TECHNICAL FIELD

Embodiments of the disclosure generally relate to methods of cleaning and encapsulating substrate materials. In particular, embodiments of disclosure relate to methods of cleaning and encapsulating microLED features.

BACKGROUND

MicroLED displays have been identified as the next-generation display technology to replace traditional thin-film transistor liquid crystal displays (TFT-LCD) and organic LED (OLED) displays. MicroLEDs have the ability to use very low power while providing high performance (e.g., produce infinite contrast and high color gamut with low response times). Further, microLEDs can enable very high resolutions, are not susceptible to burn in, and have very simple process flows in manufacturing, thereby enabling a low cost of production while allowing device manufacturers to incorporate very thin displays in devices where thickness real estate is crucial (as no backlight or polarizer is needed). For reference, a microLED measures less than 100 μm which can be 1/100 the size of a conventional LED. As noted, microLEDs are self-emissive and don't require a backlight.

However, microLEDs suffer from poor conversion of electrical energy into light, also referred to as energy conversion efficiency. At current efficiency levels, microLED technology cannot deliver on a key promise of providing better efficiency than OLED. Therefore, there are significant advances needed in this area in order to make microLED display technology viable to the mass market.

Three main factors that determine the external quantum efficiency (EQE) of a microLED: extraction efficiency, injection efficiency, and radiative efficiency. Extraction efficiency entails how produced photons get partially reflected into the device, where they may be reabsorbed and converted into heat. Injection efficiency describes how well electron-hole pairs undergo recombination to produce photons. Injection efficiency is formally defined as the proportion of electrons passing through the device that are injected into the active region. Radiative efficiency involves the proportion of all electron-hole recombination events in the active region that are radiative and producing photons.

Improvements in extraction and injection efficiency can be made by improving the GaN crystal quality in the device as well as optimizing the epitaxial layer structure to maximize radiative recombination in the active region. However, impurities and defects in the device can enhance non-radiative recombination and lower the overall efficiency of microLED (specifically the radiative efficiency). Most of these defects can arise from etching processes or atmospheric oxidization.

Accordingly, there is a need for methods to remove surface impurities, oxidation, and defects. Further, there is also a need for a device protecting encapsulation layer. These methods have the potential to enhance microLED EQE.

SUMMARY

One or more embodiments of the disclosure are directed to a method of cleaning a microLED feature. The method comprises exposing a microLED feature having a layer of etch residue to a wet clean environment to remove at least a portion of the layer of etch residue. The microLED feature having a layer of etch residue is exposed to a dry clean environment to remove a portion of the layer of etch residue. The microLED feature is encapsulated with a capping layer.

Additional embodiments of the disclosure are directed to a method of cleaning a microLED feature. The method comprises etching a layered substrate to form a microLED feature. The microLED feature has a layer of etch residue thereon. The microLED feature is exposed to a wet clean environment to form a wet-clean microLED feature. The wet clean environment comprises HCl. The wet-clean microLED feature is exposed to a dry clean environment to form a clean microLED feature. The dry clean environment comprises trimethyl aluminum. The microLED feature is encapsulated with a capping layer. The capping layer comprises aluminum nitride and is formed by atomic layer deposition.

Further embodiments of the disclosure are directed to a method of cleaning a microLED feature. The method comprises etching a layered substrate to form a microLED feature. The microLED feature has a layer of etch residue thereon which comprises carbon and/or oxide contaminants. The microLED feature is exposed to a wet clean environment to remove carbon contaminants and form a wet-clean microLED feature. The wet clean environment comprises HCl. The wet-clean microLED feature is exposed to a dry clean environment to remove oxide contaminants and form a clean microLED feature. The dry clean environment comprises trimethyl aluminum. The microLED feature is encapsulated with a capping layer comprising aluminum nitride and formed by atomic layer deposition. The capping layer and surface of the clean microLED feature are both crystalline with similar orientation.

