North American makers of microchip-making equipment saw both orders and shipments rise in December, indicating a slight improvement in the battered sector, the industry trade group said on Tuesday. 

New orders rose about 7 percent to $652.4 million in December, from $609.3 million in November, according to Semiconductor Equipment and Materials International. Shipments rose to $834.9 million from $829.5 million in November, an increase of less than one percent. 

A closely watched ratio of orders to shipments, known as the book-to-bill ratio, was 0.78 in December, an improvement from a ratio of 0.73 in November. The ratio indicates that $78 of new orders were received for every $100 of products shipped in December. 

Stanley Myers, president and chief executive of the trade group, said there were signs that chip factories were busier and increasing output, especially in the assembly and testing areas. But he also warned that chip equipment companies remained cautious. 

``Chip and equipment companies, however, remain cautious about the near-term outlook because of uncertainty with the overall economic recovery,'' Myers said in a statement.