JPH05206098A - Method of etching ceramic basic material having metallic multilayer film - Google Patents

Abstract

PURPOSE:To provide an etching method for a substrate having a metallic multilayer film in which conventionally unavoidable side etching is suppressed. CONSTITUTION:In an etching method of a basic material having a metallic multilayer film in which 2 kinds of metal or alloy, e.g. metal A and metal B which is electrochemically nobler than metal A are laminated in order of A, B on the basic material, film B is first removed by using a first etching fluid for preferentially etching B to A, and next film A is removed by using a second etching fluid for preferentially etching A to B. The etching method of a ceramic basic material having a metallic multilayer film is characterized by subsequently removing the film B on the part projecting higher than the A film by using a third etching fluid for preferentially etching B to A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for etching and removing a metal portion of a base material having a metal multilayer film used for semiconductor substrates, packages and the like.

[0002]

2. Description of the Related Art With the increase in the speed and density of LSIs, the amount of heat generated has been increasing, and characteristics such as high thermal conductivity and heat resistance have come to be particularly emphasized as properties required for a substrate material. Is coming. Glass substrates, ceramics substrates, low temperature firing substrates, and the like have been attracting attention as materials that can meet this demand. Since all of these materials are insulators and brazing materials such as solder cannot be used directly,
In the case of joining with, a so-called metallization for forming a metal film on the surface is required. In addition, in order to bond the substrate portion and the lid portion of the LSI package, metallization is required in advance at the joint portions of the substrate portion and the lid portion. The metallizing method includes (1) a thick film method in which a conductor paste and a resistance paste are applied in a pattern on a substrate by screen printing and baking, and (2) the conductor paste is screen-printed on a substrate before baking, A co-firing method in which metallization is performed simultaneously with firing, and (3) a thin film method in which a metallized film is formed by sputtering, ion plating, vapor deposition, or the like are known. Among these, the thin film method is capable of forming a dense and highly pure film, and thus is indispensable for increasing the reliability of metallization and is expected to be a technique that will be used frequently in the future. When the metallized film is formed by the thin film method, the pattern is usually formed by masking and etching steps. Two types of etching methods are used: a dry etching method in which a gas or the like is blown for etching and a wet etching method in which etching is performed with an etching solution. Among them, the wet etching method is characterized in that it is unlikely to be influenced by the surface shape of the material to be etched, and therefore wet etching is used particularly for a three-dimensional shape product.

[0003]

The joining of the substrate and the LSI or the joining of the substrate portion and the lid portion of the LSI package is usually performed by solder in many cases. However, as a metallized film for soldering, A multilayer film of two layers or more is often used in consideration of reactivity with the substrate, adhesion strength, erosion during soldering, reactivity with solder, wettability, etc. It was extremely difficult to perform etching without side etching at the boundary of, and it was extremely difficult to completely align the end of etching, which was a big problem. For example, in the case of usually two layers, a method of sequentially dissolving each layer by using two kinds of etching liquids that preferentially dissolves each layer so that etching of a specific layer does not proceed is used. It has been very difficult to perfectly align the etching end portions, that is, to just-etch by the action of the local battery of each layer. An object of the present invention is to provide an etching method capable of aligning the etching edges between two types of metal layers when removing the metal multilayer film of a substrate having a metal multilayer film by etching.

[0004]

The present inventors arrived at the present invention by observing the electrochemical properties between layers of a metal multilayer film and the progress of etching. That is, the present invention relates to an etching method for a substrate having a metal multilayer film in which two metals or alloys in which B is electrochemically nobler than A is laminated on the substrate in the order A and B. First, the B film is removed by using the first etching liquid that preferentially etches B over A, and then the second etchant preferentially etches A over B.
Metal for removing the A film by using the etching solution described above, and then removing the B film at a portion protruding from the A film by using a third etching solution that preferentially etches the B film over the A film. A method for etching a ceramic substrate having a multilayer film.

The present invention will be described in detail below. In order to solve the above-mentioned problems, the present inventor investigated in detail the progress of etching at the metallized end when the upper film is electrochemically noble than the lower film, that is, when the standard electrode potential is large. FIG. 1 shows a schematic view of a cross section at each stage of etching. Here, B is a metal or alloy that is electrochemically more noble than A, and cross-sectional views are shown at each stage of etching from the state of being masked with a resist agent for patterning. (1) is a state in which a layer A and a layer B are formed in this order on a substrate and a resist for masking is applied, and (2) is a first etching liquid for preferentially etching the layer B. The etched states (3) to (6) show changes in the state of the process of etching the A layer with the second etching liquid that preferentially etches the A layer.

In (3) to (5) of FIG. 1, the etching of the A layer progresses as compared with the portion not in contact with the B layer because the action of the local battery works in the portion in contact with the B layer. The speed increases. Therefore, at the stage (6) when the removal of the A layer is completed, side etching of the length a occurs and the A layer and the B layer are removed.
The tip portions of the layers are not aligned, and the side etching cannot be eliminated by variously adjusting the concentration, temperature, and etching time of the etching solution. Then, as a result of further study, the inventor has finally found a solution. That is, after the removal of the A layer in the above-described etching process is completed, the protruding portion of the B layer is etched with a third etching solution that preferentially etches the B layer, and thus the A layer and the B layer are etched. It is possible to obtain an etching state (7) in which the edges are aligned and side etching is not performed.

The first etching liquid and the third etching liquid used in the present invention may be the same as long as they preferentially etch B over A, or the concentrations and types of the etching liquids may be changed. May be. The etching method according to the present invention is not limited to the method in which the A layer and the B layer are directly laminated on the substrate, and a metal and / or a non-metal layer is interposed between the A layer and the base material. Even if the same effect is obtained. Further, alumina and aluminum nitride, which have high heat resistance and heat resistance, which are characteristics required for a semiconductor substrate and a package, cannot be directly bonded to each other or to an LSI, and metallization is essential. When used as a member for semiconductor applications, minute shape defects lead to defects in the product itself.Therefore, when using alumina or aluminum nitride for semiconductor applications such as semiconductor substrates and packages, the etching shape with less side etching of the present invention is used. The resulting method of the present invention is extremely effective.

[0008]

EXAMPLES The present invention will be described in more detail based on examples. (Example 1) Cu and Au were respectively deposited on an alumina substrate.
Films were formed at 0.8 μm and 0.3 μm by the ion plating method. After patterning with a masking resist, 10
% Of the KCN solution and Cu in the 20% FeCl ₃ solution. Then, etching was performed again with a 10% KCN solution. The results are shown in Table 1. In addition, as a comparative example, the etching time was changed and Au and 20% FeC were used with 10% KCN solution.
Table 1 shows the case where Cu was etched with the l ₃ solution.

[0009]

[Table 1]

From Table 1, after etching Au and Cu, A
By etching u again with a KCN solution, the side etch amount could be extremely reduced. On the other hand, compared with Comparative Examples 1 to 3, in the two-stage etching of Au and Cu, when the etching time of Cu is short, the etching of Cu becomes insufficient. The amount of etching is further increased, and it can be seen that it is difficult to reduce the side etch by the conventional two-step etching. (Example 2) Ni and Au were respectively deposited on aluminum nitride.
Films were formed to a thickness of 1.5 μm and 0.5 μm by a sputtering method. After patterning with a masking resist, 5% I ₂ + 10% NH ₄
Au was etched with the I solution and Ni was etched with the 40% FeCl ₃ solution. Then, etching was performed again with a 5% I ₂ + 10% NH ₄ I solution. The results are shown in Table 2. Further, as a comparative example, Table 2 shows a case where Au was etched with a 5% I ₂ + 10% NH ₄ I solution and Ni was etched with a 40% FeCl ₃ solution while changing the etching time.

[0011]

[Table 2]

As a result, after etching Au and Ni, Au is added to 5
By etching again with the% I ₂ + 10% NH ₄ I solution, the side etch amount could be made extremely small. Further, in the conventional two-step etching shown in the comparative example, side etching occurs at any time. The longer the time, the larger the side etching amount, and the shorter the time, the insufficient etching, and the side etching cannot be eliminated. I understand.

[0013]

According to the method of the present invention, when the metal multilayer film of the substrate having the metal multilayer film is removed by etching, side etching caused by a difference in electrochemical property between two kinds of metal layers is reduced. Therefore, it is suitable for semiconductor applications in which it is particularly necessary to reduce side etching. According to the method of the present invention, since the quality of the etching end of the metallized portion of ceramics such as alumina and aluminum nitride that requires metallization at the joint is improved,
It is an extremely effective means when using alumina or aluminum nitride for semiconductor applications such as substrates or packages.

[Brief description of drawings]

FIG. 1 is a schematic view of a cross section of a multilayer film at each stage according to the etching method of the present invention.

Claims (2)

[Claims] 1. B is electrochemically more precious than A. 2
In a method for etching a base material having a metal multilayer film in which a metal or alloy of a certain kind is laminated on the base material in the order of A and B,
First, the B film is removed using a first etching solution that preferentially etches B over A, and then the A film is removed using a second etching solution that preferentially etches A over B. , Then preferentially etching B over A
A method for etching a ceramic substrate having a metal multi-layered film, characterized in that the B film in a portion projecting from the A film is removed by using the etching solution of. 2. The method for etching a ceramic substrate having a metal multilayer film according to claim 1, wherein the substrate is alumina or aluminum nitride.