CN110718457B - 一种降低区熔poly背封单抛片边缘晶孔的加工工艺 - Google Patents

一种降低区熔poly背封单抛片边缘晶孔的加工工艺 Download PDF

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CN110718457B
CN110718457B CN201910917213.3A CN201910917213A CN110718457B CN 110718457 B CN110718457 B CN 110718457B CN 201910917213 A CN201910917213 A CN 201910917213A CN 110718457 B CN110718457 B CN 110718457B
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王虎
武卫
杨梦晨
邓碧鑫
石明
孙晨光
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Tianjin Zhonghuan Advanced Material Technology Co Ltd
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Abstract

本发明提供了一种降低区熔POLY背封单抛片边缘晶孔的加工工艺,对酸腐片依次进行POLY背封、减薄和抛光,并对减薄后的清洗工序进行了优化匹配。本发明将减薄工序调整到POLY背封工序后,可将POLY背封过程产生的晶孔现象大大降低,本发明与现有工艺相比,加工步骤一样,加工成本未增加,大大提高了成品合格率,具有很高的实际应用价值。

Description

一种降低区熔POLY背封单抛片边缘晶孔的加工工艺
技术领域
本发明属于半导体技术领域,尤其是涉及一种降低区熔POLY背封单抛片边缘晶孔的加工工艺。
背景技术
众所周知,金属杂质和表面平整度是器件原材料单晶硅抛光片的两项重要特性参数。一方面,应用于12英寸抛光片的表面磨削技术大大提升了抛光片的表面平整度,近年来,该技术逐渐应用于小于12英寸的抛光产品;另一方面,POLY背封的金属吸杂特性广泛应用于降低抛光片金属杂质。当运用这两项技术开发表面平整度要求高、金属杂质含量低的8英寸区熔抛光产品时,由于区熔产品机械性能较差,容易在POLY背封过程中产生边缘晶孔现象,大大降低成品率。
POLY背封单抛片在POLY背封过程产生晶孔现象的原理为:(1)多晶硅沉积于硅片与石英舟卡点接触的缝隙处,硅片与石英舟卡点因多晶硅的化学吸附作用连成一体;(2)POLY加工完成后,硅片与石英舟卡点分离时,由于强的化学吸附作用,硅片边缘产生崩边和掉晶,掉晶的位置在抛光片成品检验时即呈现出晶孔特征。
目前,直拉重掺POLY背封单抛片在POLY过程中,如果POLY膜厚超过1μm,也容易在边缘产生晶孔现象。一般处理方法是从产生原理出发采用叠片加工,即:(1)上片前,将硅片与陪片重叠,由陪片与石英舟卡点接触,避免了正片硅片与石英舟卡点直接接触;(2)加工完成后,首先将叠在一起的正片和陪片从石英舟分离,然后将正片和陪片分离。该方法有效降低了直拉重掺POLY背封单抛片的边缘晶孔现象,成本低廉。叠片加工虽然降低了直拉重掺POLY背封单抛片的边缘晶孔现象,却无法解决8英寸POLY背封单抛片边缘晶孔现象,其原因就在于直拉硅片氧含量比区熔硅片至少高1个数量级,导致区熔硅片的机械性能比直拉硅片差,叠片加工后更容易掉晶产生边缘晶孔现象。
因此,研究开发一种降低区熔POLY背封单抛片边缘晶孔的加工工艺具有重要的现实意义。
发明内容
有鉴于此,本发明旨在提出一种降低区熔POLY背封单抛片边缘晶孔的加工工艺,通过调整加工工艺、优化加工工艺,成功解决了8英寸区熔POLY背封单抛片边缘晶孔现象。
为达到上述目的,本发明的技术方案是这样实现的:
一种降低区熔POLY背封单抛片边缘晶孔的加工工艺,对酸腐蚀或碱腐蚀后的硅片依次进行POLY背封、减薄和抛光。
进一步的,所述POLY背封、减薄和抛光后均插入清洗和干燥工序,其中,减薄后的清洗工序为:先用HF溶液浸泡,然后进行SC2药液和SC1药液清洗步骤。
进一步的,所述HF溶液由质量分数为49%的HF和去离子水以1:(7-10)的体积比混合制成。
进一步的,所述HF溶液浸泡的浸泡时间为9-12min。
进一步的,所述SC2药液和SC1药液清洗步骤依次为:SC2药液清洗、水淋洗、SC1药液清洗、水淋洗、SC1药液清洗、QDR、水淋洗。
进一步的,所述减薄的减薄去除量为12-14μm。
进一步的,所述POLY背封采用LPCVD工艺。
进一步的,所述抛光的抛光去除量为10-13μm。
本发明的原理为:
目前抛光片的加工以减材加工为主,加工为成品后晶孔深度基本不超过10μm,本发明将POLY背封工序调整到减薄工序之前,减薄去除量为12-14μm,POLY背封后掉晶形成的晶孔所在的损伤层在减薄加工过程中可被完全去除。
加工过程的调整虽然解决了POLY背封后掉晶形成晶孔的现象,但是减薄过程中容易在非抛光面产生吸盘印,现有的解决方法是在减薄后的清洗工序中引入KOH或NaOH槽进行腐蚀,腐蚀去除量<1μm,但是引入KOH或NaOH槽会导致背面的多晶层厚度将低于客户规格下限甚至多晶层完全被去除,所以本发明对减薄后的清洗工序进行了优化匹配,根据HF溶液不与单晶硅和多晶硅反应但与二氧化硅反应的特点,减薄完成后清洗时先在HF溶液中浸泡9-12min,去除硅片表面的自然氧化层从而去除表面吸附杂质,解决吸盘印等表面不良。
相对于现有技术,本发明所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺具有以下优势:
本发明的加工工艺为:酸腐蚀或碱腐蚀后的硅片→POLY背封→减薄→抛光,现有加工工艺为:酸腐蚀或碱腐蚀后的硅片→减薄→POLY背封→抛光,本发明将减薄工序调整到POLY背封工序后,可将POLY背封过程产生的晶孔现象大大降低,与现有加工工艺相比,加工步骤一样,加工成本未增加,大大提高了成品合格率,具有很高的实际应用价值。而且本发明对减薄后的清洗工序进行了优化匹配,清洗时,先在HF溶液中浸泡9-12min,然后使用SC2药液和SC1药液清洗,不过KOH或NaOH槽,解决了减薄后清洗过程中KOH或NaOH溶液对POLY硅的腐蚀作用及减薄后背面吸盘印现象的问题。
附图说明
图1为对比例中晶孔深度最大的单抛片在显微镜下的照片。
具体实施方式
除有定义外,以下实施例中所用的技术术语具有与本发明所属领域技术人员普遍理解的相同含义。以下实施例中所用的试验试剂,如无特殊说明,均为常规生化试剂;所述实验方法,如无特殊说明,均为常规方法。
下面结合实施例及附图来详细说明本发明。
实施例
1、实验设备及原料
1.1实验设备
Figure BDA0002216461630000041
1.2实验原料
Figure BDA0002216461630000042
Figure BDA0002216461630000051
2、实验方案
Figure BDA0002216461630000052
3、实验实施
3.1实验过程
序号 加工工艺 加工设备 工艺参数
1 腐蚀片 / /
2 POLY背封 LPCVD立式炉 见3.2.1
3 减薄 减薄机及清洗机 见3.2.2及3.2.3
4 抛光 抛光机及清洗机 见3.2.4及3.2.5
3.2工艺参数
3.2.1POLY背封的工艺参数
采用LPCVD(低压力化学气相沉积法)工艺,具体工艺参数如下。
Figure BDA0002216461630000053
3.2.2减薄的工艺参数
thickness feed Rate C.T RPM
Air Cut 15μm
original
P1 Cut 0.3μm/s 185rpm
P2 Cut 0.3μm/s 185rpm
P3 Cut 0.3μm/s 185rpm
P4 Cut 0.3μm/s 185rpm
P5 Cut 0.3μm/s 185rpm
Spark out1 10rev 185rpm
Escape out1 2.0μm 0.10μm/s 185rpm
Spark out2 0 185rpm
Escape out2 0 0.10μm/s 185rpm
3.2.3减薄后清洗的工艺参数
序号 清洗顺序 药液配比 温度 清洗时间
1 HF溶液浸泡 HF:DIW=1:8 / 600sec
2 SC2 HCl:H<sub>2</sub>O<sub>2</sub>:DIW=1:1:10 / 300sec
3 Rinse DIW / 300sec
4 SC1-1 NH<sub>4</sub>·H<sub>2</sub>O:H<sub>2</sub>O<sub>2</sub>:DIW=1:1:12 75±5℃ 300sec
5 Rinse DIW / 300sec
6 SC1-2 NH<sub>4</sub>·H<sub>2</sub>O:H<sub>2</sub>O<sub>2</sub>:DIW=1:1:12 75±5℃ 300sec
7 QDR DIW / 300sec
8 Final Rinse DIW / 300sec
注:SC2指SC2药液清洗,SC1-1指第一次SC1药液清洗,SC1-2指第二次SC1药液清洗,QDR指快速排水清洗。
3.2.4抛光的工艺参数
Figure BDA0002216461630000061
3.2.5抛光后去蜡清洗的工艺参数
Figure BDA0002216461630000062
Figure BDA0002216461630000071
对比例
1、实验设备及原料
1.1实验设备
与实施例相同。
1.2实验原料
与实施例相同。
2、实验方案
Figure BDA0002216461630000072
3、实验实施
3.1实验过程
Figure BDA0002216461630000073
3.2工艺参数
3.2.1减薄后清洗的工艺参数
Figure BDA0002216461630000074
Figure BDA0002216461630000081
注:SC2指SC2药液清洗,SC1-1指第一次SC1药液清洗,SC1-2指第二次SC1药液清洗,QDR-1指第一次快速排水清洗,QDR-2指第二次快速排水清洗。
分别将实施例和对比例制得的单抛片放在强光灯下检验抛光面有无晶孔。实施例生产得到的58片单抛片中,有晶孔的单抛片的数量为0片,有晶孔的单抛片占比0%。对比例生产得到的50片单抛片中,有晶孔的单抛片的数量为15片,有晶孔的单抛片占比30%,对有晶孔的单抛片在显微镜下测试晶孔深度,发现晶孔深度最大为10μm,晶孔深度为最大的单抛片在显微镜下的照片见图1。这是由于对比例POLY背封时,多晶硅在陪片与正片的边缘缝隙有沉积,而区熔硅片机械性能较直拉硅片差,陪片与正片分离时非常容易产生掉晶现象,成品掉晶位置在强光灯下呈现晶孔现象。
本发明将减薄工序调整到POLY背封工序后,减薄去除量为12-14μm,可将POLY背封过程中产生的晶孔现象降低到0。本发明与现有工艺相比,加工步骤一样,加工成本未增加,有效解决了8英寸区熔POLY背封单抛片边缘晶孔现象,大大提高了成品合格率,具有很高的实际应用价值。
以上所述仅为本发明的较佳实施例而已,并不用以限制本发明,凡在本发明的精神和原则之内,所作的任何修改、等同替换、改进等,均应包含在本发明的保护范围之内。

Claims (7)

1.一种降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:对酸腐蚀或碱腐蚀后的硅片进行POLY背封,背封过程中硅片的减薄面与舟接触,然后对与舟接触的减薄面依次进行减薄和抛光,其中减薄通过减薄机进行磨削减薄;
所述POLY背封、减薄和抛光后均插入清洗和干燥工序,其中,减薄后的清洗工序为:先用HF溶液浸泡,然后进行SC2药液和SC1药液清洗步骤。
2.根据权利要求1所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:所述HF溶液由质量分数为49%的HF和去离子水以1:(7-10)的体积比混合制成。
3.根据权利要求1所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:所述HF溶液浸泡的浸泡时间为9-12min。
4.根据权利要求1所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:所述SC2药液和SC1药液清洗步骤依次为:SC2药液清洗、水淋洗、SC1药液清洗、水淋洗、SC1药液清洗、QDR、水淋洗。
5.根据权利要求1所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:所述减薄的减薄去除量为12-14μm。
6.根据权利要求1所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:所述POLY背封采用LPCVD工艺。
7.根据权利要求1所述的降低区熔POLY背封单抛片边缘晶孔的加工工艺,其特征在于:所述抛光的抛光去除量为10-13μm。
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