 2 having a diameter of 3 inches and a thickness of 1 mm
a, upper dummy glass 3a with a diameter of 3 inches and a thickness of 1 mm
In order. Next, the second electrode plate 26 is placed on the upper dummy glass 3a, and the first electrode plate 25 is placed on a part of the silicon wafer 1. The upper Pyrex glass substrate 2a and the upper dummy glass 3a are the first electrode plate 2
5 was partially removed in advance so that it could be placed on the silicon wafer 1. Next, the conditions in the joining process and the stress control process are input to the control unit 11. In this example, the following conditions were used. In the joining process, the third electrode plate 27 and the second electrode plate 2 are controlled by the polarity changeover switch 11a.
6 as a cathode and the first electrode plate 25 as an anode, and the heating temperature is 3
50 ° C, DC voltage value is 600 V, DC voltage is applied for 20 minutes from the start of heating, and DC voltage is energized for 2 minutes.
It was set to 0 minutes. In the stress control step, the third electrode plate 27 and the second electrode plate 26 are used as the anode and the first electrode plate 2 is used.
5 was used as the cathode, the heating temperature was 350 ° C., and the heating temperature was the same as in the bonding process, so the standby time was zero, the applied voltage value in the reverse direction was 300 V, and the reverse direction was applied to the amount of charge transferred during bonding. The amount of charge to be moved was set to 1/50. Then, the joining process is started. The temperature controller 8 is driven by a joining process start signal from the control unit 11. The temperature controller 8 controls the heater 6 based on the detection signal of the temperature sensor 7 so that the set temperature becomes 350 ° C. When the time for applying the DC voltage is reached, the control unit 11 causes the third electrode plate 27 and the second electrode plate 26 to be cathodes and the first electrode plate 25 to be an anode. After that, the control unit 11 drives the DC voltage power supply 9 to apply a DC voltage of 600 V to the members to be joined, and for a set time,
Continue to energize.

The step of reducing the joint interface stress will be described. When the set energization time has elapsed, the control unit 11 stops the DC voltage power supply 9. The amount of charge transferred in this example was 5.0 coulombs. Next, the control unit 11 controls the polarity changeover switch 11a so that the third electrode plate 27 and the second electrode plate 26 become the anode and the first electrode plate 25 becomes the cathode, and the DC voltage of 300 V is applied. Is applied by the DC voltage power supply 9. In the bonding interface stress reduction process, the calculation unit 12 continues to calculate the charge amount, and when the charge amount reaches 1/50 of the charge amount moved in the bonding process, the control unit 11 causes the DC voltage power supply 9 to operate. The driving and driving of the temperature controller 8 are stopped. The amount of charge moved in the opposite direction in the joint interface stress reduction step is 0.1 coulomb. In this example, since the Pyrex glass substrates 2a and 2b having substantially the same shape were anodically bonded to the upper and lower surfaces of the silicon wafer 1, the warpage of the bonding member caused by the stress was canceled out and was almost zero. However, the upper and lower Pyrex glass substrates 2a, 2 that have undergone only the bonding process
A compressive stress of about 30 MPa was generated in both the sodium ion deficient layers of b. The stress could be reduced to about 15 MPa by performing the stress reduction process of this example.

(Third Embodiment) A capacitive acceleration sensor manufactured using the anodic bonding apparatus of the present invention will be described.

Members and the like corresponding to those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 6 is a plan explanatory view showing the capacitive acceleration sensor, and FIGS. 7 and 8 are explanatory views of the AA cross section and the BB cross section shown in FIG. 6, respectively. ing. Silicon structure 4 of the capacitive acceleration sensor of this embodiment
0 is formed using single crystal silicon. The silicon structure 40 includes a silicon movable portion 41 including a beam 41a having a spring property formed by etching using an aqueous solution of potassium hydroxide (KOH) and a weight 41b functioning as a movable electrode. The first insulating film 4 is formed on the entire first bonding surface 40a of the silicon structure 40.
2, a silicon oxide film having a film thickness of 50 nm is formed. The movable electrode output terminal 43, the upper fixed electrode output terminal 44, the upper connection wiring 45, the upper fixed electrode output connection terminal 47, and the upper fixed electrode output terminal lead 48 have a thickness of 1 μm on the surface of the first insulating film 42. It is formed by forming an aluminum film of and forming a film by photoetching. Before forming these, an upper connection hole 46 is formed in a portion below the movable electrode output terminal 43 by photoetching so that the first insulating film 42 is opened so as to reach the silicon structure 40. Therefore, the upper fixed electrode output connection terminal 47 is connected to the silicon structure 40 via the movable electrode output terminal 43 and the upper fixed electrode output terminal 44. On the other hand, the second bonding surface 4 of the silicon structure 40
A silicon oxide film as the second insulating film 49 is formed in a film thickness of 50 nm over the entire region 0b. Then, a lower connection hole 67 is formed in a part of the second insulating film 49 by photoetching so as to open the second insulating film 49 to reach the silicon structure 40. Then, in the lower connection hole 67, a silicon connection terminal 68 made of an aluminum film having a thickness of 1 μm is formed.

First bonding surface 40a of silicon structure 40
The upper glass member 50 to be anodically bonded to is formed of Pyrex glass. The joint surface 50a of the upper glass member 50 is counterbored to a desired depth so as to cover the silicon movable portion 41 and the upper fixed electrode output connection terminal 47 of the silicon structure 40. Further, this counterbore processing is performed by the upper fixed electrode lead 5 of the upper glass member 50.
4 and the upper fixed electrode connection terminal 55 formation region. Then, an upper fixed electrode 52, an upper fixed electrode lead 54, and an upper fixed electrode connecting terminal 55 are formed as a titanium film having a thickness of 50 nm and an aluminum film having a thickness of 50 nm on the spot facing surface 51, and photoetching this. By doing so, patterning is performed. On the other hand, the silicon structure 4
The lower glass member 60 made of Pyrex glass, which is anodically bonded to the second bonding surface 40b of No. 0, is counterbored to a desired depth so as to cover the silicon movable portion 41 of the silicon structure 40. ing. This counterbore processing is also performed in the formation region of the lower fixed electrode lead 63 and the lower connection terminal 66 of the lower glass member 60. The lower fixed electrode 62, the lower fixed electrode lead 63, and the lower connection terminal 66 have a thickness of 50 nm on the spot facing surface 61.
The titanium film and the aluminum film having a thickness of 50 nm are formed and are formed by photoetching. In this embodiment, the spot facing is etched using a hydrogen fluoride solution.

Next, a method of joining the three joining members will be described.

The third electrode plate 27 is placed on the heater 6 and the lower dummy glass 100 is placed. The lower glass member 60 and the silicon structure 40 are superposed thereon so that their joint surfaces 60a and 40b contact each other. The alignment method at this time is performed by aligning the two corners of both members 60 and 40. As a result, the lower connection terminal 66 and the silicon connection terminal 68 are brought into contact with each other, and the lower glass member 60 and the silicon structure 40 are electrically connected. Next, the upper glass member 50 is placed on the silicon structure 40, and the bonding surface 40
A and 50a are overlapped so that they come into contact with each other, and alignment is performed.
The alignment method at this time is performed using an optical microscope from above the upper glass member 50. As a result, the upper fixed electrode output connection terminal 47 and the upper fixed electrode connection terminal 55 are brought into contact with each other, and the silicon structure 40 and the upper fixed electrode are electrically connected. The upper dummy glass 200 is placed on the upper glass member 50, and the second electrode plate 26 is placed thereon. The first electrode plate 25 is brought into contact with the movable electrode output terminal 43 of the silicon structure 40. After the installation, the conditions in the joining process and the stress control process are input to the control unit 11. In this example, the following conditions were used. In the joining step, the third electrode plate 27 and the second electrode plate 2
6 as a cathode and the first electrode plate 25 as an anode, and the heating temperature is 3
50 ° C, DC voltage value is 600 V, DC voltage is applied for 20 minutes from the start of heating, and DC voltage is energized for 2 minutes.
It was set to 0 minutes. In the stress control step, the third electrode plate 27 and the second electrode plate 26 are used as the anode and the third electrode plate 2 is used.
5 was used as a cathode, the heating temperature was 350 ° C., and the heating temperature was the same as that in the bonding process, so the standby time was zero, the applied voltage value in the reverse direction was 300 V, and the reverse direction to the amount of charge transferred during bonding. The amount of charge to be moved was set to 1/50. Then, the joining process is started. The temperature controller 8 is driven by a joining process start signal from the control unit 11. The temperature controller 8 controls the temperature of the heater 6 to 350 ° C. based on the detection signal of the temperature sensor 7. When the time to apply the DC voltage is reached, the control unit 1
1 controls the polarity selector switch 11a to control the third electrode plate 2
7 and the second electrode plate 26 are cathodes, and the third electrode plate 25 is an anode. After that, the control unit 11 drives the DC voltage power supply 9, applies a DC voltage of 600 V to the members to be joined, and keeps energizing for a set time.

The step of reducing the joint interface stress will be described. When the set energization time has elapsed, the control unit 11 stops the DC voltage power supply 9. The amount of charge transferred in this example was 0.05 coulomb. Next, the control unit 11 controls the polarity changeover switch 11a so that the third electrode plate 27 and the second electrode plate 26 become the anode and the first electrode plate 25 becomes the cathode, and the DC voltage of 300 V is applied. Is applied by the DC voltage power supply 9. In the process of reducing the stress at the bonding interface, the computer 12 continues to calculate the amount of electric charge, and the controller 11 drives the DC voltage power supply 9 at the time when the amount of 1/50 ions with respect to the amount of electric charge moved in the bonding process is reached. And the driving of the temperature controller 8 is stopped. The amount of charge moved in the opposite direction in the bonding interface stress reduction process is 0.00
It is one coulomb.

In the bonding step and the stress reducing step, since the silicon structure 40 and the upper fixed electrode 52 and the lower fixed electrode 62 have the same potential, it is possible to prevent the generation of electrostatic force due to the application of the DC voltage, and the silicon movable portion 41 is moved upward. There is no problem of being attracted to and fixed to the fixed electrode 52 or the lower fixed electrode 62, and the silicon structure 40, the upper glass member 40, and the lower glass member 50 are anodically bonded at their respective bonding surfaces 40a and 50a and 40b and 60a. It

After the joining process and the stress reducing process are completed, the upper connection wiring 45 and the lower connection wiring 65 are cut by dicing or laser to electrically separate the silicon structure 40 from the upper fixed electrode 52 and the lower fixed electrode 62. . As a result, the silicon movable part 41, the upper fixed electrode 52, and the lower fixed electrode 62, which are displaced by the acceleration application,
Highly sensitive acceleration measurement is possible by detecting the change in capacitance between the movable electrode output terminal 43, the upper fixed electrode output terminal 74 and the lower fixed electrode output terminal 64, which are connected to each other, and differentially outputting them. Becomes

In this embodiment, the size of one beam 41a of the silicon movable portion 40 is 670 μm in length and 250 μm in width.
m and the thickness is 10 μm. Also, the size of the weight 41b is 3
mm square, height 300 μm, two on each side of the weight,
A total of four beams were formed. Then, the upper glass member 40
And the counterbore depth of the lower glass member 60 is 1 μm. In order to evaluate the stress reduction process, the acceleration sensitivities of the capacitive acceleration sensor subjected to the bonding process and the stress reduction process and the capacitive acceleration sensor having only the bonding process were compared. Sensitivity measurement was performed using gravitational acceleration. The sensitivity of the capacitive acceleration sensor, which has been subjected to the stress reduction step, is 1.4 times that of the capacitive acceleration sensor only in the joining step. From this result, the usefulness of the anodic bonding apparatus of the present invention can be understood.

(Other Embodiments) In each of the above embodiments, the joining process and the stress reducing process are performed in the atmosphere. However, the present invention is not limited to this. Even if the joining step and the stress reducing step are performed in an inert gas, the effect of the present invention does not change. Further, in each of the above-described embodiments, the control unit 11 issues the electrode switching instruction, but the present invention is not limited to this, and other means such as manual operation may be used.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a first preferred embodiment of an anodic bonding apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing a waveform of a current flowing through a joining member.

FIG. 3 is an explanatory diagram illustrating behavior inside a glass substrate in a bonding step.

FIG. 4 is an explanatory diagram showing a behavior inside a glass substrate in a stress reducing step.

FIG. 5 is an explanatory view showing a second preferred embodiment of the anodic bonding apparatus according to the present invention.

FIG. 6 is an explanatory plan view of a capacitive acceleration sensor manufactured using the anodic bonding apparatus of the present invention.

FIG. 7 is an explanatory cross-sectional view of a capacitive acceleration sensor manufactured using the anodic bonding apparatus of the present invention.

FIG. 8 is a cross-sectional explanatory diagram of a capacitive acceleration sensor manufactured using the anodic bonding device of the present invention.

FIG. 9 is a schematic explanatory view showing a conventional anodic bonding apparatus.

[Explanation of symbols]

 4 1st electrode plate 5 2nd electrode plate 6 Heating heater 7 Temperature sensor 8 Temperature controller 9 DC voltage power supply 10 Current monitor 11 Control part 12 Computing part

Claims (3)

[Claims] 1. A first electrode abutting on a silicon wafer, a second electrode abutting on a back surface of a glass member containing movable ions abutting on the silicon wafer with respect to a silicon wafer abutting surface, and the first and second electrodes. A direct current voltage power supply for applying a direct current voltage to the second electrode, a control unit for controlling the output voltage of the direct current voltage power supply, a heating means for heating the silicon wafer and the glass member, the first and second A current monitor that monitors a current flowing between the electrodes, a mobile charge amount calculation unit that calculates the mobile charge amount in the glass member based on the output of the current monitor, and the polarities of the first electrode and the second electrode. An anodic bonding device comprising: switching means for switching. 2. A first electrode contacting the silicon wafer, and a second electrode contacting the back surface of the first glass member containing movable ions contacting the surface of the silicon wafer with respect to the silicon wafer contact surface. A third electrode that contacts the back surface of the second glass member including movable ions that contacts the back surface of the silicon wafer with respect to the silicon wafer contact surface; a space between the first and second electrodes; A direct-current voltage source for applying a direct-current voltage to each of the third electrode and the third electrode; a controller for controlling the output voltage of the direct-current voltage source; heating means for heating the silicon wafer and the insulating member; A current monitor for monitoring a current flowing between the first and second electrodes and between the first and third electrodes, and a movement within the first and second glass members based on an output of the current monitor A mobile charge amount calculating means for calculating the load volume, the first electrode, anodic bonding apparatus characterized by having a switching means for switching the polarity of said second and said third electrode. 3. The anodic bonding apparatus according to claim 1 or 2, wherein the controller moves a stress amount that is substantially equal to the charge amount calculated during the bonding step calculated by the mobile charge amount calculating means. An anodic bonding apparatus characterized by carrying out a reduction step.