On the path of the semiconductor industry toward higher integration and smaller dimensions, an innovative technology originating in 2008—TGV (Through Glass Via)—is emerging. As a revolutionary alternative to TSV (Through Silicon Via) technology, TGV is rewriting the rules of high-end chip packaging by leveraging the unique advantages of glass materials. Among its manufacturing processes, the wet etching technique, as a core step in TGV fabrication, is a precision art worthy of in-depth exploration.

Why Choose Glass? Material Properties Determine Technological Direction

Traditional silicon substrates have obvious shortcomings in high-frequency signal transmission, while glass substrates have become the ideal choice for next-generation 3D integration due to their:

• Excellent high-frequency characteristics

• Low loss

• Superior thermal stability

The key differences between glass and silicon materials require new solutions for via formation in TGV technology—and wet etching demonstrates unique value in this context.

Wet Etching: The Core Tool for TGV Via Formation

Among the five key steps in TGV manufacturing, via formation is particularly critical, and wet etching technology is the essence of this step.

I. Process Principle

The glass substrate is immersed in a hydrofluoric acid (HF)-based etchant. Chemical reactions between HF and silicon dioxide (SiO₂) in the glass selectively dissolve unprotected areas (not covered by a mask), forming vias. The byproduct—hexafluorosilicic acid (H₂SiF₆)—is water-soluble, enabling efficient glass removal.

Compared to dry etching (which relies on complex plasma equipment), wet etching uses a simple chemical dissolution process. Perfect micrometer-scale via formation is achieved by precisely controlling:

1. Time

2. Temperature

3. Etchant concentration

II. Process Flow

1. Traditional Wet Etching Steps

A standard workflow includes:

• Substrate Preparation: Clean the glass substrate (acetone → alcohol → ultrasonic cleaning with deionized water) to ensure surface purity.

• Mask Fabrication: Coat photoresist → perform photolithography → develop to create the via pattern.

• Wet Etching: Immerse the substrate in the etchant; control time to form vias.

• Mask Removal: Strip photoresist using solvents (e.g., acetone).

• Post-treatment: Ultrasonic cleaning → deionized water rinsing → drying.

2. Typical Process Flow

III. Etchant Formulation and Selection

1. Main Types of Etchants

2. Etching Characteristics of Different Glasses

IV. Process Parameter Optimization and Influencing Factors

1. Optimization of Key Parameters

2. Influence of Each Parameter on Etching Results

V. Traditional Wet Etching VS Laser-Induced Etching

VI. Challenges and Solutions of Wet Etching