JPH09237812A - Processing dimension measuring method, semiconductor device manufacturing method, and quality control method - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To use non-contact and non-destructive measurement of a lateral dimension of a pattern formed on a wafer by using ellipsometry.
In addition, it includes a workpiece dimension measuring step required at high speed, and controls the semiconductor device manufacturing process based on the obtained dimension. A polarization state parameter is obtained for a calibration pattern formed on a wafer and its dimensions are confirmed, a database is created, and the database is searched based on the polarization parameter of a measurement sample to obtain the dimension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to semiconductor device manufacturing, and more particularly to a method of manufacturing a semiconductor device including a workpiece dimension measuring step, and a semiconductor device quality control method including the workpiece dimension measuring step.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing line, the dimensions of a workpiece, such as a gate pattern, formed on a wafer are
Non-contact and non-destructive high-speed measurement is required.
In addition, it is desirable to quickly feed back such measurement results to the production line to adjust the production parameters. In particular, the gate length dimension influences the threshold characteristics of the semiconductor device, and therefore its precise control is required.

Conventionally, a wafer on which a structure such as a gate pattern is formed is scanned one by one with a scanning electron microscope (SEM), and the dimension thereof is measured. Another method is also used in which a bridge circuit is simultaneously formed on a wafer on which a gate pattern is formed, and a current is passed through the bridge circuit to measure the dimensions of the gate pattern.

[0004]

However, in the method using the SEM, each wafer flowing through the manufacturing line is SEM.
Since it has to be transferred to the vacuum chamber, it is impossible to perform a 100% inspection, and even if a sampling inspection is performed, the problem that the manufacturing throughput of the semiconductor device is lowered cannot be avoided. In addition, like recent highly integrated semiconductor devices,
When the processing dimension such as the gate length becomes about 0.1 μm, SE
Due to the influence of the electron beam diameter of M, a measurement error of about 10 nm occurs, which causes a problem in terms of accuracy and reproducibility of the measurement result.

On the other hand, although the resistance measurement method solves the problem of accuracy and reproducibility of the measurement result that occurs when using the SEM, the result cannot be obtained unless the wafer manufacturing process is completed until the end of the wafer manufacturing process. A problem arises in that the manufacturing process cannot be immediately feedback-controlled.

On the other hand, conventionally, the ellipsometry technique has been used to measure the film thickness of a semiconductor film or an insulating film in the process of manufacturing a semiconductor device. For example, in the etching process, ellipsometry is also used to control etching when forming a line and space pattern (Bl
ayo, N., et al., "Ultraviolet-visible ellipsometry
for process control during the etching of submicro
meter features, "J. Opt. Soc. Am. A, vol.12, no.3,
1995, pp.591-599).

22A and 22B show the configuration of an ellipsometer used in conventional ellipsometry. Of these, the device shown in FIG. 22 (A) is a device of the type called rotation extinction type, and the device shown in FIG. 22 (B) is a device of the type called extinction type. With reference to FIG. 22 (A), the light emitted from the light source 1 is converted into linearly polarized light having a predetermined polarization plane by the polarizer 2, and enters the sample 3 on which the film to be measured is formed. The light reflected by sample 3 is
In general, the polarization state changes to elliptically polarized light which is characterized by the rotation angle φ of the plane of polarization and the elliptical flatness ratio a _min / a _max = tan ψ as shown in FIG. 23, and after passing through the rotation analyzer 4, the detector 5 Detected in. In this device, the polarization state is obtained by measuring the intensity of the incident light with the detector 5 while rotating the rotary analyzer 4. Further, in the apparatus having this configuration, the quarter wavelength plate 4 a may be inserted between the rotation analyzer 4 and the sample 3.

In the apparatus shown in FIG. 22B, a rotating quarter-wave plate 4b is inserted between the rotating analyzer 4 and the sample 3, and the elliptically polarized light reflected by the sample 3 is once converted into linearly polarized light.
In this state, the rotation analyzer 4 is rotated to find the extinction angle at which the light reaching the detector 5 is extinguished.

As described above, these ellipsometers are widely used for measuring the film thickness in the manufacturing process of semiconductor devices, but the light beam that has passed through the structure formed on the sample 3 is used. The state of polarization is considered to contain information on the lateral dimension of such structures. However, conventionally, the idea of measuring the dimension in the lateral direction of a processed product such as a line and space pattern formed on the sample 3 by an ellipsometer has not been proposed.

SUMMARY OF THE INVENTION Therefore, it is a general object of the present invention to provide a novel and useful method for measuring a workpiece size and a method for manufacturing a semiconductor device using the method for measuring a workpiece size, which solves the above problems. And A more specific object of the present invention is to use a technique of ellipsometry to measure a dimension of a structure formed on a substrate wafer with high accuracy, quickly, and nondestructively, and measure a workpiece dimension. Another object of the present invention is to provide a method for manufacturing a semiconductor device using such a method for measuring a workpiece size.

[0011]

According to the present invention, there is provided a semiconductor device including a step of measuring a dimension of a structure formed on a substrate having a flat surface as described in claim 1. And a step of illuminating the structure with a polarized incident light beam at a predetermined angle with respect to the surface of the substrate; A measurement step of measuring a polarization state; and an evaluation step of obtaining a dimension of the structure in a direction parallel to the substrate surface from the polarization state; manufacturing a semiconductor device based on the obtained dimension. According to a method for manufacturing a semiconductor device, which is characterized by adjusting a parameter, or as described in claim 2, in the evaluation step, the polarization state and the size of the structure are determined based on the obtained polarization state. Is performed by referring to a database containing the dimensions of various structures, by the method for manufacturing a semiconductor device according to claim 1, or as described in claim 3, 2. The semiconductor device according to claim 1, wherein the state is represented by a rotation of a plane of polarization of the emitted light beam after passing through the structure and an aspect ratio, and the measuring step is executed by an ellipsometer. According to a manufacturing method or as described in claim 4, the illuminating step is performed while changing an incident angle of the polarized incident light beam, and the evaluating step includes the obtained polarization state and the incident angle. 2. The semiconductor device according to claim 1, further comprising the step of estimating an angle formed by the side wall surface defining the structure with respect to the substrate plane by a combination of the above. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the measuring step uses the reflected light of the incident light beam as the outgoing light beam, according to the method of manufacturing the device or as described in claim 5. According to a method or as defined in claim 6, the illuminating step, the measuring step is performed using as the outgoing light beam diffracted light of the incident light beam diffracted from the structure. Claim 1 characterized by the above-mentioned.
According to the method for manufacturing a semiconductor device described above, or as described in claim 7, the measuring step is performed by using, as the outgoing light beam, scattered light of the incident light beam scattered by the structure. According to the method of manufacturing a semiconductor device according to claim 1, or as described in claim 8, the evaluation step includes a step of measuring a film thickness of the structure, and the measured film thickness. 3. The method of manufacturing a semiconductor device according to claim 2, further comprising the step of selecting a database corresponding to, and the step of using the selected database to obtain the width or sectional shape of the structure from the polarization state. Or according to claim 9, the illuminating step includes a step of interrupting the incident light beam, and the measuring step is formed corresponding to the interrupted incident light beam. The polarization state of the emitted light beam intermittent, by the method of manufacturing a semiconductor device according to claim 1, wherein the measuring the irradiation state and a blocking state,
Alternatively, as described in claim 10, in a workpiece size measuring method for measuring a size of a structure formed on a substrate having a flat surface, the structure has a predetermined angle with respect to the substrate surface. An illuminating step of injecting a polarized incident light beam; a measuring step of measuring a polarization state of an outgoing light beam emitted from the structure on which the incident light beam is incident; A dimension in a direction is evaluated by a measuring method including an evaluation step for obtaining from the polarization state, or as described in claim 11, the evaluation step is based on the obtained polarization state, 11. A method according to claim 10, characterized in that the relationship between the condition and the dimensions of the structure is implemented by referring to a database containing the dimensions of the various structures. As described in claim 12, the polarization state is expressed by rotation of a plane of polarization of an outgoing light beam after passing through the structure and flatness, and the measuring step is performed by an ellipsometer. 11. The measuring method according to claim 10, or as described in claim 13, wherein the illuminating step is performed while changing an incident angle of the polarized incident light beam, and the evaluating step is performed. By the combination of the polarization state and the incident angle, the side wall surface that further defines the structure,
11. The method according to claim 10, further comprising the step of estimating an angle formed with respect to the plane of the substrate, or as described in claim 14, the measuring step includes: 11. The measuring method according to claim 10, characterized in that the reflected light of the incident light beam is used, or as described in claim 15, the measuring step is performed as the emitted light beam before being diffracted from the structure. The method according to claim 10, wherein the diffracted light of the incident light beam is used, or the measuring step is performed by using the structure as the outgoing light beam. 11. The measuring method according to claim 10, characterized in that it is carried out using scattered light of the incident light beam scattered by Measuring the film thickness of the structure, selecting a database corresponding to the measured film thickness, using the selected database, the width or line-and-space pattern of the structure from the polarization state 12. The measuring method according to claim 11, further comprising the step of obtaining a cross-sectional shape of
As described in 8, the illuminating step includes a step of interrupting the incident light beam, and the measuring step determines a polarization state of the intermittent exit light beam formed corresponding to the intermittent incident light beam. A semiconductor device including a structure formed on a substrate having a flat surface by the measuring method according to claim 10 or by measuring the irradiation state and the blocking state. In the quality control method according to claim 1, an illumination step of injecting a polarized incident light beam into the structure at a predetermined angle with respect to the surface of the substrate; an outgoing light beam emitted from the structure into which the incident light beam is incident. And a measuring step of measuring a polarization state of the structure; and an evaluation step of obtaining a dimension of the structure in a direction parallel to the surface of the substrate from the polarization state. It is solved by law.

FIG. 1 illustrates the principle of the present invention. Referring to FIG. 1, in the present invention, the width W in the lateral direction of the pattern 11 is obtained by using ellipsometry and detecting the polarization state of the light beam incident on the pattern 11 formed on the substrate 10. .

The incident light beam is incident on the pattern 11 at an incident angle θ, and the oscillating electric field components E _p and E _s orthogonal to each other form linearly polarized light having a polarization angle φ. Such an incident light beam
The pattern 11 passes from one side to the other side, but at that time, each vibration component has a different refractive index and reflectance at the boundary with the substrate 10 or the boundary with air, and occurs when passing through the inside of the pattern. Due to the phase delay, the vibration components E _p ′ and E _s ′ after passing through the pattern form elliptically polarized light.

FIG. 2 is an enlarged view showing a part of FIG. 1 in detail. Referring to FIG. 2, the pattern 11 is the pattern element 1
1a and 11b, light rays a to c forming an incident light beam in a linearly polarized state are incident on the pattern element 11a,
After being refracted and reflected, it becomes elliptically polarized light and exits.

For example, the pattern of FIG.
When a monochromatic linearly polarized light beam is incident at an angle of Θ, the difference in reflectance between the s-polarized light component and the p-polarized light component at the boundary between the surface and the base and the phase difference that occurs when passing through the pattern , The reflected light becomes elliptically polarized light. In such a case, the complex reflection coefficient ratio R _p / R _s determined by the substrate refractive index, the pattern refractive index, the pattern shape and the incident angle can be obtained by an ellipsometer.
The relationship between _p / R _s and Ψ and Δ obtained by the ellipsometer is given by the following equation.

[0016]

[Equation 1]

However, the parameter Ψ is given by tan Ψ = ρ _p / ρ _s as explained in FIG. 23, and the parameter Δ represents the phase difference and is an amount measured by ellipsometry. Further, the parameters Ψ and Δ are connected by the correspondence relationship with the polarization angle φ and the elliptic flatness described above. Further, in equation (1), the summation Σ is done for all rays that pass through the pattern 11.

In other words, the refractive index (dielectric constant) of the substrate 10
And the refractive index (dielectric constant) of the pattern 11 are defined, and the incident angle of the incident light beam is defined, the elliptical polarization state of the outgoing light beam composed of the components E _p 'and E _s ' is obtained by ellipsometry. As a result, the parameters Ψ and Δ are obtained.

As can be seen from FIG. 2, as the outgoing light beam passes through the pattern 11, each pattern element 11a, 1a
The information about the dimension 1b, particularly the dimension W in the lateral direction, is incorporated as a change in phase, and therefore the dimension W can be estimated based on Ψ, Δ obtained from the polarization state of the emitted light beam. Is. In one embodiment of the present invention, the parameters Ψ, Δ are obtained in advance as a database for various patterns whose shapes and dimensions are grasped by, for example, SEM, and the actually obtained parameters Ψ, Δ are obtained.
Is compared with Ψ and Δ in the database, the pattern dimension W is obtained.

The preferred embodiments of the present invention will be described below.
This will be described with reference to the drawings.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 3 shows the structure of a dimension measuring apparatus for a pattern formed on a substrate using ellipsometry according to the first embodiment of the present invention.

Referring to FIG. 3, the patterned substrate 22 is placed on the stage 21, and is irradiated with a light beam having a wavelength of 6328Å from the He—Ne laser 23. That is, the output light of the laser 23 has its phase adjusted by the quarter-wave plate 24, and further converted by the polarizer 25 into linearly polarized light having a predetermined polarization angle, for example, a polarization angle of 45 °, and the substrate on the stage 21. 22 is illuminated with a predetermined angle of incidence, for example 70 °. Alternatively, the laser 23
The output light of 1 may be first passed through the polarizer 25, and then the phase thereof may be adjusted by the 1/4 wavelength plate 24. Also, typically, the light beam is 50-150 on the pattern.
It has a beam diameter of μm.

The light beam that has passed through the pattern on the substrate 22 and is further reflected has an elliptically polarized state, is converted into linearly polarized light by the rotating analyzer 26, and then enters the photocell 27 and is detected. . At that time, the incident light is detected by the photocell while rotating the rotary analyzer 26.

The photocell 27 forms an output signal corresponding to the detected intensity of the incident light and sends it to the processing device 30 via the amplifier 28 and the A / D converter 29 in the form of a digital signal. The processing device 30 obtains the polarization state of the light beam incident on the photocell 27 from the supplied digital signal, and outputs the parameters Ψ and Δ from this.

FIGS. 4A and 4B are a perspective view and a sectional view, respectively, showing an example of the resist pattern 22a formed on the substrate 22. As shown in FIG. These patterns include
Although an appropriate pattern on the substrate may be used, if a pattern suitable for measurement is not available, a line and space pattern for measurement may be formed at an appropriate position on the substrate such as a scribe line.

Referring to FIGS. 4A and 4B, the substrate 2
2 is a polysilicon film 22 ₂ deposited on the Si substrate 22 ₁ to a thickness of 153 nm.
Is formed on the polysilicon film 22 ₂ . As the resist pattern 22a, for example, an electron beam exposure CMS resist (trade name) manufactured by Toyo Soda Co., Ltd. can be used.

In the resist pattern 22a, a plurality of pattern elements 22b are parallel to each other and have a predetermined pattern pitch, for example, 0.
It is a line-and-space pattern repeated at a pitch of 3 μm, and is formed in a range of, for example, 1 mm × 1 mm on the substrate 22. In addition, each pattern element 22b is formed by patterning a resist layer having a thickness of 150 nm.
It is formed to a height of 50 nm. In such a resist pattern, even if the pattern pitch is accurately determined, the width of each pattern element 22b may change with respect to a predetermined value, which results in a line and space pattern formed on the substrate 22. It causes the width to go wrong.
For example, such a line and space pattern is MO
When forming the gate electrode of the S-transistor, this deviation leads to a change in the threshold voltage of the formed transistor.

FIG. 5 shows the experimental results of the relationship between Ψ and Δ obtained when the apparatus of FIG. 3 is applied to such a line-and-space pattern for various pattern widths W. However, in the experiment, the substrate is
Using the substrate 22 shown in (A) and (B), the width W of the pattern element 22b was changed from 100 nm to 190 nm to obtain Ψ and Δ. At that time, the value of the width W uses the value confirmed by the observation with the SEM. The values of Ψ and Δ are
The measurement was performed 5 times for each pattern width W.

As can be seen from FIG. 5, one (Ψ, Δ)
One width W corresponds to the combination of, and therefore, the width W of the line-and-space pattern formed on the substrate is determined by measuring Ψ and Δ for a given substrate and checking the relationship with the relationship of FIG. Desired. The relationship of FIG.
The processing device 30 stores the data in the database, and the processing device 30 performs such collation with the database to obtain the value of the width W.

FIG. 6 is a plan view of the apparatus shown in FIG. 3. Referring to FIG. 6, a positioning member 21A that abuts an orientation flat 22A of a wafer forming a substrate 22 is formed on a stage 21. Positioning pins 21B that abut against the side surface of the substrate 22 are formed. At this time, the line and space pattern 22a is formed on the substrate 22.
However, the substrate 22 is formed so as to be orthogonal to the optical path of the light beam from the light source 23 in a state where the substrate 22 abuts on the positioning members 21A and 21B. Line and space pattern 22a
Is formed in such an azimuth, the light beam causes the line-and-space pattern 2 to move in its phase.
Efficiently capture the information of 2a. In other words, in the ellipsometer of FIG. 3, the substrate 22 is installed on the stage 21 in the orientation shown in FIG. 6 to maximize the sensitivity to the width W of the line and space pattern 22a.

The orientation of the wafer may be adjusted, for example, by forming a notch on the wafer and engaging the notch with the positioning pin. Further, the orientation of the wafer may be adjusted by using an orientation detection mechanism using LEDs. Further, in the structure of FIG. 6, the wafer 22 is arranged so that the pattern elements forming the pattern 22a are orthogonal to the optical path of the light beam. You may arrange so that it may extend in parallel with the optical path of. In this case, the pattern 22a
Information of the background of is required. [Second Embodiment] FIG. 7 shows a second embodiment of the present invention. However, in FIG. 7, the parts described above are denoted by the same reference numerals, and description thereof will be omitted.

Referring to FIG. 7, since the pattern elements 22b are formed relatively sparsely on the substrate 22 in this embodiment, a substantial part of the light beam emitted from the light source 23 is the information of the substrate 22 itself. , For example, pick up the thickness information.
As a result, the pattern width W obtained from Ψ and Δ obtained
However, there is a possibility that it will deviate from the actual one.

In the present embodiment, the fact that the light beam emitted from the light source 23 composed of a He--Ne laser is coherent light is used, and the Bragg diffraction is performed by the line and space pattern 22a formed on the substrate 22 at a predetermined pitch. The pattern width W is obtained by using the diffracted light of higher order.
In this case, a photocell is provided at the diffraction position of each diffracted light, and Ψ and Δ are obtained from the polarization state thereof. Further, similarly to the previous embodiment, the pattern width W is obtained by referring to the database formed for each diffracted light. further,
The most probable value of the pattern width W is obtained by averaging or weighted averaging the values of W obtained from the individual diffracted lights.

FIG. 8 shows the polarization state parameters Ψ and Δ obtained for a resist line and space pattern of 5 μm pitch formed on a Si substrate with a thickness of 150 nm using the configuration shown in FIG. The case where reflected light is used for detection and the case where first-order diffracted light is used are shown. However, in FIG. 7, the incident angle of the incident light is set to 77 °, and as a result, the reflected light is generated in the direction of the reflection angle of 77 °. On the other hand, in the example of FIG.
Occurs in the direction of the diffraction angle of °.

As can be seen from FIG. 8, the width W of the line and space pattern on the Si substrate is 110 to 210 nm.
By changing in the range of
The value of ψ changes, but in the reflected light, the value of Ψ is 5 to 10 °, Δ
Of the first-order diffracted light, the value of Ψ is 60 ° to 85 °, and the value of Δ is −100 to
It can be seen that it changes in the range of −110 °. As can be seen from FIG. 8, when the 1st-order diffracted light is used, the change in the phase difference Δ is small, and the width W roughly corresponds to the value of Ψ. [Third Embodiment] FIG. 9 schematically shows a semiconductor device manufacturing line according to a third embodiment of the present invention, which incorporates the workpiece size measuring apparatus of FIG.

Referring to FIG. 9, the semiconductor device manufacturing line includes a wafer process 101 including an exposure process and an etching process, a process control unit 102 for controlling the wafer process 101, and the wafer process 1
Ellipsometry part 1 for inspecting wafers processed at 01
03 is provided. The ellipsometry unit 103 includes the ellipsometer having the configuration shown in FIG.
The wafer to be processed in 1 is irradiated with the polarized light beam, and the measured values of the parameters Ψ and Δ are obtained from the obtained polarization state of the reflected light beam.

The measured parameters Ψ, Δ of the reflected light beam obtained by the ellipsometry section 103 are supplied to the process control section 102, which in turn supplies the parameters Ψ, Δ supplied from the initial condition setting section 104. Based on the result of comparison with the preset value of Δ, the exposure conditions such as the exposure dose and the exposure time or the etching conditions such as the RF power are changed in the wafer process 101.

The initial condition setting unit 104 sets shape parameters such as the film thickness and pattern width of the line and space pattern formed in the wafer process 101, or the film thickness of a layer formed under the line and space pattern. Data is supplied, and the desired values of Δ and Ψ are calculated with reference to the database 104a that holds the relationship between Δ and Ψ as shown in FIG. 5 based on the shape parameters. As described above, the process control unit 102
The combination of the parameters Δ and Ψ supplied from the initial condition setting unit 104 is compared with the combination of the parameters Δ and Ψ obtained by the ellipsometer 103, and the wafer process 101 is controlled so that the difference is minimized.

Further, in the apparatus shown in FIG. 9, a wafer whose pattern dimension is confirmed by SEM or the like is used as an ellipsometry section 10.
By checking in step 3, the set of parameters Δ and Ψ that form the database 104a is obtained. In the apparatus of FIG. 9, the theoretical calculation unit 104b calculates desired theoretical values of Δ and Ψ from given initial parameters,
This may be supplied to the process control unit via the initial condition setting unit 104.

The calculation of the theoretical value is performed as follows. The angle of incidence Θ in the environment where the refractive index is n ₁ is applied to a sample including a line-and-space pattern with a refractive index n ₂ which is periodically formed on a substrate having a refractive index n _{3.
When the} light beam is incident at ₁ , the light beam repeats refraction and reflection in the sample according to Snell's law as shown in FIG. 10, and is emitted from the sample at the same angle as the incident angle Θ ₁ . Therefore, for one cycle of the sample, the incident light is divided into m incident light beams I ₍₁₎ , I _{(2 )} ,. . . It is decomposed into I _(m) , and the optical path of each incident ray is obtained according to Snell's law. At that time, the incident light is decomposed into a p-polarized component and an s-polarized component,
The effect of attenuation due to reflection and refraction is obtained for each component. More specifically, when an incident ray is reflected, the intensity I ₀ of the p-polarized component and the s-polarized component of the incident ray and the Fresnel amplitude reflectances r _p and r _s for each reflection
Multiply by to obtain the attenuation of light amplitude due to reflection. Further, when the incident light beam is refracted, the intensity I ₀ of the p-polarized component and the s-polarized component of the incident light beam is multiplied by Fresnel's amplitude refractive index t _p , t _s , respectively, to obtain the optical amplitude associated with the refraction. Find the decay of. Further, when the light beam passes through an opaque medium, the effect of attenuation can be _obtained by multiplying by the amplitude transmittance t _k . To this, a phase delay δ associated with the optical path length is further added to obtain final intensities I _p (n) ′ and I _s (n) ′ of each polarization component. However, the amplitude reflectances r _p and r _s , the amplitude refractive indices t _p and t _s , the amplitude transmittance t _k, and the phase delay term δ are as follows: r _p = tan (Θ ₁ −Θ ₂ ) / tan (Θ ₁ + Θ _{2 ) r s = -sin (Θ 1} -Θ 2) / sin (Θ 1 + Θ 2) t p = 2sinΘ 2 cosΘ 1 / sin (Θ 1 + Θ 2)
It is given by _{cos (Θ 1 -Θ 2) t} s = 2sinΘ 2 cosΘ 1 / sin (Θ 1 + Θ 2) t k = exp (-2πkd / λ) δ = exp (-i2πnd / λ). Where λ is the wavelength of the incident light beam and d is the optical path length in the sample.

For example, in the example of FIG. 11, the incident light rays (1) to (3) having the intensity I ₀ are reflected and refracted by the line and space pattern, and then the polarization component I represented by the following equation.
_p (1) 'to _Ip (3)', _Is (1) 'to I
_Emitted as emitted light having _s (3) '. I _p (1) ′ = t _p1 t _p2 r _p3 t _p4 t _p5 × exp (−2πk ₂ d ₁ / λ) exp (−i 2πn ₂ d ₁ / λ) · I ₀ I _s (1) ′ = t _s1 t _s2 r _s3 t _s4 t _s5 × exp (−2πk ₂ d ₁ / λ) exp (−i 2πn ₂ d ₁ / λ) · I ₀ I _p (2) ′ = t _p1 r _p2 t _p3 × exp (−2πk) _{2 d 2 / λ) exp (} -i2πn 2 d 2 / λ) · I 0 I s (2) '= t s1 r rs2 t s3 × exp (-2πk 2 d 2 / λ) exp (-i2πn 2 d 2 / Λ) · I ₀ I _p (3) ′ = r _p1 · I _o I _s (3) ′ = r _s1 · I _o where n ₂ and k ₂ are the refractive index and the absorption coefficient in the line and pattern, respectively. , And d _1, d ₂
Represents the optical path lengths of rays (1) and (2) in the line and space. The subscripts 1 to 5 are
The order of the reflection points and refraction points of the light rays counted from the incident side is shown. See FIG.

In this way, the intensities I (1) 'to I of each light beam are
When (n) ′ is obtained, the complex reflection coefficient ratio (ρ = R _p /
Rs) is ρ = R _p / R _s = ΣI _p (n) ′ / ΣI _s (n) ′ = t
an Ψ exp (iΔ), from which the parameters Ψ, Δ are determined by Ψ = tan ⁻¹ (| ρ |) Δ = arg (ρ).

In the configuration of FIG. 9, the calculation unit 104
b is the parameter Ψ, Δ obtained by performing the above calculation.
Are supplied to the process control unit via the initial condition setting unit 104. FIG. 12 shows the calculation unit 104.
It is a flow chart which shows an outline of operation which b performs.

Referring to FIG. 12, first, in step 1, the film thickness of the pattern, the refractive index, the absorptivity, the film thickness of the base,
Structural conditions such as the refractive index, the absorptance, and the pattern pitch are input, and in step 2, the incident light beam is
It is decomposed into individual rays according to Snell's law, and the optical path is obtained for each individual ray (i = 1 to n). Furthermore, in step 3, for each ray i, the intensities Ip (i) ′, Is (i) ′ of the polarization components p and s are determined.

Next, in step 4, the integrated intensities ΣIp (n) ′ and ΣIs (n) ′ of the polarization components p and s are obtained.
Is calculated, and the complex reflection coefficient ratio ρ is calculated in step 5 from the calculated integrated intensity. Further, in step 6, the parameters Ψ and Δ are obtained from the complex reflection coefficient ratio ρ, and in step 7, the pattern width W is obtained by referring to the database.

In FIG. 13, the underlying polysilicon layer 22 ₂ is etched by the RIE method using the resist pattern 22a shown in the embodiment of FIGS. 4A and 4B as a mask, and the resist pattern 22a is removed. 4 shows the relationship between the parameters Ψ and Δ obtained by the measuring device of FIG. 3 in the state. However, in this case, the incident angle is set to 55 °,
Under layer 22 ₁ of the polysilicon layer 22 ₂ is in the SiO ₂ instead Si. Database 1 for such relationships
By accumulating in 04a, the pattern width can be obtained for various patterns.

Further, FIG. 14 shows that in the embodiment of FIGS. 4A and 4B, the mask pattern pitch is 150 nm.
In this case, the measurement apparatus of FIG. 3 is used to monitor changes in the parameters Ψ and Δ while changing the etching time. However, the illustrated example corresponds to the case where excessive etching of 10% and 30% is further performed with respect to the etching end point. The polarization state is the resist pattern 2
The measurement is performed with 2a removed. It is generally known from SEM observation that 30% over-etching causes side etching of about 20 nm. However, the results shown in FIG. It shows that the side etching can be detected. In other words, it has been shown that the method for measuring a workpiece size using ellipsometry according to the present invention can detect a deviation in a machining dimension with an accuracy of 10 nm or less. [Fourth Embodiment] FIG. 15 shows the principle of a fourth embodiment of the present invention.

Referring to FIG. 15, in the present embodiment, instead of the reflected light or the diffracted light of the incident light beam, the polarization state of the scattered light generated by the scattering of the incident light beam by the pattern 22b on the substrate 22. Then, the parameters Ψ and Δ are obtained.

FIG. 16 shows a configuration for performing the scattered light measurement shown in FIG. However, in FIG. 16, the same reference numerals are given to the parts described previously and the description thereof will be omitted.
In the measuring device of FIG. 16, the coherent light emitted from the light source 23 passes through the 1 / 4λ phase difference plate 23 and the polarizer 25 and then passes through the beam chopper 25A to form the pattern 22.
It is incident on the wafer 22 on which a has been formed. The beam chopper 25a is composed of a rotating disk having a cut formed in a part thereof, and controls on / off of the coherent light incident on the wafer 22 from the light source 23.

Further, in the configuration of FIG. 16, the lens 31 and the beam splitter 32 cooperating therewith are formed so as to avoid the reflected light or the diffracted light formed by the pattern 22a on the wafer 22, and the beam splitter 32 is The scattered light generated from the pattern 22a and focused by the lens 31 is decomposed into p component and s component and supplied to the detectors 27A and 27B, respectively. At that time, a rotation control signal is supplied as a synchronization signal SYNC from the beam chopper 25A to the detectors 27A and 27B.
The detectors 27A and 27B respectively have the synchronization signal S
Intensities Ip and Is of the scattered light corresponding to one cycle of YNC
Is measured. According to this structure, the intensity of the scattered light in the state where the light beam is irradiated onto the wafer 22 is compared with the intensity of the scattered light in the state where the light beam is blocked, so that the intensity of the weak scattered light is increased. Ip and Is can be accurately measured.

The intensity I of the scattered light thus obtained
p and Is are processed in the processing device 30, and the intensity I
The reflection coefficient ratio tan Ψ is obtained by executing the division Ip / Is on p and Is, and the polarization parameter Ψ is obtained from this value. FIG. 17 shows the reflection coefficient ratio tan Ψ and the pattern width W in the configuration using the scattered light of FIG.
Shows the relationship. However, in the example of FIG. 17, the thickness is 100 n.
Using a substrate in which a 180 nm-thick polysilicon line and space pattern is formed at a pitch of 300 nm on a SiO ₂ film of m, the individual pattern width W is 120 to 1
It is changed in the range of 80 nm. Also, the measurement is shown in FIG.
In this device, linearly polarized light having a polarization angle of 45 ° was used as incident light.

As can be seen from FIG. 17, the pattern width dependence of the reflection coefficient ratio tan Ψ is observed by using scattered light. That is, by obtaining the reflection coefficient ratio tan Ψ from the scattered light, the pattern width W of the line and space pattern can be obtained. [Fifth Embodiment] By the way, in the apparatus shown in FIG. 3, FIG. 7, FIG. 9 or FIG. 15, the incident angle of the light beam emitted from the light source 23 is not limited to 70.degree. You can also In addition, by measuring Δ and Ψ by changing the incident angle variously, and referring to a database that includes the incident angle as a parameter in addition to Ψ and Δ based on this, not only the width of the pattern but also the pattern It is also possible to determine the tilt angle of the side wall with respect to the substrate surface.

FIG. 18 shows a wafer in which a polysilicon film having a thickness of 182 nm is formed on a SiO ₂ film having a thickness of 102 nm, and a resist line and space pattern having a thickness of 150 nm is further formed thereon at a pitch of 500 nm. The relationship between the polarization parameters Ψ and Δ obtained from the reflected light is shown.

Referring to FIG. 18, each value of the pattern width W (W = 175 nm, W =) in the state where the resist pattern is formed and before the polysilicon film is etched.
For 150 nm and W = 125 nm), the parameters Ψ and Δ are obtained as shown in the upper left curve in FIG. Of these, white circles at each point corresponding to the value of W,
We are conducting three-point experiments indicated by white triangles and white squares,
At each point, the convergence of the obtained data is very good. However, in the above data, the incident angle of the incident light beam is set to 70 °.

Next, the polysilicon film is etched using the resist line and space pattern as a mask, and the polarization parameters Ψ and Δ obtained for the obtained structure are shown by black circles, black triangles and black squares. However, the black triangle indicates the case where the overetching amount is 0% as shown in the cross-sectional SEM photograph of FIG. 19A, and the black square indicates the overetching amount of 30% as shown in the cross-sectional SEM photograph of FIG. 19B. If the case is further black circle,
As shown in the cross-sectional SEM photograph of 9C, the case where the amount of overetching is 80% is shown.

As can be seen from FIG. 18, the curve when the overetching amount is 0%, the curve when the overetching amount is 30%, and the curve when the overetching amount is 80% are the pattern. Width W
Is 175 nm, they are different from each other except that they partially overlap each other. This is because the difference in cross-sectional shape of the polysilicon patterns shown in FIGS. 19A to 19C is detected from the combination of the polarization parameters Ψ and Δ. It shows that you can do it. That is, when the structural parameters such as the pattern width W and the film thickness or the refractive index are known in advance by some method, the cross-sectional shape of the pattern can be estimated from the combination of the polarization parameters Ψ and Δ obtained by ellipsometry. become. [Sixth Embodiment] FIG. 20 shows the relationship between the polarization parameters Ψ and Δ when the thickness of the polysilicon film is changed in the same line-and-space pattern formed on the SiO ₂ film. However, the curve indicated by the black circle in FIG.
The case where a polysilicon line and space pattern having a thickness of 178 nm is formed on a SiO ₂ film having a thickness of 100 nm, and the curve indicated by an open circle shows the case where the thickness of the polysilicon line and space pattern is 163 nm. It is a thing. In any case, the pitch of the line and space pattern is changed to 300 nm, and the pattern width W is changed in the range of 110 nm to 200 nm.

As can be seen from FIG. 20, the parameters Ψ,
The curve defined by Δ is different when the thickness of the polysilicon pattern is 178 nm and when it is 163 nm. Therefore, by first measuring the thickness of the pattern, a specific curve is selected, It becomes possible to obtain Ψ and Δ for the selected curve.

FIG. 21 is a flow chart of a pattern dimension measuring method according to the sixth embodiment of the present invention, which includes such a film thickness measuring step. Referring to FIG. 21, first, at step 11, the film thickness of the line and space pattern is measured, and then at step 12, a curve or characteristic curve corresponding to the measured film thickness is selected. Further, in step 13, measurement by ellipsometry is performed, and the pattern width W or its cross-sectional shape is obtained using the obtained parameters Ψ and Δ and the selected characteristic curve.

Furthermore, the present invention is not limited to the above embodiments, and various modifications and changes are made within the scope of the present invention.
Changes are possible.

[0060]

According to the features of the present invention as set forth in claims 1, 10 and 19, the dimensions of a pattern formed on a wafer are measured at high speed in a non-contact and non-destructive manner in a semiconductor device manufacturing process. It becomes possible to feed back the measurement result to the manufacturing process.

According to the features of the present invention as set forth in claims 2 and 11, by referring to a database constructed based on experiments based on the obtained elliptic polarization parameters,
It becomes possible to easily obtain the pattern dimension without performing complicated theoretical calculation. According to the features of the present invention set forth in claims 3 and 12, the polarization state can be easily obtained by using the ellipsometer.

According to the features of the present invention described in claims 4 and 13, by further changing the incident angle of the incident light beam for measurement, not only the pattern size but also the pattern side wall is formed with respect to the substrate surface. It is also possible to find the angle. According to the features of the present invention as set forth in claims 5 and 14, by using strong reflected light reflected from the structure,
It is possible to stably obtain the polarization state of the reflected light beam with good reproducibility.

According to the features of the present invention as set forth in claims 6 and 15, by using the diffracted light diffracted from the structure, even if the pattern is relatively rough, the influence of the underlayer on the measurement result is affected. It becomes possible to minimize it. According to the features of the present invention described in claims 7 and 16, by using the scattered light scattered from the structure, the influence of the underlayer on the measurement result is minimized even in the case of a relatively rough pattern. It will be possible.

According to the features of the present invention described in claims 8 and 17, it is possible to obtain the width or cross-sectional shape of the structure in a non-destructive and non-contact manner. According to the features of the present invention as set forth in claims 9 and 18, when the incident light beam is interrupted and the polarization state is measured for each of the irradiation state and the blocking state, weak emission light such as scattered light is used. Also, high-precision measurement is possible.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an enlarged view showing a main part of FIG. 1;

FIG. 3 is a diagram showing a configuration according to a first exemplary embodiment of the present invention.

4 is a diagram showing a line-and-space pattern to which the device of FIG. 3 is applied.

5 is a diagram illustrating an example of a database used in the device of FIG.

FIG. 6 is a diagram for explaining the positioning of the wafer in the apparatus of FIG.

FIG. 7 is a diagram showing a second embodiment of the present invention.

8 is a diagram showing an example in which reflected light and first-order diffracted light are used in the configuration of FIG.

9 is a diagram showing a third embodiment of the present invention in which the device of FIG. 3 is applied to control of a semiconductor device manufacturing process.

FIG. 10 is a diagram (part 1) showing the principle of calculating parameters Ψ and Δ in the apparatus of FIG. 9;

FIG. 11 is a diagram (No. 2) showing the principle when the parameters Ψ and Δ are calculated in the apparatus of FIG. 9;

12 is a flowchart showing a process in the apparatus of FIG.

13 is a diagram showing the relationship between the pattern width and the parameters Ψ and Δ when the present invention is applied to a line-and-space pattern formed by etching in the apparatus of FIG.

14 is a diagram showing a relationship between parameters Ψ and Δ with the progress of etching in the apparatus of FIG.

FIG. 15 is a diagram illustrating a fourth embodiment of the present invention.

16 is a diagram showing a specific configuration of the apparatus of FIG.

17 is a diagram showing an example of a characteristic curve obtained by the device of FIG.

FIG. 18 is a diagram illustrating a change in Δ-Ψ relationship depending on the cross-sectional shape of the pattern according to the fifth embodiment of the present invention.

19 (A) to (C) are diagrams showing various pattern cross-sectional shapes corresponding to FIG. 18.

FIG. 20 is a diagram illustrating a change in Δ-Ψ relationship depending on the film thickness of a pattern according to the sixth embodiment of the present invention.

FIG. 21 is a flowchart showing a pattern measurement process according to the sixth embodiment of the present invention.

FIG. 22 is a diagram showing a configuration of a conventional ellipsometer.

FIG. 23 is a diagram showing elliptically polarized light measured by ellipsometry.

[Explanation of symbols]

 1, 23 Light source 2, 25 Polarizer 3 Sample 4 Rotation analyzer 4a, 24 1/4 wave plate 4b Rotation 1/4 wave plate 5, 27, 27A, 27B Detector 10, 22 Substrate 11 Pattern 11a, 11b Pattern element 21 stage 21A positioning structure 21B positioning pin 22a pattern 22b pattern element 22A orientation flat 25A beam chopper 26 rotation analyzer 28 amplifier 29 A / D converter 30 processing device 31 lens 32 beam splitter 101 wafer process unit 102 process control unit 103 ellipsometry Part 104 initial condition setting part 104a database 104b theoretical calculation part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01L 21/3065 H01L 21/302 B

Claims (19)

[Claims] 1. A method for manufacturing a semiconductor device, which includes a step of measuring a dimension of a structure formed on a substrate having a flat surface, wherein the structure is polarized at a predetermined angle with respect to the substrate surface. Illuminating the incident light beam, and measuring the polarization state of the outgoing light beam emitted from the structure on which the incident light beam is incident; measuring the polarization state of the structure in a direction parallel to the substrate surface. And an evaluation step of obtaining the dimension from the polarization state; based on the obtained dimension, the manufacturing parameter of the semiconductor device is adjusted. 2. The evaluation step, based on the determined polarization state, a relationship between the polarization state and the size of the structure,
The method of manufacturing a semiconductor device according to claim 1, wherein the method is executed by referring to a database including dimensions of various structures. 3. The polarization state is represented by a rotation of a plane of polarization of an output light beam after passing through the structure and an aspect ratio, and the measuring step is performed by an ellipsometer. Item 2. A method of manufacturing a semiconductor device according to item 1. 4. The illuminating step is performed while changing an incident angle of the polarized incident light beam, and the evaluating step further determines the structure by a combination of the obtained polarization state and the incident angle. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising the step of estimating an angle formed by the side wall surface defining the substrate surface. 5. The method of manufacturing a semiconductor device according to claim 1, wherein in the measuring step, reflected light of the incident light beam is used as the outgoing light beam. 6. The manufacturing of a semiconductor device according to claim 1, wherein the measuring step is performed by using, as the outgoing light beam, diffracted light of the incident light beam diffracted from the structure. Method. 7. The manufacturing of a semiconductor device according to claim 1, wherein the measuring step is performed by using, as the outgoing light beam, scattered light of the incident light beam scattered by the structure. Method. 8. The evaluation step comprises the steps of measuring a film thickness of the structure, selecting a database corresponding to the measured film thickness, and using the selected database, The method of manufacturing a semiconductor device according to claim 2, further comprising a step of obtaining a width or a sectional shape of the structure. 9. The illuminating step includes a step of interrupting the incident light beam, and the measuring step irradiates a polarization state of the interrupted emission light beam formed corresponding to the interrupted incident light beam. The method for manufacturing a semiconductor device according to claim 1, wherein the state and the cutoff state are measured. 10. A workpiece size measuring method for measuring a size of a structure formed on a substrate having a flat surface, wherein an incident light polarized to the structure at a predetermined angle with respect to the substrate surface. An illuminating step of injecting a beam; a measuring step of measuring a polarization state of an outgoing light beam emitted from the structure on which the incident light beam enters; a dimension of the structure in a direction parallel to the substrate surface; And an evaluation step of obtaining from the polarization state. 11. The evaluation step is carried out by referring to a database containing relationships between polarization states and structure dimensions for various structure dimensions based on the determined polarization states. Claim 1 characterized by the above.
The measuring method described in 0. 12. The polarization state is represented by a rotation of a plane of polarization of an outgoing light beam after passing through the structure and an aspect ratio, and the measuring step is performed by an ellipsometer. Item 10. The measuring method according to Item 10. 13. The illuminating step is performed while changing an incident angle of the polarized incident light beam, and the evaluating step further determines the structure by a combination of the obtained polarization state and the incident angle. 11. The measuring method according to claim 10, further comprising the step of estimating an angle formed by the side wall surface that defines with respect to the substrate plane. 14. The measuring method according to claim 10, wherein in the measuring step, reflected light of the incident light beam is used as the outgoing light beam. 15. The measuring method according to claim 10, wherein the measuring step is performed by using, as the outgoing light beam, diffracted light of the incident light beam diffracted from the structure. 16. The measuring method according to claim 10, wherein the measuring step is performed by using, as the outgoing light beam, scattered light of the incident light beam scattered by the structure. 17. The evaluation step comprises: measuring a film thickness of the structure; selecting a database corresponding to the measured film thickness; and using the selected database, 11. The measuring method according to claim 10, further comprising a step of obtaining a width of the structure or a cross-sectional shape of the line and space pattern. 18. The illuminating step includes the step of interrupting the incident light beam, and the measuring step irradiates a polarization state of the intermittent output light beam formed corresponding to the interrupted incident light beam. The measuring method according to claim 10, wherein the state and the cutoff state are measured. 19. A quality control method for a semiconductor device including a structure formed on a substrate having a flat surface, wherein an incident light beam polarized at a predetermined angle with respect to the substrate surface is applied to the structure. An incident illumination step; a measurement step of measuring a polarization state of an outgoing light beam emitted from the structure on which the incident light beam is incident; a dimension of the structure in a direction parallel to the substrate surface, A quality control method comprising: an evaluation step obtained from a polarization state.