Method for calibrating a photoelectron spectrometer device

Abstract

The application discloses a calibration method of photoelectron spectroscopy equipment, and relates to the field of semiconductors. The calibration method comprises the following steps: performing first etching on a thin film sample; performing X-ray bombardment on the etched thin film sample, and collecting a spectrum; obtaining an etching thickness according to a current thickness of the etched thin film sample and an initial thickness of the thin film sample before etching; obtaining a relationship between element content and etching depth of the thin film sample according to the etching thickness and the spectrum, so as to determine a first etching rate; performing second etching on the thin film sample with the determined first etching rate under the same etching condition, and obtaining a second etching rate; when the first etching rate is the same as the second etching rate, it is determined that the etching of the photoelectron spectroscopy equipment is stable, and the first etching rate or the second etching rate is determined as a reference etching rate; and when the first etching rate is different from the second etching rate, the second etching rate is determined as the reference etching rate. The application can solve the problems of poor etching rate stability and poor accuracy of an X-ray photoelectron spectrometer.

Description

Technical Field

[0001] The present application belongs to the technical field of semiconductors, and specifically relates to a calibration method for photoelectron spectroscopy equipment. Background Art

[0002] X-ray photoelectron spectroscopy (XPS) is a non-destructive measurement technique that detects surface information using a beam of photons incident on a sample at a depth of 3-10 nm. The sample's layered structure, due to factors such as coatings, oxidation, and passivation, can lead to differences in its chemical state across depth.

[0003] However, if conventional XPS analysis is to meet the requirements of obtaining sample elemental and chemical state information, it is necessary to physically peel the sample surface in combination with ion etching, and then perform XPS testing and spectrum acquisition by controlling the appropriate sputtering intensity and sputtering time.

[0004] However, due to the large differences in material properties, if the etching rate is set according to the instrument reference value, the actual etching rate may differ significantly from the instrument reference value. This will cause the depth obtained from the etching analysis of the material surface to deviate significantly from the actual situation, affecting the etching rate and accuracy of the X-ray photoelectron spectrometer. Summary of the Invention

[0005] The purpose of the embodiments of the present application is to provide a calibration method for a photoelectron spectrometer, which can at least solve the problems of unstable etching rate and poor accuracy of an X-ray photoelectron spectrometer.

[0006] In order to solve the above technical problems, this application is implemented as follows:

[0007] The present invention provides a method for calibrating a photoelectron spectroscopy device, the method comprising:

[0008] Perform the first etching on the thin film sample;

[0009] Bombarding the etched thin film sample with X-rays and collecting a spectrum;

[0010] Obtaining an etching thickness according to the current thickness of the thin film sample after etching and the initial thickness of the thin film sample before etching;

[0011] Obtaining a relationship between the element content of the thin film sample and the etching depth according to the etching thickness and the spectrum to determine a first etching rate;

[0012] Etching the thin film sample for determining the first etching rate for a second time using the same etching conditions to obtain a second etching rate;

[0013] When the first etching rate is the same as the second etching rate, the etching of the photoelectron spectroscopy device is determined to be stable, and the first etching rate or the second etching rate is determined as the reference etching rate; when the first etching rate is different from the second etching rate, the second etching rate is determined as the reference etching rate.

[0014] In the embodiment of the present application, a first etching rate is determined by analyzing the etching thickness of a thin film sample and the spectrum after X-ray bombardment of the thin film sample. A second etching rate is obtained by performing the same etching conditions a second time. Thus, a baseline etching rate can be determined based on whether the two etching rates are the same. Based on this approach, the embodiment of the present application can calibrate the X-ray photoelectron spectroscopy etching rate of a photoelectron spectroscopy device, which is beneficial for improving the accuracy of the etching rate, effectively avoiding production errors caused by large testing errors in the X-ray photoelectron spectroscopy device, and ensuring production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A flow chart of a calibration method for a photoelectron spectroscopy device disclosed in an embodiment of the present application;

[0016] Figure 2 This is a characterization diagram of the thin film sample layer structure before etching disclosed in the examples of this application;

[0017] Figure 3 This is a characterization diagram of the thin film sample layer structure after etching disclosed in the examples of this application;

[0018] Figure 4 A schematic diagram of the first etching rate of the thin film sample disclosed in the examples of this application;

[0019] Figure 5 This is a schematic diagram of the second etching rate of the thin film sample disclosed in the examples of this application. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0021] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0022] The embodiments of the present application are described in detail below through specific embodiments and their application scenarios in conjunction with the accompanying drawings.

[0023] Related Art 1 proposes a method for detecting the stability of an X-ray photoelectron spectrometer, comprising:

[0024] Obtaining a first upper limit value and a first lower limit value of an oxygen-nitrogen content ratio corresponding to a calibration piece having a silicon oxynitride film formed on a surface thereof, wherein the oxygen-nitrogen content ratio refers to a ratio of a sum of an oxygen content and a nitrogen content corresponding to the calibration piece to a thickness of the silicon oxynitride film;

[0025] Measuring the calibration piece using a photoelectron spectrometer to obtain a first test value of the ratio of oxygen and nitrogen contents;

[0026] When the first test value is between the first upper limit value and the first lower limit value, the nitrogen content value of the process monitoring piece obtained using the X-ray photoelectron spectrometer is within the normal fluctuation range. It is considered that the photoelectron spectrometer can accurately test the nitrogen content of the process monitoring piece, so that it can be determined that the photoelectron spectrometer is in a stable state, and the interference caused by the further oxidation of the silicon oxynitride film of the calibration piece can be eliminated, thereby avoiding production errors caused by abnormal X-ray photoelectron spectrometer testing and reducing production costs.

[0027] However, the above method is only applicable to the case where the thickness of the silicon oxynitride film is less than 10nm.

[0028] Related technology 2 discloses a method for measuring the etching rate of a thin film layer, which specifically includes the following steps:

[0029] One or more coating layers are attached to a support layer substrate of known cost to form a thin film;

[0030] Accurately obtain the thickness value and characteristic elements of each coating;

[0031] Obtain the composition and chemical state information of the surface elements;

[0032] Clean and etch the film;

[0033] Record etching time, area, pattern and energy;

[0034] The functional relationship between the etching rate of the corresponding layer of the film by the argon ion sputtering source of the X-ray photoelectron spectrometer is established.

[0035] Based on the above steps, the second related technology mainly uses an argon ion beam to bombard the surface of the thin film layer. Then, through X-ray photoelectron spectroscopy (XPS) and functional relationship calculation, the elemental composition and chemical state information at a specified depth in the thin film layer can be obtained, and a functional relationship between the etching rate of the X-ray photoelectron spectrometer argon ion sputtering source and the corresponding coating of the thin film can be established.

[0036] However, the above method is only for film thickness calculation and does not involve the stability judgment of the argon ion gun of the X-ray photoelectron spectrometer.

[0037] Related Art 3 discloses the use of combined XPS and XRF techniques to determine the thickness and composition of silicon germanium. It specifically describes a system and approach for determining the thickness and composition of silicon germanium using combined XPS and XRF techniques. In one embodiment, the method for characterizing a silicon germanium thin film includes generating an X-ray beam, positioning a sample in the path of the X-ray beam, collecting an X-ray photoelectron spectroscopy (XPS) signal generated by bombarding the sample with the X-ray beam, and also collecting an X-ray fluorescence (XRF) signal generated by bombarding the sample with the X-ray beam, and determining at least one of the thickness and composition of the silicon germanium from the XRF signal and / or the XPS signal.

[0038] However, the above method only involves the determination of the thickness and composition of silicon germanium, and does not involve the determination of the stability of the argon ion gun of the XPS equipment.

[0039] Based on the above situation, the embodiment of the present application discloses a calibration method for a photoelectron spectroscopy device, referring to Figures 1 to 5 , the disclosed calibration method includes:

[0040] Perform the first etching on the thin film sample;

[0041] The etched thin film sample is bombarded with X-rays and the spectrum is collected;

[0042] According to the etching thickness and spectrum of the thin film sample, the relationship between the element content of the thin film sample and the etching depth is obtained to determine the first etching rate;

[0043] Using the same etching conditions, the thin film sample for which the first etching rate was determined was etched for a second time to obtain a second etching rate;

[0044] When the first etching rate is the same as the second etching rate, the etching of the photoelectron spectroscopy device is determined to be stable, and the first etching rate or the second etching rate is determined as the reference etching rate; when the first etching rate is different from the second etching rate, the second etching rate is determined as the reference etching rate.

[0045] In the embodiment of the present application, a first etching rate is determined by analyzing the etching thickness of a thin film sample and the spectrum after X-ray bombardment of the thin film sample. A second etching rate is obtained by performing the same etching conditions a second time. Thus, a baseline etching rate can be determined based on whether the two etching rates are the same. Based on this approach, the embodiment of the present application can calibrate the X-ray photoelectron spectroscopy etching rate of a photoelectron spectroscopy device, which is beneficial for improving the accuracy of the etching rate, effectively avoiding production errors caused by large testing errors in the X-ray photoelectron spectroscopy device, and ensuring production efficiency.

[0046] The above method in the embodiment of the present application can be used to calibrate the stability and accuracy of an argon ion gun in a photoelectron spectroscopy device.

[0047] Optionally, after acquiring the spectrum, the calibration method further comprises:

[0048] The relationship between the element content of the thin film sample and the etching time was obtained based on the spectrum.

[0049] It should be noted that as etching time increases, the composition and chemical state information deep within the thin film sample will be collected and analyzed by XPS. Clear differences in characteristic elemental peaks will be observed at the interface between the coatings. At this time, the etching time, as well as the etching energy of the argon ion source used, the etching mode, and the etched area are recorded. Therefore, a relationship between element content and etching time can be obtained.

[0050] Furthermore, based on the etching thickness and spectrum of the thin film sample, the relationship between the element content of the thin film sample and the etching depth is obtained, including:

[0051] Convert the etching thickness;

[0052] The relationship between element content and etching depth is obtained according to the spectrum, such as Figure 4 As shown, in order to determine the etching rate.

[0053] The above conversion logic is: Figure 4 The time corresponding to the stability of the substrate (such as a thin film) in the spectrum is the time used to etch the film layer. The etching thickness is obtained by subtracting the thickness after etching from the thickness before etching under the scanning electron microscope. The etching rate is equal to the etching thickness divided by the time corresponding to the substrate stability. After obtaining the etching rate, the equipment software converts the etching time and etching thickness to obtain a spectrum of the final element content changing with etching depth.

[0054] Optionally, a preset time interval is set between the second etching of the thin film sample and the first etching of the thin film sample, thereby reducing the influence of accidental factors on the etching rate and improving the accuracy of the etching rate to a certain extent.

[0055] Optionally, before etching the thin film sample for the first time, the calibration method further includes:

[0056] placing the thin film sample in a photoelectron spectroscopy device;

[0057] Pre-vacuuming;

[0058] When the vacuum degree in the photoelectron spectroscopy device is less than a preset vacuum degree, the thin film sample is placed in the analysis chamber of the photoelectron spectroscopy device for analysis and testing.

[0059] Furthermore, the film samples were analyzed and tested, including:

[0060] X-ray photoelectron spectroscopy was used to analyze the thin film samples to obtain the surface elements and chemical state information of the thin film samples.

[0061] Specifically, the film sample is placed in the photoelectron spectroscopy equipment and pre-vacuumed for a period of time (e.g., 6-8 hours) to make the vacuum degree in the environment where the film sample is located reach 10 -7 mbar; then the film sample is sent to the analysis chamber for analysis to obtain the composition and chemical state information of the elements on the surface of the film sample, so as to serve as reference data for the element composition and chemical state information after etching. Optionally, the vacuum degree in the analysis chamber can be 10 -8 mbar.

[0062] Optionally, before etching the thin film sample for the first time, the calibration method further includes:

[0063] Set up the etching process;

[0064] Determine etching parameters, wherein the etching parameters include etching area, etching energy, etching mode, etching time and etching depth.

[0065] The etching mode is determined according to the requirements. The argon ion source is equipped with two modes: monatomic and cluster. The cluster ion gun has a lower etching rate and is used for materials with extremely sensitive surfaces. The embodiment of the application uses the monatomic ion gun mode to increase etching efficiency.

[0066] Optionally, the monatomic ion gun can change the diameter of the ion beam through the focusing effect of the electromagnetic lens, forming two modes: high and low. In addition, the energy range used by the monatomic ion gun can be 500~4000ev. For example, including 500ev, 1000ev, 2000ev, 4000ev, etc. As the energy increases, the etching rate will increase accordingly. As the etching time increases, the elemental cost and chemical state information deep in the thin film sample will be collected and analyzed by the photoelectron spectroscopy equipment. There will be obvious differences in the characteristic element spectrum peaks at the interface between the coatings. At this time, the etching time and the etching energy, etching mode and etching area of ​​the argon ion source used are recorded.

[0067] In addition, when high-purity argon gas enters the ion gun directly, the filament heats and releases electrons. The accelerated electrons collide with gas atoms, carrying away negatively charged electrons and leaving behind positively charged argon ions. The accelerated argon ions form an argon ion beam, which can be used to bombard thin film samples. Selecting different etching energies and etching modes will result in different concentrator energy values, resulting in different intensities of the bombardment on the thin film sample.

[0068] In addition, the etching area of ​​the thin film sample can be larger than the X-ray beam diameter, thereby ensuring that data results at the same depth are obtained.

[0069] Optionally, the etching area of ​​the thin film sample by the argon ion gun of the photoelectron spectroscopy equipment can be 5 to 10 times the size of the X-ray spot beam diameter used.

[0070] Optionally, before etching the thin film sample for the first time, the calibration method further includes a step of selecting the thin film sample, wherein selecting the thin film sample includes:

[0071] Select a film with a preset thickness;

[0072] Determine whether the film is stable in air;

[0073] If it is stable, the film is determined to be a film sample.

[0074] Optionally, the thickness of the thin film sample can be less than 100 nm. Of course, other thickness ranges are possible, as long as they meet the calibration requirements. This is not specifically limited here. Furthermore, when selecting a film sample, it is important to select one that is stable in air for an extended period of time to prevent instability that could affect calibration accuracy.

[0075] Optionally, after acquiring the spectrum, the calibration method further includes obtaining the etching thickness, and obtaining the etching thickness includes:

[0076] The thickness of the film sample before etching was measured using a scanning electron microscope to obtain the initial thickness;

[0077] The thickness of the etched film sample is measured by a scanning electron microscope to obtain the current thickness;

[0078] The etching thickness is obtained according to the difference between the initial thickness and the current thickness.

[0079] Specifically, the scanning electron microscope (SEM) is used to obtain the topographic information of the film sample by collecting secondary electrons generated by high-energy electron beam bombardment of the film sample, so as to confirm the thickness of the film sample according to the topographic information. This method can obtain the thickness of the film sample before and after etching, as shown in Figure 2 and Figure 3 , so that the etching rate of the etched film sample can be calculated.

[0080] In the embodiment of the present application, the main steps of the calibration method of the photoelectron spectrometer device include:

[0081] Set the X-ray etching parameters;

[0082] Collect the etching element ratio of the film sample that can exist stably;

[0083] Obtain the film layer thickness of the film sample before and after etching by SEM;

[0084] Determine the etching rate of the film layer;

[0085] After a preset time interval, set the same etching conditions to etch the film sample with the determined etching rate;

[0086] Determine whether the etching rate of the film layer under the same etching conditions changes;

[0087] If it does not change, it is determined that the argon ion gun etching is stable, and if it changes, the new film layer etching rate is determined;

[0088] In addition, if it changes, the latest etching rate can be referred to when setting the etching scheme for in-depth analysis of other film samples.

[0089] Referring to Figure 1 , the specific steps of the calibration method of the photoelectron spectrometer device include:

[0090] Select a film sample with a certain thickness (for example, less than 100 nm), and determine whether the elements of the film sample are stable in air;

[0091] Put the film sample that can exist stably in air into the X-ray photoelectron spectrometer device, pre-evacuate, and after the vacuum value is less than 10 -7 mbar, send the sample into the analysis chamber for analysis test;

[0092] Use X-ray photoelectron spectroscopy equipment to analyze the film layer of the thin film sample to obtain the element and chemical state information of the outermost film layer as reference data;

[0093] Set the argon ion etching program, determine the etching area, etching energy, etching mode, etching time, etching depth, etc., where the etching depth range can be 60nm~100nm;

[0094] After different etching times, the etched thin film samples were bombarded with X-rays and the spectra after bombardment were collected;

[0095] The relationship between element content and argon ion etching time in the X-ray electron spectrometer is plotted on the acquired spectra;

[0096] The film thickness before and after etching was measured using a scanning electron microscope (SEM). Figure 2 and Figure 3 As shown, the etching thickness is accurately obtained;

[0097] The determined etching thickness is converted so that the spectrum can be plotted as the relationship between the element content and the etching depth of the argon ion in the X-ray photoelectron spectroscopy equipment, such as Figure 4 As shown, determine the etching rate;

[0098] After 2 to 3 weeks, the film sample with the determined etching rate is etched under the same etching conditions as above, such as Figure 5 As shown in the figure, comparing the etching rates before and after the first and second times, if the etching rate does not change, the ion gun etching of the photoelectron spectroscopy instrument is relatively stable. If the etching rate changes, the next etching rate is used as the new ion gun etching rate. In addition, other thin film samples can refer to the new ion gun etching rate for selective calibration.

[0099] In summary, the embodiments of the present application can use thin film samples with stable film thickness to calibrate the etching rate of the argon ion gun in the X-ray photoelectron spectroscopy equipment, thereby ensuring the stability and accuracy of the etching rate of the argon ion gun.

[0100] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A calibration method for a photoelectron spectroscopy device, characterized in that: The calibration method comprises: Perform the first etching on the thin film sample; Bombarding the etched thin film sample with X-rays and collecting a spectrum; Obtaining a relationship between the element content and the etching depth of the thin film sample according to the etching thickness of the thin film sample and the spectrum to determine a first etching rate; Etching the thin film sample for determining the first etching rate for a second time using the same etching conditions to obtain a second etching rate; When the first etching rate is the same as the second etching rate, the etching of the photoelectron spectroscopy device is determined to be stable, and the first etching rate or the second etching rate is determined as the reference etching rate; when the first etching rate is different from the second etching rate, the second etching rate is determined as the reference etching rate.

2. The calibration method according to claim 1, wherein: After acquiring the spectrum, the calibration method further comprises: The relationship between the element content of the thin film sample and the etching time is obtained according to the spectrum.

3. The calibration method according to claim 1 or 2, characterized in that: The obtaining of the relationship between the element content and the etching depth of the thin film sample according to the etching thickness of the thin film sample and the spectrum includes: Converting the etching thickness; The relationship between the element content and the etching depth is obtained according to the spectrum.

4. The calibration method according to claim 1, wherein: The second etching is performed on the thin film sample, and a preset time is separated from the first etching of the thin film sample.

5. The calibration method according to claim 1, wherein: Before etching the thin film sample for the first time, the calibration method further comprises: placing the thin film sample in the photoelectron spectroscopy device; Pre-vacuuming; When the vacuum degree in the photoelectron spectroscopy device is less than a preset vacuum degree, the thin film sample is placed in the analysis chamber of the photoelectron spectroscopy device for analysis and testing.

6. The calibration method according to claim 5, characterized in that: The film samples are subjected to analysis and testing, including: The thin film sample is analyzed by X-ray photoelectron spectroscopy to obtain the surface element and chemical state information of the thin film sample.

7. The calibration method according to claim 1, wherein: Before etching the thin film sample for the first time, the calibration method further comprises: Set up the etching process; Determine etching parameters, which include etching area, etching energy, etching mode, etching time and etching depth.

8. The calibration method according to claim 1 or 7, characterized in that: The etching area of ​​the thin film sample is larger than the spot beam diameter of the X-ray.

9. The calibration method according to claim 1, wherein: Before etching the thin film sample for the first time, the calibration method further includes the step of selecting a thin film sample, wherein selecting the thin film sample includes: selecting the film of a preset thickness; determining whether the film is stable in air; If stable, the film is determined to be the film sample.

10. The calibration method according to claim 1, wherein: After collecting the spectrum, the calibration method further includes obtaining the etching thickness, and obtaining the etching thickness includes: The thickness of the thin film sample before etching is measured using a scanning electron microscope to obtain the initial thickness; Using a scanning electron microscope to measure the thickness of the thin film sample after etching to obtain the current thickness; The etching thickness is obtained according to the difference between the initial thickness and the current thickness.

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