Methods for controlling the pressures of adjustable pressure zones of a work piece carrier during chemical mechanical planarization

• US 7,115,017 B1
• Filed: 03/31/2006
• Issued: 10/03/2006
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Original Assignee: Novellus Systems Incorporated (Lam Research Corporation)
• Inventors: Stotts, Thomas, Laursen, Thomas, Franzen, Paul, Quarantello, Justin
• Primary Examiner(s): Wilson, Lee D.
• Assistant Examiner(s): OJINI, EZIAMARA ANTHONY
• Application Number:
  US11/394,516
• Time in Patent Office: 186 Days
• Field of Search: 451/5, 451/6, 451/8, 451/41, 451285-290, 438/16
• US Class Current: 451/5
• CPC Class Codes: B24B 37/30 for single side lapping of plane surfaces
• CPC Class Codes: B24B 49/105 using eddy currents

Abstract

Methods are provided for controlling adjustable pressure zones of a CMP carrier. A method comprises determining a first thickness of a layer on a wafer underlying a first zone of the carrier. A first portion of the layer underlying the first zone is removed. The first zone is configured to exert a first pressure against the second surface of the wafer. A second thickness of the layer underlying the first zone is determined and a target thickness corresponding to a predetermined thickness profile is selected. A second pressure for the first zone is calculated using the first thickness, the second thickness, the first pressure, and the target thickness. The pressure exerted by the first zone against the second surface of the wafer is adjusted to the second pressure and the steps are repeated for a second zone.

Claims

1. A method for removing at least a portion of a material layer from a first surface of a work piece utilizing a CMP apparatus having a work piece carrier with a plurality of pressure adjustable zones, wherein each zone is configured to exert a pressure against a second surface of the work piece during a CMP process, the method comprising the steps of:

determining a first thickness T<sub>z,n−

1</sub> of the material layer underlying a first zone z, where z is an integer from 1 to Z_f, Z_f is the total number of zones, n is an integer from 1 to N, and N is the total number of times thickness measurements are assessed;

removing a first portion of the material layer underlying the first zone for a time interval (t_n−

t<sub>n−

1</sub>) wherein the first zone is configured to exert a first pressure P_z,n against the second surface of the work piece;

determining a second thickness T_z,n of the material layer underlying the first zone;

selecting a target thickness T_z,n+1 of the material layer within zone z corresponding to a predetermined thickness profile to be produced before the material layer is substantially removed;

calculating a second pressure P_z,n+1 using the first pressure P_z,n, the first thickness T<sub>z,n−

1</sub>, the second thickness T_z,n, and the target thickness T_z,n+1, wherein the second pressure is to be exerted against the second surface of the work piece by the first zone during removal of a second portion of the material layer;

adjusting the pressure exerted by the first zone against the second surface of the work piece to the second pressure P_z,n+1; and

repeating the foregoing steps for a second zone.

2. The method of claim 1, further comprising the step of removing a second portion of the material layer underlying the first zone, wherein the first zone is configured to exert the second pressure against the second surface of the work piece.

3. The method of claim 1, wherein the step of removing a first portion of the material layer comprises removing said first portion of the material layer using a removal rate that is constant throughout the CMP process.

4. The method of claim 1, wherein the step of removing a first portion of the material layer comprises removing said first portion of the material layer using a weighted average pressure that is constant throughout the CMP process.

5. The method of claim 1, further comprising the steps of determining a first average thickness τ

<sub>n−

1</sub> of the material layer on the first surface of the work piece before the step of removing a first portion of the material layer, and further comprising the step of determining a second average thickness τ

_n of the material layer on the first surface of the work piece before the step of calculating a second pressure P_z,n+1.

6. The method of claim 5, wherein the step of selecting a target thickness T_z,n+1 comprises the step of selecting a target average thickness T_n+1 of the material layer on the first surface of the work piece at which a substantially planar profile is desired, and wherein the step of calculating a second pressure P_z,n+1 comprises calculating said second pressure using the first thickness T_z,n−

1, the second thickness T_z,n, the first average thickness τ

<sub>n−

1</sub>, the second average thickness τ

_n, and the target average thickness T_n+1.

7. The method of claim 5, further comprising the steps of selecting a target removal amount Δ

from the material layer and selecting a target removal deviation δ

_z from the target removal amount Δ

underlying the first zone and wherein the step of calculating a second pressure P_z,n+1 comprises the step of calculating said second pressure using the first thickness T<sub>z,n−

1</sub>, the second thickness T_z,n, the first average thickness τ

<sub>n−

1</sub>, the second average thickness τ

_n, the target removal amount Δ

, and the target removal deviation δ

_z.

8. The method of claim 7, wherein the step of calculating a second pressure P_z,n+1 comprises the step of calculating the second pressure using the equation:

P_z,n+1=P_z,nC_z,n+1^(1/x),

where x is a Preston-correction exponent for zone z, and C_z,n+1 is a removal coefficient expressed according to the following equation;

9. The method of claim 1, wherein the step of measuring a second thickness of the material layer underlying the first zone comprises the step of measuring a second thickness of the material layer underlying each of the zones, and wherein the step of calculating a second pressure P_z,n+1 comprises the steps of:

comparing the second thicknesses of the material layer of each of the zones and determining a minimum second thickness;

selecting a correction control parameter K; and

calculating the second pressure using the minimum thickness, the correction control parameter K, the first thickness T<sub>z,n−

1</sub>, and the second thickness T_z,n.

10. A method for producing a target thickness profile of a material layer on a first surface of a work piece utilizing a CMP apparatus having a work piece carrier with a number Z_f of pressure adjustable zones, wherein each zone is configured to exert a pressure against a second surface of the work piece during a CMP process, the method comprising the steps of:

for each zone, determining a first thickness T<sub>z,n−

1</sub> of the material layer, where z is an integer between 1 and Z_f, n is an integer between 1 and N, and N is the total number of times thickness measurements are assessed;

calculating a first average thickness τ

<sub>n−

1</sub> of the material layer across the work piece;

for each zone, removing a first portion of the material layer, wherein each of said zones is configured to exert a first pressure P_z,n against the second surface of the work piece;

for each zone, determining a second thickness T_z,n of the material layer;

calculating a second average thickness τ

_n of the material layer across the work piece using the second thicknesses;

for each zone, selecting a target thickness T_z,n+1 corresponding to the target thickness profile of the material layer;

for each zone, calculating a removal rate coefficient C_z,n+1 using the first thickness T<sub>z,n−

1</sub>, the second thickness T_z,n, the first average thickness τ

<sub>n−

1</sub>, the second average thickness τ

_n, and the target thickness T_z,n+1; and

for each zone, calculating a second pressure P_z,n+1 from the first pressure and the removal rate coefficient, wherein the second pressure is to be exerted against the second surface of the work piece within the first zone during removal of a second portion of the material layer.

11. The method of claim 10, wherein the step of removing a first portion of the material layer comprises removing said first portion of the material layer using a removal rate that is constant throughout the CMP process.

12. The method of claim 10, wherein the step of removing a first portion of the material layer comprises removing said first portion of the material layer using a weighted average pressure that is constant throughout the CMP process.

13. The method of claim 10, wherein the step of selecting for each zone a target thickness T_z,n+1 corresponding to the target thickness profile of the material layer comprises the step of selecting the same target thickness T_n+1 for each zone, such that T_n+1 is equal to a target average thickness τ

_n+1.

14. The method of claim 10, further comprising the step of adjusting the pressure exerted by each zone against the second surface of the work piece to the second pressure P_z,n+1.

15. The method of claim 10, wherein the step of calculating a second pressure P_z,n+1 from the first pressure and the removal rate coefficient comprises the step of calculating the second pressure P_z,n+1 using the equation:

P_z,n+1=P_z,nC_z,n+1^(1/x),

where x is a Preston-correction exponent for zone z.

16. The method of claim 10, wherein the step of calculating a removal rate coefficient C_z,n+1 for each zone comprises the steps of:

selecting a target removal amount Δ

from the material layer, wherein Δ

may be expressed by the equation Δ

=τ

_n−

τ

_n+1;

selecting a target removal deviation δ

_z from the target removal amount Δ

underlying the first zone, wherein δ

_z can be expressed by the equation δ

_z=T_z,n+1−

τ

_n+1; and

calculating a removal rate coefficient C_z,n+1 using the equation;

17. A CMP apparatus comprising:

a working surface;

a work piece carrier configured to press a first surface of a work piece against the working surface, wherein the work piece carrier has a plurality of pressure zones, each pressure zone configured to exert a pressure on a second surface of the work piece;

a multi-probe thickness measuring system having a plurality of probes disposed proximate to said working surface, wherein the multi-probe thickness measuring system is configured to measure a thickness of a material layer on the first surface of the work piece; and

a controller electrically coupled to the multi-probe thickness measuring system and the work piece carrier, wherein the controller is configured to;

receive first signals from the multi-probe thickness measuring system;

determine a first thickness of the material layer underlying a first pressure zone of the work piece carrier using the first signals;

cause the first zone of the work piece carrier to exert a first pressure against the second surface of the work piece;

cause the working surface to remove a first portion from the material layer underlying the first zone;

receive second signals from the multi-probe thickness measuring system;

determine a second thickness of the material layer underlying the first zone using the second signals;

receive as input a target removal amount projected to be removed from the material layer;

calculate a second pressure from the first pressure, the first thickness, the second thickness, and the target removal amount; and

cause the work piece carrier to change the pressure exerted by the first zone against the second surface of the work piece to the second pressure.

18. The CMP apparatus of claim 17, wherein the controller is further configured to cause removal rates for the removal of the material layer across the first surface of the wafer to be kept constant.

19. The CMP apparatus of claim 17, wherein the controller is further configured to cause a weighted average pressure exerted on the second surface of the wafer to be kept constant.

20. The CMP apparatus of claim 17, wherein the multi-probe thickness measuring system is an eddy current thickness measuring system.

21. The CMP apparatus of claim 17, wherein the multi-probe thickness measuring system is an optical thickness measuring system.