JPH0588752B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a so-called inner coat resin composition for protecting the surface of a semiconductor chip. <Conventional technology> What is an inner coat for a semiconductor? When a semiconductor chip is encapsulated with a resin, it is used to protect the semiconductor surface from damage caused by shrinkage stress caused by curing of the resin, or to protect the connections of bonding wires. It is coated in advance as a protective layer. FIG. 1 shows an example of a semiconductor device in which a semiconductor chip is coated with an inner coat. In other words, a semiconductor chip 2 having an inner coat layer 1 is bonded onto a lead frame 7a serving as a semiconductor substrate using an adhesive layer 6 for die bonding. Indicates a fixed state. 3 is an electrode 5 formed on the chip 2
4 is the tip of the bonding wire connecting the lead frames 7b and 7c, and 8 is a sealing resin for each of the above-mentioned components. Usually, a device such as a dispenser is used to apply an inner coat of resin onto a semiconductor chip.
A determined amount of the resin composition is allowed to fall naturally onto the chip surface as droplets through the pores, and the droplets are spread to sufficiently cover the entire chip surface and the tip of the bonding wire, and then hardened to form a coating layer. . Conventional resins for inner coatings have been silicone-based gels and rubbers. Addition reaction crosslinked organosiloxane gels are known as such silicone-based gels, and addition reaction crosslinked organopolysiloxane rubbers, condensation reaction crosslinked type or room temperature vulcanization type organopolysiloxane rubbers are known as silicone rubbers. However, it has some major problems as described below. FIG. 2A shows an enlarged sectional view of the vicinity of the tip of the bonding wire constituting the semiconductor device, and FIG. 2B shows an enlarged sectional view of the vicinity of the inner coat layer.
The tip of the bonding wire has various shapes depending on the means of adhesion to the electrode, but in this example, a case will be described in which a ball bonding wire having the shape shown in FIG. 2A, which is commonly used, is used. When forming an inner coat layer on the surface of a semiconductor chip, care must be taken to prevent bonding wires from breaking (wire open) caused by repeated extreme temperature changes.
The inner coat layer 1 after hardening is coated so as to cover the upper part of the side curved part Q of the tip part 4 of the bonding wire. For example, the second
Assuming that the width Z of the chip shown in Figure B is 7 mm and the dimension from the chip surface to the curved part P of the tip of the bonding wire is 40 μm, the inner coating layer is applied from the chip surface to the required coating point Q at the wire tip. The thickness requires approximately 100 μm. In this case, the covering point Q
If a conventional inner coat resin is used to obtain the desired coating thickness, the maximum coating thickness X at the center of the inner coat layer reaches 500 to 600 μm.
On the other hand, due to the recent increase in the size of semiconductor chips, the improvement in packaging density, and the trend toward thinner sealing resins due to the advent of IC cards, etc., the maximum coating thickness X of the inner coat layer must be made as thin as possible. be. However, with the conventional inner coat resin, the coating thickness X is too thick, so the narrow sealing resin region Y located at the top end of the inner coat layer becomes too thin.
Therefore, the mechanical strength of Y is reduced, and repeated extreme temperature cycles cause cracks in the semiconductor sealing resin, which is a fatal problem for semiconductor devices. In addition, because the viscosity of conventional inner coating resins is inappropriate, the dispersion after dropping as droplets on the surface of a semiconductor chip during coating is poor, causing it to spread to slight grooves and irregularities on the chip surface or to the area around the bonding wire. Difficult to apply uniformly. Furthermore, conventional resins for inner coatings have a problem of poor affinity with the surface of bonding wires made of gold wires, which tends to cause wire opens. <Problems to be Solved by the Invention> The present invention has been made in view of the above-mentioned circumstances, and is particularly designed to form a uniform and thin inner coat layer, and to prevent wires from opening even under severe heat cycle conditions. The present invention provides a resin composition for inner coating. <Means for solving the problems> That is, the composition of the present invention has (A) the general formula,

[Formula] [In the formula, V is a vinyl group, Me is a methyl group, Ph is a phenyl group, and R is a methyl group or a phenyl group] Vinyl group-containing polysiloxane
100 parts by weight, (B) general formula,

[Formula] [In the formula, Me represents a methyl group].
1 to 35 parts by weight of polysiloxane containing a hydrogen atom bonded to a silicon atom, (C) General formula R ¹ Si (OR ² ) ₃ [wherein R ¹ is a lower alkenyl group, R ² is a lower alkyl group, or Alkenyl group-containing silane compounds represented by the general formula R ³ (OCH ₂ CH ₂ ) _j (R ³ is a methyl group or ethyl group, j is 1 or 2), the above (A) and (B) 0.01 for the total amount of
~2.0% by weight, (D) a platinum-based addition reaction catalyst, wherein the polysiloxane (A) has a l/(k+l) value of 0.01 to 0.2 and a temperature of 25°C.
The polysiloxane of (B) has a viscosity of 100 to 800 cps at n/(m+n) value of 0.05 to 0.3 and temperature
It is characterized by having a viscosity of 2 to 500 cps at 25°C. Hereinafter, the configuration of the present invention will be explained in more detail. The vinyl group-containing polysiloxane of component (A) is a linear polysiloxane having vinyl groups bonded to Si atoms only at both ends, and (PhRSiO) units (R is a methyl group or a phenyl group) in the polysiloxane. The ratio of the number of moles l of (indicating) to the total value of the number of moles K of (Me ₂ SiO) units and the above l is
0.01~0.2 and viscosity at 25℃ 100~
Must have 800cps. The purpose of making the main chain portion of component (A) a copolymer of (Me ₂ SiO) units and (PhRSiO) units is to create an inner coat using the composition of the present invention by introducing a phenyl group. The purpose is to improve the heat resistance of the layer. Therefore, it is more preferable that R in the (PhRSiO) unit is a phenyl group. In addition, if this l/(k+l) value is smaller than 0.01, the desired heat resistance cannot be obtained, and if it exceeds 0.2, there is no problem with heat resistance, but hydrogen atoms bonded to the Si atoms of component (B) are present. A problem arises in compatibility with polysiloxane, which causes the inner coat layer to become cloudy. A preferable range of this l/(k+l) value is 0.03 to 0.15. Also, the temperature 25
If the viscosity at °C is less than 100 cps, the diffusion to the semiconductor chip surface will be too fast, resulting in the inner coating layer becoming too thin to cover the bonding wire periphery or falling off the chip surface. On the other hand, if the viscosity exceeds 800 cps, the diffusion to the surface of the semiconductor chip will be poor, making it impossible to obtain the desired thin inner coat layer, and evenly coating the area around the bonding wire. It becomes difficult. Next, the polysiloxane containing hydrogen atoms bonded to silicon atoms as component (B) is a linear polysiloxane containing hydrogen atoms bonded to Si atoms at both ends and side chains, and is A certain ingredient (A)
It acts as a curing agent for vinyl group-containing polysiloxanes by an addition reaction of Si--H to the vinyl groups, that is, a so-called hydrosilylation reaction. This polysiloxane has the number n of moles of (MeHSiO) units in the general formula (B),
The ratio of the number of moles m of (Me ₂ SiO) units to the total value of n must be 0.05 to 0.3, and the viscosity at 25°C must be 2 to 500 cps. ) 1 to 35 parts by weight per 100 parts by weight. The n/(m+n) value is
If it is less than 0.05, there is a strong possibility that the curing will be insufficient, and if it exceeds 0.3, the film tends to be somewhat inflexible due to excessive curing reaction. This n/
Even if the (m+n) value is slightly outside the limits of the above range, it may be preferable by varying the respective viscosity of components (A) and (B) or the ratio of (B) to (A) used. Although it can be adjusted to a hardened state, the preferred range is 0.1 to 0.2. Further, if the viscosity at a temperature of 25° C. is lower than 2 cps, it is not only difficult to adjust the initial viscosity of the composition to a preferable value, but also causes problems in the cured state due to the low molecular weight of the polysiloxane. On the other hand, even when the viscosity exceeds 500 cps, there still exists the problem that it is difficult to adjust the initial viscosity of the composition to a preferable value. The preferred range of the viscosity is 5
~150cps. If the amount of polysiloxane used is less than 1 part by weight per 100 parts by weight of component (A), the inner coat layer tends to be insufficiently cured, and if the amount exceeds 35 parts by weight, the inner coat layer may become reactive. Rich Si--H tends to remain unreacted, and as a result, the stability and electrical properties of the cured film are adversely affected. The polysiloxanes of components (A) and (B) can be produced by generally well-known methods. For example, in the case of vinyl group-containing polysiloxane (A), hexamethylcyclotrisiloxane or octamethylcyclotrisiloxane and hexaphenylcyclotrisiloxane or trimethyl in the presence of divinyltetramethyldisiloxane as a terminal capping agent. Triphenylcyclosiloxane can be treated with an acid catalyst such as sulfuric acid, hydrochloric acid, activated clay, or lithium hydroxide, potassium hydroxide, cesium hydroxide, tetramethylammonium hydroxide, lithium silanolate, potassium silanolate, lithium phenoxide. After equilibration using an alkali catalyst such as, etc., the catalyst is removed by a conventional method, and low molecular weight polysiloxane is removed by heating under reduced pressure to purify. In the case of polysiloxane having silicon-bonded hydrogen groups (B),
By using tetramethyldisiloxane as the terminal capping agent and using tetramethylcyclotetrasiloxane in place of the phenyl group-containing cyclic polysiloxane, it can be produced in the same manner as in the case of (A) above. It is also known that in each of the above cases, the viscosity and the content of phenyl groups or silicon-bonded hydrogen groups can be adjusted to desired values by adjusting the ratio of raw materials used. Component (C) is a silane compound represented by the general formula R ¹ Si(OR ² ) ₃ , where R ¹ is a lower alkenyl group,
R ² is a lower alkyl group, or the general formula, R ³ (OCH ₂
CH ₂ ) _j (R ³ is a methyl group or an ethyl group, j is 1 or 2), and component (A) and component ( 0.01 to 2.0% by weight based on the total amount of B)
use. Examples of R ¹ include a vinyl group, an allyl group, a 1-propenyl group, and an isopropenyl group, among which a vinyl group is particularly preferred. or
R ² is a methyl group, an ethyl group, a propyl group,
Isopropyl group, butyl group, isobutyl group, or methoxyethylene group, ethoxyethylene group,
2-(2-methoxyethoxy)ethylene group, 2-
(2-ethoxyethoxy)ethylene group, etc. are exemplified. If the amount of the silane compound used is less than 0.01% by weight based on the total amount of components (A) and (B), the adhesion will not be improved sufficiently, and even if it is used in an amount exceeding 2.0% by weight, the adhesion will not improve. In addition, the properties will not be significantly improved, and the number of highly reactive SiOR ² groups will increase, resulting in disadvantageous effects such as adversely affecting the stability of the cured film or various electrical properties. The preferred range of the amount of the silane compound used is 0.05 to 1.0% by weight based on the total amount of (A) and (B). The platinum-based addition reaction catalyst of component (D) includes all known platinum catalysts that are effective as addition reaction catalysts between vinyl groups and silicon-bonded hydrogen, including chloroplatinic acid, chloroplatinic acid and olefin, or vinyl Representative examples include complex compounds such as group-containing polysiloxanes, platinum coordination compounds, and the like. The amount of the addition reaction catalyst used only affects the curing rate in relation to the temperature conditions and does not need to be particularly limited, but in practical terms, the total amount of (A) and (B) An amount that provides 2 to 6 ppm of platinum atoms is preferable. Further, at this time, there is no problem in using a compound having the ability to coordinate platinum, which is an addition reaction catalyst, to temporarily deactivate the catalytic ability, that is, a known compound known as an addition reaction retarder. Incidentally, it is also permissible to add an inorganic filler or a heat-resistant stabilizer to the composition of the present invention as long as it does not affect the properties required as a semiconductor inner coat. In addition, when mixing the above ingredients to form a composition, it is possible to mix all the ingredients at once, but a two-component type in which each ingredient is divided into two groups and mixed in advance. The mixing method is both practical and common. At this time, components other than the vinyl group-containing polysiloxane of component (A) cannot be mixed in advance with the silicon-bonded hydrogen-containing polysiloxane of component (B) due to the high reactivity of silicon-bonded hydrogen. The lower alkenyl group-containing silane compound of component (C), the platinum-based addition reaction catalyst of component (D), and, if necessary, addition reaction retardant, inorganic filler, or heat-resistant stabilizer, etc. are the vinyl component (A). It is used by pre-mixing it with group-containing polysiloxane. Hereinafter, the present invention will be explained with reference to Examples, but these are merely for illustration and do not limit the present invention. Unless otherwise specified, parts and % in Examples and Comparative Examples refer to parts by weight and % by weight, and viscosity refers to the value at 25°C. Example 1 The ratio of the number of moles l of (Ph ₂ SiO) units to the total value of the number k of moles of (Me ₂ SiO) units and the above l is
0.06 and a viscosity of 360 cps, a linear polysiloxane having vinyl groups at both ends, 0.4% vinyltris(2-methoxyethoxy)silane, and an amount of methylvinyl cyclic silane equivalent to 4ppm in terms of platinum atoms. 100 parts of a mixed solution prepared by adding a chloroplatinic acid complex of polysiloxane, and the ratio of the number n of moles of (MeHSiO) units to the total value of the number m of moles of (Me ₂ SiO) units and the above n is 0.04. Yes viscosity
A resin composition for inner coating was obtained by mixing 18 parts of a mixture of a linear polysiloxane having silicon-bonded hydrogen at both ends and the vinyl group-containing polysiloxane at a ratio of 10:1. Ta. The ratio of vinyl group-containing polysiloxane to silicon-bonded hydrogen-containing polysiloxane in the composition is 100:
16.1. The amount of vinyltris(2-methoxyethoxy)silane used is based on the total amount of vinyl group-containing polysiloxane and silicon-bonded hydrogen-containing polysiloxane.
0.34%, and the amount of platinum catalyst used is calculated to be 3.4 ppm in terms of platinum atoms based on the total amount of both polysiloxanes. The composition prepared as above,
Immediately after mixing, defoaming treatment is performed, and then a 256k bit of 4.5 x 7.4 m/m square is prepared using a dispenser.
It was spread by gravity on the surface of a semiconductor chip consisting of a CMOS type RAS element, and heated and cured at 150°C for 3 hours to form an inner coat layer. As a result, the maximum coating thickness X at the center of the inner coat layer shown in Figure 2B
was 230 μm. In this case, the resin composition of the present invention dropped as droplets had extremely good diffusivity, and the inner coat layer was evenly adhered to the element surface and the bonding wire. Thereafter, the semiconductor chip was sealed using an epoxy resin composition so that X+Y as shown in FIG. 2B was 700 μm. A semiconductor chip coated with the inner coat resin composition of the present invention and then sealed with an epoxy resin is subjected to MIL-
STD-883B (edited by Japan Electronics Industry Association) test number
When subjected to a 200-cycle temperature cycle test under test conditions C specified in 1010.2, there was no derailment of the bonding wire, and the thickness of the narrow sealing resin region Y located at the top of the inner coat layer was
Since the sufficient thickness of 470 μm was maintained, no damage such as cracking of the sealing resin occurred in this area. Furthermore, in order to check the moisture resistance of the semiconductor device obtained according to the present invention, a pressure vacuum test was conducted for 500 hours at 121°C and 2 atm. No corrosion was observed in the semiconductor pad or circuit section, making it practical for practical use. It was confirmed that the system had extremely high reliability. Example 2 The ratio of the number of moles l of (Ph ₂ SiO) units to the total value of the number k of moles of (Me ₂ SiO) units and the above l is
0.06 and a viscosity of 360 cps, a linear polysiloxane having vinyl groups at both ends, 0.4% vinyltris(2-methoxyethoxy)silane, and an amount of methyl vinyl cyclic silane equivalent to 4 ppm in terms of platinum atoms. 100 parts of a mixed solution prepared by adding a chloroplatinic acid complex of polysiloxane, and the ratio of the number n of moles of (MeHSiO) units to the total value of the number m of moles of (Me ₂ SiO) units and the above n is 0.04. Yes viscosity
A resin composition for inner coating was obtained by mixing 18 parts of a mixture of a linear polysiloxane having silicon-bonded hydrogen at both ends and the vinyl group-containing polysiloxane at a ratio of 10:1.5. Ta.
The ratio of vinyl group-containing polysiloxane and silicon-bonded hydrogen-containing polysiloxane in the resin composition is
100:15.3, the amount of vinyltris(2-methoxyethoxy)silane used is 0.34% based on the total amount of vinyl group-containing polysiloxane and silicon-bonded hydrogen-containing polysiloxane, and the amount of platinum catalyst used is the total amount of both polysiloxanes. Platinum atomic equivalent for amount
Calculated to be 3.4ppm. Immediately after mixing, the composition prepared as described above was subjected to defoaming treatment, and then
4.5 x 7.4 m/m square area using a dispenser.
It was spread by gravity on the surface of a semiconductor chip consisting of a 256 k-bit CMOS type RAM element, and heated and cured at 150°C for 3 hours to form an inner coat layer with a maximum coating thickness X of 230 μm. In this case, the resin composition of the present invention dropped as droplets had extremely good diffusivity, and the inner coat layer was evenly adhered to the element surface and the bonding wire. Afterwards, using an epoxy resin composition,
The semiconductor chip was sealed so that the thickness of the semiconductor chip was 700 μm. An evaluation test was conducted in the same manner as in Example 1 on a semiconductor chip coated with the inner coat resin composition of the present invention and then sealed with an epoxy resin, and the result was that the sealing resin was not damaged, and the reliability was extremely high in practical use. It had the following characteristics. Example 3 The ratio of the number of moles l of (Ph ₂ SiO) units to the total value of the number k of moles of (Me ₂ SiO) units and the above l is
0.06 and a viscosity of 410 cps, a linear polysiloxane having vinyl groups at both ends, 0.4% vinyltris(2-methoxyethoxy)silane, and an amount of methylvinyl cyclic silane equivalent to 4ppm in terms of platinum atoms. 100 parts of a mixed solution prepared by adding a chloroplatinic acid complex of polysiloxane, and the ratio of the number n of moles of (MeHSiO) units to the total value of the number m of moles of (Me ₂ SiO) units and the above n is 0.04. Yes viscosity
A resin composition for inner coating was obtained by mixing 18 parts of a mixture of a linear polysiloxane having silicon-bonded hydrogen at both ends and the vinyl group-containing polysiloxane at a ratio of 10:1.2. Ta.
The ratio of vinyl group-containing polysiloxane to silicon-bonded hydrogen-containing polysiloxane in the resin composition is
100:15.8, the amount of vinyltris(2-methoxyethoxy)silane used is 0.34% based on the total amount of vinyl group-containing polysiloxane and silicon-bonded hydrogen-containing polysiloxane, and the amount of platinum catalyst used is the total amount of both polysiloxanes. Platinum atomic equivalent for amount
Calculated to be 3.4ppm. Immediately after mixing, the composition prepared as described above was subjected to defoaming treatment, and then
4.5 x 7.4 m/m square area using a dispenser.
The inner coat layer with a maximum coating thickness X of 260 μm was obtained by gravity-diffusion on the surface of a semiconductor chip consisting of a 256K-bit CMOS type RAM element and heating and curing at 150° C. for 3 hours. In this case, the resin composition of the present invention dropped as droplets had extremely good diffusivity, and the inner coat layer was evenly adhered to the element surface and the bonding wire. Thereafter, the semiconductor chip was sealed using an epoxy resin composition so that X+Y as shown in FIG. 2B was 700 μm. An evaluation test was conducted in the same manner as in Example 1 on a semiconductor chip coated with the inner coat resin composition of the present invention and then sealed with an epoxy resin, and the result was that the sealing resin was not damaged, and the reliability was extremely high in practical use. It had the following characteristics. Comparative Example A commercially available linear polysiloxane with a viscosity of 2200 cps containing vinyl groups at both ends and a linear polysiloxane with a viscosity of 660 cps containing silicon-bonded hydrogen at both ends were blended in a ratio of 10:1, and vinyl tris The amount of (2-methoxyethoxy)silane used is 0.34% based on the total amount of vinyl group-containing polysiloxane and silicon-bonded hydrogen-containing polysiloxane, and the amount of platinum catalyst used is platinum atoms based on the total amount of both polysiloxanes. Prepared to be equivalent to 3.4ppm
An inner coat layer was formed on a semiconductor chip in the same manner as in Example 1 using a comparative resin composition for semiconductor inner coat having a viscosity of 2000 cps. The maximum coating thickness X of the obtained inner coat layer is
It was 600 μm. Thereafter, the semiconductor chip was sealed using an epoxy resin composition so that X+Y as shown in FIG. 2B was 700 μm. A temperature cycle test was conducted in the same manner as in Example 1 on a semiconductor chip coated with the comparative inner coat resin composition as described above and then sealed with epoxy resin. Cracks occurred in the resin stopper region Y, resulting in a significant lack of reliability. <Effects of the Invention> Since the present invention has the above structure, it is possible to significantly reduce the thickness of the inner coat layer on the surface of the semiconductor chip, and it is fully suitable for increasing the size of the semiconductor chip or reducing the thickness of the package. It is something.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a semiconductor device to which the resin composition for semiconductor inner coat of the present invention is applied, FIG. 2 A is an enlarged sectional view of the vicinity of the bonding wire tip, and FIG. 2 B is an inner coat layer. An enlarged sectional view of the surrounding area is shown. DESCRIPTION OF SYMBOLS 1... Inner coat layer, 2... Semiconductor chip, 3... Bonding wire, 4... Tip part, 5... Electrode, 6... Die bonding layer, 7
a, 7b, 7c... Lead frame, 8... Sealing resin, P... Side curved portion, Q... Covering point, X... Maximum coating thickness, Y... Narrow sealing resin area, Z... Width of semiconductor chip.

Claims (1)

[Claims] 1 (A) General formula, [Formula] [In the formula, V is a vinyl group, Me is a methyl group, Ph is a phenyl group, and R is a methyl group or a phenyl group]. Group-containing polysiloxane 100
Parts by weight, (B) General formula, [Formula] [In the formula, Me represents a methyl group],
1 to 35 parts by weight of polysiloxane containing a hydrogen atom bonded to a silicon atom, (C) General formula R ¹ Si (OR ² ) ₃ [wherein R ¹ is a lower alkenyl group, R ² is a lower alkyl group, or The alkenyl group-containing silane compound represented by the general formula R ³ (OCH ₂ CH ₂ ) _j (R ³ is a methyl group or ethyl group, j is 1 or 2)] is added to the above (A) and (B ) from 0.01 to the total amount of
2.0% by weight, (D) a platinum-based addition reaction catalyst; the polysiloxane (A) has a l/(k+l) value of 0.01 to 2.0 and a temperature of 25°C.
The polysiloxane of (B) has a viscosity of 100 to 800 cps at an n/(m+n) value of 0.05 to 0.3 and a temperature of
A resin composition for semiconductor inner coating, characterized by having a viscosity of 2 to 500 cps at 25°C. 2. The composition according to claim 1, wherein the polysiloxane (A) has a viscosity of 200 to 500 cps at a temperature of 25°C, and the polysiloxane (B) has a viscosity of 5 to 150 cps at a temperature of 25°C. 3 The l/(k+l) value in (A) is 0.03~
0.15. 4 The n/(m+n) value in (B) is 0.1 to 0.2
The composition according to any one of claims 1 to 3. 5. The composition according to any one of claims 1 to 4, wherein the amount of polysiloxane (B) used is 5 to 25 parts by weight based on 100 parts by weight of polysiloxane (A). 6. The composition according to any one of claims 1 to 5, wherein R in (A) is a phenyl group. 7. The composition according to any one of claims 1 to 6, wherein R ¹ in (C) is a vinyl group. 8. The method according to any one of claims 1 to 7, wherein the amount of the silane compound (C) used is 0.05 to 1.0% by weight based on the total amount of (A) and (B). Composition. 9. Any one of claims 1 to 8, wherein the amount of platinum-based addition reaction catalyst used is such that it provides 2 to 6 ppm of platinum atoms based on the total amount of (A) and (B). The composition described in .