An organic build-up film is used as the substrate material for a semiconductor multi-die package. However, the miniaturization of the organic build-up film process by the commonly used 355 nm UV laser has almost reached the limit due to its long wavelength. Therefore, to miniaturize the build-up film process, it is necessary to use an excimer laser with a shorter wavelength than the UV laser. In addition, the high photon energy due to the short wavelength of the excimer laser means the thermal effect of the material can be reduced by direct photon absorption. We have developed several types of DUV excimer lasers. One of them is a high power 248 nm excimer laser with free spectrum operation. The 248 nm excimer laser can be applied to the process of organic materials for semiconductor packages. We are developing the processing of organic materials by 248 nm excimer laser. The organic materials are processed directly by the irradiation using the mask by 248 nm excimer laser. We report microdrilling processability of less than 20 μm diameter for a build-up film using a 248 nm excimer laser. The dependence of the taper angle, processing rate on the fluence for various via hole diameters was evaluated for major commercial build-up films. The results of this study indicate the appropriate selection of build-up film material and excimer laser processing fluence to achieve the processing target diameter and taper angle.
In this study, we are developing the process of glass ablation by 248nm excimer to make micro-via to the glass material. The interposer connects many pins between both sides electrically. Therefore, the micro-via to the glass substrate must be needed. However, the micro-via machining to the glass material is difficult because the glass is brittle material. We report microdrilling processability of less than 20um diameter for glass material using a 248nm excimer laser. We also report the investigation result of the dependence of the drilling rate and laser fluence and laser pulse width.
High performance, high speed processing, and miniaturization of electronic devices are advancing, due to the rapid development of highly advanced information society in recent years. Semiconductors continue to be highly integrated according to Moore's law, and semiconductor package substrates are also required to be miniaturized and highly densified. The build-up method is one of the methods for miniaturization and high density of semiconductor package substrates. The build-up method is method of alternately forming insulation layers and conductor layers on both sides of a glass epoxy substrate. In general, an organic build-up film is used for the insulation layers, and a via is formed in the insulation layers by laser processing. However, the miniaturization of the organic build-up film process by the commonly used 355 nm UV laser has almost reached the limit due to its long wavelength. Therefore, to miniaturize the build-up film process, it is necessary to use excimer laser with shorter wavelength than the UV laser. We are developing the processing of organic build-up film by 248 nm excimer laser with free spectrum operation. The organic build-up films are processed directly by the irradiation using the mask by 248 nm excimer laser. We processed using Ajinomoto build-up films (ABF) as organic material. The type of ABF was GY50. We confirmed that it is possible to process via of 3 μm in build-up film and the DOF can be increased depending on the process conditions. We will report on the processability of build-up film using 248 nm excimer laser.
The material processing by DUV laser region has been required for wide band gap material and precise hole and groove in DUV region. It is still very hard to get high power solid-state lasers in this spectral region especially below 300 nm. The rare-gas halide excimer lasers are only the solution, and now the time has come to examine the new applications of material processing with DUV excimer lasers. We have developed several types of DUV excimer lasers. One of them is a high power 248 nm excimer laser with free spectrum operation. The 248 nm excimer laser can be applied to the process of organic materials for semiconductor packages. We are developing the processing of organic materials by 248 nm excimer laser. The organic materials are processed directly by the irradiation using the mask by 248 nm excimer laser. In this method, it is possible to process fine patterns and various patterns. We processed using Ajinomoto build-up films (ABF) as organic material. The types of ABF were GX92, GX-T31 and GY50, and their thickness was 10 μm. We confirmed that it is possible to process via of 5 μm or less in build-up film. Furthermore, it was confirmed that the L/S pattern can be processed. We will report the result of processing organic materials with 248 nm excimer laser.
A laser processing is widely applied to cutting, drilling, welding, bending and surface treatment in industry. Lasers with a wavelength of 1 μm are mainly used and the processing is realized by melting materials. This thermal process has a high productivity but the processed surface is hard to use for precision machining. This report is focusing on two materials which are classified in wide band gap. Ablation rate was measured with a laser microscope and an optical one. Excimer laser is expected to be a useful tool for these materials
Recently infrared laser has faced resolution limit of finer micromachining requirement on especially semiconductor packaging like Fan-Out Wafer Level Package (FO-WLP) and Through Glass Via hole (TGV) which are hard to process with less defect. In this study, we investigated ablation rate with deep ultra violet excimer laser to explore its possibilities of micromachining on organic and glass interposers. These results were observed with a laser microscopy and Scanning Electron Microscope (SEM). As the ablation rates of both materials were quite affordable value, excimer laser is expected to be put in practical use for mass production.
A frontier in laser machining has been required by material processing in DUV region because it is hard to get high power solid-state lasers in this spectral region. DUV excimer lasers are the only solution, and now the time has come to examine the new applications of material processing with DUV excimer lasers. The excimer lasers at 193nm and 248nm have been used in the semiconductor manufacturing for long years, and have field-proven stability and reliability. The high photon energy of 6.4 eV at 193nm is expected to interact directly with the chemical bond of hard-machining materials, such as CFRP, diamond and tempered glasses. We report the latest results of material processing by 193nm high power DUV laser.
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