LG Electronics is understood to have advanced through-glass via (TGV) processing technology, seen as the biggest hurdle to commercializing glass substrates for semiconductors. The company is said to be discussing how to apply the technology with LG Innotek, which has picked glass substrates as a next-generation business and is pushing for commercialization. With LG Electronics having built equipment technology close to commercialization, industry watchers say LG Innotek, considered a latecomer, could significantly narrow the gap with rivals.
Glass substrates are considered a next-generation packaging material that can overcome warpage and the limits of power delivery and fine circuit formation found in conventional plastic (organic) semiconductor substrates. As AI semiconductors grow larger, they are expected to solve problems arising from substrates, leading the industry to call them a "game changer."
On the 13th, the industry said LG Electronics' Production Engineering Research Institute (PRI) recently developed the AVEX-P500, a TGV laser system for glass substrates. Using this process, it also publicly unveiled physical samples in which TGVs were formed in the glass core (the glass layer in the middle of the glass substrate that supports its shape). It processed 5.45 million holes on a single substrate and implemented a process that inspects defects before etching and selectively corrects them.
◇ Processing and correcting 5.45 million holes… process technology with mass production in mind
Using its in-house TGV laser system, LG Electronics' Production Engineering Research Institute achieved holes with an aspect ratio of 1:10 in a 0.5-mm-thick glass sample (BF33). In 1.1-mm glass, it drilled microholes with an aspect ratio of 1:20. The aspect ratio is the depth of the hole divided by its diameter; in TGV, the glass thickness corresponds to the hole depth. The higher the figure, the narrower and deeper the hole made in thicker glass. Circularity, which indicates how close the hole shape is to a circle, was presented at 97%, and the upper-to-lower diameter ratio was 98%–99%. Positional accuracy is ±3 μm, and sidewall roughness is about 0.5 μm.
A small difference between the upper and lower diameters means it suppressed internal narrowing or tilting to one side. This is necessary in subsequent processes to fill with copper without gaps and to secure consistent electrical characteristics in each TGV.
Using the TGV process developed by LG Electronics, 5.45 million holes can be processed on a single substrate in about 90 minutes, depending on design conditions. It takes about 15 minutes to inspect the entire panel before etching and to selectively reprocess areas where the laser modification state is poor.
The industry notes that LG Electronics presented productivity capable of handling millions of holes at the actual panel level along with inspection and correction systems. In mass-producing glass substrates, yield (good-product ratio) is determined more by how uniformly the diameter, position, and shape are maintained across the entire panel than by the minimum hole size.
A semiconductor industry official said, "LG Electronics presented a commercialization-level TGV technology applicable to glass substrates through conditions including hole shape, position, processing time, and pre-etch inspection," adding, "Additional verification is needed for total process time and securing Production yield in real mass production environments, but it is a significant technological advance."
◇ Changing glass properties with a laser, then etching… reducing microcracks
TGV is a technology that connects circuits on the top and bottom of glass, which does not conduct electricity. It creates hundreds of thousands to millions of microholes inside the glass and fills them with conductive materials such as copper to form vertical electrical pathways.
Glass is regarded as a material that is hard and has a flat surface, allowing the substrate size to be scaled up stably. On the other hand, due to its brittleness, which makes it prone to breaking on impact, cracks or fractures can occur during microhole processing. That is why TGV is considered the key challenge to commercializing glass substrates.
In particular, to use it as a substrate for AI semiconductors, hole positions must precisely align with surface circuits. If the center of a hole narrows or the wall is rough, voids can form during the copper-filling process, leading to electrical defects, so high processing precision is required.
To solve these problems, LG Electronics applied a method of first changing the internal properties of the area where holes will be formed with a laser and then etching, instead of directly ablating the glass with a laser. It also placed inspection and correction before etching. The overall sequence is "laser modification → inspection → correction → etching → copper fill → circuit formation." Modification is a technique that selectively changes internal material properties so the targeted area can be easily removed in subsequent processes.
Directly removing glass with a laser can concentrate heat in the processed area, causing microcracks or debris. Combining modification with etching reduces thermal effects compared with direct drilling and is advantageous for making relatively straight holes in thick glass.
◇ Samsung Electro-Mechanics forms a joint venture, SKC enters customer evaluations… will TGV technology be LG Innotek's "comeback card"?
LG Innotek is seen as being behind Intel, SKC, and Samsung Electro-Mechanics in the race to commercialize glass substrates. LG Innotek began development for glass substrate commercialization in 2024 and built a pilot production line at its Gumi plant last year. The target for commercialization is 2027–2028.
Intel, by contrast, has researched related technologies for more than a decade. In 2023, it unveiled glass substrate technology for advanced packaging and is building a related supply chain with materials, equipment, and chemical companies. SKC, through its subsidiary Absolix, has established a production base in Georgia in the United States. It is currently supplying prototypes to customers for reliability evaluations. Samsung Electro-Mechanics is also producing glass substrate prototypes on a pilot line at its Sejong plant. On the 2nd, it decided to establish a joint venture to produce the core material, the glass core, with Dongwoo Fine-Chem, a subsidiary of Japan's Sumitomo Chemical.
The market view is that if LG Innotek solves the TGV challenge in collaboration with LG Electronics, it could significantly narrow the technology gap with competitors. LG Electronics is said to be discussing applications of semiconductor back-end equipment, including TGV, with LG Innotek.
An industry official said, "It appears to be a strategy to speed up development by consolidating LG Innotek's substrate technology with LG Electronics' laser and inspection equipment," adding, "As LG Electronics has secured TGV equipment technology close to commercialization, LG Innotek's process adoption could also accelerate." The official added, "LG Innotek is also collaborating with UTI, a precision glass-processing company, and the structure now adds LG Electronics' equipment and process technologies on top."
Beyond TGV, LG Electronics is developing laser direct imaging (LDI) equipment to form fine circuits on the surface of glass substrates. LDI creates circuit patterns by irradiating the substrate directly with a laser based on design data without using a photomask. It is also developing: ▲ laser drilling to create microholes in glass and printed circuit boards (PCBs) ▲ laser dicing to cut glass cores into individual substrates ▲ TGV automated optical inspection and ultrasonic internal defect inspection equipment.
Market research firm Counterpoint Research forecast that the combined market for fan-out panel-level packaging (FO-PLP) and glass substrates will grow from $650 million (about 980 billion won) in 2024 to more than $8.1 billion (about 12.215 trillion won) in 2030.