In plasma display panels, an MgO film is used as a protective layer of electrodes and dielectrics. A vacuum processing apparatus such as a deposition apparatus is used to form the MgO film.
FIG. 11 is a plan view schematically illustrating a configuration of a known vacuum processing apparatus. The vacuum processing apparatus 100 includes a heating chamber 114 for heating a processing substrate and a film forming chamber 115 for forming the MgO film on the substrate after heating. The substrate is mounted on a carrier and a plurality of carriers are sequentially moved to processing chambers while the substrates are sequentially subjected to the processes.
In the film forming chamber 115, a part of the MgO film is formed on the carrier as well as the substrate. The MgO film has a feature that it easily adsorbs moisture or carbon acid gas in the atmospheric air. The moisture adsorbed by the MgO film cannot be easily removed. Accordingly, in the case in which the carrier enters the film forming chamber 115, MgO is gasified (evaporated) by heating to destabilize the degree of vacuum of the film forming chamber 115. In the case in which the degree of vacuum of the film forming chamber 115 is destabilized, the crystal orientation of the MgO film formed on the substrate is destabilized. This is because the coexisting ratio of a (111) crystal orientation component and a (200) crystal orientation component of the MgO film varies due to the pressure at the time of forming a film; and permeability of the MgO film is also destabilized. On the other hand, in the case in which the carbon acid gas (CO2, CO) is adsorbed by MgO, C infiltrates the MgO film to lower cathode luminescence intensity. That is, C infiltrating the MgO film deteriorates a discharge characteristic of the plasma display panel.
Therefore, there was suggested a technique of preventing the moisture or the carbon acid gas from being adsorbed by the MgO film formed on the carrier by keeping the movement passage of the carrier in a vacuum state and loading and unloading the substrate to and from the carrier through a load lock chamber (for example, see Patent Document 1). In the vacuum processing apparatus shown in FIG. 11, a return transport passage (a second transport chamber 92, a third transport chamber 93, and a first transport chamber 112) of the carrier is formed from the outlet of the film forming chamber 115 to the inlet of the heating chamber 114. The transport passage, the heating chamber 114, and the film forming chamber 115 are kept in a vacuum state, thereby forming a vacuum circulation path 108 of a plurality of carriers. The first transport chamber 112 is provided with a substrate loading and unloading chamber 110 for the carrier. In the substrate loading and unloading chamber 110, before-processing substrates are loaded to the carriers circulating the vacuum circulation path 108 and after-processing substrates are unloaded from the carriers.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. H09-279341
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2001-156158