Method for measuring film sputtering rate of X-ray photoelectron spectroscopy surface analysis system

Abstract

The invention discloses a method for measuring the film sputtering rate of an X-ray photoelectron spectroscopy surface analysis system, and belongs to the technical field of characterization analysis. The method comprises the following steps: step 1, measuring a film sample by adopting an elliptical polarization spectrometer, establishing a fitting model, fitting data measured by the elliptical polarization spectrometer, and calculating the film sputtering rate of the X-ray photoelectron spectroscopy surface analysis system; obtaining film layer thickness information of the film sample; 2, analyzing the film by adopting a focused ion beam system to obtain film layer thickness information of the film sample; step 3, adopting an X-ray photoelectron spectroscopy surface analysis system to carry out a deep dissection test on the film sample, and recording the sputtering time of the film layer; and 4, according to the film layer thickness information obtained by the elliptical polarization spectrometer and the focused ion beam system and the film layer sputtering time measured by the X-ray surface analysis system, establishing a film sputtering rate function model of the X-ray surface analysis system.

Description

Technical Field

[0001] The invention belongs to the technical field of characterization analysis, and in particular is a method for measuring the sputtering rate of a thin film in an X-ray photoelectron spectrum surface analysis system. Background Art

[0002] X-ray photoelectron spectroscopy (XPS) is a high-resolution surface analysis technique. XPS uses X-rays to irradiate the sample surface and provide detailed information about the elemental composition, chemical state, and chemical environment of the sample surface. Due to its high sensitivity and accuracy, XPS is widely used in materials science, chemistry, physics, and other fields. The energy of X-rays excites the inner electrons on the sample surface. When X-rays irradiate the sample surface, the inner electrons absorb the energy of the X-rays and are released into the vacuum. This process is called the photoelectric effect, and the released electrons are called photoelectrons. The photoelectrons are guided to an energy analyzer. The energy analyzer determines their original binding energy by measuring the kinetic energy of these photoelectrons. Common energy analyzers include circular crystal energy analyzers (CMA) and magnetic angle analyzers (MCA). After passing through the energy analyzer, the photoelectrons are recorded by the detector. The signal intensity corresponds to the binding energy of the photoelectrons, forming an energy spectrum. Through this spectrum, characteristic peaks of different elements and their chemical states can be obtained. Each peak in the spectrum corresponds to a different element and its chemical environment; by analyzing the position and shape of the peaks, the composition, chemical state, binding energy, and other information of the elements on the sample surface can be determined. By etching the sample surface layer by layer and repeatedly performing XPS measurements, the depth profile information of the sample can be obtained, which enables XPS to not only analyze surface information but also provide certain depth information.

[0003] Depth profiling of X-ray photoelectron spectroscopy is a method that uses sputtering technology combined with photoelectron spectroscopy to analyze the chemical composition of the surface and subsurface of materials. It is widely used in the study of thin films, coatings and composite materials. When performing XPS depth analysis in a specific area, the sputtering depth and area can be controlled by adjusting the etching parameters so that the area of ​​interest can be accurately selected and analyzed in the XPS analysis. However, the sputtering rate of different materials is different, and the sample hardness, chemical bond strength, atomic mass, crystal structure, etc. will affect the sputtering rate. The sputtering rate refers to the thickness of the material sputtered per unit time (usually in nanometers / second), which is determined by the energy of the sputtering ion beam, the atomic density of the sample and the bond energy of the material. The sputtering rate depends on the material density and composition, and the uncertainty of the rate will affect the depth quantitative accuracy. Therefore, the reference rate given by the XPS instrument has a large error, and it cannot be used to judge the depth information of the sample film layer, and can only serve as a reference. Summary of the invention

[0004] In order to improve the accuracy of sputtering rate measurement when X-ray photoelectron spectroscopy is used to analyze the depth of a thin film, the present invention provides a method for measuring the sputtering rate of a thin film in an X-ray photoelectron spectroscopy surface analysis system.

[0005] Technical solution: A method for measuring the sputtering rate of a thin film in an X-ray photoelectron spectroscopy surface analysis system, comprising the following steps:

[0006] Step 1: Use an ellipsometer to measure the thin film sample, establish a fitting model, fit the data measured by the circular polarization spectrometer, and obtain the film thickness information of the thin film sample; the thin film sample includes a substrate and a film layer on the substrate; the substrate is a silicon substrate;

[0007] Step 2: Analyze the thin film using a focused ion beam system to obtain film thickness information of the thin film sample;

[0008] Step 3: Use an X-ray photoelectron spectroscopy surface analysis system to perform a deep dissection test on the thin film sample and record the sputtering time of the film layer;

[0009] Step 4: Based on the film thickness information obtained by the ellipsometer and the focused ion beam system and the film sputtering time measured by the X-ray surface analysis system, a sputtering rate function model of the film by the X-ray surface analysis system is established.

[0010] Furthermore, the specific steps of step one are as follows:

[0011] Place the sample at the center of the sample stage of the ellipsometer and level it so that the instrument can collect the maximum signal. Set the test parameters and start the test after the settings are completed.

[0012] Establish a fitting model, select the Spectroscopic Model model, import the sample material into the model, drag the data measured by the ellipsometer into the model, set the fitting parameters, and after the parameter setting is completed, perform fitting to obtain the fitting curve and obtain the film thickness information of the sample.

[0013] Furthermore, the specific steps of step 2 are as follows:

[0014] After the sample is cleaned, it is fixed on the focused ion beam sample stage and sent into the instrument chamber of the focused ion beam system for vacuuming;

[0015] After the sample is clearly focused, the actual sample height is obtained, and the Nav-Cam is used to take photos to obtain the position information of the sample in the instrument chamber;

[0016] Platinum is deposited under electron beam on the area of ​​the sample to be tested to protect the sample surface information;

[0017] The sample stage is rotated to 52°, and the area where platinum is to be deposited under the electron beam is found under the ion beam, and then platinum is deposited on the area under the ion beam;

[0018] Design the cutting area to perform ion beam cutting at the half-width of the deposited platinum;

[0019] After cutting is completed, the cross section is observed under the electron beam, and the magnification and beam parameters are adjusted to display the upper and lower boundaries of the film layer; on the cross section, the first layer is the deposited platinum, the second layer is the film layer to be measured, and the third layer is the substrate; the vertical distance from the upper surface to the lower surface of the film layer is recorded to obtain the film thickness information of the sample.

[0020] Furthermore, the specific steps of step three are as follows:

[0021] The sample is glued to the sample holder of the X-ray photoelectron spectroscopy surface analysis system, placed in the sample chamber, and the sample chamber is evacuated;

[0022] After the vacuum is drawn, the sample is transferred to the analysis room and the test tree is set up;

[0023] After the experimental tree is set up, the sputtering test begins;

[0024] Observe the full spectrum and fine spectrum of the sample measured before sputtering to obtain the unique elements and their peak values ​​in the film layer; when the peak value of the unique elements in the film layer appears in the fine spectrum, determine the start time of sputtering of the film layer;

[0025] Continue sputtering deeper. When the peak of the unique element in the film layer disappears in the full spectrum and the peak in the fine spectrum changes, stop sputtering and record the sputtering time.

[0026] Furthermore, the specific steps of step 4 are as follows:

[0027] The expression of the sputtering rate function model is as follows:

[0028]

[0029] Wherein, D is the measured film thickness. If the film thickness data measured in step 1 and step 2 are similar and the measurement error range is within ±10nm, take the average of the two sets of data. Otherwise, repeat the test of step 1 and step 2. T is the sputtering time measured in step 3. v represents the sputtering rate.

[0030] Beneficial effects:

[0031] 1) The present invention uses a variety of technical means to obtain detailed film information of thin film samples through ellipsometry and focused ion beam (FIB) system, and then further uses X-ray photoelectron spectroscopy (XPS) surface analysis system to perform sputtering analysis of the film layer by layer. This comprehensive method significantly improves the accuracy and reliability of the experimental results, providing a more complete technical solution for material surface interface research.

[0032] The spectroscopic ellipsometry is used to non-destructively measure the thickness and optical constants of the film, providing accurate film parameters as a whole, while the focused ion beam system verifies the actual thickness of the film through cross-sectional cutting and high-resolution observation, providing an accurate reference for subsequent analysis. On this basis, through the chemical composition analysis of layer-by-layer sputtering by XPS, element distribution and chemical state data at different depths can be obtained. Finally, the experimental data obtained by the three technologies are combined to construct a mathematical model, which can not only accurately describe the characteristics of the film, but also further deduce the specific sputtering rate of the XPS instrument on the film during the sputtering process.

[0033] 2) The present invention combines the technology of measuring film thickness with ellipsometry spectrometer and focused ion beam system, which can integrate the non-destructiveness and high efficiency of optical measurement and the high resolution and direct observation characteristics of focused ion beam, realize the complementary advantages of the two technical methods, thereby improving the accuracy, comprehensiveness and reliability of measurement, and providing a more comprehensive solution for material research and industrial applications.

[0034] 3) The present invention can not only accurately obtain the thickness information of the film, but also analyze the element distribution and chemical state of the film at the same time, which is particularly suitable for the analysis of nano-scale films and multilayer structures. Its high sensitivity, high depth resolution and non-contact measurement method enable it to effectively evaluate the thickness, stratification and interface characteristics of the film. In addition, XPS does not require complex sample preparation and can be combined with other technologies to further improve the reliability and comprehensiveness of the data. It is an efficient and comprehensive tool in thin film research. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The figure is a flow chart of the method of the present invention.

[0036] Figure 2 It is the fitting curve of the ellipsometer in the embodiment.

[0037] Figure 3 is the fitting result of the film thickness in the embodiment.

[0038] Figure 4 This is the overall area after ion beam cutting is completed.

[0039] Figure 5 It is the film layer information at the cross section cut in the embodiment.

[0040] Figure 6 It is the full spectrum of the sample without sputtering and the fine spectrum scan of Si2p.

[0041] Figure 7 It is the full spectrum of the sample when sputtered onto the substrate and the fine spectrum scan of Si2p. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described in detail below through embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0043] This embodiment provides a method for measuring the sputtering rate of a thin film by an X-ray photoelectron spectrometer. In this embodiment, a silicon nitride thin film uniformly grown on a silicon substrate is selected as a thin film sample. The thin film sample used in the present invention is a silicon nitride thin film prepared by a low pressure chemical vapor deposition (LPVCD) process, which is widely used in semiconductors, optics, MEMS and other fields due to its high quality and versatility.

[0044] The flow chart of the method of the present invention is as follows Figure 1 As shown, the following steps are included:

[0045] Step 1: Measure the silicon nitride thin film sample on the silicon substrate by ellipsometer, establish a fitting model, fit the data measured by the circular polarization spectrometer, and obtain the film thickness information.

[0046] The specific steps of step 1 are as follows:

[0047] Step 1.1, place the silicon nitride film sample on the silicon substrate at the center of the sample stage of the ellipsometer and then level it so that the signal collected by the instrument is maximized;

[0048] Set the test parameters, select the test mode as Standard, the incident angle as 70°, the integration time as 500ms, the Range as 0.6000-6.5000eV, and the Increment as 0.0500eV. After the settings are completed, start the test.

[0049] Step 1.2, establish a fitting model, select the Spectroscopic Model model, and import the sample material into the model; in this model, select c-SI_HJY.ref as the substrate material, SiNx LPCVD_nam.dsp as the film material, drag the data measured by the ellipsometry spectrometer into the model, set the fitting parameters, and after the parameter setting is completed, perform fitting to obtain the fitting curve as shown below: Figure 2 , the film thickness information of the sample is obtained as Figure 3 .

[0050] Step 2: Analyze the thin film using a focused ion beam system to obtain film thickness information.

[0051] The specific steps of step 2 are as follows:

[0052] Step 2.1. Decontaminate the silicon nitride film sample uniformly grown on the silicon substrate with an ultrasonic cleaner to remove particles or contaminants that may affect the measurement accuracy. Use conductive carbon glue to fix the sample on the FIB sample stage to ensure that the sample is stable and avoid movement during cutting or deposition. After cleaning, send it into the instrument chamber for vacuuming.

[0053] Step 2.2: Position the sample, focus the sample clearly to obtain the actual sample height, raise the sample to a suitable position, take a picture with Nav-Cam, and obtain the position information of the sample in the instrument chamber.

[0054] Step 2.3: Platinum is deposited under an electron beam on the area to be tested of the sample to protect the surface information of the sample. The deposition area is 8 μm*2 μm*0.5 μm, the electron beam voltage is 2 kV, and the current is 3.2 nA.

[0055] Step 2.4, rotate the sample stage to 52°, find the area where platinum is deposited under the electron beam under the ion beam, and then perform platinum deposition on this area under the ion beam. The deposition area is 8μm*2μm*2μm, the ion beam voltage is 30kV, and the current is 0.5nA.

[0056] Step 2.5, design the cutting area, perform ion beam cutting at the half width of the deposited platinum, set the cutting area to 8μm*5μm*5μm, and observe in real time through the electron beam window during the cutting process to prevent deviation or damage to non-target areas during the cutting process. The observation area after cutting is as follows Figure 4 shown.

[0057] Step 2.6: After cutting, observe the cross section under the electron beam and adjust the magnification, beam current and other parameters to clearly show the upper and lower boundaries of the silicon nitride film. Figure 5 As shown in the figure, the first layer is the deposited platinum, the second layer is the silicon nitride film to be measured, and the third layer is the substrate silicon. Select a position on the cross-sectional image and record the vertical distance from the upper surface to the lower surface of the silicon nitride film to obtain the film thickness information of the sample.

[0058] Step 3, performing a depth dissection test of the silicon nitride film sample on the silicon substrate using an X-ray photoelectron spectrometer, and recording the sputtering time of the film layer;

[0059] The specific steps of step 3 are as follows:

[0060] Step 3.1. Stick the sample to the XPS sample holder with conductive tape, put it into the XPS sample chamber after purging it with nitrogen, and evacuate the sample chamber to a suitable vacuum degree.

[0061] Step 3.2, after vacuuming, transfer the sample to the analysis room and start setting up the test experiment tree: add an X-ray source with a spot size of 400μm. Add test points and set the test point coordinates. Add an ion source, set the ion energy to 1000eV, the sputtering mode to Monatomic, and the sputtering area to 2.4mm*4.8mm. Add full spectrum scan, C1s fine spectrum scan, N1s fine spectrum scan, and Si2p fine spectrum scan.

[0062] Step 3.3: After the experimental tree is set up, purge the pipeline several times with argon to prevent residual gas in the pipeline from affecting the test results, check the parameter settings, and start the test.

[0063] Step 3.4: Observe the full spectrum measured without sputtering. Figure 6 It can be found that the sample contains N and Si elements and the peak value of Si2p in the fine spectrum is 103.1eV. By querying the instrument database, it is found that the spectrum peak of Si2p measured at this time represents silicon nitride.

[0064] Step 3.5: Continue sputtering deeper until the peak of N element disappears in the full spectrum scan. Figure 7 At this time, the peak value of Si2p in the fine spectrum changes from 101.7eV to 99.4eV. The instrument database is queried, indicating that the spectrum peak of Si2p at this time represents silicon alone. Sputtering is stopped and the sputtering time is recorded.

[0065] Step 4: Calculate the sputtering rate of the X-ray photoelectron spectroscopy surface analysis system:

[0066] According to the film thickness measured by the ellipsometry spectrometer, the film thickness information measured by the focused ion beam system, and the film sputtering time measured by the X-ray surface analysis system, the sputtering rate function model of the X-ray photoelectron spectrometer for this type of film is established, and the expression is as follows:

[0067]

[0068] Where D is the measured film thickness. If the film thickness data measured by the ellipsometer and the focused ion beam system are similar and the measurement error range is within ±10nm, the average of the two sets of data can be taken. If the film thickness data measured by the ellipsometer and the focused ion beam system have large errors and the measurement error range is outside ±10nm, retesting is required to obtain the correct film thickness information. Where T is the time it takes for the X-ray photoelectron spectrometer to sputter the thin film on the sample surface to disappear; v represents the sputtering rate.

[0069] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to the form and details without departing from the spirit and scope of the present invention.

Claims

1. A method for measuring the sputtering rate of a thin film in an X-ray photoelectron spectroscopy surface analysis system, characterized in that: The steps include: Step 1: Use an ellipsometer to measure the thin film sample, establish a fitting model, fit the data measured by the circular polarization spectrometer, and obtain the film thickness information of the thin film sample; the thin film sample includes a substrate and a film layer on the substrate; Step 2: Analyze the thin film using a focused ion beam system to obtain film thickness information of the thin film sample; Step 3: Use an X-ray photoelectron spectroscopy surface analysis system to perform a deep dissection test on the thin film sample and record the sputtering time of the film layer; Step 4: Based on the film thickness information obtained by the ellipsometer and the focused ion beam system and the film sputtering time measured by the X-ray surface analysis system, a sputtering rate function model of the film by the X-ray surface analysis system is established.

2. The method according to claim 1, characterized in that: The specific steps of step one are as follows: Place the sample at the center of the sample stage of the ellipsometer and level it so that the instrument can collect the maximum signal. Set the test parameters and start the test after the settings are completed. Establish a fitting model, select the Spectroscopic Model model, import the sample material into the model, drag the data measured by the ellipsometer into the model, set the fitting parameters, and after the parameter setting is completed, perform fitting to obtain the fitting curve and obtain the film thickness information of the sample.

3. The method according to claim 1, characterized in that: The specific steps of step 2 are as follows: After the sample is cleaned, it is fixed on the focused ion beam sample stage and sent into the instrument chamber of the focused ion beam system for vacuuming; After the sample is clearly focused, the actual sample height is obtained, and the Nav-Cam is used to take photos to obtain the position information of the sample in the instrument chamber; Platinum is deposited under electron beam on the area of ​​the sample to be tested to protect the sample surface information; The sample stage is rotated to 52°, and the area where platinum is to be deposited under the electron beam is found under the ion beam, and then platinum is deposited on the area under the ion beam; Design the cutting area to perform ion beam cutting at the half-width of the deposited platinum; After cutting is completed, the cross section is observed under the electron beam, and the magnification and beam parameters are adjusted to display the upper and lower boundaries of the film layer; on the cross section, the first layer is the deposited platinum, the second layer is the film layer to be measured, and the third layer is the substrate; the vertical distance from the upper surface to the lower surface of the film layer is recorded to obtain the film thickness information of the sample.

4. The method according to claim 1, characterized in that: The specific steps of step three are as follows: The sample is glued to the sample holder of the X-ray photoelectron spectroscopy surface analysis system, placed in the sample chamber, and the sample chamber is evacuated; After the vacuum is drawn, the sample is transferred to the analysis room and the test tree is set up; After the experimental tree is set up, the sputtering test begins; Observe the full spectrum and fine spectrum of the sample measured without sputtering to obtain the unique elements and their peak values ​​in the film layer; When the peak of the unique element in the film layer appears in the fine spectrum, the start time of sputtering of the film layer is determined; Continue sputtering deeper. When the peak of the unique element in the film layer disappears in the full spectrum and the peak in the fine spectrum changes, stop sputtering and record the sputtering time.

5. The method according to claim 1, characterized in that: In step 4, the expression of the sputtering rate function model is as follows: The expression of the sputtering rate function model is as follows: Wherein, D is the measured film thickness. If the film thickness data measured in step 1 and step 2 are similar and the measurement error range is within ±10nm, take the average of the two sets of data. Otherwise, repeat the test of step 1 and step 2. T is the sputtering time measured in step 3. v represents the sputtering rate.

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