Etching end point detection method and semiconductor process equipment

Abstract

The invention provides an etching end point detection method and semiconductor process equipment. The method comprises the following steps: collecting an etching progress signal capable of reflecting an etching process in an etching process; de-noising processing is carried out on the etching progress signal to obtain a curve of signal intensity changing along with time; filtering a false end point before a preset filtering time in the curve of the signal intensity changing along with the time; wherein the preset filtering time is a corresponding time point when the signal intensity rises or drops to a preset intensity threshold value after the set etching end point delay detection time; and obtaining a wave crest or a wave trough after the preset filtering time in the curve of the signal intensity changing along with the time, and carrying out extreme value verification on the wave crest or the wave trough to determine an etching end point. According to the invention, the accuracy of etching end point detection is improved, the influence of unstable etching end point detection on the key size of a product is avoided, and the stability of etching end point detection is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an etching endpoint detection method and semiconductor process equipment. Background Art

[0002] Plasma etching, especially high-density plasma etching, is an indispensable component in the manufacturing process of advanced integrated circuits. Plasma etching has a vital impact on the critical dimensions of the circuit, the final electrical properties of the device, and the product yield. In the etching process, different process steps are usually set for different film structures, and each process step is usually a timed mode, that is, the step is ended after the process is executed for a fixed time. However, due to the fluctuation of the etching rate in different chambers or the same chamber in different time periods, the actual etching amount generated at the same time is a floating value, resulting in unstable quality of the etched product. And as the critical dimensions of the product continue to shrink, the control method of timed etching is gradually unable to meet the increasing demand for process stability. The process control method of endpoint detection has gradually become the mainstream method of etching process control in the wafer process because it can adjust the wafer etching time in real time, compensate for the difference in etching rate of the etching chamber and the fluctuation of the key process of the wafer. Related etching endpoint detection technologies usually use whether the rising threshold and falling threshold of the signal meet the set values ​​as the standard for judging whether the endpoint detection is completed, resulting in large fluctuations in the detected endpoint time, and the inability to stably and accurately detect the etching endpoint of the etching process, and thus unable to meet the requirements of key processes for key dimensional stability, reducing the stability of etching endpoint detection. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide an etching endpoint detection method and semiconductor process equipment, which can improve the accuracy of etching endpoint detection, avoid the instability of etching endpoint detection affecting the key dimensions of the product, and improve the stability of etching endpoint detection.

[0004] In order to achieve the above objectives, the technical solutions adopted in the embodiments of the present invention are as follows:

[0005] In a first aspect, an embodiment of the present invention provides an etching endpoint detection method, comprising:

[0006] Collecting etching progress signals that can reflect the etching process during the etching process;

[0007] Performing noise removal on the etching progress signal to obtain a curve of signal intensity variation over time;

[0008] Filter out the false endpoints before a preset filtering time in the signal intensity versus time curve; wherein the preset filtering time is the time point corresponding to when the signal intensity rises or falls to a preset intensity threshold after the set etching endpoint delay detection time;

[0009] A peak or a trough after the preset filtering time in the signal intensity variation curve is obtained, and extreme value verification is performed on the peak or the trough to determine the etching endpoint.

[0010] Furthermore, an embodiment of the present invention provides a first possible implementation of the first aspect, wherein the etching progress signal includes at least two etching parameters, the etching parameters including a chamber light intensity signal and / or chamber equipment hardware parameters, and the denoising process of the etching progress signal to obtain a curve of signal intensity variation over time includes:

[0011] Based on the change trend of each of the etching parameter change curves over time after the set etching endpoint delay detection time, each of the etching parameter change curves over time is calculated to eliminate system noise caused by hardware problems.

[0012] Furthermore, an embodiment of the present invention provides a second possible implementation of the first aspect, wherein the change trend includes an upward trend and a downward trend, and the computing of the time-varying curves of each etching parameter includes:

[0013] Performing an addition or multiplication operation on the curves with the same change trend to obtain a first curve and a second curve respectively, wherein the change trends of the first curve and the second curve are different;

[0014] A subtraction or division operation is performed on the first curve and the second curve to obtain the curve of signal intensity variation over time.

[0015] Furthermore, an embodiment of the present invention provides a third possible implementation of the first aspect, wherein obtaining a peak or trough after the preset filtering time in the signal intensity versus time curve, and performing extreme value verification on the peak or trough to determine the etching endpoint includes:

[0016] Verify whether the signal strength continues to rise or fall for a preset period of time starting from the target time, if so, the extreme value verification is passed;

[0017] If the extreme value verification continues to pass within the preset time period, the target time is determined to be the etching endpoint, and a process termination signal is generated.

[0018] Furthermore, an embodiment of the present invention provides a fourth possible implementation of the first aspect, wherein, before the step of performing denoising on the etching progress signal, the method further includes:

[0019] Verifying the validity of the etching progress signal;

[0020] When the etching progress signal is verified to be valid, performing the noise removal process on the successfully verified etching progress signal;

[0021] When the etching progress signal is verified to be abnormal, an equipment alarm is issued to stop the etching process.

[0022] Furthermore, an embodiment of the present invention provides a fifth possible implementation of the first aspect, wherein, before the step of filtering out false endpoints before a preset filtering time in the signal strength versus time curve, the method further includes:

[0023] A normalization operation is performed on the signal intensity variation curve over time.

[0024] Furthermore, an embodiment of the present invention provides a sixth possible implementation of the first aspect, wherein the normalizing operation on the signal strength versus time curve includes:

[0025] The signal intensity after stabilization in the signal intensity versus time curve is used as a reference intensity, and the time point corresponding to the reference intensity is recorded as a reference time point; wherein the reference time point is before the etching endpoint delay detection time;

[0026] The signal intensities before the reference time point are all set as the reference intensity, and each signal intensity after the time point corresponding to the reference intensity is divided by the reference intensity to obtain a normalized curve of the signal intensity change over time.

[0027] Furthermore, an embodiment of the present invention provides a seventh possible implementation of the first aspect, wherein filtering out false endpoints before a preset filtering time in the signal strength versus time curve includes:

[0028] Filter out the false endpoints between the reference time point and the preset filtering time in the normalized signal intensity versus time curve.

[0029] Furthermore, an embodiment of the present invention provides an eighth possible implementation of the first aspect, wherein filtering out false endpoints before a preset filtering time in the signal strength versus time curve includes:

[0030] Filtering out false endpoints before the set etching endpoint delay detection time in the signal intensity versus time curve;

[0031] Filter out false endpoints between the set etching endpoint delay detection time and the preset filtering time.

[0032] Furthermore, an embodiment of the present invention provides a ninth possible implementation of the first aspect, wherein filtering out false endpoints between the set etching endpoint delay detection time and the preset filtering time includes:

[0033] When the signal intensity versus time curve shows an overall upward trend, filtering out the maximum value between the set etching endpoint delay detection time and the preset filtering time in the signal intensity versus time curve;

[0034] When the signal intensity variation with time curve shows an overall downward trend, the minimum value between the set etching endpoint delay detection time and the preset filtering time in the signal intensity variation with time curve is filtered out.

[0035] In a second aspect, an embodiment of the present invention further provides a semiconductor process equipment, comprising: a process chamber and a controller, wherein the controller comprises a processor and a storage device;

[0036] The storage device stores a computer program, which, when executed by the processor, executes the method according to any one of the first aspects.

[0037] An embodiment of the present invention provides an etching endpoint detection method and semiconductor process equipment, the method comprising: collecting an etching progress signal that can reflect the etching process during the etching process; performing denoising processing on the etching progress signal to obtain a signal strength variation curve; filtering out false endpoints before a preset filter time in the signal strength variation curve; wherein the preset filter time is the time point corresponding to when the signal strength rises or falls to a preset strength threshold after a set etching endpoint delay detection time; obtaining a peak or trough after the preset filter time in the signal strength variation curve, and performing extreme value verification on the peak or trough to determine the etching endpoint. The present invention removes radio frequency noise interference by denoising the etching progress signal of the reaction etching process collected during the etching process, and filters out false endpoints before a preset filter time when the signal strength rises or falls to a preset strength threshold after a set etching endpoint delay detection time, thereby filtering out interference signals close to the etching endpoint, thereby improving the accuracy of etching endpoint detection, avoiding unstable etching endpoint detection affecting product key dimensions, and improving the stability of etching endpoint detection.

[0038] Other features and advantages of the embodiments of the present invention will be described in the following description, or some features and advantages can be inferred or determined without doubt from the description, or can be learned by implementing the above-mentioned technologies of the embodiments of the present invention.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1a A schematic diagram showing the morphology change of the etched layer during the etching process is shown;

[0042] Figure 1b shows a graph showing the plasma concentration of reactants and products in the chamber versus etching time;

[0043] Figure 2 A flow chart of an etching endpoint detection method provided by an embodiment of the present invention is shown;

[0044] Figure 3a A graph showing a single 516nm CO signal intensity versus time curve provided by an embodiment of the present invention;

[0045] Figure 3b A graph showing a single 777nm O signal intensity versus time curve provided by an embodiment of the present invention;

[0046] Figure 3c A curve diagram showing a change in signal strength over time provided by an embodiment of the present invention is shown;

[0047] Figure 4a A graph showing a change in signal strength over time before normalization provided by an embodiment of the present invention is shown;

[0048] Figure 4b shows a normalized signal strength versus time curve provided by an embodiment of the present invention;

[0049] Figure 5 An example graph of a normalized signal strength versus time curve provided by an embodiment of the present invention is shown;

[0050] Figure 6 A flow chart of a plasma etching endpoint detection method provided by an embodiment of the present invention is shown;

[0051] Figure 7a An example graph of a signal strength variation curve over time provided by an embodiment of the present invention is shown;

[0052] Figure 7bA schematic diagram showing the standard deviation of the etching endpoint time of each chamber under different etching endpoint detection algorithms provided by an embodiment of the present invention is shown;

[0053] Figure 7c A schematic diagram showing a comparison of etching endpoint times provided by an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0055] At present, in the etching process, a timing mode is usually implemented for each process step, that is, the process step is terminated after a fixed time has passed. For example, see Figure 1a The morphology change diagram of the etched layer during the etching process is shown in FIG. The process etching steps mainly include the main etching, etching end point and over-etching process, see FIG. Figure 1b The plasma concentration of reactants and products in the chamber changes with etching time. As the etching process progresses, when the etching end point reaches the etching stop layer, the morphology of the lower end of the etched material has not been completely etched, and over-etching is required to obtain a vertical morphology. At the etching end point, the film material is about to be completely etched, and the concentration changes of the reactants and products gradually become smaller.

[0056] Related etching endpoint detection technologies usually use a single signal (light intensity signal) to smooth the waveform, filter out unnecessary noise during the delay time to avoid false endpoint detection, and then use the rising and falling thresholds of the detection signal to determine whether they meet the set values ​​as the standard for determining whether the endpoint detection is completed. Figure 1b As shown in the relevant endpoint detection schematic diagram, the concentrations of reactants and products are characterized in real time by the characteristic spectrum emitted by the plasma. The optical signal is collected by the endpoint detection system, and the photoelectric conversion module converts the optical signal into a continuous electrical signal for endpoint detection. The endpoint detection equipment performs calculations on the electrical signal to realize etching endpoint detection.

[0057] However, related etch endpoint detection technologies do not determine the validity of the signals collected for etch endpoint detection before performing etch endpoint detection, which creates the risk of wafer over-etching or under-etching, leading to scrapping, due to low signal reliability. Furthermore, related etch endpoint detection technologies typically use only a single signal band for etch endpoint detection, which cannot effectively cover the differences between the same chamber at different RF time periods and between different chambers, and cannot effectively control signal fluctuations caused by RF reflected power. Furthermore, etch endpoint detection is performed only through the rising and falling thresholds of the original signal, resulting in large fluctuations in the detected etch endpoint time, which cannot meet the critical dimensional stability requirements of key processes (such as core shaft etching in self-aligned multi-patterning technology).

[0058] In order to improve the above problems, an embodiment of the present invention provides an etching endpoint detection method and semiconductor process equipment, and the embodiment of the present invention is described in detail below.

[0059] This embodiment provides an etching endpoint detection method, which can be applied to an etching endpoint detection controller of a semiconductor process equipment. Figure 2 The etching endpoint detection method flow chart shown in FIG. 1 mainly includes the following steps:

[0060] Step S202, collecting an etching progress signal that can reflect the etching process during the etching process;

[0061] The etching progress signal may include one or more etching parameters, and the etching progress signal may include a curve showing changes of the one or more etching parameters over time.

[0062] In a specific embodiment, the above-mentioned etching progress signal includes at least two etching parameters, and the etching parameters include a chamber light intensity signal and / or chamber equipment hardware parameters. The equipment hardware parameters may include chamber valve opening, plasma self-bias voltage, RF reflection power and matching capacitor position, etc., which can reflect the etching process. The chamber valve may, for example, include a swing valve, a vertical valve, a butterfly valve, etc.

[0063] In a specific embodiment, a curve of signal intensity changing with time can be obtained, for example, see Figure 3a The single 516nm CO signal intensity curve shown as a function of time and Figure 3b The single 777nm O signal intensity variation curve shown in FIG. 1 includes a 516nm CO signal intensity variation curve and a 777nm O signal intensity variation curve. Figure 3a and Figure 3b As can be seen from the figure, due to chamber fluctuations, the signal intensities of the single signals 516nm CO and 777nm O are both disturbed. Figure 3a There are multiple false signals around 25s in the image, which may lead to false detection of the etching endpoint when the falling threshold is used to detect the etching endpoint. Figure 3b There is also U-shaped signal noise in 20s to 25s.

[0064] Step S204, performing noise removal processing on the etching progress signal to obtain a curve of signal intensity variation over time;

[0065] A denoising algorithm is used to denoise the collected etching progress signal to reduce noise interference. The denoised curve is a curve showing the change in signal strength over time. If the etching progress signal is not a single signal, a composite operation can be used for denoising. The composite operation includes but is not limited to one or more operations such as addition, subtraction, multiplication, and division.

[0066] In one embodiment, when the etching progress signal includes two etching parameters, the compound operation may be one of addition, subtraction, multiplication, and division, such as using addition or multiplication operations for two etching parameter curves with the same change trend, and using subtraction or division operations for two etching parameter curves with different change trends.

[0067] The above-mentioned variation trend is the variation trend of the etching parameter curve after it becomes stable. For example, Figure 3a The 516nm CO signal intensity curve changes with time and tends to be stable at about 10-15s. After stabilization, the curve shows a falling edge, that is, Figure 3a The 516nm CO signal intensity curve shows a downward trend over time. Figure 3b The 777nm O signal intensity curve changes with time and tends to be stable at about 10-15s. After stabilization, the curve shows a rising edge, that is, Figure 3b The curve of 777nmO signal intensity changing with time shows an upward trend. Figure 3a The curve of 516nm CO signal intensity changing with time Figure 3b The change trend of the 777nm O signal intensity versus time curve is different. For the two etching parameter curves with different change trends, subtraction or division operation is used. Figure 3a and Figure 3b Subtracting or dividing the curves in the image can remove noise interference.

[0068] For example, Figure 3a The curve in the Figure 3b The curve in the figure shows the curve of the signal strength without noise interference changing with time. Figure 3c As shown, from Figure 3c It can be seen that the signal strength after the composite operation will not have the problem of falsely grasping the etching end point caused by radio frequency disturbance.

[0069] When the above-mentioned etching progress signal includes three etching parameters, the above-mentioned composite operation can be one or two of addition, subtraction, multiplication and division, such as using addition or multiplication operations for two etching parameter curves with the same change trend, and using subtraction or division operations for two etching parameter curves with different change trends.

[0070] For example, assuming that the acquired etching progress signal includes a first etching progress signal curve and a second etching progress signal curve whose changing trends are upward, and a third etching progress signal curve whose changing trends are downward, the first etching progress signal curve and the second etching progress signal curve whose changing trends are both upward can be added or multiplied to obtain the etching progress signal curve after the addition or multiplication operation, and then the etching progress signal curve after the addition or multiplication operation is subtracted or divided from the third etching progress signal curve to remove noise interference.

[0071] In practical applications, when the etching progress signal is not a single signal, it can be filtered after denoising. The filtering methods include but are not limited to finite impulse response (FIR), infinite impulse response (IIR) and low-pass filters (LPF) of different orders.

[0072] Step S206, filtering out false endpoints before a preset filtering time in the signal strength versus time curve;

[0073] Among them, the above-mentioned preset filtering time is the time point corresponding to when the signal strength rises or falls to the preset intensity threshold after the set etching endpoint delay detection time; the false endpoint before the preset filtering time includes the false endpoint before the set etching endpoint delay detection time and the false endpoint between the set etching endpoint delay detection time and the preset filtering time. Since the etching process usually takes a certain amount of time, in order to avoid more interference in endpoint detection and a large amount of calculation for etching endpoint detection, the above-mentioned set etching endpoint delay detection time can be set according to the historical total etching time. The etching endpoint will not appear before the set etching endpoint delay detection time, and the etching endpoint detection will be performed after the set etching endpoint delay detection time. By filtering out all the false endpoints before the preset filtering time, the interference in etching endpoint detection can be removed, thereby improving the efficiency of etching endpoint detection.

[0074] The above-mentioned preset filtering time is the time point corresponding to the time when the signal strength rises or falls to the preset intensity threshold after the set etching endpoint delay detection time; the above-mentioned preset intensity threshold is greater than the signal intensity corresponding to the preset filtering time and is less than the signal intensity of the etching endpoint. The preset intensity threshold can be a fixed threshold (the fixed threshold can be determined by multiple detections of the signal intensity of the etching endpoint), or it can be a preset multiple of the signal intensity corresponding to the preset filtering time.

[0075] For example, Figure 5 As shown, Figure 5 An example diagram of signal intensity variation over time is shown. In this example, the preset filtering time is t2, which is the time point corresponding to the signal intensity rising or falling to the preset intensity threshold after the set etching endpoint delay detection time. The preset intensity threshold is a fixed threshold obtained from multiple etching endpoint detection experiments. Figure 5 In the etching process example shown, there are a total of 6 peak positions that meet the extreme value points. When the preset filtering time is not set, the probability of triggering a false alarm is relatively high. By filtering out all the maximum points before the preset filtering time t2 as false end points, the probability of false alarm can be effectively reduced.

[0076] In one embodiment, Figure 5 As shown, the extreme point between the etching start point and the set etching endpoint delay detection time t1 in the signal intensity variation curve can be first filtered out as a false endpoint, and then the extreme point between the set etching endpoint delay detection time t1 and the preset filtering time t2 can be filtered out as a false endpoint to remove the interference of the false endpoint.

[0077] Step S208 , obtaining a peak or a trough after a preset filtering time in the signal intensity versus time curve, and performing extreme value verification on the peak or the trough to determine an etching endpoint.

[0078] Obtain the peak or trough after the preset filtering time to determine the minimum or maximum value after the preset filtering time, perform extreme value verification on the peak or trough to determine whether the minimum or maximum value is the etching end point, and generate a process termination signal after verifying that the etching end point is correct, so that the semiconductor process equipment controls the process step to stop.

[0079] The above-mentioned etching endpoint detection method provided in this embodiment can remove radio frequency noise interference by denoising the etching progress signal of the reaction etching process collected during the etching process. After the set etching endpoint delay detection time, the false endpoints before the preset filtering time when the signal strength rises or falls to the preset intensity threshold are filtered out to filter out interference signals close to the etching endpoint, thereby improving the etching endpoint detection efficiency and detection accuracy, avoiding the instability of the etching endpoint detection affecting the key dimensions of the product, and improving the stability of the etching endpoint detection.

[0080] In one embodiment, this embodiment provides a specific implementation method for performing noise removal processing on an etching progress signal to obtain a curve of signal strength changing over time:

[0081] Based on the change trend of each etching parameter variation curve after the set etching endpoint delay detection time, the time variation curve of each etching parameter is calculated to eliminate system noise caused by hardware problems.

[0082] The aforementioned operations may be composite operations, such as addition, subtraction, multiplication, and division. By using the changing trend after the set etching endpoint delay detection time as the changing trend of the etching parameter variation over time curve, and performing corresponding operations based on the changing trend of the etching parameter variation over time curve, interference of radio frequency disturbances on the signal can be effectively reduced.

[0083] In a specific embodiment, the change trend includes an upward trend and a downward trend, and curves with the same change trend are added or multiplied to obtain a first curve and a second curve, respectively, wherein the change trends of the first curve and the second curve are different;

[0084] A subtraction or division operation is performed on the first curve and the second curve to obtain a curve of signal intensity variation over time.

[0085] For example, it is assumed that among the collected etching parameters, the first signal and the second signal are curves with an upward trend, and the third signal and the fourth signal are curves with a downward trend. The curve of the first signal of the rising type with the same change trend is added or multiplied with the curve of the second signal to obtain a first curve, and the first curve is still a curve with an upward trend. The curve of the third signal of the falling type with the same change trend is added or multiplied with the curve of the fourth signal to obtain a second curve, and the second curve is still a curve with a downward trend. The first curve and the second curve with different change trends are subtracted or divided to obtain a curve of signal strength changing with time, thereby offsetting signal noise.

[0086] The above-mentioned etching parameters can be the chamber light intensity signal and the chamber equipment hardware parameters. Since the equipment is prone to hardware problems such as RF system fluctuations, special interlayers in the growth process of the product incoming film layer, and poor contact of the Optical Emission Spectroscopy (OES) system, it will cause system noise to interfere with all signals at the same time. Under system interference, the change directions of different signals are consistent. Therefore, during signal processing, multiple signals are selected for processing at the same time, and the signals are classified according to rising and falling trends. The curves with the same change trend are added or multiplied, and the curves with different change trends are subtracted or divided. For example, after adding or multiplying the curve with an upward trend, subtracting or dividing it from the curve with a downward trend can offset the noise, which can effectively reduce the interference of different chambers, RF hours and RF disturbances on key signals.

[0087] In one embodiment, after the above step S204 and before step S206, the method provided by this embodiment further includes: performing a normalization operation on the curve of signal strength variation over time.

[0088] The signal intensity curve is normalized based on the normalization algorithm. In the large-scale industrial production process, it is necessary to use a single endpoint detection algorithm to cover all products as much as possible. Different products have different light intensities during the etching process due to differences in transmittance. After introducing the normalization algorithm, the fluctuation range of the signal intensity can be reduced to improve the stability of the etching endpoint detection.

[0089] In a specific embodiment, the signal intensity after stabilization in the signal intensity versus time curve is used as the reference intensity, and the time point corresponding to the reference intensity is recorded as the reference time point; wherein the reference time point is before the etching endpoint delay detection time;

[0090] The signal intensity before the reference time point is set as the reference intensity. The signal intensity after the reference intensity is divided by the reference intensity to obtain a normalized signal intensity-over-time curve. The ratio of each signal intensity to the reference intensity can also be multiplied by the amplification factor to amplify the signal by a certain multiple.

[0091] For example, see Figure 4a The graph of signal intensity variation over time before normalization is shown. Before the signal intensity is normalized, the difference in light intensity peak values ​​of different products using the same process program in the same chamber and at the same RF hours is 100%. It is impossible to use a single algorithm to cover the etching endpoint detection of all products. The signal intensity variation over time curve is normalized, and the signal intensity after stabilization in the signal intensity variation over time curve is used as the reference intensity, that is, the intensity after the signal intensity stabilizes at 45s to 50s is used as the reference intensity, and the signal intensity before the reference time point of 45s to 50s is set as the reference intensity (also called the baseline signal intensity), that is, the signal before 45s is eliminated, and the signal intensity after 50s corresponding to the reference intensity is divided by the reference intensity in real time, see FIG. Figure 4b The normalized signal intensity versus time curve shown in the figure shows that the normalized signal intensity = (real signal intensity / reference intensity) * 1000. After normalizing the signal intensity versus time curve, the fluctuation amplitude of the signal intensity is reduced to 8%. The etching detection method can be applied to the etching of different wafer products.

[0092] In the process of endpoint detection, there is often a noise signal before the real etching endpoint signal appears. If it is not processed, it is easy to cause the signal to be miscaptured and lead to product scrapping. The relevant etching endpoint detection algorithm usually controls a fixed threshold to filter out the noise and then perform signal detection. Figure 4a In the example shown, the signal shapes of the three wafer products are similar (corresponding to Figure 4a The three peaks of different heights are listed in descending order as Product 1, Product 2, and Product 3. The true signal strength of Product 3 is lower than the noise intensity of Product 1, making it impossible to filter out the noise using a fixed threshold to prevent false endpoint signal capture. See Table 1 below for a comparison of the signal strengths of each product before and after normalization:

[0093] Table 1 Comparison of signal strength of each product before and after normalization

[0094]

[0095] As can be seen from Table 1 above, after signal normalization, the signal strength differences between product 1, product 2, and product 3 are reduced. If the signal strength is set to be greater than 2.5 ( Figure 4b The normalized signal in the etching process is amplified 1000 times, so the endpoint signal is detected at the position corresponding to 2500, which can effectively avoid the influence of false signals on the capture of the etching endpoint signal.

[0096] In one embodiment, this embodiment provides two implementations for filtering out false endpoints before a preset filtering time in the signal strength versus time curve, which can be specifically implemented with reference to the following implementations 1 and 2:

[0097] Embodiment 1: When the above-mentioned signal strength versus time curve is a normalized curve, the false endpoints between the reference time point and the preset filtering time in the normalized signal strength versus time curve are filtered out.

[0098] like Figure 5 As shown, Figure 5 The dotted line portion after the start of etching is the curve segment after normalization operation. The reference time point t0 (i.e. Figure 5 Before the time point corresponding to the intersection of the dashed and solid lines (the middle dashed line), the line is straight and there are no false endpoints. Therefore, only the false endpoints between the reference time point t0 and the preset filter time t2 need to be filtered out. In one embodiment, the false endpoints between the reference time point t0 and the preset etching endpoint delay detection time t1 can be filtered out first; then, the false endpoints between the preset etching endpoint delay detection time t1 and the preset filter time t2 can be filtered out.

[0099] like Figure 5As shown in the figure, there are six peak positions that meet the extreme value point. If the etching endpoint delay detection time is not set for filtering, a false alarm will be triggered. The reference time point is t0, the set etching endpoint delay detection time is t1, and there are five extreme value points between the reference time point t0 and the preset filter time t2. The four maximum values ​​between the reference time point t0 and the set etching endpoint delay detection time t1 are eliminated, that is, the etching endpoint detection will not be performed before the etching endpoint delay detection time t1, thereby filtering out the four false etching endpoints before the etching endpoint delay detection time. The one maximum value between the set etching endpoint delay detection time t1 and the preset filter time t2 is then eliminated, that is, the etching endpoint will not exist before the preset filter time t2.

[0100] Implementation method 2: When the above-mentioned signal strength versus time curve is a curve that has not been normalized, the false endpoints before the set etching endpoint delay detection time in the signal strength versus time curve are filtered out; the false endpoints between the set etching endpoint delay detection time and the preset filtering time are filtered out.

[0101] The above-mentioned signal strength variation curve over time may refer to the variation trend of the signal strength after it becomes stable. For example, Figure 5 As shown in FIG, the signal intensity fluctuates greatly before t1, tends to be stable around t1, and gradually increases after t1, that is, the intensity variation curve over time shows an overall upward trend.

[0102] When the signal intensity versus time curve shows an overall upward trend, the maximum value before the set etching endpoint delay detection time is filtered out;

[0103] When the signal intensity versus time curve shows an overall downward trend, the minimum value before the set etching endpoint delay detection time is filtered out.

[0104] The aforementioned delayed etching endpoint detection time is the period immediately before etching begins, and the true etching endpoint will not occur within this delayed etching endpoint detection time. Since the etching endpoint will not occur before the delayed etching endpoint detection time, when the overall signal strength vs. time curve shows an upward trend, the false endpoint before the delayed etching endpoint detection time reaches a maximum value. When the overall signal strength vs. time curve shows a downward trend, the false endpoint before the delayed etching endpoint detection time reaches a minimum value. Eliminating the minimum or maximum value before the delayed etching endpoint detection time can quickly eliminate false endpoints before the delayed etching endpoint detection time.

[0105] In one embodiment, this embodiment provides a specific implementation method for filtering out false endpoints between a set etching endpoint delay detection time and a preset filtering time:

[0106] When the signal intensity versus time curve shows an overall upward trend, the maximum value between the set etching endpoint delay detection time and the preset filter time in the signal intensity versus time curve is filtered out;

[0107] When the signal intensity versus time curve shows an overall downward trend, the minimum value between the etching endpoint delay detection time set in the signal intensity versus time curve and the preset filtering time is filtered out.

[0108] like Figure 5 As shown, a preset filtering time t2 is set to remove the maximum or minimum value (i.e., the false etching end point) between the etching endpoint delay detection time t1 and the preset filtering time t2, so as to further remove the false etching end point that is closer to the etching end point, thereby filtering out the interference signal near the etching end point.

[0109] The preset filtering time may be a time corresponding to a set signal strength threshold, and the set signal strength threshold may be a fixed threshold, such as, Figure 4b The signal strength range of the real etching end point is 2800~3700, and the interference signal strength is all below 2500. The above-mentioned set signal strength threshold can be 2500, and the preset filtering time is the time corresponding to 2500. The false etching end points below 2500 are filtered out, that is, the etching end point detection is started only when the signal strength is greater than 2500. The above-mentioned set signal strength threshold can be a value between the signal strength at the etching end point delay detection time and the signal strength at the real etching end point.

[0110] The signal strength threshold can also be determined based on the signal strength at the etching endpoint delay detection time t1. The signal strength at the etching endpoint delay detection time t1 is used as a reference point, and the signal strength at the point where the signal strength rises by a preset amplitude is used as the signal strength threshold. For example, etching endpoint detection is not initiated until the signal strength rises by more than 250% relative to the signal strength at the etching endpoint delay detection time t1. By setting secondary filtering, noise near the etching endpoint can be effectively filtered out.

[0111] In one embodiment, this embodiment provides a specific implementation method for obtaining a peak or trough after a preset filtering time in a curve of signal intensity variation over time, and performing extreme value verification on the peak or trough to determine the etching endpoint:

[0112] After the preset filtering time, the derivative of the signal intensity is calculated, and the target time when the signal intensity takes the minimum or maximum value is determined based on the derivative; starting from the target time, it is verified whether the signal intensity continues to rise or continue to fall for a preset period of time. If so, the extreme value verification is passed; if the extreme value verification is continuously passed within the preset period of time, the target time is determined to be the etching end point, and a process termination signal is generated.

[0113] When the signal intensity versus time curve shows an upward trend, the etching endpoint is at its maximum value. When the signal intensity versus time curve shows a downward trend, the etching endpoint is at its minimum value. The peaks and troughs are defined as the extreme points where the slope is equal to 0. There is only one peak and trough near the etching endpoint, and the slope determines the location of the peak and trough.

[0114] When the signal strength reaches its maximum value, the system verifies whether the signal strength continues to decrease for a preset period of time starting from the target time. If the signal strength continues to decrease for a preset period of time after the target time corresponding to the maximum value, the extreme value verification passes, and the target time is determined to be the etching endpoint. When the verification passes, a process termination signal is generated. If the signal strength does not continue to decrease within the verification time, the signal strength at the target time is a false etching endpoint, and the etching endpoint is searched again.

[0115] Correspondingly, when the signal strength reaches its minimum value, the signal strength is verified to see if it continues to rise for a preset time period starting from the target time. If the signal strength continues to rise for a preset time period after the target time corresponding to the maximum value, the extreme value verification is passed, and the target time is determined to be the etching endpoint. When the verification passes, a process termination signal is generated. The above-mentioned preset time period can be determined based on the required etching time, for example, the value range can be 1 to 3 seconds, preferably 2 seconds.

[0116] For example, Figure 5 As shown, after the preset filtering time t2, the derivative of the signal strength is calculated, and the target time when the signal strength takes the maximum value is determined to be t3 based on the derivative. Starting from the target time t3, the preset time length (t4-t3) is continued to verify whether the signal strength continues to decrease. The signal strength continues to decrease during the time period from the target time t3 to t4, and the extreme value verification continues to pass. The target time t3 is determined to be the true etching end point. After the t4 time verification is passed, the process is triggered to stop.

[0117] The inventors have found that abnormal light intensity is prone to occur in plasma etching. The abnormal light intensity can be divided into two categories: one is low light intensity, which is caused by the incorrect installation of the chamber optical fiber, or false ignition in the chamber due to extreme process conditions, that is, the plasma is not ignited when the RF output and reflected power are normal, or the presence of metal contamination in the chamber leads to a decrease in the degree of ion dissociation, both of which can easily lead to a low detected light intensity signal; the other is excessive light intensity, which is caused by the replacement of accessories in the etching endpoint detection system after preventive maintenance in the chamber, or the presence of metal contamination in the chamber leads to an increase in the plasma dissociation degree, both of which can easily lead to a detected light intensity signal that is too high.

[0118] The related etching endpoint detection technology does not judge the validity of the collected etching parameters before etching endpoint detection. There is a risk that the wafer may be scrapped due to over-etching or under-etching due to the inability to judge due to low signal reliability. In order to reduce the risk of wafer scrapping, before the above step S204, the method provided in this embodiment further includes:

[0119] The validity of the etching progress signal is verified; when the etching progress signal is verified to be valid, a compound operation is performed on the successfully verified etching progress signal; when the etching progress signal is verified to be abnormal, an equipment alarm is issued to stop the etching process.

[0120] In a specific embodiment, it is determined whether the strength of the etching progress signal is within a valid value range. If so, it is determined that the etching progress signal verification is successful.

[0121] The validity of the etching progress signal involved in the etching endpoint detection is verified, and the fluctuation range of the normal signal strength of each etching parameter after the plasma ignition is stable is obtained. It is judged whether each etching parameter in the etching progress signal is within its corresponding valid value range. If each etching parameter is within the corresponding valid value range, it is determined that the etching progress signal verification is successful. If any etching parameter exceeds its corresponding valid value range, an equipment alarm is issued and the etching process is stopped.

[0122] For example, the effective value range of the light intensity signal is the median light intensity ±3 to 30 times the standard deviation of the light intensity signal. When it exceeds the corresponding effective value range, the equipment alarm is triggered and the process is stopped to avoid over-etching related to signal abnormalities and causing wafer scrapping.

[0123] The etching endpoint detection method provided in this embodiment can effectively improve the problem of product scrapping during the integrated circuit production process due to abnormalities in the machine and the failure of the endpoint detection system to identify the abnormality in advance through the light intensity signal, resulting in the etching process being performed under abnormal equipment boundary conditions; it can also improve the problem of unstable endpoint detection time caused by machine maintenance or increased use of parts, which in turn affects the key dimensions of the product, and improve the problem of false triggering of endpoint detection due to differences between chambers, resulting in reduced equipment downtime and utilization.

[0124] Based on the above embodiment, this embodiment provides an example of applying the above etching endpoint detection method. Figure 6 The plasma etching endpoint detection method flow chart shown in the figure can be specifically performed by referring to the following steps:

[0125] Step S601, collecting at least two etching parameters during plasma etching, determining whether an etching progress signal is normal, and if abnormal, issuing an alarm to trigger process stop;

[0126] Step S602, performing a composite operation on a plurality of etching parameters to obtain a signal intensity variation curve over time, and performing a denoising process on the composite operation signal intensity variation curve over time;

[0127] Step S603, performing normalization operation on the curve of signal intensity variation over time;

[0128] Step S604, filtering out the false endpoints before the etching endpoint delay detection time in the signal intensity versus time curve;

[0129] Step S605, filtering out false endpoints between the etching endpoint delay detection time and the preset filtering time;

[0130] Step S606 , obtaining a peak or a trough after a preset filtering time, and performing extreme value verification on the peak or the trough to determine an etching end point.

[0131] In order to verify the stability of the etching endpoint detection algorithm provided in the above embodiment, this embodiment provides a method for detecting the etching endpoint of a wafer based on the above etching endpoint detection algorithm. Figure 7a The signal intensity versus time curve shown in the figure is used to detect the valley of the etching end point, and the etching end point detection method is used to detect the falling threshold value. Figure 7a The signal intensity versus time curve shown in the figure is used to perform an etching endpoint detection experiment. After detecting the etching endpoint, the standard deviation of the etching endpoint time is calculated. The standard deviation of the etching endpoint time is used to characterize the stability of the algorithm. The smaller the standard deviation value, the better the stability.

[0132] See for example Figure 7b The figure shows the standard deviation of the etching endpoint time of each chamber under different etching endpoint detection algorithms. The standard deviation CIP5 of the etching endpoint time detected by the etching endpoint detection method provided by the present invention is represented by a circle. The standard deviation POR of the etching endpoint time detected by the related etching endpoint detection method based on the detection of the falling threshold is represented by a cross. PM1 and PM 2 represent the chamber codes. 319 and 317 are the numbers of wafers in the chamber that participate in the calculation of the standard deviation of the etching endpoint time. Cycle1 and Cycle2 represent different cycles of the chamber operation, which are used to compare the divergence of the endpoint time method of the chamber under different PM cycles. Figure 7bIt can be seen that the standard deviation of the etching endpoint time detected by the etching endpoint detection method provided by the present invention fluctuates by 0.05~0.13, and the standard deviation of the etching endpoint time detected by the related etching endpoint detection method based on the detection falling threshold is 0.15~0.35. The standard deviation of the etching endpoint time detected by the etching endpoint detection method provided by the present invention is all below 0.15, which is lower than the standard deviation of the etching endpoint time detected by the related etching endpoint detection method of 0.15~0.35. The etching endpoint detection method provided by the present invention improves the stability of mass production of wafer products. For the etching of the 25nm DARM process core shaft, the fluctuation of the product can be controlled within ±1nm.

[0133] For example, this embodiment provides an experiment of etching in AA Cut process in 25nm DARM using the etching endpoint detection method and related etching endpoint detection methods provided by the present invention, see Figure 7c The etching endpoint time comparison diagram shown in the figure is as follows: Figure 7c The upper part is the etching endpoint time data obtained by performing etching endpoint detection on the wafer in the same chamber using the relevant etching endpoint detection method. Figure 7c The lower half of the figure shows the etch endpoint time data obtained by using the etch endpoint detection method provided by the present invention on wafers in the same chamber. While the etch endpoint time detected by related etch endpoint detection methods fluctuates significantly, the etch endpoint time detected by the etch endpoint detection method provided by the present invention can be controlled to fluctuate within ±0.5s. The etch endpoint detection method provided by the present invention solves the problem of falsely detecting the etch endpoint and addresses the problem of reduced equipment utilization due to frequent downtime.

[0134] Corresponding to the etching endpoint detection method provided in the above embodiment, an embodiment of the present invention provides a semiconductor process equipment, including: a process chamber and a controller, the controller including a processor and a storage device; a computer program is stored on the storage device, and when the computer program is run by the processor, it executes the etching endpoint detection method provided in the above embodiment.

[0135] An embodiment of the present invention provides a computer-readable medium, wherein the computer-readable medium stores computer-executable instructions. When the computer-executable instructions are called and executed by a processor, the computer-executable instructions prompt the processor to implement the method described in the above embodiment.

[0136] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working process of the system described above can refer to the corresponding process in the aforementioned embodiment and will not be repeated here.

[0137] In addition, in the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0138] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0139] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0140] Finally, it should be noted that the above-described embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed by the present invention, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for detecting an etching endpoint, characterized in that: include: Collecting etching progress signals that can reflect the etching process during the etching process; Performing noise removal on the etching progress signal to obtain a curve of signal intensity variation over time; Filter out the false endpoints before a preset filtering time in the signal intensity versus time curve; wherein the preset filtering time is the time point corresponding to when the signal intensity rises or falls to a preset intensity threshold after the set etching endpoint delay detection time; A peak or a trough after the preset filtering time in the signal intensity variation curve is obtained, and extreme value verification is performed on the peak or the trough to determine the etching endpoint.

2. The method according to claim 1, characterized in that The etching progress signal includes at least two etching parameters, wherein the etching parameters include a chamber light intensity signal and / or chamber equipment hardware parameters. The denoising process is performed on the etching progress signal to obtain a curve of signal intensity variation over time, including: Based on the change trend of each of the etching parameter change curves over time after the set etching endpoint delay detection time, each of the etching parameter change curves over time is calculated to eliminate system noise caused by hardware problems.

3. The method according to claim 1, characterized in that The change trend includes an upward trend and a downward trend, and the calculation of the time-varying curves of each etching parameter includes: Performing an addition or multiplication operation on the curves with the same change trend to obtain a first curve and a second curve respectively, wherein the change trends of the first curve and the second curve are different; A subtraction or division operation is performed on the first curve and the second curve to obtain the curve of signal intensity variation over time.

4. The method according to claim 1, wherein The obtaining of a peak or a trough after the preset filtering time in the signal intensity versus time curve, and performing extreme value verification on the peak or the trough to determine the etching endpoint, includes: Verify whether the signal strength continues to rise or fall for a preset period of time starting from the target time, if so, the extreme value verification is passed; If the extreme value verification continues to pass within the preset time period, the target time is determined to be the etching endpoint, and a process termination signal is generated.

5. The method according to claim 1, wherein Before the step of performing noise removal processing on the etching progress signal, the method further includes: Verifying the validity of the etching progress signal; When the etching progress signal is verified to be valid, performing the noise removal process on the successfully verified etching progress signal; When the etching progress signal is verified to be abnormal, an equipment alarm is issued to stop the etching process.

6. The method according to any one of claims 1 to 5, characterized in that Before the step of filtering out the false endpoints before the preset filtering time in the signal intensity versus time curve, the method further includes: A normalization operation is performed on the signal intensity variation curve over time.

7. The method according to claim 6, characterized in that The normalizing operation of the signal intensity versus time curve includes: The signal intensity after stabilization in the signal intensity versus time curve is used as a reference intensity, and the time point corresponding to the reference intensity is recorded as a reference time point; wherein the reference time point is before the etching endpoint delay detection time; The signal intensities before the reference time point are all set as the reference intensity, and each signal intensity after the time point corresponding to the reference intensity is divided by the reference intensity to obtain a normalized curve of the signal intensity change over time.

8. The method according to claim 7, characterized in that The filtering out of false endpoints before a preset filtering time in the signal intensity versus time curve includes: Filter out the false endpoints between the reference time point and the preset filtering time in the normalized signal intensity versus time curve.

9. The method according to claim 1, characterized in that The filtering out of false endpoints before a preset filtering time in the signal intensity versus time curve includes: Filtering out false endpoints before the set etching endpoint delay detection time in the signal intensity versus time curve; Filter out false endpoints between the set etching endpoint delay detection time and the preset filtering time.

10. The method according to claim 9, characterized in that The filtering out of false endpoints between the set etching endpoint delay detection time and the preset filtering time includes: When the signal intensity versus time curve shows an overall upward trend, filtering out the maximum value between the set etching endpoint delay detection time and the preset filtering time in the signal intensity versus time curve; When the signal intensity variation with time curve shows an overall downward trend, the minimum value between the set etching endpoint delay detection time and the preset filtering time in the signal intensity variation with time curve is filtered out.

11. A semiconductor process equipment, characterized in that: include: a process chamber and a controller, wherein the controller includes a processor and a storage device; The storage device stores a computer program, which, when executed by the processor, executes the method according to any one of claims 1 to 10.

Images