Method for producing high-power microwave transistors

FIELD: electronic engineering; high-power microwave transistors and small-scale integrated circuits built around them.

SUBSTANCE: proposed method for producing high-power microwave transistors includes formation of transistor-layout semiconductor wafer on face side, evaporation of metals, application and etching of insulators, electrolytic deposition of gold, formation of grooves on wafer face side beyond transistor layout for specifying transistor chip dimensions, thinning of semiconductor wafer, formation of grooves on wafer underside just under those on face side, formation of through holes for grounding transistor leads, formation of integrated heat sinks for transistor chips around integrated heat sink followed by dividing semiconductor wafer into transistor chips by chemical etching using integrated heat sinks of transistor chips as mask.

EFFECT: enhanced power output due to reduced thermal resistance, enhanced yield, and facilitated manufacture.

2 cl, 1 dwg, 1 tbl

 

The invention relates to electronic devices, and in particular to methods of manufacturing of the power transistors microwave and MIS based on them.

The known method of manufacturing of the power field-effect transistors (VTS) microwave oven, comprising the following operations:

- formation on a semiconductor wafer - epitaxial structure of gallium arsenide topology with using electronic and photolithography, deposition of metals, deposition and etching of dielectrics, galvanic deposition of gold;

- thinning semiconductor wafer to 60-80 microns;

- formation of a through-hole for grounding the sources of transistors;

galvanic deposition of gold with a thickness of 2 μm on the back side of the semiconductor wafer;

- the separation of the semiconductor wafer on the crystals transistors sharp diamond disks (1).

The disadvantages of this method are the low power field-effect transistor due to the high thermal resistance due to the large thickness of 60-80 μm semiconductor wafer of gallium arsenide, the low yield due to mechanical damage, chips and cracks on the split operation semiconductor wafer sharp diamond disks.

The known method of manufacturing of the power field-effect transistors microwave and IIA on the basis of the prototype, including the following basic operations:

- is formirovanie on the semiconductor plate the epitaxial structure of gallium arsenide topology with using electronic and photolithography, deposition of metals, deposition and etching of dielectrics, galvanic deposition of gold;

- thinning semiconductor wafer of gallium arsenide to a thickness of 25-30 μm;

galvanic deposition of integral heat sink made of gold with a thickness of about 30 μm on the back side of the semiconductor wafer of gallium arsenide;

- the separation of the semiconductor wafer of gallium arsenide on the crystals transistors sharp diamond disks (2).

The thinning semiconductor wafer of gallium arsenide to a thickness of 25-30 μm allowed compared with the previous method to reduce thermal resistance of the VTS, and consequently, to increase its capacity.

However, on the other hand, when the separation of the semiconductor wafer on the crystals transistors to ensure its strength is required to glue a thin semiconductor wafer on a flexible carrier, which complicates the method.

And the separation of the semiconductor wafer on the crystals transistors sharp diamond disks, as in the previous method, causes mechanical damage, chips or cracks, which defines a low percentage of yield.

In addition, the process of dividing plates for crystals, including when cutting integralov the heat sink made of gold with a thickness of about 30 μm is fast "clogging" of the cutting tool and the formation of gold "collar" around the perimeter of the crystal transistor. This causes difficulties in subsequent mounting of the crystal of the transistor in the circuit of the microwave, which can have a negative impact on the yield of microwave circuits and their electrical characteristics.

The technical result of the invention is to increase capacity by reducing thermal resistance, increased yield and simplify the method of manufacturing of the power transistors microwave.

The technical result is achieved by the fact that in the known method of manufacturing of the power transistors microwave oven, comprising forming on the front side of the semiconductor wafer topology transistors using electronic and photolithography, deposition of metals, deposition and etching of dielectrics, galvanic deposition of gold, the thinning of the semiconductor wafer to a thickness less than 30 μm, etching the semiconductor wafer through the grounding holes for the pins of the transistors, the galvanic deposition on the back side of the semiconductor wafer of the integrated heat sink of gold of a thickness exceeding 30 μm, the separation of the semiconductor wafer on the crystals, transistors, before thinning semiconductor wafer on its obverse outside of the topology of the transistors form a groove depth of 5-10 μm and a width of 70-100 μm to specify the size of crystals, transistors, and after thinning the semiconductor is of a plate form a groove on its underside a depth of 5-10 μm directly under the grooves on the front side, the ratio of their width equal to 3-2, and form a groove by using photolithography and etching, after forming the integral heat sink forms an integral heatsinks crystals transistor by photolithography on the integral heat sink with its subsequent etching in the locations of the grooves on the back side of the semiconductor wafer, and dividing the semiconductor wafer on the crystals transistors carried out by chemical etching, with integral heatsinks crystals transistors serve as the mask.

As a semiconductor wafer using, for example, a wafer of gallium arsenide.

The formation of grooves on the front and back side of the semiconductor wafer opposite to each other and with predetermined dimensions in conjunction with a different sequence of operations allowed:

first, divide the semiconductor wafer on the crystals transistors when possible, the use of an integral heat sinks crystals transistors as a mask, chemical etching and thus avoid mechanical damage, chips or cracks in the case of use in the separation of the diamond cutting discs and, as a consequence, to increase the yield,

- secondly, to improve the reproducibility of the size of the crystals, which reduces the tolerances when mounting to the of Estella transistor in the circuit of the microwave and thereby reduce losses in the supply chain, therefore, to increase power,

- thirdly, to improve the quality of the installation due to the reduced thickness of the solder or glue used in the Assembly of the crystal of the transistor in the circuit of the microwave, which became possible due to the elimination of gold "collar" around the perimeter of the transistor crystal that occurs when cutting a semiconductor wafer with a diamond disk, and thereby reduce thermal resistance and, as a consequence, in addition to the above, to increase power,

- fourth, to ensure the reproducibility of the size of the crystals of the transistor due to the specified size of the grooves on the front and back side of the semiconductor wafer and removing gold "collar", and therefore, further increase the yield,

- fifthly, to simplify the method of manufacturing a separating semiconductor wafers by chemical etching and exceptions diamond cutting discs.

The formation of grooves on the front side of the semiconductor wafer and the back side of her depth is less than 5 μm is not sufficient for the subsequent set the size of the crystal, and more than 10 μm is undesirable because of the possible destruction of the plate for subsequent technological operations.

The formation of grooves on the front side of the semiconductor wafer of a width of less than 70 μm is unacceptable, as shown is the ratio of their width-the width of the grooves on the back is so small, that the conduct of subsequent operations is the formation of integral heatsinks crystal transistors and the separation of the semiconductor wafer on the crystals of the transistors becomes difficult, and more than 100 microns is impractical because of excessive consumption of a semiconductor material.

The ratio of the width of the grooves on the front and back side of the semiconductor wafer is determined by its residual thickness under the groove and the ratio of the speed of etching in the lateral and vertical direction.

Based on the above, for a given thickness of the semiconductor wafer is less than 30 μm, it is 3-2.

The invention is illustrated in the drawing,

where given the stage of separation of the semiconductor wafer fragment in the crystals of the transistor, where

- semiconductor plate 1,

the topology of the transistor 2,

- groove on the front side of semiconductor wafer - 3,

the groove on the back side of the semiconductor wafer - 4,

- the grounding hole of the findings of the transistor 5,

- integral heat sink on the transistor crystal - 6,

- powerful crystal transistor microwave - 7

Specific example:

on the front side of the semiconductor wafer 1, for example of gallium arsenide with a thickness of 520 μm form the topology of the transistor 2 known methods: the electron is Oh and photolithography, spraying of metals, deposition and etching of dielectrics, galvanic deposition of gold,

next on the front side of the semiconductor wafer 1 outside of the topology of the transistor 2 is formed of the groove 3 a depth of 8 μm and a width of 85 μm to specify the size of the transistor crystal also known methods of photolithography and etching,

next plunge semiconductor plate 1, to which it is adhesively bonded to the carrier, for example, glass with ploskoparallyel less than 1 μm and methods mechanical polishing bring her a thickness of 120 μm, then perekleivat semiconductor wafer on a carrier of sapphire and chemical-dynamic polishing plunge her to a thickness of 25-30 μm,

- form the grooves 4 a depth of 8 μm and a width of 56 on the back side of the semiconductor wafer are also known methods of photolithography and etching,

- form the ground through holes 5 for the conclusions of the transistors are also methods of photolithography and chemical etching,

- form an integral heat sink galvanic deposition of gold with a thickness of 25-30 μm,

- form an integral heat sink on the transistor crystal 6 by photolithography on the integral heat sink followed by etching in the location of the grooves 4 on the back side of the semiconductor wafer 1,

- divide the semiconductor wafer 1 on Chris is Alla transistors 7, why using integral heat sink on the transistor crystal 6 as a mask, poison semiconductor wafer of gallium arsenide 1 in the locations of the grooves 4 on the reverse side.

Thus, we have the media of the sapphire separated crystals of powerful transistors UHF, who take off from a carrier in organic solvents.

Examples 2-3.

Analogously to example 1 produced powerful microwave transistors, but with grooves on the front and back depth of 5 and 10 μm and a width on the front side 70 and 100 microns and the back side 46 and 66, respectively.

Examples 4-5.

Analogously to example 1 produced powerful microwave transistors, but with grooves on the front and back depth is less than 5 and more than 10 μm and a width on the front side is less than 70 and more than 100 microns and a width on the back side of 40 and 74, respectively.

On prepared samples of powerful transistors microwave was conducted by visual examination under a microscope LEICA INM 100 to mechanical damage, chips, cracks, reproducibility of crystal sizes of the transistors.

On the manufactured samples of high-power microwave transistors was measured power.

The data are summarized in table.

As can be seen from table microwave transistors manufactured according to the proposed method (examples 1-3) have more power than the power transistor UHF prototype p is row 10 percent and the reproducibility of the size of the crystals of the transistor 90 percent versus 70 percent in the prototype.

When forming the grooves on the front and back side of the semiconductor wafer depth, beyond that which is specified in the claims observed:

or low vosproizvodimosti (example 4) and, consequently, reducing power and yield,

or destruction of the plate (example 5).

Thus, the proposed method of manufacturing of the power transistors microwave will allow for a comparison with prototype:

- first, to reduce thermal resistance and thus increase the power transistor UHF ten percent

- secondly, to increase the yield by eliminating mechanical damage, chips, cracks and increase the reproducibility of the size of the crystals.

- third, to simplify the method of manufacturing the diamond cutting disk.

The proposed method for the manufacturing of the power transistors microwave can be used in the manufacture of MIS microwave based on them.

SOURCES of INFORMATION

1. Ivashchuk AV, Barefoot V., Kovalchuk NR. Microwave field-effect transistors medium power millimeter waves. The technology and design of electronic equipment. No. 6, 2003, p.27-31.

2. Handbook of Microwave and Optical Component Vol 2, 1990, Fabrication processes, p.518-523.

№ p/pThe depth of the groove on the front side of poluprovodn the ikovoy substrate, mcmThe depth of the groove on the back side of a semiconductor substrate, mcmThe width of the grooves on the front side of a semiconductor substrate, mcmThe width of the grooves on the reverse side, µm and the ratio of their width 3-2Power transistorsThe yield
1888556Increase power 10%The reproducibility of the size of the crystals of the order of 90%. No mechanical damage, chips, cracks
2557046Increase power 10%The same thing
3101010066Increase power 10%The same thing
4336040Power reductionThe decrease in the percentage yield of the order of 10%
5121211074Destruction plate
6the placeholder100%The reproducibility of the size of the crystals does not exceed 70%. Observed the fast mechanical damage, chips, cracks

1. A method of manufacturing a powerful microwave transistors, comprising forming on the front side of the semiconductor wafer topology transistors using electronic and photolithography, deposition of metals, deposition and etching of dielectrics, galvanic deposition of gold, the thinning of the semiconductor wafer to a thickness less than 30 μm, etching the semiconductor wafer through the grounding holes for the pins of the transistors, the galvanic deposition on the back side of the semiconductor wafer of the integrated heat sink of gold of a thickness exceeding 30 μm, the separation of the semiconductor wafer on the crystals, transistors, characterized in that before thinning semiconductor wafer on its obverse outside of the topology of the transistors form a groove depth of 5-10 μm and a width of 70-100 μm to set the size of crystals, transistors, and after thinning the semiconductor wafer to form grooves on its underside a depth of 5-10 μm directly under the grooves on the front side, the ratio of their width equal to 3-2, and form a groove by using photolithography and etching, after forming the integral heat sink forms an integral heatsinks crystals transistor by photolithography on the integral heat sink with subsequent e what about etching in the locations of the grooves on the back side of the semiconductor wafer, and the separation of the semiconductor wafer on the crystals transistors carried out by chemical etching, with integral heatsinks crystals transistors serve as the mask.

2. A method of manufacturing a powerful microwave transistors according to claim 1, characterized in that as a semiconductor wafer using, for example, a wafer of gallium arsenide.



 

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