JP2007005463A - Polishing device and method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily set a polishing rate for each region of a workpiece in a polishing (CMP) device wherein the polishing rate can be adjusted depending on each region of the workpiece. <P>SOLUTION: In this polishing device, the workpiece W is relatively moved while being pressed against a polishing pad 2 on a polishing plate by means of a polishing head. The polishing head comprises the main body 11, carrier 14 supported so as to be moved up and down, carrier pressing mechanism 12 for pressing the carrier toward the surface of the workpiece by carrier pressing force, liquid injection mechanism for injecting a liquid which provides the pressing force to the surface of the workpiece from the bottom face of the carrier, and controlling section 27 for controlling the carrier pressing mechanism and the liquid injection mechanism. The liquid injection mechanism includes a plurality of liquid sub-injection portions 15-18. When the injection pressures from some of the liquid sub-injection portions are changed, the controlling section controls the carrier pressing force so that the pressing force at the portions corresponding to the other liquid sub-injection portions may be the original one. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polishing apparatus (CMP apparatus) and a polishing method using a chemical mechanical polishing (CMP) method for polishing a plate-like workpiece such as a semiconductor wafer in the middle of a semiconductor manufacturing process, and in particular, a fluid. The present invention relates to a CMP apparatus and method capable of pressing an object to be polished against a polishing pad through a layer and partially changing the pressing force.

  In recent years, in a semiconductor manufacturing process or the like, the surface of a workpiece (wafer) in the middle of a process is subjected to CMP polishing using a CMP apparatus. The CMP device rotates the polishing platen (platen) with the polishing pad attached, and rotates the wafer held by the carrier of the polishing head while supplying slurry (polishing liquid containing abrasive particles) onto the polishing pad. While pressing against the polishing pad, the insulating film or metal film layer formed on the surface of the wafer is polished.

  The CMP apparatus needs to polish a surface of a large area wafer to a predetermined thickness. Since the polishing amount (polishing rate) per unit time changes according to the pressure with which the wafer is pressed against the polishing pad, it is required to apply a uniform pressure to the entire surface of the wafer. Therefore, various methods for applying a uniform pressure to the entire wafer surface have been proposed. For example, in Patent Document 1, a pressure fluid layer is formed between the carrier and the wafer by jetting gas toward the back surface of the wafer on the lower surface of the carrier, and the wafer is pressed against the polishing pad via the pressure fluid layer. Is described. Patent Document 2 describes a structure in which a protective sheet is provided on the lower surface of the carrier in the structure of Patent Document 1. A description of the configuration of these polishing heads is omitted.

  Even if the polishing head described in Patent Documents 1 and 2 is used to press the wafer against the polishing pad with a uniform pressing force, the wafer is rotated and polished. Make a difference. In order to solve such a problem, Patent Document 3 provides a plurality of sub-gas ejection portions capable of selectively ejecting gas on a carrier, and polishing the wafer by selecting the sub-gas ejection portions that eject gas. A CMP apparatus in which the pressure applied to the pad can be partially changed is described. Specifically, since the amount of polishing varies according to the radius, the lower surface of the carrier is divided into a plurality of regions according to the radius, and a sub-gas ejection portion that ejects gas is provided for each region. The gas ejection pressure of the sub-gas ejection section can be set for each region. Since the polishing rate changes according to the pressing force pressing the wafer against the polishing pad, the polishing rate can be changed for each region.

  FIG. 1 shows a schematic configuration of a CMP apparatus in which the lower surface of a carrier is divided into a plurality of regions in accordance with the radius and a sub-gas jetting part for jetting gas is provided in each region in the polishing head described in Patent Document 1. FIG.

  As shown in FIG. 1A, the head main body 11 is provided with fluid ejection means 12, and the gas supplied from the carrier regulator 22 is ejected into the carrier gas chamber 13 to press the carrier 20. The pressing force of the carrier 20 is defined by the pressure of the gas supplied from the carrier regulator 44. As will be described later, the pressing force of the carrier 20 becomes a reference pressing force for pressing the wafer W. Here, this pressing force is referred to as carrier pressing force.

  As shown in FIG. 1B, the lower surface of the carrier 20 is divided into six regions from P to U according to the radius. As shown in FIG. 1A, sub-fluid ejection portions 15 to 18 each having a fluid ejection port for ejecting gas are provided in the Q, R, T, and U regions. Regions A and D are not provided with a sub-fluid ejection portion.

  High-pressure gas is supplied from the gas source 21 to the carrier regulator 22 and the first to fourth partial pressure regulators 23 to 26. The carrier regulator 22 adjusts the high-pressure gas to a predetermined pressure corresponding to the pressing force of the carrier and supplies it to the fluid ejection means 12. In addition, the first to fourth partial pressure regulators 23 to 26 adjust the high-pressure gas to a set pressure and supply the high-pressure gas to the sub-fluid ejecting units 15 to 18. Although not shown, each gas path is provided with a valve so as to control whether or not gas is supplied. Further, when the wafer is attracted to the polishing head and transported onto the polishing pad, the sub-fluid ejecting portions 15 to 18 are switched so as to be connected to an intake mechanism for sucking air.

  The carrier regulator 22 and the first to fourth voltage dividing regulators 23 to 26 are controlled by control signals C and C1 to C4 from the control unit 27. The control unit 27 includes an input unit 28 for receiving a control instruction from the operator or a control signal from the host computer, and a monitor 29 for performing an instruction to the operator and display of a control state.

  The pressing force for pressing the wafer W against the polishing pad 2 is defined by the carrier pressing force with which the gas ejected from the fluid ejecting means 12 presses the carrier 20, that is, the gas pressure output from the carrier regulator 22. For example, if no gas is supplied from the first to fourth partial pressure regulators 23 to 26 to the sub-fluid ejection units 15 to 18, the lower surface of the carrier 20 comes into direct contact with the back surface of the wafer W, and the wafer W is pressed by the carrier pressing force. Press against the polishing pad 2. However, this is not preferable because the lower surface of the carrier 20 is in direct contact with the back surface of the wafer W, and the back surface of the wafer W is damaged or the pressing force of the wafer is not uniform. Therefore, gas is ejected from at least one of the auxiliary fluid ejection portions 15 to 18 at a pressure equal to the carrier pressing force.

  In the example of FIG. 1, a mechanism is used in which the fluid ejection means 12 and the carrier gas chamber 13 are provided and the gas supplied from the carrier regulator 22 to the fluid ejection means 12 presses the carrier 14. It is also possible to use a mechanism that uses a manufactured airbag.

  Further, in the polishing head having the protective sheet described in Patent Document 2, it is possible to provide a sub-gas ejection portion on the lower surface of the carrier so that the pressing force can be changed for each region.

  In the polishing head of FIG. 1, when increasing the polishing rate of one of the regions Q, R, T, and U, any one of the first to fourth voltage dividing regulators 23 to 26 is selected from the carrier regulator 22. When the gas is output at a pressure higher than the output gas pressure, the pressing force for pressing the wafer W against the polishing pad 2 increases in the region where the sub-fluid ejecting portion to which the gas is supplied from the selected partial pressure regulator is provided. . However, the carrier 14 is in a floating state, and when the pressing force in some areas increases, the pressing force in other areas decreases, and the carrier as a whole depends on the gas pressure output from the carrier regulator 22. The balance with the carrier pressing force is achieved. In other words, the non-selected sub-fluid ejecting portion and the sub-fluid ejecting portion select the value obtained by pressing the wafer W against the polishing pad 2 with a pressure smaller than the carrier pressing force and multiplying the pressure at this time by the area of this portion. The total value obtained by multiplying the pressure of the selected region by the area of the selected region is equal to the value obtained by multiplying the carrier pressing force by the area of the carrier.

  In the management of the CMP apparatus having the configuration as shown in FIG. 1, a change in film thickness on the wafer before and after the actual polishing is detected to calculate a polishing rate for each region, and a desired polishing is performed on the entire surface of the wafer. The pressures of the first to fourth voltage dividing regulators 53 to 56 are set so that the amount can be obtained. This setting is performed not only so as to obtain a uniform polishing rate over the entire surface of the wafer, but also by detecting the film thickness distribution on the wafer before polishing so that a desired polishing amount can be obtained according to the detected film thickness distribution. In other words, it may be performed so as to obtain a desired polishing rate distribution. In any case, the pressure of the gas output from the carrier regulator 22 and the first to fourth partial pressure regulators 23 to 26 is set so that a desired polishing rate distribution is obtained.

JP-A-11-347918 JP 2000-317819 A Japanese Patent Laid-Open No. 9-225821 JP 2001-212754 A

  The setting of the pressures of the first to fourth partial pressure regulators 23 to 26 is performed by an operator. When the operator polishes the wafer, the pressure of the partial pressure regulator corresponding to the region where the polishing rate is desired to be increased is increased to set the polishing rate in that region high. However, as described above, when the pressing force in some areas increases, the polishing rate in other areas decreases, causing the following problems.

  FIG. 2A is a diagram for explaining this problem. The polishing rate of the entire wafer surface in a certain state is set as a reference rate. From this state, for example, as shown in FIG. 2A, the peripheral polishing rate is increased, but the other portions (such as the central portion) want to maintain the original polishing rate. In this case, the operator increases the pressure of the voltage dividing regulator corresponding to the peripheral region among the first to fourth voltage dividing regulators 23 to 26. However, as described above, when the pressing force in a part of the region is increased, the pressing force in the other part is decreased, and the polishing rate of the central portion and the like is decreased. If polishing is performed in such a state, sufficient polishing is not performed at the center and the like, resulting in insufficient polishing. Re-polishing is performed when it is found that the polishing is insufficient. However, re-polishing causes a problem that the production efficiency is lowered. Further, if the process proceeds to the next step without knowing that the polishing is insufficient, a defective product is generated, resulting in a problem of a decrease in yield.

  Therefore, when increasing the pressing force in a part of the region, the operator sets the polishing time longer in consideration of the decrease in the polishing rate of the other part. However, since the polishing time is reset based on experience, it is difficult to set an appropriate value, and there is a problem that individual differences are likely to occur.

  In addition, it may be possible to adjust the pressure of the carrier regulator 52 and the like so that the polishing rate of other portions is restored to the original state. However, since this operation is also performed based on experience, the same problem occurs. Produce.

  An object of the present invention is to solve such a problem and to make it possible to more easily set a partial polishing rate in a polishing (CMP) apparatus in which the polishing rate can be partially adjusted.

  In order to achieve the above object, according to the polishing apparatus and the polishing method of the present invention, in response to an instruction to increase the partial polishing rate, the carrier pressure is automatically set so as to maintain the polishing rate in other regions. .

  That is, the polishing apparatus of the present invention is a polishing apparatus that moves a workpiece against a polishing pad on a polishing surface plate with a polishing head while relatively moving the workpiece, and the polishing head moves up and down the head main body and the head main body. A carrier supported in a freely movable direction, a carrier pressing mechanism for pressing the upper surface of the carrier toward the surface of the workpiece with a carrier pressing force, and a pressing force from the lower surface of the carrier to the surface of the workpiece. A polishing apparatus comprising: a fluid ejection mechanism that ejects fluid to be applied; and a control unit that controls the carrier pressing mechanism and the fluid ejection mechanism. The fluid ejection mechanism includes a plurality of sub-fluids that can selectively eject the fluid. An ejection part, and the pressing force on the surface of the workpiece can be partially changed corresponding to the sub-fluid ejection part, and the control part can When the pressure of the fluid ejected from the portion is changed from the first carrier pressing force, the pressing force on the surface of the workpiece in the portion corresponding to the other sub-fluid ejecting portion is the first carrier pressing force. Thus, the carrier pressing force of the carrier pressing mechanism is adjusted to a second carrier pressing force.

  FIG. 2B is a diagram for explaining the principle of the present invention. As shown in FIG. 2A, in order to increase the polishing rate of a part of the region by C1 from the reference average rate, the pressure of the fluid ejected from the part of the sub-fluid ejection part is changed to the first. When the carrier pressing force is increased, the polishing rate of the portion corresponding to the other sub-fluid ejection portion becomes lower by C2 than the average rate. Therefore, as shown in FIG. 2B, in the polishing apparatus of the present invention, the carrier pressing force is changed to the second carrier pressing force, and the polishing rate of the portion corresponding to the other sub-fluid ejection portion is changed to C2. Increase only to reach the average rate. This process is automatically performed by the control unit.

  In the polishing apparatus of the present invention, the polishing rate in a certain region can be set arbitrarily without considering other regions, so that a partial polishing rate can be easily set.

  The polishing apparatus (CMP apparatus) according to the embodiment of the present invention has a configuration similar to that of the conventional CMP apparatus as shown in FIG. 1, and a partial polishing rate setting process performed by the control unit 57 is different. In this embodiment, the polishing head of FIG. 1 will be described as an example. However, the present invention is described in a polishing head having a mechanism using an airbag described in Patent Document 4 and Patent Document 2. The polishing head having the protective sheet can be applied to the case where the auxiliary gas ejection portion is provided on the lower surface of the carrier so that the pressing force can be changed for each region.

  When the inventor of the present application changes the pressure of one region, the polishing rate of that region changes in proportion to the pressure, but the average polishing rate of the entire wafer does not change, and the average polishing rate of the entire wafer does not change the pressure of the carrier. We focused on the change in proportion to Based on this, it has been found that when the polishing rate of a certain region is increased, a decrease in the polishing rate of another region can be corrected by the correction principle described below. The correction principle will be described with reference to FIGS.

  As shown in FIG. 1, in the CMP apparatus of the embodiment, the sub-fluid ejection portions 15 to 18 are provided in the four regions Q, R, T, and U, and the pressure of the gas to be output can be arbitrarily set. And S have nothing. Here, the pressure of the gas injected from the sub-fluid ejection section 15 in one region, for example, the region R, that is, the pressure of the first partial pressure regulator 23 is set higher than the pressure of the carrier regulator 22 (carrier pressure), An example in which no gas is ejected from the sub-fluid ejection portions 16 to 18 in the regions R, T, and U will be described.

  As shown in FIG. 3A, it is assumed that the width of the region R (difference between the inner diameter and the outer diameter) is ZA, and the pressure of the first voltage dividing regulator 23 is ZP higher than the carrier (wafer pressure) WP. Accordingly, the pressing force is ZP in the range of the width ZA of the region R, but the pressing force in the other regions P and R to U is lower than the carrier pressure WP. Since the pressing force of the entire carrier is constant, the total increase in pressure in the portion where the pressure is high is the same as the total decrease in pressure in the portion where the pressure is low.

  The pressing force on the lower surface of the carrier 20 is as shown in FIG. 3A, but the distribution of the pressing force with which the wafer W is actually pressed against the polishing pad 2 becomes smooth, and the actual polishing rate distribution is As shown in FIG. 3B, the polishing rate in the range of the width EZA is ZR. Here, when the polishing rate ZR is expressed by the ratio ZRt (%) to the average rate, it is expressed by ZRT (%) = (ZR−AvR) / AvR.

  ZRT (%) has a predetermined relationship between the pressing force ZP and the carrier pressure WP in the region R shown in FIG. 3A, and is expressed as ZRT (%) = a1 (ZP−WP) / WP + b1. a1 and b1 are constants and can be obtained in advance by experiments.

  As shown in FIG. 4, since the pressing force of the entire carrier is constant, the average polishing rate AvR of the wafer W is constant, and the total amount of increase in the polishing rate of the portion E that is higher than the average polishing rate AvR, and the average The total amount of decrease in the polishing rate of the portion F that has become lower than the polishing rate AvR is the same value, and the area of the portion E where the polishing rate has increased is related to the area of the region R. Therefore, the ratio RbRt (%) to the average rate of the maximum reduction rate ΔRbR of the portion where the polishing rate is low has a relationship of ZRt (%) and RbRt (%) = ZRt (%) × β. Further, there is a relationship of ΔRbR = AvR × RbRt. β can be calculated in advance by experiments.

  FIG. 5 shows a change in the pressing force RR in the regions R to U other than the region Q when the carrier pressure WP is changed in a state where only the pressure in the region Q as shown in FIG. FIG. As shown in the figure, RR changes linearly with respect to WP, and is represented by RR = a2 · WP + b2. Here, since it is necessary to increase the pressing force in the regions R to U by C, ΔWP required to increase the pressing force RR1 in the regions R to U corresponding to the current WP value WPA by ΔRbR, ΔWP = ΔWP / a2 can be obtained. a2 can also be obtained in advance by experiments.

  FIG. 6 shows a flowchart when the control unit 27 of FIG. 1 executes the above-described processing. In step 101, the pressure ZP in the region where the polishing rate is increased is set. The pressure ZP is calculated, for example, by multiplying the carrier pressure by the ratio of the polishing rate to be increased with respect to the average polishing rate.

  In step 102, ZRt (%) is calculated according to the equation shown using the set ZP, carrier pressure WP, and a1 and b1 calculated in advance.

  In step 103, RbRt is calculated by multiplying ZRt (%) by β calculated in advance.

  In step 104, ΔRbR is calculated by multiplying the average rate by RbRt.

  In step 105, ΔWP is calculated by dividing ΔRbR by a2 calculated in advance.

  In step 106, a correction recipe for determining the pressure of the carrier regulator 22, that is, the carrier pressure polishing rate to WP + ΔWP, and the pressure of the partial pressure regulator corresponding to the region to be increased to ZP is determined.

  In step 107, settings are made according to the correction recipe as described above.

  In the above, the CMP apparatus of the embodiment has been described. In order to select a region where the operator increases the polishing rate and to set the pressure ZP, the control unit 27 displays the necessary information on the monitor 29 and the operator. The display which assists the data input from the input means 28 by is performed.

  According to the present invention, the setting operation in the CMP apparatus capable of adjusting the polishing rate by partially changing the pressure is facilitated, so that desired polishing can be performed precisely, and the production efficiency in the semiconductor manufacturing process and the like can be improved. Helps improve yield.

It is a figure which shows schematic structure of the grinding | polishing (CMP) apparatus to which this invention is applied. It is a figure explaining the problem of a prior art and the principle of this invention. It is a figure explaining the correction principle in the CMP apparatus of the Example of this invention. It is a figure explaining the correction principle in the CMP apparatus of an Example. It is a figure explaining the correction principle in the CMP apparatus of an Example. It is a flowchart which shows the partial pressure setting process in the CMP apparatus of an Example.

Explanation of symbols

2 Polishing pad 11 Polishing head body 12 Fluid ejection means (carrier pressing mechanism)
DESCRIPTION OF SYMBOLS 14 Carrier 15-18 Subfluid ejection part 22 Carrier regulator 23 1st partial pressure regulator 24 2nd partial pressure regulator 25 3rd partial pressure regulator 26 4th partial pressure regulator 27 Control part W Wafer (workpiece)

Claims (2)

A polishing apparatus that moves a workpiece against a polishing pad on a polishing surface plate while relatively moving the workpiece with a polishing head,
The polishing head is
The head body,
A carrier supported by the head body so as to be movable in the vertical direction;
A carrier pressing mechanism that presses the upper surface of the carrier toward the surface of the workpiece with a carrier pressing force;
A fluid ejection mechanism for ejecting a fluid that gives a pressing force to the surface of the workpiece from the lower surface of the carrier;
In a polishing apparatus comprising a control unit that controls the carrier pressing mechanism and the fluid ejection mechanism,
The fluid ejection mechanism includes a plurality of sub-fluid ejection portions that can selectively eject the fluid, and the pressing force on the surface of the workpiece is partially changed corresponding to the sub-fluid ejection portion. Is possible,
When the pressure of the fluid ejected from a part of the sub-fluid ejection part is changed from the first carrier pressing force, the control unit is configured to prevent the workpiece in a part corresponding to another sub-fluid ejection part. A polishing apparatus, wherein the carrier pressing force of the carrier pressing mechanism is adjusted to a second carrier pressing force so that a surface pressing force becomes the first carrier pressing force. A polishing method in which a workpiece is relatively moved while being pressed against a polishing pad on a polishing surface plate by a polishing head,
The polishing head is
The head body,
A carrier supported by the head body so as to be movable in the vertical direction;
A carrier pressing mechanism that presses the upper surface of the carrier toward the surface of the workpiece with a carrier pressing force;
A fluid ejection mechanism that ejects a fluid that gives a pressing force to the surface of the workpiece from the lower surface of the carrier;
The polishing rate of the entire workpiece is determined by the carrier pressing force on the surface of the workpiece by the carrier pressing mechanism,
The fluid ejection mechanism includes a plurality of sub-fluid ejection portions that can selectively eject the fluid, and the pressing force on the surface of the workpiece is partially changed corresponding to the sub-fluid ejection portion. Is possible,
When the pressure of the fluid ejected from some of the sub-fluid ejecting portions is changed from the first carrier pressing force, the pressing force of the surface of the workpiece in the portion corresponding to the other sub-fluid ejecting portions is A polishing method, wherein the carrier pressing force of the carrier pressing mechanism is adjusted to a second carrier pressing force so as to be the first carrier pressing force.

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