Thermal Processing Steps Research Articles

Temporary Bonding Technologies for Thin Wafer Handling

Thin glass substrates offer low dielectric constant and high temperature process capability for faster and thinner packages but handling is challenging due to lack of mechanical stiffness. Temporary bonding of thin wafers to stiffer carrier substrates offers a solution and has been an active area of research and development in recent years. Polymeric and tape wafer bonding solutions are available but usually for low temperature processes. In Corning, we have developed an array of surface treatment/coating technologies that offer high temperature capability (as high as 700°C). The common theme of all these technologies entails surface treatment or coating of a carrier substrate to achieve strong non-covalent bonding with the thin wafer. The desired attributes are: (a) high enough bond energy at room temperature to withstand vacuum, thermal, and wet processing steps, (b) low enough bond energy after the thermal processing steps rendering the pair mechanically separable, (c) spontaneous bonding via self-propagating bond wave, and (d) minimal outgassing or bubble formation between carrier and thin wafer due to degradation of bonding material. The technologies range from vacuum based sub-monolayer surface functionalization to vacuum based organometallic coating to high throughput solution processed ultra-thin molecular coatings. In this talk we will first describe the theoretical underpinnings of various surface and chemical forces that control the bond energy between the carrier and the thin wafer, models to predict the bond energy as function of surface chemistry and surface energy parameters, influence of surface chemistry on various process attributes such as bond wave propagation and outgassing during thermal treatment. We will also briefly review various processes developed and their relative strengths and applicability.

Structural and chemical evolution of the CdS:O window layer during individual CdTe solar cell processing steps

Oxygenated cadmium sulfide (CdS:O) is often used as the n-type window layer in high-performance CdTe heterojunction solar cells. The as-deposited layer prepared by reactive sputtering is XRD amorphous, with a bulk composition of CdS0.8O1.2. Recently it was shown that this layer undergoes significant transformation during device fabrication, but the roles of the individual high temperature processing steps was unclear. In this work high resolution transmission electron microscopy coupled to elemental analysis was used to understand the evolution of the heterojunction region through the individual high temperature fabrication steps of CdTe deposition, CdCl2 activation, and back contact activation. It is found that during CdTe deposition by close spaced sublimation at 600 °C the CdS:O film undergoes recrystallization, accompanied by a significant (∼30%) reduction in thickness. It is observed that oxygen segregates during this step, forming a bi-layer morphology consisting of nanocrystalline CdS adjacent to the tin oxide contact and an oxygen-rich layer adjacent to the CdTe absorber. This bilayer structure is then lost during the 400 °C CdCl2 treatment where the film transforms into a heterogeneous structure with cadmium sulfate clusters distributed randomly throughout the window layer. The thickness of window layer remains essentially unchanged after CdCl2 treatment, but a ∼25 nm graded interfacial layer between CdTe and the window region is formed. Finally, the rapid thermal processing step used to activate the back contact was found to have a negligible impact on the structure or composition of the heterojunction region.

Evaluation of Melanoidins Formed from Black Garlic after Different Thermal Processing Steps.

The objective of this study was to evaluate the characteristics of melanoidins formed from black garlic (BG) after different thermal processing steps. The melanoidins formed from BG during thermal processing were produced in large amounts, and the initial (280 nm), intermediate (360 nm), and final stage product (420 nm) had similar tendencies. Compounds like degraded proteins, peptides, and phenolic acids were present in the melanoidins during thermal processing. All the melanoidin samples showed different absorptions in the UV-visible spectra, although these had similar shapes. Moreover, the carbon, hydrogen, and oxygen content of melanoidins formed from BG during thermal processing decreased initially, and then increased. However, the nitrogen content increased during thermal processing. As thermal processing progressed, the molecular weight of all the melanoidin samples showed increasing intensities, whereas the major peaks of each melanoidin sample had different retention times. Furthermore, the melanoidins formed from BG after different thermal processing steps contained -OH, -CH, amide I, and III groups. The crystallinity of the melanoidins was majorly formed at 31.58° and 43.62° (2θ).

Physicochemical Characteristics of Black Garlic after Different Thermal Processing Steps.

This study investigated the physicochemical characteristics of black garlic (BG) after different thermal processing steps. Compared with fresh garlic (FG), the moisture content and pH in BG decreased significantly, while the ash content and browning intensity increased during thermal processing. The total mineral and the free sugar contents were significantly higher than that of the BG2 and BG4 samples, respectively. The free sugar content increased by 16-fold in the BG cloves compared with that of FG, while the amino acid content increased during the first stage of thermal processing, and subsequently decreased. The thiosulfinate content in all samples decreased to during thermal processing. The pyruvic acid content initially increased and then decreased during thermal processing. These results contribute to our understanding of the role of thermal processing in the quality formation of BG.

Borosilicate glass nanolayer as a spin-on dopant source: FTIR and spectroscopic ellipsometry investigations

Borosilicate glass is a potential dopant source for producing shallow boron junctions by the use of proximity rapid thermal diffusion. Interest in this technique has increased recently due to its application to the manufacture of solar cells. A borosilicate gel is spun onto a silicon wafer and the layer is rapidly thermally annealed to convert it to a borosilicate glass (BSG). Fourier transform infrared (FTIR) spectroscopy, spectroscopic ellipsometry and sheet-resistance measurements have been used to understand and subsequently optimise the conversion of the gel to a BSG nanolayer. Physical properties of the thin, spun-on layer, such as thickness, refractive index and porosity, were monitored. The optimum conversion step involved rapid thermal annealing for 45 s at 900 °C. This avoided any boron loss from the BSG layer during the thermal processing step. The position of the B–O stretching vibration around 1370 cm−1 was found to be sensitive to boron outdiffusion and it is suggested that FTIR spectroscopy provides a simple method for monitoring the outdiffusion of boron from the spin-on dopant nanolayer. Further FTIR studies using p-polarised light at oblique incidence revealed, for the first time, the LO–TO phonon splitting of the B–O stretching vibration band in the glassy layer. Investigation of the stability of BSG layers over long periods showed that unstabilised (or undensified) BSG films demonstrate a dramatic loss of boron over 6 months.

Thermal Debinding of Ceramic-Filled Photopolymers

Within the large variety of different additive manufacturing technologies stereolithography excels in high precision and surface quality. Using the Digital Light Processing (DLP) Technology a stereolithography-based system was developed, which is specifically designed for the processing of highly filled photopolymers.The powder-filled suspension enables the 3D-fabrication of a so called ceramic green part. In order to get a dense ceramic structure, subsequent thermal processing steps after the 3D-printing process are necessary. First, the polymer-ceramic composites heated up to 400°C. During this processing step, called debinding, the organic components are burned out. The resulting part, consisting of powder particles stabilized by physical interactions, is further heated to sinter the particles together, and the final, fully dense ceramic part is obtained.The debinding step is the most critical process. The used components have different evaporation or decomposition temperatures and behaviors. Thereby a reduction in weight and also in dimension occurs, which depends on the portion and composition of the organic components and especially on the temperature cycle. Furthermore, the physical characteristics of the ceramic powder, such as the particle size and the size distribution influence the debinding behavior. To measure the changes in weight and dimension a thermo-gravimetric (TGA) and a thermo-mechanical analysis (TMA) can be used. To avoid too high internal gas pressures inside the green parts a preferably constant gas evolution rate is seeked. Also the ‘surface-to-volume ratio’ affects the debinding characteristics. Therefore, optimized debinding cycles for specific geometries allow the crack-free debinding of parts with a wall thickness up to 20 mm.

The Physicochemical Changes of Black Garlic during Thermal Processing

To explore the physicochemical changes of black garlic during the thermal processing steps and further reveal the role of Maillard reaction in the formation mechanism of black garlic. The physicochemical changes including UV-Vis absorbance, fluorescence and color difference were determined. The UV absorbance at 294 nm and browning intensity at 420 nm gradually increased with increasing heating time, while the fluorescence intensity showed a maximum value at the heating time of 3 days. The color value of black garlic increased after heating at 70-80°C for 10 days. These results indicated Maillard reaction was primarily responsible for the formation of black garlic.

Biopolymer nanoparticles as potential delivery systems for anthocyanins: Fabrication and properties

Biopolymer nanoparticles and microparticles may be used as delivery systems for bioactive compounds in food and pharmaceutical applications. In this study, biopolymer nanoparticles were assembled from whey protein isolate (WPI) and beet pectin (BP) using thermal processing and electrostatic complexation. This approach involved mixing the two biopolymers at pH5.8, heating (90°C, 5min) to induce protein nanoparticle formation and then adjusting the solution to pH4.0 to promote coating of the protein nanoparticles with pectin. This process led to the formation of relatively small anionic biopolymer nanoparticles (d<200nm) at pH4. The biopolymer particles had a high negative charged from pH8 to 4.0 but became less anionic at lower pH values. The mean particle diameter was relatively small (d<200nm) around pH4.0 but increased appreciably at lower and higher pH due to particle flocculation. The biopolymer nanoparticles were loaded with an anthocyanin-rich extract. A higher loading efficiency was observed when anthocyanin was added before heating the WPI-BP solution (LE=55%) rather than after (LE=35%), which was attributed to increased protein–polyphenol interactions. The encapsulation of anthocyanins within biopolymer particles improved their heat stability. However, encapsulated anthocyanin had a lower antioxidant activity than non-encapsulated anthocyanin, which was attributed to the thermal processing step required during particle fabrication and the binding of anthocyanins to biopolymers within the nanoparticles. Color measurements indicated that the encapsulation of anthocyanin within biopolymer particles did not inhibit its degradation after ascorbic acid addition. Overall, our results show that the encapsulation of anthocyanins within the biopolymer particles fabricated in this study was not particularly effective at improving their antioxidant activity or color stability. Alternative strategies are therefore needed to encapsulate this important color and nutraceutical agent.

Waste heat and water recovery opportunities in California tomato paste processing

Water and energy efficiency are important for the vitality of the food processing industry as demand for these limited resources continues to increase. Tomato processing, which is dominated by paste production, is a major industry in California – where the majority of tomatoes are processed in the United States. Paste processing generates large amounts of condensate as moisture is removed from the fruit. Recovery of the waste heat in this condensate and reuse of the water may provide avenues to decrease net energy and water use at processing facilities. However, new processing methods are needed to create demand for the condensate waste heat. In this study, the potential to recover condensate waste heat and apply it to the tomato enzyme thermal inactivation processing step (the hot break) is assessed as a novel application. A modeling framework is established to predict heat transfer to tomatoes during the hot break. Heat recovery and reuse of the condensate water are related to energy and monetary savings gained through decreased use of steam, groundwater pumping, cooling towers, and wastewater processing. This analysis is informed by water and energy usage data from relevant unit operations at a commercial paste production facility. The case study indicates potential facility seasonal energy and monetary savings of 7.3 GWh and $166,000, respectively, with most savings gained through reduced natural gas use. The sensitivity of heat recovery to various process variables associated with heat exchanger design and processing conditions is presented to identify factors that affect waste heat recovery.

Evaluation of Alliin, Saccharide Contents and Antioxidant Activities of Black Garlic during Thermal Processing

This study aimed to explore the alliin, saccharides, antioxidant and some other physicochemical changes of black garlic during the thermal processing steps. The contents of alliin and polysaccharides decreased significantly after 10 days of heat treatment, whereas the content of reducing sugars increased correspondingly. The 57.14% of fructose, 6.78% of glucose and 7.62% of sucrose were mainly saccharides in black garlic to answer for its sweet taste. The color value of black garlic increased over time, whereas the pH decreased continually from 6.25 to 4.25 after heating at 70–80C for 10 days, which contributed a characteristic black appearance and a sour taste mouthfeel. The antioxidant activities, including 1,1-diphenyl-2-picrilhydrazyl, hydroxyl radical scavenging and ferric reducing/antioxidant power activities, increased gradually during thermal processing. Practical Applications Black garlic has been used as foods and herbal remedies mainly in Japan, Korea and China, which has a wide range of health benefits, significantly antioxidant properties. Various physicochemical changes have been found to take place during thermal processing of garlic, including alliin, allicin, saccharides, pH, color and antioxidant activities. This is the first study to investigate the changes in the molecular weight distribution of polysaccharides and the monosaccharide composition of black garlic. These changes in saccharide contents and composition could be utilized as quality factors for the production of black garlic. Therefore, the results may have some useful practical implications at both the food technology and nutritional level.

Direct imaging of thermally-activated grain-boundary diffusion in Cu/Co/IrMn/Pt exchange-bias structures using atom-probe tomography

Magnetic devices are often subject to thermal processing steps, such as field cooling to set exchange bias and annealing to crystallize amorphous magnetic electrodes. These processing steps may result in interdiffusion and the subsequent deterioration of magnetic properties. In this study, we investigated thermally-activated diffusion in Cu/Co/IrMn/Pt exchange biased polycrystalline thin-film structures using atom probe tomography. Images taken after annealing at 400 °C for 60 min revealed Mn diffusion into Co grains at the Co/IrMn interface and along Pt grain boundaries for the IrMn/Pt stack, i.e., a Harrison type C regime. Annealing at 500 °C showed further Mn diffusion into Co grains. At the IrMn/Pt interface, annealing at 500 °C led to a type B behavior since Mn diffusion was detected both along Pt grain boundaries and also into Pt grains. The deterioration of the films' exchange bias properties upon annealing was correlated to the observed diffusion. In particular, the topmost Pt capping layer thickness turned out to be crucial since a faster deterioration of the exchange bias properties for thicker caps was observed. This is consistent with the idea that Pt acts as a getter for Mn, drawing Mn out of the IrMn layer.

Robust UV/VUV/EUV PureB Photodiode Detector Technology With High CMOS Compatibility

This paper gives an assessment of old and new data relevant to the optical and electrical performance of PureB photodiodes for application in the wavelength range 2 nm to 400 nm. The PureB layer, fabricated by depositing pure boron on Si, forms the anode region of devices that function as p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> n junction diodes. The results show that the high sensitivity and high stability of the PureB diodes is related to the integrity of the interface with the Si. When measures are taken to retain a complete PureB coverage, thermal processing steps with minute long exposure to temperatures up to 900 °C do not compromise the robustness and a lower-than-ideal but still high responsivity is maintained. Besides the thermal processing considerations, other aspects that impact the integration of PureB in CMOS are reviewed.

Flexible glass substrate based dye sensitized solar cells

Dye sensitized solar cells (DSSC) on flexible substrates are ideal for making low-cost PV products available for a wide range of low power applications. In addition to lower material costs, a flexible solar cell also offers economies of scale through high volume roll-to-roll manufacturing. A disadvantage of using flexible polymer substrates, stems from their poor stability and degradation of both electrical and optical qualities when subjected to thermal processing steps required to make high efficiency TiO2 photoelectrodes. This study evaluates the potential of indium doped tin oxide (ITO) coated flexible glass, known as Corning® Willow® Glass, as an alternative to polymer substrates for fabricating flexible DSSCs. The strain point and bend radius of this glass allows it to withstand high sintering temperatures and also makes it potentially suitable for roll-to-roll manufacturing.DSSCs fabricated using a 10µm TiO2 mesoporous layer and sensitized with N719 dye demonstrate that flexible glass DSSCs show a power conversion efficiency of 4.53% compared to the 3.09% efficiency value obtained for DSSCs fabricated using commercially available ITO coated thick glass. The enhanced performance of the Willow Glass DSSC is reflected in the improved fill factors (FF). As expected, cells fabricated with similar procedures using fluorine doped tin oxide (FTO) coated glass substrates yielded a higher power conversion efficiency of 7.42% since its sheet resistance remains substantially lower even after the heat treatment unlike ITO. With FTO, instead of ITO, flexible glass DSSCs could potentially achieve higher efficiencies comparable to standard thicker glass DSSCs. This is expected when suppliers are able to produce FTO coated willow glass with reproducible electrical conductivity.This study demonstrates for the first time that DSSCs can be fabricated using light weight, flexible glass substrates with comparable efficiencies to the standard thicker glass based DSSCs.

Characterization of a large core photonic crystal fiber made of lead–bismuth–gallium oxide glass for broadband infrared transmission

We report on characterization of a large solid core, photonic crystal fiber dedicated to broadband transmission range from visible to mid-infrared. We have fabricated a multi-mode photonic crystal fiber, made of a heavy metal-oxide glass based on the $$\hbox {PbO}{-}\hbox {Bi}_{2}\hbox {O}_{3}{-}\hbox {Ga}_{2}\hbox {O}_{3}$$ system, modified with $$\hbox {SiO}_{2}$$ and CdO, synthesized in-house, which shows good transmission up to $$4.5\,\upmu \hbox {m}$$ , as well as good rheological properties that permit multiple thermal processing steps without crystallization. The core of the fiber is created by replacement of central 60 tubes with solid rods. The photonic cladding is composed of 8 rings of air holes with a filling factor of 0.42. Simulation results shows that the fiber can be used for broadband transmission in the range of 430–3,000 nm. Calculated effective mode area of the fiber is $$295\,\upmu \hbox {m}^{2}$$ . We have measured attenuation of the fiber in the range 800–1,700 nm and its sensitivity to bending losses. Attenuation ranges from 1 to 4 dB/m in the considered range and bending losses are below 0.7 dB.

Mesoporous Oxides via Carbonates

Materials Science Mesoporous oxide materials have potential applications in light harvesting and catalysis and as electrode materials. Thin films of these materials are most often formed through a soft-templating process in which a precursor gel is patterned by nanoscale micelles that form from diblock copolymers during solvent evaporates. This route has proven difficult with some oxides, notably zinc oxide (ZnO) and cobalt oxide (Co3O4), because of problems with the three main types of precursors (alkoxides, nanoparticles, and thermally decomposed precursors). Eckhardt et al. show that both mesoporous zinc and cobalt oxides can be formed from soft templates by first forming mesoporous metal carbonates. These materials were formed with triblock poly(ethylene) oxide (PEO)–poly(butadiene) (PB) copolymer (PEO-PB-PEO) micelles and used metal nitrates and citric acid in mixed ethanolwater solvent as the precursor. This solution was dip-coated on substrates at room temperature and then heated for 1 hour at 250°C for zinc and 200°C for cobalt to form the carbonates. Additional heating (25 min at 400°C for zinc and 20 min at 300°C for cobalt) formed the oxides. For zinc, the amorphous wall of the mesoporous carbonate transformed into the crystalline oxide and increased the surface area. For cobalt, the carbonate appeared to retain the micelle template, and mesoporosity developed only in the final thermal processing step as spinel oxide phase walls formed. Chem. Mater. 25 , 2749 (2013).

Magnetic Nanocrystalline Mg0.5Zn0.5Fe2O4: Preparation, Morphology Evolution, and Kinetics of Thermal Decomposition of Precursor

Mg0.5Zn0.5Fe2(C2O4)3⋅H2O was synthesized by solid-state reaction at low heating temperatures using MgSO4⋅7H2O, ZnSO4⋅7H2O, FeSO4⋅7H2O, and Na2C2O4 as raw materials. The spinel Mg0.5Zn0.5Fe2O4 was obtained via calcining Mg0.5Zn0.5Fe2(C2O4)3⋅H2O above 400 °C for 1 h in air. The Mg0.5Zn0.5Fe2(C2O4)3⋅H2O and its calcined products were characterized by thermogravimetry and differential scanning calorimetry (TG/DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The results showed that Mg0.5Zn0.5Fe2O4 obtained at 400 °C had a specific saturation magnetization of 27.3 emu g−1. The thermal process of Mg0.5Zn0.5Fe2(C2O4)3⋅H2O experienced three steps, which are: first, the dehydration of water of crystallization and decomposition of Mg0.5Zn0.5C2O4 into MgO and ZnO, then the reaction of Fe2(C2O4)3 with MgO and ZnO into amorphous Mg0.5Zn0.5Fe2O4, and at last the crystallization of Mg0.5Zn0.5Fe2O4. Based on the KAS equation and the OFW equation, the values of the activation energies associated with the thermal process of Mg0.5Zn0.5Fe2(C2O4)3⋅H2O were determined to be 69±11 and 71±9 kJ mol−1 for the first and second thermal process steps, respectively.

Reduction in lipid oxidation by incorporation of encapsulated sodium tripolyphosphate in ground turkey

Ground turkey, with 1% NaCl, was incorporated with no sodium tripolyphosphate (control, nSTP), unencapsulated STP (uSTP; 0.3% or 0.5%), encapsulated STP (eSTP; 0.3% or 0.5% active, phosphate basis), or a blend (0.3% uSTP plus 0.2% eSTP). Encapsulate (hydrogenated vegetable oil) was designed to melt at 74°C. Treatments were stored (4, 24h at 3°C) before being cooked to two different endpoints (EPT; 74, 79°C) followed by post-cooked storage (0, 5, 10days). An improvement of 77% (0.3% eSTP) and 80% (0.5% eSTP) in the reduction of TBARS was found in comparison to corresponding uSTP. The blend produced a 62% improvement compared to uSTP (0.5%) while maintaining cook yield. CIE a* values were highest at both EPT and post-cooked storage times beyond 0day for eSTP. Meat manufacturing procedures that entail a delayed thermal processing step will benefit by an improvement in lipid oxidation control through the use of encapsulated phosphates.

Conditions associated with Clostridium sporogenes growth as a surrogate for Clostridium botulinum in nonthermally processed canned butter

The objective of this study was to better understand the effect of butter composition and emulsion structure on growth and survival of Clostridium sporogenes, used as a surrogate for C. botulinum in canned butter. The lack of a thermal process step in commercially available canned butter raises questions of potential safety, because it is hermetically sealed and generally exhibits anaerobic growth conditions, which are optimal for Clostridium botulinum growth. Without thermal processing, low-acid canned foods must have inhibitory factors present to prevent C. botulinum growth. Some potential intrinsic inhibitory factors, or hurdles, within butter include: reduced water activity, acidity in cultured products, elevated salt content, and the micro-droplet nature of the aqueous phase in the butter emulsion. It was hypothesized that a normal, intact butter emulsion would have sufficient hurdles to prevent C. botulinum growth, whereas a broken butter emulsion would result in a coalesced aqueous phase that would allow for C. botulinum growth. Batch-churned butter was inoculated with C. sporogenes; butter samples with varying salt contents (0, 0.8, 1.6, and 2.4% wt/wt NaCl) were prepared and stored in coated steel cans for varying times (1 or 2 wk) and temperatures (22 or 41°C) to determine temperature and emulsion structure effects on C. sporogenes growth. Samples stored at 41°C showed a significant increase in C. sporogenes growth compared with those stored at 22°C. Furthermore, NaCl addition was found to have a significant effect on C. sporogenes growth, with 0.8% NaCl promoting more growth than 0%, but with decreases in growth observed at 1.6 and 2.4%. Uninoculated control plates were also found to have bacterial growth; this growth was attributed to other anaerobic bacteria present within the cream. It was concluded that removal of the hurdle created by the micro-droplet size of the emulsion aqueous phase could result in C. botulinum growth even at elevated salt levels and, therefore, home preparation of canned butter is not advisable. It is also possible that commercially canned butter, if heat abused, could potentially allow for C. botulinum growth and, therefore, consumption is not recommended.

Changes in the content of fat- and water-soluble vitamins in black garlic at the different thermal processing steps

The purpose of this study was to measure the content of fat- and water-soluble vitamins in garlic and to assess the influence of thermal processes on garlic. The total water-soluble vitamin content increased by about 1.15–1.92 times in black garlic than that in fresh garlic. The total water-soluble vitamin content of the BG4 (70°C and 60% RH for 60 h) sample was significantly higher than that of any other sample (p<0.05). In general, the total fat-soluble vitamin content decreased with each successive thermal processing step. The total fat-soluble vitamin content of the raw garlic cloves (FG) sample was significantly higher than that of any other sample (p<0.05).

Comparison of phenolic acids and flavonoids in black garlic at different thermal processing steps

The phenolic acid and the flavonoid constituents of garlic subjected to different thermal processing steps were examined. Black garlic was produced in a ripening chamber by using a programmed stepwise heating schedule, as follows. Step 1: 90°C and 100% RH for 34h; Step 2: 60°C and 60% RH for 6h; Step 3: 75°C and 70% RH for 48h; Step 4: 70°C and 60% RH for 60h; Step 5: 65°C and 50% RH for 192h. The results of the present investigations showed that thermal processing affected quantities of each phenolic acid and flavonoid component. The total phenolic content (TPC) and total flavonoid content (TFC) of the garlic subjected to different thermal processing steps were higher than those of fresh garlic. In particular, the black garlic cloves ripened using Step 1 (BG1), black garlic cloves ripened using Step 2 (BG2), black garlic cloves ripened using Step 3 (BG3), and black garlic cloves ripened using Step 5 (BG5) samples exhibited levels of TPC that were higher than the TFC, while the TFC in the fresh garlic (FG) and black garlic cloves ripened using Step 4 (BG4) samples were higher than the TPCs. Hydroxycinnamic acid derivatives were found to be the major phenolic acids of garlic at different processing steps. Among the four major flavonoid subgroups in garlic, flavanols were found at the highest concentrations followed by flavanones and flavones, except in the FG sample.