氮化硅涂层回收方法

范文一：氮化硅涂层回收方法

氮化硅涂层回收方法

【专利摘要】本发明属于多晶硅提纯领域，具体涉及一种应用于多晶硅提纯的氮化硅涂层回收方法，使用过后的氮化硅涂层主要含有氮化硅、二氧化硅和少量杂质元素，首先利用离心机分离，去除大部分密度较小二氧化硅部分，再利用硝酸和氢氟酸的混合液可以将剩余的二氧化硅和少量杂质元素溶解，但几乎不与氮化硅反应，再经过蒸干和清洗后，经过干燥即可提纯出满足坩埚喷涂使用要求的高纯氮化硅粉体。本发明的优点在于（1）回收工艺简单可行，氮化硅粉体回收率高，可以达到50～70%；（2）按照使用过后的氮化硅涂层计算，回收可利用的氮化硅粉体价值为800～1500元/kg；（3）回收得到的氮化硅粉体中α氮化硅质量含量92%以上，N 元素质量含量38%以上。

【专利说明】应用于多晶硅提纯的氮化硅涂层回收方法

【技术领域】

本发明属于多晶硅提纯领域，具体涉及一种应用于多晶硅提纯的氮化硅涂层回收方法。

【背景技术】

目前，我国已成为世界能源生产和消费大国，但人均能源消费水平还很低。随着经济和社会的不断发展，我国能源需求将持续增长，针对目前的能源紧张状况，世界各国都在进行深刻的思考，并努力提高能源利用效率，促进可再生能源的开发和应用，减少对进口石油的依赖，加强能源安全。

作为可再生能源的重要发展方向之一的太阳能光伏发电近年来发展迅猛，其所占比重越来越大。根据《可再生能源中长期发展规划》，到2020年，中国力争使太阳能发电装机容量达到1.8GW (百万千瓦) ，到2050年将达到600GW 。预计到2050年，中国可再生能源的电力装机将占全国电力装机的25%，其中光伏发电装机将占到5%。预计2030年之前，中国太阳能装机容量的复合增长率将高达25%以上。

太阳能光伏产业的发展依赖于对多晶硅原料的提纯。多晶硅原料的提纯工艺目前主要依赖以下几种工艺:西门子法、硅烷法、气体流化床法和冶金法。目前，冶金法以成本低、污染少和能耗低的优点正越来越多的被利用。

冶金法生产多晶硅过程中，会使用坩埚作为硅熔体的承载容器，使用到的坩埚有石英坩埚、石墨坩埚或者氮化硅坩埚等，为了防止坩埚中的杂质扩散到硅熔体中引起二次污染，所以要在坩埚的内表面需要喷涂一层高纯氮化硅(Si3N4)涂层，由于高温熔炼后氮化硅涂层会部分贴附在硅锭表面，部分会有脱落，且氮化硅涂层中也会伴有大量杂质成分，无法再重复利用，只能作为废料来处理。作为涂层用的高纯氮化硅粉成本在1000~2000元/kg,占坩埚总成本的1/4~1/3，如果能将氮化硅涂层回收再利用就可以节省很大的生产成本。

【发明内容】

根据以上现有技术的不足，本发明提出一种应用于多晶硅提纯的氮化硅涂层回收方法，将使用过的氮化硅涂层回收，经过物理法和化学法的有效结合，使其达到重新利用的标准。

本发明所述的一种应用于多晶硅提纯的氮化硅涂层回收方法，包括以下步骤:

(I)将坩埚内表面和硅锭外表面的氮化硅涂层剥落回收，利用研磨机研磨成粉体；

(2)将粉体置于离心机中进行初步分离，分离后去除占总体积20~25%的顶部部分；

(3)将剩余部分浸泡到氢氟酸和硝酸的混合酸中，再经水浴加热蒸干，残留物经去离子水冲洗后采用压滤机分离固液两相，将固相放置烘干箱内烘干即可；

(4)将烘干后的固相抽样用ICP-MS 进行成分检测，达到标准的可以重复回收利用，不达标的重复步骤(3)，直至达标。

其中，优选的方案如下:

步骤(1)中的粉体粒度为20~200目。

步骤(2)中离心机的转速为1000~2000rpm，Fr 为10000~20000，离心分离时间为10~30min。分离因素Fr 是指物料在离心力场中所受的离心力，与物料在重力场中所受到的重力之比值。常速离心机Fr ( 3500 (一般为600~1200)，这种离心机的转速较低，直径较大。高速离心机Fr=3500~50000，这种离心机的转速较高，一般转鼓直径较小，而长度较长。Fr 越大分尚能力越强。

步骤(3)中剩余部分浸泡到氢氟酸和硝酸的混合酸中，浸泡时间为10~20h，剩余部分与混合酸的配比为0.5~Ikg:1~5L，其中，混合酸中氢氟酸与硝酸的体积比为1:1，其中，氢氟酸的质量浓度为25~49%，硝酸的质量浓度为35~70%。

步骤(3)中水浴加热的温度为70~90°C 。

步骤(3)中的残留物经去离子水冲洗2~3遍。

步骤(3)中烘干箱的烘干温度为80~150°C 。

本发明中，使用过后的氮化硅涂层主要含有氮化硅、二氧化硅和少量杂质元素，首先利用离心机分离，去除大部分密度较小二氧化硅部分，再利用硝酸和氢氟酸的混合液可以将剩余的二氧化硅和少量杂质元素溶解，但几乎不与氮化硅反应，再经过蒸干和清洗后，经过干燥即可提纯出满足坩埚`喷涂使用要求的高纯氮化硅粉体，实现氮化硅涂层的可再生利用，节省工艺成本。

本发明的优点在于:(1)回收工艺简单可行，氮化硅粉体回收率高，可以达到50~70% ; (2)按照使用过后的氮化硅涂层计算，回收可利用的氮化硅粉体价值为800~1500元/kg ; (3)回收得到的氮化娃粉体中α氮化娃质量含量92%以上,N 元素质量含量38%以上。

【具体实施方式】

以下结合实施例对本发明做进一步说明。

实施例1:

按照以下步骤回收利用氮化硅涂层:

(I)将坩埚内表面和硅锭外表面的氮化硅涂层剥落回收，利用研磨机研磨成粉体，粉体粒度为80目；

(2)将粉体置于离心机中进行初步分离，离心机的转速为1000rpm ，Fr 为10000，离心分离时间为25min ，分离后去除占总体积25%的顶部部分；

(3)将剩余部分浸泡到氢氟酸和硝酸的混合酸中，浸泡时间为10h ，剩余部分与混合酸的配比为Ikg:5L，其中，混合酸中氢氟酸与硝酸的体积比为1:1，氢氟酸的质量浓度为25%，硝酸的质量浓度为35%。再经70°C 水浴加热蒸干，残留物经去离子水冲洗2遍后采用压滤机分离固液两相，将固相放置烘干箱内烘干即可，其中烘干温度

为100°C ；

(4)将烘干后的固相抽样用ICP-MS 进行成分检测，未达到标准，重复步骤(3)—次达标。

(5)最终测得回收处理的氮化娃粉体中α氮化娃质量含量为92%, N 元素质量含量为38%。

实施例2:

按照以下步骤回收利用氮化硅涂层:

(I)将坩埚内表面和硅锭外表面的氮化硅涂层剥落回收，利用研磨机研磨成粉体，粉体粒度为150目；

(2)将粉体置于离心机中进行初步分离，离心机的转速为2000rpm ，Fr 为20000，离心分离时间为20min ，分离后去除占总体积20%的顶部部分；

(3)将剩余部分浸泡到氢氟酸和硝酸的混合酸中，浸泡时间为20h ，剩余部分与混合酸的配比为Ikg:2L，其中，混合酸中氢氟酸与硝酸的体积比为1:1，氢氟酸的质量浓度为35%，硝酸的质量浓度为60%。再经90°C 水浴加热蒸干，残留物经去离子水冲洗3遍后采用压滤机分离固液两相，将固相放置烘干箱内烘干即可，其中烘干温度为120°

C ；

(4)将烘干后的固相抽样用ICP-MS 进行成分检测，达到标准。

(5)最终测得回收处理的氮化娃粉体中α氮化娃质量含量为95%, N 元素质量含量为40%。

【权利要求】

1. 一种应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于包括以下步骤: (1)将坩埚内表面和硅锭外表面的氮化硅涂层剥落回收，利用研磨机研磨成粉体； (2)将粉体置于离心机中进行初步分离，分离后去除占总体积20~25%的顶部部分； (3)将剩余部分浸泡到氢氟酸和硝酸的混合酸中，再经水浴加热蒸干，残留物经去离子水冲洗后采用压滤机分离固液两相，将固相放置烘干箱内烘干即可； (4)将烘干后的固相抽样用ICP-MS 进行成分检测，达到标准的可以重复回收利用，不达标的重复步骤(3)，直至达标。

2. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收

方法，其特征在于步骤(1)中的粉体粒度为20~200目。

3. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于步骤(2)中离心机的转速为1000~2000rpm，Fr 为10000~20000，离心分离时间为10~30min。

4. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于步骤(3)中的剩余部分与混合酸的配比为0.5~Ikg:1~5L。

5. 根据权利要求1或4所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于混合酸中氢氟酸与硝酸的体积比为1:1，其中，氢氟酸的质量浓度为25~49%，硝酸的质量浓度为35~70%。`

6. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于步骤(3)中剩余部分与混合酸的浸泡时间为10~20h。

7. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于步骤(3)中水浴加热的温度为70~90°C 。

8. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于步骤(3)中的残留物经去离子水冲洗2~3遍。

9. 根据权利要求1所述的应用于多晶硅提纯的氮化硅涂层回收方法，其特征在于步骤(3)中烘干箱的烘干温度为80~150°C 。

范文二：硅在氮化硅涂层上的形核SiO2

Journal of Crystal Growth 331(2011)64–67

Contents lists available at ScienceDirect

Journal of Crystal Growth

journal homepage:www.elsevier.com/locate/jcrysgro

Nucleation of silicon on Si 3N 4coated SiO 2

I. Brynjulfsen ?, L. Arnberg

Department of Materials Science and Engineering, Norwegian University of Science and Technology, 7491Trondheim, Norway

a r t i c l e i n f o

Article history:

Received 30May 2011Received in revised form 6July 2011

Accepted 8July 2011

Communicated by P. Rudolph Available online 19July 2011Keywords:

A1. Nucleation A1. Solidi?cationA2. Undercooling B1. Silicon

a b s t r a c t

Control of the nucleation during directional solidi?cationof solar cell silicon is important in order to be able to control the growth and number of grains formed. A certain amount of undercooling is required to obtain dendritic growth with faceted twins (whichhas shown promising results for structure control), but a too high undercooling will lead to extensive nucleation which will oppose the positive effect of a small number of large grains with controlled growth directions. In the present experiments, the nucleation undercooling of silicon on Si 3N 4coated SiO 2with variation in coating parameters has been investigated. Experiments were performed with the sessile drop method, and with differential thermal analysis, with a cooling rate of 20K/min.There were no signi?cantdifferences in nucleation undercooling between the different variations in coating. The undercooling does not seem to be dependent on coating thickness, oxygen concentration, wetting angle or roughness at the given cooling rate.

1. Introduction

The solar cell industry is developing fast in several directions, and in order for the multicrystalline solar cell to be able to compete with monocrystalline cells and other new alternatives, the ef?ciencyhas to be improved. The solidi?cationprocess of multicrystalline silicon is important for the ?nalef?ciencyof the solar cell. Grain size, grain orientation, and impurity distribution/concentrationare all proper-ties dependent on solidi?cationparameters. Some of these char-acteristics like the number of, the size, and orientation of grains are again dependent on the nucleation of silicon, and it is therefore important to able to control this mechanism.

Recently several solidi?cationexperiments have been per-formed by Fujiwara et al. [1–4].They studied grain growth, and were able to increase the crystals size by an initial faceted dendritic growth followed by traditional planar front directional solidi?cation.The dendritic growth results in fewer and larger grains, which again lead to less grain boundaries were recombi-nation can take place. Fujiwara et al. [1]investigated how different cooling rates in?uencedthe size of undercooling needed to obtain faceted dendritic growth. The present work has been performed in order to study how/ifthe substrate on which the silicon grows will in?uencethe undercooling and nucleation of silicon. Si 3N 4coated SiO 2has been chosen as a substrate since multicrystalline silicon ingots are normally cast in Si 3N 4coated SiO 2crucibles.

?Corresponding author. Tel.:t4773594903; fax:t4773550203.

Nucleation is the dominant process in the beginning of solidi?ca-tion and leads to the establishment of the ?nalgrain number. Heterogeneous nucleation undercooling depends strongly on the wetting angle between the nucleus and the nucleating substrate. This implies that the nucleation is dependent on the substrate roughness, composition, thickness, etc. [5]. Another aspect is impu-rities. Impurities in the bulk have been studied by several authors, and it has been shown that silicon often nucleate from Si 3N 4-or SiC-particles [6]. This nucleation can cause the formation of an equiaxed zone instead of the desired columnar zone [7, 8].It has been documented that particles like this are present in the bottom of the ingot [9].

The substrate’sin?uenceon undercooling for solidi?cationof silicon has not been studied thoroughly, but some investigations in the area has been done. Appapillai et al. [10]investigated nucleation undercooling for silicon samples coated with different materials among others Si 3N 4. They found ?nelyspaced nuclea-tion sites near the edge of the samples coated with dry oxides (highundercooling), which indicated that the nucleation started in this region. For the silicon nitride coated samples the nuclea-tion sites were further apart. This resulted in the conclusion that a lower undercooling gave fewer grains, which is consistent with classical nucleation theory. This shows the importance of the to control more precisely. They also showed that the chemical composition played an important role in nucleation. The oxides had a higher interfacial stability resulting in a higher undercooling than the Si 3N 4.

The present work has been performed to investigate which coating parameters in?uencethe nucleation undercooling of silicon on Si 3N 4coated SiO 2. This is done in order to be able to

I. Brynjulfsen, L. Arnberg /Journal of Crystal Growth 331(2011)64–6765

control the nucleation and undercooling needed for a dendritic growth more accurately, since this growth has shown promising results for structure control of silicon ingots.

2. Experimental procedure

Three different parameters have been studied in this work; the coating thickness; the amount of oxygen in the coating; and the roughness of the coating. Two types of experiments have been used to study the nucleation undercooling. The sessile drop method performed in a wettability furnace and differential thermal analysis (DTA).

The samples for the wettability furnace, SiO 2pieces with the dimensions 0.9?0.9?0.3cm 3, were coated both manually with a spray gun and with a coating robot. Before coating the samples were preheated on a heater to a temperature of 1501C, but this dropped rapidly when the samples were coated. The samples were coated with a variation in number of layers. The samples were dried between each layer of coating to ensure a better adherence to the substrate and a smooth coating. The amount of coating was weighed and the coating thickness was both estimated and measured after the nucleation experiments, with correlating numbers. The samples were then ?redat 11001C for 4h as a standard ?ringroutine. Firing temperatures of 900and 12001C, and holding time of 6h were used to obtain different oxygen levels in the coating. The oxygen concentration was measured by LECO. Similar samples were also produced by a commercial crucible producer, Vesuvius.

For the nucleation study in the wettability furnace a small piece of silicon (approximately20mg) was placed on the Si 3N 4coated substrate and mounted on the sample holder. The proce-dure and speci?cationsfor using the wetting furnace are explained elsewhere [11]. The sample was heated at a rate of 5K/minwhen it was close to melting and to the preset holding temperature. When the sample reached the holding temperature, which was always less than 50K above the melting point, it was cooled at a rate of 20K/min.The temperature was measured with

a thermocouple placed directly below the sample holder, and the melting point of silicon was used as a reference point for the amount of undercooling. When the droplet started solidifying it expanded in most cases, as can be seen in Fig. 1. The solidi?cationtemperature was set to be the temperature when the ?rstvisible changes in size and/orre?ectionin the middle of the droplet took place. The high cooling rate was chosen in order to be able to visually see the point of solidi?cation.A high cooling rate will give higher values of undercooling [12], but since the cooling rate was the same for all experiments it should not have in?uencedthe parameters under investigation in this study.

Some experiments were performed in a differential thermal analysis (DTA)equipment to con?rmthe undercooling measured by the sessile drop method. The same heating and cooling routine as for the wetting experiments were used in these experiments. The crucibles were Al 2O 3coated with Si 3N 4, and therefore an Al 2O 3substrate was also tested in the wetting furnace. Because of the small diameter of the DTA crucibles the coating was not easy to spray uniformly. Some crucibles were spray coated and some painted with coating to investigate if this led to differences.

3. Results and discussion 3.1. Wetting experiments

As explained in Introduction a good wetting between solid and substrate leads to a lower energy barrier for nucleation, thus a lower nucleation undercooling. The surface energy balance for a solid droplet in a liquid is shown in Fig. 2(a).

For good wetting between the solid and the substrate, g Liquid àSubstrate must be higher than the sum of the other interface energies:

g Liquid àSubstrate Z g Solid àSubstrate tg Liquid àSolid cos y

e1T

A large g Liquid àSubstrate will give wetting of the solid nucleus in Fig. 2(a).On the other hand, if g Liquid àSubstrate is large it can be

seen

Fig. 1. Melted droplet of silicon (a)before cooling and (b)solidi?ed.

Fig. 2. The ?gureillustrates the difference between contributions affecting the wetting angle for the two cases:(a)Solid nucleus in liquid silicon. (b)Liquid drop on substrate in vapour atmosphere, sessile drop experiment.

66I. Brynjulfsen, L. Arnberg /Journal of Crystal Growth 331(2011)64–67

from Fig. 2(b)that this can lead to non-wetting in the liquid on substrate case. Wetting conditions in this second case is also dependent on the liquid–vapourtension and vapour–substratetension. Both of these interface tensions are dependent on the coating, because a high oxygen concentration can lead to the formation of an oxide ?lmand/ora high production of SiO gas. This will affect the wetting and nucleation conditions on the edges of the droplet, but not the nucleation conditions inside the droplet. Therefore it is dif?cultto predict whether or not non-wetting/wettingin sessile drop experiments indicate wetting/non-wetting of the solid nucleus forming inside the droplet.

Another factor from theory that will contribute to a good wetting is a rough coating which will lead to more nucleation points [13]. In addition, in the sessile drop experiments a low oxygen concentration will lead to a higher degree of wetting [11]. Since the dendritic growth requires a certain amount of under-cooling to take place, non-wetting in Fig. 2(a)is wanted. The aim of this study is therefore not only to investigate what factors in?uencethe nucleation undercooling, but also see which gives the highest undercooling at the given cooling rate. Since several factors are affecting the wetting conditions, the only conclusion that can be drawn is that wetting in Fig. 2(b)gives a higher probability for non-wetting in Fig. 2(a).A consideration that must be taken into account, and cannot be left out of experiments with solar cell silicon, is that non-wetting in Fig. 2(b)is important to prevent the silicon from sticking to the crucible.

Large variations in the undercooling were measured, from the lowest of 12K to the highest of 37K. The undercooling did not seem to be dependent on the oxygen concentration in the coating, see Fig. 3(a),or the measured wetting angle, see Fig. 3(b).

A thicker coating will limit the diffusion of oxygen from the silica substrate and in this way affect the reactions taking place between silicon and substrate. It was therefore believed that the thickness would in?uencethe undercooling, but variations in coating thickness

Undercooling as a function of oxygen concentration in coating

40)

K ( 30g n 251100°C, 4hi l o 1100°C, 6ho 20c 900°C, 2hr e 151200°C, 4h

d n 10U 50Oxygen concentration (wt.%)Undercooling as a function

of wetting angle

4035

)

K ( 30g n 25Author i l o Vesuvius

o 20Coated aluminac r e 15Pure silicaPure alumina

d n U 1050Wetting angle (°)

Fig. 3. Variation in undercooling with:(a)oxygen concentration. The tempera-tures and time displayed are the ?ringparameters for the coating. (b)Liquid-substrate wetting

angle.

Undercooling as a function of

coating thickness

4035g

n 30i l o 25o c 20

r e d 15Vesuvius

n U 1050Coating thickness (μm) Undercooling as a function of roughness

- samples from Vesuvius

4035)

K ( 30g n i 25l o o 20c r e 15d n U 1050Roughness (μm)

Fig. 4. Display of variation in undercooling with coating thickness (a)and roughness (b).

did neither show a trend; see Fig. 4(a).These samples were produced with the same ?ringroutine and hence had the same oxygen concentrations. Samples produced by Vesuvius with an up to 20times thicker coating also gave undercooling in the same range. The variations in coating thickness were applied due to earlier investiga-tions of wetting and oxygen concentration [11].

The comparison of samples with different roughness from Vesuvius did neither show any trend; see Fig. 4(b).The average roughness given in the ?gureis smaller than 5and 10m m Ra. The last value marked as 20m m Ra is for all the experiments with variation in coating thickness. The two ?nestcoatings are some-what thinner than the rough coatings.

The coating ?redat 12001C for 6h displayed a different behaviour then the rest. It looked like the droplet reacted with the substrate after melting and formed an oxide layer around the droplet. It lost its round shape and imploded. This implies an effect of the oxygen concentration on the surface tension and hence the nucleation. Because of this behaviour the data for the coating ?redat 12001C were only plotted in Fig. 4(a).

The present results are not directly comparable with the experiments in the study by Appapillai et al. [10], since in their case they coated the silicon samples completely with the sub-strate. But, as for Appapillai, the coated Al 2O 3substrates in the present project gave a somewhat lower undercooling than the coated silica substrates. Silicon wet these substrates most, and the spreading was faster and more signi?cant.This implies that the chemical composition of the silicon nitride coating alone does not determine the undercooling.

All the samples in the present experiments were covered by a black layer, indicating a low interfacial stability, which can contribute to decrease the undercooling. This behaviour together with the clear reaction for the samples ?redat 12001C showed, in accordance with Appapillai et al. [10], Koh et al. [14]and Vallat-Sauvain et al. [15], the importance of chemical composition.

I. Brynjulfsen, L. Arnberg /Journal of Crystal Growth 331(2011)64–6767

Table 1

DTA experiments performed. M is for mixed, S is for sprayed and P is for painted crucible. DTA-results Coating

M M S S P P P Undercooling (K)

Undercooling all substrates

35)

K 30( g n 25i l o o 20c r e d 15n U 1050

Fig. 5. Variation in undercooling for all the different substrates tested in this study. Experiments with the same undercooling on the same type of substrate are placed next to each other.

As mentioned above there is also the possibility for the nucleation to take place at inclusions in the melt. Si 3N 4particles can be formed due to dissolution and re-precipitation of the coating, and carbon is also available in the furnace atmosphere giving the possibility for formation of SiC. The substrates without coating were not exposed to nitrogen. (Thecoating has been identi?edas the main source of nitrogen in silicon.) If Si 3N 4particles were the main cause of nucleation of silicon, the substrates without coating should show a higher undercooling. This is not the case in this work, but SiC can not be ruled out as a compound in?uencingnucleation.

3.2. DTA-analysis

Two series of differential thermal analysis experiments were performed on Si 3N 4coated Al 2O 3crucibles, with the same heating and cooling cycle as in the wetting furnace. Because of the small diameter of the crucible an even coating was very dif?cultto obtain. The ?rstseries of coating were therefore still on the experimental level and not very complete or uniform. Two crucibles were coated in this way and are marked M in Fig. 1. In the second series, two crucibles were spray coated, S, and three painted with coating, P. The average undercooling was ca. 21K. The shapes of two of the DTA curves were varied from the others. These were the spray coated and most evenly coated crucibles. They have a somewhat higher undercooling than the others, but not signi?cantlyenough to conclude with a real difference, see Table 1.

The undercooling of the samples in the DTA were in the same range as the sessile drop experiments. This means that even if the DTA is a more accurate measuring method, since the sessile drop experiments rely on a visual observation of start of nucleation, sessile drop experiments can be used to measure undercooling. Two of the DTA-values were somewhat lower, but as commented above these were not coated as good as they should have. This leads to an uncertainty in their accuracy. All the experiments are summarized in Fig. 5.

4. Conclusion

The results from the wetting experiments do not indicate that the coating alone plays an important role in the nucleation under-cooling. Different oxygen concentration, thickness, and roughness gave undercooling in the same range. There where on the other hand some variations in undercooling with different substrates, as the coated alumina substrates showed a lower undercooling, see Fig. 5. A very high oxygen concentration did affect the undercooling in the way that a clear reaction and deformation affected the silicon leading to a lower degree of undercooling. Even if the DTA results and the results from the sessile drop experiments were in the same range, the DTA-results showed variations, and a further study of the coating roughness should be done. Nucleation in the melt caused by inclusion should not be ruled out either. Further work is required to study if the nucleation undercooling experiments in the present investigation can be used to predict nucleation conditions during solidi?cationof large silicon ingots. Acknowledgement

This work was performed within The Norwegian Research Centre for Solar Cell Technology project number 193829, a Centre for Environment-friendly Energy Research co-sponsored by the Norwegian Research Council and research and industry partners in Norway. References

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范文三：太阳能多晶硅铸锭用石英坩埚氮化硅涂层的免烧工艺

太阳能多晶硅铸锭用石英坩埚氮化硅涂层的免烧工艺

周艳华

(江西科技学院土木工程学院

江西

南昌

330098)

摘要：本文介绍一种太阳能多晶硅片生产过程中，喷涂坩埚免焙烧的工艺，即在氮化硅浆料中加入少许水溶性有机物（粘结剂、防潮剂、分散剂），通过有机高分子的化学吸附和氮化硅粉的物理吸附作用使氮化硅粉强有力地吸附在坩埚内壁，免去了传统工艺中喷涂坩埚在坩埚烧结炉中焙烧21h ，焙烧温度为1050℃的工艺。与传统工艺相比，此工艺缩短硅片生产周期，提高生产效率，降低生产成本。

关键词：免焙烧中文分类号：TF12

氮化硅浆料

水溶性有机物

文章编码：123（2012）01-051-04

文献标识码：A

0引言

多晶硅铸锭制备过程中，高纯石英坩埚是其必备的容器，因其纯度高而能够制备出优质的多晶硅锭。多晶硅锭生产过程中，硅料在坩埚内熔化、晶体生长、退火冷却，单一使用高纯石英坩埚将面临以下危害：

①使用寿命短、安全性差：硅熔体和石英坩埚长时间接触时，会产生黏滞性，Si 与SiO 2反应生成SiO 而使得坩埚变薄甚至开裂，导致硅液溢流等重大损失，降低使用寿命、安全性差。

②硅锭利用率低：坩埚与硅液产生黏滞，在硅锭冷却过程中，由于两者的热膨胀系数不同而导致坩埚与硅锭的破裂，致使硅锭的利用率差，同时可利用的硅块可能由于残余应力较大而导致切片过程中硅片碎片率增加。

③污染硅锭：铸锭用的原料为Si 含量高达99.9999%（6N ）的高纯硅料，而高纯石英坩埚的纯度为99.7以上，直接使用石英坩埚将导致大量杂质从坩埚进入硅锭中，如C 、O 、Fe 、B 、P 等，污染硅锭，改变硅锭的电学、机械性能等。

因此，为了解决直接使用坩埚而出现的上述问题，需要在坩埚内表面进行涂层，涂层要求高纯，不与两者反应，并有适中的结合强度。

Si 3N 4是一种重要的高温结构陶瓷材料，由于具有耐高温、强度高、硬度大、耐磨损、抗冲击、抗腐蚀、质量轻、导热性能好、抗氧化和表面摩擦系数小等优点，在机械、电子、化工、航空航天等众多领域有广泛应用[1-5]。

由于Si 3N 4不含任何金属元素，且具有很高的化学稳定性，不与熔融Si 和石英发生反应，高纯度的氮化硅也比较容易制备。因此Si 3N 4成为石英陶瓷坩埚的首选涂层材料，已在多晶硅铸锭生产中成功应用[6]。

Si 3N 4喷涂在石英坩埚的内壁后、在高温下烧结，涂层与坩埚形成一体，从而隔离了硅熔体和石英坩埚的接触，其不仅能够解决黏滞问题，而且可以降低多晶硅中的C 、O 、Fe 、B 、P 等杂质浓度；另外，利用Si 3N 4涂层还可以提高石英坩埚的铸锭安全性和达到降低生产成本的目的。

Si 3N 4涂层喷涂好后，为了使氮化硅涂层与石英坩埚结合紧密，将坩埚放入抽屉窑内，焙烧至1050-1100℃左右，经过21h 的焙烧，排出坩埚和氮化硅涂层中的吸附水，使涂层和坩埚之间更好结合。然而，由于氮化硅浆料与石英坩埚之间性能存在差异，两者的结合性较差，坩埚喷涂和焙烧后，容易出现大面积掉粉和起皮现象，导致喷涂效果降低。另外，石英坩埚在焙烧过程中，温度控制不好收稿日期：2011-11-02

作者简介：周艳华(1980-)，女，江西临川人，江西科技学院土木工程学院，硕士。研究方向：材料应用及工艺研究。研究方向：

就很容易析晶，致使坩埚的抗热震性下降，从而诱发石英坩埚在冷却过程中产生龟裂缺陷，导致在铸锭过程中发生渗硅现象。为此，本文介绍一种采用坩埚涂层免烧结的工艺。

1实验过程

1.1实验原理

为了确保坩埚喷涂质量，避免因烧结过程中引发的涂层龟裂，影响硅锭质量，本文介绍一种采用坩埚涂层免烧结的工艺，即在氮化硅浆料中添加3～5wt‰的水溶性有机物高分子（分散剂，粘结剂，防潮剂），通过有机高分子的化学吸附和氮化硅粉比表面积大的物理吸附作用，使得氮化硅粉强有力地吸附在坩埚内壁。其中，分散剂的作用是将氮化硅粉末在水溶剂中分散开来，使浆料的流变特性稳定；添加粘结剂目的是提高氮化硅浆料的粘度，将喷涂在石英坩埚中的氮化硅粉通过高分子的化学吸附作用强有力地吸附在坩埚内壁，从而不易掉粉；防潮剂由于耐水性较好，能有效防止空气中的水分子进入氮化硅涂层中，从而避免氮化硅粉因吸湿膨胀导致开裂脱落。1.2试样制备

石英陶瓷选用中材高新集团生产的900型坩埚（尺寸为848×848×480mm），装料量为470kg 。其免焙烧坩埚喷涂工艺具体如下：

氮化硅粉的配比为220g 三洋粉和200gST ，氮化硅与纯水的重量比为1:2.9，量取1200ml 纯水备用，各称取2.5g 粘结剂，分散剂，防潮剂以备用；取100ml 纯水和2.5g 粘结剂倒入烧杯中，用加热器加热至沸腾，并不断搅拌直至粘结剂完全溶解；分别将分散剂和防潮剂各2.5g 加入到搅拌杯中，并倒入800ml 水，搅拌均匀，将上述粘结剂水溶液倒入其中，不断搅拌；将配好的氮化硅粉加入搅拌杯中，搅拌15min 后喷涂，喷涂温度为45-60℃；喷涂完后将坩埚静置在喷涂加热台2-3h ，保持喷涂坩埚温度在45-60℃范围内，以充分排除喷涂坩埚中的自由吸附水；待坩埚冷却后，开始装料铸锭，装料量为470kg 。1.3性能评价

采用sd-480kg-c.rcp 程序，晶锭出炉后对其进行平均少子寿命、电阻率及C 、O 含量等参数的统计。

2结果与讨论

采用传统的工艺制备坩埚喷涂，其具体热处理制度如表1所示，烧结照片如图1所示：

表1坩埚热处理制度

程序步骤12

3456

起始温度

℃2050070010501050750

结束温度

℃5007001050105075050

所需时间(小时) 3(焙烧时间) 2(焙烧时间) 3(焙烧时间) 3(保温时间) 3(冷却时间) 7(冷却时间)

图1坩埚烧结照片

从表1可知，若按一个月生产600个坩埚计算用电成本，则用烧结炉烧结的坩埚一个月用电量总计为243150度，每度电价格按0.7元计算，则一个月用电量成本为170205元。所以，每个坩埚用电量成本为284元/个，而采用免焙烧工艺制备坩埚喷涂，从用电量成本考虑，每个坩埚可节约成本284

元/个。

为了分析免焙烧坩埚喷涂的性能，表2给出了晶锭电性能参数检测结果。

表2坩埚免烧晶锭检测结果

晶锭编号1107E08106M 1107F08103M 1107I09054M 1107J01045M 1107G09069M 1107J05047M 1107G07068M 1107H08051M

平均值

平均少子寿命/μs

4.854.823.904.234.704.604.104.204.43

平均电阻率/Ω.cm

1.671.431.341.411.401.351.351.441.42

晶锭收益率/%

70.868.869.671.0170.170.169.46869.73

从表2中可以看出此种喷涂坩埚免焙烧工艺平均少子寿命为4.43μs（>2μs），电阻率为1.42Ω.cm（1-3Ω.cm）, 晶锭收益率为69.73%，均在所要求的范围内。可见，适量有机物的加入不会对晶锭的质量产生较大的影响。

此外，表3还给出了传统工艺和坩埚免焙烧工艺铸锭的晶锭头料下部和尾料上部的C 、O 含量。

表3C 、O 含量对比表

不同工艺传统工艺坩埚免焙烧工艺

头料下部（×1017cm-3）C 含量2.052.12

O 含量4.942.97

尾料上部（×1017cm-3）C 含量2.242.25

O 含量2.542.6

由表2可知，坩埚免焙烧工艺铸锭的晶锭头料下部和尾料上部的C,O 含量和传统工艺近似。这主要是因为免焙烧工艺加入的少量有机物在铸锭过程中以分子形式挥发或在1410℃前裂解为碳，由于碳的热震动性较大，加上铸锭炉中抽真空和气流对流作用，有机物已挥发殆尽。

综上述分析可知，采用此工艺不仅降低了生产成本，而且坩埚的性能也达到要求。

3结论

在氮化硅浆料中添加3～5wt‰的水溶性有机物高分子（分散剂，粘结剂，防潮剂），通过有机高分子的化学吸附和氮化硅粉比表面积大的物理吸附作用，使得氮化硅粉强有力地吸附在坩埚内壁。加入的少量有机物不会对晶锭的质量产生较大的影响。因此，此工艺和传统工艺相比，不仅简化了生产工序，而且还大大降低了成本。参考文献：

[1]吴明明，肖俊建. 氮化硅陶瓷在现代制造业中的应用[J].机电产品开发与创新. 2004,17(2)：13-15. [2]Berroth K, Prescher T. Development and industrial application of silicon nitride based ceramics[J].Key

Engineering Materials ，2005，287：3-9.

[3]陈力. 氮化硅陶瓷材料的研究现状及其应用[J].硬质合金，2002，19(4)：226-229.

[4]Elamrani A, Menous, Mahiou L,et al. Silicon nitride film for solar cells[J].Renewable Energy ，2008，33：

2289-2293.

[5]李漠，黄传真，何林，等. 氮化硅基陶瓷刀具材料的研究现状[J].陶瓷学报，2003，24（1）：58-62. [6]袁向东，刘利华，李俊国，等. 多晶硅铸锭涂层用高纯Si 3N 4微粉的研究进展与展望[J].硅酸盐通

报，2009，28（3）：548-551.

（责任编辑：陈辉）

Unfired Process for Silicon Nitride Coating of Quartz Crucible for Solar Poly-silicon

Ingots

Zhou Yan-hua

(Departmentof Civil Engineering, Jiangxi Blue Sky University, Nanchang 330098, China)

Abstract :An unfired process is introduced for the spraying crucible during the production process for

the solar poly-silicon ingots. Namely a little water soluble organic matter is added into the silicon nitride slurry(Thewater soluble organic matter is adhesive, damp-proof agent, dispersant) ，and then the silicon nitride powder is forcefully adsorbed on the inner wall of the crucible by the chemical adsorption of organic macromolecule and the physical absorption of silicon nitride. Compared to the traditional process which calcinates the spraying crucible at 1050℃for 21hours ，this process can shorten production cycle, raise production efficiency and economize production cost.

Key words :unfired process; silicon nitride slurry; water soluble organic matter

范文四：表面改性对氮化硅粉体及其涂层影响的研究

第32卷第2期 2011年6月

渤海大学学报(自然科学版)

Journal of Bohai University(Natural Science Edition)

V01.32.No.2 Jun.20ll

表面改性对氮化硅粉体及其涂层影响的研究徐金鑫,刘伟

(渤海大学科技实验中心,辽宁省硅材料工程技术研究中心,辽宁锦州121013)

摘要:采用正硅酸乙酯水解法在氮化硅粉体表面包覆二氧化硅进行表面改性,并用改性后的粉体在石英基体表面涂层,通过IR、TG—DTA、XRD等对其结果进行了表征,结果表明氮化硅粉体在硅溶胶中达到了良好的分散,且改性后的氮化硅粉体的抗氧性提高,烧结温度降低,且制得涂层表面光滑,附着力良好,与基体结合牢固。

关键词:氮化硅;表面改性;正硅酸乙酯;涂层

中图分类号:G642.0文献标识码:A 文章编号:1673—0569(2011)02—0148—05

U 引吾

氮化硅具有很高的化学稳定性、耐高温性能、良好的机械性能及优异的介电性能、高介电常数、高介电强度,因此氮化硅在高温领域,尤其是在高科技领域得到了越来越广泛的应用¨。J。在采用氮化硅结合硅溶胶作粘结剂,制备氮化硅耐高温涂层过程中,出现浆料的稳定性差,涂层不均匀,与基体结合不牢固,烧结温度高¨。63等问题。同时氮化硅在高温下使用时往往存在着氧化问题¨】。张其土等人喁’则利用在氮化硅陶瓷材料表面用溶胶一凝胶法涂覆一层莫来石涂层来提高氮化硅陶瓷材料的高温抗氧化性能。因此对氮化硅表面改性,提高氮化硅在硅溶胶中的稳定性,是制备涂层的关键。

本文采用正硅酸乙酯水解法在氮化硅表面包覆二氧化硅,通过实验研究改性氮化硅在石英基体上涂层的影响。通过沉降实验研究了改性粉体在硅溶胶中浆料的稳定悬浮性,通过红外,热分析,粒度和透射数码偏光显微镜对二氧化硅改性的氮化硅涂层粉体进行表征和分析。

1实验

1.1实验仪器和试剂

试剂:氮化硅为合肥开尔纳米公司生产,纯度99%,平均粒度50nm。实验所采用的正硅酸乙酯,硅溶胶,异丙醇等均为分析纯

仪器:x射线自动衍射仪(CuKa辐射,40kv,50mA,步宽0.02。,扫描速度2。/min,日本理学公司);透反数码偏光显微镜(6XB—PC型,上海永亨光学仪器制造有限公司);红外光谱仪(FT—IR560型,美国 Magna公司);热重分析仪(PyTis型,美国PE公司)。

1.2实验过程

称取3.0g Si,N。于250ml圆底烧瓶中,加入一定体积的异丙醇,超声分散30rain,以并流滴加的方式缓慢加入A液(A:氨水、水和异丙醇混合稀释液)和B液(B:正硅酸乙酯和异丙醇混合稀释液),并且保证 nTE∞=nm.H20=l:2,大致控制滴加速度为Id/s,电动搅拌,在40。C恒温水浴锅中反应1小时,然后在 90℃恒温水浴锅中回流3小时。

反应结束后,把样品用异丙醇洗涤三次后用离心机分离,最后把样品转移到小烧杯中,放在105。C烘

收稿日期:201l—04—13.

基金项目:辽宁省科技厅工程中心基金资助项目(No:2009402007).

作者简介:徐金鑫(1984一),女,渤海大学硕士研究生,从事纳米粉体改性研究

g 2期'\徐金鑫,刘伟:表面改性对氮化硅粉体及其涂层影响的研究 149

箱中干燥后研磨,得到SiO:改性Si,N。粉体。

1.3沉降实验

分别制备用异丙醇分散的Si,N。粉体和SiO:改性Si,N。粉体的悬浮液,调节pH值=8左右且稳定后, 分别置于10ml比色皿中,观察它们在不同时间内的沉降高度。

2结果与讨论

2.1沉降行为

未改性Si,N。粉体与SiO:改性Si,rq。粉体的沉降结果见表1。可以看出,在相同pH值下,改性浆料均比未改性浆料悬浮性好。sio:改性si,N。浆料沉降体积分数小,沉降速度慢,说明Si,N。经过表面改性,浆料的稳定悬浮性提高。这可能是由于改性粒子表面的负电荷增加,提高了颗粒间的静电斥力,同时也产生了空间斥力位能,静电斥力与位阻效应协同作用,有效阻止了颗粒间的团聚,提高了浆料的稳定悬浮性。表1沉降实验

2.2红外光谱分析

Si02改性Si,N。粉体前后的红外谱图,见图l。比较未改性Si,N。和SiO:改性si,N。粉体的IR光谱可知,未改性si,N。粉体在1059cm‘1强吸收带为si—N键的伸缩振动吸收峰,这主要由于粉体中含有H,O 等,使Si—N键吸收峰往往位于800—1100cm。1范围。468cm。1左右si—N键弯曲振动。3144cm。1为N— H键伸缩振动。969cm一为Si—OH键的伸缩振动峰。1401cm。1为N—H基团的变形剪式振动峰∽,lo】。 1610cm。1为Si—H的伸缩振动峰。而Si02改性后的Si3N4粉体在1100cm一、800era~、480cm一均出现了 SiO:红外特征峰¨¨,1107cm一为Si—O—Si键的反对称伸缩振动峰,820cm一为Si—O—Si键的对称振动吸收峰472cm。1为Si一0一Si键的弯曲吸收峰。而位于969cm。1的Si—OH键的伸缩振动峰消失,可能是由于高温灼烧使之失水导致。

零

、

图1Si02改性前后Si3N。粉体的红外谱图

150渤海大学学报(自然科学版) 第32卷

2.3热重分析

SiO:改性前后Si,N。粉体的TG/DTA图谱,见图2a、图2b所示。从图2a中可以看出,改性前TG曲线在区间50cc一95℃有一个较小的失重带,对应的DTA曲线在55℃处有一明显的吸热峰,此为失去物理吸附水的过程。此外,TG曲线在600℃一800℃区间有一增重带,是由于在空气气氛下,氮化硅粉体表面活性大,发生氧化吸氧的缘故。从图2b中可以看出,谱图上的TG曲线在区间60。C一90℃都有一小的失重带,对应的DTA曲线在60℃一90℃处有一明显的吸热峰,此为失去物理吸附水的过程。此外,TG曲线在900C一6000C区间都呈失重趋势,对应的DTA曲线在2000C处有一明显的放热峰,此为粉体中混有的有机物(异丙醇)燃烧造成的。且经改性后的氮化硅粉体在600℃以上没有氧化,说明氮化硅粉体经过SiO:改性,表面抗氧化性提高。

图2a Si02改性前Si,N。粉体的热重谱图图2b Si02改性后Si3N4粉体的热重谱图

2.4SiO,改性SiC粉体的XRD分析

图3a为未改性氮化硅的XRD谱图。从图3a中可以看出,未改性氮化硅粉体在20=20.542。出现最强吸收峰,另外,在20为22.9020、30.883。、35.207。还出现了三个峰。它们对应的d值分别为3.8800、2. 8930、2.5470,这些峰均为Si3N。的特征峰。图3b为Si02改性Si3N。粉体的XRD谱图。从图3b中可以看出,改性粉体在20=23.38。出现一个宽化峰,是非晶态的SiO:[12J,而且此时Si,N4特征峰被削弱,由此可以判断包覆粒子中有无定形SiO:存在,这与IR分析结果一致。

图3a未改性Si3N。的XRD谱图图3b Si02改性Si3N4粉体的XRD谱图

绦台鑫.刘伸:击蜥嫂性对氯化硅枋体技jC潦瑶彤响的研究

25显搬镜对改性前后氮化硅涂层形貌的对比

【冬|4a、矧4b为利川适应数码偏光娃微镜脱察改悱前后氯化硅涛屡的形貌.通过两幅l斟的对比,町以根在脱的看出未改性的氯化砟涂搓表面有很多裂痕.附拧力也小强.儿’4幕休结合,fi

田4Ⅱ政性前潦层透反数码显微镜图像囤4b改-巨后涂层连反数码显微镜图雌

3结论

奉文秉川TEos水解法,成功的制备r表面包檀二钮化硅的氯化硅粉体改性侨的氮化硅粉体息浮惟提高.机氧化性增强烧结温度降低;制得的涂联表面光滑.附精JJ世好,n‘j基体站台牢固

参考文献

[i]《#蚌.n】女&.前#*,等=-j、、。**#Ⅲm{**&女Ⅲ&n【J]《&☆自m.2∞lf6):24—29

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r3)Ⅻ{b.±朝Ⅲ.Ⅻ连“6《#自-l-H艟0*■2∞}【外光骷№*M(j)渤*^学}报自然科々&.j008.29【4)332—335

[4)Ⅻ2._庆社.张宁.等趣Ⅷ精悼∞表目&^*Rm*J)%口^{f报.j晰.19(2):16—20

5】*《.*,}Hf佳*.等*￥№#∞击Ⅲ&%&击ⅡA女m究【1:{f℃nh200534{i):49—52

。6)n建*∞∞Ⅲ忠*等*#介质

’7】※苴I s一、N.冉瓷#H帕Hmii自&“n■mgR【J】N鞋{m砌,2i(I):24?27

、8】m^i《*“%目W s】,N.目《#H∞#*m%%∞#自[J)目^¨#I狮.31(I)-M

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[12]{t,刘连靳.t柏日.*&&HmM&☆Ⅻ备**‘瓤mn(J]{l融n洒报2007.26(3):486—489

152渤海大学学报(自然科学版) 第32卷

Research of surface modification for

Si3N4powder and its coating

XU Jin—xin.LIU Wei

(Bohai University Center for Science&Technology Experiment。Liaoning Province Silicon Materials

En#neering Teehnology Research Centre,jinzhou 121013,Chinas)

Abstract:Si3N4powders coated by Si02were prepared by hydrolysis procedure of TEOS,and by using

modi-fled powders in quartz matrix surface for coating.The Si3N4powders modified were characterized by IR,TG/ DTA,XRD,and 80on.The results showed that:the stability of suspension wag improved when Si3N4was modi? fled;the Oxidation—Resistance Wag improved;the Sintering temperature was reduced;The coating with smooth surface,good adhesion and solid.

Key words:Si3N4;surface modification;TEOS;coating

表面改性对氮化硅粉体及其涂层影响的研究

作者:徐金鑫 , 刘伟 , XU Jin-xin, LIU Wei

作者单位:渤海大学科技实验中心,辽宁省硅材料工程技术研究中心,辽宁锦州,121013

刊名:

渤海大学学报(自然科学版)

英文刊名:JOURNAL OF BOHAI UNIVERSITY(NATURAL SCIENCE EDITION)

年,卷(期):2011,32(2)

参考文献(12条)

1. 颜鲁婷;司文捷;苗赫濯 Si3N4粉体表面化学分析及表面改性 2001(06)

2. CarolineM P;JamesA R;MichaelD AInfrared spectroscopic study of sol-gel derivedmixed-metaloxides

2001(223)

3. 徐博;储昭荣纳米氮化硅粉体的表面改性研究 2008(02)

4. 孟祥森;宋晨路;余京生低温APCVD法制备氮化硅薄膜 1999(03)

5. 张其土莫来石涂层对Si3N4陶瓷材料的抗氧化性能的影响 1997(01)

6. 张其土 Si3N4陶瓷材料的氧化行为及其抗氧化研究 2000(01)

7. 代建清;黄勇;谢志鹏液体介质对氮化硅粉料表面基团和悬浮特性的影响 2001(02)

8. 张蕾;张丹凤;于桂英纳米微粒的表面改性及表征方法研究 2005(01)

9. 刘吴;才庆魁;张宁超细粉体的表面改性研究进展 2007(02)

10. 刘伟;王莉丽;刘连利石英玻璃中羟基含量测定的红外光谱法研究 2008(04)

11. 王君;徐国财;吉小利纳米氮化硅粉粒的表面改性研究 2003(09)

12. 李曦;刘连利;王莉丽凝胶网格沉淀法制备纳米二氧化硅 2007(03)

本文链接:http://d.g.wanfangdata.com.cn/Periodical_jzsfxyxb201102012.aspx

范文五：8-增强氮化硅涂层及其在晶体硅铸锭中得应用

第12届中国光伏大会暨国际光伏展览会论文

增强氮化硅涂层及其在晶体硅铸锭中的应用

尹长浩1，钟根香1，黄新明1，2

1. 东海晶澳太阳能科技有限公司；2. 南京工业大学材料科学与工程学院

摘要：本文采用改进溶胶凝胶法（sol-gel ）制备增强氮化硅涂层（SG 涂层），并将其

应用于准单晶硅铸锭及普通多晶硅铸锭。实验结果显示：1）采用溶胶凝胶法制备的氮化硅涂层，早期强度较常规喷涂法制备的涂层有显著的提高；2）氮化硅涂层中有机物的添加会降低硅熔体与涂层间的非浸润性，涂层中有机物在加热过程中的碳化可能是其主要原因。铸锭应用结果显示：完整的SG 工艺制备的氮化硅涂层可以满足准单晶硅铸锭脱模需要，同时，免烧结SG 涂层可直接应用于普通多晶硅铸锭生产。

关键词: 氮化硅涂层；溶胶凝胶法；准单晶硅；多晶硅

Reinforced Si3N 4 coatings and its application in silicon demoulding

Changhao Yin1, Genxiang Zhong1, Xinming Huang1，2,

1) Donghai JA Solar Technology Co. Ltd.

2) College of Materials Sci. & Engineering, Nanjing Univ. Tech.

Abstract: In this paper, the silicon nitride coatings used in silicon casting were prepared

by improved sol-gel method (SG), which had been used in quasi-mono crystalline silicon casting and multicrystalline silicon casting successfully. The experiments showed significant reinforcement in hardness of the coatings prepared by SG method compared with the coatings prepared by spraying-sintering method (SS). The remnants of the sol added in the coatings increased the wettability in the interface between silicon melt and coating, and carbonization of the organic contents in the coating during heating process was probably responsible for the result. The silicon casting applications showed that the coatings prepared by SG could be used in quasi-mono crystalline silicon casting, and the coatings prepared by SG without sintering could be used in multicrystalline silicon casting as well.

Keywords ： silicon nitride coating, sol-gel, quasi-mono silicon, multi-crystalline silicon

1. 引言

多晶硅铸锭是目前光伏晶体硅主要的生产方法：将多晶硅料置于石英坩埚内通过定向凝固铸造而成。通过改良热场结构并调整相应的长晶工艺可获得电池转化效率更高的准单晶硅锭。无论常规多晶铸锭还是准单晶铸锭，坩埚内壁的氮化硅涂层都是必不可少的脱模剂。该脱模剂具备两大功能：一、在铸锭过程中，阻止坩埚中杂质向硅料中扩散；二、在铸锭完成后，确保硅锭与坩埚的顺利分离。

常规多晶铸锭生产中通常采用先喷涂后烧结的方法在坩埚内壁上制备氮化硅涂层，称为喷涂烧结法（spraying-sintering method, SS）；其改进方法是在氮化硅浆料中添加硅溶胶等具有粘合能力的物质，免去烧结过程，因而这种涂层制备方法称为免烧结法（Spraying Method, SM ）。对于常规多晶铸锭而言，SS 涂层及SM 涂层基本可以满足生产需求。但对于长晶条件更为苛刻的准单晶铸锭而言，上述涂层由于强度较低等因素易导致较高的粘埚率，难以直接使用。如何提高氮化硅涂层的强度成为重要课题。

目前氮化硅涂层的作用机理已得到广泛研究。普遍认为氮化硅涂层与硅熔体之间的浸润特性与粘埚现象关系密切。而氮化硅涂层与硅熔体之间的浸润性受众多因素的影响，包括影响三相界面接触角 (γS –L , γS –G , γL –G ) 的诸多因素[1]，如：氮化硅涂层的完整性、氮化硅涂层的氧化程度[2]以及氮化硅涂层与坩埚基体、硅熔体所处的氧分压[3,4]等。必须强调的是，纯净的氮化硅与硅熔体之间是相互浸润的[4-6]，因而无法直接制作涂层。大量研究表明[7-10]，氮化硅涂层中氧的存在（氮化硅颗粒表面的氧化层、自坩埚中氧的

扩散）及其在界面处的释放很可能是维持氮化硅涂层与硅熔体非浸润性的主要因素。因而调节涂层中氧含量及其释放速率是控制涂层性能的重要手段。

本文主要通过调节氮化硅涂层中的氧化物含量、烧结条件等因素控制涂层中的氧含量，另外，鉴于喷涂方法制备的涂层质地疏松，引入改进溶胶凝胶法（sol-gel ，SG ）用于制备增强氮化硅涂层，并就涂层中残余有机物引入的碳素对硅熔体与氮化硅涂层界面间浸润性的影响进行了探讨。

2．实验

本文分别采用SS 法、SM 法及SG 法在坩埚碎片制备实验涂层样品，对比不同制备方法中氧化物添加量及是否烧结处理对涂层性能的影响，采用划痕测试法检验烧结前后涂层强度的变化，采用小尺度铸锭观察涂层与硅熔体间的浸润性，并在实际铸锭生产中验证涂层的脱模性能。

3. 实验结果与分析

3.1 早期强度

表1为不同制备工艺下制备的涂层的铅笔硬度测试结果。其中所有样品在烧结前

表1涂层样品参数。

Table 1 Parameters of the coating samples.

编号成膜方法氧含量烧结前烧结后 SS spray-sinter 4H SG 4

sol-gel

20%

2B-HB

＞4H

均在空气气氛下80℃晾干2h ，以去除多余的游离水。从表中可以看出，常规喷涂涂层

由于质地疏松，其烧结前强度最低，而SG 法的样品由于有机交联结构的加强，其烧结前强度有显著的提高，这为氮化硅涂层免烧结工艺提供极好的基础。 3.2 非浸润性

图1为仅经过80℃2h 晾干去除水分而未经过烧结处理涂层样品SS （A ）和SG 1（B ）在空气气氛下的热重分析曲线。当烧

图1经 80℃2h 晾干除水分而未经过烧结处理涂层样品SS （A ）和SG 1（B ）热重曲线，其中曲线C

为温度变化。

Fig. 1 TG-analysis of coating samples (air drying: 80℃，2h) sintered at 1070℃ in air. A ：SS, B: SG1

and C: temperature curve.

结温度达到500℃时，SG 法样品快速失重约9%左右，而常规喷涂样品失重1%左右，在趋势上与Ingvild Brynjulfsen 等[11]报道的结果相一致。这是由于样品中残余少量的水分及其它杂质的挥发所致。由于SG 法在涂层中添加了有机物，其失重比例远高于不添加有机物的常规喷涂法。随着烧结温度的增加及烧结时间的延续样品失重趋于减缓，这说明500℃有氧烧结即可有效去除SG 法添加的有机粘合剂。而当烧结温度达970℃后样品即出现增重。根据Brynjulfsen [11]等的研究，这一增重很可能是烧结过程中氮化硅颗粒氧化所致。在氧化过程中，很有可能发生如下反应并生成相应氧氮化硅相（Si 2N 2O ）。

其反应式为：

2Si 3N 4(s)+3O2(g)→3Si 2N 2O (s)+N2(g) （1）根据文献报道[2,4,6,8]，基本可以确认的是，无论氮化硅涂层中氧以何种形式存在，氧在氮化硅涂层与硅熔体间的浸润性方面起到至关重要的作用。其作用机理可以概括为如下反应：

Si (l)+SiO2(s)→2SiO (g) （2）

上述反应中，可以理解为气体SiO 的产生，起到了阻碍硅熔体与涂层进一步接触的作用，但其前提是SiO 不易溶解于硅熔体，并且SiO 能够形成完美的气膜阻挡在硅熔体和氮化硅颗粒之间。

根据B. Drevet等[2]的研究结果，含氧氮

化硅涂层与硅熔体相接触瞬间硅熔体与氮化硅涂层之间表现非浸润特性，但非浸润特性在很短的时间（不超过100s ）内消失，具体表现为接触角从稍大于90°快速减小并稳定在40-50°。这可以理解为在氮化硅涂层与硅熔体接触瞬间，氮化硅涂层表面氧快速消耗，导致浸润性的变化。 3.3 碳素的影响

选取SG 法和SS 法制作涂层的坩埚角进行硅料的熔化及结晶实验，结果如图2所示。从图中可以看出SG 法制备的涂层在铸造后涂层暴露在硅熔体外的表面形成一层黑色的硬壳，这是R. Einhaus 等[12]研究者中所提到的硅次级浸润层。虽然样品较小而铸造环境中碳含量较高，硅锭表面形成不光泽的杂质层，但与之相对比，不添加有机物的喷涂涂层，在同样的气氛下没有出现硅次级浸润层现象，这恰恰证明气氛中的碳含量显然不是导致硅次级浸润层的主要原因。

实验证实，对于添加有机物的氮化硅涂层，即便在空气（氧化性）气氛下长时间

图2 坩埚角涂层铸锭实验。

Fig. 2 Coatings in casting test with crucible corners.

（1070℃，4h ）烧结也难以完全去除涂层中碳素残余。而根据热力学数据[13]可以计算出在高温低压条件下，下述反应具有较强反应倾向：

Si 3N 4(s)+3C(s)→3SiC (s)+2N2(g) （3）其中C (s)为在氮化硅涂层中的残余碳，SiC (s)为反应生成的碳化硅。实验证实通常情况下碳化硅与硅熔体具有较强的相互浸润特性，这可能是碳素残余导致氮化硅涂层与硅熔体浸润性改变的主要原因。

值得注意的是，尽管由于有机物的添加降低了氮化硅涂层与硅熔体之间的非浸润性，但在冷却后的脱模过程中却未发现SG 法的氮化硅涂层与硅锭发生任何粘连。这说明，尽管氮化硅涂层与硅熔体之间的浸润特性与粘埚现象关系密切，非浸润程度的降低并不必然导致粘埚。但为了尽可能增加耐侵蚀性能，应尽可能增加涂层与熔体间的非浸润性。

3.4 准单晶铸锭应用

为了进一步验证SG 法制备的氮化硅涂层的实用性，在实际准单晶铸锭生产中进行了如下对比实验。在坩埚四个角部的硅液面处分别制备SG 1 、SG 2 、SG 3、SG 4四种氮化硅涂层，如图3所示，硅液面以下部分涂

层均采用喷涂法制备。

图3 SG涂层在准单晶铸锭生产中应用。 Fig.3 Monocrystalline silicon ingot solidified in a silica crucible with Si3N 4 coating by SG.

从图3可以看出，SG 1的硅液面处与下部的涂层并未出现明显界线，而随着氧含量的增加，上下两种涂层之间的界线清晰可辨。这个界限是由于残余在硅锭表面的氮化硅粉所致。氧含量高的氮化硅涂层在脱模后整体性仍然保持完好，吸附于硅锭表面的氮化硅颗粒极少。而氧含量不高于的5%

的氮化

硅涂层（包括喷涂法制备硅锭下部的涂层），在脱模后可发现大量氮化硅颗粒或粉末吸附在硅锭表面。

更值得注意的是，不同氧含量的氮化硅涂层表现出不同抗粘埚性能，氧含量为5%和25%的氮化硅涂层均出现了粘埚现象，粘埚点均在硅液面处，而相比较而言，氧含量分别为10%和15%的氮化硅涂层的硅液面处基本无粘埚点。

3.5 免烧结涂层在普通多晶硅铸锭中应用

与铸锭条件较为苛刻的准单晶硅铸锭相比较，普通多晶硅铸锭对涂层强度的要求明显宽容得多。图4为SG 涂层用于普通多晶硅铸锭中结果。从结果中可以看出，完整

图4 SG涂层在多晶铸锭中应用（上：烧结，

下：未烧结）。

Fig.4 Multi-crystalline Si ingot solidified in silica crucible with SG coating (up: with sintering, down: without sintering).

的SG 涂层在脱模后，未在硅锭侧面残留氮化硅粉，而未烧结的SG 涂层脱模后在硅锭硅液线附近残留少量氮化硅粉，除此之外与完整的SG 法涂层基本没有差别，可以满足

多晶铸锭脱模需要。而未烧结的SG 涂层在硅锭表面残余的原因很可能是涂层中有碳的残余导致硅熔体与涂层非浸润性的降低。

为进一步验证SG 涂层中有机物的添加是否会对硅锭质量造成影响，分别使用完整SG 涂层、免烧结SG 涂层及SS 涂层的坩埚在其他铸锭条件完全相同的情况下进行铸锭实验，并对与坩埚接触面积最大的A 区（坩埚转角处）的硅方进行少子寿命对比。图5所示为A 区硅方不同位置硅片的少子寿命分布。从图5可以看出，使用完整SG 涂层、免烧结SG 涂层及SS 涂层的硅锭A 区少子寿命分布差别不明显。

图5 免烧结SG 法与SS 法硅方少子寿命比较。 Fig. 5 Minority carrier lifetime in the SS and SG

(with and without sintering) ingots.

尽管有机物在加热过程会有一定的碳

化残余，但SG 法在涂层中引入的碳素残余

大部分会在加热过程中挥发去除，只有少量有机物碳化后残余在涂层内。对使用不同涂层坩埚所铸硅锭的碳含量进行对比测试，结果表明SG 涂层并不会对硅锭中的碳含量造成明显影响。SG 法使用的有机物杂质浓度较石英坩埚中的杂质浓度低一个数量级，并且添加量很少，因而对硅锭纯度产生的影响基本可以忽略。

4. 结论

本文通过引入改进溶胶凝胶法（SG ）法制备了可用于准单晶铸锭的氮化硅涂层。其中免烧结SG 法涂层可用于普通多晶硅铸锭生产。在多晶硅铸锭生产中，相比较完整的SS 法、SG 法，免烧结SG 法可以显著缩短涂层工艺时间，并节省相应的成本，因而可以认为是具有潜力的涂层发展方向。今后的工作是寻找在中性或还原性气氛下加热过程中有机物残余更少的SG 方法来制备氮化硅涂层。如何进一步提纯氮化硅涂层各种原料的纯度也是今后值得关注的领域。

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