WO2012102541A2

WO2012102541A2 - Transparent sheet including optical fiber cable, and method and apparatus for detecting polishing end point in cmp process using same

Info

Publication number: WO2012102541A2
Application number: PCT/KR2012/000574
Authority: WO
Inventors: 오찬권; 김용태
Original assignee: Oh Chan Kwon; Kim Yong Tae
Priority date: 2011-01-25
Filing date: 2012-01-20
Publication date: 2012-08-02
Also published as: KR20120086077A; WO2012102541A3; KR101187453B1

Abstract

The present invention relates to a transparent sheet including an optical fiber cable, and a method and apparatus for detecting a polishing end point in a CMP process using the same, the apparatus comprising: a platen which rotates about a central rotating shaft; a polishing pad and a transparent sheet which are connected to an upper portion of the platen; a polishing head which supports a semiconductor wafer to face the polishing pad and transparent sheet, and rotates by a rotating shaft fixed to an arm; an optical fiber cable which is provided in the transparent sheet; and a light detecting unit which is connected to a rear end portion of the optical fiber cable, and is fixedly connected to a lower portion or side portion of the platen. By configuring a transparent sheet including an optical fiber cable and a polishing end point detecting apparatus using the same according to the present invention, there is no interference on an optical path, articles of consumption can be easily changed according to a simple configuration of a CMP device, a situation in which the accuracy of detection is degraded is not generated although air gaps, slurry leakages, or vapor problems are generated because the problems exert no influence upon the light detector, and a polishing end point during a CMP process can be conveniently and precisely detected.

Description

Transparent sheet containing optical fiber cable, polishing end point detection method and apparatus in CPM process

The present invention relates to a transparent sheet, a method and apparatus for detecting a polishing end point in a CPM process using the same, and more particularly, to an optical path by integrally constructing an optical fiber cable in a transparent sheet which is a component of the polishing end detecting device. There is no interference, there is no possibility of the degradation of polishing end point detection caused by air gap, slurry leakage and water vapor, and the configuration of the polishing end point detecting device is simple and consumable parts can be easily replaced. In addition, by forming a plurality of optical fiber cable sets in the polishing end detection device, a transparent sheet including an optical fiber cable which can accurately and easily detect the polishing end point in the CMP process, and the polishing end detection in the CPM process using the same. A method and apparatus are disclosed.

As semiconductor integrated circuits are highly integrated into IC, LSI, VLSI, and ULSI devices in the vacuum tube era, circuit wiring insulating films to solve the problem that the depth of focus allowed by lithography technology is reduced beyond the circuit wiring step. In order to solve the problem of non-uniformity of wiring resistance caused by the introduction of multilayer circuit wiring, the wiring film separation process became very important. A chemical mechanical planarization (Polishing) process is used as a method of planarizing the semiconductor wiring insulating film and separating the circuit wiring.

The principle of CMP is to supply a slurry containing several hundred nm sized abrasives continuously on top of the pad while mounting a wafer with a semiconductor element pattern formed on an elastic polyurethane pad (oxide film or metal film). The polishing head and the platen with the pad are rotated at high speed while inducing a chemical reaction, and the polishing target film is mechanically removed to planarize the circuit wiring insulating film or to separate the circuit wiring. It is a core technology of semiconductor front-end process.

The film to be polished using CMP technology includes oxide film (Oxide, SiO2), polycrystalline silicon film (Doped or Un-doped Poly-Silicon, x-Si), nitride film (Nitride, SixNx), metal film (Metal, Tungsten, Aluminum, Copper, Pt, Ru etc), and different types of slurry are used for each thin film.

As semiconductor circuit wiring becomes smaller from 0.25 µm to 0.18 µm or less, planarization of wiring insulation film and improvement of precision of wiring separation CMP process technology are required, and at the time when desired flatness, film thickness or wiring separation film shape is reached (polishing end point, end point) ) And the termination of the CMP process has become very important.

As a method for detecting the polishing end point, a torque detection method for detecting a coefficient of friction between the polishing target film of the wafer and the pad as a change in the torque of the upper spindle of the wafer support head or the lower platen driving motor, and the metal film remaining on the wafer. Capacitance method for detecting thickness, vibration analysis method for analyzing frequency spectrum obtained from vibration or acceleration sensor mounted on upper spindle or lower platen of wafer support head, frictional heat of slurry film on upper wafer and polishing pad, slurry and polishing object The method of measuring the reaction heat of the film by infrared radiation thermometer, the method of measuring the thickness of the film to be polished by measuring the tram time of ultrasonic waves, and the optical method of assembling the film thickness monitor mechanism by various light sources such as laser in the rotating platen is applied. It is becoming.

Among them, the optical method of assembling the film thickness monitor mechanism by various light sources such as a laser in the rotating platen is the end point of polishing of the oxide film, polysilicon film, and copper metal film CMP process, which occupies 80% or more of CMP process technology for semiconductors. It is used for detection. This optical detection method is a transparent window pad in which a light source injected from a polishing end device composed of a light source and an optical detector installed in the middle or bottom of the platen is locally installed on an elastic polyurethane pad. ) Is irradiated to the multilayer thin film such as the wafer upper polishing target film, and transmitted through the polishing target film to monitor the interference signal generated by reflection from the surface of the interlayer thin film or the single crystal silicon, and convert it into thickness, or measure the intensity or change of the interference signal. An example of the CMP apparatus of such an optical method by detecting the polishing termination point is shown in FIG. 1.

As shown in FIG. 1, the CMP apparatus 10 includes a polishing head 40 for supporting a semiconductor wafer against the platen 3. The platen 3 is composed of an upper platen 3a and a lower platen 3b, and the polishing pad 2 is coupled to the upper platen 3a. The polishing pad 2 is divided into an upper layer 2a and a lower layer 2b, and the upper layer 2a is a layer used for chemical mechanical polishing in combination with a slurry to polish the wafer 42, and is generally made of polyurethane. The lower layer 2b is bonded to the upper platen 3a.

Polishing end For the optical detection of the polishing pad (2) and the upper platen (3a) through holes are formed in the hole of the upper layer (2a) of the polishing pad 2 is provided with a transparent window pad, the lower platen (3b) The laser interferometer 5, which is a photodetector, is installed on the inner bottom so as to correspond to the window of the hole. The laser interferometer 5 is composed of a laser beam light source 5a, a beam splitter 5b, and a detector 5c, in which a beam b _i output from a light source is incident on the wafer 42 and then polished. Reflected from the target film, the multilayer thin film, or the surface of the single crystal silicon, the reflected beam b _r is detected through a detector through a beam splitter. In addition, a slip ring 75 is installed between the platen 3 and the central rotation shaft 70 to prevent the cable twisting due to the rotation of the platen 3. Further, the polishing head 40, which is the carrier of the wafer 42, rotates about the rotation axis 80 fixed to the arm 60, and rotates and moves the upper surface of the polishing platen pad on which the polishing head 40 rotates. As a result, the polishing process is performed, and ultimately, the wafer surface circuit wiring insulating film is planarized or the wiring separation process is performed.

However, such a conventional CMP apparatus not only has to install the laser interferometer at a position corresponding to the hole accurately, but also consumables such as slip rings having a replacement cycle to prevent twisting of the light source connecting cable and the connecting cable with an external monitor. And the light source and the window are spaced apart so that the direction of laser beam change or interference may be caused by external interference factors (for example, air particle composition, temperature, humidity, etc.) inside the laboratory. There may be problems such as a possibility.

In addition, in the polishing pad of the conventional CMP apparatus, peeling occurs easily at the boundary between the polishing region and the window, and a gap occurs at the boundary due to the peeling phenomenon, thereby causing a slurry leakage problem. There is a problem in that the polishing end point detection accuracy is lowered or impossible by generating an optical problem such as blur.

As a result of the intensive research, the present inventors have devised the present invention to simplify the device configuration, prevent interference with the optical path, and to easily and easily detect the polishing termination point in the CMP process.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a first object is to construct an optical fiber cable in a transparent sheet, which is one component of the polishing end point detection device, so that it does not interfere with the optical path and has excellent detection performance. To provide a transparent sheet containing a cable.

In addition, the second object of the present invention comprises a fiber optic cable containing a fiber optic cable and an optical polishing end point detection device comprising the same, it is easy to replace the consumables according to the configuration of the easy polishing end point detection device includes an optical fiber cable It is to provide a polishing end point detection method and apparatus using a transparent sheet.

In addition, a third object of the present invention is to configure a transparent sheet including an optical fiber cable and an optical polishing endpoint detection device including the same, so that air gaps, slurry leakage, and water vapor problems are not affected by the photodetector. The present invention provides a polishing end point detection method and apparatus using a transparent sheet including an optical fiber cable which does not cause a decrease in detection accuracy.

In addition, the fourth object of the present invention is to configure a plurality of transparent sheets in the CMP device including a transparent sheet including an optical fiber cable and an optical detection device comprising the same, thereby simplifying and precisely polishing termination points in the CMP process It is an object of the present invention to provide a polishing end point detection method and apparatus in a CPM process that enable detection.

In order to achieve the above object, the polishing endpoint detection device using a transparent sheet containing an optical fiber cable according to the present invention,

A platen rotating around a central axis of rotation;

A polishing pad and a transparent sheet coupled to the upper platen;

A polishing head which supports the semiconductor wafer to face the polishing pad and the transparent sheet and rotates by a rotation shaft fixed to the arm;

An optical fiber cable provided in the transparent sheet;

And a light detector connected to the rear end of the optical fiber cable and fixedly coupled to the bottom or side of the platen.

In addition, in the polishing endpoint detecting apparatus using a transparent sheet containing an optical fiber cable according to the present invention,

The upper and lower layers of the polishing pad are characterized in that the rectangular hole is formed in the center direction from the edge.

Here, the rectangular holes formed in the polishing pad may be formed in the upper layer and the lower layer, respectively, or the rectangular hole is formed in the lower layer, the upper layer is characterized in that the circular or rectangular polygonal hole is formed.

The upper surface of the platen is formed with a rectangular recess of a predetermined depth corresponding to the rectangular hole, or

An insert pad is further provided between an upper surface of the platen and a lower layer of the polishing pad, and the insert pad is formed with a rectangular hole having a position coincident with the rectangular hole of the polishing pad in a central direction from an edge thereof. .

A permeable sheet is coupled to a space formed by the recess of the platen and a rectangular hole of the polishing pad, or a space formed by the insert pad and the rectangular hole of the polishing pad.

The transparent sheet is formed integrally with the optical fiber cable and the transparent material.

Here, the transparent sheet may be formed by placing the optical fiber cable in a desired position in the space-shaped molding frame provided separately and injecting a transparent material or molding the optical fiber cable in the space portion of the polishing pad. It is disposed and injected into the permeable material, characterized in that the molding with the polishing pad.

The state in which the optical fiber cable is arranged in the transparent sheet

The optical fiber cable is bent and fixed in the space portion on the central side of the polishing pad such that the front end portion of the optical fiber cable faces upward at a position spaced downward from the height of the upper surface of the transparent sheet; or

The optical fiber cable is bent and fixed in the space portion on the central side of the polishing pad such that the front end of the optical fiber cable is located on the same plane as the upper surface of the transparent sheet and faces upward;

A reflection mirror is disposed at an inner edge portion of the space portion on the center side of the polishing pad, and the optical fiber cable is fixedly arranged so that the front end portion thereof is parallel to the transverse direction at a position spaced apart from the reflection mirror; or

A polygonal reflector is arranged so that a reflecting surface is located at an inner edge portion of the space portion on the center side of the polishing pad, and the optical fiber cable is fixedly arranged by being inserted into the rear end side of the reflecting plate, or

A reflective frame having a 45 ° reflecting surface is disposed so that a reflecting surface is located at an inner edge portion of the space portion on the center side of the polishing pad, and the optical fiber cable has a front end portion above the reflecting frame at a position spaced apart from the reflecting surface. It is characterized in that the fixed arrangement in parallel to the horizontal direction.

The optical fiber cable is composed of a combination of a plurality of light emitting optical fibers and a plurality of light receiving optical fibers, the incident light output from the light emitting optical fiber at the front end of the optical fiber cable is refracted and reflected back from the wafer after the incident light is reflected on the optical fiber Characterized in that it is input to the light receiving optical fiber at the front end of the cable.

The transparent sheet is characterized in that a plurality is provided in one polishing pad.

In addition, the side surface of the transparent sheet is characterized in that the "-" or "b" shape.

The light detector is composed of a light source and a detector,

A transmitter is connected to the detector, and a receiver configured to receive data wirelessly from the transmitter is provided externally.

The light source may be selectively used among light emitting diodes having a wavelength band of 190 to 3500 nm, preferably 350 to 1100 nm.

The detector may be a combination of an interference filter and a photodiode or a spectroscope.

The polishing endpoint detection device is characterized in that the power supply source is provided with a self-generating system such as a battery, a shaft generator or a solar cell separately in the lower or side of the platen.

In the case of the shaft generator system, the gear is installed on the central rotation shaft of the platen to receive power therefrom.

In the case of using the solar cell system is to install a plurality of solar cells around the center of the rotation axis in the lower portion of the platen, a plurality of light sources are installed on the outside or the arm to receive power generated from the solar cell,

The solar cell system is characterized in that the condensing lens is directly connected to the optical fiber cable to be a separate light source.

In addition, the method for detecting the polishing endpoint through the polishing endpoint detection device using a transparent sheet containing the optical fiber cable according to the present invention,

A polishing endpoint detection process is performed through a polishing endpoint detection device using a transparent sheet including the optical fiber cable of any one of claims 1 to 15,

Outputting a trigger signal when the wafer is positioned over the optical fiber cable on the transparent sheet;

A light source operating in association with the output trigger signal and being transmitted along the light emitting optical fiber in the optical fiber cable and incident on the multilayer thin film of the wafer via a transparent sheet;

Refracting and reflecting from the multilayer thin film of the wafer and inputting the light-receiving optical fiber in the optical fiber cable to be transmitted to the detector;

And transmitting the data of the interference signals input to the detector to the receiver wirelessly via the transmitter.

The method may further include arranging a photosensor or an electrostatic sensor on the rotating shaft of the platen to detect that the wafer is positioned on the optical fiber cable.

By using the transparent sheet including the optical fiber cable of the present invention, there is no interference in the optical path, and it is easy to replace the consumables according to the simple polishing end detection device configuration.

In addition, by constructing a CMP device including a transparent sheet including the optical fiber cable of the present invention and an optical detection device including the same, the air gap, slurry leakage and water vapor problems are not affected by the photodetector, thereby detecting the problem. No deterioration of precision occurs, and the polishing termination point can be detected accurately in the CMP process.

1 is a schematic diagram of an embodiment of a conventional polishing end detection device and a CMP device;

2 is a schematic cross-sectional view of a polishing endpoint detecting apparatus and a CMP apparatus using a transparent sheet including an optical fiber cable according to the present invention.

3 is a schematic plan view of a platen having a transparent sheet and a polishing pad including the optical fiber cable of FIG. 2 thereon;

Figure 4 (a), (b) is a schematic plan view of the insert pad and the combined cross-sectional view of the platen and the polishing pad to which the insert pad is applied,

5a to 5d are embodiments showing the optical path and the optical path disposed in the transparent sheet according to the present invention,

6 and 7 are views illustrating an embodiment provided with a plurality of transparent sheets according to the present invention,

8 (a) and 8 (b) are sectional views illustrating various arrangements of the polishing pad and the transparent sheet in FIGS. 6 and 7;

9 (a) to 9 (c) are enlarged plan views of the light emitting / receiving portion of the transparent sheet of FIG. 6 or FIG. 7, showing a state in which a plurality of light emitting optical fibers and light receiving optical fibers are provided and various arrangement states. drawing,

FIG. 10 is a graph of interference signals detected in order of each cable when four transparent sheets including optical fiber cables are provided as shown in FIG. 6 or 7;

FIG. 11 is an analysis graph showing an example of a superimposition method for detecting polishing endpoints from the detection graph of FIG. 10;

12 is a view showing that the shaft generator system can be used as a power supply source in the polishing endpoint detecting apparatus according to the present invention;

13 is a view showing that the solar cell system can be used as a power supply source in the polishing endpoint detection apparatus according to the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

Figure 2 is a schematic cross-sectional view of the polishing end point detection device and the CMP apparatus using a transparent sheet containing the optical fiber cable according to the present invention, Figure 3 is a plate having a transparent sheet and a polishing pad including the optical fiber cable of Figure 2 4 (a) and 4 (b) are schematic plan views of the insert pads and cross-sectional views of the platen and polishing pads to which the insert pads are applied, and FIGS. 5a to 5d are optical fiber cables in the transparent sheet according to the present invention. 6 and 7 are views illustrating an arrangement state and an optical path, and an exemplary embodiment in which a plurality of transparent sheets according to the present invention is provided, and FIGS. 8A and 8B are FIGS. 6 and 7 7 is a cross-sectional view illustrating various arrangements of the polishing pad and the transparent sheet in FIG. 7, and FIGS. 9A to 9C are enlarged plan views of the light emitting / receiving portion of the transparent sheet of FIG. 6 or 7. As, provided with a plurality of light emitting optical fiber and light receiving optical fiber 10 and 7 are diagrams showing the state of various arrangements, and FIG. 10 is an interference signal graph detected in order of each cable when four transparent sheets including optical fiber cables are provided as shown in FIG. 6 or 7, and FIG. 11 is a detection graph of FIG. 10. Analysis graph showing an example of the overlapping method for detecting the polishing endpoint from the figure, Figure 12 shows that the shaft generator system can be used as a power supply source in the polishing endpoint detection apparatus according to the present invention, Figure 13 is the present invention In the polishing endpoint detecting apparatus according to the present invention, it is a diagram showing that a solar cell system can be used as a power supply source.

As shown in FIG. 2, the polishing endpoint detecting apparatus and the CMP apparatus 100 using the transparent sheet including the optical fiber cable according to the present invention are rotated about a rotation axis (not shown) located at the center of the platen 30. ); A polishing pad 20 and a transparent sheet 23a positioned on the platen 30; A polishing head 40 supporting the semiconductor wafer 42 against the polishing pad and the transparent sheet, the polishing head 40 being a wafer carrier rotated by a rotation shaft 80 fixed to the arm 60; An optical fiber cable 25 provided in the transparent sheet 23a; It is configured to include a light detection unit 50 is connected to the rear end side of the optical fiber cable 25 and fixedly coupled to the lower portion or the side of the platen 30.

The platen 30 rotates at a constant speed about the central axis of the center, and is coupled to the lower layer 20b of the polishing pad 20 to be described later. Here, a rectangular concave portion 32 having a predetermined depth may be formed on the upper surface of the platen 30 in the center direction from the edge.

The concave portion 32 is considered to have a small thickness of the conventional polishing pad 20. When the bending radius of the optical fiber cable 25 used in the present invention is larger than the thickness of the polishing pad, the optical fiber It is formed for sufficient installation space of the cable (25). If the thickness of the polishing pad is suitable for the installation of the optical fiber cable, such a recess is not necessary.

Of course, without forming the recess 32 in the platen 30, the insert pad 90 as shown in Figure 4 is placed between the polishing pad 20 and the platen 30 to provide a platen ( Of course, it is possible to replace the recess 32 of the 30. At this time, the insert pad 90 is formed with a rectangular hole 92 in the direction of the center from the edge to replace the recess. This rectangular hole 92 preferably coincides with the rectangular hole formed in the upper and lower layers of the polishing pad described later.

The polishing pad 20 is divided into an upper layer 20a and a lower layer 20b, and the upper layer 20a is a layer used for chemical mechanical polishing by physicochemical reaction with a slurry to polish the wafer 42, and the lower layer 20b. Is a layer that binds onto the platen 30. The shape of the platen and the polishing pad is not particularly limited, and may be formed in a conventional disk shape or polygonal shape such as a square.

At the position of the polishing pad 20 corresponding to the recess 32 of the platen 30, like the platen 30, a rectangular hole 22 having a predetermined dimension is formed in the center direction from the edge.

The rectangular holes 22 formed in the polishing pad 20 are preferably formed simultaneously in the upper layer 20a and the lower layer 20b as shown in FIGS. 2, 3, and 8 (a). At this time, the side cross section of the space portion has a "-" shape. However, the present invention is not limited thereto, and as shown in FIG. 8B, a rectangular hole 22 is formed in the lower layer 20b, and polygonal holes such as a circle or a square are formed in the upper layer 20a to form a space portion. The side cross section may be configured to have a "b" shape.

As the material of the upper layer 20a of the polishing pad 20, halogen such as polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc. It is preferably at least one polymer material selected from the group consisting of counting paper, polystyrene, and thermoplastic resins such as olefin resins such as polyethylene and polypropylene, and epoxy resins, photosensitive resins, and the like. In particular, a polyurethane resin is preferable because a polymer having high abrasion resistance and a desired material property can be easily obtained by variously changing the raw material composition. In this case, the polyurethane resin can maintain a slurry in micropores of the surface and improve polishing speed. In order to improve the dispersibility of the slurry, grooves may be formed on the surface of the polishing pad so as to be a fine foam.

The transparent sheet 23a is a space 23 formed by the recess 32 of the platen 30 and the rectangular hole 22 of the polishing pad 20, or the insert pad 90 and the polishing pad ( It is formed in the same shape as the shape of the space part by engaging with the space part 23 which the rectangular hole of 20) makes. At this time, the transparent sheet 23a is fixed to the optical fiber cable 25 in a variety of forms in a separate molding frame having the same shape as the space portion, and then filled with a transparent material and molded.

The molded transparent sheet is fitted to the space portion 23 or is coupled to the space portion 23 by a coupling means such as an adhesive. Of course, the transparent sheet 23a may be fixedly arranged in various shapes in the space 23 in the desired position, then filled with a transparent material and may be molded integrally with the polishing pad.

Such a transparent sheet 23a should be made of a transparent material capable of transmitting light, and is preferably a non-foaming body so that light scattering can be suppressed and accurate reflectance can be detected to increase the accuracy of detection of polishing endpoints. In addition, it is preferable that the material of the permeable sheet has a hardness (Asuka D hardness of 30 to 100 degrees) such that the upper surface does not cause macro scratches by the abrasive in the slurry. This is because the abrasive remains in the macro scratch portion, causing light scattering and absorption, thereby lowering the accuracy of detecting the polishing end point.

The material of the permeable sheet material according to the present invention is a thermosetting resin such as polyurethane resin, polyester resin, phenol resin, urea resin, melamine resin, epoxy resin, and acrylic resin, polyurethane resin, polyester resin, polyamide, etc. Resins, cellulose resins, acrylic resins, polycarbonate resins, polyvinyl chloride, halogenated resins such as polytetrafluoroethylene, polyvinylidene fluoride, and thermoplastic resins such as polystyrene and olefin resins such as polyethylene and polypropylene. It is preferable that it is at least 1 sort (s) of polymeric material chosen from the group which consists of photocurable resin, photosensitive resin, etc., and especially polyurethane resin with high abrasion resistance is preferable.

However, it is preferable that the material of the transparent sheet 23a and the material of the upper layer 20a of the polishing pad have substantially the same grinding properties. This is to prevent the upper surface of the transparent sheet from protruding from the upper layer 20a of the polishing pad during the polishing process to cause scratches or the like on the wafer.

The optical fiber cable 25 is provided in the transparent sheet 23a to transmit light, and an optical fiber cable in which the optical fiber is bundled in bundles is bundled.

Generally, optical fibers are roughly classified into quartz optical fibers and plastic optical fibers. Quartz optical fibers have good transmittances for light in the ultraviolet and visible regions, but are expensive and have small disadvantages in bending strength (breaking curvature). In the case of the optical fiber, the light transmittance is slightly reduced, but the price is low and the strength for bending is great.

Plastic optical fibers consist of a core made of high-purity polymethyl methacrylate (PMMA) and a clad made of special fluorine polymethyl methacrylate (F-PMMA). Since the refractive index of the clad is lower than that of the core, light input to the one end of the optical fiber within the light receiving angle range causes total reflection at the connection surface of the core and the clad, and is output through the core to the other end to transmit light.

Many embodiments in which the optical fiber cable 25 is disposed in the

transparent sheets

23a, 23a '23a', 23a '' for transmitting light from the light source to the semiconductor wafer 42 are shown in FIGS. It is illustrated in Figure 5d. Exemplary transparent sheet is formed by integrally molding the optical fiber cable in a desired position in the molding frame of the same shape as the space according to the present invention and then injected into a transparent material. At this time, the side cross-section of the prepared transparent sheet may have a "-" or "b" shape, as shown in (a), (b) of FIG. Of course, the present invention is not limited thereto, and various modifications may be made to those skilled in the art from those illustrated.

FIG. 5A is the same as the arrangement of the transparent sheet shown in FIG. 2, and the arrangement of the optical fiber cable in the transparent sheet 23a is such that the optical fiber cable 25 is a portion of the space 23 on the central side of the polishing pad 20. In this case, the optical fiber cable 25 is bent and arranged to have a radius of curvature within the allowable curvature of breakage, and a permeable material is injected thereinto be integrally molded.

At this time, the upper surface of the transparent sheet 23a is preferably molded to be coplanar with the upper surface of the upper layer 20a of the polishing pad 20, and the front end of the optical fiber cable 25 is the upper layer of the polishing pad 20 ( The upper surface of the transparent sheet 23a may be disposed upwardly at a position spaced downward from the height of the upper surface of the transparent sheet 23a so as to have a deviation of the predetermined height h.

This is because the polishing pad upper layer 20a and the transparent sheet are worn during the CMP process, so that the optical fiber cable protruding out of the worn transparent sheet is prevented from scratching the wafer 42. Such a deviation dimension may be determined according to the polishing pad replacement cycle. For example, if 1.0 mm wear of the polishing pad is the replacement cycle, a height deviation of 1.2 mm to 5.0 mm is appropriate.

Here, when the optical fiber constituting the optical fiber cable is worn in the CMP process so as not to scratch the wafer, the front end portion of the optical fiber cable 25 and the upper surface of the upper layer 20a of the polishing pad 20 are spaced apart to have a deviation. Of course, there is no need to configure. That is, the front end portion of the optical fiber cable and the upper surface of the transparent sheet may be disposed on the same plane, in which case the optical fiber cable does not need to be provided in the transparent sheet.

At this time, the incident light output from the light emitting optical fiber at the front end portion of the optical fiber cable 25 is incident on the wafer 42 through the transparent sheet, and is returned by refractive reflection from the surface polishing target film, the multilayer thin film or the single crystal silicon surface of the wafer 42. The reflected light b _r is input to the light receiving optical fiber at the front end of the optical fiber cable 25.

In addition, as shown in FIG. 5B, in the arrangement of the optical fiber cables in the transparent sheet 23a ', the reflective mirror 57 is disposed at the inner edge of the space 23 on the center side of the polishing pad 20. In this case, the optical fiber cable 25 is fixedly arranged in parallel in the transverse direction at a position where the front end portion is spaced apart from the reflective mirror 57, and is integrally formed by injecting a transparent material therein.

At this time, the incident light b _i output from the light emitting optical fiber at the front end portion of the optical fiber cable 25 is reflected by the reflecting mirror 57 and is incident on the wafer 42, and the reflected light b _r returned by refracting and reflecting from the wafer 42. The light is reflected by the reflecting mirror 57 and input to the light receiving optical fiber at the front end of the optical fiber cable 25.

In addition, as shown in Fig. 5C, the arrangement of the optical fiber cable in the transparent sheet 23a " is 45 ° so that the reflective surface is located at the inner edge portion of the space 23 on the central side of the polishing pad 20. As shown in Figs. A polygonal reflector plate 58 having a reflecting surface 58a is disposed, and the optical fiber cable 25 is fixedly arranged by inserting a predetermined length into the rear end side of the reflector plate 58. Molded into. Here, a reflective material such as metal or aluminum is deposited on the reflective surface and the inner surface of the reflective plate so that reflection and total reflection are smoothly performed.

At this time, the incident light b _i output from the light emitting optical fiber at the front end portion of the optical fiber cable 25 is reflected on the reflecting surface 58a and is incident on the wafer 42, and the reflected light b _r returned by refraction and reflection from the wafer 42. The light is reflected by the reflecting surface 58a and input to the light receiving optical fiber at the front end of the optical fiber cable 25.

In addition, as shown in Fig. 5D, the arrangement of the optical fiber cable in the transparent sheet 23a '' 'is such that the reflecting surface is positioned at the inner edge portion of the space 23 on the central side of the polishing pad 20. The reflective frame 59 having the reflective surface 59a is disposed, and the optical fiber cable 25 is fixedly disposed in parallel to the upper side of the reflective frame 59 at a position where the front end portion is spaced apart from the reflective surface 59a. It is formed by injecting a permeable material into it. Here, the reflective surface and the reflective frame by depositing a reflective material such as metal or aluminum to facilitate the reflection.

At this time, the incident light b _i output from the light emitting optical fiber at the front end portion of the optical fiber cable 25 is reflected by the reflecting surface 59a and is incident on the wafer 42, and the reflected light b _r returned by refracting and reflecting from the wafer 42. The light is reflected by the reflecting surface 59a and input to the light receiving optical fiber at the front end of the optical fiber cable 25.

6 and 7 are schematic plan views showing that four transparent sheets 23a including an optical fiber cable 25 are provided in a set in one polishing pad 20, each of which is one embodiment. Cross-sectional views are shown in FIGS. 8 (a) and 8 (b).

Although FIGS. 6 and 7 show four optical fiber cables 25, it is obvious that the optical fiber cables 25 are not limited thereto. The transparent sheet 23 including the optical fiber cables 25 includes a plurality of optical fiber cables 25 in one polishing pad 20. FIG. Of course, the dog can be provided. By providing a plurality of transparent sheets 23a including the optical fiber cable in the polishing pad, it is possible to precisely measure the polishing termination point (in-situ monitoring is possible) of the wafer polishing process.

In addition, in the present invention, the light emitting optical fiber for outputting the incident light and the light receiving optical fiber for receiving the reflected light are installed in bundles (not shown) of several strands, and the light emitting optical fiber and the light receiving optical fiber are respectively disposed as illustrated in FIG. 9. According to the diameter and number of each optical fiber and the installation angle of each optical fiber, various arrangements are made. In the present invention, since the interference signal from the wafer is sufficiently detected by controlling the installation angle or the number of the light receiving optical fibers according to the incident angle of the incident light output from the light emitting optical fiber, it is a matter of course that the accuracy of the detection of the polishing end point can be increased. .

The photodetector 50 is connected to the rear end of the optical fiber cable 25 and fixedly coupled to the lower side or the side of the platen 30 and includes a light source 50a and a detector 50c.

The light source 50a may use a light emitting diode capable of low power and high brightness, and selectively emits light emitting diodes (eg, R) in various wavelength bands of approximately 190 to 3500 nm, preferably approximately 350 to 1100 nm. , G, B) can be used.

The detector 50c detects the light transmitted from the light source 50a by being incident on the semiconductor wafer 42 on which the multilayer thin film is deposited along the light emitting fiber, refracted and reflected from the wafer, and then input to the light receiving fiber. The detector consists of a combination of an interference filter and a photo diode that filter only the wavelength band to be detected, or a spectrometer capable of measuring broadband wavelengths (350 to 1100 nm) at a time by wavelength. (Spectrometer) can be used.

Different types of interference waveforms are obtained in the detector 50c depending on whether the multilayer thin film of the wafer 42 is a transparent film or a non-transmissive film through which an incident light source can pass. For example, when the multilayer thin film of the wafer is composed of a metal film (one to be polished) which is one of the non-transmissive films and an oxide film (stop layer) which is one of the permeable films, the metal film is polished and removed. And the end point of the polishing can be detected by the difference in reflectance when the oxide film is exposed. When each of the deposited films is a transmissive film, the thin film polished by the interference phenomenon of light refracted and reflected from each thin film The polishing termination point can be detected from the interference waveform corresponding to the thickness change.

In addition, a detector is connected to a wireless transmitter 52 as a transmitter, and the wireless transmitter 52 wirelessly transmits data detected by the detector to a wireless receiver 53 which is an externally provided receiver.

Furthermore, in the present invention, the platen 30 is provided as a power source by using a self-powered system such as a battery 55 or a shaft generator (see FIG. 12) or a solar cell (see FIG. 13) for use in a light source, a detector, and a wireless transmission / reception. Or it is preferable to provide separately in a side part.

Here, in the case of using the shaft generator 55 'as shown in FIG. 12, a gear such as a drive pulley P may be installed on the central rotation shaft of the platen 30 to generate power therefrom. .

In addition, in the case of using the solar cell system as shown in FIG. 13, a plurality of solar cells 55 ″ are installed at the lower portion of the platen 30 about a central rotation axis, and a light source 50a 'such as halogen is externally provided. Alternatively, a plurality of arms 60 may be installed to transmit light from the light source to the solar cell 55 ″. In this case, the collimation lens (L), which is a condenser lens, may be directly connected to the optical fiber cable 25 to be used as a separate light source.

The polishing head 40, which is a wafer carrier, supports the semiconductor wafer 42 to face the polishing pad and is rotated by the rotation shaft 80 fixed to the arm 60, and the polishing head 40 rotates. The wafer surface is eventually planarized by performing the polishing process with relative rotation of the platen surface. Since this is normal, description is omitted.

In addition, as shown in FIG. 6 or 7, when four transparent sheets including the optical fiber cable 25 are provided in one polishing pad 20 as a set, a data signal for detecting a polishing termination point is provided. How to handle it:

And transmitting the data of the interference signals input to the detector to the receiver wirelessly via the transmitter. The steps will be briefly described as follows.

(1) In the CMP process, the trigger signal (start signal) is outputted when the wafer is positioned on the optical fiber cable to start the polishing end detection.

In order to control this, a photo sensor or an electrostatic sensor may be arranged on the rotating shaft of the platen 30 so that a trigger signal is generated when the wafer 42 is on the optical fiber cable.

(2) In the trigger signal, all four light sources and detectors can be operated at the same time.

Of course, each may be controlled to operate separately.

(3) While the platen rotates and the wafer is being polished, interference signals from four optical fiber cables 25 are continuously detected at each detector.

In this case, the measured interference signal corresponds to a change in the thickness of the film to be polished, and the relationship between the film thickness d and the measurement wavelength λ is as follows.

d = (λ / 2n) × A; λ = measurement wavelength (nm), n = refractive index, A = number of cycles of interference signal.

That is, as the polishing proceeds, an interference signal as shown in FIG. 10 is detected for each optical fiber cable.

As can be seen in Figure 10, the starting point of the interference signal is different for each position of the optical fiber cable, because the film thickness at the moment measured by each optical fiber cable is different.

In particular, since the measurement signal on the patterned wafer is a sine wave containing a large amount of noise, filtering is required to accurately detect the polishing termination point. Since a number of filtering methods are well known, a description thereof will be omitted.

(4) As a method of processing the measured interference signal, the input signal of 4 optical fiber cables is independently processed (processing like AND, NAND, OR, NOR) and the input signal of 4 optical fiber cables are sequentially superimposed It can be made into one input signal and then processed.

Here, when processing the signals of four optical fiber cables in a superimposed manner, it is preferable to process the inclination value for each point of each input signal. If the input signal of each optical fiber cable is processed as a scalar value, it is processed as shown in FIG. 11 (a) due to the difference in input / output light quantity between each optical fiber cable, that is, mechanical tolerance. There is a difficult problem.

On the other hand, when the input signal of each optical fiber cable is first converted to the inclination value for each point, and then the input signals of the four optical fiber cables are sequentially overlapped, normalization is performed as shown in FIG. Accurate detection is facilitated.

Hereinafter, a method for detecting the polishing termination point using the CMP apparatus according to the present invention will be briefly described using a block diagram as shown in FIG. 14.

(1) Did you receive a trigger signal from the CMP device?

(2) If received, set the max timeout of the polishing endpoint detector.

(3) Then, the interference signal is obtained from the sensor of the polishing endpoint detector.

(4) Then, the interference signal value of the polishing endpoint detector sensor is converted into a signal processing algorithm.

(5) After completion of the conversion, check the completion of the process by the polishing end detector algorithm set by the user.

(6) Then, check whether the completion end algorithm of the grinding end detector is satisfied.

(7) If the process completion algorithm criteria are satisfied, the process is sent to the CMP apparatus to terminate the process.

(7-1) If the criteria of the completion algorithm are not satisfied, check the termination completion time.

(7-2) If it is checked, the polishing end point is not detected within the set time, and an "error" is sent to the CMP apparatus.

If (7-2-1) fails to check, feed back to step (3) and measure again.

Here, the sensor signal processing algorithm of the polishing endpoint detector processes a digital signal filter and an algorithm so that a user can select a digital signal processing algorithm.

In addition, the process completion algorithm of the polishing end detector detects any one of the top dead center, the bottom dead center, the top inflection point, and the bottom inflection point by using an algorithm, and detects the completion of the polishing process after these position signals. do.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, other various modifications and variations may be made without departing from the spirit and scope of the invention. Accordingly, the appended claims are intended to cover such modifications and variations as fall within the true scope of the invention.

Claims

A platen rotating around a central axis of rotation;

A polishing pad and a transparent sheet coupled to the upper platen;

A polishing head which supports the semiconductor wafer to face the polishing pad and the transparent sheet and rotates by a rotation shaft fixed to the arm;

An optical fiber cable provided in the transparent sheet;

And a light detecting unit connected to a rear end of the optical fiber cable and fixedly coupled to the lower side or the side of the platen.
The method of claim 1,

A polishing endpoint detecting apparatus using a transparent sheet including an optical fiber cable, wherein a rectangular hole is formed in an upper layer and a lower layer of the polishing pad in a central direction from an edge thereof.
The method of claim 2,

The rectangular hole formed in the polishing pad is formed in the upper layer and the lower layer, respectively, or the lower layer is formed in the rectangular hole, the upper layer is a transparent sheet containing an optical fiber cable, characterized in that the circular or polygonal hole is formed Polishing endpoint detection device using.
The method of claim 2,

The upper surface of the platen is formed with a rectangular recess of a predetermined depth corresponding to the rectangular hole, or

An insert pad is further provided between an upper surface of the platen and a lower layer of the polishing pad, wherein the insert pad is formed with a rectangular hole having a position coincident with the rectangular hole of the polishing pad in a central direction from an edge thereof. Polishing end point detection device using a transparent sheet containing an optical fiber cable.
The method of claim 4, wherein

A permeable sheet is coupled to a space formed by the recess of the platen and a rectangular hole of the polishing pad, or a space formed by the insert pad and the rectangular hole of the polishing pad.

The transparent sheet detecting device using a transparent sheet containing a transparent fiber, characterized in that the transparent sheet is integrally molded including the optical fiber cable and the transparent material.
The method of claim 5,

The transparent sheet may be formed by placing the optical fiber cable at a desired position in a space-shaped molding frame provided separately and injecting a transparent material, or placing the optical fiber cable at a desired position in the space portion of the polishing pad. A polishing endpoint detecting apparatus using a transparent sheet including an optical fiber cable, characterized in that the transparent material is injected and molded integrally with the polishing pad.
The method of claim 6,

The state in which the optical fiber cable is arranged in the transparent sheet

The optical fiber cable is bent and fixed in the space portion on the central side of the polishing pad such that the front end portion of the optical fiber cable faces upward at a position spaced downward from the height of the upper surface of the transparent sheet; or

The optical fiber cable is bent and fixed in the space portion on the central side of the polishing pad such that the front end of the optical fiber cable is located on the same plane as the upper surface of the transparent sheet and faces upward;

A reflection mirror is disposed at an inner edge portion of the space portion on the center side of the polishing pad, and the optical fiber cable is fixedly arranged so that the front end portion thereof is parallel to the transverse direction at a position spaced apart from the reflection mirror; or

A polygonal reflector is arranged so that a reflecting surface is located at an inner edge portion of the space portion on the center side of the polishing pad, and the optical fiber cable is fixedly arranged by being inserted into the rear end side of the reflecting plate, or

A reflective frame having a 45 ° reflecting surface is disposed so that a reflecting surface is located at an inner edge portion of the space portion on the center side of the polishing pad, and the optical fiber cable has a front end portion above the reflecting frame at a position spaced apart from the reflecting surface. Polishing end point detection device using a transparent sheet containing a fiber optic cable, characterized in that the fixed arrangement in parallel in the horizontal direction.
The method of claim 7, wherein

The optical fiber cable is composed of a combination of a plurality of light emitting optical fibers and a plurality of light receiving optical fibers, the incident light output from the light emitting optical fiber at the front end of the optical fiber cable is refracted and reflected back from the wafer after the incident light is reflected on the optical fiber Polishing end point detection device using a transparent sheet containing an optical fiber cable, characterized in that input to the light receiving optical fiber at the front end of the cable.
The method of claim 1,

And a plurality of transparent sheets are provided in one polishing pad, wherein the polishing end detection device using the transparent sheet including the optical fiber cable is provided.
The method of claim 1,

Side end surface of the transparent sheet is a "-" or "b" shaped abrasive end point detection device using a transparent sheet containing an optical fiber cable, characterized in that the.
The method of claim 1,

The light detector is composed of a light source and a detector,

The detector is connected to the transmitter, the polishing end detection device using a transparent sheet containing a fiber optic cable, characterized in that the receiving unit for receiving data wirelessly from the transmitter is provided on the outside.
The method of claim 11,

The light source is a polishing endpoint detection apparatus using a transparent sheet containing a fiber-optic cable, characterized in that can be selectively used among light emitting diodes of the wavelength band of 190 ~ 3500nm.
The method of claim 11,

The detector is composed of a combination of an interference filter and a photodiode, or a polishing endpoint detection device using a transparent sheet containing an optical fiber cable, characterized in that the spectrometer.
The method of claim 11,

The polishing endpoint detecting apparatus is a polishing endpoint detection using a transparent sheet including an optical fiber cable, characterized in that the power supply source is provided with a self-generation system such as a battery, a shaft generator or a solar cell separately in the lower portion or the side of the platen. Device.
The method of claim 14,

In the case of the shaft generator system, the gear is installed on the central rotation shaft of the platen to receive power therefrom.

In the case of using the solar cell system is to install a plurality of solar cells around the center of the rotation axis in the lower portion of the platen, a plurality of light sources are installed on the outside or the arm to receive power generated from the solar cell,

The solar cell system is a polishing endpoint detection apparatus using a transparent sheet containing a fiber optic cable, characterized in that the condenser lens is directly connected to the optical fiber cable to be configured as a separate light source.
A polishing endpoint detection process is performed through a polishing endpoint detection device using a transparent sheet including the optical fiber cable of any one of claims 1 to 15,

Outputting a trigger signal when the wafer is positioned over the optical fiber cable on the transparent sheet;

A light source operating in association with the output trigger signal and being transmitted along the light emitting optical fiber in the optical fiber cable and incident on the multilayer thin film of the wafer via a transparent sheet;

Refracting and reflecting from the multilayer thin film of the wafer and inputting the light-receiving optical fiber in the optical fiber cable to be transmitted to the detector;

And transmitting the data of the interference signals input to the detector to the receiver wirelessly via the transmitter. The method of claim 1, wherein the polishing endpoint is detected.
The method of claim 16,

And arranging a photosensor or an electrostatic sensor on the rotating shaft of the platen to detect that the wafer is positioned on the optical fiber cable. How to detect.