Doug Bettinger
Executive Vice President and Chief Financial Officer at Lam Research
Great. Thank you, Tim. Good afternoon, everyone, and thank you for joining our call today. Our March 2023 quarter financial results came in at or over the midpoint of our guidance ranges for all financial metrics. We generated over $1.6 billion of free-cash flow during the quarter which was a record level for the company. Overall, we not only delivered financial performance in-line with our guidance for the quarter, but we also made great progress on our business transformation and cost-saving initiatives.
Let me now move to our revenue and profitability results. Revenue for the March quarter was $3.87 billion, down 27% from the prior quarter. Systems revenue was the main driver of the decrease given the decline in WFE investments, most notably in-memory. As expected, with the improvement in supply-chain constraints, we are exiting the March quarter having completed shipments for nearly all of our outstanding back-order systems. Back orders are now at what I would characterize as normalized levels.
However, our deferred revenue balance is higher than historic levels remaining flat with the prior quarter with a balance of $2 billion. This deferred revenue balance reflects the impact of increased customer cash-in advanced deposits tied to orders from newer customers which is offset by the decline related to the completed back orders. The advanced payments will remain in deferred revenue until we shipped related tools. And I would just mention that we do expect the majority of these deposits to convert to revenue during calendar year 2023.
Looking at the revenue segment details for the March quarter. The percentage of systems revenue in memory was 32%, which is a decline from the prior quarter level of 50%. I would mention, this is the lowest level of memory concentration for us in a decade. Within memory, the NAND segment represented 23% of our systems revenue, down from the December quarter level of 39%. And DRAM decreased sequentially coming in at only 9% of systems revenue compared with 11% in the December quarter.
With the current weakness in-memory investments, we anticipate a further decline in both NAND and the DRAM revenue in the June quarter. In foundry conversely, we had a record dollar level of revenue in the March quarter, representing 46% of our systems revenue higher than the percentage contribution in the December quarter, which was 31%. We had positive momentum in both leading and mature node devices. And I'm pleased with the progress we've made in this segment of the market. We are seeing particular concentration in the mature node investments this year. The logic and other segment had continued strength with a contribution of 22% of systems revenue in the March quarter compared with 19% in the prior quarter. Investments were from a broad array of logic IBM's in multiple regions.
Let me now shift and discuss the regional contribution of our total revenue. Korea and China were at the top of the list with each coming in at 22% of the total. The Korea region had a slightly higher concentration in the March quarter, up from 20% in the December quarter. China was down from 24% in the prior quarter and the reduction was largely attributed to the U.S. government sales restrictions for certain Chinese domestic customers, which were put in-place in early October of 2022. Notably in the United States, we had a record revenue from a dollar perspective in the March quarter, which represented 16% of our total revenues, an increase from the prior quarter level of 10%. And finally, Taiwan decreased to a concentration of 18% as compared with 19% and the December quarter.
Our Customer Support Business Group generated revenue in the March quarter totaling approximately $1.6 billion which was a decrease of 7% from the December quarter, but 14% higher than the March quarter in calendar 2022. CSBG continues to be resilient part of our business model, representing over 40% of our March quarter revenue. We saw utilization leveled -- utilization levels decline at the memory customers, which negatively impacted both spares and service businesses, but reliant systems and upgrade revenues increased in the March quarter given the demand strength we're seeing in mature node devices. The specialty technology market is performing better than overall WFE and I expect this part of the business to continue to perform well during calendar year 2023.
Let me now pivot to our gross margin performance. The March quarter came in at 44%, right at the midpoint of our guided range and down from 45.1% in December quarter. The quarter-on-quarter decrease was tied to the lower business volumes, as well as customer and product mix. The company is focused on improvements in cost and efficiency to enhance profitability which is aligned with our plan to expand gross margin by at least one percentage point exiting calendar year 2023. Operating expenses were $608 million in the March quarter, down 11% from prior quarter amount of $686 million. We executed on cost-savings actions and as managed spending across the company, while prioritizing investments in support of our customers' roadmaps. R&D expenses comprised nearly 70% of our operating expenses, which is a high point for the company.
The March quarter operating margin was 28.3% and above the midpoint of guidance, mainly because of the cost-saving actions and expect expense management that we undertook. Our non-GAAP tax-rate for the quarter was 13.1% in-line with our expectations. Looking into calendar 2023, we believe the tax-rate will be in the low-to mid-teens with fluctuations expected quarter-to-quarter. Other income and expense came in for the quarter at $8 million in expense, lower by approximately $30 million from the prior quarter. The decrease in expense reflects increased interest income due to the higher cash balances as well as rising interest rates. [Indecipherable] will continue to be subject to-market related fluctuations that will cause some level of volatility each quarter.
On the capital return side of things in the March quarter, we allocated approximately $483 million to open-market share repurchases. Additionally, we paid $234 million in dividends in the quarter. We continue to track towards our long-term capital return plans of returning 75% to a 100% of our free-cash flow. First-quarter diluted earnings per share was $6.99 at the higher-end of our guided range. Diluted share count was down to 135 million shares, on-track with our expectations and obviously lower a little bit than the December quarter. From the balance sheet, cash and short-term investments including restricted cash at the end-of-the March quarter totaled $5.6 billion, up from $4.8 billion at the end-of-the December 2022 quarter. The increase was largely due to collections, offset by cash allocated to share buyback, dividends and capital expenditures.
Days sales outstanding were 77 days in the March quarter, an increase from 70 days in the December quarter. Inventory turns declined from the prior quarter to 1.9 times and we ended the March quarter, with a slightly higher inventory dollar ballast [Phonetic]. We will continue to manage inventory balances during the calendar year. Non-cash expenses for the March quarter included approximately $74 million in equity compensation, some $8 million in depreciation and $14 million for amortization. Capital expenditures for March quarter were $119 million, down from the December quarter level by approximately $44 million. March quarter investments were mainly for our Malaysia factory, the Korea technology center and other product development activities.
As we discussed in the January earnings call, we had a workforce reduction within the March quarter of approximately 1,400 people. Additionally, we reduced 700 temporary workers. We incurred a charge for the workforce actions in the March quarter of approximately $99 million, primarily reflecting severance-related payments. This chart was somewhat higher than our original estimate due to more impacted, people with the somewhat higher seniority level. We also incurred other onetime charges in the quarter for product rationalization decisions as we prioritize technology investments within the company and for transformation costs related to projects to improve our systems and operations. We anticipate will incur one-time costs in the range of $250 million within calendar year 2023 which is inclusive of the $144 million that we expensed in the March quarter. We ended the March quarter, with approximately 18,700 regular full-time employees which is a slight decrease in prior quarter. Due to the timing of our quarter-end. And our restructuring actions, a significant amount of the headcount reduction we undertook won't be reflected in the head count number until the June quarter.
Now let's turn to the non-GAAP guidance for the June 2023 quarter. We are expecting revenue of $3.1 billion, plus or minus $300 million. The sequential decline reflects a soft memory environment, and the normalization of back-order systems that occurred in the March quarter. Gross margin of 44%, plus or minus one percentage point, operating margins of 25.5% plus or minus one percentage point and finally earnings per share of $5, plus or minus $0.75 based on a share count of approximately 134 million shares.
So then, let me summarize. 2023 is proving to be a challenging environment for our memory shipments, but I'm pleased with the progress we're accomplishing against this challenging backdrop. We continue to make progress on growing our technology leadership and focusing on our operational efficiencies. We will emerge from this number led downturn as stronger, better-positioned, more efficient company.
In closing I will just mention one more thing, that as we look at the profile of WFE -- WFE spending this year, it now appears to be a little bit second half weighted. Operator, that concludes our prepared remarks, Tim and I would now like to open up the call for questions.