Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Packaging or treatment of packaged semiconductor
Utility Patent
1999-06-21
2001-01-02
Mulpuri, Savitri (Department: 2812)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Packaging or treatment of packaged semiconductor
C438S455000, C156S381000
Utility Patent
active
06168963
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the manufacturing of semiconductor devices and, in particular, to a method and apparatus for uniform and precise handling of semiconductor laser bars.
BACKGROUND OF THE INVENTION
Semiconductor laser devices such as laser diodes and photodetectors are formed from semiconductor wafer substrates. During the fabrication of such devices, the wafer substrate undergoes a series of processes. As such, the wafer substrate is first separated or cleaved into bars of semiconductor material. The resulting laser bars may be further cleaved to form discrete semiconductor chips. Conventional methods for cleaving a wafer substrate include scribing or scoring the wafer substrate and then cleaving the substrate along the scoring line by some form of physical contact of an apparatus with the substrate.
Following the cleave process and the formation of the laser bars, each end face or facet of each laser bar is coated with an optical coating in a facet coating apparatus. A facet coat holding fixture is typically employed to retain the laser bar during the facet coating and also to transport the bar into and out of the facet coating apparatus. When the coating process is finished, the laser bars are removed and placed back on a support for further processing steps.
During the processing steps enumerated above, the semiconductor products and workpieces are supported on a mounting material such as a vinyl film. Upon completion of the facet coating step, the laser bars are removed and placed back on the mounting material. At this stage, the processed laser bars may be heated to a predetermined temperature and have a predetermined pressure applied to them to ensure uniform adherence of all bars to the mounting material.
A system has been proposed in which laser bars are initially placed onto a vinyl film and then the whole assembly is heated to an adhesion temperature. Subsequently, an individual (referred to as an operator) uses his/her fingers, or a weighted object, to manually apply pressure across each laser bar. This method cannot guarantee uniform adhesion across the film. As a consequence, parts may be lost during the downstream processing steps.
The pressure on the laser bars should be applied so that the bars are not damaged and so that the semiconductor material does not crack or split. Because of the fragility of the laser bars, breakage is a significant problem. Also, since operators use their fingers to affix the bars to the film, the pressure magnitude is not repeatable and the operators can damage the products.
Accordingly, there is a need for an improved system for handling laser bars and other products and workpieces. The improved system should provide minimum handling of the resulting laser bars by employing a gentle and stress-free assembly, uniform adhesion of the laser bars to the mounting material, uniform pressure on the mounted laser bars, and an overall reduction in the number of defects due to the cracking or splitting of the semiconductor material.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for handling laser bars. Pressure is mechanically applied to the laser bars to uniformly adhere them to a mounting material. An object of the invention is to reduce damage to the bars by applying a uniform and constant pressure that, in turn, ensures the uniform adherence of the laser bars to the mounting material. The present invention also provides a method and apparatus for holding the laser bars during the fabrication process. The present invention applies a pressure whose magnitude is repeatable.
The above and other features and advantages of the invention are achieved by using isostatic pressure to uniformly apply a force on all the bars mounted on a section of a vinyl film. In accordance with a preferred embodiment of the present invention, the apparatus includes a base plate or a support with a heater and thermocouple, a movable cover plate with a port for pressurized gas, a sealed chamber containing a sealing structure, and an inlet for receiving a gas. In the sealed chamber, a vinyl film assembly has laser bars mounted on it. The laser bars come in contact with a flexible membrane. Pressurized gas is applied to the membrane so that it presses the laser bars against the vinyl film. The heater heats the film so that the laser bars are adhered to the film.
The present invention also provides a method in which uniform pressure is used to mount laser bars on a mounting material. The method includes the steps of positioning the film with the laser bars between a movable cover plate and a stationary base plate, locating the bars between a plastic membrane of the cover plate and the base plate, exerting pressure on the membrane such that the membrane exerts pressure on the laser bars, heating the laser bars, and causing the laser bars to adhere to the film. In a preferred embodiment of the invention, the pressure includes a force induced by gas pressure in a sealed chamber. The heater may be controlled by a thermocouple, if desired.
Additional advantages of the present invention will be apparent from the detailed description and drawings, which illustrate preferred embodiments of the invention.
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Diehl, Jr. Ralph J.
Freund Joseph Michael
Gault William Andrew
Przybylek George John
Romero Dennis Mark
Dickstein , Shapiro, Morin & Oshinsky, LLP
Lucent Technologies - Inc.
Mulpuri Savitri
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