US20090200171A1

US20090200171A1 - Electrochemical sensing and data analysis system, apparatus and method for metal plating

Info

Publication number: US20090200171A1
Application number: US12/305,650
Authority: US
Inventors: Jianwen Han; Monica K. Hilgarth; Mackenzie King; Steven M. Lurcott
Original assignee: Advanced Technology Materials Inc
Current assignee: Ancosys GmbH
Priority date: 2006-06-20
Filing date: 2007-06-18
Publication date: 2009-08-13
Also published as: WO2007149813A2; TW200829915A; WO2007149813A3

Abstract

An electrochemical sensing and data analysis system (and apparatus and methods) adapted for control of electroplating of various metal(s) on a wafer or other suitable substrate. Components of the system utilize multi-variate analysis (MVA) and galvanostatic, potentiodynamic or other electrical measurements (or combinations thereof) to predict, adjust or control plating parameters, e.g., to achieve improved yield of plated substrates with acceptable levels of defects (or lack thereof).

Description

CROSS-REFERENCE TO RELATED APPLICATION

The benefit of priority of U.S. Provisional Patent Application No. 60/815,206 filed Jun. 20, 2006 in the names of Jianwen Han, Monica K. Hilgarth, Mackenzie King and Steven M. Lurcott, for “ELECTROCHEMICAL SENSING AND DATA ANALYSIS SYSTEM, APPARATUS AND METHOD FOR METAL PLATING,” is hereby claimed under the provisions of 35 US 119. The disclosure of said U.S. Provisional Patent Application No. 60/815,206 is hereby incorporated herein by reference, in its entirety.

FIELD OF THE INVENTION

The present invention relates in various aspects to an electrochemical sensing and data analysis system, apparatus and method directed to control of electroplating of various metal(s) on a wafer (or other suitable substrate). In specific embodiments, the present invention relates to an electrochemical data analysis system directed at predicting defects (probabilities of defect occurrence, for example) in and/or on a wafer (or other suitable substrate) upon which one or more of a variety of metals (e.g., copper, gold, cobalt, platinum or other suitable metal species, etc.) may be deposited. Results of the data analysis may be utilized to adjust, for example, plating bath compositions (e.g., concentrations of acid, chloride or other halide, accelerators, suppressors, and/or levelers, or replacement of plating bath due to presence of too many impurities or by-products or age of bath) in order to increase the percentage of acceptable plated wafers formed having defects below a set threshold level. Typically, the electroplated wafers are used in the manufacture of various microelectronic devices.

DESCRIPTION OF THE RELATED ART

Miniaturization of microelectronic devices is a well accepted trend. Such devices are also being re-designed, re-tooled or otherwise improved to provide better performance. This miniaturization (and/or improved performance) is due in part to electronic circuit boards being developed that have smaller and more defined features. In the regime of microelectronic interconnect layers in the manufacture of semiconductor microelectronic devices, the use of aluminum (Al) as a metal layer for forming the interconnect layers has largely been replaced with copper (Cu) as the metal of choice. This is, in part, due to the fact that increasing signal speeds, performance demands, and/or decreasing feature geometries of microelectronics limits the usefulness of Al. Thus, the use of Al has been largely supplanted by the use of Cu. Copper deposition may be carried out in an electroplating bath. However, Cu deposition in an electroplating bath is prone to several problems which, if left uncorrected, leads to the formation of undesirably defective microelectronic devices or components.
It is well recognized that, left unchecked, Cu deposits at too rapid a rate (e g., depositing more quickly at the top of a feature than in the rest of the feature) in an electroplating bath leading to “necking” or the formation of bridging layers of Cu over vias, troughs and other features. Such “necking” and/or bridging leaves undesirable voids in and/or on the substrate or the deposited layer (or both). It is therefore desirable to provide ways to avoid, reduce or minimize the formation of unwanted voids or other defects. In other words, it is desirable to control the deposition of Cu to proceed in such a fashion so as to reduce or minimize the occurrence of Cu plating defects to below a set acceptable threshold level.
To overcome the too rapid deposition of Cu on and/or within microelectronic devices (or components and/or features thereof), a variety of additives including, but not limited to, suppressors, accelerators, levelers and the like may be added to a copper electroplating bath. These additives are provided to prevent, reduce, attenuate or otherwise improve the deposition (e.g., electroplating) of Cu on and/or within microelectronic devices (or components and/or features thereof) to make microelectronic devices and/or components with the desired performance characteristics—preferably in a more cost effective manner.
Levelers are organic (or other) compound(s) added to Cu electroplating baths that improve the filling of various microelectronic device features so that the roughness of the so filled layer is reduced and/or its flatness is improved.
Suppressors are organic (or other) compound(s) added to Cu electroplating baths that improve the filling of various microelectronic device features so that unwanted “necking” or bridging over vias, troughs and the like is reduced so that the proper Cu filling of the various microelectronic device features is achieved.
Accelerators are organic (or other) compound(s) added to Cu electroplating baths that also improve the filling of various microelectronic device features so that proper Cu filling of the various microelectronic device features is achieved. Typically, suppressors slow down the rate at which Cu is deposited via the use of Cu electroplating baths and accelerators have the opposite effect. Oftentimes, the proper combination of at least one accelerator together with at least one suppressor and/or at least one leveler is necessary to achieve the desired or proper Cu deposition on or within a microelectronic device or component.
However, the Cu deposition achieved by the combination of accelerator(s), suppressor(s) and/or leveler(s) is prone to wide variation because as the Cu deposition proceeds, a variety of by-products may be formed and/or the concentration of the accelerator(s), suppressor(s) and/or leveler(s) may be sufficiently changed to undesirably alter the deposition of Cu during the manufacture of microelectronic devices or components.
It has been recognized that if the proper control over the chemistry of the Cu electroplating bath could be achieved, fewer defective devices or components can be made which preferably reduces the associated waste and/or cost.
Typically, a variety of techniques have been used to measure and/or control the composition of Cu (and/or other) electroplating baths. See, for example, U.S. Pat. Nos. 5,192,404; 6,280,602 (Method and Apparatus for Determination of Additives in Metal Plating Baths); 6,592,737 (Method and Apparatus for Determination of Additives in Metal Plating Baths); 6,495,011 (Apparatus for Determination of Additives in Metal Plating Baths); 6,709,568 (Method for Determining Concentrations of Additives in Acid Copper Electrochemical Deposition Baths); 6,936,157 (Interference Correction of Additives Concentration Measurements in Metal Electroplating Solutions); 6,758,955 (Methods for Determination of Additive Concentration in Metal Plating Baths); 6,913,686 (Methods for Analyzing Solder Plating Solutions); 6,844,196 (Analysis of Antioxidant in Solder Plating Solutions Using Molybdenum Dichloride Dioxide); 7,022,215 (System and Methods for Analyzing Copper Chemistry); and 6,758,960 (Electrode Assembly and Method of Using the Same); and 6,954,560 (Attenuated Total Reflection Spectroscopic Analysis of Organic Additives in Metal Plating Solutions). Each of the foregoing listed U.S. Pat. Nos. is incorporated herein by reference in its entirety for all purposes.
See also, U.S. patent applications having Ser. Nos. 11/135,311 (Methods and Apparatuses for Analyzing Solder Plating Solutions); 10/233,943 (Electrochemical Analytical Apparatus and Method of Using the Same); 10/658,948 (Sampling Management for a Process Analysis Tool to Minimize Sample Usage and Decrease Sampling Time); 10/314,776 (Plating Bath Composition and Control); 10/672,433 (Electrode Assembly for Analysis of Metal Electroplating Solution, Comprising Self-Cleaning Mechanism, Plating Optimization Mechanism, and/or Voltage Limiting Mechanism); 10/320,876 (Process Analyzer for Monitoring Electrochemical Deposition Solutions); 10/722,174 (On-Wafer Electrochemical Deposition Plating Metrology Process and Apparatus); 10/833,193 (Methods for Analyzing Inorganic Components of an Electrolytic Solution, and/or Cleaning an Electrochemical Analytical Cell); 10/838,390 (Electrochemical Drive Circuitry and Method); 10/833,194 (Methods and Apparatus for Determining Organic Component Concentrations in an Electrolytic Solution); 10/836,546 (Methods and Apparatuses for Monitoring Organic Additives in Electrochemical Deposition Solutions); 10/819,765 (Electrochemical Deposition Analysis System Including High-Stability Electrode); and 10/833,192 (One-Point Recalibration Method for Reducing Error in Concentration Measurements for an Electrolytic Solution). Each of the foregoing listed U.S. patent application Nos. is incorporated herein by reference in its entirety for all purposes.
The time required to calibrate electroplating equipment and/or subsequent use of the same to measure and/or control the composition of Cu (and/or other metal) electroplating baths may be time consuming and sometimes cumbersome. According to an embodiment of the present invention, it is desirable to provide a more efficient system and/or method for controlling the chemistry of a Cu electroplating bath in order to reduce the number of defective devices or components made.

SUMMARY OF THE INVENTION

The invention relates in various aspects to a system for analysis of an electroplated substrate or for analysis for electroplating a substrate or for simply electroplating a substrate or adjusting the electroplating operating parameters (pursuant to the results of the analysis) during electroplating of a substrate.
According to one aspect of the present invention, the system for analysis of an electroplated substrate (or for electroplating a substrate) comprises:

(a) a galvanostatic measurement component, a potentiodynamic measurement component or a combination thereof for measuring galvanostatic data, potentiodynamic data or a combination thereof from an electroplated substrate plated in a plating bath;
(b) a storage component for storing the galvanostatic data, the potentiodynamic data or a combination thereof;
(c) a first multi-variate analysis component for correlating the galvanostatic data, the potentiodynamic data or the combination thereof with a defect profile of the electroplated substrate, a chemical profile of the plating bath, an electrical performance profile of the electroplated substrate or a combination thereof;
(d) an optional second multi-variate analysis component for correlating the defect profile with the chemical profile of the plating bath;
(e) an optional third multi-variate analysis component for correlating the galvanostatic data, the potentiodynamic data or the combination thereof with the chemical profile of the plating bath; and
(f) an optional fourth multi-variate analysis component for correlating the electrical profile of the electroplated substrate with the defect profile, the chemical profile or a combination thereof.

In one aspect, the present invention relates to a method for analysis of an electroplated substrate (or for analysis for electroplating a substrate) comprising using the aforementioned components of the above-noted system.
In another aspect, the present invention relates to a method for forming an electroplated substrate utilizing the benefit of the aforementioned analysis.
In yet another aspect, the present invention relates to an apparatus for analysis of an electroplated substrate or for analysis for forming an electroplated substrate or for adjusting the electroplating operating parameters of electroplating a substrate—either during ongoing electroplating or during future electroplating operations. Such an apparatus, pursuant to an embodiment comprises the aforementioned components of the above-described system—provided in a compact apparatus, for example.
A further aspect of the invention relates to a system adapted to defect analysis on an electroplated substrate or adapted to defect analysis for electroplating a substrate, said system comprising:

a galvanostatic measurement component, a potentiodynamic measurement component or a combination thereof for measuring galvanostatic data, potentiodynamic data or a combination thereof from a plating bath;
a storage component for storing said galvanostatic data, said potentiodynamic data or a combination thereof; and
a component for comparing said data with a rule set for determining adjustment(s) to said plating bath.

The invention in another aspect relates to a method adapted to forming an electroplated substrate, said method comprising the steps of:

performing or obtaining a galvanostatic measurement, a potentiodynamic measurement or a combination thereof relating to said electroplated substrate with a testing cell containing (aa) a reference electrode (RE), (bb) a working electrode (WE), (cc) a counter electrode (CE), (dd) electroplating driving electronics electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE), and the working electrode (WE) to electroplate metal on said working electrode in a metal electroplating bath, and (ee) electrical potential measuring circuitry electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE) and the working electrode (WE), wherein the electroplating driving electronics may further comprise stripping driving electronics to remove plated metal from the working electrode (WE);
storing said galvanostatic measurement, said potentiodynamic measurement or said combination thereof;
correlating said galvanostatic measurement, said potentiodynamic measurement or said combination thereof with a defect profile of said substrate, with a chemical profile of an electroplating bath in which said substrate is/was electroplated, or a combination thereof utilizing multi-variate analysis; and
replacing said electroplating bath or adjusting one or more chemicals in said electroplating bath if a defect profile of said electroplated substrate is outside a defect threshold range, if a chemical profile of said electroplating bath is outside a chemical threshold range or a combination thereof.

Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an example of a cell used for making galvanostatic measurements. A suitable cell or cells other than the one described in FIG. 1 may be used.

FIG. 2 is a top view of the cell of FIG. 1.

FIG. 3 is an example of galvanostatic data in the form of a plot of plating potential (mV) versus time for the electroplating of copper on a wafer.

FIG. 4 is an example of galvanostatic data in the form of a plot of plating potential (mV) versus time for the electroplating of copper on a wafer where the system shows “drift” in the galvanostatic measurement.

FIG. 5 is an example of galvanostatic data in the form of a plot of plating potential (mV) versus time for the electroplating of copper on a wafer where the system has been corrected to adjust for the “drift” in the galvanostatic measurement noted in FIG. 4.

FIG. 6 is an example of galvanostatic data in the form of a plot of plating potential (mV) versus time for the electroplating of copper on a wafer where “Fresh Sample” refers to an unused copper electroplating bath at about time (t)=0 hours; where “1 Ah/L” refers to the age (1 hour) of the copper electroplating bath in units of amp-hours per liter. The ages 2 Ah/L and 4 Ah/L indicate the age to be 2 hours and 4 hours, respectively, in units of amp-hours per liter.

FIG. 7 is a high pressure liquid chromatography (HPLC) chromatogram using a UV/VIS (ultra-violet/visible light) detector. Note that the peaks labeled SPS refers to the original accelerator used. The peaks labeled Tri-species refer to the breakdown by-product of the SPS formed upon aging and/or use of the copper plating bath. The label “Fresh sample” has the same meaning as noted above with regard to FIG. 6. Likewise, the label “4 Ah/L” has the same meaning as noted above with regard to FIG. 6. The plot labeled “Fresh sample” is a HPLC chromatogram showing peaks for SPS and its breakdown by-product(s) Tri-species. The plot labeled “4 Ah/L” is a corresponding HPLC chromatogram at age=4 hours. Note that the amount of SPS decreases and the amount of Tri-species increases from “Fresh sample” (t=0 hours) to “4 Ah/L” (t=4 hours) of the copper electroplating bath.

FIG. 8 is another HPLC plot (Gel Permeation Chromatography using an HPLC column and Refractive Index Detector) of a Cu plating bath containing suppressor. The plot labeled “Target” is for fresh (and unused) Cu electroplating bath and the plots labeled 1, 2, 3, and 4 Ah/L refer to electroplating baths that are 1, 2, 3, and 4 hours old in units of amp-hours/liter (Ah/L), respectively.

FIG. 9 is another example of galvanostatic data in the form of a plot of plating potential (mV) versus time with the indicated amounts of accelerator breakdown by-product contained in the Cu electroplating bath. As depicted, the plating potential required for plating of Cu drops with increasing amounts of accelerator. Note that with increasing amounts of accelerator in the Cu electroplating bath, there is also a corresponding increase in the amount of accelerator breakdown by-product present in the same bath.

FIG. 10 is a plot of concentration of accelerator (all), accelerator (SPS), suppressor (all) and suppressor (original MW) versus sample identified by the date on which it was tested for a concentration measurement. Note that accelerator (SPS) refers to the original accelerator itself and accelerator (all) refers to the original accelerator plus all accelerator breakdown by-products. Likewise, suppressor (original MW) refers to the original suppressor itself and suppressor (all) refers to the original suppressor plus all suppressor breakdown by-products. As depicted, both the amounts of accelerator breakdown by-products and suppressor breakdown by-products (in the corresponding Cu plating bath) gradually increase from September 26 to November 13—a roughly 45 day time period.

FIG. 11 graphically shows the increase in the amount of suppressor and accelerator breakdown by-products over roughly the same time period (September 26 to November 13). Note that the amount of accelerator breakdown by-products averages at about 5% of accelerator (all) and the amount of suppressor breakdown by-products averages at about 19% of suppressor (all).

FIG. 12 is a chart of accelerator breakdown rate versus six different electroplating baths used. Note that for baths A, B, C, and D (i.e., Tool A, Tool B, Tool C and Tool D, respectively), the electroplated wafers or substrates fell below the set acceptable defect threshold. However, for baths M and N (i.e., Tool M, and Tool N, respectively), the electroplated wafers or substrates exceeded the set acceptable defect threshold. The various bars show that when the accelerator breakdown by-products are below about 8.8%, the defect profile is acceptable (green bars) and that when the accelerator breakdown by-products are above about 8.8%, the defect profile is unacceptable (red bars). Note also that the set acceptable defect threshold may be set and adjusted up or down—depending on the device into which the particular plated substrate is to be used and on the associated performance requirements for the particular device and/or plated substrate. Also note that FIG. 12 shows a good correlation between low accelerator by-product breakdown rates and acceptable defect profiles (green bars) and vice versa (i.e., unacceptable defect profiles (red bars), and high accelerator by-product breakdown rates).

FIG. 13 is similar to FIG. 12 except that instead of breakdown rates for accelerators, breakdown rates for suppressors are plotted. However, no clear correlation between acceptable defect profiles (green bars) and unacceptable defect profiles (red bars) and amount of suppressor breakdown by-products is readily discernable from the plotted data. Without being bound by theory, it appears that the amount of accelerator breakdown by-products is better correlated to defect profiles than is the amount of suppressor breakdown by-products as noted by comparison of FIGS. 12 and 13.

FIG. 14 is represents multiple 2-D plots of plating potential (mV) versus time stacked back to back and further plotted against the sample run no. to give a 3-D plot as shown. Additionally, actual defect profiles (defect data) for each sample run no. are provided and then those actual defect profiles are correlated to the 3-D plotted data using Defect Analysis Reduction Tool which is a form of multi-variate analysis (MVA) using the mathematical relationship X=(β′β)⁻¹β′Y. For further relevant detail regarding Defect Analysis Reduction Tool and MVA, see one or more of the U.S. patents and U.S. patent applications cited herein.

FIG. 14 a describes/depicts in flow chart format the various steps involved in making defect profile predictions—using Defect Analysis Reduction Tool/MVA. The text boxes in FIG. 14 a are self-explanatory and are understood by those of ordinary skill when taken in conjunction with this application disclosure.

FIG. 14 b describes/depicts in flow chart format another embodiment of various steps that may be involved in making defect profile predictions—using Defect Analysis Reduction Tool/MVA. The text boxes in FIG. 14 b are self-explanatory and are understood by those of ordinary skill when taken in conjunction with this application disclosure.

FIG. 15 depicts in plot form the correlation made between the actual defect profiles (blue) versus predicted defect profiles (red) obtained using Defect Analysis Reduction Tool/MVA—see FIGS. 14, 14 a and 14 b—for sample run nos. September 26 to November 1. Using the September 26 to November 1 correlation data set, for sample run nos. November 3 to November 11, predicted defect profiles (red) are plotted with actual defect profiles (green). While not an exact match, between the red and green defect profiles, the predicted defect profile (red) correlates fairly well with the actual defect profile (green). Knowing that a defect profile can be predicted using, for example, the collected galvanostatic data correlated with actual empirical defect profile data, one can begin to set the corresponding acceptable threshold defect profile values, corresponding threshold plating bath chemical profiles (i.e., how much suppressor, accelerator, and/or leveler to add or whether to adjust the concentration of other components such as chloride or other halide, acid, etc. or simply to replace the plating bath with fresh plating bath) and corresponding electrical profile values without actually having to measure the concentration of the chemical components in a electroplating bath each time.

FIG. 16 provides details of one cleaning regimen for cleaning the testing cell and all the relevant parts contained therein (e.g., WE, CE, RE, tubing, the testing cell itself etc.) between measurements made on different electroplating baths or the same baths at different time intervals after usage—as may be desirable. Other suitable cleaning regimens may be used.

FIG. 17 provides a drawing of an embodiment of one system according to the present invention. In FIG. 17, reference numeral 1 refers to a testing cell, sampling head or other measurement component. Reference numeral 2 refers to a storage component that may be either long term memory, flash memory or some transient memory or no memory if the measurement(s) collected from 1 can be satisfactorily used without memory. The storage component 2 is connected to 1 as depicted. The storage component is also connected to the first multi-variate component 3. If present, the storage component 2 may also be connected to one or more of the second multi-variate component 4, the third multi-variate component 5, the fourth multi-variate component 6, and so on up to the n^thmultivariate component 7. Note that if the storage component 2 is not used or present, then 1 can be directly (or indirectly) connected to 3, 4, 5, 6, . . . , 7 or some combination thereof. Other variations or arrangements than the one specifically depicted in FIG. 17 may be used.

FIG. 18 provides a drawing of another embodiment of one system according to the present invention. In FIG. 18, reference numeral 1 refers to a testing cell, sampling head or other measurement component. Reference numeral 2 refers to a storage component that may be either long term memory, flash memory or some transient memory or no memory if the measurement(s) collected from 1 can be satisfactorily used without memory. The storage component 2 is connected to 1 as depicted. The storage component is also connected to the first multi-variate component 3. If present, the storage component 2 may also be connected to one or more of the second multi-variate component 4, the third multi-variate component 5, the fourth multi-variate component 6, and so on up to the n^thmultivariate component 7. Note that if the storage component 2 is not used or present, then 1 can be directly (or indirectly) connected to 3, 4, 5, 6, . . . , 7 or some combination thereof.

The difference between FIG. 17 and FIG. 18 embodiments is that in FIG. 18 components 3, 4, 5, 6, and 7 are connected to a comparator component 8 which in turn is connected to chemical profile manager 9 which also in turn is connected to plating bath 10. Note that the dashed lines in FIG. 18 denote optional connections. Other variations or arrangements than the one specifically depicted in FIG. 18 may be used.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

While the ensuing description herein is primarily directed to copper deposition via the use of an electroplating bath, it will be recognized that the invention is also applicable to the deposition or plating of gold, cobalt, platinum, or other suitable metals or metal species.
Embodiments of the present invention relate to an electrochemical sensing and data analysis system adapted for control of electroplating of various metal(s) on a wafer or other suitable substrate, and to an apparatus and methods using the same. Fine or suitable control is desirable to reduce, minimize or attenuate the occurrence of defects on a wafer or other suitable substrate.
In one aspect, the present invention relates to a system (or method or apparatus) for analysis of an electroplated substrate (or for analysis for electroplating a substrate), in which the system comprises:

(a) a galvanostatic measurement component, a potentiodynamic measurement component or a combination thereof for measuring galvanostatic data, potentiodynamic data or a combination thereof from a plating bath;
(b) a storage component for storing said galvanostatic data, said potentiodynamic data or a combination thereof;
(c) a first multi-variate analysis component for correlating said galvanostatic data, said potentiodynamic data or said combination thereof with a defect profile of said electroplated substrate, a chemical profile of said plating bath, an electrical performance profile of said electroplated substrate or a combination thereof;
(d) an optional second multi-variate analysis component for correlating said defect profile with said chemical profile of said plating bath;
(e) an optional third multi-variate analysis component for correlating said galvanostatic data, said potentiodynamic data or said combination thereof with said chemical profile of said plating bath; and
(f) an optional fourth multi-variate analysis component for correlating said electrical profile of said electroplated substrate with said defect profile, said chemical profile or a combination thereof.

A galvanostatic measurement includes, but is not limited to, application of a constant current over a given time period during which a measurement of a plating (or stripping) potential versus time is made. FIGS. 3, 4, 5, 6, 9, and 14 contain plots of plating potential (mV) versus time. These plots are examples of suitable galvanostatic measurements.
Typically, it is desirable to make galvanostatic measurements in a particular voltage range, using a particular cleaning solution (used to clean the testing cell between measurements), a particular reference electrode (RE) and to use suitable cleaning steps as best suited to a particular metal and to a particular substrate being electroplated with the particular metal.
For example, for copper plating on a SiO₂wafer (or other suitable substrate), it may be suitable or desirable to use any one of the following voltage ranges, including (but not limited to) ≧0.1V, ≧0.2V, ≧0.3V, ≧0.4V, ≧0.5V, ≧0.6V, ≧0.7V, ≧0.8V, ≧0.9V, ≧1.0V, ≧1.1V, ≧1.2V, ≧1.3V, . . . , ≧1.9V, ≧2.0V and so on. These voltages are relative to a standard hydrogen electrode (SHE) known to those of ordinary skill in the art. It may also be suitable or desirable to use any one of known electrode cleaning solutions. See the U.S. patents and patent applications cited herein.
A suitable cleaning regimen for cleaning the WE, CE, RE, the testing cell and all exposed surfaces therein is provided in FIG. 16. Other suitable cleaning regimens may be used in conjunction with one or more embodiments of the present invention. Suitable cleaning sequences for use in conjunction with one or more embodiments of the present invention may be carried out between various numbers of galvanostatic or potentiodynamic measurements made as is suited to the relevant substrate and plating bath being utilized.
Typically, according to an embodiment of the present invention, between each or each set of galvanostatic measurements or potentiodynamic measurements the following sequence is followed:

(1) cleaning/stripping (e.g., exposing the testing cell to the cleaning solution followed by stripping the WE for at least about 30 seconds);
(2) introducing the plating bath into the testing cell after removal and flushing out of the cleaning solution and equilibrating the testing cell and all electrodes to the plating bath;
(3) optionally applying a nucleating potential pulse to better initiate plating of the relevant metal onto the WE (e.g., plating of Cu onto the WE);
(4) applying a plating potential (e.g., usually lower than the nucleating potential) to the WE for plating the WE with the metal of choice (e.g., Cu) and making the necessary galvanostatic measurement, potentiodynamic measurement or other electrical measurement or a combination thereof; and then repeating steps (1)-(4) as necessary.

Further galvanostatic measurements, potentiodynamic measurements, other electrical measurements or a combination thereof may be made during the stripping part of step (1). As used herein, the term “cleaning/stripping” means cleaning and/or stripping. Typically, according to one embodiment of the present invention, an electrode diagnostic may also be performed to confirm that the various electrodes are operating properly and that none has been fouled with unwanted contaminants. One way to do so is to review the hydrogen wave in the cyclic voltamogram for the relevant electrode. However, other methods to confirm proper operation of the various electrodes may be used, as appropriate
Suitable reference, counter and working electrodes for electroplating of copper are known in the art. For example, a Pt WE that is encased in glass (e.g., lead glass) may be used. Also, for example, an Ag/AgCl RE (with an asbestos junction) may be used.
A galvanostatic measurement component includes, but is not limited to, a working electrode (WE), a reference electrode (RE), and a counter electrode (CE) and all other necessary hardware/software, tubing, and electronics necessary for making the galvanostatic measurement. The galvanostatic measurement component is one that includes the necessary electronics, hardware and may include software sufficient to make the necessary galvanostatic measurements of interest noted herein. For example, a testing cell as described with regard to FIG. I may be used (or an equivalent thereof) for making the galvanostatic measurement. The term ‘component’ as used herein refers to a part of the system that can be in unitary, assembly or sub-assembly form, and can include hardware, firmware and/or software, as appropriate to its structural embodiment and implementation in the system.
A potentiodynamic measurement includes, but is not limited to, application of a non-static potential (i.e., non-static voltage) over a given time period during which a measurement of a plating (or stripping) current versus time is made. Alternatively, a potentiodynamic measurement includes, but is not limited to, application of a non-static potential (i.e., non-static voltage) over a given time period during which a measurement of a plating (or stripping) current versus voltage is made.
A potentiodynamic measurement component includes, but is not limited to, a working electrode (WE), a reference electrode (RE), and a counter electrode (CE) and all other necessary hardware/software, tubing, and electronics necessary for making the potentiodynamic measurement. The potentiodynamic measurement component is one that includes the necessary hardware and may include software sufficient to make the necessary potentiodynamic measurements of interest noted herein. For example, a testing cell as described with regard to FIG. 1 may be used (or an equivalent thereof) for making the potentiodynamic measurement. The term ‘component’ as used herein refers to a part of the system that can be in unitary, assembly or sub-assembly form, and can include hardware, firmware and/or software, as appropriate to its structural embodiment and implementation in the system.
The WE may be the wafer itself being electroplated with or without a separate WE.
Galvanostatic data includes, but is not limited to, plating (or stripping) voltage as a function of time for a plurality of samples (e.g., substrates). Alternatively, the galvanostatic data may include, but is not limited to, a plurality of galvanostatic measurements taken over time for the same sample (e.g., substrate).
Potentiodynamic data includes, but is not limited to, plating (or stripping) current as a function of time for a plurality of samples (e.g., substrates) or plating (or stripping) current as a function of voltage for a plurality of samples. Alternatively, the potentiodynamic data may include, but is not limited to, a plurality of potentiodynamic measurements taken over time for the same sample (e.g., substrate).
Instead of galvanostatic data, or potentiodynamic data (or measurement thereof, respectively), any electrical data measurement or any electrical data of said electroplated substrate may be used that can be correlated with the defect profile of the electroplated substrate, the chemical profile of the plating bath or the electrical profile of the electroplated substrate.
A storage component includes, but is not limited to, any memory (e.g., physical memory, computer memory, data storage memory, magnetic storage memory, optical storage memory, flash memory or the like). The storage component may be used for the storage of galvanostatic measurement(s), galvanostatic data, potentiodynamic measurement(s), potentiodynamic data, other relevant electrical measurement(s), other relevant electrical data or a combination thereof.
With reference to the “electrical profile,” such profile includes, but is not limited to, resistivity, electromigration, impedance, capacitance, electrical failure, and/or yield (% of devices formed that satisfy operating parameters, specifications or tolerances). Other electrical parameters may include those that affect the “electrical profile” of the electroplated substrate.
With reference to the “defect profile,” such profile includes, but is not limited to, surface roughness, voids (whether on the surface or internally), bulk or surface hardness, surface contamination (e.g., reaction by-product, extraneous matter, other contaminants), crystallographic orientation (e.g., 90% 1,1,1—Cu), grain size, bulk contamination (e.g., with organics in the Cu layer), and/or structural integrity (e.g. bulk or internal—delamination, stress cracking, stress corrosion etc.). Other physical defect parameters may include those that affect the “electrical profile” of the electroplated substrate.
With reference to the “chemical profile,” such profile includes, but is not limited to, concentrations of additives (e.g., accelerators, suppressors, levelers and/or combinations thereof), by-products, inorganics, organics, metal salts (e.g., copper sulfate), acids (e g., sulfuric acid, HCl), halides, (e.g., chloride), other organic processing impurities (e.g., from prior processing steps), other inorganic processing impurities (e.g., from prior processing steps), dust, and/or air-borne contamination. Other chemical parameters may include those that affect the “electrical profile” of the electroplated substrate.
According to one or more embodiments of the present invention, it is desirable to control the “electrical profile” so that it falls within an acceptable electrical threshold range relating to any one or more of the above-noted members of the “electrical profile.” Pursuant to an embodiment, the acceptable electrical threshold range should be set such that the electronic devices or components thereof made according to the present invention provide the necessary yield of acceptable devices or components. Such acceptable electrical threshold range shall depend upon the device and components being made and their operating specifications and requirements.
According to another embodiment of the present invention, it is desirable to control the “defect profile” so that it falls within an acceptable defect threshold range relating to any one or more of the above-noted members of the “defect profile.” Pursuant to an embodiment, the acceptable defect threshold range should be set such that the electronic devices or components thereof made according to the present invention provide the necessary yield of acceptable devices or components. Such acceptable defect threshold range shall depend upon the device and components being made and their operating specifications and requirements.
According to yet another embodiment of the present invention, it is desirable to control the “defect profile” so that it falls within a defect threshold range and the “electrical profile” falls within the electrical threshold range.
According to still another embodiment of the present invention, it is desirable to control the “chemical profile” so that it falls within an acceptable chemical threshold range. Pursuant to an embodiment, the acceptable chemical threshold range should be set such that the electronic devices or components thereof made according to the present invention provide the necessary yield of acceptable devices or components. Such acceptable chemical threshold range shall depend upon the device and components being made and their operating specifications and requirements.
According to a still further embodiment of the present invention, it is desirable to control the “chemical profile” so that it falls within a chemical threshold range, the “defect profile” falls within the defect threshold range, and/or the “electrical profile” falls within the electrical threshold range.
The defect threshold range is a range of values for one or more of the above-noted defect parameters that (if within that defect threshold range) produces acceptable yields (e.g., of acceptable electroplated substrates, devices or components) (e.g., yields of at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100%).
The electrical threshold range is a range of values for one or more of the above-noted electrical parameters that (if within that electrical threshold range) produces acceptable yields (e.g., of acceptable electroplated substrates, devices or components) (e.g., yields of at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100%).
The chemical threshold range is a range of values for one or more of the above-noted chemical parameters that (if within that chemical threshold range) produces acceptable yields (e.g., of acceptable electroplated substrates, devices or components) (e.g., yields of at least about 80%, at least about 85%, at least about 90%, at least about 91%, at least about 92%, at least about 93%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, at least about 99%, or 100%).
Multi-variate analysis includes, but is not limited to, partial least squares (PLS) regression analysis (e.g., curve fitting using PLS Toolbox from Eigenvector), principle component analysis (e.g., another curve fitting method), etc.
A multi-variate analysis component includes, but is not limited to, software, hardware, a combination thereof for conducting the multi-variate analysis, for example, as noted above.
Correlating the defect profile using multi-variate analysis involves transformation of the galvanostatic data, the potentiodynamic data, or a combination thereof to an averaged data set (of the galvanostatic data, of the potentiodynamic data, or both) optionally including a linearized transformation of the same versus time against the defect profile corresponding to the galvanostatic data, the potentiodynamic data or a combination of the same. See FIGS. 14, 14 a, and 14 b. One or more variations of the step(s) or procedure(s) of FIGS. 14, 14 a, and/or 14 b may be used in conjunctions with embodiments of the present invention.
Correlating the chemical profile using multi-variate analysis involves transformation of the galvanostatic data, the potentiodynamic data, or a combination thereof to an averaged data set (of the galvanostatic data, of the potentiodynamic data, or both) optionally including a linearized transformation of the same versus time against the chemical profile corresponding to the galvanostatic data, the potentiodynamic data or a combination of the same. See FIGS. 14, 14 a, and 14 b. One or more variations of the step(s) or procedure(s) of FIGS. 14, 14 a, and/or 14 b may be used in conjunctions with embodiments of the present invention.
Correlating the electrical profile using multi-variate analysis involves transformation of the galvanostatic data, the potentiodynamic data, or a combination thereof to an averaged data set (of the galvanostatic data, of the potentiodynamic data, or both) optionally including a linearized transformation of the same versus time against the electrical profile corresponding to the galvanostatic data, the potentiodynamic data or a combination of the same. See FIGS. 14, 14 a, and 14 b. One or more variations of the step(s) or procedure(s) of FIGS. 14, 14 a, and/or 14 b may be used in conjunctions with embodiments of the present invention.
According to another embodiment of the present invention, any data collected may be used to iteratively improve the prediction ability of the MVA correlation by adding the collected data to the correlation rule set—as desired. Also, for example, to aid in quality control, an on-line design can be used to continually monitor the process input parameters (copper bath components including additives etc.) and an updated correlation (iterative or non-iterative) with the defects can be incorporated into the MVA. Furthermore, using linear regression analysis and observed concentration variations, a Monte-Carlo type analysis (e.g., Expected Value Analysis) may be implemented to adjust the process either iteratively or non-iteratively.
A comparator component may be used (pursuant to an embodiment of the present invention) that determines if the defect profile, the chemical profile, or the electrical profile is outside a defect threshold range, a chemical threshold range, or an electrical threshold range, respectively. The comparator component may be an automated piece of hardware or may be software or a combination of the two. Instead of a comparator component, a human operator may conduct the comparator function.
Another embodiment of the present invention may include a chemical profile manager (e.g., automated system of hardware, software or a combination thereof; a human operator etc.) for adjusting the chemical profile of the plating bath so that (1) if the defect profile is outside the defect threshold range, (2) if the chemical profile is outside the chemical threshold range, and/or (3) if the electrical profile is outside the electrical threshold range,—then the chemical profile manager may adjust the chemical profile to return (4) the defect profile to fall within the defect threshold range, (5) to return the chemical profile to fall within the chemical threshold range, and/or (6) to return the electrical profile to fall within the electrical threshold range, respectively.
Output of the aforementioned analysis may be provided. Output may in the form of reports, electrical signals, or other ways for conveying and/or utilizing the analysis results in improving the electroplating of substrates described herein.
According to an embodiment of the present invention, the electrochemical sensing part or end comprises a electroplating bath containing a reference electrode (RE), a working electrode (WE), a counter electrode (CE), sample tubing (for introducing a particular electroplating bath), solution tubing (for introducing cleaning solution), aid a testing cell (inside which plating of copper occurs on the end of the WE residing in the electroplating bath contained in the testing cell). See for example FIG. 1 depicting one example of a suitable electrochemical sensing/testing/measuring end or head. Note that it is envisioned that any other suitable electrochemical testing end (e.g., testing cell) may be used as would be understood by one of ordinary skill in the art. Additionally, for example, the testing cell may also be equipped with or at least connected to the appropriate driving electronics and circuitry needed to make the relevant galvanostatic or potentiodynamic measurements suitable for use with embodiment(s) of the present invention. Details of suitable circuitry and driving electronics are provided in one or more of the U.S. patents or U.S. patent applications cited herein.
Referring to FIGS. 1 and 2, as noted, WE and CE are the working electrode and the counter electrode, respectively. The working electrode contains a sample substrate (or a suitable substitute for the substrate) to be electroplated so that galvanostatic or potentiodynamic plating measurements (or other relevant electrical measurements) can be made during electroplating of the substrate. It is envisioned that the WE will contain a small piece of substrate on its end that mimics the behavior of the actual substrate(s) provided in the same electroplating bath being electroplated under essentially identical conditions—if in a different chamber—or—electroplated under identical conditions—if both the WE and the substrate are being electroplated in the same chamber or cell.
Pursuant to another embodiment of the present invention, the testing cell may comprise (aa) a reference electrode (RE), (bb) a working electrode (WE), (cc) a counter electrode (CE), (dd) electroplating driving electronics electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE), and the working electrode (WE) to electroplate metal on said working electrode in a metal electroplating bath, and (ee) electrical potential measuring circuitry electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE) and the working electrode (WE), wherein the electroplating driving electronics may further comprise stripping driving electronics to remove plated metal from the working electrode (WE)—as necessary to make the required measurement(s).
According to one embodiment, a plating bath suitable for use in conjunction with the present invention comprises a metal salt, a halide, an acid and optionally a suppressor, an accelerator, a leveler or a combination thereof. An example of a suitable metal salt is copper sulfate. A suitable halide includes, but is not limited to, a source of chloride. A suitable acid includes, but is not limited to, sulfuric acid, hydrochloric acid, other acids, or a combination thereof. The plating bath typically also contains water (e.g., de-ionized water or other water suitable for measuring the various kinds of measurements noted herein).
While the invention has been has been described herein in reference to specific aspects, features and illustrative embodiments of the invention, it will be appreciated that the utility of the invention is not thus limited, but rather extends to and encompasses numerous other variations, modifications and alternative embodiments, as will suggest themselves to those of ordinary skill in the field of the present invention, based on the disclosure herein. Correspondingly, the invention as hereinafter claimed is intended to be broadly construed and interpreted, as including all such variations, modifications and alternative embodiments, within its spirit and scope.
The subject matter of the present application relates to and encompasses the disclosure of U.S. Provisional Patent Application No. 60/815,213 filed Jun. 20, 2006 in the names of William Holber, Mackenzie King and Peter Van Buskirk for “ELECTROCHEMICAL SAMPLING HEAD OR ARRAY OF SAME.” The disclosure of such provisional application is hereby incorporated herein by reference in its entirety.

Claims

1. A system adapted to analysis of an electroplated substrate or adapted to analysis for electroplating a substrate, said system comprising:

(a) a galvanostatic measurement component, a potentiodynamic measurement component or a combination thereof adapted to measuring galvanostatic data, potentiodynamic data or a combination thereof from a plating bath;

(b) a storage component adapted to storing said galvanostatic data, said potentiodynamic data or a combination thereof;

(c) a first multi-variate analysis component adapted to correlating said galvanostatic data, said potentiodynamic data or said combination thereof with a defect profile of said electroplated substrate, a chemical profile of said plating bath, an electrical performance profile of said electroplated substrate or a combination thereof;

(d) an optional second multi-variate analysis component adapted to correlating said defect profile with said chemical profile of said plating bath;

(e) an optional third multi-variate analysis component adapted to correlating said galvanostatic data, said potentiodynamic data or said combination thereof with said chemical profile of said plating bath; and

(f) an optional fourth multi-variate analysis component adapted to correlating said electrical profile of said electroplated substrate with said defect profile, said chemical profile or a combination thereof.

2. The system of claim 1, further comprising:

(g) a comparator component adapted to determining if said defect profile, said chemical profile, or said electrical profile is outside a defect threshold range, a chemical threshold range, or an electrical threshold range, respectively.

3. The system of claim 2, further comprising:

(h) a chemical profile manager adapted to adjusting said chemical profile if said defect profile is outside said defect threshold range, if said chemical profile is outside said chemical threshold range, or if said electrical profile is outside said electrical threshold range—then—to return said defect profile to fall within said defect threshold range, to return said chemical profile to fall within said chemical threshold range, or to return said electrical profile to fall within said electrical threshold range.

4. The system of claim 1, further comprising:

(i) an output of said first, second, third, or fourth multi-variate correlation or a combination thereof.

5. The system of claim 2, further comprising:

an output of said first, second, third, or fourth multi-variate correlation or a combination thereof.

6. The system of claim 1, wherein said galvanostatic data comprises voltage versus time data of said electroplated substrate.

7. The system of claim 1, wherein said galvanostatic measurement, said potentiodynamic measurement or said combination thereof is measured in a testing cell during electroplating or stripping a metal from a working electrode, said testing cell comprising (aa) a reference electrode (RE), (bb) a working electrode (WE), (cc) a counter electrode (CE), (dd) electroplating driving electronics electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE), and the working electrode (WE) to electroplate metal on said working electrode in a metal electroplating bath, and (ee) electrical potential measuring circuitry electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE) and the working electrode (WE), wherein the electroplating driving electronics may further comprise stripping driving electronics to remove plated metal from the working electrode (WE).

8. The system of claim 7, wherein said reference electrode is an Ag/AgCl reference electrode (RE) optionally fitted with an asbestos junction.

9. The system of claim 8, wherein said working electrode is a Pt electrode optionally encased in lead glass and operated at a voltage range selected from the group consisting of ≧0.1V, ≧0.2V, ≧0.3V, ≧0.4V, ≧0.5V, ≧0.6V, ≧0.7V, ≧0.8V, ≧0.9V, ≧1.0V, ≧1.1V, ≧1.2V, ≧1.3V, ≧1.4V, ≧1.5V, ≧1.6V, ≧1.7V, ≧1.8V, ≧1.9V, and ≧2.0V relative to a standard hydrogen electrode (SHE).

10. The system of claim 7, wherein said metal plating bath comprises a copper salt, a halide, and an acid and optionally a suppressor, an accelerator, a leveler or a combination thereof.

11. The system of claim 10, wherein said copper salt is copper sulfate, said halide is chloride, and said acid is sulfuric acid or hydrochloric acid.

12. A system adapted to defect analysis on an electroplated substrate or adapted to defect analysis for electroplating a substrate, said system comprising:

(a) a galvanostatic measurement component, a potentiodynamic measurement component or a combination thereof for measuring galvanostatic data, potentiodynamic data or a combination thereof from a plating bath;

(b) a storage component for storing said galvanostatic data, said potentiodynamic data or a combination thereof;

(c) a component for comparing said data with a rule set for determining adjustment(s) to said plating bath wherein said rule set comprises a defect profile including a defect threshold range for at least one of surface roughness, voids, hardness, surface contamination, crystallographic orientation, grain size, bulk contamination and structural integrity, and wherein said adjustment(s) to said plating bath are determined without measurement of concentration of chemical components in said plating bath.

13. A method adapted to forming an electroplated substrate, said method comprising the steps of:

(a) performing or obtaining a galvanostatic measurement, a potentiodynamic measurement or a combination thereof relating to said electroplated substrate with a testing cell containing (aa) a reference electrode (RE), (bb) a working electrode (WE), (cc) a counter electrode (CE), (dd) electroplating driving electronics electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE), and the working electrode (WE) to electroplate metal on said working electrode in a metal electroplating bath, and (ee) electrical potential measuring circuitry electrically and operatively coupled between the reference electrode (RE), the counter electrode (CE) and the working electrode (WE), wherein the electroplating driving electronics may further comprise stripping driving electronics to remove plated metal from the working electrode (WE);

(b) storing said galvanostatic measurement, said potentiodynamic measurement or said combination thereof;

(c) correlating said galvanostatic measurement, said potentiodynamic measurement or said combination thereof with a defect profile of said substrate, with a chemical profile of an electroplating bath in which said substrate is/was electroplated, or a combination thereof utilizing multi-variate analysis; and

(d) replacing said electroplating bath or adjusting one or more chemicals in said electroplating bath if a defect profile of said electroplated substrate is outside a defect threshold range, if a chemical profile of said electroplating bath is outside a chemical threshold range or a combination thereof.

14. The method of claim 13, wherein said electroplating bath comprises a copper salt, a halide, and an acid and optionally a suppressor, an accelerator, a leveler or a combination thereof.

15. The method of claim 14, wherein said copper salt is copper sulfate, said halide is chloride, and said acid is sulfuric acid or hydrochloric acid.

16. The method of claim 13, wherein said reference electrode is an Ag/AgCl reference electrode optionally fitted with an asbestos junction.

17. The method of claim 13, wherein said working electrode is a Pt electrode optionally encased in lead glass and operated at a voltage range selected from the group consisting of ≧0.1V, ≧0.2V, ≧0.3V, ≧0.4V, ≧0.5V, ≧0.6V, ≧0.7V, ≧0.8V, ≧0.9V, ≧1.0V, ≧1.1V, ≧1.2V, ≧1.3V, ≧1.4V, ≧1.5V, ≧1.6V, ≧1.7V, ≧1.8V, ≧1.9V, and ≧2.0V relative to a standard hydrogen electrode (SHE).

18. The method of claim 13, wherein between said steps (a) and (b) is interposed a step of (a′) cleaning said testing cell with a cleaning solution.

19. The method of claim 13, wherein said step (a) is conducted a plurality of times to generate galvanostatic measurement data, potentiodynamic measurement data or a combination thereof and said data is stored during said step (b).

20. The method of claim 18, wherein said cleaning solution comprises sulfuric acid and water and optionally one or more additives selected from the group consisting of a suppressor, an accelerator, a leveler or a combination thereof.

21. The method of claim 20, wherein said cleaning solution contains a leveler.

22. The method of claim 21, wherein said leveler in said cleaning solutions is provided in a concentration of about 1.5 ml per liter of cleaning solution.

23. The method of claim 20, wherein said step (a) is conducted during a plating potential cycle or during a stripping potential cycle.

24. An apparatus comprising the system of claim 1.

25. The system of claim 1 comprising said second multi-variate component, said third multi-variate component, said fourth multi-variate component or a combination thereof.

26. The system of claim 1, wherein said first multi-variate analysis component is adapted to correlate at least of one said defect profile, chemical profile, and electrical performance profile by transformation of said galvanostatic data, said potentiodynamic data or said combination thereof to an averaged data set thereof including a linearized transformation thereof versus time against the defect profile corresponding to said galvanostatic data, potentiodynamic data or combination thereof.

27. The system of claim 1, wherein said first multi-variate analysis component is adapted to correlate at least of one said defect profile, chemical profile, and electrical performance profile by transformation of said galvanostatic data, said potentiodynamic data or said combination thereof to an averaged data set thereof including a linearized transformation thereof versus time against the chemical profile corresponding to said galvanostatic data, potentiodynamic data or combination thereof.

28. The system of claim 1, wherein said first multi-variate analysis component is adapted to correlate at least of one said defect profile, chemical profile, and electrical performance profile by transformation of said galvanostatic data, said potentiodynamic data or said combination thereof to an averaged data set thereof including a linearized transformation thereof versus time against the electrical profile corresponding to said galvanostatic data, potentiodynamic data or combination thereof.