JPH04202074A - Ceramic substrate for thin film - Google Patents

Abstract

PURPOSE:To increase the accuracy of positioning of a photomask by forming recessed marks for positioning in the surface of a ceramic substrate on which a circuit layer is formed. CONSTITUTION:The required number of green sheets 1a of AlN, Al2O3, etc., are molded, through holes acting as via holes 3 after firing are pierced in the sheets 1a by punching or other method and holes acting as marks 4 for positioning a photomask are pierced in the sheet 1a for the uppermost layer. The through holes are filled with electrically conductive paste and a circuit layer is formed on the surface of each of the sheets 1a by printing with electrically conductive paste. The sheets 1a are then laminated, press-bonded and fired to obtain a ceramic substrate 1. A thin circuit layer 6 and a photosensitive resist film are successively formed on the substrate 1 and exposure through a photomask and etching are carried out to form a desired circuit.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a ceramic substrate for forming a thin film wiring layer.

(Prior art) As semiconductor devices become more highly integrated, as seen in recent VLSIs, it becomes necessary to make the conductor layer formed on the surface of the ceramic substrate on which the semiconductor device is mounted more dense. Therefore, it is required to form fine wiring. A thin film conductor layer formed by applying a thin film method such as a vacuum evaporation method or a sputtering method is suitable as a conductor layer that enables the formation of such fine wiring.

A ceramic substrate having such a thin film wiring layer is produced, for example, as follows.

That is, first, a thin film conductor layer is uniformly formed on the surface of a ceramic substrate having internal wiring by vacuum evaporation, sputtering, or the like. Next, a photosensitive resist film is formed on the thin film conductor layer, and this resist film is exposed using a photomask.

Thereafter, etching is performed using the exposed resist film as a masking film to form a thin film wiring layer in a desired shape.

(Problem to be solved by the invention) By the way, the alignment of the photomask used when exposing the above-mentioned resist film is usually done by aligning the pattern on the photomask with the peer hole used as a wiring network in the ceramic substrate. It is done by doing this.

However, since the above-mentioned peer holes are filled with a conductive substance at the time of thin film formation, there are cases where the difference in color tone between the ceramic substrate and the conductive substance filled in the peer holes is small, or when the thin film conductor formed on the surface of the ceramic substrate When the thickness of the layer becomes somewhat thicker, it becomes difficult to identify the pier hole itself, resulting in a problem in that the alignment accuracy of the photomask decreases.

In particular, when a metal plating layer or the like is formed on the thin film conductor layer, alignment of the photomask becomes difficult.

The present invention has been made to address such problems, and provides a ceramic substrate for thin films that makes it possible to align a photomask with high precision even when it is difficult to identify peer holes. The purpose is to

[Structure of the Invention (Means for Solving the Problems)] The ceramic substrate for thin films of the present invention is a ceramic substrate for thin films on which a wiring layer is formed by a thin film method, in which a ceramic substrate surface on which the wiring layer is formed. The device is characterized in that a concave photomask alignment mark is provided on the photomask.

(Function) In the thin film ceramic substrate of the present invention, since the concave photomask alignment mark is provided, the photomask alignment mark can be easily set even after the thin film wiring layer is formed on the surface of the ceramic substrate. can be recognized. Therefore, it becomes possible to align the photomask with high precision.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a thin film ceramic substrate according to an embodiment of the present invention.

In the figure, 1 is a ceramic base made of various ceramic sintered bodies such as an alumina sintered body, an aluminum nitride sintered body, and a silicon carbide sintered body.

This ceramic substrate 1 includes a plurality of ceramic layers 1a
It is multi-layered by simultaneous firing.

This ceramic substrate 1 has internal wiring. This internal wiring is constituted by an internal wiring layer 2 including a ground layer, a power supply layer, etc. provided on each ceramic layer]a, and a peer hole 3 that electrically connects these internal wiring layers 2.

As shown in FIG. 2, in the uppermost ceramic layer 1a, hole-shaped photomask alignment marks 4 are provided diagonally.

The above-mentioned photomask alignment mark is not limited to the hole-shaped mark 4 as described above, but it is also possible to use a groove-shaped mark 5 as shown in FIGS. 2 and 3, for example, or a concave shape. Marks of various shapes can be used as long as they have a shape and can define the planar position.

The thin film ceramic substrate 1 as described above is manufactured, for example, as follows.

First, form the required number of clean sheets (LA) made of aluminum nitride, aluminum oxide, etc., and form = 5- according to the ceramic layer corresponding to each green sheet.
A through hole that will become the pier hole 3 after firing is formed by punching or the like.

At this time, holes that will become marks 4 for photomask alignment are also formed at the same time in the green sheet that will become the uppermost ceramic layer 1a. Furthermore, in the case of the groove-shaped photomask alignment mark 5, it is also formed at the green sheet stage.

Next, a wiring layer is formed by filling each through hole with a conductive paste and printing the conductive paste on the surface of each green sheet.

When filling the through-holes, conductive paste is not filled into the holes and grooves that serve as photomask alignment marks, and the hollow state is maintained.

After this, multiple green sheets with through-holes filled and printed wiring layers formed are stacked so that the green sheet with holes and grooves that serve as photomask alignment marks is the top layer. After being crimped and integrated, they are fired at an atmosphere and temperature depending on the ceramic used to integrate the plurality of ceramic layers [a] and form the pier holes 3 and the internal wiring layer 2.

In this way, a ceramic substrate having a concave photomask alignment mark 4 on the surface on which a thin film is formed and provided with internal wiring] or i! 7.

As shown in FIG. 5, a wiring layer 6 is formed on the surface A of the ceramic six substrate 1 on the side where the photomask alignment marks 4 are provided by a thin film method. As a method for forming the thin film wiring layer 6, various thin film forming methods such as a vacuum evaporation method, a laser evaporation method, a sputtering method, a CVD method, and a molecular beam epitaxy method can be applied.

In the ceramic substrate 1 of the above embodiment, even after the thin film wiring layer 6 is formed on the surface as described above, the cavity 7 remains within the photomask alignment mark 4.
Even in a case where the peer hole 4 cannot be identified, the photomask alignment mark 4 can be easily recognized by visual inspection or the like.

Then, a photosensitive resist film is formed on the thin film wiring layer 6, and this resist film is exposed using a photomask. At this time, even after the resist film is formed, a cavity remains in the photomask alignment 71-4.
By aligning this photomask alignment mark 4 with the pattern of the photomask, it becomes possible to align the photomask with high precision. Thereafter, etching is performed using the exposed resist film as a masking film to form a circuit of a desired shape, thereby obtaining a highly accurate and fine wiring network.

In this way, in the thin film ceramic substrate 1 of the above embodiment, the concave photomask alignment mark 4 is provided in advance on the surface on the side where the thin film wiring layer 6 is to be formed, so that the peer hole 4 cannot be identified. Even in cases where
It becomes possible to align the photomask with high precision.

[Effects of the Invention] As explained above, according to the thin film ceramic substrate of the present invention, even when it is difficult to identify the peer holes conventionally used for photomask alignment, it is possible to align photomasks with high precision. It becomes possible to do so. Therefore,
It becomes possible to obtain a ceramic substrate with a high-precision and high-definition wiring network using the thin film method.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a ceramic substrate for thin films according to one embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a cross-sectional view showing the structure of a ceramic substrate for thin films according to another embodiment of the present invention. 4 is a plan view thereof, and FIG. 5 is a sectional view showing a thin film wiring layer formed on a thin film ceramic substrate according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Ceramic substrate, 1a... Ceramic base layer, 2... Internal wiring layer, 3...
... Pier hole, 4.5 ... Photomask alignment mark, 6 ... Thin film wiring layer. Applicant Toshiba Corporation Representative Patent Attorney Sa Suyama − −9= Figure 1 Congee 3 Figure

Claims (1)

[Scope of Claims] In a thin film ceramic substrate on which a wiring layer is formed by a thin film method, a recessed photomask alignment mark is provided on the surface of the ceramic substrate on which the wiring layer is formed. Ceramic substrate for thin films featuring: