KR20050024346A - Method of manufacturing of a monolithic silicon acceleration sensor - Google Patents

Abstract

A method of making a monolithic silicon acceleration sensor is described. Monolithic silicon acceleration sensors are micromachined from silicon to form one or more sensor cells, each sensor cell having an inertial mass disposed by a beam member secured to a silicon support structure. A sandwiched etch stop layer is formed between the first silicon wafer section and the second silicon wafer section. The first section and the beam member of the inertial mass are formed by etching the U-shaped channel and the bar-shaped channel to the etch stop layer in the first wafer section of the sandwiched layer. The second section of the inertial mass is formed by aligning the U-shaped and bar-shaped channels in the first section with the frame-shaped channel in the second wafer section and etching the frame-shaped channel up to the etch stop layer. After exfoliating the exposed etch stop layer, an inertial mass disposed by the beam member secured to the silicon support structure is formed. The first cover plate structure is bonded to the first surface of the silicon support structure.

Description

Method of manufacturing monolithic silicon acceleration sensor

The present invention relates to an acceleration sensor micromachined from silicon, and more particularly to a sensor having an inertial mass disposed by a torsion or cantilever support member.

It is known in the art that small, compact acceleration sensors can be formed by micromachining silicon wafers with suitable structures capable of detecting acceleration along one axis. Micromachining processes are generally performed on batches of silicon wafers. This process consists of masking and forming a pattern of etch stop material on the wafer surface, etching exposed silicon, removing etch stop material, metallizing, and bonding. The silicon wafer is diced into individual acceleration sensor devices, which are packaged and connected to appropriate electronic circuitry to form an accelerometer. Using these techniques, biaxial or triaxial acceleration sensors require two or three discrete diced devices, respectively, to be precisely mechanically aligned along two or three orthogonal axes of acceleration. Examples of acceleration sensors formed by micromachining processes are described in US Pat. Nos. 4,574,327, 4,930,043, and 5,008,774.

Conventional silicon acceleration sensors use inertial masses that move in response to acceleration disposed by cantilever support members that can introduce asymmetry that can result in undesirable cross-axis sensitivity. To avoid this undesirable asymmetry effect, these devices are designed with flexible support members around the outer periphery of the inertial mass so that the response to acceleration is well along the axis perpendicular to the plane of the inertial mass. To further limit the acceleration response to one axis, the support member is sometimes arranged in the central plane of the inertial mass or symmetrically in the top and bottom surfaces of the inertial mass. Devices manufactured in this way exhibit wide parameter variations between devices. In addition, for multi-axis applications, many discrete devices must be precisely mechanically aligned with respect to each axis of acceleration. Difficulties encountered in manufacturing include the precise location of the central plane and the precise alignment of multiple devices, which complicates, slows, and increases the manufacturing process.

For these reasons, there is a need for a monolithic multi-axis acceleration sensor machined into silicon by a relatively simple manufacturing process that results in a device that is stable at low mechanical stress temperatures with tight parameter tolerances between devices. Rather than the precise mechanical alignment of the discontinuous device after the dicing operation, it is desirable that some desired multi-axis alignment be performed as part of the lithographic process used in manufacturing the device. It is also desirable that the manufacturing process can be adjusted on a batch basis to produce a device having a predetermined acceleration sensitivity, using a batch ranging from a low sensitivity device to a high sensitivity device.

FIG. 1A illustrates a portion of a simplified monolithic silicon acceleration sensor including one silicon acceleration sensor cell without first and second cover plate structures having an inertial mass disposed by a torsion beam secured to a silicon support structure. Partly broken perspective view.

FIG. 1B illustrates a portion of a simplified monolithic silicon acceleration sensor including one silicon acceleration sensor cell without first and second cover plate structures having an inertial mass disposed by a cantilever beam secured to a silicon support structure. Partly broken perspective view.

FIG. 2 shows four silicon accelerations, each having inertial masses oriented at different angles when viewing the beam members in the plane of the X and Y axes, each inertial mass disposed by torsion beams fixed to the silicon support structure. A perspective view illustrating a simplified monolithic multi-axis acceleration sensor without a first cover plate structure with a sensor cell.

3 is a chart showing the direction of movement of each of the movable inertial masses shown in FIG. 2 due to the acceleration of the acceleration sensor along three orthogonal acceleration axes.

4A and 4B show respective inertial masses oriented at different angles when viewing the beam members in the plane of the X and Y axes, each inertial mass disposed by a torsion beam member secured to a silicon support structure, Two perspective views showing a simplified monolithic multi-axis acceleration sensor without the first cover plate structure, with three silicon acceleration sensor cells.

5 shows two silicon, each having an inertial mass oriented at different angles when viewed in the plane of the X and Y axes, each inertial mass disposed by a torsion beam member secured to a silicon support structure. Perspective view illustrating a simplified monolithic multi-axis acceleration sensor with an acceleration sensor cell.

6 is a partially broken perspective view of a monolithic silicon acceleration sensor including one silicon acceleration sensor cell.

FIG. 7 is a partially broken perspective view showing a simplified electrically nonconductive single cell monolithic silicon acceleration sensor with piezo-resistive elements on the cantilever beam member. FIG.

8 illustrates an alternative embodiment of a cover plate structure.

9 is a perspective view of a section of an electrically conductive silicon wafer.

10A is a perspective view of a second silicon wafer section having a silicon nitride dot and a first silicon dioxide layer on one surface.

10B is a cross-sectional view of a second silicon wafer section having a first silicon dioxide layer and silicon nitride dots on one surface.

FIG. 11A is a perspective view of a second silicon wafer section having a second silicon dioxide layer scattered on silicon mesa on one surface; FIG.

FIG. 11B is a cross-sectional view of a second silicon wafer section with a second silicon dioxide layer scattered of silicon mesa on one surface; FIG.

FIG. 12A is a perspective view of the wafer section shown in FIG. 9 having a first silicon wafer section bonded to the silicon dioxide layer and erased. FIG.

FIG. 12B is a cross-sectional view of the wafer section shown in FIG. 9A having a second silicon wafer section bonded to the silicon dioxide layer and erased. FIG.

13A is a perspective view of a silicon dioxide layer grown on a silicon wafer section.

13B is a partially broken perspective view of a sandwiched layer of silicon dioxide layer between silicon wafer sections formed by an alternative fabrication method.

13C is a perspective view of a sandwiched layer of silicon dioxide between silicon wafer sections to form an alternative fabrication method.

FIG. 14A is a perspective view of the layered laminate shown in FIG. 12A having depressions formed in the first and second surfaces. FIG.

FIG. 14B is a cross-sectional view of the layered laminate shown in FIG. 12B having depressions formed in the first and second surfaces. FIG.

15A is a perspective view of a molded second cross section of an inertial mass;

15B is a sectional view of the molded second cross section of the inertial mass;

16A is a perspective view of shaped second and first cross sections of an inertial mass;

16B is a cross sectional view of the shaped second and first cross sections of an inertial mass;

17A is a perspective view of a shaped inertial mass disposed by a beam member secured to a silicon support structure.

FIG. 17B is a cross-sectional view of a molded inertial mass disposed by a beam member secured to a silicon support structure. FIG.

18 is a perspective view of a structure used to illustrate the formation of a cantilever beam member.

19 illustrates attachment of a cover plate structure to a silicon support structure.

20A is a perspective view of a partially formed cover plate structure showing a wafer section having a silicon dioxide layer.

20B is a perspective view illustrating a partially formed cover plate structure showing a trenched wafer section having a silicon mesa;

21 is a partially broken perspective view of a preferred embodiment of the lid plate structure.

22 is a cross-sectional view of a monolithic silicon acceleration sensor with a single sensor cell connected to a capacitive measurement circuit.

Summary of the Invention

The present invention relates to a monolithic multi-axis accelerometer that is stable to low mechanical stress temperature with tight parameter tolerances between devices, which are micromachined from silicon by a relatively simple manufacturing process. Since the monolithic multi-axis acceleration sensor can be aligned by the lithographic process used in manufacturing the device, the need for precise mechanical alignment of the discrete sensor device along the orthogonal axis of acceleration is eliminated. The manufacturing process of the present invention is preferably able to be adjusted on a batch basis to produce a device having a predetermined acceleration sensitivity, using a batch spanning from a low sensitivity device to a high sensitivity device.

While prior art silicon acceleration sensors attempt to avoid asymmetric cross-axis sensitivity, the present invention utilizes this cross-axis effect to enable the fabrication of monolithic multi-axis acceleration sensors. The present silicon acceleration sensor invention includes one, two, three or four silicon acceleration sensor cells, each sensor cell comprising a movable silicon inertial mass that moves in response to acceleration, the silicon inertial mass supporting a silicon And a beam member coplanar with the first surface of the silicon inertial mass attached to the structure. Means are provided for causing bending of the beam member due to acceleration of the silicon support structure and the inertial mass, or for detecting motion of the inertial mass. The relative position of each inertial mass is perpendicular to an adjacent inertial mass when looking at the first surface of each silicon mass using the position of the beam member as an angle reference. A silicon acceleration sensor device with a single sensor cell containing one movable silicon inertial mass can detect accelerations of two orthogonal axes but cannot distinguish between accelerations along one axis or the rest. Two devices with two sensor cells each comprising a movable silicon inertial mass with another sensor cell disposed at 180 ° to the inertial mass when viewed from the first surface of the inertial mass using the beam member as an angle reference It can detect the acceleration of the orthogonal axis and can distinguish between the acceleration along both axes. Each sensor cell has three sensor cells comprising movable silicon inertial masses disposed at angles of 0 °, 90 ° and 180 ° relative to each other when viewed from the first surface of the inertial mass using the beam member as an angle reference. The device can sense acceleration along three orthogonal axes and can differentiate between accelerations along each of the three axes. Four cells comprising movable silicon inertial masses disposed at angles of 0 °, 90 °, 180 ° and 270 ° with respect to each other when viewed from the first surface of the inertial mass using the beam member as an angle reference A device with can detect acceleration along three orthogonal axes and can distinguish between acceleration along each of the three axes. The device comprising four sensor cells is of a physically symmetrical shape when viewed from the first surface of each inertial mass and provides a function for offsetting opposite direction nonlinearity. Thus, multi-axis acceleration sensing can be achieved using a single monolithic device that does not require precise mechanical alignment of multiple discrete single-axis acceleration sensing devices. One means for detecting the movement of the inertial mass measures the capacity between the first surface of the movable inertial mass and the first electrically conductive layer spaced from the first surface and fixed relative to the supporting silicon structure, The capacitance between the second surface of the movable inertial mass facing the surface and the second electrically conductive layer spaced from the second surface and fixed relative to the supporting silicon structure is measured. Another means for detecting the movement of the inertial mass is to measure the resistance of the piezo resistor element disposed on the positioning beam member. The beam member may be a cantilever or torsion structure. The shape of the inertial mass is generally described as being a rectangular parallelepiped in the preferred embodiment of the present invention.

A method of fabricating a silicon acceleration sensor device having a single silicon sensor cell with electrically conductive silicon movable inertial mass forms a layered sandwich of an etch stop layer between a first wafer section of electrically conductive silicon and a second wafer section of electrically conductive silicon. Wherein the first wafer section of silicon has an exposed first surface and the second wafer section of silicon has an exposed second surface. The second section of silicon inertial mass is formed by etching a rectangular frame shaped channel in the second wafer section from the exposed second surface extending to the etch stop layer. The first section of silicon inertial mass etches the U-shaped channel and the bar-shaped channel in the first wafer section from the exposed first surface extending to the etch stop layer, and removes the bar-shaped channel and the U-shaped channel in the first wafer section. It is formed by placing it horizontally aligned with a rectangular frame shaped channel in two wafer sections and having the same planar dimensions. Means are provided for electrically connecting a second section of the inertial mass to the first section of the inertial mass on the etched surface of the inertial mass or through an etch stop layer. The silicon dioxide layer exposed by the etched framed channel, the etched U-shaped channel and the etched bar-shaped channel is then stripped off and thereby movable in a rectangular parallelepiped shape disposed by a beam member secured to the silicon support structure. To form a silicon inertial mass. An alternative means of electrically connecting the second section of the inertial mass to the first section of the inertial mass is to deposit a layer of conductive polysilicon over the resulting etched and exfoliated structure. This deposition process may also be used where it is desirable to use non-conductive silicon wafer sections. A first electrically conductive layer, spaced from the first surface of the inertial mass, is adhered to the silicon support structure for a first capacitance measurement between the first electrically conductive layer and the first surface of the inertial mass, and the second surface of the inertial mass Means are provided for detecting movement of the silicon inertial mass by adhering a second electrically conductive layer spaced from the second surface of the inertial mass relative to the silicon support structure for a second capacitance measurement between the second electrically conductive layer and the second electrically conductive layer. do. It is preferable that these electrically conductive layers are metallic in composition. Alternatively, a means for detecting the movement of the inertial mass is provided by placing the piezo-resistive element on the positioning beam member secured to the silicon support structure and measuring the change in resistance when the beam member is bent or twisted. .

In a preferred embodiment of a method of manufacturing a silicon acceleration sensor having at least one silicon acceleration sensor cell, the first section of the movable silicon inertial mass has a U shape in the first layer of silicon from the exposed first surface extending to the silicon dioxide layer. By etching the channels and the bar-shaped channels and placing the bar-shaped and U-shaped channels in the first layer of silicon horizontally aligned with the rectangular frame-shaped channels in the second layer of silicon and having the same planar dimensions. Is formed. The bar shaped channel is disposed across the open top of the U shaped channel, centered within the outer dimension of the open top of the U shaped channel, and extends the same length as the entire outer width of the top of the U shaped channel. The ends of the bar shaped channel are spatially spaced from the top of the U shaped channel such that spatial separation results in a device having a silicon inertial mass disposed by the torsion beam member.

Although the preferred embodiment of the present invention uses a silicon dioxide layer as the etch stop layer, alternative embodiments exist. These alternative embodiments include a depletion layer associated with a junction of a silicon nitride layer, a doped silicon layer and two differently doped silicon sections.

In an alternative embodiment of the method of manufacturing a silicon acceleration sensor having at least one silicon acceleration sensor cell, the first section of the movable silicon inertial mass has a U shape in the first layer of silicon from the exposed first surface extending from the silicon dioxide layer. By etching the channels and the bar-shaped channels and placing the U-shaped and bar-shaped channels in the first layer of silicon horizontally aligned with the rectangular frame-shaped channels in the second layer of silicon and having the same planar dimensions. Is formed. The bar shaped channel is disposed across the open top of the U shaped channel, centered within the inner dimension of the open top of the U shaped channel, and extends to a length less than the inner width of the top of the U shaped channel. The ends of the bar shaped channel are spatially separated from the inner top of the U shaped channel such that the spatial separation results in a device having a silicon inertial mass disposed by the cantilever beam member.

Another embodiment of a method for manufacturing a silicon acceleration sensor having at least one silicon acceleration sensor cell adjusts the thickness of the first silicon wafer section to adjust the thickness of the beam member, thereby controlling the spatial separation between the U-shaped channel and the bar-shaped channel. By adjusting the width of the beam member, or by adjusting the width of the etched channel to change the acceleration sensitivity.

A method of fabricating a device having two silicon acceleration sensors, each comprising a movable silicon inertial mass, uses a positioning beam as an angle reference to view a second inertial mass relative to the first inertial mass when viewing the exposed first surface of the silicon mass. One that includes one movable silicon inertial mass, except that the mass is lithographically and then physically disposed at an angle of 90 °, 180 ° or 270 ° (which is functionally equivalent to 90 °). It is the same as the manufacturing method of the device having the silicon acceleration sensor cell. A method of fabricating a device having three silicon acceleration sensor cells in which each sensor cell includes a movable silicon inertial mass, wherein the third inertial mass is lithographically viewed when viewing the exposed first surface of the silicon mass using a positioning beam as an angle reference. And then subsequently physically disposed at a 90 ° angle with respect to the second inertial mass and at a 180 ° angle with respect to the first inertial mass, and a method of manufacturing a device having two silicon acceleration sensor cells. same. A method of fabricating a device having four silicon acceleration sensor cells in which each sensor cell has a movable silicon inertial mass, wherein the fourth inertial mass is lithographically viewed from the exposed first surface of the silicon mass using the positioning beam as an angle reference. And then, physically, at a 90 ° angle to the third inertial mass, 180 ° to the second inertial mass, and 270 ° to the first inertial mass, It is the same as the manufacturing method of a device having three acceleration sensor cells. In this way, a monolithic multi-axis acceleration sensor is formed without requiring precise mechanical alignment of multiple discrete single axis acceleration sensors.

Detailed description of the invention

Referring now to FIG. 1A, electrically conductive movability positioned by a torsion beam member 400, an X axis 510, a Y axis 520, and a Z axis 530 secured to an electrically conductive silicon support structure 200. A portion of a simplified monolithic silicon acceleration sensor 100 is shown that includes one silicon acceleration sensor cell with a silicon inertial mass 300. Similarly, FIG. 1B illustrates electrically conductive movable silicon inertia positioned by cantilever beam member 410, X axis 510, Y axis 520, and Z axis 530 secured to electrically conductive silicon support structure 200. A simplified monolithic silicon acceleration sensor 100 is shown that includes one silicon acceleration sensor cell with mass 300. Since the preferred embodiment of the present invention uses the torsion beam member 400 shown in FIG. 1A to position the movable silicon inertial mass 300, FIG. 1A will be used as a reference for explaining the operation of the present invention. It should be understood that the discussion applies equally equally to the cantilever beam structure of FIG. 1B. Considering the acceleration about the Z axis 530, when the silicon acceleration sensor 100 is accelerated in the + Z direction along the Z axis 530, the inertial mass 300 is Z axis relative to the silicon support structure 200. Move along 530 in the -Z direction to rotate about an axis formed by the torsion beam member 400. Conversely, when the silicon acceleration sensor 100 is accelerated in the -Z direction along the Z axis 530, the inertial mass 300 moves in the + Z direction along the Z axis 530 with respect to the silicon support structure 200. Thus, it rotates around an axis formed by the torsion beam member 400. Considering the acceleration about the X axis 510, when the silicon acceleration sensor 100 is accelerated in the + X direction along the X axis 510, the inertial mass 300 is the X axis with respect to the silicon support structure 200. Move along 510 in the -X direction to rotate about an axis formed by the torsion beam member 400. Conversely, when the silicon acceleration sensor 100 is accelerated in the -X direction along the X axis 510, the inertial mass 300 moves in the + X direction along the X axis 510 with respect to the silicon support structure 200. Thus, it rotates around an axis formed by the torsion beam member 400. Considering the acceleration about the Y axis 520, when the silicon acceleration sensor 100 is accelerated along the Y axis 520 in the + Y or -Y direction, the inertial mass 300 is the force on the inertial mass due to the acceleration Rotation about the axis formed by the torsion beam member 400 can be prevented because it is aligned with respect to the axis formed by the torsion beam member 400 rather than radially. Thus, the silicon acceleration sensor structure of FIG. 1A can be sensed along two orthogonal acceleration axes, i.e., along the Z axis 530 and the X axis 510, but cannot be distinguished between these two acceleration axes.

Referring now to FIG. 2, a portion of a simplified monolithic multi-axis silicon acceleration sensor 140 that includes four silicon acceleration sensor cells each having movable silicon inertial masses 310, 320, 330, 340 is shown. have. The first cover plate structure is not shown in FIG. 2 to show the relative angular positioning of the inertial mass relative to the beam member. Each of the four inertial masses is constructed similarly to the movable silicon inertial mass 300 shown in FIG. 1A and positioned by the torsion beam member 400 secured to the silicon support structure 240. However, only the inertial mass 310 is the same as the inertial mass 300 shown in FIG. 1A with respect to the orientation of the rotational axis formed by the torsion beam member 400 about the X axis 510 and the Y axis 520. Oriented. Thus, only the inertial mass 310 responds to acceleration along the X axis 510 and Z axis 530 by rotating about an axis formed by the torsion beam member 400 similar to the inertial mass 300 of FIG. 1A. do. The direction of movement of the inertial mass 310 resulting from the acceleration direction along the three orthogonal acceleration axes is shown in the column below the symbol 310 in the chart of FIG. 3. By using a similar analysis used to determine the movement of the inertial mass of FIG. 1A in response to the acceleration of the acceleration sensor, the movement of the inertial masses 320, 330, 340 can be immediately determined. The direction of movement of the four inertial masses 310, 320, 330, 340 of the acceleration sensor 140 shown in FIG. 2 in response to the acceleration along the X axis 510 is indicated in the chart of FIG. 3.

Considering the chart of FIG. 3, the acceleration of the acceleration sensor 140 of FIG. 2 in the + X direction is the inertial mass 310 of FIG. 2 in the -Z direction, and the inertial mass 300 of FIG. 2 in the + Z direction. Combination of inherent movements of the < RTI ID = 0.0 >), < / RTI > Conversely, the acceleration of the acceleration sensor 140 of FIG. 2 in the -X direction is intrinsic movement of the inertial mass 310 of FIG. 2 in the + Z direction and the inertial mass 330 of FIG. 2 in the -Z direction. And the inertial masses 320 and 340 of FIG. Similarly considering the inertial mass movement in response to the acceleration of the acceleration sensor 140 of FIG. 2 in the + Y, -Y, + Z and -Z directions, one of three orthogonal acceleration axes from the results shown in FIG. It can be seen that there is an inherent combination of movement of the four inertial masses for any combination of simultaneous acceleration magnitudes and directions along two or both. Thus, the acceleration sensor shown in FIG. 2 is capable of simultaneously sensing the magnitude and direction of acceleration along three orthogonal acceleration axes, including components resulting from off-axis acceleration. FIG. 2 also shows the structure of four symmetrically arranged inertial masses responding according to FIG. 3, but only three inertial masses have an acceleration direction and magnitude along one, two or three of the orthogonal acceleration axis, Or any combination of off-axis acceleration components.

4A illustrates one of a simplified monolithic multi-axis silicon acceleration sensor 120 having three inertial masses 310, 320, 340 positioned by a torsion beam member 400 secured to a silicon support structure 220. The possible structure is shown. 4B illustrates another possible of the simplified multi-axis monolithic silicon acceleration sensor 130 having three inertial masses 310, 320, 340 positioned by the torsion beam member 400 secured to the silicon support structure 230. The structure is shown. The first cover plate structure is not shown in FIGS. 4A and 4B to show the relative angular positioning of the inertial mass relative to the beam member.

It can also be seen that only two inertial masses are needed to simultaneously distinguish the direction and magnitude of the acceleration along one or two orthogonal acceleration axes, as well as off-axis components. 5 shows a possible structure of a simplified monolithic silicon acceleration sensor 110 having two inertial masses 320, 340 positioned by a torsion beam member 400 secured to a silicon support structure 210. . The first cover plate structure is not shown in FIG. 5 to show the relative angular positioning of the inertial mass relative to the beam member.

Referring now to FIG. 6, FIG. 6 shows a partially broken perspective view showing the complete acceleration sensor partially shown in FIG. 1 without the lid structure. 6 illustrates a preferred embodiment of a single sensor cell version of the present invention by showing a partially broken perspective view of a monolithic silicon acceleration sensor 150 including one silicon acceleration sensor cell. The sensor cell includes an electrically conductive silicon movable silicon inertial mass 300 having a first surface 302 and an opposing second surface 304. The inertial mass 300 is fixedly positioned by an electrically conductive torsion beam member, which is not shown in FIG. 6 but shown as the torsion beam member 400 in FIG. 1A. The torsion beam member is secured to the electrically conductive silicon support structure 200, and the silicon support structure 200 has a first surface 202 and an opposing second surface 204. The first cover plate structure 600 includes a first metal layer 640 spaced from the first surface 302 of the inertial mass 300, and the first metal layer 640 is the first of the silicon support structure 200. It is formed in the first insulator 610 yarn, which is preferably glass, adhered to the surface 202. The first surface 302 and the first metal layer 640 of the inertial mass 300 form a first variable capacitor whose value depends on the position of the inertial mass 300. The second cover plate structure 700 includes a second metal layer 740 spaced from the second surface 304 of the inertial mass 300, and the second metal layer 740 is a second of the silicon support structure 200. It is formed on the second insulator 710, which is preferably glass, adhered to the surface 204. The second surface 304 and the second metal layer 740 of the inertial mass 300 form a second variable capacitor whose value depends on the position of the inertial mass 300. The magnitude of the acceleration causing the movement of the inertial mass 300 is indicated by measuring the magnitude of the difference between the first variable capacitor value and the second variable capacitor value. Preferred electrical connection means of the inertial mass 300 to the capacitive measurement circuit are formed on the outer surface of the electrically conductive silicon support structure 200 electrically connected to the electrically conductive inertial mass 300 via an electrically conductive beam member. The electrical lead wire 880 is connected to the bonding pad 870. Preferred electrical connection means of the first metal layer 640 of the first cover plate structure 600 to the capacitive measurement circuit include a first conductive silicon mesa through the first insulator 610 in electrical contact with the first metal layer 640. By a third electrically conductive silicon wafer section 620 having a 630 and a second surface 624 mounted on the first insulator 610. An electrical lead wire 880 connected to the capacitive measurement circuit is also connected to an electrical bond pad 870 on the second surface 624 of the third silicon wafer section 620 to be electrically connected to the first metal layer 640. To complete. Similarly, the preferred electrical connection of the second metal layer 740 of the second cover plate structure 700 to the capacitive measurement circuit is a second through the second insulator 710 in electrical contact with the second metal layer 740. By fourth electrically conductive silicon wafer section 720 having a conductive silicon mesa 730 and having a second surface 724 mounted on a second insulator 710. Electrical lead wires 880 connected to the capacitive measurement circuitry are also connected to electrical bond pads 870 on the second surface 724 of the fourth silicon wafer section 720 and to electrical connections to the second metal layer 740. To complete. In this preferred embodiment of the invention, the shape of the silicon inertial mass 300 is a rectangular parallelepiped, and the first surface 302 of the inertial mass 300 is from the first surface 202 of the silicon support structure 200. Slightly recessed to provide a dielectric spacing for the first variable capacitor, and the second surface 304 of the inertial mass 300 is slightly recessed from the second surface 204 of the silicon support structure 200 to form the second variable capacitor. Provides a dielectric spacing for.

An alternative embodiment of the present invention involves the use of the cantilever beam 410 shown in FIG. 1B to position the inertial mass 300 shown in FIG. 6. Another embodiment of the present invention is to form a piezoelectric resistance element on the torsion beam member 400 shown in FIG. 1A or the cantilever beam member 410 shown in FIG. 1B. FIG. 7 shows a simplified single sensor cell embodiment of a silicon acceleration sensor 100 illustrating that the silicon inertial mass 300 is positioned by a silicon cantilever beam member 410 secured to a silicon support structure 200. do. Piezo resistor 420 is bonded to beam member 410 and is electrically connected in series to electrical bond pad 870 via metallization interconnect 890. Bonding wire 880 connects these piezo-resistive elements into a resistive measurement circuit to determine the level of curvature of the beam member 410, providing a measure of the movement of the inertial mass 300, which is also inertial mass 300. Is a measure of the magnitude of acceleration experienced by

An alternative embodiment for electrically connecting the first metal layer 640 of FIG. 6 to the capacitive measurement circuitry is shown in FIG. 8 showing an alternative cover plate structure 650. Alternative cover plate structure 650 includes an alternative insulator 660 having a first surface 662 and an opposing second surface 664. Electrical bond pads 870 are located on the first surface 662 and alternative metal layers 668 are located on the second surface 664 of the insulator 660. A metallization hole 666 is positioned in the insulator 660 that connects the metal layer 668 to the bonding pad 870, and the electrical lead wire 880 bonded to the bonding pad 870 is connected to the capacitive measurement circuit. do. Two of these alternative structures form the first cover plate structure 600 and the second cover plate structure 700 shown in FIG. 6. Although the figure shows a cube shaped inertial mass, it may be formed as a rectangular parallelepiped to increase the sensor sensitivity by increasing the size of the inertial mass.

The general dimensions of some of the parts of FIG. 2 are as follows: Each cubic inertial mass 310, 320, 330, 340 has a side between about 300 μm and about 400 μm; The beam member 400 has a thickness between about 5 μm and about 10 μm; The spacing between the inertial masses 310, 320, 330, 340 and the support structure 240, known as the channel width, is about 20 μm. A conventional silicon acceleration sensor 110 with four inertial masses 310, 320, 330, 340 has a side of about 1200 μm. Common dimensions are intended only for the purpose of illustrating the common embodiments and should not be construed as limitations of any physical parameters of the device.

Typical dimensions of some of the components of FIG. 6 are as follows: The thickness of the first insulator 610 is about 75 μm and the thickness of the second insulator 710 is about 75 μm. The spacing between the first surface 302 and the first cover plate structure 600 of the inertial mass 300 is about 1 μm. The spacing between the second surface 304 of the inertial mass 300 and the second cover plate structure is about 1 μm. The thickness of the first metal layer 640 is about several milliseconds, and the thickness of the second metal layer 740 is about several milliseconds.

As described above, the structures shown in FIGS. 2, 4A, 4B, and 5 are four, three with the first cover plate structure removed to indicate the relative angular positioning of the inertial mass relative to the beam member. A monolithic silicon acceleration sensor device having two or two acceleration sensor cells. The superposition of the structures shown in FIG. 6 to the structures of the devices shown in FIGS. 2, 4A, 4B, and 5 illustrates the complete structure of these monolithic devices.

Referring now to a method for manufacturing a monolithic silicon acceleration sensor, silicon micromachining techniques are shown in the exemplary sensor device 120 shown in FIG. 6, as well as in FIGS. 2, 4A, 4B and 5. Used in the manufacture of multiple sensor cell devices. Many of these devices are typically batch manufactured using silicon wafers. The method of manufacturing a monolithic silicon acceleration sensor includes (1) forming a layered sandwich of silicon dioxide between two layers of electrically conductive silicon, (2) manufacturing a movable silicon inertial mass, a beam member, and a silicon support structure. Step (3) fabricating the first cover plate structure and the second cover plate structure and bonding the first and second cover plate structures to the silicon support structure, and (4) one, two, three final structures. Or dicing into four sensor cell devices, splicing electrical lead wires, and encapsulating the device. Since step (4) is conventional and known in the art, a detailed description of these procedures will not need to be provided. The following description describes a method of making a monolithic silicon acceleration sensor with a single sensor cell, but those skilled in the art will appreciate that multiple single sensor cell devices can be used to detect acceleration along multiple axes as well as batch manufacturing simultaneously. It is understood that multiple multiple sensor cell devices may also be batch manufactured simultaneously. The main distinguishing differences between multiple sensor cells in a single device are the angular orientation and electrical connection structure for each other sensor cell. Thus, the following description focuses on the manufacture of a single sensor cell device, since once this is understood it is easier to understand how multiple multiple sensor cell devices can be manufactured simultaneously. Note that the dimensions in the specification are typical and exemplary of the preferred embodiment of the present invention. Actual device dimensions may be changed in accordance with certain device parameters.

A preferred embodiment of the present invention is a first step of forming a layered sandwich of silicon dioxide between a first layer of electrically conductive silicon having an exposed first surface and a second layer of electrically conductive silicon having an exposed second surface. Beginning, the first layer of silicon and the second layer of silicon are in electrical contact with each other. Consider FIG. 9, which shows a section 250 of a second electrically conductive silicon wafer 292, typically 400 μm thick. Note that there are also similar first wafer sections, third wafer sections, and fourth wafer sections contemplated in subsequent manufacturing steps. The second wafer section 250 shown in FIG. 10A also has a first surface 256 and a second surface 258 that are typically 400 μm thick and 600 square μm. A preferred method of making a layered sandwich is to grow a dot 252 of silicon nitride on the first surface 256 of the second wafer section 250 at a location that does not interfere with the etching operation that may be performed in a subsequent manufacturing step. It is to let. The first surface 256 of the second wafer section 250 is then thermally oxidized to allow the optional first silicon dioxide layer 254 to grow in a location not covered by the dots 252 of silicon nitride. FIG. 10B shows a cross-sectional view of the second wafer section 250 of FIG. 10A with the silicon mesa 262 generated by the oxidation process. Next, the first silicon dioxide layer 254 is stripped from the first surface 256 of the second wafer section 250, so that the first wafer dioxide layer 254 can be removed from the second wafer section 250 with respect to the interface between the silicon and the silicon nitride dots 252. Molding depressions remain on the first surface 256. 11A and 11B show that the second silicon dioxide layer 260 is thermally grown within the forming depressions in the second wafer section 250 to a level corresponding to the interface between the silicon and silicon nitride dots 252 of FIG. 10B. The second wafer section 250 is shown after extending and after the silicon nitride dots 252 have been peeled off. Thus, the planar surface adjacent to the first surface 256 of the second wafer section 250 comprising a second silicon dioxide layer 260 interspersed with silicon mesa 262 as shown in FIGS. 11A and 11B. Is formed. 12A and 12B show a first wafer section 270 of a second electrically conductive silicon wafer having a first surface 276 and a second surface 278 that are typically 600 square μm. This first wafer section 270 is bonded to the forming flat surface of the second wafer section 250 such that the second surface 278 of the first wafer section 270 is in contact with the forming flat surface. Next, the first wafer section 270 is ground to a value that is typically 5-10 μm. The value determines the thickness of the beam member formed in subsequent manufacturing steps. This forms a layered sandwich of silicon dioxide between the first silicon wafer section 270 and the second silicon wafer section 250 having a typical thickness of about 400 μm, thereby forming the first wafer section 270 and the second Wafer sections 250 are electrically interconnected through a silicon mesa 262 through a silicon dioxide layer.

In addition to the preferred embodiments described above, there are a number of alternative embodiments that form sandwiched layers of silicon dioxide between two layers of silicon. One alternative embodiment for creating a structure similar to that shown in FIGS. 12A and 12B is a planar surface of the second silicon dioxide layer 260 on the second wafer section 250 as shown in FIGS. 12A and 12B. Prior to bonding the first silicon wafer section 270 of FIGS. 12A and 12B to, typically below the surface of the second silicon dioxide layer 260 of the second wafer section 250 shown in FIGS. 11A and 11B. It is to implant ions to a depth of 5 to 10 μm. The first wafer section is not ground but the final structure is thermally shocked as above. The thermal shock causes the second wafer section 250 to break along the junction of the ion implant and the residual silicon of the second wafer section 250, such that the second wafer section 250 is typically 5-10 μm thick. And the first wafer section 270 is typically 400 μm thick, forming a structure inverted from the structure shown in FIGS. 12A and 12B. Another alternative embodiment that produces a structure similar to that of FIGS. 12A and 12B grows a first layer 254 of silicon dioxide on a second wafer section 250, as shown in FIG. 13A, followed by a silicon dioxide layer. Exposing plural small regions 255 of the second wafer section 250 through 254, creating a puddle of molten silicon, and as shown in FIG. 13B, the first silicon dioxide layer 254. Is to suck the puddle of molten silicon onto the exposed surface of. The first layer 270 of silicon is formed on top of the silicon dioxide layer 254 when the molten silicon is cooled as shown in FIG. 13B to form a structure similar to FIGS. 12A and 12B. Another alternative embodiment that produces a structure similar to FIGS. 12A and 12B forms a first layer of silicon dioxide 254 on the first surface 256 of the second wafer section 250 as shown in FIG. 13A. It is. The second surface 278 of the first wafer section 270 is bonded to the first silicon dioxide layer 264 as shown in FIG. 13C. Multiple small holes are exposed to the first wafer section 270 or the second wafer section 250 to extend to the silicon dioxide layer 254, exfoliate the exposed silicon dioxide layer 254, and the conductive poly in the small holes. Laminate silicon or other conductive material. This forms an electrical connection between the first wafer section 270 and the second wafer section 250 as shown in FIG. 13B.

The second step of the preferred embodiment is to fabricate the movable silicon inertial mass 300, the beam member 400, and the silicon support structure 200 as shown in FIG. 1A. The layered sandwich of silicon dioxide layer 260 between the first wafer section 270 and the second wafer section 250 shown in FIGS. 12A and 12B forms a starting point for this second step. In order to provide a space for the movement of the inertial mass to be formed in a subsequent step, as shown in FIGS. 14A and 14B, a first 1 μm depression 284 is provided to the first of the first wafer section 270. Formed on the surface 276, and a second 1 μm depression 264 is formed on the second surface 258 of the second wafer section 250. Note that the second silicon dioxide layer 260 and silicon mesa 262 shown in FIG. 14B are formed at a previous stage of the fabrication process. The first depressions 284 and the second depressions 264 form a first layer of silicon nitride and a second wafer on the exposed first surface 276 of the first wafer section 270 shown in FIG. 14B. It is formed by growing a second layer of silicon nitride on the exposed second surface 258 of section 250. The first layer of silicon nitride and the second layer of silicon nitride are masked to provide first and second exposed rectangular regions for the first rectangular depressions 284 and the second rectangular depressions 264. The first and second exposed rectangular regions are positioned to be horizontally aligned with each other. The exposed first and second rectangular regions are then stripped of silicon dioxide so that the first and second rectangular regions of silicon are exposed on the first wafer section 270 and the second wafer section 250. Layers of silicon dioxide are grown on the exposed silicon in the first and second rectangular regions. Masking on the silicon nitride layer is removed and silicon nitride and silicon dioxide are stripped off so that 1 μm on the first surface of the first wafer section 270 where the layers of silicon dioxide are grown as shown in FIGS. 14A and 14B. The depressions leave a 1 μm depressions on the second surface 258 of the second wafer section 250.

The second section 308 of the movable silicon inertia mass is masked by masking a rectangular framed region having a width of typically 20 μm within the periphery of the second depression 264 of FIG. 14B as shown in FIGS. 15A and 15B. Formed within the second wafer section 250 of FIG. 14B, the rectangular framed region has major or minor dimensions. The silicon dioxide layer is grown on the remaining exposed areas of the second surface 258 of the second wafer section 250 shown in FIG. 14B, and the framed masking is removed to remove the second wafer section 250 of FIG. 14B. Exposing the framed region of silicon in a second depression 264 on the second surface 258 of the substrate. The exposed silicon is etched by resistive ion etching (RIE), preferably from resistive ion etching (RIE), from the exposed second surface 258 of FIG. 14B extending to the silicon dioxide layer 260 forming an etch stop. Framed channel 266 is formed in section 250, and second section 308 of the inertial mass and silicon support structure 200 are formed as shown in FIGS. 15A and 15B. Within the channel 266 is a second section 308 of inertial mass having a second surface 304 that is a previous portion of the second surface 258 of the second wafer section 250 of FIG. 14B. Outside of the channel 266 is a silicon support structure 200 having a second surface 204 that is a previous portion of the second surface 258 of the second wafer section 250 of FIG. 14B. The first section 306 and torsion beam member 400 of the movable silicon inertial mass 300 of FIG. 1A are typically 20 μm within the periphery of the first recess 284, as shown in FIGS. 16A and 16B. It is formed in the first wafer section 270 of FIG. 14B by masking a U-shaped region and a bar-shaped region each having a width of. The bar shaped region has an elongated dimension aligned with the major dimension of the rectangular framed channel 266 shown in FIGS. 15A and 15B. The U-shaped and bar-shaped regions have the same planar dimensions and are positioned to be horizontally aligned with the rectangular framed channel 266 of FIG. 15A already formed in the second wafer section 250 of FIG. 14A. This alignment enables the rectangular parallelepiped inertial mass to be formed after the subsequent etching process of the first section 306 inertial mass. A silicon dioxide layer is grown on the remaining exposed areas of the first surface 276 of the first wafer section 270 of FIG. 14A, and the U-shaped and bar-shaped masking is removed to remove the first wafer section 270 of FIG. 14A. U-shaped and bar-shaped regions of silicon are exposed in a first depression 284 on the first surface 276 of the substrate. The exposed silicon is etched, preferably by RIE, from the exposed first surface 276 extending to the silicon dioxide layer 260 of FIG. 14A to form an etch stop, as shown in FIGS. 16A and 16B, Create U-shaped channel 286 and bar-shaped channel 288 in first wafer session 250 of FIG. 14A. Intrusive silicon between U-shaped channel 286 and bar-shaped channel 288 forms torsion beam member 400. A first section of inertial mass having a first surface 302 in U-shaped channel 286 and bar-shaped channel 288 that is a previous portion of the first surface of first wafer section 270 shown in FIG. 14A. There is 306. Outside of the channels 286, 288 is a silicon support structure 200 having a first surface 202 that is a portion of the first surface 276 of the first wafer section shown in FIG. 14A. The final structure shown in FIGS. 16A and 16B is held in place by the torsion beam member 400 and the web of silicon dioxide secured to the silicon support structure 200. The inertial mass shown in FIG. 16B is the first section 306 that is part of the silicon dioxide layer 260 and the first silicon wafer section 270 of FIG. 14B, and the part of the second wafer section 250 of FIG. 14B. The second section 308 is included. The silicon support structure 200 shown in FIG. 16B includes a portion of the first wafer section 270 of FIG. 14B, a silicon dioxide layer 260, and a second wafer section 250.

The entire structure exfoliates exposed silicon dioxide in the etched framed channel 266, the etched U-shaped channel 286 and the etched bar-shaped channel 288 as shown in FIGS. 16A and 16B, thereby. First surface 302 positioned by torsion beam member 400 secured to silicon support structure 200 having a first surface 202 and a second surface 204 as shown in FIGS. 17A and 17B. And a rectangular parallelepiped inertial mass 300 having a second surface 304. The release agent used is usually hydrogen fluoride.

There are a number of alternatives to the preferred embodiment for manufacturing the movable silicon inertial mass 300, the beam member 400 and the silicon support structure 200 shown in FIGS. 17A and 17B. One of these alternatives includes adjusting the thickness of the beam member 400 by adjusting the thickness of the first wafer section 270 of FIG. 14A, which is an exposed first surface of the first wafer section 270. Epitaxial growth of silicon on 276 or ion milling or grinding the exposed first surface 276 of the first wafer section 270 of FIG. 14A. Another alternative embodiment is to adjust the width of the beam member by adjusting the separation distance between the U-shaped channel 286 and the bar-shaped channel 288 of FIG. 16A, or the etched channel (as shown in FIGS. 16A and 16B). 266, 286 and 288 to adjust the length of the beam member. A preferred embodiment for forming the torsion beam member 400 is a bar shaped channel 288 across the open top of the U shaped channel 286 with reference to FIGS. 16A and 16B, as shown in FIG. 1A. Position the center of the bar-shaped channel 288 within the outer dimensions of the U-shaped channel 286, and lengthen the length of the bar-shaped channel 288 equal to the overall outer width of the top of the U-shaped channel 286. And spatially separate the end of the bar shaped channel 288 from the top of the U shaped channel 286. An alternative embodiment is to form the cantilever beam member 410 as shown in FIG. 1B. Referring to FIG. 18, the cantilever beam member positions the bar shaped channel 288 across the open top of the U shaped channel 286 and moves the bar shaped channel 288 within the internal dimensions of the U shaped channel 286. Center and extend the length of the bar-shaped channel 288 smaller than the inner width of the upper portion of the U-shaped channel 286, and spatially end the end of the bar-shaped channel 288 from the inner upper portion of the U-shaped channel 286. Formed by separation. An alternative embodiment for electrically connecting the first wafer section 270 and the second wafer section 250 is a U-shaped channel 286, a framed channel after stripping the exposed silicon dioxide layer 260 in these regions. 266 and on the sidewalls of the bar shaped channel 288 is to deposit a conductive material, preferably polysilicon.

An alternative embodiment for detecting movement of the inertial mass 300 by securing the piezo resistor 420 to the beam members 410 is a simple first cover plate structure 600 and a simple second cover plate structure 700. And both are insulating materials such as glass to be bonded to the silicon support structure 200 as shown in FIG. The piezo resistor is then electrically connected to a suitable resistance measurement circuit to determine the amount of twist or curvature of the beam member due to the movement of the inertial mass in response to the acceleration.

A third step of a preferred embodiment of the present invention is to manufacture the first cover plate structure 600 and the second cover plate structure 700 and to bond the cover plate structures to the silicon support structure 200 as shown in FIG. 19. will be. A preferred embodiment for detecting the movement of an inertial mass is to measure two variable capacitances. The first variable capacitance is between the first metal layer 640 and the first surface 302 of the inertial mass 300 that are secured to the silicon support structure 200 and to the first cover plate structure 600 insulated therefrom. . The second variable capacitance is between the second metal layer 740 and the second surface 304 of the inertial mass 300 adhered to the second cover plate structure 700 secured to and insulated from the silicon support structure 200. . Since the first cover plate structure 600 is a mirror image of the second cover plate structure 700 as shown in FIG. 19, only the manufacture of the first cover plate structure will be described for simplicity.

Referring to FIG. 20A, a preferred embodiment for manufacturing the first cover plate structure 600 is a first layer 626 of silicon dioxide on the exposed first surface 622 of the electrically conductive third wafer section 620. ), And the third wafer section 620 has a second surface 624 opposite to the first surface 622. The first layer 626 of silicon dioxide on the third wafer section 620 is masked so that the silicon dioxide surface is exposed except for a small molding pattern in which the silicon dioxide surface is positioned in accordance with the position of the inertial mass. . The exposed silicon dioxide layer 626 is stripped to expose the silicon of the first surface 622 of the third wafer section 620 except for the masked molding pattern. The exposed silicon surface is typically etched to a depth of 75 μm such that a small silicon mesa 630 is formed on the first surface 622 of the third wafer section 620 as shown in FIG. 20B. The trench is then formed in a rectangular crosshatch pattern on the first surface 622 of the third wafer section 620 to a depth typically about half the depth of the thickness of the third wafer session 620 or about 200 μm. The rectangular crosshatch includes silicon mesa and is positioned to coincide with the position of the inertial mass as shown in FIG. 20B.

21 illustrates a trenched third wafer section 620 after the layer of glass is melted over the first surface of the third wafer section 620 so that the trench is filled with glass and the silicon mesa 630 is covered with glass. A partially broken perspective view of the first cover plate structure 600 described above. The glass surface is ground smoothly to form a flat glass surface 612 with the top of the mesa 630 exposed, and the second surface 624 of the third wafer section exposes the glass filled trench as shown in FIG. 21. It is ground again as much as possible. A first metal rectangular pattern layer 640 is formed on the flat glass surface 612 of the first cover plate structure such that the metal layer 640 is opposed to the electrically conductive third wafer section 620 by the electrically conductive silicon mesa 630. ) And its second surface 624. The first metal layer 640 is dimensioned and positioned to coincide with the first surface of the inertial mass 300 shown in FIG. 19.

The glass surface 612 of the first cover plate structure 600 shown in FIG. 21 is bonded to the first surface 202 of the silicon support structure 200 shown in FIG. 19, and as shown in FIG. 19. The first metal layer 640 coincides with and is spaced from the first surface 302 of the inertial mass 300 such that a first variable capacitor is formed between the first metal layer 640. Similarly, the second cover plate structure 700 may include a silicon support structure 200 such that a second variable capacitor is formed between the second surface 304 of the inertial mass and the second metal layer 740, as shown in FIG. 19. Is bonded to the second surface 204. The electrical bond pads 870 are shown in FIG. 6, the second surface 624 of the third wafer section 620, the surface of the silicon support structure 200, and the second of the fourth wafer section 720. Formed on surface 724. The electrical lead wires 880 may include the first cover plate structure 600, the silicon support structure 200, and the second cover plate structure 700 shown in FIG. 6 to determine the value of the first variable capacitor and the second variable capacitor. Connected to an electronic circuit for measuring the value, it provides a measure of the movement of the inertial mass 300 which is an indication of the magnitude and direction of acceleration experienced by the sensor. FIG. 22 shows a cross-sectional view of a monolithic silicon acceleration sensor with a single sensor cell connected to a capacitance measurement electronic circuit.

Another embodiment of manufacturing the alternative first cover plate structure 650 is an electrical insulation having a first surface 662 and a second surface 664 as shown in FIG. 8 so that the holes coincide with the position of the inertial mass. To form a small hole 666 in the section of material 660. The first rectangular metal layer 668 on the surface of the hole 666, as well as on the second surface 664 of the insulating material 660, is formed by a hole in which the rectangular metal layer 668 on the second surface 664 is metallized. It is electrically connected to one surface and metalized to be dimensioned and positioned in accordance with the first surface of the inertial mass. Electrical bond pads 870 are formed on the first surface 662 of insulating material 660 in electrical contact with the metalized holes 666. The second surface 664 of the insulating material 660 is bonded to the first surface of the silicon support structure such that the metallized layer 668 coincides with and is spaced from the first surface of the inertial mass so that a first variable capacitor is formed. do. The second cover plate structure is similarly formed and bonded to the second surface of the silicon support structure.

It should be noted that monolithic acceleration sensors with one or more sensors can be manufactured by the method described above simply by changing the angular orientation of the beam members relative to one another. FIG. 5 shows a monolithic acceleration sensor 110 having first and second acceleration sensor cells, whereby a second sensor cell having an inertial mass 320 is used to measure the inertial mass using a beam member as an angle reference. When viewed from the first surface it is oriented at a 180 ° angle from the first sensor cell with the inertial mass 340. 4A and 4B show alternatives of monolithic acceleration sensors 120, 130 with first, second and third acceleration sensor cells, whereby a first of the inertial mass using a beam member as an angle reference. As viewed from the surface, the second sensor cell with the inertial mass 310 is oriented at a 90 ° angle from the first sensor cell with the inertial mass 340 and the third sensor cell with the inertial mass 320 is the inertial mass 340. Oriented 180 ° from the first sensor cell with 2 shows a monolithic acceleration sensor 140 having first, second, third, and fourth acceleration sensor cells, whereby it is viewed from the first surface of the inertial mass using a beam member as an angle reference. When the second sensor cell with the inertial mass 310 is oriented at an angle of 90 ° from the first sensor cell with the inertial mass 340, and the third sensor cell with the inertial mass 320 moves the inertial mass 340. The fourth sensor cell with the inertial mass 330 is oriented at an angle of 270 ° from the first sensor cell with the inertial mass 340.

Although the invention has been described in considerable detail with reference to certain preferred versions, other versions are possible. The embodiments described herein are merely exemplary and many alternative and additional embodiments will be apparent to those skilled in the art. Accordingly, such alternative embodiments should be construed as being within the spirit of the invention, even if not explicitly described herein, and the invention is limited only by the scope and spirit of the appended claims.

Claims (26)

A method of manufacturing a monolithic silicon acceleration sensor, the method comprising forming at least one silicon acceleration sensor cell, (a) forming a layered sandwich of an etch stop layer between a first wafer section of electrically conductive silicon having an exposed first surface and an electrically conductive second wafer section having an exposed second surface; (b) forming a second section of movable silicon inertial mass by etching a rectangular frame shaped channel in the second wafer section of silicon from the exposed second surface extending to the etch stop layer; (c) etching a U-shaped channel and a bar-shaped channel in the first wafer section of silicon from the exposed first surface extending to the etch stop layer, and removing the bar-shaped channel and the U-shaped channel from the second of silicon. Forming a first section of the inertial mass by placing it horizontally aligned with the rectangular frame shaped channel in a wafer section and having the same planar dimensions; (d) exfoliating the etch stop layer exposed by the etched frame-shaped channel, the etched U-shaped channel, and the etched bar-shaped channel to a beam member secured to a silicon support structure having first and second exposed surfaces. Generating rectangular parallelepiped shaped inertial masses having first and second exposed surfaces, disposed by (e) providing a means for detecting movement of said inertial mass. The method of claim 1, Forming the layered sandwich, (a) growing a silicon dioxide layer on one surface of the first silicon wafer section, and (b) bonding a second silicon wafer section to the surface of the silicon dioxide layer. The method of claim 1, Forming the layered sandwich, (a) growing a silicon dioxide layer on one surface of the first silicon wafer section; (b) implanting ions into the first silicon wafer section below the surface of the silicon dioxide layer; (c) bonding a second silicon wafer section to the surface of the silicon dioxide layer, and (d) thermally impacting the resulting structure such that the first silicon wafer section is cleaved along the junction of the ion implants and residual silicon of the first wafer section. Silicon Acceleration Sensor Manufacturing Method. The method of claim 1, Forming the layered sandwich, (a) growing a silicon dioxide layer on one surface of the silicon wafer section; (b) exposing a small region of the silicon wafer through the silicon dioxide layer; (c) forming a puddle of thermally molten silicon, and (d) when the molten silicon is cooled, a fur of molten silicon from the exposed area of the silicon wafer section onto the exposed surface of the silicon dioxide layer such that a second wafer section of silicon is formed on the silicon dioxide layer. A method of manufacturing a monolithic silicon acceleration sensor, comprising the steps of: leading a light source. The method of claim 1, Forming the layered sandwich, (a) creating a plurality of electrical interconnect paths between the first wafer section of silicon and the second wafer section of silicon through the etch stop layer, and (b) patterning the interconnect path in a manner that does not interfere with any subsequent etching step. The method of claim 5, wherein Creating the plurality of electrical interconnect paths comprises: (a) forming a plurality of small holes extending to the etch stop layer in either the first wafer section of silicon or the second wafer section of silicon; (b) removing the etch stop layer exposed to the bottom of the small holes, and (c) depositing a conductive material such as polysilicon in the small holes such that electrical connections are formed between the first silicon wafer section and the second silicon wafer section through the small holes. Method for making a noli silicon acceleration sensor. The method of claim 5, wherein Creating the plurality of electrical interconnect paths comprises: (a) forming a plurality of small holes extending into the etch stop layer in either the first wafer section of silicon or the second wafer section of silicon; (b) removing the etch stop layer exposed to the bottom of the small holes, and (c) metallizing the surfaces of the holes such that an electrical connection is formed between the first and second silicon wafer sections through a metallized small hole. Manufacturing method. The method of claim 1, The layered sandwich forming step, (a) growing dots of silicon nitride on the first surface of the second silicon wafer in a pattern that does not interfere with any subsequent etching operation; (b) growing a first layer of silicon dioxide on the remaining exposed silicon on the first surface of the second silicon wafer section; (c) exfoliating the first silicon dioxide layer such that a depression is formed in the first surface of the second silicon wafer section with respect to the interface between the silicon and the silicon nitride dots, thereby forming a silicon mesa under the silicon nitride dots. Forming step, (d) growing a second silicon dioxide layer in the formed depressions, the second silicon dioxide layer extending at a height corresponding to the interface between the silicon mesa and the silicon nitride dots; (e) exfoliating the silicon nitride dots such that a flat surface is formed by the second silicon dioxide layer dispersed in the upper portion of the silicon mesa; (f) forming a first and second silicon wafer sections on a molded flat surface of silicon dioxide scattered over the silicon mesa top such that the layered sandwich is electrically interconnected through the silicon dioxide layer via a mesa of silicon. 1 bonding the silicon wafer sections, and (g) adjusting the thickness of the first silicon wafer to correspond to the desired thickness of the beam member by erasing the first silicon wafer section. . The method according to any one of claims 1 to 8, (a) forming the second section of the inertial mass dry etches a rectangular frame shaped channel having major and minor dimensions in a second wafer section of silicon extending from the exposed second surface to the etch stop layer, (b) forming a first section of the inertial mass comprises dry etching the bar-shaped and U-shaped channels with long sides in the first wafer section of silicon, extending from the exposed first surface to the stop layer. Wherein the long side dimension of the bar shaped channel is aligned with the major dimension of the rectangular frame shaped channel in the second wafer section of silicon, and thus does not change the inertia balance in a plane perpendicular to the major dimension. A method of manufacturing a monolithic silicon acceleration sensor, characterized in that it provides the function of increasing the inertial mass by increasing the dimension. The method according to any one of claims 1 to 8, Forming a second section of the inertial mass dry-etches a square frame shaped channel extending from the exposed second surface to the etch stop layer, wherein the square frame shaped channel is a cube shaped inertia positioned by a beam member. A monolithic silicon acceleration sensor manufacturing method, characterized in that it has an internal dimension substantially the same as the thickness of the layered sandwich so that a mass is formed. The method according to any one of claims 1 to 10, (f) adjusting the thickness of the beam member by adjusting the thickness of the first wafer of silicon; (g) adjusting the width of the beam member by adjusting the spatial separation between the bar-shaped channel and the U-shaped channel, and (h) adjusting the length of the beam member by adjusting the width of the etched channel. The method of claim 11, Adjusting the thickness of the beam member is performed by epitaxially growing silicon onto the exposed first surface of the first silicon wafer section. The method of claim 11, Adjusting the thickness of the beam member is performed by milling the exposed first surface of the first wafer section of silicon to a desired thickness. The method according to any one of claims 1 to 13, (a) forming the second section of the inertial mass comprises a rectangular second depression on the exposed second surface of the second wafer section of silicon prior to etching the rectangular frame shaped channel in the second depression. Further comprising generating a wealth, (b) forming the first section of the inertial mass is rectangular on the exposed first surface of the first wafer section of silicon prior to etching the bar shaped channel and the U shaped channel in the first depression. A method of manufacturing a monolithic silicon acceleration sensor, further comprising the step of creating a first depression. The method of claim 14, Generating the rectangular first depressions and the rectangular second depressions, (a) arranging a first layer of silicon nitride on the exposed first surface of the first wafer section of silicon, and a second layer of silicon nitride on the exposed second surface of the second wafer section of silicon Arranging the layers, (b) asking the first silicon nitride layer and the second silicon nitride layer to expose first and second exposed portions for rectangular depressions on the first layer of silicon nitride and the second layer of silicon nitride. Providing a rectangular area, (c) arranging the first and second rectangular regions to be horizontally aligned with each other; (d) tripping the exposed first and second rectangular regions of silicon such that the first and second rectangular regions are exposed on the first wafer section of silicon and the second wafer section of silicon, respectively. Wow, (e) growing a layer of silicon dioxide on the exposed first and second rectangular regions of silicon; (f) removing masking on the silicon nitride layer, and (g) stripping the exposed silicon nitride and the exposed silicon dioxide from the first and second silicon wafer sections. The method according to any one of claims 1 to 15, Forming the first section of the inertial mass, (a) placing the bar-shaped channel across the open top end of the U-shaped channel and centering the bar-shaped channel within an outer dimension of the open top of the U-shaped channel; (b) extending the length of the bar-shaped channel to have an overall outer width of the open upper end of the U-shaped channel, and (c) spatially separating an end of the bar-shaped channel from the open upper end of the U-shaped channel such that the inertial mass is disposed by the torsion beam member. Manufacturing method. The method according to any one of claims 1 to 15, Forming the first section of the inertial mass, (a) placing the bar-shaped channel across the open top end of the U-shaped channel and centering the bar-shaped channel within an outer dimension of the open top of the U-shaped channel; (b) extending the length of the bar-shaped channel to have an overall outer width of the open upper end of the U-shaped channel, and (c) spatially separating the end of the bar-shaped channel from inside the open top of the U-shaped channel such that the inertial mass is disposed by the cantilever beam member. Manufacturing method. The method according to any one of claims 1 to 17, Providing a means for detecting the movement of the inertial mass, (a) measuring a capacity between a first electrically conductive layer spaced from the first surface of the inertial mass stuck to and insulated from the silicon support structure and the first surface of the inertial mass; (b) measuring a capacity between a second electrically conductive layer spaced from said second surface of said inertial mass adhered to and insulated from said silicon support structure and a second surface of said inertial mass; The monolithic silicon acceleration sensor manufacturing method made into a. The method according to any one of claims 1 to 17, Providing a means for detecting the movement of the inertial mass, (a) growing a first layer of silicon dioxide on the exposed first surface of the electrically conductive third wafer section of silicon and forming a first layer of silicon dioxide on the exposed first surface of the electrically conductive fourth wafer section of silicon Growing a layer, wherein the third and fourth silicon wafer sections have a second surface opposite the exposed first surface, (b) the third and fourth silicon wafers on the third and fourth silicon wafer sections so that the silicon dioxide surface is exposed except for the small post-formed patterns so that the post-molded pattern is placed to match the position of the inertial mass. Masking the section, (c) exfoliating a silicon dioxide layer from the exposed silicon dioxide surface such that an exposed region of silicon is formed on the first surface of the third and fourth silicon wafer sections except for a post-molded pattern of masked silicon dioxide. Making a step, (d) a small mesa of silicon is formed on the first surface of the third silicon wafer section below the post-molded pattern and on the first surface of the fourth silicon wafer section below the post-molded pattern. Etching the exposed areas of the third and fourth silicon wafer sections to a depth of 75 μm, (e) the third and fourth in a rectangular social pattern at a depth of about half the thickness of the third and fourth silicon wafer sections such that the enclosed rectangle comprises at least one silicon mesa and is positioned in line with the position of the inertial mass Forming a trench on said first surface of a fourth silicon wafer section; (f) melting a glass layer on the first surface of the third and fourth silicon wafer sections having the silicon mesa and the trench such that the trench is filled with glass and the silicon mesa is covered with glass; (g) grinding the glass such that a flat glass surface having an exposed silicon mesa pattern is formed on the third and fourth silicon wafer sections; (h) the glass filled trench is exposed, and electrical isolation is formed in the rectangular social pattern to form a first cover plate structure from a third silicon wafer section, and form a second cover plate structure from the fourth silicon wafer section. Back grinding the second surface of the third and fourth silicon wafer sections to (i) a glass layer of the first and second cover plate structures such that a metal layer is electrically connected to the opposing silicon surface by the silicon mesa and sized and arranged to match the first and second surfaces of the inertial mass 1 metalizing a rectangular pattern layer on the surface, (j) the first covering plate structure of the first cover plate structure on the first surface of the silicon support structure such that the metallized rectangular pattern coincides with and is spaced from the first surface of the inertial mass to form a first variable capacitor. Bonding the glass surface; (k) the second lid plate structure of the second cover plate structure on the second surface of the silicon support structure such that the metallized rectangular pattern coincides with and is spaced from the second surface of the inertial mass to form a second variable capacitor. Bonding the glass surface, and (l) electrically connecting said silicon wafer sections of said first cover plate structure, said first support structure and said second cover plate structure to an electronic circuit for measuring values of said first variable capacitor and said second variable capacitor. Providing a means for connecting; monolithic silicon acceleration sensor manufacturing method. The method according to any one of claims 1 to 17, Providing a means for detecting the movement of the inertial mass, (a) forming a small hole in the first glass layer and the second glass layer, each having a first surface and a second surface, at a position coincident with the position of the inertial mass; (b) metallizing the surface of the small hole, (c) each metal rectangular layer is electrically connected to opposite second surfaces of the first and second glass layers by metallized holes, the metal layer coinciding with the first and second surfaces of the inertial mass. Metallizing a first rectangular layer on the first surface of the first glass layer and on the first surface of the second glass layer to be sized and disposed such that, (d) electricity on the second surface of the first and second glass layers such that each bonding pad is electrically connected to the corresponding rectangular metal layer on the first surface of the first and second glass layers by the metallized holes. Metallizing the bonding pads, (e) bonding the first surface of the first glass layer to the first surface of the silicon support structure such that the metallized rectangular layer is aligned with and spaced apart from the first surface of the inertial mass; Forming a capacitor, (f) a second variable by bonding the first surface of the second glass layer to the second surface of the silicon support structure such that the metallized rectangular layer is aligned with and spaced apart from the second surface of the inertial mass; Forming a capacitor, and (g) an electronic circuit for measuring the value of the first variable capacitor and the value of the second variable capacitor using the electrical bonding pad on the first glass layer, the silicon support structure and the electrical bonding pad on the second glass layer. Providing a means for electrically connecting to the monolithic silicon acceleration sensor. The method according to any one of claims 1 to 17, Providing a means for detecting the movement of the inertial mass, (a) attaching a piezoresistive element to the beam member, and (b) providing an electrical connection from the piezo-resistive element to a resistance measurement circuit to determine the amount of twist or curvature of the beam member due to movement of the inertial mass in response to acceleration. , Monolithic silicon acceleration sensor manufacturing method. The method according to any one of claims 1 to 21, Subsequent to peeling off the etch stop, electrically interconnecting the first and second wafer sections of silicon by depositing a layer of conductive polysilicon on the surface of the etch structure. Monolithic silicon acceleration sensor manufacturing method. The method according to any one of claims 1 to 22, A method of manufacturing a monolithic silicon acceleration sensor, further comprising forming a single monolithic silicon acceleration sensor cell for sensing planar acceleration. The method according to any one of claims 1 to 23, (a) forming a monolithic sensor comprising first and second silicon acceleration sensor cells for sensing two axis acceleration, and (b) using the beam member as an angle reference, when viewing the surface of the inertial mass, orienting the second sensor cell at an angle of 90 ° or 180 ° relative to the first sensor cell; A monolithic silicon acceleration sensor manufacturing method, characterized in that. The method according to any one of claims 1 to 23, (a) forming a monolithic sensor comprising first, second and third silicon acceleration sensors to sense three axis acceleration, (b) orienting the second sensor cell at an angle of 90 ° with respect to the first sensor cell when viewing the first surface of the inertial mass using the beam member as an angle reference; and (c) when viewing the first surface of the inertial mass using the beam member as an angle reference, orienting the third sensor cell at an angle of 180 ° relative to the first sensor cell. The monolithic silicon acceleration sensor manufacturing method made into a. The method according to any one of claims 1 to 23, (a) forming a unitary body comprising first, second, third and fourth sensor cells to sense three axis acceleration, (b) orienting the second sensor cell at an angle of 90 ° with respect to the first sensor cell when viewing the first surface of the inertial mass using the beam member as an angle reference; (c) when viewing the first surface of the inertial mass using the beam member as an angle reference, orienting the third sensor cell at an angle of 180 ° relative to the first sensor cell, and (d) when viewing the first surface of the inertial mass using the beam member as an angle reference, orienting the fourth sensor cell at an angle of 270 ° relative to the first sensor cell. The monolithic silicon acceleration sensor manufacturing method made into a.