Dual-beam laser interference detection device and detection method

Abstract

The present invention discloses a dual-beam laser interference detection device and detection method for semiconductor etching and thin film process endpoint detection. The dual-beam laser interference detection device includes an imaging unit, a detection unit, and a reference unit. The detection unit includes a first emitting element for emitting detection light, which is focused onto a wafer via the imaging unit. The first detector outputs a first reflection signal. The reference unit includes a second emitting element for emitting a reference light to the imaging unit so that the reference light is focused onto a semiconductor device window. The second detector outputs a second reflection signal. During the detection process, the difference between the first reflection signal and the second reflection signal is calculated to obtain a light intensity signal after interference elimination. The wafer etching depth or thin film deposition thickness is calculated based on the light intensity signal after interference elimination. The present invention can eliminate the problem of insufficient accuracy in wafer etching depth and thin film deposition thickness endpoint detection caused by factors such as semiconductor device vibration and environmental instability.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor detection technology, and in particular to a dual-beam laser interference detection device and a detection method. Background Art

[0002] In semiconductor manufacturing, especially during wafer processing, precise control of wafer etch depth or thin film deposition thickness is crucial to ensuring chip performance and reliability. However, in actual processes, high-frequency vibrations in semiconductor equipment and environmental instability can cause noise in detection signals. During processing, mechanical components must coordinate to rapidly move the wafer and rapidly change production conditions such as temperature, gas flow, and pressure. These rapid transitions can cause vibration in semiconductor equipment. Specifically, the main causes of semiconductor equipment vibration include wear and tear of mechanical transmission components, fluctuations in gas flow and pressure, and the impact of heavy equipment and electromagnetic interference in cleanrooms. Environmental instability can include minor airflow disturbances caused by unstable cleanroom airflow, thermal expansion and contraction of mechanical components due to temperature and humidity fluctuations, and light obstruction caused by movement of personnel. Therefore, these factors can affect the accuracy of wafer etch depth or thin film deposition endpoint detection.

[0003] In the prior art, a single-beam laser interference detection device is used to detect the etching depth or the end point of the thin film deposition thickness. Although the single-beam laser interference detection device can provide detection signals to a certain extent, the signal-to-noise ratio of its detection signal will drop significantly when faced with the above-mentioned environmental interference factors. In order to improve the signal quality, the detection signal is usually filtered. However, although the filtering process can remove some noise, there is also a delay. This delay is unacceptable for etching and thin film processes that require high-precision control, because it will cause the etching depth of the wafer and the end point of the thin film deposition thickness to be advanced or delayed, thereby affecting the performance and reliability of the chip.

[0004] Therefore, it is necessary to provide a dual-beam laser interference detection device and detection method to solve the above-mentioned problems existing in the prior art. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the present invention aims to provide a dual-beam laser interference detection device and detection method to solve the problem of insufficient accuracy in wafer etching depth and thin film deposition thickness endpoint detection caused by vibration of semiconductor equipment and environmental instability in the prior art.

[0006] To solve the above technical problems, according to an embodiment of the present application, a dual-beam laser interferometry detection device is provided for semiconductor etching and thin film process detection. The dual-beam laser interferometry detection device includes an imaging unit, a detection unit, and a reference unit;

[0007] The detection unit comprises:

[0008] a first emitting element, disposed on one side of the imaging unit, for emitting a detection light, wherein the detection light is focused onto the wafer via the imaging unit;

[0009] a first detector, disposed on one side of the imaging unit, configured to receive the detection light reflected by the wafer and output a first reflection signal;

[0010] The reference unit includes:

[0011] a second emitting element, disposed on one side of the imaging unit, for emitting reference light toward the imaging unit so that a portion of the reference light is focused on a semiconductor device window;

[0012] a second detector disposed on one side of the imaging unit to receive the reference light reflected by the semiconductor device window and output a second reflection signal;

[0013] During the endpoint detection process, the difference between the first reflection signal and the second reflection signal is calculated to obtain a light intensity signal after interference elimination, so as to calculate the etching depth or thin film deposition thickness of the wafer based on the light intensity signal after interference elimination.

[0014] A detection method for a dual-beam laser interference detection device is applied to the dual-beam laser interference detection device, the detection method comprising:

[0015] Obtaining a first reflected light intensity on the upper surface of the wafer and the second reflected light intensity of the lower surface of the wafer ;

[0016] According to the first reflected light intensity and the second reflected light intensity Calculate the interference value caused by the wafer thickness change ;

[0017] Obtain the impact value of interference on the light intensity received by the first detector ;

[0018] The first detector detects the interference value With the impact value Respond and output the first reflected signal ;

[0019] Obtaining a third reflected light intensity of the semiconductor device window ;

[0020] Obtain the impact value of interference on the light intensity received by the second detector ;

[0021] The second detector detects the third reflected light intensity and the impact value Respond and output the second reflected signal ;

[0022] The first reflected signal With the second reflected signal After calibration, the difference calculation is performed to obtain the light intensity signal after eliminating interference ;

[0023] According to the light intensity signal after interference removal The etching depth or thin film deposition thickness of the wafer is calculated.

[0024] By adopting the above technical solution, the detection light is focused onto the wafer surface, and a portion of the reference light is focused onto the semiconductor device window surface. Simultaneously, the first detector outputs a first reflected signal, and the second detector outputs a second reflected signal. During the detection process, vibration of the semiconductor device or environmental instability can affect the detection results. By introducing the reference light, the influence of these interfering factors on the detection results can be effectively detected and eliminated, thereby significantly improving the quality of the detection signal. By performing a difference calculation between the first and second reflected signals, an interference-free light intensity signal is obtained, which can then be used to accurately calculate the wafer etch depth or thin film deposition thickness. This difference calculation method effectively eliminates errors caused by device vibration and environmental instability, ensuring the accuracy of endpoint detection. By introducing the reference light, the device of the present invention can monitor and eliminate these interfering factors in real time, thereby achieving stable and high-precision detection. Compared with traditional filtering processing methods, the difference calculation method of the present invention does not introduce additional delay. This enables the detection device to respond to changes in etching and thin film processes in real time, providing accurate detection results in real time, thereby better meeting the requirements of high-precision process control.

[0025] According to an embodiment of the present application, the imaging unit includes a first beam splitter, a second beam splitter, a lens group, and a super lens arranged in sequence;

[0026] The first emitting element is provided on one side of the second beam splitter, and is used to emit detection light toward the second beam splitter, so that the detection light sequentially passes through the second beam splitter, the lens group, and the super lens and is focused onto the wafer surface;

[0027] The reference light includes a first light and a second light, wherein the first light is collimated light and forms a second light after passing through the first beam splitter, the second beam splitter, and the lens group; after passing through the metalens, a portion of the second light is focused on the semiconductor device window, and the other portion illuminates the wafer;

[0028] The second emitting element is movably disposed on one side of the first beam splitter to adapt to the change in the focal length of the lens group, so that the second light is collimated light.

[0029] According to an embodiment of the present application, the lens group includes a first fixed group, a zoom group and a second fixed group arranged in sequence along the optical path; the zoom group is movably arranged between the first fixed group and the second fixed group so as to change the focal length of the lens group when the zoom group moves.

[0030] According to an embodiment of the present application, the phase distribution on the surface of the metalens is Satisfies the following formula:

[0031]

[0032] in, is the wavelength of light; is the focal length of the metalens for this wavelength, is the radial distance from the surface point of the metalens to the optical axis, K is the modulation phase of the metalens corresponding to the wavelength range;

[0033] when K, The corresponding band is ;when hour, The corresponding band is .

[0034] According to an embodiment of the present application, the reference unit further includes a first lens, which is disposed between the second emitting element and the first beam splitter, so that the first light is diffused after passing through the first lens and irradiated onto the first beam splitter.

[0035] According to an embodiment of the present application, the reference unit further includes:

[0036] a third beam splitter, disposed between the second emitting element and the first lens, so that the first light passes through the third beam splitter and then irradiates the first lens;

[0037] a second lens, disposed between the third beam splitter and the first detector;

[0038] The second detector is arranged on one side of the third beam splitter; so that the second light is reflected and passes through the super lens, the lens group, the second beam splitter, the first beam splitter, and the first lens in sequence, is reflected by the third beam splitter, and is focused to the second detector after passing through the second lens.

[0039] According to an embodiment of the present application, the detection unit also includes a fourth spectrometer, which is arranged between the first emitting element and the second spectrometer; the first detector is arranged on one side of the fourth spectrometer, so that the detection light is reflected by the wafer and passes through the super lens, the lens group, and the second spectrometer in sequence, and is reflected by the fourth spectrometer and focused on the first detector.

[0040] According to an embodiment of the present application, the intensity of the first reflected light and the second reflected light intensity Calculate the interference value caused by the wafer thickness change include:

[0041] The interference value is calculated according to the following formula :

[0042]

[0043] in is the optical path difference caused by the thickness change of the wafer; is the wavelength of light.

[0044] According to an embodiment of the present application, the first reflected signal With the second reflected signal Perform difference calculation to obtain the light intensity signal after eliminating interference :

[0045] Calculate the light intensity signal after eliminating interference according to the following formula :

[0046]

[0047] The first reflected signal With the second reflected signal The value of is introduced into the above formula to obtain:

[0048]

[0049] in, is the impact value of the light intensity received by the first detector The influence of the light intensity received by the second detector on the value The ratio of is the optical path difference caused by the thickness change of the wafer; is the wavelength of light;

[0050] Will When the value of is defined as 0, the influence of the environment is eliminated and the elimination value is obtained. :

[0051] .

[0052] According to an embodiment of the present application, it further includes:

[0053] The elimination value Perform fast Fourier transform to obtain the spectrum X[k];

[0054] Extract the main frequency in the spectrum and calculate the number of cycles based on the main frequency ;

[0055] The etching depth of the wafer is the same as the thickness of the thin film deposition, which is defined as thickness d;

[0056] The thickness d is calculated by the following formula:

[0057]

[0058] in, is the wavelength of the detection light, and n is the refractive index corresponding to the wavelength of the detection light and the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a schematic diagram of the main structure of a dual-beam laser interference detection device according to an embodiment of the present invention;

[0060] Figure 2 A schematic diagram of an embodiment of the present invention in which part of the reference light is focused onto a semiconductor device window and part of the reference light is irradiated onto a wafer;

[0061] Figure 3 A schematic diagram of focusing detection light onto a wafer according to an embodiment of the present invention;

[0062] Figure 4 Schematic diagram of the positions of the zoom group and the compensation group of a dual-beam laser interference detection device according to an embodiment of the present invention when the working distance is 200 mm;

[0063] Figure 5 Schematic diagram of the positions of the zoom group and the compensation group of a dual-beam laser interference detection device according to an embodiment of the present invention when the working distance is 800 mm;

[0064] Figure 6 This is a curve diagram of wafer etching depth variation detected by a detection device using existing technology; the X-axis is the wafer thickness in nm; the Y-axis is the reflectivity of the wafer.

[0065] Figure 7 The figure is a curve diagram of wafer etching depth variation detected by the dual-beam laser interference detection device according to an embodiment of the present invention; the X-axis is the wafer thickness in nm; and the Y-axis is the reflectivity of the wafer.

[0066] Reference numerals:

[0067] 100, imaging unit; 110, first beam splitter; 120, second beam splitter; 130, lens group; 131, first fixed group; 132, zoom group; 133, compensation group; 134, second fixed group; 140, super lens; 200, detection unit; 210, first emitting element; 220, first detector; 230, fourth beam splitter; 300, reference unit; 310, second emitting element; 320, second detector; 330, first lens; 340, third beam splitter; 350, second lens; 400, wafer; 500, semiconductor device window; 600, camera. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the invention belongs. The words "including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0069] The following is combined with Figure 1-7 , the specific implementation methods of the present invention are further described in detail.

[0070] An embodiment of the present invention provides a dual-beam laser interferometer detection device. During the detection process, if only the detection light is used, the data obtained contains noise caused by the environment, such as equipment jitter. Direct filtering will cause delays, which will directly affect the depth etching accuracy of wafer 400. Therefore, a dual-beam laser interferometer detection device is used. The dual-beam laser interferometer detection device is used to improve the signal-to-noise ratio of the original signal when the etcher vibrates or the environment is unstable, more accurately detect etching or thin film deposition thickness, and eliminate the impact of etcher vibration or environmental instability on the detection results. Specifically, the main causes of etcher vibration include: wear and tear of the etcher's mechanical transmission components, vibration of semiconductor equipment caused by fluctuations in air flow and air pressure, and the impact of heavy equipment operation and electromagnetic interference on the etcher in the clean room. Environmental instability mainly includes: weak airflow disturbances caused by unstable airflow in the clean room, thermal expansion and contraction of mechanical components caused by temperature and humidity changes, affecting their matching accuracy during operation, and light obstruction caused by people walking. These various factors can affect the detection of the laser interferometer detection device deployed above the etcher chamber.

[0071] Reference light is focused onto the etcher window surface to detect interference caused by etcher vibration or environmental instability. The interference components in the detection light are then removed according to the algorithm. This can effectively eliminate the influence of various factors including etcher vibration or environmental instability on etching endpoint detection, provide an accurate etching endpoint, and improve the detection adaptability of laser interference detection equipment in semiconductor equipment vibration and environmental instability conditions.

[0072] The dual-beam laser interference detection device includes: an imaging unit 100, a detection unit 200 and a reference unit 300;

[0073] The detection unit 200 includes:

[0074] The first emitting element 210 is provided on one side of the imaging unit 100 and is used to emit detection light, which is focused onto the wafer 400 via the imaging unit 100;

[0075] The first detector 220 is provided on one side of the imaging unit 100 and is used to receive the detection light reflected by the wafer 400 and output a first reflection signal;

[0076] The reference unit 300 includes:

[0077] The second emitting element 310 is provided at one side of the imaging unit 100 and is used to emit a reference light beam toward the imaging unit 100 so that a portion of the reference light beam is focused on the semiconductor device window 500 ;

[0078] The second detector 320 is provided at one side of the imaging unit 100 to receive the reference light reflected by the semiconductor device window 500 and output a second reflection signal;

[0079] During the endpoint detection process, the first reflection signal and the second reflection signal are difference-calculated to obtain a light intensity signal after interference elimination, and the etching depth or thin film deposition thickness of the wafer 400 is calculated based on the light intensity signal after interference elimination.

[0080] In some embodiments, imaging unit 100 includes multiple lenses to focus light received by imaging unit 100 onto a specific location. In some embodiments, since the inspection process generally involves light irradiating wafer 400 from top to bottom, this optical path is defined as a first optical path. Therefore, the multiple lenses in imaging unit 100 are distributed along the first optical path. The specific distribution of these lenses is described below.

[0081] In some embodiments, a first emitting element 210 is disposed on one side of the imaging unit 100 and is configured to emit detection light. The detection light from the first emitting element 210 is irradiated onto the imaging unit 100 and is focused onto the surface of the wafer 400 after passing through the imaging unit 100. A first detector 220 is disposed on one side of the imaging unit 100. The detection light from the first emitting element 210 is focused onto the surface of the wafer 400 after passing through the imaging unit 100. There, the detection light is reflected from the surface of the wafer 400, and the reflected detection light is received by the first detector 220 after passing through the imaging unit 100 again. The first detector 220 is capable of receiving the detection light reflected by the wafer 400 and outputting a first reflection signal.

[0082] In some specific embodiments, the first emitting element 210 is a laser emitting element.

[0083] In some specific embodiments, the first emitting element 210 and the first detector 220 are disposed on the same side of the imaging unit 100 , and their specific locations will be described later.

[0084] In some embodiments, the second emitting element 310 is disposed on one side of the imaging unit 100 and is capable of emitting reference light. The reference light is irradiated onto the imaging unit 100, and at least a portion of the reference light is focused onto the semiconductor device window 500 after passing through the imaging unit 100. The second detector 320 is disposed on one side of the imaging unit 100. The reference light from the second emitting element 310 is focused onto the semiconductor device window 500 after passing through the imaging unit 100, and is then reflected by the semiconductor device window 500. The reflected reference light is then received by the second detector 320 after passing through the imaging unit 100 again. The second detector 320 is capable of receiving the detection light reflected by the semiconductor device window 500 and outputting a second reflection signal.

[0085] In some embodiments, the second emitting element 310 is a light emitting diode.

[0086] In some embodiments, the second emitting element 310 and the second detector 320 are disposed on the same side of the imaging unit 100 , and their specific locations will be described later.

[0087] In some specific embodiments, the first detector 220 outputs a first emission signal, and the second detector 320 outputs a second reflection signal. The first reflection signal and the second reflection signal are differentially calculated to obtain an interference-eliminated light intensity signal. This eliminates the effects of equipment vibration or environmental instability. The etching depth or thin film deposition thickness of the wafer 400 can be calculated based on the interference-eliminated light intensity signal. The specific calculation method is described below.

[0088] The imaging unit 100 includes a first beam splitter 110, a second beam splitter 120, a lens group 130 and a super lens 140 arranged in sequence;

[0089] The first emitting element 210 is provided on one side of the second beam splitter 120 and is used to emit detection light toward the second beam splitter 120 , so that the detection light sequentially passes through the second beam splitter 120 , the lens group 130 , and the super lens 140 and is focused onto the wafer 400 .

[0090] The reference light includes a first light and a second light. The first light is collimated light and forms a second light after passing through the first beam splitter 110, the second beam splitter 120, and the lens group 130. After passing through the metalens 140, a portion of the second light is focused on the semiconductor device window 500, and the other portion illuminates the wafer 400.

[0091] The second emitting element 310 is movably disposed on one side of the first beam splitter 110 to adapt to the change in the focal length of the lens assembly 130 so that the second light is collimated light.

[0092] In some embodiments, the imaging unit 100 includes a first beam splitter 110, a second beam splitter 120, a lens group 130, and a super lens 140. Specifically, the first beam splitter 110, the second beam splitter 120, the lens group 130, and the super lens 140 are sequentially arranged from top to bottom along the first optical path.

[0093] In some specific embodiments, the first emitting element 210 is disposed on one side of the second beam splitter 120. The second beam splitter 120 is configured to deflect the detection light emitted by the first emitting element 210 and the detection light reflected from the surface of the wafer 400. The first emitting element 210 emits the detection light toward the second beam splitter 120. After being deflected by the second beam splitter 120, the detection light passes through the lens assembly 130 and the super lens 140 and is focused onto the surface of the wafer 400.

[0094] In some specific embodiments, the second emitting element 310 is disposed on one side of the first beam splitter 110. The first beam splitter 110 is configured to deflect the reference light emitted by the second emitting element 310 and the reference light reflected by the semiconductor device window 500. Specifically, the second emitting element 310 emits a reference light beam toward the first beam splitter 110. After being deflected by the first beam splitter 110, the reference light beam passes through the second beam splitter 120, the lens assembly 130, and the super lens 140, and is focused onto the semiconductor device window 500. More specifically, due to the provision of the super lens 140, a portion of the reference light beam is focused onto the semiconductor device window 500, while another portion of the reference light beam is irradiated onto the wafer 400, thereby illuminating the wafer 400.

[0095] In some specific embodiments, for ease of understanding, the reference light is divided into a first light and a second light. The reference light emitted by the second emitting element 310 is the first light, and the first light passes through the first beam splitter 110, the second beam splitter 120, and the lens assembly 130 to form the second light. Part of the second light is focused on the semiconductor device window 500, while the other part is irradiated onto the wafer 400 to illuminate the wafer 400.

[0096] In some more specific embodiments, the first light is collimated light.

[0097] In some specific embodiments, to collimate the first light, a collimating lens assembly is provided between the second emitting element 310 and the third beam splitter 340. The collimating lens assembly includes a negative power lens, a positive power lens, and a positive power doublet lens, arranged in sequence along the optical path of the third beam splitter 340, from the second emitting element 310 toward the first beam splitter 110. This collimates the optical fiber emitted by the second emitting element 310. More specifically, the collimating lens assembly has a combined focal length range of 52 mm to 73 mm, achieving a beam divergence angle of 2° to 5°.

[0098] In some more specific embodiments, the focal length of the lens group 130 is adjustable; at the same time, the second emitting element 310 is movably provided on one side of the first beam splitter 110, and the second emitting element 310 moves to adapt to the focal length change of the lens group 130, so that the second light is collimated light, that is, the first light and the second light are both collimated light.

[0099] In some more specific embodiments, a gap is provided between the first beam splitter 110 and the second beam splitter 120. Since the first emitting element 210 is located on one side of the second beam splitter 120 and the second emitting element 310 is located on one side of the first beam splitter 110, a gap exists between the first emitting element 210 and the second emitting element 310, thereby preventing interference between the detection light and the reference light. More specifically, the first emitting element 210 and the second emitting element 310 can be located on the same side of the imaging unit 100 or on different sides of the imaging unit 100, without limitation, so as to enable the detection light to be focused on the wafer 400, while a portion of the reference light is focused on the semiconductor device window 500 and another portion is primarily irradiated on the wafer 400.

[0100] In some embodiments, the reference unit is movably disposed on one side of the imaging unit 100. More specifically, the reference unit 300 is moved by controlling a motor to adapt to changes in the focal length of the lens assembly 130. More specifically, when the focal length of the lens assembly 130 changes, the motor drives the detection unit 200 to move left and right as a whole, ensuring that both the first light and the second light are collimated.

[0101] In some specific embodiments, the lens assembly 130 and the metalens 140 can be considered as a whole, defined as a lens. The lens has an imaging wavelength range of 440 nm to 700 nm, an entrance pupil diameter of 28 mm to 40 mm, a focal length of 155.5 mm to 372 mm, a magnification of 3.5X to 0.87X, an object-side numerical aperture of 0.0582 to 0.0219, a working distance range of 200 mm to 800 mm, and an object-side resolution of 4 μm to 16 μm, with a resolution of 4 μm at a working distance of 200 mm and a resolution of 16 μm at a working distance of 800 mm.

[0102] In some specific embodiments, the imaging unit 100 further includes a camera 600, which is positioned along the first optical path to one side of the first beam splitter 110 and spaced apart from the first beam splitter 110. Specifically, the camera 600, the first beam splitter 110, the second beam splitter 120, the lens assembly 130, and the metalens 140 are sequentially positioned along the first optical path. In some more specific embodiments, the camera 600 utilizes a 1 / 2" (conventional optical format size, with an actual diagonal length of approximately 8.5 mm) CMOS image sensor with a photosensitive surface size of 6.48 mm x 5.4 mm, and a diagonal dimension of 8.5 mm.

[0103] The lens group 130 includes a first fixed group 131, a zoom group and a second fixed group 134 arranged in sequence along the optical path; the zoom group is movably arranged between the first fixed group 131 and the second fixed group 134 to change the focal length of the lens group 130 when the zoom group moves.

[0104] In some embodiments, lens assembly 130 includes a first fixed group 131, a zoom group, and a second fixed group 134. Specifically, first fixed group 131, zoom group, and second fixed group 134 are sequentially arranged from top to bottom along the first optical path. The positions of first fixed group 131 and second fixed group 134 are fixed, while the zoom group is positioned between first fixed group 131 and second fixed group 134 and can move between the first fixed group 131 and second fixed group 134 along the first optical path to change the focal length of lens assembly 130.

[0105] In some specific embodiments, the zoom group includes a zoom group 132 and a compensation group 133; that is, the lens group 130, from the object side to the image side, comprises a front fixed group, a zoom group 132, a compensation group 133, and a rear fixed group. The focal power distribution of each group is as follows: the front fixed group has positive focal power, the zoom group 132 has negative focal power, the compensation group 133 has positive focal power, and the rear fixed group has negative focal power. Multiple lenses can be included in each group, as is conventional technology and is not intended to be limiting. The front fixed group, the zoom group 132, the compensation group 133, and the rear fixed group cooperate to achieve focal length adjustment of the lens group 130.

[0106] Specifically, continuous zoom imaging is achieved by moving the zoom group 132 and the compensation group 133 back and forth along the optical axis. At a working distance of 200mm, the corresponding lens focal length is 155.5mm, the magnification is 3.5X, the object field of view at the wafer 400, calculated from the camera 600 diagonal, is 2.43mm, and the object numerical aperture is 0.0582. At a working distance of 800mm, the corresponding system focal length is 372mm, the magnification is 0.87X, the object field of view at the wafer 400, calculated from the camera 600 diagonal, is 9.77mm, and the object numerical aperture is 0.0219.

[0107] In some embodiments, in order to achieve that after the second light passes through the super lens 140, a portion of it can be focused on the semiconductor device window 500 and a portion of it can be irradiated on the wafer 400, the surface phase distribution of the super lens 140 is set. Satisfies the following formula:

[0108]

[0109] in, is the wavelength of light; is the focal length of the superlens 140 for this wavelength, is the radial distance from the surface point of the superlens 140 to the optical axis, and K is the modulation phase of the superlens 140 corresponding to the wavelength range.

[0110] Specifically, the light emitting wavelength of the second emitting element 310 is 450nm-650nm; the light with a wavelength of 650nm is used to focus on the semiconductor device window 500; the light with a wavelength of 450nm-640nm is used to illuminate the wafer 400. More specifically, when K, The corresponding reference light band is ;when hour, The corresponding band is ; Specifically, at 640nm The wavelength of 980nm (excluding 640nm) includes the reference light wavelength of 640nm 650nm (excluding wavelength 640nm), detection light wavelength 670nm±5nm or 905nm±5nm or 980nm±5nm.

[0111] In some more specific embodiments, the material used for the superlens 140 is at least one of titanium dioxide, silicon nitride, amorphous silicon, or aluminum oxide.

[0112] The reference unit 300 further includes a first lens 330 , which is disposed between the second emitting element 310 and the first beam splitter 110 , so that the first light is diffused after passing through the first lens 330 and is irradiated to the first beam splitter 110 ;

[0113] The second detector 320 is disposed on one side of the third beam splitter 340 .

[0114] In some embodiments, the first light is collimated light before it is irradiated by the first lens 330. After passing through the first lens 330, the first light is diffused and becomes the second light after passing through the first beam splitter 110, the second beam splitter 120 and the lens group 130 in sequence. Under the action of the lens group 130, the second light is also collimated light.

[0115] The reference unit 300 further includes:

[0116] The third beam splitter 340 is disposed between the second emitting element 310 and the first lens 330 , so that the first light passes through the third beam splitter 340 and then irradiates the first lens 330 ;

[0117] The second lens 350 is disposed between the third beam splitter 340 and the first detector 220;

[0118] The second detector 320 is arranged on one side of the third beam splitter 340; so that after the second light is reflected, it passes through the metalens 140, the lens group 130, the second beam splitter 120, the first beam splitter 110, and the first lens 330 in sequence, is reflected by the third beam splitter 340, and is focused to the second detector 320 after passing through the second lens 350.

[0119] In some embodiments, the third beam splitter 340 is disposed between the second emitting element 310 and the first lens 330, so that the second light is reflected and passes through the super lens 140, the lens group 130, the second beam splitter 120, the first beam splitter 110, and the first lens 330 in sequence, and is then reflected by the third beam splitter 340 and focused onto the second detector 320 after passing through the second lens 350.

[0120] In some specific embodiments, the second detector 320 is disposed on one side of the third beam splitter 340. Specifically, the second detector 320 is disposed on one side of the reference light emitted by the second emitting element 310. More specifically, the second detector 320 can be disposed above or below the third beam splitter 340. The placement of the third beam splitter 340 is not limited herein, but the third beam splitter 340 is capable of reflecting the second light so that it passes through the second lens 350 and is focused onto the second detector 320.

[0121] In some more specific embodiments, the first lens 330 is a negative optical power lens. The first lens 330, the lens group 130, and the super lens 140 form a Galilean telescope structure. The focal length of the Galilean telescope is the focal length of the lens group 130 and the super lens 140 minus the absolute value of the focal length of the first lens 330. That is, the focal length range of the first lens 330 is 35.5 mm-85.5 mm.

[0122] In some more specific embodiments, the second lens 350 is a positive power lens with a focal length range of 7-15 mm.

[0123] In some embodiments, the second emitting element 310 , the second detector 320 , the first lens 330 , the second lens 350 , and the third beam splitter 340 move synchronously to adapt to the change in the focal length of the lens assembly 130 .

[0124] The detection unit 200 also includes a fourth beam splitter 230, which is arranged between the first emitting element 210 and the second beam splitter 120; the first detector 220 is arranged on one side of the fourth beam splitter 230, so that the detection light is reflected by the wafer 400 and passes through the super lens 140, the lens group 130, and the second beam splitter 120 in sequence, and is reflected by the fourth beam splitter 230 and focused onto the first detector 220.

[0125] In some embodiments, the detection unit 200 further includes a fourth beam splitter 230 to enable the first detector 220 to receive the reflected detection light. The fourth beam splitter 230 is disposed between the first emitting element 210 and the second beam splitter 120, so that the detection light emitted by the first emitting element 210 passes through the fourth beam splitter 230 and then illuminates the second beam splitter 120. Specifically, the first detector 220 is disposed on one side of the fourth beam splitter 230, so that the detection light, after being reflected by the wafer 400, passes through the metalens 140, the lens assembly 130, and the second beam splitter 120 in sequence, before being reflected by the fourth beam splitter 230 and focused onto the first detector 220. More specifically, the first detector 220 is disposed on one side of the reference light emitted by the first emitting element 210. More specifically, the first detector 220 can be disposed above or below the fourth beam splitter 230 , which is related to the placement of the fourth beam splitter 230 and is not limited here, as long as the fourth beam splitter 230 can reflect the detection light to focus it on the first detector 220 .

[0126] In some specific embodiments, the dual-beam laser interference detection device can be used in etching equipment or deposition equipment, without limitation, and is mainly based on the ability to achieve dual-beam detection to eliminate equipment vibration or environmental instability. Specifically, taking the etching equipment as an example, when matching a specific etcher model, the lens needs to be focused to match the current working distance so that the detection light is focused on the surface of the wafer 400. By controlling the motor to move the reference unit 300, part of the reference light is focused on the upper surface of the etcher window. The reference light passes through the telescope structure composed of the first lens 330 and the lens and is collimated and emitted (collimated light). A portion is focused on the etcher window, and the other portion is irradiated on the surface of the wafer 400.

[0127] In the dual-beam laser interferometry detection device, the first emitter 210 is conjugated to the wafer 400, and the photosensitive surface of the camera 600 is conjugated to the wafer 400. The second emitter 310 is conjugated to the upper surface of the semiconductor device window 500 and to the object-side infinity corresponding to the lens. The second detector 320 is conjugated to the upper surface of the semiconductor device window 500. When the focal length of the lens changes, the reference unit 300 is driven by a motor to move left and right as a whole, ensuring that the first lens 330 and the lens still form a telescope structure.

[0128] An embodiment of the present invention further provides a detection method for a dual-beam laser interference detection device, which is applied to the dual-beam laser interference detection device. The detection method includes:

[0129] Obtaining the first reflected light intensity of the upper surface of the wafer 400 and the second reflected light intensity of the lower surface of the wafer 400 ;

[0130] According to the first reflected light intensity and the second reflected light intensity Calculate the interference value caused by the thickness change of wafer 400 ;

[0131] Obtain the impact value of interference on the light intensity received by the first detector 220 ;

[0132] The first detector 220 detects the interference value and impact value Respond and output the first reflected signal ;

[0133] Obtaining the third reflected light intensity of the semiconductor device window 500 ;

[0134] Obtain the impact value of interference on the light intensity received by the second detector 320 ;

[0135] The second detector 320 detects the intensity of the third reflected light and impact value Respond and output the second reflected signal ;

[0136] The first reflected signal With the second reflected signal After calibration, the difference calculation is performed to obtain the light intensity signal after eliminating interference .

[0137] According to the light intensity signal after interference removal The etching depth or the film deposition thickness of the wafer 400 is calculated.

[0138] In some embodiments, both the upper and lower surfaces of the wafer 400 reflect light. During the detection process, it is necessary to obtain the first reflected light intensity of the upper surface of the wafer 400. and the second reflected light intensity of the lower surface of the wafer 400 Specifically, during the detection process, the thickness change of the wafer 400 will affect the detection result, so it is necessary to calculate the interference value caused by the thickness change of the wafer 400. More specifically, according to the first reflected light intensity and the second reflected light intensity The interference value caused by the thickness change of wafer 400 can be calculated .

[0139] In some embodiments, environmental interference may also affect the light intensity received by the first detector 220, and its impact value is During the detection process, the first detector 220 can detect the interference value and impact value Respond and output the first reflected signal .

[0140] In some embodiments, the light intensity reflected by the semiconductor device window 500 is three times the reflected light intensity Environmental interference will also affect the light intensity received by the first detector 220, and its impact value is During the detection process, the second detector 320 can detect the intensity of the third reflected light. and impact value Respond and output the second reflected signal .

[0141] In some specific embodiments, when the first reflected signal is obtained and the second reflected signal After that, the first reflected signal With the second reflected signal After calibration, the difference calculation is performed to obtain the light intensity signal after eliminating interference According to the light intensity signal after interference removal The etching depth or the film deposition thickness of the wafer 400 is calculated.

[0142] In some embodiments, according to the first reflected light intensity and the second reflected light intensity Calculate the interference value caused by the thickness change of wafer 400 include:

[0143] The interference value is calculated according to the following formula :

[0144]

[0145] in is the optical path difference caused by the thickness variation of the wafer 400; is the wavelength of light.

[0146] In some embodiments, = + = + .

[0147] In some embodiments, = + .

[0148] In some embodiments, the first reflected signal With the second reflected signal Perform difference calculation to obtain the light intensity signal after eliminating interference :

[0149] Calculate the light intensity signal after eliminating interference according to the following formula :

[0150]

[0151] The first reflected signal With the second reflected signal The value of is introduced into the above formula to obtain:

[0152]

[0153] in, is the influence value of the light intensity received by the first detector 220 The influence value of the light intensity received by the second detector 320 The ratio of is the optical path difference caused by the thickness change of the wafer; is the wavelength of light;

[0154] Will When the value of is defined as 0, the influence of the environment is eliminated and the elimination value is obtained. :

[0155] .

[0156] In some embodiments, in order to eliminate the ambient light intensity signal The influence of , set A = ( ), B=( ), C=( ). Specifically, through B=( )=0 to eliminate the influence of the environment, where The influence value of the light intensity received by the first detector 220 is obtained by calibration. The influence value of the light intensity received by the second detector 320 More specifically, A may not be 0. When A is not 0, it will only cause the overall etching interference curve to shift up and down. C is the interference portion caused by the thickness change of the etched wafer 400, and the etching depth of the wafer 400 is calculated based on this portion.

[0157] Detection methods also include:

[0158] Elimination value Perform fast Fourier transform to obtain the spectrum X[k];

[0159] Extract the main frequency in the spectrum and calculate the number of cycles based on the main frequency ;

[0160] The etching depth of the wafer 400 is the same as the thickness of the film deposition, which is defined as thickness d;

[0161] The thickness d is calculated using the following formula:

[0162]

[0163] in, is the wavelength of the detection light, and n is the refractive index corresponding to the wavelength of the detection light and the material.

[0164] In some embodiments, according to To calculate the etching depth of wafer 400, The data after signal amplification and A / D conversion is recorded as x[n]. The radix-2 DIT-FFT (decimated-in-time fast Fourier transform) is used to calculate the etching depth of the wafer 400 corresponding to the discrete interference curve x[n].

[0165] In some specific embodiments, the spectrum X[k] corresponding to x[n] is calculated, the main frequency corresponding to the interference curve is obtained from the spectrum X[k], the period corresponding to the interference curve is calculated from the main frequency, and then the number of periods is calculated, and the etching depth of the wafer 400 is calculated from the number of periods.

[0166] More specifically, the spectrum X[k] is calculated according to the following formula:

[0167]

[0168] Where n is the index of the original sequence, that is, the time domain position identifier of the input sequence; N is the number of transformation points of FFT (Fourier transform), that is, the length of the sequence processed by the current recursive step.

[0169] By breaking it down into even and odd parts we get:

[0170]

[0171] Where r is the index of the decomposed subsequence, that is, the position identifier of the subsequence after parity decomposition.

[0172] Extract common factors from the above formula get:

[0173]

[0174] Among them will Defined as ;Will Defined as .

[0175] The final combined formula is:

[0176]

[0177] in, , specifically, is the rotation factor, that is To use the rotation factor To perform exponential operations on complex numbers. More specifically, The e and j in the equation are both mathematical symbols. e represents a natural constant, whose value is approximately 2.7182818284; j represents an imaginary unit in a complex number. In some specific embodiments, the rest The meanings of the operator symbols in the format are the same as above.

[0178] In some specific embodiments, the discrete interference curve x[n] is subjected to a fast Fourier transform using a radix-2 DIT-FFT (Fast Fourier Transform with Time Extraction) algorithm to obtain a spectrum X[k]. The dominant frequency in the resulting spectrum is then extracted, with the resolution denoted as f1. The period corresponding to the dominant frequency is then calculated as T1=1 / f1. The number of periods is obtained by dividing the etching time by the calculated period, and the number of periods is recorded as The etching depth of the wafer 400 is obtained by multiplying the number of cycles by the laser wavelength and the refractive index corresponding to the material. More specifically, the number of cycles is calculated according to the following formula :

[0179]

[0180] Among them, time is the etching time.

[0181] In some embodiments, the etching depth of the wafer 400 is the same as the film deposition thickness, which is defined as thickness d; the cycle number is obtained. Finally, calculate the thickness d according to the following formula:

[0182] d=

[0183] in, is the wavelength of the detection light, n_film is the refractive index corresponding to the wavelength of the detection beam laser and the material, and d is the etching depth of the wafer 400.

[0184] In some embodiments, reference Figure 6 and Figure 7 , Figure 6 This is a curve of wafer etching depth variation detected by a conventional detection device. The curve contains a lot of noise and reaches the etching endpoint at a depth of 3479nm. Figure 7This is a curve diagram of the wafer etching depth variation detected by the dual-beam laser interference detection device of the embodiment of the present invention, showing that the structure of alternating etching of indium gallium arsenide phosphide and indium phosphide materials corresponds to different waveforms, and accurately reaches the etching endpoint at 3451nm; in this process, the total etching depth is set to 3450nm. It can be seen that the detection of the etching endpoint by the existing technology lags by 28nm compared with the detection of the dual-beam laser interference detection device, and the error is larger than the set depth. It can be obtained that the detection curve diagram of the wafer detected by the dual-beam laser interference detection device of the present application has less noise than the detection curve diagram of the wafer detected by the conventional detection device, and the etching endpoint detection accuracy is higher. Therefore, the dual-beam laser interference detection device is particularly suitable for alternating etching or alternating deposition processes, which improves the accuracy of etching endpoint detection.

[0185] The implementation principle of a dual-beam laser interference detection device and method in an embodiment of the present application is as follows: the detection light is focused onto the surface of the wafer 400, and part of the reference light is focused onto the surface of the semiconductor device window 500. At the same time, the first detector 220 outputs a first reflection signal, and the second detector 320 outputs a second reflection signal. When the detection process is affected, such as device vibration or environmental instability, the detection result will be affected. The reference light is focused onto the surface of the semiconductor device window to detect the interference caused by the vibration of the semiconductor device or the instability of the environment. Then, by processing the first reflection signal and the second reflection signal, a light intensity signal after eliminating the interference is obtained, so as to calculate the etching depth or thin film deposition thickness of the wafer 400 based on the light intensity signal after eliminating the interference, and perform accurate end point detection of the etching or thin film process.

[0186] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A dual-beam laser interference detection device for semiconductor etching and thin film process endpoint detection, characterized in that: The dual-beam laser interference detection device includes an imaging unit, a detection unit and a reference unit; The detection unit comprises: a first emitting element, disposed on one side of the imaging unit, for emitting a detection light, wherein the detection light is focused onto the wafer via the imaging unit; a first detector, disposed on one side of the imaging unit, configured to receive the detection light reflected by the wafer and output a first reflection signal; The reference unit includes: a second emitting element, disposed on one side of the imaging unit, for emitting reference light toward the imaging unit so that a portion of the reference light is focused on a semiconductor device window; a second detector disposed on one side of the imaging unit to receive the reference light reflected by the semiconductor device window and output a second reflection signal; During the endpoint detection process, the first reflection signal and the second reflection signal are subjected to difference calculation to obtain a light intensity signal after interference elimination, and the etching depth or thin film deposition thickness of the wafer is calculated based on the light intensity signal after interference elimination; The imaging unit includes a first beam splitter, a second beam splitter, a lens group and a super lens arranged in sequence; The first emitting element is provided on one side of the second beam splitter, and is used to emit detection light toward the second beam splitter, so that the detection light sequentially passes through the second beam splitter, the lens group, and the super lens and is focused onto the wafer; The reference light includes a first light and a second light, wherein the first light is collimated light and forms a second light after passing through the first beam splitter, the second beam splitter, and the lens group; after passing through the metalens, a portion of the second light is focused on the semiconductor device window, and the other portion illuminates the wafer; The second emitting element is movably disposed on one side of the first beam splitter to adapt to the change in the focal length of the lens group, so that the second light is collimated light.

2. The dual-beam laser interference detection device according to claim 1, characterized in that: The lens group includes a first fixed group, a zoom group and a second fixed group arranged in sequence along the optical path; the zoom group is movably arranged between the first fixed group and the second fixed group to change the focal length of the lens group when the zoom group moves.

3. The dual-beam laser interference detection device according to claim 1, characterized in that: Phase distribution on the surface of the metalens Satisfies the following formula: in, is the wavelength of light; is the focal length of the metalens for this wavelength, is the radial distance from the surface point of the metalens to the optical axis, K is the modulation phase of the metalens corresponding to the wavelength range; when K, The corresponding band is ;when hour, The corresponding band is .

4. The dual-beam laser interference detection device according to claim 2, characterized in that: The reference unit further includes a first lens, which is disposed between the second emitting element and the first beam splitter, so that the first light is diffused after passing through the first lens and irradiated onto the first beam splitter.

5. The dual-beam laser interference detection device according to claim 4, characterized in that: The reference unit further includes: a third beam splitter, disposed between the second emitting element and the first lens, so that the first light passes through the third beam splitter and then irradiates the first lens; a second lens, disposed between the third beam splitter and the first detector; The second detector is arranged on one side of the third beam splitter; so that the second light is reflected and passes through the super lens, the lens group, the second beam splitter, the first beam splitter, and the first lens in sequence, is reflected by the third beam splitter, and is focused to the second detector after passing through the second lens.

6. The dual-beam laser interference detection device according to claim 1, characterized in that: The detection unit also includes a fourth spectrometer, which is arranged between the first emitting element and the second spectrometer; the first detector is arranged on one side of the fourth spectrometer, so that the detection light is reflected by the wafer and passes through the super lens, the lens group, and the second spectrometer in sequence, and is reflected by the fourth spectrometer to be focused on the first detector.

7. A dual-beam laser interference detection method, applied to the dual-beam laser interference detection device according to any one of claims 1 to 6, characterized in that: The detection method comprises: Obtaining a first reflected light intensity on the upper surface of the wafer and the second reflected light intensity of the lower surface of the wafer ; According to the first reflected light intensity and the second reflected light intensity Calculate the interference value caused by the wafer thickness change ; Obtain the impact value of interference on the light intensity received by the first detector ; The first detector detects the interference value With the impact value Respond and output the first reflected signal ; Obtaining a third reflected light intensity of the semiconductor device window ; Obtain the impact value of interference on the light intensity received by the second detector ; The second detector detects the third reflected light intensity and the impact value Respond and output the second reflected signal ; The first reflected signal With the second reflected signal After calibration, the difference calculation is performed to obtain the light intensity signal after eliminating interference ; According to the light intensity signal after interference removal The etching depth or thin film deposition thickness of the wafer is calculated.

8. The dual-beam laser interference detection method according to claim 7, characterized in that: The intensity of the first reflected light and the second reflected light intensity Calculate the interference value caused by the wafer thickness change include: The interference value is calculated according to the following formula : in, is the optical path difference caused by the thickness change of the wafer; is the wavelength of light.

9. The dual-beam laser interference detection method according to claim 7, characterized in that: The first reflected signal With the second reflected signal After calibration, the difference calculation is performed to obtain the light intensity signal after eliminating interference : Calculate the light intensity signal after eliminating interference according to the following formula : The first reflected signal With the second reflected signal The value of is introduced into the above formula to obtain: in, is the impact value of the light intensity received by the first detector The influence of the light intensity received by the second detector on the value The ratio of is the optical path difference caused by the thickness change of the wafer; is the wavelength of light; Will When the value of is defined as 0, the influence of the environment is eliminated and the elimination value is obtained. : 。 10. The detection method according to claim 9, characterized in that: Also includes: The elimination value Perform fast Fourier transform to obtain the spectrum X[k]; Extract the main frequency in the spectrum and calculate the number of cycles based on the main frequency ; The etching depth of the wafer is the same as the thickness of the thin film deposition, which is defined as thickness d; The thickness d is calculated by the following formula: in, is the wavelength of the detection light, and n is the refractive index corresponding to the wavelength of the detection light and the material.

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