Semiconductor photoelectrochemical etching device

Abstract

Semiconductor photoelectrochemical etching apparatus. A semiconductor photoelectrochemical etching apparatus and a photoelectrochemical etching method are presented. A semiconductor photoelectrochemical etching apparatus includes a photoelectrochemical flow cell, a circulating electrolyte solution propelled through the photoelectrochemical flow cell by a circulating electrolyte pump, a UV light source directed at the photoelectrochemical flow cell, wherein an optical path length between the UV light source and the photoelectrochemical flow cell is set to collect high power light from the UV light source, and a turbulence generator configured to generate turbulence in the circulating electrolyte solution.

Description

Technical Field

[0001] This disclosure generally relates to semiconductors, and more specifically, to a method and system for efficiently photoelectrochemical etching of semiconductor substrates using a photoelectrochemical etching apparatus. Background Technology

[0002] Photonic circuits, also known as integrated optical circuits, manipulate photons to perform various functions, much like electronic circuits manipulate electrons. Photonic circuits are used in applications such as telecommunications, sensing, signal processing, and quantum computing. They include components such as waveguides, modulators, detectors, and light sources integrated onto a chip.

[0003] Silicon carbide-on-insulator (SiCOI) technology is widely used in the fabrication of photonic circuits. SiCOI is a semiconductor technology that integrates a thin layer of silicon carbide (SiC) (usually silicon dioxide (SiO2)) onto an insulating substrate. SiC has a wide bandgap, allowing operation at higher frequencies and powers, thereby reducing signal loss and improving efficiency. Furthermore, SiC effectively dissipates heat, which is crucial for high-power photonic applications. In addition, SiC can withstand harsh environmental conditions, making it suitable for durable photonic devices. These properties make SiC an ideal material in photonic circuits.

[0004] The SiCOI structure comprises multiple layers. A substrate layer, such as Si, provides a mechanically supporting base. An insulating layer, such as silicon dioxide (SiO2), is formed on top of the substrate layer. The insulating layer electrically isolates the top layer, such as a thin SiC layer, from the substrate layer, thereby minimizing parasitic capacitance and leakage current. Photonic devices are fabricated on the top layer. The fabrication of SiC on Insulator (SiCOI) structures involves multiple steps, including growth, bonding, and substrate removal.

[0005] In photonic circuits, maintaining uniform cross-sectional dimensions of the wafer is crucial for consistent light propagation. Variations in SiC thickness can alter optical path length, leading to phase errors and signal degradation. Non-uniform SiC layers cause refractive index variations, impacting the performance of devices such as modulators, resonators, and filters. Thickness variation is measured as total thickness variation (TTV), which is the difference between the maximum and minimum thickness observed in the material layer on the wafer. Low TTV indicates a planar SiC layer with uniform thickness. High TTV indicates significant thickness variation, which can lead to poor device performance and problems in subsequent processing steps.

[0006] There are two traditional methods for substrate removal. The first, “smart cutting” technique, uses ion implantation to create an amorphous layer at a limited depth, such as less than 1 μm. This “smart cutting” method produces damaged regions, which can lead to unstable spin defects with poor quantum coherence, and devices with high propagation losses in photonic waveguides.

[0007] The second technique, flipping and mechanical polishing, can be used for substrate removal. Flipping and mechanical polishing introduce thickness variations greater than 3µm on the wafer, which is unacceptable for photonic components. While additional process steps such as polishing and ion etching are typically included, these techniques do not reduce the thickness variations introduced by polishing.

[0008] A process called photoelectrochemical (PEC) etching can be used to etch SiC material to the desired depth. However, the uniformity of PEC etching may not be as good as that of current methods.

[0009] Therefore, it is desirable to have a method and apparatus that takes into account at least some of the above-mentioned problems, as well as other possible problems. Summary of the Invention

[0010] Embodiments of this disclosure provide a semiconductor photoelectrochemical etching apparatus. The semiconductor photoelectrochemical etching apparatus includes: a photoelectrochemical flow unit; a circulating electrolyte solution propelled through the photoelectrochemical flow unit by a circulating electrolyte pump; a UV light source directed at the photoelectrochemical flow unit, wherein the optical path length between the UV light source and the photoelectrochemical flow unit is set to collect high-power light from the UV light source; and a turbulence generator configured to generate turbulence in the circulating electrolyte solution.

[0011] Another embodiment of this disclosure provides a method for photoelectrochemical etching of a semiconductor substrate. The semiconductor substrate is placed in the etching chamber of a semiconductor photoelectrochemical etching apparatus, the optical path length of which is configured to collect high-power light from a UV light source. The semiconductor substrate is immersed in a circulating electrolyte solution within the etching chamber. Turbulence of the circulating electrolyte solution is generated on the surface of the semiconductor substrate. The semiconductor substrate is irradiated with UV light of a selected wavelength from the UV light source to irradiate the surface of the semiconductor substrate, thereby etching the semiconductor substrate with a total thickness variation within tolerance range.

[0012] Another embodiment of this disclosure provides a method for photoelectrochemical etching of a semiconductor substrate. The semiconductor substrate is placed in the etching chamber of a semiconductor photoelectrochemical etching apparatus, the optical path length of which is configured to collect high-power light from an LED light source. The semiconductor substrate is immersed in a circulating electrolyte solution within the etching chamber. Turbulence of the circulating electrolyte solution is generated on the surface of the semiconductor substrate. A bias voltage is applied between the semiconductor substrate and the circulating electrolyte solution. The semiconductor substrate is irradiated with UV light of a selected wavelength below 300 nm from the LED light source to irradiate the surface of the semiconductor substrate with a surface light uniformity greater than 80%, thereby etching the semiconductor substrate with a total thickness variation within tolerance.

[0013] The features and functions may be implemented independently in various embodiments of this disclosure, or may be combined in other embodiments, with further details to be derived with reference to the following description and drawings. Attached Figure Description

[0014] The appended claims set forth novel features considered to have the characteristics of exemplary embodiments. However, the illustrative embodiments, their preferred modes of use, further objectives, and features will be best understood by referring to the following detailed description of illustrative embodiments of this disclosure when read in conjunction with the accompanying drawings: Figure 1 It is a block diagram illustration of a manufacturing environment according to an illustrative embodiment; Figure 2 This is an exploded view illustration of a semiconductor photoelectrochemical etching apparatus according to an illustrative embodiment; Figure 3 This is an illustration of a front view of a photoelectrochemical flow unit according to an illustrative embodiment; Figure 4 This is an illustration of a front view of a photoelectrochemical flow unit according to an illustrative embodiment; Figure 5 This is an illustration of a front view of a photoelectrochemical flow unit according to an illustrative embodiment; Figure 6 This is a flowchart of a method for photoelectrochemical etching of a semiconductor substrate according to an illustrative embodiment; and Figure 7 This is a flowchart of a method for photoelectrochemical etching of a semiconductor substrate according to an illustrative embodiment. Detailed Implementation

[0015] The illustrative example recognizes and considers several factors. It recognizes and considers that wide-gap semiconductors, including aluminum nitride (AlN), gallium nitride (GaN), and silicon carbide (SiC), are used in commercial devices such as blue light-emitting diodes, microelectromechanical systems (MEMS), and high-frequency and high-power electronic devices. It recognizes and considers that these materials cannot be grown into defect-free single crystals on common low-cost substrates such as silicon and silicon oxide due to lattice mismatch. It recognizes and considers that these defects limit the use of these wide-gap semiconductors as thin films for integrating photonic devices (linear and nonlinear) and low-loss electro-optic devices. It recognizes and considers that in the etching processes of SiC, AlN, and GaN, photoelectrochemical (PEC) etching is selected based on the material doping type, and PEC etching has been used to fabricate undercut photonic structures by in-plane or lateral etching from recesses in the Si facets etched into SiC.

[0016] The illustrative example recognizes and considers that photoelectrochemical (PEC) etching can be used to etch SiC materials to a desired etching depth, such as 1 micrometer, 5 micrometers, or 7 micrometers. The illustrative example recognizes and considers that in PEC etching, the SiC substrate is placed in an etching chamber equipped with an ultraviolet (UV) light source. The illustrative example recognizes and considers that the SiC substrate is immersed in an electrolyte solution within the etching chamber, and a bias voltage is applied between the semiconductor substrate and the circulating electrolyte solution. The illustrative example recognizes and considers that the semiconductor substrate is then irradiated with UV light emitted from the light source. The illustrative example recognizes and considers that when the UV light irradiates the surface of the semiconductor substrate, an oxidation reaction forms oxides on the surface. The illustrative example recognizes and considers that the oxides are subsequently dissolved by the circulating electrolyte solution. The illustrative example recognizes and considers that the semiconductor substrate is etched until the desired etching depth is reached. The illustrative example recognizes and considers that the etching rate and etched surface roughness of the semiconductor substrate can be controlled by varying the intensity of the UV light and by adjusting the bias voltage.

[0017] The illustrative examples recognize and take into account that conventional PEC etching tends to result in poor etching uniformity. The illustrative examples provide a PEC etching apparatus design for performing wafer-level SiC PEC etching to accommodate LED arrays with uniform, smooth, and selective etching. The illustrative examples provide designs that control aspects important for generating low TTV in SiC on insulators, including optical uniformity, electrolyte flow, and photoelectrochemical unit design.

[0018] Turn now Figure 1 The illustration depicts a block diagram of a manufacturing environment according to an illustrative embodiment. The semiconductor photoelectrochemical etching apparatus 102 can be used to etch a semiconductor substrate 156.

[0019] Etching the semiconductor substrate 156 can be used as part of a process for fabricating SiC on Insulator with a low total thickness variation 172 and a smooth surface. An example of a process for fabricating SiC on Insulator involves SiC epitaxial growth, wafer flipping and bonding, grinding / polishing, and PEC etching of the SiC sacrificial layer. Illustrative examples provide characteristics of the PEC etching step to produce a smooth surface with a low total thickness variation 172.

[0020] Wavelength 141 is important for effective PEC etching. In some illustrative examples, an LED light source 130 is used to provide wavelength 141. Additional parameters for PEC etching include optical path length 126, optical uniformity 139, and flow characteristics 112 of the circulating electrolyte solution 110.

[0021] The semiconductor photoelectrochemical etching apparatus 102 includes: a photoelectrochemical flow unit 104; a circulating electrolyte solution 110 propelled through the photoelectrochemical flow unit 104 by a circulating electrolyte pump 146; a UV light source 128 directed to the photoelectrochemical flow unit 104, wherein an optical path length 126 between the UV light source 128 and the photoelectrochemical flow unit 104 is configured to collect high-power light from the UV light source 128; and a turbulence generator 148 configured to generate turbulence 113 in the circulating electrolyte solution 110. The UV light source 128 provides UV light 131.

[0022] In some illustrative examples, the semiconductor photoelectrochemical etching apparatus 102 also includes a computer-controlled power supply 140. In some illustrative examples, the computer-controlled power supply 140 applies a bias voltage 142, which is constant or variable, and has a constant or oscillating current 144.

[0023] In some illustrative examples, the semiconductor photoelectrochemical etching apparatus 102 also includes an additional computer-controlled power supply. In some illustrative examples, the additional computer-controlled power supply may be attached to the photoelectrochemical flow unit 104 to bias different doped layers of the semiconductor stack in the semiconductor substrate 156 relative to each other.

[0024] In some illustrative examples, the circulating electrolyte solution 110 includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, hydrogen fluoride, or a buffer solution. In some illustrative examples, the UV light source 128 is selected for wavelength 141. In some illustrative examples, the UV light source 128 is a lamp that emits narrowband light or a combination of narrowband light with a wavelength less than 300 nm.

[0025] In some illustrative examples, the optical path length 126 through the photoelectrochemical flow unit 104 is sufficient to collect greater than 50 mW / cm² from the UV light source 128. 2The light. In some illustrative examples, the optical path length 126 through the photoelectrochemical flow unit 104 is sufficient to collect greater than 100 mW / cm² from the UV light source 128. 2 The light. In some illustrative examples, the optical path length 126 through the photoelectrochemical flow unit 104 is sufficient to collect greater than 150 mW / cm² from the UV light source 128. 2 The light. In some illustrative examples, the optical path length 126 through the photoelectrochemical flow unit 104 is sufficient to collect greater than 200 mW / cm² from the UV light source 128. 2 The light source 128 is selected from at least one of LED light source 130, mercury arc lamp 134, mercury-xenon arc lamp 136, excimer laser 138, or excimer lamp. In some illustrative examples, LED light source 130 is in the form of LED array 132.

[0026] The illustrative examples recognize that a uniform distribution of light intensity is crucial for high-quality low-TTV SiCOI fabrication. In some illustrative examples, when using a mercury arc lamp 134, focusing is employed to achieve sufficiently high UV-C light intensity for smooth SiCOI etching.

[0027] For the LED light source 130 without a focusing lens, the LED light source can be referred to as a divergent LED light source. The unfocused UV-C LED array 132 emits highly divergent light from each chip at a projection angle of 120°. Therefore, at the distance chosen for PEC etching, the incident light intensity is significantly more uniform on the surface 162 of the semiconductor substrate 156 than that of the mercury arc lamp 134. The greater light uniformity 139 results in a lower TTV for LED etching, even with more than double the processing area compared to mercury lamp etching. In the case of using an unfocused LED array, the light intensity pattern does not appear to be a limiting factor for TTV reduction.

[0028] In some illustrative examples, the photoelectrochemical flow unit 104 includes an optical path length 126 configured to collect high-power light from a divergent LED light source (LED light source 130). In some illustrative examples, the UV light source 128 is the LED light source 130. In some illustrative examples, the UV light source 128 includes at least one LED light source 130 without a lens.

[0029] In some illustrative examples, the UV light source 128 includes either a mercury arc lamp 134 or a mercury-xenon arc lamp 136. In some illustrative examples, the UV light source 128 is either an excimer laser 138 or an excimer lamp. In some illustrative examples, the semiconductor photoelectrochemical etching apparatus 102 also includes a frosted glass diffuser configured to provide greater than 80% light uniformity 139 on the surface 162 of the semiconductor substrate 156.

[0030] In some illustrative examples, the parameters of the circulating electrolyte solution 110 are controlled to improve etching. In some illustrative examples, the temperature of the circulating electrolyte solution 110 is in the range of 5 degrees Celsius to 50 degrees Celsius. In some illustrative examples, the circulating electrolyte solution 110 is an aqueous solution. In some illustrative examples, the concentration of the circulating electrolyte solution 110 is in the range of 0.01% by weight to 15% by weight.

[0031] The flow field of the circulating electrolyte solution 110 in the photoelectrochemical flow unit 104 is a controlled parameter of an exemplary example to achieve smooth etching on the surface 162 of the semiconductor substrate 156. Turbulence 113 can prevent the formation of a barrier layer at the surface 162 of the semiconductor substrate 156. A barrier layer can lead to local depletion of electrolyte concentration and accumulation of reaction products, resulting in a rough etched surface.

[0032] In some illustrative examples, a barrier layer can be prevented by maintaining turbulence 113 over the entire surface 162 of the semiconductor substrate 156. A relatively high flow rate is used to generate turbulence 113 using the electrolyte nozzle 108. In some illustrative examples, an electrolyte nozzle 108 with a flow rate greater than 200 standard cubic centimeters per minute (sccm) is used to generate turbulence 113. In some illustrative examples, the electrolyte inlet 106 and the electrolyte nozzle 108 are oriented such that eddy currents or low-velocity regions do not occur. If the flow inlet is positioned in a manner that allows for localized dead zones, rough regions may appear in the etched semiconductor substrate 156 compared to a fully turbulent flow field.

[0033] Turbulence 113 contributes to the success of haze-free PEC etching. In some illustrative examples, turbulence 113 can be achieved by applying ultrasonic treatment. In some illustrative examples, ultrasonic treatment can be applied during etching by applying ultrasonic treatment to the semiconductor substrate 156. In some illustrative examples, applying ultrasonic treatment to the semiconductor substrate 156 can be referred to as ultrasonic treatment of the wafer by applying acoustic waves to the SiC wafer.

[0034] In some illustrative examples, ultrasonic treatment can be applied during the etching process by applying an ultrasonic transducer 150 to the photoelectrochemical flow unit 104. The ultrasonic transducer 150 can be applied to the body of the photoelectrochemical flow unit 104 to transmit sound waves to the body of the photoelectrochemical flow unit 104.

[0035] In some illustrative examples, ultrasonic treatment can be applied during the etching process by applying an ultrasonic transducer 150 to the circulating electrolyte solution 110. In these illustrative examples, ultrasonic treatment of the circulating electrolyte solution 110 can be achieved by providing an additional port through the photoelectrochemical flow unit 104. In these illustrative examples, the ultrasonic transducer 150 can be in the form of a tip ultrasonic transducer.

[0036] In some illustrative examples, the turbulence generator 148 includes nozzles in the photoelectrochemical flow unit 104 that receive a circulating electrolyte solution 110 from a circulating electrolyte pump to generate a flow pattern in a semiconductor photoelectrochemical etching apparatus that results in turbulence 113 on the surface 162 of the semiconductor substrate 156.

[0037] In some illustrative examples, the turbulence generator 148 includes a piezoelectric element 152 positioned for vibration to induce turbulence 113 at the surface 162 of the semiconductor substrate 156. In some illustrative examples, the turbulence generator 148 includes a stirrer 154 configured to induce turbulence 113 at the surface 162 of the semiconductor substrate 156.

[0038] The photoelectrochemical flow unit 104 includes an electrolyte inlet 106 for delivering a circulating electrolyte solution 110 from a circulating electrolyte pump 146 to the photoelectrochemical flow unit 104. In some illustrative examples, an electrolyte nozzle 108 is used to guide the circulating electrolyte solution 110 into the photoelectrochemical flow unit 104. In some illustrative examples, the electrolyte nozzle 108 is used to generate turbulence 113. The photoelectrochemical flow unit 104 also includes an electrode port 114 to allow a bias voltage 142 to be applied to a counter electrode in the circulating electrolyte solution 110. The circulating electrolyte solution 110 exits the photoelectrochemical flow unit 104 through a unit outlet 116 and proceeds through an electrolyte outlet 120. Gas exits the photoelectrochemical flow unit 104 through a unit outlet 116 and a bubble removal port 118. The electrolyte outlet 120 and the bubble removal port 118 are connected to the unit outlet 116.

[0039] The photoelectrochemical flow unit 104 has a thickness 174 configured to collect a considerable irradiance from the UV light source 128. In some illustrative examples, when the LED array 132 comprises highly divergent, unfocused UV-C LEDs, the photoelectrochemical flow unit 104 is thin enough to collect greater than 50 mW / cm² from the LED array 132 at 265 nm. 2The thickness 174 of the photoelectrochemical flow unit 104 is configured to allow the circulating electrolyte solution to flow sufficiently through the photoelectrochemical flow unit 104 to exchange waste heat. The thickness 174 of the photoelectrochemical flow unit 104 is sufficient to allow turbulence 113 to pass through the surface 162 of the semiconductor substrate 156. In some illustrative examples, the thickness 174 is approximately 0.6 cm. In some illustrative examples, the optical path length 126 is less than 2.5 cm. In some illustrative examples, the thickness 174 is between 0.5 cm and 1 cm, and the optical path length 126 is less than 3 cm. The chamber is determined to be 0.6 cm, resulting in a total distance of 2.3 cm from the LED to the SiC surface. In some illustrative examples, the optical path length 126 is high enough to generate a considerable etch current with low roughness.

[0040] In some illustrative examples, the semiconductor photoelectrochemical etching apparatus 102 uses a large 265nm LED array to perform dopant-selective PEC etching on SiC. In some illustrative examples, the semiconductor substrate 156 can be a wafer with a diameter up to four inches. In some illustrative examples, the LED array 132 is unfocused and has a diameter larger than the wafer to achieve light uniformity 139 on surface 162. The semiconductor photoelectrochemical etching apparatus 102 includes a photoelectrochemical flow unit 104 and several support structures 164 to maintain uniform pressure on the semiconductor substrate 156, thereby vertically mounting the semiconductor substrate 156 for LED illumination. In these illustrative examples, the support structure 164 includes multiple gaskets 168 and multiple inserts 170. The support structure 164 also includes a quartz window 166 for allowing UV light 131 to encounter the semiconductor substrate 156. In some illustrative examples, the total distance from the UV light source 128 to the surface 162 of the semiconductor substrate 156 (i.e., the optical path length 126) is controlled to control the received UV light 131. Maintaining the total distance at the desired length allows the UV light 131 to mix uniformly while maintaining high power.

[0041] In some illustrative examples, the electrolyte nozzle 108 is arranged to flow from the bottom to the top of the photoelectrochemical flow unit 104. In some illustrative examples, the electrolyte nozzle 108 is optional, and instead, an inlet orifice is present. In these illustrative examples, the inlet orifice is arranged for bottom-to-top flow with optional inserts to allow the flow to fan out, resulting in turbulence on surface 162 at a sufficiently high flow rate. In some illustrative examples, the semiconductor photoelectrochemical etching apparatus 102 may also be connected to a second external power source for biasing the individual layers of SiC relative to each other to improve selectivity.

[0042] In some illustrative examples, the semiconductor photoelectrochemical etching apparatus 102 also includes at least one of a plurality of process monitoring ports 122 or a plurality of process monitoring windows 124. The plurality of process monitoring ports 122 can be used for counter electrodes and reference electrodes, as well as for data collection such as pH monitoring or temperature monitoring. In some illustrative examples, the plurality of process monitoring windows 124 can be used for additional data collection.

[0043] In some illustrative examples, the semiconductor substrate 156 is a complete wafer or wafer piece. In some illustrative examples, the semiconductor substrate 156 includes one of silicon carbide 158 or silicon carbide-on-insulator 160. In some illustrative examples, the semiconductor substrate 156 includes GaN or another semiconductor not mentioned herein. In some illustrative examples, the semiconductor substrate 156 includes multiple layers or undoped layers with doping concentrations ranging from 1e15 to 1e19, either n-type or p-type doped. In some illustrative examples, the semiconductor substrate 156 has contacts for biasing the layers relative to each other for the purpose of improving etch selectivity. In some illustrative examples, the semiconductor substrate 156 includes doped silicon carbide 158 or silicon carbide-on-insulator 160 semiconductors and has exposed Si or C-surface surfaces.

[0044] In some illustrative examples, photoelectrochemical etching using semiconductor photoelectrochemical etching apparatus 102 results in a smooth (roughness less than 10 nm) etching of semiconductor substrate 156, thereby enabling its use in integrated photonic devices. In some illustrative examples, at least one of optical path length 126, turbulence 113 of circulating electrolyte solution 110, optical uniformity 139, or wavelength 141 is configured to provide a roughness of less than 10 nm from the etching of semiconductor substrate 156.

[0045] In some illustrative examples, photoelectrochemical etching includes placing a semiconductor substrate 156 in an etching chamber 103 of a semiconductor photoelectrochemical etching apparatus 102 having an optical path length 126 configured to collect high-power light from a UV light source 128. In some illustrative examples, photoelectrochemical etching includes placing a semiconductor substrate 156 in an etching chamber 103 of a semiconductor photoelectrochemical etching apparatus 102 having an optical path length 126 configured to collect high-power light from an LED light source 130.

[0046] In some illustrative examples, photoelectrochemical etching further includes immersing the semiconductor substrate 156 in a circulating electrolyte solution 110 within the etching chamber 103. In some illustrative examples, photoelectrochemical etching further includes generating turbulence 113 of the circulating electrolyte solution 110 on the surface 162 of the semiconductor substrate 156.

[0047] In some illustrative examples, photoelectrochemical etching further includes applying a bias voltage 142 between the semiconductor substrate 156 and the counter electrode in a circulating electrolyte solution 110. In some illustrative examples, photoelectrochemical etching further includes irradiating the semiconductor substrate 156 with UV light 131 of a selected wavelength 141 from a UV light source 128 to irradiate the surface 162 of the semiconductor substrate 156, thereby etching the semiconductor substrate 156 with a total thickness variation 172 within tolerance. In some illustrative examples, photoelectrochemical etching further includes irradiating the semiconductor substrate 156 with UV light 131 of a selected wavelength 141 below 300 nm from an LED light source 130 to irradiate the surface 62 of the semiconductor substrate 156 with an optical uniformity 139 greater than 80%, thereby etching the semiconductor substrate 156 with a total thickness variation 172 within tolerance.

[0048] Figure 1 The illustration of manufacturing environment 100 does not imply any physical or architectural limitations on the manner in which exemplary embodiments can be implemented. Other components besides those shown, or components that replace those shown, may be used. Some components may be unnecessary. Furthermore, blocks are shown to illustrate functional components. When implemented in the illustrative embodiments, one or more of these blocks may be combined, divided, or combined and divided into different blocks. For example, in some illustrative examples, the electrolyte nozzle 108 may be optional.

[0049] Now go to Figure 2 An exploded view of a semiconductor photoelectrochemical etching apparatus is depicted according to an illustrative embodiment. The semiconductor photoelectrochemical etching apparatus 202 is... Figure 1 The physical realization of the semiconductor photoelectrochemical etching device 102. The photoelectrochemical flow unit 212 is... Figure 1 Physical realization of the photoelectrochemical flow unit 104.

[0050] In view 200, the semiconductor photoelectrochemical etching apparatus 202 is shown in exploded form. In this illustrative example, the semiconductor photoelectrochemical etching apparatus 202 includes a UV light source in the form of an LED light source 204. The LED light source 204 is a UV LED. In this illustrative example, there is no additional focusing lens between the LED light source 204 and the etching chamber 103 of the semiconductor photoelectrochemical etching apparatus 102.

[0051] In this illustrative example, multiple washers, inserts, and rings are present to form the etching chamber 103 of the semiconductor photoelectrochemical etching apparatus 102. A window retaining ring 206 and a UV window washer 210 are located on either side of the quartz window 208.

[0052] The photoelectrochemical flow unit 212 includes an active region for receiving the semiconductor substrate 220 and a circulating electrolyte solution. The photoelectrochemical flow unit 212 includes multiple features, including an electrolyte inlet, an electrolyte outlet, an electrode port, and a unit inlet with an electrolyte attachment. Modifications to aspects of the photoelectrochemical flow unit 212 can modify the etching process of the semiconductor substrate 220. Aspects of the photoelectrochemical flow unit 212 include modifying the optical path length and flow pattern thickness of the circulating electrolyte solution.

[0053] Window insertion gasket 214 and variable window insert 216 are located between photoelectrochemical flow unit 212 and mounting plate 226. Wafer / ohm gasket 218 and backing gasket 222 are located on opposite sides of semiconductor substrate 220. In this illustrative example, semiconductor substrate 220 is in the form of a 100mm wafer. Providing ideal optical uniformity and characteristics for photoelectrochemical flow unit 212 compared to conventional processes allows for etching of larger semiconductor substrates.

[0054] The semiconductor photoelectrochemical etching apparatus 202 also includes a locking insert 224 for completing the etching chamber. A mounting plate 226 provides mounting for the semiconductor photoelectrochemical etching apparatus 202.

[0055] Now go to Figure 3 The illustration depicts a front view of a photoelectrochemical flow unit according to an illustrative embodiment. The photoelectrochemical flow unit 300 may be... Figure 1 Physical realization of the photoelectrochemical flow unit 104.

[0056] The photoelectrochemical flow unit 300 is an illustrative example of a photoelectrochemical flow unit having turbulent flow of a circulating electrolyte solution (not shown) generated by introducing a circulating electrolyte solution into a cavity 306. An electrolyte inlet 302 receives the circulating electrolyte solution from a circulating electrolyte pump (not shown). The electrolyte inlet 302 is a path for circulating the electrolyte solution to a nozzle 304. The nozzle 304 guides the circulating electrolyte solution in such a way that turbulence is achieved on the surface of a semiconductor substrate (not shown) within the cavity 306. The nozzle 304 is designed to generate turbulence. The nozzles 304 can have any desired size, shape, and number, configured to generate turbulence on the surface of the semiconductor substrate within the cavity 306.

[0057] To exit chamber 306, the circulating electrolyte solution passes through unit outlet 308. The circulating electrolyte solution exits through electrolyte outlet 310. Bubble removal port 312 allows gas to exit from photoelectrochemical flow unit 300. Electrode port 314 in photoelectrochemical flow unit 300 allows electrodes to be placed in the circulating electrolyte solution within chamber 306.

[0058] Now go to Figure 4The illustration depicts a front view of a photoelectrochemical flow unit according to an illustrative embodiment. The photoelectrochemical flow unit 400 may be... Figure 1 The physical implementation of the photoelectrochemical flow unit 104. The photoelectrochemical flow unit 400 can be... Figure 1 Physical realization of the photoelectrochemical flow unit 104.

[0059] Electrolyte inlet 402 receives circulating electrolyte solution from a circulating electrolyte pump (not shown). Electrolyte inlet 402 is the path for circulating the electrolyte solution to nozzle 404. Nozzle 404 guides the circulating electrolyte solution into cavity 406.

[0060] The photoelectrochemical flow unit 400 is an illustrative example of a photoelectrochemical flow unit having turbulent flow of a circulating electrolyte solution (not shown) generated by ultrasonic treatment. In this illustrative example, an ultrasonic instrument 405 is directed to the outside of the photoelectrochemical flow unit 400.

[0061] To exit chamber 406, the circulating electrolyte solution passes through unit outlet 408. The circulating electrolyte solution exits through electrolyte outlet 410. Bubble removal port 412 allows gas to exit from photoelectrochemical flow unit 400. Electrode port 414 in photoelectrochemical flow unit 400 allows electrodes to be placed in the circulating electrolyte solution within chamber 406.

[0062] Now go to Figure 5 The illustration depicts a front view of a photoelectrochemical flow unit according to an illustrative embodiment. The photoelectrochemical flow unit 500 may be... Figure 1 The physical implementation of the photoelectrochemical flow unit 104. The photoelectrochemical flow unit 500 can be... Figure 1 Physical realization of the photoelectrochemical flow unit 104.

[0063] Electrolyte inlet 502 receives circulating electrolyte solution from a circulating electrolyte pump (not shown). Electrolyte inlet 502 is the path for circulating the electrolyte solution to nozzle 504. Nozzle 504 guides the circulating electrolyte solution into cavity 506.

[0064] The photoelectrochemical flow unit 500 is an illustrative example of a photoelectrochemical flow unit having turbulent flow of a circulating electrolyte solution (not shown) generated by ultrasonic treatment. In this illustrative example, an ultrasonic transducer 505 is positioned to contact the circulating electrolyte solution within the photoelectrochemical flow unit 500. In this illustrative example, the ultrasonic transducer 505 is a probe extending into the photoelectrochemical flow unit 500.

[0065] To exit chamber 506, the circulating electrolyte solution passes through unit outlet 508. The circulating electrolyte solution exits through electrolyte outlet 510. Bubble removal port 512 allows gas to exit from photoelectrochemical flow unit 500. Electrode port 514 in photoelectrochemical flow unit 500 allows electrodes to be placed in the circulating electrolyte solution within chamber 506.

[0066] Now go to Figure 6 A flowchart illustrating a method for photoelectrochemical etching of a semiconductor substrate is depicted according to an illustrative embodiment. Figure 1 The semiconductor photoelectrochemical etching apparatus 102 performs method 600 to etch the semiconductor substrate 156. This can be done... Figure 2 In the semiconductor photoelectrochemical etching apparatus 202, method 600 is performed to etch the semiconductor substrate 220. Method 600 can be performed to etch... Figure 3 The semiconductor substrate in the photoelectrochemical flow unit 300. Method 600 can be performed to etch. Figure 4 The semiconductor substrate in the photoelectrochemical flow unit 400. Method 600 can be performed to etch. Figure 5 The semiconductor substrate in the photoelectrochemical flow unit 500.

[0067] Method 600 places a semiconductor substrate in an etching chamber of a semiconductor photoelectrochemical etching apparatus having an optical path length configured to collect high-power light from a UV light source (operation 602). Method 600 immerses the semiconductor substrate in a circulating electrolyte solution within the etching chamber (operation 604).

[0068] Method 600 generates turbulence of a circulating electrolyte solution on the surface of a semiconductor substrate (operation 606). Method 600 irradiates the semiconductor substrate with UV light of a selected wavelength from a UV light source to irradiate the surface of the semiconductor substrate to etch the semiconductor substrate with a total thickness variation within tolerance (operation 608). Afterward, method 600 terminates.

[0069] In some illustrative examples, the step of generating turbulence in the circulating electrolyte solution includes guiding the circulating electrolyte solution into the etching chamber using an electrolyte nozzle connected to the electrolyte inlet (operation 610). In some illustrative examples, the step of generating turbulence in the circulating electrolyte solution includes applying an ultrasonic instrument to the circulating electrolyte solution (operation 612). In some illustrative examples, the step of generating turbulence in the circulating electrolyte solution includes applying an ultrasonic instrument to the photoelectrochemical flow unit forming the etching chamber (operation 614). In some illustrative examples, the step of generating turbulence in the circulating electrolyte solution includes stirring the circulating electrolyte solution in the etching chamber (operation 616).

[0070] Now go to Figure 7A flowchart illustrating a method for photoelectrochemical etching of a semiconductor substrate is depicted according to an illustrative embodiment. Figure 2 In the semiconductor photoelectrochemical etching apparatus 202, method 700 is performed to etch the semiconductor substrate 220. Method 700 can be performed to etch... Figure 3 The semiconductor substrate in the photoelectrochemical flow unit 300. Method 700 can be performed to etch. Figure 4 The semiconductor substrate in the photoelectrochemical flow unit 400. Method 700 can be performed to etch. Figure 5 The semiconductor substrate in the photoelectrochemical flow unit 500.

[0071] Method 700 involves placing a semiconductor substrate in an etching chamber of a semiconductor photoelectrochemical etching apparatus having an optical path length configured to collect high-power light from an LED light source (operation 702). Method 700 involves immersing the semiconductor substrate in a circulating electrolyte solution within the etching chamber (operation 704). Method 700 involves generating turbulence of the circulating electrolyte solution on the surface of the semiconductor substrate (operation 706). Method 700 involves applying a bias voltage between the semiconductor substrate and the counter electrode in the circulating electrolyte solution (operation 708). Method 700 involves irradiating the semiconductor substrate with UV light of a selected wavelength below 300 nm from the LED light source to irradiate the surface of the semiconductor substrate with a surface light uniformity greater than 80%, thereby etching the semiconductor substrate with a total thickness variation within tolerance (operation 710). Method 700 then terminates.

[0072] In some illustrative examples, the step of generating turbulence in the circulating electrolyte solution includes guiding the circulating electrolyte solution into the etching chamber using an electrolyte nozzle connected to the electrolyte inlet (operation 712). In these illustrative examples, the electrolyte nozzle is configured to generate turbulence on the surface of the semiconductor substrate. At least one of the size, shape, number, or location of the electrolyte nozzle is configured to generate turbulence.

[0073] As used in this article, when used with a list of items, the phrase "at least one" means that different combinations of one or more of the listed items may be used, and it may be necessary to have only one of each item in the list. For example, "at least one of item A, item B, or item C" may include, but is not limited to, item A, item A and item B, or item B. This example could also include item A, item B, and item C, or item B and item C. Of course, any combination of these items is possible. In other examples, "at least one" could be, for example, but not limited to, two items A; one item B; and ten items C; four items B and seven items C; or other suitable combinations. Items can be specific objects, things, or categories. In other words, "at least one" means any combination of items and the number of items that can be used in the list, but not all items in the list are required.

[0074] As used in this article, when referring to items, "multiple" means one or more items.

[0075] The flowcharts and block diagrams depicting different embodiments illustrate the architecture, functionality, and operation of some possible implementations of the apparatus and methods in the illustrative embodiments. In this regard, each block in a flowchart or block diagram may represent at least one of a module, segment, function, or part of an operation or step.

[0076] In some alternative implementations of the illustrative embodiments, one or more functions shown in the boxes may appear in the order shown in the figures. For example, in some cases, two blocks shown consecutively may be executed substantially simultaneously, or these blocks may sometimes be executed in reverse order, depending on the functions involved. Furthermore, in addition to the blocks shown in the flowchart or block diagram, other blocks may be added. Some blocks may be optional. For example, operations 610 through 616 may be optional. As another example, operation 712 may be optional.

[0077] The illustrative example provides an apparatus for smoothing and selectively wet etching a silicon surface of SiC that produces a smooth surface and has high dopant selectivity. In the illustrative example, dopant selectivity allows for a reduction in the total thickness variation (TTV) of the SiC film on a quantum photonics insulator.

[0078] The exemplary method utilizes a photoelectrochemical (PEC) process, in which the surface to be etched is irradiated with UV light during electrochemical oxidation. Some illustrative examples provide the use of a UV light source with narrow photoelectrochemical flow units and a quartz window. In the illustrative examples, the area power and uniformity of the UV-C LED can be used. Other UV-C light sources may also be used in some illustrative examples.

[0079] In some illustrative examples, the LED does not integrate a main lens to achieve maximum light uniformity. In some illustrative examples, when using an LED without a lens, the cell is narrow enough to allow a beam of greater than 50 mW / cm² from the radiating LED. 2 UVC light is incident on the SiC surface. In some illustrative examples, when using an LED without a lens, the flow field across the entire SiC surface is turbulent to reduce or prevent localized low-flow areas.

[0080] The descriptions of different illustrative embodiments are presented for purposes of illustration and description and are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different illustrative embodiments may provide different features compared to other illustrative embodiments. The selection and description of one or more embodiments are for the purpose of best explaining the principles of the embodiments, their practical application, and enabling those skilled in the art to understand the disclosure of various embodiments with various modifications suitable for the intended particular use.

[0081] This disclosure also includes the following provisions: Clause 1. A semiconductor photoelectrochemical etching apparatus, the semiconductor photoelectrochemical etching apparatus comprising: Photoelectrochemical flow unit; A circulating electrolyte solution, which is propelled through the photoelectrochemical flow unit by a circulating electrolyte pump; A UV light source is directed towards the photoelectrochemical flow unit, wherein the optical path length between the UV light source and the photoelectrochemical flow unit is configured to collect high-power light from the UV light source; and A turbulence generator configured to generate turbulence in the circulating electrolyte solution.

[0082] Clause 2. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the circulating electrolyte solution comprises at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, hydrogen fluoride, or a buffer solution.

[0083] Clause 3. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the UV light source is a lamp that emits narrowband light or a combination of narrowband light with a wavelength of less than 300 nm.

[0084] Clause 4. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the optical path length through the photoelectrochemical flow unit is sufficient to collect greater than 50 mW / cm² from the UV light source. 2 The light.

[0085] Clause 5. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the UV light source comprises a divergent LED light source, and wherein the photoelectrochemical flow unit comprises an optical path length configured to collect high-power light from the divergent LED light source.

[0086] Clause 6. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the semiconductor photoelectrochemical etching apparatus further comprises: A frosted glass diffuser configured to provide greater than 80% light uniformity on the surface of a semiconductor substrate.

[0087] Clause 7. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the UV light source is an LED light source.

[0088] Clause 8. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the UV light source comprises at least one LED light source without a lens.

[0089] Clause 9. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the UV light source comprises a mercury arc lamp or a mercury-xenon arc lamp.

[0090] Clause 10. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the UV light source is an excimer laser or an excimer lamp.

[0091] Clause 11. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the turbulence generator includes a nozzle in the photoelectrochemical flow unit, the nozzle receiving a circulating electrolyte solution from the circulating electrolyte pump to generate a flow pattern in the semiconductor photoelectrochemical etching apparatus that causes turbulence on the surface of the semiconductor substrate.

[0092] Clause 12. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the semiconductor photoelectrochemical etching apparatus further comprises: A piezoelectric element is positioned to vibrate in order to induce turbulence at the surface of a semiconductor substrate.

[0093] Clause 13. The semiconductor photoelectrochemical etching apparatus according to Clause 1, wherein the semiconductor photoelectrochemical etching apparatus further comprises: At least one of multiple process monitoring ports or multiple process monitoring windows.

[0094] Clause 14. A method for photoelectrochemical etching of a semiconductor substrate, the method comprising the following steps: The semiconductor substrate is placed in an etching chamber of a semiconductor photoelectrochemical etching apparatus having an optical path length set to collect high-power light from a UV light source; The semiconductor substrate is immersed in a circulating electrolyte solution within the etching chamber; Turbulence of the circulating electrolyte solution is generated on the surface of the semiconductor substrate; and The semiconductor substrate is irradiated with UV light of a selected wavelength from the UV light source to irradiate the surface of the semiconductor substrate to etch the semiconductor substrate with a total thickness variation within the tolerance range.

[0095] Clause 15. The method according to Clause 14, wherein the step of generating turbulence in the circulating electrolyte solution includes guiding the circulating electrolyte solution into the etching chamber using an electrolyte nozzle connected to an electrolyte inlet.

[0096] Clause 16. The method according to Clause 14, wherein the step of generating turbulence in the circulating electrolyte solution includes applying an ultrasonic instrument to the circulating electrolyte solution.

[0097] Clause 17. The method according to Clause 14, wherein the step of generating turbulence in the circulating electrolyte solution includes applying an ultrasonic instrument to the photoelectrochemical flow unit forming the etching chamber.

[0098] Clause 18. The method according to Clause 14, wherein the step of generating turbulence in the circulating electrolyte solution includes stirring the circulating electrolyte solution in the etching chamber.

[0099] Clause 19. A method for photoelectrochemical etching of a semiconductor substrate, the method comprising the following steps: The semiconductor substrate is placed in an etching chamber of a semiconductor photoelectrochemical etching apparatus having an optical path length set to collect high-power light from an LED light source; The semiconductor substrate is immersed in a circulating electrolyte solution within the etching chamber; Turbulence of the circulating electrolyte solution is generated on the surface of the semiconductor substrate; A bias voltage is applied between the semiconductor substrate and the counter electrode in the circulating electrolyte solution; and The semiconductor substrate is irradiated with UV light of a selected wavelength below 300 nm from an LED light source to irradiate the surface of the semiconductor substrate such that the light uniformity of the surface of the semiconductor substrate is greater than 80%, thereby etching the semiconductor substrate with a total thickness variation within tolerance.

[0100] Clause 20. The method according to Clause 19, wherein the step of generating turbulence in the circulating electrolyte solution includes guiding the circulating electrolyte solution into the etching chamber using an electrolyte nozzle connected to an electrolyte inlet.

Claims

1. A semiconductor photoelectrochemical etching apparatus, the semiconductor photoelectrochemical etching apparatus comprising: Photoelectrochemical flow unit; A circulating electrolyte solution, which is propelled through the photoelectrochemical flow unit by a circulating electrolyte pump; A UV light source is directed towards the photoelectrochemical flow unit, wherein the optical path length between the UV light source and the photoelectrochemical flow unit is set to collect high-power light from the UV light source; as well as A turbulence generator configured to generate turbulence in the circulating electrolyte solution.

2. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein, The circulating electrolyte solution includes at least one of potassium hydroxide, sodium hydroxide, lithium hydroxide, hydrogen fluoride, or a buffer solution.

3. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein, The UV light source is a lamp that emits narrowband light or a combination of narrowband light with a wavelength of less than 300nm.

4. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein, The optical path length of the photoelectrochemical flow unit is sufficient to collect more than 50 mW / cm² from the UV light source. 2 The light.

5. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein, The UV light source includes a divergent LED light source, and wherein the photoelectrochemical flow unit includes an optical path length configured to collect high-power light from the divergent LED light source.

6. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein the semiconductor photoelectrochemical etching apparatus further comprises: A frosted glass diffuser configured to provide greater than 80% light uniformity on the surface of a semiconductor substrate.

7. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein, The UV light source is an LED light source.

8. The semiconductor photoelectrochemical etching apparatus according to claim 1, wherein, The UV light source includes at least one LED light source without a lens.

9. A method for photoelectrochemical etching of a semiconductor substrate, the method comprising the following steps: The semiconductor substrate is placed in an etching chamber of a semiconductor photoelectrochemical etching apparatus having an optical path length set to collect high-power light from a UV light source; The semiconductor substrate is immersed in a circulating electrolyte solution within the etching chamber; Turbulence of the circulating electrolyte solution is generated on the surface of the semiconductor substrate; as well as The semiconductor substrate is irradiated with UV light of a selected wavelength from the UV light source to irradiate the surface of the semiconductor substrate to etch the semiconductor substrate with a total thickness variation within the tolerance range.

10. A method for photoelectrochemical etching of a semiconductor substrate, the method comprising the following steps: The semiconductor substrate is placed in an etching chamber of a semiconductor photoelectrochemical etching apparatus having an optical path length set to collect high-power light from an LED light source; The semiconductor substrate is immersed in a circulating electrolyte solution within the etching chamber; Turbulence of the circulating electrolyte solution is generated on the surface of the semiconductor substrate; A bias voltage is applied between the semiconductor substrate and the counter electrode in the circulating electrolyte solution; as well as The semiconductor substrate is irradiated with UV light of a selected wavelength below 300 nm from the LED light source to irradiate the surface of the semiconductor substrate such that the light uniformity of the surface of the semiconductor substrate is greater than 80%, so as to etch the semiconductor substrate with a total thickness variation within the tolerance range.

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