Patent Application
20180222007
This document claims priorities to Japanese Application Number 2011-158080, filed Jul. 19, 2011 and Japanese Application Number 2011-245482, filed Nov. 9, 2011, the entire contents of which are hereby incorporated by reference.
The present invention relates to a polishing apparatus and method for polishing a surface of a substrate such as a semiconductor wafer by relative movement between the surface of the substrate to be polished and a polishing pad on a polishing table while the substrate is pressed against the polishing pad, and more particularly to a polishing apparatus and method which can control a temperature of the surface (polishing surface) of the polishing pad by blowing a gas on the polishing pad.
In recent years, high integration and high density in semiconductor device demands smaller and smaller wiring patterns or interconnections and al so more and more interconnection layers. Multilayer interconnections in smaller circuits result in greater steps which reflect surface irregularities on lower interconnection layers. An increase in the number of interconnection layers makes film coating performance (step coverage) poor over stepped configurations of thin films. Therefore, better multilayer interconnections need to have the improved step coverage and proper surface planarization. Further, since the depth of focus of a photolithographic optical system is smaller with miniaturization of a photolithographic process, a surface of the semiconductor device needs to be planarized such that irregular steps on the surface of the semiconductor device will fall within the depth of focus.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). Thus, there has been employed a chemical mechanical polishing apparatus for planarizing a surface of a semiconductor wafer. In the chemical mechanical polishing apparatus, while a polishing liquid containing abrasive particles such as silica (SiO2) or ceria (CeO2) therein is supplied onto a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing pad, so that the substrate is polished.
A polishing apparatus for performing the above CMP process includes a polishing table having a polishing pad, and a substrate holding device, which is referred to as a top ring or a polishing head, for holding a substrate such as a semiconductor wafer. When the semiconductor wafer (substrate) is polished by using such a polishing apparatus, the semiconductor wafer is held and pressed against the surface (polishing surface) of the polishing pad under a predetermined pressure by the substrate holding device while a polishing liquid (slurry) is supplied from a polishing liquid supply nozzle onto the polishing pad. At this time, the polishing table and the substrate holding device are rotated to bring the semiconductor wafer into sliding contact with the polishing surface, so that the surface of the semiconductor wafer is polished to a flat mirror finish.
In the above CMP process, it is known that the step height characteristics such as dishing or erosion is severely dependent on a temperature of the polishing pad.
Further, it is confirmed that the polishing rate is also dependent on the temperature of the polishing pad, and there is a temperature range which brings about optimum polishing rate depending on the CMP process. Thus, in order to obtain the optimum polishing rate for a long time during polishing, it is necessary to maintain the optimum temperature of the polishing pad.
Therefore, the present inventors will propose a polishing apparatus in which a surface (polishing surface) of a polishing pad is cooled by ejecting a gas from gas ejection nozzles toward the polishing pad.
As described above, the polishing apparatus polishes the substrate by rotating the polishing table while the polishing liquid (slurry) is supplied from the polishing liquid supply nozzle onto the polishing pad. Therefore, there is a problem that mist of slurry supplied onto the polishing pad is scattered around. Further, after polishing of the substrate, wafer polishing of the substrate or cleaning of the substrate is performed by rotating the polishing table while pure water (deionized water) is supplied from the polishing liquid supply nozzle onto the polishing pad. Therefore, there is a problem that mist of pure water or the like supplied onto the polishing pad is scattered around. In this manner, the interior of the polishing apparatus is such an environment as to cause mist of slurry, pure water or the like, or water droplets to be scattered, and thus the scattered mist of slurry or the like is attached to surfaces of parts in the polishing apparatus and is then dried into powder. Such powder falls on the surface of the polishing pad during polishing to cause scratches on the surface of the substrate.
As in the proposed polishing apparatus, if gas ejection nozzles for blowing a gas on the polishing pad are attached to a gas supply unit (manifold) disposed above the polishing pad to control a surface (polishing surface) of the polishing pad, many parts including nozzles, nozzle attachment parts and the like are arranged so as to face the polishing pad. Therefore, slurry is attached to these many parts, and thus there is a possibility that the frequency leading to generation of powder and generation of scratches on the surface of the substrate is increased.
The present invention has been made in view of the above circumstances. It is therefore an object of the present invention to provide a polishing apparatus and method which can prevent dishing, erosion or the like from occurring to improve the step height characteristics and the polishing rate by blowing a gas from a nozzle or nozzles on a polishing pad during polishing of a substrate such as a semiconductor wafer to control a surface (polishing surface) of a polishing pad and can prevent a polishing liquid (slurry) on the polishing pad from being scattered to reduce an amount of the polishing liquid (slurry) to be attached to the nozzle or nozzles or nozzle attachment parts.
In order to achieve the above objects, according to a first aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table, the polishing apparatus comprising; a pad temperature control mechanism having at least one gas ejection nozzle for ejecting a gas toward the polishing pad and configured to blow the gas onto the polishing pad to control a temperature of the polishing pad; and an atomizer having at least one nozzle for ejecting a liquid or a mixed fluid of a gas and a liquid and configured to blow the liquid or the mixed fluid onto the polishing pad to remove foreign matters on the polishing pad; wherein the pad temperature control mechanism and the atomizer are formed into an integral unit.
According to the polishing apparatus of the present invention, during polishing of a substrate such as a semiconductor wafer, the gas is ejected toward the polishing pad from at least one gas ejection nozzle, and hence the surface (polishing surface) of the polishing pad can be cooled. Therefore, the surface of the polishing pad can be controlled at the optimum temperature in accordance with the CMP process, and thus the polishing rate can be improved and the step height characteristics can be improved by preventing dishing or erosion from occurring.
Further, according to the present invention, because the pad temperature control mechanism for controlling the temperature of the polishing pad by blowing the gas onto the polishing pad and the atomizer for removing foreign matters on the polishing pad by blowing the liquid or the mixed fluid onto the polishing pad are constructed as an integral unit, the number of parts can be reduced and the surface area of the unit can be remarkably reduced, thus reducing attachment of dirt. The pad temperature control mechanism and the atomizer can be used individually or can be used concurrently.
In a preferred aspect of the present invention, the pad temperature control mechanism comprises a fluid supply passage for supplying the gas to the at least one gas ejection nozzle.
In a preferred aspect of the present invention, the atomizer comprises a fluid supply passage for supplying the liquid or the mixed fluid to the at least one nozzle.
In a preferred aspect of the present invention, a gas ejection direction of the at least one gas ejection nozzle is not perpendicular to the surface of the polishing pad, but is inclined toward a rotational direction side of the polishing pad.
According to the present invention, by inclining the gas ejection direction of at least one gas ejection nozzle toward the rotational direction side of the polishing pad, the polishing pad can be cooled by high cooling capacity. This is because the inclination of the gas ejection nozzle can ensure the larger area, where the gas is blown, than that in the perpendicular nozzle. Further, in the case where the gas is blown vertically on the polishing pad, there is fear that the slurry is scattered around by splashing. However, the inclination of the nozzle allows slurry-scattering to be suppressed. Further, by inclining the gas ejection direction of the gas ejection nozzle toward the rotational direction side of the polishing pad, the effects on the flow of slurry by ejection of the gas can be reduced.
According to the present invention, the angle between the gas ejection direction of the gas ejection nozzle and the surface of the polishing pad is set, for example, in the range of 30 to 50 degrees, and thus the polishing pad can be cooled by high cooling capacity. This is because the above angle range is such an angle range as to ensure the area where the gas is blown and to allow the sufficient amount of gas to be blown effectively on the polishing pad. If the angle is smaller than 30 degrees, the area where the gas is blown becomes large, but the amount of air is lowered to reduce the cooling effect.
In a preferred aspect of the present invention, a concentric circle which passes through a point located immediately below the at least one gas ejection nozzle and is centered around a rotation center of the polishing pad is assumed and a tangential direction in the point on the concentric circle is defined as a tangential direction of rotation of the polishing pad, and a gas ejection direction of the at least one gas ejection nozzle is inclined toward a rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad.
According to the present invention, by inclining the gas ejection direction of at least one gas ejection nozzle toward the rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad, the polishing pad can be cooled by high cooling capacity. This is because the substrate polishing area on the polishing pad is a doughnut-shaped area (ring-shaped area), and by inclining the nozzle toward the rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad so that the gas can be ejected along the doughnut-shaped area, the substrate polishing area can be cooled efficiently.
According to the present invention, the angle of the gas ejection direction of the gas ejection nozzle with respect to the tangential direction of rotation of the polishing pad is set, for example, in the range of 15 to 35 degrees, and thus the polishing pad can be cooled by high cooling capacity. This is because the above angle range is such an angle range as to ensure the area where the gas is blown in the substrate polishing area and the angle of 35 degrees or more causes disturbance of the slurry dropping position.
In a preferred aspect of the present invention, an ejection direction of the liquid or the mixed fluid in the nozzle of the atomizer is substantially perpendicular to the surface of the polishing pad.
According to the present invention, the ejection direction of the liquid or the mixed fluid in the nozzle of the atomizer is substantially perpendicular to the surface of the polishing pad, and thus the impulse force when the liquid or the mixed fluid collides against the surface of the polishing pad can be enhanced to exert high detergency.
In a preferred aspect of the present invention, the pad temperature control mechanism and the atomizer are provided on a beam-like member which is disposed above the polishing pad and extends along substantially radial direction of the polishing pad from an outer circumferential portion to a central portion of the polishing pad.
According to the present invention, both of the pad temperature control mechanism and the atomizer are provided on the beam-like member, and thus the surface area of the entire unit can be reduced and the amount of dirt to be attached to the unit can be reduced. The beam-like member which is an elongated member is divided into right and left, and the fluid supply passage and the gas ejection nozzle for the pad temperature control mechanism are provided on one side, and the fluid passage and the nozzle for the atomizer are provided on the other side. Therefore, the pad temperature control mechanism and the atomizer can be constructed as an integral unit to become an extremely simple structure and to reduce the surface area of the entire unit.
The beam-like member is supported by the fixing arm at the outer circumferential side of the polishing table, and the fixing arm extends to the outside of the polishing table and is fixed to the apparatus frame or the like. Therefore, the beam-like member can be constructed as a cantilever and can extend above the polishing pad from the outer circumferential portion to the central portion of the polishing pad.
In a preferred aspect of the present invention, a gas ejection nozzle cover is provided at a gas ejection direction side of the gas ejection nozzle on the beam-like member.
According to the present invention, the gas ejection nozzle cover is provided so as to cover the upper side of the gas ejection nozzle, and hence the gas ejected from the gas ejection nozzle can be flowed toward the polishing pad without being diffused and the polishing pad can be cooled efficiently.
In a preferred aspect of the present invention, the gas ejection nozzle cover is inclined with respect to the surface of the polishing pad such that the gas ejection nozzle cover becomes closer to the surface of the polishing pad as the gas ejection nozzle cover becomes more distant from the beam-like member.
According to the present invention, the gas ejection nozzle cover is provided in a downwardly inclined state so as to be closer to the polishing pad in conformity with the gas ejection direction of the gas ejection nozzle, and hence the gas ejected from the gas ejection nozzle can be flowed toward the polishing pad without being diffused and the polishing pad can be cooled efficiently.
In a preferred aspect of the present invention, at least one gas direction adjustment plate for controlling a flow direction of the gas ejected from the gas ejection nozzle is provided inside the gas ejection nozzle cover, and the gas direction adjustment plate comprises a plate-like member extending from the gas ejection nozzle cover toward the polishing pad.
According to the present invention, the flow direction of the gas ejected from the gas ejection nozzle can be controlled by the gas direction adjustment plate, and thus the gas can be flowed along the polishing pad and the polishing pad can be cooled efficiently.
In a preferred aspect of the present invention, a concentric circle which passes through a point located immediately below the at least one gas direction adjustment plate and is centered around a rotation center of the polishing pad is assumed and a tangential direction in the point on the concentric circle is defined as a tangential direction of rotation of the polishing pad, and the at least one gas direction adjustment plate is inclined toward a rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad.
According to the present invention, the gas ejected from the gas ejection nozzle can be flowed toward the central side of the polishing table.
According to the present invention, the angle of the flat plate-like gas direction adjustment plate is set, for example, in the range of 15 to 45 degrees, and thus the polishing pad can be cooled by high cooling capacity. This is because the above angle range is such an angle range as to ensure the area where the gas is blown and the polishing pad can be cooled efficiently. If the angle is larger than 45 degrees, the amount of the gas which collides against the gas direction adjustment plate increases and the gas is depressurized and decelerated to reduce the cooling capacity, and the gas which collides against the gas direction adjustment plate and is then reflected causes disturbance of the slurry film thickness and the slurry dropping position on the polishing pad.
In a preferred aspect of the present invention, the polishing apparatus further comprises a mechanism for adjusting a direction of the gas ejection nozzle cover and/or a mechanism for adjusting a direction of the gas direction adjustment plate.
According to the present invention, the inclination of the gas ejection nozzle cover can be adjusted at the optimum angle in accordance with the gas approach angle between the surface (polishing surface) of the polishing pad and the gas ejection direction of the gas ejection nozzle.
According to the present invention, the directions of the plural gas direction adjustment plates can be adjusted in conjunction with one another or can be adjusted individually by the mechanism for adjusting the direction of the gas direction adjustment plate.
In a preferred aspect of the present invention, a scattering-prevention cover for the atomizer is provided at an opposite side of the gas ejection nozzle cover on the beam-like member.
According to the present invention, when the polishing pad is cleaned by the atomizer, the fluid ejected from the atomizer or the foreign matters on the polishing pad can be prevented from being scattered around.
In a preferred aspect of the present invention, the polishing apparatus further comprises: a control valve configured to control a flow rate of the gas ejected from the at least one gas ejection nozzle; a thermometer configured to detect a temperature of the polishing pad; and a controller configured to control the flow rate of the gas ejected from the at least one gas ejection nozzle by comparing a preset temperature as a control target temperature of the polishing pad and the temperature of the polishing pad detected by the thermometer and by adjusting a ratio of valve opening of the control valve.
According to the present invention, the flow rate of the gas ejected from at least one gas ejection nozzle is controlled by the control valve and the temperature of the polishing pad is detected by the thermometer, and the preset temperature as a control target temperature of the polishing pad and the temperature of the polishing pad detected by the thermometer are compared and the ratio of valve opening of the control valve is adjusted. Thus, the flow rate of the gas ejected from at least one gas ejection nozzle can be controlled. Accordingly, the surface of the polishing pad can be controlled at the optimum temperature according to the CMP process.
According to a second aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table while a polishing liquid is supplied onto the polishing pad, the polishing method comprising: ejecting a gas toward the polishing pad from at least one gas ejection nozzle; and blowing the gas onto the polishing pad by adjusting a direction of the gas ejected from the at least one gas ejection nozzle with a gas direction adjustment plate provided near the gas ejection nozzle.
According to the present invention, the gas ejected from the gas ejection nozzle can be flowed along the polishing pad by the gas direction adjustment plate, and thus the polishing pad can be cooled efficiently. Further, the flow of the polishing liquid on the polishing pad can be controlled by controlling the flow direction of the gas with the gas direction adjustment plate.
In some cases, the polishing rate or the planarization of the polished surface is changed depending on conditions of the polishing liquid (amount, concentration, product material and the like), and thus the flow of the polishing liquid on the polishing pad is controlled by controlling the flow of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate. Therefore, the polishing performance can be controlled.
In a preferred aspect of the present invention, a flow of the polishing liquid on the polishing pad is controlled by adjusting the direction of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate.
According to the present invention, by adjusting the direction of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate, the turbulance of the polishing liquid on the polishing pad can be reduced, and the film thickness of the polishing liquid can be substantially uniformized during polishing. Therefore, the entire surface of the substrate can be uniformly polished. Further, by adjusting the direction of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate, the polishing liquid is allowed to flow more (or less) to the edge or the central area of the substrate, and hence the polishing rate and the in-plane uniformity can be controlled.
In a preferred aspect of the present invention, the gas ejection nozzle and the gas direction adjustment plate are disposed at a downstream side of a dresser in a rotational direction of the polishing table; and a flow of the polishing liquid on the polishing pad is controlled at the downstream side of the dresser which conducts dressing during polishing.
According to the present invention, if a dressing process by the dresser is conducted during polishing, the flow of the polishing liquid is interrupted, and thus the film thickness of the polishing liquid tends to become in a disturbed state. However, by adjusting the direction of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate, the flow of the polishing liquid can be controlled at the downstream side of the dresser, and thus the film thickness of the polishing liquid can be controlled. Therefore, the film thickness of the polishing liquid which has been disturbed in the dressing process can be gentle, i.e., can be substantially uniformized. Thus, the entire surface of the substrate can be polished uniformly.
In a preferred aspect of the present invention, the polishing liquid which flows toward an outer circumferential side of the polishing pad is controlled so as to flow toward a central side of the polishing pad by adjusting a direction of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate.
According to the present invention, the fresh slurry supplied from the polishing liquid supply nozzle to the polishing pad can be prevented from flowing down from the polishing pad without being used for polishing, and can remain on the polishing pad. Therefore, the polishing performance can be improved and the consumed amount of the polishing liquid can be reduced.
In a preferred aspect of the present invention, old polishing liquid which has been used for polishing and is located at a downstream side of a top ring for holding the substrate in a rotational direction of the polishing table is controlled so as to flow toward an outer circumferential side of the polishing pad by adjusting a direction of the gas ejected from the gas ejection nozzle with the gas direction adjustment plate.
According to the present invention, the old polishing liquid which has been used for polishing and is located at a downstream side of the top ring for holding the substrate in the rotational direction of the polishing table can be discharged as quickly as possible. Therefore, the present invention can prevent such a situation that the old polishing liquid remains on the polishing surface and the polishing rate and the in-plane uniformity are adversely affected.
In a preferred aspect of the present invention, a polishing liquid supply nozzle for supplying the polishing liquid onto the polishing pad is swingable, and a supply position of the polishing liquid is changed during polishing.
According to the present invention, by changing the supply position of the polishing liquid during polishing, the required amount of the polishing liquid can be supplied to the most effective position for polishing on the polishing pad.
According to a third aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table while controlling a temperature of the polishing pad by ejecting a gas toward the polishing pad, the polishing method comprising: starting temperature control of the polishing pad after setting a preset temperature as a control target temperature of the polishing pad and monitoring the temperature of the polishing pad; and determining that polishing abnormality occurs in the case where the time when the temperature of the polishing pad becomes outside the range of the preset temperature exceeds a predetermined time continuously after the temperature of the polishing pad reaches the range of the preset temperature.
According to the present invention, after setting the preset temperature as a control target temperature of the polishing pad, the gas is ejected toward the polishing pad to start temperature control of the polishing pad and to monitor the temperature of the polishing pad. Then, in the case where the time when the temperature of the polishing pad becomes outside the range of the preset temperature exceeds a predetermined time continuously after the temperature of the polishing pad reaches the range of the preset temperature, it is judged that polishing abnormality in which the temperature control of the polishing pad is not performed normally occurs.
In a preferred aspect of the present invention, the becoming outside the range of the preset temperature comprises becoming outside the range of an upper limit or a lower limit of the preset temperature.
In a preferred aspect of the present invention, the preset temperature of the polishing pad is changed during polishing, and the required time from change of the preset time to reaching the changed preset temperature is measured, and then the required time and the preset time are compared and when the required time is longer than the preset time, it is judged that polishing abnormality occurs.
According to the present invention, after setting the preset temperature as a control target temperature of the polishing pad, the gas is ejected toward the polishing pad to start temperature control of the polishing pad and to monitor the temperature of the polishing pad. Then, the preset temperature of the polishing pad is changed during polishing, and the required time from change of the preset time to reaching the changed preset temperature is measured, and then the required time and the preset time are compared. If the required time is longer than the preset time, it is judged that polishing abnormality in which the temperature control of the polishing pad is not performed normally occurs.
According to a fourth aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table while controlling a temperature of the polishing pad by ejecting a gas toward the polishing pad, the polishing method comprising: starting temperature control of the polishing pad and monitoring the temperature of the polishing pad; and determining that polishing abnormality occurs in the case where the temperature of the polishing pad does not reach a target temperature after an elapse of a predetermined time from starting the temperature control.
According to the present invention, after setting the preset temperature as a control target temperature of the polishing pad, the gas is ejected toward the polishing pad to start temperature control of the polishing pad and to monitor the temperature of the polishing pad. Then, in the case where the temperature of the polishing pad does not reach the target temperature after an elapse of a predetermined time from starting the temperature control, it is judged that polishing abnormality in which the temperature control of the polishing pad is not performed normally occurs.
According to a fifth aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table while controlling a temperature of the polishing pad by ejecting a gas toward the polishing pad, the polishing method comprising: starting temperature control of the polishing pad after setting a preset temperature as a control target temperature of the polishing pad and monitoring the temperature of the polishing pad; changing the preset temperature of the polishing pad during polishing; and determining that polishing abnormality occurs in the case where the temperature of the polishing pad does not reach the changed preset temperature after an elapse of a predetermined time from changing the preset temperature.
According to the present invention, after setting the preset temperature as a control target temperature of the polishing pad, the gas is ejected toward the polishing pad to start temperature control of the polishing pad and to monitor the temperature of the polishing pad. Then, the preset temperature of the polishing pad is changed during polishing, and in the case where the temperature of the polishing pad does not reach the changed preset temperature after an elapse of a predetermined time from changing the preset temperature, it is judged that polishing abnormality in which the temperature control of the polishing pad is not performed normally occurs.
According to a sixth aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table, the polishing apparatus comprising; at least one gas ejection nozzle configured to eject a gas toward the polishing pad; and a gas supply unit configured to hold the at least one gas ejection nozzle and supply the gas to the at least one gas ejection nozzle; wherein a concentric circle which passes through a point located immediately below the at least one gas ejection nozzle and is centered around a ration center of the polishing pad is assumed and a tangential direction in the point on the concentric circle is defined as a tangential direction of rotation of the polishing pad, and a gas ejection direction of the at least one gas ejection nozzle is inclined toward a rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad.
According to the present invention, the gas is supplied from the gas supply unit to at least one gas ejection nozzle during polishing of the substrate such as a semiconductor wafer, and the gas is ejected toward the polishing pad from at least one gas ejection nozzle to cool the surface (polishing surface) of the polishing pad. Therefore, the surface of the polishing pad can be controlled at the optimum temperature in accordance with the CMP process, and thus the polishing rate can be improved and the step height characteristics can be improved by preventing dishing or erosion from occurring.
In the present invention, the concentric circle which passes through a point located immediately below at least one gas ejection nozzle and is centered around the rotation center of the polishing pad is assumed and the tangential direction in the point on the concentric circle is defined as a tangential direction of rotation of the polishing pad, and the gas ejection direction of at least one gas ejection nozzle is inclined toward the rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad. In this manner, by inclining the gas ejection direction of at least one gas ejection nozzle toward the rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad, the polishing pad can be cooled by high cooling capacity. This is because the substrate polishing area on the polishing pad is a doughnut-shaped area (ring-shaped area), and by inclining the nozzle toward the rotation center side of the polishing pad with respect to the tangential direction of rotation of the polishing pad so that the gas can be ejected along the doughnut-shaped area, the substrate polishing area can be cooled efficiently.
According to a seventh aspect of the present invention, there is provided a polishing apparatus for polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table, the polishing apparatus comprising; at least one gas ejection nozzle configured to eject a gas toward the polishing pad; and a gas supply unit configured to hold the at least one gas ejection nozzle and supply the gas to the at least one gas ejection nozzle; wherein a gas ejection direction of the at least one gas ejection nozzle is not perpendicular to the surface of the polishing pad, but is inclined toward a rotational direction side of the polishing pad.
According to the present invention, the gas is supplied from the gas supply unit to at least one gas ejection nozzle during polishing of the substrate such as a semiconductor wafer, and the gas is ejected toward the polishing pad from at least one gas ejection nozzle to cool the surface (polishing surface) of the polishing pad. Therefore, the surface of the polishing pad can be controlled at the optimum temperature in accordance with the CMP process, and thus the polishing rate can be improved and the step height characteristics can be improved by preventing dishing or erosion from occurring.
In the present invention, the gas ejection direction of at least one gas ejection nozzle is not perpendicular to the surface of the polishing pad, but is inclined toward the rotational direction side of the polishing pad. In this manner, by inclining the gas ejection direction of at least one gas ejection nozzle toward the rotational direction side of the polishing pad, the polishing pad can be cooled by high cooling capacity. This is because the inclination of the gas ejection nozzle can ensure the larger area, where the gas is blown, than that in the perpendicular nozzle. Further, in the case where the gas is blown vertically on the polishing pad, there is fear that the slurry is scattered around by splashing. However, the inclination of the nozzle allows slurry-scattering to be suppressed. Further, by inclining the gas ejection direction of the gas ejection nozzle toward the rotational direction side of the polishing pad, the effects on the flow of slurry by ejection of the gas can be reduced.
In a preferred aspect of the present invention, a height of the at least one gas ejection nozzle from the surface of the polishing pad is adjustable.
According to the present invention, by adjusting the height of the gas ejection nozzle from the surface of the polishing pad, the gas ejection nozzle can be positioned at the optimum height position. Therefore, the polishing pad can be cooled by high cooling capacity.
In a preferred aspect of the present invention, an angle of the gas ejection direction of the at least one gas ejection nozzle with respect to the tangential direction of rotation of the polishing pad is set in the range of 15 to 35 degrees.
According to the present invention, the angle of the gas ejection direction of the gas ejection nozzle with respect to the tangential direction of rotation of the polishing pad is set, for example, in the range of 15 to 35 degrees, and thus the polishing pad can be cooled by high cooling capacity. This is because the above angle range is such an angle range as to ensure the area where the gas is blown in the substrate polishing area and the angle of 35 degrees or more causes disturbance of the slurry dropping position.
In a preferred aspect of the present invention, an angle of the gas ejection direction of the at least one gas ejection nozzle with respect to the surface of the polishing pad is set in the range of 30 to 50 degrees.
According to the present invention, the angle between the gas ejection direction of the gas ejection nozzle and the surface of the polishing pad is set in the range of 30 to 50 degrees, and thus the polishing pad can be cooled by high cooling capacity. This is because the above angle range is such an angle range as to ensure the area where the gas is blown and to allow the sufficient amount of gas to be blown effectively on the polishing pad. If the angle is smaller than 30 degrees, the area where the gas is blown becomes large, but the amount of gas to be blown is lowered to reduce the cooling effect.
In a preferred aspect of the present invention, the polishing apparatus further comprises: a control valve configured to control a flow rate of the gas ejected from the at least one gas ejection nozzle; a thermometer configured to detect a temperature of the polishing pad; and a controller configured to control the flow rate of the gas ejected from the at least one gas ejection nozzle by comparing a preset temperature as a control target temperature of the polishing pad and the temperature of the polishing pad detected by the thermometer and by adjusting a ratio of valve opening of the control valve.
According to the present invention, the flow rate of the gas ejected from at least one gas ejection nozzle is controlled by the control valve and the temperature of the polishing pad is detected by the thermometer, and the flow rate of the gas ejected from at least one gas ejection nozzle can be controlled by comparing the preset temperature as a control target temperature of the polishing pad and the temperature of the polishing pad detected by the thermometer and by adjusting the ratio of valve opening of the control valve. Accordingly, the surface of the polishing pad can be controlled at the optimum temperature according to the CMP process.
In a preferred aspect of the present invention, the controller controls the flow rate of the gas ejected from at least one gas ejection nozzle by adjusting the ratio of valve opening of the control valve with a PID control on the basis of the difference between the preset temperature of the polishing pad and the detected temperature of the polishing pad.
According to the present invention, the controller selects certain PID parameters from several PID parameters on the basis of a predetermined rule, and controls the temperature of the polishing pad surface using the PID parameters selected on the basis of the pad temperature information. Therefore, the polishing rate of the substrate can be maintained optimally and constantly, and thus the polishing time can be shortened. Further, as a result, the amount of slurry to be used and the amount of waste liquid can be reduced.
According to an eighth aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table, said polishing method comprising: supplying a gas from a gas supply unit to at least one gas ejection nozzle; and ejecting the gas toward the polishing pad from said at least one gas ejection nozzle; wherein a concentric circle which passes through a point located immediately below said at least one gas ejection nozzle and is centered around a rotation center of the polishing pad is assumed and a tangential direction in said point on said concentric circle is defined as a tangential direction of rotation of the polishing pad, and a gas ejection direction of said at least one gas ejection nozzle is inclined toward a rotation center side of the polishing pad with respect to said tangential direction of rotation of the polishing pad.
According to a ninth aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table, the polishing method comprising: supplying a gas from a gas supply unit to at least one gas ejection nozzle; and ejecting the gas toward the polishing pad from the at least one gas ejection nozzle; wherein a gas ejection direction of the at least one gas ejection nozzle is not perpendicular to the surface of the polishing pad, but is inclined toward a rotational direction side of the polishing pad.
In a preferred aspect of the present invention, a height of the at least one gas ejection nozzle from the surface of the polishing pad is adjustable.
In a preferred aspect of the present invention, an angle of the gas ejection direction of the at least one gas ejection nozzle with respect to the tangential direction of rotation of the polishing pad is set in the range of 15 to 35 degrees.
In a preferred aspect of the present invention, an angle of the gas ejection direction of the at least one gas ejection nozzle with respect to the surface of the polishing pad is set in the range of 30 to 50 degrees.
In a preferred aspect of the present invention, a flow rate of the gas ejected from the at least one gas ejection nozzle is controlled by a control valve and a temperature of the polishing pad is detected by a thermometer; and the flow rate of the gas ejected from the at least one gas ejection nozzle is controlled by comparing a preset temperature as a control target temperature of the polishing pad and the temperature of the polishing pad detected by the thermometer and by adjusting a ratio of valve opening of the control valve.
In a preferred aspect of the present invention, the flow rate of the gas ejected from the at least one gas ejection nozzle is control led by adjusting the ratio of valve opening of the control valve with a PID control on the basis of a difference between the preset temperature of the polishing pad and the detected temperature of the polishing pad.
In a preferred aspect of the present invention, there is provided a polishing method of polishing a surface of a substrate as an object to be polished by pressing the substrate against a polishing pad on a polishing table while controlling a temperature of the polishing pad by ejecting a gas toward the polishing pad, the polishing method comprising: starting temperature control of the polishing pad after setting a preset temperature as a control target temperature of the polishing pad and monitoring the temperature of the polishing pad; measuring a required time from start of the temperature control to reaching the preset temperature; comparing the required time and the preset time; and determining that polishing abnormality occurs in the case where the required time is longer than the preset time.
According to the present invention, after setting the preset temperature as a control target temperature of the polishing pad, the gas is ejected toward the polishing pad to start temperature control of the polishing pad and to monitor the temperature of the polishing pad. Then, the required time from start of the temperature control to reaching the preset temperature is measured, and the required time and the preset time are compared. If the required time is longer than the preset time, it is judged that polishing abnormality in which the temperature control of the polishing pad is not performed normally occurs.
The present invention has the following effects:
(1) By cooling the surface of the polishing pad during polishing, the following two effects can be expected.
A. The polishing rate can be improved to raise productivity, and the cost of consumable goods such as a polishing liquid (slurry) per one substrate can be reduced. For example, by maintaining the surface of the polishing pad at a predetermined temperature in the main polishing step, the polishing rate can be improved to raise productivity, and the cost of consumable goods such as a polishing liquid (slurry) per one substrate can be reduced.
B. The step height characteristics can be improved by preventing dishing or erosion from occurring.
(2) By optimizing the position on the polishing pad where the gas is blown, the further increased cooling effect of the polishing pad can be expected and the further reduction of the dishing and the erosion can be expected. For example, by maintaining the surface of the polishing pad at a predetermined temperature in the finish polishing step, the step height characteristics can be improved by preventing dishing or erosion from occurring.
(3) When the error of the time when the temperature of the polishing pad does not reach the preset temperature as a control target temperature for cooling the polishing pad or the error of the time when the temperature of the polishing pad exceeds the upper limit of the preset temperature or is lowered than the lower limit of the preset temperature occurs, the process interlock works, and thus polishing of the subsequent substrate is not performed. Therefore, defective product is limited to one substrate which has been polished at the time of occurrence of the error, thus contributing to improvement of production yield.
(4) Because the pad temperature control mechanism for controlling the temperature of the polishing pad by blowing the gas onto the polishing pad and the atomizer for removing foreign matters on the polishing pad by blowing the liquid or the mixed fluid are constructed as an integral unit, the following three effects can be expected.
A. The number of parts can be reduced and the surface area of the unit can be reduced, and thus attachment of dirt can be reduced.
B. The assembling of the unit becomes simple and the reproducibility of the assembling can be improved. If the position of the nozzle is changed, there is a possibility that the process is adversely affected, and thus improvement of the reproducibility of the assembling is important.
C. The attachment space of the unit becomes small, and thus the space above the polishing table can be effectively utilized.
(5) In addition to the gas ejection nozzle, the gas direction adjustment plate for controlling the flow direction of the gas is provided on the pad temperature adjustment mechanism, and thus the following three effects can be expected.
A. The turbulance of the polishing liquid on the polishing pad can be reduced during polishing, and thus the film thickness of the polishing liquid can be substantially uniformized.
B. The polishing liquid is allowed to flow more (or less) to the edge or the central area of the substrate, and hence the polishing rate and the in-plane uniformity can be controlled.
C. The old polishing liquid which has been used for polishing can be discharged as quickly as possible, and the fresh slurry can be prevented from flowing down from the polishing pad and can remain on the polishing pad. Therefore, the polishing performance can be improved and the consumed amount of the polishing liquid can be reduced.
A polishing apparatus and method according to a first embodiment of the present invention will be described below with reference to
The polishing head 10 is connected to a shaft 11, and the shaft 11 is vertically movable with respect to a support arm 12. When the shaft 11 moves vertically, the polishing head 10 is lifted and lowered as a whole for positioning with respect to the support arm 12. The shaft 11 is configured to be rotated by operating a polishing head rotating motor (not shown). The polishing head 10 is rotated about the shaft 11 by rotation of the shaft 11.
The polishing head 10 is configured to hold the substrate W such as a semiconductor wafer on its lower surface. The support arm 12 is configured to be pivotable about a shaft 13. Thus, the polishing head 10, which holds the substrate W on its lower surface, is movable from a position at which the polishing head 10 receives the substrate to a position above the polishing table 1 by pivotable movement of the support arm 12. Then, the polishing head 10 holds the substrate W on its lower surface and presses the substrate W against the surface (polishing surface) 2a of the polishing pad 2. At this time, while the polishing table 1 and the polishing head 10 are respectively rotated, a polishing liquid (slurry) is supplied onto the polishing pad 2 from the polishing liquid supply nozzle 3 provided above the polishing table 1. The polishing liquid containing silica (SiO2) or ceria (CeO2) as abrasive particles is used. In this manner, while the polishing liquid is supplied onto the polishing pad 2, the substrate W is pressed against the polishing pad 2 and is moved relative to the polishing pad 2 to polish an insulating film, a metal film or the like on the substrate.
As shown in
As shown in
Further, as shown in
The angle (θ1) of the gas ejection direction of the gas ejection nozzle 22 with respect to the tangential direction of rotation of the polishing pad and the angle (θ2) of the gas ejection direction of the gas ejection nozzle 22 with respect to the surface (polishing surface) 2a of the polishing pad 2 can be adjusted independently in each nozzle.
Further, as shown in
Further, as advanced variation, in some cases, the angle (θ1) of the gas ejection direction of the gas ejection nozzle, the gas approach angle (θ2) of the gas ejection nozzle, and the height (H) of the manifold 21 are fixed within respective preset ranges to prevent adjustment portions from being shifted in error and to prevent deviation from original preset positions. In that case, air ejection holes are formed directly in the manifold to take the form of the integration of the nozzles and the manifold.
Further, temperature profile of the polishing pad may be monitored by a thermography during polishing, and the manifold may be moved by oscillation so that high-temperature areas can be positively cooled in accordance with temperature distribution (for example, in the case where the temperature difference within the pad surface becomes a predetermined value or higher).
Next, an example of processes of polishing the substrate W using the polishing apparatus constructed as shown in
First, a first preset temperature as a control target temperature of the polishing pad 2 is set in the temperature controller 31. Then, a supply pressure for supplying compressed air to the gas ejection nozzles 22 is confirmed. When this supply pressure is not more than a predetermined pressure, an alarm is issued and the subsequent process of the substrate is stopped. Only when the supply pressure is not less than the predetermined pressure, the polishing head 10 located at the substrate transfer position receives the substrate W from the pusher or the like and hold the substrate W under vacuum. Then, the substrate W held under vacuum by the polishing head 10 is moved horizontally from the substrate transfer position to the polishing position immediately above the polishing table 1.
Next, temperature monitoring of the polishing pad 2 by the radiation thermometer 32 is started. Then, the polishing liquid (slurry) is dropped from the polishing liquid supply nozzle 3 onto the polishing pad 2, and the polishing head 10 is lowered while the polishing head 10 is rotated to bring the surface (the surface to be polished) of the substrate W into contact with the polishing surface 2a of the rotating polishing pad 2. Then, attraction of the substrate W by the polishing head 10 is released, and the substrate W is pressed against the polishing surface 2a under a first polishing pressure. Thus, a main polishing step for polishing a metal film or the like on the substrate is started.
In the main polishing step, temperature control of the polishing pad 2 by the pad temperature control device 20 is started at the time when the substrate W is brought into contact with the polishing surface 2a. If the process in which the substrate W is brought into contact with the polishing surface 2a without rotating the polishing table 1 is employed, temperature control of the polishing pad 2 by the pad temperature control device 20 is started at the same time when rotation of the polishing table 1 is started.
Specifically, the temperature controller 31 controls the ratio of valve opening of the pressure regulating valve 30 based on the PID control according to the difference between the first preset temperature which has been preset and actual temperature of the polishing pad 2 detected by the radiation thermometer 32 to control a flow rate of compressed air ejected from the gas ejection nozzles 22. Thus, the temperature of the polishing pad 2 is controlled at the first preset temperature for obtaining the maximum polishing rate which has been determined in advance.
In this main polishing step, high polishing rate can be obtained by a combination of the high polishing pressure and cooling of the polishing pad 2, and hence the total polishing time can be shortened. This main polishing step is terminated, for example, when the film thickness measuring instrument 50 detects the state in which a thickness of a film such as a metal film reaches a predetermined value.
Next, a finish polishing step is performed. In the finish polishing step after the main polishing step, in order to place importance on improvement of the step height characteristics by preventing dishing, erosion or the like from occurring, it is necessary to control the temperature of the polishing pad 2. Specifically, a second preset temperature different from the first preset temperature is set in the temperature controller 31. After shifting to the finish polishing step, compressed air whose flow rate is controlled by the PID control so that the polishing pad 2 reaches the second preset temperature quickly is blown onto the polishing pad 2. For example, in the case where the second preset temperature in the finish polishing step is lower than the first preset temperature in the main polishing step, the flow rate of the compressed air is controlled at the maximum until the polishing pad 2 reaches the second preset temperature. In this manner, the temperature of the polishing pad 2 is controlled at the second preset temperature, and polishing is continued. In the finish polishing step, in order to improve the step height resolution characteristics mainly, the substrate W is pressed against the polishing surface 2a under the second polishing pressure which is lower than the first polishing pressure. This finish polishing step is terminated, for example, when the film thickness measuring instrument 50 detects the state in which a surplus metal film or the like located at areas other than trench or the like is polished and removed to expose a surface of an underlayer completely.
Next, ejection of the compressed air from the gas ejection nozzles 22 is stopped and supply of the polishing liquid (slurry) from the polishing liquid supply nozzle 3 is stopped, and then pure water (deionized water) is supplied onto the polishing pad 2 to conduct water polishing of the substrate W. Then, ejection of the compressed air from the gas ejection nozzles 22 is stopped, and the polished substrate W is detached from the polishing surface 2a and held under vacuum by the polishing head 10 while the compressed air is prevented from blowing against the substrate W. After that, the substrate W moves away from the polishing pad 2, and ejection of the compressed air from the gas ejection nozzles 22 remains at rest in order to prevent the polished surface of the substrate W from being dried due to blowing of the compressed air against the polished surface of the substrate W.
Next, the polishing head 10 which holds the substrate W under vacuum is lifted, and the substrate W is moved horizontally from the polishing position to the substrate transfer position. Then, the polished substrate W is transferred at the substrate transfer position to the pusher or the like. In the gas ejection nozzles 22, a cleaning liquid (water) is blown from cleaning nozzles (not shown) onto nozzle opening portions and their surrounding areas, thereby conducting cleaning of the gas ejection nozzles 22. Thus, dirt such as slurry attached to the gas ejection nozzles 22 can be prevented from falling onto the polishing pad 2 to avoid an adverse effect on the processing of the subsequent substrate.
In a state where the manifold 21 is moved to a retracting position by oscillating the manifold 21, a cleaning liquid is blown from cleaning nozzles (not shown) onto the gas ejection nozzles 22 to clean the gas ejection nozzles 22. Thus, dirt such as slurry attached to the gas ejection nozzles 22 can be prevented from falling onto the polishing pad 2.
After the temperature of the polishing pad 2 reaches the range of the first preset temperature (between the upper limit (T1max) and the lower limit (T1min)), if the time when the temperature of the polishing pad 2 exceeds the upper limit (T1max) exceeds the preset time continuously, it is judged that polishing abnormality occurs and an alarm is issued. Further, if the time when the temperature of the polishing pad 2 is lower than the lower limit (T1min) exceeds the preset time continuously, it is judged that polishing abnormality occurs and an alarm is issued.
While the presence or absence of the above polishing abnormality is monitored, the main polishing step is continued. Then, for example, when the film thickness measuring instrument 50 detects the state in which a thickness of a film such as a metal film reaches a predetermined value, the main polishing step is terminated, and then shifting to the finish polishing step. The finish polishing step is started by changing the preset value to the second preset temperature which is different from the first preset temperature. After shifting to the finish polishing step, compressed air whose flow rate is controlled by the PID control so that the polishing pad 2 reaches the second preset temperature quickly is blown onto the polishing pad 2. For example, in the case where the second preset temperature in the finish polishing step is lower than the first preset temperature in the main polishing step, the flow rate of the compressed air is controlled at the maximum until the polishing pad 2 reaches the second preset temperature. Then, after the preset temperature is changed from the first preset temperature to the second preset temperature, when the preset time (in normal case, i.e. in the case of no polishing abnormality, the preset time means the time from change of the first preset temperature to the second preset temperature to reaching the upper limit or the lower limit of the second preset temperature, and this time is determined by experiments in advance) has elapsed, the temperature of the polishing pad and the upper limit or the lower limit of the second preset temperature are compared, and if the temperature of the polishing pad does not reach the upper limit or the lower limit of the second preset temperature, it is judged that polishing abnormality occurs and an alarm is issued. The following alternative measures may be taken: The required time for reaching the upper limit (T2max) or the lower limit (T2min) of the second preset temperature is measured, and the required time and the preset time are compared, and if the required time is longer than the preset time, it is judged that polishing abnormality occurs and an alarm is issued.
After the temperature of the polishing pad 2 reaches the range of the second preset temperature (between the upper limit (T2max) and the lower limit (T2min)) if the time when the temperature of the polishing pad 2 exceeds the upper limit (T2max) exceeds the preset time continuously, it is judged that polishing abnormality occurs and an alarm is issued. Further, if the time when the temperature of the polishing pad 2 is lower than the lower limit (T2min) exceeds the preset time continuously, it is judged that polishing abnormality occurs and an alarm is issued.
While the presence or absence of the above polishing abnormality is monitored, the finish polishing step is continued. Then, for example, when the film thickness measuring instrument 50 detects the state in which a surplus metal film or the like located at areas other than trench or the like is polished and removed to expose a surface of an underlayer completely, the finish polishing step is finished.
When the error of the time when the temperature of the polishing pad does not reach the above preset temperature or the error of the time when the temperature of the polishing pad exceeds the upper and lower limits of the preset temperature occurs, the process interlock works, and thus polishing of the subsequent substrate is not performed. Therefore, defective product is limited to one substrate which has been polished at the time of occurrence of the error, thus contributing to improvement of production yield.
A polishing apparatus and method according to a second embodiment of the present invention will be described below with reference to
The top ring 110 is connected to a shaft 111, and the shaft 111 is vertically movable with respect to a support arm 112. When the shaft 111 moves vertically, the top ring 110 is lifted and lowered as a whole for positioning with respect to the support arm 112. The shaft 111 is configured to be rotated by operating a top ring rotating motor (not shown). The top ring 110 is rotated about the shaft 111 by rotation of the shaft 111.
The top ring 110 is configured to hold the substrate W such as a semiconductor wafer on its lower surface. The support arm 112 is configured to be pivotable about a shaft 113. Thus, the top ring 110, which holds the substrate W on its lower surface, is movable from a position at which the top ring 110 receives the substrate to a position above the polishing table 101 by pivotable movement of the support arm 112. Then, the top ring 110 holds the substrate W on its lower surface and presses the substrate W against the surface (polishing surface) 102a of the polishing pad 102. At this time, while the polishing table 101 and the top ring 110 are respectively rotated, a polishing liquid (slurry) is supplied onto the polishing pad 102 from the polishing liquid supply nozzle 103 provided above the polishing table 101. The polishing liquid containing silica (SiO2) or ceria (CeO2) as abrasive particles is used. In this manner, while the polishing liquid is supplied onto the polishing pad 102, the substrate W is pressed against the polishing pad 102 and is moved relative to the polishing pad 102 to polish an insulating film, a metal film or the like on the substrate.
As shown in
When the polishing surface 102a of the polishing pad 2 is dressed, the polishing pad 102 is rotated and the dresser 117 is rotated by the motor, and then the dresser 117 is lowered by a lifting and lowering mechanism to bring the dressing member 117a provided at the lower surface of the dresser 117 into sliding contact with the polishing surface of the rotating polishing pad 102. In this state, the dresser arm 116 is oscillated (swung), and thus the dresser 117 located at the forward end of the dresser arm 116 can move transversely from the outer circumferential end to the central part of the polishing surface of the polishing pad 102. By this swing motion, the dressing member 117a can dress the polishing surface of the polishing pad 102 over the entire surface including the central part.
As shown in
Next, detailed structure of the pad adjustment apparatus 120 will be described below with reference to
On the other hand, the atomizer has fluid supply passages 131 and 132 comprising circular holes formed at upper and lower parts in the main body portion 121, and the upper fluid supply passage 131 is connected to a pure water source (not shown) and the lower fluid supply passage 132 communicates with the upper fluid supply passage 131. The upper and lower fluid supply passages 131 and 132 extend in a longitudinal direction of the main body portion 121 to the base end portion of the main body portion 121. Then, a plurality of nozzles 133 are disposed below the lower fluid supply passage 132 at predetermined intervals along the longitudinal direction of the main body portion 121. Each of the nozzles 133 has a nozzle hole 133h having a small diameter, and the nozzle hole 133h extends downwardly so as to be substantially perpendicular to the surface (polishing surface) 102a of the polishing pad 102. Pure water (deionized water) supplied from the pure water source to the upper fluid supply passage 131 is supplied via the lower fluid supply passage 132 to the nozzles 133.
As shown in
A liquid such as pure water may be supplied from a liquid source to the upper fluid supply passage 131 and a gas such as nitrogen (N2) gas may be supplied from a gas source to the lower fluid supply passage 132, and after mixing the liquid and the gas in a mixing space provided in the main body portion 121, a gas-liquid mixed fluid may be ejected from the nozzles 133.
Although not shown in
Further, the fluid supply passages 123, 131 and 132 may be integrated into a single common fluid supply passage, and the gas ejection nozzles 124 and the nozzles 133 may be provided in the single fluid supply passage, and then opening and closing between the fluid supply sources (compressed air source, pure water source and the like) and the respective nozzle holes may be switched.
Next, the gas ejection nozzle cover 135 fixed to one side of the main body portion 121 and the scattering-prevention cover 140 fixed to the other side of the main body portion 121 will be described below.
As shown in
Further, as shown in
In the embodiment shown in
As shown in
As shown in
Further, as shown in
Further, as shown in
Next, a method of controlling a flow of the polishing liquid (slurry) on the polishing pad 102 by the gas direction adjustment plates 136 for controlling a flow direction of air (compressed air) ejected from the gas ejection nozzles 124 of the pad temperature control mechanism 122 will be described in detail.
As shown in
As shown in
Therefore, according to the present invention, the flow of the polishing liquid (slurry) is controlled by the gas ejection nozzles 124 and the gas direction adjustment plates 136 in the pad temperature control mechanism 122.
As shown in
Next, the gas direction adjustment plate 136 located at the innermost side of the polishing pad 102 will be described as an example with reference to
In the example shown in
As shown in
As described above, according to the present invention, by adjusting the gas guide angles (e3) of the gas direction adjustment plates 136 individually, the slurry is enabled to flow more (or less) to the edge or the central area of the substrate, and hence the polishing rate, in-plane uniformity, and the like can be controlled.
In the example shown in
In the example shown in
In the example shown in
For example, when the gas ejection nozzles 124 are fixed and the gas ejection direction cannot be changed or when the gas is supplied at a fixed flow rate, by moving the gas ejection nozzle cover 135, the amount of gas directed toward the surface 102a of the polishing pad 102 can be changed to vary the intensity of cooling. Further, the gas ejection nozzle cover 135 is opened to lose the function of the gas ejection nozzle cover 135 for guiding the gas so that the gas does not flow toward the surface 102a of the polishing pad 102. In this case, the slurry can be flowed toward the top ring 110 with the slurry film thickness changed by the gas direction adjustment plates 136.
The structure of the gas direction adjustment plates 136 within the gas ejection nozzle cover 135 is the same as that shown in
Next, a method of controlling the amount of slurry to be consumed by controlling the flow of the polishing liquid (slurry) on the polishing pad 102 by the gas direction adjustment plates 136 for controlling the flow direction of air (compressed air) ejected from the gas ejection nozzles 124 of the pad temperature control mechanism 122.
Therefore, according to the present invention, the flow of slurry is controlled by the gas ejection nozzles 124 and the gas direction adjustment plates 136 so that the slurry discharged from the area A is eliminated or minimized.
On the other hand, the gas ejection nozzles 124 and the gas direction adjustment plates 136 located at the downstream side in the rotational direction of the polishing table 101 are configured to eject air in the rotational direction of the polishing table 101 and to control the flow of air. By adjusting the gas guide angle (θ3) of the gas direction adjustment plate 136, the flow direction of air is directed inwardly of the polishing table 101, and the slurry flowing toward the outer circumferential side of the polishing pad 102 is controlled so as to flow toward the central side of the polishing pad 102, thereby allowing the slurry to remain on the polishing pad 102. As a result, the slurry discharged from the area A shown in
Although the case where the flow of the polishing liquid (slurry) on the polishing pad 102 is controlled by air (compressed air) has been mainly described in the embodiments shown in
Next, an example of processes of polishing the substrate W using a polishing apparatus constructed as shown in
First, a first preset temperature as a control target temperature of the polishing pad 102 is set in the temperature controller 147. Then, a supply pressure for supplying compressed air to the gas ejection nozzles 124 is confirmed. When this supply pressure is not more than a predetermined pressure, an alarm is issued and the subsequent process of the substrate is stopped. Only when the supply pressure is not less than the predetermined pressure, the top ring 110 located at the substrate transfer position receives the substrate W from the pusher or the like and holds the substrate W under vacuum. Then, the substrate W held under vacuum by the top ring 110 is moved horizontally from the substrate transfer position to the polishing position immediately above the polishing table 101.
Next, temperature monitoring of the polishing pad 102 by the radiation thermometer 148 is started. Then, the polishing liquid (slurry) is dropped from the polishing liquid supply nozzle 103 onto the polishing pad 102, and the top ring 110 is lowered while the top ring 110 is rotated to bring the surface (the surface to be polished) of the substrate W into contact with the polishing surface 102a of the rotating polishing pad 102. Then, attraction of the substrate W by the top ring 110 is released, and the substrate W is pressed against the polishing surface 102a under a first polishing pressure. Thus, a main polishing step for polishing a metal film or the like on the substrate is started.
In the main polishing step, temperature control of the polishing pad 102 by the pad temperature control mechanism 122 of the pad adjustment apparatus 120 is started at the time when the substrate W is brought into contact with the polishing surface 102a. If the process in which the substrate W is brought into contact with the polishing surface 102a without rotating the polishing table 1 is employed, temperature control of the polishing pad 102 by the pad temperature control mechanism 122 is started at the same time when rotation of the polishing table 101 is started.
Specifically, the temperature controller 147 controls the ratio of valve opening of the pressure regulating valve 146 based on the PID control according to the difference between the first preset temperature which has been preset and actual temperature of the polishing pad 102 detected by the radiation thermometer 148 to control a flow rate of compressed air ejected from the gas ejection nozzles 124. Thus, the temperature of the polishing pad 102 is controlled at the first preset temperature for obtaining the maximum polishing rate which has been determined in advance. In this main polishing step, high polishing rate can be obtained by a combination of the high polishing pressure and cooling of the polishing pad 102, and hence the total polishing time can be shortened.
Further, in parallel with the above process, the polishing liquid (slurry) is supplied to the optimum position on the polishing pad 102 by swinging the polishing liquid supply nozzle 103 and the flow of air ejected from the gas ejection nozzles 124 is controlled by the gas direction adjustment plates 136. Thus, the flow of the polishing liquid (slurry) on the polishing pad 102 is controlled so as to uniformize the film thickness of slurry flowing toward the top ring 110, thereby obtaining in-plane uniformity. This main polishing step is terminated, for example, when a film thickness measuring instrument (not shown) provided in the polishing table 101 detects the state in which a thickness of a film such as a metal film reaches a predetermined value.
Next, a finish polishing step is performed. In the finish polishing step after the main polishing step, in order to place importance on improvement of the step height characteristics by preventing dishing, erosion or the like from occurring, it is necessary to control the temperature of the polishing pad 102. Specifically, a second preset temperature different from the first preset temperature is set in the temperature controller 147. After shifting to the finish polishing step, compressed air whose flow rate is controlled by the PID control so that the polishing pad 102 reaches the second preset temperature quickly is blown onto the polishing pad 102. For example, in the case where the second preset temperature in the finish polishing step is lower than the first preset temperature in the main polishing step, the flow rate of the compressed air is controlled at the maximum until the polishing pad 102 reaches the second preset temperature. In this manner, the temperature of the polishing pad 102 is controlled at the second preset temperature, and polishing is continued. In the finish polishing step, in order to improve the step height resolution characteristics mainly, the substrate W is pressed against the polishing surface 102a under the second polishing pressure which is lower than the first polishing pressure. Further, in parallel with the above process, the polishing liquid (slurry) is supplied to the optimum position on the polishing pad 102 by swinging the polishing liquid supply nozzle 103, and the gas ejection nozzles 124 and the gas direction adjustment plates 136 are organically operated. Thus, the slurry is flowed more (or less) to the edge or the central area of the substrate to control the polishing rate, the in-plane uniformity and the like. This finish polishing step is terminated, for example, when the film thickness measuring instrument (not shown) provided in the polishing table 101 detects the state in which a surplus metal film or the like located at areas other than trench or the like is polished and removed to expose a surface of an underlayer completely.
Next, ejection of the compressed air from the gas ejection nozzles 124 is stopped and supply of the polishing liquid (slurry) from the polishing liquid supply nozzle 103 is stopped, and then pure water (deionized water) is supplied onto the polishing pad 102 to conduct water polishing of the substrate W. Then, ejection of the compressed air from the gas ejection nozzles 124 is stopped, and the polished substrate W is detached from the polishing surface 102a and held under vacuum by the top ring 110 while the compressed air is prevented from blowing against the substrate W. After that, the substrate W moves away from the polishing pad 102, and hence ejection of the compressed air from the gas ejection nozzles 124 remains at rest in order to prevent the polished surface of the substrate W from being dried due to blowing of the compressed air against the polished surface of the substrate W.
Next, the top ring 110 which holds the substrate W under vacuum is lifted, and the substrate W is moved horizontally from the polishing position to the substrate transfer position. Then, the polished substrate W is transferred at the substrate transfer position to the pusher or the like. After polishing is finished, pure water (or mixed fluid of nitrogen and pure water) is blown on the surface (polishing surface) 102a of the polishing pad 102 from the nozzles 133 of the atomizer 130 to remove foreign matters (polishing pad chips, polishing liquid fixation, and the like) on the polishing pad. In the gas ejection nozzles 124, a cleaning liquid (water) is blown from cleaning nozzles (not shown) onto nozzle opening portions and their surrounding areas, thereby conducting cleaning of the gas ejection nozzles 124. Thus, dirt such as slurry attached to the gas ejection nozzles 124 can be prevented from falling onto the polishing pad 102 to avoid an adverse effect on the processing of the subsequent substrate. Further, the gas ejection nozzle cover 135 and the gas direction adjustment plates 136 are cleaned in the same manner as the above. In this case, because the gas ejection nozzle cover 135 and the gas direction adjustment plates 136 are open in their inner sides, the inner sides of the gas ejection nozzle cover 135 and the gas direction adjustment plates 136 can be cleaned at the time of using the atomizer 130.
Although the embodiments of the present invention have been described herein, the present invention is not intended to be limited to these embodiments. Therefore, it should be noted that the present invention may be applied to other various embodiments within a scope of the technical concept of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-158080 | Jul 2011 | JP | national |
| 2011-245482 | Nov 2011 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14696908 | Apr 2015 | US |
| Child | 15946843 | US | |
| Parent | 13548361 | Jul 2012 | US |
| Child | 14696908 | US |
