Patent Number: 
Section: description

Hereafter, an embodiment of the present invention will be described with reference to examples. In the following description, terms xe2x80x9cellipsoidal surfacexe2x80x9d, xe2x80x9cellipsoid of revolutionxe2x80x9d, xe2x80x9cparaboloidxe2x80x9d, and xe2x80x9cparaboloid of revolutionxe2x80x9d are used. A paraboloid is obtained by making one of two focal points of an ellipsoid infinity. Note that, in the description from the another view point, a quadratic surface of revolution having a form obtained by rotating, using an x-axis (optical axis) as a center, a quadratic curve represented by a quadratic equation for orthogonal coordinates (x, y) ax2+2hxy+by2+2gx+sfy+c=0 (where each of a, b, c, f, g, and h is constant) is defined as an xe2x80x9cellipsoidal surfacexe2x80x9d, xe2x80x9cellipsoid of revolutionxe2x80x9d, xe2x80x9cparaboloidxe2x80x9d, or xe2x80x9cparaboloid of revolutionxe2x80x9d. An ellipse is represented by h2xe2x88x92ab less than 0, and a parabola is represented by h2xe2x88x92ab=0. Using a RF magnetron sputtering apparatus provided with a plurality of raw material targets, multilayer films each comprising repeatedly layered Mo layers (correspond to 2 of FIG. 1) and Be layers (correspond to 3 of FIG. 1) were produced on a substrate (corresponds to 1 of FIG. 1) by evacuating a film formation chamber to 10xe2x88x928 torr level, introducing Ar gas into the resultant film formation chamber to keep the inside of the film formation chamber in Ar atmosphere of 3xc3x9710xe2x88x928 torr pressure, and then generating electric discharge. The number of the pairs of the Mo layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The ratio of the thickness dMo of Mo to the sum thickness (the cycle length D) of a single Mo layer and a single Be layer was changed in a range of 10 to 90%. The correlation of the reflectance of the multilayer films with the wavelength was measured using a reflectance meter employing photon radiation and the results of the measurement were showed in the table 1. In the case the thickness of a Mo layer was 50% to the cycle length, the reflectance reached the maximum, which was 62%. The reflectance was as high as 40% or higher in the case the thickness was in a range 20 to 70% to the cycle length. Multilayer films comprising repeatedly layered Moxe2x80x94N layers (correspond to 2 of FIG. 1) containing 5 atomic % (at. %) of N and Bexe2x80x94N layers (correspond to 3 of FIG. 1) containing 5 at. % of N were produced on a substrate (corresponds to 1 of FIG. 1) in the same manner as that for the example 1. It should be noted that the at. % is the percentage of an element included in an object based on the number of atoms. For example, in H2O (water), since the molecule has two hydrogen atoms and one oxygen atom, the percentage of the oxygen atoms is calculated by 1/(1+2)*100=33. Thus, water contains 33 at. % oxygen atoms. The multilayer films were produced while the number of the pairs of the Moxe2x80x94N layers and Bexe2x80x94N layers being controlled to be 40 and 80 and the cycle length being controlled to be 6 nm and 5.6 nm, respectively. The ratio of the thickness dMoxe2x80x94N of Mo to the sum thickness D of one Moxe2x80x94N layer and one Bexe2x80x94N layer was changed within a range of 10 to 90%. The correlation of the reflectance of the multilayer films with the wavelength was measured using a reflectance meter in the same manner as that for the example 1 and the multilayer film with cycle length 6 nm showed 69% reflectance of soft x-rays with 114 xc3x85 wavelength in the case the thickness of a Moxe2x80x94N layer was 50% to the cycle length and as same as that of the example 1, the reflectance was as high as 45% or higher in the case the thickness of a Moxe2x80x94N layer was in a range 20 to 70% to the cycle length. Further, the multilayer film with cycle length 6 nm showed 55% reflectance of soft x-rays with 108 xc3x85 wavelength in the case the thickness of a Moxe2x80x94N layer was 55% to the cycle length and as same as that of the example 1, the reflectance of the ray with 110 xc3x85 or shorter wavelength was as high as 45% or higher, which had not been achieved before, in the case the thickness of a Moxe2x80x94N layer was in a range from 45 to 70% to the cycle length. In the same manner as that for the example 1, using Rh for one type of layers (correspond to 2 of FIG. 1) and Be for the other type of layers (correspond to 3 of FIG. 1), multilayer films comprising repeatedly formed layers of these elements were produced on a substrate (corresponds to 1 of FIG. 1) by sputtering method. The number of the pairs of the Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The ratio of the thickness dRh of Rh to the sum thickness (the cycle length D) of a single Rh layer and a single Be layer was changed within a range of 10 to 70%. The correlation of the reflectance of the multilayer films with the wavelength was measured using a reflectance meter employing photon radiation and the results of the measurement were showed in the table 2. In the case the thickness of a Rh layer was 30% to the cycle length, the reflectance reached the maximum, which was 65%. The reflectance was relatively high, not lower than 30%, in the case the thickness of a Rh layer was within a range 20 to 70% to the cycle length and was considerably high, not lower than 55%, in the case the thickness of a Rh layer was within a range 20 to 40%. In the same manner as that for the example 1, using Ru for one type of layers (correspond to 2 of FIG. 1) and Be for the other type of layers (correspond to 3 of FIG. 1), multilayer films comprising repeatedly formed layers of these elements were produced on a substrate (corresponds to 1 of FIG. 1) by sputtering method. The number of the pairs of the Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The ratio of the thickness dRu of Ru to the sum thickness (the cycle length D) of a single Ru layer and a single Be layer was changed within a range of 10 to 90%. The correlation of the reflectance of the multilayer films with the wavelength was measured using a reflectance meter employing photon radiation and the results of the measurement were showed in the table 3. In the case the thickness of a Ru layer was 50% to the cycle length, the reflectance reached the maximum, which was 67%. The reflectance was as high as 50% or higher in the case the thickness of a Ru layer was within a range 30 to 70% to the cycle length and was considerably high, not lower than 55%, in the case the thickness of a Ru layer was within a range 30 to 60%. In the same manner as that for the example 1, using Moxe2x80x94Rh alloys for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced on a substrate by sputtering method. The number of the pairs of the Moxe2x80x94Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness dMoxe2x80x94Rh of a Moxe2x80x94Rh layer to the cycle length being changed within a range of 10 to 90% and the composition ratio of Mo and Rh being changed within a range of 10 to 90%. The correlation of the reflectance of the multilayer films with the wavelength was measured in the same manner as that f or the example 1 and it was found that the multilayer films having the composition ratio of Rh in the Moxe2x80x94Rh alloys within a range 30 to 70% and dMoxe2x80x94Rh/D within a range of 30 to 70% showed a considerably high reflectance, which exceeds 60%, in the condition that the direct incident angle (the inclination angle from the normal of the multilayer films) was 3xc2x0 and peak wavelength was near 114 xc3x85. Especially, in the case that the composition ratio Rh in the Moxe2x80x94Rh alloys was 50% and dMoxe2x80x94Rh/D was 45%, the above defined reflectance was as high as 72%. In the same manner as that for the example 1, using Moxe2x80x94Ru alloys for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by sputtering method. The number of the pairs of the Moxe2x80x94Ru layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness dMoxe2x80x94Ru of a Moxe2x80x94Ru layer to the cycle length being changed within a range of 10 to 90% and the composition ratio of Mo and Ru being changed within a range of 10 to 90%. The correlation of the reflectance of those multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of Ru in the Moxe2x80x94Ru alloys within a range 30 to 70% and dMoxe2x80x94Ru/D within a range of 30 to 70% showed a considerably high reflectance, which exceeds 60%, in the condition that the direct incident angle (the inclination angle from the normal of the multilayer films) was 3xc2x0 and peak wavelength was in a wide range from near 112 xc3x85 to near 117 xc3x85. Especially, in the case that the composition ratio Ru in the Moxe2x80x94Ru alloys was 50% and dMoxe2x80x94Ru/D was 40%, the above defined reflectance was as high as 72%. In the same manner as that for the example 1, using Ruxe2x80x94Rh alloys for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by sputtering method. The number of the pairs of the Ruxe2x80x94Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness of a Ruxe2x80x94Rh layer to the cycle length being changed within a range of 10 to 90% and the composition ratio of Ru and Rh being changed within a range of 10 to 90%. The correlation of the reflectance of those multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of Rh in the Ruxe2x80x94Rh alloys within a range 30 to 70% and dRuxe2x80x94Rh/D within a range of 10 to 60% showed a considerably high reflectance, which exceeds 60%, in the condition that the direct incident angle was 3xc2x0 and peak wavelength was near 113 xc3x85. Especially, in the case that the composition ratio Ru in the Ruxe2x80x94Rh alloys was 50% and dRuxe2x80x94Rh/D was 25%, the above defined reflectance was as remarkable high as 78%. In the same manner as that for the example 1, using Mo for one type of layers and Bxe2x80x94Be compounds for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced. The number of the pairs of the Mo layers and Bxe2x80x94Be compound layers was controlled to be 60 and the cycle length was controlled to be 6 nm. The composition ratio of B and Be in the Bxe2x80x94Be compound layers was changed within a range of 20 to 90% and the ratio of the thickness dMo of a Mo layer to the cycle length D was changed within a range of 10 to 90%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having dMo/D within a range 30 to 70% showed a relatively high reflectance, which exceeds 50%, at the direct incident angle of 3xc2x0 and peak wavelength near 115 xc3x85. Especially, in the case that B2Be and B6Be were used as the Be compounds, the maximum reflectance was over 60%. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 5 to 18% to show excellent heat resistance. Especially, in the case of using B2Be and B6Be, the decrease of reflectance was as low as 5 to 9% to show excellent heat resistance. Reference 1 After the same heating treatment as that for the example 8 was carried out for a Mo/Be multilayer film produced by the example 1, the same reflectance measurement was carried out as that before heating and the reflectance was found decreasing by 45% as compared with that before heating. In the same manner as that for the example 1, using Moxe2x80x94Rh alloys for one type of layers and Bxe2x80x94Be compounds for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced. The number of the pairs of the Moxe2x80x94Rh layers and Bxe2x80x94Be compound layers was controlled to be 60 and the cycle length was controlled to be 6 nm. The composition ratio of Rh in the Moxe2x80x94Rh alloys was changed within a range of 30 to 70%, the composition ratio of B and Be in the Bxe2x80x94Be compound layers was changed within a range of 20 to 90% and the ratio of the thickness Moxe2x80x94Rh of a Moxe2x80x94Rh layer to the cycle length D was changed within a range of 30 to 70%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of Rh in the Moxe2x80x94Rh alloys within 30 to 70%, the thickness dMoxe2x80x94Rh/D within a range 40 to 60%, and the composition ratio of B in the Bxe2x80x94Be compounds within 30 to 90% showed a relatively high reflectance, which exceeds 50%, at the direct incident angle of 3xc2x0 and peak wavelength near 114 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 5 to 20% to show higher heat resistance than that of a Mo/Be multilayer film. In the same manner as that for the example 1, using Moxe2x80x94Ru alloys for one type of layers and Bxe2x80x94Be compounds for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced. The number of the pairs of the Moxe2x80x94Ru layers and Bxe2x80x94Be compound layers was controlled to be 60 and the cycle length was controlled to be 6 nm. The composition ratio of Ru in the Moxe2x80x94Ru alloys was changed within a range of 30 to 70%, the composition ratio of B and Be in the Bxe2x80x94Be compound layers was changed within a range of 20 to 90% and the ratio of the thickness dMoxe2x80x94Ru of a Moxe2x80x94Ru layer to the cycle length D was changed within a range of 30 to 70%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of Ru in the Moxe2x80x94Ru alloys within 30 to 70%, dMoxe2x80x94Ru/D within a range 40 to 60%, and the composition ratio of B in the Bxe2x80x94Be compounds within 30 to 90% showed a relatively high reflectance, which exceeds 50%, at the direct incident angle of 3xc2x0 and peak wavelength near 114 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 5 to 22% to show higher heat resistance than that of a Mo/Be multilayer film. In the same manner as that for the example 1, using Rhxe2x80x94Ru alloys for one type of layers and Bxe2x80x94Be compounds for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced. The number of the pairs of the Rhxe2x80x94Ru layers and Bxe2x80x94Be compound layers was controlled to be 60 and the cycle length was controlled to be 6 nm. The composition ratio of Ru in the Rhxe2x80x94Ru alloys was changed within a range of 30 to 70%, the composition ratio of B and Be in the Bxe2x80x94Be compound layers was changed within a range of 20 to 90% and the ratio of the thickness dRhxe2x80x94Ru of a Rhxe2x80x94Ru layer to the cycle length D was changed within a range of 10 to 60%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of Ru in the Rhxe2x80x94Ru alloys within 30 to 70%, dRhxe2x80x94Ru/D within a range 20 to 40%, and the composition ratio of B in the Bxe2x80x94Be compounds within 30 to 90% showed a relatively high reflectance, which exceeds 60%, at the direct incident angle of 3xc2x0 and peak wavelength near 114 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 5 to 24% to show higher heat resistance than that of a Mo/Be multilayer film. Using Rhxe2x80x94Ru alloys containing C for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by a sputtering method in the same manner as that for the example 1. The number of the pairs of the C-containing Ruxe2x80x94Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm, and also the number of pairs to be 80 and the cycle length to be 5.6 nm. The multilayer films were produced while the ratio of the thickness of a C-containing Ruxe2x80x94Rh layer to the cycle length D being controlled to be 25% and the composition of Ru and Rh to be 50%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of C in the C-containing Ruxe2x80x94Rh alloys within 2 to 20% and the cycle length of 6 nm showed a high reflectance, which exceeds 55%, at the direct incident angle of 3xc2x0 and peak wavelength near 113 xc3x85 and those having the cycle length of 5.6 nm showed a reflectance of 53% at 108 xc3x85 wavelength. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 4 to 14% to show excellent heat resistance. Using Rhxe2x80x94Ru alloys containing B for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by a sputtering method in the same manner as that for the example 1. The number of the pairs of the B-containing Ruxe2x80x94Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness of a B-containing Ruxe2x80x94Rh layer to the cycle length being controlled to be 25% and the composition of Ru and Rh to be 50%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of B in the B-containing Ruxe2x80x94Rh alloys within 1 to 20% showed a high reflectance, which exceeds 55%, at the direct incident angle of 3xc2x0 and peak wavelength near 113 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. f or 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 7 to 20% to show excellent heat resistance as compared with that of a Mo/Be multilayer film. Using Rhxe2x80x94Ru alloys containing O for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by a sputtering method in the same manner as that for the example 1. The number of the pairs of the O-containing Ruxe2x80x94Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness of an O-containing Ruxe2x80x94Rh layer to the cycle length being controlled to be 25% and the composition of Ru and Rh to be 50%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of O in the O-containing Ruxe2x80x94Rh alloys within 2 to 20% showed a high reflectance, which exceeds 55%, at the direct incident angle of 3xc2x0 and peak wavelength near 113 xc3x85. Further, in the case those multilayer films were heated at 40xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 6 to 17% to show excellent heat resistance as compared with that of a Mo/Be multilayer film. Using Rhxe2x80x94Ru alloys containing N for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by a sputtering method in the same manner as that for the example 1. The number of the pairs of the N-containing Ruxe2x80x94Rh layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness of a N-containing Ruxe2x80x94Rh layer to the cycle length being controlled to be 25% and the composition of Ru and Rh to be 50%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of N to Ruxe2x80x94Rh in the N-containing Ruxe2x80x94Rh alloys within 2 to 20% showed a high reflectance, which exceeds 55%, at the direct incident angle of 3xc2x0 and peak wavelength near 113 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 6 to 16% to show excellent heat resistance. Using Mo containing C for one type of layers and Be for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by a sputtering method in the same manner as that for the example 1. The number of the pairs of the C-containing Mo layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness of a C-containing Mo layer to the cycle length being controlled to be 40%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of C in the C-containing Mo within 2 to 20% showed a high reflectance, which exceeds 55%, at the direct incident angle of 3xc2x0 and peak wavelength near 113 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 1 to 9% to show excellent heat resistance. Using Rhxe2x80x94Ru alloys for one type of layers and Be to which Ca, Co, Fe, Mo, Nb, Ti, V and W were independently added for the other type of layers, multilayer films comprising repeatedly formed layers of these substances were produced by a sputtering method in the same manner as that for the example 1. The number of the pairs of the Ruxe2x80x94Rh alloy layers and Be layers was controlled to be 40 and the cycle length was controlled to be 6 nm. The multilayer films were produced while the ratio of the thickness of a Ruxe2x80x94Rh layer to the cycle length being controlled to be 25% and the composition of Ru and Rh to be 50%. The correlation of the reflectance of thus produced multilayer films with the wavelength was measured in the same manner as that for the example 1 and it was found that the multilayer films having the composition ratio of each additive in the Be layers containing independently one of Ca, Co, Fe, Mo, Nb, Ti, V and W within 1 to 33% showed a high reflectance, which exceeds 50%, at the direct incident angle of 3xc2x0 and peak wavelength near 113 xc3x85. Further, in the case those multilayer films were heated at 400xc2x0 C. for 1 hour in vacuum of 10xe2x88x925 torr and then the reflectance measurement was carried out in the same manner as that before heating, the decrease of reflectance was 7 to 18% to show excellent heat resistance. In the same manner as that for the example 1, using Ru for one type of layers and B6Be for the other type of layers, multilayer films comprising repeatedly formed layers in 40 pairs of Ru layers and B6Be layers and having the cycle length within 3.9 to 7 nm at every 2 xc3x85 were produced. The ratio of the thickness of layers was controlled to be 1:1. The correlation of the reflectance of thus produced multilayer films to the wavelength was measured in the same manner as that for the example 1 and it was found that a multilayer film type reflecting mirror comprising a multilayer film constituted of those layers in combination had a reflectance as high as 25% even to radiation about 78 xc3x85 peak wavelength corresponding to the cycle length at direct incident angle 3xc2x0, which was extremely high reflectance in such a wavelength region, further the reflectance was 35% to 100 xc3x85 wavelength, 57% to 114 xc3x85 wavelength, and at least 45% to radiation with wavelength in a range from 78 xc3x85, the wavelength longer than the foregoing value, to 140 xc3x85. In the same manner as that for the example 1, using Ru for one type of layers and B for the other type of layers, multilayer films having a repeated structure of these two layers were produced by the sputtering method. The multilayer films were produced while the number of the pairs of Ru layers and B layers being controlled to be 60 and the cycle length to be 5.1 nm or 5.5 nm. The ratio of the Ru thickness to the sum thickness of a single Ru layer and a single B layer was changed in a range of 10 to 90% and the correlation of the reflectance of the multilayer films with the wavelength was measured using a soft x-ray reflectance meter in the same manner as that for the example 1. In the case of 5.1 nm cycle length, the reflectance reached the maximum, which was 52%, to the soft x-ray wavelength of 100 xc3x85 when the thickness of a Ru layer was 45% to the cycle length. The reflectance was relatively high, 35% or higher, in the case the thickness of a Ru layer to the cycle length was in a range 30 to 60% to the cycle length and was 45% or higher, which was extremely high to the wavelength, in the case the thickness of a Ru layer to the cycle length was in a range 40 to 50%. On the other hand, in the case of 5.5 nm cycle length, the reflectance reached the maximum, which was 58%, to the soft x-ray wavelength of 108 xc3x85 when the thickness of a Ru layer was 45% to the cycle length. The reflectance was relatively high, 40% or higher, in the case the thickness of a Ru layer to the cycle length was in a range 30 to 60% to the cycle length and was 50% or higher, which was extremely high to the wavelength, in the case the thickness of a Ru layer to the cycle length was in a range 40 to 50%. In the same manner as that for the example 18, using Ru containing 5 at. % of N for one type of layers and B containing 5 at. % of N for the other type of layers, multilayer films having a repeated structure of these two layers were produced by the sputtering method. The multilayer films comprising 60 pairs of Ruxe2x80x94N layers and Bxe2x80x94N layers were produced while the cycle length being controlled to be 5.1 nm or 5.5 nm. The ratio of the Ruxe2x80x94N thickness to the sum thickness of a single Ruxe2x80x94N layer and a single Bxe2x80x94N layer was changed within a range of 10 to 90% and the correlation of the reflectance of the multilayer films with the wavelength was measured using a soft x-ray reflectance meter in the same manner as that for the example 1. In the case of 5.1 nm cycle length, the reflectance reached the maximum, which was 51%, to the soft x-ray wavelength of 100 xc3x85 when the thickness of a Ruxe2x80x94N layer was 45% to the cycle length just the same as that in the case of the example 18. The reflectance was relatively high, about 35% or higher, in the case the thickness of a Ruxe2x80x94N layer to the cycle length was in a range 30 to 60% to the cycle length and was about 45% or higher, which was extremely high to the wavelength, in the case the thickness of a Ruxe2x80x94N layer to the cycle length was in a range 40 to 50%. On the other hand, in the case of 5.5 nm cycle length, the reflectance reached the maximum, which was 56%, to the soft x-ray wavelength of 108 xc3x85 when the thickness of a Ruxe2x80x94N layer was 45% to the cycle length. The reflectance was relatively high, about 40% or higher, in the case the thickness of a Ruxe2x80x94N layer to the cycle length was in a range 30 to 60% to the cycle length and was about 50% or higher, which was extremely high to the wavelength, in the case the thickness of a Ruxe2x80x94N layer to the cycle length was in a range 40 to 50%. X-ray reflecting mirrors with an ellipsoid of revolution (in the present invention), which has multilayer films or Mo/Si multilayer films of the example 1 to the example 20 produced by the same manner as that of the example 1 were so arranged as to surround a cryotarget laser plasma x-ray point source (point-like x-ray generation part) 32, serving as a point-like x-ray generation part, at about several to several ten centimeter to the light source just as illustrated in FIGS. 3C and 3D to obtain high light concentration efficiency (about 3 steradian of solid angle) to the x-rays emitted out of the point source and simultaneously high reflectance (50% or higher). In this case, the cryotarget laser plasma x-ray point source used a rare gas element, as a target material generating the x-ray, in a liquid or solid state at a low temperature or in a low temperature gas state at vapor density near the liquid density. Since the x-ray generation efficiency of x-rays with reflected wavelength width of the foregoing multilayer film type reflecting mirrors by plasma was verified to have 1% per 1 steradian solid angle by using a pulsed laser with 500 pulses or more repeated at every several seconds, 0.5 J or higher pulse energy and about 10xe2x88x928 second pulse width, a laser plasma x-ray generation apparatus capable of taking out the x-rays with uniform spectra with 3.8 W or higher average intensity as a) a parallel beam and b) a converged beam could be constituted. FIGS. 3C, 3D, and 3E illustrate an example of the arrangement of an ellipsoid of revolution (in the example only the upper half portion is illustrated and the lower half portion is omitted) for condensing more x-rays which are emitted from the laser plasma x-ray point source by the foregoing x-ray optical system. Assuming that xcex8 is an angle from a normal (vertical line) to the laser target surface, the angular distribution of x-ray emission intensities is almost determined depending on the ratio of the concentrated light diameter of the pulse laser, i.e., the diameter of plasma to be generated, to the scale length of plasma expanding by heating. For example, when the concentrated light diameter is about 100 xcexcm, if the pulse duration of the laser is about 10 nsec, the angular distribution is isotropic; and if the pulse width is 1 nsec or shorter, the angular distribution is approximately proportional to cos xcex8. Therefore, the reflecting mirror has a shape to ensure a reflecting surface with respect to the normal, and the aperture is arranged in a part of the reflecting surface for only the incidence of a laser ray. FIGS. 3A and 3B are illustrated as the references to show the characteristic features of the present invention, in which FIG. 3A illustrates a ring-shaped paraboloid of revolution, and FIG. 3B illustrates a ring-shaped ellipsoid of revolution. In FIGS. 3A and 3B, 31 shows the incidence laser ray which is incident from an axial direction of the ring-shaped paraboloid of revolution or ring-shaped ellipsoid of revolution, 32 shows the target, 33 shows the emitted x-ray obtained by heating the target 32 by the incidence laser ray 31, and 34 is a reflecting mirror which generates, from x-rays emitted from near the surface of the target 32, parallel rays or converged rays obtained by converging the x-rays on or near a focal point. FIGS. 3C, 3D, and 3E illustrate a basic constitution of a laser plasma x-ray generation apparatus using a multilayer film type x-ray reflecting mirror according to the present invention. In FIGS. 3C, 3D, and 3E, the same reference numerals as in FIGS. 3A and 3B denote the same parts. In FIGS. 3C and 3D, the reflecting mirror 34 has the structure obtained by cutting an ellipsoid with two focal points along the major axis, and the surface of the target 32 placed on one of the two focal points is heated by an incidence laser ray to generate point-like laser plasma x-rays on that focal point. The incident laser ray 31 is incident from a direction outside a range of 30xc2x0 from the normal to the x-ray emitting surface of the target 32 which is placed almost parallel to the major axis of the ellipsoidal surface of the ellipsoid. The soft x-rays emitted from the x-ray emitting surface of the target 32 by the incidence laser ray 31 are bombarded against the multilayer film type reflecting mirror 34 positioned on the inner surface of the ellipsoid and are reflected by the multilayer film type reflecting mirror 34. The reflected x-rays 33 converge on or near the other focal point of the ellipsoidal surface. The light concentration efficiency defined as an amount obtained by dividing the light amount of the converged reflected x-rays 33 by the amount of all x-rays emitted from the target depends on the form of the angular distribution for emission of the x-rays from the x-ray emitting surface of the target, and can be adjusted by changing the angle of the x-ray emitting surface with respect to the major axis of the ellipsoid. Note that 34a is an aperture formed in the reflecting mirror 34 as shown in FIG. 3C, and through the aperture 34a, the incidence laser ray 31-1 is received from the outside. FIG. 3D illustrates a cross-sectional view taken along a surface which is perpendicular to the major axis (rotation symmetry axis) in FIG. 3C and includes the point-like x-ray source. 34b is an aperture formed in the reflecting mirror 34 as shown in FIG. 3D, and through the aperture 34b, the incidence laser ray 31-2 is received from the outside. The incidence laser 31-2 is shown as another example of 31-1, these incidence laser rays do not have the incidence direction of xcex8 less than 30xc2x0 to the normal of the target surface, and the soft x-rays emitted from the target are emitted to xcex8 less than 300 relatively intensively. Obviously, a ray source to which the present invention is applied is not limited to a soft x-ray and may be an x-ray. A laser ray is used in this example, but the present invention is not obviously limited to this as far as light is an energy beam. In the foregoing example, the structure obtained by cutting the ellipsoid along the major axis, i.e., an x-ray radiation part using the x-ray optical system which has 0.1 or more steradian condensing solid angle around an x-ray generation part with a target surface, and has a partial surface, as the x-ray reflecting mirror, of an ellipsoid of revolution (ellipsoidal surface) obtained by rotating an ellipse about its major axis as a rotation axis passing through the x-ray generation part by only a rotation angle of less than 180 degrees is used. However, the present invention may use a structure (e.g., the structure in FIG. 3F) in which a paraboloid of revolution serving as a source making infinity one focal point, of two focal points of an ellipse, at which the reflected x-rays converge, i.e., a source making the reflected x-rays parallel or almost parallel is defined as the x-ray reflecting mirror. This paraboloid of revolution with the foregoing structure has an x-ray optical system having a partial surface, as an x-ray reflecting mirror, of the paraboloid of revolution obtained by rotating the paraboloid of revolution about its major axis as a rotation axis by only a rotation angle of less than 180 degrees. Further, when a Mo/Si multilayer film is used, 2 to 20% of C are added to either of the layers, so that the reflecting mirror with excellent heat resistance can be obtained according to the finding of the present inventors. As is understood from the embodiment shown in FIGS. 3C to 3F, the portion of the reflecting mirror of the x-ray radiation part in the second focal direction is cut to have a shape so as to introduce the reflected x-rays to the outside. However, the x-ray radiation part may have any shape if reflected x-rays are guided outside, as in the case wherein the aperture for introducing the incidence ray to the inside is formed in the reflecting mirror. An aperture may be formed to guide the x-rays outside. As described above, the multilayer films of the present invention could improve the direct incidence reflectance by using materials with optical constants suitable for giving a high reflectance to wavelength within a range from 69.5 xc3x85 to 124 xc3x85, selecting the structure, and smoothing the interfaces. Further, the heat resistance of the multilayer film was improved by using compounds or mixtures having optical constants suitable for heightening the reflectance and giving excellent heat resistance. Consequently, as compared with a conventionally invented Mo/Be multilayer film type reflecting mirror, the multilayer film type mirrors of the present invention had heightened direct incidence reflectance or improved heat resistance or improved values of both. In the case a multilayer film with heightened reflectance is used (1) for various analysis methods using x-rays and soft x-rays, the sensitivity and the precision can be improved and in the case of use (2) for x-ray lithography, the throughput can be improved more than that of a multilayer film comprising Mo for one type of layers. Moreover, in the case a multilayer film type x-ray reflecting mirror with heightened reflectance is used (1) for various analysis methods using x-rays and soft x-rays, the sensitivity and the precision can be improved since the alteration of the reflectance during the use is suppressed as compared with that of a conventional multilayer film type reflecting mirror owing to the more improved heat resistance than that of the conventional reflecting mirror and in the case of use (2) for x-ray lithography, the proper exposure time can precisely be determined for the same reason as the reason of (1) and further the life of the multilayer film type reflecting mirror itself can be prolonged. In this description, materials and structures suitable for near 114 xc3x85 wavelength were exemplified, and no need to say, the reflection peak wavelength can be changed by changing the cycles according to the Bragg approximation. Also, that a high reflectance in a range from approximately the absorption edge (69.5 xc3x85) of B to approximately the absorption edge (123 to 125 xc3x85) of Si or to the longer wavelength could be obtained in the case of combination of a compound B and Be with a metal was exemplified by combining Mo with the compounds of B and Be such as B6Be and that was only one example, and it is also needless to say that the same effect can be obtained by using any one of Ru, Rh and Mo, or using their alloys, or using substances containing any one of these metals together with additives of other elements, or using alloys containing two or more of these metals together with additives of other elements, or further by using compounds or mixtures of B and Be such as BBe instead of B6Be. Especially, when the Mo/Si multilayer films or the Mo-/Si-based multilayer films with improved heat resistance are used as the materials of the multilayer films, the same effect can be obtained in the long wavelength region over the absorption edge (123 to 125 xc3x85) of Si or longer. By installing or combining x-ray optical system comprising an x-ray reflecting mirror or a plurality of x-ray reflecting mirrors having the foregoing multilayer films in the periphery of a cryotarget laser plasma x-ray point source, a constituted x-ray generation apparatus can be a compact and practical apparatus capable of generating the x-ray parallel beam, or converged beam, or condensed beam with uniform spectra and high average intensity. Owing to actualization of such an x-ray generating apparatus, applied appliances for x-ray reduction projection exposure and an x-ray beam processing apparatus can be made available for practical use.