US20150308009A1

US20150308009A1 - Phosphorous-containing copper anode for electrolytic copper plating, method for manufacturing same, and electrolytic copper plating method

Info

Publication number: US20150308009A1
Application number: US13/521,584
Authority: US
Inventors: Kiyotaka Nakaya
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 2010-01-12
Filing date: 2011-01-07
Publication date: 2015-10-29
Also published as: CN102713022B; JP5499933B2; TW201139748A; WO2011086978A1; TWI522497B; KR20120123272A; CN102713022A; JP2011162875A

Abstract

Provided are a phosphorous-containing copper anode for electrolytic copper plating, a method for manufacturing the same, and an electrolytic copper plating method using the phosphorous-containing copper anode. The phosphorous-containing copper anode obtains a crystal grain boundary structure having a special grain boundary ratio Lσ_N/L_Nof 0.4 or more. L_Nis a unit total special grain boundary length corresponding to a unit area of 1 mm²obtained by converting a total grain boundary length L. Lσ_Nis a unit total special boundary length corresponding to a unit area of 1 mm²obtained by converting a total special grain boundary length Lσ. By having the configuration described above, a black film is formed evenly on the copper anode at the early stage of the electrolytic copper plating. Plating defect can be reduced by preventing the black film being fallen.

Description

TECHNICAL FIELD

The present invention relates to a phosphorous-containing copper anode for electrolytic copper plating, a method for manufacturing the phosphorous-containing copper anode, and an electrolytic copper plating method using the phosphorous-containing copper anode. According to the phosphorous-containing copper anode, the method for manufacturing the copper anode, and the electrolytic copper plating method, formation of the anode slime from the phosphorous-containing copper anode can be suppressed during electrolytic copper plating on a semiconductor wafer or the like, for example. Also, contamination on a cathode surface made of the semiconductor wafer or the like and formation of plating defects such as the nodular deposit or the like can be prevented.
The present application claims priority on the basis of Japanese Patent Application No. 2010-003718, filed in Japan on Jan. 12, 2010, and Japanese Patent Application No. 2010-141721, filed in Japan on Jun. 22, 2010, the contents of which are incorporated herein by reference.

BACKGROUND ART

Electrolytic copper plating has been conventionally carried out using electrolytic copper or oxygen-free copper for the anodic electrode during electrolytic copper plating. However, this method has the problems of being susceptible to the generation of a large amount of anode slime. In addition, plating defects are formed on the material to be plated due to the anode slime.
In order to solve these problems, electrolytic copper plating has come to be carried out using a phosphorous-containing copper for the anodic electrode.
According to electrolytic copper plating using a phosphorous-containing copper anode, a black film composed mainly of copper oxide, copper powder and the like is formed on the anode surface during electrolysis, reducing the formation of anode slime. As a result, the occurrence of plating defects are reduced. However, in the case where fine copper wirings are formed on a semiconductor wafer, for example, contamination on the surface of the semiconductor wafer and the occurrence of nodules and other plating defects cannot be adequately prevented even by the electrolytic copper plating using the phosphorous-containing copper as an anode.
Therefore, an electrolytic copper plating using a pure copper anode, in which the oxygen content in the anode and the grain size of the anode electrode are defined (see Patent Document 1), and an electrolytic copper plating using a phosphorous-containing copper anode, in which the phosphorous content in the anode and the grain size of the anode electrode are defined (see Patent Documents 2 and 3), have been developed in recent years, in the attempt of reducing the anode formation and preventing the plating defect formation.

RELATED ART DOCUMENTS

Patent Documents

Patent Document 1: Japanese Patent (Granted) Publication No. 4011336
Patent Document 2: Japanese Patent (Granted) Publication No. 4034095
Patent Document 3: Japanese Patent (Granted) Publication No. 4076751

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

During conventional electrolytic copper plating using a phosphorous-containing copper anode, a black film mainly composed of copper powder, copper oxide, copper phosphide, copper chloride, or the like is formed on the surface of the phosphorous-containing copper anode as electrolysis progresses. As electrolysis progresses further, this black film grows in thickness, falls off from the surface of the phosphorous-containing copper anode, and causes the formation of the anode slime. In addition, the black film that has fallen off is dispersed in the plating bath and adheres to the surface of the material to be plated (cathode surface), thereby causing contamination of the surface of the material to be plated such as a semiconductor wafer and formation of plating defects such as the nodular deposit.
Therefore, an object of the present invention is to provide a phosphorous-containing copper anode for electrolytic copper plating capable of suppressing the anode slime formation, and preventing contamination of the surface of the plated material such as a semiconductor wafer and formation of plating defects such as the nodular deposit even in the case where, for example, fine copper wirings are formed on the semiconductor wafer by electrolytic copper plating.
In addition, another object of the present invention is to provide a novel method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating capable of reducing the formation of anode slime, and preventing contamination of the surface of the plated material and formation of plating defects such as the nodular deposit.
Moreover, still another object of the present invention is to provide an electrolytic copper plating method capable of reducing the anode slime formation, and preventing contamination of the surface of the plated material and formation of plating defects such as the nodular deposit.

Means for Solving the Problems

The inventors of the present invention obtained the following findings as a result of conducting extensive studies on the correlation between the structure of the crystal grain boundary of a phosphorous-containing copper anode, and the anode slime formation and formation of the plating defects during electrolytic copper plating.
In the case of conventional electrolytic copper plating using a phosphorous-containing copper anode, the growth of a thick black film and the falling of the black film as electrolysis progresses is due to the formation of metal copper and copper oxide by, for example, a disproportionation reaction of monovalent copper as indicated below.
2Cu⁺→Cu(powder)+Cu²⁺
Since the properties of the black film formed during the early stages of electrolysis influence to the plating later, it is important to form a uniform black film that produces few monovalent copper ions (Cu⁺) in the early stages of electrolysis. From this viewpoint, a study was conducted on the various conditions under which a uniform black film is formed that produces few monovalent copper ions (Cu⁺) in the early stages of electrolysis. As a result, it was found that the structure of crystal grain boundary of the phosphorous-containing copper anode has a considerable effect on the properties of the black film formed during the early stages of electrolysis.
Namely, the inventors of the present invention found that, in a phosphorous-containing copper anode for electrolytic copper plating, a black film can be uniformly formed over the entire anode during the early stages of electrolysis by having a unit total special grain boundary length Lσ_N, which is a converted value corresponding to a unit area of 1 mm²from the total special crystal grain boundary length Lσ to be higher than a unit total grain boundary length Lσ, which is a converted value corresponding to a unit area of 1 mm²from the total crystal grain boundary length L, in a specific ratio (Lσ_N/L_N≧0.4) by increasing the ratio of a so-called “special grain boundary” among the grain boundaries on the surface of the phosphorous-containing anode. As a result, it was found that the black film can be prevented from falling off, and the formation of plating defects due to the anode slime can be considerably reduced.
Here, the special grain boundary is the corresponding interface having the E value of 3≦Σ≦29, the Σ value being defined based on “Trans. Met. Soc. AIME, 185, 501 (1949)”. The special grain boundary is also defined as a crystal grain boundary in which the intrinsic corresponding site lattice orientation defect Dq at the corresponding grain boundary as described in “Acta. Metallurgica Vol. 14, p. 1479 (1966)” satisfies the following relationship, D_q15°/Σ^1/2.
In addition, the inventors of the present invention found that, during the manufacturing of a phosphorous-containing copper anode for electrolytic copper plating, by carrying out recrystallization heat treatment over a predetermined temperature range (350° C. to 900° C.) after imparting machining stress by carrying out prescribed cold working and hot working, a phosphorous-containing copper anode for electrolytic copper plating can be manufactured having a high formation rate of the so-called special grain boundary among the crystal grain boundaries present on the surface of the copper anode (Lσ_N/L_N≧0.4).
Moreover, the inventors of the present invention found that, in the case of plating copper onto a semiconductor wafer, for example, using a phosphorous-containing copper anode having a high special grain boundary formation ratio (Lσ_N/L_N≧0.4), fine copper wirings can be formed that is free of contamination of the surface of the semiconductor wafer and formation of plating defects such as nodular deposits.
A first aspect of the present invention is a phosphorous-containing copper anode for electrolytic copper plating including a grain boundary structure satisfying the following relationship: Lσ_N/L_N≧0.4, wherein (a) a total crystal grain boundary length L within a measurement area being measured with a scanning electron microscope by irradiating an electron beam to individual crystal grains on a surface of the anode under a condition that an interface between crystal grains laying side-by-side having a mutual crystal orientation difference of 15° or more is defined as the crystal grain boundary, and a unit total crystal grain boundary length L_Nbeing a converted value corresponding to a unit area of 1 mm²from the total crystal grain boundary length L; (b) locations of special crystal grain boundaries, where a special grain boundary is formed between an interface between crystal grains laying side-by-side, being determined, a total special crystal grain boundary length Lσ of the special crystal grain boundaries being measured with a scanning electron microscope by irradiating an electron beam to individual crystal grains on the surface of the anode, and a unit total special crystal grain boundary length Lσ_Nbeing a converted value corresponding to a unit area of 1 mm²from the total special crystal grain boundary length Lσ; and (c) Lσ_N/L_Nbeing a ratio of Lσ_N, which is the measured unit total special crystal grain boundary length, to L_N, which is the measured unit total crystal grain boundary length.
The phosphorous-containing copper anode for electrolytic copper plating of the first aspect of the present invention may contain 100 ppm to 800 ppm of phosphorous in terms of percentage by mass.
In the phosphorous-containing copper anode for electrolytic copper plating of the first aspect of the present invention, the average diameter of crystal grain may be 3 μm to 1000 μm.
A second aspect of the present invention is a method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating of the first aspect of the present invention including the steps of: imparting machining stress by machining the phosphorous-containing copper anode for electrolytic copper plating; and performing recrystallization heat treatment at 350° C. to 900° C. after the step of imparting machining stress, wherein the special grain boundary length ratio Lσ_N/L_Nis 0.4 or more.
In the method for manufacturing a phosphorous-containing copper anode for electrolytic copper plating of the second aspect of the present invention, the machining may be carried out by either cold working or hot working at least.
In the method for manufacturing a phosphorous-containing copper anode for electrolytic copper plating of the second aspect of the present invention, a process having the cold working and the recrystallization heat treatment, a process having the hot working and the recrystallization heat treatment, or a combination of the two processes may be carried out repeatedly until the special grain boundary length ratio Lσ_N/L_Nbecomes 0.4 or more.
In the method for manufacturing a phosphorous-containing copper anode for electrolytic copper plating of the second aspect of the present invention, the step of imparting machining stress may be carried out by hot working at a rolling reduction of 5% to 80% within a temperature range of 400° C. to 900° C., and the step of performing recrystallization heat treatment may be carried out by statically holding the phosphorous-containing copper anode for 3 to 300 seconds free of imparting the machining stress after the step of imparting machining stress.
In the method for manufacturing a phosphorous-containing copper anode for electrolytic copper plating of the second aspect of the present invention, the step of imparting machining stress may be carried out by cold working at a rolling reduction of 5% to 80%, and the step of performing recrystallization heat treatment may be carried out by heating the anode within a temperature range of 350° C. to 900° C. and statically holding the phosphorous-containing copper anode for 5 minutes to 5 hours free of imparting the machining stress after the step of imparting machining stress.
An electrolytic copper plating method of a third aspect of the present invention is an electrolytic copper plating method in which the phosphorous-containing copper anode of the first aspect of the present invention. The phosphorous-containing copper anode of the first aspect of the present invention is the phosphorous-containing copper anode for electrolytic copper plating including a grain boundary structure satisfying the following relationship: Lσ_N/L_N≧0.4, wherein (a) a total crystal grain boundary length L within a measurement area being measured with a scanning electron microscope by irradiating an electron beam to individual crystal grains on a surface of the anode under a condition that an interface between crystal grains laying side-by-side having a mutual crystal orientation difference of 15° or more is defined as the crystal grain boundary, and a unit total crystal grain boundary length L_Nbeing a converted value corresponding to a unit area of 1 mm²from the total crystal grain boundary length L; (b) locations of special crystal grain boundaries, where a special grain boundary is formed between an interface between crystal grains laying side-by-side, being determined, a total special crystal grain boundary length Lσ of the special crystal grain boundaries being measured with a scanning electron microscope by irradiating an electron beam to individual crystal grains on the surface of the anode, and a unit total special crystal grain boundary length Lσ_Nbeing a converted value corresponding to a unit area of 1 mm²from the total special crystal grain boundary length Lσ; and (c) Lσ_N/L_Nbeing a ratio of Lσ_N, which is the measured unit total special crystal grain boundary length, to L_N, which is the measured unit total crystal grain boundary length.

Effects of the Invention

According to the phosphorous-containing copper anode for electrolytic copper plating, the method for manufacturing the same, and the electrolytic copper plating method of the present invention, the anode slime formation can be suppressed, the contamination at the surface of the plated material, such as the semiconductor wafer or the like, due to the slime can be prevented, and formation of plating defects, such as the nodular deposits, can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

(a) to (d) of FIG. 1 is a schematic drawing showing the progression of the dissolving of an anode surface by electrolysis. (a) of FIG. 1 indicates the initial state at the start of electrolysis. (b) of FIG. 1 indicates the state at the start of selective dissolution of a grain boundary after a fixed amount of time has elapsed from the start of electrolysis. (c) of FIG. 1 indicates the state where current density disproportionation by a shape factor occurs due to a selective dissolving of the grain boundary, and an accelerated selective dissolving of the grain boundary is occurring consequently. (d) of FIG. 1 indicates the state of separation and falling off of a black film (surface oxide film) formed on the anode surface along with undissolved crystal grains due to dissolution of the grain boundary.

FIG. 2 shows the results of EBSD analysis of the anode 3 of the present invention in which thick lines indicate special grain boundaries and narrow lines indicate ordinary grain boundaries (same as FIGS. 3 to 9).

FIG. 3 shows the results of EBSD analysis the anode 7 of the present invention.

FIG. 4 shows the results of EBSD analysis of the anode 11 of the present invention.

FIG. 5 shows the results of EBSD analysis of the anode 13 of the present invention.

FIG. 6 shows the results of EBSD analysis of the anode 21 of the present invention.

FIG. 7 shows the results of EBSD analysis of the anode 27 of the present invention.

FIG. 8 shows the results of EBSD analysis of the anode 4 of a comparative example.

FIG. 9 shows the results of EBSD analysis of the anode 6 of a comparative example.

BEST MODE FOR CARRYING OUT THE INVENTION

The inventors of the present invention obtained the following findings as a result of investigating the progression of dissolution of the surface of a phosphorous-containing anode during electrolytic copper plating.
As shown in the schematic drawings of (a) to (d) of FIG. 1, during the initial state at the start of electrolysis (FIG. 1( a)), there are no major changes in the anode surface. However, in a state when a fixed amount of time has elapsed from the start of electrolysis (FIG. 1( b)), crystal grains on the anode surface begin to be selectively dissolved from chemically unstable grain boundaries within the grains. In a state in which electrolysis has progressed further (FIG. 1( c)), the current density disproportionation by a shape factor occurs due to a selective dissolving of the grain boundary, and an accelerated selective dissolving of the grain boundary is occurring consequently. In a state in which electrolysis has progressed further (FIG. 1( d)), due to the progression of dissolution of grain boundaries, a black film (surface oxide film) formed on the anode surface along with undissolved crystal grains separate and fall off, thereby causing the formation of anode slime and the occurrence of plating defects. In addition, a newly formed surface is formed on those portions of the anode where undissolved crystal grains have separated and fallen off, thereby causing the occurrence of voltage fluctuations and making it difficult to carry out stable electrolysis operation.
The inventors of the present invention further conducted research on an anode that prevents the occurrence of selective dissolution (non-uniform dissolution) from grain boundaries as the duration of electrolysis progresses for use as a phosphorous-containing copper anode for electrolytic copper plating. The following findings were obtained as a result of that research. The ratio of the special grain boundary, which is stable crystal-structurally and chemically, is increased in a case where the anode has a specific crystal grain structure. The crystal grain structure satisfies the relationship Lσ_N/L_N≧0.4. Lσ_N/L_Nis a rate of Lσ_N, which is a converted value corresponding to a unit area of 1 mm²from the total special crystal grain boundary length Lσ, which is a converted value corresponding to a unit area of 1 mm²from the total crystal grain boundary length L. Lσ is the total length of the special crystal grain boundary, which is defined the description above (the corresponding interface having the E value of 3≦Σ≦29, and the intrinsic corresponding site lattice orientation defect Dq of the corresponding interface satisfying the relationship D_q≦15°/Σ^1/2), on the phosphorous-containing copper anode. When the proportion of these special grain boundaries increases, the occurrence of the aforementioned selective dissolution of grain boundaries is reduced, the separation and falling off of undissolved crystal grains are suppressed, and a uniform black film is formed. As a result, the anode slime formation is reduced, and at the same time, the formation of the plating defect due to the slime is reduced.
The total crystal grain boundary length L can be determined using a scanning electron microscope. First, individual crystal grains of the anode surface are irradiated with an electron beam, and crystal orientation data is obtained from the resulting electron backscatter diffraction pattern. Next, the total grain boundary length L of crystal grains within the measuring range is determined under a condition that an interface between crystal grains laying side-by-side having a mutual crystal orientation difference of 15° or more is defined as the crystal grain boundary
Since selective dissolution of crystal grain boundaries during electrolysis cannot be suppressed, a uniform black film cannot be formed, the formation of anode slime cannot be reduced, and the formation of plating defects due to the anode slime cannot be reduced if the special grain boundary length ratio Lσ_N/L_Nis such that Lσ_N/L_N<0.4, the special grain boundary length ratio Lσ_N/L_Nwas designated to be 0.4 or higher.
The phosphorous-containing copper anode of the present invention preferably contains 100 ppm to 800 ppm of phosphorous in terms of percentage by mass. If the phosphorous content deviates from this range, a stable black film is not formed resulting in the formation of the anode slime.
In addition, the average diameter of the crystal grains of the phosphorous-containing copper anode of the present invention (as determined by counting twin crystals as crystal grains) is preferably 3 μm to 1000 μm. If the average diameter of the crystal grains deviates from this range, a large amount of anode slime is formed.
A phosphorous-containing copper anode having a crystal grain boundary structure in which the special grain boundary length ratio Lσ_N/L_Nof the unit total special boundary length Lσ_N, determined by converting a total special grain boundary length Lσ of the special grain boundaries to a value per unit area of 1 mm², to unit total grain boundary length L_N, determined by converting the total crystal grain boundary length L of the crystal grain boundaries to a value per unit area of 1 mm², satisfies the relationship of Lσ_N/L_N≧0.4 can be manufactured by imparting mechanical stress by carrying out working (cold working and/or hot working) when manufacturing the phosphorous-containing copper anode for electrolytic plating, followed by carrying out recrystallization heat treatment at 350° C. to 900° C.
In a specific example of manufacturing referred to as Manufacturing Example (A), a method for manufacturing a phosphorous-containing copper anode having the crystal grain boundary structure satisfying the relationship Lσ_N/L_N≧0.4 can be exemplified. In the method, first, hot working is performed on phosphorous-containing copper for electrolytic plating at a rolling reduction of 5% to 80% within a temperature range of 400° C. to 900° C. Then, and then recrystallization heat treatment is carried out by statically holding the copper anode free of imparting mechanical stress for 3 seconds to 300 seconds.
In addition, in another example of manufacturing referred to as Manufacturing Example (B), another method for manufacturing a phosphorous-containing copper anode having the crystal grain boundary structure satisfying the relationship Lσ_N/L_N≧0.4 can be exemplified. In the method, first, cool working is performed on phosphorous-containing copper for electrolytic plating at a rolling reduction of 5% to 80% within a temperature range of 350° C. to 900° C. Then, and then recrystallization heat treatment is carried out by statically holding the copper anode free of imparting mechanical stress for 5 minutes to 5 hours.
As a result of imparting stress by the hot working or the cold working at the specific rolling reduction as described in the aforementioned Manufacturing Examples (A) and (B), followed by recrystallization in a state of statically holding free of imparting stress within the recrystallization temperature ranges, the formation of special grain boundaries can be promoted. Consequently, the ratio of the unit total special grain boundary length Lσ_Ncan be enhanced, and the value of the special grain boundary length ratio Lσ_N/L_Ncan be adjusted to 0.4 or more.
In addition, a crystal grain boundary structure may also be obtained in which Lσ_N/L_N≧0.4 by repeatedly carrying out the aforementioned cold working or hot working as well as the recrystallization heat treatment multiple times.
As a result of carrying out electrolytic plating using as the anode for electrolytic plating a phosphorous-containing copper anode having a crystal grain boundary structure in which the special grain boundary length ratio Lσ_N/L_Nof the unit total special boundary length Lσ_Nof crystal grain boundaries to the unit total grain boundary length L_Nof crystal grain boundaries satisfies the relationship of Lσ_N/L_N≧0.4, the anode slime formation can be reduced. Moreover, in the case where copper plating is formed on the material to be plated, such as a surface of semiconductor wafer, fine copper wirings that is free of the contamination and the formation of plating defect can be formed on the surface of the semiconductor wafer
Locating the crystal grain boundary on the phosphorous-containing copper anode and the measurement of the unit total grain boundary length L_Nare carried out as explained below. First, an electron beam is irradiated to individual crystal grains on the anode surface with a scanning electron microscope. Then, an interface between crystal grains laying side-by-side having mutual crystal orientation difference of 15° or more is defined as the crystal grain boundary based on the crystal orientation data obtained from the acquired electron backscatter diffraction pattern. Then, the total crystal grain boundary length L within the measured area is measured. Then, the total crystal grain boundary length L is divided by the measured area, converting the value to the unit total grain boundary length L_Ncorresponding to a unit area of 1 mm². Similarly, locating the special crystal grain boundary on the phosphorous-containing copper anode and the measurement of the unit total special grain boundary length Lσ_Nare carried out as explained below. First, an electron beam is irradiated to individual crystal grains on the anode surface with a scanning electron microscope. Then, an interface between crystal grains laying side-by-side having the special crystal grain boundary is located. Then, the total special crystal grain boundary length Lσ within the measured area is measured. Then, the total special crystal grain boundary length Lσ is divided by the measured area, converting the value to the unit total special grain boundary length Lσ_Ncorresponding to a unit area of 1 mm².
More specifically, crystal grain boundaries and special grain boundaries can be located and their lengths can be calculated with an EBSD measuring device that uses a field emission-scanning electron microscope (S4300-SE manufactured by Hitachi, Ltd., OIM Data Collection manufactured by EDAX/TSL Inc.) and analytical software (OIM Data Analysis Ver. 5.2 available from EDAX/TSL Inc.).
In addition, measurement of average diameter of the crystal grains of the phosphorous-containing copper anode (as determined by counting twin crystals as crystal grains) can be carried out by determining crystal grain boundaries from results obtained with the aforementioned EBSD measuring device and analytical software, calculating the number of crystal grains within the measured area, calculating the crystal grain area by dividing the area of the measured area by the number of the crystal grains, and determining the average diameter of the crystal grains by converting on the basis of a circle.
The following provides a more detailed explanation of the present invention through examples thereof.

Examples

Phosphorous-containing copper anodes (referred to as anodes of the present invention) 1 to 28 having the prescribed sizes shown in Table 3 were manufactured. The anodes of the present invention 1 to 28 were manufactured by carrying out hot working (temperature, processing method, processing rate), cold working (processing method, processing rate) and recrystallization heat treatment (temperature, time) under the conditions shown in Table 1, or repeating these processes on recrystallized materials or cast materials of phosphorous-containing copper containing the prescribed amounts of P (phosphorous) shown in Table 1. After the recrystallization heat treatment, the anodes 1 to 28 of the present invention were water-cooled. The recrystallized material or the cast materials have a total content of unavoidable impurities in the form of Pb, Fe, Sn, Zn, Mn, Ni and Ag of 0.002% by mass or less.
In the examples shown in Table 1, repetitions of a process having hot working and recrystallization heat treatment, a process having cold working and recrystallization heat treatment, or the combination of the two processes performed in an identical condition are shown. However, it is not necessary to repeat the processes in the identical condition, and the processes can be repeated in different conditions (processing temperature, processing method, processing rate, holding temperature, holding time), as long as it is within the condition range defined by each of the claims.
The crystal grain boundaries and special grain boundaries of the anodes of the present invention manufactured in the manner describe above were identified with the aforementioned EBSD measuring device (S4300-SE manufactured by Hitachi, Ltd., OIM Data Collection manufactured by EDAX/TSL Inc.) and analytical software (OIM Data Analysis Ver. 5.2 available from EDAX/TSL Inc.), followed by determination of the unit total grain boundary length L_Nand the unit total special grain boundary length Lσ.
The values of L_N, Lσ_Nand special grain boundary length ratio Lσ_N/L_Nare shown in Table 3.
The values of average crystal grain diameter determined from results obtained with the aforementioned EBSD measuring device and analytical software are also shown in Table 3.
In addition, results of EBSD analysis for anodes 3, 7, 11, 13, 21 and 27 of the present invention are respectively shown in FIGS. 2 to 7.
Phosphorous-containing copper anodes 1 to 8 of the comparative examples shown in Table 4 (to be referred to as comparative examples anodes) were manufactured for comparative purposes by carrying out hot working (temperature, processing method, processing rate), cold working (processing method, processing rate) and recrystallization heat treatment (temperature, time) on phosphorous-containing copper anode materials fabricated in the manner previously described under the conditions shown in Table 2 (with at least one of these conditions being conditions outside the scope of the present invention).
In addition, the unit total grain boundary length L_N, the unit total special grain boundary length Lσ_N, the special grain boundary length ratio Lσ_N/L_N, and the average diameter of the crystal grains were determined in the same manner as in the examples for the comparative example anodes manufactured as described above.
Those values are shown in Table 4.
In addition, results of EBSD analysis for comparative example anodes 4 and 6 are respectively shown in FIGS. 8 and 9.

TABLE 1

		Recrystallization		Recrystallization
P	Hot Working	Treatment	Cold Working	Treatment

content

Starting

Temp.

Processing Method/

Temp.

Processing Method/

Temp.

Re-

No.

(wt %)

material

(° C.)

conditions

(° C.)

Time

Repeat

conditions

(° C.)

Time

peat

1	0.03	Recryst.	500	Rolling reduction: 30%	500	1	min.	2	—	—	—	—
2	0.02	Cast	550	Rolling reduction: 6%	550	10	sec.	10	—	—	—	—
3	0.04	Cast	750	Rolling reduction: 20%	750	20	sec.	6	—	—	—	—
4	0.04	Cast	900	Rolling reduction: 20%	900	30	sec.	3	—	—	—	—
5	0.04	Cast	460	Rolling reduction: 15%	460	1	min.	6	—	—	—	—
6	0.04	Cast	700	Forging, ratio: 3.0	700	10	min.	—	—	—	—	—
7	0.05	Recryst.	800	Forging, ratio: 3.0	800	5	min.	5	—	—	—	—
8	0.08	Recryst.	900	Extrusion, area reduction	900	5	sec.	—	—	—	—	—
				rate: 70%
9	0.04	Cast	800	Extrusion, area reduction	800	10	sec.	—	—	—	—	—
				rate: 90%

10	0.06	Recryst.	—	—	—	—	—	Rolling reduction: 80%	500	1.5	hr.	—
11	0.03	Recryst.	—	—	—	—	—	Rolling reduction: 35%	450	1	hr.	2
12	0.04	Recryst.	—	—	—	—	—	Rolling reduction: 15%	550	15	min.	5
13	0.05	Recryst.	—	—	—	—	—	Extraction, area reduction	800	2	hr.	—
								rate: 65%
14	0.01	Recryst.	—	—	—	—	—	Extraction, area reduction	650	20	min.	3
								rate: 25%
15	0.03	Recryst.	—	—	—	—	—	Forging, ratio: 2.0	500	2	hr.	—
16	0.06	Recryst.	—	—	—	—	—	Forging, ratio: 1.2	750	10	min.	3
17	0.04	Cast	—	—	—	—	—	Forging, ratio: 3.0	400	2	hr.	3
18	0.04	Cast	—	—	—	—	—	Forging, ratio: 4.0	350	1	hr.	4

19	0.03	Cast	800	Rolling reduction: 25%	800	30	sec.	3	Rolling reduction: 40%	450	30	min.	2
20	0.05	Cast	650	Rolling reduction: 15%	650	20	sec.	7	Rolling reduction: 15%	500	1	hr.	—
21	0.02	Recryst.	400	Rolling reduction: 20%	400	10	sec.	2	Rolling reduction: 20%	850	1	hr.	—
22	0.04	Cast	460	Rolling reduction: 80%	460	1	min.	—	Rolling reduction: 40%	400	2	hr.	—
23	0.02	Cast	700	Forging, ratio: 2.5	700	3	min.	3	Rolling reduction: 30%	350	1.5	hr.	—
24	0.01	Cast	800	Forging, ratio: 3.0	700	3	min.	3	Rolling reduction: 10%	850	2	hr.	—
25	0.04	Recryst.	650	Forging, ratio: 2.0	650	1	min.	—	Forging, ratio: 1.2	900	1.5	hr.	—
26	0.04	Cast	700	Forging, ratio: 2.5	700	10	min.	—	Forging, ratio: 1.5	500	5	min.	—
27	0.06	Cast	850	Extrusion, area reduction	850	5	sec.	—	Rolling reduction: 35%	600	1	hr.	—
				rate: 50%
28	0.04	Cast	800	Extrusion, area reduction	800	10	sec.	—	Rolling reduction: 40%	400	2	hr.	—
				rate: 80%

TABLE 2

	Recrystallization		Recrystallization
Hot Working	Treatment	Cold Working	Treatment

P content

Starting

Temp.

Processing Method/

Temp.

Processing Method/

Temp.

No.

(wt %)

material

(° C.)

conditions

(° C.)

Time

Repeat

conditions

(° C.)

Time

Repeat

1	0.005	Recryst.	—	—	—	—	—	Rolling reduction: 80%	950	2 hr.	—
2	0.1	Recryst.	—	—	—	—	—	Rolling reduction: 75%	250	2 hr.	—
3	0.04	Recryst.	—	—	—	—	—	Extrusion, area reduction	—	—	—
								rate: 70%
4	0.04	Recryst.	—	—	—	—	—	Forging, ratio: 2.0	200	30 min.	—
5	0.08	Cast	—	—	—	—	—	Rolling reduction: 95%	250	10 min.	—
6	0.03	Cast	—	—	—	—	—	Rolling reduction: 75%	350	3 min.	—
7	0.03	Recryst.	200	Rolling reduction: 35%	—	—	—	—	—	—	—
8	0.03	Recryst.	1000	Rolling reduction: 15%	1000	1 hr.	—	—	—	—	—

TABLE 3

	L_N	L_σN	L_σN/L_N×	Avg. diameter of
No.	(mm/mm²)	(mm/mm²)	100 (%)	crystal grains (nm)

1	186.3	109.1	57.2	12.3
2	150.7	97.1	61.3	14.2
3	118.7	77.3	65.1	13.3
4	51.8	30.8	57.7	44.2
5	134.0	70.8	51.7	17.3
6	91.3	53.3	58.6	26.3
7	127.7	88.6	69.4	15.0
8	80.0	35.0	44.0	26.3
9	106.4	52.7	47.2	18.5
10	104.7	66.3	62.2	20.6
11	136.3	99.9	73.3	12.4
12	84.8	61.7	75.8	26.4
13	22.5	14.8	65.6	88.3
14	65.8	37.2	55.3	32.5
15	121.3	77.2	60.8	17.8
16	43.6	31.4	73.4	44.5
17	258.1	119.3	45.7	9.6
18	202.1	107.1	53.5	10.9
19	166.4	111.4	63.6	14.3
20	79.8	55.1	70.6	28.9
21	19.6	11.5	58.6	107.3
22	194.4	123.6	62.3	10.9
23	224.8	145.5	66.0	10.0
24	8.7	4.2	48.9	278.3
25	4.2	2.8	63.3	485.7
26	55.6	34.0	61.6	38.4
27	64.1	46.5	72.6	31.3
28	208.8	136.7	64.1	10.2

TABLE 4

	L_N	L_σN	L_σN/L_N×	Avg. diameter of
No.	(mm/mm²)	(mm/mm²)	100 (%)	crystal grains (nm)

1	1.7	0.8	37.9	1271
2	27.4	8.6	31.4	83.6
3	431.8	41.0	10.1	5.2
4	183.9	47.3	25.7	7.5
5	131.5	26.6	20.2	17.3
6	137.9	48.4	35.1	17.5
7	316.1	45.0	15.2	6.5
8	1.3	0.5	37.1	1691

Electrolytic copper plating was carried out under the conditions indicated below on five semiconductor wafers using the anodes 1 to 28 of the present invention and the comparative example anodes 1 to 8 (each having an anode surface area of 530 cm²) as anodes and using the semiconductor wafers as cathodes.
Plating solution: CuSO₄.5H₂O: 200 g/L

- H₂SO₄: 50 g/L
- Cl⁻: 50 ppm
- Additive: Polyethylene glycol: 400 ppm
  - (molecular weight: 6000)

Plating conditions: Solution temperature: 25° C.

- Cathode current density: 2 A/dm²
- Plating time: 1 hr/wafer

The amount of anode slime formed from the start of electrolytic copper plating to completion of electrolytic copper plating of the five semiconductor wavers (5 hours) was measured for the aforementioned anodes 1 to 28 of the present invention and the comparative example anodes 1 to 8.
In addition, the surfaces of the plated semiconductor wafers were observed with a light microscope, and the number of nodular defects formed on the surface of the semiconductor wafers having a height of 5 μm or more was counted.
These measurement results are shown in Tables 5 and 6.

	TABLE 5

	No. of defects (no./wafer)

1st

2nd

3rd

4th

5th

Amt. of anode

Type	wafer	wafer	wafer	wafer	wafer	slime formed

Anodes of	1	0	0	0	1	1	<10
Present	2	0	0	0	0	0	<10
Invention	3	0	0	0	1	0	<10
	4	0	0	0	0	1	<10
	5	0	0	0	1	1	<10
	6	0	0	0	0	1	<10
	7	0	0	0	0	0	<10
	8	0	0	0	1	1	<10
	9	0	0	0	0	1	<10
	10	0	0	0	0	1	<10
	11	0	0	0	0	0	<10
	12	0	0	0	0	0	<10
	13	0	0	0	1	1	<10
	14	0	0	0	0	1	<10
	15	0	0	0	0	1	<10
	16	0	0	0	1	0	<10
	17	0	0	0	1	1	<10
	18	0	0	0	0	1	<10
	19	0	0	0	0	0	<10
	20	0	0	0	0	0	<10
	21	0	0	0	1	1	<10
	22	0	0	0	0	1	<10
	23	0	0	0	0	1	<10
	24	0	0	0	1	1	<10
	25	0	0	0	1	1	<10
	26	0	0	0	1	0	<10
	27	0	0	0	0	0	<10
	28	0	0	0	0	1	<10

Note:
The amount of anode slime formed indicates the total amount formed at completion of plating five wafers.

	TABLE 6

	No. of defects (no./wafer)

	1st	2nd	3rd	4th	5th	Amt. of anode
Type	wafer	wafer	wafer	wafer	wafer	slime formed

Anodes of	1	0	1	2	3	5	73
Present	2	0	0	1	3	2	57
Invention	3	0	2	2	2	4	75
	4	0	0	2	3	3	62
	5	0	2	0	3	4	68
	6	0	1	0	2	4	60
	7	0	2	2	3	3	72
	8	0	1	2	3	4	73

Note:
The amount of anode slime formed indicates the total amount formed at completion of plating five wafers.

Based on the results shown in Tables 5 and 6, followings were demonstrated. According to the phosphorous-containing copper anode for electrolytic copper plating, the method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating, and the electrolytic copper plating method of the present invention, for example even in the case where fine copper wirings are formed on a semiconductor wafer or the like, the anode slime formation can be suppressed. At the same time, the contamination on the surface of the plated material, such as the semiconductor wafer or the like, and the formation of plating defect, such as the nodular deposit or the like, can be prevented.
It was also demonstrated that in the comparative example anodes, in which the special grain boundary length ratio Lσ_N/L_Nwas less than 0.4, large amounts of anode slime were formed. Furthermore, there were large numbers of plating defects due to the anode slime.

INDUSTRIAL APPLICABILITY

As described above, the present invention has a significantly high industrial applicability, since it shows excellent effects of being able to suppress the anode slime formation and to prevent the formation of plating defect on the surface of a plated material in an electrolytic copper plating. Particularly, in the case where it is applied to formation of the fine copper wirings on a semiconductor wafer or the like, the contamination on the semiconductor wafer and formation of plating defect, such as the nodular deposit or the like, can be prevented.

Claims

1. A phosphorous-containing copper anode for electrolytic copper plating comprising a grain boundary structure satisfying the following relationship:

Lσ _N /L _N≧0.4, wherein

(a) a total crystal grain boundary length L within a measurement area being measured with a scanning electron microscope by irradiating an electron beam to individual crystal grains on a surface of the anode under a condition that an interface between crystal grains laying side-by-side having a mutual crystal orientation difference of 15° or more is defined as the crystal grain boundary, and a unit total crystal grain boundary length L_Nbeing a converted value corresponding to a unit area of 1 mm²from the total crystal grain boundary length L;

(b) locations of special crystal grain boundaries, where a special grain boundary is formed between an interface between crystal grains laying side-by-side, being determined, a total special crystal grain boundary length Lσ of the special crystal grain boundaries being measured with a scanning electron microscope by irradiating an electron beam to individual crystal grains on the surface of the anode, and a unit total special crystal grain boundary length Lσ_Nbeing a converted value corresponding to a unit area of 1 mm²from the total special crystal grain boundary length Lσ; and

(c) Lσ_N/L_Nbeing a ratio of Lσ_N, which is the measured unit total special crystal grain boundary length, to L_N, which is the measured unit total crystal grain boundary length.

2. The phosphorous-containing copper anode for electrolytic copper plating according to claim 1, wherein the phosphorous-containing copper anode contains 100 ppm to 800 ppm of phosphorous by mass.

3. The phosphorous-containing copper anode for electrolytic copper plating according to claim 1, wherein the average diameter of crystal grain is 3 μm to 1000 μm.

4. A method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating according to claim 1 comprising the steps of:

imparting machining stress by machining the phosphorous-containing copper anode for electrolytic copper plating; and

performing recrystallization heat treatment at 350° C. to 900° C. after the step of imparting machining stress, wherein

the special grain boundary length ratio Lσ_N/L_Nis 0.4 or more.

5. The method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating according to claim 4, wherein the machining is carried out by either cold working or hot working at least.

6. The method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating according to claim 4, wherein a process having the cold working and the recrystallization heat treatment, a process having the hot working and the recrystallization heat treatment, or a combination of the two processes is carried out repeatedly until the special grain boundary length ratio Lσ_N/L_Nbecomes 0.4 or more.

7. The method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating according to claim 4, wherein

the step of imparting machining stress is carried out by hot working at a rolling reduction of 5% to 80% within a temperature range of 400° C. to 900° C., and

the step of performing recrystallization heat treatment is carried out by statically holding the phosphorous-containing copper anode for 3 to 300 seconds free of imparting the machining stress after the step of imparting machining stress.

8. The method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating according to claim 4, wherein

the step of imparting machining stress is carried out by cold working at a rolling reduction of 5% to 80%, and

the step of performing recrystallization heat treatment is carried out by heating the anode within a temperature range of 350° C. to 900° C. and statically holding the phosphorous-containing copper anode for 5 minutes to 5 hours free of imparting the machining stress after the step of imparting machining stress.

9. An electrolytic copper plating method wherein the phosphorous-containing copper anode for electrolytic copper plating according to claim 1 is used.

10. The phosphorous-containing copper anode for electrolytic copper plating according to claim 2, wherein the average diameter of crystal grain is 3 μm to 1000 μm.

11. The method for manufacturing the phosphorous-containing copper anode for electrolytic copper plating according to claim 5, wherein a process having the cold working and the recrystallization heat treatment, a process having the hot working and the recrystallization heat treatment, or a combination of the two processes is carried out repeatedly until the special grain boundary length ratio Lσ_N/L_Nbecomes 0.4 or more.