TWI408739B - Systems, methods and slurries for chemical mechanical polishing - Google Patents

Description

Chemical mechanical polishing system, method and abrasive

The present invention relates to a system, method and abrasive for polishing a film containing silver (Ag) or a silver alloy.

When a integrated circuit is fabricated on a semiconductor substrate, a multilayer interconnection structure is involved, and layers are sequentially stacked between layers, and each layer also requires multiple photolithography steps. Nowadays, the ultra-large-scale integrated components, the integration density is increasing, the design specifications have reached the sub-micron level, and various precision processing technologies are constantly being researched and developed. The pattern is prepared in a selected area of the substrate (usually by depositing an insulating layer), followed by the steps of doping impurities (ion implantation), performing oxidation, preparing trenches, and embedding conductive metal. In the preparation of the integrated circuit structure, each metal layer needs to use an insulating layer such as an oxide layer to isolate another metal layer. Due to the continued miniaturization of circuit elements, multiple metal layer interconnections are required to have optimum electrical conductivity. Therefore, in order to improve the quality of the metal layer and avoid defects, the underlying surface should be very flat.

In order to meet the performance standards of the best components and future generations of new components, the wires must have better electrical conductivity and better flatness. At present, aluminum alloys are widely used in integrated circuits in many integrated circuit components. Copper has better electrical conductivity and excellent resistance to electromigration. Circuit materials such as high-performance components such as microprocessors are now widely used. Since the conductivity of silver exceeds that of copper and aluminum, silver may be used for the wiring material of high-speed components in the future. As with copper, chemical mechanical polishing is also required when preparing the desired silver-containing structure.

As described above, in order to meet the needs of larger-scale integration, various components require more metal layers and dielectric layers, and the surface topography of the substrate must meet the well depth requirements of submicrolithography. A chemical mechanical polishing (CMP) method as disclosed in U.S. Patent No. 6,663,472 is a polishing material such as a semiconductor substrate and a precision optical member. A method of achieving high flatness and high uniformity. This method was originally used to flatten the semiconductor wafer and also to eliminate the uneven shape left on the substrate when preparing the submicron circuit. When the substrate is further processed, such as by photolithography and etching to fabricate the integrated circuit structure, any difference in thickness on the plane increases the difficulty of meeting high-resolution fault tolerance requirements, while meeting the requirements for achieving high yield on the substrate. A wafer is necessary.

Chemical mechanical polishing is generally used for planarization of the interlayer insulating film and shallow trench isolation because it can completely flatten the exposed layer, reduce the burden of exposure technology, and stabilize the yield of the finished product. Another application of chemical mechanical polishing is the inlay of metal (sometimes referred to as the Damascus process) in a dielectric layer, where chemical mechanical polishing is a patterning process. In the above pattern forming process, first, the etching dielectric layer is formed into a trench, followed by depositing a metal layer, and finally the excess metal is removed by chemical mechanical polishing to make the metal layer and the surface of the dielectric layer have a plane.

A common chemical mechanical polishing process is to support and fix the substrate to align the rotating polishing pad with abrasive disposed on the polishing pad while applying a pressure to the rotating polishing pad. The pH of the polishing abrasive controls the chemical reaction, such as the oxidation of the chemical during the fabrication of the underlying insulating layer. The polishing pad is made of non-fibrous polyurethane or a polyester based material. Generally, the hardness of the polishing pad is between 50 and 70 Shore hardness. Commercially available polishing pads for semiconductors are made from a woven polyurethane material. Distributing the abrasive containing abrasive to the polishing pad adjusts the polishing characteristics of the polishing pad to enhance polishing and planarization of the substrate.

Chemical mechanical polishing is carried out by means of an abrasive which contains fine abrasive particles, such as colloidal cerium oxide or aluminum oxide, by which some of the material on the surface to be polished can be removed. In addition, the abrasive may also contain chemicals that react with the processing surface to help remove a portion of the surface material. The abrasive is between the surface of the wafer and the polishing pad. The wafer is pressed against the rotating polishing pad during polishing or planarization processing. In addition, the wafer can also be rotated and oscillated back and forth on the polishing surface to enhance the polishing effect.

Typical chemical mechanical polishing abrasives, such as ceria or alumina, are suspended in an aqueous medium having oxidation, as described in U.S. Patent No. 6,638,328. In the prior art, various mechanisms have been shown to polish the metal surface with an abrasive. When an abrasive is used to polish the metal surface without forming a surface film layer, the metal particles may be mechanically removed to continue processing. When using this method, the chemical dissolution rate must be slow to avoid wet etching. However, a better mechanism is to form a thin, soft, easy-to-remove film by reacting a metal with one or more components of the abrasive such as silver and/or an oxidizing agent, and then mechanically act. This thin, abradable layer is removed in a controlled manner. Once the mechanical polishing process is stopped, a passivation film remains on the surface to allow the wet etching process to be controlled. When a chemical mechanical polishing abrasive is polished by this mechanism, it is much easier to control the chemical mechanical polishing method.

In addition, there are many types of abrasives used in chemical mechanical polishing, and common abrasive particles include cerium oxide, aluminum oxide, cerium oxide, titanium oxide, and zirconium dioxide.

Accordingly, it is a primary object of the present invention to provide methods, systems, and abrasives for the preparation of silver interconnect and mirror patterns for use in integrated circuits, imaging techniques, and other components to address the above problems.

In integrated circuits such as imaging technology and other components, silver interconnect and mirror pattern preparation methods, systems, and abrasive systems are disclosed below. Silver has the highest conductivity and reflectivity compared to any other metal in nature; silver also has very good anti-electron migration (EM) properties depending on its atomic weight. The above properties make silver an ideal choice for the preparation of integrated circuits. It can be used in a variety of integrated circuit chips (various CPUs and logic chips, specific-purpose integrated circuit chips, memory chips such as: dynamic random access memory, static memory) Body, electrically erasable read-only memory and flash memory memory and others), silver can also be used for certain special components, such as micro-electromechanical systems Optical memory 矽-based liquid crystal display (LCOS) and LDP.

According to the purpose of manufacture, chemical mechanical polishing of two silver or silver alloys is described here, one is the thickening and flattening of a silver or silver alloy film, and the other is the surface finishing of a silver or silver alloy film layer.

In the first preferred embodiment, the following parameters are used: polishing rate: not less than 2000 angstroms per minute.

Downward pressure: no less than 3 psi.

Polished tabletop rotation rate: no less than 50 rpm.

Polishing head speed: no less than 50 rev / min.

Abrasive flow rate: from 100 to 500 ml/min, preferably 150 ml/min.

Scratch of the polishing pad: while polishing and/or before and/or after polishing.

Polishing pad: IC 1000 or IC 1010 or other polyurethane material or hard pad.

Moreover, in the second preferred embodiment, the following parameters are used: polishing rate: no more than 1000 angstroms per minute.

Downward pressure: no more than 3 psi.

Polished tabletop rotation rate: no more than 50 rpm.

Polishing head speed: no more than 50 rev / min.

Abrasive flow rate: from 100 to 500 ml/min and 150 ml/min.

Scratch of the polishing pad: while polishing and/or before and/or after polishing.

Polishing pad: Polytex polishing pad or other soft polishing pad.

Roughness: (after polishing) equal to or lower than 5 angstroms.

Reflectance: 94% or more (in the visible range).

Dishing: less than 400 angstroms.

Erosion: less than 1000 angstroms.

Number of defects: less than 1000.

Silver film loss: less than 1000 angstroms.

This system provides a method for finely processing the surface of silver by chemical mechanical polishing and an abrasive composition for obtaining high reflectivity and planarization of the mirror.

The abrasives used in the two preferred embodiments described above comprise at least one of the following components: abrasive particles, silver etchants, surfactants, silver complexing agents, corrosion inhibitors, buffers, and catalysts.

The invention discloses a chemical mechanical polishing mechanism of five silver or silver alloys in a grinding system, which are (1) oxidation-softening-polishing mechanism; (2) etching-passivation-polishing mechanism; (3) passivation-polishing-etching mechanism (4) Self-passivation-etching mechanism; and (5) Surfactant passivation mechanism. The actual mechanism may be accomplished by any one of the above five mechanisms or any combination of the above five mechanisms.

The chemical mechanical polishing method of silver or silver alloy can be applied to the integrated circuit manufacturing of new integrated circuit (IC) components of future generations by a preferred abrasive composition and chemical mechanical polishing process. The above two methods or a combination of both can achieve one or more of the following uses and benefits.

Due to its high conductivity and high reflectivity, metallic silver is important and promising for current and future integrated circuit applications, electronics and imaging components, such as for back-end interconnect or imaging wafer technology. The mirror in the middle.

The chemical mechanical polishing processes and various abrasives disclosed herein can be used to obtain a pattern of silver on a semiconductor component, a high reflectivity of a silver or silver alloy mirror, a fast component speed, and the like. At the same solids content, the various abrasives described herein are more effective than the conventional colloidal abrasive particles, and retain the low defect formation characteristics of conventional colloidal abrasives.

The results obtained by chemical mechanical polishing include the production of a thinner silver or silver alloy layer than before and the production of a metallic silver or silver alloy whose surface forms a coplanar surface with the surface of the dielectric layer, resulting in a silver or silver alloy film having a high Reflectivity surface, low corrosion and dents, reduced defect rate, precise thickness and structure. In one embodiment, the results obtained can include wafer roughness (after polishing) equal to or less than 5 angstroms, specular reflectance (in the visible range) of more than 94%, wafer defects less than 1000, and surface depressions ( Dishing) is less than 400 angstroms, corrosion (Erosion) is less than 1000 A, and silver or silver alloy wear is less than 1000 angstroms.

The silver chemical mechanical polishing abrasive of the present invention can polish a surface at high speed or fine without causing defects, and such chemical mechanical polishing does not contaminate the surface to be polished. Further, such chemical mechanical polishing abrasives, systems, and methods disclose ways to improve the smoothness of the polished surface of the substrate.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

In order to achieve the above-mentioned technical means and their effects in relation to the scope of the present invention, several preferred embodiments are described as follows: DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes a chemical mechanical polishing tool to planarize a silver or silver alloy film on a semiconductor substrate and form a finished surface, which will now be described in detail using some preferred embodiments and the accompanying drawings. It should be noted that, for convenience of description, the same reference numerals are used to refer to the same parts.

1A is a schematic view showing a manufacturing process of a semiconductor, and FIGS. 1B to 1H are schematic views showing a corresponding structure of the process of FIG. 1A. The process of Figure 1A is to form a silver or silver film S10 on the surface of the wafer; and to polish a wafer having a silver or silver film thereon.

In one embodiment, forming a silver film S10 on the surface of the wafer includes forming a dielectric layer and patterning it S12; depositing a barrier layer S14 on the dielectric layer; and depositing a silver film S16 on the barrier layer.

The polishing process S20 of the wafer having the silver film comprises placing the silver-containing surface on the polishing pad S22; applying the polishing abrasive S24 on the polishing pad; rotating the wafer and the polishing pad simultaneously and pressurizing S26, and then the residue on the wafer can be Clear.

The system comprises the preparation of a silver film and polishing of a wafer with a silver film. This silver film can be made of pure metallic silver or a silver alloy. Since pure silver is a soft metal that is susceptible to defects such as scratches, it can be hardened with a silver alloy to reduce or avoid defects, and it can also improve the electromigration resistance of the silver film. The silver alloy may be made of two or more metals such as a silver alloy made of copper, aluminum, magnesium, titanium, platinum, palladium, nickel or any other metal. The impurities contained in the alloy composition are 0.1% to 5%. However, in order to maintain the high reflectivity of silver, other metals or impurities in the metallic silver or silver alloy should be less than 1%.

The abrasive particles contained in the abrasive may be SiO ₂ , Al ₂ O ₃ , CaCO ₃ , ZrO ₂ , CeO ₂ , TiO ₂ , Si ₃ N, AlN, TiN, SiC, Al(OH) ₃ , polymer (eg Polyethylene or polytetrafluoroethylene), inorganic or organic or a combination of the above. The abrasive particles are selected based on the hardness of the passivation film and the pH of the abrasive. Since silver is a soft metal, it is basically necessary to use softer particles such as polyethylene or polytetrafluoroethylene. Since the isoelectric point of the soft particles is different from the pH of the solution, the occurrence of defects such as scratches can be reduced. In order to obtain a faster polishing rate and for a harder and thicker passivation layer, harder particles such as SiO ₂ , Al ₂ O ₃ or ZrO ₂ may be used.

To disperse these particles to form a homogeneous solution, a surfactant and/or a surface active agent may be added to the solution. Surfactants and auxiliaries can be selected from various surfactants such as ionic, nonionic, and macromolecular types, among which nonionic macromolecular surfactants are preferred because they are not affected by changes in the pH of the solution. . Nonionic macromolecular surfactants include polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, acrylic acid and acrylate copolymers, copolymers of acrylic acid and hydroxypropyl acrylate, copolymers of maleic acid and acrylic acid, Acrylic acid and hydroxypropyl acrylate terpolymer, copolymerized modified polyvinyl alcohol, methacrylic acid ester and alkanolamine copolymer, copolymer of maleic acid and styrene, polyoxyethylene a monomethyl copolymer, a carboxylic acid-treated polyvinyl alcohol, a derivative of a glycol and a polyamine copolymer, a specific copolymer dispersant, a hydroxypropyl acrylate, and any other monomer such as isobutylene or propylene oxide a copolymer of 2-hydroxyacetaldehyde, methacrylate, maleic anhydride, acrylic acid, methacrylic acid, acrylamide, methacrylamide, styrene, vinylpyridone or the like, and is not limited to the above Ingredients.

As for the silver complexing agent, since silver is a soft colloidal metal, silver ions are sensitive to chemical or physical factors, and many chemical or physical factors such as impurities, S ^2- and copper react with Ag ⁺ to form Ag or other precipitated compounds. The reaction product leaves a large amount of polishing residue, which also stains the polishing pad and makes the wafer production process unstable and prone to defects. In order to avoid this, a silver complexing agent can be used. The silver complexing agent can be obtained from NH ₄ ⁺ , X (X = Cl ^- , Br ^- , I ^- ), ethylenediaminetetraacetic acid (EDTA), cyclohexanediamine Acetic acid (CyDTA), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetrapropionic acid (EDTP), ethylene glycol diethyl ether diamine tetraacetic acid (EGTA), ethyl ethylenediamine triacetic acid (HEDTA), nitrogen It is selected from the group consisting of triacetic acid (NTA), tetraethylenepentamine, triethylenetetramine and other components.

The chemical mechanical polishing system can be used with a fixed abrasive supply system. The abrasive supply system is controlled by a computer. The computer controlled abrasive flow rate system determines the optimum flow rate of the abrasive, the optimum distance between the abrasive nozzle and the polishing head, thereby obtaining the maximum polishing rate for chemical mechanical polishing. The abrasive flow rate system controls the flow rate of the abrasive on the polishing pad and the optimum distance between the abrasive nozzle and the polishing head to optimize the flow of abrasive on the polishing pad. In order to maintain the process parameters during the chemical mechanical polishing process, it is necessary to control the rotational speed of the polishing pad and the polishing head, the pressure on the polishing head, and the pressure on the wafer under the polishing head. In one embodiment, the adjustment system employs a current detector to detect the current driving the table in the chemical mechanical polishing system to rotate the motor. This system changes the flow rate of the abrasive to the position of the abrasive nozzle because the distance between the nozzle and the polishing head can be varied until the current is reduced to a minimum.

In one embodiment, the polishing process of the wafer comprises forming a dielectric layer on the semiconductor substrate, preparing a pattern on the dielectric layer, depositing the channel and the channel with a barrier material, and filling the trench with metal silver or a silver alloy. Roads and passages. The silver or silver alloy film is then subjected to chemical mechanical polishing.

The dielectric layer can be made from high-density plasma yttrium oxide (HDP), plasma-enhanced tetraethyl yttrium oxide glass (PETEOS), yttrium-rich yttria glass (SRO), borophosphoquinone glass (BPSG), cesium fluoride. Glass (FSG), a low dielectric constant material and any other oxide and dielectric material, and the dielectric layer can be prepared by chemical vapor deposition (CVD), physical vapor deposition (PVD), spin coating or other Any suitable method. The dielectric layer pattern can be formed by dry etching or wet etching. The film on the metallic silver or silver alloy can be prepared by electroplating, electroless plating, CVD, PVD or other methods.

Chemical mechanical polishing of silver or silver alloy: the surface of the silver or silver alloy on the wafer is placed on a polishing pad, and a chemical mechanical polishing abrasive is applied to the polishing pad to rotate the wafer and the polishing pad at a specific rate, respectively. The wafer is pressed against the polishing pad at a specific downforce. The residue on the polishing pad is removed after polishing or after polishing. In addition, the wafer can be cleaned with an effective cleaning solution to remove polishing residues to keep the polished wafer clean.

The material to be polished may be silver or a silver alloy, a barrier layer and a dielectric layer. Moreover, depending on the specific conditions in the production process, there may be the same or different polishing rates between the silver and silver alloys, the barrier layer and the dielectric layer. The various abrasives used in the chemical mechanical polishing process may contain abrasive particles, surfactants, oxidizing agents, complexing agents, corrosion inhibitors, buffers, and catalysts.

In one embodiment, the chemical mechanical polishing process adopts the following parameters: a chemical mechanical polishing head under a pressure of not less than 3 psi; a table top rotation speed of not less than 50 rpm; a polishing head rotation speed of not less than 50 rpm; The flow rate of the agent is between 100 and 500 ml/min, preferably 150 ml/min. The polishing rate of silver or silver alloy is not less than 2000 angstroms/minute. Chemical mechanical polishing pads can be selected from IC1000, IC1010 or polyurethane or hard mat. In a further preferred embodiment, the downforce is 2 psi, the table top (300 mm diameter) speed is 54 rpm, the head speed is 60 rpm, and the polishing slurry flow rate is 200 ml/min. In another embodiment, the polishing process comprising the silver or silver alloy surface layer is to place the silver or silver alloy surface on the polishing pad; rotate the surface containing the silver or silver alloy with the polishing pad, and pressurize; at the same time, Applying a chemical mechanical polishing abrasive to the polishing pad (for example, the abrasive preferably comprises 5.0 wt% of polytetrafluoroethylene particles, 0.1 wt% PAA, 0.1 wt% BTA, 0.5 wt% ethylenediaminetetraacetic acid, and the balance is Water, pH 4.25, pH adjuster is ethylenediaminetetraacetic acid and hydrochloric acid); at the same time as and/or after the polishing process, the polishing residue is removed to keep the polishing pad clean.

The silver or silver alloy surface film may be present on a semiconductor substrate, a dielectric material substrate, a glass substrate, or any other substrate. Silver alloys can be used instead of silver to overcome the shortcomings of pure silver hardness. The silver alloy may be made of two or more elements such as silver which may be alloyed with copper, aluminum, magnesium, titanium, platinum, palladium, nickel or any other element. The surface of the silver or silver alloy may be the entire surface of the silver or silver alloy, or it may be partially silver or silver alloy surfaces, such as silver or silver alloy, which is coplanar with the surface of the dielectric layer. The content of impurities in the silver alloy may be between 0.1% and 5%. Since the high reflectivity of silver is required in the application, the other metal content should be no more than 1%.

The dielectric layer can be HDP, PETEOS, SRO, BPSG, FSG, low dielectric A constant material or any other oxide and dielectric material. The preparation method can be CVD, PVD, spin coating or other suitable method.

The surface of the silver or silver alloy film can be made by damascene or double damascene. The damascene method or the dual damascene method comprises forming a dielectric layer on a substrate; preparing a pattern on the dielectric layer; depositing a barrier material on the surface of the channel and the channel; and then filling the metal silver or silver alloy into the channel and the channel The polishing or etching or polishing is combined with etching so that the surface containing the silver or silver alloy film is formed.

Another method of making a silver or silver alloy surface is a dielectric material filling process comprising forming a silver or silver alloy layer on a substrate; patterning the silver or silver alloy layer; as an option, The barrier material is deposited on the surface of the channel and the channel; the dielectric material is filled; then an etching or chemical mechanical polishing method or a combination of the two is used to form a film or surface containing silver or a silver alloy, which is formed with the dielectric layer. same plane. Other methods can be used to produce the same silver or silver alloy film or surface. For example, a silver film can be produced by Lift off.

In the above integrated method, there is a typical chemical mechanical polishing process: the pressure under the chemical mechanical polishing polishing head does not exceed 3 psi; the desktop rotation speed does not exceed 50 rpm; the polishing head rotation speed does not exceed 50 rpm; the abrasive flow rate 100~500ml/min, 150ml/min; silver or silver alloy polishing rate not more than 1000A/min; polishing pad can be made with polytex pad or other pad, polishing pad before polishing or polishing needs to be Scratch.

Polishing silver or silver alloy abrasives contain abrasive particles, etchants, surfactants, complexing agents, inhibitors and buffers. The polishing mechanism of the abrasive may be: oxidation-softening-polishing mechanism, etching-passivation-polishing mechanism, passivation-polishing-etching mechanism, self-passivation-etching mechanism and surfactant inhibition mechanism, or a combination of these mechanisms. The abrasive particles may be selected from the following materials, but are not limited to the following materials, such as SiO ₂ , Al ₂ O ₃ , CaCO ₃ , ZrO ₂ , CeO ₂ , TiO ₂ , Si ₃ N ₄ , AlN, TiN, SiC, Al (OH). ₃ , MgO, polymers (such as polyethylene or polytetrafluoroethylene), inorganic or organic materials or a combination of the above. The abrasive particles are selected according to the hardness of the passivation layer and the pH of the abrasive. Because the silver film is soft, it is basically to select softer particles such as polyethylene or polytetrachloroethylene, and to make the pH value of the solution and its isoelectric point. Different, this can reduce the occurrence of defects during grinding. If it is desired to grind a hard and thick passivation layer and a higher polishing rate is required, slightly hard particles such as SiO ₂ , Al ₂ O ₃ or CeO ₂ may be used.

If the solution does not contain nitric acid or complexes (ammonia, cyanide, etc.), and silver has a strong anti-corrosion ability, the pH of various abrasives can be between -2 and 16. In the oxidation-softening-polishing mechanism, the pH value is preferably 6 to 16; while in the etching-passivation-polishing mechanism, the passivation-polishing-etching mechanism, the pH value is preferably -2 to 8; in the self-passivation-etching mechanism The pH value is preferably 5 to 10; the pH value of the surfactant inhibition mechanism can be used in all ranges, but it is preferably pH 8 to 11.

Surfactants can be selected from the following materials, such as polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, acrylic acid and acrylate copolymers, copolymers of acrylic acid and hydroxypropyl acrylate, copolymerization of maleic acid and acrylic acid. , acrylic acid and hydroxypropyl acrylate terpolymer, copolymerized polyvinyl alcohol, copolymer of methacrylate and alkanolamine, copolymer of maleic acid and styrene, Oxyethylene monomethyl copolymer, carboxylic acid treated polyvinyl alcohol, derivatives of ethylene glycol and polyamine copolymer, specific copolymer dispersant, hydroxypropyl acrylate and any other monomer such as isobutylene, ring Copolymers of oxypropane, 2-hydroxyacetaldehyde, methacrylate, maleic anhydride, acrylic acid, methacrylic acid, acrylamide, methacrylamide, styrene, vinylpyridone, etc., but are not limited thereto The above ingredients.

The complexing agent can be selected from the following materials, but is not limited to the following materials: NH ₄ ⁺ , X (X = Cl ^- , Br ^- , I ^- ), EDTA, CyDTA, DTPA, EDTP, EGTA, HEDTA, NTA, IV Ethylene pentamine, triethylenetetramine or a combination thereof. The buffer can be an organic compound such as ethylenediamine, oxalic acid, or inorganic compounds such as HNO _3, NH ₃ H ₂ O. The inhibitor may be an organic surfactant, or an element containing N or S or O or P or Zn or a compound containing a π bond, such as 1,2,3-benzotriazole, anthracene, benzothiophene (sulfur茚), hydrazine, isoindole, 3-azaindole, [2,3-d]-indole-triazole, 1-pyrazole, 1,2-benzisoxazole, oxazole, isoxazole, Benzimidazole, benzoisoxazole, 1,2,3,7-tetraazaindene, 1-pyrazolo[b]pyrazine, triazolopyrazine, ox, benzofuran, hydrazine or their combination.

The etchant can be selected from the following components, but is not limited to these components, such as HNO ₃ , HX (X = Cl, Br, I), HXO ₃ (X = Cl, Br, I), I ^- + I ₂ , Cl ^- + Cl ₂ , Br ^- + Br ₂ , AgNO ₃ or a combination of these components.

The oxidizing agent may be a salt of H ₂ O ₂ , S ₂ O ₆ ^2- or S ₂ O ₈ ^2- , KIO ₃ , KMnO ₄ , KNO ₃ , HNO ₃ , bromate, bromine, butadiene, chlorate , chloric acid, chlorine, chlorite, chromate, chromic acid, dichromate, fluorine, halogen salt, halogen element, hypochlorite, nitrous oxide, oxide, oxygen, difluorination Oxygen, ozone, peracetic acid, perborate, perhalogenate, bicarbonate, perchlorate, perchloric acid, perhydrate, peroxide, persulfate, permanganate, sodium borate, Sulfuric acid or a combination of the above ingredients.

Specific examples of various chemical mechanical polishing methods in the above process will be discussed below. 2A to 2C are schematic views showing a process of preparing a silver film pattern by the Damascus method. The material of the wafer or substrate can be selected from the following materials: HDP, PETEOS, TEOS, SRO, BPSG, FSG, low dielectric constant materials, and any oxide and dielectric materials. The channel pattern 323 is generally prepared by dry etching, but a wet etching method can also be employed. A dielectric layer 321 is prepared on the substrate and etched as appropriate. The dielectric layer 321 is prepared with a barrier layer (not shown) to prevent the diffusion of silver prior to silver deposition after etching. Next, a silver layer 325 is deposited by some suitable means including electroplating, electroless plating, electroless plating, CVD, PVD or other methods. A polishing step is then performed to remove silver or silver alloy from the surface of the dielectric layer, which provides a flat surface suitable for semiconductor processing. The polishing step may employ a chemical mechanical polishing method comprising placing a surface on the polishing pad, applying a polishing abrasive to the polishing pad, and simultaneously rotating and pressurizing the wafer and the polishing pad, and then removing the residue on the wafer.

3A to 3C are schematic views of a dual damascene method in which a silver layer 325 or a silver film on a substrate is removed by chemical mechanical polishing, leaving silver to form the same plane as the substrate. The chemical mechanical polishing process parameters as a specific embodiment are as follows: polishing rate: not less than 2000 angstroms/minute

Under the head: not less than 3 psi

Desktop speed: no less than 50 rev / min

Polishing head speed: no less than 50 rev / min

Abrasive flow rate: 100 to 500 ml/min, preferably 150 ml/min

Polishing pad scraping: polishing at the same time and / or after polishing

Polishing pad: IC1000 or 1010 or other polyurethane pad or other hard pad

In some applications, a smooth, flat, highly reflective surface is required. For these purposes, the structures in Figures 2C and 3C may require additional rework, such as a finishing step of a fine silver surface. The structure in Fig. 2C can also be accomplished by the oxide filling method shown in Figs. 4A to 4C. The chemical mechanical polishing method for silver for surface finishing differs from the chemical mechanical polishing method for silver described above. In the chemical mechanical polishing method of silver described above, the polishing rate is greater than 2000 angstroms/minute, but here the chemical mechanical machine In the polishing method, the purpose is to improve the reflectivity, smoothness and flatness of the silver plane. The amount of silver removal is not a major problem, so the polishing rate does not need to exceed 1000 angstroms/min, and only a small amount of silver needs to be removed on the surface. membrane. This chemical mechanical polishing method has many advantages, one of which is to minimize dents and corrosion. Due to the silver film, the dielectric layer on the silver film, and the dielectric layer embedded in the silver film are all light, slow, and slightly ground, providing better dents than using a fast, rough polishing method. With corrosion characteristics. Other advantages include improved flatness of the silver film surface on the silver surface, improved reflectivity, and reduced defect rate.

A typical chemical surface polishing method for silver surface processing is to be characterized as follows: grinding rate: no more than 1000 angstroms / minute

Under the head: no more than 3 psi

Desktop speed: no more than 50 rev / min

Polishing head speed: no more than 50 rev / min

Abrasive flow rate: 100 to 500 ml/min, preferably 150 ml/min

Polishing pad scraping: polishing at the same time and / or after polishing

Polishing pad: polytex pad or other cushion

Unevenness: (after polishing) 5 angstroms or less

Reflectance: 95% or more (visible range)

Surface depression: less than 400 angstroms

Corrosion: less than 1000 angstroms

Number of defects: less than 1000

Silver film loss: less than 1000 angstroms

In addition, the chemical mechanical polishing method of silver can adopt the following mechanisms:

a. Oxidation-softening-polishing mechanism

In this mechanism, the silver film is quickly oxidized to AgO or Ag ₂ O or Ag ₂ O ₂ and an oxidized layer is formed on the surface of the silver film. The silver oxidizing agent may be a salt of H ₂ O ₂ , S ₂ O ₆ ^2- or S ₂ O ₈ ^2- , KIO ₃ , KMnO ₄ , KNO ₃ , HNO ₃ , bromate, bromine, butadiene, chloric acid Salt, chloric acid, chlorine, chlorite, chromate, chromic acid, dichromate, fluorine, halogen salt, halogen element, hypochlorite, nitrous oxide, oxide, oxygen, difluoride Oxygen, ozone, peracetic acid, perborate, perhalate, bicarbonate, perchlorate, perchloric acid, perhydrate, peroxide, persulfate, permanganate, sodium borate , sulfuric acid or a combination of the above ingredients. The oxide film may be softer or harder than the metallic silver film and have a certain thickness. The oxide film separates the silver film from the solution and is in direct contact with the solution. Therefore, the interface between the oxide layer and the solution becomes weaker due to physical and chemical factors such as hydrogen bonding, surfactant or ultrasonic waves, and the connection to the underlying atoms. A polishing step is performed to remove the weakly connected portion of the surface of the oxide layer, and the oxidation of the silver film is still being performed while polishing, and in a certain chemical environment, the weak connection function on the surface is also proceeding. Since the weakly joined portion of the surface of the oxide layer is more easily removed and the lower portion thereof is relatively hard to be removed, polishing and planarization of the silver film can be obtained. The parameters of the polishing step and the hardness and size of the abrasive particles should be selected according to the hardness, density and thickness of the oxide layer. Due to the lower density, softer, and thinner characteristics of the passivation layer, a milder and slower processing parameter should be chosen, such as low spin rate, low downforce, and abrasives containing softer, smaller abrasive particles.

In the mechanism a, the abrasive may comprise, for example, 1 wt% of polytetrafluoroethylene particles, 0.05 wt% of polyethyleneimine, 0.5 wt% of H ₂ O ₂ and the balance being water, while the pH of the abrasive is 11, pH The regulator is ammonia.

b. Etch-passivation-polishing mechanism

This mechanism first dissolves the silver film in solution to form Ag ⁺ or other forms of silver ions. This can be accomplished by adding HNO ₃ or other chemicals to the abrasive. However, other chemicals or ions are also present in the solution, such as Cl ^- , Br ^- , I ^- , CH ₃ CHOO ^- , C ₆ H ₅ O ₈ ^3- , PO ₄ ^3- , C ₂ O ₄ ^2- , S ^{2 -} , C ₆ H ₄ (OH)COO ^- and the like. The above chemical substances or ions can react with Ag ⁺ or other forms of silver ions, resulting in silver precipitated compounds such as AgCl, AgI, AgBr, CH ₃ COOAg, Ag ₃ C ₆ H ₅ O ₈ , Ag ₃ PO ₄ , Ag ₂ C ₂ O ₄ , Ag ₂ S, C ₆ H ₄ (OH) COOAg, and the like. The precipitated compound is deposited on the surface of the silver film to form a passivation layer, thereby inhibiting the continued dissolution of silver in the solution. Then, when the surface is polished, the precipitated compound layer is broken, and the dissolution of the silver film can be performed again. The silver film is subjected to repeated etching, silver ion precipitation and mechanical polishing to produce a system balance, which realizes thinning and flattening of the silver film.

In the mechanism b, the abrasive may comprise, for example, 3 wt% of polytetrafluoroethylene particles, 0.03 wt% of an acrylic acid and acrylate copolymer, and benzimidazole, 0.8 wt% of ammonium chloride, and the balance being water, the grinding The pH of the agent is 3 and the pH adjuster is nitric acid.

c. Passivation-polishing-etching mechanism

This mechanism is also mainly accomplished through the above three steps. The first step is to create a passivation layer on the surface of the silver film. The passivation layer may be hard or soft. Unlike the mechanism b, the passivation layer is not formed from the precipitate but directly on the surface of the silver film, so the nature of the passivation layer is very different from the passivation layer formed by the mechanism b. The silver passivating agent may be selected from the group consisting of HCl ^- , HBr, HI, CH ₃ CHOOH, H ₃ C ₆ H ₅ O ₈ , H ₃ PO ₄ , H ₂ C ₂ O ₂ , H ₂ S, C ₆ H ₄ (OH)COOH and other ingredients. After the polishing step is applied, the passivation layer is removed while the silver etchant in the solution will act to reduce the thickness of the silver film. The silver etchant can be HNO ₃ , AgNO ₃ or other chemicals. Therefore, a passivation-polishing-etching system similar to the above-described etching-passivation-polishing mechanism is also formed, and thinning and planarization of the silver film is completed.

C in the mechanism, the abrasive may comprise: 1wt% alumina particles, 0.08wt% polyethyleneimine, 0.8% ammonium chloride, 0.5wt% KNO _3, and the balance water, pH of the abrasive is 3. The pH adjuster is hydrochloric acid.

d. Self-passivation-etching mechanism

It is well known that the two chemical reactions of silver are as follows: (1) Ag + HClO ₃ → AgCl (precipitation) + AgClO ₃ + 3 H ₂ O AgClO ₃ + 2 NH ₃ → Ag(NH ₃ ) ₂ ClO ₃ AgCl + 2 NH ₃ → Ag(NH ₃ ) ₂ Cl

The reaction formula (1) is also applicable to HBrO ₃ and HIO ₃ .

(2) Ag+HCl → AgCl (precipitation) AgCl+HCl → AgCl ₃ ^2- +2H ⁺

The reaction formula (2) is also applicable to HBr and HI.

The above chemical reaction formulas (1) and (2) illustrate the simultaneous etching and passivation in the solution. When the amount of NH ₃ or X ^- (X = Cl, Br, I) in the abrasive is properly formulated, one can be obtained. The passivation-based reaction is then achieved by a polishing process, a controlled silver film planarization and thinning process.

In the mechanism d, the abrasive may comprise, for example, 1 wt% alumina particles, 0.03 wt% polyethyleneimine, 0.8 wt% ammonium chloride, and the balance being water, the pH of the abrasive is 7, pH adjustment The agent is ammonia.

e. Surfactant inhibition mechanism

In this mechanism, as with the function of the passivation layer, an inhibitor is used to prevent corrosion of the silver film, but under the influence of mechanical action during polishing, the surface of the silver film will be partially or completely contacted with the silver etchant in the solution, resulting in silver. Surface etching. At this time, the surfactant still tends to be adsorbed on the silver film, and then the adsorption between the surfactant and the abraded action is balanced, and the result is a silver film flattening and thinning process.

The silver etchant in this mechanism can be any of the components used in the previous mechanisms. The inhibitor may be selected from the group consisting of organic surfactants, or elements containing N or S or O or P or Zn or compounds containing π bonds, such as 1,2,3-benzene. And triazole, hydrazine, benzothiophene (thiopurine), hydrazine, isoindole, 3-azaindole, [2,3-d]-indole-triazole, 1-pyrazole, 1,2-benzo Isoxazole, carbazole, isoindole Azole, benzimidazole, benzoisoxazole, 1,2,3,7-tetraazaindene, 1-pyrazolo[b]pyrazine, triazolopyrazine, benzophenone, benzofuran, hydrazine or A combination of the above ingredients. The pH of the abrasive can be between -2 and 16, because silver is highly resistant to corrosion when it contains no nitric acid or complexing substances (ammonia, cyanide, etc.). Therefore, in the mechanism a, the pH value is preferably 6 to 16; and in the mechanism b and the mechanism c, the pH value is preferably -2 to 8; in the mechanism d, the pH value is preferably between 5 and 10. In the mechanism e, the full range of pH values can be selected.

In the mechanism e, the abrasive preferably comprises: 1 wt% of cerium oxide particles, 0.006 wt% of PAA (polyacrylic acid) ammonium salt, 0.1 wt% of BTA (benzotriazole), and the balance is water, pH 3, the pH adjuster is hydrochloric acid.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patented scope of the invention should be construed as broadly construed in the

S10~S26‧‧‧ Process steps

101‧‧‧Silver or silver alloy film

103‧‧‧Substrate

121, 321‧‧‧ dielectric layer

123, 323‧‧‧ channel

141‧‧‧Block

161‧‧‧Silver or silver alloy

241‧‧‧ polishing agent

L‧‧‧down direction of pressure

X, Y‧‧‧ direction of rotation

325‧‧‧ Silver layer

1A to 1H are schematic views of a wafer polishing process and a schematic view of the structure formed by FIG. 1A.

2A to 2C are schematic cross-sectional views of the wafer when a wafer having a silver film thereon is polished by a single layer damascene method.

3A to 3C are schematic cross-sectional views of the wafer when a wafer having a silver film thereon is polished by a double damascene method.

4A to 4C are schematic cross-sectional views of the wafer when a wafer having a silver film thereon is polished by a dielectric material filling method.

S10~S26‧‧‧ Process steps

Claims (37)

An abrasive for chemical mechanical polishing comprising abrasive particles, a medium, and one or more chemicals selected from the group consisting of surfactants, etchants, complexing agents, oxidizing agents, inhibitors, passivating agents, buffers, and a catalyst, wherein the surfactant contained in the abrasive comprises a copolymer selected from the group consisting of polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, acrylic acid and acrylate copolymers, acrylic acid and hydroxypropyl acrylate, and butylene Copolymer of acid and acrylic acid, acrylic acid and hydroxypropyl acrylate terpolymer, copolymerized modified polyvinyl alcohol, methacrylic acid ester and alkanolamine copolymer, maleic acid and styrene Copolymers, polyoxyethylene monomethyl copolymers, carboxylic acid treated polyvinyl alcohols, derivatives of ethylene glycol and polyamine copolymers, specific copolymer dispersants, hydroxypropyl acrylates, and any other single The monomer comprises at least one of the following components: isobutylene, propylene oxide, 2-hydroxyacetaldehyde, methacrylate, maleic anhydride, acrylic acid, methyl propyl One group of at least one component acid, acrylamide, methyl acrylamide, styrene, and copolymers of ethylene -pyridone, polyethyleneimine, consisting of PAA; comprising the complexing agent selected from the group consisting of NH4 ^+, X (X=Cl ^- , Br ^- , I ^- ), ethylenediaminetetraacetic acid (EDTA), cyclodimidinetetraacetic acid (CyDTA), diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetrapropionic acid (EDTP) ), ethylene glycol diethyl ether diamine tetraacetic acid (EGTA), ethyl ethylene diamine triacetic acid (HEDTA), nitrogen triacetic acid (NTA), tetraethylene pentamine and triethylene tetramine At least one component of the group. The abrasive according to claim 1, which has a pH of from -2 to 16. The abrasive according to claim 1, comprising an oxidizing agent. The abrasive according to claim 3, which has a pH of 6 to 16. The abrasive according to claim 1, further comprising a chemical selected from the group consisting of Cl ^- , Br ^- , I ^- , CH ₃ CHOO ^- , C ₆ H ₅ O ₈ ^3- , PO ₄ ^{3 -} , C ₂ O ₂ ^2- , S ^2- , C ₆ H ₄ (OH)COO ^- . The abrasive according to claim 5, which has a pH of from -2 to 8. The abrasive according to claim 1, comprising a passivating agent. The abrasive according to claim 7, which has a pH of from -2 to 8. The abrasive according to claim 1, comprising NH3 or X ^- (X = Cl, Br, I). The abrasive according to claim 9, which has a pH of 5 to 10. The abrasive according to claim 1, wherein the inhibitor is included. The abrasive according to claim 11, which has a pH of 8 to 11. The abrasive according to claim 1, wherein the abrasive comprises abrasive particles selected from the group consisting of SiO ₂ , Al ₂ O ₃ , CaCO ₃ , ZrO ₂ , CeO ₂ , TiO ₂ , Si ₃ N ₄ , At least one component selected from the group consisting of AlN, TiN, SiC, Al(OH) ₃ , polyethylene, and polytetrafluoroethylene. The abrasive according to claim 1, wherein the etchant comprises selected from the group consisting of HNO ₃ , AgNO ₃ , HX (X=Cl, Br, I), HXO ₃ (X=Cl, Br, I), I ^- at least one component selected from the group consisting of +I ₂ , Cl ^- +Cl ₂ and Br ^- +Br ₂ . The abrasive according to claim 1, wherein the oxidizing agent comprises a salt selected from the group consisting of H ₂ O ₂ , S ₂ O ₆ ^2- or S ₂ O ₈ ^2- , KIO ₃ , KMnO ₄ , KNO ₃ , HNO ₃ , bromate, bromine, butadiene, chlorate, chloric acid, chlorine, chlorite, chromate, chromic acid, dichromate, fluorine, halogen salt, halogen element, hypochlorous Acid salt, nitrous oxide, oxide, oxygen, oxygen difluoride, ozone, peracetic acid, perborate, perhalate, bicarbonate, perchlorate, perchloric acid, high hydrate, At least one component selected from the group consisting of peroxides, persulfates, permanganates, sodium borate, and sulfuric acid. The abrasive according to claim 1, wherein the inhibitor is an organic surfactant, or an element containing N or S or O or P or Zn or a compound containing a π bond. The abrasive according to claim 16, wherein the inhibitor is an organic surfactant or is selected from the group consisting of 1,2,3-benzotriazole, anthracene, benzothiophene (thioindole), hydrazine, Isoindole, 3-azaindole, [2,3-d]-indole-triazole, 1-pyrazole, 1,2-benzisoxazole, oxazole, isoxazole, benzimidazole, benzo In a group consisting of isoxadiazole, 1,2,3,7-tetraazaindene, 1-pyrazolo[b]-pyrazine, triazolopyrazine, benzophenone, benzofuran, and hydrazine At least one compound. The abrasive according to claim 1, wherein the passivating agent is selected from the group consisting of HCl ^- , HBr, HI, CH ₃ CHOOH, H ₃ C ₆ H ₅ O ₈ , H ₃ PO ₄ , H ₂ C ₂ O ₂ , H ₂ S, C ₆ H ₄ (OH)COOH. The abrasive according to claim 1, wherein the buffer is selected from the group consisting of an organic compound or an inorganic compound. The application of the abrasive patentable scope of item 19, wherein the organic compound is selected from ethylene diamine or acetic acid, the inorganic compound is selected from HNO ₃ or NH ₃ H ₂ O. The abrasive according to claim 1, wherein the abrasive comprises 5.0 wt% of polytetrafluoroethylene particles, 0.1 wt% of PAA, 0.1 wt% of BTA, 0.5 wt% of ethylenediaminetetraacetic acid, and the balance of water. The pH is 4.25. The abrasive according to claim 1, wherein the abrasive comprises: 1 wt% of polytetrafluoroethylene particles, 0.05 wt% of polyethyleneimine, 0.5 wt% of H ₂ O ₂ and the balance being water, and the pH is 11. The abrasive according to claim 1, wherein the abrasive comprises: 3 wt% of polytetrafluoroethylene particles, 0.03 wt% of an acrylic acid and acrylate copolymer, and benzimidazole, 0.8 wt% of ammonium chloride, and The amount is water and the pH is 3. The abrasive according to claim 1, wherein the abrasive comprises: 1 wt% of alumina particles, 0.08 wt% of polyethyleneimine, 0.8% of ammonium chloride, 0.5 wt% of KNO ₃ , and the balance is water. The pH is 3. The abrasive according to claim 1, wherein the abrasive comprises: 1 wt% of alumina particles, 0.03 wt% of polyethyleneimine, 0.8 wt% of ammonium chloride, and the balance being water and a pH of 7. The abrasive according to claim 1, wherein the abrasive comprises: 1 wt% of cerium oxide particles, 0.006 wt% of PAA (polyacrylic acid) ammonium salt, 0.1 wt% of BTA (benzotriazole), and The amount is water and the pH is 3. A method of chemical mechanical polishing of a surface containing silver or a silver alloy, which employs the abrasive according to any one of claims 1 to 26. The method of claim 27, wherein the chemical mechanical polishing head has a pressure of at least 3 psi; the table top rotation speed is at least 50 rpm; the polishing head rotation speed is at least 50 rpm; the abrasive The flow rate is between 100 and 500 ml/min; the abrasive flow rate is 150 ml/min; and the silver film polishing rate is at least 2000 angstroms/min. The method of claim 28, wherein the polishing pad is selected from the group consisting of polymer polishing pads. The method of claim 29, wherein the polishing pad is selected from the group consisting of an IC1000 polishing pad, an IC1010 polishing pad, a polyurethane polishing pad, and a hard polishing pad. The method of claim 27, wherein the chemical mechanical polishing head under pressure is less than 3 psi; the table top rotation speed is less than 50 rpm; the polishing head rotation speed is less than 50 rpm; the abrasive flow rate The system is between 100~500 ml/min; the silver film polishing rate is less than 1000 angstroms/min; the polishing pad is a polytex polishing pad or other soft polishing pad. The method of claim 31, further comprising a soft polishing pad Polished, and the polishing pad is a polytex polishing pad. A method of fabricating a semiconductor, comprising: preparing a dielectric layer on the semiconductor; preparing a pattern on the dielectric layer; depositing a barrier layer on the dielectric layer; depositing silver or a silver alloy on the barrier layer, such as The method described in claim 27 is for chemical mechanical polishing of the surface of silver or a silver alloy. A method of fabricating a semiconductor comprising: forming a silver or silver alloy layer on a semiconductor substrate; patterning on a silver or silver alloy layer; filling a dielectric material in a silver or silver alloy pattern layer; The method described in item 27 performs chemical mechanical polishing of the surface. The method of claim 34, further comprising depositing a barrier material on the silver or silver alloy pattern layer prior to filling the dielectric material. The method of claim 34 or 35, further using etching or chemical mechanical polishing or a combination of the two. The method of claim 33, wherein the semiconductor is selected from the group consisting of a CPU, a logic chip, a dynamic random access memory, a static memory, an electrically erasable read-only memory, and a flash memory. , MEMS large-capacity optical memory 矽-based liquid crystal display (LCOS) and LDP.