WO1991010119A2 - Semiconductor deep cavity device - Google Patents
Semiconductor deep cavity device Download PDFInfo
- Publication number
- WO1991010119A2 WO1991010119A2 PCT/GB1990/002034 GB9002034W WO9110119A2 WO 1991010119 A2 WO1991010119 A2 WO 1991010119A2 GB 9002034 W GB9002034 W GB 9002034W WO 9110119 A2 WO9110119 A2 WO 9110119A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- substrate
- glass
- wafer
- bonding
- cavity
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
- G01L9/0076—Transmitting or indicating the displacement of flexible diaphragms using photoelectric means
- G01L9/0077—Transmitting or indicating the displacement of flexible diaphragms using photoelectric means for measuring reflected light
- G01L9/0079—Transmitting or indicating the displacement of flexible diaphragms using photoelectric means for measuring reflected light with Fabry-Perot arrangements
Definitions
- SEMICONDUCTOR DEEP CAVITY DEVICE ⁇ This invention relates to a semiconductor deep cavity device, and to a method of making a semiconductor deep cavity device.
- a typical known semiconductor cavity device comprises a diaphragm of semiconductive material (typically silicon) bonded 05 in spaced relationship to a non-conductive substrate (typically glass) through an annular insulating spacer layer of e.g. silicon nitride, the silicon optionally having an annular trench etched in 1t, the better to define the edge of the cavity thus formed between the diaphragm and the substrate and conducing to a more 10 uniform diaphragm movement and reduced bending.
- the glass substrate may carry a metallic electrode which is disposed between the glass and the silicon within the cavity but arranged for connection to external circuitry.
- Capacitative sensing has its limitations and it has been proposed to improve the utility of such semiconductor cavity devices by exploiting their optical addressability. Certain types of optical instrumentation work best with cavity depths 1n such devices substantially greater than the I ⁇ m which may be regarded as standard In 25 capacitative devices. The present invention therefore is aimed at deeper cavities.
- Cavities of the desired depth could be formed by etching the silicon to a defined depth, but the surface finish would not be as good as that of the unetched surface and dimensional tolerances would be worse ( ⁇ 5%) . Dimensional control could be improved by utilising an epitaxial etch stop process, but this would impose a cost penalty and the surface finish would still not be as good as a polished wafer.
- a further problem with deep cavities is that (where desired) subsequently etching the annular boundary trench is made more difficult since the deeper the cavity, the more non-planar the surface for photolithography. This could be overcome by instead forming the trench on the backside of the silicon wafer, but apart from the difficulty of double-sided mask alignment, a backside trench is not as effective at reducing bending of the diaphragm inner surface.
- a semiconductor deep cavity device comprises a relatively rigid optically transparent substrate bearing a semiconductor wafer, characterised in that between the wafer and the substrate is interposed an apertured sheet of a glass, the aperture of which defines the device cavity between the substrate and the wafer.
- the wafer may have an annular trench in its surface facing the substrate, with the boundary of the aperture of the interposed glass sheet substantially coinciding with that of the trench.
- a method according to the invention of making such a device comprises placing the apertured sheet and the wafer in their relative positions and applying an electrostatic field between them sufficient to bond them, and (previously, simultaneously or subsequently) placing the substrate and the apertured sheet in their relative positions and applying an electrostatic field between them sufficient to bond them.
- the bonding step is preferably accomplished using the field-assisted bonding process which is sometimes referred to as anodic bonding, Mallory bonding or electrostatic bonding, at a suitably elevated temperature. With this process, the semiconductive sheet and the substrate are electrostatically pulled together and it has been postulated that both the substrate and insulating layer soften to effect a bond between the insulating layer and the substrate.
- the "bond" is such that a hermetic seal is provided to the cavity.
- the substrate may have a different composition from the apertured glass sheet, In which case the glass with the greater alkali content should be treated as the anode in the electrostatic bonding. Divalent cations are so relatively Immobile 1n glass that their content can be ignored, and trivalent cations (aluminium) are even more sessile.
- one of the glass surfaces can be metallised with a thin coating and this surface can then be treated as the anode for bonding to the other glass component.
- This method is preferable for high accuracy devices since with fewer thick materials, stress effects will be reduced. Also it would enable the use of Corning 1729 glass which would extend the temperature capability of the devices to >600°C.
- the substrate carries a partially reflective coating 1n the cavity, though with some optical instrumentation it is preferable to have a large-gap (>5mm) optical cavity and therefore the partially reflecting coating would then be provided on the outer surface, with an anti-reflection coating on the inner surface.
- the structures could be made in wafer form with the spacer 7 being a polished disc or sheet of glass with an array of holes 8 machined in by e.g. ultrasonic drilling, mask etching, sand blasting, water jet drilling or laser cutting, to define cavities.
- 150 ⁇ m is a typical thickness for glass cover slips, or thicker glass may be used (for mechanical strength) and then thinned down to 150 ⁇ m after bonding to the silicon but before bonding to the substrate.
- the region of silicon within the trench 2 forms a diaphragm 9.
- the spacer 7 is drilled to form the cavities 8 and 1s then lapped and polished on both sides to produce the required thickness and surface finish.
- Standard pyrex glass (Corning code 7740) Is a suitable material for the spacer 7. This material has 4.2% alkali content (3.8% Na 2 0, 0.4% K 2 0) whereas 7070 (1.2% L1 2 0, 0.5% K 2 0) would be a suitable material for the substrate 4.
- metallised glass it is possible for the three layer structure to be bonded simultaneously. However, it is usually more convenient to perform the bonding in two stages, for example a silicon/glass bond of the spacer 7 to the silicon pill 1 followed by a glass/glass bond of the spacer to the substrate 4. Glasses of different composition can be bonded if the type with the greater alkali content is treated as the anode.
- an optical fibre 10 is bonded to the underside of the glass substrate 4.
- the device may thus be interrogated optically. Reflections (of light sent up the fibre 10) from the partly reflecting coating 5 can be differentiated interferometrically from those from the diaphragm 9 (silicon being highly reflective by itself), revealing the depression (due to pressure or acceleration) of the diaphragm 9.
- the resultant structure has a 150 ⁇ m deep cavity, one would not utilise all of this for the working or dynamic range of the device.
- the silicon diaphragm thickness can be controlled to ensure that the maximum acceptable movement equates to the upper working pressure requirement.
- the trench 2 affords a more uniform diaphragm movement and reduced bending.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Pressure Sensors (AREA)
- Joining Of Glass To Other Materials (AREA)
- Recrystallisation Techniques (AREA)
- Laminated Bodies (AREA)
- Micromachines (AREA)
Abstract
Description
Claims
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9212940A GB2255230A (en) | 1989-12-28 | 1992-06-18 | Semiconductor deep cavity device |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB898929277A GB8929277D0 (en) | 1989-12-28 | 1989-12-28 | Semiconductor deep cavity device |
GB8929277.5 | 1989-12-28 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO1991010119A2 true WO1991010119A2 (en) | 1991-07-11 |
WO1991010119A3 WO1991010119A3 (en) | 1991-09-19 |
Family
ID=10668551
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1990/002034 WO1991010119A2 (en) | 1989-12-28 | 1990-12-28 | Semiconductor deep cavity device |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0507815A1 (en) |
JP (1) | JPH05505023A (en) |
GB (1) | GB8929277D0 (en) |
WO (1) | WO1991010119A2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2259039A1 (en) * | 2009-06-05 | 2010-12-08 | Simea Optic AB | A fibre optical system and use thereof |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0196784A2 (en) * | 1985-03-14 | 1986-10-08 | Imperial Chemical Industries Plc | Fabry Perot pressure sensor with diaphragm |
GB2202936A (en) * | 1987-03-31 | 1988-10-05 | Plessey Co Plc | Optical fibre pressure or displacement sensor |
-
1989
- 1989-12-28 GB GB898929277A patent/GB8929277D0/en active Pending
-
1990
- 1990-12-28 WO PCT/GB1990/002034 patent/WO1991010119A2/en not_active Application Discontinuation
- 1990-12-28 JP JP50186990A patent/JPH05505023A/en active Pending
- 1990-12-28 EP EP19910901486 patent/EP0507815A1/en not_active Withdrawn
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0196784A2 (en) * | 1985-03-14 | 1986-10-08 | Imperial Chemical Industries Plc | Fabry Perot pressure sensor with diaphragm |
GB2202936A (en) * | 1987-03-31 | 1988-10-05 | Plessey Co Plc | Optical fibre pressure or displacement sensor |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2259039A1 (en) * | 2009-06-05 | 2010-12-08 | Simea Optic AB | A fibre optical system and use thereof |
US8752434B2 (en) | 2009-06-05 | 2014-06-17 | Simea Optic Ab | Fibre optical system and use thereof |
Also Published As
Publication number | Publication date |
---|---|
JPH05505023A (en) | 1993-07-29 |
WO1991010119A3 (en) | 1991-09-19 |
GB8929277D0 (en) | 1990-02-28 |
EP0507815A1 (en) | 1992-10-14 |
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