A Study on the Self-Stopping CMP Process for the Planarization of the High Step Height(@step height>1.5um) Pattern
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A Study on the Self-Stopping CMP Process for the Planarization of the High Step Height(@step height>1.5um) Pattern Kwang-Bok Kim, Hyo-Jin Lee, Ki-Hoon Jang, Joung-Duk Ko, Kyung-Hyun Kim, In-Seac Hwang, Yong-Sun Ko and Chang-Lyong Song. Semiconductor R&D Center, Samsung Electronics Co.Ltd., San#24, Nongseo-Ri, Kiheung-Eub, Youngin-City, Kyunggi-Do, 449-771, Korea [email protected] ABSTRACT
CMP(Chemical Mechanical Planarization) process is widely used to reduce step height in semiconductor fabrication processes. As a design rule shrinks, a highly planar surface becomes inevitable within wafer scales. In order to get a high degree of a planarization, self-stopping characteristics of a ceria-based slurry should be studied and used in semiconductor process. In this study, threshold polishing pressure for a self-stopping characteristics was obtained by optimizing down pressure, pad conditioning, and mixing ratio of ceria abrasive and additive. A series of experiments were made to optimize the threshold polishing pressure in variable line & space patterns that consist of 0.8um step height and unit oxide film. As a result, self-stopping cmp process is twice batter than conventional silica-based process with respect to planarity and WIWNU. In addition, WIWNU and step height was dramatically decreased to less than 1000Å when applying to real fabrication devices over 2um step height.
INTRODUCTION The oxide CMP(Chemical Mechanical Planarization) is applied as a process to planarize the step height of IMD(Inter Metal Dielectric) in SRAM Device. However, if Metal Density is not uniformity, the badness of planarization induces various problems in post-process. Therefore this study shows that Self-Stopping process1, optimized CMP process conditions for a non-linear characteristic of pressure by Oxide removal quantity, is performed with the abrasive and the additive of Ceria Based Slurry for the improvement of planarization. And through applying this process to IMD CMP process., the improvement of planariztion is also confirmed. EXPERIMENTAL
After PE-TEOS 20000Å was deposited on Si-Sub, the area size of high step height had been 6mm/12mm and density had split into 25% and 75%. and step height was formed to 7500Å as shown in figure1. The process conditions are summarized in Table1 were used for this study and this experiment was performed with down pressure split Table1. Process condition Down Pressure 1.0~5.0 psi Platen Speed 120 rpm
Carrier Speed Slurry Flow Rate
120 rpm 200 ml
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Figure 1. Test pattern is composite of step height 7500Å and pe-teos film on si_sub. [(a)high step height density 25%, (b) high step height density 75%, ■:high step height area, □:low step height area] RESULTS & DISCUSSION A. Self-Stopping CMP Process condition determination In order to determine Self-Stopping CMP process condition, diluted ceria based slurry was split in 1.1, 1.5, 1.9 and 2.5(wt%) additive2,3. And the oxide removal amount was measured in each split are shown in figure 2. The oxide removal amount was below
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