TW201334916A - Chemical mechanical polishing system and method for chemical mechanical polishing system - Google Patents

Abstract

A chemical mechanical polishing (CMP) system and a method for CMP are provided. The CMP system includes a polishing pad having a polishing surface, and a wafer carrier to retain a wafer proximate to the polishing surface during polishing. A motor assembly rotates the polishing pad and concurrently rotates the wafer during polishing of the wafer. A conditioning disk has a conditioning surface that is in frictional engagement with the polishing surface during polishing. A torque measurement element measures a torque exerted by the motor assembly during polishing. A surface condition analyzer determines a surface condition of the conditioning surface or the polishing surface based on the measured torque.

Description

Chemical mechanical polishing system and method

The present invention relates to a chemical mechanical polishing system and method, and more particularly to a chemical mechanical polishing system and method that can monitor the depth of the groove and trim the disk.

Over the past four decades, the density of integrated circuits has increased with the well-known Moore’s law. In simple terms, Moore's Law states that the number of transistors on integrated circuits (ICs) is approximately doubled every 18 months. Therefore, as long as the semiconductor industry can continue to maintain this simple "law," the speed and power of the integrated circuit will double every 18 months. For the most part, the superior speed and power of such integrated circuits has ushered in the dawn of the information age.

Unlike the laws of nature applicable to human activities, Moore's Law applies only to reformers to overcome technical challenges. One of the advantages created by the reformers over the last decades has been the use of chemical mechanical polishing (CMP) to planarize the layers used to build integrated circuits, thereby helping to provide precisely structured components on integrated circuits.

In order to limit the disadvantages of the planarization process, an improved planarization process is required.

In view of this, one embodiment of the present disclosure provides a chemical mechanical polishing (CMP) system. The CMP system includes a polishing pad having an abrasive surface and a wafer carrier that maintains a wafer proximate to the abrasive surface during polishing. A motor assembly rotates the polishing pad along a pad axis during polishing while simultaneously rotating the wafer along a wafer axis. A conditioning disc having a trimmed surface, wherein the trimming surface assures a frictional force to the abrasive surface during grinding. A torque measuring component that measures a moment applied by the motor component during grinding. A surface condition analyzer determines a surface condition of the trimming surface or the abrading surface based on the measured moment.

Another embodiment of the present disclosure provides a chemical mechanical polishing (CMP) system for grinding a wafer. The CMP system includes a platform configured to rotate along a platform axis, and a polishing pad disposed above the platform and rotating along the platform axis, the polishing pad having an abrasive surface, the polishing surface having a plurality of grooves . A depth measuring component measures the trench depth of the trenches during the polishing of the wafer. A feedback path adjusts a chemical mechanical polishing parameter based on the measured depths of the grooves.

Yet another embodiment of the present invention provides a chemical mechanical polishing (CMP) method. In the above method, a set of chemical mechanical polishing process parameters for planarizing one or more wafers is set. The above method provides a slurry on an abrasive surface of a chemical mechanical polishing station. The above method places a trimmed surface having a frictional force on the above-mentioned abrasive surface to trim the above-mentioned abrasive surface. A surface to be polished on which the wafer is placed is close to the trimmed surface. Then, the above-described group of chemical mechanical polishing process parameters are applied to grind the surface of the wafer to be polished. During the polishing of the wafer, the above method measures a surface condition of the polishing surface or the conditioning surface.

The following is a detailed description of the embodiments and examples accompanying the drawings, which are the basis of the present invention. In the schema or description of the specification, similar or The same part number is used for the same part. In the drawings, the shape or thickness of the embodiment may be expanded and simplified or conveniently indicated. In addition, the components of the drawings will be described separately, and it is noted that elements not shown or described in the drawings are known to those of ordinary skill in the art.

Conventional chemical mechanical polishing (CMP) techniques lack real-time feedback to properly calculate changes in the surface conditions of the polishing pad and/or the conditioning disk. For example, an over-grinded conditioning disk can cause the wafer to be planarized to proceed more slowly and/or make the wafer to be planarized less uniform than a new conditioning disk. Therefore, it is necessary to be able to monitor the surface conditions of the polishing pad and/or the conditioning disk so that the above surface conditions can be changed at an optimum time to maximize the life of the polishing pad/trimming disk, maximize wafer yield and crystal A good balance is achieved between conditions such as uniformity of the round surface.

1 is a block diagram of a chemical mechanical polishing (hereinafter referred to as CMP) system 100 according to an embodiment of the present invention. The CMP system 100 can include a platform 102, a polishing pad 104, a slurry arm 106, a wafer carrier 108, and a conditioning disk 110. In some embodiments of the invention, the CMP system can process wafers having a diameter of 450 nm, however, the CMP system can also be applied to other wafer sizes.

Prior to wafer planarization, the slurry arm 106 dispenses a slurry 111 on the polishing surface 112 of the polishing pad 104, the slurry 111 containing abrasive particles. Motor assembly 114, controlled by chemical mechanical polishing controller 116, then rotates platform 102 and polishing pad 104 along a pad axis 120 (e.g., via platform shaft 118) as indicated by first angular velocity arrow 122. When the polishing pad 104 is rotated, the scanning arm 124 can be used as the center and along A conditioning disk 110 that rotates a wafer shaft 142 moves back and forth over the polishing pad 104 such that the conditioning surface 126 of the conditioning disk 110 provides a frictional force to the abrasive surface 112 of the polishing pad 104. Under this configuration, the trim disk 110 continues to scribe or "rough up" the abrasive surface 112 during grinding to help ensure consistent and uniform planarization. As indicated by the second angular velocity arrow 132, the motor assembly 114 also simultaneously rotates the wafer within the wafer carrier 108 along a wafer axis 128 (e.g., via the wafer carrier axis 130). When a double rotation (such as the rotation indicated by the first angular velocity arrow 122 and the second angular velocity arrow 132) occurs, the wafer is "pressed" into the slurry 111 and a downward force is applied to the abrasive surface 112 by the wafer carrier 108. . The above-described abrasive slurry 111, double rotation (such as the rotation indicated by the first angular velocity arrow 122 and the second angular velocity arrow 132) and the downward force flatten the lower surface of the wafer until the end of the CMP operation is reached. .

To remedy the shortcomings of conventional CMP systems, CMP system 100 includes a surface condition analyzer 136 that determines the surface conditions of polishing pad 104 and/or conditioning disk 110 immediately during grinding. In some embodiments of the invention, a feedback path 138 provides an immediate adjustment of the CMP process parameters 140 during the grinding based on the measured surface conditions. In this manner, the CMP techniques disclosed above contribute to consistent and uniform planarization of the wafer. Moreover, because the on-time measurement limits the downtime of the CMP system 100, the wafer can be processed continuously, and the polishing pad 104 and the conditioning disk 110 can be replaced as accurately as the polishing pad 104 and the conditioning disk 110 are exhausted. These techniques can significantly improve process yield while maximizing the useful life of the polishing pad 104 and the conditioning disk 110.

In order to measure the surface condition of the polishing pad 104, the polishing pad 104 includes a bit. A plurality of trenches (eg, trenches 134a, 134b) in the surface 112 are ground. As the wear of the polishing pad 104 becomes more, the abrasive surface 112 is weakened, thereby reducing the depth of the groove. In this manner, the groove depth corresponds to the (surface) condition of the polishing pad 104. To take advantage of the above advantages, such as a depth measuring component 142 of an acoustic transducer, the trench depth of each trench is measured instantaneously during wafer polishing. Depth measuring element 142 can be disposed on a scanning arm (not shown) and scanned radially above polishing surface 112 to measure the depth of the grooves during grinding. Surface condition analyzer 136 can compare the respective measured trench depths to a predetermined trench depth onset value, and when polishing pad 104 reaches the end of its useful life, CMP controller 116 can be based on the measured trenches Depth informs a CMP operator.

To measure the surface condition of the conditioning disc 110, the CMP system 100 includes a torque measuring component 144 that measures a moment applied by the motor assembly 114 during grinding. Surface condition analyzer 136 then determines the surface condition of trim surface 126 based on the measured torque. Surface condition analyzer 136 determines the surface condition of trim surface 126 using the measured torque proportional to the frictional force between trim surface 126 and abrasive surface 112. Because the ability to trim the surface is used to determine the magnitude of the frictional force to "rough up" the abrasive surface 112, the above measured torque will generally correspond to all of the conditions of the conditioning surface 126. For example, assume that the composition of the slurry, temperature, angular velocity, and the like are all the same. The higher measured torque generally corresponds to a higher frictional force between the trimming surface 126 and the abrading surface 112, which typically corresponds to a less worn (ie, newer) trimming surface 126. Conversely, a lower moment generally corresponds to a smoother (ie, older) trim surface 126.

In some embodiments of the invention, based on the measurement of the trim surface 126 Surface conditions, CMP controller 116 can make immediate adjustments to CMP process parameters during grinding. For example, when the wear of the trim surface 126 becomes more (meaning less friction and less measured torque), the CMP controller 116 can apply more downward force to the trim disk 110 ( And/or more upward force from the platform 102, such that there is greater frictional force between the trimming surface 126 and the abrading surface 112. The CMP controller 116 can also apply more downward force to the wafer using the wafer carrier 108, increase the angular velocity of the platform (the first angular velocity arrow 122), increase the angular velocity of the wafer (the second angular velocity arrow 132), The composition of the slurry 111 is varied and/or the temperature of the slurry 111 is increased to increase the polishing rate to compensate for variations in the conditioning surface 126. Other changes to the CMP process parameters 140 can also be made.

In addition, in some embodiments of the present invention, the surface condition analyzer 136 may compare the measured torque and a certain set of predetermined torque starting values of the CMP process parameters 140, the predetermined torque starting values corresponding to the conditioning disk 110. The moment when "depleted" is determined. For example, for a particular slurry composition, temperature, angular velocity, etc.; if the torque drop is less than a predetermined predetermined torque onset (meaning that the trim surface 126 is excessively worn), the trim disk 110 is considered to be exhausted. Therefore, the CMP controller 116 can notify a CMP operator of the above situation as the moment of replacing the conditioning disc 110.

Figures 2-3 show a more detailed diagram of how to measure the groove depth of the polishing pad 200. The polishing pad 200 of FIG. 2 includes a plurality of grooves 202a, 202b having lower surfaces 204a, 204b recessed in the abrasive surface 206. Although the figure shows only two grooves, it is understood that there may be any number of grooves from one to hundreds to thousands on the polishing pad 200, depending on the relative size of the polishing pad and the width of each groove. . For example A depth measuring component 208 of the energy converter measures the trench depth of the respective trenches during the polishing of the wafer. Depth measuring component 208 can be disposed on a scanning arm (not shown) for radial scanning over polishing pad 200 during polishing of the wafer - as indicated by arrow 210.

The depth measuring component 208 in the embodiment of the present invention may be an acoustic energy converter that transmits an acoustic pulse or sound wave 214 and then measures a reflected sound pulse based on the sound pulse or sound wave 214. Or sound wave 216. Typically, this measurement is performed when a liquid 212, such as deionized water or slurry, is placed on the polishing pad 200 to help limit the attenuation of the transmitted sound pulses or sound waves. To measure the depth of the trench, the acoustic energy converter can analyze the time between the transmission of the acoustic pulse or sound wave 214 and the reception of the reflected sound pulse or sound wave 216; or can measure the transmitted sound pulse or sound wave 214 and receive the reflected sound pulse or sound wave The phase difference between 216. Therefore, in order to measure the first polishing pad thickness t1, the above-described acoustic energy transducer measures the first distance d1 based on the time or phase difference between the transmitted and reflected sound pulses or sound waves. As the acoustic energy transducer continues to scan, a change in time or phase difference is seen as it begins to pass over the trench. In particular, when the acoustic energy transducer continues to scan, a longer time delay or a corresponding phase difference change between the transmitted and reflected sound pulses or sound waves is also seen, which means a second distance d2. By obtaining the difference between the first distance d1 and the second distance d2, the acoustic energy converter can determine the corresponding groove depth. If the measured groove depth is less than a predetermined groove depth start value, it means that the polishing pad is used up. Thus, in this embodiment, a CMP controller can notify a CMP operator to replace the polishing pad 200 with a new one. Also, in some embodiments of the invention, the abrasive ability of the polishing pad 200 may change as the polishing pad wears. because this The reason, when the polishing pad 200 is worn, the instantaneous monitoring of the groove depth allows the CMP system to calculate the amount of change in the polishing characteristics of the polishing pad 200. For example, when the polishing pad wear becomes more (meaning to reduce the groove depth), the CMP controller 116 can utilize the wafer carrier 108 to apply more downward force to the wafer, which can increase the angular velocity of the platform. (First angular velocity arrow 122), may increase the angular velocity of the wafer (second angular velocity arrow 132), may change the composition of the polishing fluid 111, and/or increase the temperature of the polishing fluid 111 to increase the polishing rate, or may change the CMP process parameters. 140 to compensate for changes in the abrasive surface.

Figure 4 is a cross-sectional side view of a chemical mechanical polishing (CMP) station 400 in accordance with another embodiment of the present invention. The CMP station 400 includes a platform 402, a supported polishing pad 404 for grasping the wafer 408 to access the polishing pad 404 during polishing, and a conditioning disk 422 having a conditioning surface 424. Wafer carrier 406 includes an annular positioning ring 410 in which a pocket 412 is a storage wafer 408. The wafer carrier 406 includes a plurality of concentric, variable pressure elements (PE) 414a-414c. Proximity to the reservoir 412 applies a plurality of separate suctions or pressures to the respective concentric regions on the back side 408a of the wafer. The corresponding concentric surface of wafer front side 408b may be referred to as a "to-be-polished" wafer surface.

In some CMP processes, the wafer 408 is left in the reservoir 412 by applying an upward suction force to the back side of the wafer by the variable pressure element 414, lifting the wafer 408 and maintaining the wafer 408 above the positioning ring 410. The lower surface. The platform 402 is then rotated along the platform axis 418, which rotates the corresponding polishing pad 404. Thereafter, a polishing liquid 420 is applied to the polishing pad 404, and the conditioning disk 422 is lowered onto the polishing pad 404. Next, a platform motor (not shown) begins to rotate the wafer carrier 406 along the platform axis 418. At the same time, the wafer carrier 406 is lowered, the positioning ring 410 pressurizes the polishing pad 404, and the wafer 408 is recessed just enough for the wafer carrier 406 to reach the polishing rate. When the wafer carrier 406 reaches the wafer polishing speed, the wafer 408 located in the reservoir 412 is lowered face down to contact the surface of the polishing pad 404 and/or the abrasive slurry 420, such that the wafer 408 is substantially The positioning ring 410 is aligned and limited by an outer positioning ring 410. The positioning ring 410 and wafer 408 continue to rotate the polishing pad 404 and the polishing pad 404 rotates along the platform 402. This double rotation will gradually flatten the wafer 408. During this planarization process, the surface conditions of the conditioning disk 422 and/or the polishing pad 404 can be monitored immediately, and the CMP parameters can be adjusted based on the measured surface conditions described above.

After CMP, wafer carrier 406 and wafer 408 are lifted, and a high pressure ionized water spray is typically applied to polishing pad 404 to remove residual slurry and other particles from polishing pad 404. Other particles may include wafer residues, CMP slurry, oxides, organic contaminants, mobile ions or metal impurities. Next, a post-CMP clean process is performed on the wafer 408.

FIG. 5 is a flow chart of a planarization method according to an embodiment of the present invention. The present methods and other methods disclosed herein may be used to illustrate and/or describe a series of techniques or events, and the order of description of such techniques or events is not intended to limit the invention. For example, some techniques may occur in a different order and/or concurrently with other techniques or events other than those described and/or illustrated in the specification. In addition, not all shown techniques are required to be applied to the embodiments in the specification. And, one or more The techniques and/or stages of the separation are performed in one or more of the techniques described in the specification.

As shown in FIG. 5, method 500 begins in step 502 by setting a CMP process parameter for a CMP system. The CMP process parameters may include, but are not limited to, a grinding time of the wafer to be polished, a downward force applied by a polishing pad to a wafer to be polished, a downward force applied to a finishing surface, a polishing pad or a wafer. The angular velocity, the composition of the slurry, or the temperature. A wafer typically includes a plurality of electrical connections and electrically isolated regions, the plurality of electrically connected and electrically isolated regions being formed using alternating conductive layers and insulating layers.

In step 504, the above method provides a slurry to an abrasive surface of the CMP system.

In step 506, the method places a trimmed surface that has a frictional force on the abrasive surface to trim the abrasive surface. The trim surface described above typically has a hardness greater than the abrasive surface. For example, in various embodiments, the trim surface can be a diamond encrusted surface.

In step 508, the method described above places a surface to be polished of the wafer close to the trimmed surface.

In step 510, the method applies the CMP process parameters to grind the surface of the wafer to be polished.

In step 512, during the polishing of the wafer, the method measures a surface condition of the polishing surface and/or the conditioning surface.

In step 514, the method adjusts one or more CMP process parameters based on the measured surface conditions during the polishing of the wafer.

Accordingly, some embodiments of the invention relate to a CMP system. on The CMP system includes a polishing pad having an abrasive surface and a wafer carrier that maintains a wafer proximate to the abrasive surface during polishing. A motor assembly rotates the polishing pad along a pad axis during polishing while simultaneously rotating the wafer along a wafer axis. A conditioning disc having a trimmed surface, wherein the trimming surface assures a frictional force to the abrasive surface during grinding. A torque measuring component that measures a moment applied by the motor component during grinding. A surface condition analyzer determines a surface condition of the trimming surface or the abrading surface based on the measured moment.

Other embodiments of the invention relate to a CMP system for grinding a wafer. The CMP system includes a platform configured to rotate along a platform axis, and a polishing pad disposed above the platform and rotating along the platform axis, the polishing pad having an abrasive surface, the polishing surface having a plurality of grooves . A depth measuring component measures the trench depth of the trenches during the polishing of the wafer. A feedback path adjusts a chemical mechanical polishing parameter based on the measured depths of the grooves.

Another embodiment of the invention is directed to a chemical mechanical polishing (CMP) process. In the above method, a set of chemical mechanical polishing process parameters for planarizing one or more wafers is set. The above method provides a slurry on an abrasive surface of a chemical mechanical polishing station. The above method places a trimmed surface having a frictional force on the above-mentioned abrasive surface to trim the above-mentioned abrasive surface. A surface to be polished on which the wafer is placed is close to the trimmed surface. Then, the above-described group of chemical mechanical polishing process parameters are applied to grind the surface of the wafer to be polished. During the polishing of the wafer, the above method measures a surface condition of the polishing surface or the conditioning surface.

Although the invention has been disclosed above by way of example, it is not intended to be limiting In the present invention, the scope of the present invention is defined by the scope of the appended claims, unless otherwise claimed.

100‧‧‧Chemical mechanical grinding system

102, 402‧‧‧ platform

104, 200, 404‧‧‧ polishing pads

106‧‧‧Slurry arm

108, 406‧‧‧ wafer carrier

110, 422‧‧‧Finishing disc

111, 420‧‧‧ polishing fluid

112, 206‧‧‧ grinding surface

114‧‧‧Motor parts

116‧‧‧Chemical Mechanical Grinding Controller

118, 418‧‧‧ platform axis

120‧‧‧ polishing pad shaft

122‧‧‧First angular speed arrow

124‧‧‧Scanning arm

126, 424‧‧‧ Finished surface

128‧‧‧ wafer axis

130‧‧‧ Wafer carrier shaft

132‧‧‧second angular speed arrow

134a, 134b, 202a, 202b‧‧‧ trench

136‧‧‧ Surface Condition Analyzer

138‧‧‧Reward path

140‧‧‧Chemical mechanical polishing process parameters

142, 208‧‧‧ depth measuring components

144‧‧‧ torque measuring components

204a, 204b‧‧‧lower surface

210‧‧‧ arrow

214‧‧‧Sound pulse or sound wave

216‧‧‧Reflecting sound pulses or sound waves

T1‧‧‧First polishing pad thickness

D1‧‧‧first distance

D2‧‧‧Second distance

400‧‧‧Chemical Machinery Grinding Station

408‧‧‧ wafer

408a‧‧‧ wafer back side

408b‧‧‧ wafer front side

410‧‧‧ positioning ring

414a~414c‧‧‧Variable pressure components

500‧‧‧ method

502, 504, 506, 508, 510, 512, 514 ‧ ‧ steps

Figure 1 is a block diagram of a chemical mechanical polishing system in accordance with one embodiment of the present invention.

2 is a top view of a chemical mechanical polishing system according to an embodiment of the present invention, the chemical mechanical polishing system having a polishing pad including a series of concentric circular grooves, and a groove depth measuring component attached to the polishing Move back and forth over the pad.

Figure 3 is a cross-sectional side view of the chemical mechanical polishing system of Figure 2.

Figure 4 is a block diagram of a chemical mechanical polishing system in accordance with another embodiment of the present invention.

FIG. 5 is a flow chart of a planarization method according to an embodiment of the present invention.

500‧‧‧ method

502, 504, 506, 508, 510, 512, 514 ‧ ‧ steps

Claims (10)

A chemical mechanical polishing system comprising: a polishing pad having an abrasive surface; a wafer carrier that maintains a wafer close to the polishing surface during polishing; and a motor component along a polishing pad during polishing of the wafer A shaft rotates the polishing pad and simultaneously rotates the wafer along a wafer axis; a conditioning disk having a trimming surface, wherein the trimming surface has a frictional force on the polishing surface during polishing of the wafer; a torque measuring component that measures a moment applied by the motor component during grinding of the wafer; and a surface condition analyzer that determines a surface condition of the trimming surface or the grinding surface based on the measured torque. The chemical mechanical polishing system of claim 1, wherein the polishing pad comprises a plurality of grooves in the polishing surface, the chemical mechanical polishing system further comprising: a depth measuring component for grinding the wafer The depths of the trenches are measured separately during the period. The CMP system of claim 1, wherein the motor component rotates the polishing pad at a first angular velocity along the polishing pad axis and rotates the crystal at a second angular velocity along a wafer axis circle. The chemical mechanical polishing system of claim 3, further comprising: a feedback path that adjusts the first angular velocity or the second angular velocity based on the surface condition determined by the surface condition analyzer. The chemical mechanical polishing system according to claim 1, further comprising: a slurry dispenser, wherein a polishing liquid is applied to the polishing surface; and a feedback path is determined based on the surface condition analyzer The surface condition adjusts a slurry composition or a slurry temperature. The chemical mechanical polishing system of claim 1, wherein the wafer carrier comprises a plurality of concentric and variable downward force elements, such that the polishing pad applies a respective downward direction to the concentric wafer area. The chemical mechanical polishing system further includes: a feedback path that adjusts the respective downward forces based on the surface condition determined by the surface condition analyzer. A chemical mechanical polishing method comprising the steps of: setting a set of chemical mechanical polishing process parameters for planarizing one or more wafers; providing a polishing liquid on an abrasive surface of a chemical mechanical polishing station; Grinding surface has a trimming surface guaranteed by friction to trim the grinding surface; a surface to be polished of the wafer is placed close to the trimmed surface; and the set of chemical mechanical polishing process parameters is used to grind the crystal to be polished a rounded surface; and measuring a surface condition of the abrasive surface or the conditioning surface during polishing of the wafer. The chemical mechanical polishing method as described in claim 7 of the patent application, The method further includes: adjusting the set of chemical mechanical polishing parameters based on the measured surface condition during the grinding of the wafer. The chemical mechanical polishing method of claim 7, wherein the surface condition is measured by measuring a moment of moving the polishing surface or a motor component of the wafer during polishing of the wafer. The CMP method of claim 7, wherein the polishing surface comprises a plurality of trenches, wherein the surface conditions are measured by measuring depths of the trenches during polishing of the wafers.