Temperature Control of SC-1 and SC-2 Solutions at Different Process Nodes

In semiconductor manufacturing, SC-1 (Standard Clean-1, an ammonia-hydrogen peroxide mixture) and SC-2 (Standard Clean-2, a hydrochloric acid-hydrogen peroxide mixture) are critical wet-etching cleaning processes. Temperature control for these processes must be finely optimized based on the process node, type of contaminants, and film characteristics, in order to ensure effective cleaning while minimizing damage to the device structure.

I. Relationship Between Process Node and Temperature Control

1. Mature process node (>28 nm)

• The temperature for SC-1 is typically controlled at 70–75 ℃, with a treatment time of 5–10 minutes. Higher temperatures help accelerate the removal of organic contaminants and particulates.
• For SC-2, maintain the temperature at 70–75 ℃ to enhance its ability to complex and remove metal ions; however, avoid excessively high temperatures that could lead to loss of the thermal oxidation film or increased surface micro-roughness.

2. Advanced process nodes (14 nm and below)

• To reduce the impact of thermal stress on delicate structures, the SC-1 temperature can be lowered to 30–55 ℃, and cleaning efficiency can be balanced with structural integrity by shortening the processing time—from 30 seconds to 2 minutes.
• The temperature of SC-2 is typically controlled at 50–60 ℃, and a low-concentration solution (e.g., diluted to 1:10 or lower) is used in combination to minimize erosion of materials with high dielectric constants and ultra-thin gate oxide layers.

II. Key Measures for Temperature Optimization

1. Dynamic adjustment strategy

The response surface methodology (e.g., Box-Behnken design) can be used for synergistic optimization of temperature and formulation ratios. For example:

• When the thermal oxide film thickness requirement is ≤ 3 nm, SC-1 can minimize film loss at 30 ℃ with a ratio of 1:9:50 (NH₄OH:H₂O₂:H₂O).
• If uniformity within the wafer needs to be controlled to less than 1%, SC-1 at 60 ℃ with a ratio of 1:3:50 can achieve a thermal oxide film loss of less than 0.065 nm.

2. Thermal Stress Control

In 3D NAND or FinFET and other three-dimensional structures, a segmented temperature-control strategy can be employed: In the initial stage, the temperature is rapidly raised to the target value (e.g., 55 ℃), and after cleaning is complete, a gradient cooling approach is adopted to reduce thermal stress concentration.

The cooling medium can be selected from a system with increasing specific heat capacity (e.g., gas → deionized water), which, while achieving rapid cooling, also helps to minimize the impact of temperature fluctuations on the thin film.

3. Synergistic effect of drug solution activity and temperature

In SC-1, if the concentration of NH₄OH is reduced (e.g., to a ratio of 1:1:50), the temperature can be appropriately increased to 50–60 ℃ to maintain particle removal efficiency.

In SC-2, if the HCl concentration is significantly reduced (e.g., to 1:100), the procedure can be carried out at room temperature, and effective removal of metallic contaminants can be ensured by extending the treatment time (e.g., to 10 minutes).

3. Equipment and Process Compatibility

1. Temperature Control System Selection

It is recommended to adopt a PID closed-loop control system, coupled with real-time temperature monitoring (such as thermocouples or infrared sensors), achieving a control accuracy of up to ±0.1 ℃.

For applications such as megasonic cleaning that require uniformity, a dual-zone or multi-zone temperature-controlled jacket design can be employed to ensure a uniform temperature distribution within the tank (≤ ±1 ℃).

2. Process Compatibility Verification

At nodes below 10 nm, it is recommended to use analytical techniques such as TEM (transmission electron microscopy) to evaluate the impact of temperature on the integrity of the gate oxide layer and interface characteristics, thereby avoiding defects caused by localized overheating.

In the copper interconnect process, if the SC-2 temperature exceeds 65 ℃, it is necessary to consider adding subsequent passivation or anti-oxidation steps to prevent reabsorption of copper ions and corrosion.

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