JPH08333163A - Black aluminum nitride sinter and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a darker black aluminum nitride sintered body without reducing the thermal conductivity.

SOLUTION: This black aluminum nitride sintered body comprises aluminum nitride as a main component and titanium and chromium which are present as monomers or compounds, and the total weight of titanium and chromium in the sinter is about 0.05-1% by weight based on the weight of titanium and chromium elements. The obtained sinter is applicable to a material for an integrated circuit substrate.

COPYRIGHT: (C)1996,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body and its manufacturing method, and more particularly to a colored aluminum nitride sintered body having high thermal conductivity and its manufacturing method.

[0002]

2. Description of the Related Art In recent years, large-scale integrated circuit technology has advanced, and the improvement in the degree of integration has been remarkable. As the degree of integration is improved and the size of the integrated circuit chip is increased in this way, the amount of heat generated in a package including such an integrated circuit is increasing. Therefore, the thermal conductivity of the substrate material used as a package of an integrated circuit chip or the like is important. Alumina sintered bodies, which have been widely used as integrated circuit substrates, cannot handle a large amount of heat generated from integrated circuit chips because alumina has a low thermal conductivity and therefore heat radiation from the alumina sintered body is insufficient. Since beryllium oxide has a higher thermal conductivity than alumina, it has been studied as a substitute for such an alumina sintered body. However, beryllium oxide is difficult to handle because it is toxic.

Sintered aluminum nitride (AlN) has attracted attention as an integrated circuit board material in the semiconductor industry because it has high thermal conductivity and is not toxic.

Basic aluminum nitride formulations are well known. For example, yttrium, calcium, aluminum, boron and compounds and mixtures thereof are added to the basic aluminum nitride composition as a sintering aid. One particularly preferred composition is the one described by Harris et al., December 2, 1993.
2nd application “LOW TEMPERATURE SINTERING ROUTE FOR ALUM
It is disclosed in US patent application Ser. No. 08 / 172,032 entitled "INUM NITRIDE CERAMICS". The disclosure of which is incorporated herein by reference.

The wiring metallurgy utilized in aluminum nitride packages is a refractory metal such as tungsten or molybdenum. Under the lighting used in automated inspection equipment, this wiring metallurgy looks gray. The typical aluminum nitride package is also gray. Due to the lack of contrast between aluminum nitride and wiring metallurgy, automatic inspection of this wiring metallurgy is problematic. The darker color of aluminum nitride increases the contrast.

Therefore, it is desirable to darken the aluminum nitride in order to increase the contrast between the aluminum nitride and the wiring metallurgy.

However, a difficulty in making dark aluminum nitride is that the additives that produce the desired color simultaneously reduce the thermal conductivity of the aluminum nitride.

Therefore, it is also desirable to make dark aluminum nitride without adversely affecting the thermal conductivity of aluminum nitride.

Recently, it has been proposed to color aluminum nitride for the reason of improving the appearance as well as the functional reason.

To make the dark aluminum nitride,
Various solutions have been proposed. For example, US Pat. No. 5,264,388 to Yamakawa et al. And US Pat. No. 51 to Shimoda.
No. 47832 proposes adding a powder of a compound containing a transition metal element such as titanium, chromium or tungsten to an aluminum nitride powder in order to produce a black aluminum nitride substrate. The disclosures of both of the above patents are incorporated herein by reference. U.S. Pat. No. 5,273,700 to Yamakawa et al. Proposes adding titanium to aluminum nitride powder in the form of organometallic compounds, metal alkoxide compounds, and stearates to make black aluminum nitride substrates. There is. The disclosures of the above patents are incorporated herein by reference.

However, the inventors have often found that the "blackness" or "darkness of color" of this black aluminum nitride is less than desired and that by combining some additions of the aforementioned elements Have found that it can be improved.

[0012]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to obtain a darker black aluminum nitride substrate.

Another object of the present invention is to produce a darker black aluminum nitride without adversely affecting the thermal conductivity of aluminum nitride.

[0014]

The object of the present invention is, in the first aspect of the present invention, to include aluminum nitride as a main component, titanium and chromium, wherein titanium and chromium are present as an element or a compound, and calcined. The total weight of titanium and chromium in the bound is 0.05 as the element weight of titanium and chromium.
~ 1 wt% and the sintered body is black and is achieved by providing a black aluminum nitride sintered body.

A second aspect of the present invention relates to a method for producing a black aluminum nitride sintered body, which comprises mixing aluminum nitride powder as a main component, a solution containing titanium and chromium to obtain chromium. Exists as an element or compound, and the total weight of titanium and chromium is 0.05 to 1% by weight in terms of element weight of titanium and chromium, and a step of forming a mixture, and a step of shaping the mixture into a predetermined shape. And sintering the formed mixture in a non-oxidizing atmosphere to densify the formed mixture into a sintered body of black aluminum nitride, titanium and chromium in which titanium and chromium are present as elements or compounds. including.

[0016]

DETAILED DESCRIPTION Reflectance is a measure of the light reflected from a surface. The smaller this number is, the less light is reflected, and the more intense this substance is. The unit of reflectance is the "percentage" that indicates the percentage of light reflected from a surface that is visible on that surface. In terms of achieving the objectives of the present invention, it is desirable to achieve the lowest reflectivity possible in order to obtain the "blackest" aluminum nitride sintered body.

As illustrated in the prior art, there are many colorants added to darken the aluminum nitride sinter. Among them are titanium, chromium, tungsten, cobalt, nickel, iron, molybdenum and many others. According to the literature, these colorants lead to black aluminum nitride sinters. However, the present inventor has found that the amount of the colorant necessary to obtain a black body has a bad influence on the thermal conductivity of the sintered body, and the amount which does not have a bad influence is not enough to obtain a true black body. Etc. proved. In fact, many of the resulting aluminum nitride sinters actually have a dark shade of gray rather than black.

Further, the present inventors have determined that a true black aluminum nitride sintered body can be obtained by the following elements of the present invention. First, titanium and chromium are combined and added to the aluminum nitride powder. The total amount of titanium and chromium is at least about 0.05% by weight (percentage sufficient for dark coloring), and about 1% by weight at maximum (a sufficiently small amount so that the thermal conductivity is not substantially affected). Yes, more preferably about 0.
It is 1 to 0.4% by weight. Titanium and chromium are Ti
Since the above percentages can be added as compounds such as O, TiO ₂ and Cr ₂ O ₃ , the above-mentioned percentages are the amounts of the elements of titanium and chromium in these compounds which must be added to the aluminum nitride powder in order to obtain the desired result. It is based on. The best results for reflectance were obtained when the total combined weight of titanium and chromium was about 0.4% by weight. If the thermal conductivity is too low, a total combined weight of titanium and chromium of about 0.2% by weight would be preferred. Further, the weight of titanium in the aluminum nitride powder mixture is about 0.0 in terms of titanium element weight.
It is in the range of 25 to 0.975% by weight, and the element weight of chromium in the sintered body is about 0.025 to the element weight of chromium.
It is in the range of 0.975% by weight, with the additional limitation that the total combined weight of titanium and chromium be in the range of about 0.05-1% by weight.

Second, titanium should be added as a solution rather than as a powder. By solution is meant that the titanium metal is present as titanium ions or titanium complex ions. A solution should be distinguished from a suspension or slurry in which elemental titanium powder or titanium compound powder is simply suspended in a liquid. As the data show, there is a dramatic decrease in reflectance when titanium is added as a solution rather than as a powder.

Finally, chromium may be added as a powder or as a solution. In this case, solution means that the chromium metal is present as chromium ions or chromium complex ions. Surprisingly, it is preferred, since the best results were obtained when chromium was added as a powder.

The titanium solution and chromium solution may be a solution of an organic metal compound (eg alkoxide), nitrate, carbonate or the like.

When titanium and chromium are added as a solution, the final chemical species in the aluminum nitride sintered body may be elemental titanium and elemental chromium. Alternatively, the final species may be oxides, hydrides, depending on the particular sintering method used.
Alternatively, it may be nitride. As long as dark coloring is achieved,
The exact shape of the final titanium and chromium species in the aluminum nitride sintered body is not critical to the invention.

The mixture of aluminum nitride, titanium and chromium also contains a sintering aid. The sintering aid may be yttrium, calcium, boron, aluminum, and some or all compounds and mixtures thereof.
Examples of the compound include two or more kinds of yttrium oxide, calcium oxide, diboron trioxide, alumina, and calcium oxide-alumina-diboron trioxide glass and calcium oxide-alumina-diboron trioxide-yttrium oxide glass. There are glasses made of compounds. Further, other additives may be added to assist in forming the aluminum nitride sintered body. As such additives,
There are plasticizers, binders, solvents, wetting agents, deflocculants, all known in the art.

As long as there is a protective atmosphere, the aluminum nitride sintered body can be sintered in a conventional furnace. The preferred atmosphere is
Forming gas, that is, a mixture of nitrogen gas and hydrogen gas. A typical sintering procedure is performed as follows. The green body of aluminum nitride is placed in a sintering furnace. A protective atmosphere of dry forming gas (N ₂ + 10-20% H ₂ ) is used throughout the sintering process. The temperature is raised from room temperature to 600 ° C. for about 5 hours to thermally decompose the binder. Next, the temperature is raised to about 1550 to 1 for about 8 hours.
The sintering temperature is raised to 650 ° C. and kept at this sintering temperature for about 5 hours. Next, the temperature is lowered to room temperature over about 5 hours.

As shown in FIG. 1, the reflectance of several sintered aluminum nitride compositions containing the two preferred aluminum nitride compositions (lines 10 and 11) was graphed. This reflectance is in the order of no colorant (line 1), titanium powder colorant (lines 2, 4), titanium solution colorant (lines 8, 9), titanium solution + chromium colorant (lines 10, 11). Fell. The aluminum nitride sintered body containing no colorant is gray, and the aluminum nitride sintered body containing titanium powder is also the same. This color begins to darken when titanium solution is used as the colorant. The darkest color is obtained when the combination of titanium and chromium is the colorant.

FIG. 2, like FIG. 1, shows some of the preferred compositions of the present invention. The scale is enlarged in FIG. 2 so that the lines can be easily seen. Lines with the same number in each figure represent the same composition. In FIG. 2, the aluminum nitride composition containing no colorant (line 1) and the aluminum nitride composition containing 0.1% by weight of titanium powder as the colorant (line 2) are omitted. See also FIG. 3 and FIG. 3 which is a re-plot of the results obtained for reflectance at 660 nm from FIG. 1 and FIG. The reflectance value of each composition is shown in parentheses.
The most preferred composition is the one that contains titanium solution and chromium powder as colorants with the best reflectance results (lines 10, 11). Compositions containing titanium and chromium solutions (lines 6,7) also give comparable results. Another advantage obtained by adding both titanium and chromium is that chromium, even in such small amounts, helps adhere the surface metallurgy to the aluminum nitride sintered body.

As described above, the total total weight of titanium and chromium in the aluminum nitride sintered body is about 0.05 to 1% by weight in terms of element weight of titanium and chromium, preferably about 0.1 to 0.4. % By weight. The best results for reflectance were obtained when the total total weight was about 0.4% by weight. If the thermal conductivity is too low, a total combined weight of titanium and chromium of about 0.2% by weight would be preferred. Further, the weight of titanium in the sintered body is about 0.025 in terms of the weight of titanium element.
To 0.975% by weight, the weight of chromium in the sintered body is in the range of approximately 0.025 to 0.975% by weight in terms of elemental chromium, and the total total weight of titanium and chromium is approximately 0. There is a limitation that it is within the range of 0.05 to 1% by weight.

Surprisingly, it can be concluded from FIG. 4 that titanium and chromium cooperate unexpectedly. In this figure, the reflectance at 660 nm is measured for different weight percentages of titanium powder, titanium solution and chromium solution. It is clear that the titanium solution works well alone. It is also quite clear that the chrome solution is intense in reducing reflectance. Therefore, if the effect of the combination of titanium solution and chromium solution is simply an additive effect, the combination of titanium and chromium should increase the reflectance rather than decrease it. However, the opposite result is shown in FIGS. Further, although the reflectance of the chromium powder is not shown in FIG. 4, theoretically, the reflectance of the chromium powder as the colorant is about the same as or slightly worse than the reflectance of the chromium solution, which is similar to that of the titanium powder. Thought to be. However, it has been found that the combination of titanium solution and chromium powder as colorant gives the best result of all.
It can therefore only be concluded that the reflectance results obtained by the combined addition of titanium and chromium are surprising and unexpected.

Preparation of Sample The samples used in the graphs of FIGS. 1 to 4 were prepared as follows.

The aluminum nitride powder used was 96% AlN, 3% Y ₂ O ₃ , and 1% 1993 by weight percentage.
“AN ALUMINUM NITRIDE BODY AND MET” filed on Feb. 22
HODFOR FORMING SAID BODY UTILIZING A VITREOUS SINT
Duncombe named "ERING ADDITIVE"
A mixture of 1% glass of calcia, alumina, boria, as disclosed in other U.S. patent application Ser. No. 08 / 173,293. The disclosure of which is incorporated herein by reference.

1 micron TiO ₂ powder particles, titanium ethoxide solution, 1 micron Cr ₂ O ₃ powder particles, or Cr suitable for making the required composition shown in the figure.
A (NO ₃ ) ₃ solution, or a combination thereof, was added to this aluminum nitride mixture. Each of the compositions was shaken in a Spex mill for about 15 minutes. Then, this composition was pressed into pellets.

The above titanium solution and chromium solution can be prepared as follows. For example, to prepare a titanium solution, 0.143 g Ti (OC ₂ H ₅ ) ₄ is added to 20 g propanol. For example, to prepare the chromium solution, Cr (NO ₃₎ of 0.231g ₃ · 9H ₂ O and 20g
Add to propanol. Either of these solutions was then added to 30 g of the aluminum nitride mixture, adding 1000 ppm (0.1% by weight) of titanium or chromium. Ti (OC ₂ H ₅ ) added to propanol
₄ or _{Cr (NO 3) 3 · 9H} 2 O, or can also be prepared other solutions by adjusting the weight of both. Further, the amount of titanium and / or chromium added to the aluminum nitride mixture can be varied by adjusting the weight of the aluminum nitride mixture.

The pellets were sintered by raising the temperature to 1625 ° C., maintaining that temperature for 24 hours, and then lowering it to room temperature. The entire sintering cycle was performed in a forming gas atmosphere. Since there is no binder in the pellets,
No binder firing step was required.

To remove surface irregularities, each sintered pellet was briefly ground with a 15 micron diamond wheel. Next, to measure the reflectance of each pellet, use Opti
-Macbeth Color Eye 3000 with View software
Each pellet was placed in a reflectometer. This device works by illuminating the pellet surface and then measuring how much light is reflected.

The results of measuring the reflectance are shown in FIGS.

As a summary, the following matters will be disclosed regarding the configuration of the present invention.

(1) Aluminum nitride as a main component, titanium and chromium are contained, titanium and chromium are present as elements or compounds, and the total weight of titanium and chromium in the sintered body is the element weight of titanium and chromium. 0.05 ~
1% by weight, and a black sintered body of black aluminum nitride. (2) The sintered body according to (1) above, wherein the total weight of titanium and chromium in the sintered body is 0.1 to 0.4% by weight in terms of element weight of titanium and chromium. (3) The weight of titanium in the sintered body is 0.025 to 0.975% by weight as the elemental weight of titanium, and the weight of chromium in the sintered body is 0.025 to 0 as the elemental weight of chromium. ．
975% by weight, and the total total weight of titanium and chromium in the sintered body is 0.05 to 1 as the element weight of titanium and chromium.
The sintered body according to (1) above, characterized in that the content is% by weight. (4) The sintered body according to (1) above, which further contains a sintering aid selected from the group consisting of calcium, yttrium, boron, aluminum and compounds and mixtures thereof. (5) A method for producing a black aluminum nitride sintered body, wherein a solution containing aluminum nitride powder as a main component and titanium is mixed with chromium, and chromium is present as an element or a compound, and the total amount of titanium and chromium is Forming a mixture having a weight of 0.05 to 1% by weight in terms of elemental weight of titanium and chromium, forming the mixture into a predetermined shape, and sintering the formed mixture in a non-oxidizing atmosphere. And densifying the molding mixture into a sintered body of black aluminum nitride, titanium and chromium in which titanium and chromium are present as elements or compounds. (6) The method according to (5) above, wherein the total weight of titanium and chromium in the sintered body is 0.1 to 0.4% by weight based on the element weight of titanium and chromium. (7) The weight of titanium in the sintered body is 0.025 to 0.975% by weight as the elemental weight of titanium, and the weight of chromium in the sintered body is 0.025 to 0 as the elemental weight of chromium. ．
975% by weight, and the total total weight of titanium and chromium in the sintered body is 0.05 to 1 as the element weight of titanium and chromium.
The method according to (5) above, characterized in that the content is% by weight. (8) The method according to (5) above, which further comprises a sintering aid selected from the group consisting of calcium, yttrium, boron, aluminum, and compounds and mixtures thereof. (9) The method according to (5) above, wherein the chromium is present as a chromium solution. (10) The method according to (5) above, wherein the chromium is present as chromium powder. (11) The method according to (9) above, wherein the chromium solution is selected from the group consisting of organometallic compounds, nitrates and carbonates. (12) The method according to (5) above, wherein the titanium solution is selected from the group consisting of organometallic compounds, nitrates and carbonates. (13) The method according to (5) above, wherein in the mixing step, the mixture further contains a binder material.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between reflectance and wavelength of a preferred aluminum nitride composition for producing a black sintered body according to the present invention, as compared with a prior art aluminum nitride composition.

FIG. 2 is a graph similar to FIG. 1, but showing the relationship between reflectance and wavelength of a preferred aluminum nitride composition for producing a black sintered body according to the present invention, compared to a conventional aluminum nitride composition. is there.

FIG. 3 is a graph showing the reflectance at 660 nm of a preferred aluminum nitride composition for producing a black sintered body according to the present invention, compared with a conventional aluminum nitride composition.

FIG. 4 660 nm of an aluminum nitride sintered body prepared by using titanium powder, titanium solution or chromium solution.
3 is a graph showing the relationship between the reflectance and the weight percentage in FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Benjamin Vito Fasano 12553 New Windsor, New York Windy Hill Road 30 (72) Inventor Lester Win Heron United States 12533 Hopewell Junction, New York USA Cook Boulevard 12 (72) Inventor Gregory Marvin Johnson United States 12603 Parkesey, New York Cherry Hill Drive 410 (72) Inventor Suba Luxman Cinde United States 10520 Croton on Hudson Half State, New York Moon Bay Drive 518

Claims (13)

[Claims] 1. Aluminum nitride as a main component, titanium and chromium are contained, and titanium and chromium are present as elements or compounds, and the total weight of titanium and chromium in the sintered body is the element weight of titanium and chromium. 0.05-1% by weight
And a sintered body of black aluminum nitride in which the sintered body is black. 2. The sintered body according to claim 1, wherein the total weight of titanium and chromium in the sintered body is 0.1 to 0.4% by weight in terms of element weight of titanium and chromium. . 3. The weight of titanium in the sintered body is 0.025 to 0.975% by weight as the elemental weight of titanium, and the weight of chromium in the sintered body is 0.025 as the elemental weight of chromium.
.About.0.975% by weight, and the total total weight of titanium and chromium in the sintered body is 0.0 in terms of the element weight of titanium and chromium.
The sintered body according to claim 1, which is 5 to 1% by weight. 4. The sintered body according to claim 1, further comprising a sintering aid selected from the group consisting of calcium, yttrium, boron, aluminum and compounds and mixtures thereof. 5. A method for producing a black aluminum nitride sintered body, which comprises mixing a solution containing aluminum nitride powder as a main component and titanium, and chromium, wherein chromium is present as an element or a compound, and titanium and chromium are mixed. To form a mixture having a total weight of titanium and chromium of 0.05 to 1% by weight, forming the mixture into a predetermined shape, and baking the formed mixture in a non-oxidizing atmosphere. And densifying the molding mixture into a sintered body of black aluminum nitride, titanium, chromium in which titanium and chromium are present as elements or compounds. 6. The method according to claim 5, wherein the total weight of titanium and chromium in the sintered body is 0.1 to 0.4% by weight based on the element weight of titanium and chromium. 7. The weight of titanium in the sintered body is 0.025 to 0.975% by weight as the elemental weight of titanium, and the weight of chromium in the sintered body is 0.025 as the elemental weight of chromium.
.About.0.975% by weight, and the total total weight of titanium and chromium in the sintered body is 0.0 in terms of the element weight of titanium and chromium.
The method according to claim 5, wherein the amount is 5 to 1% by weight. 8. The method of claim 5, further comprising a sintering aid selected from the group consisting of calcium, yttrium, boron, aluminum, and compounds and mixtures thereof. 9. The method of claim 5, wherein the chromium is present as a chromium solution. 10. The method of claim 5 wherein the chromium is present as chromium powder. 11. The method of claim 9 wherein the chromium solution is selected from the group consisting of organometallic compounds, nitrates, carbonates. 12. The method of claim 5, wherein the titanium solution is selected from the group consisting of organometallic compounds, nitrates, carbonates. 13. The method of claim 5 wherein in the mixing step the mixture further comprises a binder material.