RU2799811C1 - Method for manufacturing a thin-film capacitor for electronic equipment - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to a method for manufacturing a thin-film capacitor in electronic technology and can be used as part of thin-film microcircuits, for example, for a microwave integrated circuit. The method includes formation of a dielectric element in the form of a thin film of a dielectric from silicon nitride in at least two stages, with a layer thickness at each stage of less than 25 nm, with an interval between stages formation of 20-40 s, in a single technological process of applying a thin film by photolithography and etching, whereas the number of stages of formation of a thin dielectric film N is determined from the expression N=d/s, where d is the specified total thickness of the dielectric film, nm, s is the same thickness of the dielectric film layer of the dielectric at each stage, nm.

EFFECT: increased specific capacitance, breakdown voltage, decreased in dielectric loss tangent (tg), as well as increased yield of suitable products while simplifying the manufacturing method

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Description

The invention relates to electronic engineering, to thin-film capacitors, and can be widely used in the manufacture of film microcircuits of both microwave and low-frequency wavelength ranges, for a wide range of functional purposes.

Thin film capacitors (TPC) are one of the passive elements of film microcircuits.

Main Features of Thin Film Capacitor (nominal value, stability, operating voltage, temperature and time stability, frequency properties, quality factor, polarity, reliability, etc.) depend primarily on the selected materials and the manufacturing process.

In this case, the material of the main element of the thin-film capacitor is dielectric must have:

- high values of adhesion to the materials of its other elements (lower and upper plates);

- small values of dielectric losses;

- high values of dielectric constant (ε) and correspondingly high values of specific capacitance;

- low values of the dielectric loss tangent (tg );

- low values of mechanical stresses not more than 3.0×10 ⁶ Pa;

- low values of the etching rate of the dielectric material in the buffer etchant, nm/min.

A known method of manufacturing a thin-film capacitor, including the deposition of a layer of tantalum or niobium oxide and a layer of silicon oxide.

In which, in order to improve the electrical characteristics of a thin-film capacitor, a layer of silicon oxide is applied by repeated alternating treatment of a layer of tantalum oxide or niobium oxide at a temperature of 100-180 ° C, in a vacuum with vapors of silicon tetrachloride and water, and the thickness of the silicon oxide layer is 10-100 Å (1-10) × 10 ^-9 m [A. C. 699949 RF. Method for manufacturing a thin-film capacitor /Yu.K. Yezhovsky and others/ /Bul. - 2000 - No. 20].

The disadvantage of this thin-film capacitor and, accordingly, the method of its manufacture is the low level of breakdown voltages (not more than 50 V), as well as the increased complexity and high cost of the manufacturing method due to the use of expensive materials of tantalum and niobium oxides.

A thin-film capacitor and a method for its manufacture are known, containing first and second plates made in the form of metal films, including layers of chromium Cr, copper Cu, a dielectric film of a dielectric in the form of a polyimide film located between the plates and current leads placed on opposite sides of the dielectric film.

In which, in order to simplify the technological operations of the manufacturing method and expand the scope of its application by improving the accuracy of reproducibility of small capacitance ratings, reducing the inductance and increasing the quality factor, improving the adhesion of metal films, the ratio of the thicknesses of the metal films and the polyimide film is selected in the range of 1.1-1.2, and the current leads are made in the form of a part of the metal films protruding above the end opposite sides of the polyimide film, respectively.

The method for manufacturing this thin-film capacitor consists in depositing chromium Cr - titanium Ti - copper Cu - chromium Cr layers on a polyimide film from two sides by vacuum deposition of metallization, forming a pattern print on a thin layer of sputtered copper, deposition of a thick layer of copper over a photoresistive mask by a galvanic method, etching a polyimide film to form metal current leads, chemical deposition of a tin layer Sn, which simultaneously provides two functions - protective and soldering into an external circuit [Patent No. 2046429 RF. Film capacitor / P.P. Sumin / / Bul. - 1995 - No. 29].

The disadvantage of this thin-film capacitor and, accordingly, the method of its manufacture is:

- low relative permittivity (ε) of the polyimide dielectric film 3.3-3.6, which does not allow the formation of thin-film capacitors with high specific capacitance and planar structure,

- a limited range of its application and the complexity of the method of its manufacture, due to the need to maintain a certain ratio between the thickness of the polyimide film of the dielectric and the thickness of the layers, sprayed metals.

A thin-film capacitor and a method for its manufacture are known, containing first and second plates made in the form of metal films, a dielectric film of a dielectric located between the plates, current leads made in the form of a part of metal films protruding above the end sides of the dielectric film.

In which, in order to increase the yield by reducing the high number of defects in the dielectric film of the dielectric, a second layer of the dielectric film is introduced and an intermediate metal plate located between the layers of the dielectric film, consisting of isolated fragments.

The method for manufacturing a thin film capacitor includes the following sequence of technological operations.

Formation of the lower lining and current outlet by spraying metals vanadium V - molybdenum Mo, 0.1 μm thick (1×10 ^-7 m), on the prepared surface of the substrate.

Deposition on the entire surface of the lower lining of the first layer of dielectric film dielectric silicon dioxide SiO ₂ , thickness 2×10 ^{- 7} m .

Formation of an intermediate plate of a thin-film capacitor, which consists of several metal fragments isolated from each other, having an arbitrary configuration, and their number depends on the area of the thin-film capacitor being manufactured.

Formation of an intermediate lining - by spraying metals vanadium V - molybdenum Mo, 0.1 μm thick (1×10 ^-7 m) on the first layer of the dielectric film of the dielectric, using technological operations of photolithography and etching.

Formation of the second layer of the dielectric film - deposition on the first layer of the dielectric film of the second layer of silicon dioxide SiO ₂ , 0.2 μm thick (2×10 ^-7 m).

The formation of the upper lining of the film capacitor and the current output - by spraying metals vanadium V - molybdenum Mo, 10 ^-7 m thick on the second layer of the dielectric film using technological operations of photolithography and etching [Patent 2367046 RF. Film capacitor / V.S. Galushko / /Bul. - 2009 - No. 25] - prototype.

This method of manufacturing a thin-film capacitor in comparison with the previous analogue provides an increase in the yield due to a decrease in the level of defects in the dielectric film of the dielectric.

However:

firstly, the level of defects in a thin dielectric film remains high enough, which still does not provide the proper - high level of yield,

secondly, it does not allow the formation of thin-film capacitors with a high specific capacitance and a sufficiently planar structure due to the use of silicon dioxide SiO ₂ as the material of the dielectric dielectric film, which has a low relative dielectric constant equal to 3.9,

thirdly, it is complicated due to the complexity of additional technological operations for forming the intermediate plate of a thin-film capacitor.

The technical result of the claimed method for manufacturing a thin-film capacitor is an increase in specific capacitance, an increase in specific breakdown voltage, a decrease in the dielectric loss tangent (tg ), increasing the yield, simplifying the manufacturing method.

The specified technical result is achieved by the claimed method for manufacturing a thin-film capacitor of electronic equipment, including

direct sequential formation on a given substrate of a thin film of each element of a thin-film capacitor - the lower lining, dielectric, upper lining, current leads, each thin film is made of a given thickness, by means of the technological process of the corresponding technological operations - deposition of the said thin films, photolithography and etching, with each technological operation with specified technological parameters and modes.

Wherein

when forming an element of a thin-film capacitor - a dielectric:

a thin dielectric film is formed from a material - silicon nitride,

in at least two steps

with the same thickness of the dielectric thin film layer at each stage, less than 25 nm (2.5×10^-8 m) (hereinafter referred to as nm),

with an interval between the stages of formation in time 20-40 sec,

in a single technological process of the mentioned technological operations - deposition of a thin dielectric film, photolithography and etching,

in this case, the integer number of stages of formation of a thin dielectric film N is determined from the expression:

N = d / s, where

d - given total thickness of a thin dielectric film, nm

s is the same thickness of the thin dielectric film layer at each stage, nm.

The thin-film capacitor is made - made as part of a microwave monolithic integrated circuit, or as part of a microwave hybrid integrated circuit, or as part of any thin-film microcircuit, or in the form of a discrete thin-film capacitor.

The specified substrate is made of a semiconductor material with a surface cleanliness class that ensures the subsequent technological process of epitaxial growth (EPI-READY), or Al ₂ O ₃ corundum material.

When forming a thin film of the lower lining and a thin film of the upper lining, their application is carried out by vacuum deposition of metals, or their alloys, or their systems.

When forming a thin dielectric film, its deposition is carried out by plasma-chemical deposition.

Disclosure of the essence of the invention.

The set of essential features of both restrictive and distinctive parts of the claimed method for manufacturing a thin-film capacitor in electronic technology, namely.

The formation of a thin film of dielectric material - silicon nitride Si ₃ N ₄ , which has a significantly higher value of dielectric constant (ε) equal to 7, in contrast to the value of the relative permittivity of the thin film dielectric material of the prototype - silicon dioxide SiO ₂ equal to 3.9, provides the formation of a thin-film capacitor with a higher specific capacitance at the same thickness.

Formation of a thin dielectric film from silicon nitride material Si ₃ N ₄ ,

in at least two steps

with the same layer thickness of a thin dielectric film of silicon nitride material Si ₃ N ₄ , at each stage less than 25 nm,

with an interval of formation between stages in time 20-40 sec,

in a single technological process of technological operations - the deposition of a thin dielectric film, photolithography and etching, when each technological operation is carried out with specified technological parameters and modes,

when the integer number of steps for forming a thin dielectric film N is determined from the specified expression.

It provides.

Optimal values of technological parameters and modes of technological operations - deposition of thin films, photolithography and etching of the technological process as a whole during the formation of a thin dielectric film from silicon nitride material and, thereby, the maximum possible reduction in the number of defects in a thin dielectric film and, thereby, a significant improvement in the electrical parameters of a thin-film capacitor, namely, an increase in the specific breakdown voltage, a decrease in the dielectric loss tangent (tg ) and, as a consequence, an increase in yield.

Moreover, the claimed method for manufacturing a thin-film capacitor eliminates the need to form an intermediate plate of a prototype thin-film capacitor, which involves performing complex technological operations and, as a result, simplifying the manufacturing method.

The formation of a dielectric film with the same thickness of its layer at each stage of more than 25 nm is not desirable, since it leads to an increase in the number of defects and, accordingly, an undesirable deterioration in electrophysical parameters, and less than 25 nm is limited by the technical capabilities of the technological equipment used.

The interval between the stages of formation of a thin dielectric film is less than 20 seconds,

as well as the number of stages N in the formation of a thin dielectric film less than determined from the specified expression are not desirable, since they do not fully provide the specified technical result, and more than 40 seconds is not advisable.

So, the set of essential features of the claimed method of manufacturing a thin-film capacitor fully provides the claimed technical result, namely, an increase in specific capacitance, an increase in specific breakdown voltage, a decrease in the dielectric loss tangent (tg , increasing the yield, simplifying the manufacturing method .

The invention is illustrated by drawings.

In FIG. 1 is a general view of a thin film capacitor, where:

- substrate - 1,

- the lower lining of the thin-film capacitor - 2,

- dielectric - in the form of a thin film of silicon nitride Si ₃ N ₄ - 3,

- the upper lining of a thin-film capacitor - 4,

- current leads - 5, 6 of the lower lining and the upper lining, respectively.

In FIG. 2 shows the dependence of the specific breakdown voltage of the claimed thin-film capacitor on the number of stages in the formation of a thin dielectric film from silicon nitride material Si ₃ N ₄ .

In FIG. 3 shows the dependence of the dielectric loss tangent (tg ) of the claimed thin-film capacitor on the number N of stages of formation of a thin dielectric film from silicon nitride material Si ₃ N ₄ .

Examples of a specific implementation of the claimed method for manufacturing a thin-film capacitor.

Example 1. Implementation of a thin film capacitor as part of a monolithic integrated circuit microwave power amplifier M421304.

The design parameters of the elements of a thin-film capacitor are set:

- thickness of the thin film of the lower lining - 300 nm;

- the thickness of the thin dielectric film (d) - 246 nm, which determines the capacitance (including specific capacitance) of the thin-film capacitor;

- the thickness of the thin film of the upper lining - 300 nm.

Determine, respectively, the same thickness of the thin dielectric film at each stage (less than 25 nm):

- the same thickness of the thin dielectric film layer at each stage (s) - equal to 20 nm , according to the specified expression in the claims;

- integer number N - six stages of formation of a thin dielectric film from silicon nitride material.

Thin films of each element of a thin-film capacitor are formed in direct sequence on a substrate 1 made of a semiconductor material of gallium arsenide GaAs , with a thickness of 6 × 10 ^-4 m, by means of the technological process of the indicated technological operations - deposition of thin films, photolithography and etching, with each technological operation with specified technological parameters and modes.

The lower plate 2 of a thin-film capacitor by - applying a thin film of aluminum material Al, 300 nm thick, by vacuum deposition (VAK641 installation), technological operations of photolithography and liquid etching in a solution of the composition CrO ₃ :NH ₄ F:H ₂ O at a ratio of 10:1:250.

Dielectric 2 in the form of a thin film of silicon nitride material Si ₃ N ₄ , in N - six stages, with the same thickness of the thin film layer of the dielectric at each stage, equal to 20 nm , with an interval between stages of 30 seconds, in a single technological process of technological operations - plasma-chemical deposition (installation Corial D250), from a mixture of gases, monosilane SiH ₄ - ammonia NH ₃ - nitrogen N ₂ - argon Ar, with their ratio of 1:4.7:3.27:5, respectively, technological operations of photolithography and plasma-chemical etching in a mixture of gases sulfur hexafluoride (SF6 gas) SF ₆ - oxygen O ₂ at their ratio: 1:12.

The upper plate 4 of a thin-film capacitor by applying a thin film of aluminum material Al, 300 nm thick, by vacuum deposition (VAK641 installation), technological operations of photolithography and liquid etching in a solution of the composition CrO ₃ :NH ₄ F:H ₂ O at a ratio of 10:1:250.

In this case, the current leads 5, 6 are formed simultaneously with the formation of the lower plate and the upper plate of the thin-film capacitor, respectively.

Examples 2-6.

Similarly to example 1, samples of thin-film capacitors were made, but with other technological parameters specified in the claims (examples 2-3, 6), and beyond (examples 4-5).

Example 6 corresponds to a discrete implementation of a thin film capacitor.

Example 7 corresponds to the prototype.

On the manufactured samples of thin-film capacitors, the following were measured:

- capacitance and specific capacitance (C), pF/mm ² was determined;

- specific breakdown voltage (U), V/m;

- dielectric loss tangent, (tg ) (Two-probe method. Installation KG-3377).

Defined

- yield, % (percentage).

The data are presented in the table and in Fig. 2, 3.

As can be seen from the table and Fig. 2, 3 values of electrical and other parameters are approximately:

- specific capacitance 200 pF / mm ² ,

- specific breakdown voltage 7×10 ⁸ V/m,

- dielectric loss tangent, (tg ) 2×10 ^-4 ,

- 99% good yield (examples 1-3, 6).

In contrast to samples made outside the claims, the similar values of the parameters of which are somewhat lower.

There are no similar data regarding the prototype object.

Thus, the claimed method for manufacturing a thin-film capacitor provides:

firstly, the sufficiently high above values of the electrical parameters are approximately -

- specific capacitance 200.0 pF/mm ² ;

- specific breakdown voltage 7×10 ⁸ V/m;

- dielectric loss tangent (tg ) 2.0×10 ^-4 ;

secondly, a high yield (about 98 percent).

Moreover, compared with the prototype, it provides a significant simplification of the manufacturing method, due to the elimination of the need to form an intermediate lining, which involves the implementation of complex technological operations.

Table N, p.p. Method for manufacturing a thin-film capacitor of electronic engineering Measurement results Execution type Substrate material Dielectric Material Specified thickness, ×10 ^-9 m. The same layer thickness at each stage, ×10 ^-9 m. Interval between stages of dielectric formation, s. Integer number of stages, pcs. Specific capacity C, pf / mm ² Specific breakdown voltage. U, ×10 ⁸ V/m. Dielectric loss tangent (tgδ)10 ^-4 Yield, % 1 monolithic Gallium arsenide, GaAs Silicon nitride, Si ₃ N ₄ 246 24 thirty 10 200 7.0 2 98 2 198 7.0 2 98 3 200 7.0 2 98 4 16 17 8 206 6.9 4 85 5 49 43 5 196 6.9 3 80 6 Discrete 24 thirty 10 200 7.0 2 99 7 - prototype Other technological parameters No data

Claims (5)

1. A method for manufacturing a thin-film capacitor of electronic equipment, including direct sequential formation on a substrate of a thin film of each element of a thin-film capacitor in the form of a lower plate, a dielectric, an upper plate, current leads, of a given thickness, by means of the technological process of the corresponding technological operations of applying the said thin films, photolithography and etching, each technological operation with specified technological modes, characterized in that during the formation of an element of a thin-film capacitor from a dielectric, a thin film of the dielectric is formed from a nitrile and silicon in at least two stages, with the same thin dielectric film thickness at each stage less than 25 nm, with a time interval of 20-40 s between the stages of formation, in a single technological process of technological operations for applying a thin film by photolithography and etching, while the integer number of stages of forming a thin dielectric film N is determined from the expression N=d/s, where d is the given total thickness of the thin dielectric film, nm, s is the same layer thickness of the thin dielectric film at each stage, nm. 2. The manufacturing method according to claim 1, characterized in that the thin-film capacitor is made as part of a microwave monolithic integrated circuit, or as part of a microwave hybrid integrated circuit, or as part of any thin-film microcircuit, or in the form of a discrete thin-film capacitor. 3. The manufacturing method according to claim 1, characterized in that the substrate is made of a semiconductor material with a surface finish class that provides a given subsequent epitaxial growth process (EPI-READY). 4. The manufacturing method according to claim 1, characterized in that when forming a thin film of the lower lining and a thin film of the upper lining, their application is carried out by vacuum deposition of metals, their alloys or their systems . 5. The manufacturing method according to claim 1, characterized in that when forming a thin dielectric film, its application is carried out by plasma-chemical deposition.