JPH027495A - Manufacture of aluminum nitride multilayer board - Google Patents

Abstract

PURPOSE:To acquire a multilayer wiring board having less warp or turbidity by mixing an organic binder and a burning assistant to aluminum nitride powders, by manufacturing a green sheet, by printing a desired wiring pattern thereon, and by carrying out debinder and sintering after laminating the sheet. CONSTITUTION:An organic binder is applied to powders made by mixing a burning assistant to aluminum nitride powders, a green sheet is manufactured by doctor blade method, and a through hole is formed thereto. After a conductor such as tungsten is printed to make a desired wiring pattern, the sheet is laminated. Then debinder is conducted in a mixture atmosphere consisting of nitride, hydrogen and water vapor. Sintering is carried out thereafter. According to this constitution, a wiring metal resists to oxidization and organic substances in the green sheet and paste are completely decomposed, thus remaining no carbon. When this laminate is sintered, it does not receive any detrimental effect because no carbon remains. A sintered body of high heat conductivity without warp or turbidity can be acquired in this way.

Description

Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an aluminum nitride substrate with good thermal conductivity used for semiconductor substrates, IC substrates, etc., and particularly to substrates for high-density packaging. The present invention relates to improvements in aluminum nitride multilayer wiring boards that are particularly useful.

"Prior Art" Conventionally, alumina substrates have been widely used as substrates for mounting semiconductor elements in electronic devices and the like because they are chemically stable and highly reliable.

However, in recent years, as electronic devices have become smaller and semiconductor components have become more dense and powerful, the amount of heat generated per unit area of the board on which semiconductors are mounted has increased, and heat dissipation has become a major problem. .

For this reason, it has an extremely high thermal conductivity (approximately 70~
260W/mK).

Almost the same coefficient of thermal expansion as Si (approximately 4.6 x 10-”/°C
) aluminum nitride has begun to attract attention and be used as a substrate material for semiconductor components.

However, aluminum nitride has a firing temperature of 1800
Multilayer wiring is considered difficult due to the high temperature of over ℃ and the lack of suitable wiring materials that can withstand this temperature, and highly integrated LS
It has not been put to practical use as a mounting board for I.

[Problems to be solved by the invention] However, recently, aluminum nitride powder produced by direct nitriding has been developed.
A tungsten-based conductive material is printed on a green sheet made from powder, and four sheets are stacked to form a five-layer wiring.
A multilayer substrate co-fired in an N2 atmosphere was reported (Nikkei New Materials, June 1, 1987 issue, 10
Furthermore, CaC2 powder is mixed with high-purity aluminum nitride powder as a sintering aid, an organic binder is added, a green sheet is prepared on the organic film by the doctor blade method, and VIA holes are formed on this green sheet. Formed.

An aluminum nitride multilayer wiring board has also been proposed, in which a tungsten conductor is printed, the desired sheets are laminated, the binder is removed, and then fired (2nd Microelectronics Symposium Abstracts, July 1987).
), the practical application of aluminum nitride multilayer wiring boards is rapidly progressing.

By the way, as mentioned above, the previously known method for manufacturing aluminum nitride multilayer wiring boards is similar to the manufacturing method for alumina multilayer wiring boards, etc., in which a wiring pattern is printed on a green sheet using tungsten paste or molybdenum paste. The process involves stacking the materials, removing the binder, and then sintering in a mixed gas atmosphere of nitrogen and oxygen. However, aluminum nitride has the property of being oxidized by trace amounts of oxygen or water vapor at high temperatures and easily changing into alumina or the like. For this reason, it is usually 500℃~
Binder removal is performed at a temperature of 100° C. in a nitrogen gas atmosphere or a mixed gas of nitrogen and hydrogen to prevent the wiring metal from oxidizing.

However, in this debinding process, organic matter is removed only by thermal decomposition, so some organic matter remains as carbon, and this residual carbon has an adverse effect on the next step, sintering. was. That is, there were problems in that the sintered body was warped and clouded, and the high thermal conductivity, which is a characteristic of aluminum nitride, could not be sufficiently achieved.

An object of the present invention is to provide a manufacturing method for solving the above-mentioned problems and realizing an aluminum nitride multilayer wiring board that is free from warpage and turbidity and has high thermal conductivity.

[Means for Solving the Problems] In order to solve the above problems, the present invention adds an organic binder to a powder made by mixing aluminum nitride powder with a sintering aid, and forms a green sheet by a doctor blade method. After forming through holes in this and printing a conductor such as tungsten to form the desired wiring pattern, the sheets are stacked and the binder is removed in a mixed atmosphere consisting of nitrogen, hydrogen, and water vapor. This is a method for manufacturing an aluminum nitride multilayer wiring board, characterized in that the aluminum nitride multilayer wiring board is sintered.

In the present invention, when debinding the aluminum nitride green sheet laminate in a mixed atmosphere of nitrogen, hydrogen, and water vapor, the wiring metal is hardly oxidized and the organic matter in the green sheet and paste is removed by water vapor. Since it is completely decomposed by the action, no carbon remains. Therefore, even if this laminate is sintered, since there is no residual carbon, there is no harmful effect on sintering, and a highly thermally conductive sintered body without warping or turbidity can be obtained.

Further, in the present invention, it is preferable that the partial pressure ratio of water vapor and hydrogen in the mixed atmosphere (PH20/P11□) is 0.1 to 1. If the partial pressure ratio is less than 0.1,
The decomposition effect due to water vapor cannot be expected, and the partial pressure ratio is 1.
This is because if the amount exceeds 20%, aluminum nitride may be oxidized.

In addition, the atmosphere for the sintering step in the present invention is 1
For example, nitrogen gas containing carbon vapor.

A reducing atmosphere such as vacuum or CH4 gas is preferred.

The sintering temperature is usually selected to be in the range of about 1700-1900°C.

In addition, when laminating sheets in the present invention, in order to better adhere the sheets to each other, for example,
Heating at a temperature of ~130℃ and 50Kg/aJ
It is desirable to heat and pressurize at the above pressure for about 5 to 20 minutes.6 Note that these conditions may be selected and changed as appropriate depending on the type of resin used.

[Examples] The present invention will be explained in more detail below based on Examples and Comparative Examples.

(Example) 97% aluminum nitride powder with a particle size of approximately 0.5/ffi
To a finely powdered ceramic powder in which 3% lt% of dysprosium oxide was added as a sintering aid to lt%, 7.5 g of butyral resin as an organic binder and 3.3 g of a plasticizer were added to 100 g of the ceramic powder. Furthermore, 96 ml of azeodorope consisting of trichlorethylene, tetrachlorethylene, and butanol as a solvent was added per 100 g of ceramic powder, and thoroughly mixed in a ball mill to prepare a slurry in which the ceramic powder was uniformly dispersed. Next, the slurry was degassed under low pressure while stirring to remove air bubbles in the slurry, and then thinned using a doctor blade type casting device to produce a green sheet with a thickness of 0.degree. and 25 mm. Next, this green sheet was cut to create a 100 m square sheet, in which through holes were formed to provide electrical continuity between the upper and lower wiring patterns. Note that the through holes were formed using a punching die having a cemented carbide pin.

Next, by screen printing using tungsten paste i-, the through holes formed in the green sheet were filled with paste, and a wiring pattern was printed on the green sheet. The tungsten paste used as the wiring material is 80% tungsten powder with an average particle size of 1.5-
3g of ethyl cellulose as an organic binder
and 17 g of diethylene glycol as an organic solvent were added to each, kneaded using a miller and three rolls, and then butyl carbitol acetate was added to adjust the viscosity.

Next, a predetermined number of green sheets with the predetermined wiring pattern printed on them were stacked and heated at 120°C and 60kg/c.
Hot pressing was carried out under the conditions of d and laminated.

Next, the binder was removed from the green sheet laminate after the lamination process. The binder was removed using a box-type electric furnace using molybdenum as a heating element, and the temperature was raised to 800° C. in a mixed atmosphere of nitrogen, hydrogen, and water vapor, and the temperature was maintained for 15 hours. In addition, the partial pressure ratio of water vapor and hydrogen (PH20/PH
2) was performed at 0.5.

After removing the binder, the temperature was raised to 1800° C. in a mixed atmosphere of nitrogen and oxygen using a box-type electric furnace using molybdenum as a heating element, and the temperature was maintained for 1 hour for sintering.

When the warpage of the obtained sintered body was measured using a surface roughness meter, it was found to be 15. The following warpage was observed, and no turbidity was observed. Also.

The thermal conductivity was 160 W/mK.

(Comparative Example) On the other hand, for comparison, a sample prepared in the same manner as in the above example until lamination was heated to 800° C. in a nitrogen atmosphere and held for 100 hours to remove the binder. After removing the binder, the temperature was raised to 1800'C in a mixed atmosphere of nitrogen and oxygen using a box-type electric furnace using molybdenum as a heating element, and held for 1 hour for sintering.

When the warpage of the obtained sintered body was measured using a surface roughness meter, there was a warpage of 300t11m per tooth in a length measurement range of 20mm, and the whole body was cloudy white. Also, the thermal conductivity is 50
It was W/mK.

FIG. 1 shows the relationship between the holding time for binder removal and the amount of carbon after binder removal. Almost no carbon exists in the mixed atmosphere of nitrogen, hydrogen, and water vapor according to the present invention when the mixture is maintained for 15 hours or more. On the other hand, it is clear that about 0.15 wt % of carbon remains even if the sample is held in a nitrogen atmosphere for 100 hours, which has been conventionally practiced.

Furthermore, FIG. 2 shows the relationship between the holding time for debinding and the thermal conductivity of the sintered body. In the debinding process according to the present invention in a mixed atmosphere of nitrogen, hydrogen, and water vapor, the thermal conductivity takes on a nearly constant value when the holding time exceeds 15 hours. On the other hand, in the case of conventional debinding in a nitrogen atmosphere, the thermal conductivity increases monotonically with increasing holding time;

The change is very small compared to that caused by debinding in a mixed atmosphere of water vapor.

"Effects of the Invention" As explained above, according to the present invention, it is possible to obtain a multilayer wiring board with less warpage and turbidity, and to manufacture a highly thermally conductive ceramic multilayer wiring board that takes advantage of the characteristics of aluminum nitride. I can do it.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the holding time for binder removal and the amount of carbon after binder removal in the present invention, and Figure 2 is a diagram showing the relationship between the holding time for binder removal and the thermal conductivity of the obtained sintered body. It is. Mourning drawing holding time (118 minutes) 悴图侃 Poem M藺 (KI藺) Procedural amendment (indication of self-inflicted case 1988 Patent application No. 313648 Title of invention Case for a person who amends the manufacturing method of an aluminum nitride multilayer substrate) Relationship Patent applicant address 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Name (50
8) The statements in the "Detailed Description of the Invention" column of the statement of contents of the Hitachi Metals Co., Ltd. amendment shall be amended one after another. 1, page 3, line 12 (7) rVIAJ r
Correct to. 2) Change “diethylene glycol” on page 8, line 14 to “n
-butyl carpitol acetate”. 3. Delete "After that, add butylcarpitol acetate to adjust the viscosity" in lines 16-17 of the same page. that's all

Claims (2)

[Claims] (1) Mix aluminum nitride powder with a sintering aid and an organic binder to prepare a green sheet, print a conductor such as tungsten on it to form the desired wiring pattern, and then stack the sheets. A method for producing an aluminum nitride multilayer substrate, which comprises removing the binder and sintering in a mixed atmosphere of nitrogen, hydrogen, and water vapor. (2) In the manufacturing method according to claim 1,
The partial pressure ratio of water vapor and hydrogen in the above mixed atmosphere is 0.1 to 1
A method for manufacturing an aluminum nitride multilayer substrate, characterized in that: