the present invention relates generally to a new apparatus and method for forming cavities in semiconductor substrates without the necessity of using an insert . more particularly , the invention encompasses an apparatus and a method for fabricating cavities in semiconductor substrates wherein a cured thick compressible elastic pad is placed over the cavity prior to lamination and caused to conform to the contour of the cavity , thus preventing collapse of , or damage to , the cavity shelves or corners during the lamination process . after the lamination process , the cured thick compressible elastic pad is conveniently removed from the cavity area without causing any damage to the cavity shelves or corners or having any paste pull - outs . this pad can be reused multiple number of times to form these mlc cavity substrates .