By Fanny Potkin and Eduardo Baptista

SINGAPORE/BEIJING (Reuters) -Two Chinese chipmakers are in the early stages of producing high bandwidth memory (HBM) semiconductors used in artificial intelligence chipsets, according to sources and documents.

The progress in HBM - even if only in older versions of HBM - represents a major step forward in China's efforts to reduce its reliance on foreign suppliers amid tensions with Washington that have led to restrictions on U.S. exports of advanced chipsets to Chinese firms.

CXMT, China's top manufacturer of DRAM chips, has developed sample HBM chips in partnership with chip packaging and testing company Tongfu Microelectronics, according to three people briefed on the matter. The chips are being shown to clients, two of them said.

Tongfu Microelectronics' shares surged 8% in Wednesday trade.

In another example, Wuhan Xinxin is building a factory that will be able to produce 3,000 12-inch HBM wafers a month with construction slated to have begun in February this year, documents from corporate database Qichacha show.

CXMT and other Chinese chip firms have also been holding regular meetings with South Korean and Japanese semiconductor equipment firms to buy tools to develop HBM, said two of the people.

The sources were not authorised to speak on the matter and declined to be identified. Hefei-based CXMT or ChangXin Memory Technologies and Tongfu Microelectronics did not respond to requests for comment.

Wuhan Xinxin, which has flagged to regulators that it is interested in going public, and its parent company did not respond to requests for comment. The parent company is also the parent of NAND memory specialist YMTC or Yangtze Memory Technologies. YMTC said it did not have the capability to mass produce HBM.

Both CXMT and Wuhan Xinxin are private companies which have received local government funding to advance technologies as China pours capital into developing its chip sector.

Wuhan's local government also did not respond to requests for comment.

Separately, Chinese tech behemoth Huawei - which the U.S. has deemed a national security threat and is subject to sanctions - is aiming to produce HBM2 chips in partnership with other domestic companies by 2026, according to one of the sources and a separate person with knowledge of the matter.

The Information reported in April that a Huawei-led group of companies aiming to make HBM includes Fujian Jinhua Integrated Circuit, a memory chip maker also under U.S. sanctions.

Huawei, which has seen demand soar for its Ascend AI chips, declined to comment. It is not clear where Huawei procures HBM. Fujian Jinhua did not respond to a request for comment.

LONG JOURNEY AHEAD

HBM - a type of DRAM standard first produced in 2013 in which chips are vertically stacked to save space and reduce power consumption - is ideal for processing massive amounts of data produced by complex AI applications and demand has soared amid the AI boom.

The market for HBM is dominated by South Korea's SK Hynix - until recently the sole HBM supplier to AI chip giant Nvidia according to analysts - as well as Samsung, and to a lesser extent U.S. firm Micron Technology. All three manufacture the latest standard - HBM3 chips - and are working to bring fifth-generation HBM or HMB3E to customers this year.

China's efforts are currently focused on HBM2, according to two of the sources and a separate person with direct knowledge of the matter.

The U.S. has not put restrictions on exports of HBM chips per se but HBM3 chips are made using American technology that many Chinese firms including Huawei are barred from accessing as part of the curbs.

Nori Chiou, an investment director at White Oak Capital and a former analyst who looked at the IT sector, estimates that Chinese chipmakers lag their global rivals by a decade in HBM.

"China faces a considerable journey ahead, as it currently lacks the competitive edge to rival its Korean counterparts even in the realm of traditional memory markets," he said.

"Nonetheless, (CXMT's) collaboration with Tongfu represents a significant opportunity for China to advance its capabilities in both memory and advanced packaging technologies within the HBM market."

Patents filed by CXMT, Tongfu and Huawei indicate that plans to develop HBM domestically date back at least three years when China's chip industry increasingly became the target of U.S. export controls.

CXMT has filed almost 130 patents in the United States, China, and Taiwan for different technical issues related to the manufacturing and functionalities of HBM chips, according to Anaqua's AcclaimIP database. Of those, 14 were published in 2022, 46 in 2023, and 69 in 2024.

One Chinese patent, published last month, shows the company is looking at advanced packaging techniques like hybrid bonding to create a more powerful HBM product. A separate filing shows that CXMT is also investing in developing technology needed to create HBM3.

(Reporting by Fanny Potkin in Singapore and Eduardo Baptista in Beijing; Additional reporting by Heekyong Yang and Joyce Lee in Seoul; Editing by Brenda Goh and Edwina Gibbs)

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