Eliminating Humidity’s Influence In Lithography Organic BARC Process Of Trench MOS

As vertical tunnel structure power MOSFETs, Trench MOSFET haslower turn-on resistance, small gate-drain charge density, low switchinglosses, and faster switching speed. And the high density structure leadschip size smaller, circuit more integrated and manufactures cost lower.While, the traditional IC manufacture technology encounter severely yieldloss problem of a special structure Trench MOS named “product B”. Thefail mode is IGSS abnormal (gate-source current excessive) and turn-onresistance (Rdson) excessive. This work is focused on lithography process;etch process and integration root cause identification to improve TrenchMOS product-B yield status. This work elaborates the yield loss root causeand mechanism of this product via a group of experiments and data,detailed the key parameter humidity’s influence in Lithography organicBARC (bottom anti-reflection coating) process. Experimental results showthat, during BARC coating process, the unstable humidity in coater unitreducing the BARC chemical residue post etch and low yield. The deeperanalyzes demonstrate the truly root cause of this residue is that thepre-layer AA (active area) layer’s pattern has ten times height comparedwith the current Trench layer which used BARC coating before typicalphoto resist coating. The sharply different height induces the BARCcoating’s roughness during spin motor splash. Further experiments verifythe marginal process widow of BARC residue for this product.Permanently solution aims at abandon the BARC coating step beforeTrench coating. Pi-lot results show that this method can eliminate theresidue defect in Trench step, avoid the structure technical wall existed andfinally meet the yield target. In addition, the methods can rapid decreasethe manufacturing cost. And it’s a good instruction for practical usage.