KR102171884B1 - Formation method of silver films for advanced electrical properties by using aerosol deposition process - Google Patents

Abstract

A method of forming a silver film for improved electrical properties using an aerosol deposition process is disclosed. A room temperature aerosol deposition (AD) process was used to form a silver thick film for high-efficiency metallization that can be applied to reduce resistance-capacity delay and increase signal propagation speed in integrated circuits. In order to obtain a more improved performance than the aerosol-deposited silver film reported in the previous study, the experimental parameters (nozzle orifice size and gas consumption) that can directly affect the electrical resistivity were first optimized. A suitable small orifice size was chosen to promote the reduction in electrical resistivity by activating the osmotic effect and creating relatively more conductive channels. In addition, high gas consumption reduces the electrical resistivity of the silver film, thereby forming many metal clusters. Using the experimental parameters showing the lowest resistance, a silver thick film was formed through the AD process and its properties were analyzed. The results of X-ray diffraction confirmed that the silver particles corrected the collision-induced plastic deformation. As the film thickness became thicker to 12 scans, the collided particles filled the coarse alumina substrate. After 12 scans, the silver film was densified due to severe plastic deformation of the deposited-silver particles. Therefore, the growth mechanism suggested that most of the silver particles in the initial deposition step contribute to mechanical interlocking, and the subsequent particles cause film densification.

Description

Formation method of silver films for advanced electrical properties by using aerosol deposition process

The present invention relates to a method of forming a silver film for improved electrical properties using an aerosol deposition process.

This study was carried out by a research grant from Kwangwoon University in 2018, and this result was funded by the Korean Government (MSIP; Ministry of Science, ICT and Future Planning) and the Korea Research Foundation (NRF) (Project No. 2017R1C1B5017013) Supported by the Advanced Track in Power Semiconductor Technology for Industrial and Electric Vehicles (Task Number 20174010201290).

1. Background technology

Thick film technology has recently attracted attention in the electrical and electronic field because it improves the durability and performance of display devices, different sensors, hybrid circuits, and multilayer ceramic substrates. It can be used to manufacture devices that are more economical and reliable compared to thin film technology. Research on the thick film manufacturing process and its versatile application has been extensively carried out in many industrial fields. Among many thick film applications, metallization for faster active components is widely used to mount integrated circuits and reduce the electrical resistance due to metal interconnects. In order to achieve high performance for active components, it is essential to reduce signal propagation time and crosstalk at the interconnect level, known to affect the performance of integrated circuits. Signal propagation time is highly related to passive components, such as resistive components, which can partially affect the resistance-capacitance (RC) delay. Therefore, low electrical resistivity between metal connection lines is naturally required to implement better devices, and the manufacturing process with high deposition rate is also a thick film metallization technology at a thickness of several µm. ) Should be carefully considered. For low electrical resistivity and faster signal transmission, silver is used for extremely low electrical resistance (bulk silver: ~1.59 μΩ·cm) and against corrosion and oxidation. It is considered a representative metal material because of its high electrical resistance.

The screen printing process is the most widely used processing method for metallization due to its high throughput for industrialization and cost-efficiency. It is widely used to fabricate the optimum front-side metallization of high-efficiency solar cells. However, despite being a widely used process, it has some serious drawbacks:

(1) Base materials such as haze removers and solvents can threaten the environment and human health;

(2) This process is quite complex and time-consuming; And

(3) It takes a lot of time and a high level of know-how to adjust the specific gravity of the solvent and print the required pattern.

Therefore, a new method that enables simpler and more reliable manufacturing is required for metallization.

Here, in order to overcome the problem of the conventional process described above, we propose a new powder-spray-coating method, called an aerosol deposition (AD) process. The AD process has noticeable advantages compared to the screen printing method, a 23°C room temperature process, a simple eco-friendly procedure, and thick films. ) For a high deposition rate (high deposition rate). In previous studies, silver metallization for a microwave device was carefully attempted through the AD process, achieving a resistivity of 13.4 to 17.5 μΩ·cm. However, these aerosol-deposited silver films were prepared using fixed experimental parameters, and optimized conditions for low resistance were not investigated, and the growth mechanism was also ambiguous.

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An object of the present invention to solve the above problem is to provide a method of forming a silver film for improved electrical properties using an aerosol deposition (AD) process.

까지 변경하여, 최고의 금속배선 성능(best metallization performance)을 찾았다. 최소 전기 저항도(minimum resistivity)을 보이는 실험 파라미터에 기초하여, 막 두께(film thickness)의 증분에 따라 전기 저항도의 변동(variation in electrical resistivity)이 측정되고 분석되었다. 또한, 은 필름의 성장 매커니즘이 그 미세구조를 관찰함으로써 결정되었다.The aim of our study was to evaluate the optimized methods to achieve low resistivity by forming aerosol-deposited silver films and changing the experimental parameters. While a silver film is formed using the AD process, along with consumption of the injection gas, the orifice size of the powder spray nozzle has been increased from 0.64 to 4.0.

By changing to, the best metallization performance was found. Based on the experimental parameters showing minimum resistivity, the variation in electrical resistivity with increments of film thickness was measured and analyzed. In addition, the growth mechanism of the silver film was determined by observing its microstructure.

상이한 오리피스 크기 중 어느 하나의 노즐의 오리피스를 사용하며, 에어로졸-증착 은 후막이 형성되고,
상기 단계 (b)는 4.0

의 노즐로부터의 은 필름의 전기 저항도가 최고치를 나타낸 반면, 1.0

의 노즐 면적으로부터의 전기 저항도가 최저값을 보였으며, 입자 속도가 캐리어 가스의 증가 및 노즐의 오리피스 크기의 감소에 비례하며, 노즐의 오리피스 면적(nozzle orifice area)과 전기 저항도(resistivity)에 비례한다.To achieve the object of the present invention, a method of forming a silver film for improved electrical properties using an aerosol deposition process is: (a) powder spray by an aerosol deposition (AD) process using an AD device at room temperature on a substrate. Forming a thick metal film of aerosol-deposited silver film by depositing aerosol-deposited silver powders sprayed from the powder spray nozzle using a coating method; And (b) analyzing the orifice size and gas consumption of the nozzle for electrical resistivity using a 4-10 L/min gas flow rate controlled by the flow controller,
In the step (a), the orifice of the nozzle is 4.0, 2.25, 1.0 and 0.64

Using the orifice of any one of the different orifice sizes, the aerosol-deposited silver thick film is formed,
The step (b) is 4.0

While the electrical resistivity of the silver film from the nozzle of was the highest, 1.0

The electrical resistivity from the nozzle area of was the lowest value, and the particle velocity was proportional to the increase of the carrier gas and the decrease of the nozzle orifice size, and proportional to the nozzle orifice area and the resistivity of the nozzle. do.

The substrate is an alumina substrate.

The metal thick film is characterized in that it is a silver thick film for metal wiring.

The AD device has an AD device having different nozzle orifice sizes, the AD device has an aerosol chamber and a deposition chamber, the aerosol chamber has a flow controller capable of controlling the gas flow rate,

As a starting powder for the aerosol deposition (AD) process, silver powder having the highest electrical conductivity among metals was used,

The silver powder is loaded in the deposition chamber, and helium gas is used as a carrier gas having a gas flow rate of 4-10 L/min, and the aerosol chamber is directly connected to the flow controller capable of controlling the gas flow rate,

When the carrier gas is supplied to the aerosol chamber, the silver powder is aerosolized by mixing and stirring using the carrier gas, and the aerosolized silver powder is transferred to the slit nozzle by the helium gas injected through the Teflon tube. And then sprayed into the deposition chamber.

Silver powder having an average particle diameter of 1.1㎛ is used as the silver powder.

상이한 오리피스 크기 중 어느 하나의 노즐의 오리피스를 사용하며, 에어로졸-증착 은 후막이 형성된다. In the step (a), the orifice of the nozzle is 4.0, 2.25, 1.0 and 0.64

Using the orifice of the nozzle of either of the different orifice sizes, an aerosol-deposited silver thick film is formed.

The step (b) is

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의 극도로 작은 오리피스 크기로부터의 은 필름의 전기 저항도는 1.0

의 오리피스 크기로부터의 것보다 높았으며, Unlike expected, 0.64

The electrical resistivity of the silver film from an extremely small orifice size of 1.0

Was higher than that from the orifice size of,

의 노즐의 오리피스를 사용할 때, 입자 속도는 500 내지 650 m/s 이었으며, 4.0

의 노즐의 오리피스를 사용하면 430m/s 이였으며, 이 조건은 더 많은 전도 채널을 형성할 수 있으며, 채널의 개수는 은 필름의 전기 저항도를 상당히 감소시킬 수 있으며, 상대적으로 작은 노즐의 오리피스 직경으로부터 조성된 밀한(dense) 은 필름이 전기 저항도의 감소하였을지라도, 10 L/min of carrier gas and 1

When using the orifice of the nozzle of, the particle velocity was 500 to 650 m/s, and 4.0

Using the orifice of the nozzle was 430 m/s, this condition can form more conductive channels, the number of channels can significantly reduce the electrical resistivity of the silver film, and the orifice diameter of the relatively small nozzle Even though the dense silver film formed from a decrease in electrical resistivity,

의 극도로 작은 오리피스를 사용한 은 필름은 상기 기판에 충돌되는 입자들의 높은 충격에 기인하여 표면 열화 및 에칭 효과를 가져올 수 있으므로, 결정의 전위(dislocation)를 야기한다. 0.64

The silver film using an extremely small orifice of may cause surface deterioration and etching effect due to the high impact of particles impinging on the substrate, thereby causing dislocation of crystals.

의 오리피스의 면적을 사용한 금속배선(metallization)을 위한 에어로졸-증착 은 필름을 형성하였으며, 상기 기판에 증착된 은 필름의 전기 저항도는

Ω·㎝ 으로 측정됐다. In the step (a), the orifice size of the nozzle is 1.0

An aerosol-deposited silver film was formed for metallization using the orifice area of, and the electrical resistivity of the silver film deposited on the substrate was

It was measured in Ω·cm.

To verify the effect of gas consumption on electrical resistivity of silver films deposited on the substrate, the gas consumption, which can be measured by a flow controller, is 4-10 L It was controlled as /min, and electrical resistivity decreased with increasing gas consumption,

In the case of gas consumption of 4L/min, the electrical resistivity was the highest at 64x10 ^-5 Ω·cm.

When the gas consumption was more than 7L/min, the saturation value of 9x10 ^-6 Ω·cm was finally approached.

The method includes the steps of: (c) measuring RMS roughness according to the thickness of the silver film deposited on the alumina substrate and the orifice area of the nozzle using a surface profiler; And

(d) further comprising the step of analyzing the X-ray diffraction (XRD; PANytical X'Pert Pro) pattern of the deposited silver film to check and compare the crystalinity of the raw powder and the deposited silver film. do.

노즐의 오리피스에서 상대적으로 노즐의 작은 오리피스 크기(small orifice size)와 4~10 L/min 가스 유량에서 상대적으로 많은 가스 소모량(high gas consumption)은 전기 저항도(electrical resistivity)의 감소에 크게 연관되며, 이 파라미터들이 삼투 효과를 활성화시키고 은 입자들의 미세접촉(microcontacts between the silver particles)을 증가시키며, AD 프로세스 동안 메짐성 있는 은 입자들에 대한 소성 변형이 XRD에서의 피크 시프트의 크기를 관측되었으며, 은 입자들이 기판 상에 축적됨에 따라 표면 산란과 그레인 경계 산란 모두가 감소되어 상기 전기 저항도는 필름 두께에 따라 점차 감소된다. In the AD device, 4.0, 2.25, 1.0 and 0.64

The relatively small orifice size of the nozzle at the orifice of the nozzle and the relatively high gas consumption at the gas flow rate of 4 to 10 L/min are highly related to the decrease in electrical resistivity. , These parameters activate the osmotic effect and increase microcontacts between the silver particles, and the plastic deformation of the brittle silver particles during the AD process observed the magnitude of the peak shift in XRD, As silver particles accumulate on the substrate, both surface scattering and grain boundary scattering are reduced, so that the electrical resistivity gradually decreases with the film thickness.

As the number of 4, 8, 12 scans increases, the more the collision energy of subsequent particles on the substrate is transferred to the deposited silver film, the more defects at grain boundaries gradually become. It is reduced, and the porous silver film is converted into a relatively dense structure, resulting in relatively low electrical resistivity due to the formation of relatively many clusters.

In order to investigate the growth process of silver films deposited on the aerosol on the substrate, the film thickness according to each scan number from the 2nd to the 100th scan was first measured each time. ,

When the AD process was performed up to the 16th scan, as a result of obtaining and examining the surface and cross-sectional SEM images of the silver film, there was no change in the thickness of the silver film.

The variation of film thickness with respect to the number of scans (Δfilm thickness=Δscan number) had a very low value of approximately 0.027, which means that the average deposited thickness per scan was 0.027 µm in the initial AD stage. ,

On the other hand, the deposition rate for every scan increased after more than 12 scans, in this case, the value of Δfilm thickness=Δscan number was 0.123, which was more than 4 times the value of the initial deposition rate.

When most of the rough surface of the alumina substrate was filled after 12 scans, the subsequent silver particles were successively accumulated on the deposited silver film based on the hammering effect, because the silver film was deposited by the same mechanism after 12 scans. , The film thickness was increased as a linear function, and an aerosol-deposited silver thick film was processed at room temperature for metallization.

The method of forming a silver film for improved electrical properties using the aerosol deposition process of the present invention uses a 23° C. room temperature aerosol deposition (AD) process to reduce resistance-capacitance delay and signal Silver thick films for high-efficiency metallization that can be applied to increase the signal propagation speed were formed. In order to obtain better performance than the aerosol-deposited silver films reported in previous studies, the experimental parameters (nozzle orifice size and gas consumption) that can directly affect the electrical resistivity are determined. It was optimized first. A small orifice size of a suitable nozzle was chosen to facilitate the reduction in electrical resistivity by activating the percolation effect and creating relatively more conduction channels. In addition, relatively high gas consumption reduces the electrical resistivity of silver films, thereby forming relatively many metal clusters. Using the experimental parameters showing the lowest resistivity, silver thick films were formed through the AD process and their properties were analyzed. The results of X-ray diffraction confirmed that the silver particles became collision-induced plastic deformation. As the film thickness increased to 12 scans, the colliding particles filled the coarse alumina substrate. After 12 scans, the silver film was densified due to severe plastic deformation of the deposited silver particles. Therefore, the growth mechanism suggested that most of the silver particles in the initial deposition step contribute to mechanical interlocking, and the subsequent particles cause film densification.

)에서 저항도(resistivity) 및 노즐의 오리피스 면적에 따른 표면 RMS 거칠기(surface RMS roughness)의 변화를 보인 그림이다.
도 3은 가스 소비(gas consumption)의 함수로서 전기 저항도(resistivity) 변화시킴을 보인 그림(가스 소비가 4로부터 10 L/min으로 증가)이다.
도 4는 출발 파우더(powder) 및 증착된 실버 필름의 XRD 패턴의 그림이다. 삽입 된 그림은 76-79°의 2θ 범위를 갖는 XRD 패턴의 확대를 보여준다.
도 5는 1.0

의 노즐 면적(nozzle area)과 10L/min 가스 소비량 사용시에, 에어로졸 증착된 은 필름(silver film)에 대한 막 두께에 대한 전기 저항도(resistivity on film thickness)의 의존성을 보인 그림이다.
도 6은 1.0

의 노즐 면적과 10L/min 가스 소비량 사용시에, 필름 두께(film thickness)와 스캐닝 번호(scanning number)의 관계를 보인 그림이다.
도 7은 (컬러 온라인) SEM 현미경 사진을 관찰한 5 가지 유형의 스캐닝 번호를 나타낸 바와 같이, 분류된 은 필름(silver film)의 성장 메커니즘을 보인 그림이다. (a, f) 4 회 스캔, (b, g) 8 회 스캔, (c, h) 12 회 스캔, (d, i) 16 회 스캔 및 (e, k) 60 회 스캔.1 is a diagram showing (a) a plane-SEM image of silver powder determined by a plan view and (b) a particle size distribution.
Figure 2 shows the different orifice areas (4.0, 2.25, 1.0 and 0.64) of the nozzle under a (color online) fixed gas consumption of 8 L/min.

) Shows the change in surface RMS roughness according to the resistance and the orifice area of the nozzle.
3 is a diagram showing the change in electrical resistivity as a function of gas consumption (gas consumption increases from 4 to 10 L/min).
4 is an illustration of the XRD pattern of the starting powder and the deposited silver film. The inserted figure shows the magnification of the XRD pattern with a 2θ range of 76-79°.
Figure 5 is 1.0

The figure shows the dependence of the resistivity on film thickness on the aerosol-deposited silver film when using the nozzle area and 10L/min gas consumption.
Figure 6 is 1.0

The figure shows the relationship between the film thickness and the scanning number when using the nozzle area and the gas consumption of 10L/min.
7 is a diagram showing the growth mechanism of the sorted silver film, as showing the five types of scanning numbers observed in the (color online) SEM micrograph. (a, f) 4 scans, (b, g) 8 scans, (c, h) 12 scans, (d, i) 16 scans and (e, k) 60 scans.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2. Experiment method

The method of forming a silver film for improved electrical properties using the aerosol deposition process of the present invention

)를 갖는 AD 장치를 구비하며, 상기 AD 장치는 에어로졸 챔버와 증착 챔버를 구비하며, 상기 에어로졸 챔버는 가스 유량을 제어할 수 있는 유량 제어기(mass flow controller)를 구비하며, 알루미나 기판 상에 23℃ 실온에서 후막(thick film)에 대한 높은 증착률을 갖는 에어로졸 증착(AD) 프로세스에 의해 파우더 스프레이 코팅 방법을 사용하여 파우더 스프레이 노즐로부터 분사된 에어로졸 은 파우더들이 증착되어 에어로졸 증착된 은 필름으로 된 금속 후막(은 후막, silver thick film)을 형성하는 단계; 및 (a) Different nozzle orifice sizes (4.0, 2.25, 1.0 and 0.64

), the AD device includes an aerosol chamber and a deposition chamber, the aerosol chamber includes a mass flow controller capable of controlling a gas flow rate, and 23° C. on an alumina substrate A metal thick film made of aerosol-deposited silver film by depositing aerosol silver powders sprayed from a powder spray nozzle using a powder spray coating method by an aerosol deposition (AD) process that has a high deposition rate for thick films at room temperature. Forming a (silver thick film); And

상이한 오리피스 크기 중 어느 하나의 노즐의 오리피스를 사용하며, 에어로졸-증착 은 후막이 형성되고,
상기 단계 (b)는 4.0

의 노즐로부터의 은 필름의 전기 저항도가 최고치를 나타낸 반면, 1.0

의 노즐 면적으로부터의 전기 저항도가 최저값을 보였으며, 입자 속도가 캐리어 가스의 증가 및 노즐의 오리피스 크기의 감소에 비례하며, 노즐의 오리피스 면적(nozzle orifice area)과 전기 저항도(resistivity)에 비례한다. (b) Analyzing the size of nozzle orifice and gas consumption of the nozzle with respect to electrical resistivity using the 4-10 L/min gas flow rate controlled by the flow controller. Including,
In the step (a), the orifice of the nozzle is 4.0, 2.25, 1.0 and 0.64

Using the orifice of any one of the different orifice sizes, the aerosol-deposited silver thick film is formed,
The step (b) is 4.0

While the electrical resistivity of the silver film from the nozzle of was the highest, 1.0

The electrical resistivity from the nozzle area of was the lowest value, and the particle velocity was proportional to the increase of the carrier gas and the decrease of the nozzle orifice size, and proportional to the nozzle orifice area and the resistivity of the nozzle. do.

The substrate has a rougher surface than a glass substrate and uses an alumina substrate having better adhesion. The alumina substrate was chosen as the substrate layer, which is basically a rough surface that can process dense metal films by using the enhanced adhesion between the metal film and the substrate. (rough surface). Metal films deposited on a glass substrate by the AD process are known to have worse adhesion on an alumina substrate, which ultimately results in the detachment of the metal film from the glass substrate.

At 23° C. room temperature, as a starting powder for the aerosol deposition (AD) process, silver powder (Kojundo Chemical Laboratory AGE09PB) having the highest electrical conductivity among any metals was prepared.

The AD device is provided with nozzles having different orifice sizes of different nozzles, and the AD device is mainly provided with an aerosol chamber and a deposition chamber, and the aerosol chamber is a flow controller capable of controlling the gas flow rate. (mass flow controller) is provided.

The prepared silver powder was first loaded into the aerosol chamber. The aerosol chamber was directly connected to a mass flow controller capable of controlling the gas flow rate. When a carrier gas was supplied to the aerosol chamber, the silver powders were aerosolized by mixing and stirring using a carrier gas. Helium gas with a purity of 99.99% was used as the carrier gas. Experiments were conducted using various gas flow rates (4-10 L/min) by a flow controller to investigate the effect of gas consumption on electrical resistivity. The aerosolized silver powder was transferred to a slit nozzle by helium gas injected through a Teflon tube, and sprayed into the deposition chamber. Prior to generating the aerosol, the deposition chamber was preempted with a rotary pump and mechanical booster pump to remove air resistance from the accelerated aerosol.

)의 노즐이 사용되었다. 슬릿 노즐이 에어로졸 흐름을 수렴시켜 고속으로 탈출가능한 구조를 갖기 때문에, 에어로졸은 수 백 m/s로 가속되어, 미리 설계된 X-Y 축에 대응하는 알루미나 기판의 증착 영역에 도달하고 축적되었다.In general, the orifice area of the nozzle can have a significant effect on the internal microstructure and surface of an aerosol-deposited film, which is known to be related to its electrical properties. Therefore, in the orifice of the nozzle, different orifice sizes (4.0, 2.25, 1.0 and 0.64

) Nozzles were used. Since the slit nozzle has a structure capable of escaping at high speed by converging the aerosol flow, the aerosol was accelerated to several hundred m/s, reaching and accumulating the deposition area of the alumina substrate corresponding to the predesigned XY axis.

The particle size distribution of the silver powder was measured with a particle size analyzer (PSA). To investigate the conditions of the starting silver powder that may affect aerosol formation, the initial powder morphology was observed by scanning an electron microscope (FE-SEM; Hitachi S-470). In addition, the surface and internal microstructure of the aerosol-deposited silver film were investigated by FE-SEM.

Electrical resistivity was measured with a four-point probe while varying the orifice area, gas consumption, and film thickness of the nozzle. Using a surface profiler (Ambios XP-1), the thickness of the silver film deposited on the alumina substrate and the RMS roughness according to the orifice area of the nozzle were measured. In addition, the X-ray diffraction (XRD; PANytical X'Pert Pro) pattern of the film was analyzed to confirm and compare the crystalinity of the raw powder and the deposited silver film.

3. Results

3.1 Effect of nozzle orifice size and gas consumption on electrical resistivity

,

및

의 값은 각각 0.595, 1.016 및 1.823 ㎛였다.

으로부터 계산된 파라미터 스팬(parameter span)은 에어로졸화에 적절한 값(1.356)이었는데, 이는 은 입자들(silver particles)이 유사한 평균 직경을 가짐을 나타낸다. 더욱이, 대부분의 은 입자들은 원-형 형태를 가지는 것으로 관측되었으며, 뭉쳐진 입자들은 거의 없었다. AD 프로세스에서 고품질의 고운 에어로졸을 생성하기 위해, 충분한 양의 독립적 단위 입자(primary particle)를 갖는 것이 50%의 누적 체적의 값보다 더 중요하였다. 그러므로, 균일하고 원형의 형태를 갖는 파우더 구성은 비균일 형태의 파우더보다 더 많은 에어로졸을 생성할 수 있으며, 이는 높은 증착률(high deposition rate)에 중요한 요소이다.1(a) shows the initial form of silver powder having an average particle diameter of ~1.1㎛. For cumulative volumes of 10, 50 and 90%

,

And

The values of were 0.595, 1.016 and 1.823 μm, respectively.

The parameter span calculated from was a value suitable for aerosolization (1.356), indicating that the silver particles have similar average diameters. Moreover, most of the silver particles were observed to have a circular-shape, and there were few agglomerated particles. In order to generate a high quality fine aerosol in the AD process, having a sufficient amount of independent primary particles was more important than the value of 50% cumulative volume. Therefore, a powder composition having a uniform and circular shape can generate more aerosols than a powder having a non-uniform shape, which is an important factor for a high deposition rate.

)를 갖는 노즐을 사용하여 에어로졸-증착 은 후막을 형성하였다. 4.0

의 노즐로부터의 은 필름의 전기 저항이 최고치를 나타낸 반면, 1.0

의 노즐의 오리피스의 면적으로부터는 전기 저항도가 최저값을 갖는다. 예상과 달리, 0.64

의 오리피스 크기로부터의 은 필름의 전기 저항도는 1.0

의 오리피스 크기로부터의 것보다 높았다. 또한, 노즐의 오리피스 면적에 따른 RMS 거칠기(RMS roughness)가 표면 프로파일러로써 측정되었다. 도 2에 도시된 바와 같이, 이는 전기 저항도의 변동 경향에 대응하였다.To investigate the effect of the nozzle's orifice area on the electrical resistivity, we used the different nozzle's orifice sizes (4.0, 2.25, 1.0 and 0.64) at the nozzle's orifice.

) To form an aerosol-deposited silver thick film. 4.0

While the electrical resistance of the silver film from the nozzle of was the highest, 1.0

From the area of the orifice of the nozzle of, the electrical resistivity has the lowest value. Unlike expected, 0.64

The electrical resistivity of the silver film from the orifice size of is 1.0

Was higher than that from the orifice size of. In addition, RMS roughness according to the orifice area of the nozzle was measured with a surface profiler. As shown in Fig. 2, this corresponds to the tendency of fluctuations in electrical resistivity.

의 노즐의 오리피스를 사용할 때, 입자 속도(particle velocity)는 500 내지 650 m/s인 것으로 추정되었으며, 4.0

의 노즐의 오리피스(nozzle orifice)를 사용하면 430m/s 였다. 이 조건은 상대적으로 더 많은 전도 채널(conducting channels)을 형성할 수 있으며, 채널의 개수는 은 필름의 전기 저항도(electrical resistivity of silver films)를 상당히 감소시킬 수 있다. There was a proportional relationship between the nozzle orifice area and the electrical resistivity. A rational explanation for this phenomenon is related to the plastic deformation of silver particles during collision and integration. Considering the AD mechanism, the silver particles injected from the slit nozzle have large kinetic energy due to their high velocity, and they collide strongly with the alumina substrate. If the orifice area of the slit nozzle is reduced, the velocity of the particles may have increased rapidly due to the convergent-structure nozzle, which may consequently increase the likelihood of continuous osmosis between the particles. Previous studies have reported that the particle velocity is proportional to an increase in the carrier gas and a decrease in the nozzle orifice size. Therefore, in our study 10 L/min of carrier gas and 1

When using the orifice of the nozzle of, the particle velocity was estimated to be 500 to 650 m/s, and 4.0

It was 430 m/s when the nozzle orifice of was used. This condition can form relatively more conducting channels, and the number of channels can significantly reduce the electrical resistivity of silver films.

의 극도로 작은 오리피스를 이용한 은 필름은 결정의 전위(dislocation)를 야기하였을 수 있다. 더욱이, 이러한 0.64

노즐의 오리피스 구조가 기판 상에서 입자들의 높은 충격에 기인하는 표면 열화(surface deterioration) 및 에칭 효과(etching effect)를 가져올 수 있으므로, RMS 거칠기는 도 2의 청색 선에 의해 도시된 바와 같이, 노즐의 오리피스 면적이 1

였을 때와 비교하여 약간 증가된 값을 나타냈다. 상기 전위 영역들은 금속에 있어서 가장 광범위한 결함인 것으로 잘 알려져 있으며, 따라서 심각한 소성 변형(plastic deformation)에 의한 전도 전자(conduction electrons)의 산란(scattering)이 잔여 저항도(residual resistivity)를 개선시킬 수 있다. The dense silver film created from the small nozzle's orifice diameter was 0.64, although it contributed to the reduction in electrical resistivity.

Silver films using extremely small orifices of may have caused crystal dislocation. Moreover, these 0.64

Since the orifice structure of the nozzle can bring about surface deterioration and etching effect due to high impact of particles on the substrate, the RMS roughness is as shown by the blue line in FIG. Area is 1

Compared to when was, it showed a slightly increased value. The dislocation regions are well known to be the most widespread defects in metal, so scattering of conduction electrons due to severe plastic deformation can improve residual resistivity. .

의 오리피스의 면적을 사용한 금속배선(metallization)을 위한 에어로졸-증착 은 필름을 형성하였다.As a result, from the results of the nozzle's orifice size effect, 1.0 with the best metallization performance

An aerosol-deposited silver film for metallization was formed using the area of the orifice of.

Ω·㎝로 최고치를 나타냈는데, 이는 금속배선에 부적합했다. 저항도는 가스 소모량이 높아짐에 따라 현저히 감소하였는데, 가스 소모량이 7 L/min 보다 많을 때 최종적으로 포화값

Ω·㎝에 접근하였다.To verify the effect of gas consumption on electrical resistivity of as-deposited silver films, the gas consumption, which can be measured by a flow controller, is 4-10 L/ Controlled in min. As shown in Figure 3, electrical resistivity (electrical resistivity) decreased as the gas consumption (gas consumption) increased. For gas consumption of 4 L/min, the electrical resistivity is

The highest value was displayed in Ω·cm, which was not suitable for metal wiring. The resistance decreased significantly as the gas consumption increased, but when the gas consumption was more than 7 L/min, the final saturation value

Approached to Ω·cm.

It was noted that this excessive electrical resistance is closely related to the contact area between the silver particles in the internal microstructure of the silver film. The relatively high gas flow rate implies a relatively higher collision energy of the silver particles during the AD process. When silver particles with moderately high impact energy collide with a hard substrate, they may have accumulated in an arcing or circular shape due to plastic deformation. Finally, the possibility of forming microcontacts between brittle particles can be easily raised by grouping them into clusters.

3.2 Investigation of plastic deformation and electrical resistivity using optimal experimental parameters

의 노즐 오리피스 면적과 10L/min의 가스 소모량이 고정 실험 파라미터로서 이용되었으며, 우리는 이러한 파라미터들을 사용하여 고전도성을 갖는 에어로졸-증착 은 필름을 조성하려고 하였다. Based on the above results, 1.0

The nozzle orifice area of and the gas consumption of 10 L/min were used as fixed experimental parameters, and we tried to form an aerosol-deposited silver film with high conductivity using these parameters.

4 shows the XRD pattern of raw silver powder and deposited silver film. To determine if the silver powder was subjected to plastic deformation during the AD process, we checked the local magnification of the diffraction peak 311 (inset in Fig. 4(b)). The diffraction peak 311 of the silver film shifted at a lower angle compared to the silver powder. The magnitude of the peak shift is often closely related to the presence of residual stress. As a result, it was revealed that residual stress was present in the internal structure of the silver film because the silver powder received strong impact energy on the hard alumina substrate during the AD process, which means that plastic deformation usually occurred.

5 shows the change in electrical resistivity with silver film thickness during the AD process.

Ω·㎝)을 가졌다. 이는 은 필름 두께가 0.4㎛일 때 급격하게 떨어졌다. 1㎛ 이상의 두께에서, 전기 저항도는

Ω·㎝로 포화되었다. 최저 저항을 보이는 포인트는, 은 필름 두께가 5㎛일 때,

Ω·㎝였다. 전반적으로, 그래프의 개방 형태가 전기 저항도(resistivity)와 필름 두께(film thickness)의 역관계를 나타냈다. 전기 저항도와 필름 두께의 역관계는 두 가지 매커니즘을 수반하였을 수 있다. 제 1 매커니즘은 표면 산란(surface scattering)에 관련되는 Fuchs-Sonheimer 모델이며, 다른 하나는 그레인 경계 산란(grain boundary scattering)에 관련되는, Mayadas-Shatzkes이다. Fuchs-Sonheimer 표면 산란과 Mayadas-Shatzkes 그레인 경계 산란은, 각각 식(1)과 식(2)로 주어진다:The electrical resistivity is an extremely high value (

Ω·cm). This fell sharply when the silver film thickness was 0.4 μm. At a thickness of 1㎛ or more, the electrical resistivity is

It was saturated with Ω·cm. The point showing the lowest resistance is when the silver film thickness is 5㎛,

It was Ω·cm. Overall, the open shape of the graph showed an inverse relationship between electrical resistivity and film thickness. The inverse relationship between electrical resistivity and film thickness may have involved two mechanisms. The first mechanism is the Fuchs-Sonheimer model, which relates to surface scattering, and the other is Mayadas-Shatzkes, which relates to grain boundary scattering. The Fuchs-Sonheimer surface scattering and the Mayadas-Shatzkes grain boundary scattering are given by equations (1) and (2), respectively:

Here, ρ is the measured electrical resistivity, p is the probability that electrons have been scattered from the film surface, t is the film thickness, R is the grain boundary reflection coefficient, and D is the grain boundary. Is the average distance of grain boundaries.

In general, the initial fluctuations in electrical resistivity are predominantly due to Fuchs-Sonheimer surface scattering because its surface morphology continuously changes from bumpy to smooth during the early stages of film growth.

On the other hand, since surface morphologies seldom change during successive deposition, Mayadas-Shatzkese grain boundary scattering is a more dominant factor in determining resistivity than Fuchs-Sonheimer. do.

In this case, as the number of 4, 8, 12 scans increases, the more the collision energy of subsequent particles on the substrate is transferred to the deposited silver film, the more defects at grain boundaries are. It gradually decreases, and the porous silver film is converted to a relatively dense structure than the first scan, which results in relatively low electrical resistivity due to the formation of relatively many silver clusters.

3.3 The growth mechanism of silver films

In order to investigate the growth process of silver films deposited aerosol on the substrate, the film thickness for each scan number was first measured each time. 6 shows the film thickness according to the scan number from the 2nd to the 100th scan. When the AD process was carried out up to the 16th scan, there was little change in film thickness, indicating a nonlinear graph.

The variation of film thickness with respect to the number of scans (Δfilm thickness=Δscan number) had a very low value of 0.027. This means that the average deposited thickness per scan was 0.027 μm in the initial AD stage.

On the other hand, the deposition rate for every scan was significantly increased after more than 12 scans. In this case, the value of Δfilm thickness=Δscan number was 0.123, which was more than 4 times the value of the initial deposition rate.

The surface and cross-sectional SEM images of the silver film using different scan times were acquired to determine why the deposition rate was different before and after the 16th scan.

7 shows the surface and internal microstructures of an aerosol-deposited silver film on an alumina substrate with increasing the number of scans. After four scans were performed, some silver particles filled the rough surface of the alumina substrate. Even after 8 scans, a portion of the alumina substrate was still superficially exposed from the surface, and after 12 or more scans only a silver film was observed on the surface. This is the main reason for the very small change in film thickness up to 12 scans.

The basic principle of the AD mechanism is to create a dense structure based on the reduction of the crystallite size by brittle particles. However, ductile metals behave differently during the AD process. The silver particles sprayed from the slit nozzle together with a large amount of carrier gas can deliver a strong impact to the surface of the rough alumina substrate. Since the silver particles are subjected to a high level of stress due to the rigidity of the alumina substrate, their behavior on the surface of the alumina substrate is mainly bound to severe plastic deformation. This consequently covers the valleys of the coarse alumina substrate, forming a mechanical interlock between the silver particles and the alumina substrate.

When most of the rough surfaces of the alumina substrate were filled after 12 scans, subsequent silver particles were successively accumulated on the deposited silver film based on the hammering effect. That is, since the silver film was deposited with the same mechanism after 12 scans, as shown in Fig. 6, the film thickness increased with a linear function.

Ω·㎝ 으로 측정되었으며, 이는 에어로졸-증착 은 필름의 이전 연구에서 보고된 것보다 1.5배 작았다. 더욱이, 기판 상에 증착된 은 필름의 내부 미세구조와 표면 모폴로지를 관측함으로써, 특정 스캔 횟수에 따라, 그 성장 매커니즘이 두 가지 프로세스들로 나누어짐이 밝혀졌다: In this study, an aerosol-deposited silver thick film could be processed at 23° C. room temperature for metallization. By optimizing the experimental parameters such as the nozzle's orifice area and gas consumption, without the heating process, the electrical resistivity of the deposited silver film is

It was measured as Ω·cm, which was 1.5 times smaller than that reported in previous studies of aerosol-deposited silver films. Moreover, by observing the internal microstructure and surface morphology of the silver film deposited on the substrate, it was found that, depending on the specific number of scans, its growth mechanism was divided into two processes:

1) filling the rough surface with the silver particles by forming mechanical interlocking, and

2) Densifying the silver films with a hammering effect.

Based on the experimental results, aerosol-deposited silver films using optimized experimental parameters are expected to be applied in future applications for integrated circuit metallization.

4. Conclusion

Aerosol-deposited silver films on alumina substrates have been successfully processed through a simple AD process at 23° C. room temperature for high performance metallization. Experimental parameters, such as the orifice size of nozzle and gas consumption, were changed to find low resistivity, which was the main goal of our study.

노즐의 오리피스에서 상대적으로 노즐의 작은 오리피스 크기(small orifice size)와 4~10 L/min 가스 유량에서 상대적으로 많은 가스 소모량(high gas consumption)은 전기 저항도의 감소에 크게 연관되는 점이 확인되었는데, 이는 이러한 파라미터들이 삼투 효과(percolation effect)를 활성화시키고 은 입자들 간의 미세접촉(microcontacts between the silver particles)을 증가시킬 수 있었기 때문이다. In AD devices, 4.0, 2.25, 1.0 and 0.64

It was confirmed that the relatively small orifice size of the nozzle at the orifice of the nozzle and the relatively high gas consumption at the gas flow rate of 4 to 10 L/min are strongly related to the decrease in electrical resistivity. This is because these parameters could activate the percolation effect and increase microcontacts between the silver particles.

During the AD process, plastic deformation for the silver particles was confirmed by observing the magnitude of the peak shift in XRD. The electrical resistivity gradually decreased with the film thickness, which is surface scattering and grain boundary scattering as silver particles accumulate on the substrate. Because everyone has decreased.

To observe the deposition behavior of the silver film, the growth mechanism was investigated with SEM images using different scan times. Up to twelve scans, the silver particles were subjected to plastic deformation while playing a role in filling the coarse alumina substrate. After 12 scans, it was deposited in a manner that tends to increase the film thickness as a linear function from this point. The aerosol-deposited silver thick films on the processed substrate in this study showed superior electrical properties with a clear aerosol deposition mechanism, and a reduction of RC delay with relatively low resistance. low resistivity).

The method of forming a silver film for improved electrical properties using the aerosol deposition (AD) process of the present invention is a resistance-capacitance delay in an integrated circuit using a 23°C room temperature aerosol deposition (AD) process. Silver thick films for high-efficiency metallization, which can be applied to reduce and increase signal propagation speed, were formed. In order to obtain better performance than the aerosol-deposited silver films reported in previous studies, the experimental parameters (nozzle orifice size and gas consumption) that can directly affect the electrical resistivity are determined. It was optimized first. A small orifice size of a suitable nozzle was chosen to facilitate the reduction in electrical resistivity by activating the percolation effect and creating relatively more conduction channels. In addition, relatively high gas consumption reduced the electrical resistivity of silver films, thereby forming relatively more metal clusters. Using the experimental parameters showing the lowest resistivity, silver thick films were formed through the AD process, and their properties were analyzed. The results of X-ray diffraction confirmed that the silver particles became collision-induced plastic deformation. As the film thickness increased to 12 scans, the collided particles filled the coarse alumina substrate. After 12 scans, the silver film was densified due to severe plastic deformation of the deposited-silver particles. Therefore, the growth mechanism suggested that most of the silver particles in the initial deposition step contribute to mechanical interlocking, and the subsequent particles result in film densification.

As described above, the present invention has been described with reference to preferred embodiments of the present invention, but the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims by those of ordinary skill in the relevant technical field It will be appreciated that various modifications or variations can be implemented.

Claims (13)

(a) On a substrate, aerosol deposition silver powder sprayed from a powder spray nozzle using an aerosol deposition (AD) process by an aerosol deposition (AD) process using an AD device at room temperature is deposited and aerosol deposited silver film metal Forming a thick film; And
(b) analyzing the orifice size and gas consumption of the nozzle for electrical resistivity using a 4-10 L/min gas flow controlled by the flow controller,
In the step (a), the orifice of the nozzle is 4.0, 2.25, 1.0 and 0.64

Using the orifice of any one of the different orifice sizes, the aerosol-deposited silver thick film is formed,
The step (b) is 4.0

While the electrical resistivity of the silver film from the nozzle of was the highest, 1.0

The electrical resistivity from the nozzle area of was the lowest value, and the particle velocity was proportional to the increase of the carrier gas and the decrease of the nozzle orifice size, and proportional to the nozzle orifice area and the resistivity of the nozzle. A method of forming a silver film for improved electrical properties using an aerosol deposition process. The method of claim 1,
A method of forming a silver film for improved electrical properties using an aerosol deposition process, wherein the substrate uses an alumina substrate. The method of claim 1,
The method of forming a silver film for improved electrical properties using an aerosol deposition process, characterized in that the metal thick film is a silver thick film for metal wiring. The method of claim 1,
The AD device includes an AD device having different nozzle orifice sizes, the AD device includes an aerosol chamber and a deposition chamber, and the aerosol chamber includes a flow controller capable of controlling a gas flow rate,
As a starting powder for the aerosol deposition (AD) process, silver powder having the highest electrical conductivity among metals was used,
The silver powder is loaded in the deposition chamber, and helium gas is used as a carrier gas having a gas flow rate of 4-10 L/min, and the aerosol chamber is directly connected to the flow controller capable of controlling the gas flow rate,
When the carrier gas is supplied to the aerosol chamber, the silver powder is aerosolized by mixing and stirring using the carrier gas, and the aerosolized silver powder is transferred to the slit nozzle by the helium gas injected through the Teflon tube. And sprayed into the deposition chamber, a method of forming a silver film for improved electrical properties using an aerosol deposition process. The method of claim 4,
The silver powder is a method of forming a silver film for improved electrical properties using an aerosol deposition process, in which silver powder having an average particle diameter of 1.1 μm is used. delete The method of claim 1,
The electrical resistivity of the silver film from the extremely small orifice size of 0.64mm ² was higher than that from the orifice size of 1.0mm ² ,
10 L/min of carrier gas and 1

When using the nozzle orifice of, the particle velocity was 500 to 650 m/s, and 4.0

When using the orifice of the nozzle of 430m/s, this condition can form relatively more conductive channels, the number of channels can reduce the electrical resistivity of the silver film, and the orifice of the relatively small nozzle Although the dense silver film formed from the diameter has a decrease in electrical resistivity,
0.64

Silver film using an extremely small orifice of can lead to surface deterioration and etching effect due to the high impact of particles impinging on the substrate, and thus, improved using an aerosol deposition process, which causes dislocation of crystals. Method of forming silver film for electrical properties. The method of claim 1,
In the step (a), the orifice size of the nozzle is 1.0

An aerosol-deposited silver film was formed for metallization using the orifice area of, and the electrical resistivity of the silver film deposited on the substrate was

A method of forming a silver film for improved electrical properties using an aerosol deposition process, measured to be Ω·cm. The method of claim 1,
To verify the effect of gas consumption on the electrical resistivity of silver films deposited on the substrate, the gas consumption, which can be measured by a flow controller, is 4-10 L/min. Was controlled, and the electrical resistivity decreased with increasing gas consumption,
For gas consumption of 4 L/min, the electrical resistivity is

It showed the highest value in Ω·cm,
When the gas consumption is more than 7L/min, the final saturation value

A method of forming a silver film for improved electrical properties using an aerosol deposition process approaching Ω·cm. The method of claim 1,
(c) measuring the RMS roughness according to the thickness of the silver film deposited on the alumina substrate and the orifice area of the nozzle using a surface profiler; And
(d) further comprising the step of analyzing the X-ray diffraction (XRD; PANytical X'Pert Pro) pattern of the deposited silver film to check and compare the crystalinity of the raw powder and the deposited silver film. A method of forming a silver film for improved electrical properties using an aerosol deposition process. The method of claim 1,
In the AD device, 4.0, 2.25, 1.0 and 0.64

The relatively small orifice size of the nozzle at the orifice of the nozzle and the relatively high gas consumption at the gas flow rate of 4-10 L/min are associated with a decrease in the electrical resistivity, these parameters activate the osmotic effect and the microcontact of the silver particles ( microcontacts between the silver particles), and plastic deformation of brittle silver particles during the AD process observed the magnitude of the peak shift in XRD, and surface scattering and grain boundary scattering as silver particles accumulate on the substrate. A method of forming a silver film for improved electrical properties using an aerosol deposition process, all of which are reduced so that the electrical resistivity gradually decreases with film thickness. The method of claim 1,
As the number of 4, 8, 12 scans increases, the more the collision energy of subsequent particles on the substrate is transferred to the deposited silver film, the more defects at grain boundaries gradually become. Reduced, improved electrical properties using an aerosol deposition process, where the porous silver film is converted to a relatively dense structure, resulting in relatively low electrical resistivity due to the formation of relatively many clusters. Method of forming a silver film for. The method of claim 1,
In order to investigate the growth process of silver films deposited on the aerosol on the substrate, the film thickness according to each scan number from the 2nd to the 100th scan was first measured each time. ,
When the AD process was performed up to the 16th scan, as a result of obtaining and examining the surface and cross-sectional SEM images of the silver film, there was no change in the thickness of the silver film.
The variation in film thickness with respect to the number of scans (Δfilm thickness=Δscan number) had a very low value of 0.027, which means that the average deposited thickness per scan was 0.027 μm in the initial AD stage,
On the other hand, the deposition rate for every scan was significantly increased after more than 12 scans.In this case, the value of Δfilm thickness=Δscan number was 0.123, which was more than 4 times the value of the initial deposition rate. ,
When the surface of the alumina substrate was filled after 12 scans, the subsequent silver particles were continuously accumulated on the deposited silver film based on the hammering effect, and since the silver film was deposited by the same mechanism after 12 scans, the film thickness Is increased as a linear function, and an aerosol-deposited silver thick film is processed at room temperature for metallization, using an aerosol deposition process to form a silver film for improved electrical properties.

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