FEATURE ARTICLE FEATURE ARTICLE The Evaluation Of Liquid .

citor material instead of SiO2 in nextgeneration semiconductor devices. Pentaetoxy tantalum(PETa) is used as material for Ta2O5 film, but its vaporpressure is approximately 20 Pa at 170 C. Vaporizationof liquid material becomes more stable as the vaporizertemperature or the flow rate of carrier gas becomeshigher. However, if the vaporization temperature is toohigh, thermal cracking might occur in the material. Forthis reason, the optimal temperature must be obtained.The equipment illustrated in Fig.5 was used to conductan evaluation test for the vaporization characteristics ofPETa.4.1.2 Test ResultsThe output from the MFM and the internal state ofthe vaporizer are shown in Fig.6. The output from theMFM was unstable at 0.4cm3/min when vaporization wasinsufficient with droplets noted. The output was stable at0.2cm3/min when vaporization was sufficient. Somedroplets were observed in the vaporizer at 0.3cm3/min,an intermediate level, when the output from the MFMshowed tailing at the falling part.The above test results demonstrate that the state ofvaporization can be estimated from the output from theMFM on the secondary FM0.2cm3/mPN2, F.S. 3SLM0.1MPaGooDropletLMFLiquidTa(OC2H5)5, F.S. 0.5cm3/m: 180 C: 35 CFig.5 Testing Equipment for EvaluatingVaporization Characteristics0.2cm3/m0.3cm3/m0.4cm3/mFig.6 Output from MFM and Internal State ofVaporization4.1.1 Test ProcedureThe flow rate of carrier gas was maintained at 300 to700 SCCM and the secondary side in a vacuum state ofapproximately 2.7kPa. The temperature of the vaporizerwas changed in a range between 150 C and 180 C tochange the generated amount of PETa in a range between0.1 and 0.5cm3/min, and then the state of vaporizationwas evaluated. The stability of vaporization wasevaluated by observing the stability of output from theMEM for high temperature, which was put in the pipingon the secondary side of the vaporizer, and the internalstate through the transparent window provided on thevaporizer.51

FEATURE ARTICLEThe Evaluation of Liquid Material Vaporization and Supply System for CVD4.1.3 Influence of Vaporization TemperatureFig.7 shows the changes that occurred in the outputsfrom the MFM for liquid and gas when the temperatureand flow rate of the vaporizer were changed. The risingand falling characteristics, and the stability of the MFMfor gas during vaporization show that the state ofvaporization become more stable as the generatedamount of PETa decreases. When the temperature of thevaporizer is 180 C, PETa can be stably vaporized at0.5cm3/min.Flow rate ofcarrier gas (N2)9.0SLM8.0SLM7.0SLMCondition: Vaporizer temperature 100 Cpressure 93kPa: Good: Slightly bad: BadTable 2 Characteristics of TEPO Vaporization byLiquid Injection MethodFlow rate ofcarrier gas (N2)160 C2.0SLM170 C1.5SLM3m 4m0.1cm3/m 0.2cm3/m 0.3cm3/m 0.4cm3/m0.5cm3/mFig.7 Influence of Vaporization Temperature4.2 Evaluation of Vaporization Characteristics ofTEPOAs the silicon wafer size change to 300 mm, it will benecessary to increase the flow rate of materials for thepurpose of boro-phospho silicate glass (BPSG) filmformation. The same flow as in the vaporization test ofPETa was used to conduct a TEPO[P(OC2H5)3]generation test by the liquid injection and mixinginjection methods.The evaluation results based on the MEM on thesecondary side of the vaporizer are shown in Table 2 and3. Although the pressure condition is slightly different,the vaporization efficiency is greatly improved by themixing injection method. This indicates that a high flowrate can be achieved under the same condition.52Amount of TEPO vaporization:(g/min)0.15150 C180 CAmount of TEPO vaporization: 0.05(g/min)0.1250.10.0750.051.0SLMCondition: Vaporizer temperature 100 Cpressure 80kPa: Good: Slightly bad: BadTable 3 Characteristics of TEPO Vaporization byMixing Injection Method

Technical ReportsAutomatic Delivery System for Liquid5 MaterialsTo continuously use the vaporizer for the bakingmethod or injection method in the commercialproduction line for semiconductors, it will be necessaryto automatically feed liquid material. As an example, ourTEOS automatic delivery system is introduced below.The appearance and flowchart of this system are shownin Fig.8 and 9.This system provides the following features:1. Conforming to safety regulations [CE marking/SEMISTANDARD(S2)]2. Minimize footprint3. Safety design with automatic monitoring system4. Easy operation by using two way communication5. Non stop recharging at replacement of source tanks6. Best compatibility with LSC/VC system6 ConclusionIn the semiconductor manufacturing process, liquidmaterial will become more or more important. On theother hand, the vaporization and supply system has someproblems in complying with new materials and increasingthe flow rate to handle 300mm wafers. In order to settlethese problems, the users’ needs must be graspedaccurately. We wish to take this opportunity of makinginformation exchange with our customers more frequent,and hope that we will play a part in further developmentof the semiconductor industry.Fig.8 Automatic Delivery System for Liquid MaterialSAMPLE2GSAMPLE OUT1/4" SWL TypeSAMPLE11/4" SWL TypeVACUUM1/4" VCRType MaleN21/4" VCRType MaleHe1/4" VCRType MaleTetsuo ShimizuP.S P.SEXHAUST1/4" VCRType MaleDepartment managerR&D Dept. No.2R&D DivisionSOURCE11/4" VCRType MaleSTEC Inc.PFValvePRegulatorPFFilterPSOURCE21/4" VCRType MalePressureSensorPressureSwitchPP.SSOURCE31/4" VCRType MalePValveSOURCE1/4" VCRType MalePHe OUTSOURCE INSOURCE51/4" VCRType MaleTankLOADCELLSOURCE61/4" VCRType MaleDRAIN21/4" VCRType MaleDRAIN11/4" VCRType MaleFig.9 Flow of Automatic Delivery System for LiquidMaterial53

Hot Box Fig.3 Column Method (2) Direct Injection Method The direct injection method vaporizes liquid by mixing the liquid with carrier gas while heating the flow control valve for the liquid. Since the vaporizer also serves as the control valve, the equipment can be