A method for detecting the thickness of single-crystal silicon flexible ribs based on light absorption.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2011-09-01
- Publication Date
- 2014-04-09
AI Technical Summary
破坏性测量方法具有破坏性、不准确和效率低等缺点，不能满足设计加工需求
[0013]本发明的优点是：本发明利用光的吸收原理，遵循朗伯定律：一定波长的光在同一吸收物质内通过同一距离时，到达该处的光能量中将有同样百分比的能量被该层物质吸收，即应与吸收层的厚度dx成正比：
其中k为吸收系数；通过分析单晶硅挠性筋厚度与通过光的光强变化，计算得出吸收系数k，然后在已知单晶硅挠性筋的光强变化下，根据公式I＝I0e-kx代入k值即可计算得到筋厚；本发明首先通过测量一束单色光通过单晶硅膜的光强变化，根据朗伯定律，计算得到单晶硅膜吸收系数k，然后测试被测单晶硅挠性筋的光强变化代入k值，计算得到筋厚；该方法属于光学方法，不需要测量基准面，不破坏单晶硅挠性元件和挠性筋，实现了单晶硅元件的挠性筋筋厚直接准确测量，测量精度优于0.5μm，测量方法实现简单、方便，造价低，能够进行批量快速测量，大大提高了检测效率和准确性。
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Figure CN122556229B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of testing technology and relates to a method for detecting the thickness of a single-crystal silicon flexible rib based on light absorption. Background Technology
[0002] Flexible accelerometers are a type of pendulum accelerometer widely used in inertial navigation and guidance. The flexible support, as a key sensitive component, can be made of metals such as beryllium bronze or copper-tungsten single crystal, or non-metals such as single-crystal silicon or quartz. Flexible supports made of single-crystal silicon (also known as flexible ribs) have a rib thickness of only about 10 μm. Due to the special nature of its structure and material, there is no measurement reference surface; therefore, the actual rib thickness can only be indirectly estimated by measuring the thickness of the test window using destructive methods. Destructive measurement methods have disadvantages such as being destructive, inaccurate, and inefficient, and cannot meet design and manufacturing requirements. Summary of the Invention
[0003] The purpose of this invention is to propose a method for detecting the thickness of monocrystalline silicon flexible ribs based on light absorption, which has high detection accuracy and does not damage the monocrystalline silicon flexible element and flexible rib.
[0004] The technical solution of this invention is:
[0005] (1) Fabrication of single-crystal silicon film samples
[0006] Select a silicon wafer with crystal orientation 100, 100-200mm 2 A rectangular area mask is used, and a potassium hydroxide etching solution is applied at an etching rate of 0.5-1.0 μm / min to etch a silicon wafer into a single-crystal silicon film with a thickness of 12-16 μm.
[0007] (2) Measurement of single-crystal silicon film samples
[0008] Take a set of single-crystal silicon film samples, place one single-crystal silicon film sample on the support and position it between the light source output terminal and the first detector. The light source output wavelength is 632.8nm. Read the laser output energy I after passing through the single-crystal silicon film sample from the output terminal of the first detector. i The laser output energy I0 is read from the output of the second detector, and the laser output energy I passing through the single-crystal silicon film sample is recorded. i Percentage of the laser output energy I0 The single-crystal silicon film sample was then etched with potassium hydroxide at 1.0 μm intervals. The same measurement was performed every 1.0 μm etched until the thickness of the single-crystal silicon film sample was 8-12 μm. This yielded a set of percentage changes in light intensity. A set of data was obtained from the first monocrystalline silicon film sample, along with the thickness of the silicon film. The remaining monocrystalline silicon film samples were then measured in the same manner to obtain the percentage change in light intensity for all the selected monocrystalline silicon film samples. Data related to silicon film thickness;
[0009] (3) Data processing and analysis
[0010] According to the principle of light absorption and Lambert's law, I = I₀e⁻ -kx Where I0 and I are the incident light intensity and the exit light intensity, respectively, k is the absorption coefficient, and x is the thickness of the medium through which the light passes. The slope of the fitted curve was calculated to obtain a set of single-crystal silicon film samples k i Then take k i The arithmetic mean of the values is the absorption coefficient k of the single-crystal silicon film sample;
[0011] (4) Testing of monocrystalline silicon flexible ribs
[0012] The component under test is placed on a support and positioned between the light source output and the first detector, ensuring the light beam passes horizontally and completely through the flexible rib of the component. The laser output energy I′ passing through the flexible rib of the component under test is read from the output of the first detector, and the laser output energy I0 is read from the output of the second detector. The percentage ratio of the laser output energy I′ passing through the flexible rib of the component under test to the laser output energy I0 is recorded. Then, based on the known absorption coefficient k value of the single-crystal silicon film sample, the formula I = I0e is used. -kx The thickness of the flexible ribs of the tested element is calculated.
[0013] The advantages of this invention are: This invention utilizes the principle of light absorption, following Lambert's law: when light of a certain wavelength travels the same distance within the same absorbing material, the same percentage of the light energy reaching that point will be absorbed by that layer of material, i.e. It should be proportional to the thickness dx of the absorption layer: Where k is the absorption coefficient; the absorption coefficient k is calculated by analyzing the thickness of the monocrystalline silicon flexible rib and the change in light intensity. Then, under the known light intensity change of the monocrystalline silicon flexible rib, the absorption coefficient k is calculated according to the formula I = I0e. -kx The thickness of the rib can be calculated by substituting the k value. This invention first measures the change in light intensity of a monochromatic light beam passing through a single-crystal silicon film. According to Lambert's law, the absorption coefficient k of the single-crystal silicon film is calculated. Then, the change in light intensity of the single-crystal silicon flexible rib under test is measured and substituted into the k value to calculate the rib thickness. This method is an optical method that does not require a measurement reference plane and does not damage the single-crystal silicon flexible element and flexible rib. It realizes direct and accurate measurement of the rib thickness of the single-crystal silicon element, with a measurement accuracy better than 0.5μm. The measurement method is simple, convenient, and low in cost, and can be used for rapid batch measurement, which greatly improves the detection efficiency and accuracy. Attached Figure Description
[0014] Figure 1 This is a schematic diagram of the measuring device. Detailed Implementation
[0015] The present invention will now be described in further detail.
[0016] It consists of a light source 5, a support 3, a beam splitter 4, and two detectors 1 and 2. The single-crystal silicon film sample being measured is etched into a single-crystal silicon film with a thickness of 12-16 μm using a potassium hydroxide solution etching process at a constant etching rate. A set of single-crystal silicon film samples is taken, and one sample is placed on the support 3 between the output end of the light source 5 and the first detector 1. The output wavelength of the light source 5 is 632.8 nm. The laser output energy I passing through the single-crystal silicon film sample is read from the output end of the first detector 1. i The laser output energy I0 is read from the output terminal of the second detector 2, and the laser output energy I passing through the single-crystal silicon film sample is recorded. i Percentage of the laser output energy I0 The single-crystal silicon film sample was then etched with potassium hydroxide at 1.0 μm intervals. The same measurement was performed every 1.0 μm etched until the thickness of the single-crystal silicon film sample was 8-12 μm. This yielded a set of percentage changes in light intensity. The data for the first sample with the silicon film thickness were used; the remaining single-crystal silicon film samples were measured in the same way to obtain the percentage change in light intensity for all the single-crystal silicon film samples taken. Data related to silicon film thickness. According to Lambert's law of light absorption, I = I0e^(-I / I₀ ... -kx Where I0 and I are the incident light intensity and the exit light intensity, respectively, k is the absorption coefficient, and x is the thickness of the medium through which the light passes. Substitute the percentage change in light intensity of all the single-crystal silicon film samples taken. The slope of the fitted curve was calculated to obtain a set of single-crystal silicon film samples k i Then take k i The arithmetic mean of the values is the absorption coefficient k of the single-crystal silicon film sample;
[0017] For measuring the thickness of the flexible ribs in single-crystal silicon, the component under test is placed on the support 3 and positioned between the output end of the light source 5 and the first detector 1, ensuring that the laser beam passes horizontally and completely through the flexible ribs of the component. The laser output energy I′ passing through the flexible ribs of the component under test is read from the output end of the first detector 1, and the laser output energy I0 is read from the output end of the second detector 2. The percentage ratio of the laser output energy I′ passing through the flexible ribs of the component under test to the laser output energy I0 is calculated. Record this value; then, based on the known absorption coefficient k value of the single-crystal silicon film sample, use the formula I = I0e -kx The thickness of the single-crystal silicon flexible rib of the tested component was calculated.
[0018] Method steps of the present invention
[0019] (1) Fabrication of single-crystal silicon film samples
[0020] Select a silicon wafer with crystal orientation 100, 100-200mm 2 A rectangular area mask is used, and a potassium hydroxide etching solution is applied at an etching rate of 0.5-1.0 μm / min to etch a silicon wafer into a single-crystal silicon film with a thickness of 12-16 μm.
[0021] (2) Measurement of single-crystal silicon film samples
[0022] Place the light source 5, support 3, and detector 1 in a horizontal straight line to ensure detection accuracy. Take a set of single-crystal silicon film samples, place one sample on support 3 and position it between the output of light source 5 and the first detector 1. The output wavelength of light source 5 is 632.8nm. Read the laser output energy I after passing through the single-crystal silicon film sample from the output of the first detector 1. i The laser output energy I0 is read from the output terminal of the second detector 2, and the laser output energy I passing through the single-crystal silicon film sample is recorded. i Percentage of the laser output energy I0 The single-crystal silicon film sample was then etched with potassium hydroxide at 1.0 μm intervals. The same measurement was performed every 1.0 μm etched until the thickness of the single-crystal silicon film sample was 8-12 μm. This yielded a set of data on the percentage change in light intensity and the thickness of the silicon film for the first single-crystal silicon film sample. The remaining single-crystal silicon film samples were measured in the same way to obtain data on the percentage change in light intensity and the thickness of the silicon film for all the single-crystal silicon film samples taken.
[0023] (3) Data processing and analysis
[0024] According to the principle of light absorption and Lambert's law, i = I₀e⁻ -kx Where I0 and I are the incident light intensity and the exit light intensity, respectively, k is the absorption coefficient, and x is the thickness of the medium through which the light passes. Substitute the percentage change in light intensity of all the single-crystal silicon film samples taken. The slope of the fitted curve was calculated to obtain a set of single-crystal silicon film samples k i Then take k i The arithmetic mean of the values is the absorption coefficient k of the single-crystal silicon film sample;
[0025] (4) Measurement of the thickness of the single-crystal silicon flexible rib of the tested component
[0026] The component under test is placed on the support 3 and positioned between the output end of the light source 5 and the first detector 1, so that the light beam passes horizontally and completely through the flexible rib of the component. The laser output energy I′ passing through the flexible rib of the component under test is read from the output end of the first detector 1, and the laser output energy I0 is read from the output end of the second detector 2. The percentage of the laser output energy I′ passing through the flexible rib of the component under test to the laser output energy I0 is recorded. Then, based on the known absorption coefficient k value of the single crystal silicon film sample, the formula I = I0e is used to calculate the laser output energy. -kx The thickness of the single-crystal silicon flexible rib of the tested component was calculated.
[0027] Example 1
[0028] (1) Fabrication of single-crystal silicon film samples
[0029] Five P-type 100 silicon wafers, each 400 μm thick, were selected and numbered 1#, 2#, 3#, 4#, and 5#. Silicon nitride was grown on these wafers, with a thickness of 200 mm. 2 A rectangular area mask is used to open the etching window through photolithography, and then potassium hydroxide etching solution is placed in it for etching at an etching rate of 1.0 μm / min to etch the silicon wafer into a silicon film with a thickness of 12-16 μm.
[0030] (2) Measurement of single-crystal silicon film samples
[0031] like Figure 1 As shown, the light source 5, support 3, and detector 1 are placed in a horizontal straight line. The No. 1 single-crystal silicon film sample is placed on support 3 and positioned between the output end of the light source 5 and the first detector 1. The output wavelength of the light source 5 is 632.8nm. The laser output energy I1 after passing through the No. 1 single-crystal silicon film sample is read from the output end of the first detector 1, and the laser output energy I0 is read from the output end of the second detector 2. The percentage ratio of the laser output energy I1 to the laser output energy I0 after passing through the No. 1 single-crystal silicon film sample is recorded. The No. 1 single-crystal silicon film sample was then etched with potassium hydroxide at 1.0 μm intervals. The same measurement was performed every 1.0 μm etched until the thickness of the No. 1 single-crystal silicon film sample was 8-12 μm. From this, a set of percentage changes in light intensity was obtained. The same method was used to measure the light intensity changes of all the monocrystalline silicon film samples taken, from #2 to #5, to obtain the percentage change in light intensity.
[0032] (3) Data processing and analysis
[0033] The test calculation results for single-crystal silicon film samples with wafer numbers 1#-5#, after data analysis and processing, yielded a k value of 0.33526, as shown in Table 1.
[0034] Table 1. Test and calculation results of monocrystalline silicon film samples with wafer numbers 1#-5#
[0035]
[0036] (4) Thickness detection of single-crystal silicon flexible ribs of the tested component
[0037] Five P-type single-crystal silicon wafers were selected, numbered S-1#, S-2#, S-3#, S-4#, and S-5#. The light source 5, support 3, and detector 1 were placed in a horizontal straight line. The single-crystal silicon wafer numbered S-1# was placed on support 3 and positioned between the output end of the light source 5 and the first detector 1. The output wavelength of the light source 5 was 632.8 nm. The laser output energy I after passing through the S-1# wafer was read from the output end of the first detector 1. s-1 The output energy I0 of the laser is read from the output terminal of the second detector 2, and the laser output energy I after passing through the single-crystal silicon flexible rib of the swing plate is recorded. s-1 The percentage of the ratio of ′ to the laser output energy I0 It is 7.3293; then Substituting k = 0.33526 into the formula I = I0e -kx The rib thickness x is calculated. s-1 =7.69μm; The monocrystalline silicon flexible ribs of the S-2#, S-3#, S-4#, and S-5# monocrystalline silicon slabs were measured in the same way to obtain the percentage change in light intensity of the S-2#, S-3#, S-4#, and S-5# monocrystalline silicon slabs. Then, the percentage change in light intensity of the monocrystalline silicon flexible ribs of the S-2#, S-3#, S-4#, and S-5# monocrystalline silicon slabs was substituted into the formula I = I0e -kx The thickness of the ribs was calculated. Finally, the thickness of the monocrystalline silicon flexible ribs S-2#, S-3#, S-4#, and S-5# was measured using the destructive contact measurement method and compared with the thickness of the monocrystalline silicon flexible ribs measured by the light absorption method. The measurement error was less than 0.3μm.
[0038] The measurement results and comparison of the monocrystalline silicon flexible ribs of S-1#, S-2#, S-3#, S-4#, and S-5# monocrystalline silicon slabs are shown in Table 2.
[0039] Table 2 Measurement results and comparison of the monocrystalline silicon flexible ribs for monocrystalline silicon pendulum wafers S-1# to S-5#.
[0040]
[0041] Example 2
[0042] (1) Fabrication of single-crystal silicon film samples
[0043] Five N-type 100mm silicon wafers, each 400μm thick, were selected and numbered 6#, 7#, 8#, 9#, and 10#. Silicon nitride was grown on these wafers, with a thickness of 200mm. 2A rectangular area mask is used to open the etching window through photolithography, and then potassium hydroxide etching solution is placed in it for etching at an etching rate of 1.0 μm / min to etch the silicon wafer into a silicon film with a thickness of 12-16 μm.
[0044] (2) Measurement of single-crystal silicon film samples
[0045] like Figure 1 As shown, the light source 5, support 3, and detector 1 are placed in a horizontal straight line. A No. 6 single-crystal silicon film sample is placed on support 3 and positioned between the output of the light source 5 and the first detector 1. The output wavelength of the light source 5 is 632.8 nm. The laser output energy I6 passing through the single-crystal silicon film sample is read from the output of the first detector 1, and the laser output energy I0 is read from the output of the second detector 2. The percentage ratio of the laser output energy I6 to the laser output energy I0 passing through the single-crystal silicon film sample is recorded. The No. 6 single-crystal silicon film sample was then etched with potassium hydroxide at 1.0 μm intervals. The same measurement was performed every 1.0 μm of etching until the thickness of the single-crystal silicon film sample was 8-12 μm. This yielded a set of percentage changes in light intensity. The same method was used to measure the light intensity changes of all the monocrystalline silicon film samples taken, from #7 to #10, to obtain the percentage change in light intensity.
[0046] (3) Data processing and analysis
[0047] The test calculation results for single-crystal silicon film samples with wafer numbers 6#-10#, after data analysis and processing, yielded a k value of 0.32722, as shown in Table 3.
[0048] Table 3. Test and calculation results of monocrystalline silicon film samples with wafer numbers 6# to 10#
[0049]
[0050] (4) Thickness detection of single-crystal silicon flexible ribs of the tested component
[0051] Five N-type single-crystal silicon wafers were selected, numbered S-6#, S-7#, S-8#, S-9#, and S-10#. The light source 5, support 3, and detector 1 were placed in a horizontal straight line. Wafer S-6# was placed on support 3 and positioned between the output of light source 5 and the first detector 1. The output wavelength of light from light source 5 was 632.8 nm. The laser output energy I after passing through the single-crystal silicon film sample was read from the output of the first detector 1. s-6 The laser output energy I0 is read from the output terminal of the second detector 2, and the laser output energy I passing through the single-crystal silicon film sample is recorded. s-6 The percentage of the ratio of ′ to the laser output energy I0 For; then Substitute into the formula I=I0e-kx The rib thickness x is calculated. s-6 =μm; The monocrystalline silicon flexible ribs of the S-7#, S-8#, S-9#, and S-10# monocrystalline silicon wafers were measured in the same way to obtain the percentage change in light intensity of the S-7#, S-8#, S-9#, and S-10# monocrystalline silicon film samples. Then, the percentage change in light intensity of the monocrystalline silicon flexible ribs of the S-7#, S-8#, S-9#, and S-10# monocrystalline silicon wafers was substituted into the formula I = I0e -kx The thickness of the ribs was calculated. Finally, the thickness of the monocrystalline silicon flexible ribs S-7#, S-8#, S-9#, and S-10# was measured using the destructive contact measurement method and compared with the thickness of the monocrystalline silicon flexible ribs measured by the light absorption method. The measurement error was less than 0.3μm.
[0052] The measurement results and comparison of the monocrystalline silicon flexible ribs of S-6#, S-7#, S-8#, S-9#, and S-10# crystalline silicon wafers are shown in Table 4.
[0053] Table 4. Measurement results and comparison of the flexible ribs of monocrystalline silicon oscillating wafers S-6# to S-10#.
[0054]
Claims
1. A method for detecting the thickness of a single-crystal silicon flexible rib based on light absorption, characterized in that, (1) Fabrication of single-crystal silicon film samples Select a silicon wafer with crystal orientation 100, 100-200mm 2 A rectangular area mask is used, and a potassium hydroxide etching solution is applied at an etching rate of 0.5-1.0 μm / min to etch a single-crystal silicon film with a thickness of 12-16 μm onto the silicon wafer. (2) Measurement of single-crystal silicon film samples Take a set of single-crystal silicon film samples, place one single-crystal silicon film sample on the support (3) and place it between the output end of the light source (5) and the first detector (1). The output wavelength of the light source (5) is 632.8nm. Read the laser output energy I passing through the single-crystal silicon film sample from the output end of the first detector (1). i The laser output energy I0 is read from the output terminal of the second detector (2), and the laser output energy I passing through the single-crystal silicon film sample is recorded. i Percentage of the laser output energy I0 The single-crystal silicon film sample was then etched with potassium hydroxide at 1.0 μm intervals. The same measurement was performed every 1.0 μm etched until the thickness of the single-crystal silicon film sample was 8-12 μm. This yielded a set of percentage changes in light intensity. A set of data was obtained from the first monocrystalline silicon film sample, along with the thickness of the silicon film. The remaining monocrystalline silicon film samples were then measured in the same manner to obtain the percentage change in light intensity for all the selected monocrystalline silicon film samples. Data related to silicon film thickness; (3) Data processing and analysis According to Lambert's law of light absorption, I = I₀e⁻ -kx Where I0 and I are the incident light intensity and the exit light intensity, respectively, k is the absorption coefficient, and x is the thickness of the medium through which the light passes. The slope of the fitted curve was calculated to obtain the absorption coefficient k of a set of single-crystal silicon film samples. i Then take k i The arithmetic mean of the values is the absorption coefficient k of the single-crystal silicon film sample; (4) Testing of monocrystalline silicon flexible ribs The component under test is placed on the support (3) and positioned between the output end of the light source (5) and the first detector (1), so that the light beam passes horizontally and completely through the flexible rib of the component. The laser output energy I′ passing through the flexible rib of the component under test is read from the output end of the first detector (1), and the laser output energy I0 is read from the output end of the second detector (2). The percentage ratio of the laser output energy I′ passing through the flexible rib of the component under test to the laser output energy I0 is recorded. Then, based on the known absorption coefficient k value of the single-crystal silicon film sample, the formula I = I0e is used. -kx The thickness of the flexible ribs of the tested element is calculated.