Samsung's 1c DRAM yields leap: 0% to 40% giving the greenlight for HBM4 mass production

Samsung's new 1c DRAM yields have reportedly increased from 0% to 40% recently according to new reports, with its new 1c DRAM a crucial part in the company's next-gen HBM4 memory, which gives the green light for the company to kick off HBM4 mass production later this year.

In a new report from Chosun picked up on X by insider @Jukanlosreve, where Chosun reports that a source familiar with Samsung Electronics said it had "recently improved" its 1c DRAM wafer yield for HBM4 to "about" 40% based on cold tests, and somewhere in between 40% and 50% based on hot tests.

Chosun's source said: "considering that the cold test yield of 1c DRAM was close to 0% just a year ago, the recent yield is an encouraging result". 10nm-class DRAM process technology is developed in a little bit of a confusing order, so we'll recap: 1x (1st generation), 1y (2nd generation), 1z (3rd generation), 1a (4th generation), 1b (5th generation), and the new 1c is the latest 6th generation DRAM from Samsung.

As for the "cold testing", that is a reliability test that operates the chip in extremely low temperatures to check the electrical characteristics and stability of the circuit, where Samsung will check for timing errors and other malfunctions that would happen in low-temperature environments, as well as circuit design and process consistency that have a negative impact on yields.

Samsung Electronics improved the current flow and heat dissipation characteristics by tweaking the design to adjust for circuit density and thermal design, and as a result of these changes, the company was able to secure both process consistency and product stability of its new 1c DRAM. Before the design changes, most of the 1c DRAM were defined as defective in the cold test, even though particular yields were secured in the hot testing.

The big changes were an idea from Samsung's freshly-minted Vice Chairman, Jeon Young-hyun, the head of the DS (Device Solutions) division, who personally ordered a design restructuring of its 1c DRAM. Since his return, Samsung had moved to a new strategy that prioritizes yield and product stability over process efficiency, believing that the company could find a balance in its fine process technology.

Samsung also performed some process optimization work, precisely supplementing the HBM4 alignment process, as well as improving heat distribution uniformity during the testing process of its new 1c DRAM. This is because micro-alignment errors and heat concentration are the first couple of issues that were increasing defect rates, which is due to the multi-layer structure of HBM.

All things are pointing to Samsung getting its new HBM4 memory into mass production later this year, which is a great sign after the company had tripped over itself and handed most of the HBM3 and HBM3E market dominance to South Korean memory competitor SK hynix.

Chosun adds that an insider familiar with Samsung Electronics said: "our internal goal is to increase the 1c DRAM yield to 60% in cold tests and 70-80% in hot tests within the year to enable actual mass production of HBM4".