JP2005347530A - Polishing pad adjustment method and chemical mechanical polishing equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable quantitative measurement of quality of dressing status of a polishing pad and improve dressing movement. <P>SOLUTION: This chemical mechanical polishing equipment is provided with a transparent platen 1 in which a transparent polishing pad 5 is arranged on a surface, a wafer holding mechanism 8 which is rotated while holding a wafer 7 so that the wafer 7 may be pushed against the rotating polishing pad, a slurry feeding mechanism 21 which feeds slurry 22 to the surface of the polishing pad 5, and a dressing mechanism 9 which performs dressing of the surface of the polishing pad 5. In a polishing pad adjustment method which adjusts status of the polishing pad 5 by using the chemical mechanical polishing equipment, dressing of the surface of the polishing pad is performed by supplying slurry by the slurry feeding mechanism. Raman spectrum of the surface of the polishing pad is measured through the platen and the polishing pad, and dressing treatment is controlled based on measurements of measured Raman spectrum. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for adjusting a polishing pad and a CMP apparatus used in a chemical mechanical polishing (CMP) apparatus for performing chemical mechanical polishing (CMP) on a surface of a layer formed on a wafer in a semiconductor manufacturing process.

  In recent years, in a semiconductor manufacturing process, chemical mechanical polishing (CMP) is performed on the surface of a wafer in the middle of a process using a CMP apparatus, which is described in Patent Document 1 and the like. First, a schematic configuration of a conventional CMP apparatus will be briefly described.

  FIG. 1 is a diagram showing a schematic configuration of a conventional CMP apparatus. As shown in FIG. 1, in the CMP apparatus, the platen 1 to which the polishing pad 5 is attached is rotated once and the wafer 7 held by the wafer holding mechanism 8 is supplied while supplying the slurry 22 from the slurry supplier 21 onto the polishing pad. Polishing is performed by pressing the polishing pad 5 while rotating.

  The polishing pad 5 has a structure in which an upper layer made of polyurethane and a lower layer made of polyurethane foam are bonded together, and the surface is generally provided with a groove for facilitating the supply of slurry to the polishing surface. . The polishing pad 5 is relatively smooth, and if it is used as it is, polishing cannot be performed even if slurry is supplied. Therefore, after being affixed to the platen 1, a process called dressing is performed on the polishing pad 5 using the dresser 9. The dresser 9 has a grindstone in which diamond abrasive grains are dispersed in nickel, and forms fine irregularities on the surface of the polishing pad 5 by pressing against the surface of the polishing pad 5 while rotating the grindstone surface. Further, even with the polishing pad 5 subjected to dressing, clogging occurs due to the slurry during polishing, and polishing cannot be performed. Therefore, it is necessary to perform dressing as needed during polishing. This dressing may be performed while polishing is interrupted or during polishing.

Japanese Patent Laid-Open No. 7-235520

  The quality of the dressing state of the polishing pad is considered to greatly influence not only the physical state such as the surface roughness but also the degree of impregnation of the slurry on the surface of the polishing pad. However, there has been no index for quantifying the quality of the dressing state of the polishing pad. Therefore, in the conventional dressing operation, the dummy wafer is polished while supplying the slurry, and the operator performs control while confirming the polishing result of the dummy wafer.

  However, the polishing result is affected not only by the dressing state (surface state) of the polishing pad, but also by various factors such as the pressing pressure and distribution of the wafer, the supply amount of slurry and the uniformity thereof. Therefore, it is difficult to determine whether the dressing state of the polishing pad is good or not and to accurately determine whether the dressing operation is stopped or re-executed.

  In dressing, the surface of the polishing pad is worn to polish. Therefore, excessive dressing unnecessarily consumes the polishing pad, which not only shortens the life of the polishing pad, but also increases the number of replacements of the polishing pad, thereby increasing the manufacturing cost. Conversely, insufficient dressing reduces the polishing rate, which causes a problem of reducing the throughput of the CMP apparatus.

  In view of such a problem, an object of the present invention is to quantitatively measure the quality of a dressing state of a polishing pad and to improve a dressing operation thereby.

  In order to achieve the above object, a polishing pad adjusting method for adjusting the state of a polishing pad in a chemical mechanical polishing apparatus of the present invention uses a transparent platen and a polishing pad, and the surface of the polishing pad is passed through the transparent platen and the polishing pad. It is characterized by measuring Raman spectroscopy and controlling dressing based on the measurement result of Raman spectroscopy.

  That is, the polishing pad adjusting method for adjusting the state of the polishing pad in the chemical mechanical polishing apparatus of the present invention includes a transparent platen provided with a transparent polishing pad on the surface, and a wafer on the polishing pad while rotating the platen. A chemical mechanical polishing apparatus comprising: a wafer holding mechanism that rotates while being held so as to press; a slurry supply mechanism that supplies slurry to the surface of the polishing pad; and a dressing mechanism that dresses the surface of the polishing pad. A polishing pad adjustment method for adjusting the state of the polishing pad, wherein the slurry is supplied by the slurry supply mechanism, the dressing mechanism is used to dress the surface of the polishing pad, and the polishing pad is passed through the platen and the polishing pad. Measure the surface Raman spectroscopy and use the Raman spectroscopy device And controlling the dressing on the basis of the measurement result of the constant Raman spectroscopy.

  When the Raman spectrum of the surface of the polishing pad 5 is measured from the surface of the polishing pad, it cannot be measured accurately because slurry and water are present on the surface of the polishing pad. Therefore, in the present invention, the platen and the polishing pad are made transparent, and the Raman spectrum of the surface of the polishing pad is measured through the platen and the polishing pad.

  According to the present invention, it is possible to quantitatively determine the quality of the dressing state of the polishing pad, which has been impossible until now. As a result, the quality of dressing work that has been performed by the experience of operators so far has been improved, and the deterioration of polishing characteristics due to the lack of useless dressing and dressing is reduced, and the throughput of CMP work is improved. Cost can be reduced.

  FIG. 2 is a diagram showing a schematic configuration of the CMP apparatus according to the embodiment of the present invention. The CMP apparatus of the embodiment is different from the conventional CMP apparatus in that a transparent platen 1 and a polishing pad 5 are used and a Raman spectroscopic device 11 is provided on the lower side of the platen 1. Therefore, although not shown, a slurry supplier 21 is also provided, and slurry is supplied from the slurry supplier 21 onto the polishing pad 5 during polishing and during dressing of the polishing pad. The platen 1 is made of acrylic or glass, and is entirely transparent. However, the platen 1 does not have to be transparent at all. For example, even in a structure in which a disk-shaped acrylic plate or glass plate is placed on a structure composed of metal beams, a hole is provided in the metal plate. A structure incorporating a transparent member may be used. The polishing pad 5 is made of polyurethane and is entirely transparent. The measurement may be performed with the platen rotated or with the platen stopped. When there is a beam as described above, when measuring with the platen rotated, the beam part cannot be measured, so the data of that part is not used and measurement is performed with the platen stopped. When this is done, opaque parts such as metal beams are not positioned in the Raman spectroscopic device 11. In any case, the measurement is performed in association with the rotational position of the platen, and the change with time is measured by measuring the same portion of the polishing pad.

  Since the Raman spectroscopic device 11 is known, detailed description of the Raman spectroscopic device itself is omitted here.

  As a result of the research, the quality of the dressing state of the polishing pad 5 is related to the slurry impregnation state of the surface of the polishing pad 5, and the slurry impregnation state of the surface of the polishing pad 5 is measured by Raman spectroscopy of the surface of the polishing pad 5. It became clear that it was measurable by doing. When the Raman spectrum of the surface of the polishing pad 5 is measured from the surface of the polishing pad 5, since the slurry or water is present on the surface of the polishing pad 5, it cannot be measured accurately. Therefore, in the present invention, the platen 1 and the polishing pad 5 are made transparent, and the Raman spectrum of the surface of the polishing pad 5 is measured through the platen 1 and the polishing pad 5.

  The surface of the polishing pad is not modified just by immersing a polishing pad that is not dressed in water, and the surface of the polishing pad is modified by performing dressing while supplying the slurry, and is in a state suitable for polishing. Furthermore, it has been found that it is desirable to polish the dummy wafer in parallel when dressing the surface of the polishing pad. When the surface of the polishing pad is modified, water is adsorbed on the polishing pad molecules. Raman scattering is very insensitive to water and cannot be measured, but water adsorbed on the polishing pad molecules can be measured and the amount adsorbed can be detected.

FIG. 3 is a diagram showing the measurement results of Raman spectroscopy of a polishing pad that has been dressed and is in a state suitable for polishing, and a polishing pad that has not been dressed. The graph of FIG. 3 is a result of measuring the spectral characteristics of Raman scattering by irradiating a laser having a wavelength of 532 nm, and shows a change in the wave number range from 3000 cm ⁻¹ to 3000 cm ⁻¹ . A polishing pad that has been dressed and is in a state suitable for polishing has an increased peak value in the vicinity of a wave number of 3370 cm -1 compared to a polishing pad that has not been dressed. For example, the quality of the dressing state of the polishing pad can be determined. Therefore, the quality of the dressing state can be determined based on whether the measured value of Raman spectroscopy at a predetermined wave number (near 3370 cm −1) is equal to or greater than a predetermined threshold.

  The Raman spectroscopic device 11 has a confocal microscope, and can measure Raman spectroscopy by changing the focal position of the laser beam to be irradiated. Using this function, when the Raman spectrum was measured by changing the focal position of the laser beam to be irradiated along the depth direction of the polishing pad, the surface of the polishing pad was reduced to a depth of about 5 μm from the surface by dressing. It was found that it was modified and no further depth was modified.

  Since the measurement of Raman spectroscopy varies depending on various factors such as individual differences of the polishing pad, the determination must be performed without the influence of these factors. As described above, since the surface of the polishing pad is modified to a depth of about 5 μm from the surface, and the depth portion beyond that is not modified, the Raman spectroscopy of the depth portion of 5 μm or more from the surface of the polishing pad is the same. Should be a value. Therefore, the determination accuracy can be improved if the determination is made after calibrating the value of the portion having a depth of 5 μm or more as the reference value.

  Furthermore, since dressing is not performed uniformly over the entire surface of the polishing pad and there is unevenness, the Raman spectroscopic measurement captures changes over time at different locations on the polishing pad. Then, the quality of the dressing state is determined by statistically processing the measurement results of a plurality of surface positions. For example, the determination is made by using an average value of all measurement points or making all the measurement values fall within a predetermined range.

  As described above, the quality of the dressing state of the polishing pad 5 can be determined by measuring the Raman spectrum of the surface of the polishing pad 5.

  If a new polishing pad is used, dressing is always performed. In this case, dressing was performed while measuring the Raman spectrum of the surface of the polishing pad 5, and the change in the measurement result at the above wave number (near 3370 cm −1) from the start of dressing was constantly monitored, and was above the upper threshold. Sometimes the dressing is finished and the polishing of the wafer is started.

  Since the dressing state deteriorates as the wafer is polished, the change in the Raman spectroscopic measurement result is constantly monitored, and when the measurement result at the wave number (near 3370 cm −1) exceeds the upper threshold, the dressing is stopped.

  It is also possible to measure Raman spectroscopy every time polishing of one or a plurality of wafers is completed without constantly monitoring changes in the measurement results of Raman spectroscopy during polishing.

  The present invention can be applied to the entire manufacture of semiconductor devices involving CMP processing, and the manufacturing cost can be reduced as the quality and throughput are improved.

It is a figure which shows schematic structure of the prior art example of CMP apparatus. It is a figure which shows schematic structure of the CMP apparatus of the Example of this invention. It is a figure which shows the measurement result in a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Platen 5 ... Polishing pad 7 ... Wafer 8 ... Wafer holding mechanism 9 ... Dresser 11 ... Raman spectroscopy apparatus

Claims (7)

A transparent platen provided with a transparent polishing pad on the surface;
A wafer holding mechanism that rotates while holding the wafer against the polishing pad while rotating the platen;
A slurry supply mechanism for supplying slurry to the surface of the polishing pad;
A chemical mechanical polishing apparatus comprising a dressing mechanism for dressing the surface of the polishing pad, a polishing pad adjusting method for adjusting the state of the polishing pad,
While supplying the slurry by the slurry supply mechanism, dressing the surface of the polishing pad by the dressing mechanism,
Measure the Raman spectrum of the surface of the polishing pad through the platen and the polishing pad,
A polishing pad adjustment method, wherein the dressing process is controlled based on a measurement result of the measured Raman spectroscopy.   The polishing pad adjusting method according to claim 1, wherein when the surface of the polishing pad is dressed, the polishing of the dummy wafer is performed in parallel.   The polishing pad adjustment method according to claim 1 or 2, wherein the dressing control is performed by determining whether a value at a predetermined wave number of measured Raman spectroscopy is equal to or greater than a predetermined threshold value. The measurement of the Raman spectroscopy is performed by changing the focal position of the laser beam to be irradiated along the depth direction of the polishing pad,
4. The polishing pad adjustment method according to claim 1, wherein the dressing control uses a measurement value of a stable portion inside the polishing pad as a reference value. 5. The measurement of the Raman spectroscopy is performed at a plurality of positions by changing the surface position of the polishing pad,
5. The polishing pad adjustment method according to claim 1, wherein the dressing is controlled by statistically processing the measurement results of a plurality of surface positions. A transparent platen provided with a transparent polishing pad on the surface;
A wafer holding mechanism that rotates while holding the wafer against the polishing pad while rotating the platen;
A slurry supply mechanism for supplying slurry to the surface of the polishing pad;
A dressing mechanism for dressing the surface of the polishing pad;
A chemical mechanical polishing apparatus comprising: a Raman spectroscopic device that measures Raman spectroscopy of the surface of the polishing pad through the platen and the polishing pad.   The chemical mechanical polishing apparatus according to claim 6, wherein the Raman spectroscopic apparatus has a confocal microscope system and is capable of changing a focal position of a laser beam to be irradiated along a depth direction of the polishing pad.

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