先进相移掩模(PSM)工艺技术

先进相移掩模(PSM)制造是极大规模集成电路生产中的关键工艺之一,当设计尺寸(CD)为0.18μm时,就必须在掩模关键层采用OPC(光学邻近校正)和PSM(相移技术),一般二元掩模由于图形边缘散射会降低整体的对比度,无法得到所需要的图形。通过相位移掩模(PSM)技术可以显著改善图形的对比度,提高图形分辨率。相移掩模是在一般二元掩模中增加了一层相移材料,通过数据处理、电子束曝光、制作二次曝光对准用的可识别标记、二次曝光、显影、刻蚀,并对相移、缺陷等进行分析和检测,确保能达到设计要求。     

Actinic inspection of EUVL mask blank defects by photoemission electron microscopy: Effect of inspection wavelength variation

Extreme ultraviolet (EUV) photoemission electron microscopy (PEEM), which employs standing wave field illumination of a sample, is a potential tool for at-wavelength inspection of phase defects on extreme ultraviolet lithography (EUVL) mask blank. In this paper, we will demonstrate that the contrast of an underneath multilayer programmed defect in EUV-PEEM image is strongly dependent on the inspection wavelength. The observed contrast variation at different inspection wavelengths is in good agreement with the simulation result of a standing wave field on surface of multilayer stack in the mask blank sample. We also observed some native defects on the programmed defect sample, and found that some of them reverse their contrast with varying inspection wavelengths while others do not.     

一种用于暗域交替式相移掩模设计的自适应版图划分方法

提出了一种新的用于加速 1 30 nm以下工艺交替式相移掩模设计流程的版图划分方法 ,该方法能够自适应调整版图划分的粒度 .讨论了消除相位冲突的方法和版图压缩中相位兼容性保持的策略 .利用上述算法实现的 CAD原型系统经多个工业界例子的测试表明能够有效地适应随版图尺寸而快速增长的相位冲突复杂性 ,同时提供较好的 PSM设计质量 ,并能满足不同求解精度和加速比的要求     

Reduction of CD variance by using optical proximity correction for patterning with DUV phase shift mask

Critical dimension (CD) variation with the use of attenuated phase shift mask (PSM) at 248nm wavelength has been simulated and analyzed. Optical proximity effect was found to be severe and can take up the whole CD error budget for 0.25μm process. PSM/OPC conversion rules were developed for a test pattern. Two rules-based automated PSM/OPC conversion programs, one of them with hierarchy management, were used. Bias between isolated and nested features was significantly reduced with the correction. Issues concerning computation time and data multiplication are also discussed.     

A pixel-based regularization approach to inverse lithography

Inverse lithography attempts to synthesize the input mask which leads to the desired output wafer pattern by inverting the forward model from mask to wafer. In this article, we extend our earlier framework for image prewarping to solve the mask design problem for coherent, incoherent, and partially coherent imaging systems. We also discuss the synthesis of three variants of phase shift masks (PSM); namely, attenuated (or weak) PSM, 100% transmission PSM, and strong PSM with chrome. A new two-step optimization strategy is introduced to promote the generation and placement of assist bar features. The regularization framework is extended to guarantee that the estimated PSM have only two or three (allowable) transmission values, and the aerial-image penalty term is introduced to boost the aerial image contrast and keep the side-lobes under control. Our approach uses the pixel-based mask representation, a continuous function formulation, and gradient-based iterative optimization techniques to solve the inverse problem. The continuous function formulation allows analytic calculation of the gradient in O(MNlog (MN)) operations for an M × N pattern making it practically feasible. We also present some results for coherent and incoherent imaging systems with very low k₁ values to demonstrate the effectiveness of our approach.     

Binary mask side lobe suppression using space scattering bar

Use of off-axis illumination such as dipole and cross-pole to obtain minimum dense pitch resolution limits process margin due to side lobe defect pattern formation. Side lobe or ghost images are unwanted additional patterns formed at wafer image at certain pitch range where intensity drop occurs [I. Hur, Proc. SPIE 2440 (1995) 278], and there are limited ways in which ghost images can be reduced. One way to suppress ghost image is to use multi-pole illumination and such an illumination condition is difficult to generate using diffractive optic elements so a hard aperture must be used but its use limits throughput. An alternative way is to vary the mask phase in order to somewhat increase the intensity to alleviate the formation at certain pitch range [H. Iwasaki et al., Proc. SPIE 3236 (1997) 544]. But for patterning memory devices at and below 50 nm half-pitch, it is shown that binary mask provides beneficial results over attenuated phase shift mask due so called “mask induced polarization effect” [A. Estroff et al., Proc. SPIE 5754 (2005) 555; W.H. Cheng et al., Proc. SPIE 5992 (2005) 1; S. Teuber et al., Proc. SPIE 5754 (2005) 543; Y. Aksenov et al., Proc. SPIE 5754 (2005) 576; I. Höllein et al., Proc. SPIE 5853 (2005) 194]. Nevertheless, optical proximity corrections are to be performed and maximum obtainable process margin need to be obtained. Hence, a method of optimizing space scattering assist feature positioning and sizing is discussed in this paper. A simplified analysis method to optimize space scattering assist feature insertion is formulated for an optical proximity correction. A simplified model formulation is defined a priori, and its result is compared to results obtained from an empirically calibrated model and indicated a good correlation.     

METRO-3D: an efficient three-dimensional wafer inspection simulator for next-generation lithography

Wafer inspection schemes for next-generation lithography (NGL) will play a key role in controlling defect mechanisms and maintaining an acceptable yield. Developing these wafer inspection schemes will require characterization and optimization of deep ultraviolet (DUV) wavelength illumination at high numerical apertures (greater than 0.9) to detect defects that may be a fraction of the design rule. Using wafer inspection test benches that provide the flexibility for various illumination polarizations, numerical apertures, scanning, or full-field schemes can be extremely costly; therefore, simulation of these schemes is necessary to characterize the various detection parameters. To model defects for NGL, three-dimensional (3-D) simulation tools will be required to simulate highly absorptive material in the environment of shorter wavelength illumination. Also, the simulator will be required to simulate high numerical aperture (NA) inspection schemes to capture small defects. With the development of METRO-3D, a 3-D simulation tool that rigorously solves the EM field on arbitrary wafer topographies, we are able to model and characterize the wafer inspection schemes for NGL. We will present simulation results from METRO-3D for various wafer inspection schemes, including high NA schemes, on NGL topographies with highly absorptive materials.     

超精细图案光刻技术的研究与发展

根据国内外研究和发展现状，对有望突破100nm超精细图案光刻分辨率的一些关键技术进行了阐述，其中包括曝光技术、掩模技术、光学系统改进和以离轴照明、相位移掩模、多重滤光和图形演算为代表的分辨率增强技术等。     

用于T形栅光刻的新型移相掩模技术

根据移相掩模基本原理,通过光刻工艺模拟提出了一种适于T形栅光刻的新型移相掩模技术——M-PEL。初步实验证明,M-PEL技术可在单层厚胶上经一次光刻形成理想的T形栅抗蚀剂形貌。     

解决0.18μm光刻批量生产的五大技术要素

介绍了解决０．１８μｍ 光刻批量生产的五大技术要素, 即曝光装置、倾斜（离轴） 照明技术、相移掩模技术、光学邻近效应修正技术和光刻胶及工艺     

相移迁移法在激光超声合成孔径聚焦技术中的应用

通过分析脉冲源激光辐照于工件表面激发的多模式、宽带超声体波信号并结合合成孔径聚焦技术(SAFT),实现了对工件内部微小缺陷的检测、定位和成像。首先基于有限元仿真模拟了激光激发超声波在含缺陷样品中的传播过程,编写了基于相移迁移法(PSM)的SAFT成像算法,然后在实验中使用激光在含缺陷样品表面激发超声波,使用激光测振仪探测超声波,并基于已有算法和探测结果对样品内缺陷进行了检测和定位,以验证算法的正确性。有限元仿真以及实验结果均表明,将激光超声技术与频域SAFT-PSM结合,能够有效地对微小缺陷进行检测和定位,且其图像重构速度快于时域SAFT,可为激光超声无损检测提供更快速的实时技术方案。     

硅集成电路光刻技术的发展与挑战

从微电子集成电路技术发展的趋势,介绍了集成电路技术发展对光刻曝光技术的需求,综述了当前主流的DUV光学曝光技术和新一代曝光技术中的157nm光学曝光、13nm EUV曝光、电子束曝光、X射线曝光、离子束曝光和纳米印制光刻技术的发展状况及所面临的技术挑战.同时,对光学曝光技术中采用的各种分辨率增强技术如偏轴照明(OAI)、光学邻近效应校正(OPC)、移相掩膜(PSM)、硅片表面的平整化、光刻胶修剪(resist trimming)、抗反射功能和表面感光后的多层光刻胶等技术的原理进行了介绍,并对不同技术时代可能采用的曝光技术作了展望性的评述.     

Mirror electron microscope for inspecting nanometer-sized defects in magnetic media

We developed a mirror electron microscope (MEM) for the highly sensitive inspection of defects on the magnetic storage disks of commercial hard disk drives (HDDs). Magnetic fields recorded on a magnetic disk do not affect the MEM images for inspection. We used artificial defects in a detection sensitivity evaluation to test the effectiveness of our MEM inspection tool and found that it was sensitive enough to detect defects that were 67 nm in diameter and 7 nm in height. The size of a MEM image for a defect was eight times larger than the physical size measured by an atomic force microscope. The obtained sensitivity is beyond the resolution power of the objective lens of the MEM itself. This is because MEM images the distortion of static electrical potentials spread over a larger area than the physical size of a defect itself and the image is obtained in out-of-focus condition of an objective lens. The image acquisition time was 50 ms, which corresponded to the inspection time of 4 h for the full surface inspection of a 2.5 in. magnetic disk. MEM is a promising technique for conducting a highly sensitive defect inspection and a high throughput inspection simultaneously as compared with an SEM-based inspection.     

Partitioned linear block codes for computer memory with 'stuck-at' defects

Linear block codes are studied for improving the reliability of message storage in computer memory with stuck-at defects and noise. The case when the side information about the state of the defects is available to the decoder or to the encoder is considered. In the former case, stuck-at cells act as erasures so that techniques for decoding linear block codes for erasures and errors can be directly applied. We concentrate on the complimentary problem of incorporating stuck-at information in the encoding of linear block codes. An algebraic model for stuck-at defects and additive errors is presented. The notion of a "partitioned" linear block code is introduced to mask defects known at the encoder and to correct random errors at the decoder. The defect and error correction capability of partitioned linear block codes is characterized in terms of minimum distances. A class of partitioned cyclic codes is introduced. A BCH-type bound for these cyclic codes is derived and employed to construct partitioned linear block codes with specified bounds on the minimum distances. Finally, a probabilistic model for the generation of stuck-at cells is presented. It is shown that partitioned linear block codes achieve the Shannon capacity for a computer memory with symmetric defects and errors.     

Observation of the internal defects of multilayer film

We constructed the EUV microscope (EUVM) for actinic mask inspection which consists of Schwarzschild optics (NA 0.3, 30×) and X-ray zooming tube. Using this system, EUVL finished mask and Mo/Si coated glass substrates are inspected. EUVM image of 300-nm-wide pattern of finished mask was clearly observed. Resolution can be estimated to be 50 nm or less from this pattern. The programmed phase defect on the glass substrate made by HOYA is also used for inspection. By using EUV microscope, programmed phase defect with dot patterns of over 90 nm in size and over 4 nm-height bump can be observed finely. And the programmed phase defect of 100-nm-wide and 2-nm-depth pit was also observed. Thus, in this research, observation of a programmed phase defect was advanced using the EUV microscope, in other words, it is succeeded in observation of the topological defect image inside a multilayer film. These results show that it is possible to detect internal reflectance distribution of multilayer under the EUV microscope, without being dependent on surface figure.     

Repair technique for phase-shifting masks using silicon-containingresist

A repair technique for shifter defects on phase shifting masks is described. It is based on the spin-coating of silicon-containing resist on the entire mask, electron beam exposure, and development. The new repair technique is quite simple because it does not require the deposition or removal of shifter materials. Both intrusion and extrusion shifter defects have been successfully repaired     

π相移光纤光栅制作方法的比较研究

介绍了目前最常用的两种制作相移光纤光栅的方法,即分步曝光法(或遮挡法)和相位掩膜板移动法,对比分析了两种方法引入相移的物理机制,并利用传输矩阵法理论模型,数值模拟了两种制作方法下的相移光纤光栅透射谱,并分别进行了分布反馈光纤激光器(DFB-FL)的对比实验。结果表明,分步曝光法制作相移光纤光栅时,相移量与光栅中无曝光段的长度及纤芯折射率调制量均有关,难以精确控制相移量的大小,并且存在偏振模竞争问题;而相位掩膜板移动法通过压电陶瓷直线微动台控制掩膜板和光纤相对位移,在光栅中引入相位变换,可以将相移量控制在0~2π范围之内,更容易实现π相移光栅的制作。     

基于机器视觉的印刷品缺陷检测与识别

阐述了印刷品缺陷检测在印刷成品的质量控制和印刷工艺管理中的重要地位和作用;提出了一种新的缺陷检测算法,并给出了系统的设计和缺陷检测流程;研究了一种基于小波变换的图像边缘检测方法,通过与传统缺陷检测算法进行对比,表明基于小波变换的图像边缘检测方法不仅能有效地滤除噪声、检测弱小目标在内的图像的边缘,而且还具有较强的抗噪性能,能检测出印刷品上的微小印刷缺陷;最后通过实验验证了该算法的可行性、可靠性和有效性。     

侧墙铬衰减型新结构移相掩模的应用

提出了一种全新的移相掩模--侧墙铬衰减型移相掩模（SCAPSM) ，相对于通常的衰减型移相掩模，其制造工艺仅多两步，却可以较大幅度提高光刻分辨率. 采用PROLITH光学光刻模拟软件，参考ArF步进扫描投影光刻机TWINSCAN XT:1400E的曝光参数，对侧墙铬衰减型移相掩模的工艺进行了研究，证明SCAPSM+离轴照明的方案可以将干式193nm光学光刻的分辨率提高到50nm.