CN1996143B - Cleaning process of dry film pressed on wafer - Google Patents

Abstract

The present invention provides a cleaning process for a dry film pressed onto a wafer. First, a dry film is provided and pressed onto a substrate such as a wafer. The dry film includes a photoresist layer attached to the substrate and an exposed light-transmitting carrier film. Before exposure and development, the light-transmitting carrier film of the dry film is cleaned in a dark room. The cleaning method may include the steps of chemical spraying and deionized water cleaning to remove residual contaminants on the light-transmitting carrier film and remove burrs of the dry film to improve the process yield of subsequent exposure and development.

Description

Cleaning process for dry films laminated on wafers

【Technical field】

The present invention relates to a cleaning process of a dry film laminated on a wafer, in particular to a cleaning process of laminating a dry film on a substrate such as a wafer in a wafer-level packaging process.

【Background technique】

In the field of wafer-level packaging, photoresist materials are usually used for image transfer printing for deposition or etching to form bumps or lines on a wafer. In order to achieve proper thickness and good image effect, the currently used photoresist material is dry film. The traditional dry film has a three-layer structure, which includes a transparent carrier film, at least one photoresist layer and a protective layer, wherein the photoresist layer is interposed between the transparent carrier film and the protective layer. After peeling off the protective layer, the photoresist layer of the dry film is laminated to a substrate (such as a wafer), and then exposed and developed to form a pattern image. However, when the dry film is laminated on the wafer, the contamination generated during the process will lead to inaccurate exposure, thereby reducing the process yield.

Please refer to FIG. 1. In the wafer-level packaging process, when a dry film 10 is bonded to a wafer 20 or a packaged substrate, a photoresist layer (such as acrylic photosensitive resin) in the dry film 10 11 will be attached to an active surface 21 of the wafer 20 , and a light-transmissive carrier film 12 of the dry film 10 covers the photoresist layer 11 . When performing the exposure step, a photomask 30 is set above the wafer 20 and the dry film 10, and an exposure light (such as ultraviolet light) 31 passes through the photomask 30, and then passes through the light-transmitting carrier. The film 12 is irradiated onto the photoresist layer 11 to cause a photochemical reaction at the irradiated part of the photoresist layer 11 . When the photoresist layer 11 is a positive photoresist, the irradiated part will be removed after development; when the photoresist layer 11 is a negative photoresist, the irradiated part will remain after development. Therefore, the exposure quality will determine the subsequent output yield. However, before exposure, there will be residual pollutants on the light-transmissive carrier film 12 of the dry film 10, such as residual photoresist 13 and particles 14, and these residual photoresist 13 and particles 14 will cause the exposure radiation 31 to refract or scatter , resulting in inaccurate exposure. In addition, after the conventional dry film 10 is laminated and cut, there will be dry film burrs around its periphery, which will also affect the exposure quality.

【Content of invention】

In view of the above problems, the present invention mainly provides a method for using a dry film, which cleans a light-transmissive carrier film of the dry film in a dark room after the dry film is pressed onto the substrate and before exposure to remove the transparent film. Residual photoresist, particles and other pollutants on the photocarrier film can also remove dry film burrs on the periphery to improve the accuracy of exposure and the yield of subsequent processes.

Another object of the present invention is to provide a method for forming a photoresist on a wafer, which forms a light-transmissive carrier film on the photoresist layer on the active surface of the wafer, when cleaning the light-transmissive carrier film and the wafer , this method can protect the photoresist layer from being washed off.

Another object of the present invention is to provide a cleaning process for a dry film pressed on a wafer.

In order to achieve one of the above objects, the present invention adopts the following technical solutions: provide a dry film, which includes a light-transmitting carrier film and at least one photoresist layer; press the dry film to a substrate, so that the photoresist layer is attached to the a substrate; and cleaning the light-transmitting carrier film of the dry film in a dark room. Before the step of cleaning the light-transmissive carrier film, it also includes: cutting the dry film so that the size of the dry film corresponds to the size of the substrate. The step of cleaning the light-transmissive carrier film further includes: performing a chemical spray cleaning step to remove residual photoresist and particles on the light-transmissive carrier film; performing a deionized water cleaning step; and performing a drying step.

In order to achieve the second above-mentioned purpose, the present invention adopts the following technical solutions: a wafer is provided, which has an active surface; at least one photoresist layer is formed on the active surface of the wafer; a photoresist layer is formed on the photoresist layer. The light-transmitting carrier film; and cleaning the light-transmitting carrier film and the wafer. The step of cleaning the light-transmissive carrier film further includes: performing a chemical spray cleaning step to remove residual photoresist and particles on the light-transmissive carrier film; performing a deionized water cleaning step; and performing a drying step.

In order to achieve the above object three, the present invention adopts the following technical solutions: provide a dry film, which includes at least one photoresist layer attached to the wafer and an exposed carrier film; perform a chemical spraying step to remove the carrier film remaining photoresist and particles on the film; performing a deionized water rinse step to remove the chemical solution; and performing a drying step to remove the deionized water.

Compared with the prior art, since the step of cleaning the light-transmissive carrier film is performed before exposure, the present invention can remove residual photoresist, particles and other pollutants on the light-transparent carrier film, and at the same time remove the dry film burr on the periphery , so that the quality of subsequent exposure and development can be improved.

【Description of drawings】

FIG. 1 is a schematic cross-sectional view of a traditional wafer during the exposure process after being laminated with a dry film and cut.

2A to 2H are schematic cross-sectional views of a dry film application process on a substrate according to an embodiment of the present invention.

【Detailed ways】

The method for using the dry film of the present invention is applicable to the wafer-level packaging process, and a specific embodiment is described below.

First, as shown in FIG. 2A, a dry film 110 is provided. The dry film 110 mainly includes a structure of at least three layers, which are at least one photoresist layer 111, a light-transmissive carrier film 112, and a protective film 113, wherein the The photoresist layer 111 is a photosensitive resin, which can be a positive photoresist or a negative photoresist, which is formed on the light-transmissive carrier film 112 and covered by the protective film 113 . In this embodiment, the photoresist layer 111 is a negative photoresist used as an electroplating bump. Usually, the light-transmitting carrier film 112 can be made of PET (polyester), or can be called Mylar film, and the protective film 113 can be made of PE (polyethylene).

Afterwards, as shown in FIG. 2B , the dry film 110 is pressed onto a substrate. In this embodiment, the substrate on which the dry film 110 is laminated is a wafer 120 , but the substrate can also be an IC (Integrated Circuit) carrier, a printed circuit board, or a ceramic circuit board. In the dry film bonding process, the protective film 113 is first peeled off, and then the photoresist layer 111 of the dry film 110 is attached to an active surface 121 of the wafer 120, and the attachment method can be a rolling device (not shown). The dry film 110 is rolled and attached to the active surface 121 , and the light-transmissive carrier film 112 of the dry film 110 exposes and covers and protects the photoresist layer 111 . In this embodiment, the wafer 120 is a semiconductor substrate on which an integrated circuit has been fabricated, and it has a passivation layer 122 (passivation layer) or a sealant layer, or a redistribution wiring layer (redistribution wiring) can be formed on the active surface 121. layer, RDL). Usually, a priming coat (priming coat) (not shown), such as hexamethyldisilazane (HMDS), can be preformed on the active surface 121 of the wafer 120 to increase the resistance of the photoresist layer 111 to Wafer 120 adhesion.

Referring to FIG. 2C , a cutting device 130 is used to cut the dry film 110 so that the size of the dry film 110 corresponds to the size of the wafer 120 . Usually, after cutting, the exposed surface of the light-transmissive carrier film 112 will be stained with pollutants such as residual photoresist 114 or particles 115. In addition, dry film burrs 116 (dry film) may remain on the side edge of the photoresist layer 111. burr), the residual photoresist 114, particles 115 or dry film burr 116 will affect the accuracy and quality of exposure. However, the present invention is not limited to performing the step of cutting the dry film 110 after the step of laminating the dry film 110 . In other embodiments, the cutting step of the dry film 110 may be performed in advance and then pressed onto the wafer 120 .

2D, 2E and 2F, a cleaning step is performed after the cutting step to remove the residual photoresist 114 or particles 115 left in the step of cutting the dry film 110, and remove the dry film burr 116 at the same time. The cleaning step is mainly used to clean the light-transmissive carrier film 112 and can clean the wafer 120 . The cleaning step is performed in a darkroom (darkroom), that is, the wafer 120 is placed in a darkroom or a yellow light chamber to ensure the photoactivity of the photoresist layer 111, thereby avoiding undesired photochemistry of the photoresist layer 111. reaction. The cleaning step further includes a chemical spray cleaning step and a deionized water cleaning step. In a preferred embodiment, a drying step may be included to enhance the cleaning effect. Wherein, as shown in FIG. 2D, in the chemical spray cleaning step, a chemical spray solution 140 is used to spray the exposed surface of the light-transmissive carrier film 112. The chemical spray solution 140 may contain conventional negative Type photoresist developer or positive photoresist cleaning solution, but the concentration should be relatively thin, such as xylene or propylene glycol methyl ether (PGME), which can remove foreign particles 115 in the process and adhered to during cutting The particles 115 and the remaining photoresist 114 on the light-transmitting carrier film 112 can also remove the dry film burr 116 at the side edge of the photoresist layer 111 at the same time. Under the protection of the light-transmitting carrier film 112 , the photoresist layer 111 will not be excessively removed. Afterwards, as shown in FIG. 2E , in the deionized water cleaning step, a deionized water 150 is sprayed on the exposed surface of the light-transmitting carrier film 112 to continuously remove residual foreign particles 115 and residual chemical sprays. Wash solution 140 and residual photoresist 114 that has been dissolved or loosened. Afterwards, as shown in FIG. 2F , in the drying step, a drying gas 160, such as nitrogen, is provided to remove the above-mentioned deionized water 150 and continuously remove foreign particles 115, so that the exposed surface of the light-transmissive carrier film 112 has a relatively high cleanliness. In addition, after the entire cleaning step, the photoresist layer 111 will be formed with shrinkage side edges 111a, which can be used to determine whether it has been cleaned and judge its cleaning degree.

Afterwards, referring to FIG. 2G , an exposure step is performed, usually the cleaned wafer 120 and the photoresist layer 111 of the dry film 110 and the light-transmitting carrier film 112 are placed in a yellow room (yellow room), for exposure. A photomask 170 is placed above the light-transmissive carrier film 112, an exposure light 171 passes through the photomask 170, and then passes through the light-transmissive carrier film 112 to irradiate the photoresist layer 111 in a patterned manner, so that the photoresist layer 111 is formed. An exposed area 111b and an unexposed area 111c are properly imaged, wherein the exposed area 111b represents the photoresist layer 111 where photochemical reactions have occurred. Preferably, the yellow light room in the exposure step is the same as the above-mentioned dark room for cleaning the light-transmissive carrier film 112 , so as to facilitate continuous process operation.

After that, as shown in FIG. 2H , the light-transmissive carrier film 112 is removed, and the photoresist layer 111 is developed to form a pattern. Since in this embodiment, the photoresist layer 111 is a negative photoresist, the photoresist in the unexposed area 111c is removed to form a patterned recessed area 111d for subsequent bumps, wiring formation or etching operations. Therefore, using the method of using the dry film of the present invention, the cleanliness of the light-transmissive carrier film 112 and the wafer 120 of the dry film 110 is good, and accurate exposure is achieved to form the correct patterned recessed area 111d. In the dry film exposure test on a batch of wafers, the conventional processing flow will produce a wafer defect rate of 0.58%. Using the method of using the dry film of the present invention, the defect rate after wafer processing can be effectively reduced to 0.01% %, to achieve significant process improvement. The dry film application method of the present invention can be applied to the production of bumps in the wafer-level packaging process, so that the subsequently formed bumps have a consistent shape and volume.

Although the present invention is disclosed by the aforementioned embodiments, they are not intended to limit the present invention. Those skilled in the art can make various modifications to the present invention without departing from the spirit and scope of the present invention. If the modifications to the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications.

Claims (2)

1. cleaning process that is pressed on the dry film on the wafer, described dry film comprises the film carrier that an at least one photoresist layer and that is attached at wafer appears, it is characterized in that: this flow process comprises: carry out the hydro-peening step of use dimethylbenzene or propyleneglycoles methyl ether, to remove residual photoresistance and the particle on this film carrier; Carry out a washed with de-ionized water step, to remove the solution of described dimethylbenzene or propyleneglycoles methyl ether; And carry out a drying steps, to remove this deionized water; Wherein, when the hydro-peening step of carrying out described dimethylbenzene or propyleneglycoles methyl ether, washed with de-ionized water step and drying steps, described wafer all is placed on a darkroom or a gold-tinted is indoor.

2. as claim 1 a described cleaning process, it is characterized in that: employed gas is nitrogen in the described drying steps.

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