RU2522769C1 - Method of producing indium microcontacts using positive reversible photoresist - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: semiconductor plate with metal pads for forming indium microcontacts is coated with a layer of positive reversible photoresist which, after exposure through a photomask with a pattern of the microcontacts, is subjected to special heat treatment (image reversal), followed by blanket exposure and development; an indium layer is sprayed onto the obtained negative-profile photoresist mask; the photoresist layer is then dissolved with simultaneous peeling of the indium layer in the gaps between microcontacts (explosion process), leaving the latter on the metal pads.

EFFECT: simple technique and shorter time for making indium microcontacts by lift-off photolithography.

6 dwg

Description

The invention relates to the manufacture of indium microcontacts in matrix photodetectors of infrared radiation and LSI readout of the photo signal.

Currently, a widely used method for the manufacture of hybrid IR MFPs by the method of inverted mounting of photosensitive elements with LSI readout using indium microcontacts.

It is known that one of the common methods for making microcontacts is the reverse photolithography method (“explosion method”, lift-off) [1. V.M. Akimov, E.A. Klimanov, V.P. Liseikin, A.R. Mikertumyants, M.V. Sednev, V.V. Sergeev, I.A. Shelobolin. About the "explosive" method of manufacturing metallization systems and microcontacts in the LSI for reading a photo signal // Applied Physics, 2010, No. 4. 2. Jutao Jiang, Stanley Tsao et. al .. Fabrication of indium bumps for hybrid FPA applications. Infrared Physics and Technology. 45 (2004). 143-151].

The specified method has the following disadvantage:

when forming indium microcontacts of a sufficiently high height (of the order of 10 μm), it is necessary to use a photoresist mask with a negative manifestation angle and a thickness significantly exceeding the thickness of the indium layer, which requires the use of special photoresists not manufactured by the domestic industry.

Another way to obtain a negative angle of manifestation is to use negative photoresists, the disadvantages of which are their low resolution.

A known method of manufacturing microcontacts by creating a metal mask on top of a photoresist layer with the subsequent manifestation of this layer [Shelobolin I.A., Liseikin V.P., Klimanov E.A., Sednev M.V., Mikertumyants A.R. A method of manufacturing indium columns. Patent for the invention No. 2419178], adopted as the closest analogue.

This method allows you to get a negative photoresist profile using a positive photoresist. The disadvantage of this method is a significant complication and lengthening of the process.

The objective of the invention is to create a manufacturing technology of indium microcontacts using positive reversible photoresist, which allows to achieve a simplification of the technology and reduce the time of manufacture of microcontacts by reverse photolithography.

In this case, the property of some positive photoresists is used to reverse the image with the formation of a negative image of the mask.

The technical result is achieved by the fact that a layer of positive reversible photoresist is applied to a semiconductor wafer with metal pads to form indium microcontacts, which, after exposure through a photo mask with a microcontact pattern, is subjected to special heat treatment (image inversion), followed by continuous exposure and development; a layer of indium is sprayed onto the resulting photoresistive mask with a negative profile; then the photoresist layer is dissolved with the simultaneous peeling of the indium layer in the gaps between the microcontacts (the “explosion” process), leaving the latter on metal sites.

The sequence of the technological chain of the proposed method is illustrated in figures 1-6, where:

figure 1 shows the process of exposure of the photoresist through a photomask,

figure 2 shows the heat treatment process of the photoresist,

figure 3 shows the process of continuous exposure of the photoresist,

figure 4 shows the process of manifestation of the photoresist,

figure 5 shows the deposition process of a layer of indium,

figure 6 shows the process of removing a photoresist with a layer of indium in the gaps between the microcontacts.

The figures show the following elements:

1 - photomask,

2 - photoresist layer,

3 - substrate

4 - indium.

A method of manufacturing microcontacts is carried out in the following sequence:

- a layer of reversed positive photoresist is applied to a semiconductor wafer with metal pads for indium microcontacts, followed by drying at a temperature of 95 ° C for 30 minutes;

- the exposure of the photoresist is carried out using a photomask with a given configuration of the contact pads (figure 1);

- the image is converted on the mask of the photoresist using its heat treatment at a temperature of 115-125 ° C for 30 minutes (figure 2);

- a continuous exposure of the photoresist film is carried out with a flash of 200-300 mJ / cm for 50 seconds (figure 3);

- the manifestation of photoresist in a standard developer for positive photoresist (1% KOH solution) is carried out (figure 4);

- a layer of indium of a given thickness is sprayed onto a photoresist mask (figure 5);

- removes the photoresist in a solution of dimethylformamide or a mixture of dimethylformamide with monoethanolamine with the simultaneous removal of indium (Fig.6).

Thus, in this method, for the formation of a photoresist mask with a negative profile, instead of manifesting a positive photoresistor through a metal mask, the manifestation of a positive reversible photoresist without using a metal mask is used.

Claims (1)

A method of manufacturing indium microcontacts using positive reversible photoresist, including the formation of semiconductor wafers with LSI sensors or photodiode arrays of a metal sublayer under indium, the formation of a protective photoresist mask with windows with a negative profile at the points of microcontacts, the deposition of an indium layer, the removal of a protective mask with an indium layer around microcontacts, characterized in that for the formation of a photoresist mask with a negative profile instead of manifesting a positive Through a metal mask, a manifestation of a positive reversible photoresist without using a metal mask is used.

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