Abstract:
Methods for producing beam shaping diaphragms for lithographic devices in which a silicon layer is epitaxially deposited on a semiconductor body and the epitaxial layer is formed in the central region as a self-supporting membrane and is formed with preferably straight line-shaped quadratic recesses which have perpendicular limiting surfaces. Photolithographic processes and galvanic second-casting techniques may be used in the process for producing the beam-shaping diaphragm. The beam-shaping diaphragm can also be produced in lightly doped epitaxial layers by using electro-chemical etching methods.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates in general to methods for producing beam-shaping diaphragms for lithographic devices. 
     2. Description of the Related Art 
     U.S. Pat. No. 4,724,328 discloses a lithographic device such as an electron beam writer which has an electron-beam optical column that includes an aperture diaphragm for producing a plurality of individually deflectable electron beam probes. This aperture diaphragm is disclosed in greater detail in European patent 0,191,439 Al which shows a silicon membrane provided with a line-shaped multi-hole structure which has formed on its surface an electrode structure which acts as a deflection unit. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide methods for producing beam-shaping diaphragms for lithographic devices in which the diaphragm receives a primary particle beam and comprises a semiconductor membrane having recesses for generating a plurality of particle beam probes. 
     It is an object of the invention to provide an improved method to form a beam-shaping diaphragm. 
     The advantage which can be obtained with the invention is that the recesses which define the beam cross-section of the particle probes can be produced with high precision. 
     Other objects, features and advantages of the invention will be readily apparent from the following description of certain preferred embodiments thereof taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating the beam-shaping diaphragm which is to be produced; 
     FIGS. 2a-2i illustrate a first method for forming the diaphragm of the invention; 
     FIGS. 3a-l illustrate a modification of the method of the invention; and 
     FIGS. 4a-4i illustrate a further modification of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates a beam-shaping diaphragm for an electron or ion beam writer which is formed from a semiconductor member 1 which has a silicon layer 2 formed on its upper surface by epitaxial deposition. The epitaxial layer 2 has a center portion which extends over an opening 17 formed in the semiconductor member 1 and a plurality of line-shaped quadratic recesses 14 having perpendicular side walls that form limiting surfaces. When the membrane 2 is charged with a primary particle beam 15, then a plurality of particle beam probes 16 which have beam cross-section which are determined by the geometry of the recesses 14 are obtained on the side opposite the particle source. The particle beam probe 16 can be subsequently deflected or blanked individually using a known aperture diaphragm and can be imaged onto a workpiece which is to be formed using a particle-optical unit. 
     The present invention relates to the methods for forming the beam-shaping diaphragm. 
     As shown in FIGS. 2a-2i: an epitaxial semiconductor layer 2 of, for example, silicon is deposited on a semiconductor substrate 1 which has a first conductivity type and, for example, may be a p-doped silicon having (1, 0, 0) or (1, 1, 0) orientation as illustrated in FIGS. 2a and 2b. 
     The epitaxial layer 2 is doped with boron so as to protect the epitaxial layer during later etching processes and germanium so as to reduce the mechanical stresses and the boron concentration should exceed 1×10 20  boron atoms/cm 3  and the doping is preferably accomplished during the epitaxial deposition. 
     The front wafer side of the epitaxial layer 2 and the back side of the semiconductor substrate 1 are coated with a dielectric 3 and 4 which may be, for example, silicon nitride or silicon oxide as shown in FIG. 2c. 
     Photoresist 5 and 6 are added to the layers 3 and 4 as shown in FIG. 2d and lithographic transfer of the geometry and arrangement of the recesses 14 and the through opening 17 which is to be produced in the semiconductor substrate 1 is made on the photoresist layers 5 and 6 by exposure of onto the front wafer side and the back wafer side as shown in FIG. 2d. 
     The dielectric layers 2 and 4 are reactive dry etched so as to form the openings in the layers 3 and 4 as shown in FIG. 2e. The epitaxial layer 2 is reactively dry etched as, for example, with reactive ion beam etching so as to puncture the epitaxial layer as shown in FIG. 2f. The semiconductor substrate 1 is wet chemical anistropically etched as shown in FIG. 2g. 
     The dielectric layers 3 and 4 are removed as shown in FIG. 2h. 
     The epitaxial layer 2 and the semiconductor substrate 1 are coated with metal 7 as, for example, gold as shown in FIG. 2; 
     The beam-shaping diaphragm schematically illustrated in FIG. 1 can also be produced in lightly doped epitaxial layers or diffusion layers using electro-chemical etching methods. The manufacturing process for such construction comprises the following method steps which are illustrated in FIGS. 3a-3l. A semiconductor substrate 1 is illustrated in FIG. 3a and as shown in FIG. 3b, an n-doped silicon layer 2 is epitaxially deposited on the semiconductor substrate 1, which may be, for example, p-doped silicon having (1, 0, 0) or (1, 1, 0) orientation. 
     the front wafer side of the epitaxial layer 2 and the back wafer side of the semiconductor substrate 1 are coated with a dielectric 3 and 4 of, for example, silicon nitride or silicon oxide as illustrated in FIG. 3c. 
     Photoresist layer 5 is formed on the dielectric layer 3 and the geometry and arrangement of the recesses 14 are lithographically transferred onto the photoresist layer which is whirled onto the dielectric 3 as shown in FIG. 3d. 
     The dielectric layer 3 is reactively dry etched as shown in FIG. 3 e. The epitaxial layer 2 is anisotropically dry etched as shown in FIG. 3f. 
     The photoresist layer 5 is removed and passivation layer 9 is deposited within the etching trenches or the oxidation surfaces exposed by the etching process as shown in FIG. 3g. 
     A contact window 10 is lithographically produced in the dielectric layer 3 as shown in FIG. 3h. 
     The geometry of the substrate is transferred with a lithographic process to form through opening 17 onto a photoresist layer which is whirled onto the dielectric layer 4 so as to form layer 4 as shown in FIG. 3h. 
     The front wafer side is metallized with, for example, an adhesion layer of chromium or titanium and a gold layer 11 as shown in FIG. 3i. 
     The metal layer 11 is cut with a lithographic process so as to produce an electrical contact 12 as shown in FIG. 3j. 
     The semiconductor substrate 1 is anisotropic etched, for example, with KOH using an electro-chemical etching stop so that the epitaxial layer 2 over the contact 12 is connected to the positive pole of a voltage source as shown in FIG. 3k. 
     The contact 12 is removed and the dielectric layers 3, 4 and 9 are removed. The substrate 1 and the epitaxial layer 2 are coated with a metal 7 as, for example, gold as shown in FIG. 3l. 
     FIG. 4 illustrates a further embodiment of the invention which discloses a method using lithographic methods and galvanic second-casting. 
     A semiconductor substrate is shown in FIG. 4a. 
     On both sides of a semiconductor substrate which comprises, for example, silicon with (1, 0, 0) or (1, 1, 0) orientation are coated with dielectric layers 3 and 4 of, for example, silicon oxide or silicon nitride as illustrated in FIG. 4b. 
     A starter layer 8, for example, of chrome/gold or titanium/gold is applied on the front side of the wafer as shown in FIG. 4c. 
     The geometry and arrangement of the recesses is lithographically transferred onto a photoresist layer 5 which is whirled onto the electro-plating starter layer 8 as shown in FIG. 4d. 
     A metallic layer 7 is electro-deposited which might be gold onto the top wafer side as shown in FIG. 4e. 
     The photoresist layer 5 is removed as shown in FIG. 4f. 
     The passivation layer 4 is lithographically formed according to the geometry of the through-opening 17 which is to be produced in the semiconductor substrate 1 as shown in FIG. 4g. 
     The semiconductor substrate 1 is anisotropically wet-chemically etched on the backside as illustrated in FIG. 4h to form the opening 17. 
     The passivation layer 3 and the electro-plating starter layer 8 are etched int eh region of the through substrate opening 17 as shown in FIG. 4e. 
     It is seen that this invention provides new and novel methods for forming a beam-shaping diaphragm for a lithographic device and although it has been described with respect to preferred embodiments, it is not to be so limited as changes and modifications may be made therein as defined by the appended claims.