US5282925A — Device and method for accurate etching and remova…

Claim 1

Independent Claim 120 words

An etching apparatus comprising the following components: a chamber; means for supply of reactant to said chamber; means for supporting a substrate within said chamber, said substrate having a material thereon able to be etched by said reactant; means for forming a film comprising said reactant on the surface of said material; means for controlling the nature and duration of said film; wherein the components are so arranged that when said reactant is supplied to said chamber, said reactant forms a film on the surface of said material, the nature and duration of said film being so controlled by said controlling means that said film leads to the removal of an accurately controlled amount of said material on said substrate.

Claim 2

Dependent Claim 120 words

An etching apparatus comprising the following components: a chamber; means for supply of reactant to said chamber; means for supporting a substrate within said chamber, said substrate having a material thereon able to be etched by said reactant; means for forming a film comprising said reactant on the surface of said material; means for controlling the nature and duration of said film; wherein the components are so arranged that when said reactant is supplied to said chamber, said reactant forms a film on the surface of said material, the nature and duration of said film being so controlled by said controlling means that said film leads to the removal of an accurately controlled amount of said material on said substrate.

Claim 3

Dependent Claim 20 words

The apparatus as defined in claim 1, wherein said film is a condensed or absorbed layer of the reactant molecules.

Claim 4

Dependent Claim 31 words

The apparatus as defined in claim 2, wherein said means for controlling said condensed film comprises a cooling means to ensure that the coldest point in the chamber is the substrate.

Claim 5

Dependent Claim 45 words

The apparatus as defined in claim 2, wherein said means for controlling said condensed film comprises a heating means attached to the peripheral walls of said chamber so that the temperature of said walls is higher than that of any condensed material in the chamber.

Claim 6

Dependent Claim 56 words

The apparatus as defined in claim 2, wherein said means for controlling said condensed film comprises a reservoir with a valve disposed between said means for supply of reactant and said chamber, so that an accurate amount of said reactant can be rapidly admitted to said chamber from said reservoir when said valve is rapidly opened.

Claim 7

Dependent Claim 15 words

The apparatus as defined in claim 2, further including a pump connected to said chamber.

Claim 8

Dependent Claim 57 words

The apparatus as defined in claim 6, wherein said means for controlling said condensed film comprises means for delivering an accurate amount of said reactant to said chamber, and a valve disposed between said chamber and said pump, so that when said valve is closed, the reactant remains in said chamber until substantially reacted with said material.

Claim 9

Dependent Claim 73 words

The apparatus as defined in claim 6, wherein said means for controlling said condensed film comprises means for differential pumping disposed between said means for supply of reactant and said chamber, and a pump connected to said means for differential pumping, so that molecules from said source of the reactant travel substantially without collision while in transit through said chamber to said substrate yielding a composition and flux that are constant in time.

Claim 10

Dependent Claim 30 words

The apparatus as defined in claim 2, wherein said means for controlling said condensed film comprises a computer and a program means enabling said computer to carry out predetermined operations.

Claim 11

Dependent Claim 19 words

The apparatus as defined in claim 2, wherein said reactant comprises a single or a plurality of gaseous molecules.

Claim 12

Dependent Claim 27 words

The apparatus as defined in claim 2, wherein said means for controlling said condensed film comprises a heating means attached to said means for supporting said substrate.

Claim 13

Dependent Claim 26 words

The apparatus as defined in claim 2, wherein said reactant comprises molecules of HF, H 2 O, NH 3 , ammonium bifluoride or a combination thereof.

Claim 14

Dependent Claim 19 words

The apparatus as defined in claim 10 wherein said reactant comprises a mixture of HF and NH 3 .

Claim 15

Dependent Claim 34 words

The apparatus of claim 12, wherein the source of said HF molecules is distinct from the source of said H 2 O molecules which is distinct from the source of said NH 3 molecules.

Claim 16

Dependent Claim 26 words

The apparatus of claim 14, wherein the source of supply of H 2 O is H 2 O molecules desorbed from the walls of said chamber.

Claim 17

Dependent Claim 25 words

The apparatus as defined in claim 12, wherein the source of said molecules is a solution of NH 3 , HF, or H 2 O.

Claim 18

Dependent Claim 20 words

The apparatus as defined in claim 12, wherein said reactant is ammonium bifluoride which is supplied in a gaseous phase.

Claim 19

Dependent Claim 17 words

The apparatus of claim 12, wherein said reactant is a mixture of HF and H 2 O.

Claim 20

Dependent Claim 16 words

The apparatus of claim 12, wherein said reactant is a mixture of ammonium bifluoride and HF.

Claim 21

Independent Claim 94 words

A method for etching, comprising the steps of: (a) supporting, in a vacuum chamber, a substrate having a material to be etched; (b) admitting reactant containing gas into said chamber at a sufficient pressure so as to form a film of the reactant on the surface of said material; (c) controlling the composition and residence time of said film on the surface of said material so as to etch an accurate amount of material on said substrate; and (d) removing any unwanted reactant and reaction products from the chamber or surface of said substrate.

Claim 22

Independent Claim 94 words

A method for etching, comprising the steps of: (a) supporting, in a vacuum chamber, a substrate having a material to be etched; (b) admitting reactant containing gas into said chamber at a sufficient pressure so as to form a film of the reactant on the surface of said material; (c) controlling the composition and residence time of said film on the surface of said material so as to etch an accurate amount of material on said substrate; and (d) removing any unwanted reactant and reaction products from the chamber or surface of said substrate.

Claim 23

Dependent Claim 61 words

The method of claim 20, wherein said film is a condensed or adsorbed layer of reactant molecules, and controlling the residence time and composition of said condensed or adsorbed film comprises maintaining the temperature of said substrate below the temperature of any other surface in the chamber so as to substantially eliminate condensation of said reactant on any of said surface.

Claim 24

Dependent Claim 40 words

The method of claim 21, wherein controlling the residence time and the composition of said condensed film comprises admitting said reactant at a high enough rate so as to minimize uncertainty in the onset time for condensation of said reactant.

Claim 25

Dependent Claim 28 words

The method of claim 20, wherein controlling said residence time and composition of said condensed film comprises using a microbalance to detect the presence of the reactant film.

Claim 26

Dependent Claim 51 words

The method as defined in claim 20, wherein said controlling comprises admitting an accurate amount of said reactant into said chamber which is connected to a pump through a closed valve until said reactant in said chamber has sufficiently reacted with the material to be etched, whereupon the valve is opened.

Claim 27

Dependent Claim 19 words

The method of claim 21, wherein controlling comprises employing an effusion cell or low pressure and cooling the substrate.

Claim 28

Dependent Claim 18 words

The method of claim 21, controlling comprises employing differentially pumped source and maintaining chamber pressure below 10-4 Torr.

Claim 29

Dependent Claim 62 words

The method as defined in claim 21, wherein controlling comprises maintaining the substrate temperature below solidification temperature of either product or condensed film so that etching is determined by a combination of diffusion through the solidified film and the reaction rate at the substrate temperature and where etching occurs without falling away of the product at a thickness below the self-limiting thickness.

Claim 30

Dependent Claim 26 words

The method of claim 21, wherein controlling comprises waiting for sufficient time to allow diffusion of reactant so that the same amount of material is etched.

Claim 31

Dependent Claim 24 words

The method of claim 21, utilizing NH 3 and HF as reactant at a temperature less than 50° C. during dosing with temperature cycling.

Claim 32

Dependent Claim 28 words

The method of claim 21, employing NH 3 and HF on SiO 2 substrate at a temperature greater than 50° C. so that there is no temperature cycling.

Claim 33

Dependent Claim 14 words

The method of claim 21, wherein the material to be etched is silicon dioxide.

Claim 34

Dependent Claim 19 words

The method of claim 21, wherein the material to be etched is germanium oxide using HF as a reactant.

Claim 35

Dependent Claim 22 words

The method of claim 21, wherein the reactant forms a combination of NH 3 and HF, each admitted separately into the chamber.

Claim 36

Dependent Claim 40 words

The method of claim 21, wherein the reactant forms a surface layer on the material to be etched, the reactant being selected from the group consisting of HF, H 2 O, NH 3 , ammonium bifluoride and a combination thereof.

Claim 37

Dependent Claim 22 words

The method of claim 34, wherein each of said reactant is admitted separately into the chamber under specific temperature and pressure conditions.

Claim 38

Dependent Claim 20 words

The apparatus of claim 1, wherein said means for controlling said film is a quartz crystal microbalance or an ellipsometer.

Claim 39

Dependent Claim 25 words

The apparatus of claim 1, wherein means for supply of said reactant is an unheated solid source of HF, including ammonium bifluoride or ammonium fluoride.

Claim 40

Dependent Claim 87 words

The method of claim 34, using a condensed source of HF, including ammonium bifluoride, ammonium fluoride or aqueous solution of HF whose temperature is less than or equal to the temperature of the substrate, where reaction chamber is pumped out, the source is opened and the chamber is isolated from the pump by closing a shutoff valve so that the pressure within the chamber rises rapidly to a termination pressure, then after the reaction is substantially complete, the source is closed and the chamber is pumped out.

Claim 41

Dependent Claim 65 words

The method of claim 34, using a condensed source without added inert gas, assuring that there is a flow of the reactant, with optional heating and pumping the chamber so that the pressure within the chamber is maintained at termination pressure, or within a factor of 10 of termination pressure by adjusting the pumping speed, source temperature, or flow rate of reactant into the chamber.

Claim 42

Dependent Claim 46 words

The method of claim 34, using a source comprising HF & NH 3 and forming a condensed product layer to control the amount of material to be etched, while the reaction approaches self-limiting thickness controlled by adjusting the temperature, pressure and gaseous composition in the chamber.

Claim 43

Dependent Claim 43 words

The method of claim 34, wherein the reactant comprises HF and ammonia, and optionally H 2 O, so that a condensed product layer of self-terminating thickness is formed and etching occurs without falling away of the product at thicknesses below the self-limiting thickness.

Claim 44

Dependent Claim 17 words

The method according to claim 41 of etching two layers of oxides exposed simultaneously to the reactant.

Claim 45

Dependent Claim 21 words

The method of claim 41, wherein the rate of etching is controlled by diffusion of the reactant into the product layer.

Claim 46

Dependent Claim 36 words

The method of claim 40, wherein said reactant is condensed HF or a HF/H 2 O solution in a container having a shutoff valve disposed between said container and a vacuum pump connected to the chamber.

Claim 47

Dependent Claim 25 words

The method of claim 40, wherein the temperature of the substrate or wafer is above 50° C. so that the product desorbs without temperature cycling.

Claim 48

Dependent Claim 22 words

The apparatus of claim 41, wherein a thickness of said film limits further diffusion of reactant to the material to be etched.

Claim 49

Dependent Claim 80 words

The method of claim 20, wherein controlling the residence time and composition of said film comprises pumping out reaction chamber maintaining a condensed source at a temperature less than or equal to the temperature of the substrate, the source is opened and the chamber is isolated from the pump by closing a shut-off valve so that the pressure within the chamber rises rapidly to a termination pressure, then closing the chamber after the desired degree of reaction has taken place.

Claim 50

Dependent Claim 67 words

The method of claim 20, wherein a condensed source is used without added inert gas assuring that there is a flow of the reactant with optional heating and pumping the chamber, so that the pressure entering the chamber is maintained at termination pressure or within a factor of 10 of termination pressure by adjusting the pumping speed, source temperature, or flow rate of reactant into the chamber.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-01-31	1997-08-02	1998-02-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-01-31	2001-08-02	2002-02-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-01-31	2005-08-02	2006-02-01	$7700.00	Window Closed / Lapsed

Device and method for accurate etching and removal of thin film

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