The effect of pad conditioning on planarization characteristics of chemical mechanical polishing (CMP) with ceria slurry
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The effect of pad conditioning on planarization characteristics of chemical mechanical polishing (CMP) with ceria slurry Yuichi Yamamoto1, Takaaki Kozuki1, Shunichi Shibuki1, Keiichi Maeda1, Yasuaki Inoue2, Shinji Tawara2 and Naoki Toge2 1. Semiconductor Technology Development Group., Sony Corporation, Atsugi, Kanagawa, Japan. 2. Technical Dept., Noritake Super Abrasive LTD., Ukiha-gun, Fukuoka, Japan. Abstract A ceria-based in-situ conditioning process was successfully developed. A new single layered metal bonded conditioner was developed to solve problems encountered in implementing ceria based in-situ conditioning process. The planarity was significantly improved compared with that of conventional Ni-plated in-situ conditioning. Introduction In oxide chemical mechanical polishing (CMP) processes for the 65nm generation and beyond, especially in mass production, unparalleled planarity and CMP process using ceria-based slurry is indispensable. Although in-situ processes are ideal in terms of throughput, they have critical shortcomings, so in fact ex-situ processes have so far been unavoidable. Many studies have addressed the effects conditioners on oxide CMP in silica slurries [1-3], and it has been shown that the conditioning parameters substantially affect the polishing rate [4]. Studies have also shown that slurries can affect the conditioner itself [5], and silica slurry-based oxide CMP systems have been optimized to take these finding into account. Yet now with the emergence of ceria slurry-based oxide CMP processes that will soon be indispensable, there has been very little study or analysis of the effects of this system on the conditioning. This paper will highlight a number of problems encountered in implementing ceria processes based on in-situ conditioning, and describe a successfully developed ceria-based in-situ conditioning process. Problems of ceria-based in-situ conditioning process Common problem The first problem one encounters in implementing ceria-based in-situ conditioning processes is conditioner corrosion. Ceria slurry is mildly acidic. Since conditioners usually consist of diamond that is adhesively bonded by nickel (Ni) plating, the Ni coating is eaten away by the slurry during the in-situ process until eventually the diamond grains fall off (Figure 1). This means that a corrosion resistant conditioner is absolutely essential in order to realize in-situ conditioning based on ceria slurries.
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Amount of diamond projection
Initial
After 20 hours
After 50 hours
Amount of diamond projection : 13.64um
Amount of diamond projection : 44.29um
Diamond fall off
Figure 1: Conditioner corrosion for in-situ conditioning New problem The second problem is planarity deterioration which was found in our experiments. Figure 2 reveals that when wafers are polished using ceria slurry, the planarity deteriorate from about 70 nm for ex-situ conditioning to 350 nm for in-situ conditioning. Conditioning parameters are listed in Table 1. Table 1: Conditioning parameters Global step height [nm]
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