JPS6046542B2 - semiconductor element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to protective coating materials for semiconductor devices with improved electrical properties and their manufacturing capabilities.

To date, certain methods in the prior art provide a coating on at least preselected exposed surface areas of a semiconductor device with an electrically insulating oxide material. These coatings were thin layers with virtually no resistance to mechanical abrasion and required relatively expensive processing equipment. In almost all cases, a second, thicker protective coating material is coated to protect the initial electrically insulating material. Silicone greases, varnishes, rubbers and resins have been used as overcoatings or protective materials but lack desirable physical properties. RO? in U.S. Patent No. 3,615,913 dated October 26, 1971? RtR. Shaw teaches disposing a coating of a cured protective coating material selected from the group consisting of polyimide and polyamide-polyimide over the exposed end portion of at least one P-N junction.

Although these materials have shown good wear resistance properties, improvements still need to be made given the passivation requirements of semiconductor devices. In addition, Shaw uses materials such as silicon oxide, fiberglass, boron nitride, aluminum oxide, quartz, mica, magnesium oxide, and reactivated polytetrafluoroethylene to control the consistency of polymeric materials to form selected surface areas of semiconductor devices. It also teaches that it should be suitable for application to.

Alizarin has also been incorporated into various coating materials to assist in a type of surface cleaning treatment for semiconductor devices. Currently, oxide/glass layers are widely used for passivation and encapsulation of semiconductor devices, where device stability and long life are important considerations.

However, if it is necessary to apply a vitreous layer after aluminum metallization, the selection of a suitable glass system is severely limited by the maximum allowable application temperature of about 577°C.
This limit is established by the aluminum-silicon eutectic and must be carefully observed in all processing operations following silicon aluminization. Several glass coating methods are currently in use.

These include chemical vapor deposition (CVD), glass frits and spin-on glass forming alcoholates. The last mentioned method can only form a very thin layer of glass, on the order of 2000 amps, which tends to be more reactive than desired, thus limiting its practicality in packaging. has been done. Although glass frit is widely used in packaging, it is not commonly used for surface immobilization due to the difficulty in preparing chemically stable glass that has sufficient expansion compatibility with silicon and at the same time is a suitable immobilizing agent. Not used. CVD
The method allows sufficient thickness, wide selection of compositions, expansion matching, etc., but can be tolerated by direct deposition onto the base silicon due to the difficulty of controlling sodium contamination in the CVD reactor. This makes it difficult to obtain a stable base. Therefore, this method is usually limited to the use of SiO2 as an overcoat and metallization layer. It is believed that none of these methods, in their current state of development, can provide a reliable immobilization/encapsulation method for large thyristors and other power semiconductor devices. Passive coating materials have been developed for coating electronic parts.

This material is a copolymer of the reaction product of a silicon-free organic diamine, an organic tetracarboxylic dianhydride, and a polysiloxane. This material is a significant improvement over prior art materials and exhibits better adhesion and corona resistance than available polyimide and polyamide-imide coatings. Due to their useful surface properties, it is desirable to use such materials to coat high voltage semiconductor devices. In such devices, it is desirable that the surface coating reduce the high electric field developed at the silicon surface to a value low enough that no surface breakdown or corona occurs in the surrounding air, and surface leakage is not significant. This is difficult to do with very thin layers of polymeric material. However, with suitable fillers, thicker layers of material can be applied by economical means such as painting or screen printing. In accordance with the teachings of the present invention, a semiconductor device is provided that includes a body of semiconductor material having at least two regions of opposite conductivity type.

A P-N junction is formed between the abutting surfaces of each pair of regions of opposite conductivity type. at least one P
The end of the -N junction is exposed on the surface of the main body. A layer of an organic or silicone-containing organic material is a semiconductor x structure having a polymer having 5 to 45 mol % of a single position, (c) a polyimide compound of formula (1) and a polyimide of formula (■) 15 to 45 mol %
(However, in the formula, R is a divalent hydrocarbon group, R''
is a monovalent hydrocarbon group, R'' is a tetravalent organic group, Q is a divalent silicon-free organic group that is the residue of an organic diamine, X is an integer larger than O, and m and n are 1 (integer numbers greater than or equal to each other may be equal to each other). Any of the above polymeric materials may be incorporated therein with a filler material selected from the group consisting of silica, alumina, and silicon. It's crowded.

Filler materials improve the physical and electrical properties of polymeric materials. Additionally, silica and silicon also make the polymeric materials more suitable for laser scribing of semiconductor wafers. In FIG. 1, a half body of semiconductor material 12 is positioned over selected surface areas of the device and the end of at least one P-N junction exposed at the surface.

This layer of material is an immobilizing coating and/or an encapsulating agent for the surface area covered thereby. Here, the passivation coating material is (a) a reaction product of a silicon-free diamine and an organic tetracarboxylic dianhydride, and when cured, has a repeating unit of the formula; (b) a silicon-free diamine; The reaction product of an organic tetracarboxylic dianhydride and an amino-terminated polysiloxane diamine, when cured, shows repeating structural units of formula 1 and a conductive element 10 of formula 10 intercondensed therewith.

The body 12 is prepared, for example, by sanding and lapping the two side surfaces 14 and 16 until they are parallel. The body 12 has two or more regions of opposite conductivity type with a P-N junction formed by the abutting surfaces of each pair of regions of opposite conductivity type. An end of at least one P-N junction is exposed on the surface of body 12. The main body 12 is made of silicon, for example.
It is composed of suitable semiconductor materials such as silicon carbide, germanium, compounds of Group I and Group II elements, and compounds of Group I and Group II elements. Solely to more fully describe the invention, body 12 is depicted as being comprised of a silicon semiconductor material having five conductive regions and four P-N junctions.

The element 10 having such a shape and structure can function as a thyristor. Therefore, the body 12 has regions 18 and 2 of P-type conductivity.
0, P+ type conductivity type region 19 and N type conductivity type region 2
2, 24 and 26. P-N junction 28, 30, 3
2 and 34 each pair 18 and 22 of regions of opposite conductivity type;
It is formed by abutment surfaces 22 and 20, 20 and 24, and 20 and 26. One means of controlling the surface field on such a controlled rectifier is to secure the partially treated body 12 to a large area contact or support electrode 38 by a layer 40 of a suitable ohmic solder, and then loop the sides 36. part.

Electrical contacts 42 and 44 are secured to respective regions 24 and 26. As illustrated, the ringing of surface 36 provides the well-known "double bevel" surface. Referring now to FIG. 2, a semiconductor device 50 is shown that includes a double positive bevel feature for controlling the surface electric field.

All items designated with the same reference numerals as items in device 10 of FIG. 1 are the same as reaction items in device 10 and function in the same manner. Element 50 functions as a thyristor in the illustrated configuration. Regardless of the method used to control the surface electric field, at least some selected ends of the P-N junctions are exposed at the surface area of body 12.

Therefore, it is necessary to apply a suitable material to protect the exposed end of the P-N junction. A layer of protective coating material 46 covers at least surface 36 and at least P-N junctions 28 and 3.
placed on the exposed end of 0.

The material of layer 46 adheres to surface 36 as well as the material of layer 44 and contact or support electrode 38. It is desirable to The material of layer 46 must have sufficient dielectric properties and must also be able to withstand the high temperatures encountered during processing of device 10. Additionally, the material of layer 46 must be capable of providing an adhesive bond to selected surfaces of element 10 once cured. The protective coating material, e.g. It was the preferred material when placed over the exposed ends of N-junctions 28 and 30.

The protective coating material may be disposed on surface 36 as a polymeric precursor dissolved in a suitable solvent.

Upon heating, the solvent is vaporized and the protective coating material of layer 46 is imidized in situ onto surface 36 as well as the end of the at least one P-N junction. Preferably, the material of layer 46 is applied to preselected surface areas of surface 36 of body 12 as a solution of a soluble polymeric intermediate. Application of the material to at least surface 36 of body 12 is by any suitable means such as spraying, rolling, brushing, etc. Body 12 coated with the protective coating material is then heated to cure the resinous soluble polymer intermediate. selectively converted into an insoluble material. layer 4
Suitable materials which constitute 6 and meet the above requirements include (a) a reaction product of a silicon-free organic diamine and an organic tetracarboxylic dianhydride which, when cured, forms repeating units of the formula (b) the reaction product of a silicon-free organic diamine, an organic tetracarboxylic dianhydride and an amino-terminated polysiloxane diamine in a suitable organic solvent yields a polymer having repeating structural units of formula 1; The structure of the formula mutually condensed with this has a single position of 5 to 45s, preferably 25 to
and (c) a blend of 15 to 45 mol % of a polyimide of formula 1 and a polyimide of formula 2, where R is a divalent hydrocarbon. group, R'' is a monovalent hydrocarbon group, R'' is a tetravalent organic group, Q is a divalent silicon-free organic group of the residue of an organic diamine, X is an integer of at least 1, advantageously from 1 to 8 It is preferably 1000 or more, and m and n are the same or different integers greater than 1 and preferably 10 to 1000 or more.

The block or random copolymers described above are composed of a diamine-siloxane of the general formula, a silicon-free diamino compound of the formula, and a silicon-free diamino compound of the formula where R, R'', R'''', Q, x, m and n have the above meanings. have

It can be prepared by reacting a mixture containing various components of tetracarboxylic dianhydride represented by * in an appropriate molecular ratio, where R, R'', R'', Q and X have the above meanings.

A polyimide consisting only of repeating structural units of formula 1 and a polyimide consisting only of repeating structural units of formula ■ are blended together, and the molar ratio is determined based on the total molar concentration of units of formula 15 to 4 structural units, preferably 25 to 3
Polysiloxane-
Imide compositions may be used with comparable effectiveness in appropriate solvents.

``This material formulation is applied to the appropriate surface area and the solvent is vaporized in situ.The final polyimide siloxane composition used in the practice of this invention should consist essentially of the imide structures of formulas 1 and 2. would be recognized.

However, the actual precursor material resulting from the reaction of diamino, siloxane, silicon-free organic diamine, and tetracarboxylic dianhydride was initially in the form of a polyamic acid structure consisting of structural units of the following formulas (■) and (■). Let's do it. Diaminosiloxanes of the formula (2) that can be used in practice in the present invention include compounds of the following formula.

etc.

Diamines of formula (1) have been described in the prior art and most are commercially available materials.

Typical diamines from which prepolymers can be prepared are as follows. m-phenylenediamine, p-phenylenediamine, 4,4''-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 4,4''-methylene dianiline, benzidine, 4,4''-diaminodiphenyl sulfide, 4,4 ″-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 1
, 5-diaminophthalene, 3,3'-dimethylbenzidine, 3,3-dimethoxybenzidine, 2,4-bis(
β-amino-t-butyl)toluene, bis(p-β-aminobutylphenyl)ether, bis(p-β-methyl-0j-aminopentyl)benzene, 1,3-diamino-4-isopropylbenzene, 1,2 -bis(3-aminopropoxy)ethane, m-xylene diamine, p-
Xylene diamine, bis(4-aminocyclohexyl)
Methane, decamethylene diamine, 3-methylheptamethylene diamine, 4,4-dimethylheptamethylene diamine, 2,11-dodecane diamine, 22-dimethylpropylene diamine, octamethylene diamine, 3-methoxyhexamethylene diamine, 2,5- Dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 2-methylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-cyclohexanediamine, 1,12-octahexanediamine, bis(3-aminopropyl) sulfide, N-methylbis(3-aminopropyl)amine, hexamethylene diamine, heptamethylene diamine, nonamethylene diamine, and mixtures thereof. These diamines are provided for illustrative purposes only and are not exhaustive. Other diamines not mentioned herein will be readily apparent to those skilled in the art. Expression ■
The tetracarboxylic dianhydride can be further defined as follows.

That is, R'''' is a tetravalent group, for example a group derived from or containing an aromatic group containing at least 6 carbon atoms characterized by benzenoid unsaturation, and is a dianhydride. Each of the four carbonyl groups of is bonded to a separate carbonyl atom in the tetravalent group, the carbonyl groups form pairs, and the carbonyl group in each pair is bonded to an adjacent carbon atom of the R″ group or to a separate carbon atom in the R″″ group. are bonded to two carbon atoms separated by at most one carbon atom to give a five- or six-membered ring structure. Examples of dianhydrides suitable for use in the present invention include: is included.

Show your name within the katsuko. Pyrometriic dianhydride (PM
DA), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3″4,4″-diphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride 2,2″,3,3″-diphenyltetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 2,2′-bis[4-(3
, 4-dicarboxyphenoxy)phenyl]propanihydride (BPA dianhydride), 2,2-bis[4-(2,
3-dicarboxyphenoxy)phenyl]propanihydride, benzophenonetetracarboxylic dianhydride (BP
DA), perylene-1,2,7,8-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)
Methanide dianhydride, as well as aliphatic anhydrides such as cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, butanetetracarboxylic dianhydride. It is not excluded to introduce other dianhydrides, for example trimellitic anhydride, to produce amide-imidosiloxane polymers. The novel material composition of the present invention incorporates a filler selected from the group consisting of silica, alumina and silicon.

The filler material controls the viscosity, shear properties and/or interaction with the surface of the electronic component to which it is applied, and aids in dielectric control to improve the electrical properties of the encapsulant or passivator material. Additionally, these fillers make the polymeric materials more amenable to laser scribing of semiconductor wafers. Preferably, the material of coating 46 is applied as a precursor onto surface 36.

The precursor or formulation solution is a solution of the resinous material in a suitable solvent (e.g., N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, etc.) alone or in combination with a non-solvent. It is made by dissolving the filler with or without a suitable filler. Precursor or formulation solutions with a solids content of 10-4% by weight are suitable for semiconductor work.

Preferably, the precursor or formulation solution contains 20-4% saliva.
Contains resinous material in solid content. Sufficient material is applied to surface 36 to provide layer 46 with a thickness of 1 to 100 microns. The substrate material can be applied to the surface 36 by conventional means such as dipping,
It may be applied by spraying, painting, spreading, etc.

Blends of block or random copolymers or polymers can often be dried by removing the solvent in an initial heating step at a temperature of about 75 DEG to 125 DEG C. for a sufficient period of time under vacuum. To convert the polyamic acid of the precursor solution to the corresponding polyimide siloxane, it is then heated to a temperature of 150 DEG to 300 DEG C. for a time sufficient to effect the desired conversion to the polyimide structure and final curing. Preferred curing cycles for materials of the above general formula are as follows.

(a) 15-3 Gin at 135-150 °C in dry N2 (b
) 15-6 Gin (c
) in vacuo at about 225 DEG C. for 1 to 3 hours) Alternatively, the coating material can be formed in other atmospheres, such as air, to facilitate commercial application of the invention.

A suitable polymer precursor solution containing the selected filler material is formed by reacting benzophenone tetracarboxylic dianhydride with methylene dianiline and bis(gamma-aminopropyl)tetramethyldisiloxane.

The latter two diamine materials are present in a molar ratio of 85:15 to 55:45. Preferably, the desired molar ratio of the two diamine materials ranges from 75:25 to 65:35. The preferred polymeric precursor material molar ratio is 70:30. Reactions of the chemical components are carried out at temperatures below 50° C. using suitably purified and dried materials to favor high molecular weight polymers. The polymer precursor solution is N-methyl-2-
It is dissolved in pyrrolidone in the form of polyamic acid,
The solids content is 10-4% by weight. Preferably, the solution has a solids content of about 25% by weight in polyamic acid form. Selected materials are added to this solution to improve the electrical properties of both the coating material and the selected surface area of the electronic component to which it is applied. The dielectric constant of the cured polymer is on the order of about 3J.

When an unfilled polymeric material is applied to selected surface areas of silicon with a dielectric constant of 12, the electric field strength of the silicon can reach levels of 1 to 2 x 1 CP Volts/Cm in an inverted configuration. It is almost three times as strong. Therefore, the polyimide-silicone copolymer is about 6 x 1σ volts/Cm (3 x 2 x 1
It must be possible to maintain a maximum electric field of the order of σ volts/cm). Increasing the dielectric constant of the polyimide-silicone copolymer film by introducing selected filler-materials reduces the electric field that the material must withstand. For example, if up to 5% by weight of a filler material, such as silicon, having a dielectric constant of about 12 is present, the electric field for the cured film will be 3.7/!
7.9=0.47, or about half the electric field of the unfilled material. The surface charge at the interface between the cured film of the coating material and the silicon element may be a function of the charge distributed in the coating material.

In these cases, the dielectric constant is high! This has the added benefit of lowering the effective surface charge value. This is desirable for semiconductor P-N junctions containing both lightly doped n and p regions, where minimizing the surface charge rate results in the highest dropout value and the lowest reverse leakage. For filled polymers and filled polyimide silicone materials, the maximum filler content of the cured polymer is on the order of about 5% by weight, beyond which a void structure may begin to appear and dielectric properties may deteriorate. be.

However, if the solids loading is significantly lower than 5 sq.
A significant change in shear viscosity behavior occurs, which facilitates the application of these materials to semiconductor devices using inexpensive processes such as screen printing. The best weight ratio of filler material to precursor solution depends on the material, density, particle size,
Depends on shape and polymer solids content.

Assuming that, after curing, the void-free composite is made up of spherical-sized silicon particles arranged in a cubic arrangement, the maximum weight of solids that can be effectively added to the precursor solution is:
When silica is used as a filler, it becomes, where, Ws
is the solid filler Wps is the weight of the polymer solution (precursor),
and WFp is the weight percentage of polymer in the precursor solution.

For example, certain typical values for precursor solutions incorporating silicon or silica fillers are given in the table below.

Higher weight percentages of filler than stated do not result in a void-free structure when cured. A suitable filler material dielectric material that meets the desired requirements is silicon.

The material is available in high purity, with impurity levels on the order of <0.01 ppm, and is relatively inert, without introducing unwanted impurities into the surface coating that could affect the stability of the device. Can be easily incorporated as a filler. Because the dielectric constant of silicon is relatively high compared to silica and alumina, silicon has the additional advantage of lowering the electric field within the composite coating. In general, leakage and avalanche multiplication in dielectric materials depends on the electric field strength.

The electric field strength is inversely proportional to the dielectric constant of the material. The dielectric constant has the effect of lowering the electric field in the dielectric for a given applied voltage. Therefore, silicon-loaded polymer or copolymer materials of the present invention can withstand higher applied voltages than unfilled copolymer materials. When added as a filler to polymeric coating materials, powdered silicon, like silica and alumina, greatly influences the shear viscosity properties of the mixture.

This variation is very beneficial in some applications when it is desired to apply relatively thick layers on devices that must withstand high voltages. For example, incorporating any of these materials or mixtures as fillers provides desirable shear viscosity properties for certain screen printing applications in a low cost manner. Without fillers, the low viscosity properties of the precursor solutions make them unsuitable for use in screen printing applications. When applied to a semiconductor device, the filler material thus obtained provides an excellent immobility material as well as a protective coating for the device.

This material is particularly suitable for application to selected surface areas such as eroded electrical isolation trenches in semiconductor devices. Silicon, alumina, and silica are added to control the consistency of polymer and copolymer solutions.

Furthermore, this addition lowers the coefficient of expansion of the coating or encapsulation material as formed, thereby providing a good match of the coefficient of thermal expansion, especially when the semiconductor material is single crystal silicon. Once cured, the silica-filled or silicon-filled polymeric materials withstand exposure to temperatures of up to at least 500'C in pure oxygen environments without any deleterious effects.

A particular silica that is an excellent addition to solutions is CAB-0
"SIL(CabOtCOrpOratioOn, BOs
It is a fumed silicon oxide commercially available under the trade name tOn, MaSSaChl]
．． It is on the order of 0.014 to 0.007 μm.

The specific alumina filler for this application is Benchtop Aluminum T-61 (AluminumCOrpOrati).
OnOfAmerica). Although the main reason for adding silicon, alumina, or silica to solutions is to control the solution's coefficient of thermal expansion, dielectric strength, and viscosity, this new material also offers several other unexpected benefits. It is. The cured filled material provides the coating with excellent moisture resistance. That is, the filled material after curing has reduced permeability to ambient moisture to which the cured material is exposed.
This is demonstrated by the fact that no harmful effects occur even when the coated semiconductor device is immersed in water for an extended period of time, up to about one full hour. Furthermore, the filled film coating after curing reduces light transmission through the coating material. A particularly advantageous effect of silicon, alumina or silica materials is the discovery that fillers increase the infrared absorption by the coating material. This allows laser scribing of semiconductor wafers coated with cured filled polymeric material.

[Brief explanation of the drawing]

1 and 2 are cross-sectional side elevational views of semiconductor devices containing the novel polymeric materials of the present invention. No. 10, 50... Semiconductor element, 12... Main body, 14
, 16... Main surface, 18, 20... P-type conductivity type region,
19...P+ type conductive region, 22, 24, 26...N
Type conductive region, 38... Support electrode, 42, 44... Electrical contact, 46... Protective coating layer.

Claims (1)

Claims: 1. A body of semiconductor material, a layer of encapsulant material disposed on at least one selected surface area of the body, and a layer of encapsulant material for controlling the physical properties of the encapsulant material. a silica or silicon filler material mixed into the capsule encapsulant material to improve laser scribing of the capsule encapsulant material; ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I)
Repeating structural units and formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ Copolymers formed by mutually condensing the repeating structural units of (II) (However, formula (I)
and a silicon-free organic diamine, an organic tetracarboxylic dianhydride, and an amino-terminated polydiamine in which the molar concentration of units of formula (II) is 15 to 45 mol % based on the total molar concentration of units of formula (II). a reaction product of siloxane diamine, and (b) a blend of a polyimide compound of formula (I) and a polyimide compound of formula (II) (provided that formula (I) and formula (II)
) having a molar concentration of units of formula (II) based on the total molar concentration of units of formula (II) (wherein R is a divalent hydrocarbon group, ' is a monovalent hydrocarbon group, R'' is a tetravalent organic group, Q is a divalent silicon-free organic group of the residue of an organic diamine, x is an integer greater than 0, and m and n are 1 is an integer greater than ), and
The maximum weight of silicon mixed in the precursor solution of the polymeric material is expressed by the formula [Ws/Wps]max=1.66WFp, and the maximum weight of silica mixed in the precursor solution of the polymeric material is expressed by the formula [Ws/Wps]max=1.66WFp. Ws/Wps] Maximum = 1.75WF
p (where Ws is the weight of the solid filler, Wps is the weight of the polymer solution (precursor), and WFp is the weight fraction of the polymer in the precursor solution). semiconductor element. 2 The polymer material is a copolymer and has the formula (I
2. The semiconductor device according to claim 1, wherein the mole percentage of the structural unit I) is 25 to 35%. 3. The semiconductor device according to claim 1 or 2, wherein the mole % of the structural unit of formula (II) is about 30%.