JP2023127323A - Method for measuring thickness of film, and processing apparatus - Google Patents

Abstract

To provide a technique capable of measuring the thickness of a film provided on a substrate.SOLUTION: A method for measuring the thickness of a film comprises the steps of: emitting light to a substrate arranged in a chamber and including a surface having a film; calculating the temperature of the substrate on the basis of first light interference by light reflected from the front and rear surfaces of the substrate corresponding to the light emitted by the emitting step and the known thickness of the substrate; and calculating the thickness of the film on the basis of second light interference by light reflected from the front and rear surfaces corresponding to the light emitted by the emitting step and the calculated temperature of the substrate.SELECTED DRAWING: Figure 6

Description

Exemplary embodiments of the present disclosure relate to a method of measuring film thickness and a processing apparatus.

Patent Document 1 discloses an optical interference system. This system includes a light source that generates measurement light, a collimator, an optical fiber that connects the light source and the collimator, and a calculation device. The collimator adjusts the measurement light into parallel light beams and emits the adjusted measurement light to the object to be measured. A collimator acquires reflected light from an object to be measured. The arithmetic device measures the thickness or temperature of the object to be measured based on the reflected light.

JP2013-242267A

The present disclosure provides a technique that can measure the thickness of a film provided on a substrate.

In one exemplary embodiment, a method of measuring membrane thickness is provided. The method includes the steps of emitting light, calculating the temperature of the substrate, and calculating the thickness of the film. In the step of emitting light, light is emitted to a substrate placed in a chamber and having a surface provided with a film. In the step of calculating the temperature of the substrate, the temperature of the substrate is calculated based on the first light interference caused by the light reflected from the front and back surfaces of the substrate according to the light emitted in the emitting step and the known thickness of the substrate. Calculate. In the step of calculating the thickness of the film, the thickness of the film is calculated based on the second light interference caused by the light reflected from the front and back surfaces of the film according to the light emitted in the emitting step and the calculated temperature of the substrate. Calculate the thickness of

According to one exemplary embodiment, the thickness of a film provided on a substrate can be measured.

1 is a diagram illustrating a longitudinal cross-sectional configuration of a processing device according to an exemplary embodiment; FIG. FIG. 3 is a diagram showing an example of reflected light from a wafer. It is a graph showing an example of a signal obtained by Fourier transforming a reflected light spectrum. FIG. 7 is a diagram showing another example of reflected light from a wafer. FIG. 7 is a diagram showing still another example of reflected light from a wafer. This is an example of a flowchart for measuring the thickness of a film.

Various exemplary embodiments are described below.

A conventional optical interference system calculates an optical path length corresponding to the thickness of an object to be measured based on optical interference measurement results. This system measures the temperature of the object to be measured based on the optical path length based on the measurement results and known data indicating the relationship between temperature and optical path length. In other words, this system can calculate the temperature of the object to be measured when the thickness of the object is known. This system can measure the thickness of the object if the temperature of the object is known.

2. Description of the Related Art With the miniaturization of semiconductor device structures and improvement in quality, there is a need to grasp film thickness (etching amount), etc. during processing in real time in the manufacturing process of semiconductor devices. Films undergo changes in thickness and temperature during processing. Conventional systems cannot measure the thickness of an object unless the temperature of the object is known. The present disclosure provides a technique that can measure the thickness of a film provided on a substrate.

In one exemplary embodiment, a method of measuring membrane thickness is provided. The method includes the steps of emitting light, calculating the temperature of the substrate, and calculating the thickness of the film. In the step of emitting light, light is emitted to a substrate placed in a chamber and having a surface provided with a film. In the step of calculating the temperature of the substrate, the temperature of the substrate is calculated based on the first light interference caused by the light reflected from the front and back surfaces of the substrate according to the light emitted in the emitting step and the known thickness of the substrate. Calculate. In the step of calculating the thickness of the film, the thickness of the film is calculated based on the second light interference caused by the light reflected from the front and back surfaces of the film according to the light emitted in the emitting step and the calculated temperature of the substrate. Calculate the thickness of

According to this method, the temperature of a substrate having a known thickness is measured using optical interference. Then, the thickness of the film provided on the substrate is calculated based on the temperature of the substrate. In this way, the measured temperature of the substrate is considered to be the temperature of the film provided on the substrate, so that even if the temperature of the film is unknown, the thickness of the film can be calculated. As a result, the temperature of the substrate, the thickness of the film, and even the amount of etching can be simultaneously monitored in real time even when the substrate is being processed.

In one exemplary embodiment, a first area of the substrate that is irradiated with the light that causes the first optical interference and a second area of the substrate that is irradiated with the light that causes the second optical interference overlap. Good too. In this case, the difference between the measured temperature of the substrate and the temperature of the film provided on the substrate is smaller than when the first region and the second region are different regions. Therefore, according to this method, the thickness of the film provided on the substrate can be measured more accurately than when the first region and the second region are different regions.

In one exemplary embodiment, the first optical interference and the second optical interference may be acquired simultaneously. In this case, the measurement of the temperature of the substrate and the measurement of the thickness of the film can be performed simultaneously. Therefore, according to this method, the thickness of the film provided on the substrate can be measured in a shorter time than when the first optical interference and the second optical interference are obtained separately.

In one exemplary embodiment, the step of emitting light may include emitting light to a substrate being processed. According to this method, the temperature of the substrate, the thickness of the film, and the amount of etching are simultaneously monitored in real time during processing.

In one exemplary embodiment, the step of emitting light may include emitting light to the back side of the substrate. According to this method, the first interference light is obtained without being influenced by the film provided on the surface of the substrate, compared to the case where the light is emitted to the surface of the substrate. Therefore, according to this method, the thickness of the film provided on the substrate can be measured more accurately than when light is emitted to the surface of the substrate.

In yet another exemplary embodiment, a processing device is provided. The processing apparatus includes a chamber, a substrate support, a light source, at least one optical element, a light receiver, and a controller. A substrate support is housed in the chamber and configured to support a substrate. The light source is configured to generate light. The at least one optical element is connected to the light source and configured to emit light generated by the light source toward the substrate and to receive return light reflected from the substrate. The light receiver is connected to at least one optical element and configured to output a signal in response to the returned light. A control device is connected to the light receiver. The control device is configured to execute the steps of emitting light, calculating the temperature of the substrate, and calculating the thickness of the film. In the step of emitting light, light is emitted to a substrate placed in a chamber and having a surface provided with a film. In the step of calculating the temperature of the substrate, the temperature of the substrate is calculated based on the first light interference caused by the light reflected from the front and back surfaces of the substrate according to the light emitted in the emitting step and the known thickness of the substrate. Calculate. In the step of calculating the thickness of the film, the thickness of the film is calculated based on the second light interference caused by the light reflected from the front and back surfaces of the film according to the light emitted in the emitting step and the calculated temperature of the substrate. Calculate the thickness of

This processing device has the same effect as the method described above.

Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. In the following description, the same or equivalent elements are given the same reference numerals, and overlapping descriptions will not be repeated.

[Overview of processing equipment]
FIG. 1 is a diagram illustrating a longitudinal cross-sectional configuration of a processing device 10 according to one exemplary embodiment. As shown in FIG. 1, the processing apparatus 10 includes a chamber body 12 for accommodating a wafer W and processing it with plasma. The chamber body 12 provides its internal space as a chamber 12c. Chamber body 12 is grounded. The chamber 12c is configured to be evacuated.

A support portion 14 is provided within the chamber 12c and on the bottom of the chamber body 12. The support portion 14 is made of an insulating material. The support portion 14 has a substantially cylindrical shape. The support portion 14 extends upward from the bottom of the chamber body 12 within the chamber 12c. The support portion 14 supports the mounting table 16 at its upper portion.

The mounting table 16 includes a lower electrode 18 and an electrostatic chuck 20 (an example of a substrate supporter). The lower electrode 18 includes a first member 18a and a second member 18b. The first member 18a and the second member 18b are made of a conductive material and have a substantially disk shape. The second member 18b is provided on the first member 18a and electrically connected to the first member 18a. An electrostatic chuck 20 is provided on this lower electrode 18 .

The electrostatic chuck 20 is accommodated in the chamber 12c and is configured to hold a wafer W (an example of a substrate) and an edge ring ER placed thereon. The electrostatic chuck 20 has a disc-shaped insulating layer and a film-like electrode provided within the insulating layer. A DC power supply 22 is electrically connected to the electrodes of the electrostatic chuck 20 . The electrostatic chuck 20 attracts the wafer W by electrostatic force generated by a DC voltage from a DC power supply 22 .

An edge ring ER is arranged on the peripheral edge of the lower electrode 18 so as to surround the edge of the wafer W. Edge ring ER is an annular member. The edge ring ER is provided to improve the in-plane uniformity of plasma processing on the wafer W. The edge ring ER is attracted to the electrostatic chuck 20 together with the wafer W. The edge ring ER can be removed from the mounting table 16 during maintenance and replaced with a new edge ring ER. The edge ring ER may be lifted and removed using a lift pin (not shown).

The electrostatic chuck 20 has a through hole extending from the bottom to the top. The lift pin 61 is provided within the through hole so as to be movable up and down. The lift pin 61 is driven up and down by the lift drive mechanism 60. When the lift pins 61 rise, the tips of the lift pins 61 support the wafer W and push the wafer W upward, thereby causing the wafer W to rise. The lift pin 61 receives the wafer W from the transfer hand of the transfer device by the lift drive mechanism 60, places it on the mounting table 16, lifts the wafer W from the mounting table 16, and transfers it to the transfer hand.

The processing device 10 is provided with a gas supply line 28 . The gas supply line 28 supplies a heat transfer gas, for example, He gas, from a heat transfer gas supply mechanism between the top surface of the electrostatic chuck 20 and the back surface of the wafer W.

The processing device 10 further includes a counter electrode 30 that functions as an upper electrode. The counter electrode 30 is arranged above the mounting table 16 so as to face the mounting table 16 . The counter electrode 30 is configured as a so-called shower head, and is configured to be able to supply a predetermined processing gas in the form of a shower to the wafer W placed on the mounting table 16. The counter electrode 30 is supported on the upper part of the chamber body 12 via an insulating member 32. This counter electrode 30 may include a top plate 34 and a support 36. The top plate 34 faces the chamber 12c. A plurality of gas discharge holes 34a are formed in the top plate 34.

The support body 36 detachably supports the top plate 34 and is made of a conductor. A gas diffusion chamber 36a is provided inside the support body 36. A plurality of holes 36b extend downward from the gas diffusion chamber 36a, each communicating with a plurality of gas discharge holes 34a. Further, a port 36c is formed in the support body 36 to guide the processing gas to the gas diffusion chamber 36a, and a pipe 38 is connected to this port 36c.

The chamber body 12 is provided with an exhaust port 12e. An exhaust device 50 is connected to the exhaust port 12e via an exhaust pipe 52. The exhaust device 50 has a vacuum pump. The exhaust device 50 can reduce the pressure in the chamber 12c. Furthermore, an opening 12p for loading or unloading the wafer W is provided in the side wall of the chamber body 12. This opening 12p can be opened and closed by a gate valve GV.

The processing device 10 further includes a first high frequency power source 62 and a second high frequency power source 64. The first high frequency power source 62 is a power source that generates a first high frequency wave for plasma generation. The frequency of the first high frequency is a frequency of 27 to 100 MHz, and in one example is a frequency of 40 MHz. The first high frequency power source 62 is connected to the lower electrode 18 via a matching box 66. The matching box 66 has a circuit for matching the output impedance of the first high frequency power supply 62 and the input impedance on the load side (lower electrode 18 side). Note that the first high frequency power source 62 may be connected to the counter electrode 30 via a matching box 66.

The second high frequency power source 64 is a power source that generates a second high frequency wave for drawing ions into the wafer W. The frequency of the second radio frequency is within the range of 400 kHz to 13.56 MHz, and in one example is a frequency of 3 MHz. The second high frequency power supply 64 is connected to the lower electrode 18 via a matching box 68. The matching box 68 has a circuit for matching the output impedance of the second high-frequency power supply 64 and the input impedance on the load side (lower electrode 18 side).

The processing device 10 may further include a DC power supply section 69. The DC power supply section 69 is connected to the counter electrode 30. The DC power supply unit 69 is capable of generating a negative DC voltage and applying the DC voltage to the counter electrode 30 .

The processing device 10 may further include a control unit CU. This control unit CU is a computer including a processor, a storage unit, an input device, a display device, and the like. The control unit CU is configured to be able to communicate with the system control device MC, and controls each section of the processing device 10. In the control unit CU, an operator can input commands to manage the processing device 10 using an input device. Further, the operating status of the processing device 10 can be displayed by the display device. Furthermore, the storage unit of the control unit CU stores a control program for controlling various processes executed by the processing device 10 by the processor, and recipe data. For example, the storage unit of the control unit CU stores a control program and recipe data for the processing device 10 to execute a method to be described later.

The processing device 10 includes an optical interference system 7 . The optical interference system 7 includes a light source 70, an optical circulator 71, a focuser 72 (an example of an optical element), and a spectrometer 73 (an example of a light receiver). Spectrometer 73 is communicably connected to control device 74 . The control device 74 may be a computer including a processor, a storage device such as a memory, a display device, an input/output device, a communication device, and the like. A series of operations of the optical interference system 7, which will be described later, are realized by controlling each part of the optical interference system 7 by the control device 74 according to a program stored in a storage device. The control device 74 may be integrated with the control unit CU. Note that each of the light source 70, optical circulator 71, focuser 72, and spectrometer 73 is connected using an optical fiber.

The light source 70 generates measurement light having a wavelength that passes through the measurement target. As the light source 70, for example, an SLD (Super Luminescent Diode) is used. The measurement object has a plate shape, for example, and has a front surface and a back surface opposite to the front surface. The wafer W to be measured is made of, for example, Si (silicon), SiO ₂ (quartz), or Al ₂ O ₃ (sapphire).

Optical circulator 71 is connected to light source 70, focuser 72, and spectrometer 73. Optical circulator 71 propagates measurement light generated by light source 70 to focuser 72 . The focuser 72 is arranged below the mounting table 16, and irradiates the chamber 12c with measurement light through the through hole 12q and the window 16a (an example of a light introduction path). An actuator that moves the focuser 72 in the horizontal direction may be connected to the focuser 72. The actuator is an electrically controllable drive mechanism, such as a stepping motor. The mounting table 16 may be provided with a plurality of light introduction paths having the same configuration as the light introduction path described above. In this case, a corresponding focuser is arranged in each light introduction path. In this way, a plurality of sets of windows, through holes, and focusers may be formed below the mounting table 16. The focusers 72 each emit measurement light adjusted as parallel light beams. Then, the return light (reflected light) reflected from the wafer W enters the focuser 72 . The reflected light includes not only the light reflected from the front surface but also the light reflected from the back surface. When a film is provided on the wafer W, the reflected light includes light reflected from the front and back surfaces of the film.

FIG. 2 is a diagram showing an example of reflected light from a wafer. In the example shown in FIG. 2, light is emitted to a stacked body in which a film L1 and a mask MA are sequentially stacked on a wafer W. Focuser 72 emits light toward the back surface of wafer W. Focuser 72 can emit light to region RL of wafer W corresponding to the etched region of film L1. In this case, the focuser 72 receives reflected light A from the back surface of the wafer W and reflected light B from the front surface of the wafer W. Focuser 72 may emit light to region RW of wafer W where film L1 is not provided. In this case, the focuser 72 receives reflected light C from the back surface of the wafer W and reflected light D from the front surface of the wafer W. Focuser 72 may emit light to region RM of wafer W corresponding to mask MA. In this way, the focuser 72 may emit light to any region of the wafer W. Note that when the refractive index of the wafer W is n and the thickness is d, the optical path length difference between the reflected light A and the reflected light B is 2nd. Similarly, the difference in optical path length between reflected light C and reflected light D is 2nd.

Focuser 72 propagates the reflected light to optical circulator 71 . Optical circulator 71 propagates the reflected light to spectroscope 73 . The spectrometer 73 is configured to output a signal according to the reflected light. As a more specific example, the spectrometer 73 outputs a reflected light spectrum (an example of first light interference). The reflected light spectrum is an intensity distribution that depends on the wavelength or frequency of the reflected light. Spectrometer 73 outputs the reflected light spectrum to control device 74 . The control device 74 obtains signals that strengthen each other in the 2nd period by Fourier transforming the reflected light spectrum. FIG. 3 is a graph showing an example of a signal obtained by Fourier transforming a reflected light spectrum. The horizontal axis is the position x, and the vertical axis is the intensity (amplitude). The control device 74 stores in advance the thickness d of the wafer W and data on the temperature dependence of nd on the wafer W in a storage unit. The control device 74 calculates the temperature of the wafer W based on the measured nd and the temperature dependence data of the nd stored in the storage unit.

The method described above can be applied not only to the wafer W but also to the film thickness measurement of the film L1. FIG. 4 is a diagram showing another example of reflected light from a wafer. In the example shown in FIG. 4, light is emitted to a stacked body in which a film L1 and a mask MA are sequentially stacked on a wafer W. Focuser 72 may emit light to region RM of wafer W. In this case, the focuser 72 receives reflected light E on the back surface of the film L1 and reflected light F on the front surface of the film L1. Focuser 72 may emit light to region RL of wafer W. In this case, the focuser 72 receives reflected light G from the back surface of the film L1 and reflected light H from the etched surface of the film L1. As in the measurement of the wafer W, if the refractive index of the film L1 is n _r , the initial thickness is d1, and the remaining thickness is d2, the optical path length difference between the reflected light E and the reflected light F is 2n _r d1. Become. The optical path length difference between the reflected light G and the reflected light H is 2n _r d2. The spectrometer 73 outputs a reflected light spectrum (an example of second light interference). The control device 74 obtains signals that strengthen each other at a predetermined period by Fourier transforming the reflected light spectrum, and calculates the thickness or temperature.

Note that during a process such as etching, the thickness d2 of the film L1 becomes a variable. For this reason, the control device 74 calculates or obtains the temperature of the film L1, and then calculates the thickness d2 of the film L1. The temperature of the film L1 may be the temperature of the wafer W calculated by optical interference. For example, the temperature of a region of the wafer W that overlaps the region of the film L1 that includes the location to be measured may be used. That is, reflected light A and reflected light B are employed rather than reflected light C and reflected light D in FIG. In this case, the difference in temperature between the film L1 and the wafer W is prevented from becoming large. Note that reflected light A and reflected light B in FIG. 2 and reflected light G and reflected light H in FIG. 4 can be measured simultaneously with one light beam. The temperature of the film L1 may be calculated from the reflected light spectrum of the reflected light E and the reflected light F based on the known initial thickness d1. Once the temperature of the film L1 is determined, the thickness d2 of the film L1 can be calculated from the reflected light spectrum. It is also possible to calculate the etching amount d3 based on the initial thickness d1 and the remaining thickness d2 during etching.

Measurements by the optical interference system 7 can be carried out not only during plasma etching but also during other processes. For example, measurements by the optical interference system 7 can also be performed during wet etching without plasma or during etching with gas. Alternatively, the measurement by the optical interference system 7 can be performed not only during etching but also during a CMP (Chemical Mechanical Polishing) process or during film formation. Film formation includes not only film formation using plasma but also film formation not using plasma. For example, the optical interference system 7 can also measure the thickness of a film being deposited. FIG. 5 is a diagram showing still another example of reflected light from a wafer. In the example shown in FIG. 5, light is emitted to a stacked body in which films L2 are sequentially stacked on a wafer W. Focuser 72 may emit light to region RL of wafer W on which a film has been formed. In this case, the focuser 72 receives reflected light J from the back surface of the film L2 and reflected light K from the front surface of the film L2. The method for calculating the thickness of the film L2 is the same as the method for calculating the thickness of the film L1 described above. In this way, the optical interference system 7 can measure the thickness in real time even during film formation.

[Operation of control device]
FIG. 6 is an example of a flowchart for measuring the thickness of a film. The flowchart shown in FIG. 6 is executed, for example, according to a start instruction from a worker.

First, the control device 74 executes a step of irradiating light (step S10). The control device 74 irradiates the back surface of the wafer W with light. Subsequently, the control device 74 executes a step of calculating the temperature of the substrate (step S12). The control device 74 calculates the temperature of the wafer W based on the known thickness d of the wafer W, the known temperature dependence of nd, and nd calculated from the reflected light spectra of the front and back surfaces of the wafer W. . Subsequently, the control device 74 executes a step of calculating the thickness of the film (step S14). The control device 74 calculates the thickness of the film based on the calculated temperature of the wafer W, the known temperature dependence of nd, and nd calculated from the reflected light spectra of the front and back surfaces of the film.

When the process of calculating the film thickness (step S14) is completed, the flowchart shown in FIG. 6 is completed. By executing the flowchart shown in FIG. 6, the processing apparatus 10 can measure the temperature of the wafer W and the thickness of the film provided on the wafer W in real time.

Although various exemplary embodiments have been described above, various omissions, substitutions, and changes may be made without being limited to the exemplary embodiments described above. Also, elements from different embodiments may be combined to form other embodiments.

For example, the processing apparatus 10 is a capacitively coupled plasma processing apparatus, but the processing apparatus according to another embodiment may be a different type of plasma processing apparatus. Such plasma processing equipment may be any type of plasma processing equipment. Examples of such plasma processing apparatuses include inductively coupled plasma processing apparatuses and plasma processing apparatuses that generate plasma using surface waves such as microwaves. The processing device 10 is a processing device that does not use plasma (wet etching or gas etching), a polishing device, or a film forming device (including not only film forming using plasma but also film forming not using plasma). Good too.

Moreover, although the processing apparatus 10 has shown an example in which two systems of high-frequency power sources are connected to the lower electrode 18 and a DC power source is connected to the counter electrode 30, the present invention is not limited to this. For example, the processing device 10 does not need to include the counter electrode 30. For example, in the processing device 10, a high frequency power source may be connected to the lower electrode 18 and the counter electrode 30. The processing apparatus 10 does not need to include equipment for generating plasma if plasma is not used. For example, a gas treatment device includes a gas source, a flow rate control device, and the like. For example, a polishing device includes a rotating polishing pad or the like.

Further, although an example has been shown in which the processing apparatus 10 has an electrostatic chuck as a device for supporting the substrate, the present invention is not limited to this. For example, the processing device may fix the substrate to the mounting table using a clamp or the like, may fix the substrate to the mounting table by vacuuming the back side of the substrate, or may fix the substrate to the mounting table by placing the substrate on the mounting table. You can just leave it there.

From the foregoing description, it will be understood that various embodiments of the disclosure are described herein for purposes of illustration and that various changes may be made without departing from the scope and spirit of the disclosure. Will. Therefore, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

DESCRIPTION OF SYMBOLS 10... Processing device, 12c... Chamber, 20... Electrostatic chuck, 70... Light source, 72... Focuser (an example of an optical element), 73... Spectrometer (an example of a light receiver), 74... Control device.

Claims (6)

emitting light to a substrate disposed within a chamber and having a surface provided with a film;
calculating the temperature of the substrate based on first light interference caused by light reflected from the front and back surfaces of the substrate according to the light emitted in the emitting step and a known thickness of the substrate; ,
Calculating the thickness of the film based on second light interference caused by light reflected from the front and back surfaces of the film according to the light emitted in the emitting step and the calculated temperature of the substrate. The process of
Methods of measuring membrane thickness, including: 2. The method according to claim 1, wherein a first area of the substrate irradiated with the light that causes the first optical interference and a second area of the substrate that is irradiated with the light that causes the second optical interference overlap. Method described. The method according to claim 1 or 2, wherein the first optical interference and the second optical interference are obtained simultaneously. 4. The method according to claim 1, wherein in the step of emitting light, the light is emitted to the substrate undergoing processing. 5. The method according to claim 1, wherein in the step of emitting light, the light is emitted to the back surface of the substrate. a chamber;
a substrate support housed in the chamber and configured to support a substrate;
a light source configured to generate light;
at least one optical element connected to the light source and configured to emit the light generated by the light source toward the substrate and to input return light reflected at the substrate;
a light receiver connected to the at least one optical element and configured to output a signal according to the returned light;
a control device connected to the light receiver;
Equipped with
The control device includes:
emitting light to a substrate disposed within a chamber and having a surface provided with a film;
calculating the temperature of the substrate based on first light interference caused by light reflected from the front and back surfaces of the substrate according to the light emitted in the emitting step and a known thickness of the substrate; ,
Calculating the thickness of the film based on second light interference caused by light reflected from the front and back surfaces of the film according to the light emitted in the emitting step and the calculated temperature of the substrate. The process of
A processing device configured to perform.

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