Patent Application
20180236631
This document claims priority to Japanese Patent Application Number 2017-17401 filed Feb. 2, 2017, the entire contents of which are hereby incorporated by reference.
A CMP (chemical mechanical polishing) apparatus is used in a process of polishing a surface of a wafer in the manufacturing of a semiconductor device. The CMP apparatus is configured to hold and rotate the wafer with a polishing head, and press the wafer against a polishing pad on a rotating polishing table to polish the surface of the wafer. During polishing, a polishing liquid (or slurry) is supplied onto the polishing pad, so that the surface of the wafer is planarized by the chemical action of the polishing liquid and the mechanical action of abrasive grains contained in the polishing liquid.
A polishing rate of the wafer depends not only on a polishing load on the wafer pressed against the polishing pad, but also on a surface temperature of the polishing pad. This is because the chemical action of the polishing liquid on the wafer depends on the temperature. The polishing rate is an index indicating an amount (or a thickness) of a film of the wafer removed per unit time as a result of the polishing operation. The polishing rate is also referred to as removal rate.
Therefore, a CMP apparatus capable of regulating the surface temperature of the polishing pad has been developed. This type of CMP apparatus has a pad-temperature sensor and a pad-temperature regulation system. The pad-temperature sensor is arranged so as to measure the surface temperature of an area of the polishing pad that contacts the center of the wafer. The pad-temperature regulation system is configured to bring a heat exchanger into contact with the surface of the polishing pad to regulate the surface temperature of the polishing pad based on a measured value of the surface temperature of the polishing pad.
Thus, as shown in
According to an embodiment, there is provided a heat exchanger which can allow a surface temperature of a polishing pad to promptly reach a target temperature and can realize a uniform distribution of the surface temperature of the polishing pad. According to another embodiment, there is provided a polishing apparatus having such a heat exchanger. Further, according to still another embodiment, there is provided a method of polishing a substrate using the heat exchanger.
Embodiments, which will be described below, relate to a heat exchanger for regulating a surface temperature of a polishing pad for use in polishing of a substrate, such as a wafer. The below-described embodiments also relate to a polishing apparatus having such a heat exchanger and a polishing method.
In an embodiment, there is provided a heat exchanger for regulating a surface temperature of a polishing pad by contacting a surface of the polishing pad, comprising: a pad contact surface capable of contacting the polishing pad; a heating flow passage through which a heating fluid is to flow; and a cooling flow passage through which a cooling fluid is to flow, wherein the heating flow passage and the cooling flow passage are arranged side by side from beginnings to ends thereof, and the heating flow passage and the cooling flow passage cross each other at different levels at a peripheral portion of the pad contact surface.
In an embodiment, the heating flow passage and the cooling flow passage comprise zigzag passages.
In an embodiment, folded-back portions of the heating flow passage and folded-back portions of the cooling flow passage overlap each other.
In an embodiment, folded-back portions of the heating flow passage and folded-back portions of the cooling flow passage are located right above the peripheral portion of the pad contact surface.
In an embodiment, there is provided a polishing apparatus comprising: a rotatable polishing table for supporting a polishing pad; a polishing head configured to press a substrate against a surface of the polishing pad so as to polish the substrate; the above-described heat exchanger configured to contact the surface of the polishing pad so as to regulate a surface temperature of the polishing pad; a heating-fluid supply pipe configured to supply a heating fluid to the heat exchanger; and a cooling-fluid supply pipe configured to supply a cooling fluid to the heat exchanger.
In an embodiment, there is provided a substrate polishing method comprising: holding a substrate with a polishing head; and pressing the substrate by the polishing head against a surface of a polishing pad to polish the substrate, while placing the above-described heat exchanger, through which a heating fluid and a cooling fluid flow, in contact with the surface of the polishing pad so as to regulate a surface temperature of the polishing pad.
In an embodiment, there is provided a non-transitory computer-readable storage medium storing therein a program that instructs a computer to perform the above-described substrate polishing method, the computer being configured to control operations of a polishing apparatus.
According to the above-described embodiments, both the heating flow passage and the cooling flow passage are located over the entirety of the pad contact surface. In particular, both the heating fluid and the cooling fluid exist at points where the heating flow passage and the cooling flow passage cross each other. This arrangement can prevent the local heating with only the heating fluid and the local cooling with only the cooling fluid. In other words, the heat exchanger can regulate the surface temperature of the polishing pad with both the heating fluid and the cooling fluid in the entirety of the pad contact surface. Therefore, the heat exchanger can provide a uniform distribution of the surface temperature of the polishing pad. Furthermore, the polishing apparatus having the above-discussed heat exchanger can polish a substrate, such as a wafer, to provide a uniform polishing profile.
Embodiments will now be described with reference to the drawings.
The polishing head 1 is vertically movable, and is rotatable about its axis in a direction indicated by arrow. The wafer W is held on a lower surface of the polishing head 1 by, for example, vacuum suction. A motor (not shown) is coupled to the polishing table 2, so that the polishing table 2 can rotate in a direction indicated by arrow. As shown in
Polishing of the wafer W is performed in the following manner. The wafer W, to be polished, is held by the polishing head 1, and is then rotated by the polishing head 1. The polishing pad 3 is rotated together with the polishing table 2. While the wafer W and the polishing pad 3 are rotating, the polishing liquid is supplied from the polishing-liquid supply nozzle 4 onto the surface of the polishing pad 3, and the surface of the wafer W is then pressed by the top ring 1 against the surface 3a, i.e. the polishing surface, of the polishing pad 3. The surface of the wafer W is polished by the sliding contact with the polishing pad 3 in the presence of the polishing liquid. The surface of the wafer W is planarized by the chemical action of the polishing liquid and the mechanical action of abrasive grains contained in the polishing liquid.
The pad-temperature regulation system 5 includes a heat exchanger 11 having flow passages formed therein through which fluids flow to regulate the surface temperature of the polishing pad 3. The pad-temperature regulation system 5 further includes a fluid supply system 30 for supplying a heating fluid having a regulated temperature and a cooling fluid having a regulated temperature into the heat exchanger 11. The heat exchanger 11 has a pad contact surface 65 which can contact the surface of the polishing pad 3.
The pad-temperature regulation system 5 further includes a translation mechanism 71 for moving the heat exchanger 11 parallel to the surface 3a of the polishing pad 3. The heat exchanger 11 is held by the translation mechanism 71. The translation mechanism 71 is configured to be able to move the heat exchanger 11 in a radial direction of the polishing pad 3 while the lower surface (i.e., the pad contact surface 65) of the heat exchanger 11 is in contact with the surface 3a of the polishing pad 3. The translation mechanism 71 may be composed of a combination of a servo motor and a ball screw mechanism, or a pneumatic cylinder.
The fluid supply system 30 includes a heating-fluid supply tank 31 as a heating-fluid supply source for holding the heating fluid having a regulated temperature therein, and a heating-fluid supply pipe 32 and a heating-fluid return pipe 33, each coupling the heating-fluid supply tank 31 to the heat exchanger 11. One ends of the heating-fluid supply pipe 32 and the heating-fluid return pipe 33 are coupled to the heating-fluid supply tank 31, and the other ends are coupled to the heat exchanger 11.
The heating fluid having a regulated temperature is supplied from the heating-fluid supply tank 31 to the heat exchanger 11 through the heating-fluid supply pipe 32, flows in the heat exchanger 11, and is returned from the heat exchanger 11 to the heating-fluid supply tank 31 through the heating-fluid return pipe 33. In this manner, the heating fluid circulates between the heating-fluid supply tank 31 and the heat exchanger 11. The heating-fluid supply tank 31 has a heater (not shown in the drawings), so that the heating fluid is heated by the heater to have a predetermined temperature.
A first on-off valve 41 and a first flow control valve 42 are attached to the heating-fluid supply pipe 32. The first flow control valve 42 is located between the heat exchanger 11 and the first on-off valve 41. The first on-off valve 41 is a valve not having a flow rate regulating function, whereas the first flow control valve 42 is a valve having a flow rate regulating function.
The fluid supply system 30 further includes a cooling-fluid supply pipe 51 and a cooling-fluid discharge pipe 52, both coupled to the heat exchanger 11. The cooling-fluid supply pipe 51 is coupled to a cooling-fluid supply source (e.g. a cold water supply source) provided in a factory in which the polishing apparatus is installed. The cooling fluid is supplied to the heat exchanger 11 through the cooling-fluid supply pipe 51, flows in the heat exchanger 11, and is drained from the heat exchanger 11 through the cooling-fluid discharge pipe 52. In one embodiment, the cooling fluid that has flowed through the heat exchanger 11 may be returned to the cooling-fluid supply source through the cooling-fluid discharge pipe 52.
A second on-off valve 55 and a second flow control valve 56 are attached to the cooling-fluid supply pipe 51. The second flow control valve 56 is located between the heat exchanger 11 and the second on-off valve 55. The second on-off valve 55 is a valve not having a flow rate regulating function, whereas the second flow control valve 56 is a valve having a flow rate regulating function.
The pad-temperature regulation system 5 further includes a pad-temperature measuring device 39 for measuring a surface temperature of the polishing pad 3 (which may hereinafter be referred to as pad surface temperature), and a valve controller 40 for operating the first flow control valve 42 and the second flow control valve 56 based on the pad surface temperature measured by the pad-temperature measuring device 39. The first on-off valve 41 and the second on-off valve 55 are usually open. The pad-temperature measuring device 39 is disposed above the surface of the polishing pad 3, and is configured to measure the surface temperature of the polishing pad 3 in a non-contact manner. The pad-temperature measuring device 39 is coupled to the valve controller 40.
The valve controller 40 is configured to calculate a manipulated variable for the first flow control valve 42 and a manipulated variable for the second flow control valve 56 which are necessary for eliminating a difference between a preset target temperature and the surface temperature of the polishing pad 3. The manipulated variable for the first flow control valve 42 and the manipulated variable for the second flow control valve 56 are, in other words, the degree of opening of the valve. The manipulated variable for the first flow control valve 42 is proportional to the flow rate of the heating fluid, and the manipulated variable for the second flow control valve 56 is proportional to the flow rate of the cooling fluid.
Where the manipulated variable for the first flow control valve 42 and the manipulated variable for the second flow control valve 56 are each expressed as a numerical value ranging from 0% to 100%, the valve controller 40 is configured to determine the manipulated variable for the second flow control valve 56 by subtracting the manipulated variable for the first flow control valve 42 from 100%. In one embodiment, the valve controller 40 may be configured to determine the manipulated variable for the first flow control valve 42 by subtracting the manipulated variable for the second flow control valve 56 from 100%.
When the manipulated variable for the first flow control valve 42 is 100%, it indicates that the first flow control valve 42 is fully open. When the manipulated variable for the first flow control valve 42 is 0%, it indicates that the first flow control valve 42 is fully closed. Similarly, when the manipulated variable for the second flow control valve 56 is 100%, it indicates that the second flow control valve 56 is fully open; when the manipulated variable for the second flow control valve 56 is 0%, it indicates that the second flow control valve 56 is fully closed.
The flow rate of the heating fluid when the manipulated variable for the first flow control valve 42 is 100% is equal to the flow rate of the cooling fluid when the manipulated variable for the second flow control valve 56 is 100%. Accordingly, the sum of the flow rate of the heating fluid passing through the first flow control valve 42 and the flow rate of the cooling fluid passing through the second flow control valve 56 is constant at all times.
The valve controller 40 operates the first flow control valve 42 and the second flow control valve 56 in such a manner that the sum of the manipulated variable for the first flow control valve 42 and the manipulated variable for the second flow control valve 56 is 100%.
Hot water may be used as the heating fluid to be supplied to the heat exchanger 11. The hot water that has been heated to about 80° C. by the heater of the heating-fluid supply tank 31 may be used. When it is intended to raise the surface temperature of the polishing pad 3 more quickly, a silicone oil may be used as the heating fluid. In the case of using a silicone oil as the heating fluid, the silicone oil may be heated to have a temperature of not less than 100° C. (e.g. about 120° C.). Cold water or a silicone oil may be used as the cooling fluid to be supplied to the heat exchanger 11. In the case of using a silicone oil as the cooling fluid, the polishing pad 3 can be cooled quickly by coupling a chiller as a cooling-fluid supply source to the cooling-fluid supply pipe 51, and by cooling the silicone oil to a temperature of not more than 0° C.
The heating-fluid supply pipe 32 and the cooling-fluid supply pipe 51 are completely independent pipes. Thus, the heating fluid and the cooling fluid can be supplied to the heat exchanger 11 without mixing with each other. The heating-fluid return pipe 33 and the cooling-fluid discharge pipe 52 are also completely independent pipes. Thus, the heating fluid is returned to the heating-fluid supply tank 31 without mixing with the cooling fluid, while the cooling fluid is either drained or returned to the cooling-fluid supply source without mixing with the heating fluid.
Next, an embodiment of the heat exchanger 11 will be described.
The heating flow passage 61 and the cooling flow passage 62 are arranged side by side from the beginnings to the ends thereof. In this embodiment, the heating flow passage 61 and the cooling flow passage 62 are constituted by zigzag passages which are adjacent to each other. The heating flow passage 61 has the same length as the cooling flow passage 62. The heating flow passage 61 and the cooling flow passage 62 are completely separated, so that the heating fluid and the cooling fluid are not mixed in the heat exchanger 11.
The heating flow passage 61 and the cooling flow passage 62 cross each other at different levels at a peripheral portion of the pad contact surface 65. More specifically, the heating flow passage 61 and the cooling flow passage 62 cross at different levels at a plurality of points aligned along the peripheral portion of the pad contact surface 65. The heating flow passage 61 and the cooling flow passage 62 have folded-back portions which are located right above the peripheral portion of the pad contact surface 65. Further, the folded-back portions of the heating flow passage 61 and the folded-back portions of the cooling flow passage 62 overlap each other. In this embodiment, the heating flow passage 61 and the cooling flow passage 62 cross each other right above the peripheral portion of the pad contact surface 65.
The heat exchanger 11 further includes a heating-fluid inlet 61a, a heating-fluid outlet 61b, a cooling-fluid inlet 62a, and a cooling-fluid outlet 62b. One end of the heating flow passage 61 is coupled to the heating-fluid inlet 61a, and the other end of the heating flow passage 61 is coupled to the heating-fluid outlet 61b. One end of the cooling flow passage 62 is coupled to the cooling-fluid inlet 62a, and the other end of the cooling flow passage 62 is coupled to the cooling-fluid outlet 62b. The heating-fluid inlet 61a is coupled to the heating-fluid supply pipe 32 (see
In a portion of the heat exchanger 11 indicated by symbol F2 shown in
Both the heating flow passage 61 and the cooling flow passage 62 are located over the entirety of the pad contact surface 65. In particular, both the heating fluid and the cooling fluid are present at points where the heating flow passage 61 and the cooling flow passage 62 cross each other. This arrangement can prevent the local heating with only the heating fluid and the local cooling with only the cooling fluid. In other words, the heat exchanger 11 can regulate the surface temperature of the polishing pad 3 by both the heating fluid and the cooling fluid in the entirety of the pad contact surface 65. Therefore, the heat exchanger 11 can provide a uniform distribution of the surface temperature of the polishing pad 3. Furthermore, the polishing apparatus having the above-discussed heat exchanger 11 can polish a substrate, such as a wafer, to provide a uniform polishing profile.
In order to maintain the pad surface temperature at a predetermined target temperature, the heat exchanger 11 is placed in contact with the surface (i.e. the polishing surface 3a) of the polishing pad 3 during polishing of the wafer W. In this specification, the manner of contact of the heat exchanger 11 with the surface of the polishing pad 3 includes not only direct contact of the heat exchanger 11 with the surface of the polishing pad 3, but also contact of the heat exchanger 11 with the surface of the polishing pad 3 in the presence of a polishing liquid (or slurry) between the heat exchanger 11 and the surface of the polishing pad 3. In either case, the heat exchange occurs between the polishing pad 3 and the heating fluid and cooling fluid, flowing in the heat exchanger 11, whereby the pad surface temperature is controlled.
As shown in
Each cleaning mechanism 80 includes a header tube 81 communicating with a cleaning-liquid supply source (not shown) and a plurality of spray nozzles 82 mounted to the header tube 81. The header tube 81 is arranged along the side surface of the heat exchanger 11, and the plurality of spray nozzles 82 are directed toward the side surface of the heat exchanger 11. A cleaning liquid, supplied from the cleaning-liquid supply source, is sprayed from the spray nozzles 82 toward both side surfaces of the heat exchanger 11, thereby removing the polishing liquid (for example, slurry) adhering to the side surfaces of the heat exchanger 11. Pure water may be used as the cleaning liquid. It is preferable that the heat exchanger 11 be cleaned when the heat exchanger 11 is at a retreat position.
In the above-described embodiments, the operation of the polishing apparatus is controlled by an operation controller 100 shown in
The memory 110 includes a main memory 111 which is accessible by the processing device 120, and an auxiliary memory 112 that stores the data and the program therein. The main memory 111 may be a random-access memory (RAM), and the auxiliary memory 112 is a storage device which may be a hard disk drive (HDD) or a solid-state drive (SSD).
The input device 130 includes a keyboard and a mouse, and further includes a storage-medium reading device 132 for reading the data from a storage medium, and a storage-medium port 134 to which a storage medium can be connected. The storage medium is a non-transitory tangible computer-readable storage medium. Examples of the storage medium include optical disk (e.g., CD-ROM, DVD-ROM) and semiconductor memory (e.g., USB flash drive, memory card). Examples of the storage-medium reading device 132 include optical disk drive (e.g., CD drive, DVD drive) and card reader. Examples of the storage-medium port 134 include USB terminal. The program and/or the data stored in the storage medium is introduced into the operation controller 100 via the input device 130, and is stored in the auxiliary memory 112 of the memory 110. The output device 140 includes a display device 141 and a printer 142.
The operation controller 100 operates according to the program electrically stored in the memory 110. Specifically, the operation controller 100 instructs the polishing head 1 to hold a substrate with the polishing head 1, and instructs the pad-temperature regulation system 5 to bring the heat exchanger 11 into contact with the surface 3a of the polishing pad 3 to regulate the surface temperature of the polishing pad 3, and further instructs the polishing head 1 to press the substrate against the surface 3a of the polishing pad 3 to polish the substrate, while regulating the surface temperature of the polishing pad 3 with the heat exchanger 11 through which the heating fluid and the cooling fluid flow.
The program for causing the operation controller 100 to perform these steps is stored in a non-transitory tangible computer-readable storage medium. The operation controller 100 is provided with the program via the storage medium. The operation controller 100 may be provided with the program via communication network, such as the Internet.
In one embodiment, in place of the translation mechanism 71 shown in
The previous description of embodiments is provided to enable a person skilled in the art to make and use the present invention. Moreover, various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles and specific examples defined herein may be applied to other embodiments. Therefore, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope as defined by limitation of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-17401 | Feb 2017 | JP | national |
