BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate aspects of the embodiments and, together with the background, brief summary, and detailed description serve to explain the principles of the embodiments.
FIG. 1 illustrates a composite, top view of all layers comprising a flow sensor in accordance with aspects of the embodiments;
FIG. 2 illustrates a side view of a substrate in accordance with aspects of certain embodiments;
FIG. 3 illustrates a side view of a flow sensor in accordance with aspects of certain embodiments;
FIG. 4 illustrates a side view of a substrate having dielectric and conductor layers in accordance with aspects of some embodiments;
FIG. 5 illustrates two side views of a flow sensor with patterned dielectric and conductor layers in relation to a channel and air bridge structure in accordance with aspects of some embodiments;
FIG. 6 illustrates dual spiral RTDs in accordance with aspects of the embodiments;
FIG. 7 illustrates a Wheatstone bridge in accordance with aspects of certain embodiments; and
FIG. 8 illustrates a high level flow diagram of producing a flow sensor in accordance with aspects of the embodiments.
DETAILED DESCRIPTION
The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. In general, the figures are not to scale.
FIG. 1 illustrates a composite top view of all layers representing a complete flow sensor, residing on a substrate 101 in accordance with aspects of the embodiments. A fluid can flow from a channel inlet 102 to a channel outlet 103. As the fluid flows, it passes a first upstream temperature sensor 104 and a second upstream temperature sensor 105. The fluid can then be heated by a heater 113. The heated fluid then flows past a first downstream temperature sensor 106 and a second downstream temperature sensor 107.
A first contact pad 108 and a second contact pad 109 are electrically connected to the second upstream temperature sensor 105. An electrical current can flow into the first contact pad 108, through the second upstream temperature sensor 105 and out the second contact pad 109. The other temperature sensors are similarly connected to contact pads. The contact pads can be used to connect the temperature sensors to one another and to external circuitry.
A reference resistor 110 is electrically connected across a third contact pad 111 and a fourth contact pad 112. The reference resistor 110 can be made of the same material as the temperature sensors. As such, the reference resistor 110 can be used to measure properties of the temperature sensor materials. The reference resistor 110 can also be used to measure the temperature of the substrate.
FIG. 2 illustrates a side view of a substrate 201 in accordance with aspects of certain embodiments. The substrate 201 can be a wafer such as those used in semiconductor processing. Substrates of silicon, glass, quartz, and other materials are often used in semiconductor processing.
FIG. 3 illustrates a side cross section view of a flow sensor in accordance with aspects of certain embodiments. A channel 303 through the substrate 201 provides a pathway for fluid flow. An air bridge 304 supports temperature sensors and a heater such as the first upstream temperature sensor 301 and the second upstream temperature sensor 302. A fluid such as air or water flowing through the channel 303 and possibly above the air bridge 304 transfers energy from the heater to the downstream temperature sensors. The upstream temperature sensors 301 and 302 can measure the fluid temperature before it is heated. The channel 303 is illustrated with sloped sidewalls as typically result from a KOH etch process. Other etch processes can produce other channel shapes.
FIG. 4 illustrates a side cross section view of a substrate 401 having dielectric 402 and conductor 403 layers in accordance with aspects of some embodiments. A silicon substrate can have a silicon nitride (Si3N4) layer 402 and a permalloy (NiFe) layer 403. The nitride layer can have a thickness of approximately 5000 angstroms. The permalloy layer can have a thickness ranging from 100 to 400 angstroms.
FIG. 5 illustrates two side cross section views of a flow sensor with patterned dielectric and conductor layers in relation to a channel and air bridge structure in accordance with aspects of some embodiments. In the first view, a channel 503 has been etched in the substrate 401 leaving an air bridge 402 of nitride above the channel 503. The air bridge portion of 402 supports temperature sensors and a heater such as the first upstream temperature sensor 501 and the second upstream temperature sensor 502. The second cross section view is at a right angle to the first cross section view and illustrates that the air bridge 402 supports temperature sensors and a heater 505 such as the second upstream temperature sensor 502, the second downstream temperature sensor 504 and heater 505.
FIG. 6 illustrates dual spiral RTDs in accordance with aspects of the embodiments. In the upper RTD 601, an electrical current can flow into the first contact pad 602 and then into the dual spiral. After it reaches the center 604, the current flows back out of the dual spiral and eventually flows out the second contact pad 603. The lower RTD 605 illustrates the commercially available 0680 chip which is a laser trimmed permalloy RTD manufactured by Honeywell. The dual spiral structure is ideal for ferromagnetic RTDs because it minimizes the effect of magnetic fields.
FIG. 7 illustrates a Wheatstone bridge in accordance with aspects of certain embodiments. An applied voltage 701 is applied across the Wheatstone bridge causing a current to flow through the legs of the bridge. The first leg has RTD 1702 connected in series with RTD 2703. The second leg has RTD 3704 connected in series with RTD 4705. Resistance differences among the RTDs lead to differences in the measured voltage 706 existing between node 1707 and node 2708. For example, RTD 1702 and RTD 4705 can be upstream temperature sensors while RTD 2703 and RTD 3704 are downstream temperature sensors. Fluid flowing past the heater causes resistance changes between the upstream and downstream sensors and thereby to a difference in the measured voltage 706.
FIG. 8 illustrates a high level flow diagram of producing a flow sensor in accordance with aspects of the embodiments. After the start 801, a substrate is obtained 802. Next, a dielectric layer is deposited 803, followed by deposition of a conductive layer 804. Temperature sensors, a heater, and a reference resistor are produced 805. Openings are then etched to expose the substrate 806. The air bridge is formed out of the dielectric layer of 803 by etching the flow channel 807. Temperature sensors and heater reside on the air bridge of the completed flow sensor 808.
It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
Patent Application
20070295082
