MONITORING SURFACE OXIDE ON SEED LAYERS DURING ELECTROPLATING

• US 20180282894A1
• Filed: 03/30/2017
• Published: 10/04/2018
• Est. Priority Date: 03/30/2017
• Status: Active Grant

• Current Assignee: Lam Research Corporation
• Original Assignee: Lam Research Corporation
• Inventors: Huang, Ludan, Brogan, Lee J., Spurlin, Tighe A., Ghongadi, Shantinath, Reid, Jonathan David, Ranjan, Manish, Pennington, Bryan, Berry, Clifford Raymond
• Granted Patent: US 10,443,146 B2
• Time in Patent Office: Days
• CPC Class Codes: C25D 21/12 Process control or regulation controlling or regulating in general G05
• CPC Class Codes: C25D 5/34 Pretreatment of metallic surfaces to be electroplated
• CPC Class Codes: C25D 7/123 Semiconductors first coated with a seed layer or a conductive layer

Abstract

Methods and apparatus for determining whether a substrate includes an unacceptably high amount of oxide on its surface are described. The substrate is typically a substrate that is to be electroplated. The determination may be made directly in an electroplating apparatus, during an initial portion of an electroplating process. The determination may involve immersing the substrate in electrolyte with a particular applied voltage or applied current provided during or soon after immersion, and recording a current response or voltage response over this same timeframe. The applied current or applied voltage may be zero or non-zero. By comparing the current response or voltage response to a threshold current, threshold voltage, or threshold time, it can be determined whether the substrate included an unacceptably high amount of oxide on its surface. The threshold current, threshold voltage, and/or threshold time may be selected based on a calibration procedure.

Claims

1. A method of determining whether a substrate includes an unacceptably high amount of oxide on a surface of the substrate, the method comprising:

(a) receiving the substrate in an electroplating chamber;

(b) immersing the substrate in electrolyte, wherein during and/or immediately after immersing the substrate, either;

(i) a current applied to the substrate is controlled, or

(ii) a voltage applied between the substrate and a reference is controlled;

(c) measuring either a voltage response or a current response during and/or immediately after immersion, wherein;

(i) the voltage response is measured if the current applied to the substrate is controlled in (b)(i), or

(ii) the current response is measured if the voltage applied to the substrate is controlled in (b)(ii);

(d) comparing the voltage response or current response measured in (c) to a threshold voltage, a threshold current, or a threshold time, wherein the threshold voltage, threshold current, or threshold time is selected to distinguish between (1) cases where the substrate includes the unacceptably high amount of oxide present on the surface of the substrate and (2) cases where the substrate includes an acceptably low amount of oxide present on the surface or no oxide present on the surface of the substrate; and

(e) determining, based on the comparison in (d), whether the substrate includes the unacceptably high amount of oxide on the surface of the substrate.

2. The method of claim 1, wherein during (b), the current applied to the substrate is controlled, and wherein during (c), the voltage response is measured.

3. The method of claim 2, wherein during (b), the current applied to the substrate is controlled at a non-zero current.

4. The method of claim 2, wherein during (b), the current applied to the substrate is controlled at a level of zero current, and wherein during (c), the voltage response is measured, wherein the voltage response is an open circuit voltage response.

5. The method of claim 1, wherein during (b), the voltage applied between the substrate and the reference is controlled, and wherein during (c), the current response is measured.

6. The method of claim 1, wherein the reference is an anode or a reference electrode.

7. The method of claim 1, wherein the threshold current, threshold voltage, and/or threshold time is selected based on a calibration procedure.

8. The method of claim 7, wherein the calibration procedure comprises:

(f) pre-treating a plurality of calibration substrates, each calibration substrate being pre-treated using a different set of pre-treatment conditions;

(g) immersing each calibration substrate in electrolyte;

(h) measuring a voltage response or a current response during and/or immediately after each calibration substrate is immersed in electrolyte; and

(i) analyzing the voltage responses or current responses to identify the threshold current, threshold voltage, and/or threshold time.

9. The method of claim 8, wherein at least one calibration substrate includes oxide on the surface of the substrate in an unacceptably high amount, and wherein at least one calibration substrate includes either (1) oxide on the surface of the substrate at an acceptably low amount, or (2) no oxide on the surface of the substrate.

10. The method of claim 1, wherein the voltage response or current response measured in (c) are measured at a target time.

11. The method of claim 1, further comprising analyzing the voltage response or current response measured in (c) to determine a time at which the voltage response or current response reach a target voltage or a target current, respectively, wherein (d) comprises comparing the time at which the voltage response or current response reaches the target voltage or target current, respectively, to the threshold time.

12. The method of claim 1, further comprising determining a maximum voltage response or a maximum current response measured in (c), wherein the threshold voltage or threshold current correspond to a threshold maximum voltage or a threshold maximum current, respectively, and wherein (d) comprises comparing the maximum voltage response to the threshold maximum voltage or comparing the maximum current response to the threshold maximum current.

13. The method of claim 1, further comprising determining an integrated voltage response or an integrated current response by integrating the voltage response or current response measured in (c) over a target timeframe, wherein the threshold voltage or threshold current correspond to a threshold integrated voltage or a threshold integrated current, respectively, wherein (d) comprises comparing the integrated voltage response to the threshold integrated voltage or comparing the integrated current response to the threshold integrated current.

14. A method of selecting pre-treatment conditions for removing oxide from a surface of a production substrate, the method comprising:

(a) providing a plurality of calibration substrates;

(b) pre-treating at least some of the calibration substrates to at least partially remove oxide from a surface of each calibration substrate that is pre-treated, wherein the calibration substrates that are pre-treated are pre-treated using different sets of pre-treatment conditions;

(c) immersing each calibration substrate in electrolyte;

(d) measuring a voltage response or a current response during and/or immediately after each calibration substrate is immersed in electrolyte;

(e) analyzing the voltage responses or current responses measured in (d) to identify which sets of pre-treatment conditions resulted in adequate removal of oxide from the surface of a relevant calibration substrate; and

(f) selecting pre-treatment conditions for removing oxide from the surface of a production substrate based on the analysis of (e).

15. The method of claim 14, wherein at least one calibration substrate is not pre-treated.

16. The method of claim 14, wherein at least one calibration substrate includes an oxide layer purposely deposited thereon.

17. The method of claim 14, wherein at least one calibration substrate is not pre-treated, and wherein at least one calibration substrate is pre-treated to completely remove the oxide from its surface.

18. The method of claim 14, further comprising electroplating the production substrate, wherein a composition of the electrolyte in which each calibration substrate is immersed does not substantially vary from a composition of an electrolyte in which the production substrate is electroplated, wherein a diameter of the calibration substrates does not substantially vary from a diameter of the production substrate, wherein a composition of a seed layer on the calibration substrates does not substantially vary from a composition of a seed layer on the production substrate, wherein a thickness of the seed layer on the calibration substrates does not substantially vary from a thickness of the seed layer on the production substrate, wherein a magnitude of a current and/or voltage applied to the calibration substrates during and/or shortly after immersion, if any, does not substantially vary from a magnitude of a current and/or voltage applied to the production substrate during and/or shortly after immersion, if any, wherein a vertical speed of immersion used to immerse the calibration substrates does not substantially vary from a vertical speed of immersion used to immerse the production substrate, wherein a tilt angle and tilt speed used to immerse the calibration substrates does not substantially vary from a tilt angle and tilt speed used to immerse the production substrate, and wherein a rate of rotation used to spin the calibration substrates during immersion does not substantially vary from a rate of rotation used to spin the production substrate during immersion.

19. The method of claim 14, wherein during (c), the current applied to each calibration substrate is controlled, and wherein during (d), the voltage response is measured.

20. The method of claim 14, wherein during (c), the voltage applied to each calibration substrate is controlled, and wherein during (d), the current response is measured.

21. An electroplating apparatus configured to determine whether a substrate includes an unacceptably high amount of oxide on a surface of the substrate, the apparatus comprising:

an electroplating chamber configured to hold electrolyte;

a power supply configured to (1) apply current and/or voltage to the substrate and (2) measure a voltage response and/or current response in response to the applied current and/or applied voltage;

a controller comprising executable instructions for;

(a) receiving the substrate in an electroplating chamber;

(b) immersing the substrate in electrolyte, wherein during and/or immediately after immersing the substrate, either;

(i) a current applied to the substrate is controlled, or

(ii) a voltage applied between the substrate and a reference is controlled;

(c) measuring either a voltage response or a current response during and/or immediately after immersion, wherein;

(i) the voltage response is measured if the current applied to the substrate is controlled in (b)(i), or

(ii) the current response is measured if the voltage applied to the substrate is controlled in (b)(ii);

(d) comparing the voltage response or current response measured in (c) to a threshold voltage, a threshold current, or a threshold time, wherein the threshold voltage, threshold current, or threshold time is selected to distinguish between (1) cases where the substrate includes the unacceptably high amount of oxide present on the surface of the substrate and (2) cases where the substrate includes an acceptably low amount of oxide present on the surface or no oxide present on the surface of the substrate; and

(e) determining, based on the comparison in (d), whether the substrate includes the unacceptably high amount of oxide on the surface of the substrate.