Online film stress testing method

Abstract

The invention relates to an online film stress testing method, which comprises the following steps: S11, arranging a first sample and a second sample which are arranged side by side and have different thicknesses and the same material, and shortening the free ends of a first group of cantilever beams of the first sample and a second group of cantilever beams of the second sample at equal intervals; s12, a group of parallel incident laser beams are emitted to the positions, with the same distance from the free end, of the lower surface of each cantilever beam in the first sample and the second sample before film coating and after film coating by adopting the same film preparation process, and after reflection, position information of corresponding laser spots of the reflected beams is obtained by a laser spot displacement detector; calculating to obtain the curvature radius of each cantilever beam, and calculating the arithmetic average value of the first sample and the second sample to obtain the curvature radius average value of the first sample and the curvature radius average value of the second sample; and S13, aiming at the first sample and the second sample, simultaneously establishing two Stoney equations, and calculating the film stress and the film thickness. The test method is high in test speed and high in test precision.

Description

Technical Field

[0001] This application relates to thin film stress measurement technology, and more specifically, to an on-line thin film stress test method. Background Art

[0002] Thin films prepared by physical vapor deposition technology are applied in various fields, especially various functional thin films, including semiconductor thin films, electrical thin films, magnetic thin films, hard thin films, etc. The stress existing in the thin film usually has a significant impact on its acoustic, optical, electrical, magnetic, thermal, mechanical and other properties. It is of great significance to accurately measure the thin film stress value. The currently widely used thin film stress test technology is based on the substrate bending method and applies Stoney formula to calculate the thin film stress. However, the current such test methods are all computationally complex and the test results have low accuracy. Summary of the Invention

[0003] The technical problem to be solved by this application is to provide an on-line thin film stress test method with accurate testing and test results conducive to processing in view of the above-mentioned defects of the prior art.

[0004] This application proposes an on-line thin film stress test method in the first aspect to solve its technical problems, including the following steps:

[0005] S11. Set the sample to be tested to include a first sample and a second sample arranged side by side. The first sample and the second sample have different thicknesses but the same material. The first sample is provided with a first group of cantilever beams, and the second sample is provided with a second group of cantilever beams. Moreover, the fixed ends of each cantilever beam in the first group of cantilever beams and the second group of cantilever beams are in the same position in the arrangement direction, and the free ends are shortened at equal distances. The upper surface of each cantilever beam is used as the thin film attachment surface;

[0006] S12. Use a group of parallel incident laser beams to irradiate at the positions with the same distance from the free end on the lower surface of each cantilever beam in the first group of cantilever beams of the first sample and the second group of cantilever beams of the second sample before coating and after coating with the same thin film preparation process. After being reflected by each cantilever beam, the position information of the corresponding laser spot of the reflected beam is obtained by a laser spot displacement detector, and the radius of curvature of each cantilever beam after coating is calculated as follows:

[0007]

[0008] Wherein, R is the radius of curvature of the cantilever beam after coating, H is the reflected optical path before coating, l is the length distance from the fixed end of the cantilever beam to the laser spot reflection point, and D is the spot displacement distance on the laser spot displacement detector before and after coating;

[0009] S13, respectively calculating the arithmetic mean of the curvature radius of the first group of cantilever beams of the first sample after coating and the curvature radius of the second group of cantilever beams of the second sample to obtain the average curvature radius of the first sample after coating and the average curvature radius of the second sample;

[0010] S14. For the first sample and the second sample, two Stoney equations are combined to obtain the film stress and film thickness of the first sample and the second sample:

[0011]

[0012] Where σ is the film stress, and the film stress of the first sample and the second sample is the same; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate; h f is the film thickness, the film thickness of the first sample and the second sample is the same; R f is the curvature radius of the cantilever beam after coating, and is substituted into the average curvature radius of the first sample and the average curvature radius of the second sample after coating respectively; R o is the curvature radius of the cantilever beam before coating, 1 / R in the straight state o =0.

[0013] According to an embodiment of the online thin film stress testing method described in the first aspect of the present application, step S12 of the method further includes: during the coating process, using the group of parallel incident laser beams to illuminate the first group of cantilever beams of the first sample and the second group of cantilever beams of the second sample at a predetermined time interval at a position on the lower surface of each cantilever beam that is the same as the distance between the free ends, after being reflected by each cantilever beam, using a laser spot displacement detector to obtain position information of a corresponding laser spot of the reflected beam, and calculating the curvature radius of each cantilever beam after the current film layer is coated;

[0014] Step S14 of the method further includes: during the coating process, for the first sample and the second sample, two Stoney deformation equations are combined to obtain the real-time film stress and film thickness of the first sample and the second sample or the layer-by-layer film stress and film thickness of the multilayer film:

[0015]

[0016] Among them, σ i is the film stress of the current film thickness, h i is the current film thickness; R i is the curvature radius of the cantilever beam after the current film layer is coated, and the average curvature radius of the first sample and the average curvature radius of the second sample after the current film layer is coated are substituted respectively; R i-1is the radius of curvature of the cantilever beam before coating the current film layer, and the average values of the radii of curvature of the first sample and the second sample before coating the current film layer are respectively substituted; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate.

[0017] In an embodiment of the online thin film stress testing method according to the first aspect of the present application, the method further includes:

[0018] S15. The temperature changes of the first sample and the second sample during the cooling process to room temperature after the coating is completed are recorded in real time by a temperature sensor, and the average values of the real-time radii of curvature of the first sample and the second sample are obtained in the same manner as in steps S12 and S13. Together with the film thickness obtained in step S14, they are substituted into the Stoney equation to obtain the real-time thin film stress of the first sample and the second sample, and thus the thin film stress change value corresponding to the temperature difference is the thermal stress.

[0019] In an embodiment of the online thin film stress testing method according to the first aspect of the present application, in step S12 of the method, the group of parallel incident laser beams are emitted and turned off at intervals in sequence, which is consistent with the arrangement order of the first group of cantilever beams and the second group of cantilever beams, so that the laser spot displacement detector can accurately record the positions of the corresponding laser spots.

[0020] In a second aspect, the present application proposes an online thin film stress testing method to solve its technical problems, including the following steps:

[0021] S21. Set the sample to be tested to include a first sample, a second sample, and a third sample arranged side by side, where the first sample and the second sample have different thicknesses but the same material, the third sample has a different material from the first sample, the first sample is provided with a first group of cantilever beams, the second sample is provided with a second group of cantilever beams, the third sample is provided with a third group of cantilever beams, and the fixed ends of each cantilever beam in the first group of cantilever beams, the second group of cantilever beams, and the third group of cantilever beams are in the same position in the arrangement direction, the free ends are equally spaced and shortened, and the upper surface of each cantilever beam is used as the film attachment surface;

[0022] S22. Use a group of parallel incident laser beams to irradiate the lower surfaces of each cantilever beam in the first group of cantilever beams of the first sample, the second group of cantilever beams of the second sample, and the third group of cantilever beams of the third sample at the same position from the free end before coating and after coating with the same thin film preparation process. After being reflected by each cantilever beam, the laser spot displacement detector obtains the position information of the corresponding laser spots of the reflected beams, and the radius of curvature of each cantilever beam after coating is calculated as follows:

[0023]

[0024] Wherein, R is the radius of curvature of the cantilever beam after coating, H is the reflection optical path before coating, l is the length from the fixed end of the cantilever beam to the reflection point of the laser spot, and D is the spot displacement distance on the laser spot displacement detector before and after coating;

[0025] S23, respectively calculating the arithmetic mean of the curvature radius of the first group of cantilever beams of the first sample after coating, the curvature radius of the second group of cantilever beams of the second sample, and the curvature radius of the third group of cantilever beams of the third sample, to obtain the average value of the curvature radius of the first sample after coating, the average value of the curvature radius of the second sample, and the average value of the curvature radius of the third sample;

[0026] S24. For the first sample and the second sample, two Stoney equations are combined to obtain the film stress and film thickness of the first sample and the second sample:

[0027]

[0028] Where σ is the film stress, and the film stress of the first sample and the second sample is the same; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate; h f is the film thickness, the film thickness of the first sample and the second sample is the same; R f is the curvature radius of the cantilever beam after coating, and is substituted into the average curvature radius of the first sample and the average curvature radius of the second sample after coating respectively; R o is the curvature radius of the cantilever beam before coating, 1 / R in the straight state o =0;

[0029] S25, using the film thickness obtained in step S24 and the average value of the radius of curvature of the third sample obtained in step S23 to substitute into the Stoney equation to obtain the film stress of the third sample after coating;

[0030] S26, using a temperature sensor to record in real time the temperature changes of the first sample and the third sample during the cooling process to room temperature after the coating is completed, and using the same method as step S22 and step S23 to obtain the real-time average value of the radius of curvature of the first sample and the third sample, and substituting it together with the film thickness obtained in step S24 into the Stoney equation to obtain the real-time film stress of the first sample and the third sample, thereby obtaining the thermal stress value of the first sample and the thermal stress value of the third sample that change with temperature under the same film preparation process, and combining the thermal stress calculation equations of the first sample and the third sample to obtain the thermal expansion coefficient of the film as follows:

[0031]

[0032] Among them, α f is the thermal expansion coefficient of the film, α S1 is the thermal expansion coefficient of the cantilever beam on the first sample, α S3 is the thermal expansion coefficient of the cantilever beam on the third sample, σ S1 is the thermal stress value of the first sample changing with temperature, σ S3 is the thermal stress value of the third sample changing with temperature.

[0033] According to one embodiment of the online thin film stress testing method described in the second aspect of the present application, in step S22 of the method, the group of parallel incident laser beams are emitted and turned off in intervals and sequence, which is consistent with the arrangement order of the first group of cantilever beams, the second group of cantilever beams and the third group of cantilever beams, so that the laser spot displacement detector accurately corresponds to and records the position of the corresponding laser spot.

[0034] The implementation of the online film stress test method of the present application has the following beneficial effects: the online film stress test method according to the embodiment of the present application uses a first sample and a second sample with different substrate thicknesses to form the sample to be tested, the first sample has a first group of cantilever beams, the second sample has a second group of cantilever beams, the two groups of cantilever beams on the two samples are combined together to shorten at equal distances, and then a group of parallel laser beams corresponding to the spacing between the two groups of cantilever beams are used to irradiate the free ends of the corresponding cantilever beams in turn, and the laser spot displacement detector detects the position information of the light spots reflected by the two groups of cantilever beams, and thereby obtains the average value of the curvature radius of the cantilever beams on the two samples. In the case where the two samples have the same material process but different substrate thicknesses, the Stoney equation of the two samples is solved jointly to achieve the purpose of measuring film stress and film thickness at the same time, and the test speed is fast and the test accuracy is high. The online film stress testing method according to the embodiment of the present application can also be expanded to design the first sample, the second sample and the third sample using the same film preparation process, wherein the first sample and the second sample have different thicknesses and the same material, and the third sample is made of a different material from the first sample. The film stress and film thickness can be obtained by using the Stoney equation of the first sample and the second sample, and the thermal expansion coefficient of the film can be obtained by using the thermal stress calculation equation of the first sample and the third sample. Therefore, the online film stress testing method according to the embodiment of the present application has a composite function. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present application will be further described below with reference to the accompanying drawings and embodiments, in which:

[0036] Figure 1 is a flow chart of an online film stress testing method according to an embodiment of the present application;

[0037] Figure 2It is a schematic structural diagram of a sample to be measured in an embodiment of the present application;

[0038] Figure 3 is Figure 2 The top view of the sample to be measured shown;

[0039] Figure 4 It is a schematic diagram of the optical path deflection principle caused by the bending of the cantilever beam;

[0040] Figure 5 It is a schematic diagram of the overall structure of an on-line thin film stress tester in an embodiment of the present application;

[0041] Figure 6 is Figure 5 The schematic diagram of the optical path principle of the on-line thin film stress tester shown;

[0042] Figure 7 is Figure 5 The partial structural diagram of the first end of the on-line thin film stress tester shown;

[0043] Figure 8 is Figure 5 The partial structural diagram of the second end of the on-line thin film stress tester shown;

[0044] Figure 9 It is a schematic diagram of the installation of the mirror in an embodiment of the present application;

[0045] Figure 10 It is a flowchart of an on-line thin film stress testing method in another embodiment of the present application.

[0046] Explanation of the reference numerals in the drawings: 10, 20 - on-line thin film stress testing method; 100 - on-line thin film stress tester; 101 - incident light beam; 102 - reflected light beam; 103 - light spot; 11 - first mounting base; 111 - detector bracket; 112 - convex lens support; 113 - concave lens support; 114 - fine adjustment screw mechanism; 12 - second mounting base; 121 - rotating platform; 122 - sample holder; 123 - sample pressing plate; 20 - laser emitter; 30 - convex lens; 40 - concave lens; 50 - mirror; 60 - half lens; 70 - laser spot displacement detector; 80 - sample to be measured; 81 - first sample; 811 - first group of cantilever beams; 82 - second sample; 821 - second group of cantilever beams; 91 - outer shell; 911 - opening; 92 - heater bracket; 93 - radiation heater; 94 - cold water pipe; 95 - temperature sensor. Detailed implementation manners

[0047] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. Moreover, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0048] The existing cantilever beam thin film stress measurement method measures the positions of the free ends of the cantilever beam surface before and after coating respectively, then calculates and processes to obtain the displacement of the free end, and then calculates the magnitude of the thin film stress through the modified Stoney formula. The present application designs an on-line thin film stress test method. Although it is also a deformation and evolution of the Stoney formula (substrate bending method), the design idea is different from the existing cantilever beam measurement method. The present application calculates the thin film stress on the cantilever beam sample by measuring the deflection displacement of the laser spot reflected by the free end of the cantilever beam before and after coating.

[0049] Figure 1 The flowchart of an on-line stress test method 10 according to an embodiment of the present application is shown. Refer to Figure 1 As shown, in an embodiment according to the present application, the on-line thin film stress test method 10 includes the following steps:

[0050] In step S11, in combination with Figure 2 and Figure 3 As shown, it is set that the sample 80 to be tested includes a first sample 81 and a second sample 82 arranged side by side. The first sample 81 and the second sample 82 have different thicknesses but the same material. The first sample 81 is provided with a first group of cantilever beams 811, and the second sample 82 is provided with a second group of cantilever beams 821. Moreover, the fixed ends of each cantilever beam in the first group of cantilever beams 811 and the second group of cantilever beams 821 are in the same position in the arrangement direction, the free ends are shortened at equal distances, and the upper surface of each cantilever beam is used as the thin film attachment surface.

[0051] In a specific embodiment, the first sample 81 and the second sample 82 are straight in their original states. After the first group of cantilever beams 811 and the second group of cantilever beams 821 are arranged side by side on the first sample 81 and the second sample 82, they are equally spaced, and the upper surface is used as the film attachment surface. Among them, the sizes of the five cantilever beams in the first group of cantilever beams 811 are 30×3 mm, 28.5×3 mm, 27×3 mm, 25.5×3 mm, and 24×3 mm respectively. The sizes of the five cantilever beams in the second group of cantilever beams 821 are 22.5×3 mm, 21×3 mm, 19.5×3 mm, 18×3 mm, and 16.5×3 mm respectively. When installed side by side, the length difference between any two adjacent cantilever beams is 1.5 mm, and the widths are the same. Here, the substrate thicknesses of the first sample 81 and the first sample 82 are preferably selected as 0.5 mm and 1.0 mm, and can be adjusted according to the actual measurement of the film. It is only necessary to keep the substrate thicknesses different and the cantilever beams are arranged at equal distances when arranged together.

[0052] Then in step S12, a set of parallel incident laser beams are irradiated at the positions on the lower surfaces of each cantilever beam in the first group of cantilever beams 811 of the first sample 81 and the second group of cantilever beams 821 of the second sample 82 that are at the same distance from the free end before and after coating with the same thin film preparation process. After being reflected by each cantilever beam, the position information of the corresponding laser spot of the reflected beam is obtained by a laser spot displacement detector, and the radius of curvature of each cantilever beam after coating is calculated.

[0053] For specific reference Figure 3 As shown, in this embodiment, it is designed that the distance from the position of the light spot 103 reaching the lower surface of each cantilever beam in the first group of cantilever beams 811 and the second group of cantilever beams 821 to the free end of each cantilever beam is 1.5 mm. This distance value is not absolute, as long as it is close to the free end and the distance from the free end is the same. In this way, as shown Figure 3 As shown, the straight line formed by connecting the positions of the light spots 103 on the lower surface of each cantilever beam has an angle α with the straight line in the arrangement direction (i.e., the y direction) of the first group of cantilever beams 81 and the second group of cantilever beams 82, and α = arctan(x / y) can be calculated, where x is the length difference between every two adjacent cantilever beams in the arrangement direction, and y is the midline distance between every two adjacent cantilever beams in the arrangement direction.

[0054] After coating the upper surfaces of the first group of cantilever beams 811 on the first sample 81 and the second group of cantilever beams 821 on the second sample 82 with the same thin film preparation process, due to the existence of film stress, the cantilever beams will bend. Strictly speaking, the projection curve corresponding to the bending of the cantilever beam sample due to film stress is a parabola, but in the substrate bending method stress test, it is often approximately regarded as an arc line for processing. Figure 4The figure shows a schematic diagram of the principle of optical path deflection caused by the bending of a cantilever beam. The upper surface of the cantilever beam sample is the surface where the thin film is located. Before coating, the cantilever beam sample is straight. After coating, the stress of the thin film causes the sample to bend. Among them, Figure 4 (a) shows the situation where the cantilever beam is concave upward due to the tensile stress of the thin film, Figure 4 (b) shows the situation where the cantilever beam is convex upward due to the compressive stress of the thin film. Since the deflection of the cantilever beam bending is very small, that is, the optical path change caused by the displacement of the free end of the cantilever beam can be ignored. When the cantilever beam is in the original straight state, the optical path length of the laser reflected from the lower surface passing through the semi-transparent mirror to the laser spot displacement detector is H. When the cantilever beam bends under the action of the thin film stress, it causes the laser reflection on the lower surface to deflect, and passes through the semi-transparent mirror to the laser spot displacement detector. The displacement distance of the laser spot on the laser spot displacement detector caused by this deflection is D. At this time, the radius of curvature of the cantilever beam is R. The corresponding geometric relationship is shown in Figure 4 , in the case of a very small angle, such as less than 5°, tanγ≈γ (radian). And in this test, γ is a very small angle, so it can be obtained that:

[0055]

[0056] Therefore, the calculation formula for the radius of curvature of the cantilever beam can be obtained as:

[0057]

[0058] Among them, R is the radius of curvature of the cantilever beam after coating, H is the reflected optical path before coating, l is the length distance from the fixed end of the cantilever beam to the laser spot reflection point, and D is the displacement distance of the laser spot on the laser spot displacement detector before and after coating.

[0059] In the specific test process, the group of incident laser beams can be emitted and turned off at intervals in the same arrangement order as the first group of cantilever beams 811 and the second group of cantilever beams 821, so that the laser spot displacement detector can accurately record the positions of the corresponding laser spots. The laser beams are emitted and turned off one by one. In theory, as long as the position of the reflected laser spot can be recognized, the current beam can be turned off and the next beam can be emitted. Therefore, the test time for each cantilever beam is less than 10 s, and the test speed is fast.

[0060] Then in step S13, the arithmetic means of the radii of curvature of the first group of cantilever beams 811 of the first sample 81 and the second group of cantilever beams 821 of the second sample 82 after coating are calculated respectively to obtain the average radius of curvature of the first sample 81 and the average radius of curvature of the second sample 82 after coating.

[0061] Since the substrate parameters of each cantilever beam in the first group of cantilever beams 811 are the same, the film thickness is the same, and the film preparation process is the same, the film stress value is also the same, and the corresponding curvature radius value should also be the same. Therefore, the arithmetic average value can be calculated for the five curvature radius values of the first group of cantilever beams 811 to obtain the average curvature radius R1 of the first sample 81 under the film stress. Similarly, for the second sample 82, the average curvature radius R2 can be obtained. Because the first sample 81 and the second sample 82 are made of the same material and have the same coating process, the film stress value is also the same, and the different curvature radii are generated because the substrate thicknesses of the first sample 81 and the second sample 82 are different.

[0062] Then in step S14, two Stoney equations are combined for the first sample 81 and the second sample 82 to obtain the film stress and film thickness of the first sample 81 and the second sample 82:

[0063]

[0064] Wherein, σ is the film stress, and the film stress of the first sample 81 and the second sample 82 is the same; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate; h f is the film thickness, the film thickness of the first sample and the second sample is the same; R f is the curvature radius of the cantilever beam after coating, and is substituted into the average curvature radius of the first sample and the average curvature radius of the second sample after coating respectively; R o is the curvature radius of the cantilever beam before coating, 1 / R in the straight state o =0.

[0065] Because the substrate materials of the first sample 81 and the second sample 82 are consistent and known (i.e., E S 、h S , ν S Known), film thickness h f The film stress σ1 on the first sample 81 and the film stress σ2 on the second sample 82 are consistent, and two Stoney equations can be listed. The unknowns σ and h can be obtained by combining the two equations. f , thereby achieving the purpose of simultaneous measurement of film stress and film thickness.

[0066] According to a further embodiment of the present application, the above-mentioned online thin film stress test method 10 can also be used to perform online stress real-time testing on the sample 80 to be tested or to perform layer-by-layer testing and analysis on the stress of a multi-layer film. Specifically, in step S12, during the coating process, the group of parallel incident laser beams can be used to irradiate the first group of cantilever beams 811 of the first sample 81 and the second group of cantilever beams 821 of the second sample 82 at a predetermined time interval at the same position as the free end spacing on the lower surface of each cantilever beam. After reflection by each cantilever beam, the laser spot displacement detector obtains the position information of the corresponding laser spot of the reflected beam, and the curvature radius of each cantilever beam after the current film layer is coated is calculated. Then, in step S13, the average curvature radius of the first sample and the second sample after the current film layer is coated can be obtained. Then, in step S14, the following two Stoney deformation equations can be combined for the first sample 81 and the second sample 82 to obtain the real-time thin film stress and film thickness of the first sample 81 and the second sample 82 or the layer-by-layer thin film stress and film thickness of the multi-layer film:

[0067]

[0068] Among them, σ i is the film stress of the current film thickness, h i is the current film thickness; R i is the curvature radius of the cantilever beam after the current film layer is coated, and the average curvature radius of the first sample and the average curvature radius of the second sample after the current film layer is coated are substituted respectively; R i-1 is the curvature radius of the cantilever beam before the current film layer is coated, and the average curvature radius of the first sample and the average curvature radius of the second sample before the current film layer is coated are substituted respectively; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate.

[0069] Since the film thickness is much smaller than the substrate thickness, the above Stoney deformation equation can be easily derived by applying relevant knowledge of mechanics. Applying this equation, it is possible to perform online stress real-time testing on the sample to be tested or to perform layer-by-layer stress testing and analysis on the multilayer film, and obtain more accurate test results.

[0070] According to a further embodiment of the present application, the above-mentioned online film stress testing method 10 can also measure the thermal stress of the film, and calculate its intrinsic stress based on the total stress of the film. During the film deposition process, due to the effect of plasma, the temperature of the sample 80 to be tested gradually reaches the highest value. After the coating is completed, the sample 80 to be tested gradually cools to room temperature. During this process, the film stress change value corresponding to the temperature difference of the sample to be tested is the thermal stress (it is generally believed that the film stress is generally composed of two parts of stress: intrinsic stress and thermal stress).

[0071] Therefore, the above-mentioned online thin film stress testing method 10 may also include the following steps:

[0072] In step S15, the temperature sensor is used to record in real time the temperature changes of the first sample 81 and the second sample 82 during the process of cooling to room temperature after the film coating is completed. The average value of the real-time curvature radii of the first sample 81 and the second sample 82 is obtained in the same manner as in the aforementioned steps S12 and S13. Together with the film thickness obtained in the aforementioned step S14, they are substituted into the Stoney equation to obtain the real-time thin film stress of the first sample 81 and the second sample 82. Thus, the thin film stress change value corresponding to the temperature difference, that is, the thermal stress, can be obtained, and the intrinsic stress can be calculated according to the total thin film stress. In a specific embodiment, the temperature changes of the first sample 81 and the second sample 82 can be obtained by temperature sensors attached to the lower surfaces of the first sample 81 and the second sample 82.

[0073] To implement the above-mentioned online stress testing method 10 of the present application, the present application designs Figure 5 the online thin film stress tester 100 as shown in the figure, and its optical path principle is as Figure 6 shown. Refer to Figure 5 and Figure 6 The online thin film stress tester 100 mainly consists of a first mounting base 11, a second mounting base 12, a laser emitter 20, a convex lens 30, a concave lens 40, a reflector 50, a semi-lens 60, a laser spot displacement detector 70, and a sample to be tested 80. The first mounting base 11 and the second mounting base 12 are oppositely arranged at the first end and the second end. The laser emitter 20, the convex lens 30, the concave lens 40, and the laser spot displacement detector 70 are arranged on the first mounting base 11, and the reflector 50, the semi-lens 60, and the sample to be tested 80 are arranged on the second mounting base 12.

[0074] Specifically refer to Figure 5 Combined with Figure 7 shown, the laser emitter 20 has a row of multiple laser light sources horizontally arranged facing the second mounting base 12 at the second end. The convex lens 30 is mounted on a convex lens support 112 on the side of the laser emitter 20 relatively close to the second end. The concave lens 40 is mounted on a concave lens support 113 arranged on the side of the convex lens 30 relatively close to the second end. The laser spot displacement detector 70 is mounted facing the second end on a detector support 111 and is located above the laser emitter 20. The concave lens support 113 can move back and forth in the incident light path direction relative to the first mounting base 11, driving the concave lens 40 to move back and forth to adjust the distance between it and the convex lens 30, thereby adjusting the spacing of the incident light beam 101 (refer to Figure 7As shown). Specifically, the front and rear displacement of the concave lens holder 113 can be achieved by, for example, a micro-motion screw mechanism 114 to achieve extremely small displacements. The micro-motion screw mechanism 114 is a prior art and will not be described in detail in this application. Referring further to Figure 5 Combined with Figure 8 As shown, a rotating platform 121 that rotates around an axis perpendicular to the horizontal plane and a sample holder 122 for supporting the sample to be measured 80 are provided on the second mounting base 12. The reflecting mirror 50 is installed on the rotating platform 122 at an inclination of 45° facing the concave lens 40 at the first end. The half mirror 60 is disposed above the reflecting mirror 50 at an inclination of 45° facing the laser spot displacement detector 70. The sample to be measured 80 is supported by the sample holder 122 above the half mirror 60.

[0075] Further referring to Figure 6 As shown, the optical path principle of the on-line thin film stress tester 100 according to the above embodiments of the present application is as follows: A plurality of laser light sources of the laser emitter 20 emit a set of parallel light beams, which are converged by the convex lens 30 and then adjusted by the concave lens 40 into parallel incident light beams 101 with an appropriate spacing and reach the reflecting mirror 50. The reflecting mirror 50 reflects the light upward through the half mirror 60 and reaches the position at the same distance from the free end on the lower surface of each cantilever beam in the first set of cantilever beams 811 of the first sample 81 and the second set of cantilever beams 821 of the second sample 82 (refer to Figure 3 As shown). The reflected light beam 102 after being reflected by each cantilever beam reaches the upper surface of the half mirror 60, is reflected by the half mirror 60 to the laser spot displacement detector 70, and the laser spot displacement detector 70 obtains the position information of the corresponding laser spot for calculating the thin film stress and related performance parameters. During the test, the plurality of laser light sources of the laser emitter 20 can be emitted and turned off at intervals in sequence, which is consistent with the arrangement order of the first set of cantilever beams 81 and the second set of cantilever beams 82, so as to accurately record the positions of the corresponding laser spots.

[0076] Furthermore, referring to Figure 5As shown, for the convenience of applying the on-line thin film stress tester 100 to on-line thin film stress testing, the on-line thin film stress tester 100 is further provided with a housing 91, which needs to be made of a material with good rigidity, such as aluminum alloy, to provide protection for the internal devices in the coating chamber. The first mounting seat 11 and the second mounting seat 12 are respectively fixed to the opposite first end and second end inside the housing 91. The laser emitter 20, the convex lens 30, the concave lens 40, the laser spot displacement detector 70, the reflector 50 and the semi-transparent lens 60 are all housed inside the housing 91. The first sample 81 and the second sample 82 of the sample to be tested 80 can be tightly fixed to the housing 91 through the sample pressing plate 123, so that the first group of cantilever beams 811 and the second group of cantilever beams 821 are exposed from the openings 911 correspondingly opened on the housing 91. When performing on-line thin film stress testing, insert the second end (i.e., the sample end) of the on-line thin film stress tester 100 into the coating vacuum chamber, adjust the position so that the first group of cantilever beams 811 and the second group of cantilever beams 821 exposed from the housing 91 face the target, and then the testing can be carried out while the coating operation is in progress. During the thin film deposition process, the sample to be tested 80 will gradually heat up under the action of the plasma. In order to keep the laser spot displacement detector 70 in the on-line thin film stress tester 100 at a low temperature, cold water pipes 94 are also arranged around it (see Figure 7 shown), to introduce circulating water to maintain the low temperature and ensure that the laser spot position information obtained by the laser spot displacement detector 70 is accurate. In addition, cold water pipes 94 can also be arranged around the convex lens support 112 of the convex lens 30 and even around the first mounting seat 11 to maintain the low temperature. See again Figure 8 shown, the temperature sensors 95 are attached to the lower surfaces of the first sample 81 and the second sample 82 of the sample to be tested 80, which can record the temperature of the sample to be tested 80 in real time and be used to calculate relevant performance parameters.

[0077] As mentioned above, the straight line formed by connecting the positions of the light spots 103 projected on the lower surfaces of each cantilever beam of the first sample 81 and the second sample 82 has an included angle α with the straight line in the arrangement direction (i.e., the y direction) of the first group of cantilever beams 81 and the second group of cantilever beams 82. See Figure 9 shown, in addition to being inclined at 45° to the horizontal plane and mounted on the rotating platform 121, the reflector 50 needs to have an included angle α with respect to the traveling direction of the incident light beam 101 through the rotation of the rotating platform 121, so as to ensure that a group of ten parallel light beams are respectively projected at the same distance from the free end of each cantilever beam. Moreover, the center line distance between every two adjacent cantilever beams, that is, Figure 3 the distance between adjacent laser spots 103 in the y direction in Figure 4 corresponds to the spacing between the incident light beams 101 adjusted by the concave lens 30 in

[0078] The present application also proposes an online thin film stress testing method 20 which expands and designs three samples based on the aforementioned online thin film stress testing method 10 . Figure 10 2 shows a flow chart of the online stress testing method 20. Figure 10 As shown, the online film stress testing method 20 comprises the following steps:

[0079] In step S21, the samples to be tested are set to include a first sample, a second sample and a third sample arranged side by side, wherein the first sample and the second sample have different thicknesses but the same material, the third sample is made of a different material from the first sample, the first sample is provided with a first group of cantilever beams, the second sample is provided with a second group of cantilever beams, and the third sample is provided with a third group of cantilever beams, and the fixed ends of each cantilever beam in the first group of cantilever beams, the second group of cantilever beams and the third group of cantilever beams are in the same position in the arrangement direction, the free ends are shortened at equal distances, and the upper surface of each cantilever beam is used as a film attachment surface.

[0080] In step S22, a group of parallel incident laser beams are used to irradiate the first group of cantilever beams of the first sample, the second group of cantilever beams of the second sample, and the third group of cantilever beams of the third sample at the same position as the free end spacing on the lower surface of each cantilever beam before coating and after coating using the same thin film preparation process. After reflection by each cantilever beam, the laser spot displacement detector obtains the position information of the corresponding laser spot of the reflected beam, and the curvature radius of each cantilever beam after coating is calculated as follows:

[0081]

[0082] Wherein, R is the radius of curvature of the cantilever beam after coating, H is the reflected optical path before coating, l is the length from the fixed end of the cantilever beam to the reflection point of the laser spot, and D is the spot displacement distance on the laser spot displacement detector before and after coating.

[0083] In step S23, the arithmetic mean of the curvature radius of the first group of cantilever beams of the first sample after coating, the curvature radius of the second group of cantilever beams of the second sample, and the curvature radius of the third group of cantilever beams of the third sample are calculated to obtain the average curvature radius of the first sample after coating, the average curvature radius of the second sample, and the average curvature radius of the third sample.

[0084] In step S24, two Stoney equations are combined for the first sample and the second sample to obtain the film stress and film thickness of the first sample and the second sample:

[0085]

[0086] Where σ is the film stress, and the film stress of the first sample and the second sample is the same; E S is the elastic modulus of the sample substrate, h Sis the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate; h f is the film thickness, the film thickness of the first sample and the second sample is the same; R f is the curvature radius of the cantilever beam after coating, and is substituted into the average curvature radius of the first sample and the average curvature radius of the second sample after coating respectively; R o is the curvature radius of the cantilever beam before coating, 1 / R in the straight state o =0.

[0087] In step S25, the film thickness obtained in step S24 and the average value of the radius of curvature of the third sample obtained in step S23 are substituted into the Stoney equation to obtain the film stress of the third sample after coating.

[0088] In step S26, the temperature sensor is used to record the temperature change of the first sample and the third sample during the cooling process to room temperature after the coating is completed, and the real-time average value of the curvature radius of the first sample and the third sample is obtained in the same manner as in steps S22 and S23. The average value is substituted into the Stoney equation together with the film thickness obtained in step S24 to obtain the real-time film stress of the first sample and the third sample, thereby obtaining the thermal stress value σ of the first sample changing with temperature under the same film preparation process S1 and the thermal stress value σ of the third sample changing with temperature S3 From the thermal stress calculation formula, we can know that the stress value of the first sample changes with temperature σ S1 , which corresponds to the temperature change value ΔT; the stress value σ of the third sample changes with temperature S3 , which corresponds to the temperature change value ΔT. Therefore, the following thermal stress calculation equations for the first sample and the third sample can be obtained:

[0089]

[0090] Among them, E f is the elastic modulus of the film, ν f is the Poisson's ratio of the film, α S1 is the thermal expansion coefficient of the cantilever beam on the first sample (known), α S3 is the thermal expansion coefficient of the cantilever beam on the third sample (known), α f is the thermal expansion coefficient of the film, and ΔT is the temperature change value. Usually E f With ν f It is difficult to calculate, but by combining the above two thermal stress calculation equations, the thermal expansion coefficient of the film can be calculated as follows:

[0091]

[0092] Among them, α f is the thermal expansion coefficient of the film, αS1 is the thermal expansion coefficient of the cantilever beam on the first sample, α S3 is the thermal expansion coefficient of the cantilever beam on the third sample, σ S1 is the thermal stress value of the first sample changing with temperature, σ S3 is the thermal stress value of the third sample as it changes with temperature. Under the premise of knowing the physical properties of the substrate material and measuring the thermal stress value, the thermal expansion coefficient α of the film can be calculated. f .

[0093] According to the online film stress testing method 20 of the above-mentioned extended embodiment of the present application, two Stoney equations are solved by combining the first sample and the second sample with different substrate thicknesses and the same material to test the stress and thickness of the film. By combining the first sample and the third sample with different substrate materials and the temperature change, two thermal stress calculation equations are solved to calculate the thermal expansion coefficient of the film.

[0094] Therefore, the online thin film stress testing method according to the embodiment of the present application has a composite function, can be used to measure thin film online stress, film thickness, multilayer film stress, thin film thermal stress, thin film intrinsic stress and thin film thermal expansion coefficient, and has fast testing speed and high testing accuracy.

[0095] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An on-line thin film stress testing method, characterized in that, The steps include: S11, setting the samples to be tested to include a first sample and a second sample arranged side by side, the first sample and the second sample have different thicknesses and the same material, the first sample is provided with a first group of cantilever beams, the second sample is provided with a second group of cantilever beams, and the fixed ends of each cantilever beam in the first group of cantilever beams and the second group of cantilever beams are at the same position in the arrangement direction, the free ends are shortened at an equal distance, and the upper surface of each cantilever beam is used as a film attachment surface; S12, using a group of parallel incident laser beams to illuminate the positions of the lower surface of each cantilever beam in the first group of cantilever beams of the first sample and the second group of cantilever beams of the second sample before coating and after coating using the same thin film preparation process at the same distance from the free end, after being reflected by each cantilever beam, the position information of the corresponding laser spot of the reflected beam is obtained by the laser spot displacement detector, and the curvature radius of each cantilever beam after coating is calculated as follows: Wherein, R is the radius of curvature of the cantilever beam after coating, H is the reflection optical path before coating, l is the length from the fixed end of the cantilever beam to the reflection point of the laser spot, and D is the spot displacement distance on the laser spot displacement detector before and after coating; S13, respectively calculating the arithmetic mean of the curvature radius of the first group of cantilever beams of the first sample after coating and the curvature radius of the second group of cantilever beams of the second sample to obtain the average curvature radius of the first sample after coating and the average curvature radius of the second sample; S14. For the first sample and the second sample, two Stoney equations are combined to obtain the film stress and film thickness of the first sample and the second sample: where, σ is the film stress, and the film stresses of the first sample and the second sample are the same; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate; h f is the film thickness, and the film thicknesses of the first sample and the second sample are the same; R f is the radius of curvature of the cantilever beam after coating, and the average values of the radii of curvature of the first sample and the second sample after coating are substituted respectively; R o is the radius of curvature of the cantilever beam before coating, and 1 / R o = 0 in the flat state.

2. The online thin film stress testing method according to claim 1, characterized in that, Step S12 of the method further comprises: during the coating process, using the group of parallel incident laser beams to illuminate the positions of the lower surface of each cantilever beam in the first group of cantilever beams of the first sample and the second group of cantilever beams of the second sample at the same distance from the free end at a predetermined time interval, after being reflected by each cantilever beam, obtaining the position information of the corresponding laser spot of the reflected beam by a laser spot displacement detector, and calculating the curvature radius of each cantilever beam after the current film layer is coated; Step S14 of the method further includes: during the coating process, for the first sample and the second sample, two Stoney deformation equations are combined to obtain the real-time film stress and film thickness of the first sample and the second sample or the layer-by-layer film stress and film thickness of the multilayer film: Among them, σ i is the thin film stress of the current film thickness, h i is the current film thickness; R i is the radius of curvature of the cantilever beam after coating the current film, and the average values of the radii of curvature of the first sample and the second sample after coating the current film are substituted respectively; R i-1 is the radius of curvature of the cantilever beam before coating the current film, and the average values of the radii of curvature of the first sample and the second sample before coating the current film are substituted respectively; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate.

3. The online thin film stress testing method according to claim 1, wherein The method further comprises: S15. Record the temperature change of the first sample and the second sample in the process of cooling to room temperature after the coating is completed by a temperature sensor in real time, and obtain the real-time average value of the radius of curvature of the first sample and the second sample in the same manner as steps S12 and S13. Substitute the average value together with the film thickness obtained in step S14 into the Stoney equation to obtain the real-time film stress of the first sample and the second sample, so that the film stress change value corresponding to the temperature difference is the thermal stress.

4. The online thin-film stress testing method according to claim 1, characterized in that In step S12 of the method, the group of parallel incident laser beams are emitted and turned off in an interval sequence, which is consistent with the arrangement sequence of the first group of cantilever beams and the second group of cantilever beams, so that the laser spot displacement detector accurately corresponds to and records the position of the corresponding laser spot.

5. An online thin film stress testing method, characterized in that, The steps include: S21, setting the samples to be tested to include a first sample, a second sample and a third sample arranged side by side, wherein the first sample and the second sample have different thicknesses but the same material, the third sample and the first sample have a different material, the first sample is provided with a first group of cantilever beams, the second sample is provided with a second group of cantilever beams, and the third sample is provided with a third group of cantilever beams, and the fixed ends of each cantilever beam in the first group of cantilever beams, the second group of cantilever beams and the third group of cantilever beams are at the same position in the arrangement direction, the free ends are shortened at equal distances, and the upper surface of each cantilever beam is used as a film attachment surface; S22, use a group of parallel incident laser beams to illuminate the first group of cantilever beams of the first sample before coating and after coating using the same thin film preparation process, the second group of cantilever beams of the second sample, and the third group of cantilever beams of the third sample at the same position as the free end of the lower surface of each cantilever beam, after reflection by each cantilever beam, obtain the position information of the corresponding laser spot of the reflected light beam by the laser spot displacement detector, and calculate the curvature radius of each cantilever beam after coating as follows: Wherein, R is the radius of curvature of the cantilever beam after coating, H is the reflection optical path before coating, l is the length from the fixed end of the cantilever beam to the reflection point of the laser spot, and D is the spot displacement distance on the laser spot displacement detector before and after coating; S23, respectively calculating the arithmetic mean of the curvature radius of the first group of cantilever beams of the first sample after coating, the curvature radius of the second group of cantilever beams of the second sample, and the curvature radius of the third group of cantilever beams of the third sample, to obtain the average value of the curvature radius of the first sample after coating, the average value of the curvature radius of the second sample, and the average value of the curvature radius of the third sample; S24. For the first sample and the second sample, two Stoney equations are combined to obtain the film stress and film thickness of the first sample and the second sample: where, σ is the film stress, and the film stresses of the first sample and the second sample are the same; E S is the elastic modulus of the sample substrate, h S is the thickness of the sample substrate, ν S is the Poisson's ratio of the sample substrate; h f is the film thickness, and the film thicknesses of the first sample and the second sample are the same; R f is the radius of curvature of the cantilever beam after coating, and the average values of the radii of curvature of the first sample and the second sample after coating are substituted respectively; R o is the radius of curvature of the cantilever beam before coating, and 1 / R o = 0; S25, using the film thickness obtained in step S24 and the average value of the radius of curvature of the third sample obtained in step S23 to substitute into the Stoney equation to obtain the film stress of the third sample after coating; S26, using a temperature sensor to record in real time the temperature changes of the first sample and the third sample during the cooling process to room temperature after the coating is completed, and using the same method as step S22 and step S23 to obtain the real-time average value of the radius of curvature of the first sample and the third sample, and substituting it together with the film thickness obtained in step S24 into the Stoney equation to obtain the real-time film stress of the first sample and the third sample, thereby obtaining the thermal stress value of the first sample and the thermal stress value of the third sample that change with temperature under the same film preparation process, and combining the thermal stress calculation equations of the first sample and the third sample to obtain the thermal expansion coefficient of the film as follows: where α f is the thermal expansion coefficient of the thin film, α S1 is the thermal expansion coefficient of the cantilever beam on the first sample, α S3 is the thermal expansion coefficient of the cantilever beam on the third sample, σ S1 is the thermal stress value of the first sample varying with temperature, σ S3 is the thermal stress value of the third sample varying with temperature.

6. The online thin film stress testing method according to claim 5, characterized in that, In step S22 of the method, the group of parallel incident laser beams are emitted and turned off in interval sequence, which is consistent with the arrangement sequence of the first group of cantilever beams, the second group of cantilever beams and the third group of cantilever beams, so that the laser spot displacement detector accurately corresponds to and records the position of the corresponding laser spot.

Images