双面抛光对石英掩模基板表面形貌的影响

张诚; 秦瑞; 白吉浩

doi:10.13394/j.cnki.jgszz.2024.0161

双面抛光对石英掩模基板表面形貌的影响

doi: 10.13394/j.cnki.jgszz.2024.0161

湖南普照信息材料有限公司, 长沙 410017

详细信息

通讯作者:
张诚，男，1988年生，硕士，中级职称，湖南普照信息材料有限公司研发中心主管。主要研究方向：化学机械平坦化、石英玻璃磨削抛光亚表面损伤层。E-mail：cheng.zhang@oim.com.cn

中图分类号: TG356.28
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出版历程
- 收稿日期: 2024-10-07
- 修回日期: 2024-12-02
- 录用日期: 2024-12-02
- 刊出日期: 2025-08-20

Effect of double-sided polishing on surface morphology of quartz mask blanks

Hunan Omnisun Information Material Co., Ltd., Changsha 410017, China

摘要

摘要: 随着集成电路关键尺寸的缩小，晶体管密度和芯片性能持续提升。同时，随着集成电路工艺制程的不断演进，掩模基板的平坦化加工要求也日益严苛。为揭示双面化学机械抛光对石英掩模基板的抛光去除机理，利用CeO₂磨料自制抛光液，对6025石英玻璃进行双面抛光加工，考察抛光粉粒径、抛光液浓度、抛光压力、齿圈与太阳轮转速组合对石英掩模基板材料去除率、表面形貌、平面度以及表面粗糙度的影响。结果表明，使用粒径为0.823 μm的CeO₂抛光粉抛光后，石英玻璃表面粗糙度比使用粒径为1.231 μm的CeO₂抛光粉降低40%；随着抛光液浓度的增大，正面平面度呈现先下降后上升的趋势，当质量分数达到14%时结果最优，而材料去除率持续增大；在0.26～0.43 MPa的压力范围内，材料去除率与压力呈线性关系，然而如果压力进一步增大，材料去除率反而减小。使用等效粒径D₅₀为0.823 μm的抛光粉，配制成14%浓度的CeO₂抛光液，在0.43 MPa的抛光压力下，选取齿圈与太阳轮转速分别为6.54和3.08 r/min，抛光后6025石英玻璃的表面光滑（平面度为0.573 μm，表面粗糙度R_a最低为0.96 nm），几乎没有划痕、中位裂纹等表面损伤，平面度和表面质量最佳。
- 二氧化铈 /
- 双面抛光 /
- 掩模基板 /
- 表面形貌
Abstract: Objectives As the critical dimensions in integrated circuit structures continue to shrink, transistor density and chip performance keep improving. At the same time, the continuous evolution of integrated circuit manufacturing processes increasingly demands stricter flatness requirements for mask blanks. To reveal the polishing removal mechanism of double-sided chemical mechanical polishing on quartz mask substrates, a polishing solution is made using CeO₂ abrasive to perform double-sided polishing on 6025 quartz mask substrates. Methods (1) CeO₂ polishing powders with particle size distributions D₅₀ of 0.823 and 1.231 μm respectively are placed in a beaker with deionized water. Under mechanical stirring, a certain amount of a mixture of sodium hexametaphosphate and sodium citrate is added as a dispersant, and an appropriate amount of polyacrylate as a surfactant. The pH value is adjusted using a weak alkali substance. Based on the content of CeO₂, polishing liquids with mass fractions of 6%, 10%, 14%, and 18% are prepared. (2) The CMP experiment is conducted on a 22B double-sided polisher using an LP66 polyurethane polishing pad to polish 6025 synthetic quartz substrate grinding discs. The same set of polishing parameters is used to polish 12 pieces of 6025 simultaneously, and then the flatness and roughness of the 12 pieces of glass are averaged. For the polishing slurry, experiments are conducted with two types of polishing powder particle sizes and four types of polishing slurry concentrations. The surface morphology of different particle size CeO₂ polishing powders is observed using a Zeiss Sigma field emission scanning electron microscope. The particle size distribution of the polishing powders is analyzed using a Mastersize 2000 laser particle size analyzer. The flatness of the quartz substrates before and after polishing is measured using a Tropel® UltraFlat™ flatness tester from CORNING. The change in thickness of the quartz substrates before and after polishing is measured using a KEYENCE displacement sensor to calculate the polishing rate. The roughness of the quartz substrates after polishing is measured using a Dimension ICON atomic force microscope from Bruker Germany. Results The flatness can reach 0.573 μm, and the surface roughness R_a is 0.96 nm under the following conditions: equivalent particle size D₅₀ of CeO₂ 0.823 μm, mass fraction of CeO₂ 14%, polishing pressure 0.43 MPa, and a gear ring and sun gear speed of 6.54 and 3.08 r/min, respectively. Conclusions (1) The surface roughness of quartz glass after polishing with fine-grained 230A is reduced by 40% compared to that after polishing with 1200A. (2) With the increase in the concentration of the polishing solution, the flatness of the front surface initially shows a decreasing trend. It reaches a minimum value at a mass fraction of 14%. However, if the concentration is further increased, the flatness actually increases. The removal rate of the quartz glass increases continuously with the concentration of the polishing solution. (3) As the polishing pressure increases within the range of 0.26-0.43 MPa, the removal rate basically changes linearly. However, if the pressure is further increased, the removal rate actually decreases. (4) Using abrasive particles with an equivalent diameter D₅₀ of 0.823 μm, a polishing solution with a concentration of 14% CeO₂ is prepared. Under a polishing pressure of 0.43 MPa, and a ring gear and sun gear speed of 6.54 and 3.08 r/min, respectively, the surface of the 6025 quartz glass is polished to be smooth with almost no scratches or median cracks, achieving smaller flatness and better surface quality.
- CeO₂ /
- double-sided polishing /
- mask blanks /
- surface topography

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图 1 不同CeO₂抛光粉的粒度分布

Figure 1. Particle size distribution of different CeO₂ powders

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图 2 不同CeO₂抛光粉的SEM图像

Figure 2. SEM photos of different CeO₂ powders

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图 3 不同粒径CeO₂抛光表面形貌AFM图像

Figure 3. AFM photos of surface morphology of different CeO₂ powders

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图 4 抛光液浓度对材料去除率和平面度的影响

Figure 4. Effect of polishing slurry concentration on removal rate and flatness

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图 5 抛光压力对材料去除率和平面度的影响

Figure 5. Effect of polishing pressure on removal rate and flatness

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图 6 不同抛光压力下6025石英玻璃正面形貌图像

Figure 6. Front surface morphology of 6025 quartz glass under different polishing pressures

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图 7 抛光转速差对平面度的影响

Figure 7. Effect of polishing speed differential ratio on flatness

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图 8 抛光转速差M01的AFM图像

Figure 8. AFM photos of surface morphology of polishing speed differential M01

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表 1 不同粒径CeO₂对抛光性能的影响

Table 1. Effect of different particle size CeO₂ on polishing

指标	230A	1200A
粒度分布 D₅₀ / μm	0.823	1.231
去除量 h / nm	9 048	11 867
材料去除率 R_MRR / (nm·min⁻¹)	150.8	197.8
抛光后平面度 F / μm	0.953	0.987
抛光表面	表面光滑，无划伤，光洁表面	表面光滑，但局部有点状划伤

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表 2 抛光转速差

Table 2. Polishing speed differential r·min⁻¹

转速差编号	齿圈转速 n₁	太阳轮转速 n₂	转速差 Δn
M01	6.54	3.08	3.46
M02	6.80	4.23	2.57
M03	5.52	4.23	1.29
M04	4.23	4.23	0

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