RU2081479C1 - Microwave device - Google Patents

Abstract

FIELD: semiconductor electronics; monolithic microwave integrated circuits, especially those operating in extremely-high frequency band. SUBSTANCE: monolithic microwave integrated circuit of device has metal sections of transmission line, matching components, and isolated chips that function to joint together all parts to form monolith and to perform the functions of passive and active elements; some chips are used to facilitate installation of circuit into waveguide assembly. Novelty is that bearing structure of circuit components is metallized surface and not substrate. Isolated chips of circuit perform various functions: some of them carry active and passive elements, others serve to join together metal parts of circuit into integral unit, and still other chips are used to secure circuit on installation site in waveguide assembly. EFFECT: reduced microwave power loss, simplified installation of integrated circuit in waveguide assembly. 2 cl, 4 dwg

Description

 The invention relates to semiconductor electronics and can be used to create monolithic integrated circuits of the microwave and, above all, millimeter wavelength circuits.

 It is known that the creation of monolithic microwave integrated circuits (MIS microwave) was preceded by the widespread use of hybrid integrated circuits (GIS) microwave. These circuits are widely used at present (see, for example, A.M. Temnov, R. A. Silin, A. G. Mikhalchenkov. Hybrid monolithic microwave integrated devices: design and manufacturing technology. Reviews on electronic technology. Ser. 1. Microwave electronics, issue 20 (1319), 1987), microwave GIS is formed on dielectric substrates (quartz, dyroid, etc.) with low dielectric constant and low microwave power loss. Transmission lines, matching elements, passive elements are formed on substrates by photolithography methods, and active elements are usually mounted by thermal compression. The disadvantage of GIS is that when mounting attachments, it is difficult to achieve reproducibility of the geometric arrangement and identity of the parameters of the elements (for example, in balanced circuits), which leads to a deterioration of the circuit parameters, especially in the millimeter wavelength range (MMDV). Another disadvantage is the complexity of assembling GIS and, above all, the installation of active elements.

 Monolithic microwave integrated circuits are known that are made on a gallium arsenide-semiconductor substrate, on the surface of which epitaxial layers are deposited, which are necessary for the formation of active elements (see, for example, “Gallium arsenide in microelectronics.” Translated from English under the editorship of V.N. Mordkovich, M. Mir, 1988, Ch. 5). In such schemes, the GIS disadvantages associated with the irreproducibility of the position of active elements, the non-identicalness of their parameters and the complexity of installation are eliminated.

 Monolithic integrated circuits were also created in MMDV. For example, a monolithic balanced mixer (BJ Clifton and RW Chick. Balanced monolithic mixer use at 44 GHz 10 Int. Conf. Infrared and Millim. Wawes Dig. Conf. 1985, p. 273), made with gallium arsenide rune, is known 5 • 2.5 mm with a semi-insulating substrate containing a balanced diode pair and elements of transmission lines and matching with channels of the signal, local oscillator and intermediate frequency. Arsenidogallium run is mounted in an insidious holder, and then in a waveguide assembly (device, housing). The disadvantage of such a monolithic scheme is that the microwave power loss in a semi-insulating GaAs is higher than, for example, in quartz, and grow with increasing frequency. In addition, a monolithic circuit in the form of runa is very laborious when installed in a device.

 These shortcomings are largely eliminated in the integrated millimeter-wave balanced mixer (A.S. N 1443731, class H 03 D 7/14, 86), which we took as a prototype. In this mixer, losses are reduced by removing (bleeding) the substrate. Separate sections of the substrate (crystals) are left to create active elements and matching (transforming) elements based on segments of transmission lines. In this case, the installation of the circuit in the waveguide housing is also simplified. It is attached by a simple clamp between two halves in a longitudinal section of the waveguide.

 The obvious disadvantages of this integrated mixer are due to two circumstances: it excludes the possibility of applying constant bias to the diodes (diodes are shorted by direct current), which limits the functionality of the circuit (degrades the parameters, requires an increased local oscillator power); mounting the circuit into the waveguide assembly is difficult due to the fact that it is not possible to reliably fix the position of the circuit relative to the waveguide channel, which can affect the repeatability of the parameters and the quality of the mixer as a whole.

 The aim of the invention is to expand the functionality and simplify the installation of a monolithic circuit in a waveguide assembly.

 This goal is achieved by the fact that along with crystals containing active elements (diodes) and matching segments of transmission lines, crystals containing passive elements, crystals that serve to bond individual parts of metallization together, as well as crystals used to fix circuit in the place of its installation in the waveguide assembly (housing).

 The difference between the proposed monolithic microwave circuit from the known one allows us to talk about the novelty of the technical solution, and the analysis of analogues in the studied area indicates that the criterion of "significant difference" is satisfied.

 The obvious advantage of the proposed monolithic microwave circuit is primarily to expand the functionality by applying a constant bias to the active elements. This allows you to create not only bias mixer circuits, but also bias detector detectors, multipliers, switches, etc. In this case, the bias supply either opens up possibilities for performing new functions (switches), or significantly improves the parameters (mixers, detectors, multipliers). The latter can also be interpreted as an extension of functionality.

 Simplification of the installation is due to the fact that the introduction of additional crystals allows you to fix the position of the circuit in a given place quite rigidly, and then attach it by thermal compression (or glue) to one of the halves of the waveguide.

 It is obvious that the proposed technical solution can be used for a wide range of specific monolithic microwave circuits.

 Figure 1 shows a monolithic integrated circuit switch view from the back side (from the substrate). Shaded areas of 1,4,4,6-semiconductor crystals that perform various functions, 2 terminal for supplying constant bias, isolated (separated by a gap) from the waveguide, 3 quarter-wave lengths of the slit line, 5 gap for isolating terminal 2 with direct current. Figure 2 shows from the front side a monolithic integrated circuit switch, mounted in a waveguide assembly (housing). Designations are the same. Figure 3 presents a fragment of a plate with monolithic circuits formed on it before the operation of separation into separate circuits. In FIG. 4 shows a monolithic integrated circuit of the switch (front view) made on a single crystal 7 (limited by dashed lines), on which diode triples 1 are formed, an output for applying bias 2, pieces of slot lines 3. The circuit is mounted in the E-plane of the waveguide with using metallization 8, which is clamped between the two halves of the waveguide assembly.

 On crystals 1, active elements of three series-connected diodes with a Schottky barrier (DBS) are formed. The choice of the number of diodes is determined by the level of switched power. In MMDV, taking into account the requirements for high-speed power train, the successive three power trainers are able to switch power to hundreds of milliwatts. Diode triples in pairs (left and right) are included in opposite directions.

 Crystals 4 and 4 '(Fig.1,2) are used to fasten the circuit. In their absence, the circuit “crumbles”, since the output for applying bias (2) must be isolated from the waveguide. Crystals 4 simultaneously perform another function. Capacities are formed on them (based on MIS structures or BS), which provide low resistance to a microwave signal.

Crystals 6 play a supporting role. They serve to install the circuit in the waveguide assembly (Fig. 2) in a fixed position in order to exclude its displacement during final fixing by welding, thermal compression, or another method. The crystals 4 '(FIG. 2) also serve to fix the circuit before assembly, i.e. they perform two functions. About the first for fastening the circuit
said above.

 The thickness of the gold metallization scheme is usually 6 to 12 microns. Thinner metallization is easily deformed and complicates the operation of assembling the circuit into the housing. With a greater thickness of metallization, it becomes too stiff. In this case, mechanical stresses during assembly can lead to crystal peeling.

 The circuit is attached in the E-plane of the waveguide to one of the halves of the waveguide assembly (Fig. 2). Since the thickness of the circuit (metallization) is quite small, there is no need for a special recess for the circuit. This greatly simplifies the final assembly of the assembly: the circuit can be fixed between the two halves of the assembly even with a simple mechanical clamp, without welding or thermal compression to one of them.

(λ_в длина волы СВЧ сигнала в волноводе).The operation of the switch is carried out according to the usual scheme. When applying microwave power through channel I (input), Fig. 2, the power is sent to channel II if the diode triples of the left branch of the circuit are turned on in the opposite direction (while the diode triples of the right branch of the circuit are turned on in the forward direction, which leads to reflection of the signal from -for shorting the waveguide channel). Conversely, power is routed through channel III if the polarity of the bias is reversed. The quarter-wave segments of the slit lines serve to match the resistance of the waveguide channel and diode triples. The dimensions of the circuit are

(λ _in the wavelength of the microwave signal in the waveguide).

 The method of creating the proposed monolithic integrated microwave circuit can be implemented as follows.

In ⁺ n-type arsenide-gallium structures are used as a semiconductor material: on the semi-insulating substrate, a buffer n ⁺ layer (n ⁺ > 2 • 10 ¹⁸ cm ^-3 ) with a thickness of 3 5 μm and an "working" n-type layer are grown n = (5-10) • 10 ¹⁶ cm ^-3 ) with a thickness of 0.1 - 0.3 microns. Known methods are used to form diodes on this plate with a Schottky barrier with planar leads: four groups of three diodes connected in series in each.

To form planar DBL, the method described in the article can be used: WL Bishop, K. Mokinney, RJ Maffauch, TW Crowe, G. Creen. A novel whiskerless shoffky diode for millimeter and submillimeter wave application. JEEE MTT-S, Int. Microwave Symp. Dig. 1987, v. 2, p. 607. According to this method, the Schottky barrier and ohmic contact are formed in windows opened in SiO ₂ by applying metallization Pt-Cr-Au and Sn / Ni-Ni-Au, respectively. To reduce the parasitic capacitance of the DBL, the anode terminal to the BS is isolated from the semiconductor by etching the channel with the depth go of the i-substrate under it. Metallization of Cr-Au is applied to the entire plate and serves to form the DBL and the topology of the rest of the circuit at the same time. To do this, photolithography and electrochemical deposition of gold into the windows opened in the photoresist are performed. In this case, a strip terminal 2 is formed (Fig. 1), which serves to supply a constant bias to the diodes, and slotted line elements 3.

 According to the known method, the thickness of the deposited gold is 3 μm. However, we experimentally established that such a thickness is insufficient. In order that, after dividing the plate into separate circuits, the latter retain the elasticity and strength necessary for the assembly operation, and at the same time prevent breaks in the area of the crystals are attached to the circuit during mechanical and climatic tests, gold is deposited to a thickness of 6-12 μm. Thickening of the gold metallization is carried out selectively: after reaching 2 3 μm, the regions of the active elements are protected by a photoresist and then further deposition is carried out up to 6 12 μm. After this, the photoresist and the Cr-Au sublayer under it are removed. A small metallization thickness in the region of active elements (2 3 μm) is necessary to avoid large mechanical stresses that adversely affect the characteristics of active elements (DBS).

Before dividing the plate into separate circuits, the front side of the circuit is etched with n and n ⁺ layers in the slit 5 and in the area of the slit line 3. The areas of diode triples 1 and the reverse side of the plate are masked. Etching is necessary in order to eliminate shunting in the circuit along the conductive part of the semiconductor structure.

For the operation of dividing the plate into separate circuits (see Fig. 3), the substrate is etched to a thickness of 70 to 100 μm. Then, using well-known methods (for example, using registration in infrared light), photolithography is performed on the reverse side and semiconductor material is etched from unprotected places. Only areas on which crystals 1, 4, 4 are located are protected by a photoresist ^! and 6. As a result of etching, the plate is divided into separate circuits corresponding to FIG.
Next, the circuit is attached in the E-plane of the waveguide to one of the halves of the waveguide assembly. Crystals 6 and 4 ^! they allow to fix the circuit in such a way as to exclude its shift during random shocks and touching the tool. Since the thickness of the circuit is sufficiently small (6–12 μm), the assembly can be carried out by mechanical clamping of both halves of the waveguide assembly after preliminary welding or thermal compression of the circuit to the waveguide in predetermined places.

поскольку оно зависит от степени заполнения волновода диэлектриком. ε_эф определяется диэлектрической постоянной подложечного арсенида галлия, толщиной подложки и шириной щели (щелевой линии). Оценки показывают, что λ_в при использовании арсенидогаллиевой подложки ε_эф=12,9 может быть в ≈1,5 раза меньше длины волны в вакууме λ при толщине подложки 200 мкм. Это значит, что во столько же раз уменьшается длина схемы. Ширина ее может быть уменьшена за счет заужения волновода в месте закрепления схемы. Естественно, что в такой схеме на одном кристалле потери сигнала будут больше, чем в схеме, представленной на фиг.1.Using the proposed design of a monolithic integrated circuit is effective in MMDV and, above all, in its short-wave part, since the dimensions of the circuit are comparable with the wavelength. In the centimeter range, it is ineffective, because circuit sizes are getting too big. To reduce them, it is necessary to reduce the wavelength of the signal in the waveguide. This can be achieved if you perform the circuit on a single chip (figure 4). The width of the crystal corresponds to the height of the cross section of the waveguide. This allows you to fix the circuit in the desired position (eliminates the movement of the circuit across the waveguide) and obtain the maximum possible reduction in wavelength in the waveguide:

since it depends on the degree of filling of the waveguide with a dielectric. ε _{eff is} determined by the dielectric constant of the substrate gallium arsenide, the thickness of the substrate, and the width of the slit (slot line). Estimates show that λ _in using an arsenide-gallium substrate ε _eff = 12.9 can be ≈1.5 times less than the wavelength in vacuum λ at a substrate thickness of 200 μm. This means that the length of the circuit is reduced by the same amount. Its width can be reduced due to the narrowing of the waveguide in the place of fastening of the circuit. Naturally, in such a circuit on a single chip the signal loss will be greater than in the circuit shown in figure 1.

 The considered switch circuit is a possible example of the proposed design of a monolithic integrated microwave circuit. The same design principle can be used to create control, converter, and other, including multifunctional, monolithic microwave modules.

Claims (2)

 1. Microwave device, comprising a housing with sections of a waveguide made in it and an integrated circuit mounted therein, including transmission line elements and matching elements in the form of individual metallization sections, active and passive elements connected to the electrical circuit by the said metallization sections, characterized in that the active and passive elements are made in the form of separate crystals, while the mechanical connection of individual metallization sections into a monolithic integrated circuit is ensured by said individual crystals.  2. The microwave device according to claim 1, characterized in that the fixation elements of the monolithic integrated circuit in the housing are introduced, made in the form of individual crystals.

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