Planetary Reactor Research Articles

Enabling MOCVD production on next generation 150 mm Indium Phosphide wafer size

150 mm Indium Phosphide wafers are now commercially available with crystal quality comparable to wafer of smaller radius. This may pave the way for scaling up the production of a multitude of photonic devices for Datacoms operating in the 1.30-1.55μm infrared range with a gain in wafer surface of factor 4 and a reduction of roughly 50% in die cost. To achieve this goal, it is of utmost importance to prove that both AlGaInAs and InGaAsP quaternary compound semiconductors can be grown by metal–organic chemical vapor deposition (MOCVD) on wafers of larger sizes with both thickness and composition uniformities comparable to those achievable on 75 mm. In this article, we report pioneering production technology developments based on the Planetary Reactor® design. Both reactor and related inlet geometry have been deeply revisited with the introduction of a novel 4-fold injector, which in combination with Cl2 In-situ chamber clean, prove to enable such transition in wafer size. Sub-nanometric photoluminescence in-wafer uniformities are demonstrated and historic challenges, such as drift in material composition of highly sensitive InGaAsP alloys during a production campaign, are addressed thanks to this unique combination. Uniformity, tunability and reproducibility results are thus presented for two prototypical case scenarios: a highly strained AlGaInAs multiple quantum well (MQW) and a bulk InGaAsP layer with wavelength emission of 1550 nm and 1100 nm respectively to corroborate reactor flexibility in meeting industry requirements for next device generation.

Improvement of InGaP solar cells grown with TBP in planetary MOVPE reactor

In this study, the impact of various growth parameters, such as wafer temperature, device structures, and substrate misorientation, on the quality of InGaP epitaxial layers and solar cells grown in a planetary MOVPE reactor using TBP as a P source were investigated and optimized. Results showed that the carrier lifetime in unintentionally n-doped InGaP significantly decreased as the growth temperature increased from 560 to 590 °C. At temperatures above 600 °C, the growth of InGaP was unsuccessful due to extremely rough surface morphology. The study revealed that InGaP rear homojunction and rear heterojunction solar cells using n-type InGaP base layers displayed improved photo-carrier collection and performance compared to traditional front junction solar cells with p-type InGaP base layers. Notably, InGaP grown on GaAs (001) with a 5° miscut towards (111)A was found to have better quality, while InGaP grown on GaAs (001) with a 6° tilt towards (111)B had worse results in terms of carrier lifetime, PL intensity, and solar cell performance.

Study and reduction of the surface pits in 4H-SiC epitaxial wafer

Pit defects in SiC epitaxial materials is a new issue which shows an influence on different type of SiC devices such as SBD and MOS. The surface pits generated a leakage current and caused the occurrence of a local electric field crowding in the SBD. While the original and mechanism of the surface pits is still not clear. In the paper, the original and reduction of surface pits during 4H-SiC homoepitaxial growth by a warm wall planetary reactor have been investigated. The C/Si ratio and Cl/Si ratio have great effects on the surface pits. Lower C/Si ratio and higher Cl/Si ratio will form a Si-rich environment on the wafer surface during growth, which is crucial for reduction of the surface pits in 4H-SiC epitaxial wafer. With the optimized parameters, high quality epi-wafer with lower pit defects density has been obtained.

Process Optimization and Modeling of the Silicon Growth in Trichlorosilane-Hydrogen Gas Mixture in a Planetary CVD Reactor

In this study, the effect of operating conditions of the chemical vapor deposition process on the silicon growth rate in a trichlorosilane-hydrogen (TCS-H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) system was evaluated. The influence of five parameters, including wafer rotation, TCS fraction, pressure, temperature, and mass flow rate was investigated. Response surface methodology (RSM) based on three-dimensional CFD simulations were used to analyze the coupled effect of the process parameters. A second-order polynomial model was used to predict the response. Analysis of variance showed that the model is statistically significant and only 1.22% of the total variations are not explained by the regression model. According to the RSM results, the growth rate increases as a function of the TCS fraction, pressure, and temperature. Additionally, the coupled effect of the TCS fraction and pressure has a significant effect on the growth rate while the coupled effect of wafer rotation speed and mass flow rate had the lowest effect. Finally, four confirmation tests were executed for a random combination of factors to verify the accuracy of the regression model. The maximum deviation between the CFD and regression model values of the silicon growth rate was found to be 4.4 %.

Influence of inlet structures of planetary reactor on gas reaction path in AlN-MOVPE process

Numerical study on the influence of inlet structure of planetary reactor on gas reaction path and growth rate in AlN-MOVPE was investigated. It was found that, for the conventional two-inlet reactor (base reactor), the reaction is dominated by the adduct reaction path, and the growth rate is low but evenly distributed; for the inverted inlet reactor, i.e., group-III in lower inlet and group-V in upper inlet, the reaction is dominated by the pyrolysis path, and the growth rate is higher than the base reactor but the growth uniformity is decreased. By moving the position of the inlet separator closer to the ceiling for the inverted inlet, the growth uniformity is improved. When the number of reactor inlets increases from two inlets (base reactor) to three and five inlets, the growth rate increases, the growth uniformity improves, and the reaction changes from the adduct-dominated path to the pyrolysis and adduct coexisted path. Besides varying the inlet geometry, we also found that decreasing the NH3 flow rate will enhance the pyrolysis path and the growth rate for the above reactors.

A Modeling and Experimental Study on the Growth of VCSEL Materials Using an 8 × 6 Inch Planetary MOCVD Reactor

VCSEL (vertical cavity surface emitting laser) is a promising optoelectronic device, but its high manufacturing cost limits its scope of applications. Growing on larger size wafers is an effective way to reduce the cost. However, the growth rate uniformity needs to be optimized to ensure the uniformity of the devices’ performance over the wafers. This paper investigates the factors which influence the growth rate uniformity using an 8 × 6 inch planetary reactor through experiments and simulations. At a carrier gas flow rate of 37 slm, an AsH3 flow rate of 600 sccm, an AsH3 flow rate ratio of 100:500, and a ceiling temperature of 175 °C, the growth rate uniformity of the AlGaAs layer with a relative standard deviation of 0.16%, 1σ, was obtained over the 6-inch wafers. The uniformity of the DBR stop band center and VCSEL quantum well wavelength with standard deviations of 0.142% and 0.023%, 1σ, were received over the 6-inch wafers, respectively. Based on the optimized results, 99.95% of VCSEL devices with wavelengths of 940 ± 5 nm were realized over the 6-inch wafers.

High quality 4H-SiC homo-epitaxial wafer using the optimal C/Si ratio

Epitaxial growth of 4H-SiC on 4° off-axis substrates has been performed under different C/Si ratio in order to improve the quality level of epitaxial layer. 4H-SiC homoepitaxial layer is grown in horizontal warm-wall planetary reactor. The growth rate, doping concentration, morphology defect of epitaxial layer are characterized using the Fourier transform infrared, Hg schottky contact and optical surface analyzer, respectively. Meanwhile, the epitaxial layer is etched by molten KOH and microscopy observation to understand conversion of BPDs dependence of C/Si ratio. It is suggested that the defect density in the epitaxial layer is increased under C-rich and Si-rich condition, since the increasing of 2D island nucleation and formation of silicon drops, respectively. Moreover, this low conversion ratio is considered to be induced by suppression lateral growth under the low C/Si ratio condition. As a result, epitaxial layer with high yield (99.7%) and extremely low basal plane dislocations density (＜0.05 cm−2) can be obtained by the optimization of C/Si ratio.

25‐2: Enabling MOCVD Technology for Micro LED High Volume Manufacturing

Epitaxy wafers are key to the technology development of Micro LED displays. As Micro LED chips are extremely small, the quality of epitaxy wafers including wavelength uniformity and low defect becomes crucial for further production process. We present progress on improvements to MOCVD technology of blue and red Micro LEDs based on Planetary Reactor® technology to meet the new challenging wavelength and defect requirements.

Modeling of Epitaxial Silicon Growth From the DCS-H2-HCl System in a Large Scale CVD Reactor

Multi-wafer planetary type chemical vapor deposition (CVD) reactors are widely used in thin film growth and suitable for large scale production. In this paper, numerical modeling has been carried out to simulate transport phenomena and epitaxial silicon growth in a planetary CVD reactor for the SiH2Cl2–H2–HCl system. A chemical reaction model using temperature dependent reaction rate is proposed and validated using experimental data. Based on the model, the effect of various operation conditions such as satellite rotational speed, species concentration, operating temperature and pressure is considered to determine the key factor influencing the growth rate and uniformity. The results reveal that the growth rate and uniformity are strongly related to total flow rate, species concentration and operating pressure, but are not affected by rotational speed of the satellite in case of high flow rates. Growth rates are found to be increased from 0.02 $\mu \text{m}$ /min at operating pressure of 10 torr to approximately 0.16 $\mu \text{m}$ /min at 150 torr. Growth deposition non-uniformity decreases from 80% for total flow rate of 460 slm to 13% for total flow rate of 46 slm.

Triangular Defects Reduction and Uniformity Improvement of 4H-SiC Epitaxial Growth in a Planetary Reactor

High quality SiC Epilayers are essential for the development of high performance power devices. Killer defects such as triangular defects could cause leakage current paths within the high voltage SiC devices. This paper reports on the recent advances in 4H-SiC epitaxial growth toward high-throughput production in a commercial planetary reactor. The triangular defects are suppressed by the optimized pre-etching process, and the physics behind was investigated. The doping and thickness uniformities of the intra-wafer and wafer-to-wafer have also been improved.

Si impurity concentration in nominally undoped Al0.7Ga0.3N grown in a planetary MOVPE reactor

The unintentional silicon incorporation during the metalorganic vapor phase epitaxy (MOVPE) of nominally undoped Al0.7Ga0.3N in a Planetary Reactor under various growth conditions was investigated. Dependent on growth temperature, pressure and V/III ratio, Si concentrations of below1 × 1016 up to 4 × 1017 cm−3 were measured. Potential Si sources are discussed and, by comparing samples grown in a SiC coated reactor setup and in a TaC coated setup, the SiC coatings in the reactor are identified as the most likely source for the unintentional Si doping at elevated temperatures above 1080 °C. Under identical growth conditions the background Si concentration can be reduced by up to an order of magnitude when using TaC coatings.

Numerical modeling study on the epitaxial growth of silicon from dichlorosilane

Computer simulations play an important role in determining the optimal design parameters for chemical vapor deposition (CVD) reactors, such as flow rates, positions of the inlet and outlet orifices, and rotational rates, etc. Reliability of the results of these simulations depends on the set of chemical reaction used to represent the process of deposition in the reactor. Aim of the present work is to validate the simple empirical reaction to model the epitaxial growth of silicon for a Dichlorosilane-H2 (DCS)-H2 system. Governing equations for continuity, momentum, energy, and reacting species are solved numerically using the finite volume method. The agreement between experimental and predicted growth rates for various DCS flow rates is shown to be satisfactory. The increase in growth rate with the increase in pressure is in accordance with the available data. Based on the validated chemical reaction model, a study was carried out to analyze the uniformity of the silicon layer thickness for two different flow rates in a planetary reactor. It was concluded that, based on the operating conditions, the uniformity of the silicon layer over the wafer is independent of the satellite rotational rate in the reactor.

Elimination of BPD in 5~30um Thick 4H-SiC Epitaxial Layers Grown in a Warm-Wall Planetary Reactor

The process of the epitaxial growth of 4H-SiC has been optimized to obtain higher ratio of conversion of BPDs to the TEDs on 100 mm substrates in a warm-wall planetary reactor. 100% BPD conversion ratio was successfully obtained with excellent surface morphology under optimized growth process. The high efficiency of the optimized growth process in BPD conversion is independent of the initial surface conditions and BPD density of the substrates.

Formation and Reduction of Large Growth Pits on 100 mm 4° 4H-SiC

The large growth pits (LGPs) dependence of substrate quality, growth rate, and C/Si ratio have been discussed in the 4H-SiC epitaxial growth on 100 mm N-type 4H-SiC Si-face substrates misoriented by 4° toward [11-20] with a warm-wall planetary reactor. The formation and reduction of LGPs have been investigated by adjusting the growth process parameters. With the optimized process, the perfect surface morphology with lower LGPs density has been obtained on the high quality substrate.

Kinetics of AlGaN metal–organic vapor phase epitaxy for deep-UV applications

AlxGa1−xN layers with high aluminum content of x ∼ 0.68–0.73 were grown in an 11 × 2-in. AIX 2400 G3 HT planetary reactor by metal–organic vapor phase epitaxy. Growth trends are analyzed by reaction-transport modeling in a wide range of growth conditions. Gas-phase nucleation resulting in both Al and Ga consumption into nanoparticles is a major mechanism affecting the growth efficiencies of AlN and GaN. Process windows suitable to grow multiple quantum wells (MQWs) for deep UV applications are found for a range of pressures, temperatures, and V/III ratios.

Reduction of epitaxial defects on 4°-off 4H[sbnd]SiC homo-epitaxial growth by optimizing in-situ etching process

The investigations of in-situ etching of 4HSiC epi-growth on 4° off-axis 100 mm diameter substrates under different conditions have been carried out in a commercial warm-wall multi-wafer planetary reactor. The surface morphologies of the as-etched substrates have been characterized by atomic force microscopy on 20 × 20 μm2. Based on the step height and roughness mean square, the best etching condition for 4HSiC 4° off-axis substrates was determined to be H2 + HCl at 1500 °C for 10 min. With the optimized in-situ etching process, high quality 4HSiC epitaxial layers with excellent surface morphology have been obtained, and the defect density is lowered to 0.45 cm−2 resulting in a projected 2 × 2 mm die yield of ∼98%.

Design Optimization of Induction Heater in Planetary Reactors for Semiconductor Industry

One application of induction heating is a planetary reactor for deposition of compound semiconductor layers from the gas phase. High temperature needed for the process is provided by a “pancake” induction coil. Temperature distribution in the reactor influences the deposition quality as well as the lifetime of the reactor components. The induction coil shape has been improved by numerical modelling combined with automatic optimization. The developed two-and three-dimensional models include coupled electromagnetic and thermal calculations to take into account temperature dependent material properties. Three-dimensional structural analysis, based on the predicted temperature distribution, was used to estimate the level of the appeared thermal stresses in the reactor parts. The received optimal design of the induction coil has been successfully tested in the industrial planetary reactor.

150 mm 4H-SiC Epitaxial Layer Growth in a Warm-Wall Planetary Reactor

Homo-epitaxial growth of 4H-SiC on 4o off-axis 150 mm diameter substrates has been performed in a commercial warm-wall multi-wafer planetary reactor. Based on our well developed 100 mm 4H-SiC epitaxial growth process, which can achieve excellent thickness and doping uniformities (δ/mean) of &lt;1% and &lt;5%, respectively, the growth process and hardware were further fine-tuned and improved for 150 mm 4H-SiC homoepitaxy. After the improvement, the 6 to7 μm thick epilayer uniformity has reached 1.1% with a 5mm edge exclusion while the doping uniformity has improved to 16.5% (&lt;10%) with an edge exclusion of 5 mm (10mm), respectively. Surface roughness of the as-grown 150 mm 4H-SiC epitaxial layer has an RMS value of 0.12 nm scanned by AFM on 20×20 μm2 areas. Homo-epitaxial growth on C-face 150 mm 4H-SiC substrates has also been carried out. Other than the doping concentration and uniformity, the other results are very close to the epi-growth on Si-face.

Numerical simulation of the temperature distribution in a planetary MOCVD reactor

In this study, a planetary MOCVD reactor was thermally analyzed and a numerical model was proposed to predict an actual thermal distribution, comparing the results between the numerical simulation and experiment. Numerical simulations were performed for various modifications, namely, the ceiling design and heat shield layout, to improve the heating efficiency. The reactors comprising the ceiling design and modified heat shield layout conserved 15% and 5% of the heating energy, respectively. This study provides a method for predicting the temperature distribution inside MOCVD chambers and evaluating the heating efficiency yielded by design modifications. These results could be used to expand and consolidate the design engineering knowledge database.

(Invited) MOCVD of III-V Compounds on Silicon Substrate-Status and Challenges

Next generation high speed digital circuits utilizing III/V based transistors, Solid State Lighting applications of LED as well as power management electronic applications utilizing AlGaInN/GaN HEMT on Silicon substrate require advanced, high yield and high throughput MOCVD production technology.The emerging III/V-on-Silicon technology for electronic and optoelectronic applications also has an impact on MOCVD reactor design. Besides the differences in lattice constants and thermal expansion coefficients between Silicon substrate and III-V epi layer stack additional issues such as particle formation, reproducible starting conditions, anti phase domains and substrate cleaning prior to growth need to be solved. In addition the deposition of high K material on top of the structures may be required. To address these challenges we developed the Planetary Reactor for 5x200 mm GaN-on-Si applications. The showerhead technology opens the path to grow compound semiconductor on 300/450 mm wafer.To establish most appropriate process conditions for the growth of five times 200 mm wafers using the existing horizontal flow Planetary Reactor production tool, the existing MOVPE platform was further upgraded by some features. The probably most important one is the transition from a triple-inlet injector towards a penta injector. This injector features five injection levels instead of three so far. Taking this approach very good uniformities all over the 200 mm radius are achieved.To assess the Planetary Reactor performance we grew on 200 mm Si wafer 5-fold InGaN LED structures with a total thickness of 5.9 µm using a sequence of strain relieving AlGaN layers with Al-concentrations of ~67%, ~57% and ~32% followed by an in-situ deposited SiN mask for ELOG. The GaN buffer had a total thickness of 5 µm with intermittent low temperature (LT) AlN strain management layers.Photoluminescence (PL) mappings were performed on the wafers at room temperature. The average wavelength over all wafers was determined to be lmean = 451 nm. The maximal wavelength spread from wafer to wafer was Dlw2w= 2.6 nm. No edge exclusion was used when measuring these results.Simulation results as well as evolutionary steps have led to the introduction of the Close Coupled Showerhead (CCS) reactors. The showerhead is designed to allow no mixing of incompatible sources upstream of the reactor chamber and minimises the possibility of pre-reaction before the precursors reach the diffusion/boundary layer. The showerhead reactor exhibit high wafer capacity configurations 75x2”, 19x4” and 3x8” for Crius II XL. The reactor is large enough for 200/300 mm single wafer processing. Details of the growth chamber will be discussed. The basic design rules and principles of MOCVD growth optimization and details of today’s high throughput MOCVD technology will be explained. After designing an even larger MOCVD reaction chamber based on simulation predictions first experiments on 450 mm silicon wafer were done. Elipsometry measurements of a 450 mm wafer show a layer thickness of 354 nm by taking 120 data points. The total deviation is measured to 3.16%, Standard deviation is 0.79%. Further implications for the move to 450 mm substrates will be discussed.The Cost of Ownership (CoO) of MOCVD tools is mainly determined by the used wafer size and yield, In-Situ monitoring effort and by reduction of user interaction due to automation. This paper also discusses the different developments in the field of MOCVD to facilitate further reduction in production cost and simultaneously improving the device characteristics by using nanostructures. That includes selective growth on silicon to predefine mesa area for the transistors in a CMOS logic environment and the material selection from high mobility Sb based HEMT structures to more classic InGaAs based structures on GaAs or InP based buffer layer. Finally an outlook will be given for electronic applications such as graphene and new 2D nanomaterials. But also in the field of optoelectronics recent experimental progress on silicon substrate will be discussed.