The species of plasma are a key point in the functionalization process of metal surface for molds and dies micro-pattern. The quality of the molds and dies directly affect the quality of the produced parts. Micro- and nano-textures on the metal and polymer surfaces of parts and components have functions to reduce the friction and wear to improve the joining strength. Fabrication of AISI420 molds and dies consists of two steps. In the first step, the initial 2D micro-patterns were drawn onto the AISI420 specimen and molds. The RF-DC plasma N₂-H₂ was employed for selective nitrogen concentration into their unprinted part. The present RF-DC plasma N₂-H₂ system a dipole electrode was utilized to generate RF-plasma and DC bias was directly applied to the specimens. Then, nitrogen gas was first introduced as a carrier gas for heating. After heating to the specified holding temperature, the nitrogen pre-sputtering was started at the constant pressure. Then, the hydrogen gas was added to nitrogen gas with the specified partial pressure ratio. The plasma condition was observed and identified by using optical emissive-light spectroscopy. The emissive light spectrum measured in the plasmas for pre-sputtering process (DC with N₂ only) and nitriding process (RF-DC with N₂ and H₂). NH radicals as well as the activated nitrogen atom and molecules were detected in both spectra. With use of the mixed nitrogen and hydrogen gases every peak of intensity were enhanced even with a little addition of hydrogen gas. This significant species of NH, N₂⁺, N₂, N-1, and N₂^* might be responsible for high infiltration of nitrogen atoms into the AISI420. SEM was used to observe printed mask pattern of specimen before nitriding. EDX was utilized to analyze the nitrogen content distribution at the vicinity of the border between the printed and unprinted surface. No nitrogen was presented on the printed areas. On the other hand, the carbon from the ink maps only on the printed surface area. This exclusive carbon-nitrogen mapping proves that only the unprinted parts of substrate should have high content nitrogen solutes. XRD analysis was performed to investigate whether the iron and iron nitrides were precipitated by RF-DC plasma N₂-H₂. Firstly, precipitation hardening which is usually generated by CrN precipitation formation in the matrix specimen. Nitrogen atoms diffusing into matrix reacts with chromium in AISI420. Besides for the original α’-Fe and σ-FeCr a new peak were detected at α’-FeN, ε-Fe₂N, and ε-Fe₃N. Peak was related to the extended martensitic lattice by high nitrogen extraordinary solid solution.