JP3857217B2 - Film thickness measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a film thickness measuring device that measures the thickness of a film on an object.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a film thickness measuring apparatus that irradiates a semiconductor substrate with light and measures the thickness of a film formed on the substrate is provided with a plurality of measurement units. For example, Patent Document 1 discloses a technique in which an ellipsometer and an interferometer are provided in the same apparatus, and the film thickness on the substrate is specified from the refractive index measured by the ellipsometer and the interference waveform obtained by the interferometer. In such a film thickness measurement device, the mounting position of each measurement unit on the device is adjusted accurately, so that the irradiation position on the substrate of the light from each measurement unit is matched, and the measurement by each measurement unit is performed on the substrate. Of the same position.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 61-182507
[Problems to be solved by the invention]
By the way, in a manufacturing site where a film thickness measuring device is used (for example, a semiconductor parts manufacturing factory), when work involving removal of each measuring unit is performed due to maintenance of the film thickness measuring device or parts replacement due to failure, etc. In general, since the downtime of the apparatus greatly affects the manufacturing cost, it is required to quickly and easily adjust the position after reattaching each measurement unit. However, the adjustment of the mounting position is usually difficult because it requires a high degree of adjustment, and the work takes a long time.
[0005]
The present invention has been made in view of the above problems, and aims to easily match the measurement positions (irradiation positions of light for measurement) on the substrate of each measurement section in a film thickness measurement apparatus having a plurality of measurement sections. And
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is a film thickness measuring device for measuring the thickness of a film formed on an object, and a stage for holding the object and an image of a reference object held on the stage. In addition to the first measurement unit that has an imaging unit that acquires the light and measures the thickness of the film by irradiating the object with light, the thickness of the film by irradiating the object with light separately from the first measurement unit a second measuring section for measuring, a moving mechanism for the pre-Symbol stage moves relative to the first measuring section and the second measuring unit, the first measurement unit or the second measurement unit light Based on the image obtained by the imaging unit in the irradiated state, a calculation unit for obtaining a positional deviation amount between the irradiation position of the light from the first measurement unit and the irradiation position of the light from the second measurement unit; a storage unit for storing the positional deviation amount, switching is measured between the second measuring unit and the first measurement section And a control unit that controls the moving mechanism based on the positional deviation amount when being replaced.
[0008]
Invention of Claim 2 is a film thickness measuring apparatus of Claim 1 , Comprising: When the said reference target object has the scattering part which scatters light, and the said positional offset amount is calculated | required, A plurality of images are continuously acquired by the imaging unit while the moving mechanism moves the stage.
[0009]
The invention according to claim 3, a film thickness measuring device according to claim 2, while the moving mechanism moves the stage in a first direction and a second direction, continuously by the image pickup unit A plurality of images are acquired, and a center of an irradiation region of light from the first measurement unit or the second measurement unit is obtained by the calculation unit based on the plurality of images.
[0010]
A fourth aspect of the present invention is the film thickness measuring apparatus according to any one of the first to third aspects, wherein the first measurement unit is a measurement unit of an optical interference method using white light, and the second measurement is performed. The part is an ellipsometer.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a schematic configuration of a film thickness measuring apparatus 1 according to an embodiment of the present invention. The film thickness measuring apparatus 1 includes a stage 2 on which a semiconductor substrate (hereinafter referred to as “substrate”) 9 on which a multilayer film (may be a single layer film) is formed, and a film on the substrate 9. An ellipsometer 3 that acquires information for performing polarization analysis, an optical interference unit 4 that acquires the spectral intensity of light (reflected light) from the substrate 9, a CPU that performs various arithmetic processes, a memory that stores various information, and the like The control part 5 comprised and the stage moving mechanism 21 which moves the stage 2 with respect to the ellipsometer 3 and the optical interference unit 4 are provided.
[0012]
The ellipsometer 3 emits polarized light (hereinafter referred to as “polarized light”) toward the substrate 9, and light reception that receives the reflected light from the substrate 9 and acquires the polarization state of the reflected light. Data having the unit 32 and indicating the obtained polarization state is output to the control unit 5.
[0013]
The light source unit 31 includes a semiconductor laser (LD) 312 that emits a light beam and an LD drive control unit 311 that controls the output of the semiconductor laser 312, and the light beam from the semiconductor laser 312 enters the polarizer 313. Circularly polarized light or linearly polarized light is extracted by a polarizer 313 and a wave plate (hereinafter referred to as “λ / 4 plate”) 314. Light from the λ / 4 plate 314 is guided to the surface of the substrate 9 on the stage 2 through a lens 331 at a predetermined incident angle (for example, 70 to 80 degrees). As described above, the light source unit 31 is configured by the LD drive control unit 311, the semiconductor laser 312, the polarizer 313, and the λ / 4 plate 314, and circularly or linearly polarized light is emitted toward the substrate 9. The light source unit 31 (specifically, on the optical path between the semiconductor laser 312 and the polarizer 313) is provided with an electromagnetic shutter 315 that blocks the light beam. Light irradiation is ON / OFF controlled.
[0014]
The reflected light from the substrate 9 is guided to the rotating analyzer 321 through the lens 332, and the light transmitted while the rotating analyzer 321 rotates about an axis parallel to the optical axis is guided to the light receiving element 322. A signal indicating the intensity of the received light is output to the control unit 5 via the AD converter 34. As described above, the rotation analyzer 321 and the light receiving element 322 constitute the light receiving unit 32, and the polarization state of the reflected light is acquired by associating the output of the light receiving element 322 with the rotation angle of the rotation analyzer 321.
[0015]
The optical interference unit 4 includes a light source 41 that emits white light as illumination light, a spectroscope 42 that separates reflected light from the substrate 9, an imaging unit 44 that captures the irradiation position of the illumination light on the substrate 9, and an optical system. 45, the illumination light from the light source 41 is guided to the substrate 9 by the optical system 45, and the reflected light from the substrate 9 is guided to the spectroscope 42 and the imaging unit 44.
[0016]
Specifically, illumination light from the light source 41 is introduced into one end of the optical fiber 451, and illumination light is derived from a lens 452 provided at the other end. The derived illumination light is guided to the half mirror 456 by the lens group 450a, and the reflected illumination light is applied to the surface of the substrate 9 via the objective lens 457.
[0017]
The reflected light from the substrate 9 is guided to the half mirror 456 through the objective lens 457. The light transmitted through the half mirror 456 and the half mirror 458 is guided to the half mirror 459, and a part of the light is reflected. The reflected light is guided to the imaging unit 44 through the lens 450b and received. An image of the irradiation position of the illumination light on the substrate 9 is captured by the imaging unit 44, and the acquired image data is output to the control unit 5.
[0018]
The light transmitted through the half mirror 459 is guided to the spectroscope 42 through the lens 450c, and the spectral intensity of the reflected light is acquired. The spectral intensity data is output to the control unit 5. As described above, the optical system 45 is configured by the lens group 450a, the lenses 450b, 450c, and 452, the optical fiber 451, the half mirrors 456, 458, and 459, and the objective lens 457.
[0019]
The optical interference unit 4 further includes an autofocus detection unit (hereinafter referred to as “AF detection unit”) 46 that detects the distance between the objective lens 457 and the surface of the substrate 9. The AF detection unit 46 includes a semiconductor laser 461 that emits a light beam, and an AF detection unit 463 that detects the position of the received light using a PSD element. The light beam emitted from the semiconductor laser 461 passes through the optical system 45. The surface of the substrate 9 is irradiated. The reflected light of the light beam from the substrate 9 is guided to the lens 462 of the AF detection unit 46 via the optical system 45 and further to the AF detection unit 463.
[0020]
The AF detection unit 463 detects the distance between the objective lens 457 and the surface of the substrate 9 based on the position of the received light, and the lift mechanism 24 provided on the stage 2 detects the distance between the objective lens 457 and the surface of the substrate 9. The distance is adjusted to be constant. At this time, the distance between the objective lens 457 and the surface of the substrate 9 is a distance (that is, a focal length) at which the parallel light incident on the objective lens 457 is substantially condensed on the surface of the substrate 9.
[0021]
The stage moving mechanism 21 includes an X direction moving mechanism 22 that moves the stage 2 in the X direction in FIG. 1 and a Y direction moving mechanism 23 that moves in the Y direction. In the X-direction moving mechanism 22, a ball screw (not shown) is connected to the motor 221, and when the motor 221 rotates, the Y-direction moving mechanism 23 moves along the guide rail 222 in the X direction in FIG. The Y-direction moving mechanism 23 has the same configuration as the X-direction moving mechanism 22. When the motor 231 rotates, the stage 2 moves along the guide rail 232 in the Y direction by a ball screw (not shown).
[0022]
The control unit 5 includes a calculation unit 51 that performs various calculations and a storage unit 52 that stores various types of information. Various types of information acquired by the spectroscope 42, the imaging unit 44, and the light receiving unit 32 are sent to the calculation unit 51. And the calculation result by the calculation unit 51 is stored in the storage unit 52. The light source 41, the light source unit 31, and the stage moving mechanism 21 are also connected to the control unit 5, and the film thickness measurement on the substrate 9 is performed by the film thickness measurement device 1 by the control unit 5 controlling these configurations. .
[0023]
FIG. 2 is a diagram showing a flow of processing in which the film thickness measuring device 1 measures the thickness of the film on the substrate 9. Hereinafter, the film thickness measurement by the film thickness measuring apparatus 1 will be described with reference to FIG.
[0024]
First, illumination light is emitted from the light source 41 in the optical interference unit 4 (step S11), and the illumination light is guided to the substrate 9 by the optical system 45. Part of the reflected light from the substrate 9 is guided to the imaging unit 44, and an image indicating the irradiation position of the illumination light is acquired. The control unit 5 controls the stage moving mechanism 21 based on the acquired image, and relatively moves the irradiation position of the illumination light to a desired measurement position on the substrate 9. Then, a part of the reflected light is guided to the spectroscope 42, the spectroscopic intensity of the reflected light is acquired by the spectroscope 42 (step S12), and the spectral intensity data is output to the calculation unit 51. In the calculation unit 51, the spectral reflectance of the substrate 9 is obtained from the acquired spectral intensity. At this time, spectral intensities of other substrates with known spectral reflectances are prepared in advance, and the spectral reflectance of the substrate 9 is obtained using the spectral intensities.
[0025]
Subsequently, in the film thickness measuring device 1, the measurement is switched from the optical interference unit 4 to the ellipsometer 3. That is, the polarized light is emitted from the light source unit 31 of the ellipsometer 3 to the substrate 9 (step S13), and the positional deviation amount stored in the storage unit 52 is read (step S14). Then, the control unit 5 controls the stage moving mechanism 21 based on the positional deviation amount, and the stage 2 moves to the corresponding position (step S15).
[0026]
Here, the positional deviation amount is a relative difference between the irradiation position of the illumination light by the light interference unit 4 on the substrate 9 and the irradiation position of the polarized light by the ellipsometer 3, and a positional deviation amount described later is acquired. It is obtained in advance by processing. Thereby, the irradiation position of the polarized light on the substrate 9 moves to the irradiation position of the previous illumination light (that is, the position of the stage 2 is corrected with respect to the irradiation position of the polarized light), and the spectral intensity is increased in step S12. The polarization state of the reflected light is acquired by the light receiving unit 32 at the same position as acquired (step S16). Data indicating the polarization state is input to the calculation unit 51, and the thickness of the film at a desired position on the substrate 9 is obtained based on the acquired spectral reflectance and polarization state (step S17). For example, the computing unit 51 compares the film thickness obtained from the spectral reflectance with the film thickness obtained from the polarization state, and identifies an appropriate film thickness. In the film thickness measuring device 1, the measurement by the optical interference unit 4 may be performed after the measurement by the ellipsometer 3.
[0027]
Next, a process for acquiring the above-described positional deviation amount will be described. FIG. 3 is a diagram showing a flow of processing in which the film thickness measuring device 1 obtains the positional deviation amount. First, a reference substrate on which a predetermined pattern is formed is placed on the stage 2, and illumination light is emitted from the light source 41 of the optical interference unit 4 (step S21). The imaging unit 44 acquires an image of the illumination light irradiation position, and the calculation unit 51 relatively moves the illumination light irradiation position to a specific position on the reference substrate by the stage moving mechanism 21 based on the acquired image. (Step S22).
[0028]
For example, as shown in FIG. 4 (a), a reference substrate 9a (shown with a parallel diagonal line) provided with a step 91 extending in the Y direction (for example, a step having a step of several hundred angstroms) is used. In this case, first, the illumination light irradiation position of the optical interference unit 4 is set on the edge of the step portion 91. Then, the irradiation position of the illumination light moves relative to the reference substrate 9a by an arbitrary distance L1 in the (+ X) direction (that is, moves to the position of the arrow P1 in FIG. 4A), An image 61 illustrated in FIG. 5 is acquired by the imaging unit 44. At this time, the moving amount of the stage 2 (that is, the distance L1) is stored in the storage unit 52 as the distance in the X direction between the illumination light irradiation position P1 of the optical interference unit 4 and the stepped portion 91 (step S23). .
[0029]
Further, the distance between the objective lens 457 and the surface of the reference substrate 9a on the concave portion 92 side is detected by the AF detection unit 46 and adjusted to a constant value, and then the AF detection unit 46 is turned off. In the present embodiment, the center point in the image 61 in FIG. 5 coincides with the center of the illumination light irradiation area on the reference substrate 9a, and the illumination light irradiation position P1 in FIG. Similarly, P1 is attached.
[0030]
Subsequently, polarized light is emitted from the ellipsometer 3 (step S24). At this time, since the polarized light irradiated on the reference substrate 9a is totally reflected toward the light receiving unit 32, it cannot be confirmed from the image by the imaging unit 44. Therefore, while the stage 2 moves in the (+ X) direction, a plurality of images associated with the movement amount of the stage 2 are continuously acquired by the imaging unit 44 (step S25).
[0031]
FIG. 4B is a diagram showing a state immediately after the irradiation with the polarized light (or a state immediately before the movement of the stage 2), and the irradiation position of the polarized light is indicated by an arrow P2. In FIG. 5, the irradiation position of the polarized light is indicated by a point denoted by reference numeral P <b> 2, and the irradiation area of the polarized light is illustrated as an area 62 indicated by a two-dot chain line. When the stepped portion 91 is in the state indicated by reference numeral 91a in FIG. 5 due to the movement of the stage 2, the stepped portion 91 is located outside the irradiation region 62 of the polarized light. Since it is located within the irradiation region 62, the polarized light is scattered at the edge of the step portion 91. While the stage 2 further moves and the stepped portion 91 passes through the state shown by reference numerals 91c and 91d, scattered light in the stepped portion 91 continues to be generated. Located outside 62, the scattered light disappears.
[0032]
A plurality of images (a plurality of images including the states indicated by reference numerals 91 a to 91 e in FIG. 5) continuously acquired by the imaging unit 44 during the movement of the stage 2 are output to the calculation unit 51. In the calculation unit 51, an image corresponding to immediately after the occurrence of scattered light and an image corresponding to immediately after the disappearance are specified from the plurality of acquired images, and the average value of the movement amounts of the stage 2 associated with both images is The distance L2 in the X direction between the stepped portion 91 and the center of the irradiation region 62 of polarized light (that is, the irradiation position P2) in the state immediately before the movement (that is, the state of FIG. 4B or FIG. 5) is obtained. (Step S26). Note that the distance L2 may be, for example, the amount of movement of the stage 2 associated with the image with the largest scattered light.
[0033]
In the calculation unit 51, the illumination light irradiation position P1 and the distance L1 between the stepped portion 91 specified with respect to the X direction and the illumination light irradiation position P1 and the distance L2 between the stepped portion 91 and the polarized light irradiation position P2 A displacement amount in the X direction with respect to the irradiation position P2 of the polarized light is calculated and stored in the storage unit 52 (step S27).
[0034]
Subsequently, returning to step S21 (step S28), the illumination light is emitted, and the irradiation position of the illumination light on the reference substrate 9a is relative to the position of the stepped portion extending in the X direction different from the stepped portion 91. (Step S22). Then, Steps S23 to S25 are similarly repeated with the moving direction of the stage 2 as the Y direction, and the positional deviation amount between the irradiation position P1 of the illumination light and the irradiation position P2 of the polarized light in the Y direction is calculated and stored in the storage unit 52. Stored (step S27). In the film thickness measuring apparatus 1, when the positional deviation amount in the X direction and the Y direction is obtained, the positional deviation amount acquisition process is terminated (step S28).
[0035]
As described above, in the film thickness measuring apparatus 1, the ellipsometer 3 is irradiated with polarized light by the imaging unit 44 while moving the stage 2 in the X direction and the Y direction (that is, in two directions perpendicular to each other in the horizontal plane). A plurality of images showing are continuously acquired. Then, the calculation unit 51 obtains the center of the irradiation area of the polarized light based on the plurality of images, and automatically obtains the positional deviation amount between the irradiation position of the illumination light and the irradiation position of the polarized light. Thereby, in the film thickness measuring apparatus 1, when the measurement is switched between the ellipsometer 3 and the optical interference unit 4, the irradiation positions of both lights on the substrate 9 can be easily matched based on the positional deviation amount. As a result, the film thickness at a desired position on the substrate 9 can be accurately obtained. Moreover, adjustment of the attachment position of each measurement part in the film thickness measuring apparatus 1 can be simplified.
[0036]
In addition, when the AF is performed so that the illumination light is collected on the concave portion 92 side on the reference substrate 9a and the polarized light is incident from the upper left in FIG. Strictly speaking, there is a possibility that an accurate displacement amount is not obtained because it is the upper end of the portion 91. However, this error can be ignored because the step of the step portion 91 is actually very small. Of course, when it is necessary to determine the amount of displacement more accurately, the irradiation position of the polarized light may be determined in consideration of the level difference.
[0037]
Further, in the film thickness measurement apparatus 1, the amount of positional deviation does not necessarily have to be obtained based on the amount of movement of the stage 2. For example, irradiation of polarized light from a plurality of images in which scattered light of polarized light appears by the computing unit 51 The distance in the image between the position and the irradiation position of the illumination light may be obtained, and the amount of positional deviation may be obtained based on this distance. Further, the center of the light irradiation region of the light interference unit 4 may be obtained from a plurality of images acquired while moving the stage 2.
[0038]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.
[0039]
The stepped portion 91 provided on the reference substrate 9a is not necessarily a stepped portion extending in one direction. For example, a curved stepped portion or a scattering surface that scatters light may be formed on the reference substrate.
[0040]
Further, by using a reference substrate patterns and the scale or the like for position determination are formed, the measurement unit (i.e., the ellipsometer 3 and each of the optical interference unit 4) light irradiation position of the imaging section or the like provided in the By confirming, the amount of misalignment may be obtained.
[0041]
The substrate 9 is not limited to a semiconductor substrate, and may be, for example, a glass substrate used for a liquid crystal display device or other flat panel display device.
[0042]
The ellipsometer 3 and the optical interference unit 4 and the stage 2 only need to move relatively. For example, the ellipsometer 3 and the optical interference unit 4 may be provided with a moving mechanism.
[0043]
The plurality of measuring units provided in the film thickness measuring device are not necessarily the ellipsometer 3 and the optical interference unit 4 of the optical interference system. In addition, the film thickness measuring apparatus is provided with three or more measurement units, and displacement amounts for any two of them are obtained, and the stage position is corrected based on the corresponding displacement amounts at the time of measurement of each measurement unit. It may be broken.
[0044]
【The invention's effect】
In the first to fourth aspects of the present invention, the amount of misalignment between the light irradiation position from the first measurement unit and the light irradiation position from the second measurement unit is automatically acquired, and the light from the first measurement unit is obtained . The irradiation position and the irradiation position of the light from the second measurement unit can be easily matched.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a film thickness measuring apparatus.
FIG. 2 is a diagram showing a flow of processing for measuring a film thickness.
FIG. 3 is a diagram showing a flow of processing for obtaining a positional deviation amount;
4A is a diagram illustrating an irradiation position of illumination light, and FIG. 4B is a diagram illustrating an irradiation position of polarized light.
FIG. 5 is a diagram illustrating an image acquired by an imaging unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Film thickness measuring apparatus 2 Stage 3 Ellipsometer 4 Optical interference unit 5 Control part 9 Substrate 9a Reference board 21 Stage moving mechanism 44 Imaging part 51 Calculation part 52 Storage part 61 Image 91 Step part P1, P2 Irradiation position

Claims (4)

A film thickness measuring device for measuring the thickness of a film formed on an object ,
A stage for holding the object;
A first measuring unit that has an imaging unit that acquires an image of a reference object held on the stage and that measures the film thickness by irradiating the object with light;
Separately from the first measuring unit, a second measuring unit that measures the thickness of the film by irradiating the object with light ;
A moving mechanism for moving relative to the previous SL stage the first measuring section and the second measuring unit,
Based on the image acquired by the imaging unit that the first measurement unit or the second measurement unit irradiates light, the irradiation position of the light from the first measurement unit and the light from the second measurement unit A calculation unit for obtaining a positional deviation amount from the irradiation position of
A storage unit for storing the positional deviation amount,
A control unit that controls the moving mechanism based on the amount of displacement when measurement is switched between the first measurement unit and the second measurement unit;
A film thickness measuring apparatus comprising: The film thickness measuring device according to claim 1 ,
The reference object has a scattering part for scattering light,
When the amount of positional deviation is obtained, a film thickness measuring apparatus in which a plurality of images are continuously acquired by the imaging unit while the moving mechanism moves the stage. The film thickness measuring device according to claim 2 ,
While the moving mechanism moves the stage in the first direction and the second direction, a plurality of images are continuously acquired by the imaging unit, and the first measurement is performed by the arithmetic unit based on the plurality of images. Or a center of an irradiation region of light from the second measurement unit is obtained. The film thickness measuring device according to any one of claims 1 to 3 ,
The film thickness measuring apparatus, wherein the first measuring unit is a measuring unit of an optical interference method using white light, and the second measuring unit is an ellipsometer.

Images