The Effect of Bias Voltage Application to Metals to Promote Their Nitriding and Carburizing in High-Density Inductively Coupled Plasma

纯铁样品（厚度为1 mm）在N_2-H_2（90：10）感应耦合等离子体（频率：4 MHz，压力：240 mAh）中于550 ℃处理120 min。在没有对样品施加偏压的情况下，从样品的表面朝向样品的内部出现脱氮层（厚度：~ 20 μ m）。可以估计，氢自由基加速这种反硝化。对样品施加200 V的负偏压。观察到氮化铁层（厚度：~ 25 μ m）和200 μ m铁扩散层的生长。这一事实意味着负偏压对样品的影响超过了氢自由基的影响。在SUS 304钢的渗氮中，与铁渗氮相比，在负离子作用下，表面硬度显著提高，在钛的渗氮和碳氮化中，氮或碳扩散层和氮化物或碳氮化物层显著增加。今年，一个非常高密度的R。F.采用电子密度约为8 × 10 ~（13）<13>/cm ~ 3的13.56MHz等离子体对Ti进行氮化处理。Ti样品（厚度：0.8mm）在等离子体中进行处理，在以下实验条件下产生的等离子体中进行处理：总压：8- 60 mPa，气体流量：N_2，0- 7sccm，H_2，18- 70 sccm，功率输入：70 W和350 W，时间：120 min，衬底温度：Ti的氮化和氮化钛的形成通过使用对Ti样品施加负偏压的等离子体来确认。这是一个非常有趣的现象，因为这意味着只有在大量自由基参与渗氮过程的情况下，氮离子才能促进渗氮。

Pure iron sample (the thickness : 1mm) was treated at 550ﾟC and for 120min under N_2-H_2 (90 : 10) inductively coupled plasma (frequency : 4 MHz, pressure : 240 mtorr). Without the application of bias voltage to the sample, denitrification layr (the thickness : -20mum) appeared towards the inner part of the sample from its surface. It can be estimated that hydrogen radical accelerates such denitrification. With the application of negative bias of 200V to the sample. the growth of iron nitride layr (the thickness : -25mum) and 200mum iron diffusion layr was observed. This fact means that the effect of negative bias supply to the sample exceeds that by hydrogen radical. In nitriding of SUS 304 sample, the increase of surface hardness was remarkable under the application of negative bais to the sample, comparing with the case of iron nitriding.In nitriding and carbo-nitriding of Ti, the remarkable increase of nitrogen or carbon diffusion layr and nitride or carbonitride layr were confirmed last year. This year, a very high density r. f. (13.56MHz) plasma which has about 8 x 10^<13>/cm^3 in electron density, was used for nitriding of Ti. Ti sample (the thickess : 0.8mm) was treated in the plasma generated under the next experimental conditions, total pressure : 8-60mtorr, gas flow rate : N_2, 0-7 sccm, H_2, 18-70sc cm, power input : 70W and 350W, time : 120min, substrate temperature : 300-600ﾟC.The nitriding of Ti and the formation of Ti nitride were confirmed by using a plasma with negative bias application to Ti sample. It is a very interesting phenomena, because it means that the nitriding can be only promoted by nitrogen ion in presence of plenty of radicals taking part in nitriding process.