the method for utilizing a dry film provided by the present invention is applicable to a wafer level packaging process , and an embodiment is described below . firstly , with reference to fig2 a , a dry film 100 is provided . the dry film 100 comprises at least three layers , namely at least one photoresist layer 111 , a carrier film 112 with light transmission , and a passivation film 113 . the photoresist layer 111 is a kind of photosensitive resin and may be a positive photoresist or a negative photoresist . the photoresist layer 111 is formed on the carrier film 112 and covered by the passivation film 113 . in the present embodiment , the photoresist layer 111 is a negative photoresist as a plating bump . generally , the material of the carrier film 112 is pet , i . e ., polyester , which is also referred to as mylar film and the material of the passivation film 113 is pe , i . e ., polyethylene . subsequently , with reference to fig2 , the dry film 100 is pressed onto a substrate . in the present embodiment , the substrate which the dry film 100 is pressed onto is a wafer 120 . however , the substrate can also be an ic carrier , a printed circuit board ( pcb ), a ceramic circuit board , and the like . during the process of pressing the dry film , the passivation film 113 is peeled off firstly , and then the photoresist layer 111 of the dry film 100 is attached to an active area 121 of the wafer 120 , wherein the dry film 100 may be rolled and attached to the active area 121 through a rolling device ( not shown ). the carrier film 112 of the dry film 100 is exposed , thereby covering and protecting the photoresist layer 111 . in the present embodiment , the wafer 120 is a semiconductor substrate on which an integrated circuit is formed . the wafer 120 has a passivation layer 122 or a molding layer . alternatively , a redistribution wiring layer ( rdl ) is formed on the active area 121 . generally , a priming coat ( not shown ), such as hexamethyldisilizane ( hmds ), is formed on the active area 121 of the wafer 120 in advance for increasing the adhesive force applied to the wafer 120 by the photoresist layer 111 . with reference to fig2 c , with a cutting device 130 , the dry film 100 is cut to a size corresponding to that of the wafer 120 . generally , after the dry film 100 has been cut , contaminant , such as the residual photoresist 114 or the particles 115 , is remained on the exposed surface of the carrier film 112 . furthermore , dry film burrs 116 are also remained on the lateral margin of the photoresist layer 111 . the residual photoresist 114 , the particles 115 , or the dry film burrs 116 all influence the accuracy and quality of the exposure . however , the present invention is not limited to perform the cutting step of the dry film 100 . in another embodiment , the dry film 100 may be cut in advance , and then pressed and attached to the wafer 120 . next , with reference to fig2 d , 2e , and 2 f , a cleaning step is performed to remove the residual photoresist 114 or the particles 115 remained after the step of cutting the dry film 100 , as well as the dry film burrs 116 . the cleaning step is mainly used to clean the carrier film 112 , as well as the wafer 120 . the cleaning step is performed in a darkroom . that is , the wafer 120 is placed in a darkroom or a yellow room to ensure the optical activity of the photoresist layer 111 , such that the inappropriate photochemical reaction of photoresist layer 111 is prevented from occurring . the cleaning step comprises a step of chemical spraying and a step of rinsing through di water . preferably , the cleaning step further comprises a step of drying to enhance the effect of cleaning . with reference to fig2 d , in the step of chemical spraying , the chemical spraying solution 140 is used to spray the exposed surface of the carrier film 112 , wherein the chemical spraying solution 140 comprises the material of conventional negative photoresist developer or positive photoresist cleaning liquid with a thinner concentration , such as asxylene , pgme , or di water . thereby , the particles 115 come from the outside during the process , the particles 115 and the residual photoresist 114 stuck on the carrier film 112 , as well as the dry film burrs 116 on the lateral margin of the photoresist layer 111 are all removed through the cleaning step . furthermore , under the protection of the carrier film 112 , the photoresist layer 111 is not removed excessively . subsequently , with reference to fig2 e , in the step of rinsing through the di water , a di water 150 is used to spray the exposed surface of the carrier film 112 , thereby continuously removing the particles 115 , the residual chemical spraying solution 140 , and the dissolved or loosened residual photoresist 114 . when the chemical spraying solution 140 is a di water , i . e ., it may dissolve the residual photoresist 114 , the step of chemical spraying and the step of rinsing may be integrated into one single step . then , with reference to fig2 f , in the step of drying , a dry gas 160 , such as nitrogen gas , is provided to remove the di water 150 and continuously remove the particles 115 , thereby greatly enhancing the cleanliness of the exposed surface of the carrier film 112 . furthermore , after the step of the whole cleaning , a lateral shrinkage 111 a is formed in the photoresist layer 111 and used to determine whether or not the photoresist layer 111 has been cleaned and the cleaning effect . next , with reference to fig2 g , a step of exposing is performed . generally , the cleaned wafer 120 , the photoresist layer 111 of the dry film 100 , and the carrier film 112 with light transmission are placed in a yellow room to be exposed . a mask 170 is disposed above the carrier film 112 , an exposure beam 171 passes through the mask 170 and then the carrier film 112 , and finally irradiates and patterns the photoresist layer 111 , such that the photoresist layer 111 has appropriate exposed zones 111 b and unexposed zones 111 c of an appropriate image . the exposed zones 111 b represent the photochemical reaction has occurred on the photoresist layer 111 . preferably , the yellow room in the step of exposing is the same with the darkroom for cleaning the carrier film 112 , thereby facilitating the continuity of the operation . subsequently , with reference to fig2 h , the carrier film 112 is removed and the photoresist layer 111 is developed , thereby forming a pattern . since the photoresist layer 111 is the negative photoresist , the photoresist in the unexposed zones 111 c is removed to form patterned recess regions 111 d , thereby forming or etching sequent bumps and circuits . therefore , with the method for utilizing a dry film provided by the present invention , the carrier film 112 of the dry film 100 and the wafer 120 are cleaned sufficiently for achieving the accurate exposure , thereby forming correct patterned recess regions 111 d . when the exposure tests of dry films are performed on the same batch of wafers , the low yield of the conventional operation flow is 0 . 58 %, and with the method for utilizing a dry film provided by the present invention , the low yield of the processed wafers is effectively reduced to 0 . 01 %. thus , the process is improved significantly . the method for utilizing a dry film provided by the present invention is used to manufacture bumps during a wafer level packaging process , such that the formed bumps in sequent have the same shape and size . the invention being thus described , it will be obvious that the same may be varied in many ways . such variations are not to be regarded as a departure from the spirit and scope of the invention , and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims .