Yasa Sampurno

Investigating Effect of Conditioner Aggressiveness on Removal Rate during Interlayer Dielectric Chemical Mechanical Planarization through Confocal Microscopy and Dual Emission Ultraviolet-Enhanced Fluorescence Imaging

The effect of conditioner aggressiveness is investigated in interlayer dielectric polishing on three types of pad. A method using confocal microscopy is used to analyze the effect of conditioner aggressiveness on pad–wafer contact. Results show that a more aggressive conditioner produces a higher interlayer dielectric polishing rate while at the same time a pad surface with fewer contacting summits and less contact area. It is found that the ratio of the contacting summit density to the contact area fraction is more important than either parameter measured separately since the ratio determines the mean real contact pressure. Modeling results based on contact area measurements agree well with experimental results. Moreover, it is found that a more aggressive disc also generates a thicker slurry film at the pad–wafer interface. This is in agreement with our general findings regarding pad asperity height distribution obtained using confocal microscopy.

A Method for Direct Measurement of Substrate Temperature during Copper CMP

A novel method was developed to directly measure the substrate temperature during copper chemical mechanical planarization (CMP). Using specially designed wafer carriers, substrate temperatures were obtained in real-time with an infrared camera. Results indicate that substrate temperatures are higher than pad temperatures. In addition, the substrate temperature distribution appears to be closely related to slurry flow beneath the substrate during polishing. A three-dimensional thermal model was also developed to simulate the pad and wafer temperatures. Simulations support the interpretation of the experimental data.

Tribological, thermal, and kinetic characterization of 300-mm copper chemical mechanical planarization process

In this study, the tribological, thermal, and kinetic attributes of 300-mm copper chemical mechanical planarization were characterized for two different pads. The coefficient of friction (COF) ranged from 0.39 to 0.59 for the D100 pad, indicating that boundary lubrication was the dominant tribological mechanism. In comparison, COF decreased sharply from 0.55 to 0.03 for the IC1000 pad, indicating that the tribological mechanism transitioned rapidly from boundary lubrication to partial lubrication. Consequently, the D100 pad exhibited higher pad temperatures and removal rates than the IC1000 pad. A two-step modified Langmuir–Hinshelwood model was used to simulate copper removal rates as well as chemical and mechanical rate constants. The simulated copper removal rates agreed very well with experimental data and the model successfully captured the non-Prestonian behavior. The simulated chemical rate to mechanical rate constant ratios indicated that the IC1000 pad generally produced a more mechanically controlled removal mechanism than the D100 pad.

End-point detection of Ta/TaN chemical mechanical planarization via forces analysis

This study explores the transition of shear force spectral fingerprints during tantalum (Ta) and/or tantalum nitride (TaN) chemical mechanical planarization on patterned wafers using a polisher and tribometer that has the unique ability to measure shear force and down force in real-time. Fast Fourier Transformation is performed to convert the raw force data from time domain to frequency domain and to illustrate the amplitude distribution of shear force and down force. Results show that coefficient of friction, variance of shear force and variance of down force increase during polishing when the Ta/TaN layer is removed thus exposing the inter-layer dielectric layer. Unique and consistent spectral fingerprints are generated from shear force data showing significant changes in several fundamental peaks before, during and after Ta/TaN clearing. Results show that a combination of unique spectral fingerprinting, coefficient of friction and analysis of force variance can be used to monitor in real-time the polishing progress during Ta/TaN chemical mechanical planarization for optimal polishing time.

Effect of Slurry Injection Position on Slurry Mixing, Friction, Removal Rate, and Temperature in Copper CMP

In this study, the extent of mixing of old and new slurry on the polishing pad is varied by the use of three different points of injection. Influences of the conditioner and bow wave on slurry mixing can be inferred from the experimental results, which include coefficient of friction data and pad and substrate thermal data. Results measured under identical lubrication mechanisms show that the slurry injection position can play a significant role in slurry mixing and slurry utilization efficiency. Slurry injection positions that induce lower slurry mixing are found to increase copper removal rate. Simulations of the bow wave and slurry puddle support the interpretation of the mixing phenomenon. This work underscores the importance of optimum slurry injection geometry and flow for obtaining a more cost effective and environmentally benign copper chemical mechanical polishing (CMP) process.

Analysis of A Novel Slurry Injection System in Chemical Mechanical Planarization

Slurry mean residence time (MRT), removal rate, and polishing defects were analyzed for a novel slurry injection system used in chemical mechanical planarization. The novel slurry injection system was placed adjacent to the wafer on the pad surface and slurry was injected towards the wafer through multiple holes in the trailing edge of the injector bottom. Results showed the novel slurry injection system provided more efficient slurry delivery to the pad–wafer interface and generated lower slurry MRT, higher removal rate, and lower polishing defects than the standard pad center area slurry application method currently used in the IC manufacturing industry.

Effect of temperature in titanium chemical mechanical planarization

The effect of temperature on the tribological and kinetic attributes of Ti chemical mechanical planarization (CMP) was investigated. Results indicated that processes at platen temperatures of 25 and 50 °C behaved similarly in terms of their tribological mechanism. At both temperatures, average coefficient of friction (COF) ranged from 0.19 to 0.41, indicating that boundary lubrication was the dominant tribological mechanism. Results also showed that average COF decreased with increasing platen temperature likely due to softening of pad asperities and lower slurry viscosity at the higher temperature. Due to exponentially accelerated chemical effects, Ti removal rate was higher when platen temperature was set at 50 °C. A two-step modified Langmuir–Hinshelwood model was used to simulate Ti removal rate and the chemical and mechanical rate constants under different polishing conditions. Simulated values of removal rate agreed well with experimental data. Simulated chemical rate to mechanical rate constant ratios suggested that the removal mechanism shifted from a more chemically-controlled to a more mechanically-controlled process as platen temperature was raised.

Analyses of Diamond Disk Substrate Wear and Diamond Microwear in Copper Chemical Mechanical Planarization Process

Diamond disk substrate wear and diamond microwear in the copper chemical mechanical planarization process were investigated in this study. Three types of disks (D1, D2, and D3) made by three different manufacturers were analyzed. For each type of disk, 24 h static etch tests were performed with Fujimi PL-7103 and Cabot Microelectronics Corporation icue 600Y75 slurries at 25 and 50°C. Scanning electron microscopy (SEM) analysis showed that there was no appreciable microwear on the diamond after the static etch tests for all three types of disks. Disks D1 and D3 showed no appreciable corrosion on the diamond disk substrate for both slurries at both temperatures. In comparison, disk D2 showed apparent surface corrosion using the Fujimi PL-7103 slurry at 25 and 50°C and the Cabot Microelectronics Corporation icue 600Y75 slurry at 50°C. Inductively coupled plasma-mass spectroscopy (ICPMS) analysis was performed before and after the static etch tests to investigate metal concentration increases in the slurry due to diamond disk substrate corrosion. The ICPMS analysis was consistent with the SEM images, showing a significant Ni concentration increase in the slurry for disk D2 with the Fujimi PL-7103 slurry at 25 and 50°C and the Cabot Microelectronics Corporation iCue 600Y75 slurry at 50°C. In addition to the above static etch tests, 24 h wear tests were performed on each type of diamond disks with Fujimi PL-7103 and Cabot Microelectronics Corporation iCue 600Y75 slurries at two different platen temperatures (25 and 50°C). SEM analysis was performed on selected aggressive and inactive diamonds as well as on the surrounding disk substrate before and after the wear tests. SEM images showed that there was microwear on the cutting edges of the aggressive diamonds for disks D1 and D3 with both slurries at 25 and 50°C. For disk D2, there was microwear on the cutting edges of the aggressive diamond with the Fujimi PL-7103 slurry at 25°C and with the Cabot Microelectronics Corporation iCue 600Y75 slurry at 25 and 50°C, and the aggressive diamond broke off from the disk substrate with the Fujimi PL-7103 slurry at 50°C. The SEM images also showed that there was no microwear on the inactive diamond for all three types of disks with both slurries at 25 and 50°C, confirming that the inactive diamonds did not participate in regenerating pad asperities during conditioning. The pad thickness profile was measured after the wear tests, and the effect of platen temperature on pad wear rate was investigated.

Effect of cerium oxide particle sizes in oxide chemical mechanical planarization

This study explored the effect of different cerium oxide abrasive particle sizes in chemical mechanical planarization of 200 mm blanket plasma-enhanced tetraethylorthosilicate wafers. All polishing experiments were done with a polisher and tribometer capable of measuring shear force and down force in real-time. Coefficient of friction and removal rate were found to correlate well with the slurry median particle size distribution. Removal rate modeling based on particle size was explored to support the interpretation of the experimental results.

Novel Slurry Injection System for Improved Slurry Flow and Reduced Defects in CMP

In commercial CMP tools, slurry is applied near the pad center. As the pad rotates, more than 95% of the fresh slurry flows directly off the surface due to bow wave formation and inertial forces without ever entering the pad-wafer interface, resulting in low slurry utilization [1]. Furthermore, some slurry that manages to go under the wafer stays on the pad, mixes with fresh slurry and re-enters the pad-wafer interface. This used slurry contains reaction products, foam and pad debris (due to pad conditioning) that cause wafer-level defects [2]. Such defect-causing by-products keep recirculating on the pad during polishing and accumulate near the retaining ring over time. Also, since large amounts of DI water are used between wafer polishes to rinse off the debris and reaction products, appreciable amounts of water may stay on the pad and inside the grooves. When fresh slurry is introduced to polish the next wafer, it mixes with the residual water and is diluted, resulting in lower material removal. As such, the current slurry application method does not provide efficient slurry utilization and leaves significant room for improving defect levels. Moreover, the constant sweeping of the conditioner arm during in-situ conditioning results in uneven slurry distribution and introduces additional challenges when it comes to carrier multi-zone pressure control for reduced within-wafer removal rate non-uniformity.