Patent ID: 12240074

DESCRIPTION OF EMBODIMENTS

Now, basic concepts of the present invention will be described with reference toFIG.16.

With a conventional polishing head mechanism, a processing pressure that is uniform or stepwise in the radial direction is applied to the entire area (from the center to the outer circumferential edge) of a wafer. In particular, the pressurization at the outer circumferential edge part has a significant effect on ESFQR. For example, in the FEM analysis, under conditions that a soft pad is used, the entire area of the wafer is uniformly pressurized, and the Gap value (the distance from the inner circumference of a retainer ring part105to the edge of a wafer W) is several millimeters, the maximum compression stress at the edge part is 1.5 to 2 times smaller than the central part pressure. In the case of a wafer having a diameter of 300 [mm], the stress influence range is about 15 [mm] from the edge. From this analysis result, it was found that if a reduced processing pressure is applied to the outer circumferential edge part, the edge part stress can be made equal to the central part stress.

FIG.16shows a result of analysis under conditions that a wafer having a diameter of 300 [mm] is used, and an edge part having a width of 5 [mm] of the wafer is set in a non-pressure state (the pressurized part has a diameter of 290 [mm]). Although this drawing shows displacement, the penetrating displacement of the edge part into the pad is about a half of that of the central part, which shows that the processing pressure is a reduced pressure. It is found that the pressure reduction phenomenon begins at about 30 [mm] from the edge, which is about six times greater than the non-pressure width of 5 [mm]. Based on this finding, a condition that provides ESFQR≈0 can be searched for by adjusting parameters such as the diameter of the pressurized part area, the retainer ring pressure, and the Gap value.

In the following, an example embodiment of the present invention will be described with reference to the drawings. A polishing treatment device according to this embodiment is directed to a substrate (referred to also as a wafer, hereinafter), such as a semiconductor wafer or a glass substrate, as a polishing target. In this specification, one of the surfaces of the substrate is referred to as a circular or substantially circular polished surface. A surface of the polishing pad that comes into contact with the polished surface of the wafer is referred to as a polishing surface.

The polishing treatment device includes a polishing table for horizontally rotating a polishing pad that is bonded to the polishing table and serves as a polishing member, and a polishing head for making a polished surface of a substrate face the polishing pad and bringing the polished surface into sliding contact with the polishing pad.

The substrate is pressed against the polishing pad by the polishing head. The polishing treatment of the polished surface is performed by rotating the polishing table and the polishing head while supplying a polishing liquid (slurry) to the polishing pad.

EXAMPLE EMBODIMENT

FIG.1is a schematic diagram showing a configuration of a polishing treatment device S according to an embodiment.

The polishing treatment device S shown inFIG.1includes a polishing table51, and a polishing pad50is bonded to a surface of the polishing table51.

The polishing treatment device S further includes a polishing head100that holds a substrate (wafer) W and presses a polished surface of the substrate W against the polishing pad50, a nozzle N that supplies a polishing liquid to the polishing pad50, a motor (not shown) that horizontally rotates the polishing table51and the polishing head100, a polishing liquid supply mechanism (not shown) connected to the nozzle N, and a control unit20including a computer that controls driving parts including the motor.

The polishing pad50has a disc-like shape, and the radius of the polishing pad50is greater than the maximum diameter (diameter) of the polished surface of the wafer W. With this mechanism, the number of revolutions and the direction of rotation of the polishing pad50and the polishing head100can be changed to adjust the relative polishing rate in the wafer W plane. The polishing pad50has an elasticity and may be made of a commercially-available material, such as nonwoven fabric or foamed urethane.

The polishing head100has a holding mechanism that holds the wafer W with the polished surface thereof in sliding contact with the polishing pad50, and a pressing mechanism that applies a pressure to the held wafer W in a direction toward the polishing pad50from the back (back side) of the polished surface thereof. These mechanisms will be described in detail later.

The control unit20mainly performs positioning of the nozzle N, control of the start and stop of the supply of the polishing liquid from the nozzle N, control of the amount of supply per unit time of the polishing liquid ejected and supplied from the nozzle N, and control of the start and stop of the actuation of the motor, for example. The rotational force of the motor controlled by the control unit20is transmitted to the polishing table51via a driving part (not shown). In this way, the polishing table51horizontally rotates or stops rotating.

The rotational force (torque) from the motor is also transmitted to the polishing head100via a driving part (not shown, such as a universal joint). In this way, the polishing head100horizontally rotates or stops rotating.

The direction of rotation of the polishing table51and the direction of rotation of the polishing head100are typically the same. This is because if the directions of rotation are reverse directions, the relative polishing rate in the wafer plane may be uneven, and the even amount polishing may be unable to be achieved. The polishing accuracy can be improved by adjusting the rotational speed of the polishing table51and the polishing head100that are rotating in the same direction.

The rotational force of a single motor may be transmitted to the polishing table51and the polishing head100via gears with different gear ratios, or the rotational forces of motors may be separately transmitted to the polishing table51and the polishing head100. These designs can be arbitrarily chosen. A control procedure by the control unit20will be described later.

The polishing liquid is supplied from the nozzle N to the polishing pad50for a predetermined time after the rotational speed of the polishing table51reaches a predetermined value under the control of the control unit20.

Next, the polishing head100of the polishing treatment device S and a peripheral arrangement thereof will be described in detail.

[Polishing Head and Peripheral Arrangement]

FIG.2is a schematic vertical cross-sectional view for illustrating an example of the polishing head100of the polishing treatment device S and a peripheral arrangement thereof. An example of a configuration of the polishing head100will be described with reference toFIG.2.

In the description below, in order to further improve the global backside ideal range (GBIR) or the like of the wafer surface, the wafer W is held with the polished surface thereof in sliding contact with the polishing pad50under the pressure controlled by the polishing treatment device S, and the pressure is applied to the held wafer W in a direction toward the polishing pad50from the back (back side) of the wafer W opposite to the polished surface thereof.

[Configuration of Polishing Head]

Generally speaking, the polishing head100shown inFIG.2has a holding mechanism that brings the wafer W to be polished into sliding contact with the polishing pad50in a state where a polishing pressure (processing pressure) is applied to the wafer W, for example. The polishing head100also has a pressing mechanism that applies the polishing pressure (processing pressure) to the wafer W or presses a retainer ring6against the polishing pad50.

The retainer ring6according to this embodiment prevents the wafer W energized by the rotational force of the polishing head100and the polishing table51from flying out in the radial direction. The retainer ring6is also involved with the contact pressure between the wafer edge part and the polishing pad50.

The polishing head100includes a head housing2, a membrane support ring3, a membrane4, a backing film5, the retainer ring6, and a flexible plate7.

The polishing head100is configured so that a driving force (such as a rotational force (torque) from the motor, which is actuation means) is transmitted thereto via the flexible plate7connected to the head housing2. Specifically, the membrane support ring3is connected to the flexible plate7connected to the head housing2(the connections are not shown), and the retainer ring6is connected to the membrane support ring3via a drive pin8.

Thus, the components of the polishing head100can integrally horizontally rotate or stop rotating. The flexible plate7serves as driving means that integrally horizontally rotates the membrane support ring3and the retainer ring6.

The start and stop of the rotation, the number of revolutions per unit time and the like are controlled by the control unit20based on specifications previously set.

The head housing2includes a first flange part21that extends outward from an upper position of a circumferential surface of a cylindrical body and a second flange part22that extends outward from a lower position of the circumferential surface of the cylindrical body. AlthoughFIG.2shows an example in which the head housing2is formed by a combination of the first flange part21and the second flange part22, the present invention is not limited to this, and the head housing2having the first flange part21and the second flange part22may be integrally formed.

The membrane support ring3is an annular body sized to surround the outer circumference of the second flange part22of the head housing2, and includes a third flange part31formed at an upper end part thereof and located between the first flange part21and the second flange part22. The membrane support ring3is made of SUS material, for example. AlthoughFIG.2shows an example in which the membrane support ring3has the third flange part31as a separate part, the present invention is not limited to this, and the membrane support ring3may have the third flange part31as an integrated part.

The membrane4covers a lower end-side opening part of the membrane support ring3and holds the wafer W with the backing film5pasted to a front surface of the membrane4interposed therebetween. The membrane4is an elastic body of a cylindrical shape (cylindrical elastic body) formed in a substantially cylindrical (pan-like) shape having an inner diameter that allows the membrane4to be fitted around the outer circumferential surface of the membrane support ring3. The membrane4is made of a rubber material having high strength and durability, such as ethylene propylene rubber (EPDM) or silicone rubber.

The backing film5is a thin film stretched on an outer bottom surface (outer surface) of the membrane4. The backing film5may be made of a porous material, such as nonwoven fabric. The backing film5makes the polished surface of the wafer W face (abut against) the polishing pad50and holds the wafer W in sliding contact with the polishing pad50. In this way, the membrane4and the backing film5serve as the holding mechanism that holds the wafer W.

The retainer ring6is shaped to surround the outer circumference of the wafer W. Not only does the retainer ring6prevent the wafer W energized by the rotational force of the polishing head100and the polishing table51from flying out in the radial direction, the retainer ring6is involved with controlling the contact pressure between the wafer edge part and the polishing pad50.

The polishing head100is configured so that a clearance is formed between the edge part of the wafer W and the inner circumferential wall of the retainer ring6in the polishing processing. In addition, “pad retaining”, which is pressing of the surface of the polishing pad50by the retainer ring6, can be achieved with high accuracy functionally. In this way, the retainer ring6serves as a part of the pressing mechanism of the polishing head100.

A gel-body ring10(referred to as an annular elastic body10, hereinafter) is arranged on a back surface of the membrane4of the polishing head100, and a corrective pressing ring11that applies a pressure to an upper surface of the annular elastic body10is arranged inside the membrane support ring3(annular body3). Configurations of the annular elastic body10and the corrective pressing ring11will be described in detail below.

FIG.3are schematic vertical cross-sectional views showing examples of the cross-sectional shape of the annular elastic body10.

The annular elastic body10is an elastic body formed in a ring shape and has a size smaller than the size of the wafer W. For example, the annular elastic body10can be formed to have a rectangular cross-sectional shape such as that shown inFIG.3(a)(corresponding to the annular elastic body10inFIG.2), a substantially trapezoidal shape with a larger bottom width and a smaller top width such as that shown inFIG.3(b), or a substantially semi-circular cross-sectional shape such as that shown inFIG.3(c).

The annular elastic body10may be made of H0-100·C (soft), H5-100·C7 (medium), or H15-100·C15 (hard), which are available from EXCEAL Co., Ltd., for example.

The hardness of the gel used, the width and height of the gel-body ring, the indenter shape of the corrective pressing ring11and the like are chosen according to the pressure bulb described later, and these are set by determining a “compensating pressure pattern” of a compensating pressure applied to a back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface of the wafer W. The indenter shape means the pressing surface shape of the corrective pressing ring11that presses the upper surface of the annular elastic body10.

FIG.4are schematic vertical cross-sectional views showing examples of the cross-sectional shape of the corrective pressing ring11.

The corrective pressing ring11includes an upper surface part11band a lower surface part11cthat are formed in a ring shape, and a plurality of connection parts11dformed in a cylindrical shape. The upper surface part11band the lower surface part11care connected to each other by the connection parts11d. The corrective pressing ring11is held by the flexible plate7connected to the membrane support ring3. Specifically, the corrective pressing ring11is held with the connection parts11dmovably inserted in holes (not shown) formed in the flexible plate7.

The pressing surface shape of the corrective pressing ring11may be a flat pressing surface shape such as that shown inFIG.4(a)or a pressing surface shape having a substantially semi-circular cross-sectional shape such as that shown inFIG.4(b).

The pressing surface shape of the corrective pressing ring11is designed by considering the hardness of the gel used, the width and height of the gel-body ring and the like according to the pressure bulb described later, and determined by determining the “compensating pressure pattern” of the compensating pressure applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface of the wafer W.

[Pressing Mechanism]

With the polishing head100, as shown inFIG.2, the space defined by the second flange part22of the head housing2, the membrane support ring3(annular body3) and the membrane4provides a pressure chamber (sealed air chamber) for applying a pressure to the wafer W toward the polishing pad50from the back (back side) of the polished surface thereof. The pressure chamber formed in the polishing head100is a space corresponding to a region above the part of the membrane4to which the backing film5is attached.

The second flange part22of the head housing2and the membrane support ring3(annular body3) are connected to each other by a sealing partition wall12. The sealing partition wall12is made of an elastic material, such as rubber.

The polishing head100of the polishing treatment device S is configured so that a pressure fluid (such as compressed air) can be supplied to or collected from the pressure chamber through an air pipe coupled to a fluid supply mechanism (not shown). That is, the polishing head100is configured so that a processing pressure P1 applied to the wafer W can be produced by adjusting the amount of the pressure fluid supplied to the pressure chamber (as shown by the dashed line P1 inFIG.2).

This arrangement serves as first pressure adjusting means that adjusts the processing pressure P1 applied to the back side of the wafer W opposite to the polished surface by adjusting the pressure in the space (pressure chamber) surrounded by the head housing2(second flange part22), the membrane support ring3and the membrane4under the control of the control unit20.

FIG.5is a diagram for illustrating the “pad retaining” that is pressing of the surface of the polishing pad50by the retainer ring6.

With the polishing head100of the polishing treatment device S, as shown inFIG.2, an air bag P2 is arranged between the first flange part21of the head housing2and the retainer ring6.

Furthermore, as shown inFIG.2, the polishing head100of the polishing treatment device S is configured so that the pressure fluid (such as compressed air) can be supplied to or collected from the air bag P2 through an air pipe coupled to the fluid supply mechanism (not shown). That is, the polishing head100is configured so that a pressure P2 with which the retainer ring6presses the surface of the polishing pad50can be produced by adjusting the amount of the pressure fluid supplied to the air bag P2 (as shown by the dashed line P2 inFIG.2).

The air bag P2 is formed in a ring shape, and expands when the air bag P2 is filled with the pressure fluid. As shown inFIG.5, this allows the retainer ring6to press the polishing pad50with the pressure P2 according to the amount of the pressure fluid in the air bag P2.

This arrangement serves as second pressure adjusting means that adjusts the pressure P2 applied to the polishing pad50by the retainer ring6by means of the first flange part21by adjusting the amount of the pressure fluid supplied to the air bag P2 under the control of the control unit20. In other words, the second pressure adjusting means is intended to optimize the wafer edge part stress.

FIG.6is a schematic vertical cross-sectional view for illustrating an operation of raising or lowering of the membrane support ring3.

With the polishing head100of the polishing treatment device S, as shown inFIG.2, an air bag P3 is arranged between the second flange part22of the head housing2and the third flange part31of the membrane support ring3.

Furthermore, as shown inFIG.2, the polishing head100of the polishing treatment device S is configured so that the pressure fluid (such as compressed air) can be supplied to or collected from the air bag P3 through an air pipe coupled to the fluid supply mechanism (not shown). That is, the polishing head100is configured so that the membrane support ring3can be raised or lowered by adjusting the amount of the pressure fluid supplied to the air bag P3 (as shown by the dashed line P3 inFIG.2).

The air bag P3 is formed in a ring shape, and expands when the air bag P3 is filled with the pressure fluid. As a result, as shown inFIG.6, the membrane support ring3is raised (FIG.2) or lowered (FIG.6) according to the amount of the pressure fluid in the air bag P3. That is, the membrane4and the backing film5are also raised or lowered in response to the operation of raising or lowering the membrane support ring3.

As the membrane4and the backing film5is raised or lowered as the membrane support ring3is raised or lowered, the area of the circumferential region of the wafer W that is in contact with the backing film5varies. In response to this variation, the processing surface pressure also varies which is applied to the back-side circumference region of the wafer W opposite to the polished surface of the wafer W (seeFIGS.2,6, and16).

As a result of the circumferential part of the membrane4being raised by the air bag P3, a region in which the processing surface pressure is applied (referred to as a pressurized circumferential band) and a region in which the processing surface pressure is not applied (referred to as a non-pressurized circumferential band) are formed in the circumferential part of the wafer W. The annular elastic body10is arranged with the centerline of the bottom surface thereof aligned with the boundary between the pressurized circumferential band and the non-pressurized circumferential band of the membrane4and the wafer W (seeFIG.11, for example). By arranging the annular elastic body10in this way, the principle and mechanism of ESFQR≈0, which cannot be elucidated with the conventional polishing heads, can be elucidated, and GBIR can also be dramatically improved.

This arrangement serves as third pressure adjusting means that adjusts, by means of the second flange part22, a pressurized area P1′ in which the pressure is applied to the back-side circumference opposite to the polished surface via the third flange part31, by adjusting the differential pressure against the processing pressure under the control of the control unit20.

The polishing head100of the polishing treatment device S includes a stopper13as restraining means that restrains the raising of the membrane support ring3within a predetermined range. The stopper13is foiled by a screw, for example.

FIG.7is a schematic vertical cross-sectional view for illustrating an operation of the corrective pressing ring11.

As described above, the annular elastic body10is arranged on the back side of the membrane4of the polishing head100, and the corrective pressing ring11that applies a pressure to the upper surface of the annular elastic body10is arranged. In addition, as shown inFIG.2, an air bag P4 is arranged between the second flange part22of the head housing2and the corrective pressing ring11.

Furthermore, as shown inFIG.2, the polishing head100of the polishing treatment device S is configured so that the pressure fluid (such as compressed air) can be supplied to or collected from the air bag P4 through an air pipe coupled to the fluid supply mechanism (not shown). That is, the polishing head100is configured so that the corrective pressing ring11can be raised or lowered by adjusting the amount of the pressure fluid supplied to the air bag P4 (as shown by the dashed line P4 inFIG.2).

In this embodiment, the operation of raising the corrective pressing ring11is achieved by a biasing force of a spring11a.

The air bag P4 is formed in a ring shape, and expands when the air bag P4 is filled with the pressure fluid. As a result, as shown inFIG.7, the corrective pressing ring11is raised (FIG.2) or lowered (FIG.6) according to the amount of the pressure fluid in the air bag P4. That is, the pressure applied to the upper surface of the annular elastic body10varies in response to the operation of raising or lowering the membrane support ring3.

The pressure applied to the upper surface of the annular elastic body10varies in response to the operation of raising or lowering the corrective pressing ring11. In response to this variation, the compensating pressure pattern of a compensating pressure P4 applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface also varies (seeFIGS.2and7).

This arrangement serves as fourth pressure adjusting means that adjusts, by means of the second flange part22, the compensating pressure P4 applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface by adjusting the contribution of the pressure fluid supplied to the air bag P4 to the processing pressure applied to the back side of the wafer W opposite to the polished surface under the control of the control unit20.

[Polishing Treatment]

Next, a polishing treatment performed by the polishing treatment device S according to this embodiment will be described.

The polishing treatment performed by the polishing treatment device S according to this embodiment begins with determining an operating condition (treatment condition), which is determined based on characteristics of a lot of wafers or the status of the polishing treatment device. After that, the continuous polishing treatment (mass production) of wafers is performed based on the operating condition.

Steps of determining the operating condition (treatment condition) will be described below.

[Determination of Pressure P2]

FIG.8is a graph showing an RR curve at the wafer edge part before and after polishing. The vertical axis indicates the removal rate RR [μm/min] in dimensionless numbers, and the horizontal axis indicates the radial position [mm] on the wafer. In this example, ΔRR=0.2 is observed.

As a first step, the air bag P3 is set in a non-pressure state in which no pressure fluid is supplied. As a result, the membrane support ring3is in a lowered state (seeFIG.6). The air bag P4 is also set in the non-pressure state in which no pressure fluid is supplied. As a result, the corrective pressing ring11applies no pressing force to the upper surface of the annular elastic body10.

An adjustment is then made so that RR=1.2 is achieved by applying the processing pressure P1 to the wafer W and at the same time adjusting the pressure P2 with which the retainer ring6presses the surface of the polishing pad50(Pr=1.75*P1). In this example, ΔRR=0.2 is observed.

ΔRR shown inFIG.8substantially varies with Gap. Gap varies between 0 and 1 [mm] in one rotation of the wafer about the rotational coordinate axis thereof, and therefore, ΔRR is more accurately measured by finding an average behavior from actual operation data than by using a static surface pressure sheet.

[Compensation Curve]

FIG.9(a)is a graph for illustrating a surface pressure matching method for the outermost edge part and the central part of the wafer. The vertical axis indicates the removal rate RR [μm/min] in dimensionless numbers, and the horizontal direction indicates the radial position [mm] on the wafer.

As can be seen from the graph ofFIG.9(a), a compensation curve indicated by the black solid line is obtained by averaging of the black dashed line (polishing RR) and the black dotted line (pressure attenuation).

FIG.9(b)is a diagram showing an example relationship between a pressurized region and an edge part stress attenuation, and also is a graph showing a curve showing a relationship between the edge part stress attenuation and the wafer back-side contact area with the membrane, that is, the radius (PAR) of the loaded area. The vertical axis indicates the removal rate RR [μm/min] in dimensionless numbers, and the horizontal direction indicates the radial position [mm] on the wafer.

[Position Adjustment (H) of Raising Operation of Membrane Support Ring3]

As a second step, the pressure fluid is supplied to the air bag P3. As a result, the membrane support ring3is raised (seeFIG.2). Using a stopper13(position adjustment: height H) that restrains the raising of the membrane support ring3within a predetermined range, an adjustment is made so that RR=1.0 is achieved at an edge point. The air bag P4 remains in the non-pressure state in which no pressure fluid is supplied.

The adjustment can be performed by measuring H versus RR (DL) using a surface pressure sheet. Measurement of H can be achieved using LS-100CN available from Optex Co., Ltd., for example.

FIG.10are diagrams for illustrating an example of the compensating pressure pattern designed based on the pressure bulb.FIG.10(a)shows an example of the range in which a load (surface pressure width: B, unit area pressure: q) and a stress act according to the pressure bulb.

As shown inFIGS.10, the compensating pressure P4 applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface by the corrective pressing ring11via the annular elastic body10is transmitted according to the pressure bulb behavior, and the compensating pressure pattern is thus formed.

The measurement of the compensating pressure pattern can be performed using I-SCAN20-F02 (resolution pitch: 0.2 [mm]) available from Tekscan, Inc., for example.

FIG.11is a diagram showing an example distribution curve (compensating pressure pattern) of the compensating pressure on the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface (the recessed part shown by the black solid line inFIG.9(a)is compensated for). The vertical axis indicates the removal rate RR [mm/min] in dimensionless numbers, and the horizontal axis indicates the radial position [mm] on the wafer.

Through the first step and the second step, the compensating pressure pattern of the compensating pressure P4 applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface by the corrective pressing ring11via the annular elastic body10is determined as shown inFIG.11.

[Control Procedure for Polishing Treatment]

Next, a treatment procedure by the polishing treatment device S according to this embodiment will be described.FIG.12is a flowchart for illustrating an example of a main control procedure by the control unit20when performing the polishing treatment. The treatment procedure described below is to perform the continuous polishing treatment (mass production) of wafers under the operating condition described above.

The control unit20starts the control in response to receiving a start instruction input from an operator of the polishing treatment device S (S100). It is assumed that, as the operating condition, the compensating pressure pattern of the compensating pressure P4 applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface by the corrective pressing ring11via the annular elastic body10has been obtained.

After a predetermined initial processing, the control unit20makes the holding mechanism of the polishing head100start holding the wafer W (S101).

The control unit20makes the polishing head100having received the wafer W from a wafer passing table (not shown) to a polishing treatment start position (S102).

The control unit20adjusts the processing pressure P1, the pressurized area P1′, and the pressure P2 by supplying a predetermined amount of pressure fluid to each of the pressure chamber, the air bag P2, and the air bag P3 (S103).

When it is confirmed that each pressure according to the amount of supply of the pressure fluid is appropriate (Yes in S104), the control unit20issues, to a motor (not shown), an instruction to start rotating the polishing table51and the polishing head100(S105). In response to this, the polishing table51and the polishing head100start to horizontally rotate.

After instructing to start rotating the polishing table51and the polishing head100, the control unit20instructs to position the nozzle N and issues an instruction to start the supply of the polishing liquid to the polishing liquid supply mechanism (S106). In response to this, the polishing liquid is supplied from the nozzle N to the surface of the polishing pad50. In this way, the control unit20starts the polishing (S107).

The control unit20starts the pressure adjustment of the processing pressure based on the operating condition (S108). Here, the pressure adjustment in the processing of step S108 will be described. Generally speaking, the pressure adjustment in the processing of step S108 includes a first step and a second step.

In the first step, the control unit20makes the first pressure adjusting means described above apply the processing pressure P1 to the back side of the wafer W opposite to the polished surface, makes the second pressure adjusting means apply the pressure P2 to the polishing pad50, and makes the third pressure adjusting means raise the membrane support ring3, thereby adjusting the pressurized area P1′ so that the processing pressure on the back-side circumference of the wafer W opposite to the polished surface is smaller than the processing pressure P1 applied by the first pressure adjusting means. In this step, the control unit20controls so that the air bag P4 is in the non-pressure in which no pressure fluid is supplied.

In the second step, the control unit20makes the first pressure adjusting means described above stop applying the processing pressure P1, makes the second pressure adjusting means described above apply the pressure P2 to the polishing pad50, and makes the third pressure adjusting means described above lower the membrane support ring3, thereby releasing the processing pressure-reduced state (the state of the pressurized area P1′) at the back-side circumference of the wafer W opposite to the polished surface, and controls the fourth pressure adjusting means described above to apply the compensating pressure P4 to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface.

Switching between the first step and the second step is achieved in an internal sequence while the polishing table51and the polishing head100are kept rotating.

The control unit20then determines whether or not the polishing is completed (S109). This determination is based on a detection result from a sensor, for example, and the polishing is ended when it is determined that the wafer W is polished to a desired thickness. Otherwise (No in S109), the procedure returns to the processing of step S108.

When it is determined that the polishing is completed (Yes in S109), the control unit20instructs the polishing liquid supply mechanism to stop supplying the polishing liquid (S110).

The control unit20then issues a stop instruction to the motor to stop the rotation of the polishing table51and the polishing head100(S111). The polishing head100is then moved to a table on which polished wafers W are to be placed (S112). This is the end of the polishing treatment.

Whether holding of the wafer is released or not can be determined by using various sensors (not shown), for example. The pressure fluid supplied may be collected after the rotation of the polishing table51and the polishing head100is stopped. Such a control can prevent the polished wafer W from accidentally dropping while the wafer is being conveyed.

FIG.13are schematic diagrams for illustrating the first step and the second step in the processing of step S108 shown inFIG.12.

FIGS.13(a) and13(b)show the first step, andFIGS.13(c) and13(d)show the second step. As indicated by the arrows in these drawings, the first step and the second step proceeds from (a) to (b), from (b) to (c), and from (c) to (d) as a series of steps.

In the first step, the treatment is performed by applying the processing pressure P1 to the back side of the wafer W opposite to the polished surface, applying the pressure P2 to the polishing pad50, and the membrane support ring3is raised, thereby adjusting the pressurized area P1′ so that the processing pressure on the back-side circumference of the wafer W opposite to the polished surface is smaller than the processing pressure P1. The air bag P4 is in the non-pressure in which no pressure fluid is supplied.

In the processing of the first step, as the pressurized area decreases as shown inFIG.13(a), an edge part swelling phenomenon occurs as shown inFIG.13(b).

In the second step, the treatment is performed by stopping the application of the processing pressure P1, applying the pressure P2 to the polishing pad50, and lowering the membrane support ring3, thereby releasing the processing pressure-reduced state (the state of the pressurized area P1′) at the back-side circumference of the wafer W opposite to the polished surface, and by applying the compensating pressure P4 in the compensating pressure pattern according to the operating condition to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface.

In the processing of the second step, as shown inFIG.13(c), partial corrective pressurization is performed with the compensating pressure P4 in the compensating pressure pattern according to the operating condition. After that, the pressure P2 on the polishing pad50is released (FIG.13(d), and the second step ends.

The polishing head100and the polishing treatment device S with the polishing head100according to this embodiment can steadily perform a polishing treatment with high quality by adjusting and controlling the processing pressure P1, the pressurized area P1′, the pressure P2, and the compensating pressure P4. In addition, uneven polishing, such as partial insufficient polishing or over-polishing, of the polished surface of the substrate can be prevented, and ESFQR or the like of the substrate surface can be further improved.

Furthermore, the polishing head100and the polishing treatment device S with the polishing head100according to this embodiment can provide a mechanism that sets a non-pressure region at a wafer edge part to reduce the increase of the edge part surface pressure during the entire area pressurization and applies a compensating pressure to an uneven surface pressure part to attain a proper balance of surface pressure at the wafer edge part.

[Variation]

In the following, a variation of the polishing head will be described. The same components as those of the polishing head100and the polishing treatment device S having the polishing head100described in the example embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

FIG.17is a schematic vertical cross-sectional view for illustrating an example of a polishing head200of the polishing treatment device S according to a variation and a peripheral arrangement thereof. An example of a configuration of the polishing head200will be described with reference toFIG.17.

In the description below, in order to further improve the global backside ideal range (GBIR) or the like of the wafer surface, the wafer W is held with the polished surface thereof in sliding contact with the polishing pad50under the pressure controlled by the polishing treatment device S, and the pressure is applied to the held wafer W in a direction toward the polishing pad50from the back (back side) of the wafer W opposite to the polished surface.

[Configuration of Polishing Head]

Generally speaking, the polishing head200shown inFIG.17has a holding mechanism that brings the wafer W to be polished into sliding contact with the polishing pad50in a state where a polishing pressure (processing pressure) is applied to the wafer W, for example. The polishing head200also has a pressing mechanism that applies the polishing pressure (processing pressure) to the wafer W or presses the retainer ring6against the polishing pad50.

The polishing head200includes a head housing40, the membrane support ring3, the membrane4, the backing film5, the retainer ring6, and the flexible plate7.

The polishing head200is configured so that a driving force (such as a rotational force (torque) from the motor, which is actuation means) is transmitted thereto via the flexible plate7connected to the head housing40. Specifically, the membrane support ring3is connected to the flexible plate7connected to the head housing40(the connections are not shown), and the retainer ring6is connected to the membrane support ring3via the drive pin8.

Thus, the components of the polishing head200can integrally horizontally rotate or stop rotating. The flexible plate7serves as driving means that integrally horizontally rotates the membrane support ring3and the retainer ring6.

The start and stop of the rotation, the number of revolutions per unit time and the like are controlled by the control unit20based on specifications previously set.

The membrane support ring3is an annular body sized to have an inner diameter enough to surround the outer circumference of the substrate (wafer W) to be polished. The membrane support ring3is connected to the head housing40. The membrane support ring3is made of SUS material, for example.

The membrane4covers a lower end-side opening part of the membrane support ring3and holds the wafer W with the backing film5pasted to a front surface of the membrane4interposed therebetween.

The membrane4is an elastic body of a cylindrical shape (cylindrical elastic body) formed in a substantially cylindrical (pan-like) shape having an inner diameter that allows the membrane4to be fitted around the outer circumferential surface of the membrane support ring3. The membrane4is made of a rubber material having high strength and durability, such as ethylene propylene rubber (EPDM) or silicone rubber.

The backing film5is a thin film stretched on an outer bottom surface (outer surface) of the membrane4. The backing film5may be made of a porous material, such as nonwoven fabric. The backing film5makes the polished surface of the wafer W face (abut against) the polishing pad50and holds the wafer W in sliding contact with the polishing pad50. In this way, the membrane4and the backing film5serve as the holding mechanism that holds the wafer W.

The retainer ring6is shaped to surround the outer circumference of the wafer W. Not only does the retainer ring6prevent the wafer W energized by the rotational force of the polishing head200and the polishing table51from flying out in the radial direction, the retainer ring6is involved with controlling the contact pressure between the wafer edge part and the polishing pad50.

A gel-body ring30a(first annular elastic body30a) and a gel-body ring30b(second annular elastic body30b) are arranged on the back surface of the membrane4of the polishing head200.

Furthermore, a first corrective pressing ring31athat applies a pressure to the upper surface of the first annular elastic body30aand a second corrective pressing ring31bthat applies a pressure to the upper surface of the second annular elastic body30bare arranged inside the membrane support ring3(annular body3).

As shown inFIG.17, the polishing head200is configured so that a pressure fluid (such as compressed air) can be supplied to or collected from the air bag P4 through an air pipe coupled to the fluid supply mechanism (not shown). That is, the polishing head200is configured so that the amount of the pressure fluid supplied to the air bag P4 (as indicated by the dashed line P4 inFIG.17) can be adjusted to raise or lower the first and second corrective pressing rings.

The polishing head200shown inFIG.17is configured so that the operation of raising and lowering the first and second corrective pressing rings is achieved with a spring31c. In the following, configurations of the gel-body rings and the corrective pressing rings will be described in detail.

FIG.18are schematic vertical cross-sectional views showing an example of the cross-sectional shapes of the first and second annular elastic bodies.

FIG.19is a schematic vertical cross-sectional view for illustrating operations of the first and second corrective pressing rings.

As described above, the annular elastic body of the polishing head20is divided into the first annular elastic body30aon the inner side and the second annular elastic body30bon the outer side as shown inFIG.17.

Furthermore, the polishing head200has the first corrective pressing ring31athat applies a pressure to the first annular elastic body30aand the second corrective pressing ring31bthat applies a pressure to the second annular elastic body30b.

Therefore, as shown inFIG.19, the compensating pressure applied to the back-side outer circumference vicinity (near-edge region) of the wafer opposite to the polished surface is partially applied by the first annular elastic body30aon the inner side and partially applied by the second annular elastic body30bon the outer side.

Furthermore, a deformation prevention ring33is arranged between the first annular elastic body30aand the second annular elastic body30bto reduce the interaction between the deformation of the first annular elastic body30aand the deformation of the second annular elastic body30bduring application of the compensating pressure.

In the above example embodiment (polishing head100), the annular elastic body10has been described as being arranged with the centerline of the bottom surface thereof aligned with the boundary between the pressurized circumferential band and the non-pressurized circumferential band of the membrane4and the wafer W (seeFIG.11, for example). With the polishing head200according to this variation, the deformation prevention ring33is arranged at the boundary position. In this way, the principle and mechanism of ESFQR ≈0, which cannot be elucidated with the conventional polishing heads, can be elucidated, and GBIR can also be dramatically improved.

As shown inFIG.18(a), the first annular elastic body30ais formed in a trapezoidal shape with the inner side surface being an inclined surface.

The second annular elastic body31bis formed in a trapezoidal shape with the outer side surface being an inclined surface. The second annular elastic body31bhas a smaller size than the wafer W.

As shown inFIG.18(a), the first corrective pressing ring31ais configured to cover all or part of the inclined surface (inner side surface) of the first annular elastic body30a.

The second corrective pressing ring31bis configured to cover all or part of the inclined surface (outer side surface) of the second annular elastic body30b(FIG.18(b)). In this way, the loss of the compensating pressure due to the deformation of the first annular elastic body30aand the deformation of the second annular elastic body30bduring application of the compensating pressure can be reduced. That is, the adjustment of the compensating pressure by pressure application by the fourth pressure adjusting means can be facilitated, and the compensating pressure can be more appropriately applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface.

Furthermore, as shown inFIG.18(a), the first corrective pressing ring31ais configured to cover the upper surface of the first annular elastic body30ato apply thereto the pressure from the fourth pressure adjusting means, and is configured so that the processing pressure P1 applied to the back side of the wafer opposite to the polished surface by adjusting the pressure in the space defined by the head housing40, the first corrective pressing ring31aand the elastic body (membrane4) is also applied to the upper surface of the first annular elastic body30a. In this way, since the first corrective pressing ring31acovers the upper surface of the first annular elastic body30a, the first corrective pressing ring30acan apply the processing pressure P1 to the back side of the wafer W opposite to the polished surface via the bottom surface of the first annular elastic body30a.

In the pressure adjustment processing (step S108) in which the compensating pressure P4 in the compensating pressure pattern according to the operating condition is applied to the back-side outer circumference vicinity (near-edge region) of the wafer W opposite to the polished surface, the first annular elastic body30aand the second annular elastic body30bfacilitate the adjustment of the compensating pressure at a vicinity region of the deformation prevention ring33(seeFIG.19).

The embodiment described above is intended to specifically describe the present invention, and the scope of the present invention is not limited to the embodiment.

REFERENCE SIGNS LIST

2,40head housing3membrane support ring4membrane5backing film6retainer ring7flexible plate20control unit50polishing pad51polishing table100,200polishing headS polishing treatment deviceN nozzleW wafer