The goal of this study was the investigation of the influence of processing parameters as well as material properties on the creation of specs during the production of multilayer films. Therefore so called barrier films have been produced in three different material combinations. To determine the influence of the processing parameters a 2³ factorial design was realized. As variable process parameters the temperature of die bonding layer, the temperature of the cover layer and the mass flow rate was chosen. The material of the main component of the cover layer and the bonding layer were altered. The other layers were not changed. To interpret the results in reference to the material properties DSC and rheological analyses have been performed. Further two different lots which showed different speclevels have been compared. The first task was the analyses of the used polymers by DSC testing. The bonding agents were the only materials which showed a difference in the melting enthalpy. After this one compound of every layer of the examined films was produced. These compounds were used to measure the rheological properties of the single layers of the films. It could be seen that the zero shear viscosity of the materials was different. The investigation of the specs with DSC and Raman spectroscopy could not specify the specs better. The material combination 1 is the standard material with material M10 in the cover layer and material W34 in the bonding layer. It could be seen that the increase of both temperatures reduces the spec level significantly. In the material combination 2 the material in the bonding layer had been altered from material W34 to material W35 which led to a decrease of the speclevel. The lower zero shear viscosity and the lower enthalpy can be named as reasons for this. The influence of the running in processes showed a strong impact on the speclevel. The increase of temperature of both components led also to a decrease of the speclevel. In the material combination 3 the material of the cover layer had been altered form material M10 to material M45. This combination caused a decrease of the speclevel by increasing the temperature of the cover layer or the mass flow rate. The increase of the temperature of the cover layer increased the speclevel. The theory is that the higher zero shear viscosity of material M45 in combination with the higher temperature loosens particles from the tool.