METHODS AND PROCESS CONTROL FOR REAL TIME INERT MONITORING OF ACID COPPER ELECTRODEPOSITION SOLUTIONS

Abstract

Techniques including methods and apparatuses for inert real-time measurement and monitoring of metal and acid concentrations in a processing solution are provided. Methods include performing an analytical method (e.g., spectral measurements) of the processing solution to determine a metal concentration and performing another analytical method (e.g., density measurements) of the processing solution to determine an acid concentration with compensation of raw results based on the determined metal concentration. The determination of the acid concentration can also include compensation of raw results based on another analytical method (e.g., temperature measurements) of the processing solution. The analytical methods can be performed in any order or in parallel. Both metal and acid concentrations in the processing solution can therefore be inertly and continuously measured and monitored in real time.

Claims

1. A method for determining a concentration of an acid in a processing solution including one or more acids and one or more metals, comprising: performing an analytical method of the processing solution to provide an analytical measurement, and determining a concentration of the one or more metals from the analytical measurement; measuring a density of the processing solution; and determining the concentration of the acid from the measured density of the processing solution and the concentration of the one or more metals.

2. The method of claim 1, wherein the analytical method comprises measuring an optical property of the processing solution.

3. The method of claim 2, wherein the optical property of the processing solution is measured by UV-Vis-spectroscopy.

4. The method of claim 2, wherein the method comprises measuring a transmittance of the processing solution, measuring an absorbance of the processing solution, or a combination thereof.

5. The method of claim 1, wherein the one or more metals comprises copper.

6. The method of claim 1, wherein the one or more acids comprises sulfuric acid.

7. The method of claim 1, wherein the processing solution is an electrodeposition solution.

8. The method of claim 1, wherein the method further comprises measuring a temperature of the processing solution.

9. The method of claim 8, wherein the concentration of the acid is further determined from the temperature of the processing solution.

10. The method of claim 1, wherein performing the analytical method and measuring the density of the processing solution are performed in parallel.

11. The method of claim 8, wherein performing the analytical method, measuring the density of the processing solution, and measuring the temperature of the processing solution are performed in parallel.

12. An apparatus for determining a concentration of an acid in a processing solution including one or more acids and one or more metals, comprising: a measurement module operatively connected to one or more sensors and adapted to receive a process sample; wherein the process sample comprises at least a portion of the processing solution, wherein each of the one or more sensors are adapted to receive at least a portion of the process sample, and are operative to perform one or more analytical methods, and wherein the one or more sensors comprises a spectral sensor, a density sensor, or combinations thereof.

13. The apparatus of claim 12, wherein the spectral sensor comprises a chemically inert material.

14. The apparatus of claim 12, wherein the density sensor comprises a chemically inert material.

15. The apparatus of claim 12, wherein the processing solution comprises copper and sulfuric acid.

16. The apparatus of claim 12, wherein the one or more sensors further comprises a temperature sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following figures are included to illustrate certain aspects of the present disclose and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, without departing from the scope of the disclosure.

[0017] FIG. 1 schematically illustrates an exemplary apparatus of the present disclosure;

[0018] FIG. 2 illustrates results of Vis-NIR spectroscopy measurements in absorbance versus wavelength (nm) of acid copper electrodeposition solution samples to quantitate copper (Cu) concentration in accordance with Example 1;

[0019] FIG. 3 illustrates a calibration curve of copper (Cu) (g/L) versus absorbance (at 750 nm) of acid copper electrodeposition solution samples in accordance with Example 1; and

[0020] FIG. 4 illustrates results of density (g/L) versus temperature (° C.) of acid copper electrodeposition solution samples in accordance with Example 1.

DETAILED DESCRIPTION

[0021] The present disclosure provides techniques for real-time inert measurement and monitoring of metal and acid concentrations in processing solutions such as semiconductor processing solutions. In certain embodiments, the present disclosure provides for combining an analytical method for determining the metal concentration in solution (e.g., spectroscopy measurements) with another analytical method of the solution (e.g., density measurements) in order to determine the real-time concentration of both acid and metal components the solution. The acid concentration can be determined by compensating the raw results of the separate analytical method (e.g., density measurements) with the metal concentration derived from the analytical method (e.g., spectroscopy measurements) utilized for determining the same. In certain aspects, the acid concentration can be determined by compensating the raw results of analytical methods with temperature variability. The analytical methods can be performed in any order or in parallel. In certain embodiments, the analytical methods are performed in parallel. Accordingly, both the metal concentration and acid concentration of a processing solution can advantageously be continuously and inertly measured and monitored in real-time.

[0022] The terms used in this specification generally have their ordinary meanings in the art, within the context of this disclosure and in the specific context where each term is used. Certain terms are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner in describing the compositions and methods of the present disclosure and how to make and use them.

[0023] For purposes of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with any document incorporated herein by reference, the definition set forth below shall control.

[0024] As used herein, the use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification can mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.”

[0025] As used herein, the term “about” or “approximately” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e., the limitations of the measurement system. For example, “about” can mean within 3 or more than 3 standard deviations, per the practice in the art. Alternatively, “about” can mean a range of up to 20%, preferably up to 10%, more preferably up to 5%, and more preferably still up to 1% of a given value.

[0026] As used herein, the term “accurate” or “accurately” refers to, for example, a measurement or determination that is relatively close to or near an existing or true value, standard, or known measurement or value.

[0027] The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms or words that do not preclude additional acts or structures. The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not.

[0028] As used herein, the terms “coupled” or “operatively coupled” refers to one or more components being combined with each other and as used herein is intended to mean either an indirect or a direct connection. Thus, if one device couples to a second device, that connection may be through a direct connection, or through an indirect mechanical or other connection via other devices or connections.

[0029] As used herein, the term “selective” or “selectively” refers to, for example, the monitoring, measurement or determination of a characteristic of a specific or particular component.

[0030] As used herein, the term “real time” or “real-time” refers to, for example, as happening at a rate that is substantially the same as the real current process.

[0031] The methods of the present disclosure can be applied to various types of solutions including processing solutions. In certain embodiments, the solution can be a semiconductor processing solution. For example and not by way of limitation, the solution can be an acid copper electrodeposition solution.

[0032] In certain embodiments, the solution can include one or more metals. A person skilled in the art will appreciate a wide combination of metals are suitable for use with the present disclosure. In certain embodiments, the solution can include copper (Cu). In certain embodiments, the solution can include one or more metal salts. A person skilled in the art will appreciate a wide combination of metal salts are suitable for use with the present disclosure. For example, and not by way of limitation, the solution can include copper sulfate (CuSO4). In certain embodiments, the solution can include one or more acids. A person skilled in the art will appreciate a wide combination of acids are suitable for use with the present disclosure. In certain embodiments, the processing solution can include sulfuric acid (H.sub.2SO.sub.4), hydrochloric acid (HCl), or combinations thereof. In certain aspects, the processing solution can include a blend of one or more metals, for example, as one or more metal salts, and one or more acids. A person skilled in the art will appreciate a wide variety of combinations of one or more metals and one or more acids are suitable for use with the present disclosure. In certain embodiments, the processing solution can include copper (Cu), e.g., as copper sulfate (CuSO.sub.4), and sulfuric acid (H.sub.2SO.sub.4). In certain embodiments, the processing solution can include copper sulfate (CuSO.sub.4) and sulfuric acid (H.sub.2SO.sub.4). In certain aspects, the processing solution can include one or more organic additives. In certain embodiments, the processing solution can include water.

[0033] Methods of the present disclosure provide multiple analytical methods and measurements of solutions, for example, in order to inertly measure and monitor acid concentration, metal concentration, or combinations thereof continuously in real-time. The concentration of a metal can be inertly measured and monitored in a solution by performing an analytical method of the solution. In certain embodiments, the analytical method can include measuring an optical property of the solution. For example, and not by way of limitation, the analytical method can include measuring an absorbance of the solution, a transmittance of the solution, or a combination thereof (e.g., through Vis-NIR absorption spectroscopy). In certain aspects, an optical property of the processing solution can be measured by a spectral sensor. The spectral sensor can be operable to scan and detect a wavelength (nm) of the solution. In certain embodiments, the spectral sensor can include one or more chemically inert wetted materials (e.g., quartz or sapphire). A person skilled in the art will appreciate a wide variety of methods for measuring optical properties (e.g., absorbance and/or transmittance) are suitable for use with the present disclosure.

[0034] In such embodiments, measurements of optical properties, e.g., an absorbance, of the solution can provide a metal concentration. In certain aspects, the metal concentration can be calculated using the Beer-Lambert Law (Equation I) disclosed herein in the Examples. To provide real-time inert monitoring of one or more acids in the solution, another analytical method can be conducted. In certain embodiments, the analytical method can include measuring a density of the solution, for example, with a density sensor (e.g., a densitometer). The density sensor can be operative to measure a density of the solution. In certain embodiments, the density sensor can include one or more chemically inert wetted materials, for example, polytetrafluoroethylene (e.g., PTFE or Teflon) or glass. A person skilled in the art will appreciate a wide variety of methods for measuring density are suitable for use with the present disclosure. In certain embodiments, the measurements of density of the solution can provide an acid concentration. For example, and not by way of limitation, the acid concentration can be calculated using Equation II disclosed herein in the Examples. The calculation can include the correction for the metal concentration as determined from analytical methods such as spectral properties of the solution.

[0035] In certain embodiments, the temperature of the processing solution can be measured. For example, in certain embodiments, the temperature of the processing solution can be measured by a temperature sensor. A person skilled in the art will appreciate a wide variety of methods for measuring temperature are suitable for use with the present disclosure. In certain embodiments, measurements of density can be compensated for by the temperature of the solution. As solution density can be dependent on temperature, the acid concentration in solution can be compensated with the temperature of the solution, for example, by using Equations III or IV provided in the Examples.

[0036] Accordingly, the metal concentration and the acid concentration of a solution, such as a processing solution, can be measured and monitored inertly in real-time by accurate methods. In certain aspects, these measurements can be used to selectively determine an acid concentration of a solution. In certain embodiments, an analytical method, for example, spectral property measurements of the processing solution (e.g., absorbance and/or transmittance), can be combined with another analytical method, for example, density measurements of the processing solution. From such measurements, the metal concentration and the acid concentration of the solution can be determined. Further, the acid concentration can be determined by compensating the raw results of the analytical methods utilized to determine the same with the determined metal concentration and temperature variability. Thus, an acid concentration in solution can be selectively measured and monitored by using a non-selective analytical signal (e.g., density measurements) and providing selectivity by compensation for the metal concentration in solution and temperature variability.

[0037] FIG. 1 schematically illustrates an exemplary apparatus of the present disclosure. In certain aspects, the exemplary apparatus can relate to measuring and monitoring acid and metal concentrations in solutions such as processing solutions. The apparatus can include a measurement module 100. The measurement module 100 can include one or more sensors, for example, operative to perform one or more analytical methods. In certain embodiments, the one or more analytical methods can include measuring a wavelength (e.g., an absorbance) of the solution, measuring a density of the solution, measuring a temperature of the solution, or combinations thereof. In certain embodiments, the one or more sensors can include a spectral sensor 101, a density sensor 102, a temperature sensor 103, or combinations thereof. The spectral sensor 101 can be operative to perform a spectral scan and detect a wavelength of the solution. In certain embodiments, the spectral sensor 101 can include one or more chemically inert wetted materials, for example, quartz or sapphire. The density sensor 102 can be operative to measure a density of the solution. In certain embodiments, the density sensor 102 can include one or more chemically inert wetted materials, for example, polytetrafluoroethylene (e.g., PTFE or Teflon) or glass. The temperature sensor 103 can be operative to measure a temperature of the solution. In certain embodiments, the one or more sensors can be individual or integrated. The one or more sensors can be positioned in series in any order, sequentially or in parallel. In certain embodiments, the sensors can include the spectral sensor 101, the density sensor 102, and the temperature sensor 103, positioned sequentially. In certain aspects, valves or manifolds of the apparatus, for example, for sensor installation can include a chemically inert material. For example, and not by way of limitation, in certain embodiments, the valves or manifold can include a polytetrafluoroethylene (e.g., PTFE or Teflon) wetted material.

[0038] In certain embodiments, the apparatus can further include a measurement module 200. The measurement module 200 can be operatively connected to one or more of the one or more sensors 101, 102 and 103. In certain embodiments, the measurement module 200 can be operatively connected to each of the spectral sensor 101, the density sensor 102, and the temperature sensor 103. In certain embodiments, the one or more sensors 101, 102 and 103 can be operatively connected to the measurement module 200 by fiberoptics, electrical cables, or a combination thereof. In certain aspects, the measurement module 200 can include electronics, optical elements, etc.

[0039] A process sample 301 can be introduced to the apparatus. In certain embodiments, the process sample 301 can include one or more metals (e.g., one or more metal salts), one or more acids, or combinations thereof In certain embodiments, the process sample 301 can flow through the measurement module 100 and be measured by the one or more sensors 101, 102 and 103. In certain embodiments, a standard solution 302 (or reference solution or calibration solution) can be introduced to the apparatus. In certain aspects, the standard solution 302 can include a known concentration of one or more acids, one or more metals (e.g., one or more metal salts), or a combination thereof In certain aspects, the standard solution 302 can flow through the measurement module 100 and be measured by the one or more sensors 101, 102 and 103. Optionally, the apparatus can include a selector valve 300. In certain embodiments, the selector valve 300 can be positioned at the input. In certain embodiments, the selector valve 300 can be operative to alternate between the process sample 301 and the standard solution 302.

[0040] After analytical measurements of the solution (e.g., the process sample 301 or the standard sample 302) are completed, the solution can be flowed to return to the process 401 or discarded as waste 402. Optionally, the apparatus can include a selection valve 400, for example, operative to divert the sample to either process 401 or waste 402.

EXAMPLE

[0041] The presently disclosed subject matter will be better understood by reference to the following Example. The following Example is merely illustrative of the presently disclosed subject matter and should not be considered as limiting the scope of the subject matter in any way.

Example 1

[0042] This Example provides for continuous inert real-time measurement and monitoring of acid and metal concentrations in an acid copper electrodeposition solution. The continuous inert real-time measurement and monitoring of a metal concentration (i.e., of copper sulfate) was achieved by performing an analytical method, i.e., Vis-NIR spectroscopy. The continuous inert real-time measurement and monitoring of an acid concentration (i.e., of sulfuric acid) was achieved by performing an analytical method, i.e., density measurement and compensating the same with the measured metal concentration and temperature variability.

[0043] Analytical equipment can develop drift over time. In order to compensate for such drift, samples with known compositions can be periodically measured. The offset can be automatically reset based on the potential gap between measured and expected value of a sample (e.g., New Offset=Old Offset+Expected Concentration−Measured Concentration). This approach can be performed for either a metal concentration (e.g., copper), an acid concentration (e.g., sulfuric acid), or both. A sample with known composition can be a virgin make-up solution (VMS) including copper sulfate (CuSO.sub.4), sulfuric acid (H.sub.2SO.sub.4), and hydrochloric acid at predetermined target concentrations. The solution is available in the electrodeposition tool as a raw material with certified composition. Other types of samples with known composition can be used.

[0044] Vis-NIR absorption spectroscopy was performed on ten (10) (DOE1-DOE10) samples of acid copper electrodeposition solutions each having varying concentrations of copper sulfate and sulfuric acid. The Vis-NIR absorption spectroscopy had chemically inert wetted materials (e.g., quartz or sapphire). The metal concentration measurement for copper (Cu) was performed using Vis-NIR absorption spectroscopy. Copper (Cu) has a relatively broad peak, i.e., in the range of 500-1,000 nm. Any individual wavelength or their combination was used. A flow cell of characterized pathlength was illuminated with a light source that outputted light into a segment within the 500-1,000 nm range. The intensity of the light after the flow cell was monitored at either an individual wavelength or calibration of wavelength was measured. The data was collected with a Vis-NIR absorption spectrophotometer (Agilent Cary) and provided in FIG. 2.

[0045] The Beer-Lambert Law (Equation I) was used to calculate the concentration of copper (Cu) as follows.

A=log (Io/I)=e*c*d   (I) [0046] A—absorbance [0047] Io—intensity of light in the absence of copper (Cu) [0048] I—intensity of light after interaction with a copper (Cu) sample [0049] e—molecular extinction coefficient (dependent on wavelength) [0050] c—copper (Cu) concentration [0051] d—optical pathlength

[0052] A calibration curve of absorbency versus the copper (Cu) concentration (g/L) is provided in FIG. 3.

[0053] The results demonstrating the accuracy between the calculated and actual copper (Cu) concentration is provided in Table 1 below. Accuracy (i.e., absolute analytical error)<0.033 g/L was demonstrated.

TABLE-US-00001 TABLE 1 Cu Absorbance Measured Cu Accuracy Sample (g/L) (at 750 nm) (g/L) (g/L) Sample 1 8.44 1.397186518 8.45 0.010 (DOE 1) Sample 2 3 0.490595996 3.01 0.010 (DOE 2) Sample 3 5.33 0.871707737 5.30 −0.033 (DOE 3) Sample 4 6.89 1.135486484 6.88 −0.011 (DOE 4) Sample 5 7.67 1.264282823 7.65 −0.018 (DOE 5) Sample 6 4.56 0.75053072 4.57 0.010 (DOE 6) Sample 7 6.11 1.008155346 6.12 0.005 (DOE 7) Sample 8 10 1.655110836 10.00 −0.003 (DOE 8) Sample 9 3.78 0.620568574 3.79 0.010 (DOE 9) Sample 10 9.22 1.529229641 9.24 0.022 (DOE 10)

[0054] A measurement of the density of samples 1-10 (i.e., a blend of sulfuric acid and copper sulfate) were performed using an Anton-Paar densitometer. The density sensor had chemically inert wetted materials (i.e., polytetrafluoroethylene (PTFE or Teflon)) and glass). Teflon and glass). The measured sulfuric acid concentration was calculated using Equation II below, which was corrected with the copper (Cu) concentration.

Measured Sulfuric Acid=Offset+Cu Coefficient×[Cu Result]+Density Coefficient×[Density Measurement]  (II)

[0055] The coefficients for Equation II are provided in Table 2 below.

TABLE-US-00002 TABLE 2 Coefficient Cu −4.16546 Density 1646.44 Offset −1644.85

[0056] The results demonstrating the accuracy between the measured (corrected for copper (Cu) concentration)) and actual sulfuric acid (H.sub.2SO.sub.4) concentration is provided in Table 3 below. Accuracy (i.e., absolute analytical error)<0.23 g/L was demonstrated.

TABLE-US-00003 TABLE 3 Measured Sulfuric Sulfuric Density Temp Cu Acid (g/L) (Cu Accuracy Sample (g/mL) (° C.) (g/L) (g/L) corrected) (g/L) Sample 1 1.0265 20.5 8.44 10.22 10.07 −0.15 (DOE 1) Sample 2 1.014 20.2 3 12 12.15 0.15 (DOE 2) Sample 3 1.0184 20.2 5.33 9.78 9.69 −0.09 (DOE 3) Sample 4 1.023 20.3 6.89 10.67 10.76 0.09 (DOE 4) Sample 5 1.0238 20.5 7.67 8.89 8.83 −0.06 (DOE 5) Sample 6 1.0163 20.2 4.56 9.33 9.44 0.11 (DOE 6) Sample 7 1.0194 20.2 6.11 8 8.08 0.08 (DOE 7) Sample 8 1.0295 20.2 10 8.44 8.51 0.07 (DOE 8) Sample 9 1.0152 20.4 3.78 11.11 10.88 −0.23 (DOE 9) Sample 10 1.0294 20.8 9.22 11.56 11.59 0.03 (DOE 10)

[0057] As density is temperature dependent, the results were compensated for specific temperature of each sample. The results are provided in FIG. 4 and Table 4 below. A near constant temperature slope was observed.

TABLE-US-00004 TABLE 4 Density Density Density Density Density Density Cu H.sub.2SO.sub.4 (g/mL) (g/mL) (g/mL) (g/mL) (g/mL) (g/mL) Temp Sample (g/L) (g/L) (20° C.) (21° C.) (22° C.) (23° C.) (24° C.) (25° C.) Slope LOW 3 8 1.0113 1.0110 1.0108 1.0105 1.0102 1.0099 −0.000277 TGT 5 10 1.0177 1.0175 1.0172 1.0169 1.0166 1.0163 −0.000286 HIGH 10 12 1.0316 1.0314 1.0310 1.0307 1.0304 1.0301 −0.000309 DS High 3 12 1.0139 1.0136 1.0134 1.0131 1.0128 1.0125 −0.000277 DS Low 10 8 1.0290 1.0287 1.0284 1.0282 1.0279 1.0275 −0.000289

[0058] Temperature compensation was achieved by Equation III below.

[H.sub.2SO.sub.4]=Offset+Temp.Coefficient×[Temperature]+Cu Coefficient×[Cu]+Density Slope×[Density]  (III)

[0059] The coefficients for Equation III are provided in Tables 5A and 5B.

TABLE-US-00005 TABLE 5A Density Slope Temp Corr Coefficient Cu Corr Coefficient Offset 1540.851 0.442885 −3.8843812 −1547.56

TABLE-US-00006 TABLE 5B Density Slope Temp Slope Cu Slope Offset 1540.851 0.442885 −3.88438 −1547.56

[0060] Data following temperature compensation is provided in Table 7 below.

TABLE-US-00007 TABLE 7 Measured H.sub.2SO.sub.4 (g/L) (at certain temperature) Cu H.sub.2SO.sub.4 20° 21° 22° 23° 24° 25° Sample (g/L) (g/L) C. C. C. C. C. C. LOW 3 8 7.91 7.89 8.03 8.01 7.99 7.97 TGT 5 10 10.00 10.14 10.12 10.10 10.08 10.06 HIGH 10 12 12.00 12.14 11.96 11.94 11.92 11.90 DS High 3 12 11.92 11.90 12.03 12.01 12.00 11.98 DS Low 10 8 7.99 7.98 7.96 8.09 8.07 7.90

[0061] The results demonstrating the accuracy between the measured sulfuric acid (H.sub.2SO.sub.4) concentration with temperature compensation and actual sulfuric acid (H.sub.2SO.sub.4) concentration is provided in Table 8 below. Accuracy (i.e., absolute analytical error)<0.14 g/L was demonstrated.

TABLE-US-00008 TABLE 8 g/L Avg abs error 0.06 Max error 0.14

[0062] Other temperature coefficient equations can be used, for example, Equation IV provided below.

ρ1=ρ0/(1+β(t1−t0))   (IV) [0063] β—volumetric temperature coefficient [0064] t.sub.1—measured temperature [0065] t.sub.0—reference temperature [0066] ρ.sub.1—measured density [0067] ρ.sub.0—density at reference temperature

[0068] The description herein merely illustrates the principles of the disclosed subject matter. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. Accordingly, the disclosure herein is intended to be illustrative, but not limiting, of the scope of the disclosed subject matter. Moreover, the principles of the disclosed subject matter can be implemented in various configurations and are not intended to be limited in any way to the specific embodiments presented herein.

[0069] In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having other combinations of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. The foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.

[0070] It will be apparent to those skilled in the art that various modifications and variations can be made in the systems and methods of the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.