the present invention is now described in greater detail with reference to embodiments . fig1 is a conceptual cross - sectional diagram representing the configuration of a halftone phase shift mask blank in the first embodiment ; fig2 is a conceptual cross - sectional diagram representing the configuration of a halftone phase shift mask therein ; and fig3 and fig4 are conceptual cross - sectional diagrams for describing the method of manufacturing the halftone phase shift mask blank . the halftone phase shift mask blank in this embodiment is configured with a halftone material film 11 made of a mosin - based material , a first metal film 12 made of crn , and a second metal film 13 made of crc , laminated in order on a transparent substrate 10 made of quartz . to describe this in greater detail , the main surfaces and side surfaces of a quartz substrate were precision - polished to produce a transparent substrate 10 that was 6 inches by 6 inches , and 0 . 25 inch in thickness . then , using a molybdenum ( mo ) and silicon ( si ) mixed target ( mo : si = 20 : 80 mol %), an mosin halftone material film 11 having a film thickness of 925 angstroms was formed on the transparent substrate 10 by reactive sputtering , in an argon ( ar ) and nitrogen ( n 2 ) mixed gas atmosphere ( ar = 20 %, n 2 = 90 %, pressure = 1 . 5 × 10 - 3 torr ), as diagrammed in fig6 ( a ). for the transparent substrate 10 here , besides quartz , fluorspar and various kinds of glass ( such as soda - lime glass , alumino - silicate glass , and alumino - borosilicate glass ) are used . when the composition and optical characteristics of the halftone material film 12 obtained in this manner were measured , the following results were obtained . next , a first metal film 12 of crn having a film thickness of 150 angstroms was formed on the halftone material film 11 , using a chromium ( cr ) target , by reactive sputtering , in an argon ( ar ) and nitrogen ( n 2 ) mixed gas atmosphere ( ar = 80 %, n 2 = 20 %, pressure = 1 . 5 × 10 - 3 torr ), as diagrammed in fig3 ( b ). the nitrogen ( n ) content in the first metal film 12 obtained was 20 at %, and the etching rate thereof was measured at 2 . 2 nm / sec . next , a second metal film 13 of crc having a film thickness of 600 angstroms was formed on the first metal film 12 , using a chromium target , by reactive sputtering , in an argon ( ar ) and methane ( ch 4 ) mixed gas atmosphere ( ar = 88 %, ch 4 = 12 %, pressure = 1 . 5 × 10 - 3 torr ), as diagrammed in fig3 ( c ). this was subjected to ultrasonic cleaning to yield a halftone phase shift mask blank . when the carbon content of the second metal film 13 was measured it was found to be 6 at %. the etching rate was found to be 0 . 3 nm / sec , and , in terms of optical characteristics , the optical density at a wavelength of 450 nm was 3 . 0 . when scratch tests were conducted with a load of 600 g , no peeling occurred between the halftone material film 11 , first metal film 12 , and second metal film 13 , and good film strength was obtained . next , a resist film 14 was formed on the second metal film 13 , as diagrammed in fig3 ( d ), and a resist pattern 15 was formed , as diagrammed in fig4 ( a ), by means of pattern exposure and development . when performing such patterning , stable , high - precision patterning was implemented . however , when the sheet resistance of the second metal film 13 obtained was measured , it was found to be below 0 . 5 mω /□. consequently , good electrical conductivity was obtained , which is believed to be due to the fact that , when performing electron beam exposure , described earlier , no charge buildup occurred between the second metal film 13 and the resist film 14 . after the patterning described in the foregoing , an etching fluid was prepared by adding pure water to 165 g of cerium ammonium nitrite and 42 ml of 70 % chlorine peroxide to make up 1000 ml of liquid , maintained at 19 to 20 ° c . using this etching fluid , wet etching was performed , patterning the second metal film 13 and the first metal film 12 as diagrammed in fig4 ( b ). after performing such patterning , there was no residual metal ( cr ) transferred to the halftone material film 11 from the first metal film 12 or second metal film 13 , and no damage was observed in the halftone material film 11 . it is conjectured that these results are obtained because , firstly , it is possible to etch the first metal film 12 and second metal film 13 , and the halftone material film 11 with mutual selectivity , that is , because the etching characteristics differ between the first metal film 12 and second metal film 13 , on the one hand , and the halftone material film 11 , on the other , and because , secondly , while the etching rate for the first metal film 12 contacting the halftone material film 11 is of course faster than for the halftone material film 11 , it is also faster than a simple cr body , as will be described below . as diagrammed in fig5 moreover , the difference in the post - etching width dimensions x 2 and x 1 of the first metal film 12 and second metal film 13 , respectively , which is to say the undercut amount , was 0 . 02μ , which is extremely small , wherefore the overhang shape does not become pronounced enough for the tip to be broken , and perpendicular patterns are obtained . this is believed to be due to the fact that the difference in etching rate between the first metal film 12 and second metal film 13 is small , namely 1 . 9 nm / sec . next , using the patterns in the first and second metal films 12 and 13 as masks , dry etching was performed with a gas mixture of cf 4 and o 2 to remove the exposed portion of the halftone material film 11 and form the halftone material film pattern 11 , as diagrammed in fig4 ( c ). thus , the resist pattern 15 noted earlier was peeled away by sulfuric acid , and an etching fluid was prepared by adding pure water to 165 g of cerium ammonium nitrite and 42 ml of 70 % chlorine peroxide to make up 1000 ml of liquid , which was maintained at 19 to 20 ° c . using this etching fluid , wet etching was performed , the second metal film 13 and the first metal film 12 were removed , and a halftone phase shift mask was obtained which was provided with a halftone material film pattern 11 in the pattern desired , as diagrammed in fig4 ( d ). for purposes of comparison , a halftone phase shift mask blank and halftone phase shift mask were fabricated as in the first embodiment , excepting that a first metal film made of cr and having a film thickness of 300 angstroms and a second metal film made of crn and having a film thickness of 150 angstroms were formed on the halftone material film 11 of the first embodiment . here , the first metal film was fabricated by sputtering in an ar gas atmosphere at 1 . 5 × 10 - 3 torr , while the second metal film was fabricated by reactive sputtering in an ar and n 2 mixed gas atmosphere ( ar = 80 %, n 2 = 20 %) at 1 . 5 × 10 - 3 torr . in this comparative example 1 , damage occurred in the surface of the halftone material film , for which reason a difficulty developed in that the desired phase difference was not obtained . the explanation for this is thought to be that the etching rates for the cr film and crn film are 1 . 5 nm / sec and 2 . 2 nm / sec , respectively , whereupon , when performing the patterning , the etching rate for the first metal film made of cr and contacting the halftone material film is slower than that for the second metal film made of crn formed on the first metal film . when scratch tests were performed on the halftone phase shift mask blanks obtained , peeling occurred between the first metal film and second metal film , and bonding strength was inadequate , in 8 out of 100 test pieces . embodiments 2 to 7 and comparative examples 2 and 3 are now described . for the purpose of further comparison , when forming the first metal film 12 , the quantity of n 2 contained in the gas mixture of ar and n 2 was adjusted , varying the nitrogen content in the first metal film 12 between 5 at % ( second embodiment ), 10 at % ( third embodiment ), 30 at % ( fourth embodiment ), 40 at % ( fifth embodiment ), 50 at % ( sixth embodiment ), and 60 at % ( seventh embodiment ), while keeping the other conditions the same as in the embodiment described in the foregoing . thus each embodiment was fabricated so that the phase shift amount became 180 °. second and third comparative examples were also fabricated , having nitrogen contents of 3 at % and 65 at %, respectively . measurements were then made of etching rates ( in nm / sec ) for the first metal film , differences in etching rate ( in nm / sec ) between the first metal film 12 and second metal film 13 , undercut amount ( μ ), and phase shift (°), in these embodiments and comparative examples . the results are given in the table in fig6 . as is evident from this table , when the nitrogen content in the first metal film 12 is 5 to 10 at %, the undercut becomes less than 0 . 1 μ , wherefore black flaws resulting from chips in the tips of the metal film due to overhang are suppressed . in addition , a nearly perpendicular pattern is formed , and high - precision patterning is performed . the etching rate of the metal film 12 contacting the halftone material film 11 is sufficiently fast , moreover , so there will seldom be any damage done to the halftone material film 11 , and the amount of phase shift will be confined within a range of 180 °- 2 °, yielding highly reliable halftone phase shift masks . in both of the comparative examples 2 and 3 , however , wherein the nitrogen content in the first metal film 12 is outside the range noted , not only does an overhanging shape develop , so that black faults readily occur , but perpendicular patterning cannot be effected , and high - precision patterning cannot be achieved . a halftone phase shift mask blank and halftone phase shift mask were fabricated in the same way as in the first embodiment , except in that an anti - oxidization film made of cron and having a film thickness of 250 angstroms was formed on the halftone phase shift mask blank obtained in the first embodiment . in terms of the optical characteristics of the halftone phase shift mask blank so obtained , the surface reflectance at a wavelength of 365 nm was 20 % or lower , which is good . the anti - oxidation film here was fabricated by reactive sputtering in an argon ( ar ) and nitrous oxide ( n 2 o ) mixed gas atmosphere ( ar = 80 %, n 2 o = 20 %), at 1 . 5 × 10 - 3 . the halftone phase shift mask blank thus obtained exhibited outstanding characteristics , including low surface reflectance in addition to the beneficial effects gained in the first embodiment . using the halftone phase shift mask blank described above , the anti - reflection film , metal films ( first metal film and second metal film ), and halftone material film were subjected to patterning to yield a halftone phase shift mask . a halftone phase shift mask blank pertaining to another embodiment of the present invention is diagrammed in fig7 . the halftone phase shift mask blank in this embodiment is configured with a halftone material film made of an mosi - based material , metal film , and an anti - reflection film , laminated successively on a transparent substrate made of quartz . the metal film and anti - reflection film in this embodiment are made by continuously forming , as noted in the eighth embodiment , a first metal film of crn , a second metal film of crc , and an anti - reflection film of cron , by in - line sputtering . when the compositions of these metal films and anti - reflection films were analyzed by auger spectroscopy , the results for crn were cr = 48 - 72 at %, n = 13 - 41 at %, o = 0 - 10 at %, and c = 3 - 13 at %, the results for crc were cr = 61 - 76 at %, c = 6 - 14 at %, n = 13 - 23 at %, and o = 0 - 8 at %, and the results for cron were cr = 17 - 60 at %, o = 8 - 55 at %, n = 15 - 30 at %, and c = 1 - 10 at %. the quantities ofthe elements cr , n , o , and c contained in the metal films and anti - reflection films , moreover , vary continuously in the direction of film thickness . in fig8 are plotted the results of investigating by auger spectroscopy the quantities of elements contained in each of the films in the ninth embodiment . when this halftone phase shift mask blank was subjected to scratch tests ( on 100 pieces ) under a load of 600 g , good film strength was obtained , with no film peeling between the halftone material film and the crn first metal film , between the crn first metal film and the crc second metal film , or between the crc second metal film and the cron anti - reflection film . the explanation for this is that , because of the reduction in stress due to the fineness of the crystalline grain in crn film on the transparent substrate side of the metal film contacting the halftone material film , and to forming a continuous film between the crc and the crn in the metal film , and between the crc and the cron anti - reflection film , wherein a region exists where the composition changes continuously , wherefore particles etc . do not adhere between the layers , and exposure to the atmosphere is internal , so that continuous films are formed without oxidation at the surface . as in the other embodiments described in the foregoing , the anti - reflection film , metal films ( first metal film and second metal film ), and halftone material film were subjected to patterning to yield a halftone phase shift mask . in this case , the metal film and anti - reflection film are formed integrally as a continuous layer in the thickness direction ( that is , a region exists wherein the elements making up the crn and crc that are the metal films and the cron that is the anti - reflection film vary continuously ), wherefore the same benefits as obtained in the first and eighth embodiments described in the foregoing ( i . e . good film strength , halftone material film damage prevention and overhang prevention during patterning , and low surface reflectance ) are realized . in particular , however , a perpendicular cross - section is formed from the transparent substrate side toward the surface side ( the anti - reflection film side ), without any steps , thus making it possible to effect high - precision patterning on the halftone material film . a halftone phase shift mask blank according to this embodiment was fabricated as described below . on a transistor substrate made of quartz is formed a low - transmissivity film made of cr by a sputtering method . onto this low - transmissivity film is dripped an sio 2 - based coating film forming coating liquid , which is spread over the entire surface by spin coating . this is then baked to evaporate the organic binder compound , a hightransmissivity film made of an sog ( spin on glass ) film is formed , and a half - tone material film is fashioned from the low - transmissivity film and the high - transmissivity film . thereafter , using the same sputtering method as in the eighth embodiment , a crn first metal film , crc second metal film , and cron anti - reflection film are formed to yield a halftone phase shift mask blank . as in the other embodiments described in the foregoing , the anti - reflection film , metal films ( first metal film and second metal film ), and halftone material film were subjected to patterning to yield a halftone phase shift mask . the halftone phase shift masks in the eighth , ninth , and tenth embodiment described in the foregoing exhibit a sufficiently fast etching rate for the metal film in contact with the halftone material film , wherefore the halftone material film is rarely damaged and the amount of phase shift is contained within the range of 180 °- 2 °, whereupon a highly reliable halftone phase shift mask is obtained . it should be noted that the configurations and dimensions , etc ., indicated in the embodiments described above are examples thereof . various modifications are possible according to design needs . in the foregoing embodiments , for example , a halftone phase shift mask is indicated in which the metal films 12 and 13 formed on the halftone material film 11 are completely removed , but [ the invention ] is not limited by this . it is possible to provide patterns with the first metal film and the second metal film formed at suitable locations on the halftone material film , or metal films whereon , in addition , a anti - reflection film is formed , and thus enhance the mask light blocking performance . typical examples of this halftone phase shift mask are diagrammed in fig9 and 10 . in the example diagrammed in fig9 the metal film ( with anti - reflection film ) is formed on the halftone material film in a peripheral region that is a region removed from the mask pattern formation region . this metal film provides the function of blocking light . that is , the exposure light is prevented from passing through this peripheral region . the reason for this is as follows . ordinarily , a phase shift mask is used as a mask ( reticle ) in a reductive projection exposure apparatus ( stepper ). when a pattern is being transferred using such a stepper , exposure is performed , covering the peripheral area so that only the phase shift mask transfer region is exposed by a coated member ( aperture ) provided in the stepper . however , it is very difficult to position this aperture with good precision so that only the transfer region is exposed . in many cases , the exposed portion protrudes into the non - transfer region about the periphery of the transfer region . this being so , a light - translucent film is usually formed , in the non - transfer region on the mask , which only passes light of such intensity as does not significantly contribute to exposure , so that problems are not caused by the protruding described . however , exposures are done while repeatedly stepping , wherefore cases occur wherein this portion exposed by the protrusion ( protrusion exposure portion ) overlaps the transfer region , or wherein overlapping occurs , similarly , with protrusion - exposed portions during other shots . cases arise where , due to such overlapping exposures , these accumulate until quantities are attained that do contribute to exposure . by making the peripheral region such that exposure light is completely prevented from passing through , as described in the foregoing , the danger of such flaws developing can be eliminated . in the example diagrammed in fig1 , by forming the metal film in a portion excluding the edges of the translucent portion of the mask pattern , inside the region where the mask pattern is formed , it is possible to make the blocking of light more complete in the portion where the blocking of light should be complete . in other words , inside the region where the mask pattern is formed , the function conventionally required of the translucent portion in the mask pattern need only cause light to pass the phase of which has been shifted only at the boundary with the transparent portion , while it is desirable that the other larger part ( part excluding the edges ) completely block the light . thereupon , by forming the metal film in the portion excluding the edges of the surface of the translucent portion of the mask pattern , it becomes possible to make the blocking of light more complete in the portion where the blocking of light should be complete . furthermore , in a case where , for example , there is a step or steps in the surface of the transfer medium , so that the film thickness of the resist formed on the transfer medium differs greatly depending on the location , if there is a slight exposure through a translucent portion ( portion that should block light ) of the halftone material film where the resist film thickness is thin , that thin resist will be made even thinner by development . when that happens , during etching , so - called film erosion occurs . this film erosion can be prevented by making the portions that should block light be completely light - blocking . it is preferable that an anti - reflection film be provided for these metal films . the anti - reflection film described earlier was formed in an ar and n 2 o mixed gas atmosphere , but this is not a limitation , and the atmosphere may be ar and n 2 + o 2 or no , etc . by implementing the present invention , as described in the foregoing , halftone phase shift mask blanks and halftone phase shift masks can be obtained which permit high - precision patterning , which exhibit high resistance to acids , and which are highly reliable .