Optical cable for interferometric end-point detection

Abstract

Disclosed herein is an endpoint detection having an optical beam configured to emit light via a top plate of a processing chamber. The optical beam has a plurality of optical fibers configured to emit light from a light source toward a substrate and configured to receive light reflected from the substrate. The plurality of optical fibers includes a first emission optical fiber and a first receiving optical fiber. The first receiving optical fiber is disposed at a pairing angle from the first emission optical fiber in a radial direction and is configured to receive light emitted from the first emission optical fiber. The plurality of optical fibers further includes a second emission optical fiber and a second receiving optical fiber. The second receiving optical fiber is disposed at a pairing angle from the second emission optical fiber in the radial direction. The second receiving optical fiber is configured to receive light originating from the second emission optical fiber. The pairing angle is between about 175 degrees and 185 degrees.

Description

[0001] background

[0002] field

[0003] The examples disclosed herein generally relate to an optical beam and a method for using said optical beam in endpoint detection for etching a semiconductor substrate. Background Technology

[0004] Since the introduction of semiconductor devices decades ago, the geometry of such devices has shrunk dramatically. The ever-increasing circuit density places additional demands on the processes used to manufacture semiconductor devices. For example, as circuit density increases, pitch size rapidly decreases to below 50 nm, while vertical dimensions such as trench depth remain relatively constant, resulting in an increase in the aspect ratio of features (i.e., their height divided by their width). Precise control over the dimensions of such high-density and submicron features is crucial for the reliable fabrication of semiconductor devices.

[0005] Features such as transistors and capacitors are typically formed in semiconductor devices by patterning the surface of a substrate to define the lateral dimensions of the feature, then etching the substrate to remove material and define the feature. To form features with desired electrical properties, the dimensions of the feature must be formed within controlled specifications. Therefore, dry etching or plasma etching processes may be required to partially remove one or more layers.

[0006] An interferometer measures the difference between two or more optical paths by generating interference fringes through the overlap of residual light from two optical paths. It can detect minute variations within the wavelength range of the light source. The reflected light is a combination of signals from each layer disposed on the substrate, forming unique interference fringes for each layer. For endpoint detection, the interference fringe patterns of different layers can be simulated and then compared with the measured signals during etching. This method is highly effective and can be used for monitoring the etching and endpoint detection of substrates with multiple layers on top.

[0007] Fiber optic cables can be used to transmit light from and receive light at an interferometer. Conventional fiber optic cables can measure parameters such as film quality, film thickness, or structural width on a substrate. To transmit and receive optical signals within the same cable, a beam splitter can be used to separate the signals. Separating the optical signals reduces the overall power, which necessitates amplification or filtering. Manipulating the signal in this way can introduce errors and lead to the inability to detect or accurately measure features on the substrate. Therefore, conventional fiber optic cables can exhibit low luminous throughput and low spectral fidelity in processing chamber environments. Additional measures are needed to mitigate these problems, necessitating increased chamber downtime and additional calibration processes.

[0008] Therefore, an improved fiber optic cable is needed for endpoint detection systems. Summary of the Invention

[0009] The example disclosed herein provides an endpoint detection having an optical beam configured to emit light through a top plate of a processing chamber. The optical beam has multiple optical fibers configured to emit light from a light source toward a substrate and to receive light reflected from the substrate disposed within the processing chamber. The multiple optical fibers include a first transmitting fiber and a first receiving fiber. The first receiving fiber is radially arranged at a pairing angle with the first transmitting fiber. The first receiving fiber is configured to receive light emitted from the first transmitting fiber. The multiple optical fibers further include a second transmitting fiber and a second receiving fiber. The second receiving fiber is radially arranged at a pairing angle with the second transmitting fiber. The second receiving fiber is configured to receive light originating from the second transmitting fiber. The pairing angle is between approximately 175 degrees and approximately 185 degrees.

[0010] The examples provided herein further provide an endpoint detection system including a processing chamber having a top plate, sidewalls, and a bottom defining an internal volume. A substrate support is located within the internal volume and configured to support a substrate thereon. An optical beam is configured to emit light through the top plate of the processing chamber. The optical beam has multiple optical fibers configured to emit light from a light source and receive light from the substrate. The multiple optical fibers include a first emitting row having multiple first emitting fibers configured to emit light from the light source toward the substrate. The multiple first emitting fibers include first emitting fibers and second emitting fibers. A first receiving row includes multiple first receiving fibers configured to receive reflected light originating from the emitted light. The multiple first receiving fibers include first receiving fibers and second receiving fibers. The first receiving fibers are configured to receive light emitted from the first emitting fibers. The second emitting fibers are configured to receive light emitted from the second receiving fibers. The first emitting fibers are radially arranged at a pairing angle with the first emitting fibers. The pairing angle is between approximately 175 degrees and approximately 185 degrees. The first transmit line is separated from the first receive line by an imaginary line that divides the optical beam into substantially equal cross-sectional areas.

[0011] In another example, the semiconductor processing system has an optical beam configured to emit light through a top plate of a processing chamber. The optical beam has multiple optical fibers configured to direct light from a light source toward a substrate disposed within the processing chamber. The multiple optical fibers include a first transmitting fiber, a first receiving fiber, a second transmitting fiber, and a second receiving fiber. Instructions are stored in a non-transitory computer-readable medium. When executed by a processor, the instructions cause a controller coupled to the light source to perform a method. The method includes emitting first light from the first transmitting fiber. The method further includes receiving the first light at a first receiving fiber. The first receiving fiber is radially arranged at a mating angle with the first transmitting fiber. Furthermore, the method includes emitting second light from the second transmitting fiber. The method includes receiving the second light at a second receiving fiber. The second receiving fiber is radially arranged at a mating angle with the second transmitting fiber. The second receiving fiber is configured to receive light originating from the second transmitting fiber. The mating angle is between approximately 175 degrees and approximately 185 degrees. Attached Figure Description

[0012] To gain a more detailed understanding of the features described above, reference can be made to the embodiments for a more specific description of the present disclosure, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only typical embodiments of the present disclosure and should not be considered as limiting its scope, as the present disclosure may allow for other equally effective embodiments.

[0013] Figure 1 It is a schematic cross-sectional view of a processing chamber with an optical beam.

[0014] Figure 2 It is configured to be in Figure 1 A plan view of the optical beams that emit and receive light in the processing chamber shown.

[0015] Figure 2A It is a cross-sectional view of the opening of the optical beam taken along line AA.

[0016] Figure 3 yes Figure 2 A plan view of the alternative construction of the optical beam shown.

[0017] Figure 4 This is a graph illustrating the distribution of light received by the optical beam compared to a conventional fiber optic cable.

[0018] Figure 5 It is to utilize Figures 1 to 3 The flowchart shows a method for collecting reflected light in a processing chamber using an optical beam. Detailed Implementation

[0019] Examples of this disclosure relate to an optical beam and a method of utilizing said optical beam in an endpoint detection system configured for etching a semiconductor substrate. Advantageously, the optical beam disclosed herein achieves an improved beam distribution when emitted light is incident on the substrate. Therefore, the beam spot created on the substrate by the emitted light is generated in substantially the same region at the wavelength of the incident light (e.g., about 200-800 nm). Thus, the optical beam collects reflected light more efficiently, reduces signal loss of the reflected light signal, and ensures that the reflected light signal has a larger overall amplitude than conventional fiber optic cables. It should be understood herein that the term "about" has its common meaning as understood by one of ordinary skill in the art. Therefore, with respect to the numerical ranges described herein, the term "about" can be reasonably interpreted as + / - 10% of the value, amplitude, or degree modified by the term. Where such a construction cannot be reasonably interpreted by one of ordinary skill in the art in this way, the term should not be limited to such interpretation.

[0020] Figure 1 This is a schematic cross-sectional view of a plasma processing chamber 100 having an optical beam 104, according to an example of this disclosure. Suitable processing chambers include inductively coupled and capacitively coupled plasma etching chambers, such as... Photomask etching system and Etching systems, etc., both of which are available from Applied Materials, Inc., Santa Clara, California. Other types of processing chambers may be adapted to benefit from this invention, including, for example, capacitively coupled parallel plate chambers and magnetically enhanced ion etching chambers, as well as inductively coupled plasma etching chambers.

[0021] The processing chamber 100 includes a chamber body 102 and a top plate 103, the top plate 103 being energy-transparent, i.e., allowing energy and light to pass through it. The chamber body 102 also has a chamber bottom 107. The chamber body 102 is made of a metal such as anodized aluminum or stainless steel. The top plate 103 is mounted on the chamber body 102. The top plate 103 can be flat, rectangular, arcuate, conical, dome-shaped, or multi-radius. The top plate 103 is made of an energy-transparent material such as ceramic or other dielectric materials. An induction coil 126 is disposed above the top plate 103 of the processing chamber 100 and is used to excite the gas within the chamber 100 during processing.

[0022] A substrate support 116 is disposed in a processing chamber 100, which has a substrate support surface 188 to support a substrate 120 during processing. The substrate support 116 may include an electrostatic chuck, wherein at least a portion of the substrate support 116 is conductive and can be used as a process bias cathode.

[0023] Processing gases are introduced from a processing gas source 148 into the processing chamber 100 via a gas distributor 122. The gas distributor 122 may be disposed in the top plate 103 or the chamber body 102, above the base plate support 116. A mass flow controller (not shown) is provided between the gas distributor 122 and the processing gas source 148 for each processing gas or, alternatively, for mixtures of processing gases, to regulate the corresponding flow rate of the processing gas entering the chamber body 102.

[0024] Internal volume 114 is defined within a chamber body 102 between substrate support 116 and top plate 103. Plasma is formed in internal volume 114 by process gas using coil power supply 127, which powers induction coil 126 to generate an electromagnetic field in internal volume 114 via RF matching network 135. Substrate support 116 may include electrodes disposed therein, which are powered by electrode power supply 125 and generate a capacitive electric field in processing chamber 100 via RF matching network 128. RF power is applied to the electrodes in substrate support 116 while chamber body 102 is electrically grounded. The capacitive electric field is transverse to the plane of substrate support 116 and influences the directionality of charged material more perpendicular to substrate 120 to provide more vertically oriented anisotropic etching of substrate 120.

[0025] Processing gases and etching byproducts are discharged from the processing chamber 100 via an exhaust system 130. The exhaust system 130 may be located in the chamber bottom 107 of the processing chamber 100 or in another part of the chamber body 102 of the processing chamber 100 for removing processing gases. A throttle valve 132 is located in the exhaust port 134 for controlling the pressure in the processing chamber 100.

[0026] Figure 1 Further illustration shows an optical beam 104 configured to detect the endpoint of an etching process or feature disposed within or on a substrate 120 within the processing chamber 100. In one example, the optical beam 104 is included in an endpoint detection system 164. The endpoint detection system 164 may be an interferometer endpoint (IEP) detection system. The endpoint detection system 164 is positioned to abut against the substrate 120 via a portion of a top plate 103. In one example, the endpoint detection system 164 is positioned to abut against a peripheral portion of the substrate 120 via a portion of the top plate 103 that is off-center from the top plate 103.

[0027] In one example, the endpoint of one or more stages of the etching process can be determined by the endpoint detection system 164. For example, the endpoint of an etching stage may occur when a layer of substrate 120 has been sufficiently removed or etched through to expose the underlying layer. In another example, the endpoint of an etching state may occur when desired dimensions (such as the desired height of a feature) have been achieved. Determining the endpoint of an etching stage allows etching of substrate 120 to be stopped once the stage is complete, thereby reducing the occurrence of over-etching or under-etching of substrate 120. The endpoint of one or more stages can be determined by monitoring radiation emission from plasma in the processing chamber 100, the intensity and wavelength of which vary depending on the composition of the excited gas. For example, a change in the composition of the excited gas may be caused by etching through the overlayer to expose the underlying layer on substrate 120. Therefore, the endpoint detection system 164 monitors radiation emission to determine the degree of etching of the substrate or other conditions in the processing chamber 100.

[0028] The endpoint detection system 164 further includes a light source 166, a collimation assembly 168, a photosensor 170, and a controller 150. The light source 166 is configured to emit a light beam via an optical beam 104. The light beam strikes a substrate 120 and is reflected back via the optical beam 104. The light beam returns to the photosensor 170 after passing through the optical beam 104. For example, the collimation assembly 168 is configured to focus the light beam into an incident beam 176. The incident beam 176 passes through a top plate 103 in a direction perpendicular to the substrate support surface 188 and illuminates an area or beam spot 180 on the surface 121 of the substrate 120. The incident beam 176 is reflected by the surface 121 of the substrate 120 to form a reflected beam 178. At least a portion of the reflected beam 178 is guided through the top plate 103 in a direction perpendicular to the substrate support surface 188 back to the photosensor 170. The photosensor 170 is configured to measure the intensity of the reflected beam 178. An exemplary photosensor 170 is a spectrometer. The controller 150 calculates portions of the real-time measured waveform spectrum of the reflected beam 178 reflected from the beam spot 180 on the substrate 120, and processes the spectrum using advanced spectral analysis techniques, including comparing the spectrum with stored characteristic waveform patterns.

[0029] Alternatively, the optical beam 104 can be used without the collimation assembly 168, such that the optical beam 104 is directly coupled to the top plate 103, having a single collimator disposed between the optical beam 104 and the top plate 103. For example, the focusing lens 174b (i.e., as a collimator) can be disposed directly between the optical beam 104 and the top plate 103.

[0030] Light source 166 has a monochromatic or multicolor light source that generates an incident beam 176 for illuminating a beam spot 180 on substrate 120. The intensity of the incident beam 176 is selected to be sufficiently high so that the reflected beam 178 can have a measurable intensity. In one example, light source 166 (such as a Xe lamp) provides multicolor light and produces an emission spectrum of light with wavelengths from about 200 nm to about 800 nm. Multicolor light source 166 can be filtered to selectively include frequencies of the incident beam 176. Before measuring the intensity of the reflected beam 178 entering photodetector 170, a color filter can be placed in front of photodetector 170 to filter out all wavelengths other than the desired wavelength(s). Light source 166 may also include a monochromatic light source, such as a He-Ne or ND-YAG laser that provides light of a selected wavelength.

[0031] One or more focusing lenses 174a, 174b may be used to collimate the incident beam 176 from the light source 166 to form a beam spot 180 on the surface 121 of the substrate 120 and focus the reflected beam 178 back onto the effective surface of the photodetector 170. The size or area of ​​the beam spot 180 should be large enough to compensate for variations in the surface topography of the substrate 120 and device design features. The size of the beam spot 180 enables the detection of etch endpoints at a target depth for design features with small openings, such as vias or narrow trenches (e.g., Figure 2 (248) The design features can be densely packed or more isolated. The area of ​​the reflected beam is large enough to activate most of the effective light detection surface of the photodetector 170.

[0032] Incident beam 176 and reflected beam 178 are guided through transparent window 182 of processing chamber 100. Transparent window 182 allows beams 176 and 178 to pass into and out of the processing environment of processing chamber 100. The substrate support surface 188 of substrate support 116 for placing substrate 120 is configured to be parallel to top plate 103 and perpendicular (90°) to beams 176 and 178.

[0033] In one example, a transparent window 182 is located in the top plate 103 of the processing chamber 100, oriented relative to the substrate 120 and the substrate support 116. The transparent window 182 is configured to receive an incident light beam from the endpoint detection system 164. The transparent window 182 allows the incident light beam 176 to be transmitted to the substrate 120 at an angle perpendicular to the substrate 120 and the substrate support 116. The transparent window 182 further allows a reflected light beam 178 to pass through the transparent window 182 after being reflected from the substrate 120. The transparent window 182 is further configured to transmit the reflected light beam 178 to the endpoint detection system 164 at an angle perpendicular to the endpoint detection system 164.

[0034] In one example, the diameter of the beam spot 180 is from about 2 mm to about 10 mm. However, if the beam spot 180 covers a large isolation area of ​​a substrate with only a few etched features, a smaller beam spot 180 may be needed to focus on the features of interest. Therefore, the size of the beam spot can be optimized depending on the design features of the specific substrate 120.

[0035] Optionally, beam positioner 184 can be used to move the incident beam 176 across the entire substrate 120 to locate a suitable portion of the substrate surface where the beam spot 180 is to be placed for monitoring the etching process. Beam positioner 184 may include one or more primary mirrors 186 that rotate at small angles to deflect the beam from light source 166 to different locations on the substrate surface. Additional secondary mirrors (not shown) can be used to intercept reflected beams 178 from the substrate 120 surface and focus them onto photodetector 170. Beam positioner 184 can also be used to scan the beam in a grating pattern across the entire surface of substrate 120. In this version, beam positioner 184 includes a scanning assembly (not shown) with a movable stage on which light source 166, collimation assembly 168, and photodetector 170 are mounted. The movable stage can be moved at set intervals via a drive mechanism (such as a stepper motor) to move the beam spot 180 across the entire surface of substrate 120.

[0036] The photodetector 170 includes photosensitive electronic components (such as a charge-coupled device (CCD), photodiode, or phototransistor) that provide a signal in response to a measured intensity of a reflected light beam 178. The reflected light beam 178 is thus reflected from a surface 121 of the substrate 120. The signal may be in the form of a change in the current level passing through the electronic components or a change in the voltage applied across the entire electronic components. The reflected light beam 178 undergoes constructive and / or destructive interference, which increases or decreases the intensity of the beam. Therefore, the photodetector 170 provides an electrical output signal related to the measured intensity of the reflected light beam 178. The electrical output signal is plotted as a function of time to provide a waveform spectrum having a plurality of waveform patterns corresponding to the varying intensity of the reflected light beam 178.

[0037] A computer program coupled to controller 150 compares the shape of the measured waveform pattern of the reflected beam 178 with a stored characteristic waveform pattern, and determines the endpoint of the etching process when the measured waveform pattern matches the characteristic waveform pattern. Therefore, the period of the interference signal as a function of time can be used to calculate the depth and etching rate. The program can also manipulate the interference trend to detect characteristic patterns, such as inflection points. These manipulations can be simple mathematical operations, such as evaluating the shift derivative to detect inflection points.

[0038] Although the endpoint detection system 164 is positioned to dock with the substrate 120 via a substantially horizontal portion of the top plate 103, the endpoint detection system 164 can be horizontally positioned above the processing chamber 100. Therefore, the endpoint detection system 164 further includes a folding reflector above the chamber 100 to bend the incident beam 176 and the reflected beam 178 from a vertical position to a horizontal position. A transparent window 182 can be placed on one side of the chamber 100 or on the bottom of the chamber 100.

[0039] The controller 150 is coupled to the endpoint detection system 164. The controller 150 includes a processor 152, a memory 154, and support circuitry 156 coupled to each other. The controller 150 is electrically coupled to the endpoint detection system 164 via a wire 158, the endpoint detection system including a photodetector 170, the controller 150, and a light source 166.

[0040] Processor 152 can be any form of general-purpose microprocessor or general-purpose central processing unit (CPU), each of which can be used in an industrial environment, such as a programmable logic controller (PLC), supervisory control and data acquisition (SCADA) system, or other suitable industrial controller. Memory 154 is non-transitory and can be readily available memory, such as random access memory (RAM), read-only memory (ROM), or any other form of local or remote digital storage. Memory 154 contains instructions that, when executed by processor 152, facilitate the execution of method 500. The instructions in memory 154 are in the form of a program product (such as a program implementing the methods of this disclosure). The program code of the program product can conform to any of a variety of different programming languages. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer, such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips, or any type of solid-state non-volatile semiconductor memory), on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks in a disk drive or hard disk drive, or any type of solid-state random access semiconductor memory), on which changeable information is stored. Such computer-readable storage media are examples of this disclosure when carrying computer-readable instructions that instruct the functions described herein.

[0041] Figure 2 It is configured to be in Figure 1 A plan view of the optical beam 104 that emits and receives light in the processing chamber shown. Figure 2AThis is a cross-sectional view of the opening 204 of the optical beam 104 taken along line AA. An incident beam 176 originating from the light source 166 exits the optical beam 104 and passes through the focusing lens 174b. Upon passing through the focusing lens 174b, the incident beam 176 becomes incident light rays 236 that are substantially parallel to each other. The opening 204 of the optical beam 104 is positioned at or near the focal point of the focusing lens 174b. Therefore, the incident light rays 236 become substantially parallel and collimated before contacting the substrate 120 at an incident angle 201. The incident angle 201 is created by deflecting the opening 204 of the optical beam 104 away from the center 244 of the focusing lens 174b. After impacting the substrate 120, the incident beam 176, as the incident light ray 236, is reflected back to the optical beam 104 as a reflected light ray 240. Together, the reflected light ray 240 constitutes the reflected beam 178. The reflected light ray 240 returns to the focusing lens 174b at a reflection angle 203. After passing through the focusing lens 174b, the reflected light ray 240 returns to the optical beam 104. In one example, the optical beam 104 may be concentric with the focusing lens 174b. In one example, the diameter of the optical beam 104 is between approximately 0.20 mm and 1.50 mm.

[0042] Multiple optical fibers 200 are shown terminating at an opening 204 of an optical bundle 104. For the purpose of illustrating this disclosure, the opening 204 of the multiple optical fibers 200 is shown rotated 90 degrees relative to the substrate 120. The multiple optical fibers 200 are arranged around a center 208 of the opening 204 of the optical bundle 104. In a non-limiting example, the multiple optical fibers 200 are illustrated as having three pairs of fibers; however, it should be understood that additional fiber pairs may be included in the multiple optical fibers 200 without departing from this disclosure. An insulating material 232 is disposed within the optical bundle 104. The insulating material 232 separates each of the multiple optical fibers 200, thereby minimizing or substantially eliminating interference or crosstalk between adjacent fibers. The insulating material 232 also maintains the position of each fiber relative to the remaining multiple optical fibers, such that the fiber pairs remain aligned, as described below.

[0043] The first transmitting fiber 212a and the first receiving fiber 212b are radially separated by a pairing angle 224. Because the insulating material 232 maintains the relative positions between the multiple fibers 200, the second transmitting fiber 216a and the second receiving fiber 216b are radially separated by a pairing angle 224, and the third receiving fiber 220b and the third transmitting fiber 220a are radially separated by a pairing angle 224. The pairing angle 224 is between approximately 175 degrees and approximately 185 degrees. In one example, the pairing angle 224 is 180 degrees. The first transmitting fiber 212a and the second transmitting fiber 216a are separated by a separation angle 228. Furthermore, the second transmitting fiber 216a and the third transmitting fiber 220a are separated by a separation angle 228. In yet another example, the fiber pairs are symmetrical about the center 208 of the optical bundle 104.

[0044] In one example, the separation angle 228 between each fiber in the plurality of optical fibers 200 is equal. In another example, the separation angle 228 between each fiber in the plurality of optical fibers 200 can be different. For example, the separation angle 228 between the first transmitting fiber 212a and the second transmitting fiber 216a can be less than or greater than the separation angle 228 between the second transmitting fiber 216a and the third transmitting fiber 220a. The separation angle 228 can be any angle less than ±180 degrees, provided that each transmitting fiber is paired with its corresponding receiving fiber. In one example, the separation angle 228 is equal to N+1 / 180 degrees, where N is equal to the number of transmitting fibers in the plurality of optical fibers 200. In another example, the separation angle 228 is greater than N+1 / 180 degrees, and in yet another example, the separation angle 228 is less than N+1 / 180 degrees. The separation angle 228 can be approximately 0.25 degrees and less than approximately 180 degrees, such as approximately 5 degrees and less than approximately 180 degrees.

[0045] As described above, the insulating material 232 pairs the light-emitting optical fiber with the corresponding light-receiving optical fiber. Therefore, after reflection from the substrate 120, each incident light ray 236 projected from the first emitting optical fiber 212a returns as a reflected light ray 240 to the first receiving optical fiber 212b. Similarly, each incident light ray 236 originating from the second emitting optical fiber 216a is reflected as a reflected light ray 240 to the second receiving optical fiber 216b. Additionally, each incident light ray 236 projected from the third emitting optical fiber 220a returns as a reflected light ray 240 to the third receiving optical fiber 220b. Each pair of optical fibers 200 can independently emit incident light rays 236 and / or receive reflected light rays 240 from the other optical fiber pairs. In a non-limiting example, the first emitting optical fiber 212a can emit incident light rays 236 independently of the second emitting optical fiber 216a. Therefore, the second receiving optical fiber 216b receives light independently of the first receiving optical fiber 212b. Therefore, each incident light ray emitted by the transmitting fiber is essentially entirely received by the corresponding receiving fiber, such that the intensity of the incident beam 176 is maintained within the intensity of the reflected beam 178. Thus, the optical beam 104 advantageously provides greater fidelity in the total light intensity associated with the aforementioned parameters of the endpoint detection system 164 for detection and measurement.

[0046] The reflected light ray 240, as a reflected beam 178, is emitted to the photodetector 170 via the optical beam 104. As previously described, in one example, the photodetector 170 is a spectrometer. Advantageously, as disclosed herein, the optical beam 104 maximizes the intensity of the reflected beam 178 collected by the photodetector 170 because, when the multiple optical fibers 200 are paired, the reflected beam 178 has substantially the same light intensity as the incident beam 176. Compared to conventional fiber optic cables, the optical beam 104 exhibits less light intensity loss between the emitted and received light than conventional systems that may employ beam splitters or unpaired fibers. Although the multiple optical fibers 200 are shown as a single concentric row, it should be understood that the optical beam 104 is not limited to the number of rows shown, and the number of rows may increase inversely proportional to and / or directly proportional to the diameter of each fiber. The diameter of each fiber is between about 0.01 micrometers and about 400 micrometers.

[0047] Figure 3This is a plan view of an alternative configuration of the optical beam 104. Multiple optical fibers 200 are arranged in pairs of fiber rows 300. A centerline 304 divides the pairs of fiber rows 300 into a transmitting section 301 and a receiving section 302. As shown, the pairs of fiber rows 300 include a first transmitting row 328 paired with a first receiving row 332, and a second transmitting row 336 paired with a second receiving row 340. For simplicity, discussed from left to right, the first transmitting row 328 has a first transmitting fiber 212a, a fourth transmitting fiber 308a, a fifth transmitting fiber 312a, and a sixth transmitting fiber 316a. The first receiving row 332, from left to right, has a sixth receiving fiber 316b, a fifth receiving fiber 312b, a fourth receiving fiber 308b, and a first receiving fiber 212b. Because the fiber pairs (e.g., the first transmitting fiber 212a and the first receiving fiber 212b) are symmetrical about the center 208, the ordering of the fiber pairs ensures fiber pair alignment. Furthermore, the distance from the first transmitting line 328 to the center line 304 is the same as the distance from the first receiving line 332 to the center line 304. Therefore, the center line 304 (i.e., the imaginary line) divides the optical beam 104 into substantially equal cross-sectional areas. The pairing angle 224 is between approximately 175 degrees and approximately 185 degrees, and in one example, the pairing angle 224 is approximately 180 degrees.

[0048] The second transmitting fiber 216a and the third transmitting fiber 220a are disposed in the second transmitting row 336. The second receiving row 340 has a third receiving fiber 220b and a second receiving fiber 216b disposed in the second receiving row 340. The second transmitting row 336 is further away from the center line 304 than the first transmitting row 328. Therefore, the second receiving row 340 is further away from the center line 304 than the first receiving row 332. The distance of the second transmitting row 336 from the center line 304 is the same as the distance of the second receiving row 340 from the center line 304. The ordering of the fiber pairs ensures that each transmitting fiber and receiving fiber in the paired fiber rows 300 is aligned, thereby aligning multiple fibers 200. The alignment of multiple fibers 200 as disclosed herein enables the intensity of the incident beam 176 to be maintained within the reflected beam 178 when the reflected beam 178 returns to the optical beam 104. Advantageously, the amount of light emitted via optical beam 104 onto substrate 120 and reflected back to photodetector 170 (e.g., spectrometer) increases linearly with the increase in the number of fiber pairs.

[0049] Figure 4This is a graph 400 showing the distribution of light received by optical beam 104 compared to a conventional fiber optic cable. The horizontal axis corresponds to the diameter of optical beam 104, and the vertical axis corresponds to the amplitude of the light intensity received at photodetector 170. Exemplary x-values ​​on the horizontal axis can be any value between about 1 and about 20. y-values ​​on the vertical axis can have values ​​between about 10 and about 200, such as about 50, or about 100, or 150. Graph 400 shows the intensity distribution 404 of optical beam 104 relative to the diameter of optical beam 104 (such as center 208). The diameter of optical beam 104 can be between about 0.20 mm and 1.50 mm, such as about 0.25 mm or about 0.55 mm. The intensity distribution 404 is essentially a Gaussian distribution with a single peak at or near the center of optical beam 104. Advantageously, the spectrum or shape of the intensity curve is substantially the same between processing chambers, thus reducing the time required to calibrate the photodetector 170 or controller 150 across processing chambers utilizing optical beam 104.

[0050] As mentioned above, Figure 2 and Figure 3 The multiple optical fibers 200 shown enable a greater proportion of the light intensity signal to be maintained when light originating from the light source 166 returns to the photodetector 170 and is measured there. Advantageously, when the incident beam 176 is projected onto the substrate 120 at an incident angle 201, the intensity distribution 404 has a peak intensity at the center 208 of the optical beam 104. A conventional intensity distribution 999 has two intensity peaks because conventional fiber optic cables lack paired fibers, resulting in a loss of total intensity of reflected light. Furthermore, with conventional fiber optic cables, the beam spot generated on the substrate will vary with the amplitude of the intensity signal as the wavelength of the light changes.

[0051] Figure 5 This is a flowchart of a method for collecting reflected light from a substrate using the optical beam disclosed herein. The method begins in operation 504, in which a first light is emitted from a first emitting fiber, and subsequent light is emitted from adjacent emitting fibers of the optical beam. For example, an incident light beam is emitted from the first emitting fiber 212a, and subsequent incident light beams are emitted from a second emitting fiber 216a. Proceeding to operation 508, the first light is focused in a first receiving fiber of the optical beam. The optical beam 104 is an example of an optical beam from which method 500 can be performed. For example, a reflected beam 178 is focused in the first receiving fiber 212b because the first receiving fiber 212b is paired with the first emitting fiber 212a, i.e., aligned radially with the first emitting fiber 212a. Therefore, when an incident beam 176 is emitted from the first emitting fiber 212a, the incident beam 176 is reflected by the surface 121 of the substrate 120 to form a reflected beam 178 received by the first receiving fiber 212b.

[0052] like Figures 2 to 3 As shown and as described above, the first receiving fiber 212b is offset radially from the first transmitting fiber 212a by a pairing angle 224. Furthermore, the first receiving fiber 212b and the first transmitting fiber 212a are paired, i.e., separated by a pairing angle 224. The pairing angle 224 is between approximately 175 degrees and approximately 185 degrees, such as approximately 180 degrees, such that substantially all the intensity of light from the incident beam 176 is received as the reflected beam 178 at the first receiving fiber 212b.

[0053] At operation 512, another beam is focused in the adjacent receiving fiber of optical beam 104. For example, when the incident beam 176 emitted by the second transmitting fiber 216a is reflected from the surface 121 of substrate 120, the reflected beam 178 is focused in the second receiving fiber 216b, as... Figure 2 and Figure 3 As shown, when the incident light beam 176 originating from the third transmitting fiber 220a is reflected from the substrate 120 and received at the third receiving fiber 220b, the reflected light beam 178 is concentrated by the third receiving fiber 220b. More specifically, after the incident light ray 236 is projected onto the substrate 120 by the second transmitting fiber 216a, the reflected light ray 240 is received at the second receiving fiber 216b. Therefore, each pair of fibers (e.g., the second transmitting fiber 216a and the second receiving fiber 216b) can independently transmit and receive light beams 176 and 178. In other words, the transmission and reception of light beams 176 and 178 by the paired optical beams occur continuously and substantially simultaneously.

[0054] As described above, each pair of optical fibers in the fiber pair is bundled. Therefore, the second receiving fiber 216b is radially offset from the first transmitting fiber 212a, and the third receiving fiber 220b is radially offset from the third transmitting fiber 220a by an amount between approximately 175 degrees and approximately 185 degrees, such as approximately 180 degrees. Figure 2 and Figure 3 As shown.

[0055] At operation 516, the first light and all emitted reflected light rays are concentrated in the photodetector 170 for a predetermined time period. The reflected beam 178 is concentrated at the photodetector 170. For example, the reflected light ray 240 returns to the optical beam 104 after passing through the focusing lens 174b.

[0056] Proceeding to operation 520, method 500 continues to determine the endpoint of the opening 248 within the substrate 120. For example, the endpoint of the opening in the substrate 120 is determined by an algorithm or computer program loaded onto the controller 150.

[0057] Proceeding to operation 524, the method returns to operation 512, in which the additional fiber pair is offset and the additional light is accumulated for a predetermined time. It should be understood that the terms "another," "subsequent," or "additional" do not require a time-dependent order of operation for emitting the incident beam 176 and receiving the reflected beam 178.

[0058] This document discloses examples of optical beams and methods for using said optical beams in endpoint detection systems for etching semiconductor substrates. Advantageously, the optical beams enable the intensity of the incident beam to be maintained within the reflected beam measured by a photodetector, thereby enabling more precise detection of feature endpoints within the substrate. Although the foregoing is directed to specific examples, other examples can be devised without departing from the scope of this disclosure.

Claims

1. An endpoint detection system, comprising: An optical beam configured to emit light via a top plate of a processing chamber, the optical beam having a plurality of optical fibers arranged around a center, the plurality of optical fibers being configured to emit light from a light source toward a substrate and to receive light reflected from the substrate disposed in the processing chamber, the plurality of optical fibers comprising: Multiple transmitting optical fibers; and A plurality of receiving optical fibers, wherein each of the plurality of receiving optical fibers is paired with a corresponding transmitting optical fiber of the plurality of transmitting optical fibers, wherein each receiving optical fiber is configured to form a pairing angle with the corresponding transmitting optical fiber, and wherein the pairing angle extends through the center at an angle between 175 degrees and 185 degrees.

2. The endpoint detection system as described in claim 1, further comprising: A collimator is disposed between the optical beam and a substrate support configured to support the substrate, and the collimator is configured to focus the light emitted from the optical beam.

3. The endpoint detection system of claim 2, wherein the diameter of the optical beam is between 0.20 mm and 1.50 mm.

4. The endpoint detection system as claimed in claim 1, wherein the first transmitting fiber among the plurality of optical fibers is configured to form a separation angle with the adjacent transmitting fiber among the plurality of optical fibers, wherein the separation angle is smaller than the pairing angle.

5. The endpoint detection system of claim 1, wherein the diameter of each of the plurality of optical fibers is between 0.01 micrometers and 400 micrometers.

6. The endpoint detection system of claim 1, wherein the optical beam further comprises: An insulating material surrounds each of the plurality of optical fibers, the insulating material being configured to maintain the pairing angle.

7. An endpoint detection system, comprising: A processing chamber having a top plate, side walls, and a bottom that define an internal volume; A substrate support, located within the internal volume, configured to support a substrate thereon; An optical beam, configured to emit light through a top plate of the processing chamber, the optical beam having multiple optical fibers arranged around a center, the multiple optical fibers being configured to emit light from a light source and receive light from the substrate, the multiple optical fibers comprising: A first transmission line, the first transmission line including a plurality of first transmission optical fibers, the plurality of first transmission optical fibers being configured to transmit light from a light source toward the substrate; as well as A first receiving line, comprising a plurality of first receiving optical fibers configured to receive reflected light originating from emitted light, and a plurality of first receiving optical fibers configured to receive light emitted from a plurality of first transmitting optical fibers, the plurality of first receiving optical fibers and the plurality of first transmitting optical fibers being radially arranged around the center and each of the plurality of first transmitting optical fibers forming a pairing angle with a corresponding first receiving optical fiber of the plurality of first receiving optical fibers, wherein the pairing angle extends through the center and the pairing angle is between 175 degrees and 185 degrees.

8. The endpoint detection system as described in claim 7, further comprising: A collimator is disposed between the optical beam and the substrate support, and the collimator is configured to focus the light emitted from the optical beam.

9. The endpoint detection system of claim 8, wherein the diameter of the optical beam is between 0.20 mm and 1.50 mm.

10. The endpoint detection system of claim 7, wherein the optical beam further comprises: An insulating material surrounds the plurality of optical fibers, the insulating material being configured to maintain the pairing angle.

11. The endpoint detection system of claim 7, wherein the plurality of optical fibers further comprises: The second transmission row includes a plurality of second transmission fibers configured to transmit light from the light source toward the substrate support. The second receiving line includes a plurality of second receiving optical fibers configured to receive reflected light originating from emitted light. The plurality of second receiving optical fibers and the plurality of second transmitting optical fibers are radially arranged around the center and concentric with the plurality of first receiving optical fibers and the plurality of first transmitting optical fibers. Each of the plurality of second transmitting optical fibers is paired with a corresponding second receiving optical fiber among the plurality of second receiving optical fibers at the pairing angle.

12. A semiconductor processing system, comprising: An optical beam is configured to emit light through a top plate of a processing chamber. The optical beam has multiple optical fibers arranged around a center and configured to emit light from a light source toward a substrate disposed in the processing chamber. The multiple optical fibers include multiple transmitting fibers and multiple receiving fibers, wherein each of the multiple receiving fibers is configured to form a pairing angle with a corresponding transmitting fiber among the multiple transmitting fibers, and wherein the pairing angle extends through the center at an angle between 175 degrees and 185 degrees. A non-transitory computer-readable medium storing instructions, which, when executed by a processor, cause a controller coupled to the light source to perform a method comprising the following steps: A first light is emitted from the first transmitting fiber among the plurality of transmitting fibers; The first light is received at a corresponding first receiving fiber among the plurality of receiving fibers, and the corresponding first receiving fiber is arranged radially at a pairing angle with the first transmitting fiber. A second light is emitted from the second transmitting fiber among the plurality of transmitting fibers; and The second light is received at a corresponding second receiving fiber among the plurality of receiving fibers, the corresponding second receiving fiber being arranged radially at the pairing angle with the second transmitting fiber, and the corresponding second receiving fiber being configured to receive light originating from the second transmitting fiber.

13. The semiconductor processing system of claim 12, wherein the method further comprises the following steps: The first light and the second light are passed through a collimator disposed between the optical beam and a substrate support member, the substrate support member being used to support the substrate thereon, and the collimator being configured to focus the first light and the second light.

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