JP2005311246A - Chemical mechanical polishing apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a CMP apparatus and a method, whereby the temperature distribution of the surface of a wafer present in the process of polishing can be measured. <P>SOLUTION: In the CMP apparatus, for polishing a wafer 7, which has a polishing pad 35 provided on its surface, a rotating platen 31, and a rotational wafer holding mechanism 8 for holding the wafer 7 by pressing the wafer 7 to the polishing pad, the platen 31 and the polishing pad 35 are transparent; and there is provided a thermography device 41 for measuring the temperature distribution of the whole of the wafer 7 in the process of polishing, through the platen 31 and the polishing pad 35. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a chemical mechanical polishing (CMP) apparatus and a chemical mechanical polishing (CMP) method for performing chemical mechanical polishing (CMP) on a surface of a previously formed layer 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 the figure, the platen 1 with the polishing pad 5 attached thereto is rotated to supply the slurry (polishing liquid containing polishing particles) 6 onto the polishing pad 5 while the wafer 7 held by the wafer holding mechanism 8 is held. By pressing against the polishing pad 5 while rotating, the insulating film or metal film layer formed on the surface of the wafer is polished. In the chemical mechanical polishing, the surface of the wafer is mechanically scraped, and at the same time, the polishing liquid chemically reacts with the surface of the wafer to perform polishing. Therefore, the wafer surface generates heat mechanically or with chemical reaction as it is polished. The progress of polishing may be affected by the temperature rise of the wafer surface due to this heat generation.

  The important point that needs to be controlled by the CMP apparatus is to accurately detect the polishing amount and stop polishing. This is called end point detection. The end point detection method detects the change in film thickness of the film to be polished on the wafer surface by irradiating the surface of the wafer being polished with a light beam and measuring the spectral characteristics of the reflected light and interference of the reflected light. Various methods have been proposed, such as a method for determining the rotation load of the platen and the wafer holding mechanism. Regardless of which end point detection method is used, as described above, the temperature of the wafer surface affects the progress of polishing, so it is necessary to detect and manage the temperature during polishing.

  The progress of the polishing changes according to changes in the pressure or the like that presses the wafer against the polishing pad, and similarly changes as the temperature of the wafer surface changes. How it changes depends on various factors such as the material of the film to be polished and the slurry, but in general, the higher the pressure, the faster the polishing progress, and the higher the temperature, the faster the polishing progress. Become. Here, it is assumed that the polishing progresses faster when the temperature is higher, but the present invention is not limited to this.

  If the progress of the polishing is made faster, even a small error in end point detection will cause a large amount of polishing during that time, which will be a serious problem. On the other hand, if the progress of the polishing is slowed, even if there is an error in the end point detection, the amount of polishing in the meantime is small, so there is no big problem. However, this has a problem that the throughput of the CMP apparatus is low. Therefore, at present, various conditions of the CMP process are set in consideration of the accuracy and throughput of end point detection.

  Therefore, the accuracy of the end point detection is improved by measuring and managing the temperature of the wafer being polished or the temperature corresponding thereto. For example, it has been proposed to provide a thermistor in each part of a wafer holding mechanism for holding a wafer to predict and manage the temperature of the wafer being polished. However, since this method does not measure the temperature of the wafer itself, there is a problem that the temperature of the wafer cannot be detected with sufficient accuracy.

  Patent Document 1 describes a configuration for measuring the temperature of the back surface of a wafer being polished. FIG. 2 is a diagram showing a schematic configuration of the CMP apparatus described in Patent Document 1. In FIG. As shown in the figure, the platen 1 with the polishing pad 5 attached is rotated, and the wafer holding plate 11 holding the wafer 7 is placed on the polishing pad 5 and rotated while being pressed. Wafer holding plate 11 is rotated by a rotation drive mechanism provided in fixed housing 13. A hole is provided in the center of the wafer holding plate 11, and a transparent plate is provided in the hole. The central portion of the housing 13 is also hollow, and the temperature of the back surface of the wafer 7 being polished can be measured by an infrared radiation thermometer 14 provided on the top of the housing 13. Since the wafer 7 is a thin plate, the back surface and the front surface are considered to have substantially the same temperature, and a temperature corresponding to the surface temperature of the wafer being polished can be measured. Therefore, in the CMP apparatus of Patent Document 1, the temperature of the wafer being polished can be measured with high accuracy, so that the accuracy of end point detection can be improved. Accordingly, the present invention can be applied to various measures for improving the throughput of the CMP process, such as increasing the polishing rate.

JP 2002-301660 A JP-A-7-52032

  A plurality of layers of films are formed on a wafer according to a plurality of semiconductor circuit patterns, and the temperature distribution due to polishing of the wafer surface is complicated. In addition, there is a partial pressing pressure difference due to the height difference of the polishing pad, and the wafer pressing pressure distribution also depends on the distribution of the upper slurry flow rate, which depends on the pattern. The entire surface of the wafer is not at the same temperature but has a complicated temperature distribution.

  The CMP apparatus described in Patent Document 1 cannot measure the temperature distribution on the entire surface of the wafer only by measuring the temperature at the center of the wafer being polished. For this reason, it is not sufficient to perform various controls by measuring only the temperature at the center of the wafer, and there is a problem that the accuracy of end point detection cannot be improved sufficiently.

  An object of the present invention is to realize a CMP apparatus and method capable of measuring the temperature distribution on the entire surface of a wafer being polished in the CMP process with high accuracy.

  In order to achieve the above object, the chemical mechanical polishing apparatus and method of the present invention are characterized in that the temperature distribution of the entire wafer being polished is measured with a thermography apparatus through a transparent platen and polishing pad.

  That is, the chemical mechanical polishing apparatus of the present invention has a polishing pad on the surface, and includes a rotating platen, and a wafer holding mechanism that rotates while holding the wafer against the polishing pad, and polishes the wafer. In the chemical mechanical polishing apparatus, the platen and the polishing pad are transparent, and a thermography apparatus is provided for measuring a temperature distribution of the entire wafer being polished through the platen and the polishing pad.

  The chemical mechanical polishing method of the present invention is a chemical mechanical polishing method in which a polishing pad provided on the surface of a rotating platen is pressed against the polishing pad while rotating the wafer held by a wafer holding mechanism and polished. The platen and the polishing pad are transparent, and the temperature distribution of the entire wafer during polishing is measured through the platen and the polishing pad.

  The transparent platen is made of, for example, quartz glass. The transparent polishing pad is made of polyurethane, for example.

  According to the present invention, since the temperature distribution of the entire wafer being polished can be detected, the accuracy of various controls can be improved and the accuracy of quality control can be improved.

  For example, as described above, the progress of polishing differs depending on the temperature of the wafer surface. For this reason, if the temperature of the wafer is partially different, the progress of polishing in each portion will be different. Patent Document 2 describes a method of measuring the film thickness of a portion of the surface of a wafer being polished. For example, if the place where the film thickness is measured is higher in temperature than the other part, when the polishing is finished based on the film thickness of that part, the other part is insufficiently polished. On the contrary, if the temperature of the place where the film thickness is measured is lower than that of the other part, when the polishing is finished based on the film thickness of the part, the other part is overpolished. By measuring the temperature distribution of the wafer according to the present invention and determining the end of polishing in consideration of the temperature at which the film thickness is measured compared to other parts, the polishing amount can be further increased. It can be controlled with high accuracy.

  Further, the entire surface of the wafer needs to be polished in the same manner, and there is an allowable range for the difference in the partial polishing amount. When this allowable range is exceeded, some dies (chips) of the wafer become defective. As described above, when the temperature of the wafer is partially different, a difference occurs in the polishing amount in each part, but this difference is required to fall within an allowable range. Therefore, according to the present invention, the temperature distribution of the wafer being polished is measured, the relationship between the temperature distribution and the difference between the actual polishing amounts is examined in advance, and the critical temperature difference corresponding to the allowable range of the polishing amount is stored. According to the present invention, the temperature distribution of the wafer being polished is measured, and when the temperature difference within the wafer exceeds the limit temperature difference, it is possible to perform control such as slowing the polishing rate.

  FIG. 3 is a diagram showing a schematic configuration of the CMP apparatus according to the embodiment of the present invention. In the CMP apparatus of the embodiment, the entire surface of the polishing pad 35 made of polyurethane is pasted, and the entire quartz glass platen 31 is rotated to supply a slurry onto the polishing pad 35, while holding a wafer holding mechanism thereon. The wafer 7 held at 8 is pressed while being rotated. The platen 31 does not have to be transparent at all. For example, the platen 31 may have a structure in which a disk-shaped transparent plate such as quartz glass or transparent resin is placed on a metal structure composed of beams (ribs). . In this case, if a metal beam portion enters the imaging range, that portion cannot be imaged, but there is no particular problem if the preceding and following temperature distribution images are combined.

  A thermography device 41 is provided below the platen 31 and measures the temperature distribution of the entire wafer 7 being polished in real time.

  The wafer holding mechanism 8 chucks and transports the wafer 7 by vacuum suction when transporting the wafer 7 onto the polishing pad, but releases the vacuum suction during polishing and has a guide having an inner diameter slightly larger than the diameter of the wafer 7. The ring prevents the wafer 7 from jumping out of the holding mechanism 8 during polishing. During the polishing, the wafer holding mechanism 8 may be rotated while chucking the wafer 7 by vacuum suction. During polishing, the holding mechanism 8 presses the wafer 7 against the polishing pad 35 with a predetermined pressure.

  Since the slurry causes clogging of the polishing pad 35, the surface of the polishing pad 35 is periodically dressed by a dresser (not shown).

  The temperature image signal from the thermography device 41 is sent to the image processing device 42, and the image processing device 42 performs the following processing. As described above, the wafer 7 rotates. Therefore, the image of the temperature distribution of the wafer rotates with the wafer, and in order to accurately measure the temperature distribution of the wafer, the rotation of the wafer is detected and the change according to the rotation position of the temperature distribution image is tracked. There is a need.

  The wafer 7 is provided with an orientation flat (OF) 21 as shown in FIG. 4A or a notch 22 as shown in FIG. 34B in order to show the crystal direction of the wafer. . If the positions of the OF 21 and the notch 22 are detected, the rotational position of the wafer 7 can be detected. Therefore, the image processing device 42 detects the positions of the OF 21 and the notch 22 and synthesizes the temperature distribution image in consideration of the rotational position.

  The image processing device 42 sends temperature distribution information regarding the wafer 7, the platen 31, and the polishing pad 35 to the control device 43. The control device 43 performs various controls based on the sent temperature distribution information. This temperature distribution information can be applied in various ways.

  For example, the progress of polishing differs depending on the temperature of the wafer. For this reason, if the temperature of the wafer is partially different, the progress of polishing in each portion will be different. As described above, it is very important to accurately detect the end point in the CMP apparatus. For example, a method of measuring the film thickness of a portion of the surface of the wafer being polished as described in Patent Document 2 When the end point detection is performed by using, if the temperature of the surface part of the wafer whose thickness is being measured is higher than the other part, polishing is completed based on the information on the film thickness thus measured. Then, the other portions are insufficiently polished. On the contrary, if the temperature of the part where the film thickness is measured is lower than that of the other part, the other part is overpolished.

  In the CMP apparatus of the present embodiment, the temperature distribution of the wafer 7 can be measured. Therefore, when the temperature of the portion where the film thickness is measured is higher than that of the other portions, the end of the polishing is delayed accordingly, and the film thickness When the temperature of the portion measuring the temperature is lower than that of the other portions, control is performed so that the end of polishing is accelerated accordingly.

  Further, the relationship between the temperature distribution of the wafer and the difference between the actual polishing amounts is examined in advance, and the critical temperature difference in one wafer corresponding to the allowable range of the polishing amount is determined and stored. Then, the temperature distribution of the wafer being polished is measured, and when the temperature difference within the wafer exceeds the limit temperature difference, the pressure for pressing the wafer 7 against the polishing pad 35 is reduced to control the polishing rate to be slow. To do. In general, when the polishing rate is slowed, the temperature difference in one wafer decreases, thereby reducing the temperature difference in the wafer.

  Further, in the case of a CMP apparatus in which the polishing pressure can be partially changed, it is possible to change the corresponding portion of the polishing pressure so that uniform polishing is performed according to the measured temperature distribution of the wafer.

  Conventionally, since the temperature difference in the wafer could not be measured, the polishing rate was set so as not to cause the difference in the polishing amount in the wafer as described above. In other words, the polishing rate is set sufficiently low to reduce the temperature difference in one wafer so as not to cause a difference in the polishing amount in the wafer. Therefore, sufficient throughput has not been obtained. On the other hand, in this embodiment, the polishing rate can be increased until immediately before the temperature difference in the wafer exceeds the limit temperature difference, so that the throughput is improved.

  As mentioned above, although the Example of this invention was described, calibration is important in order to improve the temperature detection accuracy by a thermography apparatus. Since the wafer surface temperature is considered to be uniform in the state before starting polishing when the wafer is set in the polishing state, it is detected during polishing based on the temperature distribution of the wafer surface in this state detected by the thermography device. If the temperature distribution change is calibrated, the detection accuracy can be improved.

  According to the present invention, since the temperature distribution on the surface of the wafer being polished can be measured, the accuracy of various controls can be improved and the quality control system can be improved. As a result, the throughput and yield of the CMP apparatus and method can be improved, and as a result, costs in the semiconductor manufacturing process can be reduced.

It is a figure which shows the basic composition of CMP apparatus. It is a figure which shows the structure of the CMP apparatus of the prior art example which enabled the measurement of the temperature of the wafer in grinding | polishing. 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 orientation flat and notch of a wafer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 31 ... Platen 5, 35 ... Polishing pad 7 ... Wafer 8 ... Wafer holding mechanism 41 ... Thermography apparatus 42 ... Image processing apparatus 43 ... Control apparatus

Claims (2)

A rotating platen having a polishing pad on the surface;
A chemical mechanical polishing apparatus comprising a wafer holding mechanism that rotates while holding the wafer so as to press against the polishing pad, and polishing the wafer;
The platen and the polishing pad are transparent,
A chemical mechanical polishing apparatus comprising: a thermography device that measures a temperature distribution of the entire wafer being polished through the platen and the polishing pad. In the chemical mechanical polishing method for polishing by pressing the wafer held by the wafer holding mechanism against the polishing pad provided on the surface of the rotating platen while pressing the polishing pad against the polishing pad,
The platen and the polishing pad are transparent,
A chemical mechanical polishing method comprising measuring a temperature distribution of the entire wafer being polished through the platen and the polishing pad.

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