JP3515228B2 - Aluminum nitride circuit board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride circuit board used for semiconductor packages and the like.

[0002]

2. Description of the Related Art In recent years, high integration of semiconductor devices, high speed operation,
The demand for ceramic substrates is increasing year by year with the increase in power consumption and the increase in size of chips. In particular, aluminum nitride (AlN) substrates have high thermal conductivity, excellent heat dissipation, and have a linear thermal expansion coefficient close to that of Si. Therefore, aluminum nitride (AlN) substrates are suitable for semiconductor packages that replace alumina (Al ₂ O ₃ ) substrates. The application as a circuit board etc. is advanced. The manufacturing process of a semiconductor package using an AlN substrate is based on the existing manufacturing process of an Al ₂ O ₃ package, and its technology has been diverted and improved.

A major difference between AlN and Al ₂ O ₃ in terms of materials is that Al ₂ O ₃ is a stable oxide, while AlN is an unstable nitride. .
Since most electric and electronic parts are used in the atmosphere that coexists with water, at least the moisture resistance and water resistance are required to be at least minimum. However, AlN has the disadvantage that it reacts with water in the atmosphere to form hydroxides such as AlOOH and ammonium hydroxide.The formation of these hydroxides and ammonium hydroxide causes corrosion of AlN by water. Can be regarded as

A produced by the above-described corrosion of AlN
Since lOOH has a lower electric resistance than AlN, it causes a decrease in the resistance of the substrate surface among the electrical characteristics of the AlN substrate, causing various problems. For example, an AlN substrate used for a semiconductor package or the like is used by forming a wiring layer with a metallization layer on the surface thereof, but when AlOOH is formed on the surface of the AlN substrate corresponding to such a wiring layer, the wiring layer Resistance decreases, especially when the resistance value between the wiring layers becomes 1 × 10 ⁹ Ω or less, it becomes difficult for the semiconductor element to operate normally.

The decrease in resistance between wiring layers due to corrosion of AlN is
Although it depends largely on the distance between wiring layers, environmental temperature, environmental humidity, etc., the mounting method of semiconductor elements is changing from the conventional hermetic seal to a simple method that omits this,
A more stable structure on the AlN substrate surface is required. Here, the conventional Al ₂ O ₃ substrate is not attacked except by hydrofluoric acid and concentrated alkali, and is not corroded by water. For this reason, in wet processing and storage in the manufacturing process of AlN circuit boards, a unique method considering the corrosiveness of AlN is required.

[0006]

[Problems to be Solved by the Invention] As described above, AlN
Has the drawback that AlOOH is generated due to corrosion by water and the resistance value tends to decrease. In AlN circuit boards used for semiconductor packages, etc., the resistance between wiring layers decreases due to the generation of AlOOH, and the decrease in the resistance value of this AlN board hinders the normal operation of mounted semiconductor elements. Problem is occurring.

The present invention has been made in response to such a problem, and by suppressing the generation of AlOOH, it is possible to stably obtain a normal circuit operation, which is excellent in environmental resistance. It is intended to provide an aluminum circuit board.

[0008]

A first aluminum nitride circuit board according to the present invention comprises an aluminum nitride substrate and a metallization layer formed on the aluminum nitride substrate. In the aluminum nitride circuit board, the palladium simple substance adheres to the surface of the aluminum nitride substrate except the formation region of the metallized layer , and the palladium simple substance adheres.
It is characterized in that the concentration is the range of ^{1 × 10 16 ~1 × 10 21} atms / cm 3.

The second aluminum nitride circuit board may be the aluminum nitride circuit board having an aluminum nitride substrate and a metallization layer formed on the aluminum nitride substrate.
A boron compound is attached to the surface of the aluminum nitride substrate excluding the region where the metallized layer is formed ,
The attachment concentration of the boron compound is 1 x 1 as the concentration of boron alone.
It is characterized by a range of ^{0 17 ~5 × 10 21 atms /} cm 3.

[0010]

In the first aluminum nitride circuit board of the present invention, palladium having a predetermined concentration is present on the surface of the aluminum nitride board excluding the metallized layer formation region. Therefore, the unbonded portion of the surface atoms of the AlN substrate is modified by Pd, so that the reaction with moisture in the atmosphere is extremely reduced, and the generation of AlOOH and the like due to the corrosion of AlN is significantly suppressed. And because Pd has a higher resistance than AlOOH,
It is possible to suppress a decrease in resistance value between metallized layers and the like.

Further, in the second aluminum nitride circuit board of the present invention, a boron compound having a predetermined concentration is made to exist on the surface of the aluminum nitride board excluding the metallized layer forming region. Therefore, unbound portion of the surface atoms of the AlN substrate, because it is modified by these borated compounds, reaction with atmospheric moisture extremely reduced. Therefore, generation of AlOOH and the like due to corrosion of the AlN substrate is significantly suppressed, and it is possible to suppress reduction in resistance value between metallized layers and the like.

[0012]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a diagram showing the structure of an aluminum nitride (AlN) circuit board according to a first embodiment of the present invention. In the figure, 1 is an AlN substrate made of an AlN sintered body,
A metallized layer 2 is formed on the surface 1 a of this AlN substrate 1. The metallized layer 2 functions as the surface wiring layer 3, the element mounting portion 4, and the like. As the AlN substrate 1, it is also possible to use a multilayer circuit substrate in which an internal wiring layer is formed by simultaneous firing of W or the like.

As the metallized layer 2, those formed by various methods can be used, and the formation method is not particularly limited. The metallization layer 2 may be formed by, for example, a co-firing method in which a coating layer of a high-melting-point metal paste such as W is co-firing with the AlN substrate 1 to form the metallization layer 2, or Cu or Ag-Cu alloys such as Ti, Zr A thin film forming method such as a thick film method, a sputtering method, an evaporation method, or the like, in which a paste of a metallizing composition to which an active metal such as Hf, Nb, or the like is added is applied onto an AlN substrate 1 and the metallized layer 2 is formed by baking the paste. The thin film method of forming various metal thin films as the metallized layer 2 or the sol-gel method is exemplified. Examples of the constituent material of the metallized layer 2 include W, Ni, Co, Cu, Pd, Pt, Au, Ti, Mo, and the like. Specific examples of the constituent material include Au and W on the W layer formed by the co-firing method. Examples thereof include those provided with a plated film of Ni / Au or the like, an Ag-Cu-Ti alloy film formed by a thick film method, a Ti / Ni / Au laminated film formed by a thin film method, and the like.

On the surface 1a of the AlN substrate 1, a Pd adhesion layer 5 is formed as shown in the enlarged view except the region where the metallized layer 2 is formed. This Pd adhesion layer 5 has a Pd concentration of 1 × 10 ¹⁶ to 1 × 10 ²¹ on the surface 1 a of the AlN substrate 1.
The thickness, density, etc. are set so that the range is atms / cm ³ . The Pd concentration on the surface 1a of the AlN substrate 1 is 1
If it is less than × 10 ¹⁶ atms / cm ³ , the surface 1a of the AlN substrate 1
The protection effect of 1 × 10 ²¹ a
When it exceeds tms / cm ³ , the contrast of Pd concentration is lowered and the pattern resolution of the metallized layer 2 is lowered. A more preferable Pd concentration is in the range of 1 × 10 ¹⁷ to 5 × 10 ²¹ atms / cm ³ .

The above-mentioned Pd adhesion layer 5 does not necessarily have to be entirely formed on the surface 1a of the AlN substrate 1, but it may be formed depending on the formation density of the surface wiring layer 3 and the like.
It suffices if it is formed at least in a region where high resistance is required. The Pd adhesion layer 5 does not necessarily have to be uniformly formed on the surface 1a of the AlN substrate 1, and the Pd adhesion layer 5 may be formed in an island shape. In this case, it is preferable that 30% or more (area ratio) of the surface 1a of the AlN substrate 1 has Pd adhered with the above-described concentration.

By forming the Pd adhesion layer 5 as described above on the surface 1a of the AlN substrate 1 excluding the region where the metallized layer 2 is formed, the environment resistance of the AlN substrate 1 is improved, and water resistance and corrosion resistance are improved. It is possible to improve. That is, AlN
When Pd is present on the surface 1a of the substrate 1, unbonded portions of surface atoms of the AlN substrate 1 are modified with Pd, and as a result, the reaction with moisture in the atmosphere is extremely reduced. As a result, the AlN substrate 1
The generation of AlOOH, etc. due to the corrosion of aluminum is greatly suppressed. Since Pd has a higher resistance than AlOOH or the like, it is possible to suppress a decrease in the resistance value between the metallized layers 2 and the like. Further, when the Pd adhesion layer 5 is formed in an island shape, even if AlOOH or the like is partially produced, A
Since the generation of lOOH and the like is suppressed, it is possible to suppress a decrease in resistance value in terms of resistance between the metallized layers 2 and the like.

The Pd adhesion layer 5 as described above can be formed by various methods, for example, a wet method or a dry method can be applied. In the wet method, Pd chloride, sulfide,
After forming the metallized layer 2 in an aqueous solution of Pd salt such as nitrification
AlN substrate 1 or AlN substrate 1 before formation of metallized layer 2
The Pd adhesion layer 5 is formed on the surface 1 a of the AlN substrate 1 by immersing. At this time, the concentration of the aqueous solution of the Pd salt used is preferably in the range of 0.5 to 1500 mg / l in terms of Pd concentration. The concentration of the Pd salt solution is 0.5 in terms of Pd concentration.
If it is less than mg / l, the amount of Pd attached will be extremely reduced, and
The concentration range of the Pd adhesion layer 5 cannot be satisfied, and the effect of improving water resistance and corrosion resistance cannot be sufficiently obtained.
On the other hand, when it exceeds 1500 mg / l, the density of the Pd adhesion layer 5 becomes too high, the contrast of the Pd density is lowered, and the pattern resolution of the metallized layer 2 is lowered. The more preferable concentration of the Pd salt aqueous solution is in the range of 1 to 1000 mg / l.

In the dry method, after the metallized layer 2 is formed by a general thin film forming method such as a sputtering method or an evaporation method.
AlN substrate 1 or AlN substrate 1 before formation of metallized layer 2
An adhesion layer 5 of Pd is formed on the surface 1a of the. At this time, the film thickness of the Pd film is preferably in the range of 200 pm to 50 nm. Pd
If the film thickness is less than 200 pm, the amount of Pd adhered will be extremely reduced, and the concentration range of the Pd adhered layer 5 described above cannot be satisfied, and sufficient effects of improving water resistance and corrosion resistance can be obtained. I can't. On the other hand, if it exceeds 50 nm, the concentration of the Pd adhesion layer 5 becomes too high, and the contrast of the Pd concentration decreases,
The pattern resolution of the metallized layer 2 is reduced. The more preferable Pd film thickness is in the range of 300 pm to 40 nm.

The AlN circuit board having the above-mentioned structure is
The semiconductor element is bonded and mounted on the element mounting portion 4 provided on the surface 1a of the lN substrate 1 through a bonding material such as solder, a brazing material, or a glass-based adhesive, and the semiconductor element and the surface wiring layer 3
It is used as a semiconductor module or the like by electrically connecting and with a bonding wire or the like. Also, Al
By using a multilayer wiring board as the N substrate 1 and forming input / output terminals such as pins and bumps on the other surface, it can be used as a semiconductor package.

In the AlN circuit board of the above embodiment, A
Since the Pd adhesion layer 5 is formed on the surface 1a of the lN substrate 1 except for the area where the metallized layer 2 is formed, the AlN substrate 1 is exposed to the atmosphere during the manufacturing process, use, storage, etc. of the AlN circuit substrate. It is possible to suppress the generation of low-resistance substances such as AlOOH by being corroded by water, etc., and also to suppress the decrease in the resistance value between the surface wiring layers 3 because Pd has a higher resistance than AlOOH. You can Therefore, for example, the resistance value between the surface wiring layers 3 can be maintained at 1 × 10 ⁹ Ω or more, and the normal operation of the mounted semiconductor element can be stably ensured. Next, a specific example of the AlN circuit board according to the first embodiment and its evaluation result will be described.

Example 1 An AlN circuit board on which a W metallized layer was formed by the co-firing method was prepared, and this AlN circuit board was immersed in a palladium chloride aqueous solution (Pd conversion concentration = 200 mg / l) at a temperature of 323K. When the Pd concentration on the AlN substrate surface after immersion was measured by SIMS, the Pd adhesion concentration was 1 × 10 ¹⁸ atms / cm ³ , and it was confirmed that the Pd adhesion layer with such concentration was formed uniformly. confirmed.

For such an AlN circuit board, 394K, 0.
After conducting the pressure cooker test for 100 h under the condition of 2 MPa, the resistance value between the W metallized layers formed on the AlN substrate surface was measured. As a result, the resistance value between wiring layers is 3 ×
The performance was 10 ¹⁰ Ω, which was sufficient.

Example 2 A TiN / Ni / Au laminated film was formed on the surface of an AlN substrate by a sputtering method, and the laminated film was patterned into a circuit shape.
A circuit board was prepared, and this AlN circuit board was immersed in an aqueous palladium chloride solution (Pd conversion concentration = 900 mg / l) at a temperature of 323K. When the Pd concentration on the surface of the AlN substrate after the immersion was measured by SIMS, the adhesion concentration of Pd was 3 × 10 ¹⁹ atms / cm ³ ,
It was confirmed that the Pd adhesion layer having such a concentration was uniformly formed.

For such an AlN circuit board, 394K, 0.
After performing a pressure cooker test for 100 h under the condition of 2 MPa, the resistance value between the metallized layers formed of the Ti / Ni / Au laminated film formed on the AlN substrate surface was measured. as a result,
The resistance value between the wiring layers was 3 × 10 ¹² Ω, which was sufficient for performance.

Example 3 An AlN circuit board on which a W metallization layer was formed by the co-firing method was prepared, and the film thickness of Pd was 1 n with respect to this AlN circuit board.
Pd was sputtered under the conditions of a substrate temperature of 323 K, an RF power of 500 W, and an Ar gas pressure of 1 Pa so as to obtain m. In addition, thickness 1
The Pd film of nm has a concentration of 1 × 10 ²⁰ atms / cm ³
Becomes

For such an AlN circuit board, 394K, 0.
After conducting the pressure cooker test for 100 h under the condition of 2 MPa, the resistance value between the W metallized layers formed on the AlN substrate surface was measured. As a result, the resistance value between wiring layers is 5 ×
The performance was 10 ¹⁰ Ω, which was sufficient.

Comparative Example 1 An AlN circuit board having a W metallized layer formed by the co-firing method was subjected to a pressure cooker test for 100 hours under the conditions of 394 K and 0.2 MPa, and then W formed on the surface of the AlN board. The resistance value between the metallized layers was measured. as a result,
The resistance between wiring layers was as low as 1 × 10 ⁸ Ω, which was insufficient for mounting semiconductor devices. Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a view showing the structure of an aluminum nitride (AlN) circuit board according to the second embodiment of the present invention. The AlN circuit board shown in the figure is the same as the first embodiment except that a boron compound adhesion layer 6 is formed on the surface 1a of the AlN substrate 1 excluding the formation region of the metallized layer 2 as shown in the enlarged view. It has the same structure as the AlN circuit board according to the embodiment .

The above-mentioned boron compound adhesion layer 6 is formed of AlN.
The concentration of elemental boron on the surface 1a of the substrate 1 is 1 × 10
^The boron compound should be in the range of ^{17 to} 5 × 10 ²¹ atms / cm ^3.
The existence form, thickness, density, etc. of the object are set. The concentration of boron on the surface 1a of the AlN substrate 1 is 1 × 10 ¹⁷ atms /
If it is less than ³ cm ³ , the effect of protecting the surface 1 a of the AlN substrate 1 cannot be sufficiently obtained, while if it exceeds 5 × 10 ²¹ atms / cm ³ , adhesion will start on the wiring metal and the solderability will deteriorate. Degradation occurs. More preferable concentration is 5 × 10 ¹⁷ to 1 × 10 ²¹ atms / cm ³
Is the range.

The above-mentioned boron compound adhesion layer 6 does not necessarily have to be entirely formed on the surface 1a of the AlN substrate 1, and at least has a high resistance depending on the formation density of the surface wiring layer 3 and the like. It only has to be formed at a required site. Further, the adhesion layer 6 of the boron compound is
The AlN substrate 1 does not necessarily have to be uniformly formed on the surface 1a of the AlN substrate 1, and the boron compound adhesion layer 6 may be formed in an island shape. In this case, the adhered portion of the boron compound having the above-mentioned concentration is formed on the surface 1a of the AlN substrate 1 by 30%.
% (Area ratio) or more is preferably present.

The boron compound adhesion layer 6 as described above is formed on the surface 1a of the AlN substrate 1 excluding the region where the metallized layer 2 is formed.
By forming the AlN substrate 1, the environment resistance of the AlN substrate 1 is improved, and the water resistance and the corrosion resistance can be improved. That is, when the boron compound on the surface 1a of the AlN substrate 1 is present, the unbound portion of the surface atoms of the AlN substrate 1 is modified with boric fluorinated compounds, reaction with water resulting in the atmosphere is extremely reduced. Since the adhesion layer 6 of boron compound is stable, AlN
The generation of AlOOH etc. due to the corrosion of the substrate 1 is significantly suppressed,
It is possible to suppress a decrease in resistance between the metallized layers 2. In addition, when the boron compound adhesion layer 6 is formed in an island shape, even if AlOOH or the like is partially generated, boron
Since the generation of AlOOH and the like is suppressed in the portion where the compound is present, a decrease in resistance value can be suppressed in terms of resistance between the metallized layers 2.

Adhesion layer 6 of boron compound as described above
Can be formed by various methods. For example, in the dimethylaminoborane (H ₅ B ₂ —N (CH ₃ ) ₂ ) aqueous solution, the AlN substrate 1 after forming the metallized layer 2 or the AN before forming the metallized layer 2 can be formed.
It can be formed by a wet method such as dipping the lN substrate 1. As a result, the adhesion layer 6 of dimethylaminoborane and boron hydride (B ₂ H ₆ ) which is a decomposition product thereof is formed on the surface 1 a of the AlN substrate 1. At this time, the concentration of the dimethylaminoborane aqueous solution used is preferably in the range of 100 mg / l to 100 g / l. If the concentration of the dimethylaminoborane aqueous solution is less than 100 mg / l, the amount of dimethylaminoborane or borohydride attached will be extremely reduced, and the effects of improving water resistance and corrosion resistance cannot be sufficiently obtained. On the other hand, when it exceeds 100 g / l, the surface 1a of the AlN substrate 1 is etched and dissolved by dimethylaminoborane, which may cause the AlN crystal grains to fall off. The more preferable concentration of the dimethylaminoborane aqueous solution is in the range of 500 mg / l to 90 g / l.

The AlN circuit board having the above-described structure is
The semiconductor element is bonded and mounted on the element mounting portion 4 provided on the surface 1a of the lN substrate 1 through a bonding material such as solder, a brazing material, or a glass-based adhesive, and the semiconductor element and the surface wiring layer 3
It is used as a semiconductor module or the like by electrically connecting and with a bonding wire or the like. Also, Al
By using a multilayer wiring board as the N substrate 1 and forming input / output terminals such as pins and bumps on the other surface, it can be used as a semiconductor package.

In the AlN circuit board of the above embodiment, A
Since the boron compound adhesion layer 6 is formed on the surface 1a of the lN substrate 1 except for the region where the metallization layer 2 is formed,
AlN is used in the manufacturing process of circuit boards and during use and storage.
Since it is possible to prevent the substrate 1 from being corroded by moisture in the atmosphere and generating a low-resistance substance such as AlOOH, the surface wiring layer 3
It is possible to suppress a decrease in resistance value during the period. Therefore,
For example, the resistance value between the surface wiring layers 3 can be maintained at 1 × 10 ⁹ Ω or more, and the normal operation of the mounted semiconductor element can be stably ensured.

Next, a concrete example of the AlN circuit board of the second embodiment and its evaluation result will be described.

Example 4 An AlN circuit board having a W metallized layer formed by the co-firing method was prepared, and this AlN circuit board was immersed in an aqueous dimethylaminoborane solution (concentration = 900 mg / l) at a temperature of 323K. When the concentration of boron on the AlN substrate surface after immersion was measured by SIMS, the deposition concentration was 8 × 10 ¹⁹ atms / cm ³ ,
It was confirmed that the boron compound adhesion layer was uniformly formed.

For such an AlN circuit board, 394K, 0.
After conducting the pressure cooker test for 100 h under the condition of 2 MPa, the resistance value between the W metallized layers formed on the AlN substrate surface was measured. As a result, the resistance value between wiring layers is 3 ×
The performance was 10 ¹¹ Ω, which was sufficient.

Example 5 A laminated film of Ti / Ni / Au was formed on the surface of an AlN substrate by a sputtering method, and then this laminated film was patterned into a circuit shape.
A circuit board was prepared, and the AlN circuit board was immersed in an aqueous dimethylaminoborane solution (concentration = 30 g / l) at a temperature of 323K.
When the concentration of boron on the surface of the AlN substrate after the immersion was measured by SIMS, the deposition concentration was 9 × 10 ²⁰ atms / cm ³ , and it was confirmed that the deposition layer of the boron compound was uniformly formed.

For such an AlN circuit board, 394K, 0.
After performing a pressure cooker test for 100 h under the condition of 2 MPa, the resistance value between the metallized layers formed of the Ti / Ni / Au laminated film formed on the AlN substrate surface was measured. as a result,
The resistance value between the wiring layers was 3 × 10 ¹² Ω, which was sufficient for performance.

[0041]

As described in the foregoing, according to the aluminum nitride circuit board of the present invention, be present in a predetermined concentration of an <br/> direction also less of palladium alone and boron compounds on the surface of the aluminum nitride substrate Therefore, it is possible to suppress the generation of AlOOH and the like due to the corrosion of aluminum nitride, and thus to suppress the decrease in the resistance value between the metallized layers. Therefore, it is possible to provide an aluminum nitride circuit board that can stably and normally operate electric / electronic components such as mounted semiconductor elements.

[Brief description of drawings]

FIG. 1 is a sectional view showing a structure of an AlN circuit board according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of an AlN circuit board according to a second embodiment of the present invention.

[Explanation of symbols]

1 ... AlN substrate 2 ... Metallization layer 3 ... Surface wiring layer 4 ... Device mounting part 5 ... Pd adhesion layer 6 ... Boron compound adhesion layer

Claims (2)

(57) [Claims] 1. An aluminum nitride circuit board comprising an aluminum nitride substrate and a metallization layer formed on the aluminum nitride substrate, wherein the surface of the aluminum nitride substrate excluding a region where the metallization layer is formed contains palladium alone. Is attached,
The adhesion concentration of the palladium alone is 1 × 10 ¹⁶ to 1 × 10 ²¹ at
aluminum nitride circuit board which is a range of ms / cm ^3. 2. An aluminum nitride circuit board comprising an aluminum nitride substrate and a metallization layer formed on the aluminum nitride substrate, wherein a boron compound is formed on a surface of the aluminum nitride substrate excluding a region where the metallization layer is formed . Is attached to the
The attachment concentration of the boron compound is 1 x 1 as the concentration of boron alone.
Aluminum nitride circuit board which is a range of ^{0 17 ~5 × 10 21 atms /} cm 3.