RU2339116C1 - Method for manufacturing chips of power nitride uhf-transistors - Google Patents

Abstract

FIELD: electricity, semiconductors.

SUBSTANCE: invention is attributed to manufacturing technology for semiconductor devices and can be used in manufacturing of power UHF-transistors using heterostructures on the base of the III group nitrides. Essence of invention: in the method for manufacturing the chips of power UHF-transistors containing epitaxial plate manufacturing, dielectric carrying plate manufacturing, overlapping of the epitaxial plate and the dielectric carrying plate, dividing the epitaxial plate and the dielectric carrying plate into separate elements and forming the chips, dividing the epitaxial plate and the dielectric carrying plate into separate elements is performed after overlapping of the epitaxial plate and the dielectric carrying plate.

EFFECT: prevention of redistribution of residual mechanical stresses in the epitaxial heterostructure/sapphire base-plate system forming epitaxial plate when he latter is divided into separate elements (chips) and providing of retention of electrophysical characteristics of epitaxial heterostructure.

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Description

The invention relates to a technology for the production of semiconductor devices and can be used in the manufacture of high-power microwave transistors using heterostructures based on group III nitrides.

Group III nitrides have the maximum band gap among related compounds A3B5, high thermal, chemical, and radiation resistance. For this reason, nitride heterostructures are suitable for manufacturing opto - and microelectronic devices of increased power, the active region of which is heated to 300-750 ° C during operation. At the same time, the technological difficulties in obtaining bulk crystals of group III nitrides are the reason that there is currently no mass production of substrates from these materials worldwide. Practically all applied developments of nitride devices are based on the use of foreign substrates, to some extent mismatched with group III nitrides in terms of the lattice parameter and thermal expansion coefficient. The most common and commercially viable option for mass production is the use of sapphire substrates that provide sufficient quality nitride heterostructures and devices based on them at a relatively low cost of manufacture. However, sapphire substrates have low thermal conductivity, limiting the power capabilities of devices due to overheating of the active region in conditions of insufficient heat removal. To achieve the necessary performance characteristics of high-power nitride microwave transistors, epitaxial heterostructures grown on sapphire substrates are mounted on dielectric carrier plates equipped with means for heat removal.

A known method of manufacturing nitride semiconductor devices based on GaN, including the manufacture of an epitaxial plate by growing a semiconductor heterostructure on a sapphire substrate, separation of the obtained epitaxial plate into individual active elements (chips), subsequent attachment of chips to a heat-conducting dielectric carrier plate, thinning or removal of a sapphire substrates on the back of the heterostructure, separation of the carrier plate with attached chips into individual elements and their packaging, WO 2006065046 A1. The method can be used for the manufacture of nitride microwave transistors, however, its significant disadvantage is the consequences of preliminary separation of the epitaxial plate into separate elements, as well as thinning (removal) of the sapphire substrate of individual elements. Sapphire substrates of epitaxial plates are chemically and mechanically stable, and the methods used for their separation into chips (diamond cutting, diamond cutting or laser cutting), as well as their thinning (removal), often lead to redistribution of mechanical stresses in the heterostructure / substrate system. In nitride transistor heterostructures with a two-dimensional electron gas, subject to the influence of internal polarization fields, a change in the residual mechanical stresses leads to a change in the electrophysical characteristics of the active layer of the heterostructure, and often to their complete degradation (the disappearance of a two-dimensional electron gas).

There is also a known method of manufacturing chips of high-power nitride microwave transistors, which includes the following operations: manufacturing an epitaxial plate, dividing it into separate elements (chips), manufacturing a dielectric carrier plate, attaching an epitaxial plate with individual elements to a dielectric plate, dividing the dielectric plate into individual elements, corresponding to epitaxial plate elements attached to a carrier plate, R. Vandersmissen, W. Ruythooren, J. Das, M. Germain, D. Xiao, D. Schreurs and G. Borghs, "Transfer from MHEMT to GaN HEMT Techn ology: Devices and Integration ", International Conference on Compound Semiconductor Manufacturing Technology (MANTECH), New Orleans, Louisiana, USA, pp. 237-240, April 11-14, 2005.

This method is adopted as a prototype of the present invention. The prototype, like the analogue described above, has the same drawback caused by the preliminary separation of the epitaxial plate into separate elements: an undesirable redistribution of residual mechanical stresses in the epitaxial heterostructure / sapphire substrate system, and, as a result, a change in the electrophysical characteristics of the active layer of the heterostructure or even its complete degradation (disappearance of two-dimensional electron gas). Often during preliminary separation of the epitaxial plate into separate elements and when the sapphire substrate of individual elements is thinned (removed), the epitaxial plate is physically destroyed.

The objective of the present invention is to prevent the redistribution of residual mechanical stresses in the epitaxial heterostructure / sapphire substrate system forming the epitaxial wafer when the latter is divided into separate elements (chips) and thereby ensure the electrical properties of the epitaxial heterostructure are preserved.

According to the invention, in a method for manufacturing chips of high-power microwave nitride transistors, including manufacturing an epitaxial plate, manufacturing a dielectric carrier plate, attaching an epitaxial plate to a dielectric carrier plate, separating the epitaxial plate and dielectric carrier plate into separate elements and forming chips, separating the epitaxial plate and the dielectric carrier plate on the individual elements and the formation of chips is carried out after attaching the epitaxial plates to the dielectric carrier plate.

The applicant has not identified sources containing information about technical solutions identical to the present invention, which allows us to conclude that it meets the criterion of "novelty."

Due to the fact that the epitaxial plate is not divided into separate elements previously, but simultaneously with the dielectric carrier plate, with which the epitaxial plate is previously firmly connected to form a monolithic block, the epitaxial heterostructure, being in the monolithic block, acquires increased resistance to mechanical stress; this provides a very important technical result, which consists in the fact that the redistribution of residual mechanical stresses in the epitaxial heterostructure / sapphire substrate system is almost completely prevented and the electrophysical characteristics of the active layer of the heterostructure are maintained.

In all methods known to the applicant for manufacturing chips of high-power microwave nitride transistors, the epitaxial plate was attached to the carrier plate in the form of separate parts previously obtained by separating the epitaxial plate with all the ensuing negative consequences. The applicant has not identified any sources of information that would contain information about the distinguishing features of the present invention and their connection with the achieved technical result. This allows us to conclude that the claimed invention meets the criterion of "inventive step".

The method is illustrated by schematic drawings, which depict (in longitudinal section):

figure 1 - epitaxial plate;

figure 2 - dielectric carrier plate;

figure 3 - dielectric carrier plate with contacts;

figure 4 - epitaxial plate, combined with a dielectric carrier plate;

figure 5 - epitaxial plate attached to a dielectric carrier plate;

in Fig.6 is the same as in Fig.5, made thinning of the sapphire substrate of the epitaxial plate;

in Fig.7 - the same as in Fig.6, interconnected plates are divided into separate elements (chips);

on Fig - chips with attached heat sink elements.

The claimed method is implemented as follows.

An epitaxial plate is made (Fig. 1), for which an epitaxial nitride heterostructure 2 is grown on a sapphire substrate 1, and then elements 3 of the instrument topology are formed on it using standard planar operations. Then, a dielectric carrier plate 4 (FIG. 2) is made from a dielectric material, in particular polycor, and through holes 5 of small diameter are made in it, the arrangement of which corresponds to the arrangement of elements 3 of the instrument topology of the epitaxial plate, and through holes 6 of larger diameter located in areas of inter-instrument isolation. Then, photolithography method makes contacts 7 (Fig. 3), the arrangement of which corresponds to the arrangement of elements 3. Next, the epitaxial plate is combined with a dielectric carrier plate, while the elements of the instrument topology 3 are combined with contacts 7 (Fig. 4). After that, the space between the plates is filled through the holes 6 with a heat-conducting self-hardening compound 8. As a result, the epitaxial heterostructure 2 is enclosed in a durable “sandwich” formed by the substrate 1 and the plate 4 (Fig. 5). Then, the sapphire substrate 1 is thinned by means of a chemical-dynamic method and a thin metal coating is applied to it (not shown in the drawings) (Fig. 6). Then the resulting structure (block) is separated, for example, by cutting with a diamond disk into individual elements - chips, as shown in Fig.7. After that, heat transfer elements 10 are attached to the thin metal coating of each chip using standard solder 9.

The claimed method allows the manufacture of chips while providing increased stability of the epitaxial heterostructure, prevents the residual mechanical stress and allows you to save the electrical characteristics of the epitaxial heterostructure and manufactured chips.

Claims (1)

A method of manufacturing chips of high-power nitride microwave transistors, including the manufacture of an epitaxial plate by growing an epitaxial nitride heterostructure on a sapphire substrate and forming elements of a transistor topology on it, manufacturing a dielectric carrier plate, combining the epitaxial plate and the dielectric carrier plate, separating the epitaxial plate and the dielectric plate -carrier into individual elements and chip formation, characterized in that the separation of epitaxial Lastin and dielectric carrier plate into separate elements and the formation of chips is performed after the alignment of the epitaxial wafer and the dielectric carrier plate.

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