WO2003049156A2

WO2003049156A2 - System and method for micro electro mechanical etching

Info

Publication number: WO2003049156A2
Application number: PCT/US2002/038679
Authority: WO
Inventors: Robert W. Grant
Original assignee: Primaxx Inc
Current assignee: Primaxx Inc
Priority date: 2001-12-04
Filing date: 2002-12-04
Publication date: 2003-06-12
Anticipated expiration: 2004-06-04
Also published as: WO2003049156A3; AU2002353039A1

Abstract

A method for Micro Electro Mechanical Etching (MEMS) etching comprising: providing a reactor 100 positioning a MEMS substrate 302 within said reactor, and release etching said substrate with a gas phase mixture 312 of a halide-containing compound and an-OH containing solvent to produce a MEMS device. The gas also includes an inert carrier gas and is at reduced pressure, preferably about 26.66 • 103 N/m2 (200 Torr). The gas is heated to between 50°C and 75°C. The process conditions in said reactor are controlled such that the etch rate is surface-reaction limited. A plurality of substrates 302, 304, 306 are positioned within said reactor with their substrate planes parallel and the reactive gas is flowed in a direction parallel to the substrate planes.

Description

SYSTEM AND METHOD FOR MICRO ELECTRO MECHANICAL ETCHING BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to etching of MEMS (Micro Electro Mechanical Systems) and in particular to efficient gas etching of these structures.

2. Statement of the Problem

The MEMS field has experienced rapid growth in recent years. Accordingly, techniques are needed for constructing miniscule features of MEMS structures such as floating beams, springs, accelerometers among other structures. Generally these structures are created by undercutting a layer of silicon oxide, or polysilicon, until the mechanical part is freed or released so that they can move, and is known as release etching. One approach to constructing such features is liquid etching of MEMS substrates. One typical liquid etch process involves immersing a substrate in a liquid etch solution, such as liquid HF (Hydrogen Fluoride). The substrate material is etched for a period of time after which the substrate is moved to a liquid alcohol bath. Immersion in alcohol substantially displaces the etchant and stops the etch process. The substrate is then moved to a super-critical dryer which surrounds the substrate with supercritical CO2 (CO which has some liquid-like properties but which is nevertheless a gas) at about 13.78 • 10⁶ N/m² (Newtons per square meter) which CO₂ displaces the alcohol and any remaining etchant. Thereafter, the supercritical dryer pressure is relieved, and the CO₂ reverts to a fully gas phase and dissipates, thereby leaving the substrate substantially dry. The above-described process presents a complex and expensive approach for MEMS manufacturing.

In addition to being complex and expensive, existing liquid etch processes introduce product failures for certain MEMS structures. For example, one desired MEMS construction process involves undercutting a thickness of material, such as SiO₂, while leaving the undercut portion in place. This process could be used for, among other things, the creation of a floating beam. Sometimes liquid etch materials remaining after a liquid etch process cause an etched beam to be unintentionally bound to a lower surface because of surface tension in residual liquid present on the substrate surface. This phenomenon is called "stiction" and constitutes a significant impediment to the use of liquid etching for MEMS substrates. To avoid the problem of stiction, another approach to MEMS production involving gas-phase etching of MEMS substrates has been employed. See, United States Patent

No. 6,162,367 issued December 19, 2000 to Yu-Chong Tai et al. and United States

Patent No. 6,290,864 B1 issued September 18, 2001 to Satyadev R. Patel et al. However, these processes are typically much slower than wet etches, and thus they have yet to replace wet release etches of MEMS devices despite the problems of wet etching.

A gas-phase etch process utilizing a halide gas and a high vapor pressure solvent for use in integrated circuits is disclosed in U.S. Patent No. 5,439,553, issued August, 8,

1995, entitled "CONTROLLED ETCHING OF OXIDES VIA GAS PHASE REACTIONS", the disclosure of which patent is hereby incorporated herein by reference. In this process, a flow of reactive gas is typically directed toward the integrated circuit substrate along a path normal to the plane of the substrate. Suitable control of the temperatures and pressures in the reactor for gas-phase etching helps ensure that the etch compound, etch solvent, and surface reaction by-products are maintained in a gas phase for the duration of the etch process. However, this process is also typically a slow process, and therefore has up to now been used primarily for removing native oxide prior to gate oxide formation in integrated circuits. A similar process utilizing hydrogen fluoride and isopropyl alcohol has been used for cleaning oxides on microelectronics substrates.

See United States Patent No. 6,221 ,168 B1 issued April 24, 2001 to Lawrence E. Carter et al. The cleaning process only requires the removal of a very small thickness of material, typically one nanometer (nm), and thus the slowness is not a problem.

However, in MEMS release etches, typically it is necessary to remove several hundred nm and thus this process has not been considered for MEMS release etching.

Accordingly, there is a need in the art for a MEMS release etching process which avoids the problem of stiction while achieving substantially greater production rates than existing gas-phase etching of MEMS substrates.

SOLUTION The present invention advances the art and helps to overcome the aforementioned problems by providing a system and method for gas-phase MEMS substrate etching sufficiently fast to permit its use for release etching.

The invention provides a method for Micro Electro Mechanical Etching (MEMS) release etching, the method comprising: providing a reactor; positioning a MEMS substrate within the reactor; and release etching the substrate with a gas phase mixture of a halide-containing compound and an -OH containing solvent to produce a MEMS device. Preferably, the release etching is carried out at a pressure less than normal atmospheric pressure. Preferably, the pressure is 39.99 • 10³ N/m² (300 Torr) or less. Preferably, the gas phase mixture further comprises an inert carrier gas. Preferably, the method further comprises heating the gas. Preferably, the gas is heated to a temperature of between 20 °C and 200 °C. Preferably, the method further comprises stopping the etch. The etch may be stopped by one or more of rapid pressure reduction, rapid heating, and rapid change of a process gas. Preferably, the etching process is surface-reaction limited. Preferably, the positioning comprises positioning a plurality of the substrates in the reactor, each of the substrates defining a substrate plane. Preferably, the etching comprises flowing the gas phase mixture across the substrates in a direction parallel to the substrate planes. Preferably, halide-containing compound is hydrogen fluoride. Preferably, the -OH containing solvent is selected from methanol, ethanol, actinol, propanol, acetic acid and acetone. In another aspect, the invention provides a method for Micro Electro Mechanical

Etching (MEMS) etching, the method comprising: providing a reactor; positioning a plurality of MEMS substrates within the reactor; flowing reactive gas over surfaces of the positioned substrates; and controlling process conditions in the reactor such that an etch rate on the substrate surfaces in surface-reaction limited. Preferably, the positioning comprises arranging the substrates substantially parallel to one another. Preferably, the positioning comprises positioning three substrates within the reactor. Preferably, the flowing comprises moving the reactive gas substantially parallel to the substrate surfaces.

Preferably, the flowing comprises flowing hydrogen fluorine gas over the substrates.

Preferably, the flowing comprises flowing methanol gas over the substrate surfaces. Preferably, the flowing comprises providing substantially uniform gas flow conditions over the plurality of substrate surfaces. Preferably, the controlling comprises providing a temperature between 50° C and 75° C in the reactor. Preferably, the controlling comprises providing a temperature of substantially 50° C in the reactor. Preferably, the controlling comprises providing a pressure between 13.33 • 10³ N/m² (100 Torr) and 39.99 • 10³ N/m² (300 Torr) in the reactor. Preferably, the controlling comprises providing a pressure of substantially 13.33 • 10³ N/m² (100 Torr) in the reactor.

The invention further provides a method for Micro Electro Mechanical Etching (MEMS) etching, the method comprising: providing a reactor; positioning a plurality of MEMS substrates within the reactor, each of the substrates defining a substrate plane; and etching the substrates by flowing reactive gas over surfaces of the positioned substrates in a direction parallel to the substrate planes. Preferably, the reactive gas is flowed at a pressure less than normal atmospheric pressure. Preferably, the flowed reactive gas comprises a halide-containing gas. Preferably, the reactive gas comprises and -OH containing solvent.

The invention also provides a system for Micro Electro Mechanical Etching (MEMS) etching comprising: a reactor; a substrate mounting assembly configured to hold a plurality of substrates in an interior of the reactor, each of the substrates defining a substrate plane; and a gas flow assembly arranged to provide a reactive gas flow over surfaces of the substrates in a direction substantially parallel to the substrate planes. Preferably, the reactor is made of stainless steel, which preferably is nickel plated. Preferably, the reactor is substantially metallic, thereby providing thermal uniformity to the reactor interior. Preferably the substrate mounting assembly is configured to hold three substrates. Preferably, the volume of the interior of the reactor is between 1 liter and 5 liters, and most preferably substantially two liters. Preferably, the gas flow assembly includes a pressure reduction system for maintaining the pressure of the gas in the reactor at less than atmospheric pressure.

A feature of the invention is that a plurality of substrates are simultaneously etched in a single reactor in a manner enabling uniform etching among the plurality of substrates while avoiding stiction. In a preferred embodiment, a plurality of substrates is positioned in parallel within a single reactor. A flow of reactive gas is preferably directed substantially parallel to the plurality of substrate surfaces. Preferably, process conditions within the reactor are controlled to provide a surface-reaction limited etch process which is substantially uniform over the plurality of substrates.

The inventors have recognized that the surface-reaction limitation can provide advantages in MEMS etching. Providing a surface-reaction limited etch process preferably prevents variations in gas flow velocity and direction within the reactor from causing variation in etch rates in different parts on the reactor interior. The provision of gas flow parallel to, rather than perpendicular to, the plane of the substrates, preferably bolsters the homogeneity of etch rates among the substrates by minimizing or eliminating variation in dynamic gas flow conditions between different substrates. The above- described preferred embodiment preferably enables an increased production rate of MEMS substrates while preserving the beneficial characteristics of gas-phase MEMS substrate etching.

The above and other advantages of the present invention may be better understood from a reading of the following description of the preferred exemplary embodiments of the invention taken in conjunction with drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of a MEMS etch reactor according to a preferred embodiment of present invention;

FIG. 2 is a perspective view of an assembled reactor as shown in FIG. 1 ; FIG. 3 is a side section view of a portion of the reactor of FIG. 1 ; and

FIG.4 is a plot of etch rate as a function of pressure employing the reactor of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In one existing etch process in which gas is flowed in a direction normal to the plane of substrate, it was found that reaction uniformity was enhanced by etching a single wafer at a time. The inventor wished to increase the etch production rate to better meet the needs of the MEMS industry. One approach to increasing the production rate involved processing multiple substrates within a single reactor employing the traditional gas down-flow arrangement. However, the existing gas flow arrangement tended to provide a desired boundary layer and flow conditions on the substrate closest to the source of gas flow but only diffusive flows on other substrates in the reactor. The disparity in the dynamic gas flow conditions experienced by different substrates in the reactor lead to corresponding differences in the etch rates, or reaction rates, for the various substrates, thereby defeating the objective of achieving etch rate uniformity. It was determined that reaction uniformity among a plurality of substrates could be provided by controlling the reactor conditions such that etch rates were surface-reaction- limited rather than diffusion-flow-limited. Under these controlled conditions, the etch rates on the various substrate surfaces are preferably independent of differing dynamic gas flow conditions over the substrates. Moreover, etch rates would preferably also be independent of a substrate's location within the reactor under conditions supporting surface-reaction-limited etching.

Separately, the inventor believed it desirable to provide gas flow conditions which do not bias the gas flow dynamics in favor of any substrate location over any other. Moreover, upon identifying reactor conditions supporting surface-reaction-limited etching, the inventor desired to implement the determined conditions as uniformly as possible throughout the reactor. A preferred embodiment reactor implementing the characteristics described above is described in FIGS. 1-4. In this disclosure, the term "gas flow assembly" is a flow path of gas through gas inlet gas assembly 300, reactor interior 250, and gas outlet assembly 350. FIG. 1 is an exploded perspective view of a MEMS etch reactor 100 according to a preferred embodiment of present invention. In this embodiment, reactor 100 includes reactor housing 160, substrate mounting assembly 200, reactor interior 250, gas inlet assembly 300, gas outlet assembly 350, reactor mounting assembly 400, and reactor top assembly 450.

In this embodiment, reactor top assembly 450 preferably includes clamp ring 102 which preferably includes four screw holes. Cushioning o-ring 104 is preferably below clamp ring 102 to prevent chipping and breaking of metal parts. A preferred material for o-ring 104 and other o-rings described herein is Chemraz 560 or equivalent material. However, other o-ring materials may be employed. Quartz window 106 is preferably located below O-ring 104. Process-whetted o-ring 108 is preferably located below quartz window 106. Reactor top plate 114 is below o-ring 108 (in the exploded view) and preferably connects to reactor housing 160 with screws 110 and 112. Reactor top plate 114 is preferably made of nickel-plated stainless steel, however other materials may be used. Preferably, when reactor 100 is assembled, the bottom side of top plate 114 is flush with the interior surface of reactor housing 160 to form a flat surface for unobstructed gas flow. Process whetted o-ring 116 is preferably located between top plate 114 and reactor housing 160. Circumferential recess 128 in housing 160 preferably receives top plate 114.

In this embodiment, substrate mounting assembly 200 includes substrate mounts 120. Screws 118 preferably attach substrate mounts 120 to reactor housing 160. In this embodiment, three substrate support pins are located on each substrate mount 120 to enable support of three substrates. However, fewer or more than three support pins may be used. The support pins are preferably made of ceramic, but other materials may be used. Channels 122 preferably each house one substrate mount 120. The embodiment of FIG. 1 preferably includes three channels 122, although one of these channels is partially hidden in FIG. 1. Preferably, substrates positioned on substrate mounts 120 may be accessed through gate slot 162 in reactor housing 160 either manually or with automated equipment such as a robot manipulator.

In this embodiment, gas preferably enters reactor 100 through gas inlet assembly 300. At right, support plate 146 preferably connects to mica heater 184 which heater is connected to power leads 144. Heater 184 is preferably connected to inlet manifold 148. Preferably, Inlet manifold 148 is to the left of power leads 144. To the left of inlet manifold 148, recessed surface 150 preferably houses inlet diffuser 152. Gas inlet 164, located below inlet manifold 148, preferably receives processed gas from an external source (not shown) and directs this processed gas to inlet manifold 148. Spacing device 154 is preferably located to the left of inlet diffuser 152. Spacing device 154 preferably enables control of variations in the thickness of diffuser 152. O-rings 156 and 158 are preferably located to the left of spacing device 154. Preferably, O-ring 158 cushions inlet gas diffuser 152, while o-ring 156 is the reactor seal.

In this embodiment, gas outlet assembly 350 preferably conducts gas from reactor housing 160 to exhaust port 138. Preferably, o-ring 132 is a reactor 100 seal. O-ring 134 preferably cushions outlet gas diffuser 136. Preferably, o-ring 134 is located between diffuser 136 and reactor housing exhaust orifice 168. Exhaust manifold 180 is located to the left of outlet gas diffuser 136 and preferably receives diffused gas therefrom. Exhaust port 138 is connected to exhaust manifold 180 and preferably exhausts gas received therefrom. Exhaust port 138 preferably includes a standard NW vacuum connection flange. Preferably, power leads 140 connect to heater 182, which is preferably a mica type resistive heater. Support plate 142 preferably connects heater 182 to exhaust manifold 180.

In this embodiment, mounting assembly 400 preferably includes reactor support 174 located below and toward reactor housing 160 from exhaust manifold 180. Reactor support 174 preferably includes attachment flange 176. A second reactor support 166, which is preferably identical to reactor support 174, is preferably located below gate slot 162. Bracket 170 is below o-rings 132 and 134 and is preferably positioned between reactor support 174 and reactor 160 in assembled reactor 100. Support plate 178 preferably connects heater 186 to the bottom of reactor housing 160. Likewise, support plate 188 preferably connects heater 172 to another portion of the bottom of reactor housing 160. Heaters 172 and 186 are preferably located on opposite sides of reactor housing 160 (one on the left and one on the right in the view of FIG. 1). However, heaters 172 and 186 could be located elsewhere on the bottom surface of reactor housing 160.

In this embodiment, process surfaces in reactor 100 are preferably constructed of 316 stainless steel. Process surface in reactor 100 are preferably plated with nickel, although other materials, such as rhodium and platinum, may be used. This combination of materials preferably prevents the creation of volatile metal species during etching of SiO₂ substrates. FIG. 2 is a perspective view of an assembled version of the reactor 100 shown in FIG. 1. A reactor for use in connection with an alternative embodiment of the present invention is disclosed in U.S. Patent No. 5,228,206, which patent is hereby incorporated by reference.

FIG. 3 is a side section view of a portion of reactor 100 of FIG. 1. In this embodiment, gas 312 preferably flows through gas inlet assembly 300 creating gas inflow 308, over substrates 302, 304, and 306, in reactor interior 250, and out through gas outlet assembly 350, generating gas outflow 352. Each of substrates 302, 304 and 306 define a substrate plane, which is the horizontal plane along the upper surface of each of the substrates in FIG. 3. The substrate planes are preferably parallel, and the gas flow is substantially parallel to the substrate planes. While three substrates 302, 304, and 306 are shown in FIG. 3, it will be appreciated that fewer or more than three substrates may be etched employing the inventive principles disclosed herein. Preferably, gas 312 is a blend of a halide-containing gas, such as HF (hydrogen fluoride), and any -OH containing solvent, preferably an alcohol, such as methanol, preferably in an inert carrier gas at reduced pressure. Preferably, the halide-containing compound and the solvent are anhydrous. While hydrogen fluoride is preferred, NF₃, CIF₃, and F₂ have also been used to etch sample MEMS devices with success. The solvent is preferably one that will stimulate a selective SiO₂ reaction at the surface of a MEMS substrate. However, other etching gases and solvents may be employed. Other solvents that have been used successfully include ethanol, actinol, propanol, acetic acid and acetone. Preferably, substrates 302, 304, and 306 are made of silicon with SiO₂ sacrificial oxides. However other substrate materials may be employed. The inert carrier gas is preferably nitrogen, although argon has also been used successfully. Since the byproducts of the etch are carried away in a gas phase, the etch according to the invention has the ability to undercut several hundred nanometers of SiO₂, typically isotropically, without creating a liquid byproduct such as fluorosilicic acid, which can cause collapse of the MEMS structure.

In this embodiment, the conditions in reactor interior 250 are preferably established to create uniformity throughout interior 250 and to provide a surface-reaction- limited etch process on substrates 302, 304, and 306. Substrates 302, 304, and 306 are preferably oriented in parallel. Moreover, the flow of gas 312 is preferably directed parallel to the surfaces of substrates 302, 304, and 306. Preferably, the orientation of the substrates 302, 304, and 306 and the direction of gas flow over the three substrates cooperate to provide uniform gas flow conditions over the surfaces of substrates 302, 304, and 306. Otherwise stated, the substrate and gas flow arrangements of this embodiment preferably do not effect different etch rates in different parts of reactor interior 250. This situation differs from existing down-flow gas flow arrangements which, if employed in a multiple substrate reactor, would expedite etch rates on the first substrate encountered by flowing gas at the expense of substrates located downstream from this first substrate. In addition to the described gas flow uniformity, the all-metal construction of reactor 100 preferably provides temperature uniformity throughout reactor 100.

In this embodiment, ambient conditions in reactor interior 250 are preferably established to ensure surface-reaction-limited etching on the surfaces of substrates 302, 304, and 306. These conditions preferably further the aim of ensuring uniform etch rates on all substrate surfaces. It has been found that ambient conditions supporting surface- reaction-limited etching include a temperature between 50°C (Celsius) and 75°C, and more preferably of about 50°C. The desired pressure is preferably 39.99 • 10³ N/m² (300 Torr) or less, more preferably between 13.33 • 10³ N/m² (100 Torr) and 39.99 • 10³ N/m² (300 Torr), and most preferably about 26.66 • 10³ N/m² (200 Torr). In this embodiment, the volume of reactor interior 250 is preferably minimized to minimize gas consumption and to minimize the time required to minimize gas filling and gas evacuation times for reactor interior 250. Toward this end, substrate separation distance 310 is preferably about 0.64 cm (centimeters). Preferably, one to five liters of gas 312 are needed to fill reactor 100, and most preferably substantially two liters. FIG. 4 is a plot of etch rate as a function of pressure employing reactor 100 of FIG.

1. Pressures between 13.33 • 10³ N/m² (100 Torr) and 39.99 • 10³ N/m² (300 Torr) are preferred for reactor interior 250. It is a feature of the invention that the etch can be easily controlled. For example, if necessary, the etch can be rapidly stopped. This can be done by a rapid pressure reduction, rapid heating, rapid change of a process gas or combinations thereof.

The process of the invention has been performed with each of the exemplary combinations of halide, solvent, and pressures described in United States Patent No. 5,439,553 with and without water present. The processes in which water was absent provided a better controlled etch. All of these combinations provided significant etching with substrates heated within the ranges described above. Generally, heating the substrates above 200°C or reducing the pressure below 1.333 • 10³ N/m² (10 Torr) quenches the reaction, particularly in anhydrous conditions. There have been described what are, at present, considered to be the preferred embodiments of the invention. The method of the invention is very much simplified over the prior art methods, and can achieve up to 100 percent yield for sacrificial SiO₂ etching.

It will be understood that the invention can be embodied in other specific forms without departing from its spirit or essential characteristics. For instance, each of the inventive features mentioned above may be combined with one or more of the other inventive features. That is, while all possible combinations of the inventive features have not been specifically described, so as the disclosure does not become unreasonably long, it should be understood that many other combinations of the features may be made. The present embodiments are, therefore, to be considered as illustrative and not restrictive. The scope of the invention is indicated by the appended claims.

Claims

CLAIMS:We claim:

1. A method for Micro Electro Mechanical Etching (MEMS) release etching, the method comprising: providing a reactor 100; positioning a MEMS substrate 302 within said reactor; and release etching said substrate with a gas phase 312 mixture of a halide-containing compound and an -OH containing solvent to produce a MEMS device.

2. A method as in claim 1 wherein said release etching is carried out at a pressure less than normal atmospheric pressure.

3. A method as in claim 1 wherein said pressure is 39.99 • 10³ N/m² (300 Torr) or less.

4. A method as in claim 1 wherein said gas phase mixture further comprises an inert carrier gas.

5. A method as in claim 1 and further comprising heating said gas.

6. A method as in claim 5 wherein said gas is heated to a temperature of between 20 °C and 200 °C.

7. A method as in claim 1 and further comprising stopping said etch.

8. A method as in claim 7 wherein said stopping comprises one or more of rapid pressure reduction, rapid heating, and rapid change of a process gas.

9. A method as in claim 1 wherein said etching process is surface-reaction limited.

10. A method as in claim 1 wherein said positioning comprises positioning a plurality of said substrates 302, 304, 306 in said reactor, each of said substrates defining a substrate plane.

11. A method as in claim 10 wherein said etching comprises flowing said gas phase mixture across said substrates in a direction parallel to said substrate planes.

12. A method as in claim 1 wherein said halide-containing compound is hydrogen fluoride.

13. A method as in claim 1 wherein said -OH containing solvent is selected from methanol, ethanol, actinol, propanol, acetic acid and acetone.

14. A method for Micro Electro Mechanical Etching (MEMS) etching, the method comprising: providing a reactor 100; positioning a plurality of MEMS substrates 302, 304, 306 within said reactor; flowing reactive gas 312 over surfaces of said positioned substrates; and controlling process conditions in said reactor such that an etch rate on said substrate surfaces in surface-reaction limited.

15. The method of claim 14 wherein said positioning comprises arranging said substrates substantially parallel to one another.

16. The method of claim 14 wherein said positioning comprises positioning three substrates within said reactor.

17. The method of claim 14 wherein said flowing comprises moving said reactive gas substantially parallel to said substrate surfaces.

18. The method of claim 14 wherein said flowing comprises flowing hydrogen fluorine gas over said substrates.

19. The method of claim 14 wherein said flowing comprises flowing methanol gas over said substrate surfaces.

20. The method of claim 14 wherein said flowing comprises providing substantially uniform gas flow conditions over said plurality of substrate surfaces.

21. The method of claim 14 wherein said controlling comprises providing a temperature between 50° C and 75° C in said reactor.

22. The method of claim 14 wherein said controlling comprises providing a temperature of substantially 50° C in said reactor.

23. The method of claim 14 wherein said controlling comprises providing a pressure between 13.33 ^• 10³ N/m² (100 Torr) and 39.99 • 10³ N/m² (300 Torr) in said reactor.

24. The method of claim 14 wherein said controlling comprises providing a pressure of substantially 26.66 • 10³ N/m² (200 Torr) in said reactor.

25. A method for Micro Electro Mechanical Etching (MEMS) etching, the method comprising: providing a reactor 100; positioning a plurality of MEMS substrates 302, 304, 306 within said reactor, each of said substrates defining a substrate plane; and etching said substrates by flowing reactive gas 312 over surfaces of said positioned substrates in a direction parallel to said substrate planes.

26. A method as in claim 25 wherein said reactive gas is flowed at a pressure less than normal atmospheric pressure.

27. A method as in claim 25 wherein said flowed reactive gas comprises a halide-containing gas.

28. A method as in claim 25 wherein said reactive gas comprises and -OH containing solvent.

29. A system for Micro Electro Mechanical Etching (MEMS) etching comprising: a reactor 100; a substrate mounting assembly 200 configured to hold a plurality of substrates 302, 304, 306 in an interior 250 of said reactor, each of said substrates defining a substrate plane; and a gas flow assembly arranged to provide a reactive gas 312 flow over surfaces of said substrates in a direction substantially parallel to said substrate planes.

30. The system of claim 29 wherein said reactor is made of stainless steel.

31. The system of claim 30 wherein said reactor is nickel plated.

32. The system of claim 29 wherein said reactor is substantially metallic, thereby providing thermal uniformity to said reactor interior.

33. The system of claim 29 wherein said substrate mounting assembly is configured to hold three substrates.

34. The system of claim 29 wherein the volume of the interior of said reactor is between 1 liter and 5 liters.

35. The system of claim 29 wherein the volume of the interior of said reactor is substantially 2 liters.

36. The system of claim 29 wherein said gas flow assembly includes a pressure reduction system for maintaining the pressure of said gas in said reactor at less than atmospheric pressure.