JP3040223B2 - Pretreatment method to make plating easy to reach the surface of metallized layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method as a pretreatment for plating the surface of a metallized layer formed on the surface of an aluminum nitride sintered body.

[0002]

2. Description of the Related Art In recent years, with the miniaturization, higher density, and higher output of semiconductor components of electronic technology, how to dissipate heat generated from semiconductor components has become a major problem. On the other hand, aluminum nitride sintered bodies have high thermal conductivity, good electrical insulation, and have excellent properties such as almost the same coefficient of thermal expansion as Si. I have.

[0003] When an aluminum nitride sintered body is used as a semiconductor substrate, a conductive layer (metallized layer) of a conductive metal is usually formed on the surface of the aluminum nitride sintered body, and the metallized layer is processed by etching. In the case where plating is performed on the metallized layer, the etching process is performed as a pretreatment (soft etching) for facilitating plating on the surface of the metallized layer.

[0004] Conventionally, as a method of etching an aluminum nitride sintered body having a metallized layer, generally, there is a general method of etching.
The method used for the alumina substrate having the metallized layer has been adopted. In this method, a metallized layer of an alumina substrate is etched with an alkaline etchant containing sodium hydroxide, potassium hydroxide, lithium hydroxide or the like as an etching component.

[0005]

However, in the method for etching an aluminum nitride sintered body having a metallized layer by the above method, the metallized layer is etched and the etching solution is alkaline at the same time.
There is a disadvantage that erosion of the aluminum nitride sintered body proceeds. When the erosion of the aluminum nitride sintered body proceeds, not only does the surface roughness of the aluminum nitride sintered body deteriorate, but also the problem that the adhesion strength between the sintered body and the metallized layer decreases.

Therefore, development of a method of etching a metallized aluminum nitride sintered body without causing erosion of the aluminum nitride sintered body is desired.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, the concentration of hydrogen peroxide was 3 to 40% by weight and the pH was adjusted to 7 or less. The inventors have found that the etched etching solution can selectively and effectively etch the metallized layer without eroding the aluminum nitride sintered body, and have completed the present invention.

That is, according to the present invention, the metallized layer formed on the aluminum nitride sintered body has a hydrogen peroxide concentration of 3 to 3.
This is a pretreatment method for facilitating plating on the surface of the metallized layer, characterized in that the surface of the metallized layer is etched by being brought into contact with an etching solution composed of an aqueous solution having a pH of 7 or less at 40% by weight.

The etching solution used in the present invention contains hydrogen peroxide at a concentration of 3 to 40% by weight, preferably 5 to 30% by weight.
At a concentration of When the concentration of hydrogen peroxide is lower than 3% by weight, the etching effect of the metallized layer is weak and the metallized layer cannot be sufficiently etched. That is, the pretreatment by the etching is insufficient, and the problem that the adhesion between the metallized layer and the plating layer is weak occurs. Further, when the content of hydrogen peroxide exceeds 40% by weight, not only does the etching effect of the metallized layer plateau, but also it is difficult to control the finish of the etching and the control of the etching solution, which is a problem in industrial implementation. It may be.

It is important that the pH of the etching solution used in the present invention is adjusted to 7 or less. That is, when the pH exceeds 7, erosion of the aluminum nitride sintered body occurs along with the etching of the metallized layer, and the surface of the aluminum nitride sintered body is roughened and the commercial value is reduced. The problem of lowering occurs. Further, the pH of the etching solution is preferably 1 to
Adjustment to 3 is preferable in order to exhibit a stable and good etching effect in the hydrogen peroxide concentration range.

As a method of adjusting the pH of the etching solution to 7 or less, a method of adding an acid is generally used. Known acids are used without any particular limitation as the above-mentioned acids. For example, inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, and organic acids such as acetic acid can be mentioned.

Known additives may be added to the etching solution of the present invention as long as the effects of the present invention are not significantly reduced. Examples of such additives include phosphate, uric acid, acetate, sodium citrate and the like.

In the present invention, the aluminum nitride sintered body having the metallized layer is not particularly limited, and includes all manufactured by a known method. Known methods for producing aluminum nitride having the metallized layer include a co-fire method, a post-fire method, and a thin film method.
In the present invention, an effect is expected for the metallized layer obtained by these methods. The cofire method is a method in which a metal film is baked simultaneously with sintering of the aluminum nitride sintered body. In general, to a molded body obtained by molding aluminum nitride powder using an organic binder,
A method of applying a paste of a high melting point metal powder, degreased, and subsequently sintered is adopted. The post-fire method is
After degreasing the molded body of the aluminum nitride powder and subsequently obtaining a sintered body by sintering, the sintered body is subjected to a sputtering method, a vacuum deposition method, an ion plating method, or the like.
This is a method for forming a metal film.

In the present invention, as a material of the metallizable layer which can be etched, typical metals are exemplified by W,
Examples include metals such as Mo, Ag, Pd, Ru, Cu, Ni, Mn, and Ti. Among these, as the high melting point metal,
W, Mo and the like. These metals are used in the form of a simple substance or a compound, and are used alone or in the form of a mixture of two or more kinds. Among the materials of the metallized layer, the present invention
In particular, it is suitable for the etching treatment of the refractory metal.

In the present invention, the etching is performed by wet etching in which the metallized layer is brought into contact with an etching solution. Examples of a method for bringing the etching solution into contact with the metallized layer include a dipping method, a shower method, and a spraying method. Among these, the immersion method is particularly suitable because it can be uniformly etched. As a condition for contact with the etching solution, a processing temperature is from room temperature (RT) to 50 ° C., preferably 3 ° C.
5-45 ° C. When the processing temperature is lower than room temperature, the etching effect of the metallized layer tends to be weak, and when the processing temperature is higher than 50 ° C., the metallized layer is sufficiently etched. There is a tendency that the management of the etchant is difficult and industrial implementation is difficult.

The etching time may be appropriately determined in accordance with the performance of the etching solution.
20 minutes, preferably 1 to 10 minutes.

[0017]

The etching solution used in the present invention is capable of effectively etching the metallized layer without eroding the aluminum nitride sintered body when etching the metallized layer of the aluminum nitride sintered body having the metallized layer. it can. Further, the etching method of the present invention can form a plating film having extremely excellent adhesion strength on the treated metallized layer, and its industrial value is extremely large.

[0018]

EXAMPLES The present invention will now be specifically illustrated by way of examples, but the present invention is not limited to these examples.

In the examples and comparative examples, various tests were performed by the following methods. (1) Surface roughness Surface roughness shape measuring instrument [Surfcom 5 manufactured by Tokyo Seimitsu Co., Ltd.]
50A]. (2) Adhesion strength between metallized layer and plated layer After nickel plating on the surface of the metallized layer, nail head pins were vertically soldered. The nail head pin used had a nail head diameter of 1.1 mm, a pin diameter of 0.5 mm, made of 42-alloy, and had a nickel-plated surface. The solder has a composition of 60% by weight of tin and 40% by weight of lead. This was set on a strograph M2 manufactured by Toyo Seiki Seisaku-sho, Ltd., and the breaking strength when the nail head pin was pulled in the vertical direction was measured. The pulling speed was 10 mm / min. Also, the peeling mode is shown at the same time. In the peeling mode, the state of the pin and the sintered body after peeling was observed with a stereoscopic microscope and an X-ray microanalyzer. (3) Etching rate A 15 μm-thick aluminum nitride sintered body having a metallized layer made of W having an area of 4 × 8 cm ² was used as a test piece.
The test piece was placed in an etching solution at 40 ° C., the time until the metallized layer disappeared was measured, and the etching rate (m
g / min).

Example 1 5% by weight of Y ₂ O ₃ as a sintering aid in aluminum nitride powder
The slurry was added and mixed with an appropriate amount of an organic binder, a plasticizer, a dispersant, and an organic solvent, and formed into a sheet having a thickness of about 0.8 mm by a doctor blade method.

Next, an appropriate amount of terpineol, ethylcellulose, and a dispersant were added to W (tungsten) powder having an average particle size of 2 μm and mixed to form a paste, thereby obtaining a high melting point metal paste.

This W paste was double-sided printed on the previous sheet by a screen printing method (this is hereinafter referred to as a printed body).

The printed material was placed in a graphite setter and subjected to heat treatment under vacuum at a temperature of 1000 ° C. to be degreased (hereinafter referred to as a degreased material).

The degreased body was placed in a setter made of an aluminum nitride sintered body, and sintered at a temperature of 1800 ° C. in a nitrogen atmosphere to obtain an aluminum nitride sintered body having a W metallized layer (hereinafter referred to as a test. Substrate).

The test substrate was immersed in an etching solution comprising an aqueous solution containing 15% by weight of hydrogen peroxide and adjusted to pH = 2 with hydrochloric acid, treated at 40 ° C. for 3 minutes, and the metallized layer was etched. . As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the metallized layer was sufficiently etched, and the aluminum nitride sintered body was not eroded. As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 0.6 μm, Rmax
= 7.8 μm. Furthermore, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength of the metallized layer and the nickel plating film was measured.
Performed by the Pull strength test method.

As a result, on average, 11 kg / mm ² (n =
The strength of 10) was obtained. The peel mode was breakage in the solder. Further, the etching rate of the etching solution is
13 mg / min.

EXAMPLE 2 A test substrate obtained in the same manner as in Example 1 was treated with an aqueous solution containing 5% by weight of hydrogen peroxide and adjusted to pH = 2 with hydrochloric acid at 40.degree. Then, the metallized layer was etched. As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the metallized layer was sufficiently etched, and the aluminum nitride sintered body was not eroded. As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 0.6 μm,
Rmax = 8.2 μm. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, on average, 10 kg / mm ² (n =
The strength of 10) was obtained. The peel mode was breakage in the solder. Further, the etching rate of the etching solution is
It was 6 mg / min.

Example 3 A test substrate obtained in the same manner as in Example 1 was replaced with hydrogen peroxide 25
Immersed for 3 minutes in an etching solution at 40 ° C., comprising an aqueous solution containing 2% by weight and adjusted to pH = 2 with hydrochloric acid,
The metallized layer was etched. As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the metallized layer was sufficiently etched, and the aluminum nitride sintered body was not eroded. As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 0.6 μm, Rm
ax = 8.1 μm. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, on average, 12 kg / mm ² (n =
The strength of 10) was obtained. The peel mode was breakage in the solder. Further, the etching rate of the etching solution is
20 mg / min.

Example 4 A test substrate obtained in the same manner as in Example 1 was replaced with hydrogen peroxide 12
Immersed in an etching solution at 40 ° C. for 3 minutes, comprising an aqueous solution containing 5% by weight and adjusted to pH = 5 with hydrochloric acid,
The metallized layer was etched. As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the metallized layer was sufficiently etched, and the aluminum nitride sintered body was not eroded. As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 0.6 μm, Rm
ax = 8.0 μm. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, on average, 10 kg / mm ² (n =
The strength of 10) was obtained. The peel mode was breakage in the solder. Further, the etching rate of the etching solution is
It was 6 mg / min.

Example 5 5% by weight of Y ₂ O ₃ as a sintering aid in aluminum nitride powder
The slurry was added and mixed with an appropriate amount of an organic binder, a plasticizer, a dispersant, and an organic solvent, and formed into a sheet having a thickness of about 0.8 mm by a doctor blade method. (Hereinafter, this is referred to as a sheet molded body) The sheet molded body is placed in an alumina setter, and heated at a temperature of 600 ° C. under air.
Degreasing was performed (hereinafter, this is referred to as a degreased body).

The degreased body was placed in a setter made of an aluminum nitride sintered body and sintered at a temperature of 1800 ° C. in a nitrogen atmosphere (hereinafter, referred to as a sintered body).

Next, appropriate amounts of terpineol, ethyl cellulose and a dispersant were added to Mo and Mn powders having an average particle size of 5 μm and mixed to form a paste. The Mo and Mn pastes were printed on one side of the sintered body by a screen printing method.

The printed sintered body was placed in an alumina setter and fired in a humidified hydrogen atmosphere at a temperature of 1250 ° C. to obtain an aluminum nitride sintered body having a Mo—Mn metallized layer (hereinafter referred to as “Mo-Mn”). Mn metallized substrate).

The Mo-Mn metallized substrate was immersed for 1 minute in an etching solution of 30% of an aqueous solution containing 15% by weight of hydrogen peroxide and adjusted to pH = 2 with hydrochloric acid to etch the metallized layer. Was. As a result of SEM observation of the surface of the etched Mo—Mn metallized substrate, the metallized layer was sufficiently etched, and the aluminum nitride sintered body was not eroded.
As a result of measuring the surface roughness of the aluminum nitride sintered body, R
a = 0.6 μm and Rmax = 8.0 μm. Further, after etching the Mo-Mn metallized substrate under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plated film was measured by Pull.
It was performed by a strength test method.

As a result, on average, 8 kg / mm ² (n = 1
0) was obtained. The peeling mode was breaking in AlN.

Comparative Example 1 A test substrate obtained in the same manner as in Example 1
The metallized layer was etched by immersing it in an etching solution of sodium hydroxide aqueous solution at 0 ° C. for 3 minutes.

The surface of the test substrate subjected to the etching treatment was subjected to SE
As a result of M observation, the metallized layer was sufficiently etched, but the aluminum nitride sintered body was also eroded. As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra
= 2.1 μm, Rmax = 18.8 μm. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, an average of 4.0 kg / mm ² (n
= 10), the peeling mode was peeling between the W metallized layer and the aluminum nitride sintered body. The etching rate of the etching solution was 10 mg / min.

Comparative Example 2 A test substrate obtained in the same manner as in Example 1 was immersed in an etching solution of a 20% by weight nitric acid aqueous solution at 40 ° C. for 4 minutes to etch the metallized layer. As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the aluminum nitride sintered body was not corroded, and the metallized layer was not etched. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the measurement of the adhesion strength between the metallized layer and the nickel plated film was performed using Pull.
It was performed by a strength test method.

As a result, on average, 4.5 kg / mm ² (n
= 10), and the peeling mode was peeling between the W metallized layer and the nickel plating film. The etching rate of the etching solution was 0 mg / min.

Comparative Example 3 A test substrate obtained in the same manner as in Example 1
The metallized layer was etched by immersion in an etching solution of an 8% by weight aqueous solution of potassium permanganate at 4 ° C. for 4 minutes. As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the aluminum nitride sintered body was not eroded,
The metallized layer was not etched. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, an average of 4.6 kg / mm ² (n
= 10), and the peeling mode was peeling between the W metallized layer and the nickel plating film. The etching rate of the etching solution was 0 mg / min.

Comparative Example 4 Various tests on the etching solution were conducted in the same manner as in Example 1, except that the pH was adjusted to 8 with sodium hydroxide instead of the addition of the acid.

The surface of the test substrate subjected to the etching treatment was subjected to SE
As a result of M observation, the metallized layer was sufficiently etched, but the aluminum nitride sintered body was also eroded.

As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 1.8 μm and Rmax = 18.0 μm
Met. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, on average, 4.8 kg / mm ² (n
= 10). The peeling mode was peeling between the W metallized layer and the aluminum nitride sintered body. The etching rate of the above-mentioned etching solution was 14 mg /
Minutes.

Comparative Example 5 Various tests were performed on the etching solution in the same manner as in Example 1 except that the concentration of hydrogen peroxide was changed to 2% by weight.

The surface of the test substrate subjected to the etching treatment is
As a result of M observation, the metallized layer was hardly etched, and the aluminum nitride sintered body was not eroded.

As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 0.6 μm and Rmax = 7.7 μm. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, an average of 4.6 kg / mm ² (n
= 10). The peeling mode was peeling between the W metallized layer and the nickel plating layer. The etching rate of the etching solution was 1 mg / min.

Example 6 A test substrate obtained in the same manner as in Example 1 was replaced with hydrogen peroxide 15
Immersed for 3 minutes in an etching solution at 40 ° C., comprising an aqueous solution containing 2% by weight and adjusted to pH = 2 with phosphoric acid,
The metallized layer was etched. As a result of SEM observation of the surface of the test substrate subjected to the etching treatment, the metallized layer was sufficiently etched, and the aluminum nitride sintered body was not eroded. As a result of measuring the surface roughness of the aluminum nitride sintered body, Ra = 0.6 μm, Rm
ax = 8.0 μm. Further, after the test substrate was etched under these etching conditions, nickel plating was performed, and the adhesion strength between the metallized layer and the nickel plating film was measured by a pull strength test method.

As a result, on average, 10 kg / mm ² (n =
The strength of 10) was obtained. The peel mode was breakage in the solder. Further, the etching rate of the etching solution is
It was 11 mg / min.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-305518 (JP, A) JP-A-63-47382 (JP, A) JP-A-2-57680 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) H01L 21/306-21/308 H05K 3 / 06,3 / 18 C23C 18/18

Claims (1)

(57) [Claims] 1. A metallized layer formed on an aluminum nitride sintered body is brought into contact with an etching solution comprising an aqueous solution having a hydrogen peroxide concentration of 3 to 40% by weight and a pH of 7 or less, so that the surface of the metallized layer is formed. A pretreatment method for facilitating plating on the surface of a metallized layer, characterized by etching.