JP2003191165A - Dresser for abrasive cloth for semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dresser for an abrasive cloth for a semiconductor substrate capable of manufacturing a semiconductor having a long serviceable life and high quality and yield by removing clogging of the abrasive cloth and stabilizing polishing speed in a metal CMP (Chemical Mechanical Polishing) using acid slurry. <P>SOLUTION: This dresser for the abrasive cloth used for a flattening polishing process of the semiconductor substrate is characterized in that a single layer of diamond particles is brazed on a support member comprising a metal and/or an alloy by an alloy containing 0.5-20 wt.% of at least one type selected from titanium, zirconium and chromium and containing 30-99.5 wt.% of at least one type selected from gold, platinum and silver and having a melting point of 600°C-1200°C. The thickness of the alloy with a melting point of 600°C-1200°C is 0.2-1.5 times as thick as the grain size of the diamond particles and is provided with a highly acid-resistant thin film of a thickness 0.1 to 100 μm on its surface. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a metal CMP (Chemical Mechanical Planarizati) using an acidic slurry.
on), the present invention relates to a dresser for a polishing cloth for a semiconductor substrate, which is used for eliminating clogging of the polishing cloth in the flattening polishing step of the semiconductor substrate.

[0002]

2. Description of the Related Art In polishing a semiconductor wafer, a polishing method is required which secures a polishing rate and does not cause defects such as mechanical strain. In the conventional mechanical polishing method, it is possible to secure the polishing rate by increasing the grain size of the abrasive grains and the polishing load. However, various defects are introduced by polishing, and it has been difficult to maintain both the polishing rate and the defect-free material to be polished. Therefore,
A polishing method called chemical and mechanical planarization (CMP) has been devised. This method makes it possible to achieve both the securing of the polishing rate and the defect-free polishing of the material to be polished by superposing the chemical polishing action on the mechanical polishing action. In recent years, it has become necessary to perform CMP polishing on the surface of a semiconductor substrate having a conductive metal layer formed on a wafer surface at a predetermined stage of manufacturing an integrated circuit as devices are highly integrated.

As one example of the metal CMP process, for example, a polishing cloth made of a chemical slurry containing alumina particles as abrasive grains, iron nitrate as an oxidizing agent and adjusted to pH = 1.5 with nitric acid, and a polyurethane resin is used. Is used.
During the polishing, the semiconductor substrate is brought into contact with the polishing cloth and relatively rotated while the chemical slurry is being spread, whereby the polishing is performed. At this time, since the polishing rate is reduced due to the clogging of the polishing cloth, dressing of the polishing cloth is indispensable. Conventionally, as a dressing method for a polishing cloth, while dressing water or a chemical slurry on the polishing cloth, dressing of the polishing cloth is performed by a dresser having nickel electroplated diamond abrasive grains.

The dresser used in the CMP process is essentially different from the conventional diamond tools used in cutting and grinding in the following points. Even if a small amount of diamond abrasive grains fall off with a cutting tool, if another diamond remains on the new surface after the diamond falls off, the cutting ability will not decrease, whereas with CMP dresser the lost diamond abrasive grains will be polished. This is because even if a small amount of diamond is not allowed to fall off, it will damage the cloth and the surface of the semiconductor substrate. Further, since it is used in a wet condition at a low rotation speed, it does not require the heat resistance and large wear resistance required for a cutting tool. As a conventional diamond tool in which the removal of diamond abrasive grains is a problem, there is a diamond bite in which relatively large single diamond particles are bonded to a metal holding material.
However, it is essentially different from the dresser used in the CMP process in the following points. With conventional diamond tools, relatively large diamonds (typically 1m in diameter
While a single grain is used for joining (about m or more), the dresser used in the CMP process is relatively small (diameter 50-
(300 μm) The point that diamonds are bonded in a plane in a single layer is different.

[0005]

In the conventional dressing of a polishing cloth, a dressing method using a grindstone in which diamond grains are electrodeposited by nickel is used. Electrodeposition of nickel has been widely used because it can be applied to metal support members relatively easily. However, nickel is easily corroded by acid. Therefore, when a nickel electrodeposition dresser is used for dressing when using the acidic slurry, corrosion of nickel by the acidic slurry occurs. As a result, the life of the dresser becomes extremely short, scratches are generated due to the drop of diamond grains in a short time, and the polishing rate is decreased due to the deterioration of the dressing performance. Therefore, there has been a demand for a diamond dresser having high durability against the acidic slurry.

Therefore, it is an object of the present invention to provide a dresser for a polishing cloth for semiconductor substrates, which has a high durability against an acidic slurry in the dressing of the polishing cloth.

[0007]

Means for Solving the Problems and Embodiments of the Invention
The present invention is a dresser for a polishing cloth used in a flattening polishing step of a semiconductor substrate, which comprises 0.5 wt% of at least one selected from titanium, zirconium and chromium.
% To 20 wt% and at least one selected from gold, platinum and silver 30 wt% to 99.5 wt%
With the alloy having a melting point of 600 ° C to 1200 ° C contained, a single layer of diamond particles is brazed to a supporting member made of a metal and / or an alloy, and the melting point is 600 ° C to 120 ° C.
The alloy at 0 ° C. has a thickness of 0.2 to 1.5 times the particle diameter of the diamond particles, and has a thin film having a high acid resistance of 0.1 μm or more and 100 μm or less on the surface. It is a dresser for a polishing cloth for semiconductor substrates.

The thin film having high acid resistance is preferably an organic film, more preferably a film made of fluororesin. The thin film having high acid resistance is a film made of at least one selected from gold, gold alloy, platinum, platinum alloy, rhodium and rhodium alloy. An organic film generally has excellent acid resistance, and a film made of a fluororesin has particularly good acid resistance. In addition, a film made of at least one selected from gold, gold alloys, platinum, platinum alloys, rhodium and rhodium alloys has excellent acid resistance, and at the same time, has an adhesive property with the alloy having a melting point of 600 ° C to 1200 ° C. Is also good. Therefore, organic film or gold,
By providing a film made of at least one selected from gold alloy, platinum, platinum alloy, rhodium and rhodium alloy on the surface of the alloy having a melting point of 600 ° C. to 1200 ° C., the acid resistance of the dresser is improved. The long life of the dresser can be realized. In addition, diamond grains are
The diameter is preferably 50 μm or more and 300 μm or less, and the thickness of the thin film on the surface of the alloy of the dresser is preferably 0.1 μm or more and 100 μm or less.

As a disclosed technique in the same field as the present invention, in JP-A-10-12579, a melting point of 700 ° C. to 110 containing at least one selected from gold, silver, copper and titanium.
It discloses a dresser for a polishing cloth for semiconductor substrates, in which diamond grains are brazed to a supporting member with an alloy of 0 ° C. However, while Japanese Unexamined Patent Publication No. 10-12579 is a technique aimed at preventing falling of diamond grains,
The present invention is a technique aimed at improving durability against an acidic slurry. Further, Japanese Patent Application Laid-Open No. 10-12579 does not describe the constituent composition of the alloy, but in the present invention, as a result of intensive research and development, in order to improve the acid resistance of the alloy, gold in the alloy, It was revealed that it is essential to contain at least 30 wt% of noble metals such as platinum and silver. That is, the present invention is disclosed in
It has an effect different from that of -12579.

Further, JP-A-10-175156 discloses a melting point 650 containing 0.5 to 20 wt% of at least one selected from titanium, zirconium and chromium.
Disclosed is a dresser for a polishing cloth for semiconductor substrates, in which diamond grains are brazed to a supporting member with an alloy of ℃ to 1200 ℃. However, as in Japanese Patent Laid-Open No. 10-175156, which is similar to Japanese Patent Laid-Open No. 10-12579, a technique aimed at preventing diamond particles from falling off, the present invention is a technique aimed at improving durability against acidic slurries. Is. Further, in Japanese Patent Laid-Open No. 10-175156, the constituent composition of an alloy other than at least one selected from titanium, zirconium and chromium contained in 0.5 to 20 wt% is not described, but in the present invention, In order to improve the acid resistance of the alloy, at least 30 wt% of noble metals such as gold, platinum and silver are added to the alloy.
It has been clarified that the above inclusion is essential.
That is, the present invention has an effect different from that of JP-A-10-175156.

The dresser for a semiconductor substrate polishing cloth of the present invention has a longer life as a result of improved durability against acidic slurries, and can minimize scratches due to a decrease in polishing rate and drop of diamond grains. it can. As a result, it is possible to manufacture semiconductor substrates and semiconductors with high processing accuracy and high yield at low cost.

The inventors have found that the alloy for bonding diamond particles contains 30 wt% or more of at least one selected from gold, platinum and silver, whereby the corrosion resistance to an acidic solution is remarkably improved. I found it.

On the other hand, in the joining of diamond and a brazing alloy, the joining strength is remarkably increased by forming a layer made of titanium carbide, zirconium carbide, chromium carbide or the like at the interface between the two. The inventors have found that the use of a brazing alloy containing at least one selected from titanium, zirconium and chromium forms a metal carbide layer at the interface between diamond and the brazing alloy. confirmed. In order for the metal carbide layer to be formed at the interface, the brazing alloy must contain at least 0.5 wt% of at least one selected from titanium, zirconium, chromium and the like. The improvement of the bonding strength by forming the metal carbide layer at the interface can be sufficiently achieved if the content of titanium, zirconium, chromium, etc. is 20 wt%.
Wt% or less.

The melting point of the brazing alloy is 600 ° C. to 1200 ° C.
The alloy of is that at brazing temperatures below 600 ° C,
This is because it is not preferable because the bonding strength cannot be obtained and the brazing temperature exceeding 1200 ° C. deteriorates the diamond. A suitable brazing alloy thickness is 0.2 to 1.5 times the diamond grain size. If it is too thin, the bonding strength between the diamond and the brazing alloy will be low, and if it is too thick, the brazing material and the supporting member will be easily separated.

The diameter of diamond grains is 50 μm or more and 30
It is preferably 0 μm or less. A diamond having a diameter of less than 50 μm cannot provide a sufficient polishing rate, and a diamond having a thickness of 300 μm can provide a sufficient polishing rate. Also, fine particles of diamond less than 50 μm tend to agglomerate easily, and if agglomerates form clusters, they easily fall off, causing scratches. Coarse-grained diamond with a particle size of more than 300 μm causes a large concentration of stress during polishing and is easily dropped.

The thickness of the thin film having high acid resistance applied to the surface of the alloy metal of the dresser is preferably 0.1 μm or more and 100 μm or less. This is because a thin film having a thickness of less than 0.1 μm cannot obtain a sufficient effect of improving acid resistance, and a thickness of 100 μm can obtain a sufficient effect of improving acid resistance.

[0017]

EXAMPLE Melting point 8 containing 70 wt% silver and 2 wt% titanium
Using an alloy at 20 ° C. and diamond grains having an average grain size of 150 μm, diamond was brazed to a stainless steel support base at 880 ° C. in a vacuum of 10 −5 Torr. The number of dressers created is four, and for three of them,
A thin film was formed on the surface of the bonding alloy. Ie 1
One was fluoropolymer coated, another was gold coated and the last one was rhodium coated.

Four dressers according to the present invention (brazing, brazing + fluorine resin thin film, brazing + gold thin film,
Brazing + rhodium thin film) and a conventional Ni electrodeposited dresser as a comparative example are used to form a tungsten thin film on the surface by C
A polishing experiment was performed on a silicon wafer prepared by VD.
The number of wafers to be polished is 400 for each dresser. As the slurry, an iron nitrate / nitric acid-based slurry having a pH of 1.5 with alumina as abrasive grains was used. Polishing time is 2 minutes,
The dressing was performed for 2 minutes for each polishing. 100
The polishing rate was measured every 50 sheets up to 100 sheets and thereafter every 100 sheets. The results are shown in Table 1. In the conventional dresser, which is a comparative example, the dressing performance was significantly deteriorated, and the polishing rate started to decrease from the time of polishing the 50th sheet. Since the polishing rate was significantly decreased, the experiment was stopped after polishing the 100th sheet. . On the other hand, in the four types of dressers of the present invention, which are examples, no decrease in the polishing rate was observed even after polishing the 400th sheet. Therefore, it was found that the dresser according to the present invention has a significantly improved durability against acidic slurries as compared with the conventional dresser.

[0019]

[Table 1]

[0020]

Industrial Applicability According to the present invention, a dresser for a polishing pad for a semiconductor substrate, which has a significantly improved durability against an acidic slurry, can be obtained. By using the dresser of the polishing cloth for a semiconductor substrate of the present invention, not only is the life of the dresser extended and is effective in reducing costs, but it is not necessary to replace the dresser frequently, thus improving throughput and reducing costs. It was realized.

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Claims (2)

[Claims] 1. A dresser for a polishing cloth used in a flattening / polishing step of a semiconductor substrate, comprising 0.5 or more of at least one selected from titanium, zirconium and chromium.
wt% to 20 wt% and at least one selected from gold, platinum and silver 30 wt% to 99.5 w
An alloy having a melting point of 600 to 1200 ° C. containing t%
A single layer of diamond particles is brazed to a support member made of a metal and / or an alloy, and the melting point is 600 ° C. to 1 ° C.
The alloy at 200 ° C. is characterized by having a thickness of 0.2 to 1.5 times the particle diameter of the diamond particles, and having a thin film having a high acid resistance of 0.1 μm or more and 100 μm or less on the surface. Dresser for polishing cloth for semiconductor substrates. 2. The thin film is a film made of at least one selected from gold, gold alloys, platinum, platinum alloys, rhodium and rhodium alloys.
A dresser for a polishing cloth for a semiconductor substrate as described above.