Patent Application
20140315386
Present invention discloses metal compound coated colloidal particles, methods of making, and use therefor. The metal compound coated colloidal particles have an important role in the slurry for chemical mechanical polishing (CMP) applications. For example, they can be used as the catalyst in CMP slurry. The metal compound coated colloidal particles include, but are not limited to metal ion, metal oxide coated colloidal particles.
There are a large number of materials used in the manufacture of integrated circuits such as a semiconductor wafer. The materials generally fall into three categories—dielectric material, adhesion and/or barrier layers, and conductive layers. The use of the various substrates, for instances, dielectric material such as TEOS (TEOS refers to Tetraethyl orthosilicate which is the precursor for making silicon dioxide films through chemical deposition process), plasma-enhanced TEOS (PETEOS), and low-k dielectric materials; barrier/adhesion layers such as tantalum, titanium, tantalum nitride, and titanium nitride; and conductive layers such as copper, aluminum, tungsten, and noble metals are known in the industry.
In semiconductor manufacturing process, metalized vias or contacts are formed. Typically, via holes are etched through the interlevel dielectric (ILD) to interconnection lines or to a semiconductor substrate. Next, a thin adhesion layer such as titanium nitride and/or titanium is generally formed over the ILD and is directed into the etched via hole. Then, a conducting film is blanket deposited over the adhesion layer and into the via. The deposition is continued until the via hole is filled with the conductive material. The excess conductive material is removed by chemical mechanical polishing (CMP) to form metal vias.
During the CMP process the chemicals present in CMP slurry develop an oxide layer onto the surface and this surface is mechanically abraded by abrasive particles. The CMP process must provide a high removal rate and good planarity through the simultaneous actions of chemical dissolution and mechanical abrasion.
In one particular semiconductor manufacturing process, via holes are etched through the interlevel dielectric (ILD) to interconnection lines or to a semiconductor substrate. Next, a thin adhesion layer such as titanium nitride and/or titanium is generally formed over the ILD and is directed into the etched via hole. Then, a tungsten film is blanket deposited over the adhesion layer and into the via. The deposition is continued until the via hole is filled with tungsten. Finally, the excess tungsten is removed by chemical mechanical polishing (CMP) to form metal vias.
A CMP slurry usually consists of abrasive, catalyst and oxidizer, and optionally a corrosion inhibitor. Work has been done in making various types of the catalyst.
U.S. Pat. No. 4,478,742 disclosed a method of producing iron acetate coated silica sol which comprising the steps of passing a mixture of ion-free colloidal silica and an inorganic iron salt in contact with a strong base anion exchange resin in the acetic acid salt from under conditions whereby the iron salt is converted to the iron acetate and is coated on the silica sol, thereby producing an iron acetate coated silica sol.
J. Colloid & Inter. Sci. 2010, 349, 402-407, taught a new method of Fe (metal) precipitation on colloidal silica with commercially available fumed silica slurry containing Fe ions, to overcome the stability problem (responsible in producing defects), The slurry was developed by using sodium silicate (Na2SiO3) as a raw material and the concentration of precipitation of metal was controlled by addition of Fe salt (Fe(NO3)3). To compare the concentration of precipitated Fe with directly added Fe ions in slurry solutions, static electrochemical and peroxide decomposition experiments were performed. Although the performance of the Fe precipitation appeared to be lower than Fe ion addition during these experiments, nearly equal removal rates were observed due to the dynamic condition during polishing.
J. Colloid & Inter. Sci. 2005, 282, 11-19, studied the synthesis and characterization of iron oxide-coated silica. A three-level fractional factorial study was used to determine the optimum conditions for producing goethite-coated silica. The amount of coating achieved was between 0.59 and 21.36 mg Fe g-1 solid. The most significant factor in coating using either adsorption or precipitation was the particle size of silica, where Fe increased from an average of 0.85 to 9.6 mg Fe g-1 solid as silica size decreased from 1.5 to 0.2 mm. Other factors investigated, including coating temperature, initial iron concentration, and contact time, were of less importance. The iron oxide coatings were observed to be non-uniform, concentrated in rough concave areas. FTIR revealed a band shift as well as a new band indicating changes in the chemical environment of Fe—O and Si—O bonds; these results along with abrasion studies suggest that the interaction between the oxide coating and silica surface potentially involves chemical forces. Because the nano-sized iron oxide coatings increased surface area, introduced small pores, and changed the surface charge distribution of silica, the coated system demonstrates a greater affinity for Ni compared to that of uncoated silica.
Tribology 2010, 30(3): 268-272A synthesized silicon/ferric oxide core-shell abrasive by using HNO3, NaOH, Fe (NO3)3 and SiO2 through chemical co-precipitation. The structure and dispersibility of the silicon/ferric oxide core-shell abrasive were characterized by X-ray diffraction (XRD), time-of-flight secondary ion mass spectroscopy (TOF-SIMS) and scanning electron microscope (SEM). The silicon/ferric oxide core-shell abrasive was then used to perform CMP of hard disk substrate.
US 2013/0068995 discloses a silica having metal ions absorbed thereon and a fabricating method thereof. The method includes following steps. A solution is provided, and the solution includes silica and persulfate salt therein. The solution is heated to react the silica with the persulfate salt, so as to obtain silica modified with the persulfate salt. Metal compound source is added in the solution, the metal compound source dissociates metal ions, and the silica modified with persulfate salt absorbs the metal ions to obtain the silica having metal ions absorbed thereon.
A stable, well-dispersed solution is very critical for CMP slurry. A unstable or separated CMP slurry often contains a lot of aggregates or large particles, which cause defects on the film polished.
There is still a need for making solid metal compound coated colloidal particles in a simple, low cost way. The solid metal compound coated colloidal particles are needed in CMP process(es) and slurry(s) to provide high removal rate and good planarity.
In one aspect, the invention provides particulates comprising:
solid metal compound coated colloidal particles formed by bonding metal compound particles on surfaces of colloidal particles; and
spaces among solid metal compound coated colloidal particles are free of the metal compound particles;
wherein
size of the metal compound particles ranging from 0.01-10 nm;
size of the colloidal particles ranging from 10-1000 nm; and
the size of the metal compound particles is smaller than the size of colloidal particles.
In another aspect, the invention provides a method of making solid metal compound coated colloidal particles comprising:
providing a solution comprising colloidal particles;
providing a soluble metal compound precursor;
providing a base;
adding the soluble metal compound precursor and the base to the solution comprising colloidal particles; and
forming the solid metal compound coated colloidal particles;
wherein the soluble metal compound precursor reacting with the base solution and turning into solid metal compounds; and the solid metal compounds are coated onto colloidal particle surfaces through bonding.
In yet another aspect, the invention provides a composition for chemical-mechanical polishing comprising:
solid metal compound coated colloidal particles; and
an oxidizer;
wherein the solid metal compound coated colloidal particles comprising metal compounds having size ranging from 0.01 to 10 nm coated on surfaces of colloidal particles having size ranging from 10 to 1000 nm; the size of the metal compounds is smaller than the size of colloidal particles; and metal compounds are solely coated on the surfaces of colloidal particles through bonding.
In yet another aspect, the invention provides a method of chemical mechanical polishing, comprising the steps of:
The chemical-mechanical polishing composition further comprises an abrasive, and optionally a corrosion inhibitor.
The colloidal particles are particles selected from silica particles, lattice doped silica particles, germania particles, alumina particles, lattice doped alumina particles, titania particles, zirconium oxide particles, ceria particles, organic polymeric particles, and combinations thereof; the metal compounds are compounds selected from Fe compounds, Cu compounds, Ag compounds, Cr compounds, Mn compounds, Co compounds, Ni compounds, Ga compounds, and combinations thereof; and the base is selected from the group consisting of KOH, NH4OH, KHCO3, K2CO3, quaternary ammonium hydroxides, organic amines, phosphonium hydroxides, N-heterocyclic compounds, and combinations thereof.
The weight % ratio of the metal compound precursor to the colloidal particles ranges from 0.001 to 3; and molar ratio of the base to the metal compound precursor is higher than 2.5.
In the accompanying drawings forming a material part of this description, there are shown:
The present invention discloses metal compound coated colloidal particles, the process of making the metal compound coated colloidal particles, and the use of the metal compound coated colloidal particles in chemical mechanical polishing (CMP) applications.
A colloidal particle solution containing 0.01 to 50 wt % of colloidal particles is prepared. The remaining is solvent, such as distilled water, and deionized (DI) water.
The colloidal particles include but are not limited to silica, lattice doped silica, alumina, lattice doped alumina, zirconium oxide, ceria, organic polymeric particles, and combinations thereof.
The organic polymeric particles include, but are not limited to carboxylic acid polymers such as those derived from monomers like acrylic acid, oligomeric acrylic acid, methacrylic acid, crotonic acid and vinyl acetic acid. Molecular weight of these polymers may be from 20000 to 10000000.
The colloidal particles can have various sizes. The size of colloidal particles ranges between 10-1000 nm, preferably 10-500 nm, most preferably 15-250 nm for CMP application. The colloidal particles can have various kinds of shapes, such as spherical, cocoon, cubic, rectangular, aggregate, tec.
Soluble metal compound precursors include but are not limited to iron Fe, copper Cu, silver Ag, manganese Mn, chromium Cr, gallium Ga, cobalt Co, nickel Ni, and combinations thereof.
Iron precursors include but are not limited to, ferric nitrate, ferric sulfate, ferric oxide and combinations thereof. The metal compound precursor can be metal ion precursors, include but are not limited to the salt of metal ion with nitrate, sulfate, chloride, and combinations thereof.
Soluble metal compound precursor is added to the colloidal particle solution. The weight ratio of metal compound precursor to colloidal particles in the solution is ˜0.001 to 3. As an example, 1.0 gram of metal compound can be added into the colloidal particle solution that contains 100 gram of colloidal particles which gives the weight ratio of 0.01 between the metal compound precursor and colloidal particles in the solution.
A base solution is added to the colloidal particle solution. Bases include but are not limited to KOH, NH4OH, KHCO3, K2CO3, quaternary ammonium hydroxides, organic amines, phosphonium hydroxides, N-heterocyclic compounds, and combinations thereof.
The alkyl groups of quaternary ammonium hydroxides can be the same, such as methyl groups, ethyl groups, or can be different, such as dibutyl-dimethyl-ammonium hydroxide. Examples include but are not limited to tetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide (TEAH), tetrabutylammonium hydroxide (TBAH), tetraalkylammonium hydroxide (TAAH). The quaternary ammonium hydroxides may also include aryl groups as well.
The organic amines include but are not limited to methylamine, dimethylamine, trimethylamine as well as alcohol amines such as ethanol amine.
Examples of phosphonium hydroxides include, but are not limited to tetrabutylphosphonium hydroxide and tetramethylphosphonium hydroxides. Examples of N-heterocyclic compounds include, but are not limited to compounds containing pyridine, imidazole, histidine groups.
The soluble metal compound precursor, and the base solution can be added to the colloidal particle solution separately or at the same time. The molar ratio of base to soluble metal compound precursor should be higher than 2.5.
Metal compound precursors react with the base, turn into solid metal compound. The soluble metal compound precursor can be ˜100% converted into solid metal compounds through the reaction. The solid metal compounds are then deposited or coated onto colloidal particle surfaces through bonding (such as chemical bonding) to obtain metal compound coated colloidal particles. The metal compound coated colloidal particles have solid metal compounds immobilized bonded on the surfaces of colloidal particles.
Solid metal compounds include, but are not limited to Fe compounds, Cu compounds, Ag compounds, Cr compounds, Mn compounds, Co compounds, Ni compounds, Ga compounds,
According to Derjaguin and Landau, Verwey and Overbeek (DLVO) theory, the energy barrier between charged colloidal particles will become smaller upon increased ionic strength. During the deposition or coating process, excess ions result from the soluble metal compound precursor increase ionic strength of the solution. If these excess ions stay in the solution, the solution is not stable and will show some settlement slowly over the time. The higher loading density (weight ratio of ions to colloidal particles) of ion, the more critical the stability is.
Excess ions in the metal compound coated colloidal particle solution are removed by ultrafiltration process to obtain the stable metal compound coated colloidal particle solution. Ultrafiltration is an in-line technique. The process removes anything whose size is smaller than the cut-off size of the filter membrane.
Soluble ions (for example, metal ions, NO3− from ferric nitrate, K+ from KOH) with sizes smaller than the cut-off size of the filter membrane are easily removed from the solution. During the ultrafiltration process, the metal compound coated colloidal particles which are much bigger than filter cut-off size, remain in the solution without any aggregation.
The metal ions left in the solution after the ultrafiltration process can be measured by centrifugation process. The supernatant of the result solution after centrifugation should contain less than 2 ppm, preferred less than 1 ppm metal ions. Thus, the metal compound coated colloidal particle solution is substantially free of excess metal ions after the ultrafiltration process.
Furthermore, in addition to removal of excess ions in the metal compound coated colloidal particle solution, the ultrafiltration also serves function of concentrating the solution.
After the amount of soluble ions are lowered to the desired level (monitored by conductivity meter), the amount of solids (the metal compound coated colloidal particles) can be increased by reducing the amount of the compensated distilled water being added into the solution that contains metal compound coated colloidal particles. Thus, the solution is more concentrated.
The concentrated solution allows the production of the more concentrated CMP slurry products. This is important since the cost of ownership can be greatly reduced.
Ultrafiltrated solution can be heated at a temperature ranging from 40° C. to 100° C. for 0.5 to 72 hours.
The invented process herein yielded the unique results, the solid metal compounds are substantially coated uniformly on the surface of colloidal particles. The solid content of such solid metal compound coated colloidal particle solutions ranges from 0.1 wt % to 40 wt %.
The size of the solid metal compounds coated on the colloidal particle surfaces ranges from 0.01 to 10 nm with the standard deviation of size less than 20%. The solid metal compounds coated on the colloidal particle surfaces can be in amorphous form, crystalline form, and combinations thereof.
The metal compound coated colloidal particles thus obtained have an important role in the slurry for chemical mechanical polishing (CMP) applications.
A CMP slurry usually comprises of abrasive, corrosion inhibitor, catalyst and oxidizer.
The catalyst could be in the soluble form or solid state form. The metal compound coated colloidal particles described in present invention are the solid state form of catalysts.
Any suitable abrasive includes but are not limited to silica, alumina, titania, ceria, zirconia can be used in the CMP slurry. The amount of abrasive in the slurry ranges from 0 to 25 wt %.
Any suitable corrosion inhibitors include but are not limited to polyethyleneamine; and other organic amine oligomers, and molecules. The amount of corrosion inhibitor in the slurry ranges from 0.0001 wt % to 2 wt %.
Any suitable oxidizer includes but is not limited to H2O2 and other per-oxy compounds; can be used in the CMP slurry. The amount of oxidize in the slurry ranges from 0.1 wt % to 10 wt %.
The metal compound coated colloidal particles are then used as the solid state catalyst in a CMP polishing compositions. The amount of the solid catalyst in the slurry ranges from 0.01 wt % to 10 wt %.
The metal compound coated colloidal particles can be used as both the solid state catalyst as well as the abrasive in a CMP polishing compositions.
For a CMP slurry, removable rate (RR) (Å/min.) and Within Wafer non-uniformity % (WIWNU %) are used to measure the performance of the slurry. An increased RR and reduced WIWNU % are indications of better performance of a slurry.
Removal Rate (RR) is the average amount of material removed in a given time, typically calculated over a great number of points:
Suitable surface uniformity (typically measured using known wafer profiling techniques) is reflected by within-wafer nonuniformity, or WIWNU %. It is the standard deviation of the removal rate of material from the wafer expressed in percent. The lower values typically reflecting better process control.
WIWNU % is calculated using the following equation:
WIWNU %=(pre-polishing W film thickness−post-polishing W film thickness)/mean of total W film thickness×100%
When the metal compound coated particles from the present invention are used in a CMP slurry, unexpected performances have been observed, Removable rate (RR) (Å/min,) is increased, while the reduced Within Wafer non-uniformity % (WIWNU %) can be achieved. RR can be tunable ranging 500-6000 Å/min., and WIWNU % is less than about 4%, preferably, 3%, and most preferably 2%.
The iron compound coated colloidal particles, and CMP slurry using the iron coated colloidal particles as the catalysts have been made in the working examples. The performance of the CMP slurry was measured.
In this example, iron compound coated colloidal silica particles were made by the process described below.
Iron precursor (soluble iron compound, such as, ferric nitrate, ferric sulfate or the combinations); colloidal silica; and KOH or ammonium hydroxide; were chosen as the soluble metal precursor, the colloidal particles and the base, respectively.
2.87 wt % colloidal silica solution was used. The size of the colloidal silica was around 40-50 nm.
The transmission electron microscopy (TEM) images of colloidal silica particles were shown in
431 ppm iron precursor was added into 2.87 wt % colloidal silica solution. The solution was stirred for 5 min.
Adding the base solution (Khmer ammonium hydroxide) into the above solution under stirring. The molar ratio of base to soluble metal compound precursor was 3.5 when KOH was used as the base; and was 5 when ammonium hydroxide was used as the base.
The solution was stirred for 10 min.
The resulted solution was sent to a ultrafiltration process to remove excess ions.
Conductivity was monitored during the ultrafiltration process. The resulted solution was ultrafiltered until conductivity was lowered to certain level, in this example: 100 μS/cm.
The resulted colloidal solution had a neutral pH. The solution was stable over a wide pH range. The pH of such iron compound coated colloidal silica solution can be adjusted as needed.
The wt % of the solid content in the solution could be increased by decrease the flow of compensating DIW into the solution, for example 14 wt % was achieved.
The resulting solution was transferred into a reactor. The temperature for the reactor was increased to 80° C. The solution was kept stirred at this temperature for 2 hours.
Soluble iron test was conducted next to check the amount of soluble iron left in the solution. The solution was centrifuged at 13,500 RPM for 1 hour. The supernatant was obtained. Full digestion of supernant (by mixture of H2O2 and sulfuric acid) was conducted by Inductively coupled plasma atomic emission spectroscopy-(ICP-AES) measurement of iron level. The iron level obtained was less than 1 ppm, thus confirming that there was substantially no soluble iron left in the solution.
The solid iron compound on the silica surface was amorphous, having a size of 1-10 nm with the standard deviation of size less than 20%.
The solution can be further heated under 100° C. for 1-24 hours to have iron compounds in crystalline form, and combinations of amorphous and crystalline.
More specifically,
The energy dispersive spectra (EDS) from the prepared iron coated silica particles were shown in
It is understood that the amount of soluble metal precursor, the colloidal silica particles and the base used depended on the desired loading of catalyst, metal compounds or desired coating density of metal compounds.
The iron compound coated colloidal silica particles were used as solid catalyst in a CMP slurry for polishing wafer or semiconductor substrates containing tungsten (W) and TEOS.
Polishing performance of the slurry containing the iron coated silica particles was measured.
As shown in Table 1, the new solid catalyst made with the process disclosed in present invention increased W RR and decreased TEOS RR, which in turn resulted in a higher selectivity of W:TEOS.
Most importantly, with the use of new solid state catalysts in W CMP polishing composition, the W removal profile was unexpected uniform across the whole wafer.
As illustrated in
A stable, well-dispersed solution is very critical for CMP slurry. A unstable or separated CMP slurry often contains a lot of aggregates or large particles, which cause defects on the film polished.
The solid metal compound coated colloidal particles made with present invention sustain dispersed state, which means the solution containing the solid metal compound coated colloidal particles is a uniform solution, does not separate into layers. The CMP slurry comprise the solid metal compound coated colloidal particles directly combined with other additives gave unexpected performance.
The embodiments and working examples of present invention listed above, are exemplary of numerous embodiments and working examples that may be made of present invention. It is contemplated that numerous other configurations of the process may be used, and the materials used in the process may be elected from numerous materials other than those specifically disclosed.
This application claims priority to U.S. provisional application 61/813,950 filed on Apr. 19, 2013, the entire contents of which is incorporated herein by reference thereto for all allowable purposes.
| Number | Date | Country | |
|---|---|---|---|
| 61813950 | Apr 2013 | US |
