JPS6014453A - Forming method of metallic layer pattern - Google Patents

Abstract

PURPOSE:To form a fine wiring pattern thickly by applying a first metallic layer on a substrate, selectively plating the first metallic layer with a second metallic layer, evaporating a third metallic layer on the second metallic layer and etching the first metallic layer while using the third metallic layer as a mask. CONSTITUTION:A chromium layer 2, a first platinum layer 3 and a first gold layer 4 are evaporated on an insulating substrate 1, and a resist film 5 is formed, and patterned. A second gold layer 6 is applied on the surface of the exposed gold layer 4 through electroplating, and a second platinum layer 7 is formed through an evaporation on the whole surface. The resist 5 is dissolved and removed, the first gold layer 4 is etched selectively while using the second platinum layer 7 as a mask, and the second platinum layer 7, the first platinum layer 3 and the chromium layer 2 are removed through ion milling, thus forming a precise pattern of a metallic wiring in approximately 6-8mum thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method of forming a metal pattern, and more particularly to a method of forming a thick metal wiring used for wiring such as a microwave circuit.

Background of the Technology In microwave circuits, large amounts of power and current flow, so if the resistance of the wiring is large, the loss of power will be large and there will be problems such as burnout of the wiring. The resistance of wiring is proportional to the cross-sectional area of the wiring, but with the recent trend towards higher density devices, the width of the wiring has to be reduced.

Therefore, it is necessary to form thick wiring. Furthermore, from the point of view of Skidbus, a certain amount of thickness is actually required when high frequency waves propagate on the wiring surface, and it is particularly necessary to increase the thickness in the range of 1 to 10 GHz.

Conventional technology and problems Conventionally, forming a thick wiring layer was simply done.

There is a method of completely applying a resist on a thickly deposited metal layer, buttering it, and then using the resist to etch the metal layer. However, since the metal layer is inevitably side-etched during etching, it is difficult to precisely form fine patterns on a thick metal layer. Another method is to deposit a thin metal layer on the entire surface and then apply a thick resist to the entire surface.
There is a method of patterning the resist, selectively plating the exposed metal layer, removing the resist, and selectively removing the exposed evaporated metal. However, even with this method, the current Vzistra is about 3 μmJl:,! 7. Since it is not possible to form a thick film, the thickness of the metal layer that can be satisfactorily formed by the one-select plating method is also limited. This is because a plating layer deposited beyond the thickness of the resist is no longer constrained in the lateral direction by the pattern of the resist, so that the contact with the plate is as short as 9 times, making it extremely difficult to create fine patterns. In addition, if there is a high step in the base layer to be selectively plated, even if a resist is applied on top of it, it will not be able to completely cover the step part and the base layer at the shoulder of the step will be exposed, leaving it in an undesired position. This is because there are problems with step coverage such as adhesion of plating.

Purpose of invention The present invention is in view of one or more of the current state of the art.

It is an object of the present invention to provide a method for forming a fine wiring (metal layer) pattern having a thickness of 3 μm or more.

Composition of the invention One aspect of the present invention is to achieve the above object.

A first metal layer is fully deposited on the substrate, a resist is selectively applied thereon, and a second metal layer is selectively applied over the exposed surface of the first metal layer using the pattern of the resist. A third metal layer is deposited on the second metal layer and the entire surface of the resist, and the resist is dissolved and removed together with the third metal layer on top of the resist. ,
A method is then provided which includes selectively etching the entire first metal layer as a residual partial mask for the third metal layer.

Implementation of one invention will be described below using an example.

Embodiment of the Invention In FIG. 1, a chromium layer 2 is formed over the entire surface of an insulating substrate 1 made of, for example, alumina or sapphire.
First platinum layer3. Then, the first metal layer 4 is deposited in this order. The chromium layer 2 is used to improve adhesion to the insulating substrate, and the white metal 3 is used to suppress undesirable reactions between chromium and gold. The thickness of each layer is as follows: chromium layer 2 has a thickness of 500~
700X, the platinum layer 3 has a thickness of 500 to too'A, and the gold layer 4 has a thickness of 4 to 6 μm. Next, a negative resist, for example, AZ1350 manufactured by Silaplay Co., Ltd., was applied at a rotation speed of 1.50 Orp, p.
, m, to form a resist film 6 having a thickness of 3 μm and patterning. The width of the portion where the resist is removed, that is, the portion where wiring is to be formed, is, for example, 15 μm.

In FIG. 2, the substrate is treated with an electrolytic plating bath to selectively deposit a second gold layer 7 on the surface of the platinum layer 5 exposed between the resists 6 to a total thickness of about 2 μm. After removing from the plating bath and cleaning, a second platinum layer 7 is deposited on the entire surface from above the resist 5 and the second gold layer 6 to a thickness of 500 to 100 mm.
Form into OX.

In FIG. 3, when the resist 5 is dissolved and removed by spraying acetone onto the substrate, the second platinum layer 7 deposited on the resist 5 is also removed together.

Next, in FIG. 4, when the substrate is immersed in an iodine+potassium iodide solution and bubbled, the first gold layer 4 is selectively etched using the second platinum layer 7 as a mask. Subsequently, in FIG. 5, the second platinum layer 7 is removed by ion milling using Ar gas, and the exposed first platinum layer 3 is removed by milling with an iodine + potassium iodide solution, and then the exposed chromium layer is removed. υ selectively removed by ion milling with 2'iAr.

In this way, a precise 15 μm wide pattern of metal wiring with a thickness of about 6 to 8 μm is formed on the insulating substrate 1. The width is approximately 11 μm at the upper end of the pattern and 13 μm at the lower end.

Optionally, after the above-mentioned lift-off or removal of the resist 5 1
For example, the entire surface of the second gold layer 6 is plated with a thin layer of nickel, silver, etc., including the side surfaces of the second gold layer 6, and only the plating layer on the first gold layer 4 and the second platinum layer 70 is removed by milling. ,
If bubble etching is performed on the first gold layer 4, the plating layer remains on the side surfaces of the second gold layer 6, so that the amount of side etching is reduced to a negligible extent.

Furthermore, if titanium, chromium, etc. are used instead of the second platinum layer 7, the selectivity with gold is high, so reactive ion etching is used to remove the layer 7 of titanium, chromium, etc.
Selective etching of the first gold layer 4 is possible using as a mask. This further reduces the amount of side etching and improves pattern accuracy.

Effects of the Invention As is clear from the above description, depending on the present invention, it is possible to form a pattern of a metal layer having a film thickness exceeding 3 μm with high accuracy even if the pattern width and the pattern interval are narrow.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing the steps of forming a wiring pattern for explaining the present invention in detail. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Chromium layer, 3...1st platinum layer. 4... First gold layer, 5... Resist, 6... Second
gold layer. 7...Second platinum layer. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A first metal layer is deposited on a substrate, a resist is selectively applied thereon, and a pattern of the resist is used to selectively apply a second metal layer to the exposed surface of the first metal layer. A third metal layer is deposited on the second metal layer and the entire surface of the resist, and the resist is melted to remove the second metal layer on top of the resist. A method for forming a metal layer pattern, comprising the steps of removing the first metal layer together with the third metal layer, and selectively etching the first metal layer using the remaining portion of the third metal layer as a mask.