Rotating Electrochemical Etching Cell

Abstract

The present disclosure provides a reaction chamber and a method for using the same, the reaction chamber including a mesh cathode, a first anode, a second anode, and a reaction chamber body, the reaction chamber body being hollow and having a first opening and a second opening, capable of sealing a semiconductor wafer to be electrochemically etched. One advantage of the reaction chamber and method disclosed herein may be that it allows multiple etching operations to be performed with minimal or no operator contact with an etching solution such as hydrofluoric acid.

Description

[Technical Field]

[0001] Government support This invention was made with government support under awards W81XWH-12-1-0414 and W81XWH-17-1-0389 from the Department of Defense. The U.S. Government has certain rights in this invention.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This PCT application claims priority to U.S. Provisional Patent Application No. 63 / 409,129, filed September 22, 2022, which is incorporated by reference in its entirety.

[0003] The present disclosure generally relates to a reaction chamber for electrochemical etching of semiconductor wafers. Advantages of the reaction chamber may include the ability to electrochemically etch multiple semiconductor wafers in batches or sequentially using hazardous etchants while minimizing potential worker exposure to the hazardous etchants. [Background technology]

[0004] Hydrofluoric acid (HF) and hydrofluoric acid solutions are essential to the semiconductor industry. For example, porous silicon structures can be produced by electrochemically (EC) etching crystalline silicon in hydrofluoric acid (HF) solutions. Controlled, selective electrochemical etching of silicon can yield porous structures with various properties depending on the dopant level, applied current, and electrolyte concentration. Generally, electrochemical etching equipment is required to perform EC etching.

[0005] However, hydrofluoric acid solutions are extremely dangerous. They can be fatal if absorbed through the skin, inhaled, or swallowed. HF-containing solutions can pass through a worker's skin without the worker realizing they have been exposed, resulting in burns that often go unnoticed until the next day, at which point they are no longer mitigated, making them a recognized danger. Even moderate exposure to concentrated HF solutions can be fatal if left untreated. Simply put, HF solutions are one of the most important yet dangerous materials in the semiconductor industry.

[0006] A need exists for a reaction chamber or electrochemical etching apparatus that allows HF solution to be safely applied to as many semiconductor wafers as possible while minimizing the risk of operator contact with the HF solution.A need exists for a reaction chamber or electrochemical etching apparatus that efficiently uses, stores, and reuses HF solution to electrochemically etch a series or batch of semiconductor wafers while minimizing unnecessary waste, handling, and storage of HF. Summary of the Invention

[0007] The present disclosure relates to a reaction chamber. In some embodiments, the reaction chamber includes a mesh cathode, a first anode, a second anode, and a reaction chamber body. The reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip. The first anode is reversibly secured to the first lip by a first fastener, and the second anode is reversibly secured to the second lip by a second fastener. In some embodiments, the mesh cathode is positioned between the first opening and the second opening, and the mesh cathode is substantially parallel to the first lip. In some embodiments, the inner edge of the first lip has a shortest distance across the first opening of about 2.5 cm to about 46.0 cm. In some embodiments, the inner edge of the second lip has a shortest distance across the second opening of about 2.5 cm to about 46.0 cm. In some embodiments, the first opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm, or the second opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm. In some embodiments, the first opening and the second opening have circular shapes with inner diameters about 2.0 mm to about 5.0 mm smaller than the diameter of the semiconductor wafer. In some embodiments, the reaction chamber comprises one or less mesh cathodes, the mesh cathodes being positioned substantially parallel to the equidistant line between the first anode and the second anode within a range of about 0.0 mm to about 5.0 mm. In some embodiments, the mesh cathodes are positioned about 1.0 cm to about 10 cm from the first anode, or the mesh cathodes are positioned about 1.0 cm to about 10 cm from the second anode. In some embodiments, the reaction chamber comprises a first mesh cathode and a second mesh cathode, wherein the first mesh cathode is positioned substantially parallel to the first anode at a distance of about 1.0 cm to about 10 cm from the first anode, or the second mesh cathode is positioned substantially parallel to the second anode at a distance of about 1.0 cm to about 10 cm from the second anode.In some embodiments, the first lip includes 3 to 20 first pegs and a first recess extending around the first opening, the first recess being located closer to the inner surface than the pegs. In some embodiments, the second lip includes 3 to 20 second pegs and a second recess extending around the second opening, the second recess being located closer to the inner surface than the second pegs. In some embodiments, the reaction chamber further includes a first gasket, the first gasket configured to fit into the first recess. In some embodiments, the reaction chamber further includes a second gasket, the second gasket configured to fit into the second recess. In some embodiments, at least one of the first gasket and the second gasket is an O-ring, and the first gasket and the second gasket comprise a rubber, an elastomer, or a fluoropolymer. In some embodiments, the reaction chamber body comprises a polymer or a fluoropolymer. In some embodiments, the mesh cathode comprises a nickel alloy or a nickel-copper alloy. In some embodiments, at least one of the first anode and the second anode comprises a nickel alloy, a nickel-copper alloy, a p-doped silicon plate, an n-doped silicon plate, or a combination thereof. In some embodiments, the mesh cathode is electrically connected to a DC power source through the reaction chamber body. In some embodiments, the reaction chamber body includes a liquid port, the liquid port being a tube extending through the reaction chamber body and through the outer surface to the outer surface.

[0008] Disclosed herein are methods of operating a reaction chamber. In some embodiments, the method includes providing a reaction chamber comprising a mesh cathode, a first anode, a second anode, and a reaction chamber body, the reaction chamber body being hollow and having an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip, the mesh cathode being positioned between the first opening and the second opening, the mesh cathode being substantially parallel to the first lip, and the first anode being reversibly securable to the first lip by a first fastener. providing a second anode reversibly securable to the second lip by a second fastener; forming a sealed reaction chamber by positioning a first semiconductor wafer between the first lip and the first anode to form a first seal between the first semiconductor wafer and the first lip, and by positioning a second semiconductor wafer between the second lip and the second anode to form a second seal between the second semiconductor wafer and the second lip; and adding reactants to the sealed reaction chamber.

[0009] In some embodiments, the method further includes orienting the sealed reaction chamber by positioning a second anode substantially perpendicular to gravity and closer to the ground than the first anode, and etching a second surface of a second semiconductor wafer by applying a DC current between the mesh cathode and the second anode. In some embodiments, the method further includes orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode, and etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode. In some embodiments, the method further includes removing the second semiconductor wafer before, during, or after etching the first semiconductor wafer. In some embodiments, the method further includes orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode, and etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode. In some embodiments, the method further includes orienting the sealed reaction chamber by positioning a second anode substantially perpendicular to gravity and closer to the ground than the first anode, and etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode. In some embodiments, the reactant includes HF.

[0010] In some embodiments, the method further includes etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and a first anode, and then etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and a second anode. In some embodiments, the method includes etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and a second anode, and then etching the first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode.

[0011] The foregoing summary and the following detailed description of the embodiments will be better understood when read in conjunction with the accompanying drawings. For purposes of illustration, there are shown in the drawings certain embodiments which may be preferred. It is understood that the described embodiments are not limited to the exact details shown. Unless otherwise noted, the drawings are not to scale. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a conventional electrochemical etching apparatus. [Figure 2] FIG. 1 is a schematic diagram of another conventional electrochemical etching apparatus. [Figure 3A] FIG. 1 is an exploded view of one embodiment of a reaction chamber disclosed herein. [Figure 3B] 3B is an exploded view of the embodiment of the reaction chamber shown in FIG. 3A upside down or rotated 180 degrees about the cathode. [Figure 4] FIG. 1 is a schematic diagram showing a cutaway view of one embodiment of a reaction chamber disclosed herein in operation. [Figure 5] FIG. 2 is a top view of the reaction chamber with the first anode and first semiconductor wafer removed. [Figure 6] 1 is a cross-sectional view of one embodiment of a reaction chamber having four openings, each holding a semiconductor wafer for processing. DETAILED DESCRIPTION OF THE INVENTION

[0013] All measurements are in standard metric units unless otherwise noted.

[0014] Unless otherwise noted, all reactions are conducted under standard atmospheric pressure and temperature.

[0015] Unless otherwise noted, all occurrences of the words "a," "an," or "the" may refer to one or more of the words that they modify.

[0016] Unless otherwise noted, the phrase "at least one of" means one or more of the objects. For example, "at least one of the first anode and the second anode comprises a nickel alloy, a nickel-copper alloy, a p-doped silicon plate, or an n-doped silicon plate, or a combination thereof" means a single first anode, a plurality of first anodes, a first anode comprising a plurality of anodes, a single first cathode, a plurality of first cathodes, a first cathode comprising a plurality of cathodes, or any combination thereof, that comprises a "nickel alloy, a nickel-copper alloy, a p-doped silicon plate, or an n-doped silicon plate, or a combination thereof."

[0017] Unless otherwise noted, the term "about" refers to ±10% of a non-percentage numerical value, rounded to the nearest numerical value to the stated precision. For example, about 105.3 mm includes 94.8 mm to 115.8 mm. Unless otherwise noted, the term "about" refers to ±5% of a percentage numerical value. For example, about 20% would include 15 to 25%. When the term "about" is used in connection with a range, it refers to the appropriate amount less than the lower limit and more than the upper limit. For example, about 100.0 mm to about 200.0 mm would include 90.0 mm to 220.0 mm.

[0018] Unless otherwise noted, when referring to an object oriented in space relative to another object, the term "substantially" refers to plus or minus 10 degrees. For example, a cathode that is "substantially parallel" to a first lip is parallel within plus or minus 10 degrees. When referring to an object oriented in space relative to the ground, earth, or gravity, "substantially" refers to plus or minus 25 degrees. For example, a second anode that is "substantially perpendicular" to gravity means that the anode is perpendicular to gravity within plus or minus 25 degrees of the Earth's gravitational force.

[0019] Unless otherwise noted, the terms "provide," "provided," or "providing" refer to the supply, production, purchase, manufacture, assembly, formation, selection, configuration, conversion, introduction, addition, or incorporation of any element, amount, component, reagent, quantity, measurement, or analysis of any method or system of any embodiment herein.

[0020] Unless otherwise noted, the terms "reversibly fastened" or "reversibly sealed" refer to joining or sealing one object to another via mechanical means and exclude welding or chemically bonding the objects together.

[0021] Unless otherwise noted, the term "mesh" refers to an object made from woven wires or strands.

[0022] Unless otherwise noted, the term "depression" refers to a spatial depression, hole, groove, mark, engraving, or three-dimensional pattern in a surface material.

[0023] In many embodiments, the reaction chambers disclosed herein are symmetrical in design. Thus, unless otherwise noted, the terms "first," "second," "third," and "fourth" are arbitrary designators that distinguish one end or opening and portion of a reaction chamber from another end or opening and portion thereof. That is, these terms merely indicate which opening or associated portion is being referred to. Unless otherwise noted, the terms "first," "second," "third," and "fourth" do not imply any sequence, order, or orientation.

[0024] Unless otherwise noted, properties (height, width, length, ratios, etc.) described herein are understood to be averaged measurements.

[0025] Most reported research and manufacturing production of porous silicon uses a basic electrochemical (EC) etching cell and a DC power source. There are two basic EC cell configurations that are traditionally used. For comparison, these are shown in Figures 1 and 2 of this disclosure.

[0026] As illustrated in FIG. 1 , a first EC cell configuration 100 includes an open cylindrical tank 102 filled with an HF solution 103, a cathode 104, and a solid anode 106, which provides a horizontal mount for a semiconductor wafer 108 between the anode and the HF solution. The semiconductor wafer is sealed against a seal 110 at the bottom of the tank to prevent or reduce leakage of the HF solution. The EC cell is powered by a DC voltage power supply 112. In this conventional EC cell, the HF bath is placed above the wafer being etched, requiring each semiconductor wafer to be added and removed individually. Furthermore, between the etching of each wafer, the HF acid bath must be drained and properly stored before proceeding with the addition and etching of another wafer, which significantly slows the etching process in mass production and increases the likelihood of chemical spills and chemical burns.

[0027] Referring to FIG. 2, another conventional EC cell 200 configuration includes two chambers 202 and 204, where chamber 202 includes a cathode 206 and chamber 204 includes an anode 208. A wafer 210 is attached to a wafer holder 212 and inserted between chambers 202 and 204 for vertical wafer etching, and both chambers 202 and 204 are filled with an etching solution 214 (e.g., an HF solution). With this conventional EC cell, the operator is exposed to many of the same risks as the EC cell shown in FIG. 1 because the operator must use a wafer holder to contact each sample with the HF solution, which increases the potential for HF spills, splashes, and surface contamination. Additionally, each sample must still be added and removed separately, which significantly slows the etching process for mass production and increases the potential for contamination and operator injury. After processing a batch of wafers, the HF acid bath must be emptied and properly stored between etches until the HF solution is depleted of HF. The primary improvement of the conventional reaction chamber of FIG. 2 over that of FIG. 1 is that the HF solution in FIG. 2 can be reused between individual wafers instead of having to be drained between each etched wafer.

[0028] The present disclosure provides a reaction chamber or electrochemical device that can solve the above problems. In some embodiments, one or more substrates to be processed, such as silicon semiconductor wafers, can be positioned and sealed over various openings with gaskets or O-rings to provide a sealable reaction chamber for electrochemical etching that safely contains an HF solution. Furthermore, one substrate or semiconductor wafer can be safely added or removed before, during, or after etching another substrate or silicon wafer. An advantage of the reaction chamber of the present disclosure may be that a semiconductor wafer can be added to the reaction chamber, etched, and then removed without the need for an operator or worker to come into contact with the HF solution, either directly or via a handheld tool. This advantage can eliminate or reduce the risk of HF spills, splashes, and surface contamination. Another advantage of the reaction chamber of the present disclosure may be that the HF solution can be used, stored, reused, and even replenished within the reaction chamber of the present disclosure without the need to drain it. For example, the HF solution can be reused or stored within the reversibly sealable reaction chamber until the solution is depleted by HF etching. This centralized storage and depletion significantly reduces the risk of worker exposure to the HF solution by eliminating or reducing the steps of repeatedly filling and draining the HF solution from the reaction chamber.

[0029] In some embodiments, a reaction chamber is disclosed. FIGS. 3A and 3B show exploded views of some embodiments of the reaction chamber disclosed herein. As can be seen in FIGS. 3A and 3B, the reaction chamber 300 comprises a mesh cathode 302, a first anode 304, a second anode 306, and a reaction chamber body 308. In some embodiments, the reaction chamber body 308 is hollow and defines an inner surface 310, an outer surface 312, a first opening 314, and a second opening 316. In this embodiment, FIGS. 3A and 3B show the same embodiment from different perspectives. In FIG. 3A, the first opening faces upward, and in FIG. 3B, the second opening faces upward.

[0030] As best seen in FIG. 3A , the first opening 314 has a first lip 318. The first anode 304 can be reversibly secured to the first lip 318 by a first fastener 320. A first semiconductor wafer 322 can be positioned between the first lip 318 and the first anode 304. In some embodiments, the first lip 318 includes a first peg 324 and a first recess 326 that extends around the first opening 314. In some embodiments, the first recess 326 is located closer to the inner surface 310 than the first peg 324. In some embodiments, the first lip 318 includes between 3 and 20 first pegs, collectively indicated as 324.

[0031] As can be seen in FIG. 3B , the second opening 316 has a second lip 328. The second anode 306 can be reversibly secured to the second lip 328 by a second fastener 330. In some embodiments, a second semiconductor wafer 332 is positioned between the second lip 328 and the second anode 306. In some embodiments, the second lip 328 includes a second peg 334 and a second recess 336 that extends around the second opening 316. In some embodiments, the second recess 336 is located closer to the inner surface 310 than the second peg 334. In some embodiments, the second lip 328 includes between 3 and 20 second pegs, collectively indicated as 334.

[0032] 3A and 3B, in some embodiments, a mesh cathode 302 is positioned between a first opening 314 and a second opening 316, with the mesh cathode 302 being substantially parallel to a first lip 318. Referring to FIG. 4, this figure shows a cutaway view of some embodiments of a reaction chamber disclosed herein. As can be seen in FIG. 4, the reaction chamber 400 includes a mesh cathode 402, a first semiconductor wafer 422 positioned or secured between a first anode 404 and a first lip 418, and a second semiconductor wafer 432 positioned or secured between a second anode 406 and a second lip 428, with a hollow reaction chamber body 408 between the first anode and the second anode.

[0033] 4, first lip 418 and second lip 428 feature pegs, collectively shown as 424 and 434, respectively, which may aid in positioning the respective wafers before or during etching. Reaction chamber 400 includes a first gasket 438 configured to fit into first recess 426 and a second gasket 440 configured to fit into second recess 436, creating a reversibly sealable, leak-tight reaction chamber.

[0034] In some embodiments, at least one of the first gasket 438 and the second gasket 440 is an O-ring. In some embodiments, the mesh cathode 402 is electrically or operatively connected to a DC power source through the reaction chamber body 408 by a cathode lead 442. In some embodiments, the reaction chamber body 408 includes liquid ports, collectively indicated as 444, which are one or more tubes that extend through the reaction chamber body 408 to the exterior surface 412. These tubes can be used to fill the reversibly sealable reaction chamber with an HF-containing solution 446 even while the etching chamber is sealed during the etching process.

[0035] 5 shows a top view of an embodiment of the reaction chamber without the first anode and first semiconductor wafer. As can be seen in FIG. 5, the first lip 518 includes a plurality of first pegs, collectively indicated as 524, and a first recess 526 that extends around the first opening 514, with the first recess 526 being located closer to the inner surface 510 than the first pegs 524.

[0036] The reaction chambers shown in Figures 3-5 allow for reversible sealing of the EC cells containing the etching solution by placing one semiconductor wafer over each opening. By being able to seal all openings of the reaction chamber in this manner, embodiments disclosed herein may allow the reaction chamber or electrochemical etching apparatus to be transported, rotated, turned over, or even shaken without or with reduced risk of leaking harmful etching chemicals, such as HF acid. Furthermore, with the second opening facing downward and the first opening facing upward, the HF solution remains at the bottom of the reaction chamber, allowing the first semiconductor wafer to be removed and replaced with a new (unetched) semiconductor wafer for electrochemical etching. Once the electrochemical etching of the second semiconductor wafer is complete and the first semiconductor wafer is securely sealed over the first opening, the entire reaction chamber can be rotated so that the first opening faces downward and the second opening faces upward. The second semiconductor wafer can then be removed before, during, or after etching the first semiconductor wafer. This electrochemical etching process can be repeated as necessary while avoiding operator contact with the HF solution.

[0037] The present disclosure relates to a reaction chamber. In some embodiments, the reaction chamber includes a mesh cathode, a first anode, a second anode, and a reaction chamber body. In some embodiments, the reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip. In some embodiments, the first anode can be reversibly secured to the first lip by a first fastener, and the second anode can be reversibly secured to the second lip by a second fastener.

[0038] In some embodiments, the reaction chamber is a reversibly sealable electrochemical cell for semiconductor etching. In some embodiments, the mesh cathode can be made of any etchant-compatible conductive material, such as an HF acid-compatible material, including, but not limited to, nickel alloy, nickel-copper alloy, or other conductive rare metals. In some embodiments, the mesh cathode comprises a nickel alloy or a nickel-copper alloy. In some embodiments, the mesh cathode is porous. In some embodiments of the reaction chamber, the cathode can be a mesh cathode or a porous cathode. The advantage of a mesh cathode or a porous cathode is that such a cathode allows the etchant (e.g., HF solution) to pass freely from one side of the reaction chamber to the other, eliminating or reducing gas accumulation at the cathode. In contrast, a non-mesh cathode can result in the formation of gas bubbles on the surface of the cathode, which creates irregularities in the electric field on the surface of the semiconductor and results in uneven etching. Similarly, if the cathode is not spread evenly across the width of the semiconductor wafer or the inner surface of the inner edge of the reaction chamber body, electric field gradients can form on the surface of the semiconductor, resulting in non-uniform etching.

[0039] In some embodiments, the reaction chamber may contain one or more mesh cathodes for simultaneously processing multiple substrates or semiconductor wafers. For example, the reaction chamber may contain a single mesh cathode positioned substantially parallel to the equidistant line between the first and second anodes, thereby evenly spreading the cathode across the chamber relative to the anodes and eliminating or reducing variations in chemical etching due to the unintended formation of electrochemical etching gradients. In another example, the reaction chamber may contain two mesh cathodes, one of which is positioned substantially parallel to one of the anodes.

[0040] In some embodiments, the reaction chamber includes no more than one mesh cathode. In some embodiments, the mesh cathode is positioned substantially parallel to the equidistant line between the first anode and the second anode, within a range of about 0.0 mm to about 5.0 mm. In some embodiments, the mesh cathode is positioned about 1.0 cm to about 10 cm from the first anode, or the mesh cathode is positioned about 1.0 cm to about 10 cm from the second anode, or both.

[0041] In some embodiments, the reaction chamber comprises a first mesh cathode and a second mesh cathode, the first mesh cathode being positioned substantially parallel to the first anode at a distance of about 1.0 cm to about 10 cm from the first anode. In some embodiments, the reaction chamber comprises a first mesh cathode and a second mesh cathode, the second mesh cathode being positioned substantially parallel to the second anode at a distance of about 1.0 cm to about 10 cm from the second anode.

[0042] In some embodiments, the mesh cathode is positioned between the first opening and the second opening, and the mesh cathode is substantially parallel to the first lip. In some embodiments, the mesh cathode is operatively or electrically connected to a power source, such as a direct current (DC) power source, through the reaction chamber body.

[0043] In some embodiments, the first and second openings may be any shape, such as circular, square, etc., modified as needed to match or complement the shape of the semiconductor wafer being etched. For example, by convention, semiconductor wafers in the microchip industry are usually circular, while semiconductor wafers in the solar cell industry are typically square.

[0044] In some embodiments, the first opening and the second opening can have the same shape or different shapes. In some embodiments, the first opening and the second opening can be any size as long as the semiconductor wafer can be reversibly sealed to the first opening or the second opening. In some embodiments, the first opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm. In some embodiments, the second opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm. In some embodiments, the first opening and the second opening have a circular shape with an inner diameter that is about 2.0 mm to about 5.0 mm smaller than the diameter of the semiconductor wafer, for example, a commercially available semiconductor wafer. In some embodiments, the inner edge of the first lip has a shortest distance across the first opening of about 2.5 cm to about 46.0 cm. In some embodiments, the inner edge of the second lip has a shortest distance across the second opening of about 2.5 cm to about 46.0 cm.

[0045] In some embodiments, the first lip and the second lip may include a plurality of pegs to assist in wafer alignment and attachment. An advantage of such pegs may be to help an operator quickly, easily, and consistently align the semiconductor wafer with the opening to provide a consistent contact area for the etching solution. An advantage of such pegs may be to avoid spills, since a misaligned semiconductor wafer can result in an insufficient seal of the reaction chamber.

[0046] In some embodiments, the first lip and the second lip can include one or more recesses extending around the respective openings for receiving or accommodating a gasket, such as an O-ring. The benefit of providing recesses and gaskets on the reaction chamber lips can be to provide a leak-proof sealed chamber or a liquid-tight, reversibly sealable chamber, thereby reducing the risk of harmful chemicals leaking during repeated use. In some embodiments, the first lip includes 3-20 first pegs and a first recess extending around the first opening, the first recess being located closer to the inner surface than the pegs. In some embodiments, the pegs are located closer to the inner surface than the first recesses. In some embodiments, the second lip includes 3-20 second pegs and a second recess extending around the second opening, the second recess being located closer to the inner surface than the pegs. In some embodiments, the pegs are located closer to the inner surface than the second recesses.

[0047] In some embodiments, at least one of the first gasket and the second gasket is an O-ring. In some embodiments, the first gasket and the second gasket can be made of any material that is resistant and inert to etching solutions, including HF acid or HF solution. In some embodiments, the first gasket and the second gasket comprise rubber, elastomer, or fluoropolymer.

[0048] In some embodiments, the reaction chamber body can be made of any non-conductive material that is resistant and inert to the etching solution, such as one or more non-conductive fluorinated polymers. In some embodiments, the reaction chamber body comprises a polymer or a fluoropolymer. In some embodiments, the reaction chamber body includes a liquid port or gas port, where the liquid port is a tube or channel extending through the reaction chamber body from the outer surface to the inner surface. In some embodiments, the reaction chamber body can include a liquid port that includes two or more tubes. An advantage of two or more tubes is that one can be attached to a source of etching solution, such as a container, and the other can be attached to a drain for removing the etching solution.

[0049] In some embodiments, the first anode and the second anode can be made from any etchant-compatible conductive material, such as, but not necessarily limited to, nickel alloys and nickel-copper alloys. In some embodiments, at least one of the first anode and the second anode comprises a nickel alloy, a nickel-copper alloy, a p-doped silicon plate, or an n-doped silicon plate, or a combination thereof.

[0050] During operation, some embodiments of the reaction chamber can be assembled by positioning a first semiconductor wafer on the first lip and aligning the first semiconductor wafer with the aid of an O-ring and possibly a first peg. Then, a first anode can be positioned and secured to the first lip with the aid of a first fastener (such as a screw or bolt), such that the first semiconductor wafer is sandwiched, contained, or positioned between the first anode and the first lip. Furthermore, in some embodiments, the reaction chamber can be flipped or turned over so that the first anode faces the ground, and then a second semiconductor wafer is positioned on the second lip and aligns the second semiconductor wafer with the aid of an O-ring and possibly a second peg. Then, a second anode can be positioned and secured to the second lip with the aid of a second fastener (such as a screw or bolt), such that the second semiconductor wafer is sandwiched, contained, or positioned between the second anode and the second lip. In some embodiments, the etching liquid can be added to the reaction chamber before, during, or after positioning the second semiconductor wafer on the second lip. For example, in some embodiments, the etching liquid can be added to the sealed (or otherwise sealed) etching chamber using a liquid port.

[0051] In some embodiments, the sealed reaction chamber can be oriented so that the anode corresponding to the wafer that needs to be etched first is substantially perpendicular to gravity and closer to the ground or earth than the other anodes. In some embodiments, the necessary DC current can be applied between the mesh cathode and the anode closer to the ground to etch the corresponding semiconductor wafer. The benefit of applying a DC current to the etching solution can be to promote electrochemical etching. For example, crystalline silicon can be etched clearly by an HF solution only when a DC current is applied.

[0052] As noted above, the terms "first" and "second" are arbitrarily assigned adjectives that designate or refer to the opening of the reaction chamber and the associated features and portions of the opening to provide context in lieu of sequential or directional information. For example, a sealed reaction chamber can be oriented such that the first anode is substantially perpendicular to gravity and closer to the ground than the second anode (exposing the first semiconductor wafer to the etching solution), and a DC current is applied between the mesh cathode and the first anode to etch the first semiconductor wafer. Then, once etching of the first semiconductor wafer is complete, the reaction cell or chamber can be flipped, rotated, or inverted so that the second anode is substantially perpendicular to gravity and closer to the ground than the first anode, exposing the second semiconductor wafer to the etching solution. A DC current can then be applied between the mesh cathode and the second anode to etch the second semiconductor wafer.

[0053] In some embodiments of the method, the first etched semiconductor wafer can be removed and / or replaced with a new semiconductor wafer (thus resulting in a new or unetched first etched semiconductor wafer) before, during, or after etching the second semiconductor wafer. For example, after etching of the first semiconductor wafer is complete, the reaction cell can be flipped, turned over, or rotated so that the second anode is closer to the ground, exposing the second semiconductor wafer to the etching solution. A DC current can then be applied between the mesh cathode and the second anode to etch the second semiconductor wafer. While etching of the second semiconductor wafer is occurring, the first etched semiconductor wafer can be removed from the reaction chamber by removing the first anode from the first lip, and a new first semiconductor wafer (to be etched) or an unetched first semiconductor wafer can be positioned in place of the first etched semiconductor wafer.

[0054] Once etching of the second semiconductor wafer is complete, the reaction cell is again flipped, turned over, or rotated so that the first anode is closer to the ground, exposing a third semiconductor wafer to the etching solution. In some embodiments of the method, this process can be repeated to etch a series of semiconductor wafers. An advantage of the reaction chambers and methods using same disclosed herein can be that they provide a continuous etching process, reusing the same etching solution until it is depleted, avoiding or reducing the need to drain or store the etching solution after each etching cycle.

[0055] Electrochemical etching of semiconductor wafers (such as silicon-based semiconductor wafers) consumes an etchant (e.g., HF acid), resulting in depletion of the etchant during the etching operation. In some embodiments of the present method, the consumed etchant can be compensated for or replenished by adding fresh etchant to the reaction chamber. For example, fresh etchant can be added to the reaction chamber during semiconductor wafer replacement or removal of an etched semiconductor wafer. Alternatively, fresh etchant can be added to the sealed reaction chamber through a liquid port, either intermittently or continuously.

[0056] Disclosed herein are methods for operating a reaction chamber. In some embodiments, the method includes providing a reaction chamber, the reaction chamber comprising a mesh cathode, a first anode, a second anode, and a reaction chamber body. In some embodiments of the method, the reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip. In some embodiments of the method, the mesh cathode is positioned between the first opening and the second opening, and the mesh cathode is substantially parallel to the first lip. In some embodiments of the method, the first anode is reversibly secureable to the first lip by a first fastener, and the second anode is reversibly secureable to the second lip by a second fastener. In some embodiments of the method, the method includes forming a sealed reaction chamber by positioning a first semiconductor wafer between the first lip and a first anode to form a first seal between the first semiconductor wafer and the first lip, and positioning a second semiconductor wafer between the second lip and a second anode to form a second seal between the second semiconductor wafer and the second lip. In some embodiments of the method, the method includes adding reactants to the sealed reaction chamber. In some embodiments, the method of sealing the reaction chamber may eliminate or reduce the possibility of solution leakage and contamination.

[0057] In some embodiments, the method further includes orienting the sealed reaction chamber by positioning a second anode substantially perpendicular to gravity and closer to the ground than the first anode, and etching a second surface of a second semiconductor wafer by applying a DC current between the mesh cathode and the second anode. In some embodiments, the method further includes orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode, and etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode. In some embodiments, the method further includes removing the second semiconductor wafer before, during, or after etching the first semiconductor wafer.

[0058] In some embodiments, the method further includes orienting the sealed reaction chamber by positioning a first anode substantially perpendicular to gravity and closer to the ground than the second anode, and etching a first surface of a first semiconductor wafer by applying a DC current between the mesh cathode and the first anode. In some embodiments, the method further includes orienting the sealed reaction chamber by positioning a second anode substantially perpendicular to gravity and closer to the ground than the first anode, and etching a second surface of a second semiconductor wafer by applying a DC current between the mesh cathode and the second anode. In some embodiments, the reactant includes HF or a solution including HF.

[0059] In some embodiments, the method further includes etching a first surface of a first semiconductor wafer by applying a DC current between the mesh cathode and a first anode, and then etching a second surface of a second semiconductor wafer by applying a DC current between the mesh cathode and a second anode. In some embodiments, the method includes etching a second surface of a second semiconductor wafer by applying a DC current between the mesh cathode and a second anode, and then etching the first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode. In some embodiments, the anode does not contact the etchant and remains dry throughout the process. Advantages of avoiding or reducing anode contact with the etchant can include eliminating or reducing contamination, corrosion, and cleaning steps.

[0060] 3 to 5 show an embodiment of a reaction chamber having two openings that allows for the loading of two semiconductor wafers. The advantage of a reaction chamber having two openings is that the reaction chamber is small, not complicated to operate, and easy to access even in a small laboratory.

[0061] In some embodiments, the reaction chamber of the present disclosure can be configured with three or more openings to hold three or more semiconductor wafers for more efficient processing. For example, FIG. 6 shows a cross-sectional view of a variation of the reaction chamber of the present disclosure having four openings, each holding a separate semiconductor wafer. As can be seen in FIG. 6, the reaction chamber 600 includes a first mesh cathode 602a, a second mesh cathode 602b, a third mesh cathode 602c, and a fourth mesh cathode 602d paired with respective anodes, i.e., a first anode 604a, a second anode 604b, a third anode 604c, and a fourth anode 604d. An advantage of pairing the anodes and cathodes in this manner can be that electrochemical gradients can be avoided or minimized by controlling the distance between the respective anode portions and the cathodes.

[0062] In operation, the reaction chamber body 606 can be rotated by a central shaft 630 that rotates about a central pivot point 632. In some embodiments, the reaction chamber body 606 is hollow and includes an inner surface 608, an outer surface 610, a first opening 612a, a second opening 612b, a third opening 612c, and a fourth opening 612d.

[0063] More specifically, the reaction chamber is disclosed with particular emphasis on each opening. FIG. 6 shows a cutaway view of the reaction chamber. Regarding the first opening, as can be seen in FIG. 6, the reaction chamber 600 includes a first mesh cathode 602a, a first anode 604a, and a reaction chamber body 606. In some embodiments, the reaction chamber body 606 is hollow and includes an inner surface 608, an outer surface 610, and a first opening 612a. The first opening 612a has a first lip 614a. The first anode 604a can be reversibly secured to the first lip 614a by a first fastener (not shown). A first semiconductor wafer 622a is positioned between the first lip 614a and the first anode 604a. In some embodiments, the first lip 614a includes a first peg 616a and a first recess 618a that extends around the first opening 612a. In some embodiments, the first recess 618a is located closer to the inner surface 608 than the first peg 614a. In some embodiments, the first lip 614a includes between 3 and 20 first pegs, collectively referred to as 616a. In some embodiments, the reaction chamber 600 includes a first gasket 620a configured to fit or be received in the first recess 618a, creating a reversibly sealable, leak-tight reaction chamber to prevent an etching solution 634, such as an HF solution, from leaking from the reaction chamber during use or storage.

[0064] Regarding the second opening, as can be seen in FIG. 6 , the reaction chamber 600 includes a second mesh cathode 602b, a second anode 604b, and a reaction chamber body 606. In some embodiments, the reaction chamber body 606 is hollow and defines an inner surface 608, an outer surface 610, and a second opening 612b. The second opening 612b has a second lip 614b. The second anode 604b can be reversibly secured to the second lip 614b by a second fastener (not shown). A second semiconductor wafer 622b is positioned between the second lip 614b and the second anode 604b. In some embodiments, the second lip 614b includes a second peg 616b and a second recess 618b extending around the second opening 612b. In some embodiments, the second recess 618b is located closer to the inner surface 608 than the second pegs 614b. In some embodiments, the second lip 614b includes between 3 and 20 second pegs, collectively designated as 616b. In some embodiments, the reaction chamber 600 includes a second gasket 620b configured to fit into the second recess 618b to create a reversibly sealable, leak-tight reaction chamber to prevent an etching solution 634, such as an HF solution, from leaking from the reaction chamber during operation or storage.

[0065] Regarding the third opening, as can be seen in FIG. 6 , the reaction chamber 600 includes a third mesh cathode 602c, a third anode 604c, and a reaction chamber body 606. In some embodiments, the reaction chamber body 606 is hollow and defines an inner surface 608, an outer surface 610, and a third opening 612c. The third opening 612c has a third lip 614c. The third anode 604c can be reversibly secured to the third lip 614c by a third fastener (not shown). A third semiconductor wafer 622c is positioned between the third lip 614c and the third anode 604c. In some embodiments, the third lip 614c includes a third peg 616c and a third recess 618c that extends around the third opening 612c. In some embodiments, the third recess 618c is located closer to the inner surface 608 than the third pegs 614c. In some embodiments, the third lip 614c includes between 3 and 20 third pegs, collectively designated as 616c. In some embodiments, the reaction chamber 600 includes a third gasket 620c configured to fit into the third recess 618c to create a reversibly sealable, leak-tight reaction chamber to prevent an etching solution 634, such as an HF solution, from leaking from the reaction chamber during operation or storage.

[0066] Regarding the fourth opening, as can be seen in FIG. 6 , the reaction chamber 600 includes a fourth mesh cathode 602d, a fourth anode 604d, and a reaction chamber body 606. In some embodiments, the reaction chamber body 606 is hollow and defines an inner surface 608, an outer surface 610, and a fourth opening 612d. The fourth opening 612d has a fourth lip 614d. The fourth anode 604d can be reversibly secured to the fourth lip 614d by a fourth fastener (not shown). A fourth semiconductor wafer 622d is positioned between the fourth lip 614d and the fourth anode 604d. In some embodiments, the fourth lip 614d includes a fourth peg 616d and a fourth recess 618d that extends around the fourth opening 612d. In some embodiments, the fourth recess 618d is located closer to the inner surface 608 than the fourth peg 614d. In some embodiments, the fourth lip 614d includes between 3 and 20 fourth pegs, collectively designated as 616d. In some embodiments, the reaction chamber 600 includes a fourth gasket 620d configured to fit into the fourth recess 618d, creating a reversibly sealable, leak-tight reaction chamber to prevent an etching solution 634, such as an HF solution, from leaking from the reaction chamber during operation or storage. In some embodiments, the reaction chamber can have 4, 6, 8, 12, or more openings.

[0067] In operation, in some embodiments, in a manner similar to assembling a reaction chamber having two openings, the reaction chamber is assembled by positioning a first semiconductor wafer on the first lip, aligning the first semiconductor wafer with the O-ring with the aid of a first peg, and then positioning and securing the first anode to the first lip with the aid of a first fastener (such as a screw or bolt) so that the first semiconductor wafer is sandwiched between the first anode and the first lip. Then, the reaction chamber is rotated so that the second opening is parallel to the ground and faces away from the ground (i.e., the second opening is at the top and farthest from the ground compared to the other openings), a second semiconductor wafer is positioned on the second lip, and the second semiconductor wafer is aligned with the O-ring with the help of the second peg, and then the second anode is positioned and fixed to the second lip with the help of a second fastener (such as a screw) so that the second semiconductor wafer is sandwiched between the second anode and the second lip, and the reaction cell is rotated so that the third opening is parallel to the ground and faces away from the ground (i.e., the third opening is at the top and farthest from the ground compared to the other openings), a third semiconductor wafer is positioned on the third lip, and the third semiconductor wafer is aligned with the third peg. The fourth semiconductor wafer can be aligned with the O-ring, and then the third anode can be positioned and fixed to the third lip with the aid of a third fastener (such as a screw) so that the third semiconductor wafer is sandwiched between the third anode and the third lip, the reaction cell can be rotated so that the fourth opening is parallel to the ground and faces away from the ground (i.e., the fourth opening is at the top and farthest from the ground compared to the other openings), the fourth semiconductor wafer can be positioned on the fourth lip, the fourth semiconductor wafer can be aligned with the O-ring with the aid of a fourth peg, and then the fourth anode can be positioned and fixed to the fourth lip with the aid of a fourth fastener (such as a screw) so that the fourth semiconductor wafer is sandwiched between the fourth anode and the fourth lip, thereby creating a sealed reaction chamber.

[0068] In some embodiments of the method, etching liquid can be safely added to the reaction chamber before, during, or after any semiconductor wafer is positioned on its respective lip. In some embodiments of the method, etching liquid can be added into the etching chamber using a liquid port before, during, or after the entire reaction chamber is sealed. In some embodiments of the method, the sealed reaction chamber can be oriented so that the anode corresponding to the wafer that needs to be etched first is substantially perpendicular to gravity and closer to the ground than the other anodes, and sufficient DC current is applied between the mesh cathode and the anode closer to the ground to subject or induce electrochemical etching of the corresponding semiconductor wafer. In some embodiments of the method, for example, the sealed reaction chamber can be oriented so that a first anode is substantially perpendicular to gravity and closer to the ground than the other anodes (exposing the first semiconductor wafer to the etching solution), a DC current is applied between the mesh cathode and the first anode to etch the first semiconductor wafer, and once etching of the first semiconductor wafer is complete, the reaction chamber can then be rotated so that a second anode is substantially perpendicular to gravity and closer to the ground than the other anodes to expose the second semiconductor wafer to the etching solution. In some embodiments of the method, a DC current can then be applied between the mesh cathode and the second anode to etch the second semiconductor wafer. In some embodiments of the method, once etching of the second semiconductor wafer is complete, the reaction chamber can again be rotated so that a third anode is substantially perpendicular to gravity and closer to the ground than the other anodes to expose the third semiconductor wafer to the etching solution. In some embodiments of the method, a DC current can then be applied between the mesh cathode and a third anode to etch a third semiconductor wafer. In some embodiments of the method, once etching of the third semiconductor wafer is complete, the reaction cell is again rotated so that the fourth anode is substantially perpendicular to gravity and closer to the ground than the other anodes, and the fourth semiconductor wafer is exposed to the etching solution.In some embodiments of the method, a DC current can then be applied between the mesh cathode and a fourth anode to etch a fourth semiconductor wafer. In some embodiments of the method, before, during, or after etching any of the second, third, and fourth semiconductor wafers, the etched semiconductor wafer(s) can be removed and / or replaced with new (to-be-etched) or unetched semiconductor wafers. In some embodiments of the method, this process can be repeated to etch semiconductor wafers using potentially the same etchant until the etchant is depleted, preventing or reducing the need to drain and store the etchant after each etching cycle.

[0069] Although the reaction chamber and method disclosed herein are designed to provide a safe and efficient apparatus and method for electrochemically etching semiconductor wafers with an HF solution, embodiments of the reaction chamber and method can be used for other types of processes with other process solutions and other substrates. In some embodiments, the method includes adding an HF acid or HF-containing solution to the reaction chamber. In some embodiments, the method includes adding a process solution, such as a caustic base, such as a KOH or NOH solution, to the reaction chamber. In some embodiments, the semiconductor wafer may include a semiconductor wafer comprising crystalline silicon. In some embodiments, the semiconductor wafer may include gallium nitride. In some embodiments of the methods disclosed herein, no current is applied during the process step; the process solution is simply brought into contact with the semiconductor surface to facilitate processing.

[0070] Further description of the embodiments

[0071] Embodiment 1. A reaction chamber comprising a mesh cathode, a first anode, a second anode, and a reaction chamber body, the reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip; the mesh cathode is positioned between the first opening and the second opening, the mesh cathode being substantially parallel to the first lip; The reaction chamber, wherein the first anode is reversibly securable to the first lip by a first fastener and the second anode is reversibly securable to the second lip by a second fastener.

[0072] Embodiment 2. The inner edge of the first lip has a shortest distance across the first opening of about 2.5 cm to about 46.0 cm, or the inner edge of the second lip has a shortest distance across the second opening of about 2.5 cm to about 46.0 cm; or the first opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm, or the second opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm; or 8. The reaction chamber of one or more of embodiments 1-7, wherein the first opening and the second opening have a circular shape with an inner diameter that is about 2.0 mm to about 5.0 mm smaller than the diameter of a semiconductor wafer.

[0073] Embodiment 3. The reaction chamber comprises one or less mesh cathodes, the mesh cathodes being positioned substantially parallel to an equidistant line between the first anode and the second anode within a range of about 0.0 mm to about 5.0 mm; or the mesh cathode is located about 1.0 cm to about 10 cm from the first anode, or the mesh cathode is located about 1.0 cm to about 10 cm from the second anode; or 8. The reaction chamber of one or more of embodiments 1-7, wherein the reaction chamber comprises a first mesh cathode and a second mesh cathode, the first mesh cathode being located at a distance of about 1.0 cm to about 10 cm from the first anode and substantially parallel to the first anode, or the second mesh cathode being located at a distance of about 1.0 cm to about 10 cm from the second anode and substantially parallel to the second anode.

[0074] Embodiment 4. The first lip includes 3 to 20 first pegs and a first recess extending around the first opening, the first recess being located closer to the inner surface than the pegs; or 8. The reaction chamber of one or more of embodiments 1-7, wherein the second lip comprises 3-20 second pegs and a second recess extending around the second opening, the second recess being located closer to the inner surface than the second pegs.

[0075] Embodiment 5. The method further comprising: providing a first gasket; the first gasket configured to fit into the first recess; or further comprising a second gasket, the second gasket configured to fit into the second recess; or at least one of the first gasket and the second gasket is an O-ring; 8. The reaction chamber of one or more of embodiments 1-7, wherein the first gasket and the second gasket comprise rubber, elastomer, or fluoropolymer.

[0076] Embodiment 6. The reaction chamber body comprises a polymer or a fluoropolymer; or the mesh cathode comprises a nickel alloy or a nickel-copper alloy; or 8. The reaction chamber of one or more of embodiments 1-7, wherein at least one of the first anode and the second anode comprises a nickel alloy, a nickel-copper alloy, a p-doped silicon plate, or an n-doped silicon plate, or a combination thereof.

[0077] Embodiment 7. The reaction chamber of one or more of embodiments 1-7, wherein the mesh cathode is electrically connected to a DC power source through the reaction chamber body, or the reaction chamber body includes a liquid port, the liquid port being a tube extending through the reaction chamber body from the outer surface to the outer surface.

[0078] Embodiment 8. A method of operating a reaction chamber, comprising: providing a reaction chamber, the reaction chamber comprising: a mesh cathode, a first anode, a second anode, and a reaction chamber body; the reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip; the mesh cathode is positioned between the first opening and the second opening, the mesh cathode being substantially parallel to the first lip; providing the first anode reversibly securable to the first lip by a first fastener and the second anode reversibly securable to the second lip by a second fastener; A sealed reaction chamber positioning a first semiconductor wafer between the first lip and the first anode to form a first seal between the first semiconductor wafer and the first lip; Positioning a second semiconductor wafer between the second lip and the second anode to form a second seal between the second semiconductor wafer and the second lip. and forming the adding reactants to the sealed reaction chamber.

[0079] Embodiment 9. Orienting the sealed reaction chamber by positioning the second anode substantially perpendicular to gravity and closer to the ground than the first anode; etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode; 16. The method of operating a reaction chamber of one or more of embodiments 8-15, further comprising:

[0080] Embodiment 10. Orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode; etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode; 16. The method of operating a reaction chamber of one or more of embodiments 8-15, further comprising:

[0081] Embodiment 11. A method of operating a reaction chamber of one or more of embodiments 8-15, further comprising removing the second semiconductor wafer before, during, or after etching the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode.

[0082] Embodiment 12. Orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode; etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode; 16. The method of operating a reaction chamber of one or more of embodiments 8-15, further comprising:

[0083] Embodiment 13. Orienting the sealed reaction chamber by positioning the second anode substantially perpendicular to gravity and closer to the ground than the first anode; etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode; 16. The method of operating a reaction chamber of one or more of embodiments 8-15, further comprising:

[0084] Embodiment 14. A method of operating a reaction chamber of one or more of embodiments 8-15, wherein the reactant comprises HF.

[0085] Embodiment 15. Etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode, and then etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode; or etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode, and then etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode. 16. The method of operating a reaction chamber of one or more of embodiments 8-15, further comprising: [Example]

[0086] Etching chamber construction An exemplary rotary dual electrochemical etching cell can be designed and machined for 150 mm wafers as described below. The complete etching cell consists of three main parts: 1) A cylindrical etching chamber with O-rings on both ends for wafer mounting and sealing. This two-end design allows the electrochemical (EC) cell containing the solution to be sealed by two mounted wafers. Operators can then carry, rotate, flip, or even shake the cell without worrying about spilling dangerous chemicals. In an actual EC etching operation, an operator loads a wafer on one end, completes electrochemical etching on the wafer, then loads and seals another wafer on the other end, flips the cell over without handling or spilling the HF-based etchant, and then removes the first wafer and completes EC etching on the second wafer. This procedure can be repeated multiple times, thereby minimizing HF handling and use and saving processing time. Alignment pins allow for easy and quick wafer alignment and correct mounting. 2) A mesh cathode fixed in the center of the chamber with a sealed connecting lead wire. Fixing the mesh cathode within the cell with connecting lead wires eliminates the need to remove and replace the cathode after EC etching each wafer, thus eliminating the loss of solution and the possibility of contamination. 3) Anode plates on back support plates that can be mounted on both ends. The anode plate or anodes on the back support plate do not come into contact with the etching solution and remain dry throughout the process, eliminating the need for anode cleaning and reducing concerns about anode plate corrosion. Added screw hole buffer pads allow for the use of power tools to tighten and loosen screws without overtightening. This system can be easily modified for industrial automation using clamping mechanisms such as robotic arms. Two wafers can be etched simultaneously when positioned vertically, and a bubble release mechanism is used. Because most solutions used for electrochemical etching of porous silicon contain HF and surfactants, chemically compatible materials must be adapted for cell construction.

[0087] Operating Procedure The sample handling protocol for operating the rotating dual electrochemical etching cell is described below. 1) Place the first silicon wafer into one end of the cylindrical etching chamber, aligning it with the O-ring and leaving some overhang by placing the wafer inside a rubber stub or pin provided to aid in positioning. 2) The metal anode plate with supporting backplate is placed on top of the wafer and the screw holes are aligned with the help of two Teflon pins. 3) Place the screws into the threaded holes and tighten to seal the wafer against the O-ring on the etching cell. 4) The assembled cell is turned upside down so that the cylindrical open end faces upward. An etching solution is poured into the etching cell assembly. The electrodes are connected to a power supply, and a programmed current is applied to obtain the porous silicon structure. 5) For the next wafer, place the wafer on top of the etching cell assembly by placing the wafer inside the stubs or pins provided to aid in positioning. 6) Place the second metal anode plate with backplate on top and align the screw holes with the help of two Teflon pins. 7) Place the screws into the threaded holes and tighten to seal the etching cell. 8) Flip the cell over so that the newly placed wafer is on the bottom and the originally etched wafer is on top of the assembly. 9) Loosen and remove the screws on the top plate to release the top anode plate. The anode plate with backplate is then removed from the top of the etching assembly. The first etched wafer is removed from the assembly and prepared for a DI water rinse. 10) Connect the electrodes to a power supply and provide a programmed current to etch the second wafer for the porous silicon structure. 11) Next, place the third wafer on top of the cell. Repeat the above procedure to etch more wafers with the same solution or the HF compensation solution.

[0088] HF consumption and substitution Electrochemical etching of porous silicon consumes HF. The amount of HF consumed can be calculated according to the total current applied during the process. Therefore, HF compensation to maintain a constant HF concentration can be easily performed. When fabricating a multilayer stack of porous silicon disks on a 150 mm micropillar wafer, it is estimated that approximately 0.4% of HF is consumed to EC etch 10 layers of particles per wafer in a 12.5% ​​HF etchant.

Claims

1. A reaction chamber comprising a mesh cathode, a first anode, a second anode, and a reaction chamber body, the reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip; the mesh cathode is positioned between the first opening and the second opening, the mesh cathode being substantially parallel to the first lip; The reaction chamber, wherein the first anode is reversibly securable to the first lip by a first fastener and the second anode is reversibly securable to the second lip by a second fastener.

2. the inner edge of the first lip has a shortest distance across the first opening of about 2.5 cm to about 46.0 cm, or the inner edge of the second lip has a shortest distance across the second opening of about 2.5 cm to about 46.0 cm; or the first opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm, or the second opening has a circular shape with an inner diameter of about 2.5 cm to about 46.0 cm; or 2. The reaction chamber of claim 1, wherein the first opening and the second opening have a circular shape with the inner diameter being about 2.0 mm to about 5.0 mm smaller than a diameter of a semiconductor wafer.

3. the reaction chamber comprises no more than one mesh cathode, the mesh cathode positioned substantially parallel to an equidistant line between the first anode and the second anode within a range of about 0.0 mm to about 5.0 mm; or the mesh cathode is located from about 1.0 cm to about 10 cm to the first anode, or the mesh cathode is located from about 1.0 cm to about 10 cm to the second anode; or 10. The reaction chamber of claim 1, wherein the reaction chamber comprises a first mesh cathode and a second mesh cathode, the first mesh cathode being positioned substantially parallel to the first anode at a distance of about 1.0 cm to about 10 cm from the first anode, or the second mesh cathode being positioned substantially parallel to the second anode at a distance of about 1.0 cm to about 10 cm from the second anode.

4. the first lip includes 3 to 20 first pegs and a first recess extending around the first opening, the first recess being located closer to the inner surface than the pegs; or 2. The reaction chamber of claim 1, wherein the second lip includes 3 to 20 second pegs and a second recess extending around the second opening, the second recess being located closer to the inner surface than the second pegs.

5. further comprising a first gasket, the first gasket configured to fit into the first recess; or further comprising a second gasket, the second gasket configured to fit into the second recess; or at least one of the first gasket and the second gasket is an O-ring; The reaction chamber of claim 4 , wherein the first gasket and the second gasket comprise a rubber, an elastomer, or a fluoropolymer.

6. the reaction chamber body comprises a polymer or a fluoropolymer; or the mesh cathode comprises a nickel alloy or a nickel-copper alloy; or 10. The reaction chamber of claim 1, wherein at least one of the first anode and the second anode comprises a nickel alloy, a nickel-copper alloy, a p-doped silicon plate, or an n-doped silicon plate, or a combination thereof.

7. the mesh cathode is electrically connected to a DC power source through the reaction chamber body; or 10. The reaction chamber of claim 1, wherein the reaction chamber body includes a liquid port, the liquid port being a tube extending through the reaction chamber body from the outer surface to the outer surface.

8. 1. A method of operating a reaction chamber, comprising: providing a reaction chamber, the reaction chamber comprising: a mesh cathode, a first anode, a second anode, and a reaction chamber body; the reaction chamber body is hollow and has an inner surface, an outer surface, a first opening with a first lip, and a second opening with a second lip; the mesh cathode is positioned between the first opening and the second opening, the mesh cathode being substantially parallel to the first lip; providing the first anode reversibly securable to the first lip by a first fastener and the second anode reversibly securable to the second lip by a second fastener; A sealed reaction chamber positioning a first semiconductor wafer between the first lip and the first anode to form a first seal between the first semiconductor wafer and the first lip; Positioning a second semiconductor wafer between the second lip and the second anode to form a second seal between the second semiconductor wafer and the second lip. and forming the adding reactants to the sealed reaction chamber.

9. orienting the sealed reaction chamber by positioning the second anode substantially perpendicular to gravity and closer to the ground than the first anode; etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode; The method of claim 8 further comprising:

10. orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode; etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode; 10. The method of claim 9, further comprising:

11. 11. The method of claim 10, further comprising removing the second semiconductor wafer before, during, or after etching the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode.

12. orienting the sealed reaction chamber by positioning the first anode substantially perpendicular to gravity and closer to the ground than the second anode; etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode; The method of claim 8 further comprising:

13. orienting the sealed reaction chamber by positioning the second anode substantially perpendicular to gravity and closer to the ground than the first anode; etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode; The method of claim 12 further comprising:

14. The method of claim 8 wherein the reactant comprises HF.

15. Etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode, and then etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode; or etching a second surface of the second semiconductor wafer by applying a DC current between the mesh cathode and the second anode, and then etching a first surface of the first semiconductor wafer by applying a DC current between the mesh cathode and the first anode; The method of claim 8 further comprising:

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