CN105801127A - Method for preparing high-thermal-conductivity aluminum nitride ceramic substrate for integrated circuit package - Google Patents

Abstract

The invention discloses a method for preparing an aluminum nitride ceramic substrate with high thermal conductivity for integrated circuit packaging. The steps are: (1) firstly take anhydrous lithium carbonate and anhydrous yttrium oxide and put them in a muffle furnace to synthesize yttrium lithium oxide, and then Through wet ball milling, slurry is made; (2) after ball milling, the slurry is put into a dryer for drying, and the dried material is screened to obtain yttrium lithium oxide powder; (3) according to mass percentage, lithium acid Put the yttrium, calcium fluoride and AlN powders in an anhydrous ethanol medium, and ball mill for 24 hours to make a slurry; (4) put the ball milled slurry into a dryer for drying, and screen the dried dry material to obtain a mixed powder; (5) dry-press and static-press the obtained powder to obtain a plain embryo; (6) place the plain embryo in a high-temperature nitrogen furnace, in a nitrogen and hydrogen atmosphere, heat up to 1450 ° C, sinter and keep it warm for 1 hour, Then the temperature was raised to 1735° C., sintered and kept for 8 hours, and then cooled to room temperature to obtain an AlN ceramic substrate with high thermal conductivity. The AlN ceramic substrate prepared by the method has high thermal conductivity, compact structure, fine grains and uniform distribution.

Description

Preparation method of high thermal conductivity aluminum nitride ceramic substrate for integrated circuit packaging

technical field

The technology of the invention relates to the field of nitride ceramics, in particular to a method for preparing an aluminum nitride ceramic substrate with high thermal conductivity for integrated circuit packaging.

Background technique

Most of the substrates of existing integrated circuits use AlN aluminum nitride substrates and AlN ceramic substrates, which cannot meet the needs of the development of existing electronic power devices. Therefore, improving the heat dissipation performance of AlN aluminum nitride substrates and AlN ceramic substrates makes The ability of chips to work at normal temperatures has become an urgent problem to be solved.

AlN aluminum nitride substrates and AlN ceramic substrates are covalently bonded compounds with small self-diffusion coefficients and are difficult to sinter by themselves. In order to improve the compactness of the AlN substrate, it is generally used to add sintering aids for synergistic sintering. The sintering aids and alumina form a suitable liquid phase distribution at a lower temperature, which greatly promotes the particle rearrangement and mass transfer process, and the AlN ceramics are completed. densification. When the sintering aid is usually used in representative AlN ceramics for integrated circuit packaging, the sintering temperature of the AlN ceramic is high, the energy consumption is high, the pass rate is low, and the loss of production equipment is serious; in addition, the sintering aid contained in Oxygen will increase the content of lattice oxygen at high temperature and hinder the improvement of thermal conductivity. Therefore, reducing the sintering temperature of AlN ceramics is one of the important research directions for the preparation of AlN ceramics for integrated circuit packaging.

During the sintering process of AlN ceramic substrates, different proportions of mixed reducing atmosphere not only affect the sintering of the ceramic substrate itself, but also affect the sintering effect of various additives when sintering the ceramic substrate. In the late sintering stage of the ceramic substrate, the isolated pores in the green body gradually decrease, and the pressure increases, which gradually offsets the surface tension as the driving force of sintering, and the sintering densification process tends to be slow. When the AlN ceramic substrate is sintered in a hydrogen atmosphere, because the hydrogen atom has a small radius, it is easy to diffuse, which is beneficial to the elimination of the pores of the AlN ceramic and improves the thermal conductivity. However, when the AlN ceramic substrate is sintered in a hydrogen atmosphere, if the ratio of hydrogen to nitrogen is too large, it will not only increase the sintering cost, but also fail to promote the densification of pressureless sintered aluminum nitride ceramics due to the reduction of alumina and sintering aids. It is also not conducive to improving the thermal conductivity of aluminum nitride ceramics. At the same time, the reduction reaction of alumina and sintering aids is carried out gradually from the outside to the inside. If the internal and external shrinkage of the sintered body of aluminum nitride ceramics is inconsistent, the surface of aluminum nitride ceramics will be cracked in a large area.

Contents of the invention

Aiming at the technical problems to be solved in the above-mentioned prior art, the present invention provides a method for preparing an aluminum nitride ceramic substrate with high thermal conductivity for integrated circuit packaging. The AlN ceramic substrate prepared by the method has high thermal conductivity and a compact structure. , AlN ceramic substrate with fine grains and uniform distribution.

In order to achieve the above object, the present invention adopts the following technical solutions

A method for preparing a high thermal conductivity aluminum nitride ceramic substrate for integrated circuit packaging, characterized in that the method has the following specific steps:

(1). According to the mass percentage, take 24.67% of anhydrous lithium carbonate and 75.33% of anhydrous yttrium oxide and mix them in a muffle furnace, raise the temperature to 1400°C, keep it warm for 3 to 4 hours, and take out the synthetic yttrium lithium oxide after cooling , placed in absolute ethanol as a medium for wet ball milling for 6 hours to make a mixed slurry;

(2). Put the mixed slurry after ball milling into a dryer, set the temperature at 80°C for drying treatment, and the drying time is 4 hours. The dried material after drying is screened through a 100-mesh sieve to obtain yttrium lithium oxide powder ;

(3). According to the mass percentage, take 4% of yttrium lithium oxide, 0.5% of calcium fluoride and 95.5% of AlN powder and put them into an anhydrous ethanol medium for ball milling for 24 hours to make a mixed slurry;

(4). Put the mixed slurry after ball milling into a dryer, set a temperature of 80°C for drying treatment, and the drying time is 4 hours. The dried material after drying is screened through a 100-mesh sieve to obtain a mixed powder. The particle size is 2-10μm;

(5). The obtained powder is then dry-pressed and static-pressed to obtain a plain embryo of the desired shape, wherein,

The dry pressing and static pressing molding are as follows: put the obtained mixed powder into the mold, apply a pressure between 90-100Mpa, keep the pressure for 20-30s, and then apply a pressure between 180-200Mpa, and press the static pressure for 70-90s , demolded, and made into a plain embryo of the desired shape;

(6). Place the plain blank of the desired shape in a high-temperature nitrogen furnace, and protect it in a mixed atmosphere of nitrogen and hydrogen, where the flow rate of hydrogen accounts for 10-20% of the total flow rate of the mixed gas, and the temperature rises at a rate of 3-5°C/min. Raise the temperature to 1420-1450°C, sinter and hold for 0.5-1 hour, then raise the temperature to 1720-1735°C at the same heating rate, sinter and hold for 2-8 hours, and then cool to room temperature at the same cooling rate to obtain AlN with high thermal conductivity Ceramic substrate.

The selected particle size of the AlN powder in the above step (2) is 2-10 μm.

Compared with the prior art, the present invention has the following significant advantages:

The present invention is obtained by using appropriate amount of yttrium lithium and calcium fluoride as sintering aids, changing the proportion of hydrogen in the sintering atmosphere, and fully sintering the preparation; the sintering aids first react with alumina to form a liquid phase to promote sintering, and volatilize at a certain temperature to reduce The homogenization of the liquid phase can promote the densification of AlN ceramics; the method controls the proportion of hydrogen in the sintering process, which not only satisfies the need to reduce the oxygen content of the lattice in the reducing atmosphere, but also ensures that the surface of the AlN ceramic sintered body does not crack, and can also reduce production. Cost; this method is not only suitable for small-area AlN ceramic sintering preparation in the laboratory, but also suitable for large-area AlN ceramic sintering preparation.

detailed description

Specific embodiments of the present invention are described below.

Example 1

A method for preparing a high thermal conductivity aluminum nitride ceramic substrate for integrated circuit packaging The specific preparation process and steps are as follows:

(1). First, mix 24.67% anhydrous lithium carbonate and 75.33% anhydrous yttrium oxide in a muffle furnace according to the mass percentage, heat up to 1400°C, keep warm for 4 hours, cool and take out the synthetic yttrium lithium oxide, put Wet ball milling in absolute ethanol as medium for 6h;

(2). Put the mixed slurry after ball milling into a dryer, set the temperature at 80°C for drying treatment, and the drying time is 4 hours. Screen the dried material through a 100-mesh sieve to obtain yttrium lithium oxide powder;

(3). According to the mass percentage, take 4% of yttrium lithium oxide, 0.5% of calcium fluoride and 95.5% of AlN powder and put them into anhydrous ethanol medium for wet ball milling for 24 hours to make a mixed slurry;

(4). Put the mixed slurry after ball milling into the dryer, set the temperature at 80°C for drying treatment, and the drying time is 4 hours. The dried material after drying is screened through a 100-mesh sieve to make a mixed powder , whose particle size is 10 μm ;

(5). The mixed powder obtained in step (4) is dry-pressed and static-pressed to obtain a blank of the desired shape, wherein the dry-pressed and static-pressed molding is as follows: the resulting mixed powder is put into a mold , apply a pressure between 100Mpa, keep the pressure for 30s, then apply a pressure between 200Mpa, static pressure for 90s, demould, and make the blank of the desired shape;

(6). Place the plain blank of the desired shape in a high-temperature nitrogen furnace, and in a mixed atmosphere of nitrogen and hydrogen, where the hydrogen flow accounts for 20% of the total flow of the mixed gas, heat up to 1450°C, sintering and holding for 1 hour, then raising the temperature to 1735°C at the same heating rate, sintering and holding for 6 hours, and then cooling to room temperature at the same cooling rate to obtain an AlN ceramic substrate with high thermal conductivity.

Performance testing of the AlN ceramic substrate prepared by sintering:

Observing the AlN ceramic substrate under a scanning electron microscope, its microstructure is dense, its porosity is low, and its grains are fine and evenly distributed. The AlN ceramic substrate was tested with a thermal conductivity meter, and its thermal conductivity was measured to be 103W·m ^-1 ·k ^-1 .

Claims (2)

1. A method for preparing a high thermal conductivity aluminum nitride ceramic substrate for integrated circuit packaging, characterized in that, the specific steps of the method are as follows: According to the mass percentage, mix 24.67% anhydrous lithium carbonate and 75.33% anhydrous yttrium oxide, put them in a muffle furnace, raise the temperature to 1400°C, keep it warm for 3-4 hours, cool down and take out the synthetic yttrium lithium oxide, put it in a dry Wet ball milling in water and ethanol for 6 hours to make a mixed slurry; Put the mixed slurry after ball milling into a dryer, set the temperature at 80°C for drying treatment, and the drying time is 4 hours. The dried material after drying is screened through a 100-mesh sieve to obtain yttrium lithium oxide powder; According to the mass percentage, take 4% of yttrium lithium oxide, 0.5% of calcium fluoride and 95.5% of AlN powder and put them into an anhydrous ethanol medium for ball milling for 24 hours to make a mixed slurry; Put the mixed slurry after ball milling into a dryer, set the temperature at 80°C for drying treatment, and the drying time is 4 hours. The dried material after drying is screened through a 100-mesh sieve to obtain a mixed powder with a particle size of 2 -10μm; The obtained powder is then dry-pressed and static-pressed to obtain a plain embryo of the desired shape, wherein, The dry pressing and static pressing molding are as follows: put the obtained mixed powder into the mold, apply a pressure between 90-100Mpa, keep the pressure for 20-30s, and then apply a pressure between 180-200Mpa, and press the static pressure for 70-90s , demolded, and made into a plain embryo of the desired shape; Place the plain embryo of the desired shape in a high-temperature nitrogen furnace, and in a mixed atmosphere of nitrogen and hydrogen, where the hydrogen flow accounts for 10-20% of the total flow of the mixed gas, the temperature is raised to 1420 at a heating rate of 3-5°C/min. ~1450°C, sintering and holding for 0.5~1 hour, then heating up to 1720~1735°C at the same heating rate, sintering and holding for 2-8h, and then cooling to room temperature at the same cooling rate to obtain AlN ceramic substrate with high thermal conductivity. 2. the preparation method of a kind of high thermal conductivity aluminum nitride ceramic substrate for integrated circuit packaging according to claim 1, is characterized in that, the selected particle size of the AlN powder described in the above-mentioned step (2) is 2- 10 μm.