JP2712548B2 - Surface mount type resin encapsulated semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a surface-mounted resin-sealed semiconductor device, and more particularly, to a resin-sealed resin device capable of suppressing the occurrence of resin cracks during surface mounting. The present invention relates to improvement of a stop type semiconductor device.

[Prior Art] As the area of a semiconductor chip increases, semiconductor components are mounted by surface mounting,
There are two issues that need to be resolved. One is wiring sliding and passivation crack due to thermal stress due to the difference in thermal expansion coefficient between the sealing resin and the semiconductor chip. The other is that the sealing resin cracks due to the stress applied when the absorbed moisture evaporates due to the weak adhesion between the semiconductor chip and the sealing resin due to rapid heating in the solder bath. It is. In order to solve the former problem, polyimide is applied on a passivation film as a stress absorbing film. In order to solve the latter problem, the adhesion to the semiconductor chip has been improved by improving the sealing resin, but it has not been perfect yet.
A method of performing dehydration by heating before mounting, a method of wrapping in a special package, and the like are performed.

In order to solve such a problem, it is effective to apply polyimide having excellent adhesiveness to both the semiconductor chip and the sealing resin. In view of such circumstances, the present inventors have conducted many synthesis experiments on many polyimide resins, and have studied in detail the relationship between the raw material components and the adhesiveness of the sealing resin. U.S. Pat.
No. 7964 (du Pont), CESroog, “Polimides”, J.
Polym.Sci.::Maromol.Rev., 11 , 161-208 (1976), NAAd
Various types have been proposed as shown in rova et al., Dokl. Akad. Nauk. SSSR, 165 , 1069, (1965). However, very few are actually used. The only reported or commercially available products are those using pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride or biphenyltetracarboxylic dianhydride and diaminodiphenyl ether or diaminodiphenylmethane as raw materials. However, since the adhesion of these polyimides to the sealing resin becomes almost zero after the pressure cooker test, no effect of preventing the resin crack is observed.

However, as a result of further synthesis experiments, the present inventors have found that when a polyimide obtained from a specific aromatic diamine and tetracarboxylic dianhydride is used, adhesion to a sealing resin is higher than that of a conventional polyimide. The present inventors have found that the property increases, and have reached the present invention.

[Problems to be Solved by the Invention] An object of the present invention is to provide a surface-mounted semiconductor device which does not have the above-mentioned disadvantages, that is, does not cause resin cracks even if special treatment is not performed before surface mounting. Is what you do.

[Means for Solving the Problems] The object of the present invention is achieved by the following configurations.

(1) In a resin-encapsulated semiconductor device having a stress-absorbing film made of polyimide on a passivation film made of an inorganic film, the polyimide forming the stress-absorbing film has a main dispersion (α dispersion) determined by dynamic viscoelasticity measurement and Having a secondary dispersion (β dispersion) occurring at a temperature lower than the main dispersion,
A surface-mounted resin-sealed semiconductor device comprising a polyimide whose β dispersion temperature is equal to or lower than the post-curing temperature of the sealing resin.

(2) The polyimide having a main dispersion (α dispersion) by dynamic viscoelasticity measurement of a polyimide forming the stress absorbing film and a sub-dispersion (β dispersion) generated at a temperature lower than the main dispersion according to (1) above, 3,4,3 ', 4'-benzophenonetetracarboxylic acid and 2,2-bis (4-aminophenoxy)
Diphenylpropane, 3,4,3 ', 4'-benzophenonetetracarboxylic acid and 3,4'-diaminodiphenylether, 3,4,3', 4'-diphenylethertetracarboxylic acid and 3,4'-diaminodiphenylether, 3 , 4,3 ′, 4 ′
-Diphenyl ether tetracarboxylic acid and 2,2-bis (4-aminophenoxy) diphenylpropane, 3,4,
3 ', 4'-benzophenonetetracarboxylic acid and 2,2-bis (4-aminophenoxy) diphenylhexafluoropropane, and 3,4,3', 4'-diphenylethertetracarboxylic acid and 4,4'-diaminodiphenylether And a polyimide synthesized from at least one kind selected from the group consisting of:

Is achieved.

In the present invention, a surface-mount type semiconductor device is a system in which components are fixed by soldering only on one side in order to perform high-density mounting, for example, SOJ (Small Out-line J Packag).
e), SOP (Small Out-line Package), and QFP (Qua
d Flat Package). The semiconductor device adopting these sealing forms has a smaller package and a smaller thickness of the sealing resin than the conventional resin-sealed type semiconductor device, so that the mechanical strength of the sealing resin portion is reduced. And resin cracks are likely to occur.

In a semiconductor device, an integrated circuit is formed on a semiconductor substrate such as a silicon substrate or a gallium arsenide substrate.
In order to prevent intrusion of moisture and ionic components from the outside, it has a passivation film made of an inorganic film, such as silicon nitride, silicon oxide, phosphorus glass (PSG), and boron-doped phosphorus glass (BPSG). And generally CVD (Chemical Vapor Deposition)
It is formed by a method. This passivation film may be formed of one type or two or more types.

The polyimide used to form the stress-absorbing film used in the present invention is a polyimide having a main dispersion (α dispersion) measured by dynamic viscoelasticity and a sub-dispersion (β dispersion) generated at a temperature lower than the main dispersion. Yes, and may be anything as long as it is made of polyimide whose β dispersion temperature is equal to or lower than the post cure temperature of the sealing resin,
Preferably, a specific tetracarboxylic acid and a specific diamine compound are selectively combined and reacted in a polar solvent to form a varnish of a polyimide precursor, and then the varnish of the polyimide precursor is used as a semiconductor chip. It can be obtained by coating on the substrate, performing heat treatment in the range of 200 ° C. to 400 ° C., and performing dehydration condensation.

The polyimide for forming a stress-absorbing film in the present invention has a peak of the loss elastic modulus due to β dispersion at a lower temperature in addition to the main dispersion (α dispersion) in the dynamic viscoelasticity measurement. The peak of the loss elastic modulus due to this β dispersion means that polyimide can cause stress relaxation in this temperature range, and by setting the temperature of this peak lower than the post cure temperature of the sealing resin, It is possible to alleviate distortion generated during molding during post-curing of the sealing resin.

Further, from the viewpoint of the heat resistance of polyimide, those composed of aromatics are preferred. Such polyimides include, for example, 3,4,3 ', 4'-benzophenonetetracarboxylic acid and 3,4'-diaminodiphenyl ether, or 3,3
Examples thereof include those synthesized from 4,3 ', 4'-biphenyltetracarboxylic acid and 3,4'-diaminodiphenyl ether. These polyimides have an α dispersion in the range of 250 ° C. to 400 ° C. and a β dispersion at 170 ° C. or lower. More preferred are, for example, 3,4,3 ',
4'-benzophenonetetracarboxylic acid and 2,2-bis (4
-Aminophenoxy) diphenylpropane, or 3,4,
3 ', 4'-Benzophenonetetracarboxylic acid and 2,2-bis (4-aminophenoxy) diphenylhexafluoropropane are listed, and these polyimides have an α dispersion of 25.
It has a β dispersion in the range of 0 ° C. to 400 ° C. and occurs at 150 ° C. or less.

When a polyimide having an α dispersion of less than 250 ° C. is used, the heat applied when mounting a semiconductor device is reduced to α of the polyimide.
The mechanical strength of the polyimide is lost to exceed the dispersion,
It is not preferable because it causes a failure of the semiconductor device.

Further, the polyimide in the present invention may be composed of only one kind of tetracarboxylic acid and diamine, or may be a copolymer of several kinds or more.

Further, in order to improve the adhesion to the silicon wafer, it is possible to copolymerize an aliphatic diamine having a siloxane structure as long as the heat resistance is not reduced.

As a preferred specific example Is mentioned.

In the present invention, an adhesion aid may be used to improve the adhesion between a polyimide such as silicon and a semiconductor substrate such as silicon.

As an adhesion aid, an organosilicon compound such as oxypropyltrimethoxysilane or γ-aminopropyltriethoxysilane, or an aluminum chelate compound such as aluminum monoethylacetoacetate or aluminum tris (acetylacetonate) or titanium bis (acetylacetonate) ) And the like are preferably used.

Next, an example of a method for forming a stress absorption film made of polyimide will be described. The polyimide used in the present invention is applied before the varnish of the polyimide precursor is cut for each chip, and the polyimide is etched simultaneously with the development of the positive resist using the positive resist as a mask (for example, RADine-Hart, et al., Br. .Polym.J.3,222 (197
1)) Using a negative resist as a mask and etching the polyimide with an organic alkali such as hydrazine after developing the negative resist (for example, JP-A-53-49701), imparting photosensitivity to the polyimide precursor and directly forming a pattern A method of processing a pattern for wiring by a method of forming (for example, JP-A-54-145794) or a method of fixing a chip cut for each chip to a lead frame, bonding the wiring, and then dropping polyimide. is there.

The semiconductor chip thus obtained is subjected to transfer molding and resin sealing. Further, post-curing of the sealing resin is performed to obtain a final product.

As a typical sealing resin used for resin sealing of a semiconductor, an epoxy resin-based resin is exemplified. For example, an epoxy resin-based resin is mainly composed of a novolak-based epoxy resin and silica particles. Crosslinking using phenylphosphine and the like can be mentioned. Of course, it is needless to say that various epoxy curing agents and curing catalysts that open the epoxy group upon crosslinking can be used.

For this crosslinking, the sealing resin is post-cured. This post cure temperature is, for example, 170 ° C. in the case of the above resin.
It can be done before and after. If the post-cure temperature is too low, the crosslinking reaction does not proceed completely, causing a problem in reliability thereafter. Further, if the temperature of the post cure is too high, the sealing resin is deteriorated, which causes a problem in reliability. That is, the post cure temperature is appropriately selected according to the sealing resin used, and the polyimide used is also selected according to the resin.

[Measurement of properties] Measurement of dynamic viscoelasticity The measurement of dynamic viscoelasticity in the present invention is performed by measuring a width of 2 mm and a length of 5 cm.
Measure the 4 cm center part of the polyimide film cut into pieces using Orientec's Leo Vibron DDV-II-EA type at a drive frequency of 110 Hz and a heating rate of 2 ° C / min in the range of -150 ° C to 400 ° C. did.

Adhesion strength with sealing resin The adhesion strength with the sealing resin in the present invention was measured by the following method.

(1) A polyimide having a thickness of 2 μm is applied on a silicon wafer and heat-treated up to 350 ° C. is placed on a hot plate at 170 ° C.

(2) Silicon rubber (thickness: 2 mm) reinforced with glass fiber with a hole of 4 mmφ was placed, and a sealing resin (Novolac epoxy resin TH-7006, manufactured by Toray) was embedded therein.

(3) Put a 5kg weight on top of them.
Let stand for minutes.

(4) After cooling, peel off the silicon rubber, 4mmφ, thickness 2
A pad of a sealing resin having a thickness of mm was obtained. This was heat-treated at 170 ° C. for 5 hours to obtain a sample.

(5) Of the samples obtained in (4), a part was at 121 ° C. and 2
A pressure cooker test was performed at atmospheric pressure for 168 hours to obtain a sample.

(6) This sample was measured by a pull-down method (Applied Physics 56, 925, 1987) using Tensilon manufactured by Orientec.

Resin crack test In the present invention, a resin crack test was performed by the following method.

(1) 2μ of polyimide on 9mm × 9mm silicon chip
After applying a heat treatment up to 350 ° C., it is fixed on a 48-pin lead frame using silver paste, and heat treated at 100 ° C. for 1 hour.

(2) This was subjected to transfer molding in a 16 mm × 16 mm mold. (Sealing resin: TH-8003, manufactured by Toray) Mold temperature: 175 ° C., molding time: 120 seconds, molding pressure: 20 kg / cm ² , and post-curing was performed at 175 ° C. for 5 hours.

(3) The thus obtained sample was subjected to a pressure cooker test (PCT test) at 121 ° C. and 2 atm for 72 hours to absorb moisture to obtain a sample.

(4) This was immersed in a solder bath at 260 ° C. for 5 seconds, and the occurrence of cracks in the resin was examined.

Although the surface-mount type semiconductor device of the present invention is particularly effective for a device such as a 4 Mbit DRAM having a large semiconductor chip, an effective effect can be expected for other resin-encapsulated semiconductor devices.

[Examples] Next, the present invention will be specifically described using examples, but the present invention is not limited thereto.

Example 1 A line and space of 8 μm on a silicon wafer
5,000 angstrom silicon nitride film was formed by plasma method, and 1 mol of benzophenonetetracarboxylic dianhydride and 0.96 mol of 2,2-bis (4-aminophenoxy) diphenylpropane , 3-bis (aminopropyl) dimethylsiloxane
A varnish of 0.04 mol of a polyimide precursor was applied so that the film thickness after heat treatment was 2 μm. As a result of measurement of dynamic viscoelasticity of this polyimide, the peak of α dispersion was 260 ° C.,
The peak of β dispersion was 104 ° C. In addition, as a result of measuring the adhesion strength with the sealing resin, the adhesion strength before the PCT test was 5.0 kg.
/ mm ² PCT adhesion strength after the test was that 4.5 kg / mm ^2.

After applying this varnish, 80 ℃, 200 ℃, 300 ℃ and 350 ℃
Heat treatment was performed at 30 ° C. for 30 minutes each, and cut into a size of 9 mm × 9 mm. This chip is packaged in a 16mm x 16mm QFP package.
Using a Toray TH-7006 as a sealing resin, resin sealing was performed at a mold temperature of 170 ° C. and a molding time of 120 seconds, and then at 170 ° C. for 5 hours under post-curing conditions.

The test specimen thus obtained was subjected to a thermal shock test of 300 cycles at −65 ° C. and 150 ° C. for 30 minutes each. When the peeling state of the internal chip and the sealing resin after the test was observed with an ultrasonic microscope, no peeling was observed. No cracks occurred in the resin crack test.

Example 2 A line and space of 8 μm on a silicon wafer
5,000 angstrom silicon nitride film was formed by plasma method, and 1 mol of benzophenonetetracarboxylic dianhydride and 0.96 mol of 2,2-bis (4-aminophenoxy) diphenylhexafluoropropane And a varnish of a polyimide precursor comprising 0.04 mol of 1,3-bis (aminopropyl) dimethylsiloxane was applied so that the film thickness after heat treatment was 2 μm. As a result of measuring dynamic viscoelasticity of this polyimide, the peak of α dispersion was 275 ° C. and the peak of β dispersion was 117 ° C. As a result of measuring the adhesion strength between the sealing resin, the adhesion strength before PCT test the adhesion strength of 4.0 kg / mm ^2, PCT after the test was that 3.5 kg / mm ^2. After applying this varnish, 80 ℃, 200
Heat treatment at 30 ° C, 300 ° C and 350 ° C for 30 minutes each, 9m
It was cut into a size of mx 9 mm. This chip is 16mm x 16mm
Using Toray's TH-7006 as a sealing resin for the QFP package,
The resin was sealed under a post-curing condition at a mold temperature of 170 ° C. and a molding time of 120 seconds, and then at 170 ° C. for 5 hours. The test specimen thus obtained was subjected to a thermal shock test of 300 cycles at −65 ° C. and 150 ° C. for 30 minutes each. When the peeling state of the internal chip and the sealing resin after the test was observed with an ultrasonic microscope, no peeling was observed. No cracks occurred in the resin crack test.

Example 3 A line and space of 8 μm on a silicon wafer
m Aluminum wiring was attached, and a silicon nitride film was formed 5,000 angstroms by the plasma method.
1 mol of 4,4'-diphenylethertetracarboxylic dianhydride, 0.96 mol of 4,4'-diaminodiphenylether and 1,3-bis (aminopropyl) dimethylsiloxane 0.0
A varnish of 4 mol of a polyimide precursor was applied so that the film thickness after heat treatment was 2 μm. As a result of measurement of dynamic viscoelasticity of this polyimide, the peak of α dispersion was 365 ° C, β
The peak of dispersion was 164 ° C. In addition, as a result of measuring the adhesion strength with the sealing resin, the adhesion strength before the PCT test was 3.6 kg / m
m ² , and the adhesive strength after the PCT test was 2.4 kg / mm ² .

After applying this varnish, 80 ℃, 200 ℃, 300 ℃ and 350 ℃
Heat treatment was performed at 30 ° C. for 30 minutes each, and cut into a size of 9 mm × 9 mm. This chip was sealed in a 16mm x 16mm QFP package using Toray's TH-7006 as a sealing resin, with a mold temperature of 170 ° C and a molding time of 120 seconds, followed by post-curing at 170 ° C for 5 hours. Was.

The test specimen thus obtained was subjected to a thermal shock test of 300 cycles at −65 ° C. and 150 ° C. for 30 minutes each. When the peeling state of the internal chip and the sealing resin after the test was observed with an ultrasonic microscope, no peeling was observed. No cracks occurred in the resin crack test.

Comparative Example 1 A line and space of 8 μm on a silicon wafer
Aluminum wiring was attached, and a silicon nitride film was formed to a thickness of 5000 angstroms by a plasma method. On top of this, 1 mol of pyromellitic dianhydride, 0.96 mol of 4,4'-diaminodiphenyl ether and 1,3-bis (aminopropyl) A varnish of a polyimide precursor consisting of 0.04 mol of dimethylsiloxane was applied so that the film thickness after heat treatment was 2 μm. As a result of the measurement of the dynamic viscoelasticity of this polyimide, no β dispersion peak appeared. Further, as a result of measuring the adhesion strength with the sealing resin, the adhesion strength before the PCT test was peeled off after the 1.5 kg / mm ² PCT test.

After applying this varnish, a chip obtained by treating in the same manner as in Example 1 was packaged in a 16 mm × 16 mm QFP package using TH-7006 manufactured by Toray at a mold temperature of 170 ° C. and a molding time of 12 mm.
Resin sealing was performed under post-curing conditions of 0 seconds and then at 170 ° C. for 5 hours.

The test specimen thus obtained was subjected to a thermal shock test of 300 cycles at −65 ° C. and 150 ° C. for 30 minutes each. When the peeling state of the internal chip and the sealing resin after the test was observed with an ultrasonic microscope, peeling was observed. In the resin crack test, cracks occurred.

Comparative Example 2 A line-id space of 8 μm on a silicon wafer
5,000 angstrom silicon nitride film was formed by plasma method, and 1 mole of biphenyltetracarboxylic dianhydride, 0.96 mole of paraphenylenediamine and 1,3-bis (aminopropyl) dimethylsiloxane A varnish of 0.04 mol of a polyimide precursor was applied so that the film thickness after heat treatment was 2 μm.
As a result of measuring dynamic viscoelasticity of this polyimide, the peak of α dispersion was 400 ° C. or more, and the peak of β dispersion was 223 ° C. As a result of measuring the adhesion strength between the sealing resin, the adhesion strength of the adhesion strength is 1.2 kg / mm ^2, PCT after the test before the PCT test is 0.3 kg / mm
^{Was 2} .

After applying this varnish, chips obtained in the same manner
Toray TH-70 as encapsulation resin in a mm x 16 mm QFP package
Using mold 06, mold time 170 seconds at mold temperature 120 seconds, then 17
Resin sealing was performed at 0 ° C. for 5 hours under post-curing conditions.

The test specimen thus obtained was subjected to a thermal shock test of 300 cycles at −65 ° C. and 150 ° C. for 30 minutes each. When the peeling state of the internal chip and the sealing resin after the test was observed with an ultrasonic microscope, peeling was observed. In addition, cracks occurred in the resin crack test.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to obtain a surface-mounted semiconductor device that does not generate resin cracks without performing special processing before surface mounting as in the related art.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-54-106599 (JP, A) JP-A-62-184025 (JP, A) JP-A-62-253621 (JP, A) JP-A-63-253 193927 (JP, A) JP-A-59-76451 (JP, A) JP-A-63-276045 (JP, A)

Claims (2)

(57) [Claims] In a resin-encapsulated semiconductor device having a stress absorbing film made of polyimide on a passivation film made of an inorganic film, the polyimide forming the stress absorbing film has a main dispersion (α dispersion) measured by dynamic viscoelasticity. And a sub-dispersion (β-dispersion) generated at a temperature lower than the main dispersion, and a polyimide having a β-dispersion temperature equal to or lower than the post-curing temperature of the sealing resin. Resin-sealed semiconductor device. 2. The method according to claim 1, wherein the main dispersion (α-dispersion) of the polyimide forming the stress absorbing film by dynamic viscoelasticity measurement and the sub-dispersion (β-dispersion) generated at a temperature lower than the main dispersion.
Dispersion) is 3,4,3 ', 4'-benzophenonetetracarboxylic acid and 2,2-bis (4-aminophenoxy) diphenylpropane, 3,4,3', 4'-benzophenonetetracarboxylic acid And 3,4'-diaminodiphenylether, 3,4,3 ', 4'-diphenylethertetracarboxylic acid and 3,4'-diaminodiphenylether, 3,4,
3 ', 4'-diphenylethertetracarboxylic acid and 2,2-
Bis (4-aminophenoxy) diphenylpropane, 3,
4,3 ', 4'-benzophenonetetracarboxylic acid and 2,2-bis (4-aminophenoxy) diphenylhexafluoropropane and 3,4,3', 4'-diphenylethertetracarboxylic acid and 4,4'-diamino A surface-mounted resin-sealed semiconductor device, which is a polyimide synthesized from at least one selected from diphenyl ether.