SAN FRANCISCO -- If Micron ( MU) knows any arm-twisting bill collectors, now might be a good time to call them. The chipmaker's tally of money that it's owed swelled more than 18% in the most recent quarter, leaving Micron carrying roughly $1 billion in accounts receivable. True, it's not unprecedented for Micron to run up big receivables at this time of year: In two of the previous five years, Micron's accounts receivables in its fiscal fourth-quarter have experienced similar jumps. But with the DRAM memory market proving stubbornly depressed, the ballooning receivables may pack a more pernicious payload for Micron this time around. And with Micron's shares off 25% so far this year, and trading near their 52-week low, the unpaid bills represent another overhang that could weigh the stock down. Shares of Micron were up 1.8% at $10.80 in midday trading Friday. One potential reason for concern about Micron's receivables lies in Taiwan, where many of the so-called module makers -- companies that buy DRAM memory and assemble the chips onto circuit boards -- are currently under severe financial strain. A recent report by Digitimes, a Taiwanese trade publication, noted that certain second-tier and third-tier memory module makers in Taiwan are having trouble paying the bills, with checks bouncing and banks cutting off funding.