Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K13/00—Etching, surface-brightening or pickling compositions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
  • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
  • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
  • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
  • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
  • C23G1/04—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors
  • C23G1/06—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors organic inhibitors
  • C23G1/061—Cleaning or pickling metallic material with solutions or molten salts with acid solutions using inhibitors organic inhibitors nitrogen-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/16—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions using inhibitors
  • C23G1/18—Organic inhibitors
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/20—Other heavy metals
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/42—Stripping or agents therefor
  • G03F7/422—Stripping or agents therefor using liquids only
  • G03F7/425—Stripping or agents therefor using liquids only containing mineral alkaline compounds; containing organic basic compounds, e.g. quaternary ammonium compounds; containing heterocyclic basic compounds containing nitrogen
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02041—Cleaning
  • H01L21/02057—Cleaning during device manufacture
  • H01L21/0206—Cleaning during device manufacture during, before or after processing of insulating layers
  • H01L21/02063—Cleaning during device manufacture during, before or after processing of insulating layers the processing being the formation of vias or contact holes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
  • H01L21/02041—Cleaning
  • H01L21/02057—Cleaning during device manufacture
  • H01L21/02068—Cleaning during device manufacture during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers
  • H01L21/02071—Cleaning during device manufacture during, before or after processing of conductive layers, e.g. polysilicon or amorphous silicon layers the processing being a delineation, e.g. RIE, of conductive layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
  • H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
  • H01L21/76814—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics post-treatment or after-treatment, e.g. cleaning or removal of oxides on underlying conductors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
  • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
  • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
  • H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
  • H01L21/76838—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the conductors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S438/00—Semiconductor device manufacturing: process
  • Y10S438/963—Removing process residues from vertical substrate surfaces

Definitions

• the present invention relates generally to manufacture of semiconductor devices incorporating a metal interconnect. More specifically, it relates to a composition and process to clean post etch residues at an interconnect level, such as with a copper metallurgy, preferably incorporating a damascene / dual damascene structure. The invention further relates to a composition for other post etch residue- cleaning applications, such as aluminum, or aluminum alloy interconnects with misaligned tungsten plugs.
• This application is directed to solving some of the difficulties in integrating this type of interconnects, and a new strategy for the post dielectric etch cleaning process.
• the development of new cleaning chemistries and processes for their use, which are compatible with copper and low-k dielectric materials, is essential for process integration.
• photoresist material is used to pattern, and transfer patterns onto the appropriate material.
• the appropriate material will be either metal for electrically conducting paths or dielectric for isolating material in-between the conducting lines.
• Traditional interconnects are made of aluminum or aluminum alloys isolated by dielectric material, for example silicon dioxide. More recently developed interconnects use copper as the conducting material and low-k dielectric material (a dielectric, having a dielectric constant ⁇ smaller than the dielectric constant of silicon dioxide).
• Figures 1 and 2 show a typical structure used in this case.
• the pattern is transferred from the photoresist (3) through the dielectric (2). The gaps are then filled up by the conducting layer.
• This process is called damascene and can integrate either one level of interconnect only (single damascene) or both the horizontal interconnects and the vertical interconnects called vias (dual damascene). Vias always open atop the underlying metal lines (1) and good cleanliness of the via is required in order to minimize electrical resistance along the interconnect.
• Various processes have been developed to build those structures, as disclosed, for example, in US Patents 5,739,579; US 5,635,423; US 5,705,430 and US 5,686,354, which can include optional layers into the dielectric stack (5, 6) but all those processes have in common:
• choline base can act as a etching agent of metal for thin film layer definition (PAJ 62,281,332, US 4,172,005) and that adding choline atoms into an etching chamber when etching copper helps to lower the process temperature and hence minimize copper oxidation.
• US 5,846,695 discloses aqueous solutions of quaternary ammonium hydroxides, including choline, in combination with nucleophilic amines and sugar and/or sugar alcohols, for removal of photoresist and photoresist residues in integrated circuit fabrication. The present invention is aimed at cleaning residues left after etching dielectric material and openings on a copper layer.
• DHF dilute hydrofluoric acid solutions
• the photoresist might or might not be removed before the copper is exposed.
• Using traditional photoresist removal techniques is not ideal for the following reasons:
• an oxygen plasma step will be detrimental to organic dielectric material, if used, by etching the material in an uncontrolled manner.
• a traditional solvent used to remove photoresist such as, for example, products containing N-methyl pyrrolidone might require an extra cure step to recover the dielectric constant and properties of an organic dielectric. The demand for faster devices has driven down the scale of the design rules.
• a solution for reduced capacitance between adjacent metal lines is to decrease the dielectric constant of the material in-between the lines. This can be achieved by the use of emerging new low-k materials.
• the main drawbacks of this material are first its high diffusivity into silicon, introducing risk of a killing defect in the front end device, and second the difficulty to dry etch it and integrate it in traditional processes.
• copper does not form an oxide passivation layer under ambient conditions (as aluminum does), making this metal very difficult to work with.
• the SIA Roadmap predicted the merging of the work done on the one hand with copper integration, and on the other hand with low-k materials, by the end of 1998.
• the strategy chosen here is the introduction of copper first followed by the transfer of the process to low-k material.
• both projects are progressing together and a cleaning strategy has to be developed at this stage, taking into account the requirements of all the materials that will be used in the final process.
• Dual damascene structures have the advantage of incorporating both lines and vias in one deposition step; this reduces the number of process steps and is therefore cost effective.
• the main reason for the emergence of such structures nowadays is the fact that this is the easiest way to introduce copper.
• Variations of the dual damascene structure exist, incorporating a series of layers for process purposes such as anti-reflective coatings, adhesion promoters, moisture barriers, diffusion barriers, polishing stops, buried etch mask and so on.
• process purposes such as anti-reflective coatings, adhesion promoters, moisture barriers, diffusion barriers, polishing stops, buried etch mask and so on.
• the choice of whether those have to be used or not and what material (SiO x N y or Si x N y ) should be used for them often depend upon the final choice of the low-k material.
• a further object of the invention is to provide such a cleaning composition and cleaning process which is compatible with most low-k dielectric materials, and does not substantially modify the FT-IR spectrum, dielectric constant, refractive index (RI) or thickness of such materials after use.
• a "2 step etch process” can be used to achieve the requirement of ULSI manufacturing.
• a new cleaning chemistry is provided in order to address the problem of dual damascene fabrication.
• This work starts with a wide screening of possible candidates compatible with copper and SiLK, the two main materials of interest in this aspect of the invention, resulting in the design of a new chemistry.
• This new cleaning chemistry is evaluated on damascene structures.
• This work is supported by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analyses on the features integrating copper, and by FT-IR and C(V) measurement for the integration of SiLK.
• a composition for removal of residues from integrated circuits comprises a choline compound, water and an organic solvent.
• a process for the removal of a residue from an integrated circuit comprises contacting the integrated circuit with a composition comprising a choline compound, water and an organic solvent at a temperature and for a time sufficient to remove the residue from the integrated circuit.
• an etch stop inorganic layer at the bottom of the dual damascene structure protects the underlying interconnect of copper and allows us to proceed to a better cleaning.
• an integrated circuit fabrication process comprises forming a first silicon compound etch stop layer over a copper conducting line in the integrated circuit.
• a second silicon compound bulk dielectric is formed over the first silicon compound etch stop layer.
• the second silicon compound bulk dielectric is etched to expose the etch stop layer. Residues are removed from the integrated circuit.
• the etch stop layer is etched away to expose the copper conducting line. Residues are removed from the integrated circuit with a residue removal composition containing an effective amount of a choline compound.
• FIG. 1 is a cross section view of an example of a prior art dual damascene structure.
• Fig. 2 is a cross section view of a modified dual damascene structure in accordance with the invention.
• Fig. 3 is a set of scanning electron microscope (SEM) and TEM photographs showing results obtained with the invention.
• Figs. 7-10 are FT-IR spectra showing results obtained with the invention.
• Figs. 11-22 are SEM photographs further showing results obtained with the invention.
• Figs. 23-24 are graphs of results obtained with the invention.
• Figs. 25a-33 are SEM and TEM photographs further showing results obtained with the invention.
• Figs. 34-35 are graphs of results obtained with the invention.
• Figs. 36-37 are SEM photographs further showing results obtained with the invention.
• Figs. 38-39 are graphs of results obtained with the invention.
• Fig. 40 shows results of x-ray photo spectroscopy (XPS) analyses obtained through use of the invention.
• the choline compound in the hydroxide or salt form, such as choline hydroxide, choline bicarbonate or choline chloride.
• the term "choline compound” also embraces related quaternary ammonium compounds, such as tetramethylammonium hydroxide (TMAH), tetrabutyl ammonium hydroxide (TBAH), their salts, and the like.
• Suitable organic solvents in the composition and for practice of the process include such polar solvents as dimethyl sulfoxide, ethylene glycol, ethylene glycol alkyl ether, diethylene glycol alkyl ether, triethylene glycol alkyl ether, propylene glycol, propylene glycol alkyl ether, N-substituted pyrrolidone, ethylene diamine and ethylene triamine. Additional polar solvents as known in the art can also be used in the composition of the present invention.
• a corrosion inhibitor may be included in a formulation used to clean damascene structures with exposed copper present.
• the corrosion inhibitors are present to protect copper from being corroded, and may be chosen from a variety of classes of chemical compounds, including any compounds used for the prevention of copper corrosion in other systems comprising the art. More specifically, compounds of the general class may be employed, where X, Y, and Z are chosen from C, N, O, S, and P. Under these conditions the valence requirements and presence of pendant R groups may be set appropriately.
• R1-R5 may be chosen independently as H, optionally a substituted C1-C6 straight, branched or cyclo alkyl, alkenyl or alkynyl group, straight or branched alkoxy group, optionally a substituted acyl group, straight or branched alkoxy group, amidyl group, hydroxyl group, a halogen, carboxyl group, alkoxyalkyl group, alkylamino group, alkylsulfonyl group or sulfonic acid group; or the salt of such compounds.
• X, Y and Z are nitrogen, nitrogen and carbon, respectively, and R1-R5 are hydrogen.
• R3 is hydrogen and R4 and R5 constitute a benzene ring.
• R6 may be present from 2-5 times and may be chosen independently as H, optionally a substituted C1-C6 straight, branched or cyclo alkyl, alkenyl or alkynyl group, straight or branched alkoxy group, optionally a substituted acyl group, straight or branched alkoxy group, amidyl group, a halogen, carboxyl group, alkoxyalkyl group, alkylamino group, alkylsulfonyl group or sulfonic acid group; or the salt of such compounds.
• Suitable specific examples of corrosion inhibitors include catechol, t-butyl catechol and benzotriazole.
• the composition optionally contains hydroxylamine or a hydroxylamine salt. If present, the composition desirably contains from about 2 to about 12% by weight of the hydroxylamine or hydroxylamine salt. In practice, the composition contains from about 10 percent by weight to about
• the corrosion inhibitor is typically provided in an amount of from about 0.5 to about 5 percent by weight. Because of its inability to create a passivation layer, traditional cleaning solvents are not well suited to work with copper as they usually contain aggressive complexing agents. A screening has been undertaken to evaluate new candidates to gently remove copper etch residues without damaging the existing interconnects. Etch rates on blanket copper were measured by sheet resistance measurement using a four point probe.
• Some solvents including hydroxylamine chemistries, show a severe incompatibility with copper.
• the incompatibility of Cu with hydroxylamine- containing chemistries is most likely a result of two factors: the known strength of hydroxylamine as a reducing agent, and its propensity (along with amine solvents and other chelating agents) to effectively complex and solubilize metal ions.
• Copper- containing etch residues in a high oxidation state (Cu 11 ) may be reduced and solubilized to Cu", then reoxidized by water or dissolved oxygen back to Cu 11 in an equilibrium process:
• Reaction 1 serves to assist in breaking up what is probably an amorphous, highly oxidized Cu residue of ill-defined stoichiometry, while (2) complexes the Cu, most likely oxidizing it back to Cu 11 (especially in the presence of water) in the process.
• dissolved water and/or oxygen can oxidize native copper (Cu°) to an oxidized form that can be dissolved by the strong complexing agents (including hydroxylamine) comprising an hydroxylamine- containing chemistry.
• the strong complexing agents including hydroxylamine
• the main purpose of this invention is to clean damascene type structures when copper is exposed.
• the sample is a blanket copper with a single layer of TEOS (silicon dioxide type of dielectric) etched.
• TEOS silicon dioxide type of dielectric
• the etch has been realized in two steps: first the main etch through the bulk dielectric, followed by a cleaning step where photoresist and main post etch residues are removed into conventional solvent while copper is still protected by a thin nitride layer; then a second short etch is realized to open the structure to copper, leaving a minimum of residues on the bottom and sidewall of the structure.
• solution B6 A solution of choline hydroxide (solution B6) was used to successfully clean those residues at 50°C for 10 min (Fig. 3).
• XPS X-Ray Photo Spectroscopy analysis of such a structure shows the effect of the invention at removing CuO and CuO 2 compounds (Fig. 4).
• Table 1 summarizes various compositions used to clean such a structure, and their result on the cleaning efficiency and copper attack at the bottom of the structure. Results are rated from 0 to 10 by subjectively analyzing SEM pictures. A 0 rating means bad and 10 is good. However we note that if cleaning is bad, corrosion inhibition is usually good only because the residues protect the copper material. This is for example the case of pure water (Al).
• FIG. 5 shows the example of residue found at the bottom of the structure.
• Figure 6 shows that the invention was not able to clean such a residue under the conditions employed.
• Dual damascene structures have the advantage of reducing process steps for interconnect manufacture. Hence, process engineers research the simplest structure possible in order to preserve this cost advantage. Also, the introduction of too many layers participates in the increase of the global dielectric constant of inter-metal dielectric materials. This increase can be as high as 20%, in which case the benefits earned by using a new dielectric material are lost.
• the simplest structure, the first approach tested, consisted of etching both lines and via levels down to the underlying copper.
• a buried hard mask is included and used to pattern the via level, while photoresist was used to pattern the line level.
• FIG. 25 A typical example is shown in Fig. 25, where the opening on copper forms some "mushroom" -type residues.
• photoresist removal can proceed in the absence of exposed copper.
• the weakness of the natural copper oxide layer makes the photoresist removal step an issue. Indeed, traditional methods of photoresist stripping (such as plasma O 2 ) will in most cases oxidize and attack the metal.
• Lithography was performed on the DUV 248 nm ASML/90 stepper and damascene structures are etched on the TEL Unity 85 DRM.
• the photoresist was removed by a combination of downstream oxygen and forming gas plasma (IPC Branson 3500L) followed by a copper compatible product, to compensate for the possibility of premature punch-through of the Si x N y layer.
• Posistrip®EKC®LE is used in WSST 640 from SEMITOOL at 60°C for 15 minutes.
• the TEM cross section (Fig. 27) shows the cleaning efficiency of solution B6 at the bottom of the via and on the sidewalls.
• a slight attack of the metal at the bottom of the via is due the ability of the chemistry to remove damaged or oxidized copper.
• the structure of the exposed copper is mechanically changed (hammer-hardened) by the etching. It is necessary to remove this transformed material, which would increase the via resistance.
• the resulting shape of the material is not a problem as the lateral attack is lower than 50nm and the via will next be filled by fresh copper.
• a TOF-SIMS analysis on the top of the surface shows the quantitative reduction of copper contamination from 9x1014 atoms/cm2 before cleaning to 9x1013 atoms/cm2 after use of solution B6.
• the detection limit of the equipment is about 1012 atoms/cm2.
• VPD-TXRF vapor phase decomposition total reflection x-ray fluorescence
• Figs. 28-33 demonstrate the cleaning efficiency of solution B6 on large areas of exposed copper (Figs 28-29), trenches (30-31), and holes (32-33).
• an artifact due to sample cross sectioning breaks some TEOS lines which allows a comparison between the copper exposed to the etch process and that which was protected by the dielectric. This shows that solution B6 effectively cleans the residues, with no global attack of the copper (as demonstrated in figure 23), but the gentle action of the product is shown by the clear definition of the grain boundaries.
• Figures 38 and 39 show electrical results on an integrated circuit with 2 levels of copper.
• Via resistance is a measure of the cleaning efficiency at the contact between the 2 layers.
• the via resistance after cleaning with solution B6 corresponds to the theoretical via resistance, which proves a good cleaning with the via dimension being respected.
• Figure 40 shows the efficiency of solution B6 to reduce post etch residues.
• Curve (1) shows the composition of the blanket copper in ambient air, with a high peak intensity at 932.5 eV. for Cu 2 O.
• Curves (2) and (3) show the composition of the blanket copper after an O 2 /N 2 plasma etch for 34 sec. and 68 sec. respectively. The residues consist of CuO detected at 935 eV.
• Curves (4) and (5) show the composition of the blanket copper surface after processing through plasma etch, followed by cleaning in solution B6 for 2min. and 20 min., respectively. This shows a reduction of the CuO residues to a less oxidized state.
• Etch rates The main purpose of this invention is to clean damascene type structures when copper is exposed. For this reason a series of solvents were tested for compatibility with copper. Etch rates on metals are measured by using a four point probe on blanket sample, measuring the evolution in sheet resistance of the material versus time processed into the solution. The resultant etch rates are converted into Angstrom per minute (A/min), as in table 2.
• choline solutions for example solutions A5, D19, or D3 are compatible with copper material and will not attack the copper material when it is exposed to the solution during cleaning.
• the invention shows good compatibility with most low-k dielectric materials used in integrated circuit fabrication. Compatibility with dielectric materials is evaluated by the two following methods: • thickness measurement by ellipsometry (table 3);
• TEOS silicon dioxide
• HSQ hydrogen silsesquioxane
• MSQ methyl silsesquioxane
• organic dielectric in solutions of choline hydroxide 50%> (A5), propylene glycol 100% (El 3), and mixtures of both (solution B6) (Figs. 7-10).
• Figure 34 shows the FT-IR spectrum of the material as deposited (reference), and after treatment in solution B6 (processed at 50°C for an extended period of 30 minutes). As shown in the graph, no structural change of the material through processing is observed.
• the change in the dielectric constant of SiLK was followed by the mercury probe method.
• the mercury probe measures the capacitance of the dielectric between a mercury droplet and the bulk silicon.
• the dielectric constant is calculated from the equation:
• the C(V) curve gives an indication of the behavior of the dielectric under stress conditions.
• the C(V) curve in Fig. 35 shows that the material is not modified, as no hysteresis is induced in the material by processing in solution B6.
• Tests on patterned SiLK corroborate the blanket SiLK data, as no change in the morphology (e.g., bowing) is observed between the before treatment sample (Fig. 36) and the after treatment sample (Fig. 37). Again, solution B6 was used in the SEMITOOL apparatus at 50°C for 10 min.
• the recent introduction of copper as the new interconnect material challenges standard processing and requires new strategies. Etching and cleaning steps need to be redesigned in coordination with each other for optimum results.
• This invention deals with one of the problems encountered during etching: creating residues difficult to remove by any traditional cleaning treatment.
• the new etching strategy consists of a "2-step etch" process, in which a protecting layer helps to deal with easier to remove residues.
• a new chemistry has been developed in order to deal with the results of this process flow. This new chemistry, exemplified by solution B6, efficiently cleans post etch residues containing copper, without damaging the metal and with perfect compatibility with SiLK.
• the invention has been tested to remove photoresist on a sample covered with photoresist.
• the sample in this example is a dual damascene structure etched in a double layer of TEOS.
• the solutions reported in table 4 were successful in attacking the photoresist in various degrees:
• Solvents can be dimethyl acetamide (DMAc), DMSO, propylene glycol (PG), dipropylene glycol monomethyl ether (DPM), N-methyl pyrrolidone (NMP), or cyclohexyl pyrrolidone (CHP), while the bases consist of morpholine, MEA, diethanolamine, diglycolamine, choline bicarbonate, tetramethyl ammonium hydroxide (TMAH), or choline hydroxide.
• DMAc dimethyl acetamide
• DMSO propylene glycol
• DPM dipropylene glycol monomethyl ether
• NMP N-methyl pyrrolidone
• CHP cyclohexyl pyrrolidone
• MEA diethanolamine
• diglycolamine diglycolamine
• choline bicarbonate tetramethyl ammonium hydroxide
• TMAH tetramethyl ammonium hydroxide
• a chemistry composed of 2% to 12% of hydroxylamine with a strong base such as a quaternary ammonium hydroxide compound can be used to remove tough resist on inorganic substrate with an organic material exposed.
• the chemistry is compatible with both copper and the organic material.
• Table 7 efficiency of post via etch residues removal.
• TBC t-butyl catechol
• choline hydroxide is commercially available as a 40 to 50 weight percent aqueous solution from a variety of sources, including E.I. Du Pont de Nemours and Company, Wilmington, Delaware; Chinook Chemical, Toronto, Ontario, Canada; Japan Hydrazine Co., Tokyo, Japan and Mitsubishi Gas Chemical Company, Tokyo, Japan.
• the formulations in the above table include the water in these commercial choline hydroxide solutions in the amount of water specified.

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• 1999
  • 1999-06-30 US US09/343,532 patent/US6417112B1/en not_active Expired - Lifetime
  • 1999-07-02 KR KR1020017000187A patent/KR100645619B1/ko not_active Expired - Fee Related
  • 1999-07-02 EP EP99933689A patent/EP1127370A1/en not_active Withdrawn
  • 1999-07-02 WO PCT/US1999/015157 patent/WO2000002238A1/en not_active Ceased
  • 1999-07-02 AU AU49690/99A patent/AU4969099A/en not_active Abandoned
  • 1999-07-02 JP JP2000558545A patent/JP2002520812A/ja active Pending
  • 1999-07-06 TW TW088111444A patent/TW428241B/zh not_active IP Right Cessation

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