Patent Application
20160001418
The presently disclosed embodiment relates to a chemical mechanical polishing (CMP) apparatus and CMP method for polishing unevenness on a surface of an insulation film, a metal film, or a semiconductor film formed on a main surface of a semiconductor wafer or resin mold to be flat.
Today's semiconductor integrated circuits have a multi-layer wiring structure due to miniaturization and high integration. Conventional wiring forming processes for a multi-layer wiring structure process a metal such as Al deposited on an insulation film by lithography and dry etching to form a metal wiring pattern. However, recent multi-layer wiring forming processes have employed a damascene process for copper wiring.
In addition, in producing an electronic component with fine line widths, such as a coil element using a transfer mold made of metal or resin, copper deposited on a mold by a plate processing is polished to be flat by CMP, and is left only in via holes or wiring gutters to form an embedded copper wiring.
Conventionally, a load was maintained constant over the entire surface of the polishing object 730 and combined speed of the speed generated by the rotation of the polishing pad 710 and the speed of the polishing object 730 was controlled so as to be substantially uniform in the surface to be processed, in order to improve in-plane uniformity of polishing rate on the polishing object 730.
However, in the above-mentioned CMP method, when the cross-sectional shape in a through-thickness direction of the polishing object 730 is uniform, or has no waviness over the entire surface to be polished and is flat, polishing is performed so that polishing range has a certain thickness as shown in
Japanese Patent Publication No. 2000-263425 and Japanese Patent Publication No. 2002-246346 describe CMP apparatuses which can polish a wafer having a cross-sectional shape with waviness according to the waviness.
The CMP apparatus described in Japanese Patent Publication No. 2000-263425 has a rotational axis orthogonal to a central axis of a rotating table (turn table), is provided with a tool holder movable in a direction parallel to the rotational axis by a linear movement mechanism, places a plurality of arc-like grind stones along an outer circumference of this tool holder, and individually controls forces for pressing these grind stones against a polishing object so as to follow the waviness.
In addition, the apparatus described in Japanese Patent Publication No. 2000-246346 holds a wafer in a wafer holder while maintaining initial deformation and amount of warpage constant, includes a plurality of tubes for partially pressing a polishing pad depending on surface conditions such as unevenness on a surface of the wafer, and controls pressures applied by these respective tubes to uniformly polish in the surface of the wafer.
However, all the above apparatuses have a disadvantage of complicated control mechanism.
The presently disclosed embodiment is made to solve the above-mentioned problems and has an objective to provide a CMP method and CMP apparatus able to polish a polishing object having a cross-sectional shape with waviness according to the waviness and capable of attaining stable polish processing, using a relatively simple control mechanism.
In order to achieve the above-mentioned objective, the chemical mechanical polishing apparatus in a first aspect of the presently disclosed embodiment is a chemical mechanical polishing apparatus, wherein a rotating head having a polishing pad mounted thereon whose contact area with a polishing object is smaller than surface area of the polishing object is pressed against and brought into contact with a surface of the polishing object mounted face up on a table, and is rotated with the table at rest while supplying slurry onto a contact surface to polish for a predetermined time, and then the rotating head is moved within the surface of the polishing object to polish the entire surface of the polishing object sequentially, comprising a pressure adjustment mechanism for maintaining a pressing load on the contact surface constant during polishing.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, the pressure adjustment mechanism comprises a support shaft supporting the table along its central axis, a cylinder slidably holding the support shaft along the central axis, a pressure chamber having an air inlet and an air outlet and formed in the cylinder, and an air pressure adjustment means provided on the support shaft located in the pressure chamber.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, the air pressure adjustment means comprises a separation wall separating the pressure chamber into a first pressure chamber having the air inlet and a second pressure chamber having the air outlet, and adjusts the amount of air moving from the first pressure chamber to the second pressure chamber through a minute opening provided in the separation wall or a clearance between the separation wall and an inner wall surface of the cylinder to control air pressure in the pressure chamber.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, the pressure adjustment mechanism comprises an inner cylinder horizontally holding the table on its upper surface and having a pressure chamber formed therein, an outer cylinder slidably holding the inner cylinder along its central axis, a base having an air inlet and an air outlet and holding the outer cylinder, and an air pressure control unit adjusting the amount of air flowing in the air inlet and out the air outlet to control air pressure in the pressure chamber.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, the table is removably attached to the support shaft.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, the table is removably attached to the upper surface of the inner cylinder.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, a nozzle for supplying slurry is placed close to the rotating head and supplies slurry while moving in synchronization with the movement of the rotating head.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, a container capable of storing slurry is attached to the table.
In the chemical mechanical polishing apparatus of the presently disclosed embodiment, a recess is provided near the center of a polishing object facing surface of the rotating head.
In addition, the chemical mechanical polishing method in a second aspect of the presently disclosed embodiment is a chemical mechanical polishing method, wherein a rotating head having a polishing pad mounted thereon whose contact area with a polishing object is smaller than surface area of the polishing object is pressed against and brought into contact with a surface of the polishing object mounted face up on a table, and is rotated with the table at rest while supplying slurry onto a contact surface to polish for a predetermined time, and then the rotating head is moved within the surface of the polishing object to polish the entire surface of the polishing object sequentially, wherein a pressing load on the contact surface is maintained constant during polishing.
In the chemical mechanical polishing method of the presently disclosed embodiment, the surface of the polishing object is divided into a plurality of regions to be polished, and the rotating head is sequentially pressed against and brought into contact with them to polish as polishing time is varied according to section thickness of each divided region to be polished.
According to the chemical mechanical polishing apparatus and method of the presently disclosed embodiment, even though waviness exists on a surface to be polished of a polishing object, polishing according to the waviness is possible. Stable polish processing can therefore be attained.
Preferred aspects of the presently disclosed embodiment will be described below by reference to the accompanying drawings.
A rotating head 140 having a polishing pad 110 mounted thereon is operated to be pressed against and brought into contact with the surface of the polishing object 130. It should be noted that it is clearly shown in
Thus, in the CMP apparatus of the presently disclosed embodiment, polishing is performed by rotating and moving only the rotating head 140 while the table 120 does not rotate and remains at rest. In addition, a nozzle 150 which is close to the rotating head 140 and supplies slurry onto a contact surface is placed, and this nozzle 150 supplies slurry while moving in synchronization with the movement of the rotating head 140. In this manner, the synchronization of the movement of the nozzle 150 and that of the rotating head 140 makes it possible to supply slurry onto the contact surface efficiently.
The main feature of the presently disclosed embodiment is to reduce a contact surface and maintain a pressing load on the contact surface during polishing constant. This makes polishing amount in a thickness direction per a predetermined time over the entire contact surface constant.
As seen above, the CMP apparatus of the presently disclosed embodiment is designed so that the area of the contact surface is considerably smaller than the surface area of the polishing object 130. Thus, even with waviness on a surface of the polishing object 130, the contact surface is placed along the waviness, which makes polishing amount constant.
As a result, polishing range can be maintained at a certain thickness along the waviness of the polishing object, as shown in
As described above, the presently disclosed embodiment divides the surface of the polishing object into a plurality of regions to be polished and polishes them sequentially with a certain load for a predetermined time, however, some unevenness in section thickness may be caused depending on the degree of waviness of the polishing object.
In this case, polishing time should be varied in response to the section thickness. As mentioned above, the CMP apparatus of the presently disclosed embodiment has the main feature of maintaining a load on a contact surface (hereinafter referred to as a local load) constant. Next, an aspect of a pressure adjustment mechanism for realizing such a feature will be described.
The pressure chamber 210 is separated into a first pressure chamber 206 having the air inlet 202 and a second pressure chamber 208 having the air outlet 204. A separation wall for this separation can be formed by providing a part of the support shaft 160 located in the pressure chamber 210 with a first shaft diameter expanded portion 162 and a second shaft diameter expanded portion 164 and bringing an outer diameter portion of the second shaft diameter expanded portion 164 into slidable contact with an inner wall surface of the pressure chamber 210. This second shaft diameter expanded portion 164 is formed thinly and has one or more minute openings 166 whose each diameter is about 100 μm formed therein. It should be noted that this opening 166 is not indispensable if a prescribed clearance is provided between the second shaft diameter expanded portion 164 and the inner wall surface of the cylinder 200.
In the cylinder 200 configured as described, when compressed air 260 of a predetermined air pressure flows in the first pressure chamber 206 through the air inlet 202, the air then flows into the second pressure chamber 208 through the opening 166 and flows out through the air outlet 204. The support shaft 160 is pushed upward by a pressure difference between the first pressure chamber 206 and the second pressure chamber 208 which difference is caused because the opening 166 is minute, and rests at a position which balances gravity of total mass of the support shaft 160 and the table 120 supported thereby. This rest position is determined by the pressure of the compressed air 260 flowing in the air inlet 202.
Hence if the lower surface of the rotating head 140 is controlled so as to be set below a raised position of the table 120, it is pressed against and brought into contact with the table 120 with a certain load determined by the pressure of the compressed air 260.
A certain load required for polishing can be set by controlling the pressure of the compressed air.
The CMP apparatus of the presently disclosed embodiment is provided with an up-and-down/movement/rotation control unit 302 for controlling up-and-down/movement/rotation of the rotating head 140, a slurry supply unit 304 for supplying slurry to the nozzle 150, an air pressure control unit 306 for controlling air pressure of the compressed air 260, a pressure sensor 308 for detecting a pressing load on the contact surface, and a main control unit 310 for controlling the up-and-down/movement/rotation control unit 302, the slurry supply unit 304, and the air pressure control unit 306.
The up-and-down/movement/rotation control unit 302 is to control a stop position of the rotating head 140, an amount or timing of movement in X-Y directions, and the number of rotations of the rotating head 140, and controls them by sending a control command 402 to the rotating head 140 based on a control command 404 from the main control unit 310.
The slurry supply unit 304 is to control to supply slurry while moving the nozzle 150 in synchronization with the movement of the rotating head 140, and controls the nozzle 150 based on a control command 408 from the main control unit 310.
The air pressure control unit 306 is to control air pressure of the compressed air 260 supplied to the air inlet 202, and controls it based on a control command 410 from the main control unit 310.
In the presently disclosed embodiment, the pressure adjustment mechanism shown in
The air pressure control unit 306 includes a pressure control circuit 450 which operates receiving the control command 410 from the main control unit 310, a pressure source 420, a valve 430, and a pressure gauge 440. For example, the pressure source 420 is a bottle of compressed air. Compressed air from the pressure source 420 passes through the valve 430 and the pressure gauge 440, becomes the compressed air 260 for supply, and is supplied to the air inlet 202. The pressure control circuit 450 adjusts an opening/closing amount of the valve 430 based on a measured value by the pressure gauge 440 to control air pressure of the compressed air 260 for supply to a desired level.
The outer wall surface of the inner cylinder 610 is brought into slidable contact with the inner wall surface of the outer cylinder 620.
In the pressure adjustment mechanism configured as described, when compressed air of a predetermined air pressure flows in the pressure chamber 600 through the air inlet 602 via the air pressure control unit 640, the air pressure in the pressure chamber 600 increases according to an amount of air flowing out the air outlet 604.
The inner cylinder 610 is pushed upward due to the increase in air pressure and rests at a position which balances gravity of total mass of the inner cylinder 610 and the table 120 held thereby. This rest position is determined by the air pressure in the pressure chamber 600.
Hence, if the lower surface of the rotating head 140 is controlled so as to be set below a raised position of the table 120, it is pressed against and brought into contact with the table 120 with a certain load determined by the air pressure in the pressure chamber 600.
As described above, a certain load required for polishing can be set by controlling the air pressure in the pressure chamber 600 with the air pressure control unit 640.
The air pressure control unit 640 includes a compression pump 642 which compresses air from the outside to produce compressed air, an air valve 644 which adjusts an amount of compressed air to be supplied, a mass flow controller (MFC) 646 which controls a flow rate of the compressed air flowing in an air inlet 602, a needle valve 648 which is connected to an air outlet 604 and controls an amount of air flow, and a pressure relief valve 650. Controlling the opening of the needle valve 648 by a control command 646a from the MFC 646 makes it possible to maintain a flow rate of the compressed air flowing in the air inlet at a predetermined value, control the air pressure in the pressure chamber 600 to a desired level, and obtain a certain load required.
It should be noted that although the table 120 is fixedly attached to the support shaft 160 or the upper surface 612 of the inner cylinder 610 in the above-described embodiment, the table 120 can be attached removably.
In addition, slurry is supplied from the slurry supply unit 304 through the nozzle 150 in the above-described embodiment, but the polishing object 130 can be polished in a state of being constantly immersed in slurry.
A container 500 capable of storing slurry is attached to the table 120 or the support shaft 160 and polishing is performed in the container 500 filled with slurry 550.
The table 120 must have a predetermined thickness and its upper and lower surfaces must have sufficient flatness. In order to removably mount the slurry liquid attachment 800 on the upper surface 612 of the inner cylinder 610 shown in
Polishing amount can be controlled by changing a concentration, particle diameter, or material of the slurry liquid according to the nature of a film to be polished or polishing amount.
Exchange of the slurry liquid can be easily performed by changing the attachment 800. It can also be performed by sucking out the currently-used slurry liquid and replacing it with slurry liquid of a different concentration, particle diameter, or material.
The rotating head 140 is attached to a high speed rotary motor 170, which is attached to a 3-axis (X, Y, Z) control robot.
The 3-axis control robot 180 controls rotation and movement in axial directions of the rotating head 140.
Attaching the rotating head 140 to the high speed rotary motor 170 clampedly makes it easy to replace the rotating head 140 according to polishing conditions. In addition, preparing the necessary number of 3-axis control robots 180 makes it possible to replace the 3-axis control robot 180 entirely.
It should be noted that controlling factors on polishing according to the presently disclosed embodiment include the following:
Controlling each of these factors appropriately makes it possible to realize a desired polishing.
In addition, the reason is uncertain, but an observation result by the present inventors revealed that the surface of the polishing object 130 could be polished more uniformly along waviness by providing a recess 145 near the center of a polishing object facing surface 147 of the rotating head 140 as shown in
It is presumed that this is either because a pressing load applied to the polishing pad decreases at the recess 145 or because slurry easily collects at the recess 145, but details are unknown.
When polishing was performed using the rotating head 140 which has a hole 148 opened near the center and is provided with connection holes 149 reaching the hole 148 from the side wall as shown in
In addition, when the polishing surface of the rotating head 140 was provided with connecting grooves 144 connecting toward the recess 145 near the center as shown in
This is considered to be because the slurry is taken more due to the connecting grooves 144.
As above, the presently disclosed embodiment has been described based on the aspects, but it is not limited thereto.
It is obvious to one having ordinary skill in the art that the pressure adjustment mechanism used in the presently disclosed embodiment may be variously modified. For example, the above-described aspect is designed to provide a pressure sensor and feed back a pressure signal from this pressure sensor to adjust air pressure, but the magnitude of the pressing load set once may be designed not to have to be changed during polishing without using the pressure sensor. In addition, providing a mechanism to tilt the rotating head along waviness makes it possible to uniformly polish more accurately along the waviness.
In addition, the area of the contact surface of the rotating head may be adjusted, depending on the period of the waviness, so as to be large when the period is long or to be small when the period is short. The presently disclosed embodiment can be preferably applied to a mirror finish of a mold, or release of a thin film of up to 100 nm in film thickness.
In addition, it can be applied not only to a surface finish of a three-dimensional structure, lens, and an object fabricated by stereo lithography but also to such as a spherical silicon or nanoimprinting.
This application is the National Stage of International Application No. PCT/JP2013/000917 having an International Filing Date of 19 Feb. 2013, which designated the United States of America, and which International Application was published under PCT Article 21 (s) as WO Publication 2014/128754 A1, the disclosures of which are incorporated herein by reference in their entireties.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/000917 | 2/19/2013 | WO | 00 |
