Endpoint detection in low open area and / or high aspect ratio etch applications

Abstract

This document discloses a method for determining the endpoint of an etching operation for forming high aspect ratio features and / or low open areas (<1%) on a substrate in a processing chamber. The method begins by obtaining a reference emission profile. An etching operation is performed on a patterned substrate. Plasma emission intensity is measured for each etching cycle. A difference curve between the reference emission and the plasma emission is calculated. The endpoint of the etching operation on the first substrate is determined based on inflection point detection or other unique features identified through the pattern in the difference curve, thereby stopping the etching of the first substrate.

Description

[Technical Field]

[0001] The examples of this disclosure generally relate to a method for detecting the end point of a semiconductor etching operation. [Previous Technology]

[0002] Since the introduction of semiconductor devices decades ago, the geometry of these 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, the pitch dimension rapidly decreases to below 50 nm, while vertical dimensions (e.g., 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 of the dimensions of these high-density, submicron features is critical for the reliable fabrication of semiconductor devices.

[0003] 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, followed by etching the substrate to remove material and define the feature. In order to form features with the required electrical performance, the dimensions of the feature must be formed within precise specifications.

[0004] Reliable endpoint detection is crucial for consistent etching results, regardless of incoming wafer, chamber condition drift, and differences between chambers. Traditional endpoint detection in etching applications relies on the analysis of emission trends or spectra collected in real time only from the current etching step. Traditional endpoint systems require the presence of a stop layer, an open area greater than 3%, or a high aspect ratio (HAR) of less than 30:1. However, in etching applications with low open areas less than 3% of the substrate surface area or high aspect ratios (HAR) greater than 30:1 (e.g., 50:1), conventional model algorithms may not have enough ions to detect to extract endpoint information from emission background noise. Detecting the endpoint of an etching operation is challenging in low open area and HAR etching applications because changes in plasma emission signals are significantly weaker than intensity changes caused by other factors, such as step transitions, interactions with chamber elements, or combinations of these factors.

[0005] Therefore, improved etching endpoint detection technology is needed. [Summary of the Invention]

[0006] This document discloses a method for determining the endpoint of an etching operation for forming high aspect ratio features and / or low open areas (<1%) on a substrate in a processing chamber. The method begins by obtaining a reference emission profile. An etching operation is performed on a patterned substrate. Plasma emission intensity is measured for each etching cycle. A ratio profile between the reference emission and the plasma emission is calculated. The endpoint of the etching operation on a first substrate is determined based on the inflection point in the ratio profile, and etching of the first substrate is stopped based on the endpoint.

Implementation Method

[0013] An example of this disclosure relates to a method for detecting the endpoint of etching on a semiconductor substrate. In substrates having a low open area (LOA) of less than 1% of the substrate's top surface area and a high aspect ratio (HAR) etching feature greater than 30:1, the method disclosed herein for detecting the endpoint of an etching operation is possible even when changes in the plasma emission signal are significantly weaker than intensity changes caused by other factors, such as step transitions, interactions with chamber elements, or combinations thereof. The method enables reliable endpoint detection for consistent etching results regardless of variations in incoming wafer and chamber conditions. By capturing a reference emission signal and comparing it with the processed emission signal, emission background can be filtered out using current operating data, which significantly improves the sensitivity of endpoint detection.

[0014] Advantageously, this new endpoint detection method is simpler because it utilizes a reference wafer or reference operation to capture complex plasma emission behaviors that typically require sophisticated modeling and exceed the typical modeling capabilities of LOA and HAR etching applications. Furthermore, the endpoint detection method disclosed below is applicable to LOA and HAR etching applications implemented in conventional processing systems, and therefore these systems do not need to be replaced by more complex and expensive equipment.

[0015] Figure 1 is a schematic cross-sectional view of a plasma processing chamber 100 suitable for performing etching operations according to an example of this disclosure. Suitable processing chambers include inductively and capacitively coupled plasma etching chambers, such as the TETRA® photomask etching system and the SYM3® etching system, both of which are available from Applied Materials, Inc., Santa Clara, California. Other types of processing chambers may 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, and other chambers, etc.

[0016] The processing chamber 100 includes a chamber body 102, a flow module 106, and a top plate 103. The top plate 103 is energy-transparent, i.e., it allows energy to be transferred through it. The top plate 103 is mounted on the chamber body 102. The chamber body 102 is mounted on the flow module 106. The chamber body 102 and the flow module 106 may be made of metal, such as anodized aluminum or stainless steel. The top plate 103 may be flat, rectangular, arched, 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 provide energy to the gas within the chamber 100 during processing.

[0017] A substrate support 116 is disposed in the processing chamber 100 and has a substrate support surface 188 for supporting the substrate 120 during processing. The substrate support 116 may include an electrostatic chuck, and at least a portion of the substrate support 116 is conductive and can be used as a processing bias cathode.

[0018] Processing gas is introduced into the processing chamber 100 from the processing gas source 148 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) for each processing gas or alternatively for a mixture of processing gases is disposed between the gas distributor 122 and the processing gas source 148 to regulate the corresponding flow rate of the processing gas entering the chamber body 102.

[0019] An internal space 114 is defined in a chamber body 102 between a substrate support 116 and a top plate 103. Plasma is formed in the internal space 114 by process gas using a coil power supply 127, which supplies power to an induction coil 126 via an RF matching network 135 to generate an electromagnetic field in the internal space 114. The substrate support 116 may include electrodes disposed therein, which are powered by an electrode power supply 125 and generate a capacitive electric field in the processing chamber 100 via an RF matching network 128. When the chamber body 102 is electrically grounded, RF power is applied to the electrodes in the substrate support 116. The capacitive electric field is transverse to the plane of the substrate support 116 and influences the orientation of charged material to be more perpendicular to the substrate 120 to provide a more vertically oriented anisotropic etching of the substrate 120.

[0020] Processing gases and etchant byproducts are discharged from the processing chamber 100 through the flow module 106. The flow module 106 includes an outer wall 160, an inner wall 162, two or more pairs of radial walls 165 connecting the inner wall 162 and the outer wall 160, and a bottom wall 167 attached to the inner wall 162 and the two or more pairs of radial walls 165. The outer wall 160 may include two or more through holes 171 formed between each pair of radial walls 165. A base frame 155 is hermetically disposed over the inner wall 162 and the two or more pairs of radial walls 165. A substrate support 116 is disposed on the base frame 155.

[0021] The outer wall 160 and the inner wall 162 may be concentrically arranged cylindrical walls. During assembly, the central axes of the outer wall 160 and the inner wall 162 coincide with the central axis 110 of the plasma processing chamber 100. The inner wall 162, the bottom wall 167, the radial wall 165, and the base frame 155 divide the internal space of the outer wall 160 into an exhaust channel 115 and an atmospheric space 168. The exhaust channel 115 connects the internal space 114 of the main body 102 to the exhaust module 108 through the flow module 106.

[0022] The discharge module 108 includes a symmetrical flow valve 132 and a vacuum pump 182 attached to the symmetrical flow valve 132 via a pump port 184. The symmetrical flow valve 132 is connected to the discharge passage 115 to provide symmetrical and uniform flow in the plasma processing chamber 100. During operation, the process gas flows from the internal space 114 to the vacuum pump 182. The symmetrical flow valve 132 also helps control the pressure in the processing chamber 100.

[0023] The substrate support 116 is positioned along the central axis 110 to symmetrically position the substrate 120 relative to the central axis 110. A plasma screen may be disposed around the substrate support 116 to confine the plasma above the substrate 120 within the internal space 114. The flow module 106 and the discharge module 108 are configured to maintain symmetry with respect to the central axis 110 for the plasma and exhaust gas to enhance processing uniformity, for example, during etching operations.

[0024] Fiber optic bundle 104 is configured to detect the endpoint of an etching process performed in processing chamber 100. Fiber optic bundle 104 is included in endpoint detection system 164. Endpoint detection system 164 may be an interferometer endpoint (IEP) detection system. Endpoint detection system 164 is positioned to contact substrate 120 via a portion of top plate 103. In one example, endpoint detection system 164 is positioned to contact an outer peripheral portion of substrate 120 via a portion of top plate 103 that is off-center from the center of top plate 103.

[0025] 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 one layer of the substrate 120 has been sufficiently etched through to expose the underlying layer. Determining the endpoint of the etching operation allows etching of the substrate 120 to be stopped after the operation is completed, thereby reducing the occurrence of over-etching or under-etching of the substrate 120. The endpoint detection system 164 monitors ions in the plasma to determine the degree of etching of the substrate or other conditions in the processing chamber 100.

[0026] The endpoint detection system 164 may include a light source 166, a collimation assembly 168, a photodetector 170, and a controller 150. The light source 166 is configured to emit a light beam via an optical fiber bundle 104. The light beam exiting the optical fiber bundle 104 strikes the substrate 120 and is reflected back via the optical fiber bundle 104. The reflected light beam returns to the photodetector 170 via the optical fiber bundle 104. For example, the collimation assembly 168 is configured to focus the light beam into an incident light beam 176. The incident light beam 176 passes through the top plate 103 in a direction perpendicular to the substrate support surface 188 and illuminates an area or spot 180 on the surface 121 of the substrate 120. The incident light beam 176 is reflected by the surface 121 of the substrate 120 to form a reflected light beam 178. At least a portion of the reflected light beam 178 is guided through the top plate 103 in a direction perpendicular to the substrate support surface 188 back to the photodetector 170. A photodetector 170 is configured to measure the intensity of a reflected light beam 178. An exemplary photodetector 170 is a spectrometer. A controller 150 calculates a portion of the waveform spectrum of the reflected light beam 178 reflected from a beam point 180 on substrate 120 by means of an instantaneous measurement, and processes the spectrum using advanced spectral analysis techniques, including comparing the spectrum with stored characteristic waveform patterns. Chemical substances in plasma excite their electrons to higher energy states during ion formation. Ions release this energy in the form of light (a process called photoemission). Each substance produces light at unique wavelengths. For example, hydrogen atoms produce visible light with wavelengths of 486 nm and 656 nm. Analysis of these wavelengths is called optical emission spectroscopy (OES).

[0027] OES data can be used to examine the immediate behavior of chemicals in plasma to determine the stopping time, i.e., the endpoint. OES data is characterized by plasma light emission intensity as a measure of wavelength and time to determine the relative measurement of chemical changes. When the upper material is etched away to expose the lower material, the chemical properties of the emission change, indicating a layer breakthrough and marking the end of the etching process.

[0028] The controller 150 includes a processor 152, a memory 154, and a support circuit 156 coupled to each other. The controller 150 is electrically coupled to the endpoint detection system 164 via a wire 158, which includes a photodetector 170, the controller 150, and a light source 166.

[0029] Processor 152 can be any form of general-purpose microprocessor or general-purpose central processing unit (CPU), each of which can be used in industrial environments, such as programmable logic controllers (PLCs), monitoring and data acquisition (SCADA) systems, or other suitable industrial controllers. Memory 154 is non-transitory and can be one or more readily available memories, such as random access memory (RAM), memory-only memory (ROM), or any other form of digital storage, local or remote. 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 may 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 discs 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 disc drive or hard drive, or any type of solid-state random access semiconductor memory), on which variable information is stored. Such computer-readable storage media are examples of this disclosure when carrying computer-readable instructions that direct the function of the methods described herein.

[0030] A computer program coupled to the controller 150 operates on the measured waveform pattern to determine the endpoint of the etching process when the measured waveform pattern matches a characteristic waveform pattern. Therefore, the waveform signal is used to calculate the depth and etching rate. The program can also perform simple mathematical operations, such as simple subtraction or division, to evaluate the moving derivative used to detect the endpoint of the etching operation.

[0031] Figures 2A-2C illustrate the chemical substances within the plasma during an etching operation in a single layer of a substrate in the processing chamber shown in Figure 1. Figures 2A-2C show a substrate 120 having a base layer 240, a second layer 220, and a third layer 230. Plasma 210 is held above the substrate 120. Plasma 210 has at least ions 212 from the chemical substances, which are excited to a high energy state and configured to etch the substrate 120. Before etching the substrate, plasma 210 has only ions 212, which release energy as light, i.e., light emission. The endpoint detection system 164 uses analysis of the light emission to determine the presence of certain chemical substances within the plasma. Figure 2B shows a HAR / LOA etching operation by means of a mask 201 to form features extending into the third layer 230. The etching process introduces material from the third layer, i.e., the chemical substances, into the plasma 210 as ions 232 excited by layer 3. In HAR / LOA etching operations, the number of ions 232 excited in layer 3 of plasma 210 is less than the number of ions 212 in plasma 210. The second layer 220 can serve as an etching stop layer marking the end of the etching operation. The etching process introduces material from the second layer 220 into plasma 210 as a layer 2 excited chemical substance 222. The endpoint detection system 164 uses the detection of layer 2 excited ions 222 in plasma 210 to determine the end of the etching operation. For HAR / LOA etching operations, the number of detectable layer 2 excited ions 222 in the plasma is very small.

[0032] Figures 3A-3C illustrate the chemical substances within the plasma during etching operations in multiple layers of a substrate in the processing chamber shown in Figure 1. Figures 3A-3C show a substrate 120 having a base layer 350, an etch stop layer 340, a third layer 330, a second layer 320, and a first layer 310. A mask 301 is provided for establishing features in the substrate 120. Plasma 210 is held above the substrate 120. Plasma 210 has at least ions 212 from the chemical substances, which are excited to a high energy state and configured to etch the substrate 120. The mask 301, together with the plasma 210, can be configured to perform HAR / LOA etching operations in some layers of the substrate 120. Before etching the substrate, plasma 210 has only ions 212, which release energy as light, i.e., light emission. The endpoint detection system 164 uses analysis of the light emission to determine the presence of certain chemical substances within the plasma. Figure 3B illustrates a HAR / LOA etching operation via mask 301 to form features extending into substrate 120. The etching process introduces material, i.e., chemicals, from the first layer 310 and the second layer 320 into plasma 210 as layer 1 excited ions 312 and additionally as layer 2 excited ions 322. In the HAR / LOA etching operation, the amount of layer 1 excited ions 312 and layer 2 excited ions 322 in plasma 210 is smaller than that of ions 212 in plasma 210. The third layer 320 is etched, also introducing layer 3 excited ions 332 into the plasma, as shown in Figure 3C. As etching continues through the third layer 330, the via extends to the etch stop layer 340, marking the end of the etching operation. The etch stop layer 340 introduces ESL excited ions 342 into plasma 210. The endpoint detection system 164 uses the ESL excited ions 342 to determine the end of the etching operation. For HAR / LOA etching operations, the number of detectable excited ions in the plasma is small, and detection is more complicated when the via extends through several layers of the substrate before the etch stop layer 340.

[0033] Because plasma emission changes little to no noticeable due to small transitions, conventional endpoint techniques struggle to detect endpoints when etching substrates with low open areas and high aspect ratios. As the high aspect ratio of the features becomes greater than 30:1 and / or the low open area on the substrate is less than 1% of the substrate's top surface area, the change in emission intensity due to the removal of etched material decreases and becomes virtually undetectable in the emission trend at any single wavelength. Therefore, Figures 4 and 5 disclose two different endpoint detection methods that amplify endpoint transitions in the OES signal by selecting the most sensitive wavelength, normalizing the background emission during signal-relative operation, and distinguishing it from a reference run used in the signal normalization, thereby enabling reliable detection of endpoints in HAR and / or LOA etching processes.

[0034] Figure 4 is a flowchart of a first method for detecting the endpoint of a high aspect ratio etching operation on a semiconductor substrate. The method begins at operation 410 by performing an etching operation on the substrate. The etching operation can be cyclic or a single step. The substrate can be a reference substrate. Alternatively, the substrate can be a patterned substrate in a production batch on which a substrate with a high aspect ratio of 30:1 or greater, such as 40:1 or 50:1, will be formed. The substrate has a processing recipe in which it is known that a stop layer has not been reached or that the operation is known to be confined within one or more known layers of the substrate in the early stages of the etching operation.

[0035] In operation 420, the plasma light emission intensity is measured as a function of wavelength and time during the etching operation. For example, during the etching operation, light emission at one or more wavelengths as a function of time can be recorded. As shown in Figure 2A, the plasma contains ions from a chemical substance. When etched into the material layer, the plasma only receives additional ions from the material layer, as shown in Figure 2B. The measured plasma light emission is from both the plasma and the etched material layer.

[0036] In operation 430, the measurement of plasma light emission is stored as reference light emission. The reference light emission provides an indication of those etching operations that belong only to a reference layer, i.e., one or more layers etched before reaching the next layer. For example, emission may originate from an etching operation of a photoresist layer and be stored as a reference or indicator of emission from etching operations occurring only in the photoresist layer. Similarly, reference light emission may be obtained for another layer such as a hard mask and / or a silicon layer, and the storage of emission data from etching operations in the hard mask and / or silicon layer can be used as a reference for etching operations on these same material layers. The stored reference light emission may originate from an earlier operation during substrate etching. For example, the stored reference light emission may originate from an earlier operation in an etching cycle, where it is known that the etching operation being performed is passing through a layer before reaching another material layer.

[0037] In operation 440, a curve or alternatively a trend model is fitted to reference light emission data. The curve may be calculated as the best fit and used as a baseline indicator for future emission assessment. Similarly, a regression line may be used to predict ions in the plasma before ions are introduced from the underlying layer. The reference light emission data is used to establish a baseline or reference for calculating the endpoint of future etching operations. Alternatively, a trend model may be used to predict future light emission. The trend model may be linear or a curve that gives the best average fit to the light emission data. The trend model may be logarithmic. Alternatively, the trend model may be linear. In yet another alternative, the trend model may be a binomial curve.

[0038] In operation 450, the difference between the curve or trend model and the instantaneous plasma emission of the substrate is calculated. Plasma emission is observed and recorded as the substrate is etched to the desired endpoint of the etching operation. The difference can be determined by dividing or subtracting the curve or trend model from the earlier instantaneous plasma emission of the substrate. The difference can be plotted to form a composite curve or ratio curve. The plasma emission in Figure 2B begins to change as etching introduces ions from a new (second) layer (or multiple layers) of plasma, as shown in Figure 2C. The identification of changes in the plasma emission signal is more easily detected by the difference curve to determine the endpoint of the etching operation.

[0039] In operation 460, a unique pattern is determined in the difference curve. The unique pattern indicates the endpoint of the etching operation. For example, where plasma ions are no longer represented solely by reference light emission. When new ions are introduced, the difference between the curve or trend model and the plasma light emission begins to diverge, causing a change in the difference curve. Etching is stopped when an inflection point is detected in the difference curve. Advantageously, etching operations that form features with a high aspect ratio of 30:1 or higher, such as 50:1, are detectable when the reference light emission is compared with the observed light emission to detect small changes in the observed light emission.

[0040] Figure 5 is a flowchart of a second method for detecting the endpoint of a low open area (LOA) etching operation on a semiconductor substrate. The LOA is the area of ​​the opening for the etching feature on the semiconductor substrate, which is less than 1% of the total surface area of ​​the semiconductor substrate. The method begins at operation 510 by performing an etching operation on the substrate. The etching operation can be a cyclic or single-step operation. The substrate is a reference substrate. The reference substrate has a layer of material on which the etching operation is performed and ions are contributed to the plasma for detection. In one example, the material layer may comprise multiple layers or compounds, such that a variety of different chemical ions contribute to the plasma. In another example, the material layer may be monolithic and contribute a limited number of chemical ions to the plasma, such as one.

[0041] During operation 520, the plasma light emission intensity is measured during the etching operation of the reference substrate. The light emission is measured as a function of wavelength and time and is provided as a reference emission. Measurements may include multiple wavelengths. For example, the reference emission may be measured at 434 nm and 440.5 nm, although other wavelengths may be used. The wavelength may be determined based on expected ions in the plasma and / or ions that will ultimately be introduced into the plasma etching operation and the reference emission will be used to determine when etching stops. In one example, two or more wavelengths of plasma light emission are measured.

[0042] In operation 530, measurements of two or more wavelengths of plasma light emission are stored as reference emission profiles. For example, a first reference emission profile may contain measurements at a wavelength of 434 nm. A second reference emission profile may contain measurements at a wavelength of 440.5 nm. Further reference emission profiles at different wavelengths may be stored based on the material etched onto the reference substrate. The wavelength selected for the measurement corresponds to the ions of the material introduced into the reference layer in the plasma, for example, as shown in Figure 2B.

[0043] In operation 540, an etching operation is performed on the patterned substrate. The etching operation can be a cyclic or single-step operation. The etching operation can form features on the patterned substrate having a low open area (LOA). For example, the etching operation on the patterned substrate forms features having a LOA less than 3% of the substrate surface area. In one example, the area of ​​the opening for the etched feature of the first substrate is less than 1% of the substrate surface area.

[0044] During operation 550, two or more wavelengths of plasma light emission intensity are measured during the etching operation of the patterned substrate. The two or more wavelengths correspond to wavelengths measured with a reference substrate. For example, a first emission profile may include measurements at a wavelength of 434 nm. A second emission profile may include measurements at a wavelength of 440.5 nm. Further emission profiles may be stored based on the material etched on the patterned substrate along with associated corresponding reference emission data.

[0045] In operation 560, a differential curve is calculated between two or more wavelengths of the patterned substrate, and differential curves are calculated separately for two or more wavelengths of the reference substrate. The reference differential is compared with the measured values ​​of two or more independent wavelengths of the reference plasma emission. The reference differential is formed by calculating the difference between a first curve of the first wavelength of two or more wavelengths and a second curve of the second wavelength of two or more wavelengths, and so on for the remaining wavelengths, to form a third curve of the reference emission. The differential ratio can be determined by dividing the first curve of the first wavelength of two or more wavelengths by the remaining curves of various recorded wavelengths to form the third curve of the reference emission. Alternatively, the differential curve is calculated in a similar manner by subtracting the various wavelength curves. The patterned substrate differential is compared with the measured values ​​of two or more individual wavelengths of the plasma emission of the patterned substrate. The patterned substrate differential is determined by dividing or alternatively subtracting the first curve of the first wavelength of two or more wavelengths from the remaining wavelength curves of the two or more wavelengths to form the third curve of the patterned substrate.

[0046] In operation 570, an incremental curve (delta curve) is calculated for the difference between the third curve of the reference emission and the third curve of the patterned substrate. The difference can be determined by subtracting the third curve of the reference emission from the third curve of the patterned substrate. Alternatively, the difference can be determined by dividing the third curve of the reference emission by the third curve of the patterned substrate.

[0047] In operation 580, a unique pattern in the incremental curve is determined. The unique pattern can be an inflection point in the incremental curve. Alternatively, the unique pattern can be observed as another change in the incremental curve. The unique pattern indicates the end point of the etching operation. The unique pattern in the incremental curve shows a change in plasma ions. This change in ions indicates that new material has been introduced from a new layer (e.g., the etch stop layer) as the etching operation moves through the etch layer to the etch stop layer.

[0048] Advantageously, the method disclosed herein captures plasma background emission signals independent of the endpoint by running an etching process on a reference wafer (LOA case) and / or running an etching process in the early portion of the etching operation, prior to the start of the endpoint on the patterned wafer (HAR case). The difference between the instantaneous emission signal and the reference signal enables endpoint detection. Furthermore, the method disclosed herein advantageously provides endpoint detection for LOA and / or HAR etching applications in conventional processing chambers without requiring the replacement of expensive hardware.

[0049] Although the foregoing is directed to a specific example, other examples may be devised without departing from the scope of this disclosure. [Simplified Explanation of the Diagram]

[0007] Therefore, the methods with the above-described features of this disclosure can be understood in detail. A more specific description of this disclosure, briefly summarized above, can be referred to in the embodiments, some of which are depicted in the accompanying drawings. However, it should be noted that the accompanying drawings only show typical embodiments of this disclosure and should therefore not be considered as limiting its scope, as this disclosure may acknowledge other equivalent embodiments.

[0008] Figure 1 is a schematic cross-sectional view of a processing chamber with an optical fiber bundle.

[0009] Figures 2A-2C illustrate the chemicals in the plasma during an etching operation in a single layer of a substrate in the processing chamber shown in Figure 1.

[0010] Figures 3A-3C illustrate the chemicals in the plasma during the etching operation of multiple layers of a substrate in the processing chamber shown in Figure 1.

[0011] Figure 4 is a flowchart of a first method for detecting the endpoint of a high aspect ratio etching operation performed on a semiconductor substrate.

[0012] Figure 5 is a flowchart of a second method for detecting the endpoint of a low open area etching operation performed on a semiconductor substrate.

Claims

1. A method for detecting an endpoint of an etching operation on a semiconductor substrate, the method comprising the steps of: obtaining a reference emission from a first material layer of a first substrate of a first pattern type for a first etching operation, the first material layer having a first thickness; performing a second etching operation on a second material layer of a second substrate of the first pattern type, the second material layer having a second thickness, wherein the first thickness is greater than the second thickness; measuring plasma emission during the etching operation on the second substrate; using a processor to calculate a differential curve between the reference emission and the plasma emission; determining an endpoint of the second etching operation on the second substrate based on a detection of a pattern in the differential curve to stop the etching operation; and stopping the second etching operation based on the determination that the endpoint of the etching operation has been reached.

2. The method as claimed in claim 1, wherein the first etching operation on the first substrate is for forming a feature having a high aspect ratio of 30:1 or greater, and the step of obtaining the reference emission further includes the following steps: measuring the intensity of the plasma emission of the first substrate at an early stage of the etching operation; and storing the measurement of the plasma emission as the reference emission.

3. The method as described in claim 2 further includes the step of: fitting a curve or trend model to the reference emission.

4. The method as described in claim 3, wherein the difference curve can be determined by dividing or subtracting the curve or trend model from the plasma emission.

5. The method as claimed in claim 1, wherein the second etching operation on the second substrate is for forming a low open region having a top surface area of ​​about 1% or less, and the step of obtaining the reference emission profile further includes the steps of: measuring two or more wavelengths of the intensity of the plasma emission of the first substrate; and storing the measured values ​​of the plasma emission of the first substrate.

6. The method as claimed in claim 5, wherein storing the reference emission curves is plasma emission at two or more wavelengths of the reference emission curves, and measuring the intensity of the plasma emission of the second substrate during the second etching operation is for at least two of the same wavelengths as the reference emission.

7. The method as claimed in claim 6 further includes the steps of: establishing the reference emission by combining the intensities of the plasma emission of the two or more wavelengths of the reference emission curve; and calculating a pattern curve by combining the intensities of the plasma emission of the two or more wavelengths of the second substrate, wherein the pattern curve is used as the plasma emission when calculating the difference curve.

8. A non-transitory computer-readable storage medium, comprising a program product that, when executed, is configured to perform an operation for detecting an endpoint of an etching operation on a semiconductor substrate, the operation comprising: A reference emission is obtained from a first etch operation on a first material layer of a first substrate of a first pattern type, the first material layer having a first thickness; a second etch operation is performed on a second material layer of a second substrate of the first pattern type, the second material layer having a second thickness, wherein the first thickness is greater than the second thickness; a plasma emission is measured during the etch operation on the second substrate; a processor is used to calculate a differential curve between the reference emission and the plasma emission; an endpoint of the second etch operation on the second substrate is determined based on a detection of a pattern in the differential curve to stop the etch operation; and the second etch operation is stopped based on the determination that the endpoint of the etch operation has been reached.

9. The non-transitory computer-readable storage medium as described in claim 8, wherein the first etching operation on the first substrate is for forming features with a high aspect ratio of 30:1 or greater, and obtaining the reference emission further includes the steps of: measuring the intensity of the plasma emission of the first substrate at an early stage of the etching operation; and storing the measurement of the plasma emission as the reference emission.

10. The non-transitory computer-readable storage medium as described in claim 9, further comprising: Fit a curve or trend model to the reference emission.

11. The non-transitory computer-readable storage medium as described in claim 10, wherein the difference curve can be determined by dividing or subtracting the curve or trend model from the plasma light emission.

12. The non-transitory computer-readable storage medium as claimed in claim 8, wherein the second etching operation on the second substrate is for forming a low open area having a top surface area of ​​about 1% or less, and obtaining the reference emission profile further includes the steps of: measuring two or more wavelengths of the intensity of the plasma emission of the first substrate; and storing the measured values ​​of the plasma emission of the first substrate.

13. The non-transitory computer-readable storage medium as described in claim 12, wherein the storage of the reference emission profiles is plasma emission at two or more wavelengths of the reference emission profiles, and the intensity of the plasma emission of the second substrate is measured during the second etching operation at at least two of the same wavelengths as the reference emission.

14. The non-transitory computer-readable storage medium as described in claim 13, further comprising: The reference emission is established by combining the intensity of plasma light emission from two or more wavelengths in the reference emission curve; A pattern curve is calculated by combining the intensities of plasma light emission from two or more wavelengths of the second substrate, wherein the pattern curve is used as the plasma light emission when calculating the difference curve.

15. A system for detecting the endpoint of an etching operation on a semiconductor substrate, comprising: A central processing unit (CPU); The memory is communicatively coupled to the CPU; A program operable to provide instructions to a CPU controlling an etching operation in a plasma processing system, wherein the program is stored in memory and configurable to be executed by the CPU, the program comprising: instructions for obtaining a reference emission from a first material layer of a first substrate of a first pattern type for a first etching operation, the first material layer having a first thickness; instructions for performing a second etching operation on a second material layer of a second substrate of the first pattern type, the second material layer having a second thickness, wherein the first thickness is greater than the second thickness; instructions for measuring a plasma emission intensity during the etching operation on the second substrate; instructions for using the CPU to calculate a differential curve between the reference emission and the plasma emission; instructions for determining an endpoint of the second etching operation on the second substrate based on a detection of a pattern in the differential curve to stop the etching operation; and instructions for stopping the second etching operation based on the determination that the endpoint of the etching operation has been reached.

16. The system as claimed in claim 15, wherein the first etching operation on the first substrate is for forming a feature having a high aspect ratio of 30:1 or greater, and obtaining the reference emission further includes: Instructions for measuring the intensity of plasma light emission from the first substrate early in the etching operation; And instructions for storing the measurement of such plasma light emission as the reference emission.

17. The system as described in claim 16, further comprising: Instructions for fitting a curve or trend model to the reference emission, wherein the difference curve can be determined by dividing or subtracting the curve or trend model from the plasma emission.

18. The system as claimed in claim 15, wherein the second etching operation on the second substrate is for forming a low open region having a top surface area of ​​about 1% or less, and obtaining the reference emission profile further includes: Instructions for measuring the intensity of light emission from the first substrate using two or more wavelengths; And instructions for storing the measured values ​​of plasma light emission from the first substrate.

19. The system of claim 18, wherein storing the reference emission profiles is plasma emission at two or more wavelengths of the reference emission profiles, and measuring the intensity of the plasma emission of the second substrate during the second etching operation is for at least two of the same wavelengths as the reference emission.

20. The system as described in claim 19, further comprising: Instructions for establishing the reference emission by combining the intensities of plasma light emission through the combination of the two or more wavelengths in the reference emission curve; A pattern curve is calculated by combining the intensities of plasma light emission from two or more wavelengths of the second substrate, wherein the pattern curve is used as the plasma light emission when calculating the difference curve.

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