FR2887645A1 - IMPROVED ILLUMINATOR OF A PHOTOLITHOGRAPHIC DEVICE - Google Patents

Abstract

The invention relates to an illuminator of a photolithography device comprising an illumination source (1 ') (20) and a pupil-forming element, characterized in that the element comprises a suitable optical rod (100). receiving illumination (20) from the source (1 ') on one (103) of its faces and adapted to form the pupil at the output of another (104) of its faces.The invention also relates to a method of forming a pupil using the aforementioned illuminator.

Description

GENERAL TECHNICAL FIELD

  The present invention relates to an illuminator of a photolithography device.

  STATE OF THE ART Photolithography also called microlithography - has been used for many years for the manufacture of semiconductor devices and uses for this purpose electromagnetic radiation to generate fine patterns on semiconductor devices. For this purpose, an illuminator of a photolithography device illuminates a mask whose image is projected on a semiconductor wafer (or wafer according to the English terminology generally used by those skilled in the art) which provides a circuit after a treatment ad hoc known to those skilled in the art.

  As shown in Figure 1, the illumination system called illuminator in the following description of a photolithography device is complex. It must take into account several parameters simultaneously to satisfy the needs of microlithography. The parameters in question are in particular: the illumination profile in the pupil of the device; - uniformity of illumination on the mask (and therefore the slice); and - the illumination profile on the mask.

  For this purpose, a known illuminator generally comprises a diffractive optical element 1 (also called diffractive optical element (DOE in English) which is illuminated by a source 1 'of illumination. The element 1 may be any element generally used to produce diffraction, such as for example a two-dimensional network of spherical microlenses, a Fresnel lens, a diffraction grating, etc. The element 1 plays the role of an optical diffuser and its main function is to produce at its output a pupil of general desired pattern, for example a disk-shaped pattern or ring, or a dipole or quadrupole pattern. Element 1 is interchangeable because an element 1 of a given type can only generate one pattern at a time.

  The illuminator comprises at the output of the element 1 a zoom 2 formed of several lenses. The function of the zoom 2 is to bring the image of the pupil to a finite distance and to be able to vary it in dimension.

  The output of the zoom 2 is directed to axicons 3 which give its final shape to the pupil. For example, in the case of axicons composed of conical lenses, the inner diameter of a ring-shaped pupil can be controlled.

  The element 1 zoom 2 axicons 3 together allows to obtain a desired illumination profile in the pupil.

  The light beam is generally folded at 45 by a plane mirror 4 so that the output of the aforementioned assembly illuminates a diffractive optical element 5. The element 5 is preferably a two-dimensional network of spherical microlenses that cuts the pupil obtained in FIG. output of the set element 1 zoom 2 axicons 3. The pupil of the zoom 2 is found at the level of the element 5 whose output illuminates a condenser 6.

  The condenser 6 comprises a plurality of lenses which make it possible to superpose at the level of the shutter 7 the sub-beams coming from the diffractive element 5.

  The condenser element assembly 6 thus uniformizes the illumination in the plane of a shutter 7.

  Indeed, the output of the condenser 6 illuminates a shutter 7 (also called slit in English) including blades including some are movable for sealing. The shutter can be done at a speed of about 160 mm / s. The shutter 7 makes it possible to control the dose, the image format, and the illumination profile on a mask 11 by means of a group 8 of illumination lenses (or illumination lens group (ILG)) placed at the exit of the shutter 7.

  The group 8 forms an optical relay that combines the plane of the shutter 7 and the mask. In fact, without the group 8, the shutter 7 and the mask 11 should be located in the same plane, which is impossible from the mechanical point of view.

  A mirror 9 and a series of lenses 10 respectively make it possible to fold the beam coming from the group 8 and to control the magnification of the beam.

  Mirrors 4 and 9 are optional and the arrangement of Figure 1 may well be in a straight line.

  The illuminators of the prior art have disadvantages.

  The pupil is generated by a large number of optical components, namely the diffractive optical element 1, the zoom 2 and the axicons 3. The components comprise in particular large lenses. Large lenses are difficult and expensive to manufacture (this is particularly the case of 3 axicons).

  The plurality of optical components is more difficult and expensive to mount and move mechanically firstly on large runs and secondly accurately.

  PRESENTATION OF THE INVENTION The invention proposes to overcome at least one of the aforementioned drawbacks.

  For this purpose, the invention proposes an illuminator of a photolithography device comprising an illumination source and a pupil-forming element, characterized in that the element comprises an optical rod adapted to receive the illumination resulting from of the source on one of its faces and able to form the pupil at the exit of another of its faces.

  The invention is advantageously completed by the following characteristics, taken alone or in any of their technically possible combination: the bar is a cylinder whose cross section is a square, a rectangle or a disc; the receiving face of the illumination and the exit face of the pupil are opposite bases of the bar; the bar is made of a refractive material capable of allowing a wavelength of illumination to pass; the illuminator further comprises means for focusing the illumination on one face of the bar; the illuminator comprises means able to move the focusing means in a direction substantially parallel to a longitudinal axis of the bar, so that the focusing means form a zoom; - The illuminator further comprises a goal of recovery of the pupil, the lens having a fixed focal length; the illuminator comprises means capable of translating and rotating the source in a plane substantially parallel to the reception face and / or the exit face of the bar; the illuminator comprises a matrix of bars.

  The invention also relates to a method of implementing the illuminator.

  The invention has many advantages.

  The multiplicity of optical components participating in the prior art to the generation of the pupil is replaced by an assembly comprising fewer components, in particular a bar. The bar makes it possible to replace the numerous optical components and large lenses of the prior art.

  The bar is of compatible size with easy manufacture. It is easy to assemble and does not require any movement.

  Only the illumination source is moved or modified in a mounting according to the invention, which requires a simple and inexpensive mechanical assembly, while providing a very good accuracy on the generation of the pupil.

PRESENTATION OF FIGURES

  Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the accompanying drawings in which: - Figure 1, already commented, schematically represents a known illuminator; - Figures 2A to 5B show schematically several forms of bars used in an illuminator according to the invention, and the corresponding formed pupils; FIG. 5C is a front view of a preferred configuration in which a pupil according to FIG. 5B is obtained; FIG. 6 represents possible positions of illumination incidence on a face of a bar of an illuminator according to the invention; and FIG. 7 schematically represents an illuminator according to the invention. In all the figures, similar elements bear identical reference numerals.

DETAILED DESCRIPTION

  An illuminator according to the invention, the illuminator being adapted to be placed in an otherwise conventional photolithography device, comprises mainly, as shown in FIG. 7, a source 1 'of illumination 20 and a formation element 123 of a pupil 21.

  The source 1 'is conventional and is not described in more detail later in this description. The illumination 20 is typically in the UV range, for example with a wavelength between 150 nm and 250 nm.

  Similarly, the optical components numbered 4 to 11 of Figure 7 are identical to the known components of the state of the art and commented with reference to Figure 1, and are not described again below.

  It is found that the invention consists mainly in replacing the assembly of FIG. 1 composed of element 1, zoom 2 and axicons 3 by element 123.

  With reference to FIGS. 2A to 6, it can be seen that the element 123 mainly comprises an optical rod 100 able to receive the illumination 20 coming from the source 1 'on one of its faces 103. Moreover, the bar 100 is able to forming the pupil 21 at the exit of another of its faces 104. The light rays of the illumination 20 are injected into the bar 100 by the face 103, thus pass through the bar 100 and exit through the face 104 to form a pupil 21.

  Very preferably, the bar 100 is a cylinder whose cross section is a square, a rectangle or a disc. Very preferably still, the face 103 and the face 104 are opposite bases of the bar 100.

  As will now be described, the shape of the bar 100, as well as the way the illumination is received by the face 103, to control the illumination profile in the pupil 21 at the output of the bar.

  In the case of Figure 2A, the bar 100 is a rotationally symmetrical cylinder and has a disc-shaped cross section. 101 is a longitudinal axis of the cylinder and 103 and 104 the bases of the cylinder. The lateral wall extending between the faces 103 and 104 is referenced 102. The geometric center of the face 103 is referred to as 107. The axis 101 passes through the center 107.

  The bar 100 is located between focusing means 12 on the side of the face 103 and an objective 13 for taking up the pupil 21 located on the side of the face 104.

  The focusing means 12 comprise at least one converging lens which makes it possible to focus the illumination 20 from the source 1 'and optically to infinity, so that the illumination 20 can be received by the face 103 of the bar. The focus point of the illumination 20 is indicated by 108 and a principal axis of propagation of the illumination 20 by 200 after the passage of the focusing means 12. The opening angle of the injection, namely the angle between the axis 200 and an extreme radius of the envelope of the illumination 20, is called 0. 0 characterizes the angular width by which the illumination is received. by the bar 100. 0 is the half-angle of the illumination 20 at the top 108.

  Very preferably, the objective 13 has a fixed focal length. The assembly is therefore simplified with respect to an illuminator of the prior art in which a zoom is arranged at the output of the diffractive optical element.

  Objective 13 is very simple in design. Its only function is to recover the pupil 21 at the output of the bar 100 and send it to the diffractive optical element 5, possibly via a mirror 4, as shown in FIG. 7.

  FIG. 2B shows that when the axis 200 of the illumination 20 coincides with the axis 101 and that the focusing point 108 coincides with the center 107, the pupil 21 at the output of the face 104 has a disc shape radius r. In general, in order to obtain an illumination profile of the disk-shaped pupil 21, the main axis 200 of the illumination after focusing and the point of focus 108 must be merged with the axis 101.

  By increasing the angle θ with respect to the axis 200, the radius r of the pupil disk 21 is increased at the outlet of the face 104. It can thus be seen that the illumination profile of the pupil 21 can be easily controlled. .

  To control the value of 0, the focusing means 12 comprise means 15 for moving lenses in a direction parallel to the axis 101, or perpendicular to the faces 103 and 104, so that the means 12 can form a zoom. The means 15 are actuated and the zoom value is adjusted until a pupil 21 is obtained whose radius r is satisfactory for the application in question.

  Figures 3A to 3C show another embodiment of the element 123 to obtain an illumination profile in the pupil 21 which is dipolar, with two poles 211 and 212 diametrically opposite on the pupil. The poles are separated by a distance R and have a radial width r.

  The bar 100 is always cylindrical symmetry of revolution.

  In contrast to the case of FIG. 2A - where the illumination 20 is incident on the reception face 103 with an axis 200 parallel to and coincident with the axis 101 - FIG. 3A shows that the illumination 20 is incident on the face 103 of FIG. receiving with an injection opening angle 0 and an angle of incidence 0 between the longitudinal axis 101 and the axis 200.

  The angle θ corresponds to the opening angle of the injection optics of the illumination in the bar 100. In the example of FIG. 3A, the focusing point 108 and the center 107 coincide.

  The injection angle θ between the axis 101 and the axis 200 makes it possible to control the radius R visible in FIG. 3C. The larger the angle θ, the larger R is and the more the poles 211 and 212 are diametrically spaced from each other.

  The angle is controlled by moving the source 1 'through means 14 which make it possible to translate the source 1' in a plane substantially parallel to the receiving face 103 and / or the exit face 104, as shown in FIG. 3B. The angle is also controlled by rotating the source 1 'through the means 14 in a plane parallel to the receiving face 103 and / or the output face 104, that is to say by rotating around it. an axis substantially parallel to the axis 101. The position and the inclination of the source 1 'are varied to obtain the angle which gives the desired distance R for the application in question.

  The angle 0 makes it possible to control the radial width r of the two poles 211 and 212. The greater the angle θ, the greater the width r of the poles 211 and 212 is large.

  As before, in order to control the value of 0, the focusing means 12 comprise means 15 for moving lenses, so that the means 12 can form a zoom. The means 15 are actuated and the zoom value is adjusted until a pupil 21 is obtained whose radius r is satisfactory for the application in question.

  The area of each pole 211 or 212 is determined by the shape of the input radius. The width and length of each pole vary proportionally. To obtain poles 211 and 212 of different shape from that of the input radius, it is necessary to introduce anamorphic zoom before the bar, comprising for example cylindrical lenses or blades.

  FIG. 4A and FIG. 4B show that, on the one hand, the illumination 20 is injected into the bar 100 on the face 103 with an angle of incidence between the longitudinal axis 101 and the axis 200 and that if on the other hand, the focal point 108 is not located at the center 107 of the face 103, whereas the pupil 21 has the shape of a ring of internal diameter R and of radial width r. The pupil 21 of FIG. 4B does not have a disk shape or a dipole.

  As before, the angle controls the value of R while the angle 0 controls the radial width of the ring. The larger the angles and 0, the larger the respective values of R and r.

  The value of is controlled by the position and inclination of the source 1 'in a plane parallel to the face 103 and / or 104. The value of 0 is controlled by the zoom value of the focusing means 12.

  In the case of Figure 5A, the bar 100 is a cylinder whose cross section is square. The faces 103 and 104 are the bases of the cylinder. The lateral wall extending between the faces 103 and 104 is referenced 102 and a lateral edge 105. The reference is 107 the geometric center of the face 103. The longitudinal axis 101 passes through the center 107.

  As before, the bar 100 is located between the focusing means 12 on the side of the face 103 and a lens 13 for taking up the pupil 21 located on the side of the face 104. The point 108 is the focal point of the 20, and 200 is the main axis of propagation of the illumination 20 after the passage of the means 12 focusing.

  FIG. 5A shows that the illumination 20 is injected into the bar 100 by the face 103 with an opening angle θ, with an injection angle between the longitudinal axis 101 and the axis 200, but also with an angle tilt 45, so that the axis 200 intersects the stop 105 in the bar. Point 108 is not confused with center 107.

  The pupil 21 of FIG. 5B is thus obtained, namely a quadrupole pupil with four poles 211, 212, 213 and 214 separated by a distance R and having a radial width r.

  As for the previous examples, the angle between the axis 101 and the axis 200 makes it possible to control the radius R visible in FIG. 5B. The larger the angle $, the larger R is, and the more the poles 211 and 212 are diametrically spaced from each other. By increasing the angle θ with respect to the axis 200, the radial width r of the poles 211 to 214 is increased.

  The adjustment of the angles and 0 is carried out as previously by the translation and / or the pivoting of the source 1 'with respect to the faces 103 and 104 and by the zooming of the means 12 respectively.

  FIG. 6 shows that the point 108 does not need to be on the face 103 so that there is generation of a pupil at the exit of the bar 100. It is more the radial position of 108 relative to the 101 which is important, rather than the longitudinal position of 108 relative to the face 103.

  Thus, the three positions 108, 108 '- where the focusing of an illumination 20' takes place before the face 103, namely outside the bar - and 108 "where the focusing of an illumination 20" takes place after the face 103, namely in the bar 100 - we obtain the same pupil profiles.

  It should be noted that for a good transmission efficiency of the illumination in the bar, the entire illumination must hit the face 103, that is to say that even in the case of a convergence before the face 103, the latter must capture all divergent rays. There is therefore a maximum distance not to be exceeded between the focusing point 108 'and the face 103.

  Solution 108 'is preferred because of lower bar heating.

  Thus, FIG. 5C shows a front view of a preferred configuration in which a pupil according to FIG. 5B is obtained. The focus of the illumination 20 'at the point 108' before the face 103 is very preferred.

  The illuminator according to the invention may comprise a plurality of bars to form a matrix of at least two bars. In this case, the injection optics, ie the focusing means 12, may comprise a matrix of corresponding lenses.

  In all cases, the bar 100 is made of a refractive material capable of passing a wavelength of illumination 20, for example silica, fluorine and / or optical glass.

  The uniformity of illumination in the pupil depends on the length / diameter ratio of the bar. The higher the ratio, the more uniform illumination in the pupil. The ratio is preferably between 10 and 100, for example of the order of 50. Thus, for a bar having a length of 100 mm, the straight section of the bar has a side of 2 mm, or a diameter of 2 mm. .

Claims (1)

11 CLAIMS   1. Illuminator of a photolithography device comprising a source (1 ') of illumination (20) and a element (123) for forming a pupil (21), characterized in that the element (123) comprises a optical rod (100) adapted to receive the illumination (20) from the source (1 ') on one (103) of its faces and able to form the pupil (21) at the output of another (104) of its faces.   2. Illuminator according to the preceding claim, wherein the bar (100) is a cylinder whose cross section is a square, a rectangle or a disc.   The illuminator according to one of the preceding claims, wherein the illumination receiving face (103) and the pupil exit face (104) are opposed bases of the bar.   4. Illuminator according to one of the preceding claims, wherein the bar (100) consists of a refracting material capable of passing a wavelength of the illumination (20).   5. Illuminator according to one of the preceding claims, further comprising means (12) for focusing the illumination (20) on a (103) face of the bar.   6. Illuminator according to the preceding claim, comprising means (15) adapted to move the focusing means (12) in a direction substantially parallel to a longitudinal axis (101) of the bar (100), so that the focusing means form a zoom.   7. Illuminator according to one of the preceding claims, further comprising a lens (13) recovery of the pupil (21), the lens having a fixed focal length.   8. Illuminator according to one of the preceding claims, comprising means (14) adapted to translate and rotate the source (1 ') in a plane substantially parallel to the face (103) of reception and / or the face ( 104) of the bar (100).   9. Illuminator according to one of the preceding claims, comprising a matrix of bars (100).   10. A method of forming a pupil (21) of an illuminator of a photolithography device comprising an illumination source (1 ') (20) and a pupil-forming element (1), characterized in that it comprises a step according to which the illumination (20) coming from the source (1 ') is sent onto one (103) of the faces of an optical rod (100) of the formation element (1) and retrieves the pupil (21) at the output of another (104) face of the bar.   11. Method according to the preceding claim, wherein the shape of the pupil (21) is controlled by controlling in particular the width (0) of the illumination and the angle (0, 6) of incidence of the illumination (20). ) on the bar (100).