Systems And Methods For Monitoring Plating And Etching Baths

• US 20080264801A1
• Filed: 10/04/2007
• Published: 10/30/2008
• Est. Priority Date: 04/08/2005
• Status: Active Grant

• Current Assignee: Trustees Of Columbia University In The City Of New York (Columbia University)
• Original Assignee: Trustees Of Columbia University In The City Of New York (Columbia University)
• Inventors: West, Alan C., Willey, Mark J., von Gutfeld, Robert J.
• Granted Patent: US 8,475,642 B2
• Time in Patent Office: Days
• US Class Current: 205/775
• CPC Class Codes: G01N 27/42 Measuring deposition or liberation of materials from an electrolyte; Coulometry, i.e. measuring coulomb-equivalent of material in an electrolyte

Abstract

Methods and systems for monitoring electrolyte bath fluids are provided. The electrolyte bath fluids can be electroplating, electroless plating or etching solutions. The monitoring systems employ microfluidic devices, which have built in microfluidic channels and microfabricated thin-film electrodes. The devices are configured with fluid pumps to control the movement and mixing of test fluids through the microfluidic channels. The microfabricated thin-film electrodes are configured so that the plating or etching bath fluid composition can be characterized by electrochemical measurements. The monitoring methods and system provide faster measurement times, generate minimal waste, and occupy dramatically reduced physical space compared to conventional bath-monitor systems. The monitoring systems and method also provide low-cost system and methods for measuring or monitoring electroless plating bath rates.

Claims

1. A system for monitoring the composition of electrolyte bath fluids, the system comprising:

(a) a sampling probe comprising;

(i) a substrate having a measurement microchannel adapted for connection to a fluid pump mechanism; and

(ii) a set of electrodes disposed on an inner surface of the measurement microchannel; and

(b) monitoring electronics connected to the set of electrodes, wherein the monitoring electronics and set of electrodes are configured to measure one or more electrochemical properties of a predetermined volume of the bath fluids pumped through the measurement microchannel.

2. The system of claim 1 wherein electrolyte bath fluid comprises one of a plating solution and an etching solution.

3. The system of claim 1 wherein the measurement microchannel has areal dimensions of less than one of about 1 sq. mm, about 0.1 sq. mm, and about 0.01 sq. mm.

4. The system of claim 1 wherein the electrodes are thin film metallic electrodes.

5. The system of claim 1 further comprising an external fluid pumping arrangement, and wherein the substrate further comprises an inlet disposed at an end of the measurement microchannel, the inlet being connectable to the external fluid pumping arrangement.

6. The system of claim 5 wherein the external fluid pumping arrangement comprises a mixing manifold, whereby samples of bath fluids and other fluids can be mixed prior to insertion in the measurement microchannel.

7. The system of claim 1 wherein the substrate further comprises a micro mixing manifold connected to the measurement microchannel, whereby samples of bath fluids and other fluids can be mixed prior to insertion in the measurement micro channel.

8. The system of claim 1 wherein the substrate further comprises a waste reservoir disposed at an end of the microchannel.

9. The system of claim 1 further comprising a waste reservoir, which is disposed external to the substrate and adapted for connection to an end of the microchannel.

10. The system of claim 1 wherein the sampling probe comprises:

a substrate having an array of microchannels including at least one measurement microchannel, each microchannel adapted for connection to a fluid pump mechanism;

a set of electrodes disposed on an inner surface of the measurement microchannel; and

monitoring electronics connected to the set of electrodes, wherein the monitoring electronics and set of electrodes are configured to measure one or more electrochemical properties of predetermined volumes of fluids pumped through the measurement microchannel.

11. The system of claim 10 wherein the array of microchannels comprises a pair of microchannels in fluid communication with the measurement microchannel, whereby a pair of fluids inserted in the pair of microchannels are mixed prior to flow through the measurement microchannel.

12. The system of claim 10 wherein the array of microchannels comprises a set of a number of microchannels in fluid communication with the measurement microchannel, whereby any combination of a corresponding number of fluids can be inserted in the measurement microchannel.

13. The system of claim 10 comprising a plurality of measurement microchannels.

19. The systems of claims 1, 14 or 15, wherein the fluid pumping mechanism comprises a gravity flow arrangement disposed on the sampling probe.

14. A system for measuring plating rates in plating baths, the system comprising:

a sampling probe comprising;

a substrate having an array of microchannels including at least one measurement microchannel, each microchannel adapted for connection to a fluid pump mechanism; and

a set of electrodes disposed on an inner surface of the measurement microchannel, wherein the fluid pump mechanisms are configured to insert plating bath fluids and stripping solutions over an electrode, whereby plating and stripping can occur on a surface of the electrode; and

monitoring electronics connected to the electrodes, wherein the monitoring electronics and set of electrodes are configured to measure currents as a function of voltages applied to the electrodes, wherefrom a plating rate is calculated.

15. A system for determining additive concentrations in an etching bath solution, the system comprising:

a) a substrate having at least one microchannel and a set of thin film electrodes disposed on an interior surface of the microchannel;

b) at least one pump connected to the microchannel for flowing fluids through the microchannel;

c) at least one of a potentiostat and a power supply that are electrically connected to the electrodes; and

f) means for measuring an electric current when a voltage is applied to said electrodes, wherein the electric current is a function of the composition of fluids through the microchannel;

16. The system of claim 15 further comprising means for controlling the temperature of the substrate and the microchannel.

17. The system of claim 15 wherein the fluids flowing through the microchannel comprise one of an etching bath sample, a second fluid, a plating fluid, a reference fluid, an electrode cleaning fluid, an electrode conditioning fluid, a calibration fluid, and any combination thereof.

18. The system of claim 15 wherein the thin film electrodes comprise at least one of a working electrode, a reference electrode and a counter electrode.

20. A sampling probe for use in electrolyte bath monitoring systems, the sampling probe comprising reversible mechanical connectors for physically connecting a microchannel to a corresponding fluid pumping mechanism and for electrically connecting the set of electrodes to the electronics, whereby the sampling probe can be used as a disposable part.

21. A method of monitoring the composition of plating or etching bath fluids, the method comprising:

(a) providing a sampling probe that comprises;

a substrate having a measurement microchannel adapted for connection to a fluid pump mechanism; and

a set of electrodes disposed on an inner surface of the measurement microchannel;

(b) flowing a test sample of the bath fluids through the measurement channel; and

(c) applying and measuring electrical voltages and/or currents at the electrodes to determine one or more electrochemical properties of the test sample of the bath fluids flowing through the measurement microchannel, wherein the determined electrochemical properties correspond to a composition of the bath fluids.

22. The method of claim 21, wherein the test sample of the bath fluids comprises a mixture of the bath fluids and another testing fluid.

23. The method of claim 21, wherein the sampling probe comprises a number of microchannels in fluid communication with the measurement microchannel, and wherein differently prepared test samples are sequentially drawn through the number of microchannels and inserted in the measurement microchannel to determine one or more electrochemical properties of the test sample of the bath fluids flowing through the measurement microchannel.

24. The method of claim 21, wherein the sampling probe comprises an additional measurement channel having disposed therein a reference electrode, wherein flowing a test sample of the bath fluids through the measurement channel further comprises flowing a reference fluid through the additional measurement channel.

25. A method of measuring the plating rate obtained in a given plating bath, the method comprising:

(a) providing a sampling probe, the sampling probe comprising;

a substrate having a measurement microchannel adapted for connection to a fluid pump mechanism; and

an electrode disposed on an inner surface of the measurement microchannel;

(b) flowing a sample of the plating bath fluids through the measurement channel so that plating occurs on the electrode surface for a predetermined period of time;

(c) next, flowing a stripping solution through the measurement channel so that the plating that has occurred on the electrode surface is stripped from the electrode surface;

(d) measuring the stripping charge on the electrode during stripping of the plating that has occurred on the electrode surface; and

(e) using the measured stripping charge as an indication of the plating rate obtained in the given plating bath.

26. The method of claim 25, wherein the given plating bath is an electrochemical plating bath, and wherein flowing a sample of the plating bath fluids through the measurement channel further comprises applying a potential to the electrode so that the electrode is electroplated.

27. A method of monitoring an etching bath, the method comprising:

controlling a flow rate of a test solution of the etching bath through a microchannel having working, and reference electrodes disposed therein;

applying a voltage between the working and reference electrodes;

measuring and recording the current flowing between the working and reference electrodes.

28. The method of claim 27 wherein the working electrode comprises an etchable material, and the method further comprises measuring the dissolution of the etchable material from the working electrode.

29. The method of claim 27 further comprising heating the test solution flowing through the microchannel.