JP3430561B2 - Method for removing mold release agent remaining on aluminum nitride substrate - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a highly heat conductive aluminum nitride substrate having excellent surface properties. The highly heat conductive aluminum nitride substrate obtained by the present invention is used for an IC and LSI insulating substrate, a HIC substrate, and the like, which are required to have high heat dissipation characteristics, particularly in the field of electronic materials.

[0002]

2. Description of the Related Art In recent years, with the progress of semiconductor technology, various characteristics have been required for semiconductor substrate materials.
One of them is the improvement of the heat dissipation characteristics of the substrate material accompanying the higher density and higher output of semiconductor chips. As a conventional substrate material, an alumina substrate has been most often used because of its insulating properties, mechanical strength, and price. However, in the alumina substrate, the heat dissipation characteristics are limited due to the thermal conductivity and thermal expansion coefficient of the material.

Up to now, beryllia substrates have been used in the field where such high heat dissipation characteristics are required, but there are drawbacks that beryllia is toxic and very expensive. Due to these facts, aluminum nitride substrates, which have material characteristics similar to those of alumina and have high heat dissipation characteristics, have been developed in recent years.
Came to be used. However, aluminum nitride is a material that is difficult to sinter, so a sintering aid such as yttria is added in normal pressure firing, which has a lower manufacturing cost than pressure firing (for example, Japanese Examined Patent Publication No. 63-31434). As a result, liquid phase sintering is performed.

In the manufacturing process of an aluminum nitride substrate, in order to reduce the manufacturing cost in the firing process, generally, the surface of an unfired aluminum nitride substrate (called an aluminum nitride green sheet) made of resin and aluminum nitride powder is nitrided. It has been practiced to apply a release agent such as boron powder (hereinafter, also referred to as spread powder) by spraying or the like, and fire a multi-layered stack (hereinafter referred to as multi-stage firing).

However, the boron nitride used as the mold release agent is a very stable ceramic, and if it remains on the surface of the aluminum nitride substrate, it becomes a factor that reduces the adhesive strength of the metal metallization later. On the surface of such a multi-stage fired aluminum nitride substrate, in the liquid phase,
Alternatively, boron nitride used as a release agent remains in the recesses on the surface, and various methods for removing it have been taken. For example, grindstone polishing, belt polishing, wet / dry honing and the like are performed.

[0006]

However, grinding with a grindstone has a problem of high cost, and belt grinding, wet / dry honing, etc. require a long treatment time in order to sufficiently remove boron nitride. However, there is a problem in that the size of the device must be increased.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and removes spread powder used in multi-step firing of an aluminum nitride substrate by using a brush made of a composite of resin and diamond. Provided is a method for removing spread powder, which is used to obtain an excellent aluminum nitride substrate without residual spread powder . That is, a method for removing the release agent remaining on the surface after firing the aluminum nitride substrate, which is characterized in that brushing is performed with a brush to which diamond powder is attached, and a method for removing the release agent remaining on the aluminum nitride substrate. that provides.

Here, a particularly preferable brush in which diamond powder is attached to the bristles is a brush in which the diamond powder is partially exposed and embedded in the bristles. For example, when a resin such as nylon is used as the material for the hair, it can be produced by kneading diamond powder into the material and molding the hair as a unit when molding the hair. By doing so, the diamond powder is less likely to be released from the hair, and even when it is released, the diamond powder embedded in the resin is exposed to the outside and contributes to polishing, so that the life of the diamond brush is practically used. Can be extended to any extent.

[0009]

EXAMPLE First, aluminum nitride powder which is a raw material, yttrium oxide which is a sintering aid and a molding binder are mixed at a predetermined ratio and then molded into a predetermined shape by a doctor blade method, a pressing method or the like. In order to perform multi-stage firing on the surface of the aluminum nitride compact thus obtained, a release agent (this time, a boron nitride powder having a particle size of 0.5 to 5.0 microns was used) was dispersed in an organic solvent. A suspension was prepared and sprayed onto the surface of the compact to form a boron nitride powder layer uniformly.

Thirty sheets of the obtained aluminum nitride compacts were stacked and placed on a boron nitride sintered body, and the mixture was placed in a nitrogen atmosphere at 600.
The binder was removed at ˜700 ° C. for 5 hours and then fired at 1900 ° C. for 10 hours in a nitrogen atmosphere. Boron nitride remained on the surface of the obtained aluminum nitride sintered body, and the remaining boron nitride was removed by various surface treatment apparatuses described below.

The various surface treatment devices are wet honing, dry honing, diamond brush polishing, and diamond belt polishing. Wet honing is a method in which an abrasive is dispersed in water and is sprayed onto the substrate surface at high pressure to perform surface treatment.Dry honing is a method in which only the abrasive is sprayed onto the substrate surface at high pressure using air, diamond brush polishing. Is a method of rubbing (polishing) the substrate surface by rotating a brush having bristles of fine diamond powder dispersed in resin such as nylon of the brush, and diamond belt polishing is a belt to which fine diamond powder is fixed. Is rotated to polish the substrate surface.

[0012] Next subjected to ultrasonic cleaning, dried boron amount remaining in the obtained aluminum nitride sintered body on by <br/> constant amount to order, on a platinum dish, a carbonate fusion As an agent, heat the reaction gas until it stops, let it cool, and dissolve with hydrochloric acid.
The amount of boron per unit area was measured by CP.

Further, for those print a commercial aluminum for silver-palladium paste nitride on the surface of the aluminum nitride substrate obtained as described above were form sintered for 1 hour at 850 ° C. in air, per unit area of silver The relationship between the amount of blistering generated at the interface between the palladium layer and the aluminum nitride substrate was examined, and a wire was soldered on the silver-palladium metallized layer, and a tensile test was conducted in the direction of 90 degrees to the metallized surface to examine the adhesion strength. The respective results are shown in Table 1.

[0014]

[Table 1]

[0015] Among the Table 1, there a rate Ru injection velocity der at the nozzle. Unit of processing time is Ru der (seconds / sheet).
The residual B is the amount of residual boron per unit area, and the unit is μg / cm ² . The adhesion strength is the metallized adhesion strength, and the unit is kg / mm ^2.
Is. X indicates that they were not joined. WA indicates white alundum, and D indicates diamond.

The display of the number of blisters is 0: none,
1: 2 or less, 2: 5 to 10, 3:10 to 50, 4: partially large, 5: large all over.

As shown in Table 1, as the amount of boron remaining on the aluminum nitride substrate, which is a component of boron nitride in the spread powder during firing, and the amount of boron is smaller, the silver paste is less likely to cause blistering and the adhesion strength is improved. Is high. The one using a brush in which a resin and diamond are combined is particularly excellent. This is probably because the amount of residual boron is zero. It should be noted that it is not impossible to reduce the residual boron to zero by other surface polishing, but the cost is increased due to a long time.

[0018]

As described above, a method has been found that has a higher effect of removing the spread powder than the conventional method of removing the spread powder, which is generally performed in a short time.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C04B 35/581 C04B 35/64 B24B 1/00-15/00

Claims (2)

(57) [Claims] 1. A method of removing a release agent remaining on a surface of an aluminum nitride substrate after firing, which comprises brushing with a brush to which diamond powder is attached, the release agent remaining on an aluminum nitride substrate. Removal method. 2. A method of removing a release agent remaining on a surface after firing an aluminum nitride substrate, wherein brushing is performed by a brush embedded in bristles with a part of diamond powder exposed. A method for removing a release agent remaining on an aluminum substrate.