1. Field of the Invention
The present invention relates to a nozzle device for spraying raw material powder toward a substrate so as to form a film, and a film forming apparatus and method using the device. Furthermore, the present invention relates to an inorganic electroluminescence (EL) device, an inkjet head and an ultrasonic transducer array fabricated by using such a film forming method.
2. Description of a Related Art
Recent years, when fabricating a hard and brittle material such as ceramics, it has been under study to use film forming technologies by which thick films can be formed without mixing a binder. Among them, the aerosol deposition (AD) method by which dense and strong thick films can be formed receives attention. The AD method is a film forming method of depositing the raw material by spraying ultrafine particles of a raw material toward a substrate so that the particles impinge on the substrate or a previously formed film. The AD method is also referred to as injection deposition method or gas deposition method.
In the AD method, when a film is formed in a region having a certain area, the substrate is scanned by using a nozzle for injecting ultrafine particles of the raw material. However, as the film forming area becomes larger, scanning with the nozzle must be repeated, and it takes a lot of time to forming a film. Accordingly, in response to the request to make the film forming region larger, the nozzle size has been made larger into a slit form, or the nozzle has been made to move over a broader range regularly. However, when the nozzle size is made larger, since it is difficult to stably supply an aerosol to the nozzle or to stably inject the aerosol from the nozzle, it is inevitable that streaky defects are produced in the formed film or the film thickness becomes nonuniform.
By the way, recent years, in various technology fields, phenomena based on the chaos theory have been utilized. According to Aihara (Department of Mathematical Engineering and Information Physics, the University of Tokyo), a chaos is defined as “a phenomenon in which, although a system changes according to a firm rule, the system behaves very complexly and unstably and a state in some distant future is completely unpredictable”. Further, he also stated that, when one chaos exists, an infinite number of orders are included therein, and since the orders are inherent, the chaos can be predicted and controlled.
For example, in a film forming method in which a film forming source (e.g., target) has an area equal to or larger than a substrate like the sputtering method or the like, in order to fabricate a uniform film, sometimes the substrate is chaotically moved by giving the substrate rotation motion and revolution motion. This is because, when the substrate exhibits chaotic behavior, the substrate no longer traces the same track again because of orbit instability of chaos, and a uniform film can be formed over a broad range. However, in the AD method, unlike the sputtering method or the like, the nozzle as a film forming source can be regarded as small as a dot or line relative to the substrate. Accordingly, it is unsuitable for utilizing the above-described technique without change.
Further, Japanese Patent Application Publications JP-A-7-31575 (the first page, FIG. 1) and JP-P 2004-654A (the first page, FIG. 1) disclose that a nozzle formed by plural links is used and the nozzle is made into a chaotic state by setting injection angle of injection openings or the like to suitable values. By applying the orbit instability of chaos to the rotational nozzle device, water can be uniformly distributed from the nozzle. However, in the AD method, unlike the case of water distribution, since the injected ultrafine particles of the raw material must be deposited on the substrate, the above-described rotational nozzle device can not be applied to the method.