Mask blank for charged particle beam exposure, method of forming mask blank and mask for charged particle beam exposure

#The present invention relates to a method of forming a mask blank and a mask used for the lithography for manufacturing semiconductor devices and, more particularly, to a structure of a mask blank for fabricating a mask which transcribes a mask pattern onto a wafer using charged particle beams such as electron beams and ion beams and a method for forming a mask blank and a mask used for the charged particle beam exposure.

#With miniaturization and increase in integration of semiconductor elements in semiconductor integrated circuits, an electron-beam projection lithography for transcribing a predetermined configuration onto a wafer using charged particle beams, especially using electron beams, was developed instead of the conventional photolithography using light. Recently, the development of EPL (Electron-beam Projection Lithography) method achieving higher throughput has advanced. As an electron-beam projection lithography, there is a method in which a prescribed mask pattern is divided into a plurality of sections, stencil masks formed with opening patterns each having a predetermined size and a predetermined arrangement are prepared, and electron beams are incident on the sections so that electron beams thus formed by the opening patterns are transcribed onto a wafer as a subject substrate on some reduced scale. There has been developed a system for forming a device pattern by combining prescribed patterns separately formed on the mask onto the subject substrate (for example, see Patent Document 1).

#The stencil mask used for the aforementioned electron-beam projection lithography comprises a silicon membrane defining through-holes for transmitting electron beams in which a pattern region is divided and reinforced by a supporting grillage, referred to as “strut”, from the back, thereby reducing the distortion of the pattern region and improving the accuracy of position of the pattern region. The typical method of forming a stencil mask will be described with reference to FIGS. 5(a)-5(e).

#FIG. 1 is a partial sectional view showing an embodiment of a mask blank used for the electron-beam exposure according to the present invention;

#FIG. 2 is a partial sectional view showing another embodiment of a mask blank used for the electron-beam exposure according to the present invention;

#FIGS. 3(a)-3(e) are process charts showing a method of forming a mask blank and a mask used for the electron-beam exposure according to the embodiment of the present invention;

#Hereinafter, embodiments of the present invention will be described, taking electron-beam exposure which is most likely expected to be in practical use among charged particle beam exposure technologies for example. Description will now be made as regard to a mask blank used for the electron-beam exposure and its forming method, and a method of forming a mask used for the electron-beam exposure with reference to the attached drawings.

#(Mask Blank Used for the Charged Particle Beam Exposure)

#FIG. 1 is a partial vertical sectional view schematically showing an embodiment of a mask blank used for the electron beam exposure according to the present invention which is used for a stencil mask used for an electron-beam projection lithography. In FIG. 1, a mask blank 1 used for the electron-beam exposure has a structure comprising struts (supporting silicon layer) 4 made of silicon, a silicon membrane 2 which is bonded to the supporting silicon layer 4 with a silicon oxide film 3 interposed therebetween and in which a pattern is formed, a hard mask layer 5 formed on the silicon membrane 2, an opening 6 to be an exposed region which is formed by partially removing the back-side silicon of an SOI substrate and the silicon oxide film 3, and an etching stop layer 7 having lower stress which is formed in the opening.