JPS6273758A - Microwave monolithic integrated circuit - Google Patents

Abstract

PURPOSE:To obtain an MMIC which has a sort developing period at a low price by disposing in parallel a plurality of at least one of FET, a diode and a resistor on a substrate, depositing metal on the back surface, forming a distributed constant line on the formed dielectric thin film, and connecting the line with the FET, diode and resistor of the positions from which the thin film is removed. CONSTITUTION:A microwave monolithic integrated circuit MMIC is formed of a 3-layer basic structure. The uppermost layer is formed of a thin metal film, and formed with a microstrip line of a high frequency circuit and the upper metal of an MIM capacitor. An intermediate layer is formed of a dielectric thin film layer adapted for an MMIC such as SiO2, Si3N4, polyimide, and operates as a protective film for the FET of the lower layer, and an insulator of the MIM capacitor. The lower layer is a semiconductor substrate having sufficient crystallinity to form a semiconductor element, the FET, resistor on the surface, and the lower layer metal of the capacitor and an earth electrode formed of viahole. The electrode of the lower layer substrate and the upper layer metal are connected in a portion (window) W in which the dielectric film of the intermediate layer is partly removed in a circuit manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a microwave monolithic integrated circuit that can be developed in a short period and at a low cost.

[Technical background of the invention and its problems]

MMIC (Monolithic Microwave)
IntegratedC1rcuit) is a microwave circuit consisting of a capacitor, an inductor, a distributed constant line, etc. formed integrally on a semiconductor substrate on which semiconductor active elements are formed, and is compact, highly reliable, high performance, and mass-produced. Conventional MIC (Microwave In
tsgratedClrcuit) is excellent and we look forward to its future development.

Semiconductor materials for MMICs need to have high carrier mobility to enable high frequency operation, and
High insulation properties are also required as a dielectric substrate material for microstrip lines.

From these points of view, GaAs is mainly used as a semiconductor material, and currently the semiconductor material is
MMICs such as amplifiers, oscillators, and mixers are being researched and prototyped, and practical application is about to begin (Rob@rt
A, Puel @'Design Con5ide
ratio for Monolithic Micro
owaveC1rcuit 'IFJEETrans
PP513-534MIT-2946.1981).

Figure 7 explains the structure of MMIC (V,
Re CH'EN and D, R, Dsck@sr,
``MMIC'S'', The Next Gvn*r
atton of Miorovave Com
ponents 'Mlorowave Jour
nal, PP 66-78, May-1980).

The main circuit elements that make up an MMIC are FETs, capacitors, inductors, lines, resistors, and peer holes Vh (Vi
a-hole).

In FIT J, a surface layer (~0.2 μm) of a highly pure single crystal layer (~1 μm) epitaxially grown on a highly insulating GaAa substrate 2 is formed by a method such as ion implantation.
9n shape, elongated fine f-)i pole (width 0, 25 Am
~1 μm, length l on the order of 00 am) with a source and drain voltage of 1 J (r-) and a source spacing of several μ on both sides.
rn) t-provided.

Because it requires precision close to the limit of semiconductor microfabrication technology, the MMIC process also takes time and is the most critical factor for yield.

Further, the FET manufacturing process requires advanced technology, expensive equipment, and well-controlled processes at each stage of epitaxial crystal growth, ion implantation, fine pattern drawing using electron beams, and etching.

Capacitors have a ZAI type structure. One of them is Interdino Tarkya iJ? The cover 4 is formed by arranging electrodes such that many comb-shaped fins face each other. This interdinotal capacitor cannot have a very large capacitance. Finger length, width, and spacing (S) are determined by capacity, but L = 50~200Am, W = 3~30#
+s, S=3 to 30 μm, and requires pattern processing with relatively high precision.

The other = MIM (Metal -In5ulaLo
Metal) Cano 4? A dielectric layer (0.1 μm
% 0.5 μm), a large capacity of several tens of PF or more can be obtained.

The inductor and the line 6 are four strips made of metal thin film, and the width of the IJ tag body is also relatively thin (minimum of 5 μm order for the inductor, 5 μm).
The 00 line requires a width of 100 μm), but the basic technology is the same as the high frequency circuit pattern of conventional MIC.

Further, the resistor 7 is formed by forming n or n''[-.

The channel between the source and drain of the FET with the dirt open can also be used as a resistor.

As shown in FIG.
A hole penetrating from the front surface to the back surface is made in the diameter (00 to 200 μm) to connect the front conductor 9 to the ground conductor on the back surface, and is used to realize an almost ideal ground potential on the front surface. For example, in the case of a source-grounded FET Ang, the source is connected to a peer hole)
Ground.

To form this peer hole, MMIC! Holes are made by etching the substrate from the A side, but accurate machining is not always easy due to the anisotropy of etching and the thickness of the substrate to be etched.

Instead of relying on peer holes, there is also a method of grounding by connecting the ground conductor and surface conductor 2 around the MMIC chip. In this case, an extra step is required for the Chig assembly, and Mli
There are also considerable restrictions on the iIC/# turn layout.

This completes the overview of the basic configuration of MMIC. M
In the specific manufacture of MIC, each manufacturer often uses its own unique process, and the number of steps in the process is extremely large.

As mentioned above, there are many critical factors during the process, and the final MMX C yield is generally very low.

Particularly in relation to the present invention, which will be described later, the problem with conventional MMICs is that semiconductor main electrode formation and microwave circuit configuration are performed in the same process. This is M
This is especially important during MIC development. In other words, it is extremely difficult to design a high frequency circuit completely accurately, so even if the process for circuit components such as semiconductors is good, the desired characteristics cannot be achieved as an MMIC due to insufficient high frequency circuit design. There are many cases.

Also, if the circuit functions to be developed differ, for example, the F used
Since it is necessary to change characteristics at the semiconductor or component level, such as the total length and resistance value of the ET, it is easy to cause a decrease in yield in the semiconductor process. For this reason, MMIC
The following difficulties exist before the future development of

(1) The development period for MMIC is not long. That is,
It takes approximately six months to develop an MMIC from circuit design to completion of the MMIC process.

(2) Cost is high. That is, microwave circuits require a relatively small amount and a wide variety of components. Since development costs are enormous to convert these components into MMICs, the price of each component becomes extremely high.

(3) Manufacturers are limited. In other words, MMIC requires a large amount of technology, accumulated know-how, and expensive equipment. For this reason, the development of MMIC is limited to a few dog manufacturers, and small and medium-sized manufacturers that have traditionally had a considerable market share in MIC cannot benefit from MMIC. This is FiMI
This is one of the factors that hinder the development of C.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned conventional drawbacks, and an object thereof is to provide a microwave monolithic integrated circuit which can be developed in a short period of time and is inexpensive.

[W1 essential point of the invention] The microwave monolink integrated circuit of the present invention has a plurality of at least one of active elements, diodes, and resistors arranged in parallel on the front surface of a semiconductor substrate, metal is vapor-deposited on the back surface of the semiconductor substrate, A dielectric thin film is formed on a semiconductor substrate, a distributed constant line is formed on this dielectric thin film, and this distributed constant line is connected to active elements, diodes, resistors, etc. in areas where the dielectric thin film has been removed. The high frequency circuit is completely formed.

[Embodiments of the invention]

Embodiments of the microwave monolithic integrated circuit of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing the configuration of the -'iA embodiment.

The MMIC shown in FIG. 1 is an example of a resistive RI amplifier as shown in FIG. 2, which is often used as a microwave broadband amplifier.

As shown in Fig. 2, the high frequency human input signal RFIN is passed through the capacitor C4 and the distributed constant line tlf to the FIET Q
1 r-). The capacitor C4 and the distributed constant line t1 are grounded via a resistor R3f.

The source of FET Q1 is grounded through a parallel circuit of capacitor C1 and source resistor R1.

The dray/of FgT Q 1 is distributed constant line t2 and 1
3. Capacitor C4 via capacitor C2 and resistor R2i
and the distributed constant line 41, forming a feedback circuit 1c.

The connection point between the distributed constant lines t2 and 63 is the capacitor C65.
(A distributed constant line t4, which is grounded through
A high frequency output RFOUT is output through a capacitor C5 and a microstrip line L6.

A voltage VD is applied to ' from the connection point between the distributed constant line t4 and the condenser C3 and the distributed constant line t5 through the distributed constant line t5 and the capacitor C3. I try to do that.

Next, the MlvlIC shown in FIG. 1 based on the circuit shown in FIG. 2 will be explained. The MMIC shown in FIG. 1 has a basic structure of three layers. The shaded area in FIG. 1 is the uppermost metal thin film, which forms the microstrip line of the high frequency circuit and the upper metal of the MIM capacitor. The middle layer is MiVI such as 5io2, si, R4, polyimide, etc.
A thin film layer (omitted in FIG. 1) of a dielectric material suitable for an IC, which functions as a protective film for the underlying FET, etc., and as an insulator for the MIM capacitor.

The lower layer is a semiconductor substrate having sufficient crystallinity to create a semiconductor element (for example, a GaA substrate with a normal growth layer as a surface layer), and the FgT and resistance described in the conventional example are formed on the surface of the semiconductor substrate. In addition, a ground electrode made of the lower metal of the MIM capacitor and the peer hole is also formed.

The electrodes on the lower substrate and the upper metal are connected in a circuit through a portion (window) where the intermediate dielectric film is partially removed (Figure 3 shows a cross-section of the structure. Junior high school 10
1 is peer hole, 102 is ground, XO3 is resistor, 10
4 is FET.

105 is the MIM capacitor/mother, 106 is the lower layer metal, 1
07 indicates a GaAs substrate, 10 & indicates a ground conductor on the back side of the substrate)
The above configuration can be easily realized using the conventional FiMIC technology.

The feature of the MWI C of this invention is that multiple elements such as fcFET, resistor, MIM lower layer metal, and ground electrode are formed on the lower substrate in advance and are separated independently on the lower substrate. Each of these elements is selectively connected by an upper layer metal forming a line to constitute a microwave circuit. Therefore, there may be unconnected circuit elements on the lower substrate that are not part of the microwave circuit configuration.

Next, a detailed explanation of the embodiment shown in FIG. 1 will be given by itemizing the three basic structures of the gold (I) lower layer structure, (II) dielectric intermediate layer, and (g) upper layer metal.

(I), Substructure In this substructure, 11 is earth 'Ii! The electrode is made by a pier hole (all E symbols in the figure are earth electrodes). In addition to the purpose of grounding for DC, this is also used as the lower metal of a bias high-frequency bypass capacitor (for example, capacitor CJ in Figure 2) that requires a relatively large capacity (4PF to 200PF'). It is convenient for

Since the shape of the ground electrode 11 in FIG. 1 is 250 μm x 250 μm, for example, the thickness (
d) If a dielectric intermediate layer of 1000X SL, N, (11R7,o) is adopted, C=t0,4,38.5 pF
' capacity can be obtained.

In addition, 12 is a unit FBT, and in the figure, an FE with an electrode width of 200 μm) having two fingers (length 100 μm)
T is shown. Microwave circuits that handle analog signals target signals of various power levels, and the higher the power level, the longer the dart width becomes necessary.

MMIC of the present invention to accommodate various power levels.
In this case, a plurality of FET basic cells are arranged in parallel sufficiently close to each other so that the distributed inductance during parallel connection does not become a problem, and an appropriate number is connected in parallel depending on the power level.

In this embodiment, the FIT t-
By preparing 5 pieces, it is possible to substantially expand the width to 1000 μml'-).

13 has two unit FISTs connected in parallel and has a diameter of 400 μm.
This is an example of using it as an FET.

14 is a resistor with an electrode made by introducing impurities, and the mesh-shaped portion is the conduction path of the resistor. Since microwave circuits require various resistances, a plurality of independent unit resistances are arranged in parallel in close proximity, similar to FETs.

15 is the source resistance R for self-bias shown in FIG.
This is an example realized by connecting two unit resistors in parallel.

In addition, resistors R2 and R3 shown in FIG. 2 are connected to the circuit as resistors. To connect the resistor, provide a window above both electrodes of the resistor and wire the upper metal.

Electrode 16 (c) An electrode that serves as the lower layer metal of the MIM capacitor. In the MMIC of the present invention, the capacitors CI, C2, C4, and C5 shown in FIG. 2 are realized as pMIM capacitors by the upper metal wiring. The maximum value of the capacitance is determined by the area of the lower electrode, but any desired capacitance value can be achieved by changing the area of the two-part metal electrode.

Note that the MIM capacitor T4 requires a window 17 to connect the lower metal to the circuit.

Further, the electrode 18 is an elongated X-pole prepared for the convenience of a high-frequency circuit using an upper metal layer, and is used as a prixel 19g of a spiral line, for example, as shown by the reference numeral 19. Thus, a GaAs substrate 107 coated with a dielectric thin film is formed, and a ground conductor 108 (FIG. 3) is formed on the back surface of the substrate by metal vapor deposition.

(■), dielectric intermediate layer Although not shown in Figure 1 because it would be complicated, MMI
It covers the entire surface of the C chip, and the part indicated by the thick broken line is the window W (portion from which the metal body has been removed) provided to connect the upper metal layer and the lower layer electrode.

(6) Upper layer metal In Fig. 1, the shaded part is the upper layer metal, and the times W made in the lower layer! Used to connect elements and form distributed constant lines. tl to t6 are distributed constant lines corresponding to FIG. In particular, the distributed constant t6 is a 50Ω transmission chain,
In the MMIC of this invention, the line has a width W=110 ttm (substrate thickness H=150 μm). Incidentally, in the MMIC of the present invention, the shunt capacitor C6 is also made of an Ogunstap line. Also, C1 to C in Figure 1
6 is the core in Figure 2! /lc 1 to C6 and R1 to R3 in FIG. 1 correspond to resistors R1 to R3 in FIG. 2.

As shown in FIG. 1, the MMIC of the present invention has many unconnected circuit elements on a lower substrate, and a distributed constant line is formed by overlapping these unconnected elements with a dielectric intermediate layer in between. In a strict sense, such overlapping wires affect the characteristics of the MyFrost relag line, so care has been taken to avoid such a structure in conventional microwave circuits containing LiMc gold.

However, if the overlapping circuit elements are small, the effect is small. The effect is negligible, especially if the element is completely covered by the track. It is also possible to take into account the influence of circuit elements relatively accurately. For example, the influence due to the overlap between the 50Ω distributed constant line t6 and the unconnected circuit element 8 can be incorporated into the equivalent circuit shown in FIG. 4 when designing the circuit.

Here, C is the capacitance of the MIM capacitor created by the storm between the distributed constant line t6 and the electrode 18, and ze is the distributed constant line t.
6, L is the corner, and R is the wavelength shortening rate.

In the MMIC of this invention, pi? Large circuit elements such as the MIM cano 4-shita lower layer metal used for ski/zeshita are placed around the semiconductor chip, and a distributed constant circuit is placed in the center of the chip, so that the overlap effect due to small circuit elements can be completely ignored or calculated. is formed.

Figure 5 shows the process of commercializing the MMI C of this invention. Its characteristics are firstly the semiconductor process that requires ultra-fine processing, beautiful equipment, and long process steps, and the conventional MMI C process.
The point is that the 7" process of vapor deposition and etching performed in C is completely separated in time series. The previous process, that is, the semiconductor process is
This is the process up to the lower substrate and intermediate layer a-conductor coating. The post-process, that is, the MIC process, includes dielectric window opening for connection, upper layer metal deposition, and pattern etching for the MIC circuit, and the 79 turn rule is approximately 30μ.
Since it is a process that takes place over m or more, it can be processed with simple equipment and in a short time.

Second! A distinctive feature is that the circuit elements created in the first half of the semiconductor process are standardized. Microwave analog ICs handle (I and δ) power ranges from small I and δ to several watts, and have a wide range of functions.Therefore, in this invention, a single circuit board can support a large number of ICs. In order to achieve this, components that depend on the power level, such as FETs and resistors, are divided into several closely spaced segments, and these segments are connected in parallel depending on the power level.

Furthermore, since various circuit components are prepared on the circuit board, by appropriately and selectively connecting these components, it is possible to create an MMI with various functions from one standardized circuit board.
C't - It is possible to make a second crop. This is a significant difference from the previous F611C, which was a fully custom design.

Because of these features, the MMIC of the present invention can be developed with the required characteristics in a very short period of time if the semiconductor processing process of the previous process is completed. In the seventh development process, there is no need to spend all the gross proceeds each time a prototype is produced, so the product price can be made very low.

Furthermore, in high-frequency equipment, it is necessary to develop many different types of circuits in a short period of time, although the amount of C is small, and this invention exactly answers that need.

Furthermore, since the semiconductor process and the MIC process are separated, it is possible to check the results of device variations after the semiconductor process and design the MIC accordingly, resulting in an improvement in the yield of the semiconductor process.

Furthermore, the fact that semiconductor processing is completely independent of MIC grossing, which is high-frequency circuit technology, makes it possible to divide industrial labor. Companies with IC semiconductor processes can sell semiconductors that have completed all the pre-processing, and many companies with circuit technology can make full use of their specialized high-frequency circuit design technology to produce the desired MMIC in a short period of time. This will lead to the emergence of high-performance, inexpensive single-frequency equipment, and the revitalization of industrial waste.

In addition, in the above explanation of J, FETs, resistors, thin metal pieces (for example,
Although we have taken only MIM subordinate metals and metals for prisms as examples, other parts used in microwave circuits, such as mixer diodes, varactor diodes, interdigital capacitors that require semiconductor gross-level microfabrication, etc. Needless to say, it is also possible to standardize circuit elements such as spiral inductors and shadow them on the semiconductor substrate.

In addition, in the explanation of this invention, the upper layer is a four-metal film formed by vapor deposition, but it is obvious that the same effect can be achieved even if metallization is performed by other means such as printed thick film. .

Furthermore, with the recent MIC technology, it is not only possible to use metal conductors, but also to vapor-deposit and etching a resistive thin film such as nichrome to easily form a resistor element using gold.

Therefore, if the desired resistance value cannot be obtained on the half board, it is also possible to fabricate the entire resistive thin film together with the distributed constant line on the upper part.

Needless to say, this also falls within the scope of the gist of the invention.

Furthermore, similar to the fiff example, with MIC technology, it is possible to make a MIM canister by laminating dielectric materials. When these two methods are combined, the method shown in FIG. 6 is used.

That is, in the pre-process (semiconductor processing), after the dielectric 202 (intermediate layer) is completely formed on the GaAs substrate 201, in the post-process (MICf process), the upper layer metal 203 of the MMIC of the present invention is formed on the dielectric 202. Then, a dielectric material 204fc is formed on it (a part of it is completely removed), and the MIM carrier/f-shield electrode 205 is completely formed, resulting in a five-layer structure.In this case, in addition to the upper layer metal referred to in this invention, Dielectric material 204 and MIM capacitor electrode 205 thereon
Although it has a five-layer structure with the addition of , it can be said to be a modified example that extends this invention in that it is based on the idea of this invention.

In this invention, the circuit elements formed on the lower substrate include FET, resistor, MIM carrier center lower layer metal,
Although I mentioned the grounding αff1k using a peer hole, it goes without saying that other circuit elements such as diodes can also be used as standard components, and conversely, for example, it is also possible to omit the circuit elements of the pier, such as the C hole grounding pole. can.

〔Effect of the invention〕

As described above, according to the microwave monolithic integrated circuit of the present invention, the development period of MldIC can be shortened. This will lead to lower prices, encourage companies without MMIC growth technology to enter the MMIC business, and as a result, revitalize the industry.

[Brief explanation of drawings]

FIG. 1 is a plan view of an embodiment of the microwave monolithic integrated circuit of the present invention, FIG. 2 is a circuit diagram of a resistive feedback amplifier configured into the same microwave monolithic integrated circuit, and FIG. 3 is a plan view of an embodiment of the microwave monolithic integrated circuit of the present invention. 4th cross-sectional view of the part where the electrode of the lower substrate and the upper metal in the monolithic integrated circuit are connected by a window in which the intermediate layer dielectric film is partially removed;
The figure is an equivalent circuit diagram of the overlapping pattern part in the microwave monolithic integrated circuit of FIG. 1, FIG. FIG. 7 is a perspective view of a conventional microwave monolithic integrated circuit; FIG. . 11... Earth electrode, 12... Unit FET, 1.1
...Two connected FETs, 14...Resistor, 15.
...2 resistors connected, 16...MIM capacitor lower layer metal, no...window provided in intermediate layer dielectric, 18...4 poles, 19...brittle, 61-t6.
...Distributed constant line, C1 to C6...Capacitor, RJ
~R3...Resistance. Applicant's agent Patent attorney Suzuko Takehiko 21~! 6:
Now threatening Tatsusamai Figure 2 Figure 4

Claims (4)

[Claims] (1) A semiconductor substrate having a plurality of active elements, diodes, and/or resistors arranged in parallel on one side and metal on the other side, a dielectric thin film formed on the semiconductor substrate, and a dielectric thin film formed on the semiconductor substrate. A microstrip line conductor having the metal as a ground conductor is formed on the body thin film, and the microstrip line conductor is connected to the active element, diode, resistor, etc. at a portion where the dielectric thin film is selectively removed from the semiconductor substrate. A microwave monolithic integrated circuit that connects to part of the. (2) The microwave monolithic integrated circuit according to claim 1, wherein the semiconductor substrate has a thin metal piece on its surface that faces the microstrip line conductor and forms a capacitor. (3) The semiconductor substrate has a rectangular metal thin piece, and the microstrip line conductor has a spiral shape, and one end of the microstrip line conductor is connected to one end of the metal thin piece at a portion where the dielectric thin film is removed. , the microwave according to claim 1, characterized in that the inner conductor of the spiral microstrip line conductor is connected to a high frequency circuit disposed outside the spiral microstrip line conductor by means of this thin metal piece. Monolithic integrated circuit. (4) The microwave monolithic integrated circuit according to claim 1, wherein the microstrip line conductor formed on the dielectric film forms a resistor or a capacitor to constitute a microwave circuit.