Display MEMS

Digital Micromirror Device

In recent, projection display market has grown rapidly to meet the demand of high resolution and large size image in flat panel display. CRT and LCD projection displays are the main stream in the current projection. However they have a lot of limitations in making a higher definition and larger size image. So, many engineers have researched to overcome scientifically those problems. In particular, a new projection display with DLP(Digital Light Processing) had been developed and used commercially. A very important DMD(Digital Micromirror Device) chip in DLP projection was made by applying MEMS technique and had many advantages as below.

  • high resolution
  • high contrast
  • high response time
  • high efficiency

However, Texas instruments had monopolized DLP market with those many advantages and scale of this market also increases more and more. Our laboratory focused on this point with MEMS technology accumulated in many years and originally proposed and developed DMD with other structure different from TEXAS’s DMD. Figure as seen below is the SAM images of DMD being developed.

Mirror_WholeMirror_Top

Mirror_Panel
Micro Shutter

Microshutter is evaluated as a next-generate flat panel display, because it directly controls light using mechanical movement. Microshutter has high efficiency and operating velocity, so it can express full color gamut and is less affected from temperature and humidity.Figure as seen below is the SAM images of microshutter being developed.


Shutter_wholeShutter_One

Shutter_Panel
AMOLED driving with MEMS Switch

Recently, AMOLED displays have been investigated actively due to their powerful advantages of high contrast ratio, ultra slimness, fast response time, and flexible capability. As an OLED is a current driven device, thin film transistors (TFTs) are essentially required in active-matrix driving. The active-matrix backplane has been made with amorphous silicon (a-Si), poly-silicon, or organic technology, but all of which suffer from nonnegligible threshold voltage shift and/or mismatch problems, causing brightness nonuniformity over the display panel. Using compensation circuits based on poly-Si technology, there has been considerable progress in providing stable and uniform brightness. However it is not cost effective in comparison with other TFT technologies. Although, organic technology has received increasing attention because of the possibility of reduced processing cost and perhaps also roll-to-roll manufacturing, they still need to be addressed in degradation problems. For decades, a-Si TFT technology, with cheaper manufacturing cost and lower equipment investment due to less process steps, has attracted interest within the industry. However, output current of a-Si TFT tends to saturate at a certain level that may be insufficient to drive the OLEDs to high brightness levels. To accommodate the higher current requirements for the large display applications, and at the same time maintain the potential to be integrated on the low cost plastic substrates, we have proposed the concept that using MEMS switch as a switching device in AMOLED.


OLED_WholeOled_Unit

Oled_Panel
Micro Optical Components

Using 3-D diffuser lithography which is a simple and effective micro-fabrication method of 3-D microstructures, various micro-optical components were fabricated and applied to many applications such as optical fiber-to-fiber coupling, LCD backlights, etc. Following SEM images show high fill-factor microlens arrays and a 3-D planar microlens for optical interconnection and microlens arrays having high aspect ratio and an inverse-trapezoidal microstructure for LCD backlights.


LENS_CylinderlensLENS_Microlensarray
LENS_MIicrolens_CrosssectionLENS_Inversetrapezoidal


LENS_Panel
Investigators

  • Lee Kyung-Ho (Ph.D. Candidate, 6th year)
  • Lee Joo-Hyung (Ph.D. Candidate, 4th year)
  • Lee Jeung-Oen (Ph.D. Candidate, 3rd year)
  • Yeun Jueng-Ho (Ph.D. Candidate, 2nd year)
  • Lim Kuen-Seo (M.S. Candidate, 2nd year)
  • Kim Hyeon-Don (M.S. Candidate, 1st year)
Published Paper

[1] J.-W. Jeon, B.-I. Kim, J.-H. Kim, H.-K, Lee, J.-B. Yoon, E. Yoon and K. S. Lim, “Electrostatic Digital Micromirror using Interdigitated Cantilevers,” IEEE 15th International MEMS Conference Tech. Dig., Las Vegas, NV, pp. 528-531, 2002.

[2] S.-I. Chang, J.-B. Yoon, “Shape-controlled, high fill-factor microlens array fabricated by a 3D diffuser lithography and plastic replication method,” Optics Express, vol. 12, no. 25, pp. 6636-6371, 2004.

[3] S.-I. Chang, and J.-B. Yoon, “3D Diffuser Lithography: A Novel Method to Fabricate Various Rounded Microstructures,” The 15th International Conference on Solid-State Sensors and Actuators Tech. Dig. (Transducers’05), Seoul, Korea. vol. 2, pp 1457-1460, 2005.

[4] J.-W. Jeon, D.-H. Kim, J.-B. Yoon, and K.- S. Lim, “High Fill-Factor Micromirror Array and Its Fabrication Process,” IEEE/LEOS International Conference on Optical MEMS and Their Applications (OMEMS 2005 Flyer), Oulu, Finland . pp. 53-54, 2005.

[5] S.-I. Chang and J.-B. Yoon, “3D Integration of Microlenses to Realize a Low-Power and High-sensitivity Optical Detection System for a Disposable Lab-on-a-chip,” The Ninth International Conference on Miniaturized Chemical and Biochemical Analysis Systems (MicroTAS 2005) Boston, Massachusetts, USA. pp.449-451, 2005.

[6] S.-I. Chang and J.-B. Yoon, “A High Efficiency 3D Planar Microlens for Monolithic Optical Interconnection System,” The 18th Annual meeting of the IEEE Laser & Electro-Optics Society LEOS2005, Sydney, Australia. pp.733-734, 2005.

[7] S.-I. Chang and J.-B. Yoon ,”A 3D Planar Microlens For an Effective Monolithic Optical Interconnection System,” IEEE Photonic Technology Letters, 2006.

[8] J.-W. Jeon ,Joon-Yong Choi , J.-B. Yoon and K.- S. Lim “A new three-dimensional lithography using polymer dispersed liquid cystal (PDLC) films,” 19th IEEE International Conference on MEMS, Istanbul,Turkey, 2006.

[9] J.-W. Jeon, J.-B. Yoon, and K.- S. Lim, “Sloping profile and pattern transfer to silicon,” Asia-Pacific Conference of Transducers and Micro-Nano Technology 2006. Singapore, 2006

[10] S.-I. Chang, J.-H. Lee and J.-B. Yoon, “High Fill-Factor Paraboloidal Microlens Arrays,” IEEE/LEOS International Conference on Optical MEMS and Their Applications (Optical MEMS 2006), Montana, USA

[11] Joo-Hyung Lee, Joon-Yong Choi, Sang-Min Bae, and Jun-Bo Yoon, “A Novel LCD Backlight Unit using a Light-guide Plate with High Fill-factor Microlens Array and a Conical Microlens Array Sheet,” Society For Information Display Conference 2007, Long Beach, California. vol. 38, book 1, pp. 465-468, 2008

[12] J.-W. Jeon, J.-B. Yoon, K. S. Lim, “Sloping profile and pattern transfer to silicon by shape-controllable 3-D lithography and ICP,” Sensors and Actuators A, vol. 139, no. 1/2, pp.281-286, 2007

[13] Jin-Wan Jeon, Jun-Bo Yoon, and Koeng-Su Lim, “Fabrication of 3-D Periodic Photoresist Microstructures for High Fill-Factor Microlens Array Replication”, HARMST 2007, 7th International Workshop on High-Aspect-Ratio Micro-Structure Technology, Besancon, France, pp. 35-36

[14] Joo-Hyung Lee, Hong-Seok Lee, Byung-Kee Lee, Won-Seok Choi, Hwan-Young Choi, and Jun-Bo Yoon, “Design and Fabrication of a Micropatterned Polydimethylsiloxane (PDMS) Light Guide Plate for Sheet-less LCD Backlight Unit,” Journal of the Society for Information Display, vol.16, no.2, pp.329-335, 2008

[15] Xing-Jiu Huang, Joo-Hyung Lee, Jong-Won Lee, Jun-Bo Yoon, and Yang-Kyu Choi, “A One-Step Route to a Perfectly Ordered Wafer-Scale Microbowl Array for Size-Dependent Superhydrophobicity,” Small, vol.4, no.2, pp.211-216. 2008

[16] Dae-Hyun Kim, Jin-Wan Jeon, Koeng Su Lim, and Jun-Bo Yoon, “Development of 16μm×16μm Digital Micromirror Array Suitable for Seamless-picture Projection Display System”, The 7th International Meeting on Information Display (IMID) 2007, DaeGu, Korea, pp. 1159-1162, 2007

[17] Jun-Bo Yoon, “3-D Diffuser Lithography and Its Application to LCD/LED Backlight Unit and Flexible Front-light Unit”, IDW 2007, Sapporo, Japan, pp.1345-1348. 2008

[18] Jun-Bo Yoon, Jeong Oen Lee, Hyun-Ho Yang, and Weon Wi Jang, “A Novel Use of MEMS Switches in Driving AMOLED”, Society for Information Display 2008, LA, CA. pp.13-16

[19] Joo-Hyung Lee, Won-Seok Choi, Kyung-Ho Lee and Jun-Bo Yoon, “A simple and effective fabrication method of various 3-D microstructures: Backside 3-D diffuser lithography”Journal of Micromechanics and Microengineering. doi:10.1088/0960-1317/18/12/125015

[20] Hong-Seok Lee, Hoon Song, Yong-Kweun Mun, Yoon-Sun Choi,Jeong-Ho Yeon, Joo- Hyung Lee, Jun-Bo Yoon,Hwan-Young Choi, Sangyoon Lee, “Improving Light Extraction Efficiency of Monolithically Fabricated Micropatterned Light Guide Plate” IDW 2008, Niigata,Japan. pp.1851-1852

[21] Won-Seok Choi, Joo-Hyung Lee, Jeung-Ho Yeon, and Jun-Bo Yoon, “See-through LCDs Using Transparent Light-Guide Plates” IDW 2008, Niigata,Japan. pp 459-462

[22] Hong-Seok Lee, Hoon Song, Yong-Kweun Mun, Yoon-Sun Choi, Jeong-Ho Yeon, Joo- Hyung Lee, Jun-Bo Yoon,Hwan-Young Choi, Sangyoon Lee, “Improving Light Extraction Efficiency of Monolithically Fabricated Micropatterned Light Guide Plate” IDW 2008, Niigata,Japan. pp.1851-1852