JPH0363226B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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]

As shown in Figure 1, a pressure sensor that converts mechanical quantities such as pressure and strain into electrical quantities has a disc-shaped diaphragm 2 made of Si single crystal in which a round hole 1 is formed.
is adhered to a disk-shaped pedestal 4 made of Si single crystal, which also has a through hole 3 in the center thereof, so that the through hole 3 communicates with the round hole 1. A strain resistance layer 5 is formed by diffusion treatment on the surface of the diaphragm 2 opposite to the surface on which the round hole 1 is formed. Thus, pressure measurement is performed by converting the differential pressure between pressures A and B (see FIG. 1) applied to the diaphragm 2 into an amount of electricity by straining the strain resistance layer 5. 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 immersing it and removing the missing part 6.

[Problems with background technology]

When the diaphragm 2 is processed by etching, the removal rate is very slow, several μm per minute, and the processing efficiency is poor. Furthermore, 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, the depth
It was impossible to process a round hole 1 with a diameter of 300 μm or more.
Furthermore, when etching is used, the inner circumferential surfaces are not perpendicular to each other near the bottom of the round hole 1, resulting in a rounded cross-sectional shape. Furthermore, since the amount of etching is affected by the concentration, temperature, convection state, etc. of the etching solution, processing accuracy is low and reproducibility is poor. Due to the combination of the above-mentioned difficulties, it has not only been difficult to improve the detection accuracy as a pressure sensor, but also the yield has been low, contributing to high costs.

[Purpose of the invention]

An object of the present invention is to provide a diaphragm processing device that can process a round hole for forming a diaphragm of a pressure sensor with high efficiency and precision.

[Summary of the invention]

A diaphragm is formed by machining a round hole in a material for a pressure sensor using a grinding wheel, and by executing a machining program corresponding to the shape of the workpiece using an arithmetic and control device.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on embodiments 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. A surface plate 11 is fixed to the base 10.
An X-table support 12 is fixed on this surface plate 11, and an X-table 13 is mounted on this X-table support 12 in the X direction in FIG.
It is slidably supported. This X table 1
3 is threadedly engaged with a feed screw 14, and one end of the feed screw 14 is connected via a coupling 15 to a rotating shaft 17 of an X step motor 16 fixed on the surface plate 11. A Y table support 18 is then fixed on the X table 13. On this Y-table support 18, a Y-table 19 is mounted in the Y direction in FIG.
It is slidably supported. This Y table 1
A part of the feed screw 20 is screwed into the feed screw 20, and one end of the feed screw 20 is attached to the Y table 13, which is attached to the X table 13 by a holder 22, via a coupling ring 21.
It is connected to a rotating shaft 24 of a step motor 23. X table 13, X step motor 16, Y
The table 19 and the Y step motor 23 constitute a positioning section. A cylindrical workpiece holder 25 is placed on the Y table 19 so as to be rotatably adjustable. This workpiece holder 25 holds a workpiece 26 in a fixed position on its upper surface by vacuum suction. Workpiece holder 25
Although not shown, a plurality of protrusions for positioning the workpiece 26 are erected on the suction surface. Further, a plurality of suction holes (not shown) are opened on the suction surface and are connected to a vacuum source (not shown). On the other hand, a column 27 is erected at one end of the surface plate 11. The column 27 has a recess 28 on the side facing the workpiece 26, and a Z table 30 is mounted on two side walls 29a and 29b forming the recess 28 in the Z direction (see FIGS. 3 and 4). ) is slidably supported. A part of this Z table 30 is threadedly engaged with a feed screw 31, and one end of this feed screw is inserted into a housing 34 fixed on a mounting plate 33 in the center of the recessed part 28 via a coupling ring 32. Connected to a worm gear. A feed screw 35 is meshed with the worm gear, and the feed screw 35
is connected to the rotating shaft of a Z step motor 36 fixed to the mounting plate 33 shown in FIG. 3 via a coupling. 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, the support body 39 has an axial center 4
Eccentric bearing 4 that is eccentric by eccentricity e with respect to 0
1 (the amount of eccentricity e is adjustable).A high-speed spindle 42 driven by an air turbine is supported on this eccentric bearing 41. A cup-shaped grindstone 43 is fixed to the tip of the high-speed spindle 42 coaxially with the high-speed spindle 42 . Although not shown, the support 3
9 is equipped with a pressurized air supply device for driving the high-speed spindle 42. On the other hand, a pulley is attached to the upper end of the low-speed spindle 37, and this pulley and the Z table 3 shown in FIG.
A belt 46 is wound around a pulley attached to the tip of a rotating shaft 45 of a drive motor 44 fixed on the drive motor 44. The low-speed spindle 37, bearing body 38, support body 39, eccentric bearing 41, high-speed spindle 42, and grindstone 43 constitute a grinding section. Further, 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 scattering of the grinding fluid are provided near the workpiece holder 25. It is provided. A positioning microscope is also attached for use in positioning the workpiece 26 at a predetermined position. FIG. 6 shows an electric circuit system diagram of a calculation control section such as a microcomputer, which forms a part of the diaphragm processing apparatus of this embodiment.
The Y and Z step motors 16, 23 and 36 are connected to an oscillator 50 via drivers 47, 48 and 49, respectively.
It is connected to the. This oscillator 50 transmits pulse signals so that the X step motor 16 and the Y step motor 23 can rotate in forward and reverse directions, and the step motor 36 can rotate in two forward and reverse directions for reasons that will be explained later. It is structured as follows. This oscillator 50 is connected to a CPU 52 (Central Processing Unit) via a system bus 51. In addition, the oscillator 50
is connected to a counter 53 and counts the number of pulses of the pulse signal output from the oscillator 50. Furthermore, the CPU 52 has, for example,
Storage device 54 consisting of RAM (Read Only Memory), timer 55 and input/output interface 5
6 is connected via the system bus 51 and the CPU 5
Together with 2, it constitutes an arithmetic control section. The input/output interface 56 is electrically connected to a solenoid valve control mechanism 57 for, for example, air turbine drive control, vacuum source control for vacuum suction, and grinding fluid supply control.

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

First, the workpiece 26, which is a Si 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 58, as shown in FIG. Therefore, while looking at the positioning microscope, set the 16 and Y step motor 23 to move the X table 13 and Y table 19. Further, the workpiece holder 25 is rotated and adjusted so that the lattice forming each pellet shown by broken lines in FIG. 7 is parallel to the X direction and the Y direction. By the way, the storage device 54 contains the eighth
A main routine 59 for positioning the workpiece 26 as shown in the figure is stored. That is,
This main routine 59 includes a Z-axis operation mode subroutine 60 and an X-axis operation mold subroutine 6.
1, a Y-axis operation mode subroutine 62, and a solenoid valve control subroutine 63. Therefore, when the positioning of the workpiece 26 is completed, the arithmetic control section shown in FIG. 6 is activated to execute the main routine 59 described above. First, according to the flowchart shown in FIG. 9, it is determined whether or not the Z-axis operation mode is active (block 63). In this case, the X axis,
Since the positioning in the Y-axis direction has been performed, the Z-axis operation mode is set, and the Z step motor 36 starts in the fast-forward mode (block 64), and the grinding wheel 43
moves downward toward the workpiece 26 as the Z table 30 moves in the Z direction. However, during round hole machining, due to the solenoid valve control subroutine 63, the CPU
52 outputs a control signal to the electromagnetic valve control mechanism 57 via the input/output interface 56, and air turbine drive, grinding fluid supply, and vacuum suction are performed. The CPU 52 determines whether the grinding wheel 43 has descended by a predetermined amount (block 65), 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 6).
6). The position detection in the Z-axis direction at this time is obtained by counting the number of pulses in the counter 53. That is, the pulse signal SA is output from the oscillator 50 to the driver 49 based on the Z-axis fast forward command,
The driver 49 drives the 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 53, and this counter 53 outputs a digitized count value of the number of pulses to the CPU 52. CPU52
In step 1, the counted value from the counter 53 is compared with the setting value stored in advance in the storage device 54,
When the two match, a signal from the oscillator 50 is sent.
Stop SA output. Note that the same process is also performed for driving the X and Y step motors 16 and 23. Further, the feed speed is changed by changing the oscillation cycle of the pulse signal from the oscillator 50. Then, the grinding process as shown in FIG. 11 progresses using the grindstone 43. That is, since the rotational axis 40 of the support body 39 rotating at low speed and the rotational axis of the high-speed spindle 42 are eccentric by an eccentric amount e (see FIG. 5), the high-speed spindle 42
is integrally driven by the low-speed spindle 37, and the grinding wheel 4
3 rotates at high speed in the direction of arrow 68 while making planetary motion in the direction of arrow 67 in FIG. 11 at low speed, and the round hole machining gradually progresses. On the other hand, the CPU 52 determines whether the cutting feed amount in the Z-axis direction has reached a preset value (block 67).
When the predetermined cut is completed, the cut feed is stopped and at the same time the timer 55 is set (block 68). This timer 55 has a fixed time set in advance, and within this set time the grindstone 43 is held at the final cutting position (first
This is the spark-out time shown in Figure 0. ) As soon as this sparkout ends (block 69),
The Z step motor 36 enters the fast return mode (block 70), and the grindstone 43 moves upward to return to its original position (block 71). When the round hole machining of one pellet 58 shown in FIG. 7 is completed, the main routine 59 of FIG. 8 is executed again, and each pellet 58 is
...round hole machining is performed. In this case, since the Z-axis is not in the operating mode in block 63 of FIG. 9, the X-axis operating mode subroutine 61 is executed. (Block 72). That is, the X-axis operation mode subroutine 61 first performs the following steps as shown in FIG.
A determination is made whether the X-axis operating mode is present (block 72). In this case, the round hole machining of one pellet has just been completed and the positioning in the X-axis and Y-axis directions has not been completed, so the pulse signal SB is output from the oscillator 50 to the driver 47, and the X step motor 16
is activated, X-axis feeding is started, and the X table 13 moves in the X direction. When this X-axis feed reaches a predetermined amount, the output of the pulse signal SB is stopped (block 74), and the Y-axis operation mode subroutine 6
2 (block 75), the oscillator 50
The pulse signal SC is outputted to the driver 48,
The Y table 19 moves in the Y direction in the same manner as the X axis, and the workpiece 26 is positioned at a predetermined position. Thus, the Z-axis operation mode subroutine 60 described above is repeated. In this way, the diaphragm processing apparatus of this embodiment can process each pellet 58 of the workpiece 26.
By quickly and accurately drilling a round hole using the cup-shaped grindstone 43, the bottom edge of the diaphragm does not have a rounded shape unlike etching, and the bottom edge is rounded as shown by the two-dot chain line in Fig. 5. The section will be sharp. Therefore, the detection accuracy as a pressure sensor is increased, and the reliability as a product is improved. Furthermore, reproducibility is increased and yield is improved. Furthermore, the inner diameter of the round hole can be easily changed by appropriately adjusting the eccentricity e shown in FIG. Since it can be easily adjusted by changing , it can be applied to the production of pressure sensor diaphragms of various sizes. Furthermore, since the positioning of the workpiece 43 is performed according to the program stored in the storage device and based on the pulse count value of the pulse signal for driving the step motor, all that is required is to first set the position. Automatic positioning becomes possible, a particularly complicated positioning mechanism is not required, and the device is not complicated and is easy to handle.

In the above embodiment, a step motor is used as the drive source, but a DC motor may be used and a signal from a rotary encoder connected to the DC motor may be used for positioning.
In addition, although the workpiece 26 is positioned using the X table 13 and the Y table 19, the present invention is not limited to this, and the workpiece 26 is fixed and the grindstone 43 side is
It may be provided so as to be movable not only in the X direction but also in the Y direction. Furthermore, in the above embodiment, the round hole is machined by the planetary motion of the grindstone 43;
Without being particularly limited to this, grinding may be performed using only normal rotational motion. Further, although the high-speed spindle 42 is driven by an air turbine mechanism, it may be driven by another drive source such as an induction motor.

〔Effect of the invention〕

The diaphragm processing apparatus of the present invention can form the diaphragm of a pressure sensor more quickly and with higher precision than when forming it by etching. Therefore, the characteristics as a pressure sensor are improved and the reliability is higher than in the case of etching, and the product yield is also increased. Furthermore, compared to etching processing, complicated pre-processing and pre-processing processes are not required, and automation can be easily achieved, resulting in significant labor savings and contributing to production rationalization. Furthermore, since the present invention relies on software processing based on the count value of the number of pulses for positioning control, the device does not become complicated and is easy to handle.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the operating principle of the pressure sensor.
FIG. 2 is a diagram showing the formation of a diaphragm of a pressure sensor by etching process, FIGS. Figure 4 is an explanatory diagram of the main parts of the grinding wheel part of the diaphragm processing device shown in Figure 4. Figure 6 is an electric circuit diagram of the diaphragm processing equipment shown in Figures 3 and 4. Figure 7 is a plane view of the workpiece that becomes the pressure sensor. Figure 8 is a flowchart of the main routine, Figure 9 is a flowchart of the X-axis operation mode subroutine, Figure 10 is a graph showing the relationship between the moving distance of the grindstone and time, and Figure 11 is a graph showing the relationship between the moving distance of the grindstone and time. FIG. 12 is an explanatory diagram showing the motion locus of the grindstone, and is a diagram showing the X-axis operation mode subroutine. 13: X table (positioning section), 16: X step motor (positioning section), 19: Y table (positioning section), 23: Y step motor (positioning section), 25: Workpiece holder (holding section), 26 : Workpiece, 30: Low speed spindle (grinding part), 42:
High-speed spindle (grinding part), 43: Grinding wheel, 52:
CPU (arithmetic control unit), 54: storage device (arithmetic control unit).

Claims (1)

[Scope of Claims] 1. A diaphragm processing device for forming a diaphragm of a pressure sensor at the bottom of each round hole by drilling a plurality of round holes with bottoms in a workpiece made of a single silicon single crystal substrate, A diaphragm processing device characterized by having the following configuration. (a) A holding part that holds the above-mentioned workpiece. (b) It has a cup-shaped grindstone, a high-speed spindle to which this grindstone is attached and rotates, and a low-speed spindle that is installed eccentrically with respect to the high-speed spindle and revolves, Grinding section that processes holes. (c) It has a step motor that is digitally controlled by a pulse signal, and the step motor drives the holding part and the grinding part relatively, and moves the grindstone to each round hole drilling position of the workpiece. A positioning unit that performs sequential positioning. (d) It has a counting means for counting pulse signals for controlling the step motor, and a storage means for storing a machining program for machining the round hole, and the counted value of the counting means and the processing program are stored in the storage means. an arithmetic control section that controls the grinding section and the positioning section based on a machining program;