CN1769549A - A heat treatment process for single crystal silicon polished sheet - Google Patents

Abstract

This invention relates to a heat treatment technology for the silicon obtaining the lustration area, the steps as follows: first, heat treatment for the silicon; second, oxygenation anneals technology; third, anneal technology; fourth, oxygen deposition growing up. This invention obtains the oxygen deposition starting core distribution by joining the rapid anneal and conventional anneal together: it injects vacancy by rapid anneal to get the oxygen deposition with high density; it injects gap silicon atom neutralizes the surface vacancy and restrains the surface oxygen deposition through oxygen anneal to ensure the production of the lustration anneal.

Description

Translated fromChinese

一种单晶硅抛光片热处理工艺A heat treatment process for single crystal silicon polished sheet

技术领域technical field

本发明涉及一种单晶硅抛光片热处理工艺，特别涉及一种利用快速热处理(RTA)工艺和普通退火相结合处理单晶硅抛光片获得洁净区的工艺方法。The invention relates to a heat treatment process for a single crystal silicon polishing sheet, in particular to a process method for treating a single crystal silicon polishing sheet to obtain a clean area by combining a rapid thermal treatment (RTA) process and ordinary annealing.

背景技术Background technique

单晶硅片是现代超大规模集成电路的主要衬底材料，一般通过直拉(Czochralski法，简称CZ法)获得硅单晶，然后经过切片，导角，磨片，腐蚀，抛光等工艺后获得集成电路级半导体硅抛光片。CZ法工艺，在国内通常被称为直拉法，或切克劳斯基法。这种工艺是将多晶硅放入石英坩埚内，加热熔化，然后把一支特定晶向的硅单晶(称为籽晶)浸入熔体硅中，缓慢提升籽晶就可以获得单晶棒。由于硅的熔点(1420℃)附近，石英坩埚会分解，使得熔体硅受到各种外来物质的沾污，这些沾污的物质主要是氧。在拉晶过程中，氧会进入单晶内部，处于间隙位置。由于氧在硅中的溶解度随温度的下降而急剧的降低。所以，通过CZ法拉制出来的硅单晶，内部的氧都一般都处于过饱和态。Single crystal silicon wafer is the main substrate material of modern ultra-large-scale integrated circuits. Generally, silicon single crystal is obtained by Czochralski method (CZ method for short), and then obtained after slicing, chamfering, grinding, corrosion, polishing and other processes. Integrated circuit level semiconductor silicon polishing wafer. The CZ method process is usually called the Czochralski method or the Czochralski method in China. This process is to put polycrystalline silicon into a quartz crucible, heat and melt it, and then immerse a silicon single crystal (called a seed crystal) with a specific crystal orientation into the molten silicon, and slowly lift the seed crystal to obtain a single crystal rod. Due to the vicinity of the melting point of silicon (1420° C.), the quartz crucible will decompose, so that the molten silicon is contaminated by various foreign substances, mainly oxygen. During the crystal pulling process, oxygen will enter the interior of the single crystal and be in the interstitial position. Because the solubility of oxygen in silicon decreases sharply with the decrease of temperature. Therefore, the oxygen in the silicon single crystal drawn by the CZ method is generally in a supersaturated state.

CZ法拉制的硅单晶一般的氧杂质含量在5×10¹⁷atom/cm³到9×10¹⁷atom/cm³之间，处于晶格的间隙位置。当单晶生成后，在1420℃到750℃的温度区间冷却过程中，氧沉淀会在单晶内部成核。通过不超过1300℃的热处理就会使得初始沉淀成核消失。但是在1000～700℃的温度范围内处理硅片，硅片内氧沉淀成核就会被稳定下来，长时间保温可以使这些氧沉淀成核长大，形成氧沉淀。一般认为氧沉淀的基本单元为SiOx(x≈2)，其体积要增大。所以氧沉淀核心的形成和生长需要克服很大的应变应力。空位在高温能够快速扩散，缓解氧沉淀在形核过程中导致的晶格畸变或者形成O-V和O₂V的复合体促进氧沉淀的形核长大。因此空位会增进氧的沉淀。相反地，自间隙原子的存在会抑制氧沉淀的形成。The silicon single crystal drawn by the CZ method generally has an oxygen impurity content between 5×10¹⁷ atom/cm³ and 9×10¹⁷ atom/cm³ , which is located in the interstitial position of the crystal lattice. After the single crystal is formed, oxygen precipitates will nucleate inside the single crystal during cooling in the temperature range of 1420°C to 750°C. The initial precipitation nucleation disappears by heat treatment not exceeding 1300°C. However, if silicon wafers are treated at a temperature range of 1000-700°C, the nucleation of oxygen precipitation in the silicon wafers will be stabilized, and long-term heat preservation can make these oxygen precipitations nucleate and grow to form oxygen precipitation. It is generally believed that the basic unit of oxygen precipitation is SiOx (x≈2), and its volume should increase. Therefore, the formation and growth of the oxygen precipitation core needs to overcome a large strain stress. The vacancies can diffuse rapidly at high temperature, alleviate the lattice distortion caused by oxygen precipitation during the nucleation process, or form a complex of OV and O₂ V to promote the nucleation and growth of oxygen precipitation. The vacancies thus enhance the precipitation of oxygen. Conversely, the presence of self-interstitial atoms inhibits the formation of oxygen precipitates.

在器件制造中引入的热处理工艺导致硅片中氧的聚集，最终生成氧沉淀。硅片中的氧沉淀有双重作用：处于器件工作区的氧沉淀会导致器件失效，如栅氧化层的击穿，形成结漏电电流等；而处于非器件工作区的氧沉淀会作为吸杂中心，俘获器件制造中引入的有害的过渡族金属杂质。The heat treatment process introduced in the device fabrication leads to the accumulation of oxygen in the silicon wafer, eventually generating oxygen precipitation. Oxygen precipitation in the silicon wafer has a dual role: the oxygen precipitation in the device working area will lead to device failure, such as the breakdown of the gate oxide layer, the formation of junction leakage current, etc.; and the oxygen precipitation in the non-device working area will act as a gettering center , to trap harmful transition metal impurities introduced during device fabrication.

在IC制作过程中，硅片的加工工艺日益复杂，在工艺过程中会引入很多金属杂质。已经证实：快速扩散的过渡金属(如Fe，Cu，Ni等)，能够在硅片内部成核，或者进入晶体缺陷形成深能级缺陷。这些金属以及形成的缺陷会产生漏电电流、降低少子寿命、导致SiO₂膜击穿和影响MOSFET的C-t特性。所以超大规模集成电路制造要求极其努力地降低工艺过程中引入的金属沾污。In the IC manufacturing process, the processing technology of silicon wafers is becoming more and more complex, and a lot of metal impurities will be introduced in the process. It has been confirmed that fast-diffusing transition metals (such as Fe, Cu, Ni, etc.) can nucleate inside the silicon wafer, or enter crystal defects to form deep-level defects. These metals and the formed defects will generate leakage current, reduce the minority carrier lifetime, cause_SiO2 film breakdown and affect the Ct characteristics of MOSFET. VLSI fabrication therefore requires extreme efforts to reduce the metal contamination introduced during the process.

内吸杂技术是一种有效地从有源器件区移走过渡族金属的吸杂技术。它是利用氧沉淀的双重性质和金属扩散速度快的性质，通过热处理工艺在硅片体内形成足够密度的氧沉淀，作为金属杂质的俘获中心；而在器件工作区域内通过抑制氧沉淀形核长大，使得器件工作区内形成没有氧沉淀的洁净区。在器件工艺完成后，通过高温退火(1000℃左右的退火)处理晶圆，使得金属沾污迅速向硅片体内扩散，在氧沉淀附近被固定。Internal gettering technology is a gettering technology that effectively removes transition metals from active device regions. It uses the dual nature of oxygen precipitation and the property of fast metal diffusion to form sufficient density of oxygen precipitation in the silicon wafer through the heat treatment process as the trapping center of metal impurities; Large, so that a clean area without oxygen precipitation is formed in the working area of the device. After the device process is completed, the wafer is treated by high-temperature annealing (annealing at about 1000 ° C), so that the metal contamination quickly diffuses into the silicon wafer and is fixed near the oxygen precipitation.

衡量内吸除工艺好坏的关键参数在于：洁净区的厚度和氧沉淀密度。一般希望洁净区较薄(比器件工作区厚10～20微米)，同时洁净区下面的氧沉淀要足够的高。The key parameters to measure the quality of the internal absorption process are: the thickness of the clean area and the density of oxygen precipitation. It is generally desired that the clean area is thinner (10-20 microns thicker than the device working area), and the oxygen precipitation below the clean area should be sufficiently high.

常规的内吸除工艺是三步退火法：The conventional internal gettering process is a three-step annealing method:

第一步.高温退火，使得表面区域内氧发生外扩散。退火温度约为1100～1150℃：Step 1. High temperature annealing, which causes out-diffusion of oxygen in the surface region. Annealing temperature is about 1100～1150℃:

第二步.氧沉淀形核热处理。通过低温(600～800℃)下的热处理，使得过饱和间隙氧发生氧沉淀形核；The second step. Oxygen precipitation nucleation heat treatment. Through heat treatment at a low temperature (600-800°C), the supersaturated interstitial oxygen undergoes oxygen precipitation and nucleation;

第三步.氧沉淀长大。通过在高温(1000～1150℃)下的热处理，氧沉淀形核开始长大形成吸除陷阱，并在硅片表面区域形成洁净区。The third step. Oxygen precipitation grows up. Through heat treatment at high temperature (1000-1150°C), oxygen precipitation nucleation begins to grow to form gettering traps, and a clean area is formed on the surface area of the silicon wafer.

这种传统的退火方法有着严重的缺陷，主要表现在洁净区厚度对初始氧依赖程度大。由于单晶拉制条件的限制，获得的单晶沿轴向的氧含量分布不均匀，一般在单晶的头部氧含量比较高，在中部比较低，尾部有开始升高，加上热场的影响，使得同一单晶上获得的硅片的氧含量有差异，氧沉淀成核也不一致。而传统的退火方法一般会大批次(如100片/批)进行热处理，这样带来的严重的问题就是，由于氧含量和氧沉淀形核状态的不同，将导致该批在氧外扩散工艺中氧外扩散的深度不一致，最终结净区的厚度不一样。其次该工艺强烈依赖硅片中的初始氧浓度，对于氧浓度较低的硅片很难形成足够的吸杂中心。This traditional annealing method has serious defects, mainly in the fact that the thickness of the clean area is highly dependent on the initial oxygen. Due to the limitation of single crystal pulling conditions, the oxygen content of the obtained single crystal is unevenly distributed along the axial direction. Generally, the oxygen content is relatively high at the head of the single crystal, relatively low in the middle, and begins to rise at the tail, coupled with the thermal field The influence of the influence makes the oxygen content of silicon wafers obtained on the same single crystal vary, and the oxygen precipitation nucleation is also inconsistent. However, the traditional annealing method generally conducts heat treatment in large batches (such as 100 pieces/batch). The serious problem brought about by this is that due to the difference in oxygen content and oxygen precipitation nucleation state, the batch will be damaged in the oxygen out-diffusion process. The depth of oxygen out-diffusion is inconsistent, and the thickness of the final clean zone is different. Secondly, the process strongly depends on the initial oxygen concentration in the silicon wafer, and it is difficult to form sufficient gettering centers for silicon wafers with low oxygen concentration.

发明内容Contents of the invention

本发明的目的是提供一种能够获得高的氧沉淀密度和宽的洁净区的硅片快速热处理工艺。The object of the present invention is to provide a rapid heat treatment process for silicon wafers capable of obtaining high oxygen precipitation density and wide clean area.

本发明的目的是通过如下技术方案达到的：The purpose of the present invention is achieved through the following technical solutions:

第一步工艺就是对硅片进行快速热处理，该步骤工艺可以在任何商用的RTP退火炉中进行。RTP退火炉是使用卤素灯加热，能够使得硅片迅速加热到设定温度，加热的最高温度一般为1250℃。在该步工艺中，采用氨气作为保护气氛。让硅片在1200℃保温5～40秒后，快速降温。降温速率保持在20～100℃/S。快速退火一般采用单片退火工艺，每片硅片的处理时间约为4分钟左右。The first step is rapid thermal treatment of the wafer, which can be performed in any commercial RTP annealing furnace. The RTP annealing furnace is heated by a halogen lamp, which can quickly heat the silicon wafer to the set temperature, and the maximum heating temperature is generally 1250°C. In this step process, ammonia gas is used as the protective atmosphere. Keep the silicon wafer at 1200°C for 5-40 seconds, then cool down quickly. The cooling rate is kept at 20-100°C/S. Rapid annealing generally adopts a single-chip annealing process, and the processing time for each silicon chip is about 4 minutes.

使用快速热处理工艺的目的主要有两条。首先是消除初始热历史导致的氧沉淀形核，尤其是消除表面区10μm～100μm范围内的氧沉淀核心。如果这些氧沉淀的初始形核不能够被消除的话，在后序的热处理工艺中这些氧沉淀初始形核会在表面长大，导致洁净区形成困难。其次，获得高浓度的过饱和空位。由于氨气在高温下能够分解，会生成部分的游离氮原子。游离态的氮原子能够和硅片反应，在硅片表面发生不完全氮化，使得硅片表面会发生氮化生成氮化硅(Si₃N₄)。氮化硅的生成使得在氮化硅和硅的界面处形成大量空位。在1200℃时空位可以迅速扩散到达硅片内部。同时根据Schottky和Frenkel机制，硅片中形成大量的自间隙原子和空位。在这个过程中，空位不断的向内部扩散，同时还自间隙原子复合，在最终形成了图1所示的空位分布。There are two main purposes of using the rapid heat treatment process. The first is to eliminate the nucleation of oxygen precipitation caused by the initial thermal history, especially the elimination of oxygen precipitation nuclei in the range of 10 μm to 100 μm in the surface area. If the initial nucleation of these oxygen precipitations cannot be eliminated, the initial nucleation of these oxygen precipitations will grow on the surface in the subsequent heat treatment process, resulting in difficulties in the formation of clean areas. Second, a high concentration of supersaturated vacancies is obtained. Since ammonia gas can be decomposed at high temperature, some free nitrogen atoms will be generated. The free nitrogen atoms can react with the silicon chip, and incomplete nitriding occurs on the surface of the silicon chip, so that the surface of the silicon chip will be nitrided to form silicon nitride (Si₃ N₄ ). The growth of silicon nitride results in the formation of a large number of vacancies at the interface of silicon nitride and silicon. At 1200°C, the vacancies can rapidly diffuse to the inside of the silicon wafer. At the same time, according to the Schottky and Frenkel mechanism, a large number of self-interstitial atoms and vacancies are formed in the silicon wafer. During this process, the vacancies continuously diffuse to the interior, and at the same time recombine from the interstitial atoms, finally forming the vacancy distribution shown in Figure 1.

工艺的第二步为氧化退火工艺，与快速退火工艺不同的是该步工艺在卧式炉内进行，为批处理工艺。退火温度在850～950℃之间最佳。退火气氛为含氧气氛，氧气的比例不低于40％，处理时间为10到60分钟。The second step of the process is the oxidation annealing process, which is different from the rapid annealing process in that it is carried out in a horizontal furnace and is a batch process. The annealing temperature is best between 850-950°C. The annealing atmosphere is an oxygen-containing atmosphere, the proportion of oxygen is not lower than 40%, and the treatment time is 10 to 60 minutes.

硅片在含氧气氛下退火会发生表面氧化。形成一层氧化硅膜。在形成氧化膜的过程中，在Si-SiO₂的界面处，由于硅的不完全氧化，能够在界面处生成大量自间隙硅原子，这样将导致自间隙原子向晶体内部的注入。和表层区域的空位发生反应，导致将来形成洁净区。Surface oxidation of silicon wafers occurs when annealed in an oxygen-containing atmosphere. A silicon oxide film is formed. In the process of forming the oxide film, at the interface of Si-SiO₂ , due to the incomplete oxidation of silicon, a large number of self-interstitial silicon atoms can be generated at the interface, which will lead to the implantation of self-interstitial atoms into the crystal. React with the vacancies in the surface area, resulting in the formation of a clean zone in the future.

提高退火温度、保温时间、氧气分压，则可以导致洁净区变宽，反之变窄。Increasing the annealing temperature, holding time, and oxygen partial pressure can cause the clean area to widen, and vice versa.

第三步退火工艺，即氧沉淀成核长大工艺。就是让硅片在800℃保温4小时，在低温阶段(800℃)氧沉淀开始成核。The third step of annealing process is oxygen precipitation nucleation and growth process. It is to keep the silicon wafer at 800°C for 4 hours, and oxygen precipitation begins to nucleate in the low temperature stage (800°C).

第四步.氧沉淀长大。通过在高温(900～1000℃)下的热处理，氧沉淀成核开始长大形成吸杂陷阱。并在硅片表面区域形成洁净区。处理时间为4小时，氮气为保护气氛。该退火工艺一般由器件厂家在器件制造工艺中实施。The fourth step. Oxygen precipitation grows up. Through heat treatment at high temperature (900-1000°C), oxygen precipitates nucleate and grow to form gettering traps. And a clean area is formed on the surface area of the silicon wafer. The treatment time is 4 hours, and nitrogen is the protective atmosphere. The annealing process is generally implemented by the device manufacturer in the device manufacturing process.

确定工艺性能好坏的参数主要有：洁净区的厚度，体内氧沉淀的密度。现代器件工艺希望获得较薄的洁净区，同时希望有足够的氧沉淀来充当吸杂中心。具体的工艺性能参数的检测方法是：在第四步退火后，在将硅片沿(111)或(100)晶面解理，然后由wright腐蚀液腐蚀5分钟；再由去离子水漂洗、吹干后即刻用金相显微镜观测。根据显微镜内的标尺，可以测出洁净区的厚度。通过目测视场内氧沉淀的数量，可以获得氧沉淀密度。The parameters to determine the quality of the process performance mainly include: the thickness of the clean area, and the density of oxygen precipitation in the body. Modern device technology hopes to obtain a thinner clean area, and at the same time, it is hoped that there will be enough oxygen precipitation to act as a gettering center. The detection method of specific process performance parameters is: after the fourth step of annealing, the silicon wafer is cleaved along the (111) or (100) crystal plane, then corroded by wright etching solution for 5 minutes; then rinsed with deionized water, Immediately after drying, observe with a metallographic microscope. According to the scale inside the microscope, the thickness of the clean area can be measured. The oxygen precipitation density can be obtained by visually observing the amount of oxygen precipitation in the field of view.

第二步工艺在洁净区的形成过程中起着关键作用，对没有进行第二步处理的硅片解理、腐蚀后，在金相显微镜下观测，发现解理面上氧沉淀密度很高但是没有洁净区生成。The second-step process plays a key role in the formation of the clean area. After cleavage and corrosion of the silicon wafers that have not undergone the second-step treatment, it is observed under a metallographic microscope that the density of oxygen precipitation on the cleavage surface is very high but No clean zone is generated.

快速退火和氧化退火是决定氧沉淀密度和洁净区厚度的决定性工艺。对比不同工艺条件下获得的数据发现：提高快速退火保温温度、保温时间、降温速率将会获得较高的氧沉淀密度。提高氧化退火的温度、保温时间、氧气分压可以使得洁净区变宽。Rapid annealing and oxidation annealing are decisive processes for determining the density of oxygen precipitation and the thickness of the clean area. Comparing the data obtained under different process conditions, it is found that increasing the rapid annealing holding temperature, holding time, and cooling rate will obtain a higher oxygen precipitation density. Increasing the oxidation annealing temperature, holding time, and oxygen partial pressure can widen the clean area.

现代硅片生产工艺一般要经历以下步骤：单晶拉制-单晶滚磨-切片-导角-磨片-腐蚀-热施主消除退火-抛光-清洗-封装。本发明对硅片制造工艺非常实用，使用本发明可以替代热施主消除退火，即在抛光工艺过后实施快速退火处理。使用本发明后硅片制造工艺改为单晶拉制-滚磨-切片-导角-磨片-腐蚀-粗抛光-快速退火-氧化退火-清洗-精抛光-清洗-封装。The modern silicon wafer production process generally goes through the following steps: single crystal pulling-single crystal barrel grinding-slicing-chamfering-grinding-corrosion-thermal donor elimination annealing-polishing-cleaning-packaging. The invention is very practical for the silicon chip manufacturing process, and the invention can replace the heat donor to eliminate the annealing, that is, implement the rapid annealing treatment after the polishing process. After using the present invention, the silicon wafer manufacturing process is changed to single crystal drawing-rolling-slicing-chamfering-grinding-corrosion-rough polishing-rapid annealing-oxidation annealing-cleaning-finish polishing-cleaning-encapsulation.

在本发明中提出使用氨气气氛作为快速退火的保护气体，以求在整个硅片内部获得较高的空位浓度(高的空位浓度将导致高的氧沉淀密度)；同时在快速退火工艺后引入了950℃的氧化退火，通过氧化硅片表面，达到自间隙硅原子注入的目的。通过注入的自间隙原子抵消表层区域内的空位浓度，使得表层空位浓度降低。氧沉淀成核长大的工艺是在950℃退火处理后进行的，工艺参数和常规退火一致(800℃保温4小时，1000℃保温16小时)。在800℃成核工艺中，由于表层区域自间隙原子的注入，空位浓度降低，抑制了自间隙氧原子的聚集成核，随后形成洁净区。In the present invention, it is proposed to use an ammonia atmosphere as a protective gas for rapid annealing, in order to obtain a higher vacancy concentration inside the entire silicon wafer (a high vacancy concentration will cause a high oxygen precipitation density); Oxidation annealing at 950°C is performed to achieve the purpose of self-interstitial silicon atom implantation by oxidizing the surface of the silicon wafer. The vacancy concentration in the surface region is offset by the implanted self-interstitial atoms, resulting in a decrease in the surface vacancy concentration. The process of oxygen precipitation nucleation and growth is carried out after annealing at 950°C, and the process parameters are consistent with conventional annealing (4 hours at 800°C, 16 hours at 1000°C). During the 800°C nucleation process, due to the implantation of self-interstitial atoms in the surface region, the concentration of vacancies decreases, which inhibits the aggregation and nucleation of self-interstitial oxygen atoms, and subsequently forms a clean area.

本发明工艺为快速退火和常规退火相结合获得氧沉淀初始核心的分布：通过快速退火注入空位保证最终获得很高的氧沉淀密度；通过氧化退火注入自间隙硅原子，中和表层空位，抑制表层氧沉淀形成氧沉淀，最终保证表层有洁净区的生成。The process of the present invention combines rapid annealing and conventional annealing to obtain the distribution of the initial core of oxygen precipitation: injecting vacancies through rapid annealing ensures a high oxygen precipitation density; injecting self-interstitial silicon atoms through oxidation annealing neutralizes surface vacancies and suppresses the surface layer Oxygen precipitation forms oxygen precipitation, which finally ensures the generation of clean areas on the surface.

下面通过附图和具体实施例对本发明做进一步解释和说明，并不意味着对本发明保护范围的限制。The present invention will be further explained and illustrated by the accompanying drawings and specific embodiments below, which does not mean to limit the protection scope of the present invention.

附图说明Description of drawings

图1.为快速退火和氧化退火后空位在硅片内部的分布图。Figure 1 shows the distribution of vacancies inside the silicon wafer after rapid annealing and oxidation annealing.

图2a.为无氧化退火的硅片解理面的腐蚀图。Figure 2a. Corrosion diagram of the cleavage plane of a silicon wafer without oxidation annealing.

图2b.有氧化退火的硅片解理面的腐蚀图。Figure 2b. Etching diagram of the cleavage plane of a silicon wafer with oxidation annealing.

图3.为氧化退火对洁净区厚度的影响曲线。Figure 3 is the influence curve of oxidation annealing on the thickness of the clean area.

具体实施方式Detailed ways

实施例Example

在氨气气氛下，对硅片进行RTA处理工艺，然后对硅片进行氧化退火。在其它工艺条件都相同的情况下，改变氧化退火的时间，最后对硅片进行800℃保温4小时，1000℃保温16小时的热处理工艺生成氧沉淀并获得洁净区并对之分析。具体工艺参数和实验结果如表1所示。In an ammonia atmosphere, the silicon wafer is subjected to an RTA treatment process, and then the silicon wafer is oxidized and annealed. In the case of other process conditions being the same, the time of oxidation annealing was changed, and finally the silicon wafer was heat-treated at 800°C for 4 hours and 1000°C for 16 hours to generate oxygen precipitates and obtain a clean area and analyze it. The specific process parameters and experimental results are shown in Table 1.

可以看到洁净区厚度随着氧化退火时间增加而增加。没有氧化退火处理过的硅片没有出现洁净区，但是腐蚀的解理面上有很高的氧沉淀密度。It can be seen that the thickness of the clean area increases with the increase of oxidation annealing time. Silicon wafers that have not been oxidized and annealed have no clean area, but there is a high density of oxygen precipitation on the etched cleavage surface.

                                        表1 快速热处理工艺     1200℃，在NH₃气氛下保温30s降温速度为       70℃/s 氧化退火工艺 没有处理   900℃下，N₂/O₂气氛，O₂含量为50％保温15分钟   900℃下，N₂/O₂气氛，O₂含量为50％保温30分钟   900℃下，N₂/O₂气氛，O₂含量为50％保温45分钟 氧沉淀形核长大工艺   800℃1000℃   保温4小时保温16小时 间隙氧含量(ppma) 18.6   18.6   18.6   18.6 氧沉淀密度(个/cm²) 6×10⁶   6×10⁶   9×10⁶   9×10⁶ 洁净区厚度(μm) None   10   14   20Table 1 rapid heat treatment process 1200°C, keep warm for 30s under NH₃ atmosphere, cooling rate is 70°C/s oxidation annealing process not dealt with At 900°C, N₂ /O₂ atmosphere, O₂ content is 50% for 15 minutes At 900°C, N₂ /O₂ atmosphere, O₂ content is 50% for 30 minutes At 900°C, N₂ /O₂ atmosphere, O₂ content is 50% for 45 minutes Oxygen Precipitation Nucleation and Growth Process 800℃1000℃ Keep warm for 4 hours Keep warm for 16 hours Interstitial oxygen content (ppma) 18.6 18.6 18.6 18.6 Oxygen precipitation density (unit/cm² ) 6×10⁶ 6×10⁶ 9×10⁶ 9×10⁶ Clean area thickness (μm)none 10 14 20

如图1、2、3所示，图1为快速退火和氧化退火后空位在硅片内部的分布示意图，由图可知：在快速退火过程中，空位被大量注入且在快速冷却时保留在硅片内部。并且空位在硅片内部保持均匀分布；经过氧化退火后，部分自间隙硅原子有表面向硅片表层注入中和了硅片表层中的空位，使得硅片表层的空位浓度较低在随后退火中被中和的区域不会有氧沉淀生成，形成洁净区。图2a为无氧化退火的硅片解理面的腐蚀图，图2b为有氧化退火的硅片解理面的腐蚀图，由图可知，本发明工艺中快速退火和氧化退火缺一不可。图3为氧化退火对洁净区厚度的影响曲线，增加氧化退火时间使得洁净区变宽。As shown in Figures 1, 2, and 3, Figure 1 is a schematic diagram of the distribution of vacancies inside the silicon wafer after rapid annealing and oxidation annealing. tablet interior. And the vacancies remain evenly distributed inside the silicon wafer; after oxidation annealing, part of the silicon atoms from the interstitial surface are implanted into the surface of the silicon wafer to neutralize the vacancies in the surface layer of the silicon wafer, so that the concentration of vacancies in the surface layer of the silicon wafer is lower in the subsequent annealing The neutralized area will not generate aerobic precipitation, forming a clean area. Fig. 2a is the corrosion diagram of the cleavage surface of the silicon wafer without oxidation annealing, and Fig. 2b is the corrosion diagram of the cleavage surface of the silicon wafer with oxidation annealing. It can be seen from the figure that rapid annealing and oxidation annealing are indispensable in the process of the present invention. Figure 3 is the influence curve of the oxidation annealing on the thickness of the clean area, increasing the oxidation annealing time makes the clean area wider.

Claims (4)

1, a kind of thermal treatment process to silicon chip acquisition clean area, its step is as follows: the first step, silicon chip is carried out rapid thermal process; Second step, oxidation annealing process; The 3rd step, annealing process; In the 4th step, oxygen precipitation is grown up.

2, silicon chip quick thermal treatment process according to claim 1 is characterized in that:

The described the first step is carried out in the quick anneal oven of any commercialization, adopts ammonia as protective atmosphere, and the top temperature of heating is 1250～1150 ℃, and silicon chip is 5～40 seconds in this temperature soaking time, and rate of temperature fall remains on 20～100 ℃/S;

The oxidation annealing process in described second step is batch process, and annealing temperature is between 850～950 ℃, and annealing atmosphere is an oxygen-containing atmosphere, and the ratio of oxygen is not less than 40%, and the treatment time is 10～120 minutes.

3, silicon chip quick thermal treatment process according to claim 1 is characterized in that: the rate of temperature fall in the described the first step is 50～90 ℃/S, pure ammonia atmosphere; The ratio of oxygen is not less than 50% in oxygenous part of described second step.

4, the silicon chip of wafer heat art breading according to claim 1, clean area thickness are 5～40 μ m, and oxygen precipitation density is 6～9 * 10⁶Individual/cm²

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