Patent ID: 12196629

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, systems, and components have not been described in detail so as not to unnecessarily obscure aspects of the various embodiments.

Hereinafter, embodiments of a measuring jig and a measuring device disclosed in the present application will be described in detail with reference to the drawings. The disclosed measuring jig and measuring device are not limited by the present embodiment.

When an attraction force distribution on a wafer held by an electrostatic chuck is nonuniform, the temperature distribution on the wafer becomes nonuniform, and thus processing characteristics of etching, film formation, or the like change. When the attraction force distribution on a wafer is increased as a whole or locally, the attraction surface of the electrostatic chuck may be scraped by the wafer and particles may be generated. Therefore, it is desired that an attraction force distribution on a wafer held by an electrostatic chuck is appropriately measured.

[Configuration of Measuring Device]

A measuring device according to an embodiment is a device for measuring an attraction force distribution on a wafer held by the electrostatic chuck arranged in a chamber of a semiconductor manufacturing apparatus. The semiconductor manufacturing apparatus is, for example, a plasma processing apparatus that performs a process such as etching or film formation using plasma. The electrostatic chuck is disposed, for example, in a chamber in which plasma processing of the plasma processing apparatus is performed. The measuring device according to an embodiment uses a measuring jig in which an optical fiber including therein reflection elements capable of reflecting light having a wavelength corresponding to the strain of a measurement target due to stress is fixed on a substrate that simulates a wafer. The measuring device measures an attraction force distribution on the wafer by emitting light to the optical fiber in a state in which the measuring jig is held by the electrostatic chuck, and calculating the strain amount of the substrate at positions based on the light reflected by the reflection elements.

FIG.1is a top view illustrating a configuration example of a measuring device1according to an embodiment. As illustrated inFIG.1, the measuring device1includes a measuring jig10, a measuring instrument20, and a recorder30.

The measuring jig10includes a substrate11having substantially the same shape as a wafer for semiconductor manufacturing, an optical fiber12fixed on the top surface of the substrate11, and a temperature sensor13provided on the top surface of the substrate11.

The substrate11is a substrate that simulates a wafer that is held by an electrostatic chuck disposed in a chamber of a semiconductor manufacturing apparatus. The shape of the substrate11has substantially the same shape as a wafer for semiconductor manufacturing, and has, for example, a disk shape having a thickness of about 775 μm and a diameter of about 300 mm. The substrate11may have a dimension other than the above dimensions. As the material for forming the substrate11, for example, silicon, a resin having higher flexibility than silicon, or the like may be used.

The optical fiber12includes therein fiber Bragg gratings (FBGs)12a. Each FBG12ahas a higher refractive index than the refractive index of a portion of the optical fiber12in which the FBGs12aare not formed. Each FBG12acan selectively reflect light having a wavelength corresponding to the strain of the substrate11due to stress with a predetermined reflectance. In each FBG12a, the wavelength of the reflected light (hereinafter, appropriately referred to as a “reflected wavelength”) changes depending on a change in stress applied from the substrate11. That is, each FBG12acan detect the amount of change in the reflected wavelength as the strain amount of the substrate11. The optical fiber12reflects the light output from the measuring instrument20to the optical fiber12by the FBGs12a, and transmits the light to the measuring instrument20as light for measuring the strain of the substrate11due to the stress. The FBGs12aare an example of reflection elements.

The optical fiber12is fixed on the top surface of the substrate11in a state in which the FBGs12aare disposed at plural positions, respectively, on the top surface of the substrate11. For example, as illustrated inFIG.1, the optical fiber12is fixed on the top surface of the substrate11such that the FBGs12aare disposed at spirally arranged positions, respectively, from the center of the substrate11toward the peripheral edge on the top surface of the substrate11.

In this way, by fixing the optical fiber12on the top surface of the substrate11in the state in which the FBGs12aare arranged at the plural positions, respectively, on the top surface of the substrate11, it is possible to calculate the strain amount of the substrate11at the plural positions in the measuring instrument20. Therefore, the measuring device1according to the embodiment can appropriately measure an attraction force distribution on the wafer and held by the electrostatic chuck.

The temperature sensor13is provided on the top surface of the substrate11adjacent to each FBG12a. The temperature sensor13detects the temperature of the substrate11at each of the plural positions at which the FBGs12aare respectively disposed. The temperature sensor13is connected to the recorder30, and the temperature of the substrate11detected by the temperature sensor13is recorded in the recorder30. The temperature of the substrate11recorded in the recorder30is used to compensate for the strain amount of the substrate11calculated by the measuring instrument20. In a case where the temperature of the substrate11can be considered to be uniform as a whole, one temperature sensor13may be provided at an arbitrary position on the top surface of the substrate11.

Here, the configuration on the top surface of the substrate11will be described with reference toFIG.2.FIG.2is a schematic cross-sectional view illustrating the measuring jig10according to an embodiment.FIG.2schematically illustrates a cross-section of the substrate11and the optical fiber12along the longitudinal direction of the optical fiber12. As illustrated inFIG.2, the optical fiber12is fixed on the top surface of the substrate11. Inside the optical fiber12, the FBGs12aare formed at predetermined intervals in the longitudinal direction of the optical fiber12. The optical fiber12is disposed in a groove portion11aformed in a spiral shape on the top surface of the substrate11, and is bonded at positions, where each FBG12ais interposed therebetween, on the top surface of the substrate11by an adhesive14.

The FBGs12aare disposed at plural positions, respectively, on the top surface of the substrate11. Specifically, recesses11barranged in a spiral shape are formed on the top surface of the substrate11, and the FBGs12aare disposed at the positions of the recesses11b, respectively, to be spaced apart from the bottom surfaces of the recesses11b. By spacing the FBGs12aaway from the bottom surfaces of the recesses11b, a change in the refractive index of each FBG12aaccording to the temperature change of the substrate11is suppressed, and the amount of change of the reflected wavelength of each FBG12adetected as the strain amount of the substrate11is less likely to be affected by the temperature change of the substrate11. As a result, the accuracy of detecting the strain amount of the substrate11in each FBG12acan be improved.

In addition, a temperature sensor13is provided adjacent to each FBG12aon the top surface of the substrate11. The temperature sensor13is bonded at one of the positions, where each FBG12ais interposed therebetween, on the top surface of the substrate11by an adhesive14that bonds the optical fiber12. This makes it possible to measure the temperature of the substrate11used for compensating for the strain amount of the substrate11with high accuracy by the temperature sensor13. The temperature sensor13may be installed at any position as long as it is located adjacent to each FBG12a. For example, the temperature sensor13may be provided on the bottom surface of each recess11bcorresponding to each FBG12a.

A description will be made referring back toFIG.1. The measuring instrument20is connected to the optical fiber12of the measuring jig10. In addition, the measuring instrument20is connected to the recorder30in a wired or wireless manner. The recorder30may be a memory device, a hard disk drive or solid state drive.

FIG.3is a block diagram illustrating an example of the measuring instrument20according to an embodiment. As illustrated inFIG.3, the measuring instrument20includes a light source21, a circulator22, a light receiver24, and an arithmetic device25.

The light source21is, for example, a wavelength sweep type light source, and emits light of which the wavelength changes with time to the circulator22. Specifically, the light source21emits light of which the wavelength changes with time to the circulator22in a state in which the measuring jig10is held by the electrostatic chuck disposed in the chamber of a semiconductor manufacturing apparatus.

The light emitted from the light source21to the circulator22is emitted to the optical fiber12via an input/output port22aby the circulator22. The light emitted from the light source21to the optical fiber12via the circulator22and the input/output port22ais reflected by the FBGs12alocated inside the optical fiber12and transmitted to the measuring instrument20as reflected light. The reflected light input to the circulator22via the input/output port22ais output to the light receiver24by the circulator22.

The light receiver24is, for example, a photo diode (PD), which receives the reflected light output from the circulator22to the light receiver24, generates light intensity data, and outputs the light intensity data to the arithmetic device25. The light intensity data indicate intensities corresponding to plural wavelengths. The intensity corresponding to a certain wavelength among the intensities indicates the intensity of the reflected light of that wavelength among the reflected light received by the light receiver24.

The arithmetic device25is, for example, a central processing unit (CPU) or a computer, and calculates strain amounts of the substrate11at plural positions on the top surface of the substrate11(that is, the positions at which the FBGs12aare disposed) based on the light intensity data output from the light receiver24. Specifically, the arithmetic device25calculates an amount of change of the wavelength of reflected light (i.e., the reflected wavelength of each FBG12a) in the light intensity data when the measuring jig10is held by the electrostatic chuck, as a strain amount of the substrate11. A strain amount can be converted into stress applied to a wafer, that is, an attraction force of a wafer, using the so-called Hooke's law. Therefore, strain amounts of the substrate11at the positions on the top surface of the substrate11indicate an attraction force distribution on the wafer that is held by an electrostatic chuck.

In the measuring jig10, the reflected wavelength of each FBG12aused for calculating the strain amount of the substrate11changes depending on the temperature change of the substrate11. Therefore, there is a possibility that an error due to the temperature change of the substrate11may occur in the strain amount of the substrate11calculated by the arithmetic device25.

Therefore, the arithmetic device25may compensate for the calculated strain amounts of the substrate11at the positions on the top surface of the substrate11(i.e., the positions at which the FBGs12aare disposed) using the temperature of the substrate11recorded in the recorder30. For example, the arithmetic device25holds in advance a correspondence relationship between a temperature of the substrate11and an error caused by a temperature change of the substrate11. The arithmetic device25obtains an error based on the correspondence relationship and the temperature of the substrate11recorded in the recorder30, and compensates for the calculated strain amount of the substrate11by subtracting the obtained error from the calculated strain amount of the substrate11. This makes it possible for the measuring device1according to the embodiment to calculate the strain amount of the substrate11in which the error caused by the temperature change of the substrate11is canceled. Therefore, the attraction force distribution on the wafer held by the electrostatic chuck can be measured more appropriately.

[Method of Determining Abnormality of Electrostatic Chuck Using Measuring Device]

An abnormality of an electrostatic chuck may be determined using the above-described measuring device1. Hereinafter, a method for determining an abnormality of an electrostatic chuck using the measuring device1will be described.

First, the measuring jig10is held by an electrostatic chuck having no abnormality (hereinafter referred to as a “reference electrostatic chuck”). Subsequently, in the state in which the measuring jig10is held by the reference electrostatic chuck, the measuring instrument20is controlled to calculate the strain amounts of the substrate11at plural positions on the top surface of the substrate11.

Subsequently, the measuring jig10is held by an electrostatic chuck to be evaluated. Subsequently, in the state in which the measuring jig10is held by the electrostatic chuck to be evaluated, the measuring instrument20is controlled to calculate the strain amounts of the substrate11at plural positions on the top surface of the substrate11.

Subsequently, it is determined whether or not the difference between the strain amounts of the substrate11calculated for the electrostatic chuck to be evaluated and the strain amounts of the substrate11calculated for the reference electrostatic chuck is within a predetermined allowable range. As a result of the determination, when the difference is not within the predetermined allowable range, it is determined that an abnormality has occurred in the electrostatic chuck to be evaluated.

According to such an abnormality determination method, an abnormality of the electrostatic chuck can be easily determined.

[Modification]

Next, a modification of the measuring device1according to the embodiment will be described with reference toFIG.4. In the following description, the same reference numerals will be given to the configurations common to the above-described embodiments, and a detailed description thereof will be omitted.

FIG.4is a schematic cross-sectional view illustrating a measuring jig10according to a modification of the embodiment.FIG.4schematically illustrates a cross-section of the substrate11and the optical fiber12along the longitudinal direction of the optical fiber12. The measuring jig10illustrated inFIG.4is different from the measuring jig10illustrated inFIG.2in that one of FBGs is mainly used as a temperature sensor and a cover member is provided for the FBG used as the temperature sensor. For example, a case in which the FBG12alocated at the leftmost side ofFIG.4is used as a temperature sensor among the FBGs12awill be described. Hereinafter, the FBG12aused as a temperature sensor will be referred to as an “FBG temperature sensor12a”.

The FBG temperature sensor12acan selectively reflect light having a wavelength corresponding to the strain of a substrate11due to a temperature change with a predetermined reflectance. In the FBG temperature sensor12a, the reflection wavelength changes depending on the temperature change of the substrate11. That is, the FBG temperature sensor12acan detect the amount of change in the reflection wavelength as the temperature of the substrate11. The optical fiber12reflects the light output from the measuring instrument20to the optical fiber12by the FBG temperature sensor12aand transmits the light to the measuring instrument20as light for measuring the strain of the substrate11due to the temperature change.

As illustrated inFIG.4, the portion of the optical fiber12corresponding to the FBG temperature sensor12ais covered with a cover member15. The cover member15is a metal-made circular tube-shaped member having an inner diameter larger than the diameter of the optical fiber12and blocks stress from the substrate11to the FBG temperature sensor12aby the optical fiber12being inserted thereinto. The cover member15is bonded to the bottom surface of the recess11bcorresponding to the FBG temperature sensor12aby an adhesive15a. The recess11bcorresponding to the FBG temperature sensor12ahas a shallower depth from the top surface of the substrate11than the other recesses11b.

By covering a portion of the optical fiber12corresponding to the FBG temperature sensor12awith the cover member15, the change in the refractive index of the FBG temperature sensor12adue to the stress from the substrate11is suppressed, and thus it becomes difficult for the FBG temperature sensor12ato be affected by stress. As a result, according to the measuring device1according to the modification, the accuracy of detecting the temperature of the substrate11in the FBG temperature sensor12acan be improved.

When one of the FBGs12ais used as the FBG temperature sensor12a, the strain amount of the substrate11detected by another FBG12amay be compensated by using the temperature of the substrate11detected by the FBG temperature sensor12a. In this case, the arithmetic device25of the measuring instrument20operates as follows.

The arithmetic device25calculates a temperature of the substrate11based on the reflected light reflected by the FBG temperature sensor12aand received by the light receiver24(i.e., light intensity data). The arithmetic device25calculates a strain amount of the substrate11at the position corresponding to the other FBG12abased on the reflected light reflected by the other FBG12aand received by the light receiver24(i.e., light intensity data). Then, the arithmetic device25compensates for the calculated strain amount of the substrate11at the position corresponding to the other FBG12ausing the calculated temperature of the substrate11. For example, the arithmetic device25holds in advance a correspondence relationship between a temperature of the substrate11and an error caused by a temperature change of the substrate11. The arithmetic device25obtains an error based on the correspondence relationship and the temperature of the substrate11recorded in the recorder30, and compensates for the calculated strain amount of the substrate11by subtracting the obtained error from the calculated strain amount of the substrate11. This makes it possible for the measuring device1according to the modification to calculate the strain amount of the substrate11in which the error caused by the temperature change of the substrate11is canceled. Therefore, the attraction force distribution on the wafer held by the electrostatic chuck can be measured more appropriately.

In the above-described modification, the case in which one of the FBGs12ais used as a temperature sensor is illustrated as an example, but two or more FBGs12amay be used as the temperature sensor. In addition, a temperature distribution on the wafer held by the electrostatic chuck may be measured by obtaining the temperature distribution on the substrate11using all the FBGs12aas temperature sensors.

As described above, the measuring jig according to an embodiment (e.g., the measuring jig10) includes a substrate (e.g., the substrate11) and an optical fiber (e.g., the optical fiber12). The substrate is a substrate having substantially the same shape as a wafer for semiconductor manufacturing. The optical fiber includes therein reflection elements (e.g., the FBGs12a) capable of reflecting light having a wavelength corresponding to the strain of the substrate due to stress. The optical fiber is fixed on one surface of the substrate in a state in which the reflection elements are disposed at plural positions, respectively, on the one surface of the substrate. Therefore, according to the present embodiment, it is possible to appropriately measure the attraction force distribution on the wafer that is held by the electrostatic chuck.

In the measuring jig according to an embodiment, the substrate may have one or more recesses (e.g., the recesses11b) on the one surface. The reflection elements may be disposed at the positions of the one or more recesses, respectively, to be spaced apart from the bottom surfaces of the one or more recesses. Therefore, according to the present embodiment, it is possible to improve the accuracy of detecting the strain amount of the substrate in each reflection element.

The measuring jig according to an embodiment may further include a temperature sensor (e.g., the temperature sensor13) provided on the one surface of the substrate. The temperature sensor may be provided adjacent to each reflection element. Therefore, according to the present embodiment, the temperature of the substrate used for compensating for the strain amount of the substrate can be measured with high accuracy by the temperature sensor.

In addition, in the measuring jig according to an embodiment, the optical fiber may be bonded to positions, where each reflection element is interposed therebetween, on the one surface of the substrate by an adhesive (e.g., the adhesive14). The temperature sensor may be bonded to one of the positions, where each reflection element is interposed therebetween, on the one surface of the substrate by an adhesive that bonds the optical fiber. Therefore, according to the present embodiment, the temperature of the substrate used for compensating for the strain amount of the substrate can be measured with high accuracy by the temperature sensor.

In the measuring jig according to an embodiment, at least one reflection element (e.g., the FBG temperature sensor12a) among the reflection elements may be used as a temperature sensor. In addition, the measuring jig may further include a cover member (e.g., the cover member15) that covers a portion of the optical fiber corresponding to at least one reflection element used as the temperature sensor to block stress from the substrate to the at least one reflection element. Therefore, according to the present embodiment, it is possible to improve the accuracy of detecting the temperature of the substrate in the at least one reflection element used as a temperature sensor.

In the measuring jig according to an embodiment, the substrate may be formed of a resin having higher flexibility than silicon. Therefore, according to the present embodiment, the strain of the substrate due to stress can be easily generated, and thus it is possible to further improve the accuracy of detecting the strain amount of the substrate in each reflection element.

The measuring device according to an embodiment includes a measuring jig (e.g., the measuring jig10), a light source (e.g., the light source21), a light receiver (e.g., the light receiver24), and an arithmetic part (e.g., the arithmetic device25). The measuring jig includes a substrate (e.g., the substrate11) and an optical fiber (e.g., the optical fiber12). The substrate is a substrate having substantially the same shape as a wafer for semiconductor manufacturing. The optical fiber includes therein reflection elements (e.g., the FBGs12a) capable of reflecting light having a wavelength corresponding to the strain of the substrate due to stress. The optical fiber is fixed on one surface of the substrate in a state in which the reflection elements are disposed at plural positions, respectively, on one surface of the substrate. The light source emits light to the optical fiber of the measuring jig in a state in which the measuring jig is held by an electrostatic chuck disposed in a chamber of a semiconductor manufacturing apparatus. The light receiver receives the light reflected by each of the reflection elements. The arithmetic part is configured to calculate a strain amount of the substrate at the positions on the one surface of the substrate based on the light received by the light receiver. Therefore, according to the present embodiment, it is possible to appropriately measure the attraction force distribution on the wafer that is held by the electrostatic chuck.

Here, it is also conceivable to detect a strain amount of a substrate using a strain gauge that detects a resistance value of a resistance element for an electric signal as a strain amount. However, when a strain amount of a substrate is detected using a strain gauge, the electrical characteristics of the strain gauge change due to radio frequency noise in the chamber of the semiconductor manufacturing apparatus and a voltage applied to the electrostatic chuck. Therefore, the accuracy of detecting the strain amount of the substrate is lowered. In contrast, according to the present embodiment, a strain amount on a substrate can be detected without using a strain gauge. As a result, according to the present embodiment, an attraction force distribution can be measured with high accuracy without being affected by radio frequency noise in a chamber of a semiconductor manufacturing apparatus and a voltage applied to an electrostatic chuck.

In addition, in the measuring device according to an embodiment, the measuring jig may further include a temperature sensor (e.g., the temperature sensor13) provided on one surface of a substrate. The measuring device may further include a recorder configured to record the temperature of the substrate detected by the temperature sensor. Therefore, according to the present embodiment, the temperature of the substrate recorded in the recorder can be used to compensate for the strain amount of the substrate.

In addition, in the measuring device according to an embodiment, the arithmetic part may compensate for the calculated strain amounts of the substrate at the plural positions on one surface of the substrate using the temperature of the substrate recorded in the recorder. Therefore, according to the present embodiment, it is possible to calculate the strain amount of the substrate from which an error caused by the temperature change of the substrate is canceled. Therefore, an attraction force distribution on a wafer held by the electrostatic chuck can be measured more appropriately.

In the measuring device according to an embodiment, at least one reflection element (e.g., the FBG temperature sensor12a) among the reflection elements may be used as a temperature sensor. The measuring jig may further include a cover member that covers a portion of the optical fiber corresponding to the at least one reflection element used as the temperature sensor to block stress from the substrate. Therefore, according to the present embodiment, it is possible to improve the accuracy of detecting the temperature of the substrate in the at least one reflection element used as a temperature sensor.

In addition, in the measuring device according to an embodiment, the arithmetic part may calculate the temperature of the substrate based on the light reflected by the at least one reflection element among the reflection elements and received by the light receiver. The arithmetic part may calculate the strain amount of the substrate at a position corresponding to the other reflection element based on light reflected by the other reflection element among the reflection elements and received by the light receiver. The arithmetic part may compensate for the calculated strain amount of the substrate at the position corresponding to the other reflection element using the calculated temperature of the substrate. Therefore, according to the present embodiment, it is possible to calculate the strain amount of the substrate from which an error caused by the temperature change of the substrate is canceled. Therefore, an attraction force distribution on a wafer held by the electrostatic chuck can be measured more appropriately.

Although embodiments have been described above, it should be considered that the embodiments disclosed herein are exemplary in all respects and are not restrictive. Indeed, the above-described embodiments can be implemented in various forms. In addition, the embodiments described above may be omitted, replaced, or modified in various forms without departing from the scope and spirit of the claims.

For example, in the above-described embodiments, the case in which the light source21of the measuring instrument20is a wavelength sweep type light source has been described as an example, but the disclosed technique is not limited thereto. The light source21may be a wideband type light source capable of emitting light including wavelength components. In this case, an optical spectrum analyzer may be used as the light receiver24.

In addition, in the above-described embodiments, the case in which the recesses11bare formed on the top surface of the substrate11has been described as an example, but the recesses11bmay be formed as a single continuous recess.

Furthermore, in the above-described embodiments, the case in which the measuring instrument20and the recorder30are different devices has been described as an example, but the measuring instrument20and the recorder30may be incorporated in a single device.

According to the present disclosure, an attraction force distribution on a wafer held by an electrostatic chuck can be appropriately measured.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.