Patent Application
20240207995
This application claims the priority benefits of Japanese application no. 2022-204319, filed on Dec. 21, 2022. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
The disclosure relates to a polishing device and a method for adjusting a pressure control unit.
Chemical mechanical polishing (CMP) is known as a technique used in the manufacturing process of a semiconductor device. A polishing device for performing CMP includes a polishing table which supports a polishing pad and a polishing head which holds a wafer.
When polishing a wafer by using such a polishing device, the wafer is pressed against a polishing surface of a polishing pad with a predetermined pressure while being held by a polishing head having multiple pressure chambers. At this time, the wafer slides into contact with the polishing surface by relatively moving the polishing table and the polishing head, and the surface of the wafer is polished. Pressures of gases supplied to the pressure chambers are adjusted by pressure regulators.
A polishing device which includes a buffer tank configured to relatively reduce pressure fluctuations in a pressure chamber (for example, see Patent Literature 1 (Japanese Patent Application Laid-Open No. 2015-131360)) is known. According to Patent Literature 1, the buffer tank has a volume that is equal to or larger than a volume of the pressure chamber, and can reduce pressure fluctuations in the pressure chamber.
In order to perform precise polishing control, quickly changing the pressure within the pressure chamber in accordance with a change in a target pressure value is needed. However, multiple gas transfer lines connected to the pressure chambers may have different lengths, and the pressure chambers may also have different volumes.
If the lengths of the gas transfer lines and the volumes of the pressure chambers are different respectively, the responsiveness of the pressure regulators connected to the pressure chambers (in other words, the response time or pressure fluctuation behavior until a secondary side pressure of the pressure regulator reaches a target pressure value) differs. As a result, the responsiveness of the pressure regulators may vary.
Accordingly, the disclosure is intended to provide a polishing device and a method for adjusting a pressure control unit that are capable of reducing variations in responsiveness of multiple pressure regulators.
According to an aspect of the disclosure, there is provided a polishing device that includes: a polishing table which supports a polishing pad; a top ring which has multiple pressure chambers for pressing a substrate against a polishing surface of the polishing pad; multiple pressure regulators which control pressures of gases in the pressure chambers; multiple pressure sensors which detect pressures adjusted by the pressure regulators; and multiple buffer tanks which are connected to multiple gas transfer lines connecting the pressure chambers and the pressure regulators. Each of the buffer tanks includes a tank section made of a rigid body and a volume adjustment device which adjusts a volume of the buffer tank.
According to an aspect of the disclosure, the volume adjustment device includes: a closing member which is disposed inside the tank section and closes off a part of an internal space of the tank section; a reciprocating mechanism which reciprocates the closing member; and a positioning member which positions the closing member moved by the reciprocating mechanism.
According to an aspect of the disclosure, the polishing device includes a control device that controls a pressure of each of the pressure chambers through each of the pressure regulators, and the control device measures a secondary side pressure of each of the pressure regulators and determines a volume of the buffer tank so that a change in the secondary side pressure when a target pressure value of each of the pressure regulators changes falls within a predetermined allowable range.
According to an aspect of the disclosure, the control device adjusts control parameters input to the pressure regulators after adjusting the volume.
According to an aspect of the disclosure, when each of the pressure sensors is defined as a first pressure sensor and each of the pressure regulators is defined as a first pressure regulator, the polishing device includes a second pressure sensor prepared in place of the first pressure sensor and a second pressure regulator prepared in place of the first pressure regulator.
According to an aspect of the disclosure, the polishing device includes a control device that controls a pressure of each of the pressure chambers through each of the pressure regulators, and the control device inputs predetermined control parameters to the second pressure regulator, measures a secondary side pressure of the second pressure regulator based on the second pressure sensor, and determines the volume of the buffer tank so that a change in the secondary side pressure when a target pressure value of the second pressure regulator changes falls within a predetermined allowable range.
According to an aspect of the disclosure, there is provided a method for adjusting a pressure control unit that supplies gases to multiple pressure chambers built into a top ring for polishing a substrate. The pressure control unit includes: multiple pressure regulators which control pressures of gases in the pressure chambers; multiple pressure sensors which detect pressures adjusted by the pressure regulators; and multiple buffer tanks which are connected to multiple gas transfer lines connecting the pressure chambers and the pressure regulators. A volume of each of the buffer tanks is variable, and the volume is determined based on a pressure value measured by each of the pressure sensors corresponding to the volume.
According to an aspect of the disclosure, the volume is determined so that a change in a secondary side pressure of each of the pressure regulators when a target pressure value of each of the pressure regulators changes falls within a predetermined allowable range.
According to an aspect of the disclosure, control parameters of the pressure regulator are adjusted after the volume is adjusted.
According to an aspect of the disclosure, when each of the pressure sensors is defined as a first pressure sensor and each of the pressure regulators is defined as a first pressure regulator, a pressure in the pressure chambers is controlled by using a second pressure regulator in place of the first pressure regulator, and a second pressure sensor is installed in place of the first pressure sensor to measure the pressure.
The polishing device includes the volume adjustment device that adjusts the volume of the buffer tank. Therefore, even if the lengths of the gas transfer lines and the volumes of the pressure chambers are different, by adjusting the volumes of the buffer tanks, the polishing device is capable of reducing variations in responsiveness of the pressure regulators.
The polishing table 22 is connected to a table motor (not shown) disposed therebelow via a table shaft 22a, and is rotatable around the table shaft 22a. The polishing pad 23 is attached to an upper surface of the polishing table 22, and a surface of the polishing pad 23 constitutes a polishing surface 23a for polishing a wafer W.
The polishing device includes a polishing liquid supply nozzle (not shown) disposed above the polishing table 22. The polishing liquid supply nozzle is configured to supply polishing liquid onto the polishing pad 23.
The top ring 30 includes a top ring body 31 which presses the wafer W against the polishing surface 23a and a retainer ring 32 which holds the wafer W and prevents the wafer W from flying out from the top ring 30. The top ring 30 is connected to a top ring shaft 27, and the top ring shaft 27 is configured to move up and down with respect to a top ring head 64 by an up-down movement mechanism (not shown). The top ring shaft 27 raises and lowers the entire top ring 30 with respect to the top ring head 64 by the up-down movement thereof.
As shown in
Polishing of the wafer W is performed as follows. The top ring 30 and the polishing table 22 are rotated, respectively, polishing liquid is supplied onto the polishing pad 23 from the polishing liquid supply nozzle (not shown) disposed above the polishing table 22. In this state, the top ring 30 is lowered to a predetermined position (predetermined height), and the wafer W is pressed against the polishing surface 23a of the polishing pad 23 at the predetermined position. The wafer W is brought into sliding contact with the polishing surface 23a of the polishing pad 23, and as a result, the surface of the wafer W is polished. The structure of the top ring 30 is to be described below.
The top ring 30 includes a flexible membrane (elastic membrane) 34 which contacts the wafer W and a chucking plate 35 which holds the membrane 34. The membrane 34 and the chucking plate 35 are disposed below the top ring body 31. The top ring 30 has multiple pressure chambers C1 to C6 for pressing the wafer W against the polishing surface 23a of the polishing pad 23.
Among the pressure chambers C1 to C6, four pressure chambers (airbags) C1, C2, C3, and C4 are disposed between the membrane 34 and the chucking plate 35. The pressure chamber C1 in the center is circular, and the other pressure chambers C2, C3, and C4 are annular. The pressure chambers C1, C2, C3, and C4 are arranged concentrically.
The polishing device includes gas transfer lines F1, F2, F3, and F4 that are connected to pressure chambers C1, C2, C3, and C4, a gas supply source (fluid supply source) 40 that supplies pressurized gases (pressurized fluid) via the gas transfer lines F1, F2, F3, and F4, and vacuum lines V1, V2, V3, and V4 that are connected to the gas transfer lines F1, F2, F3, and F4.
The vacuum lines V1, V2, V3, and V4 are configured to form negative pressures in the pressure chambers C1, C2, C3, and C4. The internal pressures of the pressure chambers C1, C2, C3, and C4 may be changed independently of each other, and the polishing pressures for four corresponding regions of the wafer W, namely, a central section, an inner intermediate section, an outer intermediate section, and a peripheral section can be adjusted independently.
The polishing device further includes a gas transfer line F5 connected to the pressure chamber C5 formed between the chucking plate 35 and the top ring body 31 and a vacuum line V5 connected to the gas transfer line F5. The pressurized gas supplied from the gas supply source 40 is supplied to the pressure chamber C5 via the gas transfer line F5. The pressure chamber C5 forms a negative pressure through the vacuum line V5.
The retainer ring 32 surrounds the peripheral section of the wafer W so that the wafer W does not fly out of the top ring 30 during polishing. A part of the membrane 34 that constitutes the pressure chamber C3 has an opening, and by forming a vacuum in the pressure chamber C3, the wafer W is sucked and held by the top ring 30 through the opening of the membrane 34. The wafer W is released from the top ring 30 by supplying a pressurized gas such as nitrogen gas or clean air to the pressure chamber C3.
The top ring 30 includes an annular rolling diaphragm 36 which is disposed between the top ring body 31 and the retainer ring 32. The rolling diaphragm 36 has the pressure chamber C6 formed therein.
The polishing device includes a gas transfer line F6 connected to the pressure chamber C6 and a vacuum line V6 connected to the gas transfer line F6. The pressure chamber C6 is connected to the gas supply source 40 via the gas transfer line F6. The gas supply source 40 supplies a pressurized gas to the pressure chamber C6, and the rolling diaphragm 36 presses the retainer ring 32 against the polishing pad 23. The pressure chamber C6 forms a negative pressure through the vacuum line V6.
The polishing device includes electropneumatic regulators (i.e., pressure regulators) R1, R2, R3, R4, R5, and R6 that are connected to the gas transfer lines F1, F2, F3, F4, F5, and F6 communicating with the pressure chambers C1, C2, C3, C4, C5, and C6. Pressurized gases supplied from the gas supply source 40 are supplied into the pressure chambers C1 to C6 through the electropneumatic regulators R1 to R6. The electropneumatic regulators R1 to R6 control the pressures of the gases in the pressure chambers C1 to C6 by adjusting the pressures of the pressurized gases supplied from the gas supply source 40. The pressure chambers C1 to C6 are connected to an atmosphere release valve (not shown). The atmosphere release valve is configured to open the pressure chambers C1 to C6 to the atmosphere.
The polishing device includes flow meters G1, G2, G3, G4, G5, and G6 that are connected to the gas transfer lines F1 to F6. The flow meters G1 to G6 are configured to measure flow rates of gases flowing through the gas transfer lines F1 to F6. The gas transfer lines F1 to F6 extend from the pressure chambers C1 to C6 to the electropneumatic regulators R1 to R6 via a rotary joint 82. The vacuum lines V1 to V6 are disposed between the pressure chambers C1 to C6 and the flow meters G1 to G6.
The polishing device includes buffer tanks T1, T2, T3, T4, T5, and T6 that are disposed between the electropneumatic regulators R1, R2, R3, R4, R5, and R6 and the top ring 30, which is the point of use for the pressurized gas, and pressure sensors P1, P2, P3, P4, P5, and P6 that detect pressures adjusted by the electropneumatic regulators R1, R2, R3, R4, R5, and R6.
The buffer tanks T1, T2, T3, T4, T5, and T6 are connected to the gas transfer lines F1, F2, F3, F4, F5, and F6, respectively, through branch lines B1, B2, B3, B4, B5, and B6. The buffer tanks T1 to T6 are disposed between the electropneumatic regulators R1 to R6 and the flow meters G1 to G6.
The pressure sensors P1 to P6 are configured to detect pressures on downstream sides (i.e., secondary sides) of the electropneumatic regulators R1 to R6 in transfer directions of the pressurized gases. The pressure sensors P1 to P6 may be built into the electropneumatic regulators R1 to R6, alternatively, may be connected to the gas transfer lines F1 to F6 at positions downstream of the electropneumatic regulators R1 to R6.
The polishing device includes a control device 50 which controls a pressure in each of the pressure chambers C1 to C6 through each of the electropneumatic regulators R1 to R6. The electropneumatic regulators R1 to R6 are electrically connected to the control device 50. The control device 50 inputs predetermined control parameters (for example, PID parameters) to each of the electropneumatic regulators R1 to R6 and controls the operation of each of the electropneumatic regulators R1 to R6.
The control parameters are parameters that determine the responsiveness (in other words, the response time or pressure fluctuation behavior until secondary side pressures of the electropneumatic regulators R1 to R6 reach target pressure values) of each of the electropneumatic regulators R1 to R6, and are set for each of the electropneumatic regulators R1 to R6.
The electropneumatic regulators R1 to R6 control pressures and flow rates of gases supplied to the pressure chambers C1 to C6 based on input control parameters. The secondary side pressures are the pressures on the downstream sides of the electropneumatic regulators R1 to R6 in flow directions of the gases supplied to the pressure chambers C1 to C6.
The pressing force of the wafer W held by the top ring 30 against the polishing pad 23 depends on the pressures of the gases supplied to the pressure chambers C1 to C6. Therefore, if variations occur in the pressure characteristics of the pressure chambers C1 to C6, an appropriate pressing force is not applied to the wafer W, and as a result, the variations may adversely affect polishing of the wafer W. Thus, it is exemplary to reduce variations in the pressure characteristics of the pressure chambers C1 to C6. More specifically, it is exemplary that the pressure stability and responsiveness be within a predetermined threshold in all of the pressure chambers C1 to C6.
The buffer tanks T1 to T6 maintain the stability of the pressures and the flow rates of the pressurized gases while supplying the pressurized gases to the pressure chambers C1 to C6. However, the gas transfer lines F1 to F6 connected to the pressure chambers C1 to C6 may have different lengths, and the pressure chambers C1 to C6 may also have different volumes.
Due to such a configuration, the pressure characteristics of the pressure chambers C1 to C6 (that is, the responsiveness of the electropneumatic regulators R1 to R6) differ, variations may occur in the pressure characteristics of the pressure chambers C1 to C6 (that is, the responsiveness of the electropneumatic regulators R1 to R6). Therefore, the buffer tanks T1 to T6 have variable volumes, and by adjusting the volumes of the buffer tanks T1 to T6, variations in the responsiveness of the electropneumatic regulators R1 to R6 can be reduced.
The tank section 120 is connected to the gas transfer line F1 (and F2 to F6) at a lower part thereof, and the pressurized gas supplied from the gas supply source 40 flows into the tank section 120. The tank section 120 has a cylindrical pressure-resistant structure and is, for example, made of metal.
The volume adjustment device 122 includes a closing member 121 which is disposed inside the tank section 120 and closes off a part of an internal space of the tank section 120, a reciprocating mechanism 124 which reciprocates the closing member 121, and a positioning member 127 which positions the closing member 121 moved by the reciprocating mechanism 124.
The closing member 121 has a plate shape disposed perpendicularly to the direction in which the tank section 120 extends. In the embodiment, the volume adjustment device 122 includes an O-ring 123 attached to an outer peripheral surface of the closing member 121. By disposing the O-ring 123 between the closing member 121 and an inner surface of the tank section 120, the O-ring 123 can prevent leakage of the pressurized gas.
In the embodiment shown in
The screw shaft 125 is connected to the closing member 121 disposed inside the tank section 120. By rotating the screw shaft 125, the closing member 121 moves back and forth. In the embodiment, when the closing member 121 is moved in a direction approaching the lower part of the tank section 120, the volume of the buffer tank T1 becomes smaller. Conversely, when the closing member 121 is moved in a direction approaching the upper part of the tank section 120, the volume of the buffer tank T1 becomes larger.
An operator manually moves the closing member 121 via the screw shaft 125 in order to adjust the volume of the buffer tank T1. The reciprocating mechanism 124 is not limited to a ball screw mechanism. In an embodiment, the reciprocating mechanism 124 may be a rack and pinion mechanism or a piston mechanism.
In the embodiment shown in
In an embodiment, the reciprocating mechanism 124 may include a drive motor (not shown) connected to the screw shaft 125. In this case, the drive motor can position the closing member 121 connected to the screw shaft 125 by driving the drive motor. When the reciprocating mechanism 124 includes a drive motor, the reciprocating mechanism 124 does not need to include the nut 127, and the drive motor may also serve as the positioning member.
Each of the pressure sensors P1 to P6 detects each of pressure values of the pressurized gases adjusted by the electropneumatic regulators R1 to R6. Based on the pressure values detected respectively by the pressure sensors P1 to P6, the operator measures the responsiveness (that is, the response time or pressure fluctuation behavior until the secondary side pressures of the electropneumatic regulators R1 to R6 reach the target pressure values) of each of the electropneumatic regulators R1 to R6 for each of the pressure chambers C1 to C6 (see step S102). Similarly, each of the flow meters G1 to G6 detects each of flow rate values of the pressurized gases adjusted by the electropneumatic regulators R1 to R6.
As shown in step S103, the operator compares the responsiveness of each of the electropneumatic regulators R1 to R6 that operate based on the control parameters (that is, the pressure characteristics of each of the pressure chambers C1 to C6) with predetermined allowable conditions, and determines whether the responsiveness (that is, pressure characteristics) satisfies the allowable conditions.
In other words, the operator determines whether the change (i.e., the behavior of the pressure change or a curve showing the pressure change) in the secondary side pressure when the target pressure value of each of the electropneumatic regulators R1 to R6 changes falls within a predetermined allowable range.
If the responsiveness satisfies the allowable conditions (see “YES” in step S103), the operator does not change the volumes of the buffer tanks T1 to T6 that correspond to the responsiveness that satisfies the allowable conditions (see step S104). If the responsiveness does not satisfy the allowable conditions (see “NO” in step S103), the operator changes the volumes of the buffer tanks T1 to T6 corresponding to the responsiveness that does not satisfy the allowable conditions so that the responsiveness satisfies the allowable conditions (see step S105).
According to the embodiment, the polishing device includes the volume adjustment device 122 which adjusts the volumes of the buffer tanks T1 to T6. Therefore, even if the lengths of the gas transfer lines F1 to F6 and the volumes of the pressure chambers C1 to C6 are different respectively, by adjusting the volumes of the buffer tanks T1 to T6, the polishing device is capable of reducing variations in responsiveness of the electropneumatic regulators R1 to R6.
In addition, in order to keep the changes in the secondary side pressures of the electropneumatic regulators R1 to R6 within the predetermined allowable range, after adjusting the volumes of buffer tanks T1 to T6, it is exemplary to check the stability of the pressures and the flow rates (when target pressures are constant, are fluctuation ranges of the pressures and the flow rates within the predetermined allowable range?)
In the embodiment described above, the flow in which the operator determines the volumes of the buffer tanks T1 to T6 has been described, but in an embodiment, the control device 50 may determine the volumes of buffer tanks T1 to T6. In this case, the control device 50 may operate a drive motor (not shown) connected to the screw shaft 125 and automatically adjust the volumes of the buffer tanks T1 to T6.
After the operator (or the control device 50) adjusts (determines) the volume of each of the buffer tanks T1 to T6, the control parameters may be optimized for each of the pressure chambers C1 to C6 to further improve the uniformity of responsiveness. More specifically, after performing steps S101 to S105, the operator may individually adjust the control parameters for each of the pressure chambers C1 to C6. With such a configuration, variations in responsiveness of the electropneumatic regulators R1 to R6 can be further reduced.
As shown in
The pressure sensors P1+ to P6+ are high-precision pressure sensors that detect pressures with higher accuracy than the pressure sensors P1 to P6. The electropneumatic regulators R1+to R6+ are high-precision electropneumatic regulators that operate with higher accuracy than the electropneumatic regulators R1 to R6. The flow meters G1+ to G6+ are high-precision flow meters that detect flow rates with higher accuracy than the flow meters G1 to G6. The pressure sensors P1+ to P6+, the electropneumatic regulators R1+ to R6+, and flow meters G1+ to G6+ are provided to suppress measurement errors due to individual differences.
The control device 50 inputs control parameters to the electropneumatic regulators R1+ to R6+, measures responsiveness of the electropneumatic regulators R1+ to R6+based on the pressure sensors P1+ to P6+ (and the flow meters G1+ to G6+), and determines the volumes of the buffer tanks T1 to T6 so that the responsiveness satisfies predetermined allowable conditions (see steps S101 to S105 in
According to the embodiment, the control device 50 uses the adjustment set 130 to adjust the volumes of the buffer tanks T1 to T6, and by eliminating the influence of individual differences among the pressure sensors P1 to P6, the electropneumatic regulators R1 to R6, and the flow meters G1 to G6, the uniform responsiveness of the electropneumatic regulators R1 to R6 can be improved.
The lengths of the gas transfer lines F1 to F6 and/or the volumes of the pressure chambers C1 to C6 may vary from one polishing device to another. Therefore, even if the variations in responsiveness of the pressure regulators may be reduced in one polishing device, in another polishing device, variations in responsiveness of the pressure regulators may not be reduced.
According to the embodiment described above, the volume adjustment device 122 which adjusts the volumes of the buffer tanks T1 to T6 can reduce variations in the pressure characteristics of the pressure chambers C1 to C6 (i.e., the responsiveness of the electropneumatic regulators R1 to R6). Therefore, the volume adjustment device 122 not only keeps all the responsiveness of the pressure chambers C1 to C6 of each of polishing modules provided in one polishing device within a predetermined allowable range, but also keeps all the responsiveness of the pressure chambers C1 to C6 of each of polishing modules provided in multiple polishing devices within a predetermined allowable range.
In an embodiment, based on pressure detection values detected by each of the external pressure sensors P1 to P6 (for example, see
The embodiments described above have been described to enable those skilled in the art to carry out the disclosure. Various modifications of the above embodiments can be naturally made by those skilled in the art, and the technical idea of the disclosure can be applied to other embodiments. Therefore, the disclosure is not limited to the described embodiments, but is to be construed in the broadest scope according to the spirit defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-204319 | Dec 2022 | JP | national |
