This invention relates generally to a novel system and method for protecting a substrate from damage and in particular to a substrate protection system for use with semiconductors wafers that contain integrated circuit dies formed on the substrate.
Currently, a substrate may not be protected during its manufacture. For example, in the semiconductor area, a substrate such as semiconductor wafer may be used. In accordance with well known manufacturing techniques, a plurality of integrated circuit dies are formed simultaneously on top of the semiconductor wafer. The process to form those integrated circuit dies requires numerous process steps. Once those integrated circuit dies are formed, the semiconductor wafer is separated into individual semiconductor dies which are then packaged and tested as is well known. The process steps to form the integrated circuit dies are performed in clean rooms in which contaminants are kept to a minimum since even the smaller contaminant may render one or more of the integrated circuit dies on the semiconductor wafer non-functional. The number of integrated circuit dies that are viable at the end of the manufacturing process is known as the yield of the process. An increase in the yield results in an increase in the revenue generated by the company manufacturing the integrated circuits.
When the integrated circuit dies are separated from each other (using a well known process such as sawing the semiconductor wafer), there is typically no protection provided to the integrated circuit dies. Thus, the separation process may result in damage to one or more integrated circuit dies which will therefore decrease the yield of the process. Therefore, it is desirable to provide a substrate protection system and method which, in a preferred embodiment, protects the integrated circuit dies from damage during the separation process. It is further desirable to provide a substrate protection system that protect bond pads during a bonding and testing process, encapsulates air-borne debris generated during manufacturing steps and processes, provide an anaerobic (sealed) environment to retard oxide growth on bonds and leads. The substrate protection process also has other advantages over typical systems as described below in more detail.
In accordance with the invention, a method for protecting a substrate having devices formed thereon is provided. In one example, the devices are protected from damage during the separation of the substrate into dies. On other examples, the devices and its bond pads are protected during a bonding and testing process. In a preferred embodiment, the substrate is a semiconductor wafer that is separated onto individual dies.
Thus, in accordance with the invention, a method for protecting a substrate having one or more devices formed thereon is provided. In accordance with the method, a protective layer is formed over the surface of the substrate including the one or more devices formed on the substrate. The substrate is then separated into one or more dies wherein a device is contained on each die and wherein the protective layer protects the devices during the separation process.
In accordance with another aspect of the invention a substrate is provided wherein one or more devices formed on the substrate and a protective layer is formed over the surface of the substrate including the one or more device wherein the one or more devices are protected from damage when the substrate is separated into individual dies wherein each die contain a device. In accordance with yet another aspect of the invention, a method for protecting a device on a die of a semiconductor wafer during probing is provided. In accordance with the method, a protective layer is formed over the device on the die prior to separating the die from the semiconductor wafer. Each separated die may be probed using a probe device wherein the probing occurs through the protective layer which reduces the oxide build-up on the contact pads on the separated die. In accordance with yet another aspect of the invention, a method for protecting a device on a die of a semiconductor wafer during wire bonding is provided. In a first step, a protective layer is formed over the device on the die prior to separating the die from the semiconductor wafer. Then, each contact pad of the separated die is wire bonded through the protective layer so that the separated die remains protected until it is encapsulated into a package.
The invention is particularly applicable to a system and method for protecting a semiconductor wafer with integrated circuits formed thereon and it is in this context that the invention will be described. It will be appreciated, however, that the system and method in accordance with the invention has greater utility since the substrate protection system and method may be used to protect a variety of different substrates and a variety of different devices formed on top of the substrate. For example, the substrate protection system and method may be utilized to protect the devices on the substrate and elements of the devices, such as bonding pads, etc., during die testing and/or probing processes, wafer level testing and probing processes, such as bare copper probing, separation processes, micromachining processes, surface milling processes, laser cutting processes, or surface micromachining processes. The substrate protection system and method may perform one or more of protecting the substrate and devices from damage, encapsulating air-borne debris and providing a sealed environment to retard oxide growth. Now, the preferred embodiment of the substrate protection system in which a semiconductor wafer and its integrated circuit dies are being protected will be described.
The protective layer 22 may remain on the substrate during the separation process, such as the sawing of the substrate, to protect the devices from damage. The protective layer 22 may then be removed/stripped off of each separated device 16 once the separation process is completed. Alternatively, the protective layer may be left covering each separated device 16 and then the probing/testing of each separated device 16 may occur through the protective layer. The probing/testing of the device 16 through the protective layer will reduce the oxide layer that builds up on the contacts of the device since the contacts of the device are not exposed to the air (the contacts are covered by the protective layer) which causes the oxidation. Furthermore, probing/testing through the protective layer will result in a better connection to the pads/contacts of the device during the testing as the pads/contacts will have fewer contaminants. The protective layer may also be left in place following the probing/testing and well known wire bonding may be performed through the protective layer so that the device remains protected from contaminants until it is encapsulated into a package. The protective layer may also protect a device during other operations, such as laser cutting, surface micromachining applications, or high precision surface milling methods. Now, a preferred method for protecting a substrate 30 in accordance with the invention is described.
While the foregoing has been with reference to a particular embodiment of the invention, it will be appreciated by those skilled in the art that changes in this embodiment may be made without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims.