Surface planarization

Embodiments of methods and apparatus in accordance with the present invention provide a chemical mechanical planarization (CMP) process that provides single or multiple polishing pads to have a different rotational velocity, applied pressure and oscillation frequency on the surface of the substrate to address and compensate for the WIW (with-in-substrate) and WID (with-in-die) non-uniformities in planarization ability. The velocity of each polishing pad is adjustable providing a closer match to the substrate surface velocity over a particular zone to yield a linear velocity on the surface of the substrate.

FIELD OF THE INVENTION

The present invention relates to apparatus and methods for chemical mechanical planarization and, more particularly, to large substrate planarization using multi-translational adaptive cylindrical polishing pads.

BACKGROUND OF INVENTION

Chemical mechanical planarization (CMP) is a popular method of planarizing the surface of a semiconductor substrate. CMP combines chemical etching and mechanical polishing to remove raised features on the surface of the semiconductor substrate. Planarity of the surface is a critical dimension for integrated circuit fabrication.

Standard practice is the use of a polishing pad mounted on a flat rotating platen, or turntable. The substrate is held in a carrier facing down and in contact with the polishing pad on the platen. The WIW (with-in-substrate) and WID (with-in-die) non-infirmities on the substrate surface are addressed by adjusting the back-pressure on the substrate, which in turn, alters the substrate's local shape with respect to the polishing pad. Platen to carrier rotational speed and carrier oscillation are also utilized to address these issues. Both approaches have their limitations due to the limited number of process parameters that can be controlled.

In an effort to increase production efficiencies, larger substrate sizes are becoming available. The current method for CMP is not adequate for these larger sizes. The polish non-uniformities are amplified with the increase in substrate diameter, which can contribute greatly to the WIW (with-in-substrate) and WID (with-in-die) non-uniformities.

The move of the industry toward using low and ultra low-K materials is also challenging current CMP processes. Metal delamination during the planarization process is caused by the weak adhesion between the low-K dielectric and the metal layer. CMP of low-K and ultra low-K substrate requires a process that provides low applied pressure and high velocity that is not easily obtainable with the current methods due to the limited number of process parameters that can be controlled.

Suitable apparatus and methods are needed for planarizing larger substrate, as well as improving the planarization of all substrate sizes, that are more reliable, consistent, and uniform.

DESCRIPTION

Embodiments of methods and apparatus in accordance with the present invention provides a CMP methods and apparatus that provide single or multiple polishing pads each with individual control over various parameters to address and compensate for the WIW and WID non-uniformities in planarization ability. The velocity of each polishing pad is adjustable providing a closer match to the substrate surface velocity over a particular zone to yield a linear velocity on the surface of the substrate.

FIGS. 1-4are top, side, side, and top views, respectively, of a CMP apparatus2comprising a rotating substrate holder12and a single cylindrical polishing pad20coupled to a control arm16, in accordance with an embodiment of the present invention. The substrate holder12carries the substrate13in a horizontal position with the surface14of the substrate13to be polished facing upward. The substrate holder12is adapted to rotate the substrate13at a constant or variable velocity (Vs)35predetermined for a particular purpose.

The polishing pad20is cylindrically shaped and adapted to couple with the control arm16through the long axis. The length of the polishing pad20is less than the radius of the substrate13. In the embodiment ofFIG. 1, the length of the polishing pad20is approximately one-third of the radius of the substrate13. In other embodiments, the polishing pad20is a given fraction of the radius of the substrate13.

The control arm16, when in operation, extends above the substrate holder12and substantially parallel with the substrate surface14. The control arm16is adapted to pivot about a fixed point15adjacent the substrate holder12with a rotation velocity39and position45. The control arm16is adapted to accept a cylindrical polishing pad20. The control arm16is adapted to linearly translate the polishing pad20along the control arm16at a translation velocity (Vt)34and parallel with the substrate surface14. The control arm16is adapted to position the polishing pad20at predetermined locations on the substrate surface14from at least the rotation axis17of the substrate holder12to the edge18of the substrate13. In the embodiment ofFIG. 1, three polishing pad20positions are defined as the center25, middle26and edge27positions. The control arm16is adapted to linearly translate the polishing pad20within the three polishing pad positions and overlapping some portion of one or more polishing pad positions.

The control arm16is adapted to rotate the polishing pad20about the polishing pad's20long axis. The rotation velocity (Vp)30of the polishing pad20is variable and is selected for a particular purpose. In one embodiment of the method of the present invention, the Vp30of the polishing pad20is adjusted with radial position on the substrate13.

The control arm16is adapted to place the polishing pad20in contact with the substrate13at a predetermined pressure (P)40. The pressure40can be constant or continuously varied at one location or varied with position (Pc41, Pm42, Pe43), along the radius of the substrate13.

In an embodiment of the method of the invention, the pressure40is continuously varied across the substrate13and the polishing pad20is translated back and forth along the control arm16to compensate for the velocity differential along the radius of the substrate13, from the rotation axis17to the edge27. The velocity differential is greater as the radius of the substrate13is larger. The polishing pad20position and translation velocity (Vt)34, polishing pad rotation velocity (Vp35, Vc36, Vm37, Ve38), pad pressure (P)40, control arm rotation velocity (Cv)39and position (Cp)45, and substrate13rotation velocity (Vs)35are controlled based on the feedback from an in-situ process/substrate surface14metrology system to address a particular non-uniformity on the surface14of the substrate13.

In an embodiment of the method of the invention, the pad velocity (Vp)30of the polishing pad20is adjusted to provide a closer match to the substrate surface velocity (Vc36, Vm37, Ve38) over a particular position to yield a linear velocity over the substrate surface14.

FIGS. 5-8are top, side, side, and top views, respectively, of a CMP apparatus4comprising a rotating substrate holder12with multiple cylindrical polishing pads20a,20b,20cco-axially coupled to a control arm46, in accordance with an embodiment of the present invention. The substrate holder12carries the substrate13in a horizontal position with the substrate surface14to be polished facing upward. The substrate holder12is adapted to rotate the substrate13at a constant or variable velocity predetermined for a particular purpose.

The polishing pads20a-care cylindrically shaped and adapted to couple with the control arm through the long axis. The length of each polishing pad20a-cis less than the radius of the substrate13. A plurality of polishing pads20a-cis used simultaneously to cover the substrate surface14. In the embodiment ofFIG. 5, a plurality of polishing pads20a-cis utilized and the length of each polishing pad20a-cis approximately one-third of the radius of the substrate13. In other embodiments, the length of each polishing pad20a-cis a given fraction of the radius of the substrate13.

The control arm46, when in operation, extends above the substrate holder12and substantially parallel with the substrate surface14. The control arm46is adapted to pivot about a fixed point15adjacent the substrate holder12in a sweeping manner with a control arm rotation velocity (Cv)39and position (Cp)45. The control arm46is adapted to accept multiple cylindrical polishing pads20a-c. The polishing pads20a-cremain at a fixed position along the length of the control arm46. The control arm46is adapted to place the polishing pads20a-cparallel and in contact with the substrate surface14. In the embodiment ofFIG. 5, each of the three polishing pads20a-cdefines either a center25, middle26or edge27position.

The control arm46is adapted to rotate the polishing pads20a-cabout the polishing pad's long axis. Each pad rotation velocity (Vpc31, Vpm32, Vpe33) is variable, independent, and selected for a particular purpose. In one embodiment of the method of the present invention, the rotation velocity31,32,33of the polishing pads20a-cis adjusted with radial position on the substrate13.

The control arm46is adapted to place the polishing pads20a-cin contact with the substrate13at a predetermined pressure (Pc41, Pm42, Pe43). The pressure41,42,43can be constant or varied.

In an embodiment of the method of the invention, each pad rotation velocity31,32,33of each polishing pad20a-cis selected to compensate for the substrate velocity36,37,38differential along the radius of the substrate13. The velocity differential is greater as the radius of the substrate13is larger. The polishing pad rotation velocity (Vpc31, Vpm32, Vpe33), polishing pad pressure (Pc41, Pm42, Pe43), control arm rotation velocity (Cv)39and position (Cp)45, and substrate rotation velocity35are controlled based on the feedback from an in-situ process/substrate13surface metrology system to address a particular non-uniformity on the substrate surface14.

In an embodiment of the method of the invention, the velocity of each polishing pad31,32,33is adjusted to provide a closer match to the substrate surface velocity35over a particular position to yield a linear velocity over the substrate surface14.

FIG. 9is a top view of a CMP apparatus6comprising a rotating substrate holder12and a single cylindrical polishing pad21a-ccoupled to each of three independent control arms47a-ccoupled in parallel relationship to each other as a unit47at a single pivot point15, in accordance with an embodiment of the present invention. The substrate holder12carries the substrate13in a horizontal position with the substrate surface14to be polished facing upward. The substrate holder12is adapted to rotate the substrate13at a constant or variable velocity predetermined for a particular purpose.

Each polishing pad21a-cis cylindrically shaped and adapted to couple with one of the control arms47a-cthrough the long axis. The length of each polishing pad21a-cis less than the radius of the substrate13. In the embodiment ofFIG. 9, the length of each polishing pad21a-cis approximately one-third of the radius of the substrate13. In other embodiments, each polishing pad21a-cis a given fraction of the radius of the substrate13.

Each control arm47a-c,when in operation, extends above the substrate holder12and substantially parallel with the substrate surface14. The control arms47a-care adapted to pivot as a unit47about a fixed point15adjacent the substrate holder12in a sweeping manner at a rotational velocity (Cv)45. Each control arm47a-cis adapted to accept a cylindrical polishing pad20a-c. Each control arm47a-cis adapted to linearly translate a polishing pad20a-calong the control arm47a-cand parallel with the substrate surface14. In the embodiment ofFIG. 3, three polishing pad positions are defined as the center25, middle26and edge27. Each control arm47a-cis adapted to position a polishing pad20a-cat predetermined locations on the substrate surface14: one control arm47apositioning a polishing pad20aat a defined center25position; one control arm47bpositioning a polishing pad20bat a defined middle26position; and one control arm47cpositioning a polishing pad20cat a defined edge27position. Each control arm47a-cis adapted to linearly translate the polishing pad20a-ceither within at least one of the three polishing pad positions25,26,27and overlapping some portion of one or more polishing pad positions25,26,27.

Each control arm47a-cis adapted to rotate the polishing pad20a-cabout the polishing pad's20a-clong axis. The polishing pad rotation velocity (Vpc31, Vpm32, Vpe33), polishing pad pressure (Pc41, Pm42, Pe43), control arm rotation velocity (Cv)39and position (Cp)45, and substrate rotation velocity35are controlled based on the feedback from an in-situ process/substrate13surface metrology system to address a particular non-uniformity on the substrate surface14.

The rotation velocity of each polishing pad20a-cis variable and independent, and is selected for a particular purpose. In one embodiment of the method of the present invention, the rotation velocity of each polishing pad20a-cis adjusted with radial position on the substrate13.

Each control arm47a-cis adapted to place the polishing pad20a-cin contact with the substrate13at a predetermined pressure, independent from the other polishing pads20a-c. The pressure can be constant or varied at one location or variable with position along the radius of the substrate13.

In an embodiment of the method of the invention, the polishing pressure of each polishing pad20a-cis varied across the substrate13and the polishing pad20a-cis translated back and forth along the control arm47a-cto compensate for the velocity differential along the radius of the substrate13. The velocity differential is greater as the radius of the substrate13is larger. The polishing pad position25,26,27and translation velocity (Vtc34a, Vtc34b, Vte34c), polishing pad rotation velocity (Vpc31, Vpm32, Vpe33), polishing pad pressure (Pc41, Pm42, Pe43), control arm rotation velocity (Cv)39and position (Cp)45, and substrate rotation velocity35are controlled based on the feedback from an in-situ process/substrate13surface metrology system to address a particular non-uniformity on the substrate surface14.

In an embodiment of the method of the invention, the velocity of each polishing pad20a-cis adjusted to provide a closer match to the substrate surface14velocity over a particular position to yield a linear velocity over the surface of the substrate13.

FIG. 10is a top view of a slurry delivery system54, in accordance with an embodiment of the present invention. In an embodiment in accordance with the present invention, the slurry and polishing solution distribution is through a slurry dispensing head50directly dispensed onto the substrate surface14at one or multiple ports51.FIG. 11is a side cross-sectional view of a polishing pad20wherein the slurry and polishing solution is distributed through perforations52in each polishing pad20, in another embodiment in accordance with the present invention.

FIG. 12is a side cross-sectional view of a polishing pad conditioning piece53, in accordance with an embodiment of the present invention. The conditioning piece53has a semi-cylindrical shape with an inside diameter and length substantially the same as the outer diameter and length of the polishing pad20. The conditioning piece53is adapted to condition, or clean, the polishing pad20.

The embodiments of apparatus and methods in accordance with the present invention provide the ability to process larger semiconductor substrates more reliably, consistently and uniformly during the planarization process. The control over multiple process parameters provides the ability to process substrate13using very low pressure and very high rotational velocity that is particularly useful for planarization of ultra low-K materials. Similarly, the control over multiple process parameters provides the ability to prevent metal delamination during the planarization process, which is caused by the weak adhesion between the low-K dielectric and the metal layer.

The embodiments of apparatus and methods in accordance with the present invention provide the planarization to address the WIW (with-in-substrate) and WID (with-in-die) non-uniformities far more efficiently than any other systems on the market. As the diameter of substrate increases the velocity gradient across the substrate also increases; this methodology can address this issue efficiently by allowing single or multiple polishing pads move at different velocities and applied pressures on the substrate with an additional benefit of having the polishing solution dispensed at three different flow rates at different locations on the substrate. Furthermore, the embodiments enable the process of very low pad pressure on the substrate with a high substrate rotational velocity, which is required for ultra low-K integration.

The embodiments of apparatus and methods in accordance with the present invention provide single or multiple polishing pads to have a different rotational velocity, applied pressure and rate of linear positioning on the surface of the substrate to address and compensate for the WIW (with-in-substrate) and WID (with-in-die) non-uniformities in planarization ability. In this configuration, the velocity of each polishing pad can be adjusted such that it will match the substrate surface velocity over a particular zone to yield a linear velocity on the surface of the substrate. This enhances planarization of WIW and WID, and will allow the processing of very low pad pressure on the substrate with a high rotational velocity, which is required for ultra low-K integration.