For illumination-grade applications, the spatial homogeneity of the white light emitted is an important issue which is directly associated with the geometry and the composition of the color conversion layer in phosphor-converted LEDs. In order to create a phosphor coating of high quality surrounding the LED chip surface, an improved slurry method with self-exposure technique was applied and investigated. The conformal phosphor layer of self-adaptability to angular intensity distribution of LED emitting light was realized. Plasma treatment was introduced to improve the aging performance of white LEDs with this advanced slurry method. The effect of the self-adaptive coating on the improvement of angular color uniformity of white LEDs was measured and discussed.