硅中硼离子注入层的卤钨灯辐照快速退火研究

本文研究了SiO_2掩蔽膜硼离子注入硅的卤钨灯辐照快速退火,测量了注入层表面薄层电阻与退火温度及退火时间的关系,得到了最佳的退火条件。对于采用920(?)SiO_2膜,25keV、1×10~(15)cm~(-2)的~(11)B离子注入样品,经不同时间卤钨灯辐照退火后,测量了注入层的载流子浓度分布,并与950℃、30分钟常规炉退火作了比较。结果表明,卤钨灯辐照快速退火具有电激活率高、注入杂质再分布小以及快速、实用等优点。     

离子注入硼的注入损伤和反常瞬时扩散

本文研究了注入硅离子对离子注入硼的反常瞬时扩散的影响,发现硅离子剂量远低于使晶格无序化必需的剂量,并且明显地减小随后注入的硼的反常瞬时扩散。但是,由于额外的硅注入使薄层电阻增大了。硅离子注入到被激活的硼层中,在远超过硅离子射程处引起附加反常扩散。在损伤较大的地方反常移动亦减小。根据退火时可以消除的点缺陷群的产生以及填隙型扩展缺陷的形成而导致高损伤区点缺陷湮没的观点可以解释这些影响。     

磷（P31^＋）注入Si的快速退火电特性

本文报告了P_(31)~+离子注入Si中快速退火的电特性研究结果。采用高精度四探针测量了P_(31)~+注入层在不同注入剂量下,薄层电阻与退火温度和退火时间的关系。采用自动电化学测量仪PN-4200,测量了P_(31)~+离子注入Si中的载流子剖面分布。     

离子注入多晶硅的电子束退火

本文介绍利用扫描电子束对离子注入掺杂磷的多晶硅进行退火、研究退火条件对多晶硅载流子激活率,迁移率和结构的影响,并与热退火进行了对比。实验结果表明电子束退火的多晶硅载流子激活率比热退火有明显提高,薄层电阻率也有所降低。     

通过离子注入前后快速热退火改善多晶硅薄层电阻

对氧化后硅片上的多晶硅膜,进行了砷离子注入前的快速热处理退火。离子注入之后,这种膜进行了另外的快速热处理退火以活化砷。注入前退火使得刚淀积的晶粒尺寸增大到10倍。这些膜的薄层电阻比只是注入后进行退火处理的膜的要低20～30％。注入前退火引起的晶粒尺寸增大,使得晶粒边界区域减小,从而使相对于晶粒的晶粒边界中掺杂剂数量减少至最低限度。     

离子注入后检测设备的掺杂均匀性和剂量精度的方法

测定离子注入后掺杂总数的方法可分为二大类。一类是对注入层进行直接分析;另一类是借助于对物理性能和器件参数的测量而间接地测定其掺杂数量。对这些方法作了简要的评述后,报导了对离子注入的剂量精度和均匀性的一次国际性的调研结果:它是用直径为76mm的硅片,注入硼离子,并在一组规范的条件下进行了退火,用四探针法对被调研的注入后的每一块硅片上的118个点进行了薄层电阻值的自动测量。调研中的85台离子注入机所测的方块电阻的总平均值为169.7Ω/□,相对它的标准偏差为8.1Ω/□,这表明了工业用离子注入机存在的定标范围。等值薄层电阻轮廊图曾用于鉴别均匀性问题,它提供了一个易于解积的图示方法。在一个硅片内薄层电阻值的非均匀性(一个标准偏差)变化范围是0.37％到4.76％,其中值为0.72％。     

红外辐照退火砷离子注入硅的后热处理特性研究

本文研究了硅中砷离子注入层经红外辐照退火后的热处理特性,测量了表面薄层电阻随后热处理温度的变化关系.实验结果表明,对于红外辐照~(75)As离子注入样品,表面薄层电阻随后热处理温度的升高而发生规律性的变化,在900℃附近达到最小值,此时注入杂质的电激活率大于100%.     

离子注入MOS晶体管的电学性质与注入剂量分布的依赖关系

制作了离子注入MOS晶体管,测量了诸如阈值电压、有效迁移率等电学性质。发现在注入硼离子(~(11)B~ )的p型沟道的情况下,阈值电压V_T随注入剂量的变化呈线性关系。其变量△V_T完全由进入硅中的净剂量决定。另一方面,在注入硼离子的n型沟道的情况下,阈值电压变量△V_T随剂量呈亚线性变化,并且表现出对剂量分布的强烈依赖关系。剂量分布随注入能量和退火时间的改变而变化。根据最大表面耗尽层X_(dmax)随注入剂量的增加而迅速地减小这一事实,能够解释这些结果。把非均匀注入分布造成的阈值电压变化的计算值与观测结果进行了比较,两者相符甚好。注入硼离子的p型和n型沟道MOS晶体管的有效迁移率μ_(eff)也表现出对剂量的不同依赖关系。在低剂量范围内,注入硼离子的p型沟道MOSFET的有效迁移率几乎保持不变,但对于n型沟道,有效迁移率却随剂量的增加而单调下降。本文还给出了考虑到表面散射和杂质散射作用的定性解释和近似计算。     

薄层电阻标样及Mapping在IC制造中的应用研究

提出对集成电路在线监控中使用相关薄层电阻标样的必要性和重要性。着重介绍了薄层电阻标样和 Mapping技术在验证仪器各档测量薄层电阻误差 ,对外延生长工艺监控 ,判断离子注入退火后薄层电阻均匀性差的原因 ,监视扩散炉内部温度与气流对扩散影响和监控溅射铝层厚度质量等应用。     

离子注入白光退火特性

本文研究了离子注入后碘钨灯的退火效果;测量了离子注入和瞬态退火样品的电阻率、迁移率、电激活率和注入层电阻率的均匀性;用背散射和扩展电阻仪得到As浓度和载流子浓度分布;获得了制备浅结的工艺条件。用超高压电镜分析了注入层的剩余缺陷。同热退火比较表明白光退火技术更适于超大规模集成电路的微细加工工艺的要求。     

Material and electrical properties of ultra-shallow p+-njunctions formed by low-energy ion implantation and rapid thermalannealing

A study of low-energy ion implantation processes for the fabrication of ultrashallow p⁺-n junctions is presented. The resulting junctions are examined in terms of four key parameters: defect annihilation, junction depth, sheet resistance, and diode reverse leakage current. In the realm of very-low-energy ion implantation, Ge preamorphization is found to be largely ineffective at reducing junction depth, despite the fact that the as-implanted boron profiles are much shallower for preamorphized substrates than for crystalline substrates. Transmission electron microscopy (TEM) analysis of residual defects after rapid thermal annealing (RTA) reveals that the use of either a preamorphization implant or the implantation of BF₂ as a B source results in residual damage which requires higher RTA temperatures to be removed. A reasonable correlation is observed between residual defect density observed via TEM and junction leakage current. It is concluded that the key to an optimized low-energy implantation process for the formation of ultrashallow junctions appears to be the proper selection of preamorphization and annealing conditions relative to the dopant implant energy     

Characterization of single-crystal diamond grown from the vapor phase on substrates of natural diamond

The results of studies of single-crystal diamond layers with orientation (100) grown on substrates of IIa-type natural diamond by chemical-vapor deposition and of semiconductor diamond obtained subsequently by doping by implantation of boron ions are reported. Optimal conditions of postimplantation annealing of diamond that provide the hole mobility of 1150 cm² V^?1 s^?1 (the highest mobility obtained so far for semiconductor diamond after ion implantation) are given.     

n/p ultra-shallow junction formation with plasma immersion ion implantation

n⁺/p ultra-shallow junctions formed by PH₃ plasma immersion ion implantation (PIII) have been studied and diodes with good electrical characteristics have been obtained. The influence of annealing conditions and carrier gas on junction depth and sheet resistance have been studied. It is found that a higher content of H and/or He in silicon can slow down the diffusion of phosphorus and the activation ability of implanted dopant ions in silicon; a shallower junction can been obtained with He rather than H₂ as the carrier gas; and the influence of annealing at 850°C for 20 s on sheet resistance is opposite to that of annealing at 900°C for 6 s on sheet resistance. In addition, mechanisms of unusual electrical characteristics for some diodes are discussed and analyzed in this paper.     

Sensitivity analysis of ion implanted silicon wafers after rapid thermal annealing

In this study, we have investigated sensitivities of the ion implanted silicon wafers processed by rapid thermal annealing (RTA), which can reveal the variation of sheet resistance as a function of annealing temperature as well as implantation parameters. All the wafers were sequentially implanted by the arsenic or phosphorous implantations at 40, 80, and 100 keV with the dose level of 10¹⁴ to 2 × 10¹⁶ ions/cm². Rapid thermal annealing was carried out for 10 s by the infrared irradiation at a temperature between 850 and 1150°C in the nitrogen ambient. The activated wafer was characterized by the measurements of the sheet resistance and its uniformity mapping. The values of sensitivities are determined from the curve fitting of the experimental data to the fitting equation of correlation between the sheet resistance and process variables. From the sensitivity values and the deviation of sheet resistance, the optimum process conditions minimizing the effects of straggle in process parameters are obtained. As a result, a strong dependence of the sensitivity on the process variables, especially annealing temperatures and dose levels is also found. From the sensitivity analysis of the 10 s RTA process, the optimum values for the implant dose and annealing temperature are found to be in the range of 10¹⁶ ions/cm² and 1050-1100°C, respectively. The sensitivity analysis of sheet resistance will provide valuable data for accurate activation process, offering a guideline for dose monitoring and calibration of ion implantation process.     

The effect of argon implantation on the conductivity of boron implanted silicon

Silicon wafers have been implanted with boron (3 × 10¹⁴ or 1 × 10¹⁵ ions cm^?2) and with argon (up to 1 × 10¹⁵ ions cm^?2). The energies were chosen to approximately superimpose the two impurity distributions. After the boron and argon implantations the sheet resistance of each wafer was measured following annealing in nitrogen at temperatures in the range 400–1050°C. The highest dose argon implantation produced an increase in sheet resistance which persisted throughout the entire temperature range. Lower argon doses produced a reduction in sheet resistance for anneal temperatures between 550 and 800°C. The magnitude of the reduction is a function of the boron and argon doses and of the anneal temperatures. The greatest reduction, observed after a 600°C anneal, was by a factor of 5.8. Above 800°C the low dose argon did not affect the sheet resistance.The observed reduction in sheet resistance is expected to lead to an improvement in metal to p-type silicon contacts. A particular application is in the contacts to resistors in fast bipolar logic circuits. As high electrical activity can be obtained at moderate annealing temperatures with combined boron and argon implantations, these implantations can be carried out at a late stage in an integrated circuit process schedule without the danger of additional movement of existing junctions.     

Junction depth versus sheet resistivity in BF2+-implanted rapid-thermal-annealed silicon

Conditions to achieve shallow p+-junctions with low sheet resistance by using ion implantation and rapid thermal annealing (RTA), are presented. This work shows that (junction depth) × (sheet resistivity)rho_{s}X_{j}has a smaller value with increasing implant dose and anneal temperature (boron solubility), and decreasing implant energy. However, the value is saturated for higher doses than 10¹⁶Xjcm², where Xjis junction depth in micrometers, and anneal temperature should be lower than 1100°C, because of considerable boron diffusion even in 10-s RTA.rho_{s}X_{j} = 18Ω.µm is achieved by BF2+ implantation with 5 × 10¹⁵-cm^-2dose at 30 keV and 1000°C RTA. The possibility of further improvement inrho_{s}X_{j}value is discussed.     

Plasma immersion ion implantation doping using a microwavemultipolar bucket plasma

Using plasma immersion ion implantation, silicon has been doped with boron in a high-voltage pulsed microwave multipolar bucket plasma system. Diborane gas (1%) diluted in helium is used as an ion source. A sheet resistance of 57 Ω/□ and an implanted dose of 1.9×10¹⁵/cm² are obtained in 10 min. when the target potential is pulsed to -10 kV with a 1% duty cycle. The boron profile in the silicon substrate is different from that predicted for a conventional 10-keV ion implantation. Silicon p-n junctions fabricated by this technique are of good quality     

Nonmelt laser annealing of 5-KeV and 1-KeV boron-implanted silicon

Nonmelt laser annealing has been investigated for the formation of ultrashallow, heavily doped regions. With the correct lasing and implant conditions, the process can be used to form ultrashallow, heavily doped junctions in boron-implanted silicon. Laser energy in the nonmelt regime has been supplied to the silicon surface at a ramp rate greater than 10 ¹⁰°C/s. This rapid ramp rate will help decrease dopant diffusion while supplying enough energy to the surface to produce dopant activation. High-dose, nonamorphizing boron implants at a dose of 10¹⁵ ions/cm² and energies of 5 KeV and 1 KeV are annealed with a 308-nm excimer laser. Subsequent rapid thermal anneals are used to study the effect of laser annealing as a pretreatment. SIMS, sheet resistance and mobility data have been measured for all annealing and implant conditions. For the 5-KeV implants, the 308-nm nonmelt laser preanneal results in increased diffusion. However, for the 1-KeV implant processed with ten laser pulses, the SIMS profile shows that no measurable diffusion has occurred, yet a sheet resistance of 420 Ω/sq was produced     

Aluminum and boron ion implantations into 6H-SiC epilayers

Aluminum and boron ion implantations into n-type 6H-SiC epilayers have been systematically investigated. Redistribution of implanted atoms during high-temperature annealing at 1500°C is negligibly small. The critical implant dose for amorphization is estimated to be 1 × 10¹⁵ cm⁻² for Al⁺ implantation and 5 × 10¹⁵ cm^-2 for B⁺ implantation. By Al⁺ implantation followed with 1500°C-annealing, p-type layers with a sheet resistance of 22 kΩ/^— can be obtained. B⁺ implantation results in the formation of highly resistive layers, which may be attributed to the deep B acceptor level.     

Mo- and Ti-silicided low-resistance shallow junctions formed using the ion implantation through metal technique

Mo-and Ti-silicided junctions were formed using the ITM technique, which consists of ion implantation through metal (ITM) to induce metal-Si interface mixing and subsequent thermal annealing. Double ion implantation, using nondopant ions (Si or Ar) implantation for the metal-Si interface mixing and dopant ion (As or B) implantation for doping, has resulted in ultrashallow ( ≤ 0.1-µm) p⁺-n or n⁺-p junctions with ∼30-Ω sheet resistance for Mo-silicided junctions and ∼5.5-Ω sheet resistance for Ti-silicided junctions. The leakage current levels for the Mo-silicided n⁺-p junctions (0.1-µm junction depth) and the Mo-silicided p⁺-n junction (0.16-µm junction depth) are comparable to that for unsilicided n⁺-p junction with greater junction depth ( ∼0.25 µm).