An effective procedure for sensor variable selection and utilization in plasma etching for semiconductor manufacturing

a b s t r a c t Plasma etching processes have a potentially large number of sensor variables to be utilized, and the number of the sensor variables is growing due to advances in real-time sensors. In addition, the sensor variables from plasma sensors require additional knowledge about plasmas, which becomes a big burden for engineers to utilize them in this filed. Thus an effective procedure for sensor variable selection with minimum plasma knowledge is needed to develop in plasma etching. The integrated squared response (ISR) based sensor variable selection method which facilitates collecting and analyzing sensor data at one time with regard to manipulated variables (MVs) is suggested in this paper. The reference sensor library as well as sensor ranking tables constructed on the basis of ISR can give insight into plasma sensors. The ISR based sensor variable selection method is incorporated with relative gain array (RGA) or nonsquare relative gain array (NRGA) for effective variable selection in building a virtual metrology (VM) system to predict critical dimension (CD) in plasma etching. The application of the technique introduced in this paper is shown to be effective in the CD prediction in plasma etching for a dynamic random access memory (DRAM) manufacturing. The procedure for sensor variable selection introduced in this paper can be a starting point for various sensor-related applications in semiconductor manufacturing

Systematic Regeneration of Waste Sulfuric Acid in Semiconductor Manufacturing Using Batch Vacuum Distillation

We describe herein a systematic regeneration of waste sulfuric acid produced in semiconductor manufacturing, using batch vacuum distillation (BVD). During the recycling process, dilute sulfuric acid feed was continuously concentrated and fed back to the original wafer washing step. It consisted of a batch tank to charge the feed solution, condenser to capture generated vapor, receiving tank to receive condensed distillate liquid, and vacuum pump to reduce the system pressure. The improper control of the vacuum operation led to incomplete condensation; consequently, the vacuum pump became dysfunctional. The goal of this study was to prevent such mishap. After the feed condition was defined, a basic design was conceived, and the main characteristics of the BVD were determined. The results of sensitivity analyses on the feed and operating conditions have been discussed. The strategies for designing the vacuum pump’s capacity should be changed depending on phase equilibria at the target pressure

Repeat Targeted Prostate Biopsy under Guidance of Multiparametric MRI-Correlated Real-Time Contrast-Enhanced Ultrasound for Patients with Previous Negative Biopsy and Elevated Prostate-Specific Antigen: A Prospective Study

<div><p>Objectives</p><p>To prospectively determine whether multi-parametric MRI (mpMRI) - contrast-enhanced ultrasound (CEUS) correlated, imaging-guided target biopsy (TB) method could improve the detection of prostate cancer in re-biopsy setting of patients with prior negative biopsy.</p><p>Methods</p><p>From 2012 to 2014, a total of 42 Korean men with a negative result from previous systematic biopsy (SB) and elevated prostate-specific antigen underwent 3T mpMRI and real-time CEUS guided TB. Target lesions were determined by fusion of mpMRI and CEUS. Subsequently, 12-core SB was performed by a different radiologist. We compared core-based cancer detection rates (CaDR) using the generalized linear mixed model (GLIMMIX) for each biopsy method.</p><p>Results</p><p>Core-based CaDR was higher in TB (17.92%, 38 of 212 cores) than in SB (6.15%, 31 of 504 cores) (p < 0.0001; GLIMMIX). In the cancer-positive TB cores, CaDR with suspicious lesions by mpMRI was higher than that by CEUS (86.8% vs. 60.5%, p= 0.02; paired t-test) and concordant rate between mpMRI and CEUS was significantly different with discordant rate (48% vs. 52%, p=0.04; McNemar’s test).</p><p>Conclusion</p><p>The mpMRI-CEUS correlated TB technique for the repeat prostate biopsy of patients with prior negative biopsy can improve CaDR based on the number of cores taken.</p></div

Patient demographics of the real-time contrast enhanced ultrasound guided biopsy.

<p>PCa = Prostate cancer; PSA = Prostate specific antigen; DRE = digital rectal examination; mpMRI = multiparametric Magnetic resonance imaging; PI-RADS = Prostate Imaging Reporting and Data System; CEUS = contrast enhanced ultrasound;</p><p>* No. of patients</p><p>Patient demographics of the real-time contrast enhanced ultrasound guided biopsy.</p

Agreement between mpMRI and CEUS in positive TB cores (Numbers of cores containing cancer detected by targeted biopsy).

<p>CEUS = contrast enhanced ultrasound; mpMRI = multi-parametric MRI; TB = Target biopsy; PI-RADS = Prostate Imaging Reporting and Data System</p><p>Agreement between mpMRI and CEUS in positive TB cores (Numbers of cores containing cancer detected by targeted biopsy).</p