Microemulsion cleaning agent for flip chip bonding technology and preparation method and application thereof

Abstract

The invention relates to a microemulsion cleaning agent for a flip chip bonding technology and a preparation method and application thereof. The cleaning agent is prepared from 1.5-3% of an oil phase component, 2-5% of a surfactant compound, 2-3% of a cleaning aid, 0.2-0.6% of a corrosion inhibitor compound and the balance of ultrapure water. The cleaning agent is used for cleaning a semiconductor chip in a flip chip bonding technology, and polar, non-polar and particulate pollutants generated after flip chip bonding can be effectively cleaned.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor cleaning, and specifically relates to a microemulsion cleaning agent for flip chip bonding technology, a preparation method and application thereof, wherein the cleaning agent is used in flip chip bonding technology to clean semiconductor chips. Background Art

[0002] Semiconductor chip packaging technology includes wire bonding technology, flip chip bonding technology, tape automated bonding technology, etc. Flip chip bonding technology has a lower package height and lower bump pitch, which brings great challenges to the post-solder cleaning process. Compared with ordinary wire bonding technology, it is more difficult to clean.

[0003] The existing technology mostly uses solvent cleaning agents, semi-aqueous cleaning agents, and water-based cleaning agents. Solvent cleaning agents have good cleaning effects and do not corrode materials. However, ethanol and isopropanol are flammable solvents, which have the risk of combustion and explosion, and pose safety hazards. Halogenated hydrocarbon cleaning agents are not easy to volatilize and have high safety, but they are generally toxic or pose potential threats to the environment and human health. Many countries and regions have or are restricting their use. The working fluid of semi-aqueous cleaning agents is mostly emulsions, and its droplet particle size is about 0.1-10μm, which is much larger than the 10-100nm droplet particle size of microemulsions. It cannot effectively penetrate into the gap of flip chips and has poor cleaning effect on pollutants. Water-based cleaning agents are difficult to effectively penetrate into the flux. Although some water-based cleaning agents have added organic solvents and saponifiers to reduce surface tension and enhance cleaning ability, they may still not be able to completely clean the flux residues. In addition, the addition of organic amines or inorganic bases may also cause problems such as poor material compatibility.

[0004] The following types of cleaning agents are disclosed in the existing patented technologies:

[0005] 1. A semiconductor chip cleaning agent and its preparation method and application (CN 112266832 A)

[0006] (1) Purpose: After the grinding and polishing process of sapphire, silicon carbide, gallium nitride, gallium arsenide, germanium and other substrates, the wax layer, polishing powder residue, polishing liquid residue, metal particles, etc. are cleaned and removed. (Post-polishing cleaning, not post-bonding cleaning, belongs to a different process cleaning agent from the present invention)

[0007] (2) Technical measures: The cleaning agent is composed of a wetting stripping agent and a wetting stripping composition composed of a perfluoro terminal polyoxyethylene ether, a penetrant, a solubilizer, a composite functional agent, a nitrogen-containing complexing agent, an organic auxiliary agent and ultrapure water. Among them, the organic auxiliary agent is a polyol amine compound, which has the risk of corroding the aluminum substrate. The cleaning process is a 20-25% aqueous solution, soaking the semiconductor chip at 80-95°C for 5-15 minutes, rinsing in ultrapure water at least twice, and completing the cleaning.

[0008] (3) Effect: The wax layer, grinding dirt and other pollutants attached to the chip can be cleaned thoroughly and can be completely removed from the chip without forming wax on the surface of the solution or causing dirt to stick back to the chip. There is no corrosion to the chip. There are no special requirements for the cleaning process, and no ultrasonic treatment is required. The wax, organic pollutants, and various particles attached to the chip can be completely washed off by just soaking. Afterwards, it only needs to be rinsed with pure water, and no dirt remains after washing.

[0009] 2. A semiconductor chip cleaning agent and its preparation method (CN 116496851 A)

[0010] (1) Purpose: In the step of bonding the semiconductor chip to the frame, tin-lead solder is usually used for welding. Therefore, after vacuum reflow soldering, a large amount of flux contaminants will remain on the surface and periphery of the chip. Cleaning agents are used to remove such contamination. Failure to clean will affect the subsequent bonding failure of the gold wire and the aluminum layer, and will reduce the reliability of the subsequent packaging process. (Since incomplete cleaning will affect the subsequent bonding failure of the gold wire and the aluminum layer, this technology belongs to the cleaning agent used in the wire bonding technology, not the cleaning agent used in the flip chip bonding technology of the present invention)

[0011] (2) Technical measures: sulfonic acid type fluorinated surfactant, nonionic surfactant, complexing agent, ethanol, diethylene glycol monobutyl ether, the balance is deionized water. Suitable for ultrasonic cleaning process or spray cleaning process. (Not the microemulsion in the present invention)

[0012] (3) Effect: It can effectively remove tin paste, solder paste, flux residue, etc. on semiconductor chips. After cleaning, there is less residue on the chip surface, which effectively improves the phenomenon that water-based cleaning agents cannot clean the slits properly and avoids discoloration of the chip surface. The cleaning agent can be used in ultrasonic cleaning process or spray cleaning process.

[0013] The cleaning agent of the present invention can effectively remove pollutants and impurities generated in the process of reflow soldering, hot pressing bonding or surface activated bonding of the flip chip bumps interconnected with the substrate, carrier or circuit board, thereby improving the bonding quality and reliability. The necessity lies in that these residues can cause the adhesion of the bottom filling glue to decrease, affect the filling effect, and cause interface defects such as delamination, voids and stripes. At the same time, the residual soldering flux may also damage the interconnection of the solder bumps, affecting the quality of the device. Summary of the invention

[0014] As electronic packaging technology develops towards miniaturization, high frequency, sustainability, intelligence and diversified applications, the interconnection technology in the packaging process is also constantly developing. Including wire bonding technology, flip chip bonding technology, carrier automatic bonding technology, etc. Flip chip bonding technology has more I / O numbers within the same packaging area, and its IC pin pattern is only 5% of the flat package, and the package height is greatly reduced. At the same time, the spacing between the bumps is constantly decreasing, from 500μm, 300μm to 150μm fine spacing, and even ultra-fine spacing below 100μm. The reduction in package height and bump spacing brings great challenges to the post-weld cleaning process. In order to solve the above-mentioned problems existing in the prior art, the present invention designs the specific composition of the cleaning agent based on the advanced bump manufacturing technology and the bump manufacturing materials used, and matches the best cleaning method, which can effectively clean the polar, non-polar and particulate pollutants generated after flip chip bonding.

[0015] In order to achieve the purpose of the invention, the present invention adopts the following technical scheme: a microemulsion cleaning agent for flip chip bonding technology, the cleaning agent consists of 1.5-3% oil phase component, 2-5% surfactant complex, 2-3% cleaning aid, 0.2-0.6% corrosion inhibitor complex, and ultrapure water to 100%.

[0016] The oil phase component is any one of d-limonene, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, ethylene glycol hexyl ether, ethylene glycol monophenyl ether, tripropylene glycol methyl ether and dipropylene glycol butyl ether.

[0017] The surfactant complex is composed of surfactant A, surfactant B and surfactant C; wherein the weight percentages of surfactant A, surfactant B and surfactant C are 0.4-1.2%, 1.6-3.5% and 0.2-0.4%.

[0018] In a preferred embodiment of the present invention, the surfactant A is any one or a combination of anionic surfactants such as fatty alcohol sulfates (sodium dodecyl sulfate K12, sodium fatty alcohol polyoxyethylene ether sulfate AES), alkylbenzene sulfonates (sodium dodecylbenzene sulfonate LAS-90, sodium dodecyl diphenyl ether disulfonate), alkylamine esters (OTE), and sodium fatty acid methyl ester sulfonate (MES).

[0019] In a preferred embodiment of the present invention, the surfactant B is a nonionic surfactant isomeric fatty alcohol polyoxyethylene ether ( TO series, EN series, etc.), long-chain carboxylate polyoxyethylene ether (LMEO-18), alkyl polyglycoside (APG series, series), ethylenediamine oleate (EDO-86), fatty acid methyl ester ethoxylate (long carbon chain fatty acid methyl ester ethoxylate FMEE-70, PO block fatty acid methyl ester ethoxylate FMEE-98) or any one or combination thereof.

[0020] In a preferred embodiment of the present invention, the surfactant C is any one of the biosurfactants rhamnolipid, trehalolipid and sophorolipid.

[0021] In the present invention, the composite surfactant is a compound of anionic surfactant, nonionic surfactant and biosurfactant, and the surfactant having the properties of decontamination, emulsification, solubilization and penetration improves the oil removal performance of the microemulsion. In addition to having an amphiphilic structure similar to that of chemically synthesized surfactants, the biosurfactant can also be adsorbed on the interface and change the properties of the interface. It has the characteristics of good selectivity, small dosage, non-toxicity, being completely biodegradable, not polluting the environment, and being able to introduce new chemical groups that are difficult to synthesize by chemical methods using microbial methods. In order to further improve the cleaning performance of the detergent, a biosurfactant is added to reduce the surface tension of the cleaning solution, which has a good wetting and emulsifying effect on dirt. The agglomeration effect between microemulsion droplets is weakened, and the system is more stable.

[0022] The cleaning aid is any one of ethanol, n-propanol, isopropanol, n-butanol and n-pentanol in the medium and short chain alcohols. The cleaning aid can change the distribution of the surfactant in the oil phase and the water phase, participate in the process of the surfactant forming micelles, adjust the water-oil balance of the system, increase the flexibility and strength of the microemulsion system interface film, reduce the interfacial tension of the microemulsion system, form a more stable cleaning agent system, and at the same time reduce the viscosity of the cleaning agent, further improving the cleaning ability.

[0023] The corrosion inhibitor compound is compounded by corrosion inhibitor A and corrosion inhibitor B; wherein the weight percentages of corrosion inhibitor A and corrosion inhibitor B are 0.04-0.2% and 0.1-0.4% respectively.

[0024] In a preferred embodiment of the present invention, the corrosion inhibitor A is any one of mercaptobenzothiazole (MBT), benzotriazole (BTA), naphthotriazole (NTA), dithiothiadiazole (DMTDA), thiazolylbenzimidazole (TBZ), and mercaptobenzimidazole; and the corrosion inhibitor B is siloxane ketone.

[0025] On the other hand, the present invention also protects a method for preparing the cleaning agent, comprising the following steps: adding ultrapure water, a surfactant complex, a cleaning aid, and a corrosion inhibitor complex to a stirring kettle in sequence at 20°C-40°C, and stirring until the solution is uniform and transparent; while stirring, slowly adding an oily component, and stirring until the solution is completely transparent or translucent and stable.

[0026] In another aspect, the present invention also protects the use of the cleaning agent in flip chip bonding technology.

[0027] In a preferred embodiment of the present invention, the cleaning method comprises the steps of low-frequency ultrasonic cleaning, rinsing and drying in sequence; more preferably, the low-frequency ultrasonic cleaning is at a frequency of 28-40kHz, a temperature of 55-65°C, and a cleaning time of 5-15min; the rinsing temperature is 15-35°C, the rinsing time is 2-3min, and the number of rinsing times is 2-4 times; the drying temperature is 70-80°C, and the drying time is 10-20min.

[0028] The present invention adopts a cleaning agent of a microemulsion system to achieve effective cleaning of the residues after flip chip bonding. Compared with ordinary emulsions, the droplet size of microemulsions is smaller, generally 10-100nm, and has ultra-low oil-water interfacial tension, while the droplet size of ordinary emulsions is about 0.1-10μm. The dispersed phase droplets of microemulsions are roughly between surfactant micelles and common hydrophobic colloid particles, and can remove polar dirt and non-polar dirt at the same time, have strong dissolving ability for oil-soluble dirt, have good solubilizing ability for water-soluble dirt, and the surfactant contained in them has good adsorption and removal ability for solid dirt. Microemulsions are usually thermodynamically and kinetically stable systems with good interfacial film flexibility, which makes the microemulsions have strong physical stability and cannot be separated under ordinary centrifugal forces. The cleaning ability is better than that of emulsion-type and water-based cleaning agents, and the stability is better than that of emulsion-type cleaning agents.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The microemulsion cleaning agent prepared by the present invention has better cleaning ability than water-based cleaning agents and traditional semi-aqueous cleaning agents. As the packaging height and bump spacing of flip-chips continue to shrink, the cleaning difficulty is much greater than the cleaning in wire bonding technology. The microemulsion cleaning agent prepared by the present invention can form stable tiny emulsion particles, firstly wet the surface of the dirt and reduce its surface tension, and then these microemulsion particles can more effectively penetrate into the dirt. The double electric layer and solvation formed loosen the originally tightly bound dirt, expand the gaps between the dirt, reduce the binding force between the dirt, and at the same time, with the help of the physical cleaning force, the dirt is quickly removed from the surface of the substrate, thereby achieving more thorough cleaning. Traditional semi-aqueous cleaning agents may not be able to form such effective tiny particles, and water-based cleaning agents do not contain non-polar components that can be efficiently cleaned, so their cleaning ability is relatively weak.

[0031] (2) Microemulsion cleaning agents have better stability than semi-aqueous cleaning agents because they are composed of oil phase, surfactant complex, cleaning aid, ultrapure water and other components, which can form a stable system in water. Semi-aqueous cleaning agents, on the other hand, may be prone to stratification or demulsification due to the unstable interaction of the components.

[0032] (3) The microemulsion cleaning agent prepared by the present invention does not contain toxic and harmful substances such as phosphorus, halogens, and nitrites, and is safer for the human body and the environment; it does not contain alkaline components such as inorganic alkalis or organic alkalis, has good compatibility with metal and non-metal materials, has a wider range of uses, and can be applied to the cleaning of various semiconductor substrates.

[0033] In summary, the microemulsion cleaning agent has beneficial effects in terms of cleaning ability, stability, environmental protection and scope of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further description is given below in conjunction with the accompanying drawings.

[0035] Figure 1 This is a surface image of the flip chip after cleaning using Example 1.

[0036] Figure 2 This is a surface image of the flip chip after cleaning using Example 2.

[0037] Figure 3 This is a surface image of the flip chip after cleaning using Example 3.

[0038] Figure 4 This is a surface image of the flip chip after cleaning using Example 4.

[0039] Figure 5 This is a surface image of the flip chip after cleaning using Example 5.

[0040] Figure 6 This is a surface image of the flip chip after cleaning using Comparative Example 1.

[0041] Figure 7 This is a surface image of the flip chip after cleaning using Comparative Example 2.

[0042] Figure 8 This is a surface image of the flip chip after cleaning using Comparative Example 3.

[0043] Fig. 9 This is a surface image of the flip chip after cleaning using Comparative Example 4. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0045] Sample preparation for Examples 1-5 and Comparative Examples 1-4: According to the raw material ratios in Table 1, ultrapure water, surfactant complex, cleaning aid, and corrosion inhibitor complex are sequentially added to a stirring kettle at 20°C-40°C, and stirred until the solution is uniform and transparent. Under stirring, the oil phase component is slowly added and stirred until the solution is completely transparent or translucent and stable.

[0046] Table 1 Sample formulations of Examples 1-5

[0047]

[0048] Table 2 Sample formula of comparative examples 1-4

[0049]

[0050] The cleaning methods of Examples 1-5 and Comparative Examples 1-4 are as follows: low-frequency ultrasonic (28-40kHz) cleaning, cleaning temperature 60°C, cleaning time 10 min; rinsing temperature 25°C, rinsing time 2 min, rinsing times 3 times; drying temperature 80°C, drying time 10 min.

[0051] The following cleaning performance tests were performed on Examples 1-5 and Comparative Examples 1-4:

[0052] (1) Visual inspection: Use the built-in optical system of the hot pressing flip chip welder to align the center of the hot pressing head with the center of the flip chip. Use the "crosshairs" to assist in calibration and ensure that the hot pressing head is parallel to the chip plane. Start the heating program and press the hot pressing head vertically down to the chip surface. Monitor the temperature curve in real time and start the pressure holding countdown after the set temperature is reached. After the pressure holding is completed, the hot pressing head will automatically lift up and the chip will be immediately adsorbed and removed with a vacuum suction pen. Operate in sequence according to the "M" shape or matrix layout. Cool the substrate to below 80°C after each disassembly before continuing. Use a 50x microscope to observe the cleanliness of the chip surface. The results are shown in the figure. Figure 1-5 As shown, after the samples of Examples 1-5 were cleaned, there was basically no visible contaminant (such as white spots of flux, carbonized black spots, and solder balls) on the surface of the pads, and there was no oxidation discoloration or corrosion marks on the metal layer of the pads, meeting the Class 3 standard in IPC-610H. Figure 6-9 It can be seen that after cleaning the samples of Comparative Examples 1 to 4, the pads all showed some flux residue, among which Comparative Example 2 had the worst cleaning effect, with a large amount of dirt remaining.

[0053] (2) Surface ion residue test: The ion contamination test was performed on the components of Examples 1-5 after cleaning according to the method in Chapter 10 of GB / T 4677. The test showed that the ion residue content was less than 1.56 μg (NaCl) / cm 2 , meeting the requirements for Class III electronic products specified in GJB 5807.

[0054] The above is a description of the preferred embodiments of the present invention, not a limitation of the scope of the present invention. Without departing from the design spirit and principles of the present invention, technicians in this field can still modify and improve the technical solutions of the above examples, but the modifications and improvements should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A microemulsion cleaning agent for flip chip bonding technology, characterized in that: The cleaning agent is composed of 1.5-3% of oil phase components, 2-5% of surfactant compound, 2-3% of cleaning aid, 0.2-0.6% of corrosion inhibitor compound and ultrapure water to 100%.

2. The microemulsion cleaning agent according to claim 1, characterized in that The oil phase component is any one of d-limonene, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, ethylene glycol hexyl ether, ethylene glycol monophenyl ether, tripropylene glycol methyl ether and dipropylene glycol butyl ether.

3. The microemulsion cleaning agent according to claim 1, characterized in that The surfactant complex is composed of surfactant A, surfactant B and surfactant C; wherein the weight percentages of surfactant A, surfactant B and surfactant C are 0.4-1.2%, 1.6-3.5% and 0.2-0.4%.

4. The microemulsion cleaning agent according to claim 3, characterized in that The surfactant A is any one or a combination of anionic surfactants such as fatty alcohol sulfate (sodium dodecyl sulfate K12, sodium fatty alcohol polyoxyethylene ether sulfate AES), alkylbenzene sulfonate (sodium dodecylbenzene sulfonate LAS-90, sodium dodecyl diphenyl ether disulfonate), alkylamine ester (OTE), and sodium fatty acid methyl ester sulfonate (MES); the surfactant B is a nonionic surfactant such as isomeric fatty alcohol polyoxyethylene ether ( TO series, EN series, etc.), long-chain carboxylate polyoxyethylene ether (LMEO-18), alkyl polyglycoside (APG series, series), ethylenediamine oleate (EDO-86), fatty acid methyl ester ethoxylate (long carbon chain fatty acid methyl ester ethoxylate FMEE-70, PO block fatty acid methyl ester ethoxylate FMEE-98), any one or combination thereof; the surfactant C is any one of the biosurfactants rhamnolipid, trehalolipid, and sophorolipid.

5. The microemulsion cleaning agent according to claim 1, characterized in that The cleaning aid is any one of ethanol, n-propanol, isopropanol, n-butanol and n-pentanol among medium and short chain alcohols.

6. The microemulsion cleaning agent according to claim 1, characterized in that The corrosion inhibitor compound is compounded by corrosion inhibitor A and corrosion inhibitor B; wherein the weight percentages of corrosion inhibitor A and corrosion inhibitor B are 0.04-0.2% and 0.1-0.4% respectively.

7. The microemulsion cleaning agent according to claim 6, characterized in that: The corrosion inhibitor A is any one of mercaptobenzothiazole (MBT), benzotriazole (BTA), naphthotriazole (NTA), dithiothiadiazole (DMTDA), thiazolylbenzimidazole (TBZ), and mercaptobenzimidazole; the corrosion inhibitor B is siloxane ketone.

8. The method for preparing a microemulsion cleaning agent according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: adding ultrapure water, a surfactant complex, a cleaning aid, and a corrosion inhibitor complex into a stirring kettle in sequence at 20° C. to 40° C., and stirring until the solution is uniform and transparent; While stirring, slowly add the oily component and stir until the solution is completely transparent or translucent and stable.

9. Use of the microemulsion cleaning agent according to any one of claims 1 to 7 in flip chip bonding technology.

10. The use according to claim 9, characterized in that: The cleaning method comprises the steps of low-frequency ultrasonic cleaning, rinsing and drying in sequence; more preferably, the low-frequency ultrasonic cleaning is performed at a frequency of 28-40kHz, a temperature of 55-65°C, and a cleaning time of 5-15min; the rinsing temperature is 15-35°C, the rinsing time is 2-3min, and the number of rinsing times is 2-4 times; the drying temperature is 70-80°C, and the drying time is 10-20min.

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