Abrasive tool making process – material – or composition – With inorganic material
Reexamination Certificate
1999-07-29
2001-10-30
Turner, Archene (Department: 1775)
Abrasive tool making process, material, or composition
With inorganic material
C051S295000, C051S309000
Reexamination Certificate
active
06309433
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a conditioner used to eliminate loading of a polishing pad in flat polishing processes for a semiconductor substrate in metal CMP (Chemical Mechanical Planarization) employing acidic slurry.
BACKGROUND ART
Polishing of semiconductor wafers requires a polishing method which ensures the necessary polishing speed while preventing defects such as mechanical warping. In conventional mechanical polishing methods, the polishing speed can be ensured by increasing the size of the abrasive grits or the applied polishing load. However, because polishing results in various defects, it has been difficult to both ensure polishing speed and keep polishing targets defect-free. One method that has been proposed is known as chemical mechanical planarization (CMP). This method takes advantage of a chemical polishing action in addition to a mechanical polishing action, making it possible to both guarantee polishing speed and obtain defect-free polishing targets. With the higher integration of devices in recent years, CMP polishing of surfaces of semiconductor substrates having conductive metal layers formed on wafer surfaces has become important at certain stages in the production of integrated circuits.
One example of a metal CMP process is one that uses a polishing pad comprising a polyurethane resin, and a chemical slurry containing alumina particles as abrasive grits and iron nitrate as an oxidizing agent and prepared to have a pH of about 1.5 with nitric acid. For polishing, a semiconductor substrate is contacted with the polishing pad while circulating chemical slurry so that polishing is accomplished by relative rotation. Because the polishing speed is reduced at this time due to loading of the polishing pad, conditioning of the polishing pad is essential. Conditioning of a polishing pad has conventionally been accomplished by running water or chemical slurry over the polishing pad while a conditioner with nickel electrodeposited diamond abrasive grits is used to level the polishing pad.
The conditioner used for the CMP process differs from a conventional diamond tool used for cutting and grinding in essentially the following aspect. With cutting tools there is no loss of cutting power even if some shedding of the diamond abrasive grits occurs, so long as other diamonds are left on the new surface after the diamond shedding, whereas with a CMP conditioner, the shedded diamond abrasive grits damage the polishing pad or semiconductor substrate surface, and therefore diamond shedding is unacceptable even in small amounts. In addition, since wet systems are employed at a low rotation rate, there is no need for the heat resistance or high abrasion resistance demanded for cutting tools. Conventional diamond tools for which shedding of the diamond abrasive grits is a problem include diamond bits wherein single-grain, relatively large diamonds are bonded in a metal supporting material. However, these are essentially different from conditioners used in CMP processes in the following aspect. With conventional diamond bits, relatively large diamonds (generally with a diameter of about 1 mm or greater) are bonded as single grains, whereas conditioners used for CMP processes have relatively small (50-300 &mgr;m diameter) diamonds bonded in a sheet-like manner in a single layer.
Conventional conditioning of a polishing pad has employed a conditioning method which uses a grinding stone having nickel electrodeposited diamond grains. Nickel electrodeposition has become widely used because it can be applied relatively easily to metal supporting materials. However, nickel is readily corroded by acid. Consequently, when nickel electrodeposited conditioners are employed for conditioning when using acidic slurry, corrosion of the nickel occurs because of the acidic slurry. As a result, the usable life of the conditioner is considerably shortened, scratch damage due to shedding of the diamond grains occurs within a shorter time, and the polishing speed is reduced because of deteriorating conditioning performance. For this reason there has been a demand for diamond conditioners with high durability against acidic slurry.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a conditioner with particularly high durability against acidic slurry for conditioning of a polishing pad.
The conditioner of the present invention is a conditioner for a polishing pad used for flat polishing processes for semiconductor substrates, characterized in that diamond grains are supported by monolayer brazing in/on a supporting material comprising a metal and/or alloy, using an alloy with a melting point of 600-1200° C., the alloy containing 0.5-20 wt % of at least one metal selected from the group consisting of titanium, zirconium and chromium and 30-99.5 wt % of at least one metal selected from the group consisting of gold, platinum and silver.
BEST MODE FOR CARRYING OUT THE INVENTION
The conditioner of the present invention is a conditioner for a polishing pad used for flat polishing processes for semiconductor substrates, characterized in that diamond grains are supported by monolayer brazing in a supporting material comprising a metal and/or alloy, using an alloy with a melting point of 600-1200° C. which contains 0.5-20 wt % of at least one metal selected from the group consisting of titanium, zirconium and chromium and 30-99.5 wt % of at least one metal selected from the group consisting of gold, platinum and silver.
According to a preferred mode of the present invention, the alloy with a melting point of 600-1200° C. in the conditioner has a highly acid-resistant thin film on its surface for the purpose of further enhancing the durability against the afore-mentioned acidic slurry. Here, the highly acid-resistant thin film is preferably a film made of an organic material, and is more preferably a film made of a fluorine resin. Besides, the highly acid-resistant thin film may also be a film comprising at least one metal selected from the group consisting of gold, gold alloy, platinum, platinum alloy, rhodium and rhodium alloy. Films made of organic materials generally have excellent acid resistance, and in particular films made of fluorine resins have very satisfactory acid resistance. Films comprising at least one metal selected from the group consisting of gold, gold alloy, platinum, platinum alloy, rhodium and rhodium alloy have excellent acid resistance as well as satisfactory adhesion with the alloy having a melting point of 600-1200° C. in the conditioner. Thus, by forming a film made of organic materials or a film comprising at least one metal selected from the group consisting of gold, gold alloy, platinum, platinum alloy, rhodium and rhodium alloy on the surface of the alloy with a melting point of 600-1200° C. in the conditioner, it is possible to achieve improvement in the acid resistance of the conditioner and a longer usable life for the conditioner.
According to the present invention, the diamond grains preferably have a size of 50 &mgr;m to 300 &mgr;m, and the thickness of the thin film formed on the surface of the alloy of the conditioner is preferably from 0.1 &mgr;m to 100 &mgr;m.
As publicly disclosed technology in the same technical field of the invention, there is disclosed in Japanese Patent Laid-Open Publication No. 10-12579 a conditioner for a polishing pad for semiconductor substrates having diamond grains supported by brazing in a supporting material using an alloy with a melting point of 700-1100° C. containing at least one metal selected from the group consisting of gold, silver, copper and titanium. However, Japanese Patent Laid-Open Publication No. 10-12579 is a technique aimed at preventing shedding of the diamond grains, whereas the present invention is a technique aimed at improving the durability against acidic slurry. Furthermore, Japanese Patent Laid-Open Publication No. 10-12579 does not mention the structural composition of the alloy. The present inventors have found, unexpectedly, that including at least
Kenyon & Kenyon
Nippon Steel Corporation
Turner Archene
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