JPS62197372A - Manufacture of aluminum nitride sintered body with electroconductive metallized layer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing an aluminum nitride (A!LN) sintered body having a conductive metallized layer formed on its surface with high bonding strength. relates to a method of sintering an AIH sintered precursor and simultaneously forming a conductive metallized layer on its surface with high bonding strength.

[Prior art and its problems] AfLN sintered bodies have good thermal conductivity, excellent heat dissipation, and electrical insulation properties, so they are attracting attention as substrate materials for semiconductors.

This AIN sintered body is generally manufactured as follows. That is, y2o3 to AIN powder.

A predetermined amount of sintering aids such as Sm203 and CaO are added, and an acrylic resin binder is added as needed, the whole is thoroughly mixed, and the resulting mixture is, for example, pressure molded to form a predetermined shape. After forming an A4N sintered precursor (formed body) in the shape, this is sintered at a predetermined temperature in, for example, a nitrogen atmosphere.

By the way, when using an AIN sintered body as a substrate for a semiconductor, it is necessary to form a conductive thin layer on the surface of this A, Q-N sintered body. Traditionally, this thin layer is AIN
DBC method (Direct Band C) is applied to the surface of the sintered body.
copper (Cu upper method) or thick film method.
), gold (Au), and silver-palladium (Ag-Pd) metallized layers.

However, this conventional substrate has the following problems.

The first problem is that the bonding strength between the formed metallized layer and the surface of the AfLN sintered body is low, and a peeling phenomenon often occurs between the two, resulting in low reliability of the substrate.

The second problem is a problem that occurs when a predetermined semiconductor element or wire is brazed or high-temperature soldered to the formed metallized layer. That is, for example, in the case of brazing, it is carried out in a hydrogen-nitrogen mixed gas at a temperature of around 800°C, however, the temperature during the process of baking the metallized layer is usually as low as 600-toooo°C. Brazing sometimes involves a metallized layer and AR
This means that the bonding strength with the surface of the N sintered body is significantly reduced, making brazing virtually impossible. A similar problem also occurs in the case of high-temperature soldering.

The third problem is a problem based on the difference in coefficient of thermal expansion between the AQN sintered body and the metallized layer. That is, as in the case of brazing and high-temperature soldering, a substrate on which a semiconductor element is mounted, such as a silicon wafer, undergoes severe thermal cycles of heating and cooling during use. As a result, at the bonding surfaces of the AIN sintered body - metallized layer - brazing layer (or solder layer) - semiconductor element, thermal stress is generated due to the difference in the coefficient of thermal expansion of each layer, causing each layer to peel off. occurs.

In the case of the above metallized layer, the value is about 2 to 4 times larger than that of the AIN sintered body (the coefficient of thermal expansion is about 4.6XlO-6/"C), and the brazing layer (or solder layer ), and the difference from AIN is large, so micro-cracks are likely to occur at the interface between the metallized layer or brazing layer (or solder layer) and AIH during thermal cycling. As the load is applied, these microcracks gradually develop and may eventually lead to peeling of the mounted semiconductor element.

Such a problem is extremely inconvenient because it reduces the reliability of a device mounted with a substrate on which a semiconductor element is mounted.

The fourth problem is that the bonding strength between the metallized layer and the AiN sintered body at high temperatures is low, and as in the second case, reliability during high temperature use is low.

Fifth, when looking at the manufacturing process from the perspective of a completed board, it is uneconomical in terms of thermal energy usage. That is, in order to obtain a completed board, A9. The problem is that a N sintered precursor is sintered, and then the sintered material is fired again to form a metallized layer.

[Objective of the Invention] The present invention solves the above-mentioned problems, and at the same time sintering the AIN sintered precursor, the surface thereof has a coefficient of thermal expansion similar to that of the AfLN sintered body, and has high heat resistance. Moreover, the object of the present invention is to provide a method for forming a conductive metallized layer with high bonding strength.

[Summary of the Invention] As a result of intensive research to achieve the above object, the present inventors have found that an excellent metallized layer can be formed by applying the paste described below to the /IN molded body before sintering and sintering both at the same time. A! 2
．． After confirming the fact that it can be formed on the surface of a N sintered body, we developed the method of the present invention.

That is, A! having the conductive metallized layer of the present invention! ;
The method for manufacturing the LN sintered body uses molybdenum (Mo) and tungsten (W) as sintering precursors of Amon.

At least one member selected from the group consisting of tantalum (T a) and compounds containing one or more of them, and elements of group II of the periodic table, elements of group IVa, and rare earth elements (rare earth elements include Sc and Y). A paste containing at least one selected from the group of lanthanum-based elements (containing lanthanum-based elements), actinide-based elements, and compounds containing one or more of these elements is applied, and then the whole is sintered at the same time. In particular, the AIN sintering precursor to which the method of the present invention is applied is, for example, AMN powder of a predetermined particle size.

A powder of a sintering aid such as Y202, YF3, Sm203, or CaCO3 is mixed with a wax-based or plastic-based binder component in a predetermined ratio, and this mixture is molded under pressure or with a doctor blade at room temperature. This is a molded body formed into a sheet shape. Particle size of A-mon powder and sintering aid powder.

The mixing ratio, molding pressure, etc. are appropriately selected in relation to the characteristics of the intended AuN sintered body.

In the method of the present invention, it is preferable that the AIN sintered precursor has a thermal conductivity of 50 W/■· or more after sintering.

A paste having a composition described below is applied to this AIN sintered precursor. Application methods include screen printing,
Well-known methods such as brush coating and spin roller coating may be applied.

The paste according to the method of the invention consists of two group components I, IT, which are converted into a metallized layer after sintering, and a medium in which they are dispersed.

First, the group component works are MO and W.

It is at least one selected from the group of compounds containing Ta and one or more of these elements.

Specifically, the ingredients are as follows. That is, M o
, W, Ta; various oxides thereof;
These various carbides; These various borides; These various silicides; These various oxynitrides; These various carbonitrides; These various halides; These various hydrides; These various hydroxides; nitrites, nitrates, sulfites, sulfates, borates, carbonates, silicates, phosphates of these elements.

Various salts such as sulfur salt, hydrochloride, chlorate, oxalate, and ammonium salt; various types of flucoxide and sol-gel such as Atron NTa/700 (trade name manufactured by Nippon Soda Co., Ltd.); an organometallic compound; and two of the above-mentioned components.
A mixture of more than one species may be used.

These components may be used alone or in combination of two or more appropriately selected.

In terms of increasing the conductivity of the metallized layer to be formed, single metals such as Mo, W, and Ta are particularly preferable.

Group II components include group II elements of the periodic table, T
At least one element selected from the group of Va group elements, rare earth elements (rare earth elements are lanthanum elements including Sc and Y), actinide elements, and compounds containing one or more of these elements.

Among these, as a group ■ element, it is A sentence.

Ga and In can be mentioned. An is particularly suitable. Group IVa elements include Ti and Zr.

Hf can be increased. In particular, Ti is suitable because it can form a good metallized layer after sintering, regardless of the group I components. As a rare earth element, Sc.

Examples include Y, La, Ce, Pr, Nd, Sm, and Gd. Particularly suitable are Y and Sm. Actinide elements include Ac, Th, and the like. Ac is particularly suitable.

Specific examples of Group II components include the following: In other words, group ■ elements.

■Each of group A elements, rare earth elements, and actinide elements; oxides of these elements; nitrides of these elements; carbides of these elements; borides of these elements; Silicides; oxynitrides of these elements; carbonitrides of these elements; halides of these elements; hydrides of these elements; hydroxides of these elements; pseudosalts of these elements , nitrates, sulfites, sulfates, boric acid 111, carbonates, silicates, phosphates,
Various salts such as phosphorous acid, hydrochloride, chlorate, oxalate, and ammonium salt; various organometallic compounds such as flucoxide and sol-gel such as Atron NTi (trade name manufactured by Nippon Soda ■); and a mixture of two or more of the above-mentioned components as appropriate. These components may be used alone or in combination of two or more appropriately selected.

The paste according to the present invention is prepared by uniformly dispersing these Group E components and Group H components in a medium. Examples of the medium used include ethylcellulose and nitrocellulose, and their solvents include terpineol, tetralin, and butylcarpitol.

In addition, the components of group I are effective components mainly for maintaining the conductivity and heat resistance of the formed metallized layer at a high level, and the components of group
It is thought that this is an effective component for binding the above-mentioned group components and maintaining the strength of the metallized layer.

At this time, the quantitative ratio relationship between group IyL and group ■ components varies depending on the type of each component selected, but usually, in terms of weight ratio, group ■ component / group ■
It suffices if component = l/100-10/1. However, if it does not contain group I component, that is, group I component/
Although it may be the case that group ■ component = O/100,
It is preferable that the metallized layer is composed of both the group I component and the group (II) component because a good metallized layer can be formed with a flexible f distance.

In addition, among the Group II components, the weight ratio of Group II components is 1/2 to 2/l, and the weight ratio of Group II components is 115 to 1/1.
It is preferable that

If the Group E component is too much than the Group II component, the strength of the formed metallized layer will decrease;
In the opposite case, the conductivity does not reach a satisfactory level.

Group I ingredients and Group II ingredients into the medium/
l&ffi is determined as appropriate in relation to the viscosity of the obtained paste. If the former amount is too large, the resulting paste will become highly viscous, making it difficult to uniformly apply it to the surface of the A-type N sintered precursor. In the opposite case, the paste viscosity becomes low and the applied paste flows down from the surface of the AILN sintered precursor.Normally, the paste viscosity is 1.0.
The former may be dispersed into the latter so that Xlo' to 2.5X10' poise.

In the method of the present invention, the above-described paste is applied to the surface of the A-type N sintered precursor, and then the whole is sintered at the same time. Prior to this co-sintering, the binder components of the A-N sintered precursor and the paste medium are removed at a temperature of 1, e.g., 50-700°C.
Degreasing treatment may be performed at such a temperature.

Sintering takes place in a nitrogen atmosphere. Sintering temperature.

The sintering time is set as a condition such that the AiN sintered body after sintering has a desired property 1, for example, a thermal conductivity of 50W11IIK or more. Specifically, the sintering temperature is 1600 to 200
The temperature is 0°C, preferably 1700-1800°C, and the sintering time is 0.2-5 hours.

Preferably it is 0.5 to 1.5 hours.

In this way, a metallized layer of the applied paste is formed as a conductive thin layer on the surface of the AfLN sintered body.

[Examples of the invention] Example 1 (1) Preparation of paste Prepare MO grain powder with a particle size of 0.5 to 1.0μ as a component of group I, and a particle size of 1.0 to 2 as a component of group II.
．． 0-TiN powder was prepared.

50 parts by weight of the former and 50 parts by weight of the latter were mixed.

100 parts by weight of the obtained mixed powder was dispersed in 7 parts by weight of ethyl cellulose to form a paste with a viscosity of 2.0 x 105 voids.

(2) Formation of metallized layer The paste prepared in (1) was applied with a roller to a thickness of 15% on one side of an AiN green sheet containing 3% by weight of Y2O3 as a sintering aid.

Then, after degreasing by firing in a nitrogen atmosphere at 700°C for 180 minutes, the whole was heated at a temperature of 180°C in a nitrogen stream.
Sintering was performed at 0°C for about 1 hour.

A metallized layer was formed on the surface of the obtained AIIN sintered body sheet. The constituent phase of this metallized layer is Mo
It was confirmed by X-ray diffraction that it was T i N.

(3) Bonding strength between metallized layer and /IN sintered sheet On the metallized layer obtained in (2), a Ni plating layer with a thickness of approximately 3 to 5 mm was formed by electroless plating. Then, after annealing the plating layer in a homing gas at 800°C, a wire with a wire diameter of 0.5 mm and a tensile strength of 55
Kovar wire of kg/a+s+2 was brazed using silver solder. Brazing temperature is 800″C1 atmosphere is hydrogen 5
The atmosphere was a mixed gas of 0Vo1% and nitrogen 50Vo1%.

Thereafter, the A-mon N sintered body sheet was fixed and a Kovar wire was pulled at room temperature (20° C.), and the peeling state of the metallized layer was observed.

The brazed portion of the metallized layer and Kovar wire was torn off when the tensile strength was 5 kg/mm2. That is,
The bonding strength between the AIN sintered sheet and the metallized layer is 5
It was found that the weight was 2 kg/kg or more.

Examples 2 to 5 Various pastes were prepared by selecting Group E components and Group H components as shown. These pastes were applied to the surface of the same AuN green sheet as in Example 1, subjected to degreasing treatment, and then sintered under the indicated conditions.

The metallized layer and A in the various sintered sheets obtained
The bonding strength with the IN sintered sheet was measured in the same manner as in Example 1. The results are summarized in the table.

Comparative Example 1 Three sheets of Af having a thermal conductivity of 7ON130 W/m-
The thick film method was applied to the surface of the LN sintered plate to deposit Au and C, respectively.
u, Ag-Pd layer was baked.

After soldering a nickel-plated copper pin to each of the obtained metallized layers, the pins were pulled to measure the bonding strength between the metallized layer and the surface of the AIN sintered plate. In both cases it was approximately 1 kg/mm2.

Comparative Example 2 The paste used in Example 3 was applied to the surface of an AffiN sintered plate with a thermal conductivity of 70 to 130 W/mm.
Baked at 0°C. 700-80 to the obtained metallized layer
Kovar pins were brazed at 0℃ and the joint strength was measured by pulling the pins.・2・Okg/ts+
"Met.

Comparative Example 3 A metallized layer was formed in the same manner as in Comparative Example 2 except that the paste used was the paste used in Example 2. The bonding strength was approximately the same value as Comparative Example 2.

[Effect of the invention] As is clear from the above explanation, the method of the present invention has ■AIN
A conductive metallized layer with high bonding strength can be formed on the surface of the sintered body. ■The metallized layer is made of Mo.
, contains high melting point metals such as W and Ta, has excellent heat resistance, and has a coefficient of thermal expansion similar to that of the A-N sintered body, so it also functions as a thermal shock layer.
It is thermoeconomically advantageous because the applied paste is converted into a metallized layer at the same time as the N sintering precursor is sintered.
It has the following effects and has great industrial value.

Since the AfLN sintered body produced by the method of the present invention exhibits the above-mentioned effects, it can be used for substrate members such as igniters, high-frequency transformers, and capacitors; insulating tubes for laser tubes, insulating envelopes for power tubes, and high-frequency traveling magnetic wave tubes. windows, high-energy beam irradiation windows, components such as magnetrons; tube heaters, surface heaters, sheath heaters, soldering irons, press plates for irons, moxibustion equipment, heaters for coffee makers, trouser presses, hot plates.

Toilet seats, cooking pots, thermal transfer printer heads.

It is useful because it can be applied to members such as plugs, thermocouple protection tubes, crucible scissor tips, metal melting crucibles, and single crystal pulling crucibles.

Claims (1)

[Claims] The sintered precursor of aluminum nitride contains at least one member selected from the group of molybundenum, tungsten, tantalum, and compounds containing one or more thereof, and group III elements, group IVa elements, and rare earth elements of the periodic table. element(
A paste containing at least one element selected from the group of rare earth elements (a lanthanum element including Sc and Y), an actinide element, and a compound containing one or more of these elements is applied, and then the whole is coated at the same time. A method for producing an aluminum nitride sintered body having a conductive metallized layer, the method comprising sintering the aluminum nitride sintered body.