JPH0341307B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a diaphragm processing apparatus for forming a diaphragm of a pressure sensor.

[Technical background of the invention and its problems]

As shown in Fig. 1, a pressure sensor that converts mechanical quantities such as pressure and strain into electrical quantities is made by inserting a disk-shaped diaphragm 2 made of silicon (Si) single crystal obtained by forming a round hole 1 into the center. A through hole 3 is formed in a disc-shaped pedestal 4 made of Si single crystal with a through hole 3 bored in the part.
are bonded so as to communicate with the round hole 1. On the other hand, on the side of the diaphragm 2 opposite to the round hole 1 side, a strain resistance layer 5 is formed by diffusion treatment. Thus, pressure measurement is performed by converting the strain acting on the strain resistance layer 5 into an electrical quantity based on the differential pressure between the pressures A and B (see FIG. 1) applied to the diaphragm 2. By the way, the above-mentioned round hole 1 is formed by depositing a protective film 7 with a cutout 6 in the area where the round hole 1 is to be formed on the Si material 8, and placing it in an etching bath 9 for a certain period of time, as shown in FIG. This was done by removing the missing portion 6 by immersion. However, when forming a diaphragm by such etching, the diaphragm 2 is formed by etching.
When processed, the removal speed is extremely slow at several μm/min, resulting in extremely poor processing efficiency. Moreover, since etching is performed based on the difference in etching speed between the protective film 7 and the Si material, there is a limit to the depth of etching. Therefore, it was impossible to machine the round hole 1 with a depth of 300 μm or more. Therefore, the diaphragm 2 is susceptible to thermal distortion when the glass is bonded to the pedestal 4.
This was a cause of a decrease in yield. Furthermore, when etching is used, the inner circumferential surface of the bottom peripheral edge of the round hole 1 is not perpendicular to each other and becomes rounded, which causes a decrease in the inspection accuracy as a pressure sensor. Furthermore, since the amount of etching is affected by the concentration, temperature, convection state, etc. of the etching solution, it is difficult to control the processing conditions, resulting in poor reproducibility.

[Purpose of the invention]

An object of the present invention is to provide a diaphragm processing apparatus that can form a diaphragm for a pressure sensor with high efficiency and high precision.

[Summary of the invention]

The diaphragm is formed by grinding while applying ultrasonic waves to the workpiece or the grindstone, and the positioning of the workpiece and the grindstone is digitally controlled.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings.

3 and 4 show a front view and a side view, respectively, of the diaphragm processing apparatus of this embodiment. In these figures, a surface plate 11 is fixed on a base 10. On this surface plate 11,
A table support 12 is fixed, and an X table 13 is supported on the X table support 12 so as to be slidable in the X direction in FIG. 3 (perpendicular to the paper plane in FIG. 4). A part of this X table 13 is the feed screw 1
4, and one end of this feed screw 14 is connected to an X fixed on the surface plate 11 via a coupling ring 15.
It is connected to a rotating shaft 17 of a step motor 16. A Y table support 18 is then fixed on the X table 13. A Y table 19 is supported on the Y table support 18 so as to be slidable in the Y direction in FIG. 4 (direction perpendicular to the plane of the paper in FIG. 3). A part of this Y table 19 is a feed screw 20
One end of the feed screw 20 is connected via a coupling 21 to a rotating shaft 24 of a Y step motor 23 attached to the X table 13 by a holder 22. X table 13,
The step motor 16, the Y table 19, and the Y step motor 23 constitute a positioning section. A cylindrical workpiece holder 25 serving as a holder is fixedly mounted on the Y table 19 so as to be able to freely adjust its rotational position. The upper end surface of this workpiece holder 25 is a suction surface 25a for vacuum suctioning a workpiece 26, which is a silicon wafer, and this suction surface 25a has a plurality of suction holes (not shown) connected to a vacuum source. is open. Further, a protrusion (not shown) is provided on the suction surface 25a so that the workpiece 26 can be positioned at a predetermined position on the suction surface 25a. On the other hand, a column 27 is erected at one end of the surface plate 11. This column 27 has a recessed portion 28 on the side facing the workpiece 26,
Two side walls 29a, 2 forming this recessed portion 28
A Z table 30 is supported on the Z table 9b so as to be slidable in the Z direction (see FIGS. 3 and 4). This Z
A part of the table 30 is threadedly engaged with a feed screw 31, and one end of the feed screw 31 is inserted into a housing 34 fixed on a mounting plate 33 in the center of the recess 28 via a coupling ring 32. Connected to a worm gear. The placement plate 33 is located in the recessed portion 2 of the column 27.
8 and is connected and fixed to the support body 11
It is fixed to the surface plate 11 via a and 11b, and the surface plate 1
1 and extends parallel to the upper surface of the surface plate 11 over the entire upper area. The worm gear above has a feed screw 3.
The feed screw 35 is connected via a coupling to the rotating shaft of a Z step motor 36 fixed to a mounting plate 33 shown in FIG. Further, a bearing body 38 that pivotally supports a low-speed spindle 37 is fixed on the Z table 30, and a cylindrical support body 39 is fixed coaxially with the low-speed spindle 37 at the lower end of this low-speed spindle 37. . As shown in FIG. 5, an eccentric bearing 41 is attached to the support 39, and has an axial center 41a that is eccentric by an eccentric amount e with respect to the axial center 40 of the low-speed spindle 37 (the eccentric amount e is It is adjustable.) A high-speed spindle 42 is supported on this eccentric bearing 41 by an air turbine drive. As shown in FIG. 6, the high-speed spindle 42 is formed into a cylindrical shape, and has an ultrasonic application mechanism 42a built therein. The ultrasonic wave applying mechanism 42a is made of, for example, nickel or ferrite, and is applied with an amplitude of 5 to 5 through a slip ring 42b.
A vibrator that is wound with a coil connected to an ultrasonic oscillator 42c that outputs an alternating current that generates ultrasonic vibrations of 50 μm, and that generates ultrasonic waves by exchanging the alternating current output to the ultrasonic oscillator 42c with mechanical vibrations. 4
2d, a cone 42e that is connected to the lower end of the transducer 42d and expands the amplitude of the ultrasonic wave propagated from the transducer 42d, and an ultrasonic wave that is connected to the lower end of the cone 42e and amplified by the cone 42e. and a horn 42f that further expands the amplitude of the signal. A cup-shaped grindstone 43 is detachably attached to the tip of the horn 42f. Although not shown, the support body 39 includes:
A pressurized air supply device for driving the high speed spindle 42 is arranged around the ring. On the other hand, a pulley is attached to the upper end of the low-speed spindle 37.
A belt 46 is wound between this pulley and a pulley attached to the tip of a rotating shaft 45 of a drive motor 44 fixed on the Z table 30 shown in FIG. The low speed spindle 37, the bearing body 38,
Support body 39, eccentric bearing 41, high speed spindle 4
2. The grindstone 43 constitutes a grinding section. moreover,
Although not shown, in the diaphragm processing apparatus of this embodiment, a nozzle for supplying grinding fluid to the workpiece 26 and a shielding plate for shielding the scattering of this grinding fluid are provided close to the workpiece holder 25. ing. Also,
A column 2 is provided on the workpiece holder side of the mounting plate 33.
A positioning microscope 47, which is used when positioning the workpiece 26 at a predetermined position, is protrudingly provided adjacent to the workpiece 7. FIG. 7 shows an electric circuit diagram of a calculation control unit such as a microcomputer, which is a part of the diaphragm processing apparatus of this embodiment.
are connected to an oscillator 65 via drivers 62, 63, and 64, respectively. This oscillator 65 is
For reasons to be described later, the X step motor 16 and the Y step motor 23 are configured to transmit pulse signals so that they can rotate in forward and reverse directions, and the step motor 36 is configured to transmit pulse signals so that forward rotation can be changed to two speeds and reverse rotation can be performed. . This oscillator 65 is connected to the system bus 66
CPU67 (Central Processing Unit;
central processing unit). . Further, the oscillator 65 is connected to a counter 68, and the oscillator 65
The number of pulses of the pulse signal output from the sensor is counted. Furthermore, a storage device 69 consisting of, for example, RAM (Read Only Memory), a timer 70 and an input/output interface 71 are connected to the CPU 67 via a system bus 66.
Together with the CPU 67, it constitutes an arithmetic control section 72. The input/output interface 71 includes, for example, a solenoid valve control mechanism 7 for air turbine drive control, vacuum source control for vacuum suction, and grinding fluid supply control.
3 and the ultrasonic wave applying mechanism 42a are electrically connected.

Next, the operation of the diaphragm processing apparatus of this embodiment will be described in detail.

First, the workpiece 26, which is a silicon wafer, is vacuum-adsorbed to a predetermined position on the workpiece holder 25. From this workpiece 26, round holes are machined for each of a plurality of pellets 74, as shown in FIG. Therefore, while looking at the positioning microscope 47, set the Motor 1
6 and Y step motor 23 are driven to move the X table 13 and Y table 19. Further, the workpiece holder 2 is placed so that the lattice forming each pellet shown by the broken line in FIG. 8 is parallel to the X direction and the Y direction.
Adjust by rotating 5. By the way, storage device 6
9 stores a main routine 75 for positioning the workpiece 26 as shown in FIG. That is, this main routine 75 is composed of a Z-axis operation mode subroutine 76, an X-axis operation mold subroutine 77, a Y-axis operation mode subroutine 78, a solenoid valve control subroutine 79, and an ultrasonic wave addition subroutine 80. Therefore, when the positioning of the workpiece 26 is completed, the arithmetic control section 72 shown in FIG. 7 is activated to execute the main routine 75 described above. First, according to the flowchart shown in FIG. 10, it is determined whether or not the Z-axis operation mode is active (block 81). In this case, since positioning has been performed in the X-axis and Y-axis directions, the Z-axis operation mode is set, and the Z step motor 36 is started in the fast-forward mode (block 82).
The grindstone 43 moves toward the workpiece 26 and descends as the Z table 30 moves in the Z direction. however,
During round hole machining, the input/output interface 7 is controlled from the CPU 67 by the solenoid valve control subroutine 79.
A control signal is output to the electromagnetic valve control mechanism 73 via the solenoid valve control mechanism 73, and the grinding wheel 43 is rotated by an air turbine, and grinding fluid is supplied and vacuum suction is performed. At the same time, the ultrasonic addition subroutine 80
A control signal is output from the CPU 67 to the ultrasonic adding mechanism 42a via the input/output interface 71, and the ultrasonic oscillator 42c outputs a control signal to the slip ring 42.
An amplitude of 5 to 50μ is applied to the coil of the vibrator 42d via b.
m alternating current is applied. Then, the vibrator 42
This alternating current is converted into mechanical vibrations at d. Thus, the mechanical vibration generated by the vibrator 42d is amplified by the cone 42e and the horn 42f, and the amplified mechanical vibration is propagated to the rotating grindstone 43. The CPU 67 determines whether the grinding wheel 43 has descended by a predetermined amount (block 83), and if it has reached the predetermined position (the position immediately before cutting into the workpiece 26), the grinding wheel 43 is moved down as shown in FIG. The feed speed is reduced to start cutting feed (block 8).
4) The position detection in the Z-axis direction at this time is obtained by counting the number of pulses in the counter 68. That is, based on the Z-axis fast-forward command, the oscillator 65 outputs the pulse signal SA to the driver 64, and the driver 64 drives the Z step motor 36 during the input period of the pulse signal SA. On the other hand, pulse signal
The number of SA pulses is also output to a counter 68, and this counter 68 outputs a digitized count value of the number of pulses to the CPU 67. CPU67
At step 68, the counted value from counter 68 is compared with the setting value stored in advance in storage device 69,
When the two match, the signal from the oscillator 65
Stop SA output. Further, the feed speed is changed by changing the oscillation cycle of the pulse signal from the oscillator 65. In this way, the grinding process as shown in FIG. 12 progresses using the grindstone 43.
That is, the rotation axis 4 of the support body 39 rotating at a low speed
0 and the rotational axis of the high-speed spindle 42 are eccentric by the amount of eccentricity e (see Fig. 5), so the high-speed spindle 42 integrally follows the low-speed spindle 37, and the grinding wheel 43 moves at low speed as shown in Fig. 12. It rotates at high speed in the direction of arrow 86 while making planetary motion in the direction of arrow 85,
Round hole machining progresses gradually. On the other hand, the CPU 67 determines whether the cutting feed amount in the Z-axis direction has reached a preset value (block 87), and when the predetermined cutting is completed, the cutting feed is stopped and at the same time the timer 70 is activated. is set (block 88). This timer 70 has a fixed time set in advance, and the grindstone 43 is held at the final cutting position during this set time (this is the spark-out time shown in FIG. 11). At the same time as this spark-out ends (block 89), the Z step motor 36 enters the fast return mode (block 90), and the grindstone 43 moves upward and returns to its original position (block 91). Then,
Based on the X-axis movement subroutine 77 and the Y-axis movement subroutine 78, the X table 13 and Y table 19 are moved to predetermined positions. In other words, the oscillator 65
The counter 68 counts the number of pulses of the pulse signals SB and SC output from the grinding wheel 43 until the counted value reaches a set value stored in advance in the storage device 69, that is, directly below the pellet 74 to be processed next by the grinding wheel 43. X, Y step motor 1 until
6 and 23. In this manner, the main routine 75 in FIG. 9 is repeated, and round holes are machined in each pellet 74 in the order indicated by the arrow W in FIG. 8.

As described above, the diaphragm processing apparatus of this embodiment performs the round hole drilling process for forming the diaphragm by applying ultrasonic vibration to the grinding wheel 4, which is rotated at high speed by the air turbine mechanism and is provided in a planetary motion. Since the positioning of the workpiece 26 and the grindstone 43 is digitally controlled, the machining efficiency is significantly improved and the machining time is significantly shortened. Furthermore, the life of the grinding wheel can be extended. Furthermore, chips generated during grinding can be removed more smoothly by the action of ultrasonic waves, and desired machining accuracy can always be stably obtained.

In the above embodiment, the high speed spindle 42 is provided with the ultrasonic wave applying mechanism 42a, but the ultrasonic wave is applied to the low speed spindle 37 to indirectly apply the ultrasonic wave to the grindstone 43 and the workpiece 26. It's okay. Furthermore, the workpiece holder 25 is equipped with an ultrasonic applying mechanism 42a, and the workpiece holder 2
Ultrasonic waves may be applied to the workpiece 26 from the 5 side.

〔Effect of the invention〕

The diaphragm processing device of the present invention forms a diaphragm by grinding using a grindstone that rotates at high speed and revolves at low speed using an air turbine mechanism while applying ultrasonic waves to the workpiece.
In addition, since the positioning of the workpiece and the grindstone is digitally controlled, the processing efficiency and processing accuracy are significantly improved and the product yield is increased. Further, the cutting chips can be smoothly removed by the action of ultrasonic waves.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the operating principle of the pressure sensor, Figure 2
The figure shows the formation of a diaphragm of a pressure sensor by etching, Figures 3 and 4 are front and side views of a diaphragm processing device according to an embodiment of the present invention, respectively, and Figure 5 is an explanation of the main parts of the grindstone. figure,
Figure 6 is a cross-sectional view of the high-speed spindle, Figure 7 is the 3rd
Fig. 8 is a plan view of the workpiece that becomes a pressure sensor, Fig. 9 is a flowchart of the main routine, and Fig. 10 is a flowchart of the Z-axis operation mode subroutine. , FIG. 11 is a graph showing the relationship between the moving distance of the grindstone and time, and FIG. 12 is an explanatory diagram showing the locus of movement of the grindstone on the workpiece. 13:X table, 16:X step motor,
19: Y table, 23: Y step motor, 2
5: workpiece holder, 26: workpiece, 42a: ultrasonic application mechanism, 43: grindstone, 72: calculation control section.

Claims (1)

[Claims] 1. In a diaphragm processing device that forms a plurality of diaphragms by drilling a plurality of round holes at predetermined positions in a workpiece, which is a silicon wafer,
A holding part that holds the workpiece; a cup-shaped grindstone provided opposite to the workpiece held in the holding part; a high-speed spindle that holds the grindstone coaxially and rotates it; and a high-speed spindle that rotates the high-speed spindle at high speed. It has an air turbine to drive, a low-speed spindle that holds the high-speed spindle eccentrically and makes it revolve, and a motor that drives the low-speed spindle at low speed. Drilling of the plurality of round holes is performed by relatively moving the grinding part to be drilled, the holding part, and the grinding part based on a digital control signal to position and drive the workpiece to each of the round hole machining positions. A positioning unit that sequentially performs the machining, an ultrasonic application mechanism that applies ultrasonic waves to the workpiece held by the grindstone or the holding unit, and a machining program for the round hole machining are stored and are processed based on the machining program. A diaphragm machining device comprising: an arithmetic control section that digitally controls the round hole machining by applying the digital control signal to the grinding section and the positioning section.