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Journal of The Electrochemical Society, 155 7 H496-H503 2008
0013-4651/2008/155 7 /H496/8/$23.00 © The Electrochemical Society

Ultrathin CVD Cu Seed Layer Formation Using Copper Oxynitride Deposition and Room Temperature Remote Hydrogen Plasma Reduction
Hoon Kim, Harish B. Bhandari, Sheng Xu, and Roy G. Gordon*,z
Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA Cu seed layers for future interconnects must have conformal step coverage, smooth surface morphology, and strong adhesion. Conformal deposition had been achieved by chemical vapor deposition CVD , but CVD Cu ﬁlms have rough surfaces and poor adhesion. In this paper, conformal, smooth, adherent, continuous, and thin 9 nm Cu ﬁlms were made by CVD. CuON was deposited from a Cu-amidinate precursor, H2O, and NH3 at 140–180°C on Ru. Crystallites in the deposited ﬁlm have either a Cu2O or Cu3N structure depending on the ratio of H2O to NH3. As-deposited CuON ﬁlms have a smooth surface morphology 0.5 nm root-mean-square rms roughness and are highly conformal 95% step coverage in 40:1 aspect ratio holes . The CuON ﬁlms were then reduced with remote hydrogen plasma near room temperature to minimize agglomeration of the thin Cu ﬁlms during reduction. After reduction, CuON ﬁlms having a Cu2O crystal structure showed a higher density Cu ﬁlm 95% than those having a Cu3N crystal structure 84% . Both reduced Cu ﬁlms had a smooth morphology 1 nm rms roughness . Thus, deposition of a CuON ﬁlm having a Cu2O crystal structure and then reduction with remote hydrogen plasma can make Cu layers that can serve as seed layers of future Cu interconnects. © 2008 The Electrochemical Society. DOI: 10.1149/1.2912326 All rights reserved. Manuscript submitted January 18, 2008; revised manuscript received February 15, 2008. Available electronically May 5, 2008.

Cu is used as the interconnect material for ultralarge-scale integrated circuits due to its low resistivity and excellent stability against stress migration and electromigration. Cu is ﬁlled by electrochemical deposition ECD , which has the merits of a low process temperature, a high deposition rate, a cost effective process, and a complete via ﬁlling capability. This ECD method requires a thin Cu seed layer as an electrode. In current technology, the Cu seed layer is deposited by sputtering on Ta over a TaN diffusion barrier. However, beyond the 45 nm generation, sputtering cannot cover the sidewalls of vias and trenches uniformly due to its poor step coverage, which results in void formation during ECD and a reduced durability of interconnects.1 Thus, a conformal deposition method for Cu seed layer deposition is required.2 Chemical vapor deposition CVD and atomic layer deposition ALD are well-known methods of conformal Cu seed layer deposition.3-9 From the viewpoint of productivity, CVD is the most promising candidate for Cu seed layer deposition. For the 32 nm generation, considering the metal linewidth 32 nm and the thickness of the barrier/cladding 2.4 nm , a conformal, smooth, adherent, and continuous CVD Cu seed layer less than 10 nm thick is required.10 To deposit 10 nm of continuous CVD Cu, new underlayers should be considered because Ta/TaN underlayers cause a rough morphology and poor adhesion.4,5 Ru is an air-stable metal with a low resistivity and no solubility in Cu, and it does not form any intermetallic compounds with Cu.11 More importantly, Ru has a strong adhesion to CVD Cu compared with Ta or TaN.6,7,12,13 Although Cu has a fairly high wettability on Ru, 10 nm of continuous CVD Cu seed layer cannot be deposited on Ru, because metallic Cu made by CVD has typical three-dimensional 3D island growth and requires a thickness of at least 20 nm to form a continuous layer.5 To deposit a thin 10 nm , smooth, and continuous CVD seed layer, a different approach is required. Cu compounds, such as Cu oxide or nitride, have a better wettability than metallic Cu, which results in a higher nucleation density, and continuous thin layers with a smoother and more continuous morphology than metallic Cu. There is a report of CVD Cu2O deposition for seed layer application.14 However, the reduction process temperature is 275°C, which is too high to form a thin, continuous, and smooth seed layer for future Cu interconnect processing. The Ta underlayer used for that experiment is oxidized during oxide deposition, which de-

creases the adhesion strength of Cu to Ta and increases the contact resistance. Thus, there is need for a new precursor having a low deposition temperature and a new underlayer that can be easily reduced. Deposition of Cu3N can also be a good candidate. ALD Cu3N deposition and reduction shows the possibility of thin seed layer fabrication,15,16 but ALD is too slow for large-scale production. The reported CVD process for Cu3N required a high deposition temperature 400°C and it did not mention the morphology, which is most important in this application.17 Reduction of a deposited Cu2O or Cu3N ﬁlm to copper metal must be done at a low enough temperature to avoid agglomeration of the Cu. The reduction of a Cu oxide or nitride at too high a temperature produces rough and discontinuous Cu ﬁlms.14,15,18,19 Thus, the reduction of Cu compounds should be conducted at as low a temperature as possible to maintain the smooth and continuous morphology of as-deposited Cu compound ﬁlms. In this study, we deposited Cu oxide, nitride, and oxynitride CuON using CVD, and then these compounds were compared from the viewpoint of morphology and ﬁlm density before and after reduction to copper metal. A Cu amidinate, N,N -di-sec-butylacetamidinato copper I dimer abbreviated Cu sBu-Me-amd 2 , was used to decrease the deposition temperature. This precursor’s reactivity at a low substrate temperature has been reported under ALD conditions.9,15 Cu oxide, Cu nitride, and CuON are formed by using Cu amidinate with H2O and NH3 as reactant gases. The Cu compound ﬁlms were then reduced by H2 remote-plasma treatment because atomic hydrogen is one of the strongest reducing agents, which can enable room temperature reduction and minimize agglomeration of the copper.19,20 Cu2O reacts with atomic hydrogen to form pure Cu and water by the following reaction Cu2O + 2H → 2Cu + H2O 1

* Electrochemical Society Active Member.
z

E-mail: gordon@chemistry.harvard.edu

Provided that no kinetic limitations exist, this reaction will occur because the Gibbs energy change of this reaction is −118.3 kcal/mol at 25°C.21 Thus, Cu2O might be reduced with atomic hydrogen even at room temperature. In this work, we found that the crystal structure of as-deposited CuON ﬁlms differed depending upon the ratios of H2O to NH3 during depositions. A high H2O ratio makes ﬁlms with a Cu2O crystal structure, while a high NH3 ratio makes a Cu3N crystal structure. Even though a ﬁlm has a Cu2O or Cu3N crystal structure, both oxygen and nitrogen are incorporated in the ﬁlm when a mixture of H2O and NH3 is used as a reactant gas during deposition. However,

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Journal of The Electrochemical Society, 155 7 H496-H503 2008 the overall deposition rate of the ﬁlm is mainly determined by the H2O ﬂow rate. CuON ﬁlm shows a smooth surface morphology root-mean-square rms roughness 1 nm . CuON ﬁlms having Cu2O structure have higher density than ﬁlms having Cu3N structure. After 1 min reduction with H2 remote plasma at room temperature, both ﬁlms are fully reduced to Cu metal that has smooth morphology rms roughness 1 nm and low resistivity 12 cm at 9 nm thickness . CVD CuON ﬁlms having Cu2O structure form Cu with higher density after reduction than CuON ﬁlms having Cu3N structure do. Room temperature remote hydrogen plasma reduction is the best method to maintain smooth surface morphology. Thus, this process can be a promising candidate of thin CVD Cu seed layer deposition for future Cu interconnects. Experimental The deposition of CuON was done in a tube-furnace type reactor which has 36 mm inner diameter i.d. . Copper I N,N -di-sec-butylacetamidinate Cu sBu-Me-amd 2 was used as a Cu precursor, which was delivered by bubbling with 40 sccm of N2 carrier gas. The bubbler temperature was 130°C, which maintained the Cu precursor as a liquid phase because its melting point is 77°C. All the gas lines, bubbler, and valves were located in an oven which maintained a good temperature uniformity. H2O was used as an oxygen source, which was evaporated from a reservoir at room temperature without any carrier gas. The ﬂow rate of water vapor was controlled by a needle valve that was calibrated by comparing with the pressure increase of the chamber by a measured N2 ﬂow rate. NH3 was supplied as a nitrogen source whose ﬂow rate was controlled by a mass ﬂow controller. The total ﬂow rate of reactant gases H2O and NH3 was maintained at 40 sccm, and the ratio of H2O to NH3 was set to the values 40:0, 30:10, 20:20, 10:30, or 0:40. The reaction gases were mixed with Cu precursor vapor in a small 5 mm i.d. tube just prior to entering the reactor tube 36 mm i.d. to ensure thorough mixing. The ﬁlms were deposited at substrate temperatures from 140 to 220°C under a total chamber pressure of 8 Torr. The ﬁlms were reduced with H2 remote plasma, which heated the substrates from room temperature to temperatures as high as 50°C. A toroidal plasma generator ASTRON I type AX7670, MKS was supplied with 180 sccm of Ar for plasma ignition and 200 sccm of H2, which upon dissociative excitation acted as a reducing agent. The reduction time was varied from 30 to 180 s. A Si wafer with a 100 nm thermal oxide was used as the substrate. Ru was deposited by sputtering to a 20 nm thickness and exposed to the atmosphere prior to CVD. The surface morphologies of the as-deposited CuON and reduced ﬁlms were evaluated by an atomic force microscope AFM, Asylum MFP-3D AFM . The thickness and composition of the deposited ﬁlms were measured using 2 MeV He+ Rutherford backscattering spectroscopy RBS . The physical thicknesses of CuON and reduced Cu ﬁlms were measured by AFM after making stripe patterns by photolithography and etching in dilute nitric acid. CuON and Cu ﬁlms were etched with nitric acid diluted by deionized water in a volume ratio 1 acid :40 water or 1:10, respectively. The resistivities of reduced Cu ﬁlms were evaluated by a four-point probe Miller Design & Equipment FPP-5000 . The phases of as-deposited Cu oxynitride and reduced ﬁlms were evaluated by transmission electron microscopy TEM diffraction JEOL JEL2010 TEM using as a substrate a 50 nm thick Si3N4 membrane TEM grid Ted Pella, Inc., prod. no. 21500–10 . Results and Discussion Cu oxynitride deposition with Cu sBu-Me-amd 2, H2O, and NH3.— Temperature effect on CuON ﬁlm deposition.— CuON was deposited from Cu sBu-Me-amd 2 vapor and a mixture of H2O vapor and NH3 gas. Figure 1 shows the deposition rate of Cu oxynitride at different deposition temperatures. The ratio of H2O ﬂow to NH3 ﬂow was 30:10 in these depositions. The deposition rate increased with increasing deposition temperature, up to a value over

H497

Figure 1. Color online Arrhenius plot of CuON deposition rate from Cu sBu-Me-amd 2 vapor and a mixture of 30 sccm of H2O and 10 sccm of NH3.

4 nm min−1. Over the range of temperature studied 140–220°C , the deposition rate has an Arrhenius form, which means that the CVD reaction is kinetically controlled in that temperature range. The activation energy of this reaction was found to be 44 kJ/mol. The morphology of CuON depends on the deposition temperature, as shown in Fig. 2 for ﬁlms with thicknesses about 20 nm. These ﬁlms are all smooth, with a rms roughness 1 nm. The smoothest ﬁlm was deposited at 160°C, with a roughness of only 0.5 nm, which is just slightly larger than the roughness of the Si substrate. The surface grain size of CuON is constant at about 20 nm up to a deposition temperature of 180°C. At 220°C, some large particles 400–600 nm in diameter were observed on the ﬁlm surface, although the ﬁlm still had a smooth surface morphology rms roughness 1.04 nm and a fairly small grain size 40 nm . These particles seemed to be formed by gas-phase reaction at the highest temperature. Thus, CuON for a seed layer can be deposited over the temperature range from about 140–180°C from the viewpoint of surface morphology. This result is different from the temperature effect on morphology of Cu2O and Cu3N. The morphology of pure Cu compounds such as Cu2O and Cu3N was very sensitive to deposition temperature.15,19 A deposition temperature only 30 or 40°C higher than the optimized condition always made ﬁlms with a rough morphology in the deposition of pure Cu compounds. However, CuON is less affected by deposition temperature, so smooth CuON ﬁlms are obtained over a wider process window than for Cu2O or Cu3N ﬁlms. The composition of CuON deposited at different temperatures is shown in Fig. 3. The atomic percentages of Cu, O, and N are compared at 140, 180, and 220°C as measured by RBS for ﬁlms deposited on amorphous carbon substrates. The composition does not change much over that temperature range, which means that CuON is a stable phase under these deposition conditions. Thus, CuON has a relatively wide process window in which to get a uniform composition and morphology because it is less sensitive to the deposition temperature. Pure Cu2O and Cu3N showed a single phase and smooth morphology only in a narrower temperature range.15,19 The effect of H2O to NH3 ratio on CuON ﬁlm deposition.— The deposition rate of CuON depends on the H2O to NH3 ratio at 140°C as shown in Fig. 4. The deposition rate is mainly determined by the H2O ﬂow rate, showing that H2O is more reactive than NH3 with the Cu amidinate precursor. Without H2O, no ﬁlm was deposited at 140°C, which shows that the Cu precursor and NH3 alone cannot nucleate a Cu3N ﬁlm at 140°C. At substrate temperatures over 200°C, some Cu3N ﬁlm was deposited, but it has a very rough morphology. Thus, CuON ﬁlm was investigated due to its smoother morphology and higher deposition rate.

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Journal of The Electrochemical Society, 155 7 H496-H503 2008

Figure 2. Color online AFM images of CuON ﬁlms grown from Cu sBu-Me-amd b 160, c 180, and d 220°C, which have about 20 nm thickness.

2

vapor and a mixture of 30 sccm of H2O and 10 sccm of NH3 at a 140,

Figure 3. Color online The composition of CuON ﬁlms deposited on carbon substrates from Cu sBu-Me-amd 2 vapor and a mixture of 30 sccm of H2O and 10 sccm of NH3 at different temperatures, as measured by RBS.

Figure 4. Color online Deposition rate of CuON ﬁlm at different H2O and NH3 ratios at 140°C, 8 Torr working pressure. Total ﬂow rate of H2O and NH3 is maintained at 40 sccm. Thus, the NH3 ﬂow rate is equal to 40 sccm minus the H2O ﬂow rate.

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Journal of The Electrochemical Society, 155 7 H496-H503 2008

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Figure 5. Color online Composition of CuON ﬁlms deposited with different H2O to NH3 ratios at 140°C, 8 Torr working pressure. The NH3 ﬂow rate is equal to 40 sccm minus the H2O ﬂow rate. The composition was measured by RBS from ﬁlms deposited on amorphous carbon substrates.

Figure 6. The ratio of Cu in the CuON ﬁlm for different H2O and NH3 ﬂow rates. The Cu ratio is deﬁned by the ratio of Cu thickness from RBS and calculated at the bulk density of Cu to physical thickness of CuON.

Compositions of CuON ﬁlms deposited with different H2O to NH3 ratios at 140°C are shown in Fig. 5. The oxygen content of the ﬁlms exceeds the nitrogen content, even for the ﬁlm grown from an excess of ammonia H2O to NH3 ﬂow ratio of 10:30 . This is another indicator that water vapor is more reactive with the copper precursor than ammonia is. If we assign the conventional oxidation states to O −2 and N −3 , these compositions all correspond closely to copper in the +1 oxidation state. Because the copper in the precursor is also in the +1 oxidation state, the reactions with H2O and NH3 do not produce any oxidation or reduction of the copper during CVD of the ﬁlms. The “Cu ratio” is deﬁned by the ratio of Cu thickness to physical thickness of CuON. The physical thickness of CuON ﬁlm was measured by AFM after etching a stripe pattern. Cu thickness was measured by RBS and calculated as if it were pure copper with bulk density. From Fig. 6 the Cu ratio in the CuON ﬁlms reached a maximum for the conditions of 30 sccm of H2O and 10 sccm of NH3. Films with a high Cu ratio contain more Cu that may be obtained by the reduction of a given thickness of CuON. All the CuON ﬁlms have a very smooth surface morphology. The morphology of deposited CuON depends on the ratio of H2O to NH3 as shown in Fig. 7. With increasing the H2O ratio, the grain size increased, but the rms roughness value decreased, so the grains became wider, ﬂatter, and less tall. The crystal structure of CuON ﬁlm depended on the ratio of ﬂow rates of H2O to NH3. The structure was evaluated by electron diffraction in a TEM image Fig. 8 . The diffraction patterns were obtained from CuON ﬁlms deposited in three different conditions: Fig. 8a for 10 sccm H2O and 30 sccm NH3, Fig. 8b for 30 sccm H2O and 10 sccm NH3, and Fig. 8c for 40 sccm H2O. The electron diffraction pattern of Fig. 8a high NH3 matches with the Cu3N structure.22 Those of Fig. 8b and c high H2O coincide with the crystal structure of Cu2O.23 The peak assignments are summarized in Tables I and II for the Cu3N and Cu2O structures, respectively. Although the CuON ﬁlms have similar compositions, the ﬁlms show different crystal structures. The high ratio of NH3 only makes a Cu3N structure, even though that ﬁlm contains 24 atom % oxygen. The high ratio of H2O makes CuON ﬁlms having only the crystal structure of Cu2O. We ﬁnd no additional diffraction peaks that could arise from a crystalline mixed oxynitride phase, nor did we ﬁnd any such phases reported. Thus, it seems likely that these ﬁlms contain a signiﬁcant amount of amorphous copper oxynitride that only has broad diffraction patterns and a smooth surface morphology. It is thought that H2O reacts with the Cu precursor on a surface, followed by the reaction of NH3 with Cu–O on the surface because CuON ﬁlm is not deposited without H2O. Thus, a high NH3 ﬂow and low H2O ﬂow make a low deposition rate of Cu2O, causing a longer time for NH3 reaction on the surface, which results in the formation of a Cu3N structure containing oxygen. This result coincides with ALD Cu3N deposition using a pulse sequence of Cu

precusor/H2O/NH3.16 Torndahl et al.16 made Cu oxide, ﬁrst using Cu hfac 2 and H2O; then it was nitriﬁed by a NH3 pulse, which resulted in the formation of Cu3N. Thus, Cu2O and Cu3N can be formed by controlling the reaction gas ratio because the kinetic competition between H2O and NH3 with Cu atoms on the surface can make both structures. The step coverage of CVD CuON was tested by depositing ﬁlm on a silicon substrate with holes having aspect ratios of 40:1. The scanning electron microscopy SEM image of a cleaved cross section in Fig. 9 shows a step coverage of about 95% at the bottom of these very narrow holes. Reduction of CuON with remote H2 plasma at room temperature.— CuON ﬁlms can be deposited with different crystal structures and Cu densities depending on the ratio of H2O to NH3. The CuON ﬁlm high H2O CuON with high H2O ratio H2O:30 sccm, NH3:10 sccm has a Cu2O crystal structure and a high Cu ratio 53% . Low H2O CuON from low H2O ratio H2O:10 sccm, NH3:30 sccm has the crystal structure of Cu3N and a low Cu ratio 41% . Thus, these two ﬁlms were used to compare the reduction behavior because these can represent high or low density ﬁlms. High H2O CuON has about a 12% higher Cu ratio than that of low H2O CuON. The CuON ﬁlms were reduced with remote H2 plasma. The ﬁlms were not heated deliberately, but their temperature did rise from room temperature to about 50°C because of the heat released by the recombination of hydrogen atoms to form H2 and by reaction with oxygen and nitrogen on CuON surfaces. The as-deposited thicknesses of these high H2O CuON and low H2O CuON ﬁlms were 16 and 14 nm, respectively. The sheet resistance of the ﬁlms depends on reduction time as shown in Fig. 10. After 1 min reduction treatment, both CuON ﬁlms were reduced to Cu. The sheet resistance is not changed further after 3 min reduction, which means that reduction for 1 min is sufﬁcient to reduce 14–16 nm thick CuON ﬁlms with either crystal structure. The morphology of reduced CuON was evaluated by AFM, shown in Fig. 11. Both high H2O and low H2O CuON a showed smooth surface morphology 1.1–1.2 nm rms roughness even after 3 min reduction. Thus, the reduced Cu ﬁlms were not agglomerated even at a longer reduction time. Because the ﬁlms retain their smooth morphology even after over-reduction for longer times, we expect that ﬁlms can also be reduced successfully inside the whole length of deep trenches. Film near the top of a trench will be reduced before ﬁlm deeper in the trench, which only receives a smaller ﬂux of hydrogen atoms depleted by reactions at the walls during their diffusion down the trench. Because these ﬁlms were reduced at nearly room temperature, they can maintain their smooth surface morphology by avoiding diffusion of the Cu over the Ru surface to form agglomerates. How-

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Journal of The Electrochemical Society, 155 7 H496-H503 2008

Figure 7. Color online AFM image of CuON ﬁlm grown at 140°C with the ﬂow rate of H2O and NH3; a 10:30, b 20:20, c 30:10, and d 40:0 sccm.

ever, CuON ﬁlms deposited on SiO2 underlayers were agglomerated under the same reduction condition, as shown by the increase in rms roughness from 0.7 to 3.5 nm Fig. 12 . Any surface oxide on ruthenium can be reduced during the CuON reduction because the stabilities of Cu2O and RuO2 are similar. The Gibbs energies of the reduction reactions for these oxides are similar,21 which implies both metal oxides can be reduced under similar reduction conditions. The Cu is bonded strongly to the reduced metallic surface of Ru. However, Cu on Si having a native oxide can be agglomerated during reduction even at room temperature due to the high mobility of Cu atoms on oxide surfaces9 and the difﬁculty of reducing silicon oxides. Thus, an easily reducible underlayer like Ru is essential for maintaining a smooth surface morphology during the reduction of CuON. The volume shrinkage of two CuON ﬁlms was evaluated by comparing the thickness of CuON ﬁlm before and after reduction. The physical thickness of high H2O CuON is changed from 16 to 9 nm, which is a shrinkage of volume by 45%. Low H2O CuON showed that the thickness is changed from 14 to 7 nm, which means a 50% volume shrinkage. These samples are evaluated by RBS to measure the density of reduced Cu ﬁlm. The RBS result shows that

the thickness of high or low H2O CuON would be 8.5 or 5.9 nm, respectively, if they had bulk Cu density. Thus, comparing these values with the physical thicknesses, the density of the reduced copper from high Cu2O CuON or low H2O CuON is 95 or 84%, respectively, of the bulk value. Summarizing the density of the CuON ﬁlms, high Cu2O CuON has a higher density not only in the asdeposited ﬁlm but also after reduction. Thus, high Cu2O CuON ﬁlm should be used as the most suitable Cu compound for reduction to deposit a dense, reduced Cu ﬁlm. cm at a The resistivity of reduced high Cu2O CuON is 12 cm at thickness of 9 nm. That of low H2O CuON ﬁlm has 15 a thickness of 7 nm. These values are similar to the resistivity of sputtered Cu at the corresponding thicknesses.15 Thus, the reduced Cu ﬁlm has a high density and high purity. All the reduced copper ﬁlms on ruthenium pass the tape test for adhesion, whereas the ones on silica are easily pulled off by tape. More quantitative 4-point bend tests of adhesion are underway. Conclusions Smooth, continuous, dense, and conformal Cu ﬁlms with 1 nm rms roughness and thickness 10 nm were fabricated by

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Journal of The Electrochemical Society, 155 7 H496-H503 2008

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(a)

(b)
45 3 12

5 43 2 1 2 43 5 1

(c)
Figure 8. TEM diffraction pattern of CuON ﬁlms grown at 140°C with the ﬂow rate of H2O and NH3 at a 10:30, b 30:10, and c 40:0 sccm.

CVD of CuON followed by reduction with remote hydrogen plasma at room temperature. The crystal structure of CuON can be controlled by the ratio of H2O and NH3, although the elemental composition of the ﬁlm was not changed signiﬁcantly. A high H2O ratio makes the CuON ﬁlm having a Cu2O crystal structure. A low H2O ratio, meaning high NH3 partial pressure, makes CuON ﬁlms having a Cu3N crystal structure. The reduction rate of the ﬁlms does not show any difference depending on the crystal structure. CuON ﬁlm with a Cu2O structure produces a higher density of Cu after reduction. Thus, CuON having a Cu2O structure is the best Cu compound

Table I. Electron diffraction results for low H2O CuON ﬁlm from TEM. The index of plane „hkl… and interplanar spacing „d… shown in this table represents the Cu3N crystal structure. Error means the difference between reference data and measured data. Measured d A 3.83 2.69 2.20 1.91 1.69 Error % −0.26 0.21 −0.02 −0.29 0.89 Figure 9. SEM image of a CuON ﬁlm deposited at 140°C with 30 sccm of H2O and 10 sccm of NH3 on an oval hole diameter 0.13 0.19 m, length 6.7 m . Scale bar is 200 nm.

No. 1 2 3 4 5

hkl 100 110 111 200 210

d A 3.82 2.70 2.20 1.91 1.71

Int. 60 30 100 80 30

Table II. Electron diffraction result for high H2O CuON ﬁlm from TEM. The index of plane „hkl… and interplanar spacing „d… shown in this table represents the Cu2O crystal structure. Error means the difference between reference data and measured data. Measured d A 3.03 2.46 2.14 1.74 1.50 Error % 0.32 0.04 −0.13 −0.24 0.66

No. 1 2 3 4 5

hkl 110 111 200 211 220

d A 3.04 2.46 2.14 1.74 1.51

Int. 20 100 70 20 90

Figure 10. Sheet resistance of a low and b high H2O CuON ﬁlm depending on reduction time at room temperature.

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Journal of The Electrochemical Society, 155 7 H496-H503 2008

Figure 11. Color online AFM image of reduced Cu ﬁlms from a low and b high H2O CuON at room temperature for 3 min on Ru substrates.

Figure 12. Color online AFM image of reduced Cu ﬁlms from a low and b high H2O CuON at room temperature for 3 min on SiO2 substrates.

for this deposition and reduction process, which is a promising method for Cu seed layer deposition for future Cu interconnects. Acknowledgments The copper precursor was supplied by the Advanced Thin-Film Technologies Group, Rohm and Haas Electronic Materials. Silicon substrates with deep trenches were supplied by Qimonda. Support for this work was provided by the Rohm and Haas Company, Intel Corporation, and the National Science Foundation.
Harvard University assisted in meeting the publication costs of this article.

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Journal of The Electrochemical Society, 155 7 H496-H503 2008
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