Semiconductor device having heat detecting element and insulating cavity and method of manufacturing the same

#1. Field of the Invention

#The present invention relates to a semiconductor device and a method of manufacturing the same. More particularly, the present invention relates to a semiconductor device with a thermoelectric conversion function and discloses a technique suitable for a thermal image input device that is used for providing security or in the field of an ITS (Intelligent Transportation System).

#2. Description of the Related Art

#FIG. 1 is a process drawing illustrating an example of a manufacturing method according to the present invention.

#FIG. 2 is a cross-sectional view showing an example of a semiconductor device according to the present invention.

#FIG. 3 is a cross-sectional view showing another example of a semiconductor device according to the present invention.

#As described above, in the embodiment of the present invention, a closed cavity is included in a heat insulating layer. This heat insulating layer includes at least a silicon oxide film. This silicon oxide film is partially removed to form at least a portion of the closed cavity (or a hole).

#In a typical embodiment of the present invention, the heat insulating layer includes a partially oxidized silicon polycrystalline film arranged above the closed cavity. In the case where the heat insulating layer includes a hole, the layer includes a partially oxidized silicon polycrystalline film, the oxidized portion of the silicon polycrystalline film surrounding the opening of the hole. The closed cavity or hole in a semiconductor device can be formed by a method involving partial oxidization of the silicon polycrystalline film. When formed by this method, the closed cavity or the hole whose interior has been expanded contains the silicon polycrystalline film as described above. A film formed as a silicon polycrystalline film may be oxidized substantially entirely so that the film ultimately turns to a silicone oxide film. In this case, another silicon oxide film (an additional silicon oxide film) is present above the closed cavity (alternatively, the film is present so as to surround the opening of the hole).

#The heat insulating layer preferably includes a silicon nitride film formed on the silicon oxide film. The silicon nitride film has a high strength and thus is suitable for maintaining a strength of the layer including the hole and/or closed cavity. In the case where the closed cavity is formed, the silicon nitride film has an opening, for example, above the closed cavity. On the other hand, in the case where the hole is formed, an opening of the hole, for example, extends through the silicon nitride film. In a typical embodiment of the present invention, the opening is formed by applying dry etching. On the silicon nitride film, another partially oxidized silicon polycrystalline film may be formed. Further, by forming the silicon nitride film between the silicon polycrystalline film and the closed cavity or the expanded interior of the hole, a structure in which the silicon polycrystalline film is supported by the silicon nitride film above the closed cavity or the like can be realized. This structure is advantageous from the viewpoint of strength. In this case also, the partially oxidized silicon polycrystalline film may be oxidized entirely to be a silicon oxide film.