In high-end manufacturing fields such as semiconductor packaging, micro-electro-mechanical systems (MEMS), and AR/VR optical devices, glass wafers have become one of the core basic materials due to their excellent dielectric properties, light transmittance and structural stability. The precise processing of glass wafers directly determines the performance and accuracy of end products, among which laser drilling, laser induction and etching processes are the three most widely used core technologies. However, many industry practitioners have a vague understanding of the boundaries of their roles and confuse their application scenarios, leading to low processing efficiency and insufficient product qualification rates. This article will detail the core roles, principle differences and application scenarios of the three processes in glass wafer processing, helping industry practitioners select models accurately, improve processing efficiency, and provide technical reference for relevant enterprises to promote the standardized application of glass wafer processing technology.
The core demand of glass wafer processing is to achieve precise, efficient and low-damage microstructural forming. The core positioning and roles of different processes are completely different: laser drilling focuses on "direct forming", laser induction on "precision preprocessing", and etching process on "precision finishing". The three can be applied independently or collaboratively to meet the processing needs of different precisions and scenarios. Clarifying the differences in their roles is the key to improving the processing quality of glass wafers and reducing production costs.

1. Laser Drilling: Direct Forming for Efficient Perforation/Grooving of Glass Wafers

Laser drilling is the most direct physical forming process in glass wafer processing. Its core role is to directly remove glass materials through high-energy laser beams, quickly form basic microstructures such as through-holes, blind holes and blind grooves on glass wafers, and complete forming without subsequent auxiliary processes. It is the core method to meet the "perforation" demand of glass wafers.
Its working principle is to use ultra-short pulse lasers (such as femtosecond and picosecond lasers) to focus on the target area of the glass wafer, and instantly vaporize and strip the material through thermal effect or "cold processing" (ultra-fast nonlinear optical effect of ultra-short pulse lasers), thereby forming the required hole or groove structure. Different types of lasers have a significant impact on processing results: nanosecond lasers tend to produce a large heat-affected zone (HAZ), which may cause melting of surrounding materials and microcracks; femtosecond lasers can achieve "cold ablation", significantly reducing thermal impact, reducing processing defects, and improving the surface roughness of holes .
In glass wafer processing, the core advantages of laser drilling are high efficiency, speed and simple process. It can quickly process hole structures with different apertures and aspect ratios, and is suitable for scenarios with moderate precision requirements and pursuit of processing efficiency, such as the initial forming of through-glass vias (TGV) and the processing of airtight holes in automotive camera substrates. Domestic enterprises such as Xiamen Yuntian Semiconductor have used laser drilling technology to achieve the processing of through-holes/blind holes with apertures larger than 20μm, and the hole forming rate can reach more than 290 TGV/s [1]. At the same time, laser drilling is a non-contact processing method, which can avoid stress damage to glass wafers caused by mechanical processing and adapt to the processing of glass wafers with different thicknesses (0.1~5mm) [2].
Its limitation is that traditional laser drilling is prone to defects such as burrs and recast layers. For scenarios with aspect ratio greater than 50:1 and aperture precision requirements at the nanometer level, laser drilling alone is difficult to meet the demand and needs to be trimmed with subsequent etching processes.

2. Laser Induction: Modified Preprocessing for "Directional Navigation" of Precision Processing

Different from the "direct removal" of laser drilling, the core role of laser induction process is to selectively modify local areas of glass wafers without directly removing materials, only changing the physical or chemical properties of the target area (such as lattice structure changes), providing "target sites" for subsequent etching processes. It is an efficient preprocessing auxiliary technology, often combined with etching processes to form LIDE technology .
Its working principle is to adopt laser direct writing method. According to the material absorption rate of glass wafers, a laser with appropriate parameters (such as femtosecond laser) is selected to irradiate the target area, causing modification of the area. The corrosion rate of the modified area is much higher than that of the unmodified area, thus realizing precise positioning of subsequent etching processes without photolithography or mask assistance, greatly simplifying the processing flow. The core value of this process lies in "precision control", which can realize nanometer-level precision modification area planning and solve the pain point of "unable to accurately delineate processing scope" in traditional processing .
In glass wafer processing, the core application scenarios of laser induction include the preprocessing of high-precision microstructures, such as the graphical positioning of microchannels and MEMS devices, and the positioning of holes in TGV technology. Germany's LPKF company has adopted picosecond pulse laser-induced denaturation combined with HF etching to achieve low-cost and high-quality deep hole graphical processing ; domestic enterprises have also used this technology to fabricate TGV structures with diameter of 80μm and spacing of 150~200μm on 400μm thick alkali-free glass wafers, providing support for vertical interconnection of 3D stacked chips .
The significant advantages of laser induction are extremely small heat-affected zone, high positioning accuracy, ability to realize precise planning of complex graphics, and no physical material removal, which will not cause damage to glass wafers. It is an indispensable preprocessing step in high-end glass wafer processing. Its limitation is that it cannot complete microstructural forming alone and must be used in conjunction with etching processes to achieve selective material removal.

3. Etching Process: Precision Finishing for High-Precision Forming of Glass Wafer Microstructures

The etching process is the "precision finishing" link in glass wafer processing. Its core role is to selectively remove glass materials in target areas (mostly laser-induced modified areas) through chemical or physical effects, trim the structures after laser drilling or laser induction, improve processing accuracy and surface smoothness, and is the key step to achieve high-precision microstructural forming.
Etching processes are mainly divided into two categories: wet etching (such as HF aqueous solution) and dry etching (such as plasma etching). Wet etching dissolves glass materials in the target area through chemical reactions, with simple process and low cost, suitable for large-area processing; dry etching removes materials through the combination of plasma physical bombardment and chemical effects, with higher processing accuracy, suitable for scenarios with extremely high precision requirements . Both processes rely on pre-positioning (such as laser-induced modified areas) to achieve selective removal, which is more efficient and lower cost than the traditional photolithography combined with chemical etching method.
In glass wafer processing, the core role of the etching process is reflected in two aspects: first, trimming the burrs, microcracks and recast layers generated by laser drilling, improving the surface smoothness of holes or grooves to meet the assembly needs of high-end devices; second, performing selective etching in laser-induced modified areas to achieve high-verticality and high-aspect-ratio microstructural forming, which can obtain microholes with aspect ratio greater than 50, far exceeding the processing capacity of laser drilling alone [1]. For example, in TGV technology, the hole area is first positioned by laser induction, then the hole is expanded to the required size by wet etching, and finally a through-hole structure with precise and controllable aperture and smooth surface is realized [2].
In addition, the etching process can also be used for graphical etching on the surface of glass wafers. For example, on the photosensitive glass substrate, high-precision microfluidic structures are processed through laser induction combined with etching processes, which are widely used in biomedicine, microfluidic chips and other fields. Its limitation is that it cannot achieve precise positioning when used alone, must rely on preprocessing steps such as laser induction or photolithography, and wet etching has a certain impact on the environment, requiring corresponding environmental protection treatment equipment.

 

4. Summary of Core Differences and Collaborative Application of the Three Processes

To help industry practitioners quickly distinguish the boundaries of their roles and select models accurately, the core differences of the three are summarized from four dimensions: core role, processing essence, core advantages and application scenarios:
1. Differences in core roles: Laser drilling is "direct forming" to solve the "existence" problem; laser induction is "modified preprocessing" to solve the "positioning" problem; etching process is "precision finishing" to solve the "precision" problem.
2. Differences in processing essence: Laser drilling is physical material removal, laser induction is material modification (no removal), and etching process is selective material removal (relying on pre-positioning).
3. Differences in core advantages: Laser drilling is efficient and fast, laser induction is precise and controllable, and etching process is precise and smooth.
4. Differences in application scenarios: Laser drilling is suitable for medium and low precision, high efficiency perforation needs; laser induction + etching process is suitable for high precision, high aspect ratio microstructural processing, such as TGV, microchannels, MEMS devices, etc.
In actual production, the three processes are not isolated, but often applied in the combined form of "laser induction → etching" and "laser drilling → etching" to balance efficiency and precision. For example, in the processing of glass wafers for Mini/MicroLED packaging, the through-hole area is first positioned by laser induction, then the hole is trimmed by etching process, and finally a high-precision TGV structure is realized to meet the vertical interconnection needs of 3D stacked chips ; in the processing of microfluidic chips, the microchannel path is planned by laser induction, then formed by etching process to improve the smoothness and tightness of the microchannel .
With the rapid development of semiconductor packaging, AR/VR, MEMS and other fields, the requirements for processing precision and efficiency of glass wafers are constantly improving. Clarifying the differences in the roles of laser drilling, laser induction and etching processes and using them reasonably can reduce processing costs and improve product qualification rates. In the future, with the iteration of laser technology (such as intelligent algorithm optimizing laser path) and the environmental upgrading of etching processes, the collaborative application of the three will be more extensive, providing core support for technological breakthroughs in the high-end manufacturing field.