COMPOSITION OF POLISHING SUSPENSION FOR CHEMICAL-MECHANICAL PLANARIZATION OF SURFACE OF DIELECTRIC LAYER (SiO2) FOR MICROELECTRONIC PRODUCTION
The addition of potassium carbonate in the polishing suspension addresses the issues of low removal rates and high defects by preventing colloidal silica flocculation, resulting in improved dielectric layer polishing efficiency.
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Patents
- Current Assignee / Owner
- ROSSIJSKAJA FEDERATSIJA OT IMENI KOTOROJ VYSTUPAET MINISTSTVO PROMYSHLENNOSTI I TORGOVLI ROSSIJSKOJ FEDERATSII
- Filing Date
- 2024-09-25
- Publication Date
- 2026-07-01
AI Technical Summary
Existing polishing suspensions for dielectric layers in microelectronics suffer from low dielectric removal rates and high residual defects, primarily due to colloidal silica flocculation and the use of certain pH-adjusting agents that contaminate the surface or reduce efficiency.
Incorporating potassium carbonate into the polishing suspension to form a double electrical layer around silica particles, preventing flocculation and enhancing the dielectric removal rate while reducing residual defects.
The proposed suspension achieves a higher dielectric removal rate and lower residual defects on the polished surface compared to existing technologies, optimizing the polishing process.
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Abstract
Description
[0001] Technical field
[0002] The invention relates to the production of polishing suspensions for chemical-mechanical planarization of the surface of a dielectric layer (SiO2) in microelectronic production.
[0003] Technology Level
[0004] Chemical-mechanical polishing (CMP) is a technology of leveling (planarization) and polishing in order to ensure the flatness of the treated surface.
[0005] In microelectronics, CMP technology is used in the manufacture of semiconductor products for processing conductive and non-conductive surfaces, and in particular, in the production of ICs (integrated circuits) for processing functional layers at the stages of forming fully isolated circuit elements, connections of circuit elements and metal wiring [1, 2].
[0006] A suspension for polishing dielectric layers is known from the EPO patent [3]. The polishing suspension contains: an abrasive from 0.1 wt. % to 50 wt. % based on colloidal silicon dioxide or fumed silica with a particle size of 5 to 200 nm, pH> 7, adjusted with potassium hydroxide or sodium hydroxide, and a nitrogen-containing salt based on ammonium, additionally contains surfactants, water-soluble polymers. The specific electrical conductivity of the polishing suspension is from 0.01 to 0.55 S / m.
[0007] The disadvantage of this polishing suspension is the low dielectric removal rate, which is in the range of 850-1800 Å / min.
[0008] A polishing suspension for polishing dielectric layers is known from a US patent [4]. The polishing suspension contains an abrasive obtained by hydrolysis of tetraethyl silicate. The abrasive obtained by this technology has a looser structure compared to abrasive obtained by traditional technology from liquid glass.
[0009] The disadvantage of this suspension is the low removal rate due to its lower hardness, as well as the presence of ethyl alcohol in this polishing suspension up to 9 wt.%, which leads to a decrease in the dielectric removal rate.
[0010] A polishing suspension for polishing dielectric layers of the Klebosol 30N50PHC brand (USA) is known to be produced based on colloidal silica with a particle size of 75-78 nm stabilized by sodium oxide and ammonium hydroxide, pH = 10.6-11.1 pH units and a concentration of abrasive particles of 29.4-30.8 mass % [5].
[0011] The disadvantage of this polishing suspension is that when ammonium hydroxide is used in the suspension, ammonia is released into the atmosphere, which leads to a decrease in the pH of the polishing suspension and, consequently, a decrease in the dielectric removal rate. The use of sodium hydroxide contaminates the polished surface more than potassium hydroxide [4].
[0012] A suspension for polishing dielectric layers is known [6]. The polishing suspension contains an abrasive from 15 wt. % to 30 wt. % based on colloidal silicon dioxide with a particle size of 50-60 nm, pH = 9.4-10.8, regulated by potassium or ammonium hydroxides, potassium or ammonium bicarbonate in an amount of 0.3 wt. % to 2 wt. % and a viscosity modifier - xanthan gum in an amount of 0.1 wt. % to 3 wt. %, the rate of removal of silicon oxide from 3200 to 4200 Å / min.
[0013] The disadvantage of this polishing suspension is that it is not possible to assess the presence and quantity of defects >0.16 µm on the plate after polishing.
[0014] The closest to the proposed invention is a polishing suspension for polishing dielectric layers [7]. The polishing suspension contains as initial components: an abrasive from 0.1 wt. % to 40 wt. % based on colloidal silicon dioxide with a particle size of 10 to 200 nm, an organic additive from 0.001 wt. % to 5 wt. %, pH = 10-12, an agent for adjusting pH is selected from nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and potassium hydroxide.
[0015] The disadvantage of this polishing suspension is the low dielectric removal rate, which is in the range of 1000-2500 Å / min and a high number of residual defects on the plate >16 μm equal to 70.
[0016] The aim of the invention is to reduce the number of defects on the polished surface of a dielectric.
[0017] The stated objective is achieved in that the suspension for polishing dielectric layers (SiO2), containing colloidal silica, potassium hydroxide (KOH) and water, additionally contains potassium carbonate (K2CO3).
[0018] When colloidal silica particles are pressed tightly together due to polishing pressure, colloidal silica flocculation occurs. This flocculation results in the formation of aggregates, which increases the number of defects on the polished surface and reduces the dielectric removal rate. The addition of potassium carbonate induces the formation of a double electrical layer around the silica particle, preventing flocculation. Potassium carbonate is superior to potassium hydroxide in suppressing colloidal silica flocculation.
[0019] Brief description of polishing suspension components.
[0020] Colloidal silica (TU 2145-012-61801487-2016, Appendix 1) is a milky liquid with the following physical and mechanical properties:
[0021]
[0022] Potassium hydroxide (KOH) grade Ch.D.A. (GOST 24363-80)
[0023] Potassium carbonate (K2CO3) grade Ch.D.A. (GOST 4221-76)
[0024] The invention is illustrated by the following examples:
[0025] Example No. 1.
[0026] The polishing slurry was prepared as follows. A calculated amount of aqueous solutions of KOH (solution concentration 3 wt%) and K2CO3 (solution concentration 3 wt%) were added to colloidal silica with a concentration of 33 wt% (SiO2) while stirring. The mixture was stirred for 2 hours, and the silica concentration was adjusted to 30 wt% with water. The resulting polishing slurry had the following composition (wt%):
[0027]
[0028] Examples 2-14 are similar to example 1. The compositions of the polishing suspensions are given in Table 2.
[0029] Polishing tests with suspensions were carried out on a MIRRA-MESA Integrated CMP System 200 polishing machine from Applied Materials (USA).
[0030] The polishing characteristics of the suspension were determined on 200 mm diameter silicon wafers with a smooth PETEOS film of 13000 Å thickness deposited on them.
[0031] To test the polishing properties of the suspension on PETEOS films, the corresponding standard polishing recipes were used. The parameters and their values in these polishing recipes are presented in Table 1.
[0032]
[0033] Table 2 shows the compositions of polishing suspensions and the polishing result of dielectric plates.
[0034]
[0035]
[0036] Analysis of the tabular data (Table 2) shows that the prototype has a lower average material removal rate and a higher number of residual defects >0.16 μm on the wafer after polishing. The proposed suspension (examples 2, 3, 4, 5) has a higher material removal rate and a lower number of defects >0.16 μm on the wafer compared to the prototype. With component concentrations in the suspension below and above the stated concentration, the number of residual defects on the wafer increases. Increasing the amount of potassium carbonate (example 6) is not cost-effective, as it does not improve the results after polishing.
[0037] Sources of information
[0038] 1. Krasnikov G.Ya., Zaitsev N.A. Physical and technological foundations of VLSI quality assurance. - M., 1999. Part 2.
[0039] 2. Evdokimov V.L., Ranchin S.O. Requirements for the cleanliness of process environments in the production of integrated nanoelectronics crystals / / Electronic engineering. Series 3: Microelectronics. 2016 No. 1 (161). pp. 59-71.
[0040] 3. EPO Patent EP 0846741 A1 (IPC C09G 1 / 02, C23F 3 / 00, published 10.06.1998).
[0041] 4. US Patent US 6322600 B1 (IPC B24D 3 / 02, published 11 / 27 / 2001).
[0042] 5. https: / / www.dupont.com / products / klebosol-slurries.html
[0043] 6. US Patent US 7351662 B2 (IPC H01L 21 / 302, published 01.04.2008).
[0044] 7. US Patent US 9012327 B2 (IPC H01L 21 / 302, C09G 1 / 02, H01L 21 / 306, published 04 / 21 / 2015).
Claims
A polishing suspension for SiO2 dielectric layers containing colloidal silica stabilized with potassium hydroxide with a particle size of 75-85 nm, water, characterized in that it additionally contains potassium carbonate in the following ratio of components, mass %: colloidal silica, calculated as SiO2 29-31 potassium hydroxide 0,3-0,39 potassium carbonate 0,05-0,07 water rest