Thin film stress detection device and system

Abstract

The utility model discloses a thin film stress detection device and system. The thin film stress detection device comprises a detection module, a scanning module and a processing module, the detection module comprises a laser unit, an adjustable attenuation unit and a detection unit; the detection module is fixedly connected with the scanning module, and the scanning module and the detection unit are electrically connected with the processing module; the scanning module drives the detection module to move in the first direction to scan the to-be-detected film and obtain displacement data of the detection module; detection laser emitted by the laser unit passes through the adjustable attenuation unit, then enters the surface of the to-be-detected thin film, is reflected by the surface of the to-be-detected thin film and then enters the detection unit, and the detection unit obtains light spot motion data of the detection laser entering the to-be-detected thin film at different positions; and the processing module calculates the stress of the to-be-measured film according to the displacement data and the light spot motion data. The stress detection device provided by the utility model not only simplifies the calibration process and reduces the measurement error, but also can detect a material with a larger reflectivity range.

Description

Technical Field

[0001] This utility model relates to the field of thin film stress measurement technology, and in particular to a thin film stress detection device and system. Background Technology

[0002] Traditional thin-film stress detection methods are mainly based on the principles of elasticity and light reflection, combining the Stoney equation and the optical lever method. The former is the most classic calculation method for thin-film residual stress testing, while the latter amplifies and captures minute curvature changes on the wafer surface using an optical lever. The sensor typically used to receive the light signal is a charge-coupled device (CCD). However, to test materials with weak surface reflectivity, a beam splitter is used to superimpose the energies of two lasers to enhance the intensity of the light signal.

[0003] When the light intensity received by the surface of a photosensitive sensor (such as a CCD) is too strong, it will cause its signal to saturate and distort. Therefore, when selecting a laser, a laser with a power lower than the saturation light power of the CCD after being reflected by silicon is usually selected.

[0004] To ensure compatibility with materials that have low reflectivity at certain wavelengths, a separate laser wavelength is selected, and a beam splitter is used to make the two lasers share a common optical path to enhance signal strength. This introduces several challenges. For example, for materials with higher reflectivity than silicon, such as copper, the light intensity may directly saturate, making testing impossible. Furthermore, adding a laser introduces two modes: either two lasers operating individually or both operating simultaneously. This increases the time required for setup and requires calibration for each mode, significantly increasing equipment maintenance and debugging time. Additionally, the two lasers cannot always share a perfect optical path, leading to inaccurate test results. Utility Model Content

[0005] This invention provides a thin-film stress detection device and system. The laser output power is adjusted by an adjustable attenuation unit, which can be adapted to different materials without changing the optical path. This not only simplifies the calibration process and reduces measurement errors, but also allows the detection of materials with a wider range of reflectivity, eliminating concerns about light intensity saturation of the photosensitive sensor.

[0006] According to a first aspect of the present invention, a thin film stress detection device is provided, comprising a detection module, a scanning module, and a processing module; the detection module includes a laser unit, an adjustable attenuation unit, and a detection unit; the detection module is fixedly connected to the scanning module, and both the scanning module and the detection unit are electrically connected to the processing module.

[0007] The scanning module drives the detection module to move along the first direction to scan the film to be tested and acquire the displacement data of the detection module;

[0008] The detection laser emitted by the laser unit passes through the adjustable attenuation unit and is incident on the surface of the film under test. After being reflected by the surface of the film under test, it is incident on the detection unit. The detection unit acquires the spot motion data of the detection laser incident on the film under test at different positions. The processing module calculates the stress of the film under test based on the displacement data and the spot motion data.

[0009] Wherein, the first direction is parallel to the plane where the film to be tested is located.

[0010] Optionally, the adjustable attenuation unit includes multiple attenuation plates and a turntable mechanism;

[0011] Multiple attenuators are disposed on the turntable mechanism, the rotation center axis of the turntable mechanism is parallel to the optical axis of the detection laser, and the multiple attenuators are arranged in a ring uniformly around the rotation center axis of the turntable mechanism;

[0012] The turntable mechanism rotates to feed different attenuators into the transmission path of the detection laser incident on the film under test.

[0013] Optionally, the adjustable attenuation unit further includes a stepper motor;

[0014] The stepper motor is fixedly connected to the turntable mechanism, and the stepper motor drives the turntable mechanism to rotate.

[0015] Optionally, the attenuation rates of the multiple attenuators may be different.

[0016] Optionally, the adjustable attenuation unit further includes a position sensor;

[0017] The position sensor is connected to the stepper motor.

[0018] Optionally, the detection module further includes a reflection unit;

[0019] The detection laser is reflected by the surface of the film under test and then incident on the reflection unit, where it is reflected back to the detection unit.

[0020] Optionally, the detection module includes an optical backplate;

[0021] The laser unit, the adjustable attenuation unit, the detection unit, and the reflection unit are all integrated on the optical backplate.

[0022] Optionally, the scanning module includes a linear motor.

[0023] Optionally, the reflecting unit includes a reflector.

[0024] According to a second aspect of the present invention, a thin film stress detection system for a wafer is provided, comprising a wafer to be tested and any of the thin film stress detection devices described in the first aspect of the present invention.

[0025] This utility model discloses a thin film stress detection device, including a detection module, a scanning module, and a processing module. The detection module includes a laser unit, an adjustable attenuation unit, and a detection unit. The detection module is fixedly connected to the scanning module, and both the scanning module and the detection unit are electrically connected to the processing module. The scanning module drives the detection module to move along a first direction to scan the thin film under test and acquires the displacement data of the detection module. The detection laser emitted from the laser unit passes through the adjustable attenuation unit and is incident on the surface of the thin film under test. After being reflected by the surface of the thin film under test, it is incident on the detection unit, and the detection unit acquires the spot motion data of the detection laser incident on the thin film under test at different positions. The processing module calculates the stress of the thin film under test based on the displacement data and the spot motion data. The first direction is parallel to the plane where the thin film under test is located. The thin film stress detection device provided by this utility model adjusts the output power of the laser through the adjustable attenuation unit, thereby adapting to different materials without changing the optical path. This not only simplifies the calibration process and reduces measurement errors, but also allows the detection of materials with a wider range of reflectivity, eliminating concerns about the light intensity saturation problem of the charge-coupled device of the photosensitive sensor. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a thin film stress detection device provided in an embodiment of this utility model;

[0028] Figure 2 This is an optical path diagram of a thin film stress detection device provided in this embodiment of the invention, in which detection lasers are emitted at different positions.

[0029] Figure 3 This is an internal structural diagram of an adjustable attenuation unit in a thin-film stress detection device provided in this embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of another thin-film stress detection device provided in this embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of a thin film stress detection device provided in an embodiment of this utility model. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] Thin film stress refers to the stress present within a thin film material deposited on a substrate. This stress is typically caused by factors such as the difference in thermal expansion coefficients between the film and the substrate, microstructural changes during film growth, and interface effects. Stress includes intrinsic stress, thermal stress, and external stress. Traditional thin film stress detection methods are mainly based on elasticity principles and light reflection, combining the Stoney formula and the optical lever method. The former is the most classic calculation method for residual stress testing in thin films, while the latter amplifies and captures minute curvature changes on the wafer surface using an optical lever. The sensor typically used to receive the light signal is a charge-coupled device (CCD). However, to test materials with weak surface reflectivity, a beam splitter is used to superimpose the energies of two lasers to enhance the light signal intensity, significantly increasing the detection cost.

[0035] Figure 1This is a schematic diagram of a thin film stress detection device provided in an embodiment of the present invention, including a detection module 1, a scanning module 2, and a processing module 3. The detection module 1 includes a laser unit 11, an adjustable attenuation unit 12, and a detection unit 13. The detection module 1 is fixedly connected to the scanning module 2, and both the scanning module 2 and the detection unit 13 are electrically connected to the processing module 3. The scanning module 2 drives the detection module 1 to move along the first direction X to scan the thin film 4 under test and acquires the displacement data of the detection module 1. The detection laser emitted from the laser unit 11 passes through the adjustable attenuation unit 12 and is incident on the surface of the thin film 4 under test. After being reflected by the surface of the thin film 4 under test, it is incident on the detection unit 13. The detection unit 13 acquires the spot motion data of the detection laser incident on the thin film 4 under test at different positions. The processing module 3 calculates the stress of the thin film 4 under test based on the displacement data and the spot motion data. The first direction X is parallel to the plane where the thin film 4 under test is located.

[0036] Specifically, in this embodiment, the laser unit 11 of the detection module 1 is mainly used to emit detection laser. For example, it can be a solid-state laser or a semiconductor laser. The adjustable attenuation unit 12 is mainly used to adjust the intensity of the detection laser emitted by the laser unit 11 to the thin film under test. The scanning module 2 can drive the detection module 1 to move. The processing module 3 can control the scanning module 2 to move the detection module 1 with a preset step size. Specifically, in this embodiment, the scanning module 2 drives the detection module 1 to move along the first direction X with a preset step size to achieve a complete scan of the film 4 to be tested. During the scanning process of the film 4 to be tested, the scanning module 2 simultaneously acquires the displacement data Δx of the detection module 1. The detection laser emitted by the laser unit 11 is incident on the adjustable attenuation unit 12. After being adjusted by the adjustable attenuation unit 12, it is incident on the surface of the film 4 to be tested, and then reflected by the surface of the film 4 to be tested to the detection unit 13. The detection unit 13 simultaneously acquires the spot motion data Δy of the detection laser at different positions on the surface of the film 4 to be tested. The processing module 3 calculates the stress of the film 4 to be tested based on the displacement data Δx and the spot motion data Δy. Figure 2 This is an optical path diagram of the thin film stress detection device provided in this embodiment, showing the laser emitted at different locations. (Refer to...) Figure 2 Driven by the scanning module 2, the optical path of the detection laser sweeps across a diameter of the surface of the film 4 to be tested. The incident angle of the detection laser remains unchanged, but the tilt angle of the surface of the film 4 to be tested is different. This causes the direction of the reflected light of the detection laser to change with the change of the tilt angle of the surface of the film 4 to be tested.

[0037] Figure 3This is an internal structural diagram of an adjustable attenuation unit in a thin film stress detection device provided in this embodiment. Optionally, the adjustable attenuation unit 12 includes multiple attenuation plates A and a turntable mechanism 121. The multiple attenuation plates A are disposed on the turntable mechanism 121, and the rotation center axis of the turntable mechanism 121 is parallel to the optical axis of the detection laser. The multiple attenuation plates A are arranged in a ring uniformly around the rotation center axis of the turntable mechanism 121. The turntable mechanism 121 rotates to send different attenuation plates A into the transmission path of the detection laser incident on the thin film 4 to be tested.

[0038] Attenuator A is an optical element that reduces the intensity of light signals. It is widely used in laser systems, fiber optic communications, and optical measurements. It primarily reduces light intensity by absorbing, reflecting, or scattering some light energy, while maintaining other light properties (such as wavelength, polarization, and beam quality) as much as possible. Attenuator A can be a fixed attenuator, a variable attenuator, a neutral density filter, or a polarization attenuator. Optionally, multiple attenuators A can have different attenuation rates, allowing attenuators with a wider range of attenuation rates to be integrated into the transmission path of the detection laser incident on the surface of the film under test 4.

[0039] For example, the first time, an attenuator with an attenuation rate of 3dB can be used to cut into the transmission path of the detection laser incident on the surface of the thin film under test 4, and the second time, an attenuator with an attenuation rate of 6dB can be used to cut into the transmission path of the detection laser incident on the surface of the thin film under test 4.

[0040] The thin film stress detection device provided in this embodiment features an adjustable attenuation unit, within which multiple attenuators with different attenuation rates are incorporated. These attenuators intersect the transmission path of the detection laser incident on the surface of the thin film under test, without altering the optical path of the detection laser. This eliminates the need for additional calibration, thus simplifying the calibration process. Optionally, refer to [reference needed]. Figure 3 The adjustable attenuation unit 12 also includes a stepper motor 122. The stepper motor 122 is fixedly connected to the turntable mechanism 121. The stepper motor 122 drives the turntable mechanism 121 to rotate. The stepper motor 122 controls the intensity of the detection laser reaching the surface of the film 4 by inserting different attenuators A into the transmission path of the detection laser through a fixed pulse signal. The lower the reflectivity of the material, the lower the attenuation rate of the attenuator used. The stepper motor 122 is an actuator that converts electrical pulse signals into angular or linear displacement. Each time a pulse signal is received, the motor rotates a fixed angle (step angle) in a set direction. By controlling the number and frequency of pulses, precise position and speed control can be achieved.

[0041] Optionally, the adjustable attenuation unit 12 also includes a position sensor 123; the position sensor 123 is connected to the stepper motor 122. The position sensor 123 can detect the rotation starting point of the stepper motor 122 and monitor the real-time position information of the stepper motor 122, so that the attenuator A with different attenuation rates can be accurately cut into the transmission path of the detection laser incident on the surface of the film 4 under test.

[0042] The intensity of the laser incident on the surface of the thin film under test is changed by switching attenuators with different attenuation rates in the adjustable attenuation unit. Furthermore, by using a high-power detection laser, various thin film materials with reflectivity stronger or weaker than silicon can be easily detected.

[0043] Figure 4 This is a schematic diagram of another thin film stress detection device provided in this embodiment of the present invention. The detection module 1 also includes a reflection unit 14. The detection laser is reflected by the surface of the thin film 4 to be tested and then incident on the reflection unit 14. The reflection unit reflects the detection laser to the detection unit 13.

[0044] Specifically, the detection laser emitted by the laser unit 11 first enters the adjustable attenuation unit 12, and after passing through the adjustable attenuation unit 12, it enters the surface of the thin film 4 to be tested. After being reflected by the surface of the thin film 4 to be tested, the detection laser enters the reflection unit 14. The reflection unit 14 adjusts and reflects the optical path of the detection laser, thereby changing the transmission path of the detection laser so that the detection laser enters the detection unit 13 at an appropriate angle.

[0045] This embodiment, by employing a reflection unit, not only changes the transmission path of the detection laser but also significantly reduces the size of the detection device.

[0046] Figure 5 This is a schematic diagram of a thin film stress detection device provided in this embodiment, for reference. Figure 4 and Figure 5 The working principle of the thin film stress detection device provided in this embodiment is as follows:

[0047] During the scanning process driven by the scanning module 2 and the detection module 1, the motion data of the light spot reflected onto the detection unit 13 is Δy, and the corresponding tilt angle change on the surface of the film 4 under test is θ. According to the theory of planar reflection optical systems, it can be known that when the reflecting surface rotates by an angle θ, the angle of the reflected light will rotate by an angle 2θ in the same direction. According to the law of reflection, the angle of reflection is equal to the angle of incidence, where the angle of incidence is the angle between the incident ray and the normal to the reflecting surface, and the angle of reflection is the angle between the reflected ray and the normal to the reflecting surface. When the reflecting surface rotates by an angle θ, the normal to the reflecting surface also rotates by an angle θ. Therefore, the angle of displacement of the reflected ray relative to the center position is 2θ, such as... Figure 5As shown, since the value of θ is generally small, the value of 2θ is also generally small. It can be assumed that the diameter of the thin film 4 being scanned by the scanning module 2 and the detection module 1 is approximately equal to the arc length of the sector, which in turn is approximately equal to the chord length of the sector. Therefore, we can obtain:

[0048] Δy≈L×2θ=2Lθ (I)

[0049] θ=Δx / R (II)

[0050] Δy=2LΔx / R (III) Simplifying formulas (I), (II) and (III), we can see that:

[0051] Δy / Δx=2L / R (IV)

[0052] Where Δy is the light spot motion data, Δx is the displacement data of detection module 1, L is the distance between the detection laser emission point and the sensor virtual image, and R is the radius of curvature of the film 4 to be tested.

[0053] In formula (iv), Δy is the light spot motion data, which can be measured by the detection unit 13, and Δx is the displacement data of the detection module 1, which can be measured by the scanning module 2. When the optical path is set, L can be measured and regarded as a known quantity, so the radius of curvature R of the film 4 to be tested can be calculated.

[0054] Thin-film coating is a technique that deposits one or more thin films on the surface of a substrate material to alter the physical, chemical, or optical properties of the material's surface. The thickness of the thin films is typically in the nanometer to micrometer range. Thin-film coating technology has wide applications in optics, electronics, mechanics, energy, and biomedicine.

[0055] The thin film stress detection device provided in this embodiment of the invention scans and detects the thin film 4 before it is coated, and calculates the first radius of curvature R of the thin film 4. s Then, using the thin film stress detection device provided in this embodiment of the invention, the thin film 4 to be tested is scanned and detected before coating, and the second radius of curvature R of the thin film 4 to be tested is calculated. f The stress of the thin film under test can be calculated using the Stoney formula.

[0056] The Stoney formula is as follows:

[0057]

[0058] Among them, E s V represents the elastic modulus of the thin film material to be tested. s t is the Poisson's ratio of the substrate material of the thin film to be tested. s t represents the thickness of the substrate to be measured. fThe thickness of the film to be measured is given. Optionally, the detection module 1 includes an optical backplate; the laser unit 11, the adjustable attenuation unit 12, the detection unit 13, and the reflection unit 14 are all integrated into the optical backplate.

[0059] Specifically, the detection module 1 can be an optical backplate. The laser unit 11, adjustable attenuation unit 12, detection unit 13, and reflection unit 14 are all integrated on the optical backplate. The optical backplate can provide stable support, facilitate optical measurement, and allow light signals to pass through it, ensuring that the stress distribution of the thin film is not affected by external interference during the measurement process. The material of the optical backplate needs to meet the following requirements:

[0060] 1. Optical transparency: such as quartz, glass or transparent polymer.

[0061] 2. Thermal stability: Maintains dimensional stability under temperature changes.

[0062] 3. Mechanical strength: It can withstand the mechanical stress during the thin film growth or measurement process.

[0063] 4. Chemical inertness: Avoids chemical reactions with thin film materials.

[0064] Optionally, scanning module 2 includes a linear motor.

[0065] Specifically, the scanning module 2 includes a linear motor, which is an electric motor that directly converts electrical energy into linear motion. Its working principle is similar to that of a traditional rotary motor, but the motion is linear rather than rotational. It consists of a primary stator and a secondary mover. For example, the linear motor can be a permanent magnet linear motor or an induction linear motor. This embodiment of the utility model does not limit the type of linear motor, as long as it can achieve precise displacement control of the detection module 1.

[0066] Optionally, the reflecting unit 14 includes a reflector.

[0067] Specifically, the reflecting unit 14 includes a reflector, which is an optical element that uses the principle of reflection to change the light path. It is usually composed of a base material (such as glass or metal) and a reflective coating (such as a metal film or a dielectric film). For example, the reflector can be a plane reflector, etc.

[0068] This utility model embodiment also provides a wafer thin film stress detection system, including the wafer to be tested and the thin film stress detection device in any of the above utility model embodiments.

[0069] The wafer thin film stress detection system provided in this embodiment of the present invention can achieve the same technical effect as the thin film stress detection device provided in any of the above embodiments of the present invention, and will not be described in detail here.

[0070] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A thin film stress detection device, characterized in that, It includes a detection module, a scanning module, and a processing module; the detection module includes a laser unit, an adjustable attenuation unit, and a detection unit. The detection module is fixedly connected to the scanning module, and both the scanning module and the detection unit are electrically connected to the processing module. The scanning module drives the detection module to move along the first direction to scan the film to be tested and acquire the displacement data of the detection module; The detection laser emitted by the laser unit passes through the adjustable attenuation unit and is incident on the surface of the film under test. After being reflected by the surface of the film under test, it is incident on the detection unit. The detection unit acquires the spot motion data of the detection laser incident on the film under test at different positions. The processing module calculates the stress of the film under test based on the displacement data and the light spot motion data; Wherein, the first direction is parallel to the plane where the film to be tested is located.

2. The thin film stress detection device according to claim 1, characterized in that, The adjustable attenuation unit includes multiple attenuation plates and a turntable mechanism; Multiple attenuators are disposed on the turntable mechanism, the rotation center axis of the turntable mechanism is parallel to the optical axis of the detection laser, and the multiple attenuators are arranged in a ring uniformly around the rotation center axis of the turntable mechanism; The turntable mechanism rotates to feed different attenuators into the transmission path of the detection laser incident on the film under test.

3. The thin film stress detection device according to claim 2, characterized in that, The adjustable attenuation unit also includes a stepper motor; the stepper motor is fixedly connected to the turntable mechanism, and the stepper motor drives the turntable mechanism to rotate.

4. The thin film stress detection device according to claim 2, characterized in that, The attenuation rates of the various attenuators are all different.

5. The thin film stress detection device according to claim 3, characterized in that, The adjustable attenuation unit also includes a position sensor; the position sensor is connected to the stepper motor.

6. The thin film stress detection device according to claim 1, characterized in that, The detection module further includes a reflection unit; the detection laser is reflected by the surface of the film under test and then incident on the reflection unit, and the detection laser is reflected back to the detection unit by the reflection unit.

7. The thin film stress detection device according to claim 6, characterized in that, The detection module includes an optical backplate; the laser unit, the adjustable attenuation unit, the detection unit, and the reflection unit are all integrated on the optical backplate.

8. The thin film stress detection device according to claim 1, characterized in that, The scanning module includes a linear motor.

9. The thin film stress detection device according to claim 6, characterized in that, The reflecting unit includes a reflector.

10. A thin film stress detection system, characterized in that, It includes the wafer to be tested and the thin film stress detection device according to any one of claims 1 to 9.

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