Information
-
Patent Grant
-
6533951
-
Patent Number
6,533,951
-
Date Filed
Thursday, July 27, 200024 years ago
-
Date Issued
Tuesday, March 18, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Gulakowski; Randy
- Smetana; J
Agents
- Stevens; Walter S.
- Rushefsky; Norman
-
CPC
-
US Classifications
Field of Search
US
- 216 2
- 216 17
- 216 27
- 216 75
- 216 77
- 216 79
- 216 99
- 216 102
- 137 147
- 137 282
- 137 4544
- 137 56501
- 137 56511
- 137 56532
- 417 51
- 417 53
- 417 54
- 417 55
-
International Classifications
-
-
Disclaimer
Terminal disclaimer Term Extension
23
Abstract
A method of manufacturing a pump [10] for pumping various primary fluids. A body is formed from silicon dies [102,104]. A primary fluid channel [110] is formed in the body and a primary fluid supply [122] is coupled to the primary fluid channel [110] to supply a primary fluid to the primary fluid channel [110]. A mechanism for introducing a secondary fluid to an interface region of the primary fluid channel [110] is formed in the body. An energy delivery device is formed in the body to deliver energy to an interface between region between the primary fluid and the secondary fluid to create a thermal gradient along the fluid interface. The thermal gradient results in a surface tension gradient along the interface. The primary fluid will move to compensate for the surface tension gradient. Various semiconductor fabrication processes can be used to form the elements on the body.
Description
FIELD OF THE INVENTION
The present invention relates generally to pumping devices, and more particularly to a method of manufacturing a fluid pump, such as a microscale fluid pump, using semiconductor fabrication techniques
BACKGROUND OF THE INVENTION
It is well known to utilize microscale fluid pumps to pump various fluids. The term “microscale,” as used herein, refers to an apparatus or method using a minimum amount of fluid to effectively perform a function. Many microscale pumps incorporate thermal technology, whereby heat is used to move the fluid. For example, in a bubble jet printer ink in a channel is heated to a boil to create a bubble until the pressure ejects a droplet of the ink out of a nozzle. The bubble then collapses as the heating element cools, and the resulting vacuum draws fluid from a reservoir to replace the fluid that was ejected from the channel. Thermal technology requires that the fluid to be pumped be resistant to heat, i.e. capable of being boiled without significant breakdown. Also, the need for a cooling period between ejecting successive droplets from a nozzle places speed limitations on thermal microscale pumps.
Piezoelectric microscale pumps, such as that disclosed in U.S. Pat. No. 5,224,843, have a piezoelectric crystal in the fluid channel that flexes when an electric current flows through it to force a drop of fluid out of a nozzle. Piezoelectric technology is faster and provides more control over the fluid movement as compared to thermal technology. Also, because the fluid to be pumped is not heated significantly, the fluid can be selected based on its relevant properties rather than its ability to withstand high temperatures. However, piezoelectric microscale pumps are complex and thus expensive to manufacture. U.S. Pat. Nos. 5,362,213 and 5,499,409 disclose microscale pumps having movable parts. Such pumps are relatively complex and required high maintenance.
Further, microscale fluid pumps find use in various other applications in which a high degree of control is required and high temperatures are to be avoided. For example, microscale fluid pumps can be used in biological heat-pipe type devices, devices which administer small doses of fluid into a larger stream of fluid, devices which pump various solutions that are unstable when boiled, devices which pump biological materials and other materials that must be maintained at a constant temperature, and other generic pumping applications. Accordingly, there is a need for a microscale fluid pump that is simple in construction and capable of pumping fluid quickly and accurately without boiling the fluid. Further, there is a need for a microscale fluid pump design and manufacturing method that easily can be manufactured using semiconductor fabrication techniques.
It is known to utilize semiconductor manufacturing technology to form devices having fluid channels, For example, U.S. Pat. No. 5,890,745 discloses a fluid coupler that includes a fluid channel formed by etching a semiconductor wafer. However, the fluid coupler disclosed in this patent has no mechanism for moving fluid and merely serves as a conduit between fluid systems.
SUMMARY OF THE INVENTION
An object of the invention is to increase the control accuracy of microscale fluid pumps by employing precision semiconductor manufacturing techniques.
Another object of the invention is to simplify the construction of microscale fluid pumps.
Another object of the invention is to utilize semiconductor fabrication techniques to manufacture a fluid pump.
Another object of the invention is to utilize standard CMOS processes to manufacture a microscale fluid pump.
Another object of the invention is to impart motion to fluid without the need for moving parts or boiling of the fluid.
Another object of the invention is to reduce the power required by microscale fluid pumps.
The invention achieves these and other objects through a first aspect of the invention which is a method for manufacturing a fluid pump comprising the steps of defining a primary fluid channel in a body, forming a primary fluid aperture in communication with the primary fluid channel, forming a mechanism on the body for introducing a secondary fluid to an interface region of the primary fluid channel, and forming an energy delivery device proximate the interface region.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments of the invention, and the accompanying drawings, wherein:
FIG. 1
is a top view of a pump in accordance with a first preferred embodiment of the invention with portions rendered transparent;
FIG. 2
is a perspective view of the pump of
FIG. 1
;
FIG. 3
is a sectional view taken along line
3
—
3
of
FIG. 1
;
FIG. 4
is an enlarged view of portions of
FIG. 3
;
FIGS. 5-13
illustrate the steps of manufacturing a first die of the first preferred embodiment;
FIGS. 14-19
illustrate the steps of manufacturing a second die of the first preferred embodiment;
FIGS. 20 and 21
illustrate a first preferred procedure of bonding the first and second dies of the first preferred embodiment;
FIG. 22
illustrates a second preferred procedure of bonding the first and second dies of the first preferred embodiment;
FIG. 23
illustrates a third preferred procedure of bonding the first and second dies of the tint preferred embodiment.
FIG. 24
is a top view of a pump in accordance with a second preferred embodiment of the invention with portions rendered transparent;
FIG. 25
is a perspective view of the pump of
FIG. 24
;
FIG. 26
is an enlarged sectional view taken along line
26
—
26
of
FIG. 25
;
FIG. 27
is a perspective view of a pump in accordance with a third preferred embodiment of the invention;
FIG. 28
is a perspective view of a pump in accordance with a fourth preferred embodiment of the invention; and
FIGS. 29-33
illustrate the steps of manufacturing a first die of the second preferred embodiment.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1-4
illustrate a first preferred embodiment of the invention. The preferred embodiment is formed from a silicon substrate using known semiconductor fabrication techniques as described in detail below. However, the invention can be formed of various materials using various fabrication techniques. Microscale pump
10
includes silicon substrate
100
(serving as a pump body) having primary fluid channel
110
formed therein, through an etching process or the like. Primary fluid ports
120
communicate with primary fluid channel
110
. One of primary fluid ports
120
can be coupled to supply
122
of primary fluid to be pumped (as illustrated schematically by the dotted line in
FIG. 3
) and the other of primary fluid ports
120
can be coupled to a nozzle or any other orifice, channel, or the like through which fluid is to be ejected or otherwise transported. As will become apparent below, microscale pump
10
can be operated in either a forward or reverse direction and thus primary fluid ports
120
are interchangeable with one another.
As best illustrated in
FIGS. 3 and 4
, secondary fluid channel
130
is formed in substrate
100
in communication with an interface region of primary fluid channel
110
. Secondary fluid channel
130
is coupled to external supply
132
of a secondary fluid, such as a pressurized supply of nitrogen, hydrogen, air or oxygen. Secondary fluid channel
130
and external supply
132
are operative to introduce the secondary fluid to the interface region of primary fluid channel
110
. The secondary fluid is used to create a fluid interface with the primary fluid, as described in detail below, and preferably is not pumped by microscale pump
10
.
As illustrated in
FIG. 4
a first insulating layer, such as a thermal oxide layer
140
, is grown on a surface of substrate
100
using techniques described below. Heating elements
150
and
160
are formed on insulating layer
140
respectively at opposing sides of the interface region of primary fluid channel
110
. Heating elements
150
and
160
can include resistive elements and can each comprise doped polysilicon layer
152
/
162
deposited on thermal oxide layer
140
and aluminum layers
154
/
164
formed thereon to serve as an electrical conductor. As illustrated in
FIG. 1
, aluminum layer
154
defines contact pads
158
and conductor
159
and aluminum layer
164
defines contact pads
168
and conductor
169
. Accordingly, electric power can be supplied to the resistive elements of heating elements
150
and
160
to generate heat at the interface region. Silicon dioxide layer
156
/
166
can be formed as a second insulating layer to insulate the other components the manufacturing method of the first preferred embodiment is discussed in detail below.
During operation of microscale pump
10
, a primary fluid to be pumped is supplied to primary fluid channel
110
through one of primary fluid ports
120
. Further, a relatively small metered amount of a secondary fluid, such as a gas, is introduced into the interface region of primary fluid channel
110
through secondary fluid channel
130
to form bubble
170
of the secondary fluid as illustrated in
FIGS. 3 and 4
. A fluid interface is thus defined between the primary fluid and the secondary fluid in the interface region of primary fluid channel
110
. In this state, contact pads
158
and
168
can be coupled to a source of electric power that is controlled in a desired manner to selectively supply current to one of heating elements
150
or
160
. For example, when electric current is supplied to heating element
150
, through contact pads
158
and conductor
159
, heating element
150
generates heat at one side of the interface region. Accordingly, a temperature gradient is defined in the interface region along the interface between the primary fluid and the secondary fluid. Since the surface tension between two dissimilar fluids is dependent on the temperature at the interface of the fluids, a surface tension gradient is formed along the fluid interface. The primary fluid will naturally move in the direction of decreasing temperature, i.e. the direction indicated by arrow x in
FIGS. 1 and 2
, to compensate for the surface tension gradient. Accordingly, motion is imparted to the primary fluid in response to activation of heating element
150
. Heating element
160
can be activated in a similar manner to move the primary fluid in the direction of arrow y. Further, heating elements
150
and
160
can be activated together or separately to varying degrees to precisely control the temperature gradient along the fluid interface and thus precisely control movement of the primary fluid.
The method of manufacturing the first preferred embodiment will be described in detail below with respect to
FIGS. 5-21
. The preferred embodiment is comprised of two dies and each die is processed simultaneously with other dies as part of a respective wafer which is subsequently cut into plural dies, as is well known. However, for the sake of clarity, only one die of the wafer is illustrated and discussed. Accordingly, the various layers and films are not illustrated on the sides of each die because the die is processed as part of a larger wafer. Also, the term “die, as used herein, refers to any body place, such as a wafer, portion of a wafer, or the like. Specifically substrate
100
can be comprised of first die
102
and second die
104
(see FIG.
3
), made of silicon for example. Dies
102
and
104
can be processed separately and subsequently joined together through a bonding process or the like. Beginning with die
102
as bare silicon illustrated in
FIG. 5
, thermal oxide layer
140
is grown thereon, as illustrated in
FIG. 6
for the purpose of insulating the electronics from the silicon beneath. For example a steam oxidation process can be performed at 1100° C., for 240 minutes. This process will yield about 1.3 microns of oxide, i.e. thermal oxide layer
140
will be about 1.3 microns thick. However, 2000-3000 angstroms of oxide is adequate to insulate the silicon from the electronics. The additional thickness of thermal oxide layer
140
allows for possible degradation or damage during later processes.
Next, as illustrated in
FIG. 7
, doped polysilicon layer
152
/
162
of polysilicon is deposited on thermal oxide layer
140
using a low pressure chemical vapor deposition (LPCVD) process. Polysilicon layer
152
/
162
can be n-doped or p-doped. For example the LPCVD process can be conducted for 120 minutes at 610° C. This recipe will yield polysilicon layer
152
/
162
of about 3000 angstroms in thickness on both faces of die
102
. The next step is to anneal polysilicon layer
152
/
162
to reduce the resistively thereof to about 25 ohms/mm
2
(about a factor of ten difference with respect to the polysilicon layer
152
/
162
prior to annealment). The annealment step can be accomplished by heating die
102
in a nitrogen environment at 1 atmosphere and 900° C. for about one to two hours.
Next, as illustrated in
FIG. 8
, pads
158
/
168
and conductors
159
/
169
can be formed by sputtering aluminum layer
154
/
164
on polysilicon layer
152
/
162
, on the top face of die
102
. A photoresist lithography process can be used to etch the pattern of pads
158
/
168
and conductors
159
/
169
. For example, wafer
102
can be dehydrated and coated with HMDS (Hexamethyldisilazane) to facilitate adhesion between aluminum layer
154
/
164
and the subsequent photoresist layer. A photoresist layer can then be coated on aluminum layer
154
/
164
and spun to about 1.2 microns in thickness. The layer can be soft baked for about 60 seconds at 90° C., exposed, developed, and hard bake for about 45 minutes at 120° C. A wet etch process can be used until portions of aluminum layer
154
/
164
beneath the exposed areas are removed to form the desired patterns in aluminum layer
154
/
164
. Subsequently, the photoresist layer can be stripped and die
102
can be cleaned in de-ionized water to yield the pattern illustrated in FIG.
9
. Of course since
FIG. 9
is in cross section, the entire pattern is not visible. However,
FIGS. 1 and 2
above illustrate the pattern more clearly. Note that, polysilicon layer
152
/
162
on the front and back of die
102
will be exposed to the aluminum etchant but will not be removed or otherwise affected thereby.
Next, polysilicon layer
152
/
162
is patterned into resistive elements (leaving conductors
159
/
169
and pads
158
and
168
) using a similar photolithography process as that described above. In particular, a zig-zag or other pattern can be formed of polysilicon layer
152
/
162
to form resistive heating elements. The etching process will stop at thermal oxide layer
140
but polysilicon layer
152
/
162
on the back face will be removed in the wet etch bath as illustrated in FIG.
10
. The photoresist can then be stripped and die
102
can be cleaned.
Next, the electrical components are insulated with silicon dioxide layer
156
/
166
deposited with an LPCVD process to a thickness of about 3000 angstroms, as illustrated in FIG.
11
. Both faces of die
102
are subject to the LPCVD process to form a conformal layer that will follow the existing contours formed by the etching steps discussed above, as illustrated in FIG.
11
. Holes are then formed in silicon dioxide layer
156
/
166
to remove the insulation from contact pads
158
/
168
and from the surface where the bulk silicon must be etched to form secondary fluid channel
130
as illustrated in
FIG. 12. A
plasma etching process can be accomplished in a reactive ion etcher (RIE) so only the top side is etched to form secondary fluid channel
130
, as illustrated in FIG.
13
. In particular, a thick lithography process can be used to pattern the hole and thermal oxide layer
140
can be etched using the RIE process. The same photoresist layer can be used in an inductively coupled plasma (ICP) etching process to get an anisotropic etch all the way through die
102
(this typically requires the attachment of a wafer to the back side of the device wafer to prevent damage to the etcher when the hole though die
102
is completed). The thin membrane of thermal oxide on the back side can be etched, but will be broken by the pressure from the external supply
132
if it is not ruptured during etching.
Second die
104
of the preferred embodiment is formed in the following manner with reference to
FIGS. 14-19
. Thermal oxide layer
142
is grown on silicon die
104
(see
FIG. 14
) as a masking layer as illustrated in FIG.
15
. For example a steam oxidation process at 1100° C. for 240 minutes will yield thermal oxide layer
142
of about 1.3 microns in thickness. Primary fluid channel
110
is then patterned in oxide layer
142
, as illustrated in
FIG. 16
, using the standard lithography process disclosed above. The photoresist is then stripped and wafer
104
is cleaned.
As illustrated in
FIG. 17
, fluid ports
120
are patterned in the silicon after oxide has been selectively removed from these portions of die
104
using the photo resist step disclosed above. The photoresist is then stripped and die
104
is cleaned again. An RIE process can be used to etch primary fluid channel
110
to a specified depth, e.g. 100 micrometers, using oxide layer
142
as a mask, as illustrated in FIG.
28
. Subsequently, oxide layer
142
can be stripped by submersing die
104
in hydrofluoric acid until hydrophobic, as illustrated in
FIG. 19
(this step can be omitted if the oxide layer is desirable in the bonding process as discussed below).
Dies
102
and
104
are bonded to form substrate
100
in the following manner. First, epoxy layer
200
is spread onto one of dies
102
and
104
, as illustrated in FIG.
20
. Dies
102
and
104
are then aligned and held under pressure to form a bond as epoxy layer
190
cures, as illustrated in FIG.
21
. Alternatively, dies
102
and
104
can be aligned and placed under pressure while being heated to a moderate temperature (preferably below 500° C. to avoid melting the aluminum) to form a fusion bond as illustrated in FIG.
22
. Further, as illustrated in
FIG. 23
, oxide layer
142
can be left on the lower surface of die
104
and fusion can be accomplished between oxide layer
142
and silicon dioxide layer
156
/
166
.
FIGS. 24-26
illustrate a second preferred embodiment of the invention. Microscale pump
200
is similar to microscale pump
10
of the first preferred embodiment. However, microscale pump
200
does not have a secondary fluid channel for introducing a secondary fluid. In microscale pump
200
, bubble
220
is formed, i.e. the secondary fluid is introduced, in-situ. In particular, a pair of electrodes
210
are provided proximate an interface region of primary fluid channel
110
. Electrodes
210
are coupled to an external source of electric power. After an aqueous fluid is introduced into primary fluid channel
110
as the primary fluid, electrodes
210
can be energized, i.e. an electric potential can be placed across electrodes
210
, to thereby dissociate the primary fluid into components of hydrogen and oxygen to form bubble
220
of hydrogen and oxygen in the interface region. Other than the in situ formation of bubble
220
, the structure and operation of microscale pump
200
is similar to that of microscale pump
10
and like reference numerals are used to label similar parts in
FIGS. 5-7
. Any primary fluid can be dissociated or otherwise transformed to form the secondary fluid.
FIGS. 29-33
illustrate the method of manufacturing the second preferred embodiment. First, the steps illustrated in
FIGS. 5-11
disclosed above are accomplished in a manner similar to the manufacturing process of the first preferred embodiment. Then, as illustrated in
FIG. 29
, a photolithography process is used to make a negative of the pattern for electrodes
210
(see
FIG. 24
) in photoresist layer
171
. As illustrated in
FIG. 30
platinum layer
172
(or any other appropriate material) can be deposited, through an evaporation process, to about 3000 angstroms thick over photoresist layer
171
. Die
102
can then be dipped in acetone for approximately 1 hour to dissolve photoresist layer
171
using a “liftoff process”. In such a process, photoresist layer
171
is dissolved away and platinum layer
172
lifts off, except for locations where photoresist layer
171
was not present. This leaves platinum layer
172
only at portions corresponding to electrodes
210
as illustrated in FIG.
31
. Subsequently, electrodes
210
can be insulated with oxide layer
174
, in a manner similar to the process discussed above, as illustrated in FIG.
32
. Oxide layer
174
can then be etched away over contacts and a tip of electrode
210
, in a process similar to that described above, as illustrated in FIG.
33
. Die
104
of the second preferred embodiment can be manufactured similar to die
104
of the first preferred embodiment and the dies can be bonded in any one of the processes described above with respect to the first preferred embodiment.
FIG. 27
illustrates a third preferred embodiment of the invention. Microscale pump
300
is similar to microscale pump
10
of the first preferred embodiment and microscale pump
200
of the second preferred embodiment. However, microscale pump
300
includes plural interface regions each having a mechanism for introducing a secondary fluid, i.e. producing bubble
320
. The mechanism for introducing each bubble
320
of secondary fluid can be similar to that of the first preferred embodiment, i.e. external, or the second preferred embodiment, i.e. in-situ. Microscale pump
300
can create a temperature gradient along one or more fluid interfaces and thus a surface tension gradient along one or more interfaces between the primary fluid and the secondary fluid. Each fluid interface can be used to impart motion to the primary fluid in the manner described above. Because the fluid interfaces are in serial relationship with each other along the flow direction, the pressure or flow volume can be increased as compared to a pump having only one interface region.
FIG. 28
illustrates a fourth preferred embodiment of the invention. Microscale pump
400
is similar to microscale pump
10
of first preferred embodiment and microscale pump
200
of second preferred embodiment. However, microscale pump
400
has a slot opening that supports a long secondary fluid interface oriented appropriately to induce flow when heaters or electrodes
150
and
160
are energized. The high aspect ratio secondary fluid interface provides a large surface area that increase the capacity of the pump. The mechanism for introducing a bubble secondary fluid can be similar to that of first preferred embodiment, i.e. external, or the second preferred embodiment, i.e. in-situ. In addition, a plurality of long bubbles may be utilized to create a multiple fluid interface pump described in the third preferred embodiment.
The secondary fluid can be introduced in any manner. As noted above, the bubble of secondary fluid can be formed in situ or through an external fluid supply. Further, the in situ bubble can be formed through a chemical reaction, through electrical dissociation of molecules, through heat, or in any other manner. The primary fluid can be any fluid that is to be pumped, such as a liquid or gas. The secondary fluid can be any fluid that presents an interface with the primary fluid having the desired surface tension and other properties. The secondary fluid can be selected based on the primary fluid, the pump structure, and other considerations of each application. Any mechanism can be used to introduce the secondary fluid. In fact, one pump may have different types of mechanisms for introducing the secondary fluid.
The pump can be constructed using standard CMOS compatible semiconductor fabrication techniques or any other techniques. The pump can be formed using a silicon substrate as a body or using any other type of body in which the necessary channels can be formed. The body can be comprised of one or more pieces. The pump can be of any size and the components thereof can have various relative dimensions. Accordingly, the pump can be a microscale pump or a larger or smaller device. The heating elements can be any type of energy delivery device, such as resistive heaters, radiation heaters, convection heaters, heat pumps (such as Peltier coolers), chemical reaction heaters (endothermic or exothermic), nuclear reaction heaters, or the like. The pump can be controlled in any appropriate manner, such as with a microprocessor based device having a predetermined program. The heating elements can be activated to provide a desired temperature gradient in any manner. For example, the heating elements can be controlled by adjusting the current therethrough or by intermittent activation in a predetermined manner. There can be one heating element or plural heating element. The various layers and coatings can be formed using any process and of any materials. The pump can be applied to pumping of various fluids, such as ink in a print head, biological materials, medicaments, or any other fluids.
While the foregoing description includes many details and specificities, it is to be understood that these have been included for purposes of explanation only, and are not to be interpreted as limitations of the present invention. Many modifications to the embodiments described above can be made without departing from the spirit and scope of the invention, as is intended to be encompassed by the following claims and their legal equivalents.
|
PARTS LIST
|
Reference No.
Description
|
|
10
Microscale Pump
|
100
Silicon Substrate
|
102
First Die
|
104
Second Die
|
110
Primary Fluid Channel
|
120
Primary Fluid Ports
|
122
Primary Fluid Supply
|
130
Secondary Fluid Channel
|
132
External Supply of a Secondary Fluid
|
140, 142
Thermal Oxide Layer
|
150, 160
Heating Elements
|
152, 162
Polysilicon Layer
|
154, 164
Aluminum Layers
|
156, 166
Silicon Dioxide Layer
|
158, 168
Contact Pads
|
159, 169
Conductor
|
170
Bubble of Secondary Fluid
|
171
Photoresist Layer
|
172
Platinum Layer
|
174
Oxide Layer
|
190
Epoxy Layer
|
200, 300, 400
Microscale Pump
|
210
Electrodes
|
220
Bubble
|
320
Bubble of Secondary fluid
|
|
Claims
- 1. A method for manufacturing a fluid pump comprising the steps of:defining a primary fluid channel in a body; forming a primary fluid aperture in communication with the primary fluid channel; forming a mechanism on the body for introducing a secondary fluid to an interface region of the primary fluid channel; and forming a thermal energy delivery device proximate the interface region, the thermal energy delivery device being adapted to establish a temperature gradient along the interface region of the primary and secondary fluids without boiling of either fluid whereby the primary fluid will move in a direction of decreasing temperature in response to the temperature gradient at the interface region.
- 2. A method as recited in claim 1, wherein said step of forming a mechanism comprises forming an elongated slot for defining an elongated fluid interface.
- 3. A method as recited in claim 1, wherein said steps of defining, forming a primary fluid aperture, forming a mechanism, and forming a thermal energy delivery device each comprise performing semiconductor fabrication steps on the body.
- 4. A method as recited in claim 3, wherein said body comprises first and second dies that are bonded to each other to form the primary fluid channel between them.
- 5. A method as recited in claim 4, wherein said step of forming an energy delivery device comprises forming a first insulation layer on the first die, forming a doped polysilicon layer on the first insulation layer, forming a conductive layer on the polysilicon layer, patterning the conductive layer into a desired form, patterning the polysilicon layer into resistive elements, and forming a second insulation layer over desired portions of the conductive layer and the polysilicon layer.
- 6. A method as recited in claim 5, wherein said step of forming a first insulation layer comprises growing a thermal oxide layer on the first die.
- 7. A method as recited in claim 5, wherein said step of forming a doped polysilicon layer comprises depositing polysilicon on the first insulation layer using an LPCVD process.
- 8. A method as recited in claim 5, wherein said step of forming a conductive layer comprises sputtering aluminum on the polysilicon layer.
- 9. A method as recited in claim 5, wherein said steps of patterning the conductive layer and patterning the polysilicon layer each comprise photolithographic etching.
- 10. A method as recited in claim 5, wherein said step of forming a mechanism comprises forming a secondary fluid channel through said first die.
- 11. A method as recited in claim 10, wherein said step of forming a primary fluid channel comprises forming a channel pattern in the second die, and attaching the second die to the first die with the channel pattern facing the energy delivery device.
- 12. A method as recited in claim 5, wherein said step of forming a mechanism comprises forming electrodes proximate the interface region.
- 13. A method as recited in claim 12, wherein said step of forming a primary fluid channel comprises forming a channel pattern in the second die, and attaching the second die to the first die with the channel pattern facing the energy delivery device.
US Referenced Citations (19)