Mini-LED

Mini-LED is an LCD enhancement technology and part of the ongoing effort by LCD makers to narrow the performance gap between LCD and OLED. Mini-LED LCDs employ arrays of very small LEDs (100-1,000 micron size range) in the backlight, behind the LCD panel, to provide more control of pixel illumination (see Figure 2). Mini-LED backlights provide better dark/light contrast versus traditional LCDs by taking advantage of local dimming of multiple zones; this partially narrows the contrast performance gap relative to OLEDs. The challenge with Mini-LED technology comes down to a cost/benefit tradeoff. To get anywhere close to the contrast ratio of OLED, mini-LED LCDs need more than 10,000 individual chips and an active matrix backplane to drive a high-performance backlight. This backlight backplane is needed in addition to the primary backplane already used to drive the LCD pixels. The result is a display that looks better than traditional LCD but not as good as OLED—with a cost that’s at least as high as OLED today. Mini-LED LCDs retain the other deficits versus OLED—a lower color range, slower response times and a thicker form factor.

Micro-LED

Whereas mini-LED is just an LCD backlight enhancement, micro-LED is a self-emitting display technology (like OLED) using LEDs less than 50-100 microns in size, each becoming an individual red, green or blue sub-pixel (see Figure 3). Micro-LED technology matches or exceeds OLED and LCD in almost every performance area. It has the image quality and form factor benefits of OLED without the robustness and lifetime issues. It exceeds LCD and OLED in terms of brightness and also has lower power consumption.  Micro-LED is indeed the “holy grail” of displays.

But there is a catch—actually two, related catches—manufacturability and cost. One example of the manufacturing challenges is the pick-and-place step. Placing each individual micro-LED into the pixel areas is difficult. In a 4K display there are ~24 million sub-pixels and 8K displays use ~100 million. So, to make a micro-LED display, tens of millions of sub-micron LEDs must be removed from the substrate they are produced on and precisely placed in their designated sub pixel with good electrical contact. This “pick and place” manufacturing step is fraught with yield risks. It’s as delicate as using robotic machinery to handle pollen. There are many pick and place technologies under development today, but none yet meet the productivity and yield requirements of manufacturing mainstream consumer displays. And then there is the cost issue. Due to the manufacturability problems plus the fundamental high cost of millions of LED chips, the cost of micro-LED displays remains far too high for mainstream applications. To illustrate this, we know that the micro-LED TVs for sale today are priced well above $100K dollars. A cost reduction of more than 100x is needed to reach even the very high-end consumer TV market.

Because of these cost and manufacturability challenges, we expect micro-LED to be limited to niche applications, such as augmented reality (AR), wearables and extreme high-end public information displays, for the next several years at least. But with innovations and improvements, micro-LED might pose a challenge to OLED in the mainstream consumer applications after 2030. I can’t wait!

Micro-OLED

Micro-OLED is another interesting technology emerging in displays. It enables very high resolution (greater than 1,000 pixels per inch) and can be used in near-eye applications like virtual and augmented reality (VR/AR). Micro-OLED can be manufactured with a frontplane similar to the White OLED (WOLED) technology used in TVs today (blanket OLED layers are evaporated onto a substrate to emit white color; then a color filter renders the light red, green or blue). But to enable the high resolution and small pixels, the backplane is built on silicon wafers using semiconductor manufacturing technology (see Figure 4). Micro-OLED is a viable technology, but its application is expected to be limited to small, near-eye or projected displays, and we do not expect it to challenge conventional OLED for mainstream applications.

Summary

LCD has been the dominant display technology for nearly 30 years. The next technology inflection, OLEDs, is upon us and will drive a new wave of fab investments for the next decade. While this will be the dominant inflection, we will see other technologies vying to gain traction as well. For Applied Materials, all of these inflections are positive for our business. OLED roughly doubles the equipment capex per fab versus traditional LCD, significantly increasing our opportunity in both the backplane and the frontplane. Mini-LEDs require a second backplane for the backlight which increases the number of process equipment steps. Micro-LED requires further innovation on die manufacturing and high-end backplanes, which potentially creates significant opportunities for our display and semiconductor technologies on the frontplane. And while targeting a small subset of the market, micro-OLED also provides opportunities for Applied’s display and wafer-based capabilities.

We see a bright future for the display industry over the next decade, with dramatic new technologies on the horizon. Together with our customers, peers and partners, we will create even more dynamic and stunning visual experiences for consumers.

Tags: LCD, OLED, Mini-LED, Micro-LED, Micro-OLED