等離子體浸沒離子注入論文：等離子體浸沒離子注入 充電效應 PIC

1、【關鍵詞】等離子體浸沒離子注入 充電效應PIC-MCC模型 混 合PIC圓柱形介質圓管【英文關鍵詞】Plasma Immersion Ion ImplantationCharging effects Particle In Cellplus Monte CarloCollision(PIC/MCC)model Hybrid PIC Cylindrical dielectric tube等離子體浸沒離子注入論文:等離子體浸沒離子注入介質靶 鞘層特性的粒子模擬研究【中文摘要】等離子體浸沒離子注入(plasma immersion ion implantation,簡稱Pill)是在傳統(tǒng)的束線離子注

2、入(PBII)的基礎上提 出的一種新的離子注入技術，由于其具有成本低、設備簡單、易操作、 適合處理復雜形狀樣品等諸多優(yōu)點，在材料表面改性、半導體和微電 子材料加工等方面得到廣泛的應用。然而,由于介質材料的導電性能 較差,在對介質材料進行表面改性時容易出現注入離子電荷在表面積 累的現象，出現充電效應,從而導致注入離子能量達不到預期負脈沖 電壓幅值,嚴重影響注入效果；同時，對于空心圓柱形介質圓管的內表 面的離子注入過程，除了充電效應，隨著離子注入過程的進行，介質圓 管內的鞘層不斷向圓管中心擴展，鞘層在圓管中心會出現重疊現象， 導致離子的注入劑量和注入能量降低。為了解決上述問題，對介質靶 PIII過

3、程中鞘層演化特性進行理論上的深入研究就顯得尤為必要。因 為注入材料表面的離子主要是在鞘層中獲得加速，鞘層特性直接影響 被加工材料的離子注入效果，同時，理論研究的結果可以揭示離子注 入過程的物理機理，為實際離子注入工藝的優(yōu)化提供一定的參考。本 文主要采用粒子模擬(particle in cell,簡稱PIC)方法，對介質靶材 料等離子體浸沒離子注入過程中的鞘層演化規(guī)律和靶表面的離子注 入特性進行了模擬研究，分析討論了各種參數對PIII過程中鞘層演化 和注入特性的影響。本論文的具體安排如下：第一章，介紹了 pm技 術的特點及其發(fā)展應用、pm技術在平板介質靶和圓管介質靶的應用 研究現狀及意義，綜述了

4、對pm過程進行計算機模擬時常用到的模擬 方法。第二章，對等離子體模擬中使用的PIC/MCC模擬方法進行了詳 細的介紹，把PIC/MCC分成PIC和MCC兩個部分進行講述。同時，結合 本文要用到的算法,在討論模型時對一維平板模型和柱坐標下的二維 模型都做了相應的推導。第三章，采用二維混合PIC(Hybrid PIC)的 方法對介質圓管內表面的PIII過程進行了數值模擬，得到了空間鞘層 演化的規(guī)律,并且對離子注入劑量和注入能量均勻性的進行了討論。 結果顯示：在介質圓管內表面PIII過程中，隨著積累電荷的增多，充電 效應越來越明顯，導致介質表面的電勢降低，注入能量減??；其次，離 子注入劑量在介質圓管

5、內表面的分布不均勻，在介質圓管管口附近位 置注入劑量明顯偏大。當介質圓管內離子完全注入到介質內表面后， 由于管口外端離子還會繼續(xù)注入到管口內表面，隨著注入時間的增加, 這種不均勻性變得越來越嚴重。因此，在介質圓管內離子完全注入到 內壁前結束一個脈沖周期就變得尤為必要；最后，適當延長金屬電極 的長度，可以有效的提高介質圓管內表面離子注入劑量和離子注入能 量的均勻性。第四章,我們針對混合PIC在處理短脈沖PIII中的不足 (假設電子滿足波爾茲曼分布，從而忽略了電子的運動和效應對離子 注入的影響)，采用完全自洽的一維PIC/MCC模型對一維平板介質靶P III過程進行了模擬。該模型完全跟蹤電子和離子

6、的運動軌跡，對帶電 粒子運動過程中與中性氣體間的碰撞過程及介質表面的二次電子發(fā) 射過程進行了全面的考慮；同時討論了介質厚度和氣體壓強對注入過 程的影響。結果表明，為了獲得較好的注入效果,應該盡量采用較薄的 介質、短的脈沖上升時間和低的放電氣壓?！居⑽恼縋lasma immersion ion implantation (PII) is a new ion implantation technology based upon the traditional ion-beam ion implantation (PBII) technology, as PII has many advanta

7、ges such as low costs, simple equipment, easily operation and is capable to process the work-piece with complex shape. Presently, PIII technology has been widely used in the modification of materials, semiconductor treatment, and microelectronic materials processing, etc. However, when treating the

8、dielectric substrate with PIII, the implanted ions can accumulate at the dielectric surface owing to the low electric conductivity of the dielectric materials, and this result in the charging effects. So the implanted ions cari t get the full acceleration with the same amplitude of the applied negat

9、ive pulse. What s more, with the time extend, the converging plasma sheaths from the inner surfaces of the cylindrical dielectric tube could get overlapping in the central axis, the implanted dose and energy decrease further. In order to solve these problems, it is necessary to sduty theoretically t

10、he sheath evolution near the inner of the cylindrical dielectric tube during the PH processing. Because the implanted ions mainly get acceleration from the plasma sheath, the characteristics of the plasma sheath directly affect the final properties of the target materials after P III process. With t

11、he theoretical investigation, the physical mechanism of ion implantation can be revealed, and the results can give some guidance for the optimization of an actual P I process.In this thesis, we adopt the particle-in-cell method to study the principles of the sheath expansion and implantation charact

12、eristics in PHI process with a dielectric target. The influences of many parameters on the PHI are discussed. The thesis is organized as:In Chapterl, we briefly introduce the characteristics and applications of PHItechnology, the current research state and significance of thePill in flat and cylindr

13、ical dielectric materials, and also review the investigation methods of computer simulation for P III. In Chapter2, we give a detailed description about the Particle-In-Cell plus Monte Carlo Collision (PIC/MCC) method which is used in plasma computer simulation. We divide the PIC/MCC method into two

14、 parts, and introduce the PIC and MCC method, respectively. At the same time, we also make a corresponding derivation of the one-dimension flat plate model and two-dimension cylindrical model.In Chapter3, the sheath expansion near the inner surface of a cylindrical dielectric tube is investigated by

15、 using a two-dimension hybrid PIC model. The influence of experimental parameters (such as the metal electrode length and dielectric thickness) on the uniformity of implanted ions dose and energy along the inner surface of the dielectric tube is analyzed and discussed. It finds that during the Pi pr

16、ocess, as there are increasingly amount of charges accumulate on the dielectric surface, the charging effect become much more significant, leading a lower surface potential and lower implanted energy. Secondly, with a finite length cylindrical dielectric tube, the distribution of theimplanted ion do

17、se along the inner surface is nonuniform, the implanted dose near the top of the bore is much bigger than the other region. When all the ions inner the tube get implanted, many ions originate from outside of the bore continued to implant into the inner surface, this make the nonuniformity of the imp

18、lanted dose more serious. So, it is very important for improving the implanted dose uniformity to end a single pulse period before all of the ions in the tube get exhaust. At last, the implanted ions energy distribution uniformity along the inner surface of the dielectric tube can been improved by u

19、sing a longer metal electrodeIn Chapter4, In order to overcome the shortage of hybrid PIC in the simulation of a nanosecond pulse Pill (in the hybrid PIC model, electrons are supposed to be Boltzmann s distribution and thus lack the movement effect of electrons to Pill), we employ a self-consistent

20、PIC/MCC model to study Pill to PET substrate. With the model, ions and electrons are both dynamically traced simultaneously. The various collision processes of electrons collision and the secondary electron emission (SEE) on the surface of PET substrate are included. We have studied the influence of

21、 the thickness of dielectric film and the gas pressure on IH. Thesimulation results demonstrate that it is necessary to use a lower pressure and thinner PET substance to get better Pill property in Pill of dielectric film.【日錄】等離子體浸沒離子注入介質靶鞘層特性的粒子模擬研究 摘要 4-6 Abstract 6-71 引言 10-201.1 等離子體浸沒離子注入技術及其發(fā)展應用10-141.1.1等離子體浸沒離子注入技術10-121.1.2等離子體浸沒離子注入技術的發(fā)展及