JP2015195268A - Polishing progress estimation method and polishing progress estimation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve estimation accuracy of polishing process progress.SOLUTION: A polishing progress estimation method supplies an abrasive pad for polishing an object to be polished with polishing abrasive liquid, presses the object to be polished against the abrasive pad supplied with the polishing abrasive liquid, and performs polishing (step S101). The estimation method includes: acquiring a measurement signal that is outputted by a sensor in the state where the polishing abrasive liquid after polishing the object to be polished faces at least any sensor of an electrostatic capacitance sensor, a magnetic sensor, and an eddy current sensor (an area B outside the object to be polished) (step S102); and estimating polishing progress of the polishing object on the basis of the acquired measurement signal (step S103).

Description

  The present invention relates to a polishing progress estimation method and a polishing progress estimation apparatus.

  In recent years, with higher integration and higher density of semiconductor devices, circuit wiring has become increasingly finer and the number of layers of multilayer wiring has increased. In order to realize multilayer wiring while miniaturizing a circuit, it is necessary to planarize the surface of a semiconductor device with high accuracy.

As a technique for planarizing the surface of a semiconductor device, chemical mechanical polishing (CMP (Chemical)
Mechanical Polishing)) is known. A polishing apparatus for performing CMP includes a polishing table to which a polishing pad is attached, and an object to be polished (for example, a substrate such as a semiconductor wafer, or various films such as a metal film and a barrier film formed on the surface of the substrate). And a top ring for holding. The polishing apparatus supplies a polishing abrasive liquid (slurry) to the polishing pad while rotating the polishing table, and polishes the polishing object by pressing the polishing object held on the top ring against the polishing pad.

  Generally, in a polishing apparatus, in order to polish an object to be polished to a desired thickness, the progress of the polishing process is estimated (for example, determination of the polishing end point). For example, in the prior art, it is known that the polishing end point is determined based on the measured value of the electrical resistance of the polishing abrasive liquid by utilizing the change in the electrical resistance of the polishing abrasive liquid during the polishing process.

JP 2000-306872 A

  However, the prior art does not consider improving the estimation accuracy of the progress of the polishing process.

  That is, the conventional technique continuously measures the electrical resistance of the polishing abrasive liquid while polishing the substrate on which the first layer and the second layer of different materials are laminated, and polishes when the electrical resistance changes drastically. The end point. This utilizes the property that when a two-layer laminated substrate is polished and the layer to be polished is switched, a by-product (polishing shaving powder) having different conductivity is generated in the polishing liquid.

  However, according to the prior art, for example, when a layer to be polished is switched, as in the case of polishing a laminated substrate made of a material having similar conductivity, byproducts having different conductivity are not generated in the polishing abrasive liquid. In such a polishing process, it may be difficult to accurately estimate the progress of the polishing process.

  Therefore, an object of one embodiment of the present invention is to improve the estimation accuracy of the progress of the polishing process.

One aspect of the method for estimating the progress of polishing according to the present invention is made in view of the above-mentioned problems. A polishing abrasive liquid is supplied to a polishing pad for polishing an object to be polished, and the polishing is supplied with the polishing abrasive liquid. The polishing object after pressing the polishing object against the pad and polishing the polishing object is opposed to at least one of a capacitance sensor, a magnetic sensor, and an eddy current sensor. In the state, the measurement signal output from the sensor is acquired, and the progress of polishing of the polishing object is estimated based on the acquired measurement signal.

  In one form of the method of estimating the progress of polishing, the step of supplying the polishing abrasive liquid and the step of polishing the object to be polished are applied to the polishing pad while rotating the polishing table to which the polishing pad is attached. A polishing abrasive liquid is supplied, the polishing object is polished by pressing the polishing object against a polishing pad supplied with the polishing abrasive liquid, and the sensor is installed on the polishing table. Along with the rotation, a first state where the polishing object and the sensor do not face each other and a second state where the polishing object and the sensor face each other appear alternately, and the measurement signal is acquired. The step of performing can acquire a measurement signal output from the sensor in the first state.

  Further, in one form of the polishing progress estimation method, the step of estimating the polishing progress can estimate the total polishing amount of the object to be polished based on the acquired measurement signal.

  Further, in one mode of the method of estimating the polishing progress, the step of estimating the progress of the polishing in the case where the polishing target includes the first polishing target and the second polishing target stacked. Based on the change of the acquired measurement signal, it can be estimated whether or not the polishing object is switched from the first polishing object to the second polishing object.

  Further, in one form of the method of estimating the progress of polishing, the step of acquiring the measurement signal includes the influence of capacitance that correlates with the amount of polishing powder contained in the polishing abrasive liquid in the first state. Obtaining a measurement signal from the sensor, obtaining a measurement signal including an influence of an eddy current generated in the polishing object in the second state from the sensor, and estimating the progress of the polishing, Based on the change in the measurement signal acquired in the first state, it is estimated whether the polishing object has been switched from the first polishing object to the second polishing object, and in the second state. Based on the acquired measurement signal, the progress of polishing of the polishing object can be estimated.

  In addition, according to one aspect of the polishing progress estimation apparatus of the present invention, at least one of a capacitance sensor, a magnetic sensor, and an eddy current sensor, and a polishing object supplied to a polishing pad supplied with a polishing abrasive liquid are used. An acquisition unit for acquiring a measurement signal output from the sensor in a state where the polishing abrasive liquid after polishing the polishing object and the sensor face each other during the pressing and polishing step; And an estimation unit that estimates the progress of polishing of the object to be polished based on the acquired measurement signal.

  According to this aspect of the present invention, it is possible to improve the estimation accuracy of the progress of the polishing process.

FIG. 1 is a diagram schematically illustrating the entire configuration of a polishing apparatus and a polishing progress estimation apparatus. FIG. 2 is a diagram showing a trajectory when the eddy current sensor scans a polishing object. FIG. 3 is a diagram showing the configuration of the eddy current sensor. FIG. 4 is a schematic diagram showing a configuration example of a sensor coil used in the eddy current sensor. FIG. 5 is a schematic diagram showing a detailed configuration of the eddy current sensor. FIG. 6 is a diagram for explaining the reaction of the eddy current sensor as a capacitance sensor. FIG. 7 is a flowchart of the estimation apparatus according to the first embodiment. FIG. 8 is a diagram illustrating a polishing object including a first polishing object and a second polishing object that are stacked. FIG. 9 is a diagram schematically showing measurement signals of the eddy current sensor in the region B outside the object to be polished. FIG. 10 is a flowchart of the estimation apparatus according to the second embodiment. FIG. 11 is a diagram illustrating an outline of processing by the estimation unit. FIG. 12 is a flowchart of the estimation apparatus according to the third embodiment.

  Hereinafter, a polishing progress estimation method and a polishing progress estimation apparatus according to an embodiment of the present invention will be described with reference to the drawings.

<Polishing device>
FIG. 1 is a diagram schematically illustrating the entire configuration of a polishing apparatus and a polishing progress estimation apparatus. First, the polishing apparatus will be described.

  As shown in FIG. 1, a polishing apparatus 100 is a polishing device for polishing an object to be polished (for example, a substrate such as a semiconductor wafer, or various films such as a metal film and a barrier metal formed on the surface of the substrate). A polishing table 110 to which the pad 108 can be attached on the upper surface, a first electric motor 112 that rotates the polishing table 110, a top ring 116 that can hold the object to be polished 102, and a second that rotates the top ring 116. The electric motor 118 is provided.

  The polishing apparatus 100 further includes a slurry line (polishing abrasive liquid supply unit) 120 for supplying an abrasive liquid containing abrasive grains (polishing agent) on the upper surface of the polishing pad 108. Further, the polishing apparatus 100 includes a polishing apparatus control unit 140 that outputs various control signals related to the polishing apparatus 100.

  When polishing the polishing object 102, the polishing apparatus 100 supplies a polishing abrasive liquid containing polishing abrasive grains from the slurry line 120 to the upper surface of the polishing pad 108, and the polishing table 110 is rotationally driven by the first electric motor 112. To do. Then, the polishing apparatus 100 presses the polishing object 102 held by the top ring 116 against the polishing pad 108 in a state where the top ring 116 is rotated around a rotation axis that is eccentric from the rotation axis of the polishing table 110. . As a result, the polishing object 102 is polished and flattened by the polishing pad 108 holding the polishing abrasive liquid.

<Estimation device for polishing progress>
Next, the polishing progress estimation apparatus 200 will be described. As shown in FIG. 1, the estimation apparatus 200 includes an eddy current sensor 210 and a polishing progress state estimation apparatus main body 220 connected to the eddy current sensor 210 via rotary joint connectors 160 and 170. In this embodiment, an example in which the eddy current sensor 210 is used is shown, but the present invention is not limited to this, and a capacitance sensor or a magnetic sensor may be used.

<Eddy current sensor>
First, the eddy current sensor 210 will be described. The polishing table 110 is formed with a hole through which the eddy current sensor 210 can be inserted from the back side of the polishing table 110. The eddy current sensor 210 is inserted into a hole formed in the polishing table 110.

FIG. 2 is a diagram showing a trajectory when the eddy current sensor 210 scans the object to be polished 102 (scanning). As shown in FIG. 2, the eddy current sensor 210 is installed at a position that passes through the center Cw of the object to be polished 102 being held by the top ring 116. Reference symbol _CT denotes the center of rotation of the polishing table 110.

The polishing object 102 rotates about the center Cw. On the other hand, as the polishing table 110 rotates, the eddy current sensor 210 rotates along the locus 212 with the center _CT as an axis. As a result, in the polishing process for polishing the polishing object 102, the eddy current sensor 210 does not pass below the polishing object 102 and the eddy current sensor 210 and the polishing object 102 are not opposed to each other. A region B) outside the polishing object is included. Further, the polishing process includes a second state in which the eddy current sensor 210 and the polishing target object 102 face each other as the eddy current sensor 210 passes below the polishing target object 102 (region A in the polishing target object). It is.

  The first state and the second state appear alternately as the polishing table 110 rotates. In the present embodiment, an example in which the eddy current sensor 210 is installed on the polishing table 110 and the eddy current sensor 210 is rotated is shown, but the present invention is not limited to this. The present embodiment can be applied as long as the polishing process includes the first state and the second state.

In addition, the polishing abrasive liquid is supplied onto the polishing pad 108, receives the centrifugal force due to the rotation of the polishing table 110, moves toward the outside of the polishing pad 108, and rotates with the rotation of the polishing table 110. Accordingly, a polishing object outside the area C of the far especially in the rotational direction of the polishing table 110, which is θdeg rotated around the center C _T exceeds the polishing object region A among polishing object outside region B, abrasive It becomes an area | region where much polishing powder of the grinding | polishing target object 102 is contained in a liquid. θ can be set to 0 deg to 180 deg. Preferably, θ can be 0 deg to 90 deg. More preferably, θ can be 0 deg to 45 deg. In the following description, the state in which the polishing abrasive liquid after polishing the polishing object 102 and the eddy current sensor 210 are opposed to each other is described as the region B outside the polishing object. The region C outside the object can be set.

  FIG. 3 is a diagram showing a configuration of the eddy current sensor 210. 3A is a block diagram showing the configuration of the eddy current sensor 210, and FIG. 3B is an equivalent circuit diagram of the eddy current sensor 210. As shown in FIG.

  As shown in FIG. 3A, the eddy current sensor 210 includes a sensor coil 260 disposed in the vicinity of the polishing object 102 such as a metal film to be detected. An AC signal source 262 is connected to the sensor coil 260. Here, the polishing object 102 to be detected is, for example, a thin film such as Cu, Al, Au, or W formed on a semiconductor wafer. The sensor coil 260 is disposed, for example, in the vicinity of about 0.5 to 5.0 mm with respect to the polishing object 102 to be detected.

The eddy current sensor 210 includes a frequency type that detects a conductive film based on a change in the oscillation frequency of the AC signal source 262 caused by an eddy current generated in the object to be polished 102. Further, the eddy current sensor 210 includes an impedance type that detects a conductive film based on a change in impedance viewed from the AC signal source 262 caused by an eddy current generated in the object to be polished 102. That is, in the frequency type, in the equivalent circuit shown in FIG. 3B, by eddy current I ₂ is changed, the impedance Z is changed, resulting in the oscillation frequency of the AC signal source (variable-frequency oscillator) 262 is changed. The eddy current sensor 210 can detect the change of the oscillation frequency by the detection circuit 264 and detect the change of the conductive film. In the impedance type, in the equivalent circuit shown in FIG. 3B, the impedance Z changes as the eddy current I ₂ changes. As a result, the impedance Z viewed from the AC signal source (fixed frequency oscillator) 262 changes. The eddy current sensor 210 can detect the change of the impedance Z by the detection circuit 264 and detect the change of the conductive film.

  In the impedance type eddy current sensor, signal outputs X, Y, phase, and combined impedance Z are taken out. Measurement information of the conductive film can be obtained from the frequency F or the impedances X and Y. As shown in FIG. 1, the eddy current sensor 210 can be built in a position near the inner surface of the polishing table 110, and is positioned so as to face the polishing object 102 via the polishing pad. Can detect a change in the conductive film from the eddy current flowing in the polishing object 102.

The impedance type eddy current sensor will be specifically described below. The AC signal source 262 is an oscillator having a fixed frequency of about 1 to 50 MHz, and for example, a crystal oscillator is used. The current I ₁ flows through the sensor coil 260 due to the AC voltage supplied from the AC signal source 262. When a current flows through the sensor coil 260 disposed in the vicinity of the polishing object 102, the magnetic flux generated from the sensor coil 260 is linked to the polishing object 102. As a result, a mutual inductance M is formed between the sensor coil 260 and the polishing object 102, and an eddy current I ₂ flows in the polishing object 102. Where R1 is the resistance of the primary side including the sensor coil 260, L ₁ is self inductance of the primary side including the sensor coil 260 as well. In polishing object 102 side, R2 is the resistance corresponding to eddy current loss, L ₂ is the self-inductance of the polishing object 102. Terminal a, the impedance Z viewed sensor coil 260 side from b of the AC signal source 262 is changed under the influence of the magnetic force lines generated by the eddy current I _2.

  FIG. 4 is a schematic diagram showing a configuration example of a sensor coil used in the eddy current sensor. As shown in FIG. 4, the sensor coil 260 of the eddy current sensor includes three coils 272, 273, and 274 wound around a bobbin 270. The coil 272 is an exciting coil connected to the AC signal source 262. The exciting coil 272 is excited by the alternating current supplied from the alternating current signal source 262, and forms an eddy current in the polishing object 102 disposed in the vicinity. A detection coil 273 is disposed on the polishing object 102 side of the bobbin 270 to detect a magnetic field generated due to an eddy current formed on the polishing object 102. A balance coil 274 is disposed on the opposite side of the detection coil 273 across the excitation coil 272.

  The coils 272, 273, and 274 are formed by coils having the same number of turns, and the detection coil 273 and the balance coil 274 are connected in mutually opposite phases. When the polishing object 102 exists in the vicinity of the detection coil 273, magnetic flux generated by eddy current formed in the polishing object 102 is linked to the detection coil 273 and the balance coil 274. At this time, since the detection coil 273 is arranged at a position closer to the conductive film, the balance of the induced voltages generated in the coils 273 and 274 is lost, thereby detecting the interlinkage magnetic flux formed by the eddy current of the conductive film. can do.

  FIG. 5 is a schematic diagram showing a detailed configuration of the eddy current sensor. The AC signal source 262 has an oscillator with a fixed frequency such as a crystal oscillator, and supplies an AC current with a fixed frequency of 1 to 50 MHz to the sensor coil 260, for example. The alternating current formed by the alternating current signal source 262 is supplied to the sensor coil 260 (excitation coil 272) via the band pass filter (BPF) 282. On the other hand, the signal output from the terminals of the sensor coil 260 (the detection coil 273 and the balance coil 274) includes a cos synchronous detection circuit 292 and a sin synchronous detection circuit 293 via a bridge circuit 284 and a high frequency amplifier (RF Amp) 286. The signal is sent to the synchronous detector 291. Further, the signal output from the phase shift 288 is also sent to the synchronous detection unit 291. Then, the resistance component and the inductive reactance component of the impedance are extracted by the synchronous detection unit 291.

  From the resistance component and the inductive reactance component output from the synchronous detection unit 291, unnecessary high-frequency components (for example, high-frequency components of 5 KHz or more) are removed by a low-pass filter (LPF / AF AMP) 294 and 295, and the impedance resistance component And a signal Y as an inductive reactance component are output. The signal X and the signal Y are sent to the estimation apparatus main body 220.

<Estimation of polishing progress>
<First Embodiment>
Next, estimation of the progress of polishing will be described. As illustrated in FIG. 1, the estimation apparatus main body 220 includes an acquisition unit 222 and an estimation unit 224.

  In the estimation of the progress of polishing in the first embodiment, the acquisition unit 222 outputs from the eddy current sensor 210 during the process of pressing the polishing object 102 against the polishing pad 108 supplied with the polishing abrasive liquid and polishing. Measurement signals (signal X and signal Y) to be obtained are acquired. Specifically, the acquisition unit 222 acquires a measurement signal in a state where the polishing abrasive liquid after polishing the object 102 and the eddy current sensor 210 face each other during the polishing process. In other words, the acquisition unit 222 outputs the eddy current sensor 210 from the eddy current sensor 210 in the first state where the eddy current sensor 210 and the object to be polished 102 are not opposed to each other during the polishing process. Get the measurement signal.

  The estimation unit 224 estimates the progress of polishing of the polishing object 102 based on the acquired measurement signal. Specifically, the estimation unit 224 estimates the total polishing amount of the polishing object 102 based on the measurement signal acquired by the acquisition unit 222.

  That is, since the polishing object 102 is shaved by the polishing process, the polishing abrasive liquid after polishing the polishing object 102 includes the shaving powder (polishing powder) of the polishing object 102. Further, the amount of polishing powder contained in the polishing abrasive fluid varies in correlation with the polishing rate of the object 102 to be polished. Here, in the region B outside the polishing object where the eddy current sensor 210 and the polishing object 102 do not face each other, the eddy current sensor 210 reacts as a capacitance sensor.

FIG. 6 is a diagram for explaining the reaction of the eddy current sensor as a capacitance sensor. As shown in FIG. 6, in the region B outside the polishing target object, the polishing target object 102 does not exist on the polishing pad 108 and only the polishing abrasive liquid 111 exists. Here, the facing area between the detection coil 273 and the polishing abrasive liquid 111 is S, and the distance between the detection coil 273 and the upper surface of the polishing abrasive liquid 111 is d. In this case, the capacitance C measured by the eddy current sensor 210 is represented by C = ε × ε ₀ × S / d. ε ₀ is a dielectric constant in a vacuum, and ε is a dielectric constant that varies in correlation with the amount of polishing powder contained in the polishing abrasive liquid 111. Therefore, if ε ₀ , S, and d are constant, the measurement signal when the eddy current sensor 210 reacts as a capacitance sensor varies in correlation with the amount of polishing powder contained in the polishing abrasive liquid 111. To do. Therefore, the eddy current sensor 210 outputs a measurement signal corresponding to the amount of polishing powder contained in the polishing abrasive liquid in the region B outside the polishing object.

  The estimation unit 224 determines the value of the measurement signal (measurement signal output from the eddy current sensor 210 in the region B outside the object to be polished) and the amount of abrasion of the object 102 to be polished by experiments or simulations in advance. And have a correlation. Accordingly, the estimation unit 224 can estimate the polishing rate of the polishing object 102 at that moment based on the measurement signal acquired by the acquisition unit 222. Further, the estimation unit 224 can estimate the total polishing amount up to that point by accumulating the estimated polishing rate in time series.

  The estimation unit 224 is connected to a polishing apparatus control unit 140 that performs various controls relating to the polishing apparatus 100. When the estimation unit 224 detects the polishing end point of the polishing object 102 based on the estimation of the total polishing amount, the estimation unit 224 outputs a signal indicating that to the polishing apparatus control unit 140. When receiving the signal indicating the polishing end point from the estimation unit 224, the polishing apparatus control unit 140 ends the polishing by the polishing apparatus 100.

<Flowchart>
Next, operation | movement of the estimation apparatus 200 of 1st Embodiment is demonstrated. FIG. 7 is a flowchart of the estimation apparatus 200 of the first embodiment.

  First, polishing of the polishing object 102 is started by the polishing apparatus 100 (step S101). Specifically, a polishing abrasive liquid is supplied to the polishing pad 108, and the polishing object 102 is pressed against the polishing pad supplied with the polishing abrasive liquid to be polished. Subsequently, the acquisition unit 222 acquires a measurement signal of the eddy current sensor 210 in the region outside the polishing object B at a timing when the eddy current sensor 210 exists in the region B outside the polishing object (step S102).

  Subsequently, the estimation unit 224 estimates the total polishing amount of the polishing object 102 based on the acquired measurement signal (step S103). Subsequently, the estimation unit 224 determines whether or not it is the polishing end point based on the estimated total polishing amount of the polishing object 102 (step S104).

  If it is determined that it is not the polishing end point (No at Step S104), the estimation unit 224 returns to Step S102 and continues the process. On the other hand, when it is determined that the polishing end point is reached (Yes in step S104), the estimation unit 224 outputs a signal indicating the polishing end point to the polishing apparatus control unit 140, and finishes polishing (step S105).

  As described above, according to the first embodiment, since the total polishing amount is estimated by using the reaction as the capacitance sensor in the region B outside the polishing object, the estimation accuracy of the progress of the polishing process can be improved. it can. In the first embodiment, an example of using a reaction as a capacitance sensor in the region B outside the object to be polished is shown, but the present invention is not limited to this. For example, if the polishing object 102 is a ferromagnetic material (eg, iron, cobalt, nickel, etc.), the total polishing amount can be estimated using a reaction as a magnetic sensor in the region B outside the polishing object. it can. Further, if the polishing object 102 is a substance having a high conductivity, the total polishing amount can be estimated using a reaction as an eddy current sensor in the region B outside the polishing object.

Second Embodiment
Next, a second embodiment will be described. The second embodiment assumes a case where the polishing object 102 includes a stacked first polishing object and second polishing object. In this case, the acquisition unit 222 acquires the measurement signal in the state where the polishing abrasive liquid after polishing the object 102 and the eddy current sensor 210 face each other during the polishing process. In other words, the acquisition unit 222 outputs the eddy current sensor 210 from the eddy current sensor 210 in the first state where the eddy current sensor 210 and the object to be polished 102 are not opposed to each other during the polishing process. Get the measurement signal.

  Based on the measurement signal acquired by the acquisition unit 222, the estimation unit 224 estimates whether the polishing target has been switched from the first polishing target to the second polishing target.

  This point will be described with reference to the drawings. FIG. 8 is a diagram illustrating a polishing object including a first polishing object and a second polishing object that are stacked. FIG. 8A shows the polishing object 102 before polishing, and FIG. 8B shows the polishing object 102 after polishing.

  As shown in FIG. 8A, the polishing object 102 has a laminated structure. Specifically, a barrier metal (second polishing object) 320 is laminated on a silicon substrate 310 on which a plurality of grooves 312 are formed. The barrier metal 320 is made of, for example, titanium (Ti) or tantalum (Ta). A plurality of grooves 322 are formed in the barrier metal 320 corresponding to the grooves 312 of the silicon substrate 310.

  A metal film (first polishing object) 330 is laminated on the barrier metal 320. The metal film 330 is formed of, for example, tungsten (W) or copper (Cu). A portion of the metal film 330 formed in the groove 322 of the barrier metal 320 becomes a metal wiring 332.

  When polishing is performed from the state of FIG. 8A, the metal film 330 is first scraped, and thus the polishing powder contains polishing powder of the metal film 330. On the other hand, as shown in FIG. 8B, when the polishing process proceeds and the metal film 330 is polished while leaving the portion of the metal wiring 332, the barrier metal 320 is exposed. Of abrasive powder.

  Here, in the polishing process of the metal film 330 and the barrier metal 320, an oxidizing agent is mixed with the polishing abrasive liquid. The surfaces of the metal film 330 and the barrier metal 320 are oxidized and hardened by the oxidizing agent, and the hardened parts are mainly scraped off by the polishing process. When the metal film 330 is tungsten, tungsten oxide is generated by an oxidation reaction. Assuming that tungsten trioxide is generated as an example, the relative dielectric constant of tungsten trioxide is 1000 or more. On the other hand, when the barrier metal 320 is titanium or tantalum, titanium oxide or tantalum oxide is generated by an oxidation reaction. For example, the relative dielectric constant of titanium oxide is 83 to 183. For example, assuming that tantalum pentoxide is generated, the relative dielectric constant of tantalum pentoxide is about 27. As described above, when the relative dielectric constants of the first polishing object and the second polishing object are greatly different, the measurement signal of the eddy current sensor 210 in the region B outside the polishing object is as shown in FIG. Become.

  FIG. 9 is a diagram schematically showing measurement signals of the eddy current sensor 210 in the region B outside the polishing object. When the metal film 330 (first object to be polished) is polished, as shown in FIG. 9, the measurement signal 410 changes from the region 420 so that the signal X generally increases and the signal Y decreases.

  On the other hand, when the metal film 330 is polished leaving the portion of the metal wiring 332 and the barrier metal 320 (second polishing target) is exposed, the polishing target is changed from the first polishing target to the second polishing target in the region 430. You can switch to a thing. Then, as shown in a region 440, the output tendency of the measurement signal 410 changes greatly.

  Therefore, the estimation unit 224 can estimate whether or not the polishing target has been switched from the first polishing target to the second polishing target based on the change in the measurement signal. Specifically, the estimation unit 224 determines that the object to be polished has been switched from the first object to be polished to the second object to be polished when the change rate of the measurement signal is equal to or greater than a preset threshold value. Further, the estimation unit 224 determines that the object to be polished is not switched from the first object to be polished to the second object to be polished if the change rate of the measurement signal is less than a preset threshold value.

<Flowchart>
Next, operation | movement of the estimation apparatus 200 of 2nd Embodiment is demonstrated. FIG. 10 is a flowchart of the estimation apparatus 200 of the second embodiment.

First, polishing of the polishing object 102 is started by the polishing apparatus 100 (step S20).
1). Specifically, a polishing abrasive liquid is supplied to the polishing pad 108, and the polishing object 102 is pressed against the polishing pad supplied with the polishing abrasive liquid to be polished. Subsequently, the acquisition unit 222 acquires a measurement signal of the eddy current sensor 210 in the region outside the polishing target B at a timing when the eddy current sensor 210 exists in the region B outside the polishing target (step S202).

  Subsequently, the estimation unit 224 determines whether or not the object to be polished is switched from the first object to be polished (metal film 330) to the second object to be polished (barrier metal 320) based on the change in the acquired measurement signal. Estimate (step S203). Subsequently, when the estimation unit 224 determines that the polishing target has not been switched (No at Step S204), the estimation unit 224 returns to Step S202 and continues the process.

  On the other hand, when the estimation unit 224 determines that the polishing target has been switched (Yes in step S204), the estimation unit 224 outputs a signal indicating that the polishing is finished to the polishing apparatus control unit 140, and ends the polishing (step S205). .

  As described above, according to the second embodiment, it is possible to improve the estimation accuracy of the progress of the polishing process. That is, in the prior art, the electrical resistance of the polishing abrasive liquid is continuously measured, and the point at which the electrical resistance changes drastically is determined as the end point of the polishing process. This utilizes the property that when two layers of the laminated substrate are polished and the layer to be polished is switched, a polishing powder having different conductivity is generated in the polishing abrasive liquid.

  However, according to the prior art, for example, when a layer to be polished is switched, as in the case of polishing a laminated substrate of a material having similar conductivity, polishing powder having different conductivity is generated in the polishing abrasive liquid. In a polishing process that is not performed, it may be difficult to accurately estimate the progress of the polishing process.

  On the other hand, in the present embodiment, when the layer to be polished is switched, the fact that the output tendency of the measurement signal as the capacitance sensor in the region B outside the polishing object of the eddy current sensor 210 changes greatly is used. To do. Therefore, even when a laminated substrate made of a material having similar conductivity is polished, if the output tendency of a measurement signal as a capacitance sensor changes, it can be estimated that the layer to be polished has been switched. As a result, the estimation accuracy of the progress of the polishing process can be improved. In the second embodiment, an example is shown in which a reaction as a capacitance sensor in the region B outside the polishing target is used. However, the present invention is not limited to this. For example, if the polishing object 102 is a laminated substrate made of a material having different magnetism, the switching of the layer to be polished can be estimated using the reaction as the magnetic sensor in the region B outside the polishing object.

<Third Embodiment>
Next, the estimation apparatus 200 of 3rd Embodiment is demonstrated. In the third embodiment, in addition to the second embodiment, the progress of polishing of the polishing object 102 is further estimated using the original reaction of the eddy current sensor 210. Description of the contents similar to those of the second embodiment will be omitted as appropriate.

  In the third embodiment, the acquisition unit 222 generates an eddy current measurement signal that includes an influence of capacitance that correlates with the amount of polishing powder contained in the polishing abrasive liquid in the first state (the region B outside the polishing target). Obtained from the sensor 210. In addition to this, the acquisition unit 222 acquires from the eddy current sensor 210 a measurement signal that includes the effect of eddy current generated in the polishing object in the second state (the polishing object inner region A).

In addition, the estimation unit 224 performs the second polishing object (barrier) from the first polishing object (metal film 330) based on the variation of the measurement signal acquired in the first state (the area B outside the polishing object). It is estimated whether the object to be polished has been switched to the metal 320). In addition to this, the estimation unit 224 estimates the progress of polishing of the polishing object 102 based on the measurement signal acquired in the second state (the area A within the polishing object).

  Specifically, the estimation unit 224 processes the measurement signals (signal X and signal Y) output from the acquisition unit 222 in the polishing object inner region A by a rotation process, a parallel movement process, and the like, and performs a monitoring signal. The distance Z is calculated. Based on the change in the distance Z, the progress of polishing of the polishing object 102 is estimated.

FIG. 11 is a diagram showing an outline of processing by the estimation unit 224. In FIG. 11, the horizontal axis indicates the intensity of the signal X, and the vertical axis indicates the intensity of the signal Y. A point T∞ indicates a state where the film thickness of the polishing object 102 is ∞, and a point T0 indicates a state where the film thickness of the polishing object 102 is 0. As the film thickness of the polishing object 102 decreases, the point Tn positioned from the values of the signals X and Y advances toward the point T0 while drawing an arcuate locus. The distance Z (= (X ² + Y ² ) ^1/2 ) from the origin O to the point Tn in the XY coordinate system becomes smaller as the film thickness is reduced except in the vicinity of the point T∞.

  The estimation unit 224 calculates a distance Z that changes according to the film thickness of the polishing object 102. If the estimation unit 224 knows the relationship between the distance Z and the progress of polishing (for example, the film thickness of the polishing object 102) in advance by experiment or simulation, the estimation unit 224 monitors the distance Z, thereby progressing polishing. The situation can be estimated.

  The estimation unit 224 calculates the distance Z calculated based on the measurement signal acquired in the second state (polishing target region A) or the measurement signal acquired in the first state (polishing target region B). When the polishing end point of the polishing object 102 is detected based on the fluctuation, a signal indicating that is output to the polishing apparatus control unit 140. When receiving the signal indicating the polishing end point from the estimation unit 224, the polishing apparatus control unit 140 ends the polishing by the polishing apparatus 100.

<Flowchart>
Next, operation | movement of the estimation apparatus 200 of 2nd Embodiment is demonstrated. FIG. 12 is a flowchart of the estimation apparatus 200 of the third embodiment.

  First, polishing of the polishing object 102 is started by the polishing apparatus 100 (step S301). Specifically, a polishing abrasive liquid is supplied to the polishing pad 108, and the polishing object 102 is pressed against the polishing pad supplied with the polishing abrasive liquid to be polished. Subsequently, the acquisition unit 222 acquires a measurement signal of the eddy current sensor 210 in the polishing target outside region B at a timing when the eddy current sensor 210 exists in the polishing target outside region B (step S302).

  Subsequently, the estimation unit 224 determines whether or not the object to be polished is switched from the first object to be polished (metal film 330) to the second object to be polished (barrier metal 320) based on the change in the acquired measurement signal. Estimate (step S303). Subsequently, when the estimation unit 224 determines that the object to be polished has not been switched (step S304, No), the process proceeds to step S305.

  Subsequently, the estimation unit 224 acquires a measurement signal of the eddy current sensor 210 in the polishing object inner area A at a timing when the eddy current sensor 210 exists in the polishing object inner area A (step S305).

Subsequently, the estimation unit 224 estimates the film thickness of the polishing object 102 based on the acquired measurement signal (step S306). Subsequently, the estimation unit 224 determines whether or not the polishing object 102 has a desired film thickness (step S307).

  If the estimation unit 224 determines that the object to be polished 102 does not have a desired film thickness (No at Step S307), the estimation unit 224 returns to Step S302 and continues the process. On the other hand, when the estimation unit 224 determines that the polishing target object 102 does not have a desired film thickness (step S307, Yes), or when it is determined that the polishing target is switched in step S304 (step S304, Yes), a signal indicating that it is the polishing end point is output to the polishing apparatus control unit 140, and the polishing is terminated (step S308).

  As described above, according to the third embodiment, similarly to the second embodiment, it is possible to improve the estimation accuracy of the progress of the polishing process. In addition to this, in this embodiment, while estimating the film thickness of the polishing object 102 based on the measurement signal acquired in the region A within the polishing object, based on the measurement signal acquired in the region B outside the polishing object. Estimate whether or not the object to be polished has been switched. Therefore, according to the present embodiment, the progress of the polishing process is estimated by using one eddy current sensor 210 to estimate the progress of the polishing process using the reaction as the eddy current sensor and the reaction as the capacitance sensor. The situation estimation accuracy can be improved.

DESCRIPTION OF SYMBOLS 100 Polishing apparatus 102 Polishing object 108 Polishing pad 110 Polishing table 111 Polishing abrasive liquid 140 Polishing apparatus control part 200 Estimating apparatus 210 Eddy current sensor 220 Estimating apparatus main body 222 Acquisition part 224 Estimating part 310 Silicon substrate 320 Barrier metal 330 Metal film 332 Metal Wiring 410 Measurement signal A Area within polishing object B Area outside polishing object C Area outside polishing object

Claims (6)

A polishing abrasive liquid is supplied to a polishing pad for polishing an object to be polished,
Polishing by pressing a polishing object against a polishing pad supplied with the polishing abrasive liquid,
In the state where the polishing abrasive liquid after polishing the polishing object and at least one of a capacitance sensor, a magnetic sensor, and an eddy current sensor face each other, a measurement signal output from the sensor Acquired,
Estimating the progress of polishing of the object to be polished based on the acquired measurement signal,
A method of estimating the progress of polishing. In the method of estimating the polishing progress of claim 1,
In the step of supplying the polishing abrasive liquid and the step of polishing the object to be polished, the polishing abrasive liquid is supplied to the polishing pad while rotating the polishing table to which the polishing pad is attached, and the polishing abrasive liquid is supplied. Polishing the polishing object by pressing the polishing object against the polished pad,
The sensor is installed on the polishing table,
With the rotation of the polishing table, a first state where the polishing object and the sensor do not face each other and a second state where the polishing object and the sensor face each other appear alternately,
The step of acquiring the measurement signal acquires the measurement signal output from the sensor in the first state.
A method of estimating the progress of polishing. In the method for estimating the polishing progress of claim 1 or 2,
The step of estimating the progress of the polishing is based on the acquired measurement signal to estimate the total polishing amount of the object to be polished.
A method of estimating the progress of polishing. In the method for estimating the polishing progress of claim 1 or 2,
In the case where the polishing object includes the stacked first polishing object and second polishing object, the step of estimating the progress of the polishing is based on the change in the acquired measurement signal. Estimating whether the polishing object has been switched from the first polishing object to the second polishing object;
A method of estimating the progress of polishing. In the method for estimating the polishing progress of claim 4,
The step of acquiring the measurement signal acquires from the sensor a measurement signal that includes an influence of capacitance that correlates with the amount of polishing powder included in the polishing abrasive liquid in the first state, and the second state. A measurement signal including an influence of an eddy current generated in the polishing object in the state is acquired from the sensor,
In the step of estimating the progress of the polishing, whether or not the polishing object has been switched from the first polishing object to the second polishing object based on a change in the measurement signal acquired in the first state. And estimating the progress of polishing of the polishing object based on the measurement signal acquired in the second state,
A method of estimating the progress of polishing. At least one of a capacitance sensor, a magnetic sensor, and an eddy current sensor;
In the state of pressing the polishing object against the polishing pad supplied with the polishing abrasive liquid and polishing the polishing object, the polishing abrasive liquid after polishing the polishing object and the sensor face each other. An acquisition unit for acquiring a measurement signal output from the sensor;
An estimation unit that estimates the progress of polishing of the object to be polished based on the acquired measurement signal;
An apparatus for estimating the progress of polishing.