US5726480A — Etchants for use in micromachining of CMOS Microa…

Claim 1

Independent Claim 112 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM device through said standard IC processing, said MEM device being completely fabricated except for at least one etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM device with a noble gas fluoride to define said structural element with respect to said substrate.

Claim 2

Dependent Claim 112 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM device through said standard IC processing, said MEM device being completely fabricated except for at least one etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM device with a noble gas fluoride to define said structural element with respect to said substrate.

Claim 3

Dependent Claim 18 words

The improvement of claim 1 wherein etching said MEM device is performed with a gas phase xenon difluoride.

Claim 4

Dependent Claim 17 words

The improvement of claim 2 wherein etching said MEM device is at ambient temperature without external heating.

Claim 5

Dependent Claim 16 words

The improvement of claim 3 wherein etching said MEM device is performed under a partial vacuum.

Claim 6

Dependent Claim 23 words

The improvement of claim 1 wherein etching said MEM device is performed in a aqueous solution of tetramethyl ammonium hydroxide with silicic acid.

Claim 7

Dependent Claim 106 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM device, said device being substantially completely fabricated except for a single etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM device with xenon difluoride in a gas phase to define said structural element from said substrate.

Claim 8

Dependent Claim 106 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM device, said device being substantially completely fabricated except for a single etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM device with xenon difluoride in a gas phase to define said structural element from said substrate.

Claim 9

Dependent Claim 79 words

A microelectromechanical (MEM) accelerometer sensor defined in a semiconductor substrate comprising: a proof mass fabricated in or on said substrate using integrated circuit processes; at least one beam coupling said proof mass to said substrate, said beam being at least in part unsupported and extending from said proof mass to said substrate; and at least one polysilicon piezoresistor disposed in said beam, a pair of leads coupled to said piezoresistor to provide means for electrically coupling to said piezoresistor.

Claim 10

Dependent Claim 79 words

A microelectromechanical (MEM) accelerometer sensor defined in a semiconductor substrate comprising: a proof mass fabricated in or on said substrate using integrated circuit processes; at least one beam coupling said proof mass to said substrate, said beam being at least in part unsupported and extending from said proof mass to said substrate; and at least one polysilicon piezoresistor disposed in said beam, a pair of leads coupled to said piezoresistor to provide means for electrically coupling to said piezoresistor.

Claim 11

Dependent Claim 32 words

The accelerometer sensor of claim 7 further comprising at least two unsupported beams coupling said proof mass to said substrate, each of said beams having at least one polysilicon piezoresistor disposed therein.

Claim 12

Dependent Claim 38 words

The accelerometer sensor of claim 7 wherein said substrate is generally planar and further comprising a hinge which is deformed so that said proof mass is oriented in a predetermined position out of the plane of said substrate.

Claim 13

Dependent Claim 113 words

The accelerometer sensor of claim 9 further comprising: at least three of said proof masses fabricated from said substrate using integrated circuit processes; at least three hinges, each of said hinges coupling one of said three proof masses to said substrate, at least three beams coupled to corresponding ones of said three hinges, each of said beams being at least in part unsupported and extending from said proof mass to said substrate; and at least three polysilicon piezoresistors, one of three polysilicon piezoresistors being disposed in each of said three beams, wherein said proof masses are each oriented in a different plane relative to said substrate so that a three-axis accelerometer is provided.

Claim 14

Dependent Claim 13 words

The accelerometer sensor of claim 7 wherein said hinges are comprised of aluminum.

Claim 15

Dependent Claim 31 words

The accelerometer sensor of claim 11 wherein said beams are fabricated using xenon difluoride as a gas-phase ambient temperature etchant to define said beams apart from said substrate and proof mass.

Claim 16

Dependent Claim 32 words

The accelerometer sensor of claim 11 wherein said beams are fabricated using a tetramethyl ammonium hydroxide aqueous solution with silicic acid to define said beams apart from said substrate and proof mass.

Claim 17

Dependent Claim 18 words

The accelerometer sensor of claim 7 wherein said proof mass and polysilicon piezoresistor are formed using CMOS processes.

Claim 18

Dependent Claim 31 words

The accelerometer sensor of claim 14 wherein said beams are fabricated using xenon difluoride as a gas-phase ambient temperature etchant to define said beams apart from said substrate and proof mass.

Claim 19

Dependent Claim 27 words

The accelerometer sensor of claim 14 wherein said beam is defined and separated from said substrate through use of solution of tetramethyl ammonium hydroxide in silicic acid.

Claim 20

Dependent Claim 19 words

The accelerometer sensor of claim 9 wherein said proof mass, hinge and polysilicon piezoresistor are formed using CMOS processes.

Claim 21

Dependent Claim 122 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM device, said device being substantially completely fabricated except for a single etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM device with an etchant selected from the group of xenon difluoride and an aqueous solution of tetramethyl ammonium hydroxide and silicic acid to define said structural element with respect to said substrate.

Claim 22

Dependent Claim 122 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM device, said device being substantially completely fabricated except for a single etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM device with an etchant selected from the group of xenon difluoride and an aqueous solution of tetramethyl ammonium hydroxide and silicic acid to define said structural element with respect to said substrate.

Claim 23

Dependent Claim 109 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM CMOS device, said device being substantially completely fabricated except for at least one etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM CMOS device with a noble gas fluoride to define said structural element with respect to said substrate.

Claim 24

Dependent Claim 109 words

In a method for fabricating a microelectromechanical (MEM) device, said MEM device being formed in or on at least one semiconductor substrate, including an integrated circuit formed therein by standard IC processing and including a microelectromechanical assembly, an improvement comprising: providing a substantially completed MEM CMOS device, said device being substantially completely fabricated except for at least one etching step, said etching step defining a structural element within said microelectromechanical assembly from said at least one substrate to complete said device and to render said MEM device operable; and etching said MEM CMOS device with a noble gas fluoride to define said structural element with respect to said substrate.

Claim 25

Dependent Claim 57 words

The improvement of claim 19 wherein said substantially completed MEM CMOS device is an accelerometer having an integrated circuit substrate, a proof mass and a piezoresistive sensing element coupling said substrate to said proof mass, but remaining undefined from them, wherein said etching defines said sensing element by a single etch step by said generally isotropic etchant.

Claim 26

Dependent Claim 102 words

In a method for mass fabrication of microelectromechanical devices, an improvement comprising: providing a multiplicity of devices each having portions which must be oriented to predetermined three dimensional positions in order assume a final configuration for each said device, selected portions of each said device having an electrically isolated structure for receiving and holding charge for at least a temporary period; and selectively disposing selected amounts of electric charge on said selected portions of each said device to generate mutually repulsive or attractive electrostatic forces between said selected portions to move said selected portions of each said device to said final configuration.

Claim 27

Dependent Claim 102 words

In a method for mass fabrication of microelectromechanical devices, an improvement comprising: providing a multiplicity of devices each having portions which must be oriented to predetermined three dimensional positions in order assume a final configuration for each said device, selected portions of each said device having an electrically isolated structure for receiving and holding charge for at least a temporary period; and selectively disposing selected amounts of electric charge on said selected portions of each said device to generate mutually repulsive or attractive electrostatic forces between said selected portions to move said selected portions of each said device to said final configuration.

Claim 28

Dependent Claim 40 words

The improvement of claim 21 where selectively depositing selected amounts of electric charge on said electrically isolated structures is performed by selective control of a scanning electron microscope which is directed to deposit electron charges on said electrically isolated structures.

Claim 29

Dependent Claim 56 words

An improvement in a microelectromechanical (MEM) device having a substrate and a movable part separate from said substrate formed as part of said microelectromechanical (MEM) device, said improvement comprising a conductive and permanently deformable hinge coupling said substrate and said movable part to allow permanent spatial reconfiguration of said movable part with respect to said substrate.

Claim 30

Dependent Claim 56 words

An improvement in a microelectromechanical (MEM) device having a substrate and a movable part separate from said substrate formed as part of said microelectromechanical (MEM) device, said improvement comprising a conductive and permanently deformable hinge coupling said substrate and said movable part to allow permanent spatial reconfiguration of said movable part with respect to said substrate.

Claim 31

Dependent Claim 22 words

The improvement of claim 23 wherein said hinge is deformed so that said substrate and separate part form a three dimensional structure.

Claim 32

Dependent Claim 23 words

The improvement of claim 24 further comprising a sensing means for generating a position signal indicative of the spatial orientation of said part.

Claim 33

Dependent Claim 25 words

The improvement of claim 24 further comprising force means disposed on said substrate and part for deforming said hinge to form said three dimensional structure.

Claim 34

Dependent Claim 26 words

The improvement of claim 25 further comprising circuit means disposed on said substrate or part and coupled to said sensing means for processing said position signal.

Claim 35

Dependent Claim 13 words

The improvement of claim 23 wherein said part is interacts with electromagnetic radiation.

Claim 36

Independent Claim 59 words

A method for fabricating a microelectromechanical (MEM) device on or in at least one substrate by removing mechanical constraints disposed between and connecting at least two components of said microelectromechanical (MEM) device after said at least two components have been formed, said mechanical restraints being removed by vapor phase etching said microelectromechanical (MEM) device in a noble gas fluoride.

Claim 37

Independent Claim 59 words

A method for fabricating a microelectromechanical (MEM) device on or in at least one substrate by removing mechanical constraints disposed between and connecting at least two components of said microelectromechanical (MEM) device after said at least two components have been formed, said mechanical restraints being removed by vapor phase etching said microelectromechanical (MEM) device in a noble gas fluoride.

Claim 38

Dependent Claim 16 words

The method of claim 29 wherein said vapor phase etching is performed using XeF 2 .

Claim 39

Dependent Claim 28 words

The method of claim 30 further comprising vapor phase etching said microelectromechanical (MEM) device using an inter-halogen fluoride gas in place of etching with a noble gas fluoride.

Claim 40

Dependent Claim 42 words

The method of claim 29 in which at least one of said components is a thin film or thick film component and removing mechanical constraints comprises releasing said component from said at least one substrate by vapor phase etching of said substrate.

Claim 41

Dependent Claim 46 words

The method of claim 29 in which at least one of said components is a thin film or thick film component and removing mechanical constraints comprises releasing said component from said at least one substrate by vapor phase etching of said thin or thick film component.

Claim 42

Dependent Claim 42 words

The method of claim 29 in which said components comprise at least two thin film or thick film components and removing mechanical constraints comprises releasing said components by vapor phase etching one of said at least two thin or thick film components.

Claim 43

Dependent Claim 44 words

The method of claim 29 in which at least one of said components is comprised of insulating material and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device by vapor phase etching in noble gas fluoride releases said insulating material.

Claim 44

Dependent Claim 70 words

The method of claim 35 in which at least one of said components is comprised of insulating material selected from the group of silicon dioxide, silicon nitride, photoresist, or other polymers and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device by vapor phase etching in noble gas fluoride releases said insulating material selected from the group of silicon dioxide, silicon nitride, photoresist, or other polymers.

Claim 45

Dependent Claim 43 words

The method of claim 29 in which at least one of said components is comprised of a conductor and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device by vapor phase etching in noble gas fluoride releases said conductor.

Claim 46

Dependent Claim 59 words

The method of claim 29 in which at least one of said components is comprised of a conductor selected from the group of gold and aluminum and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device by vapor phase etching in noble gas fluoride releases said conductor selected from the group of gold and aluminum.

Claim 47

Dependent Claim 43 words

The method of claim 29 in which at least one of said components is comprised of a semiconductor and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device by vapor phase etching in noble gas fluoride releases said semiconductor.

Claim 48

Dependent Claim 55 words

The method of claim 29 in which said components are comprised of a combination of two or more of the layers chosen from the categories of insulators, conductors, or semiconductors and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device by vapor phase etching in noble gas fluoride releases said combination.

Claim 49

Dependent Claim 24 words

The method of claim 29 wherein said vapor phase etching has a rate which is modified by the application of electrical or thermal bias.

Claim 50

Dependent Claim 52 words

The method of claim 29 in which at least one of said substrates has a composition selected from the group of silicon, glass, quartz, pyrex, and plastic and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device is by vapor phase etching in noble gas fluoride said substrate.

Claim 51

Dependent Claim 40 words

The method of claim 42 in which said substrate contains integrated circuitry and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device is by vapor phase etching in noble gas fluoride without affecting said integrated circuitry.

Claim 52

Dependent Claim 52 words

The method of claim 42 in which said substrate contains integrated circuitry fabricated by standard IC processing techniques and removing mechanical constraints between at least two components of said microelectromechanical (MEM) device is by vapor phase etching in noble gas fluoride without affecting said integrated circuitry fabricated by standard IC processing techniques.

Claim 53

Dependent Claim 19 words

The method according to claim 44 in which said vapor phase release etching is performed with no further masking.

Claim 54

Dependent Claim 32 words

The method of claim 29 further comprising plastically deforming at least one of said components in order to rotate at least one of said components relative to another one of said components.

Claim 55

Dependent Claim 19 words

The method of claim 46 wherein plastically deforming at least one of said components plastically deforms an aluminum component.

Claim 56

Dependent Claim 18 words

The method of claim 46 wherein plastically deforming at least one of said components rotates a sensing component.

Claim 57

Dependent Claim 37 words

The method of claim 48 wherein said sensing elements are rotated relative to each other and/or the substrate in order to sense more than one axis of a given field such as acceleration, light, magnetic flux, rotation.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2001-03-09	2001-09-08	2002-03-10	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2005-03-09	2005-09-08	2006-03-10	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2009-03-09	2009-09-08	2010-03-10	$7700.00	Window Closed / Lapsed

Etchants for use in micromachining of CMOS Microaccelerometers and microelectromechanical devices and method of making the same

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