JPS61279166A - Substrate for hybrid integrated circuit - Google Patents

Abstract

PURPOSE:To increase the capacitance of a thin film capacitor to a large extent, by forming an irregular surface on a part, where the thin film capacitor is formed, on an insulating substrate. CONSTITUTION:On the forming part of a thin film capacitor on an insulating substrate 1, a glass layer 2, which has irregularities on the surface, is formed. The thin film capacitor, which has a dielectric layer along the irregular surface of the glass layer 2, is formed. Then, the effective area of the dielectric layer along the irregular surface is larger than the apparent plane area, which is obtained by the vertical projection of the effective area. Thus, the capacitance of the thin film capacitor is increased to a large extent.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to forming passive elements such as capacitors and resistors on an insulating substrate using film technology, and further mounting active elements such as integrated circuit chips. The present invention relates to a substrate for forming a hybrid integrated circuit.

[Conventional technology]

$2[1(a) to (d) are cross-sectional views for explaining a method of manufacturing a thin film capacitor in a conventional hybrid integrated circuit. First, as shown in FIG. 2(a), a glass layer 12 is applied to the capacitor formation portion on an insulating substrate 1 made of alumina ceramic or the like to make the surface as smooth as possible, and then ), a metal that can be made into a dielectric by a method such as anodization, such as tantalum, is deposited on the entire surface by a method such as sputtering, and then tantalum 3 is left in a predetermined shape on the glass layer 2. Then, it is patterned by chemical etching. Next, from the same figure (C),
A part of the tantalum layer 3 is formed into a dielectric layer 4 by a method such as anodization.
Change to Next, as shown in FIG. 4(d), the lower extraction electrode 7 is drawn out from the unformed portion 5 of the tantalum 3, and the upper electrode 6 is provided on the dielectric layer 4, and the dielectric layer 4 is connected to the unformed portion 5 on the lower surface. A thin film capacitor sandwiched between tantalum and an electrode 6 on the top surface is formed on the top surface of the insulating substrate 1.

[Problem that the invention seeks to solve]

It is well known that the capacitance value of a thin film capacitor as described above is determined by its area and the thickness of the dielectric layer. Therefore,
In order to obtain as large a capacity as possible, it is natural to increase the area or reduce the thickness of the dielectric layer. However, reducing the thickness of the dielectric layer has a limit in terms of withstand voltage, and increasing the area naturally increases the area occupied by the capacitor, which in turn leads to an increase in the size of the board. Problems such as increased area and increased costs arise.

[Means for solving problems]

In order to solve the above problem, in the present invention, at least the part where the thin film capacitor is formed on the insulating substrate forming the hybrid integrated circuit is made into an uneven surface, and the uneven surface allows the thin film capacitor formed on this part to be formed on the uneven surface. This significantly increases the capacitance of the capacitor compared to conventional thin film capacitors formed on flat surfaces.

〔Example〕

Next, the present invention will be explained using examples.

FIG. 1 is a partial cross-sectional view of one embodiment of the present invention.

In the figure, a glass layer 2 with an uneven surface is placed on an insulating substrate 1 made of alumina ceramic, etc., where a thin film capacitor is formed.
is formed. The surface of the glass layer 2 is smooth enough not to cause defects in the thin film capacitor formed thereon, and its unevenness is approximately the thickness of the dielectric layer of the thin film capacitor on the glass layer 2. It has barbs at a constant distance of 100 times or more.

In the above embodiment, the capacitor forming part is made of glass separate from the substrate body to form an uneven surface, but this is not limited to glass and may be made of other materials, or the desired unevenness may be directly formed on the substrate itself. Needless to say, you can also attach it.

〔Effect of the invention〕

Using the substrate for a hybrid integrated circuit of the present invention, a metal that can be made into a dielectric material is deposited on the uneven glass layer 2 by anodization, as shown in FIGS. 2(b), (C), By adding the same steps as in the conventional example shown in (d), a thin film capacitor having a dielectric layer along the uneven surface of the glass layer 2 can be easily manufactured. The effective area of the dielectric layer along the uneven surface of this capacitor is larger than the apparent planar area of the surface projected perpendicularly. This has the effect of making it possible to create thin film capacitors with much larger capacitance regardless of the occupied area.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of an embodiment of the present invention, and FIG. 2(a)
-(d) are cross-sectional views showing the sequence of steps for explaining a method of manufacturing a thin film capacitor using a conventional substrate for a hybrid integrated circuit. 1... Insulating substrate, 2... Uneven surface glass layer, 3...
Tantalum layer, 4... Dielectric layer, 6... Upper electrode, 7
. . . lower extraction electrode, 12 . . . flat surface glass layer. Flower 1 Figure $ 2 Figure

Claims (1)

[Claims] 1. A hybrid integrated circuit substrate having a thin film capacitor formed on an upper surface thereof, wherein at least the thin film capacitor forming portion has an uneven surface.