In this article we describe electron beam writing methods to suppress image placement errors due to the thermal distortion and drift of x-ray masks. Parts of device patterns are written outside of the writing area of a mask before the device pattern writing step to stabilize the temperature of the mask (preparatory writing method). The seesaw writing method, which divides a pattern into many slit parts that are written reciprocally, is used to compensate for the nonuniformity of the heating rate of the mask according to the mask's position on the stage. The absorber fiducial mark is formed on the mask instead of the cassette or the stage to prevent the drift of the mask, and furthermore, to reduce mask-to-mask overlay errors. The writing is performed by referring to the absorber coordination marks on the mask after the registrations of the marks are measured with an image placement (IP) measurement system (mark-on-the-mask method). The effectiveness of these methods is evaluated through the fabrication of a full-chip mask of a 64 Mbit dynamic random access memory, and an IP accuracy close to 20 nm is obtained.