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--- front-end.md [2026/06/19 16:39] – [Processes] eric.fourboul.ext
+++ front-end.md [2026/07/09 21:05] (current) – [Processes] eric.fourboul.ext
@@ Line 1084: / Line 1084: @@
 ### Processes
 Key elements of CMP are:
-  * The polishing pad
+  * The polishing pad. This is the mechanical pad that rubs against the surface of the wafer.
-  ** This is the mechanical pad that rubs against the surface of the wafer.
+  * The slurry. This is a liquid mixture that generally contains:
-  * The slurry
+       - water;
-  * This is a liquid mixture that generally contains:
+       - abrasive particles (silica, alumina, ceria, depending on the process);
-  ** water;
+       - chemical agents to oxidise, complex or adjust pH;
-  ** abrasive particles (silica, alumina, ceria, depending on the process);
+There are three primary types  of CMP: oxide CMP, tungsten CMP, and copper CMP
-  ** chemical agents to oxidise, complex or selectively etch the material;
+#### 9.1. Oxide CMP
-#### 9.1. Planarization
+Oxide CMP is primarily used to flatten dielectric layers.
-  * Silicon dioxide (SiO2)
+It is used to:
-  * Aluminium oxide (Al2O3)
+  * flatten an interlayer dielectric (ILD);
-  * Cerium oxide (CeO2)
+  * STI (Shallow Trench Isolation): after filling the isolation trenches;
-  * Deionized water (DI Water)
+  * restoring the surface to a flat state before a new lithography or metallisation step;
-  * Hydrofluoric acid (HF)
+  * reducing the topography created by the previous steps.
-  * Sulfuric acid (H2SO4)
-  * Sodium hydroxide (NaOH)
-  * Potassium hydroxide (KOH)
-  * Ammonium hydroxide(NH4OH)
 ##### Inputs
-  * test
+  * Silica (SiO2) as abrasive
-  * test
+ Derived from TEOS (tetraethyl orthosilicate): Si(OCH₂CH₃)₄ or Si(OEt)₄ TEOS forms SiO₂ through simple hydrolysis, releasing ethanol (CH₃CH₂OH) :
+Si(OCH2CH3)4 + 2 H2O → SiO2 + 4 CH3CH2OH
+  * Ceria (CeO₂)
+Ceria slurries achieve much higher oxide removal rates and superior planarization efficiency, making them preferred for "Shallow Trench Isolation" (STI), i.e. the technique that electrically isolates adjacent transistors.
+  * hydroxide ions (OH⁻)
+  * Amoniac (NH3) as pH adjustor
+  * Potassium hydroxyde (KOH) as pH adjustor
 ##### Outputs
+  * Silicon Nitride Si₃N₄
+  * poly-Si
-  * test
-  * test
+#### 9.2. Tungsten CMP
+Tungsten CMP is used to remove excess tungsten after it has filled openings.
+It is used to:
+  * form contacts;
+  * form tungsten-filled vias;
+  * remove tungsten deposited everywhere except in the required cavities.
+The most widely used approach uses ferric nitrate (Fe(NO₃)₃) or hydrogen peroxide (H₂O₂) as the oxidising agent to convert the tungsten surface to a soft tungsten oxide (WO₃) layer, which is then mechanically removed by the abrasive.
+##### Inputs
+  * Alumina (Al₂O₃) as abrasive
+  * Tungsten(W)
+  * ferric nitrate (Fe(NO₃)₃)
+  * hydrogen peroxide (H₂O₂)
+  * Titanium nitride (TiN)
+  * Silica (SiO2)
+##### Outputs
+  * tungsten oxide (WO₃)
 ##### Formula
+  * 2W + 3H₂O₂ → WO₃ + 3H₂O (oxidation)
+followed by:
+  * WO₃ + abrasive contact → material removal
-to add
+#### 9.3. Copper CMP
+Copper CMP is used to form copper interconnections, particularly in Damascene or dual-layer schemes
+It is used to:
+  * remove excess copper deposited on the surface;
+  * leave copper only in the trenches and vias intended for interconnect lines;
+  * planarise after metallisation.
+The most specific feature of copper CMP slurry is the use of benzotriazole (BTA) as a corrosion inhibitor.
+##### Inputs
+  *  5-Methyl-1H-benzotriazole (C7H7N3)
+  * Copper (Cu)
+  * Silica (SiO2) as abrasive
+  * hydrogen peroxide (H₂O₂)
+  * Tantalum nitride (TaN)
+  * Tantalum (Ta)
+  * Amoniac (NH3) as pH adjustor
+  * Sodium hydroxyde (NaOH) as pH adjustor
+d
 ### Manufacturers
   * [Applied Materials](https://www.appliedmaterials.com/eu/en/product-library.html)
   * [EBARA](https://www.ebara.com/global-en/products/?type=Semiconductor%20manufacturing%20equipment)
   * [Hwatsing](https://www.hwatsing.com/en/)
 ### Equipment
   * Applied Materials [Opta CMP](https://www.appliedmaterials.com/eu/en/product-library/opta-cmp.html): metal and non-metal CMP; single-step batch and balanced/unbalanced multi-step sequential polishing; thick and thin film removal / advanced logic and memory (3D) <5nm
@@ Line 1131: / Line 1167: @@
   * Ebara [F-REX300XA](https://www.ebara.com/global-en/products/FREX300XA/): 300mm
   * Ebara [F-REX200M2](https://www.ebara.com/global-en/products/FREX/): 200mm
 ### Misc
   * [Ebara catalog](https://www.ebara.com/content/dam/ebara/grand-masters/entities/en/products/precision-pump/pdf/80002E_26_20.pdf)
   * Chemical Mechanical Planarization, [CMP Process Fundamentals: CMP Tools and Process](https://www.youtube.com/watch?v=2z4lq-Ms_OU) ; [CMP Process Fundamentals: CMP Slurries](https://www.youtube.com/watch?v=lWvvKGkFDfk)
+  * [jeez-semicon](https://jeez-semicon.com/fr/blog/copper-cmp-vs-tungsten-cmp-vs-oxide-cmp-full-comparison/)
 ### Sources
   * Zantye, P. B., Kumar, A., & Sikder, A. K. (2004). Chemical mechanical planarization for microelectronics applications. Materials Science and Engineering: R: Reports, 45(3-6), 89-220.
@@ Line 1143: / Line 1177: @@
   * Kim, H. J. (2018). Abrasive for chemical mechanical polishing (pp. 183-201). Rijeka: InTech
   * Lee, J., He, S., Song, G., & Hogan Jr, C. J. (2022). Size distribution monitoring for chemical mechanical polishing slurries: An intercomparison of electron microscopy, dynamic light scattering, and differential mobility analysis. Powder Technology, 396, 395-405.
+  * XU, Qinzhi, CHEN, Lan, YANG, Fei, et al. Influence of slurry components on copper CMP performance in alkaline slurry. Microelectronic Engineering, 2017, vol. 183, p. 1-11.
+  * PARK, Seonghyun et LEE, Hyunseop. Electrolytically ionized abrasive-free CMP (EAF-CMP) for copper. Applied Sciences, 2021, vol. 11, no 16, p. 7232.
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