TW201443389A - Thickness measuring system and method for a bonding layer - Google Patents

Abstract

In a thickness measuring system for a bonding layer according to an exemplary embodiment, an optical element changes the wavelength of a first light source to enable at least one second light source passing through a bonding layer to be incident to an object, wherein the bonding layer has an upper interface and a lower interface that are attached to the object; and an optical image capturing and analysis unit receives a plurality of reflected lights from the upper and the lower interfaces to capture a plurality of interference images of different wavelengths, and analyzes the intensity of the plurality of interference images to compute the thickness information of the bonding layer.

Description

Bonding layer thickness measuring system and method

The present disclosure relates to a thickness measurement system and method for a bonding layer.

Wafer thinning and thin wafer handling technologies are one of the most important technologies for 3D wafer stacking, temporarily bonding device wafers to one outside. Carrier wafers avoid the risk of damage to the wafer due to gravity and other factors after thinning and backside processing. The voids on the interface of the external wafer and the particles, the adhesive thickness, the dent, etc. all affect the thickness uniformity of the thin wafer. . It is therefore important to detect defects before thinning the wafer.

Techniques such as Scanning Acoustic Microscope (SAM) and IR transmission imaging are commonly used to detect voids and particles in the interfacial adhesive layer where the wafer is temporarily bonded. For example, using ultrasonic technology to A 12-inch wafer was measured with a measurement time of about 10 minutes, a measurement spatial resolution of about 50 μm, and the wafer was immersed in a liquid. Some prior art techniques do not require immersing the wafer in a liquid, but require spraying liquid between the test probe and the wafer. Infrared transmissive imaging technology is a global detection technology that detects large bubbles inside the adhesive layer. Microbubbles are combined with other algorithms to enhance the display of defects. These two techniques can detect the voids of the bonding layer, but cannot measure the thickness information of the bonding layer, such as thickness variation, total thickness, absolute thickness, and the like.

Infrared Ray wavelength scanning interferometry is one of the methods used to measure the thickness of germanium wafers. For example, the Fourier transform method based phase-shifting technique and the zero-crossing detection method are the most commonly used to analyze the interference signal. In the Fourier transform based method, the measurable minimum thickness and minimum thickness sensitivity is limited by the varying wavelength range. The phase shift technique energy measures the thickness variation of the wafer. The zero point detection method can be used to instantly measure the surface shape of the wafer.

Using an infrared interferometer to measure the thickness of the wafer itself, when an object is a double-sided polished wafer, the infrared light will produce reflected light on the surface and back of the wafer due to reflection through the wafer. The light path is shortened so that the reflected light frequency produces a Doppler shift, resulting in a slight change in frequency, taking advantage of this frequency change. The thickness variation of the wafer can be measured.

Using the infrared McKesson architecture to measure the thickness of the wafer itself, including the use of broadband sources and changing the optical path difference, is achieved by taking continuous interference images and analyzing the interference packets. Round thickness. The thickness of the wafer itself and the topography of the wafer surface can also be measured using the infrared McKesson architecture and based on reflectometry analysis theory. The surface of the wafer, the back side of the wafer, and the reference plane can be obtained using the McKinson interference architecture. The three reflected light, the three light interfere with each other, and the interference fringes can obtain the interference spectrum by means of spectrum analyzer or wavelength scanning, and then analyze the thickness of the wafer and the surface topography of the wafer.

Embodiments of the present disclosure can provide a thickness measurement system and method for a bonding layer.

One embodiment of the present disclosure is directed to a thickness measurement system for a bonding layer. The system can include an optical component and an optical image capture and analysis unit. The optical element changes a wavelength of the first light source such that the at least one second light source penetrates a bonding layer and is incident on an object, wherein the bonding layer has an upper and lower interfaces, and the upper and lower interfaces are attached to the object; The image capturing and analyzing unit receives the plurality of reflected lights reflected by the upper and lower interfaces to extract interference images of different wavelengths, and analyzes the light intensity of the plurality of interference images to calculate the thickness information of the bonding layer.

Another embodiment of the present disclosure is directed to a method of measuring the thickness of a bonding layer. The method may include: changing a wavelength of a first light source such that at least one second light source penetrates a bonding layer and is incident on an object, wherein the bonding layer is provided with upper and lower interfaces, and the upper and lower interfaces are attached to the object; Receiving a plurality of reflected lights reflected from the upper and lower interfaces of the bonding layer; and analyzing the intensity of the light interference light of the plurality of reflected lights, and calculating the thickness information of the bonding layer.

The above and other advantages of the present invention will be described in detail below with reference to the following drawings, detailed description of the embodiments, and claims.

100‧‧‧thickness measurement system

101‧‧‧First light source

102‧‧‧Optical components

104‧‧‧ objects

→‧‧‧Second light source

106‧‧‧Connection layer

106a‧‧‧Upper interface

106b‧‧‧ lower interface

103‧‧‧Light Image Capture and Analysis Unit

←‧‧‧Reflected light

1031‧‧‧ thickness information

102a‧‧‧Interference filter

102b‧‧‧Light collimator

102c‧‧‧Light source beam expander

102d‧‧‧ lens

102e‧‧‧beam splitter

210‧‧‧ Changing the wavelength of a first light source such that at least one second light source penetrates a bond Layer and incident on an object

220‧‧‧Multiple reflected light received from the upper and lower interfaces of the bonding layer

230‧‧‧Analyze the intensity of the interference light of the plurality of reflected lights to calculate the thickness information of the bonding layer

301‧‧‧ adjustable wavelength source

304‧‧‧ Temporary bonding wafer

304a‧‧ ‧ layer

304b‧‧‧ wafer

303a‧‧‧Light image capture unit

303b‧‧‧ computer

Upper and lower interfaces of 34a and 34b‧‧ ‧ layers

405‧‧‧ Calculate the thickness of a single point of the bonding layer and the thickness variation of the bonding layer

415‧‧‧ Combine the data of this single point thickness with the data of the thickness variation of the whole area to establish the global thickness distribution information of the joint layer

△ L‧‧‧ average thickness of the rubber layer

h ( x, y ) ‧ ‧ thickness of the glue layer at the pixel ( x, y )

605‧‧‧Use a rotating interferometer to change the wavelength of the light source and capture multiple interference images of different wavelengths

610‧‧‧To establish a relationship between the wavelength of a single point of interference signal and the intensity of light in the multiple interference images

615‧‧‧ Use the signal simulated by the optical interference theory to fit the interference spectrum to curve, and find the single point thickness

The first figure illustrates a thickness measurement system for a bonding layer in accordance with an embodiment of the present disclosure.

The second figure illustrates a method of measuring the thickness of a bonding layer according to an embodiment of the present disclosure.

The third figure is a schematic diagram illustrating an application example according to an embodiment of the disclosure.

The fourth figure illustrates how to calculate the thickness information of the bonding layer according to an embodiment of the present disclosure.

The fifth figure is an example of the temporary bonding of the wafer in the third figure, and illustrates the relationship between the intensity of the light interference light of the reflected wave at the upper and lower interfaces of the adhesive layer and the thickness of the adhesive layer.

The sixth figure illustrates how to calculate a single point thickness of the bonding layer in accordance with an embodiment of the present disclosure.

The seventh figure is a curve fitting of a signal curve simulated by the optical interference theory and an interference spectrum of a single point in a plurality of interference images according to an embodiment.

The eighth figure is a phase shift and a wavelength of five interference images using a five-step phase shift method according to another embodiment of the present disclosure.

The ninth drawing is a measurement result illustrating the thickness variation of the bonding layer according to an embodiment of the present disclosure.

Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, which will be readily understood by those skilled in the art. The inventive concept described above may take a variety of variations, and should not be limited to only these embodiments. The disclosure omits the description of well-known parts, and the same reference numerals represent the same elements in the present disclosure.

Embodiments of the present disclosure may provide a technique that provides a thickness measurement of a bonding layer. The bonding layer is, for example, but not limited to, a temporary bonding interface (eg, a glue layer) of the wafer. For example, if the object is a wafer, the bonding layer is, for example, a temporary bonding interface of the wafer. The bonding layer has an upper interface and a lower interface, and the upper and lower interfaces are bonded to the wafer. The technology can measure the thickness information of the interface glue by using an optical component such as an interferometer, a theory based on phase shift theory and reflection, for example, the thickness and thickness of the interface glue, and the interface glue The thickness of the single point and the thickness of the interface glue change to establish the thickness distribution of the temporary bonding interface layer of the wafer.

The first figure illustrates a thickness measurement system for a bonding layer in accordance with an embodiment of the present disclosure. Referring to the first figure, the thickness measurement system 100 includes an optical component 102 and an optical image capture and analysis unit 103. The optical element 102 changes the wavelength of a first light source 101 such that at least one second light source (indicated by an arrow →) penetrates a bonding layer 106 and is incident on an object 104. The bonding layer 106 has an upper interface 106a and a lower interface 106b. The upper and lower interfaces (106a and 106b) are attached to the object 104. The optical image capturing and analyzing unit 103 receives the plurality of reflected lights 1061 reflected by the upper and lower interfaces to capture multiple interference images of different wavelengths. And analyzing the light intensity of the plurality of interference images to calculate the thickness information 1031 of the bonding layer 106.

In the embodiment of the present disclosure, the object is, for example, a wafer. The bonding layer is an interface glue layer bonded to the wafer. In the optical component, the different angles of the interference filter can be rotated, for example, by a light spindle, and the first light source 101 is adjusted through the interference filter from 10° every time by 0.25° rotation to 45°. Different wavelengths. For example, the optical component can collimate the first light source 101 into an interference filter 102a by using a light collimator 102b. The at least one second light source is further passed through, for example, a light source expander 102c and a lens 102d. The bonding layer 106 is incident on the object. The plurality of interference images captured by the light image capturing and analyzing unit are the at least one second light source incident (indicated by an arrow) to the upper and lower interfaces of the bonding layer, and the light is reflected by the upper and lower interfaces (indicated by an arrow ←) Producing a plurality of light-dryings that interfere with each other and are reflected by a beam splitter 102e Light intensity image. The thickness information of the bonding layer includes at least one single point absolute thickness data of the bonding layer and global thickness distribution information of the bonding layer. With at least one single point absolute thickness data of the bonding layer and global thickness distribution information of the bonding layer, the thickness measurement system 100 can also analyze information about the object, for example, a surface fitting method can be used to generate the object. Information on the surface topography.

In view of the above, according to an embodiment of the present disclosure, a method for measuring the thickness of a bonding layer can be provided, as shown in the second figure. Referring to the second figure, the thickness measurement method can change the wavelength of a first light source such that at least one second light source penetrates a bonding layer and is incident on an object (step 210). There are two upper and lower interfaces, and the upper and lower interfaces are attached to the object. Then, the thickness measuring method can receive a plurality of reflected lights reflected from the upper and lower interfaces of the bonding layer (step 220), and can analyze the optical interference light intensity of the plurality of reflected lights to calculate the thickness of the bonding layer. Information (step 230).

In an embodiment of the present disclosure, the thickness measurement method may change the wavelength of the first light source by using different angles of the rotation-interference filter to generate the at least one second light source. The following describes a technique for thickness measurement of the present disclosure by using a temporarily bonded wafer as an application example. In this application example, the first light source is a tunable wavelength light source; the temporary bonding wafer includes an object such as a wafer, and a bonding layer, for example, a bonding layer having an upper interface and a lower interface.

The third figure is a schematic diagram illustrating an application example according to an embodiment of the disclosure. In this application example, a tunable wavelength light source 301 is expanded and collimated by the light source beam expander 102c and the lens 102d in the optical element 102, and then incident (indicated by an arrow) to A wafer 304 is temporarily bonded. The temporary bonding wafer 304 includes a glue layer 304a for temporarily bonding a wafer 304b. The reflected light (indicated by the arrow ←) of the upper and lower interfaces (34a and 34b) of the adhesive layer 304a bonded to one surface of the temporarily bonded wafer 304 interferes with each other, and is transmitted through the light image capturing and analyzing unit such as an optical image. The taking unit 303a captures the intensity of the light interference light of the reflected wave, and analyzes the data of the intensity of the light interference light by a thickness analyzing unit such as a computer 303b, a computing device, a processor, etc., to calculate the thickness information of the adhesive layer 304a. .

According to an embodiment of the present disclosure, as shown in the fourth figure, calculating the thickness information of a bonding layer may include: calculating a single point thickness of the bonding layer and a global thickness variation of the bonding layer (step 405); and combining the single point The thickness data and the global thickness variation data are used to establish global thickness distribution information for the bonding layer (step 415).

The thickness measurement of the disclosed embodiments can be calculated based on optical interference theory (e.g., infrared wavelength scanning interferometry), phase shifting techniques, and spectral curve fitting techniques. Using the optical interference theory, the relationship between the optical interference light intensity and the thickness of the glue layer of the multiple interference images captured by the optical image capture and analysis unit can be expressed as follows: I ( k ; x , y ) = I ₀ ( x , y ) + A ( x , y )cos{2 kn . L(x,y)}..............(1) where L( x,y ) is the bonding layer at a pixel point ( x,y ) Corresponding bonding layer thickness; I(k; x, y) is the optical interference light intensity of the reflected wave of the bonding layer at the pixel point ( x, y ); I ₀ ( x , y ) is the background of the interference image at the pixel point ( x,y ) light interference light intensity; A(x,y) is the light interference amplitude at the pixel point ( xy ) in micrometers; n is the resistivity of the bonding layer; and λ is the reflected wave The wavelength of light, in nanometer (nm). This bonding layer is a pixel (x, y) corresponding to the absolute thickness L (x, y) = △ L + h (x, y), where △ L is the average thickness of the bonding layer; h (x, y) The thickness of the bonding layer at the pixel point ( x, y ) varies; and k = 2 π / λ . Therefore, in equation (1), the intensity of light interference at a single point ( x, y ) of the surface of the bonding layer can be expressed as follows: I ( k ; x , y ) = I ₀ ( x , y ) + A ( x , y )cos{2 kn . [△ L + h ( x , y )]} (2)

According to different wavelengths λ , the intensity of light interference at a single point (x, y) can be expressed as follows: And its corresponding specific phase ψ( x,y ) can be expressed as

As described earlier, the reflected light at the upper and lower interfaces of the bonding layer interfere with each other, and the phase change of the two-wavelength interference can be expressed as follows: Here, Δλ is a wavelength change amount. That is

Taking the temporary bonding wafer of the third figure as an application example, according to the above calculation formula, the fifth figure illustrates the relationship between the light interference light intensity of the reflected wave from the upper and lower interfaces (34a and 34b) of the adhesive layer 304a and the thickness of the adhesive layer. . The absolute thickness corresponding to the surface of the glue layer 304a at any pixel point ( x, y ) is the average thickness ΔL of the glue layer 304a plus the thickness variation h ( x, y ) of the glue layer 304a at this pixel point ( x, y ). . This thickness change h ( x, y ) can be expressed as follows: Here, λ is the wavelength of the reflected wave, n is the reflectance of the adhesive layer 304a, and ψ is the phase corresponding to the intensity of the light interference light of the reflected wave at the pixel point ( x, y ).

In view of the above, the sixth figure illustrates how to calculate a single point thickness of the bonding layer according to an embodiment. Referring to the sixth figure, first, a rotating interferometer can be used to change the wavelength of the light source, and multiple interference images of different wavelengths are captured (step 605), and then the wavelength of the interference signal of a single point in the multiple interference images is established. A relationship with the light intensity (i.e., the interference spectrogram) is obtained (step 610), and the signal simulated by the optical interference theory is fitted to the interference spectrogram for curve fitting to determine the single point thickness (step 615).

The seventh figure is a curve fitting of a signal curve simulated by the optical interference theory and an interference spectrum of a single point in a plurality of interference images according to an embodiment, wherein the solid line curve represents an interference signal simulated by the optical interference theory. (interference signal), the dotted curve represents the curve fitting made by using a single point interference spectrum in multiple interference images. The variable on the horizontal axis represents 1/λ, that is, 1/wavelength, and the variable on the vertical axis represents amplitude. (amplitude). The average thickness Δ L of the bonding layer can be initially determined by fitting the spectral curve from the interference spectrogram. The single point thickness can be set to the average thickness Δ L determined from the fit of the spectral curve.

After determining the thickness of a single point, by changing the amount of wavelength (ie, Δλ), an interference image of a specific phase can be selected in a plurality of interference phase diagrams, and a phase algorithm such as three steps, four steps, or five steps is utilized. The phase shift method and the phase unwrapping method calculate the phase of each pixel point ( x, y ). As shown in the example of the eighth figure, five phase shifts can be used with a five-step phase shift, ie Δψ=(i-1)×π/2 and i=1,2,3,4 5, to extract five different wavelength interference images, then the light intensity I ₁ ~ I ₅ of each pixel ( x, y ) of the five interference images can be expressed as follows: Therefore, the pixel (x, y) a specific phase ψ (x, y) can be expressed as the corresponding That is, the specific phase ψ( x, y ) can be calculated from the light intensities I ₁ to I ₅ of the respective pixel points ( x, y ) of the five interference images described above. Then, the thickness variation h ( x, y ) of the global (Full-Field) bonding layer can be utilized Come to draw. Thus, the thickness variation of the global bonding layer is calculated from the phase values.

That is, calculating the thickness variation of the global bonding layer may include: selecting a plurality of interference images of a plurality of specific phases in the plurality of interference phase maps by changing the amount of the wavelength; and calculating the bonding layer by using a phase shift method The phase corresponding to each pixel point ( x, y ) is used to calculate the thickness variation of the global bonding layer based on the calculated phases. Finally, by integrating the data of the single point thickness with the data of the global thickness variation of the bonding layer, the thickness distribution of the global bonding layer can be established. The ninth drawing is a measurement result of the thickness distribution of the bonding layer according to an embodiment of the present disclosure, wherein the horizontal axis represents the position of the pixel of the bonding layer, and the vertical axis represents the thickness of the bonding layer (in micrometers (μm) )). In the experimental example of the ninth figure, according to the result of the curve distribution, the maximum thickness of the bonding layer is 19.86 μm at the position 450, and the minimum thickness of 16.09 μm is about the position 50. That is, the thickness of this bonding layer can be changed from 16.09 μm to 19.86 μm. In other words, the total thickness variation of this bonding layer is 3.76 μm, that is, the difference between the maximum thickness and the minimum thickness.

In summary, the embodiments of the present disclosure provide a thickness measurement system for a bonding layer. System and method. The technology can use an optical component such as an interferometer, phase shift theory and reflection theory, spectral curve fitting, etc. to analyze the light intensity of multiple interference images and measure the thickness information of the bonding layer. The thickness information is, for example, but The thickness of the bonding layer of an object may be established by the single-point thickness value of the bonding layer and the thickness variation of the bonding layer, without being limited to the single-point thickness and the thickness variation of the entire bonding layer.

The above is only the embodiment of the disclosure, and the scope of the disclosure is not limited thereto. That is, the equivalent changes and modifications made by the scope of the present invention should remain within the scope of the present invention.

100‧‧‧thickness measurement system

101‧‧‧First light source

102‧‧‧Optical components

104‧‧‧ objects

→‧‧‧Second light source

106‧‧‧Connection layer

106a‧‧‧Upper interface

106b‧‧‧ lower interface

103‧‧‧Light Image Capture and Analysis Unit

←‧‧‧Reflected light

1031‧‧‧ thickness information

102a‧‧‧Interference filter

102b‧‧‧Light collimator

102c‧‧‧Light source beam expander

102d‧‧‧ lens

102e‧‧‧beam splitter

Claims (16)

A thickness measurement system for a bonding layer, the system comprising: an optical component that changes a wavelength of a first light source such that at least one second light source penetrates a bonding layer and is incident on an object, wherein the bonding layer is provided with two upper and lower An interface, the upper and lower interfaces are attached to the object; and an optical image capturing and analyzing unit receives the plurality of reflected lights reflected by the upper and lower interfaces to capture a plurality of interference images of different wavelengths, and analyzes the plurality of images The light intensity of the image is interfered to calculate the thickness information of the bonding layer. The system of claim 1, wherein the object is a wafer. The system of claim 1, wherein the bonding layer is an interface layer of the article. The system of claim 1, wherein the optical element rotates a different angle of the interference filter to adjust different wavelengths of the first light source through the interference filter. The system of claim 4, wherein the optical component collimates the first light source into an interference filter by using a light collimator, and the at least one second light source is further passed through a light source beam expander The bonding layer is incident on the object. The system of claim 1, wherein the plurality of interference images captured by the optical image capturing and analyzing unit are reflected by the upper and lower interfaces after the at least one second light source is incident on the upper and lower interfaces. The light generates a plurality of light interference light intensity images generated by mutual interference. The system of claim 1, wherein the thickness information of the bonding layer includes at least a single point thickness of the bonding layer and a total of the bonding layer Domain thickness distribution information. The system of claim 1, wherein the system uses the thickness information of the bonding layer to generate information on the surface topography of the object. A method for measuring a thickness of a bonding layer, comprising: changing a wavelength of a first light source, causing at least one second light source to penetrate a bonding layer and incident on an object, the object bonding with the bonding layer, wherein the bonding layer is prepared Having upper and lower interfaces, the upper and lower interfaces are attached to the object; receiving a plurality of reflected lights reflected from the upper and lower interfaces of the bonding layer; and analyzing the intensity of the interference light of the plurality of reflected lights, and calculating the bonding layer Thickness information. The method of claim 9, wherein calculating the thickness information of the bonding layer further comprises: calculating a single point thickness of the bonding layer and a global thickness variation of the bonding layer; and combining the single point thickness The data and the global thickness variation data are used to establish the global thickness distribution information of the bonding layer. The method of claim 9, wherein the method uses a different angle of the rotation-interference filter to change the wavelength of the first source to generate the at least one second source. The method of claim 10, wherein calculating the single point thickness of the bonding layer further comprises: using a rotating interferometer to change a wavelength of the first light source, and extracting multiple interference images of different wavelengths ; Establishing an interference spectrogram of the wavelength and the intensity of the interference signal of the single point in the plurality of interference images; and fitting a plurality of signals simulated by the optical interference theory to the interference spectrum to perform the curve fitting Single point thickness. The method of claim 10, wherein calculating the global thickness variation of the bonding layer further comprises: selecting a plurality of specific phases in the plurality of interference phase maps by changing the amount of the wavelength of the first light source And interfering with the image; and calculating a phase corresponding to each pixel of the bonding layer by using a phase shift method, and calculating a global thickness variation of the bonding layer according to the calculated phase corresponding to each pixel. The method of claim 13, wherein the plurality of specific phases are calculated from light intensities of respective pixels of the plurality of interference images. The method of claim 12, wherein an average thickness of the bonding layer is initially determined from a spectral curve fit of the interference spectrogram. The method of claim 15, wherein the single point thickness is set to the average thickness determined from the spectral curve fit.