I 1111111111111111 11111 111111111111111 111111111111111 IIIII lll111111111111111
`US009801415B2
`
`c12) United States Patent
`Tu
`
`(IO) Patent No.:
`(45) Date of Patent:
`
`US 9,801,415 B2
`Oct. 31, 2017
`
`6,136,212 A * 10/2000 Mastrangelo ........ BOlJ 19/0093
`216/27
`A61M 1/0281
`392/443
`6,821,819 Bl* 11/2004 Benavides .......... HO lL 23/4334
`257 /E23 .092
`A61K 9/007
`128/203.27
`2/2007 Moon ..................... BOlF 5/061
`137/15.01
`
`6,748,164 Bl*
`
`6/2004 Kuzyk
`
`7,088,914 B2 *
`
`8/2006 Whittle .
`
`7,171,975 B2 *
`
`8,678,012 B2
`8,739,786 B2
`8,742,974 Bl
`8,757,147 B2
`2002/0084510 Al*
`
`2003/0106551 Al*
`
`3/2014 Li et al.
`6/2014 Po strna et al.
`6/2014 Sishtla et al.
`6/2014 Terry et al.
`7/2002 Jun ..................... B81C 1/00119
`257 /536
`........ A61M 11/041
`128/203.16
`
`6/2003 Sprinkel, Jr.
`
`(Continued)
`
`OTHER PUBLICATIONS
`
`Innovative Sensor Technology; published Mar. 31 2014 www.ist(cid:173)
`ag.com/eh/ist-ag/en/home.nsf/contentview/
`EBOD258CF05CA816Cl2578930071FD43.*
`
`Primary Examiner - David Angwin
`Assistant Examiner -
`Justin Dodson
`(74) Attorney, Agent, or Firm -
`James M. Wu; JW Law
`Group
`
`ABSTRACT
`(57)
`A MEMS vaporizer is described which can be used for
`electronic cigarettes. The vaporizer mainly composes: a
`silicon substrate, a micro-channel array, a membrane sus(cid:173)
`pending over the micro-channel array and supported by the
`silicon substrate, a resistance heater and a resistance tem(cid:173)
`perature sensor are disposed on the membrane. Since the
`vaporizer is a silicon-based integrated actuator which pro(cid:173)
`vides advantages including small size, compact structure,
`lower power consumption, lower cost, increased reliability,
`higher precision, and more environmental friendliness.
`
`25 Claims, 4 Drawing Sheets
`
`(54) MEMS VAPORIZER
`
`(71) Applicant: Xiang Zheng Tu, San Jose, CA (US)
`
`(72)
`
`Inventor: Xiang Zheng Tu, San Jose, CA (US)
`
`(73) Assignee: POSIFA Microsytems, Inc., San Jose,
`CA (US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 102 days.
`
`(21) Appl. No.: 14/329,709
`
`(22) Filed:
`
`Jul. 11, 2014
`
`(65)
`
`Prior Publication Data
`
`US 2016/0007653 Al
`
`Jan. 14, 2016
`
`(51)
`
`(2006.01)
`(2006.01)
`(2006.01)
`(2006.01)
`
`Int. Cl.
`A24F 47100
`B23K 31102
`G03F 7120
`F22B 1128
`(52) U.S. Cl.
`CPC ............ A24F 471008 (2013.01); F22B 11282
`(2013.01); F22B 11284 (2013.01)
`( 58) Field of Classification Search
`CPC ....... A24F 47/008; B23K 31/02; F22B 1/284;
`G03F 7/20
`USPC .................................................. 392/403-405
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,808,009 A *
`
`5,644,676 A *
`
`2/ 1989 Sittler ..................... F25D 21/02
`338/22 SD
`GOlJ 5/522
`219/544
`
`7/1997 Blomberg
`
`I I 7
`
`116
`
`NJOY Exhibit 1015.001
`
`

`

`US 9,801,415 B2
`Page 2
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`2004/0056016 Al*
`
`2005/0155615 Al*
`
`2007/0095507 Al*
`
`2008/0087629 Al *
`
`4/2008 Shimomura
`
`3/2004 Tian .................... F27B 17 /0025
`219/408
`7/2005 Rohdewald .............. A24D 3/14
`131/334
`5/2007 Henderson ............ F28D 15/043
`165/104.26
`B23K 26/0661
`216/11
`2008/0248613 Al * 10/2008 Chen ..................... B81B 3/0005
`438/115
`2008/0257367 Al * 10/2008 Paterno ................. A24F 47/008
`131/328
`
`* cited by examiner
`
`NJOY Exhibit 1015.002
`
`

`

`U.S. Patent
`
`Oct. 31, 2017
`
`Sheet 1 of 4
`
`US 9,801,415 B2
`
`117
`
`116
`
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`ll:2
`JOS 109 103
`
`ll(J
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`106 105
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`102
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`210
`
`FIG. 2
`
`NJOY Exhibit 1015.003
`
`

`

`U.S. Patent
`
`Oct. 31, 2017
`
`Sheet 2 of 4
`
`US 9,801,415 B2
`
`303
`
`304
`
`306
`
`307
`
`FIG. 3
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`FIG .. 5
`
`NJOY Exhibit 1015.004
`
`

`

`U.S. Patent
`
`Oct. 31, 2017
`
`Sheet 3 of 4
`
`US 9,801,415 B2
`
`7
`403
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`
`NJOY Exhibit 1015.005
`
`

`

`U.S. Patent
`
`Oct. 31, 2017
`
`Sheet 4 of 4
`
`US 9,801,415 B2
`
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`
`NJOY Exhibit 1015.006
`
`

`

`US 9,801,415 B2
`
`1
`MEMS VAPORIZER
`
`FIELD OF THE INVENTION
`
`The present invention relates to a vaporizer used for
`vaporizing a liquid for a variety of applications. More
`specifically, the present invention relates to a MEMS (Mi(cid:173)
`cro-electro-mechanical-systems) vaporizer and a tempera(cid:173)
`ture sensor both integrated in a single silicon substrate which
`can be used for inhaling the active ingredients of plant
`material, commonly cannabis, tobacco, or other herbs or
`blends for the purpose.
`
`BACKGROUND OF THE INVENTION
`
`15
`
`2
`and reveal ends of the glass fiber yam are pressed tightly
`between the cotton cloth layer and the glass fiber tube; a
`synthetic fiber layer is filled within the annular shape space
`between the cotton cloth layer and the fixing sleeve for
`holding the tobacco solution.
`It can be seen from the above described vaporizers that
`each vaporizer generally consists of a small heating element
`responsible for vaporizing e-liquid, as well as a wicking
`material that draws liquid in. Along with a battery, the
`10 vaporizer is the central component of every electronic
`cigarette. The vaporizer is assembled by putting together of
`all separately manufactured parts. Several disadvantages can
`be found with these vaporizers:
`(1) Due to discrete parts, the design, commissioning and
`installation of the vaporizer is relatively complicated.
`(2) Jointing and connecting of the discrete parts signifi(cid:173)
`cantly reduce the reliability of the vaporizer.
`(3) Power consumption is relatively high because the
`heater is not allowed to contact with the vaporized
`liquid directly.
`( 4) No temperature sensor for measuring the temperature
`of the heating element directly.
`( 5) Vaporized liquid amount cannot be controlled since no
`air flow sensor is used for measuring the air flow rate.
`Therefore, a need exists to overcome the problems with
`the prior art as discussed above.
`
`20
`
`A vaporizer is a device used for vaporizing a liquid for the
`purpose of inhalation. It is well known that draw-over
`vaporizers can be used for both civilian and military anes(cid:173)
`thesia. The earliest vaporizer is an oxford miniature vapor(cid:173)
`izer which has been in service over 40 years.
`Since an electronic cigarette was developed the vaporizer
`has become popular. The electronic cigarette is a battery(cid:173)
`powered vaporizer which simulates tobacco smoking by
`producing a vapor that resembles smoke. In order to meet
`the needs of the electronic cigarettes many vaporizers have 25
`been designed and manufactured. Some of them can be
`described in the following US patents.
`U.S. Pat. No. 8,742,974 discloses a vaporizer in which the
`heating device can be configured by fixing heater plates to
`cover the front, rear, left and right side surfaces and the 30
`upper and bottom surfaces of the chamber. The heater plate
`may be formed by, for example, incorporating a heater in a
`plate made of aluminum or copper, etc.
`U.S. Pat. No. 8,739,786 discloses a portable hand-held
`vaporizer for electronic cigarette application. The heating 35
`element of the vaporizer is a tungsten-based metallic alloy in
`the form of a coil that is disposed at least partially within the
`airflow passage. In other embodiments, the heating element
`is made from nickel-chrome, other types of metals, or
`metal-based composites that have a generally low thermal 40
`resistivity and are generally safe to pass air through for
`human consumption. In further embodiments, the heating
`element may be in the form of a plate or other shape, and
`may be located within a piece of glass or in close proximity
`to the airflow passage, but yet still able to effectively transfer 45
`heat.
`U.S. Pat. No. 8,757,147 discloses a personal vaporizer
`unit which comprises a first wick element and a second wick
`element having a porous ceramic. The first wick element is
`adapted to directly contact a liquid held in a reservoir. The 50
`reservoir may be contained by a cartridge that is removable
`from the personal vaporizer unit. A heating element is
`disposed through the second wick element. An air gap is
`defined between the first wick element and the second wick
`element with the heating element exposed to the air gap. Air
`enters the first wick element through a hole in a housing
`holding the first wick element.
`U.S. Pat. No. 8,678,012 discloses a tobacco solution
`atomizing device for electronic cigarette which comprises a
`glass fiber tube, a glass fiber yarn, a heating coil, a cotton
`cloth layer and a synthetic fiber layer, wherein the glass fiber
`yarn is insert into the heating coil which is then located
`inside the glass fiber tube; the ends of the glass fiber silk and
`two wires which are used to electronically connect the
`heating coil to the positive and negative electrode connec- 65
`tors extends outward through the glass fiber tube; the cotton
`cloth layer enwraps the outside wall of the glass fiber tube
`
`SUMMARY OF THE INVENTION
`
`An objective of the present invention is to provide a
`MEMS vaporizer which can overcome the above mentioned
`problems with the prior art.
`In order to achieve this goal a MEMS vaporizer is
`provided by the present invention. The MEMS vaporizer
`composes: a silicon substrate, a micro-channel array created
`in the silicon substrate, a membrane suspending over the
`micro-channel array and supported by the silicon substrate,
`a resistance heater disposed on one side portion of the
`membrane and laterally across one end portion of the top of
`the micro-channel array, a resistance temperature sensor
`disposed on the membrane and adjacent to the resistance
`heater, two cavities are recessed in the silicon substrate and
`connected to the two end exits of the micro-channel array
`respectively, which all are integrated to be a vaporizer chip,
`a printed circuit board for packaging the vaporizer chip, a
`reservoir for inserting the printed circuit board therein so as
`to dispose one cavity of the vaporizer on its bottom and
`connect its inside with one end exit of the micro-channel
`array, a liquid stored in the reservoir, and an air filter
`disposed on the top of the reservoir which allows air entering
`the reservoir and a same volume of the liquid in the reservoir
`entering the micro-channel array continually.
`According to the present invention the MEMS vaporizer
`is installed in an electronic cigarette. The electronic cigarette
`55 usually comprises: a housing, a battery; a reservoir, an air
`flow sensor, a microcontroller, a MEMS vaporizer, a tem(cid:173)
`perature sensor, a small cloud of smoke, an air inlet, a light
`emitting diode, and a mouthpiece.
`In the electronic cigarette the vaporizer is electrically
`60 heated for vaporizing the active ingredients of plant mate(cid:173)
`rials including cannabis, tobacco, or other herbs or blends
`for the purpose of inhalation. However, they also can be used
`with pure chemicals when mixed with plant material ( e.g.
`tobacco-free nicotine).
`According to the present invention the vaporizer is fab(cid:173)
`ricated using a Micro-Electro-Mechanical Systems technol(cid:173)
`ogy. The MEMS technology in its most general form can be
`
`NJOY Exhibit 1015.007
`
`

`

`3
`defined as miniaturized mechanical and electro-mechanical
`elements that are made using the techniques of micro(cid:173)
`fabrication. The most significant advantage of MEMS is
`their ability to communicate easily with electrical elements
`in semiconductor chips. Other advantages include small
`size, compact structure, lower power consumption, lower
`cost, increased reliability and higher precision.
`The vaporizer is operated by filling a liquid in the reser(cid:173)
`voir, which automatically flows into the micro-channel array
`due to the surface tension of the liquid in the micro-channel 10
`array, and by heating the liquid using an electrical current
`passing through the resistive heater so that a certain amount
`of the liquid in the micro-channel array can be vaporized and
`a cloud of vapor can come out from the outlet of the
`micro-channel array.
`According to the present invention, a method of manu(cid:173)
`facturing the MEMS vaporizer comprises steps of:
`Providing a silicon substrate having a resistivity ranging
`from 0.1 to 0.001 ohm-cm and a (100) crystal orien(cid:173)
`tation;
`Depositing a silicon nitride layer on the surface of the
`silicon substrate by LPCVD (low pressure chemical
`vapor deposition);
`Performing a lithographic process for creating a silicon
`revealed rectangular array in the silicon nitride layer; 25
`Performing an anodization process in a HF solution for
`converting the silicon revealed rectangular array into a
`porous silicon array;
`Depositing a bottom silicon nitride layer or the like by
`LPCVD or PECVD (plasma enhance chemical vapor 30
`deposition) on the surface of the porous silicon array;
`Depositing a central polysilicon layer by LPCVD, or a
`central amorphous silicon layer by PECVD, or a central
`amorphous silicon carbide layer by PECVD on the
`surface of the bottom silicon nitride layer or the like; 35
`Depositing a top silicon dioxide layer or the like on the
`surface of the central polysilicon layer, or central
`amorphous silicon layer, or central amorphous silicon
`carbide;
`Creating a resistance heater on the top of the porous 40
`silicon array by sputtering and photolithography;
`Creating a resistance temperature sensor, an electrical
`interconnection, and several bonding pads on the top of
`the silicon substrate including the porous silicon array
`by photolithography process, sputtering, and plating;
`Depositing a passivation layer on the top of the resistance
`heater and resistance temperature sensor by PECVD
`which consists of a bottom silicon nitride layer and a
`top amorphous silicon carbide layer;
`Performing a photolithography process and a dry etching 50
`for creating two cavities recessed in the silicon sub(cid:173)
`strate and connecting to the two side end portions of the
`porous silicon array respectively;
`Etching porous silicon in a dilute KOH solution for
`creating a micro-channel array and a membrane, which 55
`all result in a completed vaporizer chip.
`Looking at the vaporizer design and its fabrication
`method provided by the present invention their advantages
`can be summarized as the follows:
`An advantage of the present invention is that the MEMS 60
`vaporizer is fabricated using the techniques of micro-fabri(cid:173)
`cation, which provides with lower cost, increased reliability
`and higher precision.
`Another advantage of the present invention is that the
`heater of the vaporizer is disposed on a membrane that helps 65
`to achieve thermal isolation of the heater from its supporting
`substrate.
`
`20
`
`45
`
`US 9,801,415 B2
`
`4
`Another advantage of the present invention is that the
`heater of the vaporizer allows for contacting the heated
`liquid directly which can result in very high heating effi(cid:173)
`ciency.
`Still another advantage of the present invention is that the
`temperature sensor of the vaporizer allows for measuring the
`vaporization temperature of the liquid precisely, which is
`necessary for controlling the heater of the vaporizer.
`Still another advantage of the present invention is that the
`vaporizer allows to be combined with an air flow sensor
`which can make its applications such as electronic cigarettes
`digital and intelligent.
`Still another advantage of the present invention is that the
`15 vaporizer is a silicon-based integrated actuator which pro(cid:173)
`vides advantages including small size, lower power con(cid:173)
`sumption, lower cost, increased reliability, higher precision,
`and environmentally friend.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The various features of the present invention are shown in
`the drawings in which like numerals indicate similar ele(cid:173)
`ments.
`FIG. 1 is a sectional side view of a MEMS vaporizer
`packaged in a printed circuit board and assembled in a
`plastic molded reservoir.
`FIG. 2 is a sectional side view of an electronic cigarette
`with a MEMS vaporizer.
`FIG. 3 is a schematic block diagram of a preferred
`controller circuit for a MEMS vaporizer.
`FIG. 4 to FIG. 11 show sectional side views in each
`fabrication step of a MEMS vaporizer with a MEMS tem(cid:173)
`perature sensor therein.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The following detailed description of the invention is
`merely exemplary in nature and is not intended to limit the
`invention or the application and uses of the invention.
`Furthermore, there is no intention to be bound by any theory
`presented in the preceding background of the invention or
`the following detailed description of the invention.
`As shown in FIG. 1, the present invention provides a
`MEMS vaporizer composing: a silicon substrate 102, a
`micro-channel array 103 created in the silicon substrate 102,
`a membrane 104 suspending over the micro-charmel array
`103 and supported by the silicon substrate 102, a resistance
`heater 105 disposed on one side portion of the membrane
`104 and laterally across one end portion of the top of the
`micro-channel array 103, a resistance temperature sensor
`106 disposed on the membrane 104 and adjacent to the
`resistance heater 105, two cavities 111 ( another not shown in
`FIG. 1) are recessed in the silicon substrate 102 and con(cid:173)
`nected to the two end exits of the micro-channel array 103
`respectively, which all are integrated to be a vaporizer chip
`101, a printed circuit board 114 for packaging the vaporizer
`chip 101, a reservoir 115 for inserting the printed circuit
`board 114 with the vaporizer chip 101 therein so as to
`dispose one cavity on its bottom and connect its inside with
`one end exit of the micro-channel array 103, a liquid 116
`stored in the reservoir 115, and an air filter 117 disposed on
`the top of the reservoir 115 which allows air entering the
`reservoir 115 and a same volume of the liquid 116 in the
`reservoir 115 entering the micro-charmel array 103. The
`liquid filled the micro-charmel array 103 is marked as 112.
`
`NJOY Exhibit 1015.008
`
`

`

`5
`It is noted that the MEMS vaporizer provided by the
`present invention is a phase change actuator by which a
`liquid can be changed to a vapor. This change is governed by
`the conservation equations of mass, momentum, and energy.
`Since the change takes place in the micro-channels which
`have a large surface-to-volume ratio, the capillary force can
`provide sufficient pressure to push liquid flow in the micro(cid:173)
`channels.
`Reference to FIG. 1, the liquid 112 in the micro-channel
`array 103 comes from the reservoir 115. Under the capillary 10
`force the liquid is pumped from the reservoir 115 into the
`micro-channel array 103. An electrical power is dissipated as
`heat in the resistance heater 105, which then diffuses to the
`liquid 112 in the micro-channel array 103. The energy
`balance on the micro-channel array 103 is determined by 15
`three terms: (1) the electrical power dissipated as heat in the
`vaporizer, (2) the sensible heat conducted out of the vapor(cid:173)
`izer, and (3) the latent heat carried away by liquid vaporizing
`from the micro-channels.
`The first term, the thermal power transferred into the
`vaporizer by dissipating electrical power in the resistance
`heater 105, is determined by measuring the voltage drop
`across the resistance heater 105 and the voltage drop across
`a power resistor in series with the resistance heater 105. The
`voltage drop across the power resistor is used to calculate the 25
`current through the resistance heater 105 using Ohm's Law.
`The power P,n dissipated in the resistance heater 105 is then:
`
`where V and I are the voltage and current applied to the
`resistance heater 105 respectively.
`The second term, the sensible heat is conducted out of the
`vaporizer by the micro-channel array 103, membrane 104
`and liquid 112 and 116, which can be determined from the
`temperatures measured by the temperature sensor 106 posi(cid:173)
`tioned on the membrane 104.
`The third term in the energy balance, the latent heat
`carried away by the vaporization of the liquid 112, can be
`determined by measuring the mass transfer rate from the
`micro-channel array 103, Jm. The latent heat transfer rate
`from the micro-channels, Q1, is then:
`
`(2)
`where Hfg is the latent heat of vaporization of the liquid 112.
`Micro-channel vaporization efficiency, llvap' is defined to
`be the ratio of latent heat transfer rate by vaporization over
`the power into the vaporizer:
`
`The driving force for liquid flow along the micro-channel
`array 103 is the capillary pressure Pc, given by the equation:
`
`(3)
`
`50
`
`(4)
`where y is the surface tension between the liquid 112 and air,
`8 is the contact angle between the liquid 112 and the wall of
`the micro-channel array 103, r is the smallest dimension of
`the micro-channel array 103.
`The liquid flow rate can then be found using force
`balance, by equating capillary pressure forces driving flow
`with liquid viscous force retarding flow. With assumptions:
`steady fluid flow in the micro-channel array 103; neglecting 60
`temperature variation in liquid properties; and fully devel(cid:173)
`oped laminar flow. The following expression can be
`obtained:
`
`u~(r'/8µ,)/(2y cos 0/r)
`
`(5) 65
`where u is the liquid velocity, µ is the liquid viscosity, L is
`the distance over which liquid has traveled.
`
`US 9,801,415 B2
`
`6
`The mass flow rate of liquid 112 in the micro-channel
`array 103 is then:
`
`(6)
`where p is the density of the liquid 112, A is the cross(cid:173)
`sectional area of the micro-channel array 103.
`Knowing the mass flow rate the vapor generating rate in
`the micro-channel array 103 can be found:
`
`(7)
`where M is the molecular weight of the average liquid 112,
`Ru is the universal gas constant, Pa is the atmospheric
`pressures and Ts is the saturation temperatures of the liquid
`112.
`Several factors have been identified as having a signifi-
`cant impact on the vaporizer performance, which include:
`the compliance and thermal isolation of the membrane 104;
`the electrical and thermal properties of the resistance heater
`105 and temperature sensor 106; and the length and size of
`20 the micro-channel 103.
`In order to optimize all these factors the flowing require(cid:173)
`ments applied to the vaporizer design are appropriate and
`necessary:
`The vaporizer further composes: an electrically insulating
`layer such as a silicon nitride layer or the like disposed on
`the top 108 and bottom 109 of the membrane 104, and a
`passivation layer 110 such as a double layer consisting of a
`silicon nitride layer and a silicon carbide layer, which covers
`the top of the resistance heater 105 and the resistance
`30 temperature sensor 106.
`The micro-channel array 103 of the vaporizer is config(cid:173)
`ured to consist of 1 to 30 micro-channels in which each
`micro-channel having a length ranging from 50 to 500
`micron, a width ranging from 20 to 200 micron, and a height
`35 ranging from 10 to 50 micron and two adjacent micro(cid:173)
`channels are separated by a trapezium-shape side wall with
`a top width ranging from 2 to 20 micron;
`The membrane 104 of the vaporizer is made of polysili(cid:173)
`con layer, or amorphous silicon, or amorphous silicon car-
`40 bide layer with a thickness ranging from 2 to 5 micron;
`The resistance heater 105 of the vaporizer is made of
`Ta-Al or Ni-Cr alloy thin film, or the like with a resis(cid:173)
`tance ranging from 1 to 100 ohm; The resistance temperature
`sensor 106 of the vaporizer is made of Ni metal thin film or
`45 the like with a resistance ranging from 100 to 1000 ohm.
`The MEMS vaporizer provided by the present invention
`has several applications. A main application is for electronic
`cigarettes.
`As shown in FIG. 2, an electronic cigarette with a MEMS
`vaporizer provided by the present invention which usually
`comprises: a housing 201; a battery 202; a reservoir 203, an
`air flow sensor 204, a microcontroller 205, a MEMS vapor(cid:173)
`izer 206, a temperature sensor 207, a small cloud of smoke
`208, an air inlet 209, a light emitting diode 210, and a
`55 mouthpiece 211. The reservoir 203 is filled with a liquid
`usually containing a mixture of propylene glycol, vegetable
`glycerin, nicotine, and flavorings. When inhalation is made
`by a user an air flow takes place in the housing 201. The air
`flow starts from the air inlet 209 and flows over the air flow
`sensor 204 along an air way channel perpendicular to the
`housing 201. Then the air flow turns to the longitudinal
`direction of the housing 201, passes through a channel of the
`reservoir 203, and proceeds to the vaporizer 206. The air
`flow is detected by the air flow sensor 204 for providing a
`signal to the microcontroller 205 which turns the buttery 202
`on. Then the heater of the MEMS vaporizer 206 is heated so
`as to start vaporizing the liquid supplied by the reservoir
`
`NJOY Exhibit 1015.009
`
`

`

`US 9,801,415 B2
`
`7
`203, which provides the user a cloud of smoke. When the
`inhalation is too hard the temperature of the heater of the
`vaporizer 206 may drop down to below the boiling point of
`the liquid. In response the temperature sensor 207 sends a
`signal to the microcontroller 205 for increasing the heating 5
`current of the heater and restoring the temperature of the
`heater to the boiling point of the liquid. As a result the user
`still has necessary smoke to inhale.
`The operation of the MEMS vaporizer in an electronic
`cigarette provided by the present invention can be run as 10
`shown in FIG. 3. The vaporizer 301 is applied with a voltage
`308 and connected with a power field-effect transistor (FET)
`302. The power field-effect transistor 302 functions as a
`switch for heating the vaporizer on demand. An air flow
`sensor 303 is used to measure the air flow rate caused by an 15
`inhalation made by a user.
`A signal produced by the air flow sensor 303 is amplified
`by a pre-amplifier 304 and then send to a microcontroller
`305 for digital processing. The temperature of the vaporizer
`306 is measured by a temperature sensor 306. A signal 20
`produced by the temperature sensor 306 is amplified by a
`pre-amplifier 307 and then send to the microcontroller 305
`for digital processing. After digital processing the micro(cid:173)
`controller 305 send a pulse-width modulation (PWM) to the
`gate of the power field-effect transistor 302 which allows the 25
`voltage 308 being applied to the vaporizer 306 according to
`both the air flow rate signal and the heating temperature
`signal of the vaporizer 306.
`It is noted that the MEMS vaporizer has been getting more
`and more attention due to its compact structure and high heat 30
`transfer efficiency. Compared with a conventional vaporizer,
`the MEMS vaporizer offers higher heat and mass transfer
`rate. Therefore MEMS vaporizer has been applied in many
`other fields, such as chemical industry, medical instrument,
`mechanical engineering and electric chip cooling.
`FIG. 4 to FIG. 11 shows the major fabrication steps for
`manufacturing the MEMS vaporizer. It can be seen that the
`used technologies are derived from semiconductor inte(cid:173)
`grated circuit (IC) processing. These fabrication steps can be
`run on any stander IC production lines. Since most of the 40
`manufacturing steps are routine IC processes there is no
`need to describe in detail.
`At the start of the process, a silicon substrate 401 with one
`side polished is provided which has a resistivity ranging
`from 0.1 to 0.001 ohm-cm and a (100) crystal orientation.
`In step 1, as shown in FIG. 4, a silicon nitride layer is
`deposited on the surface of the silicon substrate 401 by
`LPCVD (low pressure chemical vapor deposition), which
`has a thickness ranging from 2000 to 3000 angstroms. Then
`a lithographic process is performed for creating a silicon(cid:173)
`revealed rectangular array 402 in the silicon nitride layer.
`Each silicon-revealed rectangular region has a length rang-
`ing from 50 to 500 micron, a width ranging from 20 to 200
`micron, and two adjacent silicon-revealed rectangular
`regions are separated by a width ranging from 2 to 20
`micron.
`In step 2, as shown in FIG. 5, an anodization process is
`carried out in a HF solution. From this step the silicon(cid:173)
`revealed rectangular array 402 is converted into a porous
`silicon array 403. The anodization process is performed in a 60
`two-chamber cell. The HF solution consists of one or two
`parts 48 wt % HF and 1 part ethanol or isopropyl alcohol
`(IPA). The used anodic current density is ranging from 40 to
`80 mA/cm.sup.2.
`Each porous silicon rectangular region of the porous 65
`silicon array 403 has a length ranging from 50 to 500 micron
`and a width ranging from 20 to 200 micron. The thickness
`
`8
`of the porous silicon layer depends upon the anodic current
`intensity and the process timing. The resulted thickness of
`the porous silicon layer is ranging from 10 to 50 micron.
`Two adjacent porous silicon rectangular regions are sepa(cid:173)
`rated by a trapezium side wall with a top width ranging from
`2 to 20 micron.
`In step 3, as shown in FIG. 6, a bottom silicon nitride layer
`or the like 404 is deposited by LPCVD on the surface of the
`silicon substrate 401 including the porous silicon array 403.
`The bottom nitride layer or the like 404 can also be depos(cid:173)
`ited by PECVD (plasma enhance chemical vapor deposi(cid:173)
`tion), which allows depositing a silicon nitride layer or the
`like with a lower residue stress. The thickness of the bottom
`silicon nitride layer or the like 404 is ranging 1000 to 8000
`angstrom.
`In step 4, as shown in FIG. 6, a polysilicon layer 405 is
`deposited by LPCVD on the surface of the bottom silicon
`nitride layer or the like 404. As an alternative an amorphous
`silicon layer 405 is deposited by PECVD on the surface of
`the bottom silicon nitride layer or the like 404. Still as an
`alternative an amorphous silicon carbide layer 405 is depos(cid:173)
`ited by PECVD on the surface of the bottom silicon nitride
`layer or the like 404.
`The thickness of the polysilicon layer, or amorphous
`silicon layer, or amorphous silicon carbide layer 405 is
`ranging from 2 to 5 micron. It is noted that the polysilicon
`layer, or amorphous silicon layer, or amorphous silicon
`carbide layer 405 functions as the basic structure material
`for the membrane of the vaporizer which will be formed.
`In step 4, as shown in FIG. 7, a top silicon nitride layer
`or the like 406 is deposited by LPCVD or PECVD on the
`surface of the polysilicon layer, or amorphous silicon layer,
`35 or amorphous silicon carbide layer 405, which has a thick(cid:173)
`ness ranging from 1000 to 8000 angstrom. It can be seen that
`from this step a sandwich structure is formed in which the
`central layer 406 is sandwiched between the bottom layer
`404 and the top layer 405. It is noted that such sandwich
`structure helps to prevent the structure from bending owing
`to the residue stresses of the three layers forming the
`sandwich structure.
`Reference to FIG. 8, in step 5, at least a resistance heater
`407 is created on the top of the porous silicon layer 403 by
`45 sputtering and photolithography process. The heater is made
`of Ta-Al or Ni-Cr alloy thin film, or the like. The
`sputtering target consists of Al-55% and Ta-45% or Ni-80%
`and Cr-20%. The Ni-Cr alloy is etched using Ni-Chrome
`etchant (TFE). The resistance of the created heater 407 is
`50 ranging from 1 to 100 ohm.
`Then a Ni metal thin film resistance temperature sensor
`408 is created on the top of the porous silicon array 403 and
`adjacent to the resistance heater 407. Since there is no
`etchant available for wet etching Ni metal a lift-off process
`55 is needed. Using a photo-resist pattern as mask a Ni metal
`thin film deposition is performed by sputtering. In order to
`increase the thickness of the Ni metal thin film an additional
`chemical plating process may be performed hereafter. After
`removing the ph