Method of lowering of ohmic resistance of indium microcontacts using thermal annealing

FIELD: physics, photography.

SUBSTANCE: invention relates to technology of manufacture of indium microcontacts in IR array photodetectors with photoelectric signal reading LSI circuits. A method of lowering of ohmic resistance of indium microcontacts using thermal annealing with semiconductor wafers with arrayes the LSI circuit of reading or photodiode arrays includes the forming of metal underlayer under indium, forming of protective photoconductivity mask with windows in places of microcontacts, deposition of indium layer, manufacture of indium contacts and annealing of structures in recovery atmosphere or vacuum at the temperature minimum 240°C within 30 minutes.

EFFECT: invention provides manufacture of indium microcontacts with low resistance and high homogeneity of their values within large arrays.

5 dwg

 

The invention relates to the technology of indium point contacts in a matrix photodetectors infrared radiation and BIS reading photosignal.

Currently widely used a method of manufacturing a hybrid IR multi-element photodetectors (mppu) method of the inverted mounting of the photosensitive elements with BIS reading using indium point contacts.

Known methods of making point contacts are:

- inverse lithography ("method explosion, lift-off) [C. M. Akimov, E. A. Klimanov, V. P. Liseikin, A. P. Mikerman, M. C. Sednev in. A. Sergeev, I. A., Shelobolina "About "explosive" method of manufacturing systems metallization and point contacts in BIS reading photosignal" // Applied physics, 2010, No. 4; Jutao Jiang, Stanley Tsao et. al. Fabrication of indium bumps for hybrid FPA applications. Infrared Physics and Technology. 45 (2004) 143-151];

method ion etching;

a method of chemical etching.

There is also known a method of forming a high and homogeneous indium point contacts by the method of melting in pairs weak acid at a temperature slightly above the melting point of indium (~170-200°C) previously created point contacts one of the above methods [J. Jiang, S. Tsao, T. O'sullivan, G. J. Brawn. Infrared Physics and Technology, 45 (2004), p.143-151].

All of these methods have the following drawbacks: when forming the indium point contacts performs the I several operations deposition of metal layers: create a sublayer under the Indies (for example, Cr-Ni, V-Al-V-Mo-Au, Ti-TiN and other) and the coated layer of indium with the subsequent removal India around the point contacts of the various methods mentioned above. When the metallic layers, as a rule, napylyaetsya various methods for deposition of the underlayer is used ion sputtering of the corresponding metal targets, and a layer of indium - method of thermal evaporation. This fact often leads to the impossibility of sequential deposition of all layers in a single vacuum unit without depressurization. Depressurization, in turn, can lead to oxidation of the metal substrate, resulting in increased resistance of indium point contacts with 2-5 1-2 Ohms to ohms and more due to the formation of the barrier layer, and a significant spread of their values in the multi-element structures.

A known method of manufacture of point contacts by creating a metal mask over a layer of photoresist and subsequent manifestation of this layer [I. A., Shelobolina, B. N. Liseikin, E. A. Klimanov, M. C. Sednev, A. P. Mikerman "Method of making indium columns". Patent for invention No. 2419178], adopted as the nearest equivalent.

This method also does not exclude the possibility of oxidation of the metal substrate before the deposition of a layer of India, resulting in increased resistance of the point contacts.

The objective of the invention is to establish what their technology indium point contacts using known methods, listed above, to ensure low resistance indium point contacts and homogeneity of the values within large arrays.

It uses mutual diffusion of indium and the metal substrate at an elevated temperature (>240°C), leading to the destruction of the oxide layer between the metal and a sharp decrease in resistance microcontact.

The technical result is achieved by the fact that the semiconductor wafer by vacuum deposition is made of a metal pad (sublayer) for the formation of indium point contacts, put a layer of positive photoresist, which after exposure through a photomask with a pattern of boxes under the point contacts and the manifestation of the sprayed layer, India, by photolithography to form a mask for etching of India and produce etching India one of the following methods; then remove the layers of photoresist and conduct annealing structures in a reducing atmosphere (for example, H2or vacuum at a temperature far above the melting point of indium (not less than 240°C) for at least 30 minutes.

In another embodiment, on a semiconductor wafer put a layer of positive photoresist, which after exposure through a photomask with a pattern of boxes under the point contacts and the manifestation of the sprayed metal layers (sublayer), and ZAT is m layer of indium (in another setting or time interval), by photolithography to form a mask for etching of India and produce etching India one of the following methods; then remove the layers of photoresist and for at least 30 minutes to carry out the annealing structures in a reducing atmosphere (for example, H2or vacuum at a temperature far above the melting point of indium (not less than 240°C).

The sequence of the technological chain of the proposed method is illustrated in Fig.1-5, where:

in Fig.1 shows the process of exposing the photoresist through the photomask;

in Fig.2 shows the heat treatment process of the photoresist;

in Fig.3 shows the process of spraying India;

in Fig.4 shows the process of dissolution of the photoresist;

in Fig.5 shows the process of annealing of point contacts.

On the figures presents the following elements:

1 - the photomask;

2 - the layer of photoresist;

3 - substrate;

4 - Indies.

The manufacturing method of point contacts is performed in the following sequence:

- on semiconductor wafer with a metal sites for indium point contacts a layer of positive photoresist, followed by drying;

- is the exposure of the photoresist using a photomask with a predetermined pattern configuration of the pads (Fig.1);

- is the manifestation of the photoresist in a standard developer for POS is the positive photoresist (1% KOH solution) (Fig.2);

- is the deposition of a layer of indium specified thickness on a mask of photoresist (Fig.3).

Next is the formation of indium point contacts one of the methods (Fig.4):

- dissolution of the lower layer of photoresist with simultaneous destruction of India (method of explosion);

- etching method, for which:

- is the formation of a photoresist mask for trawling India;

- etching is carried out, India is one of the known methods (chemical, ion) to form point contacts;

- remove the photoresist in a solution of dimethylformamide, or a mixture of dimethylformamide with monoethanolamine, or plasma-chemical etching in an oxygen plasma.

Next, annealing is carried out structures in reducing atmosphere or vacuum at a temperature of at least 240°C (Fig.5) within 30 minutes.

The way to reduce the ohmic resistance of indium point contacts using thermal annealing on the semiconductor wafer with matrices BIS reading or photodiode matrices, including the formation of the metal sublayer under the Indies, the formation of a protective photoresistive mask with Windows in the places of point contacts, the plating layer, India, manufacturer of indium point contacts one of the methods:
- the removal of the protective mask with a layer of India around the point contacts (method of explosion),
- formation of a mask for travlin the I layer, India followed by etching of the layer of one of the known methods (chemical etching, ion etching) with subsequent removal of the layer of photoresist,
characterized in that after the formation of a system of point contacts is annealing structures in reducing atmosphere or vacuum at a temperature of at least 240°C for 30 minutes.



 

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