Investigation On Surface Morphology Sample Biology Essay

Published:

This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.

For this project, the main objective is to do the investigation on surface morphology sample that used direct current (DC) and alternative current electroplating techniques respectively.

Besides that, effects of DC current electroplating and alternative current (AC) electroplating techniques on plating metal are study. Resistance measurements results from the deposition film will be obtained for difference electroplating conditions.

1.2 Overview of the Project

The project started off by doing a detailed research on the basic theory, material used and setup method of electroplating. Firstly, chemical reactions in electrodeposition process are studied.

Based on research, material of this project used are copper film and copper sulfate, CuSO4 solution in terms of low costs, low resistance and common used in current industry.

Other than that, the resistance measurement results will be obtained by interface of LabVIEW within those apparatus such as power supply, keithley 2000 multiammeter and keithley 6485 picoammeter. Meanwhile, direct current (DC) electroplating and alternative current (AC) electroplating setup will have a difference on power supply apparatus used. It used DC power supply and function generator respectively.

Lastly, the observation on surface morphology of deposited copper film by alternative current (AC) direct current (DC) electroplating techniques will be performed.

1.3 Motivation

Development in DC current electroplating techniques is led the usage of electroplating with its achievement nowadays. Other than that, new and innovative electroplating technique is concerned by current experts in electronics field. This is due to the needs of enhance interconnect in electronics such as microchip IC with micron meter, µm to nanometer, nm scales while the sizes of electronic devices is tiny. Hence, improvement of electroplating techniques is needs to achieve it. However, how the AC current electroplating influences the electrodeposition process is not fully developed yet. Thus, it would be challenging and interesting to research and learn the basic theory of electrodeposition and some of the actual experiment. It would be a bonus if worked in the R&D field.

1.4 Purpose of Report

This project includes a comprehensive study on DC current electrodeposition process and AC current electrodeposition process. This project is divided into two main aspects which is research and experiment.

The observation of surface morphology obtained will be discussed in this report. The methodology and tools used to complete this project also will be provided in this report. All the progress will be discussed in details to provide understanding for all readers.

1.5 Thesis Organizations

This report consists of five chapters. Chapter 1 provides a brief description of the objectives and aims of this project. The motivation and overviews of the project are also discussed in this chapter.

In Chapter 2, theoretical background of DC current and AC current electroplating process, fundamental principles to implement this project and theory of measurement are provided.

Next in Chapter 3, an overview of the methodology applies in the project is provided. The hardware and software used and the steps in succeeding this project are described.

In Chapter 4, the data results of the experiment in the forms of figure and table are carried out. On the other hand, the further discussion of the results also will be provided.

Lastly in Chapter 5, conclusion of the project and some recommendations for potential future developments of the project are given.

CHAPTER 2: LITERATURE REVIEW

2.1 History of Electroplating

The invention of electroplating is an excellent discovery. Without the brilliant scientist and researcher in few decades ago, electroplating techniques might not be able to be introduced today and electroplating techniques will not wide range of uses in different way of applications. A chemist Luigi V. Brugnatelli from Italy had discovered the electroplating technique in 1805 [7]. However, those inventions were concealed by the French Academy of Sciences. Hence, general industry that time not used Brugnatelli's invention and all the works was anonymous outside of Italy.

During 1800's to 1845, gold electroplating was introduced and developed. At the same time, two types of gold electroplating dependently with costs were discovered. For low costs, very low concentration of gold chloride solution is used to coat thin layer of gold onto inexpensive objects. Precious objects required higher gold chloride concentration to be used to deposit thick gold layer over a surface.

Based on the basis behaviors of electrochemical, development in chemical field has led to sophisticated plating bath formulas. Therefore, better plating thickness controlled with greater plating rate and higher quality plating is achieved. Meanwhile, the scope of the applicable area using electroplating processes is increased. The used of bright nickel, silver and zinc for electroplating process are accommodated in commercial purposes. In the mid-1940, the betterment of electroplating technique was discovered due to the emergence of electronics industrial. The improvement of electroplating techniques in electronics industrial was widely used to enhance the interconnectors and circuit boards. Nevertheless, the costs of electroplating are high due to expensive materials used such as platinum, ruthenium and gold.

Furthermore, the advances implementation of electroplating techniques will benefit many industrials nowadays. For example, automobiles industries use chromium plating to protect steel component such as kettles, tower rails and car bumper. The figure 2.1 and 2.2 shows applications of electroplating.

Figure 2.1: Kettles Figure 2.2: Tower Rails

For electronics industries application, interconnectors in electronics devices such as IC are enhanced by electroplating techniques to fill up interconnect via between IC. From the latest research, the general electroplating technique used in the electronic semiconductor nowadays is DC current techniques. Copper materials are used in semiconductor industrial due to good electrical properties of copper, low resistivity and low cost to implement it. Meanwhile, improvement in electronics not only in terms of good functions provided but it also makes the sizes smaller. Therefore, distances between interconnects of IC electronic device will become closer (less than 0.2m) and increases the defects of wiring interconnect by machine. So, it would increase costs of losses if disposed the defects devices. Hence, DC copper electroplating technique is used to make interconnect between inner IC. The copper metal ion produced will do deposition on via at inner IC part. The metal ion will continuously deposits from bottom of via until interconnect between inner parts of IC is achieved as figure 2.3 shows.

Figure 2.3: Via Filling Process

Nowadays, development in electroplating techniques with DC power supplies is led in the electroplating usage with its achievement. Meanwhile, AC electroplating techniques also get attention due to better electroplating outcome is expected. However, research regards AC electroplating is still not fully developed. More researches and investigations using AC electroplating is needed to prove the outcome in terms of surface roughness, area and uniformity plating is comparable with DC electroplating techniques.

2.2 Electroplating Process

In the recent decade, electroplating technique is undergoing development from an art to an exact science. With the improvement of technology, the ability to deposit very thin multilayer (micron meter, µm to nanometer, nm) surface via electroplating forms a new line of approaches to produce new materials [2]. Therefore, electroplating has wide range of applications in technological areas such as electronic component and automobile industry. One of the common reasons for electroplating is economical and convenience. However, DC current electroplating technique was commonly used in current technology instead of AC current electroplating technique.

Figure 2.4: Structure of an electroplating setup for plating metal "C" from a solution

of the metal salt "CA".

Electroplating is also called "electrodeposition" and which define as process of coating on a surface by applied electric current [6]. For further understanding of readers, figure 2.4 shows basic structure of an electroplating setup for plating metal "C" from a solution of the metal salt "CA". A wire from positive terminal of power supply is connected to anode metal while wire from negative terminal is connected to cathode metal. Then solution of the metal salt "CA" is filled to immerse the metal. The process of producing coating between cathode and anode would start to react under applied electric current. The equation 2.1 shows reaction of electroplating process happened at cathode metal.

Cn+ + ne- = C (2.1)

On the other hand, this equation 2.2 shows reaction of electroplating process happened at anode metal.

C = Cn+ + ne- (2.2)

The cathode metal to be coated is connected to the negative terminal, negatively charge anions electron, ne- produced to attract cations, Cn+ deposited on cathode metal, C. At the anode plate, positively charge cations, Cn+ produced and migrated to cathode plate which attracted by anions, ne-. Therefore, cathode metal was coated by Cn+ and the reduction of metal occurred at anode metal.

2.3 Limitation

There are a few limitations using electroplating method. Firstly, the process electroplating is highly depending on the characteristic of metal to obtain uniform plating. Therefore, it is very important to conduct a proper study on the plating metal used. Furthermore, the surface cleaning method is applied to increase the plating rate to a satisfied level. Secondly, there is the limitation of resistance and current measurement due to measurement apparatus. Therefore, measurement using 4 point probe method with its high accuracy and stable characteristics were introduced. Lastly, the high sensitivity and high scale microscopes such as atomic force microscopes machine (AFM) are essential to study the condition of electroplating surface. This is because the deposited metal is micron to nanometer-scale of surface thickness on plating metal.

2.4 Material Used in Current Applications

From the research, various type of metal such as copper, zinc, argentums, gold, platinum and so on are widely used for electroplating. Most of the concerns regards metal used are in terms of cost, availability and its properties. Among those materials, applications of electroplating using copper were highly get attention by current researcher in industrial.

2.5 Surface Cleaning Method

Dust, contaminants and films on surface are the factor that causes the limitation of uniformity plating. However, method to remove those impurities on surfaces is important to avoid damage and scratch produced. Therefore, chemical approach of surface cleaning method is studied to get uniformity surface plating.

2.5.1 Chemical Approach

Types of chemical approaches for surface cleaning are solvent degreasing and acid cleaning.

2.5.1.1 Solvent Degreasing

Solvent degreasing is using appropriate organic solvents to remove contaminants such as oil, grease and impurity organic materials. Table 2.5.1.1 below shows three most common degreasing solvent used and their properties.

Table 2.1: Properties of Common Degreasing Solvent Used

Furthermore, solvent degreasing has two degreasing systems which are liquid phase degreasing and vapour phase degreasing.

2.5.1.2 Alkaline Cleaning

Work pieces are immersed in tanks of hot alkaline cleaning solutions to remove dirt and solid soil [11]. There are few types of influences can affect the alkaline cleaner such as type of basis metal, type and concentration of the cleaner, cleaner temperature and the time of immersion.

2.5.1.3 Acid Cleaning

Acid cleaning can move heavy scale, heat-treat scale, oxide, and the like [11]. Sulphate acid and hydrochloric was the most common used acid for cleaning method. To be more effective, pickling is connected with current during acid cleaning process.

2.6 Measurement Method

Measurement method of electroplating is usually in terms of current, resistance that relate with the study of the surface morphology. Therefore, the electroplating process on surface can be proved from the measurement results and surface observation. In order to measure low resistivity of thin firm, 4 point probe method is introduced. For study the surface morphology, atomic force microscopy, AFM is introduced. More details theory of 4 point probe and AFM is introduced respectively.

2.6.1 Theory of 4 Point Probe Method

The purposes implementation of four point probes method is to measure the sheet resistance of thin film or bulk resistance. Basically, there are two methods of resistance measurement which is 2 point probe and 4 point probe method. The difference between them is an additional 2 probes used in 4 point probe method for measured the voltage potential of the surface. Note that, the disadvantage of using 2 point probe method is unwanted resistance such as contact resistance, Rc (produced between probe and sample surface) and the spreading resistance, Rsp (produced during current flow through sample surface) when do the measurement. By the way, resistance surface Rs is the only resistance need to be concerned. Therefore, the total resistance obtained would increase. This equation 2.3 shows the total resistance measured by 2 point probe method [16].

Rtotal = Voltage, (V)/Current, (I) = 2Rc + 2Rsp + Rs (2.3)

With the used of additional 2 probe to measure voltage of sample surface in 4 point probe method, those unwanted resistance Rsp and Rc can be eliminated. Figure 2.5 shows schematic of 4 point probe.

V3

V2

Figure 2.5: Schematic of 4 Point Probe

4 probes are connected to film in a row with "s" spacing. A current source is placed between two outer probes. On the other hand, voltmeter is placed between 2 inner probes. The measurement of 4 point probe is started with the injection of current through two outer probes; voltage is measures between two inner probes to determine the sample resistance and the using equation 2.4 [16],

V2 = ρI/2πs (2.4)

Where "ρ" is the resistivity of a material, "I" is the current in the probe, and "s" is the distance between the voltage measurement and the current probe.

Using figure 2.2, the equation 2.5 used to measure voltage at V2 is [16],

V2 = ρI/2π {(1/s1) - (1/ (s2+s3))} (2.5)

For the equation voltage at V3 is [16],

V3 = ρI/2π {(1/ (s1+ s2)) - (1/s3)} (2.6)

Then, the total voltage by subtract voltage at V2 with V3 is [16],

V = ρI/2π {(1/s1) + (1/s3) - (1/ s2+s3)) - (1/ (s1+s2))} (2.7)

After arrangement, the resistivity is [16],

ρ = 2π (V/I) / {(1/s1) + (1/s3) - (1/ (s2+s3)) - (1/(s1+s2))} (2.8)

Besides that, the configuration of current source and voltmeter will be changed dependently with resistance of sample to be measured. For high resistance sample, current is reducing to avoid excessive large voltage at the contacts. On the other hand, the configuration is different for low resistance sample. Current is increase and the voltmeter is set to a lower scale.

Other than that, there also have limitations of measurement capability needed to be concerned. At first, the probes must be able to measure resistance from material [12]. Secondly, only 100's of Angstroms up to 1 micron thickness of thin films can be measured. Lastly, impurity sample surface would lead to inaccurate resistance measurement obtained [12].

2.6.2 Theory of Atomic Force Microscopy (AFM)

The Atomic Force Microscopy, AFM is being applied to study the surface morphology of sample after etching, plating and polishing. The purposes of using Atomic Force Microscopy, AFM is due to its ability to measure surface atoms that are extremely small. Besides that, atomic force microscope also able to provide topographic information from surface measured with 3 dimensional, 3D. From the figure 2.6 below, it shows how AFM functions. Firstly, the AFM fine stylus is mounted on end of cantilever spring and move in Z direction to approach the sample. Meanwhile, detector which acts as light level sensor to detects the deflection of the cantilever. Then, force sensor and feedback control is applied to measure the force and keep the "fixed" distance between tips and sample during scanning surface.

Figure 2.6: Basic Structures of AFM

Other than that, AFM has 3 types operating mode of surface measuring techniques as figure 2.7 shows.

Figure 2.7: Operating Mode of AFM

First operating mode was introduced is contact mode. During scanning the surface, the stylus is followed the topography of the surface with constant low force applied on it. However, the weakness of contact mode is the probe might causes damage on sample by immoderate tracking forces applied during scanning.

Next, the non-contact mode is introduced to solve the contact mode's weakness. Stylus is move in the air during scanning the sample surface. Attractive Van der Waals forces acting between the tip and the sample are detected, and topographic images are constructed by scanning the tip above the surface.

Lastly, tapping mode is introduced. AFM tip-cantilever taps the sample surface while rastering and only touch the sample at the bottom of each oscillation [14]. The advantages of tapping mode is can be performed on both wet and dry sample surfaces, prevents the tip from sticking to the surface and causing damage during scanning.

CHAPTER 3: METHODOLOGY

This chapter discusses about the methodology used and the experiment setup to accomplish this project. This project is mainly about research and experiment that divide into two parts. For part I, DC current electroplating experiment will be conducted and part II will conduct AC current electroplating experiment. Each part is doing same measurement such as electrical properties and study surface morphology. To succeed in realized this experiment; there exist 5 stages, which are:

3.1 Research

In order to implement a good experiment, research was the first step. Information about implementing the experiment was studied through reference books, journals and internet sources. Information that was studied includes pros and cons of different material used, current and resistance measurement during electroplating and the machine used to do investigation on surface morphology of electroplating. On the other hand, difference between DC current electroplating and AC electroplating setup were studied too. This information was important because they were the main criteria to accomplish this experiment.

3.2 Materials, Software and Apparatus Used

After sufficient research was done, materials and apparatus used to implement electroplating experiment were chosen and gathered. The materials used are copper metal, copper sulphate solution and sulphuric acid solution. Besides that, the apparatus used are DC power supply, function generator, Keithley 2000 multiammeter, keithley 6485 picoammeter and PH 5/6 meter. In order to connect apparatus and materials, software named LabView is used. By the way, knowledge of materials characteristics is very important due to its dangerous and harmful characteristics. Thus, precaution method during handle it can be implemented. Besides that, further studied on those apparatus' characteristics used are important too. Therefore, false connection that will causes the damage or malfunction on apparatus can be prevented.

3.2.1 Setting and Functions of Materials

The setting, characteristic and usage of materials were introduced respectively as below:

3.2.1.1 Copper

Copper metal film was chosen as electroplating metal due to its low resistance, low cost and good conductivity properties. The thickness of copper metal used is 0.05mm and considered as thin film.

3.2.1.2 Solution Copper Sulphate, CuSo4 · 5H2O

Besides that, electrolyte solution used is copper sulphate, CuSO4· 5H2O. According the theory of electroplating, copper ion in electrolyte solution produced by action of current will be coated on cathode metal during process. On the other hand, copper ion coated on surface can provide good conductivity properties and it also easier to produce copper ion by applied lower current.

3.2.1.3 Acid Cleaning, Sulphuric Acid, H2SO4

Acid cleaning is the cleaning method used to remove impurity on film surface and enhance its plating rate. The common used of sulphuric acid, H2SO4 with 98% of concentration in acid cleaning were chosen. Firstly, 98% of sulphuric acid, H2SO4 is poured into 400ml of distill water. Then copper film is immersed for 10 minutes to do the cleaning. Due to the acidic characteristic of sulphuric acid is hazard and able to cause severe burns, eye protector and glove needed to wear during handle it.

3.2.2 Setting and Function of LabVIEW Software

LabVIEW is a graphic user interface, GUI software to make an interface between measurement device and plating sample for electroplating process. Therefore, simulated results during measurement can be obtained at the same time.

3.2.3 Setting and Functions of Apparatus

The functions, characteristics and usage of apparatus were introduced respectively as table 3.1 shows:

Table 3.1: Functions of Apparatus Used

Apparatus Type

Functions

DC Power Supply

To provide fixed 50mV DC voltage into cathode and anode metal for part I experiment.

Function Generator

To provide fixed 50mV AC voltage and provided 50Hz and 125Hz sine wave frequency into cathode and anode metal for part II experiment.

Oscilloscope

Used to set the waveform of function generator with 2V peak to peak amplitude.

Keithley 2000 Multiammeter

To do the resistance measurement at plating (cathode) metal with fast, accuracy and highly stable condition using 4 point probe method.

Keithley 6485 Picoammeter

To measure the current across the plating (cathode) metal with its low voltage burden, high accuracy current measurement up to nano-scale amperes and high speed auto range functions.

pH 5/6 & Ion 5/6 Meter

Used to measure the pH level of the electrolyte before electroplating and after electroplating process done.

3.3 Materials Preparation

Materials preparation is the following step after the apparatus ready.

3.3.1 Copper Preparation and Acid Cleaning

Firstly, figure 3.1 shows the copper metal film is cut into zigzag shape. This zigzag shape copper film is act as cathode metal for the experiment. Main purpose of cutting the metal zigzag is to control its resistance according the theory of conductive resistance. Theory of conductive resistance is proven by equation 3.1 below shows [15].

(3.1)

Where "ρ" is a constant resistivity dependently with the material used. For copper, its resistivity is 1.678*10-8 ohm-centimetre (Ω-cm) [15]. Besides that, "l" is length of copper metal while "A" is the cross-sectional area of copper metal. From here, it indicated copper resistance is increase if the length is longer.

Figure 3.1: Zigzag Shape Metal

Next, a rectangular shape of copper film is cut and acts as anode metal. For surface cleaning, cathode copper metal and the anode copper metal cut were immersed into 34ml of 98% H2SO4 acidic concentration in 250ml H2O for 10 minutes. The metal were taken out and washed by distill water after 10 minutes.

3.3.2 CuSO4 Solution Preparation

For solution preparation step, 40g of CuSO4· 5H2O powder is measured then poured into beaker contains 400ml of distilled water. The powder is dissolved in distilled water and stir with rod slowly. On the order hand, heater is set to 60 oC and it used to make sure powder form is fully dissolved in distilled water. The figure 3.2 shows heater used during solution preparation.

Figure 3.2: Heater with Beaker contains Solution

3.3.3 Precaution during Material Preparation

During handling with material, there are some step is needed to precaution.

Wear eye protector

Wear the glove

No direct handling contact with material

Use tweeze to handling material

3.4 Experiment Procedures

Refer to the apparatus, characteristics and usages have been studied at previous step. The connection between apparatus and materials setup is showed as figure 3.3 below. Sample showed in the figure 3.3 are the materials used such as copper film and copper sulphate solution. After the apparatus setting, materials preparation and acid cleaning is performed, DC current electroplating experiment in Part I is implemented as figure 3.3 showed. Firstly, LabVIEW software to make interconnectors between measurement apparatus with sample is setup. Secondly, voltage power supply is set to 50mV. Next, wire used for resistance measurement apparatus keithley 2000 multiammeter and current measurement apparatus keithley 6485 picoammeter is plugged in.

Figure 3.3: Connection of Apparatus with Materials Setup

Connection of apparatus with materials is showed at figure 3.4. Cathode copper film and anode copper film is put in beaker. Positive terminal is connected to anode copper film while negative terminal is connected to cathode copper film. As shown from figure, four point probes from keithley 2000 multiammeter are connected to cathode copper film. Then, resistance of cathode copper film is start measured after poured 40g CuSO4· 5H2O concentration of solution in beaker. Power supply is turn on for 40 minutes continuously. This step is repeated for 10g CuSO4· 5H2O concentration of solution. The measured data is collected.

Figure 3.4: Connection of Apparatus with Materials

However, the experiment procedures for AC current electroplating experiment in Part II is repeated as described above during setup in experiment Part I . Besides that, the only one change which is the DC power supply during DC current electroplating is replaced with function generator to supply AC current during AC current electroplating experiment. After performed the AC and DC current electroplating experiment, all resistance measurement data is gathered.

3.5 Studied Surface Morphology Procedures

After electroplating experiment done, the plating cathode film is taken out to do surface morphology studied by AFM. The AFM used is showed as figure 3.5.

Figure 3.5: Structure of AFM Machine

Firstly, solid frame pump is turned on to supports the entire AFM microscope and avoid vibration during scanning process. Then, icon nanosuft easy scan2 on computer is clicked to operate the AFM microscope. Next, cathode film sample is cut into small pieces and placed on the glass slide. Following, the sample is placed on the stage and translator is adjusted to make the AFM head approached the surface sample until certain level. Next, "approach" is clicked and the translator will be adjusted downward with closer distances (1~2µm) between sample surface. Surface sample started to scan as showed in figure 3.6 when it successfully approaches the surface. At imaging area, to get better resolution of image, image size "10µm", time/line 1 s, points/line "256" values is set respectively. The scanning surface process will stopped when scanning process ended. Results of scanning image are saved in bitmap format. The same steps are repeated for next samples.

Figure 3.6: Nanosurf Easy Scan2 Operating Software

CHAPTER 4: RESULTS AND DISCUSSIONS

4.1 DC Current Electroplating Results and Discussions

Table 4.1 shows the characteristics of the cathode film due to different concentration in DC current electroplating. The characteristics measured are resistance before, resistance after, percentage of resistance drop, and surface roughness. The concentrations used in the process are 10g CuSO4· 5H2O / 400ml and 40g CuSO4· 5H2O / 400ml. The results of the resistances are measured in ohm, Ω whereas the surface roughness is measure in nanometer, nm.

Table 4.1: Percentage of Resistance Drops, %∆R and Surface Roughness, Rq for

Different Concentration

This is the equation given to calculate the percentage of resistance drops,

(4.1)

Resistance of deposited copper film after electroplating, Rafter is always smaller due to the deposition process. Therefore, the absolute is included in the equation to make the percentage of resistance drop is always in positive value.

Based on the observation from table 4.1, drop of resistance of the deposited copper film at 40g of CuSO4· 5H2O / 400ml is slightly higher compared to the resistance of the deposited film at 10g of CuSO4· 5H2O / 400ml. This indicated that deposition rate at high concentration 40g of CuSO4· 5H2O / 400ml is faster. It can be proven by surface morphology of deposited copper film as shown in figure 4.1(a) and figure 4.2(a). The surface roughness of deposited copper film obtained at 40g of CuSO4· 5H2O / 400ml is 24.2nm, which is larger than surface roughness obtained at 10g of CuSO4· 5H2O / 400ml (21.3nm).

Figure 4.1(a) shows the surface morphology of the deposited copper film at 10g of CuSO4· 5H2O / 400ml of concentration and the figure 4.1(b) shows enlarge surface morphology from square box. The surface morphology of deposited film with triangle-like is obtained.

Sq=21.3nm

Figure 4.1(a): Surface morphology of the Figure 4.1(b): Enlarged surface morphology

copper deposited at 10g of CuSO4· 5H2O of the square box area in figure 4.1(a)

/ 400ml of concentration

Sq=24.2nm

Figure 4.2(a): Surface morphology of the Figure 4.2(b): Enlarged surface morphology

copper deposited at 40g of CuSO4· 5H2O of the square box area in figure 4.2(a)

/ 400ml of concentration

On the other hand, the observation at figure 4.2(b) shows enlarge surface morphology of deposited film at 40g of CuSO4· 5H2O / 400ml is gives an irregular spike-like morphology. Meanwhile, it also results in higher surface roughness. This is due to the rate of copper metal ion Cu2+ ­ produced from solution is high. Hence, it led the high deposition rate on copper film.

4.2 AC Current Electroplating Results and Discussions

Table 4.2 shows the percentage of the change of resistance for concentrations of 10g of CuSO4· 5H2O / 400ml and 40g of CuSO4· 5H2O / 400ml at 50Hz and 125Hz and its corresponding surface roughness.

Table 4.2: Percentage of Resistance Drops, %∆R and Surface Roughness, Rq for

Different Concentration and Frequency

It can be seen from table 4.2 for concentration of 10g of CuSO4· 5H2O / 400ml, the resistance of the deposited copper film at 50 Hz decreases about four times compared to the resistance of the deposited copper film at 125 Hz. This indicates that deposition at low frequency 50Hz yields better film quality. It can be verified by the surface morphology of the deposited copper film as shown in figure 4.3(a) and figure 4.4(a) where the copper film that was deposited at 50 Hz has smaller surface roughness (8.28nm) compared to the copper film that was deposited at 125 Hz (12.85nm).

Sq=8.28nm

Figure 4.3(a): Surface morphology of the Figure 4.3(b): Enlarged surface morphology

copper deposited at 10g of CuSO4· 5H2O of the square box area in figure 4.3(a)

/ 400ml of concentration and 50Hz

Sq=12.85nm

Figure 4.4(a): Surface morphology of the Figure 4.4(b): Enlarged surface morphology

copper deposited at 10g of CuSO4· 5H2O of the square box area in figure 4.4(a)

/ 400ml of concentration and 125Hz

Figure 4.3(a) shows the surface morphology of the deposited copper film at 10g/400ml CuSO4 5H2O at 50Hz and the enlarged surface morphology of the square box area is shown in figure 4.3(b). The surface of the deposited film at 50Hz gives clearly mountain-like morphology. However, for the deposited film at 125 Hz gives a spiky-like morphology and results in higher value of surface roughness. This is due to Cu2+ ions have enough time to diffuse on and deposit themselves on the surface of the copper cathode.

Besides that, observation from table 4.2 for concentration of 40g of CuSO4· 5H2O / 400ml showed the resistance of deposited film drop at 50Hz is decreases about seven times compared to the resistance of the deposited copper film at 125 Hz. Therefore, it indicated that deposition rate at 50Hz is higher and favor compare to deposition at 125Hz for both concentrations. This can be proven by surface morphology of deposition film as shown in figure 4.5(a) and 4.6(a) where the surface roughness of deposition film at 50Hz is smaller (9.96nm) than 125Hz (18.58nm).

Figure 4.5(a) shows the surface morphology deposited film at 40g/400ml CuSO4 5H2O at 50Hz and enlarged surface morphology from square box area is shown as figure 4.5(b). The surface morphology of deposited film shows the mountain-like morphology more clearly and smooth.

Sq=9.96nm

Figure 4.5(a): Surface morphology of the Figure 4.5(b): Enlarged surface morphology

copper deposited at 40g of CuSO4· 5H2O of the square box area in figure 4.5(a)

/ 400ml of concentration and 50Hz

Sq=18.58nm

Figure 4.6(a): Surface morphology of the Figure 4.6(b): Enlarged surface morphology

copper deposited at 40g of CuSO4· 5H2O of the square box area in figure 4.6(a)

/ 400ml of concentration and 125Hz

From observation of deposited film at 125Hz as figure 4.6 (a) shown, the deposited film gives an irregular mountain-like morphology and results in higher surface roughness. This is due to deposition rate at 125Hz is faster while ion produce is high. Meanwhile, low surface roughness of deposition film for 50Hz is due to ion have no enough time to diffuse on the film.

Meanwhile, same frequency 50Hz is compared between 40g of CuSO4· 5H2O / 400ml and 10g of CuSO4· 5H2O / 400ml for both concentrations. Drop of resistance of the deposition film at high concentration, 40g of CuSO4· 5H2O / 400ml is slightly higher than that of the sample at low concentration, 10g of CuSO4· 5H2O / 400ml. This is due to more copper ions are available in the electrolyte solution at high concentration, 40g of CuSO4· 5H2O / 400ml. Then, it led the cross section area increases at faster rate and contributed resistance drop. However, refer to figure 4.3(a) shows, this high deposition rate resulted in poor surface morphology.

At 125Hz, it can be observed from table 4.2 for the low concentration is favors the deposition process since the drop of the resistance after deposition process is higher in 10g of CuSO4· 5H2O /400ml compared to concentration at 40g of CuSO4· 5H2O /400ml. Refer to figure 4.4(a) and 4.6(a), it showed the surface roughness have larger value at 10g of CuSO4· 5H2O /400ml due to less ion Cu2+ produce and it led the high deposition rate on copper film with enough time.

CHAPTER 5: CONCLUSION AND FUTURE RECOMMENDATIONS

5.1: Conclusion

The investigation on surface morphology of deposition film for this project is divided into 2 parts where the deposition film is results from DC electroplating and AC electroplating techniques respectively. Therefore, few conclusions can be making from the results.

For DC electroplating techniques, higher the drop of resistance at high concentration of CuSO4· 5H2O, cross section area is larger. From the analysis of surface morphology, deposition film by DC electroplating techniques shows the surface roughness is higher when high electrolyte of CuSO4· 5H2O used. This is due to the rate of copper metal ion Cu2+ ­ produced from solution is high and led to high deposition rate.

For AC electroplating techniques, the cross section area of deposition film is larger at low frequency with smoother surface while high frequency is smaller in cross section area with non-uniform surface. However, the surface roughness is high when frequency is higher. This is due to the ion available has enough time to diffuse on the film.

5.2 Future Recommendation

There are few limitation during studied the composition of surface morphology. Results of copper plating surface might include the dust besides the metal ion salt. So, it was hard to confirmed that metal coating on surface is the metal ion salt. This limitation of studied the composition of surface can be improve by using energy dispersive X-ray spectroscopy, EDX. The advantages usage of EDX is it able to characterize and analyzed the composition volume. Therefore, it helps to prove and enhance the results if refer to both observations.

Meanwhile, more range of frequency and different concentration needed to add in order to improve the research.

Writing Services

Essay Writing
Service

Find out how the very best essay writing service can help you accomplish more and achieve higher marks today.

Assignment Writing Service

From complicated assignments to tricky tasks, our experts can tackle virtually any question thrown at them.

Dissertation Writing Service

A dissertation (also known as a thesis or research project) is probably the most important piece of work for any student! From full dissertations to individual chapters, we’re on hand to support you.

Coursework Writing Service

Our expert qualified writers can help you get your coursework right first time, every time.

Dissertation Proposal Service

The first step to completing a dissertation is to create a proposal that talks about what you wish to do. Our experts can design suitable methodologies - perfect to help you get started with a dissertation.

Report Writing
Service

Reports for any audience. Perfectly structured, professionally written, and tailored to suit your exact requirements.

Essay Skeleton Answer Service

If you’re just looking for some help to get started on an essay, our outline service provides you with a perfect essay plan.

Marking & Proofreading Service

Not sure if your work is hitting the mark? Struggling to get feedback from your lecturer? Our premium marking service was created just for you - get the feedback you deserve now.

Exam Revision
Service

Exams can be one of the most stressful experiences you’ll ever have! Revision is key, and we’re here to help. With custom created revision notes and exam answers, you’ll never feel underprepared again.