JPH05326649A - Anode coupling system and electrode wiring method - Google Patents

Abstract

PURPOSE:To realize highly reliable coupling by providing a pair of heating/ power supply electrodes having a flat plane contacting with an object to be coupled thereby heating the object uniformly. CONSTITUTION:An object to be coupled is placed on a lower electrode 22 and an upper electrode 21 is lowered, and then power is fed to a sheath heater while holding the object between the electrodes 21, 22 thus heating the object. Upper and lower temperature control sections 11, 12 are provided independently in order to heat an anode coupling jig through a small sheath heater while controlling the temperature by means of a temperature detecting thermocouple. A copper heating part is heated through embedded PID control and in order to transmit heat produced from heating sections 23, 24 effectively to an object to be coupled, thermal capacity at power supply sections 27, 28 is lowered and copper having high thermal conductivity is employed. Furthermore, heat insulating materials 30, 31 are placed between the electrodes and housing in order to suppress heat transmission loss.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit manufacturing method for small sensors, actuators and the like to which anodic bonding technology is applied, and is applied to so-called micromachining technology.

[0002]

2. Description of the Related Art Micromachining technology is being developed for the practical application of the ultimate technology by innovating the concept of conventional mechanical technology. Anisotropic etching technology that has been cultivated in semiconductor manufacturing technology and anodic bonding technology, which form the technical field of the technology, and technology that enables the movement of substances at the atomic level, have been widely studied. However, on the other hand, in order to put the product into practical use, the conventional technology was changed to Nikkei Electronics No. 480P150-152 ('89 8.21)
As shown in, there are many technical problems. That is, in the anodic bonding technique, as shown in FIG. 6, an anodic bonding device having a flat plate electrode and a needle electrode with a one-sided heater structure is used. The thermal expansion coefficient of the joints is
Anodic bonding was possible as long as the materials had a uniform bonding temperature (high temperature) to room temperature. However, in the anodic bonding apparatus, the temperature difference between the surface temperature of the object to be contacted with the heater and the free surface of the object to be bonded was large, and residual stress was generated in the object after bonding was completed. Further, in the anodic bonding method, anodic bonding could not be performed if there were even irregularities on the interface between the objects to be bonded. Therefore, if a metal thin film for electrode wiring is present even in a part, stress is concentrated around the electrodes, the strength of anodic bonding is significantly reduced, and reliable bonding strength cannot be obtained. .

Further, the density of the electrode wiring connecting the layers to each other is low, and there is a drawback that the packaging density cannot be increased.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to reduce the residual stress caused by the temperature distribution generated in the conventional anodic bonding apparatus and increase the anodic bonding strength or alleviate the anodic bonding conditions. It also enables electrical wiring between anodic bonding materials.

[0005]

The present invention comprises an electrothermal heating means for contacting the material to be bonded from both sides in order to reduce the temperature distribution generated in the material to be bonded. This is to obtain a bond with little loss. Furthermore, the discharge phenomenon due to the high voltage applied in the anodic bonding step is utilized to interconnect the electrode wirings on the respective surfaces of the materials to be bonded.

[0006]

EXAMPLES Details of the present invention will be described below with reference to examples.

Example 1 A block diagram of an anodic bonding apparatus according to the present invention is shown in FIG. The functional part of the anodic bonding jig is shown in FIG. The upper heating / feeding electrode 21 and the lower heating / feeding electrode 22 that come into contact with the article 1 are the sheath heater 25,
It comprises heating parts 23 and 24 containing 26 and power feeding parts 27 and 28 for applying a voltage to the object to be joined, and the surface of the power feeding part in contact with the object to be joined is flat. After the article to be joined 1 is placed on the lower electrode (the heating / power feeding electrode is abbreviated as an electrode) 22, the air cylinder 29 is operated to move down the upper electrode 21 to sandwich the article to be joined, The sheath heater is energized to heat the object to be joined by the electrode to a predetermined temperature. In order to minimize the cycle time of anodic bonding, rapid heating in a short time and stable temperature control with less ripple are required. For this reason, the upper temperature control unit 11 and the lower temperature control unit 12 are provided independently, and the capacitance 3 is controlled while the temperature is controlled by the temperature detecting thermocouple.
The anodic bonding jig is heated by a small 00 W sheath heater. The heating portion made of copper or aluminum is embedded and heated by PID control.
In order to effectively transfer the heat generated in 4 to the object to be welded 1,
The heat capacity of the power supply parts 27 and 28 is small (thin design)
However, copper, aluminum, or ceramics is used as a material having good thermal conductivity.

Further, in order to prevent heat conduction loss to the outer casing as much as possible, heat insulating materials 30 and 31 are provided between the electrodes and the outer casing.
To use. Here, free-cutting ceramics having low thermal conductivity was used.

In order to perform anodic bonding of a silicon wafer having a diameter of 3 inches as a material to be bonded and borosilicate glass, the temperature is set to 250 to 300 ° C. and the voltage of the power supply 14 is set to direct current 30.
It was possible to obtain a bonding strength exceeding the breaking strength of glass by setting it to 0 volt and taking 10 minutes for the temperature raising step and the bonding step.

In order to carry out the joining at a high voltage exceeding the joining voltage, an insulator 32 having a higher breakdown voltage is required between the heating section and the voltage applying section. Therefore, an insulating ceramic plate is installed between the heating unit and the power feeding unit. The location may be on either side of the upper and lower parts of the joining jig, but by placing it on the upper side as shown in the figure, it plays a dominant role in heating the objects to be joined, that is, conductive heating and convection heating. The lower heating electrode can be efficiently functioned. As a result, the anodic bonding between the sapphire glasses using the ITO thin film as the bonding film could be bonded by applying a high voltage of 1,000 volts.

(Embodiment 2) An electrode wiring method during anodic bonding according to the present invention will be described. Here, the object to be bonded is composed of a 4-inch diameter silicon wafer having a three-dimensional shape formed by etching and electrode wiring, and a borosilicate glass substrate. These objects to be bonded are aligned / temporarily bonded after cleaning and set on the lower electrode of the anodic bonding jig. After lowering the upper electrode to sandwich the object to be bonded, the sheath heater is energized to raise the temperature to 300 ° C. in about 3 minutes. When the temperature of the object to be bonded is stable, a DC voltage of 600 V is applied between the upper and lower electrodes. Immediately after applying the voltage, as shown in FIG. 3, positive ions are injected from the silicon substrate side, while negative ions are induced on the surface of the borosilicate glass substrate facing the silicon substrate, and the borosilicate glass substrate and the silicon substrate are Attract each other by electrostatic force. In addition, since the electric resistance of the borosilicate glass decreases and becomes electrically conductive at high temperature, electric charges having different polarities are concentrated on the unbonded interface between the borosilicate glass substrate and the silicon substrate, and the electrostatic attraction occurs. As the above progresses, the substance moves in the vicinity of the electrostatic adsorption interface and the joining progresses. The current value during the bonding between the borosilicate glass and the silicon wafer decreases with the passage of time after passing the peak. When the measured current was below 1/5 of the initial peak current value, the end point of anodic bonding was determined, and the required time was 5 minutes.

As a result, sufficient bonding strength with few voids on the entire surface could be obtained.

In the anodic bonding apparatus according to the present invention, since the upper and lower heaters are respectively provided to suppress the temperature distribution in the sample, the residual stress is reduced and the good bonding strength is achieved in combination with the uniform electric field to the entire bonded sample by the plate electrode. Is obtained.

Next, the electrode wiring method of the present invention will be described. FIG. 4 shows a perspective view of a unit cell of the borosilicate glass substrate 41 and the silicon substrate 42 which are bonded to each other, and FIG. 5 shows a cross section of the electrode conducting portion before discharge conducting connection. In these substrates, electrode wirings 43 and 4 each made of a 1500A-thick gold electrode with chromium of a 1500A-thickness as a base on the surfaces of the substrates facing each other as electric wiring electrode materials.
4 and 45 (hereinafter abbreviated as Cr-Au electrodes). In the anodic bonding of substrates having protrusions with an electrode having a film thickness of 3000A, the protrusions may cause cracks in the substrates or the bonding force may be significantly reduced. Therefore, the substrate of the conductive connection portion is partially etched to form the etching groove 48 for accommodating the protrusion of the wiring electrode. In the illustrated example, the etching groove is provided on the silicon substrate, but it may be on the glass side. The Cr-Au electrode 44 on the silicon wafer has a silicon oxide film 46 as an insulating film between itself and the silicon substrate. A part of the oxide film is removed to remove the Cr-Au electrode.
Contact hole 47 for electrically connecting the electrode and the silicon substrate
have.

Under this electrode wiring structure, when a high voltage is applied for the bonding, electric charges are induced in the borosilicate glass substrate electrode 43 and the silicon substrate electrode 44, and in the minute gap, A high voltage is applied and discharge occurs. Due to this discharge energy, the electrode on the borosilicate glass substrate or the electrode on the silicon substrate is melted and electrically connected. It should be noted that, even after the initial generation of the induced charges, the injection of the charges by the high voltage continues. Further, when the applied anodic bonding voltage is low, discharge (including direct emission) does not occur, the anodic bonding strength is low, and the practical strength is limited. Further, at a high voltage, the increase in discharge energy causes a large erosion due to the scattering of the electrode wiring, so that stable conduction cannot be obtained. Therefore, the applied voltage is 25
A voltage of 0 to 500 volts is desirable.

The electrode wiring that connects the borosilicate glass substrate and the silicon substrate thus formed is
One end thereof is terminated in the silicon substrate layer at the contact hole 47. In order to obtain electrical wiring independent of the silicon substrate layer, irradiation intensity of YAG laser light is 5 mJ /
Irradiation with cm2 ^ is performed to cut the Cr-Au electrode. By the high-energy irradiation, not only the Cr-Au electrode but also the underlying silicon oxide film is cut. As a result, the oxide film covering the silicon layer is lost, and the Cr-Au electrode and the silicon layer may be electrically short-circuited while having a high resistance value. In order to prevent a decrease in insulation resistance, the intensity of the laser beam can be reduced by using an attenuator, and only the desired Cr-Au electrode can be cut.

As an electrode cutting method, in addition to this, electrode separation by simultaneous cutting of the wiring electrode and the silicon substrate by electric discharge machining cutting or dicing can also be used.

In this way, it is effective to improve reliability by coating the exposed edges with silicon resin or epoxy resin in order to protect the conductive electrodes and improve the environment resistance. is there.

In this embodiment, the Au-Cr electrode has been described as an example, but any metal electrode such as an aluminum electrode or a silver electrode can be applied.

(Embodiment 3) Silicon substrate 5 according to the present invention
1 and borosilicate glass substrate (hereinafter abbreviated as glass substrate)
52, 53, 54 and a diaphragm pump 55
And input valve 56 and output valve 57 with a diaphragm structure
A micropump provided with is shown in FIG. A switch projection 59 is formed on the diaphragm film 58 of the output valve on the side opposite to the output valve projection, and detects the operating state of the output valve 57 and controls the operation of the diaphragm pump 55. An electrode (the electrode wiring can be omitted when the specific resistance of the silicon substrate is small) is formed on the switch protrusion 59, and an electrode 60 is also formed on the glass substrate facing the switch protrusion. , A contact type switch circuit or a capacitance type switch circuit. In this embodiment, a contact type switch that can reduce the influence of the stray capacitance with the substrate due to the electrode wiring, and its gap is set to about 5
μm. In order to extract the switch signal, two external output terminals 61 and 62 are provided on the silicon insulating film,
A first wiring (which does not necessarily need to have an insulating film between itself and the silicon substrate in this wiring) that is routed over the silicon substrate and reaches the switch protrusion, and a silicon substrate (insulating film that is connected at the time of anodic bonding) Upper wiring) wiring 63
And a second wiring including the electrode wiring 64 on the glass substrate are connected. In the second electrode wiring, the wiring 63 on the silicon edge film is provided in advance in a clearance groove of about 1 μm on the silicon substrate in a portion overlapping with the glass substrate. Extends beyond the dicing line 65 indicated by the alternate long and short dash line to the adjacent cell and is in contact with the silicon substrate layer at the 10 μm square contact hole provided in the oxide film. The wirings 63 and 64 are connected to the silicon substrate and the glass substrate by discharge connection as described in the previous embodiment during the joining process of applying a positive and negative high voltage to each other to perform anodic joining. To be done. The electric flow path thus formed is cut along the dicing line when the unit cell is cut out, and the switch electrode on the glass substrate is insulated with high resistance from the silicon substrate. If the insulation resistance is lowered, the purpose of insulation can be achieved by forming the insulating film between the switch electrode on the silicon substrate side and the silicon substrate.

In the above embodiment, the example in which the contact hole is provided in the oxide film as the discharge flow path has been described. However, in addition to that, the electrode area facing the silicon substrate through the insulating film is increased to form the capacitive coupling wiring. By doing so, the discharge is generated and the electrodes can be connected. Further, in the present embodiment, the example in which the electrodes are collectively output on the silicon substrate has been described, but it is also possible to collectively output the electrodes on the glass substrate.

In the present embodiment, by providing the electrode output on the silicon substrate, the precipitation of ions generated at the interface between the glass substrate and the negative electrode at the anodic bonding is prevented at the interface between the silicon substrate and the electrode wiring. it can. Therefore, the adhesion strength of the wiring electrode to the silicon substrate is high and the electrode can be formed with high reliability. At the same time, since it is localized on the silicon substrate, high-density batch mounting can be performed.
The output electrode formed in this way became a strong output terminal that can withstand soldering in the connection method with an external circuit.

[0023]

According to the present invention, a pair of heating / feeding electrodes having a flat surface in contact with an object to be bonded can perform uniform heating without temperature unevenness and achieve stable and reliable bonding even at a low temperature. What is obtained, and in a structure in which a plurality of objects are joined in layers, it is possible to form electric wiring that easily conducts the layers of the plurality of objects to each other. The electric wiring according to the present invention has an improved electric wiring density and excellent adhesion strength with the substrate.

[Brief description of drawings]

FIG. 1 is a block diagram of an anodic bonding apparatus according to the present invention.

FIG. 2 is a functional diagram of an anodic bonding jig according to the present invention.

FIG. 3 is a state diagram of anodic bonding according to the present invention.

FIG. 4 is a diagram showing electrical connection during anodic bonding according to the present invention.

FIG. 5 is a structural diagram of a micropump according to the present invention.

FIG. 6 is a schematic view of a conventional anodic bonding jig.

[Explanation of symbols]

 11 Upper Temperature Control Section 12 Lower Temperature Control Section 13 Anodic Bonding Jig 14 Power Supply

Claims (5)

[Claims] 1. A pair of heating / power-supplying electrodes for anodic bonding, wherein the heating / power-supplying electrode comprises a heating part including a heating element and a power-supplying part for applying a voltage. The part that sandwiches is a pair of flat electrodes,
An anodic bonding apparatus having a heat insulating support between the outer casing and one of the pair of heating / power feeding electrodes has a movable structure. 2. A pair of heating / feeding electrodes arranged vertically for anodic bonding, wherein an electric insulator is provided between the heating part and the feeding part of the heating / feeding electrodes arranged above. The anodic bonding apparatus according to claim 1. 3. A first substrate and a second substrate which are bonded to each other, wherein the first substrate and the second substrate are:
Each has a first substrate electrode wiring and a second substrate electrode wiring, and the bonding of the first substrate and the second substrate is performed by an anodic bonding method using high temperature and high voltage, and during the anodic bonding, An electrode wiring method, comprising conducting connection between a first substrate electrode and the second substrate electrode. 4. A micropump comprising a silicon substrate having a diaphragm and a glass substrate, comprising a first electrode formed on the diaphragm, and a second electrode facing the first electrode on the diaphragm. First
The electrode wiring method, characterized in that the electrode and the second electrode have output electrode terminals which are integrated on one of the silicon substrate and the glass substrate. 5. The electrode wiring method according to claim 4, wherein the electrode on the silicon substrate and the electrode on the glass substrate are connected during the anodic bonding process.