JP3190908B2 - Aluminum nitride substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aluminum nitride substrate.

[0002]

2. Description of the Related Art In the range of use of ceramics which has been expanding over the years, the electronic component field has occupied an important position, and semiconductor substrates have also become important applications. Among them, the technology of applying aluminum nitride ceramics to substrates for semiconductors has recently been developed and has reached the level of practical use, but the current situation is that vigorous research is being conducted in detail.

[0003] A field that will be particularly specialized in the future is mass production technology. Therefore, the process of devising various techniques for mass production this time will be described with reference to mass production of semiconductor substrates as an example. First, an ordinary method for manufacturing a semiconductor substrate will be described.

A ceramic substrate having a size of 10 mm long × 10 mm wide × 0.7 mm thick is prepared. Next, a metallized layer is formed on the substrate. Then, electroless plating is formed thereon. Further, a silicon semiconductor chip is mounted on a part of the plating, electrically connected to the other part of the plating layer by a bonding wire, and further covered with a protective layer of resin to form a transistor module.

The inventors of the present application have noticed the following. First, it is not advisable to perform such a process for each small substrate. Further, as the size of the semiconductor substrate becomes smaller, the yield becomes worse.

Accordingly, the present inventors have devised a method using a large ceramic substrate. That is, this method includes several steps for processing a large ceramic substrate. First, a large ceramic substrate is prepared. On this substrate, a metallized layer is provided in each pattern portion for each semiconductor substrate. Next, an electroless plating layer is applied thereon. Further, the ceramic substrate is divided for each semiconductor substrate, a semiconductor chip is mounted on the plating of the semiconductor substrate, and bonding wires are provided on the semiconductor chip and the plated portion. Next, if necessary, it is covered with a resin or the like to form a final product transistor module.

In this case, as a method of dividing the substrate into a predetermined size, a high-density energy processing method is used. Examples of the high-density energy method include a laser method and an electron beam method, and a laser method which is simpler and cheaper than the electron beam method is preferable.

In the laser method, a predetermined portion of a substrate is directly irradiated with a laser beam to form a plurality of holes, or holes and / or grooves (hereinafter, referred to as processed portions). Is a method of cutting the substrate along.

[0009]

When a processed portion is formed on the surface of such an aluminum nitride substrate by a high-density energy method, precipitation of metallic aluminum was found near the surface to be processed exposed to the high-density energy. by the way,
It has been found that the presence of this metallic aluminum significantly affects the characteristics of the semiconductor substrate. That is, the substrate is covered with a plating layer as an electric conductive layer required for an electronic component. At this time, metal aluminum is also plated, thereby impairing the withstand voltage characteristics required for the substrate used as the electronic component. In addition, it has been found that the withstand voltage characteristics are reduced only by metal aluminum which is least plated.

Therefore, the present inventors made a trial production method of removing metallic aluminum. This is a mechanical method using honing and a method of irradiating a substrate placed in water with a laser. However, in the above, it is difficult to prove whether or not the metal aluminum has been completely removed, and in the latter case, a disadvantage that the required system becomes complicated is inevitable.

The present invention has been made under such circumstances, and has the following objects. First. The first is to eliminate the drawbacks that occur when forming an aluminum nitride substrate, and the second is to form an aluminum nitride substrate having predetermined withstand voltage characteristics by this simple method.

[0012]

SUMMARY OF THE INVENTION In an aluminum nitride substrate having a portion (a plurality of holes or holes and / or grooves) processed by a high-density processing method, the processed substrate is heated at a temperature of 1000 ° C. to 1800 ° C. A re-solidified layer in the vicinity of the processed portion, the re-solidified layer comprising a group consisting of an oxide, nitride or oxynitride of aluminum and / or a group consisting of a sintering aid for the aluminum nitride substrate The compound selected from the above has characteristics of the aluminum nitride substrate according to the present invention.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum nitride substrate according to the present invention is manufactured by a processing step of forming a processed portion by high-density energy processing and a cutting step. In particular, the processing step will be described.

Prior to cutting the aluminum nitride substrate into a predetermined size, metallic aluminum is formed by high-density energy processing, for example, laser processing, applied to the surface thereof, as described above. However, the following 10
The metal aluminum is extinguished by the heat treatment process at 00 ° C. to 1800 ° C., and the group consisting of aluminum oxide, nitride or oxynitride and / or oxide, nitride or oxynitride of aluminum nitride sintering aid It has been found that a re-solidified layer is formed from at least one compound selected from the group consisting of materials. In this case, examples of the sintering aid for aluminum nitride include yttrium and calcium.

The present invention has been completed on the basis of this fact. Even if a high-density processing method is applied, no new conductive layer is formed, and an aluminum nitride substrate having excellent withstand voltage characteristics can be obtained.

That is, the method of the present invention is characterized in that after high-density energy processing, metal aluminum is removed by heating (1000 ° C. to 1800 ° C.). In this case, the heating is preferably performed in the air or in nitrogen.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The aluminum nitride substrate according to the present invention utilizes high-density energy processing in the step of forming a processed portion such as a groove, but the high-density energy processing method may be used for forming and cutting holes. .

FIGS. 1 to 4 which are provided to explain the embodiments according to the present invention are electron microscope photographs required. FIG.
FIG. 4 is an electron micrograph of a cross-sectional view of the aluminum nitride substrate after a processing portion forming step performed by laser processing, magnified 400 times. The cross section of the hole formed by the laser is generally inverted triangular and has a depth slightly less than one third of the thickness of the aluminum nitride substrate.

This drawing shows a photograph of a cross section along a processed portion 2 (continuous hole) formed in an aluminum nitride substrate 1 as shown in FIG. 6b. As can be seen from this photograph, several shining parts (for example, part (1) in FIG. 1) are present on the surface of the hole in the aluminum nitride substrate.

This part was made of metallic aluminum. In this case, a laser processing method is used as a high-density energy processing method, and a peak power (10K) is used.
W) "YAG" laser was used.

FIG. 2 shows a process portion forming heating (about 1
400 showing the cross section of aluminum nitride which was
It is an electron micrograph of the magnification. It was confirmed that metallic aluminum had disappeared from the surface of the hole of the aluminum nitride substrate shown here. Some shining portions (3) can be seen on the surface of the holes, but these were re-solidified layers and were insulating portions. In addition, the grain boundary at that portion is clearly formed, and it is clear that the grain boundary has a structure different from that of the surrounding aluminum nitride substrate.

FIG. 3 is an enlarged view of a portion (a) of FIG. 1 and an electron microscope photograph of a cross-sectional view of the aluminum nitride substrate after forming a processed portion with a laser at a magnification of 4000 times. In FIG. 3b, what shines on the surface of the hole is the part (1) metallic aluminum, and (2)
Is AlN.

FIG. 4 is an enlarged view of FIG. 2B. This figure is an electron microscope photograph of a partial cross section of the aluminum nitride substrate heated at about 1600 ° C. after forming a laser-processed portion on the aluminum nitride substrate at a magnification of 4000 times. As can be seen in this figure, the granular resolidified layer (3) (3)
Y ₂ O ₃ .5Al ₂ O ₃ ) was grown adjacent to the original structure of the aluminum nitride substrate, and the thickness was
It is about 2-3 μm.

FIG. 5 shows EPMA (Electron P) in which the vertical axis indicates Al-Kβ spectrum intensity and the horizontal axis indicates wavelength.
FIG. 3 is a diagram of a probe micro analyzer. Curve A is the measurement result of the bright portion of the surface of the hole shown as (a) in FIG. 1, curve B is the measurement result of the aluminum nitride substrate shown in (2) in FIG. 1, and curve C is (1) in FIG. )
It is the measurement result of the shining part of the surface of the hole which was set as the.

Curve A has a peak at 86.56. This curve shows metallic aluminum. Curve b has a peak at 86.64 and 87.28 (a)
Has a bulge. This curve represents aluminum nitride. Curve c has a peak at 86.72 and 8
There is a bulge at 7.56 (b), which represents aluminum yttrium oxide (3Y ₂ O ₃ .5Al ₂ O ₃ ). The yttrium component appearing in the curve C is a sintering aid for aluminum nitride. That is, when a heat load is applied to the metallic aluminum, the metallic aluminum disappears and an insulating component is obtained.

As described above, it is clear that the resolidified layer of the present invention is composed of oxides of sintering aids of aluminum and aluminum nitride. Although not shown in these experimental results, the formation amounts of oxides, nitrides, and oxynitrides are determined depending on the type and amount of the sintering aid for aluminum nitride and the laser processing conditions.

The case where the present invention is applied to a metallized layer has been described above. However, the invention of the present application is a technique other than the metallization method (metal direct bonding method, thick film method, thin film method, etc.)
Of course, it can also be applied. Therefore, an example of application of the present invention to a copper direct bonding substrate [trademark of Toshiba Corporation] will be described below. That is, the aluminum nitride substrate is processed by laser. When heating in air at 1050 ° C. to 1250 ° C. in order to extinguish the metallic aluminum generated at that time, the metallic aluminum present in the processed portion is converted to alumina. Then, a copper plate having a thickness of 0.1 mm to 1 mm is placed on the surface of the aluminum nitride substrate and the temperature is set to 1000 ° C. to 1
The two are joined by heating in nitrogen maintained at 100 ° C. for 10 minutes.

Thereafter, the aluminum nitride substrate is divided along the processed portion to form a divided substrate of a predetermined size, and in some cases, a copper plate is plated. In such a process, if the heating in the air is insufficient, all the metallic aluminum does not change to Al ₂ O ₃ , a conductive portion remains in the processed portion, and the electrical characteristics of the substrate such as withstand voltage are reduced. Getting worse.

Further, an example relating to a thick film substrate will be described. It has a structure of an aluminum nitride substrate + alumina layer + thick film, and Ag-Pb / Ag-Pt / Au / Cu or the like can be applied as a type of the thick film. That is, the aluminum nitride substrate is processed by laser. When heating is performed in air at 1050 ° C. to 1250 ° C. in order to dissipate the metal aluminum generated at that time, the metal aluminum existing in the processed portion is converted to alumina. Thereafter, a thick Au paste is applied, and 9
The circuit is formed by heating in air maintained at 00 ° C. In order to form a thick film on an aluminum nitride substrate, a process similar to that for forming a metallized layer on an aluminum nitride substrate (heating in a non-oxidizing atmosphere) is performed, and then Ag-Pt is applied and dried. To form a circuit.

As described above, the resolidified layer formed on the laser-treated surface of the aluminum nitride substrate according to the present invention, which is composed of the oxide and nitride of Al and the sintering aid of the aluminum nitride substrate, is clearly shown. I have. However, although not shown in the experimental results, an oxynitride based on the sintering aid for the aluminum nitride substrate is also formed depending on the laser treatment conditions.

Another embodiment of the present invention will be described with reference to FIGS. 6A, 6B and 6C. As shown in FIG. 6A, the aluminum nitride substrate 1 is a substrate having a thickness of 0.635 × 2 inches square and a thermal conductivity of 130 W / mK. This substrate was an aluminum nitride substrate which was then laser processed and provided with a 1-inch square groove (see FIG. 6b). Thereafter, the substrate is treated for one hour in a nitrogen atmosphere maintained at 1600 ° C. (the heat treatment of the present invention). Further, the substrate shifts to a step of providing a pattern corresponding to each portion. By this patterning step, the metallized pattern 3 is arranged within a 1-inch square defined by the processed portion (groove) 2. This pattern is formed by screen printing using a paste made of a compound such as Group 4A consisting of Mo, W and Ti, Zr and Hf and TiO, for example.

Next, the metallized pattern 3 is baked as shown in FIG. 6c by processing in a nitrogen mixed atmosphere maintained at 1700 ° C. Subsequently, the metallized pattern 3 is coated with a 4 μm thick Ni layer (not shown) by an electroless plating method. Thereafter, the aluminum nitride substrate 1 was cut along the division grooves. As a result of a withstand voltage test performed on each substrate, each substrate showed an excellent withstand voltage value.

[0033]

As described above, the aluminum nitride substrate according to the present invention can exhibit excellent withstand voltage characteristics even when subjected to a high-density energy method such as laser processing, and is also extremely effective as a substrate for a semiconductor device. .

[Brief description of the drawings]

 Each drawing is based on the original application.

FIG. 1 is a cross-sectional view after a laser processing is performed on an aluminum nitride substrate to perform a processing portion forming step, showing two holes (the bottom is below the paper surface) and a continuous metal structure of 40;
It is an electron microscope photograph of 0 time.

FIG. 2 is a diagram showing a process portion forming heating (1600) by laser.
2C) is a 400 × electron micrograph of the two holes (bottom part is below the paper surface) obtained and the continuous metal structure.

FIG. 3 is an electron micrograph of a metal structure obtained by enlarging the portion (a) in FIG. 1 by 4000 times.

FIG. 4 is an electron micrograph of a metal structure obtained by enlarging the portion (b) in FIG. 2 by 4000 times.

FIG. 5 is an EPMA curve with the spectrum intensity on the vertical axis and the wavelength on the horizontal axis.

FIG. 6a shows a specific part of the aluminum nitride substrate, FIG. 6b shows a specific part of the aluminum nitride substrate formed with a processed part shown as a groove, and FIG. 6c shows a divided aluminum nitride substrate. FIG. 3 shows a specific portion of the substrate.

[Explanation of symbols]

 1: Aluminum nitride substrate 2: Scribe line 3: Metallized pattern

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-134587 (JP, A) JP-A-60-203383 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 23/15 B23K 26/00 C04B 41/80

Claims (6)

(57) [Claims] 1. An aluminum nitride substrate on which high-density energy processing has been performed, wherein a group consisting of an oxide, nitride or oxynitride of aluminum or aluminum and an oxide of a sintering aid for the aluminum nitride substrate are provided on the surface of the substrate. , A compound containing at least one selected from the group consisting of nitrides and oxynitrides, for high-density energy processing on the substrate surface.
An aluminum nitride substrate, which does not include formed aluminum. 2. The aluminum nitride substrate according to claim 1, wherein said compound contains yttrium. 3. The aluminum nitride substrate according to claim 1, wherein a hole or a groove is formed in said aluminum nitride substrate. 4. The aluminum nitride substrate according to claim 3, wherein said compound is formed near holes, holes or grooves. 5. The compound according to claim 1, wherein said compound is aluminum yttrium oxide.
The aluminum nitride substrate according to any one of the above. 6. The method according to claim 1, wherein the aluminum nitride substrate is formed by cutting a large substrate.
The aluminum nitride substrate according to claim 5.