DE2454750B2 - Method and arrangement for the production of image patterns for masks of integrated circuits by means of aberration-free pixels of point holograms - Google Patents

Description

The present invention relates to a method and an arrangement for manufacturing Masks for integrated circuits (IC), which consist of a large number of identical image patterns, using point holograms.

The use of point holograms for the production of IC masks is z. B. from the article »G. Groh: "Multiple Imaging by Means of Point HoIograms" in Appl. Optics, 7 (1968), p. 1643.

Point holograms are special holograms that can multiply a point light distribution in the reconstruction structure. In image multiplication (IC mask manufacturing), the reference source is replaced with an illuminated object (single IC circuit pattern). Instead of the point spreads, an corresponding place the multiplied images of the object. Due to the imaging errors (astigmatism, field curvature and distortion) that occur in the holographic multiplication occur, the usable object field and the image field of the multiplication are limited, see G. Groh, C. H. F. Velzel: "Sources of error in holographic image multiplication", Optik 30 (1969), p. 257. bS

With the requirements of IC technology that still applied a few years ago (single image field approx. 3 χ 3 mm ² , total image field approx. 50 χ 50 mm ² , resolution approx.

3001p / mm), the distortion could be reduced to an acceptable level by means of specially corrected lens systems, with today's LSL (Large Scale Integration) technology with single image (5 χ 5 mm ² ) and total image field sizes (> 80 χ 80 mm ² ) and 1 ^ structures (> 500 lp / mm), however, error correction is no longer possible.

The object of the invention is to provide a method in which when using conventional Objective aberrations are avoided, and it is solved by the image pattern through Juxtaposition of aberration-free, multiplied image points of a point hologram are generated, in such a way that the points are modulated in their intensity according to a preselected program and on a slidable receiving plate serving as a mask, the sequence of movements of which is coordinated with the intensity modulation, can be written in.

The point hologram does not multiply entire individual IC patterns, but only individual pixels which the pattern by programmed HelJ dark control of the pixels and z. B. is built up by meandering displacement of the recording plate, e.g. photo plate. A single point can help with of a point hologram can always be imaged and multiplied without aberrations.

With new point holograms that can be recorded by extensive structures - which have a very narrow autocorrelation Points of about 1 μπι 0 generated and structures of 1 μπι width can be "written".

No high demands are made on the imaging system required for this, only one single point (1 μπι 0) must be transferred, in contrast to conventional manufacturing processes of IC masks (“step and repeat” method), in which the same requirements for image quality are met by a extended image field (several mm) apply. Such lenses are commercially available. With the new one In the process, the image field can be of any size, it is always error-free. The writing speed grows with increasing bilufield size, but can also be due to the large overall field of view that is also possible and the The associated high rate of multiplication of the point hologram can again be partially compensated for. To keep the writing speed as low as possible hold, larger structures in the IC pattern can also be exposed with a larger point size, since the Image errors for points in the vicinity of the aberration-free image points are also very small.

The components to be used for the process, such as L.B. laser as an exposure source, light modulator for controlling the laser beam (light-dark), lens systems for focusing the laser beam and measurement-controlled cross table for moving the receiving plate (e.g. photo plate) are inherent known. The table movement is equal to the length of an individual pattern (mm range) and is therefore much smaller than with the "step and repeat" method, where the entire mask has to be moved. The requirements are therefore much lower.

With the new method there is basically the possibility of using the previously used relatively cumbersome and time-consuming method for the production of Circuit masks (production of the template - reduction stage - 2nd reduction stage and multiplication on the »repeater«) and replace it with a direct method. The point-by-point production

offers greater flexibility in mask generation.

The invention is explained in more detail with the aid of the figures of the drawings.

It shows

1 shows a schematic diagram for multiplication with a point hologram,

2 shows the distortion caused by the point hologram,

3 shows an exemplary embodiment of the “point hologram image pattern generator”. 1Ü

Fig. 1 shows a holographic image multiplication structure. The object point P is imaged with the imaging lens L \ in the reference point Pr (dashed beam path). The point hologram H behind the lens L \ multiplies this point into many identical points P ₅ (solid beam paths), the position of which is determined by the positions of the point light sources when the hologram // is recorded

FIG. 2 shows the distortion occurring in a point hologram in the f and % directions. The distortion is through

Ai =

An =

-, ftan ² "

- η tan ² α

25th

given. The dimension of the rod change caused by the distortion is three times as large in the! -Direction as in the direction of the η- coordinate. A square (dashed) is distorted into a rectangle (solid), as shown in FIG. 2 is shown greatly exaggerated.

The angle α in the formula is the angle between the reference point Pr and the signal point Ps considered in each case (FIG. X). The distortion increases with increasing image angle x.

The mapping of the reference point Pr in the signal point Ps (£ = 0, Tj = 0), on the other hand, is aberration-free and is used in the following arrangement to generate image patterns.

The basic structure of a “point hologram image pattern generator” is shown in FIG. An argon ion laser Q (λ = 0.457μπι) can be used to expose not only photographic materials but also conventional photographic materials (e.g. SHIPLEY AZ 1350).

The laser beam LS is modulated in its intensity (signal S) by a modulation cell Mo. B. programmed on a punched tape With this punch a core memory is programmed, which in turn controls the modulator Mo via a signal generator G. With the lens system Li (telescopic system) the laser beam LS is focused in a nulker mode in point P. The diameter of this point can be on a Value in the order of magnitude of the light wavelength (approx. 1 μm) can be reduced. With the lens system L \ the point P is mapped to Pr. The point hologram H immediately behind the line L \ multiplies this point into many (3 points in the sketch) identical Büdpunkt Ps. These lie in the ΛΎ-plane and have their focus on the mask Ma (e.g. a photo plate). The points are stationary and are only controlled light-dark with the help of the modulator Mo. To "write" a pattern, the mask Ma is moved on a cross table T which is measurement -controlled in the x and ^ directions. automatically and in y-direction at the start-stop operation (movement W) according to any one to the modulator MO.. "program tuned off. The screen section MaS schematically shows a program written with the signal 5 points patterns. The mask Ma was in x -Direction moved The signal 5 (1) expose; the photographic material (black point e.g. Ps (I)). Unexposed (light point e.g. Ps (O) the mask Ma remains at signal 5 (0). At For a new line, the mask Ma is shifted by one pixel diameter in the y-direction (point Ps drawn interrupted). Then the new line can be "written" in the ^ -direction. By repeating this process, entire IC individual patterns are generated. In practice the points are overlapped icht so that straight edges result.

Several arrangements can also be put together to form a unit, with each arrangement operated with a different intensity modulation, while a common displacement system is provided for the mounting plates, so that at the same time different image patterns - whole Mask sets - can be made.

For this purpose 3 sheets of drawings

Claims (5)

Patent claims: 1. Process for the production of masks for integrated circuits (IC), consisting of a multitude of s identical image patterns exist, by means of point holograms, characterized in that the image patterns are generated by juxtaposing aberration-free multiplied image points of a point hologram, such that the points are modulated in their intensity according to a preselected program and on a sliding plate serving as a mask, whose The sequence of movements is coordinated with the intensity modulation. is 2. The method according to claim 1, characterized in that the sequence of movements of the receiving plate ejne xy displacement 1st 3. The method according to claim 1 or 2, characterized in that several arrangements to one Unit composed and with a different intensity modulation for each arrangement be operated while a common displacement system is provided for the receiving plates 4. The method according to claim 1 or one of the following, characterized in that the laser light beam is modulated by a signal generator which at the same time controls the movement of the mounting plate 5. Arrangement for performing the method according to one of the preceding claims, characterized characterized in that a point hologram is attached behind the optics, as well as a measurement-controlled one Cross table, the movement of which can be controlled by a signal generator, which is also the Controls the laser light beam with a modulator installed in front of the optics