Monitoring electrolytes during electroplating

Patent metadata

Field	Value
Publication number	US-2016298256-A1
Application number	US-201514685512-A
Country	US
Kind code	A1
Filing date	Apr 13, 2015
Priority date	Apr 13, 2015
Publication date	Oct 13, 2016
Grant date	—

Abstract

Methods of and apparatuses for monitoring electroplating bath quality in electroplating cells using voltage readings are described herein. Methods involve obtaining real-time voltage readings during an electroplating process and determining whether the voltage readings are within a threshold deviation of an expected voltage reading at a given time.

First claim

1 . A method of controlling an electroplating cell by monitoring conditions of an electroplating bath, the method comprising:
(a) reading an initial voltage between a substrate as a first electrode and a second electrode; (b) during electroplating on the substrate in the electroplating cell, repeatedly reading a voltage between the substrate and the second electrode; (c) comparing each of the repeated readings of the voltage to a corresponding expected voltage that drifts from the initial voltage during the electroplating,
wherein the drift is determined from substrate electroplating operations that produce satisfactory electroplating results;
(d) determining that one or more of the repeated readings of the voltage deviate from the corresponding expected voltage by a value greater than a threshold deviation; and (e) in response to determining that the one or more of the repeated readings of the voltage deviate from the corresponding expected voltage by a value greater than the threshold deviation, sending a notification and/or suspending operation of the electroplating cell.

2 . The method of claim 1 , wherein (e) further comprises placing the electroplating cell into an error state.

3 . The method of claim 1 , wherein the second electrode is an anode.

4 . The method of claim 1 , wherein the second electrode is a reference electrode in proximity to the substrate.

5 . The method of claim 1 , wherein the electroplating cell is coupled to a power source configured to make the repeated readings of voltage between the substrate and the second electrode.

6 . The method of claim 1 , wherein the substrate comprises recessed features, and the electroplating on the substrate comprises depositing a metal layer on the substrate in a manner that preferentially fills the recessed features.

7 . (canceled)

8 . (canceled)

9 . The method of claim 1 , wherein all of one or more of the repeated readings of the voltage are read while applying a constant current between the substrate and the second electrode.

10 . The method of claim 2 , wherein the one or more of the repeated readings of the voltage are the only voltage readings used to determine whether the electroplating cell is placed in an error state in (e).

11 . The method of claim 2 , wherein placing the electroplating cell in an error state is determined only in response to determining that the one or more repeated readings of the voltage deviate from the corresponding expected voltage by a value greater than the threshold deviation in (e).

12 . The method of claim 2 , wherein magnitudes of the repeated readings are not used to determine whether the electroplating cell is placed in an error state in (e).

13 . (canceled)

14 . (canceled)

15 . The method of claim 1 , further comprising:
determining the corresponding expected voltage by adding the initial voltage to a drift parameter that varies during the electroplating, wherein the initial voltage between the substrate and the second electrode is read before repeatedly reading the voltage between the substrate and the second electrode, wherein the drift parameter is independent of the total magnitude of the repeated readings of voltage between the substrate and the second electrode, and wherein the drift parameter corresponds to the drift determined from substrate electroplating operations that produce satisfactory electroplating results.

16 . The method of claim 1 , wherein the drift is a linear function of time.

17 . The method of claim 1 , wherein the drift is a logarithmic function of time.

18 . (canceled)

19 . (canceled)

20 . (canceled)

21 . The method of claim 1 , wherein the electroplating comprises one or more steps of electroplating, and wherein a constant current is applied in each of the one or more steps.

22 . (canceled)

23 . (canceled)

24 . The method of claim 1 , wherein the expected voltage drift comprises linear fragments modeled from voltage readings obtained for one or more substrates determined to have the satisfactory electroplating results.

25 . The method of claim 1 , wherein the expected voltage comprises normalized and averaged voltage readings for one or more substrates determined to have the satisfactory electroplating results.

26 . The method of claim 1 , wherein comparing each of the repeated readings of the voltage to a corresponding expected voltage that drifts from the initial voltage during the electroplating comprises taking one or more derivatives of the repeated readings of the voltage and comparing said derivatives to one or more averaged derivatives of corresponding voltage readings for one or more substrates determined to have the satisfactory electroplating results.

27 . An apparatus for monitoring conditions of a plating solution during electroplating of a substrate comprising one or more recessed features, the apparatus comprising:
(a) a plating vessel configured to hold the plating solution, wherein the apparatus is configured for electrodepositing a metal from the plating solution onto the substrate; (b) a power supply; (c) an electrode; (d) a controller comprising program instructions and/or logic for: (i) detecting an initial voltage between the substrate and the electrode; (ii) electroplating a metal layer on the substrate in the plating solution; (iii) repeatedly reading a voltage between the substrate and the electrode during (ii); (iv) determining whether voltage reading in (iii) is greater than a corresponding expected voltage by a value greater than a threshold deviation; and (v) in response to determining that the deviation in (iv) is greater than the threshold deviation, sending a notification and/or suspending operation of the plating vessel, wherein the threshold deviation is based on an expected voltage, wherein the corresponding expected voltage drifts from the initial voltage, and wherein the drift was determined from voltage readings in an electroplating process that produced satisfactory electroplating results.

28 . (canceled)

29 . (canceled)

30 . The apparatus of claim 27 , wherein the expected voltage comprises normalized and averaged voltage readings for one or more substrates determined to have the satisfactory electroplating results.

31 . The apparatus of claim 27 , wherein determining whether voltage reading in (iii) is greater than the corresponding expected voltage by a value greater than the threshold deviation comprises taking one or more derivatives of the repeated readings of voltage and comparing said derivatives to one or more averaged derivatives of corresponding voltage readings for one or more substrates determined to have the satisfactory electroplating results.

Assignees

• Lam Res Corp

Inventors

• Thorum Matthew Sherman
• Mayer Steven T

Classifications

• G01N27/301

  Reference electrodes · CPC title

• G01N27/07

  Construction of measuring vessels; Electrodes therefor · CPC title

• C25D21/12 Primary

  Process control or regulation (controlling or regulating in general G05) · CPC title

• C25D17/001

  Apparatus specially adapted for electrolytic coating of wafers, e.g. semiconductors or solar cells · CPC title

• C25D7/123

  Semiconductors first coated with a seed layer or a conductive layer · CPC title