DE2050590A1 - Projection method and arrangement for implementation - Google Patents

Description

Boblingen, Sept. 28, 1970 pr-ba

Official file number: New registration File number of the applicant: Docket GE 970 004

Pjcpj ^ tion processes and "arrangement for implementation 2

The invention relates to a projection method, in particular a projection method for exposing the photoresist layer in the manufacture of integrated circuits and an arrangement for carrying out this method.

When transferring the image of very fine structures, for example when transferring the image of the masks the manufacture of integrated circuits on semiconductor wafers coated with a layer of photoresist, become optical Systems are required which, in addition to a very high resolution, also have the property of images with negligible To generate distortions and aberrations. In addition, the image field should be as large as possible so that the Exposure of the relatively large semiconductor wafers can be done at once. With the ever smaller dimensions of the individual elements of the integrated circuits are the requirements for the above-mentioned properties of the imaging Systems are getting higher and higher so that these requirements are no longer met with the available optical aids can be. There have therefore already been methods used in

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each of which only has a small area of the original on the recording area mapped and the overall picture by a multitude is formed from individual images. For this purpose, the image is flat relative to the imaging system and the template (mask) moved gradually. This method has a number of serious disadvantages. Once the individual steps of the Displacement to be equal to each other and precisely matched to the size of the partial images except for very small tolerances. on the other hand a very large number of individual exposures is required, since only one is possible with a single exposure self-contained and independent area of the entire mask should be transferred. Keeping in mind that Even the smallest vibrations occurring during an exposure improve the resolution and the freedom from distortion of an image strongly affect, so it is easy to see that an exposure only after the expiration of a certain for the decay of the Vibrations required time span after completion of a movement s step may occur. In other known systems, at where the relative movement is continuous, extremely short flashes of light are used. Despite the brevity of the available standing flashes of light, the relative movement is allowed a certain speed do not exceed if extremely sharp images are required. As a result, the times for the elimination of a whole semi-conductor plate can be very long, what severely restricts the applicability of this method. The large number of single steps or single exposures and the relative long times required to carry out an exposure result in the exposure of a semiconductor wafer of average size takes times on the order of hours.

In spite of the greatest structural effort in terms of the mechanical means for the gradual shifting of the imaging systems and when designing the optical systems themselves, it has not been possible to date to produce step-by-step cameras which the transfer of the images of masks to the light

209817/0491

Docket GE 970 OO4

sensitive layer of semiconductor chips with the required goods was possible in an economically viable time. Ee For this reason, methods were also tested in which the imaging of a mask was carried out using a large number of individual lenses lying next to one another, so-called fly's eye lines. Ee However, it has been shown that, especially in the case of very fine circuit structures, the individual images could not be produced with the required quality.

The invention is based on the object, a method indicate with which the advantages of the step-by-step camera, namely the high resolution of the transmitted overall image when using optical systems of relatively low quality, without their disadvantages, which are mainly in the high technical effort and, above all, "the length of the time required to transmit a complete image" can be exploited.

This object is achieved according to the invention by means of a projection method, in particular a projection method for the exposure of the Photoresist layer released during the production of integrated circuits, which is characterized in that a template and a receiving surface can be arranged non-displaceably with respect to one another and that a respective sub-area of the template is placed on one Subarea of the recording surface imaging system is moved relative to this one after the other over all subareas to be imaged.

A particularly advantageous embodiment of the inventive The method is characterized in that the imaging system moves continuously relative to the original and to the receiving flee will.

Another particularly advantageous further development of the inventive method is characterized in that the imaging system is moved line by line relative to the original and the recording surface.

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Docxet «jE 970 004

Another advantageous development of the method according to the invention is characterized in that, in synchronism with the imaging system, a lighting device illuminating the respective area to be imaged is relatively displaced.

A particularly advantageous arrangement for carrying out the method is characterized by one in two perpendicular to one another lying directions parallel to the template and receiving surface displaceable, the template and the receiving surface parallel to each other and immovable against each other holding support and a An optical system that is permanently arranged between the original and the receiving surface and reproduces the original on the receiving surface.

Another particularly advantageous embodiment of the projection arrangement according to the invention is characterized by an in two mutually perpendicular directions displaceable, the Template and the receiving surface side by side in one or in parallel planes holding support and through an optical system consisting of lenses and prisms deflecting the beam in a U-shape, each imaging a sub-area of the original onto a sub-area of the receiving surface.

Another particularly advantageous embodiment of the projection arrangement according to the invention is characterized by an in two mutually perpendicular directions can be displaced, the original and the recording surface parallel and in close proximity to each other as well as immovably against each other holding support and by a lens and prisms for redirecting the beam from the Outside of the template around the support to the outside of the receiving surface, each imaging a partial area of the template on a partial area of the receiving surface, as well as a rigidly arranged to this, between template and receiving surface, preferably consisting of a light guide, a deflecting prism and a bulb lighting device .

Docket ge 970 004 209817/0491

Another advantageous embodiment of the invention according to the ' Projection arrangement is characterized in that an aperture stop between the lenses within the imaging system sharp delimitation of the area shown in each case is arranged.

The invention will then be explained in more detail with reference to the figures. Show it:

Fig. 1 shows a particularly clear embodiment

game of invention;

Fig. 2 is a schematic representation of the scanning of the

entire field to be mapped;

Fig. 3 and 4 particularly advantageous embodiments of the

Invention.

The arrangement shown in Fig. 1 consists of a stationary stand 1 and one in two perpendicular to each other Directions χ and y displaceable support 2. In the stationary stand 1 is a lighting arrangement consisting of an illumination source 3 and a condenser lens 4 and an optical one System 5 arranged, which consists of lenses 6, 7, 8 and 9 and a diaphragm 10. This system consists practically of two microscope tests arranged one behind the other with a common one Intermediate image plane. The common field lens, which images the objectives into one another, consists of two plano-convex lenses with an aperture stop between them. The movable support 2 is by means of Xugel guides 11 and 12 in the direction of the coordinates χ and y arranged to be movable. The shift takes place, for example, by means of electrically actuatable devices (not shown) Fine drives. In the upper part of the U-shaped support 2 is a frame-shaped arrangement 13 for receiving and Holder of a mask 14 is provided. On the lower part of the U-shaped support 2 is an old photo to be exposed

Docket GE 970 004 2 0 9 8 17/0491

coated with tolacke «! Semiconductor wafers 15. The arrangement Is taken so that by the optical system 5 only a great area of the mask 14 is mapped on a corresponding sub-area of the small plate 15 on a scale of 1: 1, on the right side.

In 71g. 2, the circular area surrounded by a thick solid line represents the mask 14 or the half- conductor plate 15. The overall image transferred from the mask to the semi-conductor plate is outlined by the thin line. The image field of the optical system 5 defined by the diaphragm 10 and represented by a hatched square 17 is transmitted by a single exposure when the support is stationary. It is easy to see that the gas-red xu transmitting image field can be transmitted by continuous movement of the central axis 19 of the optical system 5 along the line 18 drawn in FIG.

From the representation according to Flg. 1 is still easy to see, that the resolving power of the optical systems 5, each only has to depict a small sub-area of the total image area to be transferred, a much less technical one Requires effort / than is the case with systems serving for the simultaneous transmission of the entire image area. In addition, there are vibrations of the support in the direction of the xy axes and also in a direction perpendicular to it, provided that the oscillation in the last-mentioned direction is not greater than the depth of field of the optical system 5, uncharacteristic, since it does not affect the sharpness of the image. It should also be pointed out that the partial image designated by 17 in FIG. was rewarded, "for the practical application of the" rfinung "· - With this arrangement, the ratio between the surface is a «« Partial image and the area of the total image in the "" "el et-

Docket 08 970 004

209817/0491

wa between 1 t 50 and 1: 200. A deterioration in the transmitted image can only occur when the support 2 tilts. It is therefore important to ensure that this support is run well in parallel.

The in Fig. 3 shown arrangement provided.

In this embodiment, one is arranged in a stationary manner Stand 21 with "ine" provided by fine drives, not shown, vertically displaceable carrier 29, which is the imaging Contains optical system 25 deflecting the beam path in a U-shape. This optical system consists of lenses 26, 27, 28 and 29 as well as deflecting prisms 40 and 41, an inverting prism 42 and a diaphragm 30 delimiting the image field. The mask 14 to be imaged on the semiconductor wafer 15 coated with a photoresist layer is on one of two mutually perpendiculars Directions (x and y direction) arranged by means of devices, not shown, controllably displaceable support 22. This support consists of a lower part 43 / which is guided by a ball guide 31 from left to right and an upper part 44 which is arranged to be displaceable from the front to the rear by a ball guide 32. The shift takes place via not illustrated, preferably automatically driven arrangements. The parts 43 and 44 have openings 45 and 46 through which the radiation from a lighting arrangement consisting of a lamp 23 and a lens 24 can pass through to the mask 14. The mask 14 is attached to a ring 47. The arrangement is made so that the optical system 25 only one images small sub-area of the mask 14 on the corresponding sub-area of the semiconductor wafer 15 with the correct side, which is ensured by the deflecting prism 42.

The embodiment of the support 22 shown in FIG. 3 has the advantage over the arrangement shown in FIG. 1 that Tilting movements of the support have a much smaller influence

Docket GE 970 004 209817/0491

have on the image good. Otherwise, it is the mask 14 and the support 22 carrying the semiconductor plate 15 to be exposed is moved in the manner indicated in FIG. 2 as in connection with the description of the arrangement shown in FIG. 1. While the in Flg. 3 arrangement shown is almost insensitive to tilting movements of the support 22, can in the Rotational movements occurring in the plane of displacement of the support 22 deteriorate the image quality.

A particularly advantageous embodiment of the inventive concept is shown in FIG. A stander S1 contains a C-shaped optical system which consists of lenses 56, 57, 58, 59, deflecting prisms 70, 71, 72, 75 and a diaphragm 60. Between The lenses 56, 57 are arranged in support 52 which can be displaced in two mutually perpendicular directions by means which are not shown and which can preferably be actuated automatically. This Support consists of a lower plate 73, which is guided by a ball guide 61 from left to right and an upper plate 74, which 1st guided by a ball guide 62 displaceably from the front to the rear. As I said, the plates are moved by not shown, preferably automatically actuatable drive means. An annular element 77 for receiving the mask 14 is provided on the upper plate 74 of the support 52. About that an annular recess for receiving the half-liner 15 is arranged. Between the mask 14 and the semiconductor wafer 15 and their holders, a light guide 76, preferably consisting of a glass fiber bundle, is arranged, the is firmly connected to the stand 51 and which transmits light from a light source 53 to a deflecting prism 78. That of the Light emanating from the light source 53 is guided through the light guide 76 to the deflecting prism 78 and directed through this onto the respective region of the mask 14 to be imaged. The arrangement is like this made that only a small portion of the mask 14 by the optical system 55 on the corresponding portion of the semiconductor plate coated with a photoresist layer 15 is shown. To transfer the entire figure of the

209817/0491 Docket GE 970 004

Mask 14 on the semiconductor wafer 15 is the support 52 ao shifted that the central axis of the optical system, as in Connection with the function of the in FIGS. 1 and 3 shown Arrangements described by the drawn in FIG Line 18 describes the path shown on the semiconductor die and the mask.

Because of the small distance between the mask 14 and your Semiconductor wafers 15 are affected by tilting movements of the support 52 only slightly affects the sharpness of the transferred images. Since in this embodiment the mask 14 and the Platelets 15 are arranged concentrically to one another, rotational movements of the support also have no adverse effect on the quality of the images transferred to the photoresist layer of the semiconductor wafer 15. Since perpendicular to the optical Displacements or vibrations occurring in the axis and movements or in the direction of the optical axis Vibrations, provided their amplitude is not significantly greater than the depth of focus of the optical system, have no significant influence on the quality of the transmitted images this arrangement is largely insensitive to disturbances of any kind.

20981 7/0491 Docket GE 970 004

Claims (8)

PATENT CLAIMS 1. Projektloneverfahren, in particular for the exposure of the Photoresist layer in the production of integrated circuits, characterized in that a template and a receiving surface that cannot be displaced relative to one another are arranged and that a respective sub-area of the template on a sub-area of the receiving surface imaging system is moved relative to these successively over all sub-areas to be imaged. 2. Projection method according to claim 1, characterized in that the imaging system is relative to the original and is continuously moved to the receiving surface. 3. Projection method according to claim 1 and / or 2, characterized characterized in that the imaging system is moved line by line relative to the original and the recording surface. 4. Projection method according to one or more of claims 1 to 3, characterized in that synchronously with the imaging system, a lighting device illuminating the respective sub-area to be imaged is relatively displaced. 5. Arrangement for performing the method according to claims l to 4, characterized by one in two directions perpendicular to each other parallel to the template and receiving surface displaceable, the template and the support (2) holding the support surface parallel to each other and immovably against each other and a support (2) which is fixedly arranged between the template and the support surface, the Template (14) on the receiving surface (15) imaging 2098 1 7/0491
Docket QE 970 004 optical system (5). 6. Projection arrangement stubbornly carrying out the method according to one or more of claims 1 to 4, characterized by a displaceable in two mutually perpendicular directions, the template (14) and the receiving surface (15) side by side in one or in parallel planes holding support (22) and by a prism consisting of lenses and a U-shaped deflecting beam, each part of the original (14) on a partial area of the receiving surface (15) imaging optical system (25). 7. Projection arrangement for performing the method according to one or more of claims 1 to 4, characterized by a displaceable in two mutually perpendicular directions, the template and the receiving surface support (52) and through a made of lenses and prisms for redirecting the beam from the outside of the template (14) to the support Existing outside of the receiving area, one each An optical system (55) which images a partial area of the original onto a partial area of the receiving surface, as well as an rigidly arranged to this, lying between template and receiving surface, preferably made of a light guide (76), an Ural prism (78) and a pear (53) existing lighting device. 8. Projection arrangement according to one or more of claims 5 to 7, characterized in that between the lenses an aperture diaphragm (10, 30, 60) within the imaging system for the sharp delimitation of the respective imaged Area arranged 1st. 209817/0491 Docket GE 970 OO4 Blank page