SU516210A1 - Photomask - Google Patents

Description

one

The invention relates to electronics, in particular to the design of auxiliary devices used in the manufacture of integrated circuits and semiconductor devices.

A photomask is known which contains a glass substrate, on the surface of which a two-layer pattern of masking materials is made.

However, the well-known photomask with thickened edges along the perimeter of the copied pattern has the following disadvantages: during operation of the photomask the edge of the pattern to be copied is subjected to friction against the contact surface of the microcircuit; low resolution due to the diffuse edge of the replicated pattern formed during the diffusion of copper into the glass base of the photomask; an increased concentration of defects in a single layer coating, especially in the middle part of the copied elements; low contrast of the masking transparent elements in the visible region of the spectrum (it is complicated to combine the photomask pattern with the elements of integrated circuits).

In order to increase the wear resistance of the photomask, the resolution and accuracy of the combination in the proposed photomask, the elements of the upper layer are identical in

the elements of the lower layer are smaller in size, and the symmetry of the corresponding elements of the two layers are the same; in addition, the lower layer is made of a material that is transparent in the visible and opaque in the ultrapholethosis and the upper layer is made of opaque in the aforementioned spectral regions, for example, from silicon and a nickel-phosphorus alloy, respectively.

The drawing shows the proposed photomask with glass poppy 1, a transparent (replicated) pattern 2, an opaque (protective) pattern 3.

During the operation of such a photomask, the friction of the edges of the transparent pattern, which determine the accuracy of reproduction of a given copy, on the exposed surface of the IC substrate, is eliminated, and thereby ensures a high wear resistance of the photomask. On the other hand, the execution of the edges of the copied pattern of the photomask on one layer determines its high resolution. The thickness of the masking layer that is transparent to the visible region of the spectrum can be very small (100-1000 A °); it is usually optimized in accordance with the optical characteristics of the masking material and the UV lamps used in the blueprint processes. The photo template withstands about 500 contacts without any changes. The very structure itself makes it possible to produce on the surface of oxidized silicon wafers copies of the pattern with blank areas 2.5 μm wide, with a stroke width of 2.5 μm with an edge unevenness not exceeding +0.3 μm.

A film of silicon was thermally sprayed onto the surface of a plane-parallel billet. After that, the metallized preform is successively treated in a solution of chromicum — 5 minutes, distilled water — 5 minutes, distilled running water — 10 minutes, and dried to remove traces of nitric acid at 120–150 ° C for 15 minutes.

After preparation, the substrate is subjected to sensitization, for example, in a solution of tin chloride 40 g / l and HCl 40 ml for 2-5 minutes, washed from traces, activated in an acidified solution of palladium chloride 1-2 g / l or another solution containing: salts of platinum group metals. Then it is thoroughly washed off traces of palladium ions (or ions of another activator) in distilled water. After drying at a temperature of 120 ° C, glass is manganized for 60-120 seconds to a solution of the following composition, g / l:

Nickel sulfate18,0

Sodium hypophosphite 7.5

Sodium acetic acid7.5

Solution temperature 72-75 ° C; The pH of the solution is 4.5-5 (adjusted with acetic acid). You get a film with a thickness of 0.1-0.3 microns.

Annealing of metallized substrates is carried out at 300-350 ° C in an inert environment, for example, in argoe for 3-4 hours or in vacuum not lower than 2-3-10 mm Hg. Art. within 2-3 hours In both cases, samples are cooled with the furnace.

As a result of the aforementioned technology, a double-layered stitch is obtained, the low translucent layer of which is inert to the etchant, which dissolves the upper layer. After photolithography and etching of the upper layer (chemically precipitated nickel-phosphorus alloy) in the etchant composition, ml:

Water250.0

Glycerol 150.0

Nitric acid450,0

Sulfuric Acid150.0

Photolithographic defects are found in the top layer of the photomask, which are eliminated by retouching with an acid-resistant marking paint. After drying, the lower silicon film is etched with a solution at 60-70 ° C for 2 hours: nitric acid 10-100 parts, hydrofluoric acid, 1 part of which etches the upper layer. The amount of undercutting is adjusted depending on the complexity of the circuit by the ratio of nitric and hydrofluoric acids. The dimensions and evenness of the edge are determined by the elements formed in the lower layer of the silicon film (base film).

Claims (2)

1. A phototemplate containing a glass substrate, on the surface of which a two-layer pattern of masking materials is made, characterized in that, in order to increase the durability of the photomask, resolution and alignment accuracy, the elements of the upper layer pattern are identical in shape to the elements of the lower layer pattern, but less their area, and the symmetry axis of the corresponding elements of the pattern of both layers coincide. 2. The photo pattern according to claim 1, characterized in that the lower layer is made of a material that is transparent in the visible and non-transparent in the ultraviolet region of the spectrum, and the upper layer is made of a material that is opaque in the aforementioned spectral regions, such as silicon and nickel alloy with phosphorus, respectively.