This invention relates generally to semiconductor manufacture, and more particularly to a method and system for attaching semiconductor components, such as dice and packages, to a substrate, such as a leadframe or panel, in which a dicing tape for the dice is locally cured using radiation.
One well known semiconductor processing step involves dicing a semiconductor wafer into singulated components. Typically the wafer includes a plurality of semiconductor dice or semiconductor packages, which are referred to herein as xe2x80x9csemiconductor componentsxe2x80x9d.
One technique for dicing a wafer is saw cutting. With saw cutting, the wafer is mounted to a support member, and a diamond tipped saw rotating at high rpms saws the wafer along pre-formed lines known as streets. Another technique for dicing a wafer is scribing. With scribing, the wafer is again mounted to a support member, scribed along the streets, and then broken along the scribe lines by application of pressure exerted through a roller or other mechanism.
One conventional support member for dicing a wafer is known as a film frame. The film frame includes a metal frame, and an adhesive dicing tape stretched across the metal frame. The dicing tape can comprise a polymer film having an adhesive on one or both sides or a polymer layer having adhesive qualities. The dicing tape is formulated to provide a high adhesion with the wafer in order to prevent the wafer, and the singulated components, from moving during the dicing process. The high adhesion of the dicing tape is also advantageous for transporting the singulated components on the film frame for further processing, such as packaging.
However, the high adhesion of the dicing tape is a disadvantage when the singulated components must be removed from the tape. For example, mechanisms such as pushers and vacuum picks are utilized to either push or pull the singulated components from the dicing tape. These mechanisms are hampered by the high adhesion of the dicing tape, which must be overcome to separate the singulated components from the tape.
One prior art approach for reducing the adhesion of the dicing tape, is to construct the tape using an adhesive that is sensitive to a radiation, such as ultraviolet radiation. With a radiation sensitive dicing tape, exposure of the back side of the tape to the radiation reduces the adhesion of the tape, allowing the singulated components to be more easily separated from the tape. Typically, the entire backside of the dicing tape is exposed to the radiation, and adhesion of the tape can be reduced by a factor of ten or more.
One shortcoming of this approach is that not all of the singulated components are removed from the dicing tape at the same time. For example, semiconductor components are often graded according to speed, and the premium components are utilized in some products, while the non-premium components are utilized in other products. The premium components may thus be removed from the dicing tape for processing prior to the non-premium components (or vice versa). However, if all of the dicing tape has been exposed to radiation, the non-premium components remaining on the tape may not be secured for further transport. Accordingly, these components can move, or separate entirely from the dicing tape. This movement and separation can chip and damage the dice and cause problems in handling and in subsequent processing steps.
Another prior art approach for processing singulated components is disclosed in U.S. Pat. No. 6,140,151 to Akram. This approach involves exposing only selected portions of the dicing tape to radiation. For example, the selected portions can be adjacent to the premium components, permitting these components to be easily removed, while the non-premium components remain attached to the tape. With this technique a mask and a wafer stepper can be used to expose only selected portions of the dicing tape. One shortcoming of this technique is that additional equipment (e.g. mask, stepper), and an additional process step are required to expose the dicing tape.
The present invention is directed to a method and system for attaching semiconductor components to substrates, in which radiation curing of the dicing tape is incorporated into a component attach process. In addition, the present invention incorporates a radiation curing system into the component attach system, and performs the curing step simultaneously with a component attach step.
In accordance with the present invention, an improved method and system for attaching semiconductor components to a substrate, are provided. In the illustrative embodiment the components comprise semiconductor dice or packages, and the substrate comprises a leadframe or a panel. In addition, the components are initially contained on a component substrate, which in the illustrative embodiment comprises a semiconductor wafer or portion thereof.
The method includes the steps of providing a support member having a radiation sensitive dicing tape thereon, mounting a component substrate to the dicing tape, and then dicing the component substrate on the dicing tape into singulated components. The dicing step can be performed using any suitable process, such as sawing, scribing etching or water jetting. The method also includes the step of providing a component attach system configured to attach adhesive members to the substrate, and then to attach the singulated components to the adhesive members.
In the illustrative embodiment, the component attach system includes a component attach mechanism, and a stepper mechanism configured to step the support member in x and y directions, such that a single component on the dicing tape is aligned with the component attach mechanism. The component attach mechanism includes a housing having a contact surface with vacuum openings for holding the dicing tape, and an opening having an outline that matches the outline of a singulated component. The component attach mechanism also includes a source of radiation (e.g., UV radiation), a fiber optic cable in communication with the source, and a lens on the fiber optic cable. The lens is configured to direct the radiation through the opening in the housing, and onto the backside of the dicing tape.
The component attach mechanism also includes an ejector pin configured to move through the opening, and to push the singulated component from the support member. In addition, the component attach mechanism includes a vacuum pick and place mechanism configured to pick up the component as it is pushed from the support member, and then to place the component on substrate.
During the component attach step the stepper mechanism moves the support member in x and y directions, to align a selected component on the dicing tape to the component attach mechanism. The component attach mechanism is then moved such that the opening in the housing aligns with the backside of the component, with the contact surface and the vacuum openings on the housing in contact with the backside of the dicing tape adjacent to the component. With the component attach mechanism aligned with the component, the radiation source is actuated to direct the radiation through the lens, through the opening in the housing, and onto the backside of the dicing tape. This locally cures the dicing tape in the area adjacent to the backside of the component, such that the tape loses its adhesiveness in this area. Prior to, or simultaneously with the component attach step, the substrate with the adhesive members thereon, is indexed into a position proximate to the component. The ejector pin is then actuated to push the component off the dicing tape, as the pick and place mechanism simultaneously picks and places the component on the substrate.
The system includes the support member and the radiation sensitive dicing tape for holding the diced components on the support member. The system also includes the component attach system which is configured to attach adhesive members to the substrate, and to attach the components to the adhesive members. The component attach system includes the component attach mechanism which comprises the housing with the opening corresponding to the outline of the component, the flexible fiber optic cable, the lens and the ejector pin.