Feedforward and feedback control for conditioning of chemical mechanical polishing pad

• US 7,101,799 B2
• Filed: 11/30/2001
• Issued: 09/05/2006
• Est. Priority Date: 06/19/2001
• Status: Expired due to Fees

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Paik, Young Joseph
• Primary Examiner(s): Coleman, W. David
• Assistant Examiner(s): NGUYEN, KHIEM D
• Application Number:
  US09/998,384
• Publication Number:
  US 20030027424A1
• Time in Patent Office: 1,740 Days
• Field of Search: 438/689, 438/691, 438/692, 451/5
• US Class Current: 438/692
• CPC Class Codes: B24B 37/013 Devices or means for detecting lapping completion
• CPC Class Codes: B24B 37/042 operating processes therefor
• CPC Class Codes: B24B 49/03 according to the final size of the previously ground workpiece
• CPC Class Codes: B24B 49/18 taking regard of the presence of dressing tools
• CPC Class Codes: B24B 53/017 Devices or means for dressing, cleaning or otherwise conditioning lapping tools
• CPC Class Codes: G05B 19/00 Programme-control systems
• CPC Class Codes: G05B 19/19 characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
• CPC Class Codes: G05B 19/41865 characterised by job scheduling, process planning, material flow
• CPC Class Codes: G05B 2219/32053 Adjust work parameter as function of other cell
• CPC Class Codes: G05B 2219/32065 Synchronise set points of processes
• CPC Class Codes: G05B 2219/45031 Manufacturing semiconductor wafers
• CPC Class Codes: H01L 21/31053 involving a dielectric removal step
• CPC Class Codes: H01L 21/67253 Process monitoring, e.g. flow or thickness monitoring
• CPC Class Codes: H01L 21/67276 Production flow monitoring, e.g. for increasing throughput program-control systems per se G05B19/00, e.g. total factory control G05B19/418
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: Y02P 80/40 Minimising material used in manufacturing processes
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

A method, apparatus and medium of conditioning a planarizing surface includes installing a wafer to be polished in a chemical mechanical polishing (CMP) apparatus having a polishing pad and a conditioning disk, polishing the wafer under a first set of pad conditioning parameters selected to maintain wafer material removal rates with preselected minimum and maximum removal rates, determining a wafer material removal rate occurring during the polishing step, calculating updated pad conditioning parameters to maintain wafer material removal rates within the maximum and minimum removal rates, and conditioning the polishing pad using the updated pad conditioning parameters, wherein the updated pad conditioning parameters are calculated using a pad wear and conditioning model that predicts the wafer material removal rate of the polishing pad based upon pad conditioning parameters, such as the conditioning down force and rotational speed of the conditioning disk.

Claims

1. A method of conditioning a planarizing surface in a chemical mechanical polishing (CMP) apparatus having a polishing pad against which a wafer is positioned for removal of material therefrom and a conditioning disk is positioned for conditioning of the polishing pad, comprising the steps of:

a) providing a pad wear and conditioning model that defines wafer material removal rate as a function of at least one pad conditioning parameter, said at least one conditioning parameter having maximum and minimum values;

b) polishing a wafer in the CMP apparatus under a first set of pad conditioning parameters selected to maintain wafer material removal rates within preselected minimum and maximum removal rates;

c) determining a wafer material removal rate occurring during said polishing step;

d) calculating at least one updated pad conditioning parameters based upon said determined wafer material removal rate of said step (c) and the pad wear and conditioning model to maintain wafer material removal rates within the maximum and minimum removal rates; and

e) conditioning the polishing pad using at least one the updated conditioning parameters.

2. The method of claim 1, wherein the conditioning parameters comprise conditioning down force.

3. The method of claim 2, wherein the conditioning parameters comprise rotational velocity of the conditioning disk.

4. The method of claim 2, wherein the conditioning parameters comprise one or more parameters selected from the group consisting of rotational velocity of the disk, frequency of conditioning, duration of conditioning and translational speed of the conditioning disk.

5. The method of claim 1, wherein the step of calculating updated conditioning parameters includes calculating parameters such that the parameter is within the determined minimum and maximum values.

6. The method of claim 1, wherein the updated pad conditioning parameters are calculated by determining the difference between an output of the pad wear and conditioning model and said determined wafer material removal of step (c).

7. The method of claim 6, wherein said difference is adjusted using an estimate gain prior to calculating updated conditioning parameters.

8. The method of claim 1, wherein the updated pad conditioning parameters are updated according to the equation k=(k₁)+g*(k−

(k₁)),where k is a measured wafer material removal rate, k₁, is a calculated wafer material removal rate, g is the estimate gain, and (k−

(k₁)) is the prediction error.

9. The method of claim 1, wherein the steps (b) through (e) are repeated.

10. The method of claim 1, wherein the first set of pad conditioning parameters are determined empirically.

11. The method of claim 1, wherein the first set of pad conditioning parameters are determined using historical data.

12. The method of claim 1, wherein the first set of pad conditioning parameters are determined using the results of a design of experiment (DOE) used to develop the model.

13. The method of claim 1, wherein the maximum value for wafer material removal rate is the saturation point of the wafer material removal rate vs. conditioning down force curve.

14. The method of claim 1, wherein the minimum value for wafer material removal rate is defined by the maximum acceptable wafer polishing time.

15. The method of claim 1, wherein the step of calculating updated pad conditioning parameters in step (d) comprises executing a recursive optimization process.

16. The method of claim 7, wherein the estimate gain is an indication of variability or reliability in the measured parameter.

17. The method of claim 1, wherein pad life is defined according to the equation:

PadLife=f(F_disk, ω

_disk, t_conditioning, f, T₂),

where F_disk is the down force applied by the conditioning disk to the CMP pad during conditioning, ω

_disk is the angular velocity of the conditioning disk during conditioning of the polishing pad, t is the time of conditioning, f is the frequency of condition and T₂ is the sweeping speed of the conditioning disk during conditioning.

18. The method of claim 1, wherein the wafer material removal rate is defined by the equation ${\hspace{1em}}_{}^{}$

RemovalRate]minmax=f(Fdisk]minmax, 

ω

disk]minmax, 

f]minmax, 

tconditioning]minmax, 

T2]minmax),

where F_disk is the down force applied by the conditioning disk to the CMP pad during conditioning, ω

_disk is the angular velocity of the conditioning disk during conditioning of the polishing pad, t is the time of conditioning,f is the frequency of condition, and T₂ is the sweeping speed of the conditioning disk during conditioning.

19. The method of claim 1, wherein the wafer material removal rate is determined according to the equation:

ŷ

_i=p_ix_i+I_i,

where ŷ

_i is the wafer material removal rate for a conditioning parameter x_i, p_i is the slope and I_i is the intercept of the curve of the defining the relationship between ŷ

_i and x_i.

20. The method of claim 19, wherein the updated pad conditioning parameter, x_i+, is determined by solving the equation:

$x_{i+}=\frac{{\hat{y}}_{i+}-I_i-\frac{W_i}{W_T}·<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\hat{y}}{{\mathrm{\rho <br><br>}}_i},$

where ŷ

_i+ is the target wafer material removal rate, W_i is the weighing factor for conditioning parameter x_i, and Δ

y is the prediction error for wafer material removal rate.

21. A method of developing a pad wear and pad conditioning model for optimization of the pad conditioning, comprising the steps of:

determining the relationship between at least one pad conditioning parameter and wafer material removal rate;

determining maximum and minimum values for each of the at least one pad conditioning parameters and the wafer material removal rate; and

recording the relationships and minimum and maximum values of the at least one pad conditioning parameter and the wafer removal rate.

22. The method of claim 21, wherein the at least one pad conditioning parameter comprises a plurality of parameters and the wafer removal rate is defined as a weighted function of the plurality of pad conditioning parameters.

23. The method of claim 21, wherein the at least one pad conditioning parameters comprises conditioning disk down force.

24. The method of claim 23, wherein the at least one pad conditioning parameter further comprises conditioning disk rotational rate.

25. The method of claim 21, where the at least one pad conditioning parameter comprises one or more parameters selected from the group consisting of conditioning disk down force, conditioning disk rotational rate, frequency of conditioning, and conditioning disk translational speed.

26. The method of claim 21, wherein the relationship between the at least one conditioning parameter and wafer removal rate is determined by incrementally varying the conditioning parameter and measuring the resultant wafer removal rate.

27. The method of claim 21, wherein the maximum value for the conditioning parameter is the value above which no incremental increase of the wafer removal rate is observed.

28. The method of claim 21, wherein the minimum value for the conditioning parameter is the value which provides the minimum wafer removal rate.

29. The method of claim 21, further comprising the steps of:

polishing a wafer in the CMP apparatus under a first set of pad conditioning parameters selected to maintain wafer material removal rates within preselected minimum and maximum removal rates;

determining a wafer material removal rate occurring during said polishing step;

calculating updated pad conditioning parameters based upon said determined wafer material removal rate and the pad wear and conditioning model to maintain wafer material removal rates within the maximum and minimum removal rates; and

conditioning the polishing pad using the updated pad conditioning parameters.

30. The method of claim 29, wherein the updated pad conditioning parameters are calculated by determining the difference between an output of the pad wear and conditioning model and said determined wafer material removal.

31. The method of claim 29, wherein the updated pad conditioning parameters are updated according to the equation k=(k₁)+g*(k−

(k₁)), where k is a measured wafer material removal rate, k₁ is a calculated wafer material removal rate, g is the estimate gain, and (k−

(k₁)) is the prediction error.

32. A method of conditioning a planarizing surface in a chemical mechanical polishing (CMP) apparatus having a polishing pad against which a wafer is positioned for removal of material therefrom and a conditioning disk is positioned for conditioning of the polishing pad, comprising the steps of:

(a) developing a pad wear and pad conditioning model by;

(i) determining the relationship between at least one pad conditioning parameter and wafer material removal rate;

(ii) determining maximum and minimum values for each of the at least one pad conditioning parameters and the wafer material removal rate; and

(iii) recording the relationships and minimum and maximum values of the at least one pad conditioning parameter and the wafer removal rate,

(b) polishing a wafer in the CMP apparatus under a first set of pad conditioning parameters selected to maintain wafer material removal rates within preselected minimum and maximum removal rates;

(c) determining a wafer material removal rate occurring during said polishing step;

(d) calculating at least one updated pad conditioning parameters based upon said determined wafer material removal rate of said step (c) and the pad wear and conditioning model to maintain wafer material removal rates within the maximum and minimum removal rates,

wherein the wafer material removal rate is determined according to the equation;

ŷ

_i=ρ

_ix_i+I_i,

where ŷ

_i is the wafer material removal rate for a conditioning parameter x_i, ρ

_i, is the slope and I_i, is the intercept of the curve of the defining the relationship between ŷ

_i and x₁, and the updated pad conditioning parameter, x_i+, is determined by solving the equation;

$x_{i+}=\frac{{\hat{y}}_{i+}-I_i-\frac{W_i}{W_T}·<br><br>\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\hat{y}}{{\mathrm{\rho <br><br>}}_i},$

where ŷ

_i+ is the target wafer material removal rate, W_i is the weighing factor for conditioning parameter x_i, and Δ

y is the prediction error for wafer material removal rate; and

(e) conditioning the polishing pad using at least one the updated conditioning parameters.

33. A system for conditioning a planarizing surface in a chemical mechanical polishing (CMP) apparatus having a polishing pad and a conditioning disk, comprising:

a) a pad wear and conditioning model that defines wafer material removal rate as a function of at least one pad conditioning parameters including rotation and direction of the conditioning disk;

b) polishing means for polishing a wafer in the CMP apparatus

c) measuring means for determining a wafer material removal rate; and

d) calculating means for the at least one updating pad conditioning parameters based upon said determined wafer material removal rate of said step (c) and the pad wear and conditioning model to maintain wafer material removal rates within the maximum and minimum removal rates.