Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
  • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
  • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
  • G01B11/0641—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of polarization
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
  • G01N21/21—Polarisation-affecting properties
  • G01N21/211—Ellipsometry

Definitions

• the present invention relates to an ellipsometry, and more particularly to an ellipsometry suitable for measuring a film thickness in a manufacturing process of a semiconductor device and measuring a cross-sectional shape such as an etched shape.
• FIG. 2 shows an outline of optical film thickness measurement using such an ellipsometer.
• the light from the light source 101 is divided into a polarizer 102 for adjusting the polarization state and a compensation plate 103 for adjusting the phase.
• incident light in an elliptically polarized state is formed, and the sample 107 is irradiated.
• An analyzer 104 for examining the polarization state, a spectroscope 105 for selecting light of a predetermined wavelength, and a detector 106 are provided on the optical path of the reflected light from the sample 107. Then, the polarization state is measured for each wavelength of the reflected light to obtain a spectrum.
• an oxide film such as a gut oxide film
• the P-polarized light component and the s-polarized light component are calculated for the light as described above.
• the film thickness is calculated from the phase difference ⁇ and the amplitude ratio ⁇ .
• the p-polarized light component (r ip) and the s-polarized light component (r ls ) of the light reflected on the Si substrate 202 surface are calculated by the following equations, respectively.
• the p-polarized light component (R P ) and the s-polarized light component (R s ) of the detected light are r lp , r ls, and the polarized light component (r 0p) of the light reflected on the oxide film 201 surface.
• the s-polarized component (r 0s ) the polarization state is calculated by the following equation.
• Rp (r on + ri p exp, 1 2 i ⁇ )) / (1 + r Q p 'rj n exp — 2 i ⁇ ))
• a wavelength-dependent spectrum can be obtained. Then, by comparing the actually measured spectrum with the theoretical spectrum using the film thickness value t of the oxide film 201 as a parameter, the film thickness value t can be calculated.
• an oxide film 20 formed on the Si substrate 202 is formed.
• 1 has a grating structure
• the pattern part is divided into L equal parts
• the grating part is divided into L parts.
• the grating structure is divided into L layers, and the dielectric constant is calculated for each layer based on the volume ratio between air and the grating part.
• the dielectric constant is calculated for each layer based on the volume ratio between air and the grating part.
• the substrate surface (the lower reflective surface) is made of a material having a large light absorption coefficient k such as Si, Al, or Cu (a low light transmissive material). (Light transmissive material), and can be applied to the case where the film thickness is large and flat and non-transmissive.
• the above-described film thickness measurement method and cross-sectional shape measurement method have a problem that the film thickness measurement and the cross-sectional shape measurement cannot be performed for a sample having a multilayer wiring structure under the oxide film to be measured. is there.
• a metal wiring 302 is formed below the a layer composed of the oxide film 301 whose thickness is to be measured.
• a b-layer made of the inter-brows insulating film 303 and a c-layer made of the metal wiring 304 and the interlayer insulating film 305 are formed.
• the b-layer metal wiring is formed. It has a multilayer wiring structure formed so that 302 and c-layer metal wiring 304 are orthogonal to each other.
• oxide film The 301 and interlayer insulating films 303, 305 are made of a material having high light transmittance such as silicon dioxide, and the metal wires 302, 304 are made of Cu, Al. , W, etc. are made of a low light transmitting material having a low light transmitting property.
• reference numerals 36 and 307 denote stopper layers made of a SiN film, a SiC film and the like and used in a CMP (Chemical Mechanical Polishing) process.
• the oxide film 301 further has a grating structure.
• a test piece wafer is put in the manufacturing process separately from a product wafer, and a test piece wafer (bare Si) is provided. A film to be measured is formed on top, and the film thickness is measured by an optical method.
• a test piece wafer is loaded, the film formation, resist coating, exposure, and etching processes are performed, and the cross section is observed by SEM to control the shape.
• an object of the present invention is to provide a polarization analysis method capable of measuring the film thickness and measuring the cross-sectional shape of a film formed on a multi-layer wiring at a high throughput without breaking.
• the present invention relates to a p-polarized component of reflected light reflected from an object to be measured when the object having a film to be measured on its surface is irradiated with incident light of a predetermined wavelength in an elliptically polarized state at a predetermined incident angle.
• a value based on the phase difference ( ⁇ ) of the s-polarized component and a value based on the amplitude ratio ( ⁇ ) are obtained by theoretical calculation to obtain reference data. Reflection that is reflected when the object is actually irradiated with the incident light.
• the film is analyzed by determining a value based on the phase difference ( ⁇ ) between the P-polarized component and the s-polarized component of the light and a value based on the amplitude ratio ( ⁇ ) and comparing them with the reference data.
• ⁇ phase difference
• ⁇ amplitude ratio
• the present invention is characterized in that the comparison is made based on at least two or more wavelengths.
• the present invention is characterized in that the comparison is made based on at least two or more incident angles. Further, the present invention is characterized in that the value based on the phase difference ( ⁇ ) is cos ⁇ , and the value based on the amplitude ratio ( ⁇ ) is tan ⁇ .
• the present invention provides a method according to the present invention, wherein the object to be measured is formed on an uppermost layer, the first layer is made of a high light-transmitting material having a high light-transmitting property, and provided below the first layer.
• a second layer composed of a highly light-transmissive material with high light transmittance and a low light-transmissive material with low light transmittance, and a high light-transmissive material with high light transmittance provided under the second layer
• a substrate provided below the third layer and made of a low-light-transmitting material having low light-transmitting property.
• the second layer has a linear wiring structure in which the high light-transmitting material and the low light-transmitting material are alternately arranged in a layer plane direction. Is characterized in that the polarization plane is parallel to the linear wiring. Further, according to the present invention, between the substrate and the third layer, a high light-transmitting material having a high light-transmitting property and a low light-transmitting material having a low light-transmitting property are alternately arranged in a layer plane direction.
• a fourth layer having at least a linear wiring structure on a surface thereof, wherein a direction of the linear wiring of the fourth layer is a direction orthogonal to a direction of the linear wiring of the second layer.
• the present invention is characterized in that the s-polarized light component is reflected on the second layer, and the p-polarized light component is transmitted through the second layer and reflected on the fourth layer.
• the present invention is characterized in that the second layer in the theoretical calculation has a different refractive index for the p-polarized component and a different refractive index for the s-polarized component.
• the present invention is characterized in that the low-light-transmitting material having low light-transmitting property is a metal wiring material, and the high-light-transmitting material having high light-transmitting property is an insulating material.
• the present invention provides a method for measuring the thickness, refractive index, and cross-sectional shape of a film to be measured. It is characterized by measuring at least one of them.
• FIG. 1 is a diagram for explaining an embodiment of the measuring method of the present invention.
• FIG. 2 is a diagram showing a schematic configuration of an ellipsometer used in the method of the present invention.
• FIG. 3 is a diagram showing a schematic configuration of a cross section of a substrate for explaining a conventional film thickness measuring method.
• FIG. 4 is a diagram showing a schematic configuration of a substrate cross-section for explaining a conventional cross-sectional shape measuring method.
• FIG. 5 is a view showing a schematic configuration of a substrate cross section for explaining a conventional cross-sectional shape measuring method.
• FIG. 6 is a diagram showing a schematic configuration of a cross section of a substrate for explaining a problem of the conventional technology.
• FIG. 7 is a diagram showing a schematic configuration of a cross section of a substrate for explaining a problem of the conventional technology.
• FIG. 8 is a diagram showing a schematic configuration of a cross section of a substrate for explaining a problem of the related art.
• FIG. 1 shows an example in which the thickness (t A) of the oxide film 301 of the sample having the multilayer wiring structure shown in FIG. 6 described above is measured. For this reason, illustration of the stopper layers 306 and 307 shown in FIG. 6 is omitted. Also, in the figure, (a) shows the behavior of the s-polarized light component of the irradiated light, and (b) shows the behavior of the p-polarized light component.
• the configuration of the ellipsometer used for measurement is As shown in FIG. 2 described above, it is composed of a light source 101, a polarizer 102, a compensator 103, an analyzer 104, a spectrometer 105, a detector 106, etc. .
• the s-polarized light component of the incident light that irradiates the A layer consisting of the oxide film 301 with a refractive index of NA from air with a refractive index of NO from 30 ° is one.
• the part is reflected from the surface of layer A at a reflection angle ⁇ 0 (r Os), and the rest enters layer A.
• the s-polarized light component entering the A layer passes through the A layer and reaches the interface between the metal wiring 302 and the B layer formed of the interlayer insulating film 303, but the s-polarized light component is Since the amplitude is in the direction perpendicular to the wiring direction of the wiring 302 (the longitudinal direction of the wiring), it can pass through the region where the interlayer insulating film 303 formed between the metal wirings 302 in the B layer is formed. No, it is reflected at the interface with layer B at a reflection angle ⁇ 1. The amplitude reflectance r Is of this reflected light is
• NBs is the refractive index of the B layer for the s-polarized light component.
• the reflected light (rls) passes through the layers S and B, and interferes with the reflected light (r0s) reflected on the surface of the layer A.
• the amplitude reflectance Rs of the interference light is
• Fig. 1 (b) shows the behavior of the p-polarized light component of the irradiated light.
• An oxide film with a refractive index of NA out of air with a refractive index of N0 A part of the p-polarized light component of the incident light irradiating the A layer consisting of 1 is partially reflected from the surface of the A layer at a reflection angle of 00 (r Op), and the rest enters the A layer.
• the p-polarized light component entering the A layer passes through the A layer and reaches the interface between the metal wiring 302 and the B layer composed of the interlayer insulating film 303, but the ⁇ -polarized light component is Since the amplitude is in the direction parallel to the wiring direction of the wiring 302 (the longitudinal direction of the wiring), the wiring may pass through the region where the interlayer insulating film 303 formed between the metal wirings 302 in the B layer is formed. it can.
• the p-polarized component that has passed further passes through the C layer consisting of only the interlayer insulating film 303 and reaches the interface between the metal wiring 304 and the D layer consisting of the interlayer insulating film 305. To reach. As shown in the figure, at the interface with the layer B and the interface with the layer C, some P-polarized light components are reflected at reflection angles 0 1 and ⁇ 2.
• the p-polarized light component is the interlayer insulating film formed between the metal wiring 304 of the D layer.
• the p-polarized light component that cannot pass through the formation region of the 305 and reaches the interface with the D layer is reflected at the reflection angle 03 here.
• the amplitude reflectance r 3P of this reflected light is
• r 3P (ND cos ⁇ 3 _NC cos ⁇ 4) / (ND cos ⁇ 3 + NC cos ⁇
• the refractive index NBs of the B layer for the s-polarized light component and the p-polarized light ND NBs holds between the refractive index ND of the D layer for the component.
• the reflected light (r3p) reflected at the interface with the D layer passes through the C layer and interferes with the reflected light (r2p) reflected at the interface with the C layer.
• the amplitude reflectance of the interference light R 2p is
• R2p (r 2p + r 3pexp (-2 i 5)) / (l + r 2p-r 3pexp (one 2 i ⁇ ))
• the layer B will be described.
• the refractive index of the layer B has been defined as NBs, but the refractive index of the layer B changes depending on the film thickness, such as Cu, W, and A1. It is a layer containing a metal. In the case of such a layer, the refractive index differs between when it functions as a substrate surface (non-transmitting surface) for the s-polarized component and when it functions as a transmission film for the P-polarized component. NBp.
• R lp (r lp + R2pexp (-2 i ⁇ )) / ( ⁇ + r lpR2pexp (one 2 i ⁇ ))
• r 1 ⁇ (NBpcos ⁇ 1 ⁇ ⁇ A cos ⁇ 2) / (NBpcos ⁇ 1- ⁇ A cos ⁇ 2)
• R p (r 0p + R lpexp (-2 i 6)) / (l + r 0p-R lpexp (one 2 i ⁇ ))
• the s-polarized light component and the p-polarized light component are calculated from the amplitude reflectances R s and R p calculated by dividing the reflecting surface acting like the substrate surface (non-transmitting surface) into the s-polarized light component and the p-polarized light component.
• the tan ⁇ and cos ⁇ ⁇ which are functions of the amplitude ratio ⁇ of the polarization component and the phase difference ⁇ , can be calculated from the following equations.
• the spectrum data of the reference data obtained in this way for the different layer thickness t A of the layer A and the actually measured spectrum data obtained by actual measurement are compared with the film thickness and film quality.
• the thickness of the oxide film 301 (A layer) formed on the multi-layer wiring is measured by comparing the parameters while varying the parameter, and using the film thickness that minimizes or maximizes the statistic indicating the error as the output value. can do.
• the method of calculating the wavelength dependence of tan ⁇ and cos ⁇ and comparing with the measured spectra is shown in FIG.
• the cross-sectional shape such as the etching shape of the grating structure.
• a method is used in which the pattern portion is divided into n equal parts, and the shape is determined as an n-layer laminated film, as shown in Fig. 5.
• the metal wirings 302 and 304 orthogonal to each other are formed in the B layer and the D layer has been described.
• the layer not only the metal wiring 304 but also a non-transmissive surface such as a substrate surface can be similarly applied.
• the same effect can be obtained by making the incident angle variable instead of the wavelength.
• the incident angle dependence of cos ⁇ and tan ⁇ can be obtained by performing measurement with variable incident angle 0 0. Then, by calculating at a plurality of incident angles based on the above equation, reference data of ⁇ one cos ⁇ and 0 ⁇ tan ⁇ can be obtained. By comparing the reference data and the measured spectrum data, it is possible to obtain the physical quantity relating to the desired film thickness and cross-sectional shape.
• the film thickness measurement and the cross-sectional shape measurement of the film formed on the multilayer wiring can be performed without crushing and with high throughput. Industrial applicability
• the polarization analysis method according to the present invention can be used in the semiconductor manufacturing industry that manufactures semiconductor devices. Therefore, it has industrial applicability.

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