Potential Causes of CMP Defects and possible Solutions

Potential Causes of CMP Defects and possible Solutions

Material Name: No data
Record No.: 44
Primary Chemical Element in Material: No data
Sample Type: Wafer
Uses: Polishing
Etchant Name: None
Etching Method: Polishing
Etchant (Electrolyte) Composition: No data
Procedure (Condition): No data
Note: In the manufacturing of IC chips, the wafer is polished several times using the CMP process. CMP has been applied for polishing various types of surfaces, including oxides, Cu, W and others. However, several defects induced by CMP depend on the type of surface being polished. This may be attributed to the effects of various chemicals and abrasive particles as well as the pressure exerted on the wafer surface. Defects typically formed during the CMP process include organic residues, water marks, particle adherence and impingement, corrosion pit, and scratches. However, the removal of organic residues and water mark formation are trivial in oxide CMP, but other types of defects, such as scratch formation, are critical, as they affect the yield and reliability of the devices. Table 1 shows the CMP process induced defects and their specific effects on the replacement metal gate (RMG) process.

Scratches are one of the most commonly generated defects during the CMP process. It was found that CMP scratches could cause an initial failure as well as long term reliability failure. The failure mechanism in the shallow trench isolation (STI), inter-level dielectric (ILD), and poly-Si CMP processes is very similar in nature. Scratches cannot be detected after CMP, but are usually identified after etching using the HF solution. The periodic arc scars generated on brittle materials such as oxide, BPSG, and poly-Si are called chatter mark-type scratches. Figure 1 shows some examples of chatter mark scratches after STI CMP. Scratch shape is influenced by the mechanical properties of the material. A wide variety of scratches are formed on a metal surface like Cu, which is shown in Fig. 2.
Reference: Tae-Young KWON, Manivannan RAMACHANDRAN, Jin-Goo PARK, Scratch formation and its mechanism in chemical mechanical planarization (CMP), Friction 1(4): 279–305 (2013).

Table 1: Potential causes of CMP defects and possible solutions.

Figure 1: Chatter mark scratches observed in STI CMP.

Figure 2: Various scratches formed in Cu CMP.