Pinhole density

The pursuit of further miniaturization of electronic circuits has made submicrometer resolution Hthography a cmcial element in future computer engineering. LB films have long been considered potential candidates for resist appHcations, because conventional spin-coated photoresist materials have large pinhole densities and variations of thickness. In contrast, LB films are two-dimensional, layered, crystalline soHds that provide high control of film thickness and are impermeable to plasma down to a thickness of 40 nm (46). The electron beam polymerization of CO-tricosenoic acid monolayers has been mentioned. Another monomeric amphiphile used in an attempt to develop electron-beam-resist materials is a-octadecylacryUc acid (8). 

Such a pinhole density test was performed on the AZ/PMMA two-layer deep-UV PCM system (26). The result is shown in Table IX where a pinhole density of 8 and 6 per cm was obtained for the capped (A) and uncapped (B) systems. Because only three wafers were used for each test, the result should be taken only qualitatively and the numerical difference between 6 and 8 pinholes/cm should be taken as being indicative of measurement fluctuations only. It should not be attributed to the use of different developers or O2 plasma because in the subsequent tests of batches C and D in which the DUV exposure was omitted, the numbers were 0 and 1 pinhole/cm with the capped system giving the smaller pinhole density. The low pinhole density in batch E in which the AZ development step was omitted suggests that the pinholes arise during the development of the AZ layer. Presumably, a small portion of the AZ base resin molecules were not linked up with the photoactive compound and therefore still exhibited their intrinsic high solubility in the AZ developer. After development, these high solubility spots became pinholes. These pinholes are apparently larger than the diffraction - limited sizes so that they can be transferred into the PMMA film by deep-UV exposure. 

However, the pinhole density in the imaging layer has to be reduced. This can be done by searching among all the commercial novolak - based resists for an acceptable candidate or by setting an MLR specification for resist vendors improve their quality control. Because thin resists have been used for mask making with an acceptable defect level, no fundamental pinhole problem is anticipated. 

The pinhole density of polyimide was assessed by a statistical evaluation of shorts using an TiWAu - polyimide - TlWAu multilevel structure where each die contained 3275 crossovers of first and second metal. The probability of good crossovers was taken as... 

Insulation Integrity. Insulation integrity is a function of an interlayer dielectric/passivant defined by specific electrical, mechanical and passivation properties. The D.C. electrical property of interest is the I-V characteristic which is used to deduce conductivity and breakdown field strength. The corresponding A.C. electrical property is dissipation factor. The pertinent mechanical and passivation properties are, respectively, pinhole density and performance rating as a diffusion barrier to Na" " and H2O. 

The breakdown field strength is a thickness dependent property, a probable reflection of pinhole density variation with thickness. For a typical value of Interlevel dielectric film thickness (1 - 2 p), the breakdown field strength is 1 - 2.5 x 10 V/cm which is adequate for most applications. 

Pinhole density is another property of interest in defining insulation integrity. It was indirectly assessed from the number of shorts in a statistical number of probed die where the die was a multilevel test structure consisting of TiWAu-polyimide-TlWAu with 3275 crossovers of first and second metal per die. The results indicated that the probability of a short in a crossover for 1.2 y thick PI2545 was 1 in 133,333. 

Pinhole density was Indirectly assessed by measuring shorts In a series of crossovers of first and second metal with Intervening polylmlde. For 1.2 y thick PI2545, the probability of a short was estimated at 1 In 133,333 crossovers. 

A 3/8 inch diameter aluminum or titanium-tungsten dot pattern WLs fabricated on top of the cured polyimide film to make electrical leakage to substrate measurements for pinhole density estimation. An etch decoration technique was used to visually determine pinhole densities in polyimide films. The polyimide film was cast on substrates comprised of a layer of 200 nm thick alumimmi on blue colored field oxide with a grid pattern for area computation. Replicate holes were etched in the aluminum by a hot phosphoric acid solution. With the polyimide film removed, a good visual contrast was achieved for pinhole density counting. 

The ability to cover a surface and to reduce pinhole density in the film is affected by addition agents and deposition waveform. Throwing power, the ability of the depositing material to plate inside a deep, narrow recess, depends on a number of factors, including complexing of the ions, electrode polarization, current density, etc. Additives to increase throwing power are usually organic materials. 

The investigation of epitaxial Si growth atop atomically-clean Si surface implanted with Fe" (Cr ) ions and subjected to PLA or PIBT was carried out. It was established that epitaxial Si growth by MBE is possible for minimal fluence by mechanism of 2D nucleation and lateral 3D growth. The continuous epitaxial Si films can be obtained larger than 500 nm at 700°C for small implantation fluence of Fe and Cr ( 10 cm ). For the maximal fluence (6-10 cm ) the number of pinholes in the Si layer increases sharply and epitaxial growth is failed. In the case of the Si growth (up to 500 nm) on the surface of non-annealed samples the pinhole density increases for 3-4 times and Si layer is polycrystalline only. 

Radial striations, Z of thickness Film density, g/cc Refractive index Pinhole density, less -Particulate density, less -... 

Rosin and its derivatives are frequently used as polymer additives in different capacities. Their role as plasticizers is illustratedby recent work related to the paper coating for foodpackaging with a 3-hydroxybutirate/3-hydroxy valerate copolymer (PHBW) [112, 113]. The addition of tall oil rosin to the copolymer was found to improve its water vapour barrier properties as well as to reduce the pinhole density of the corresponding laminated papers. 

Guo etal.[19] showed that the blocking properties of SAMs change with the pinhole density, decreasing dramatically as the substrate is made smoother. For evaporated gold on mica, they showed that (1) the gold surface roughness was... 

Thin-clad copper. Etched printed boards with epoxy laminate ofoz (9 /nn) copper or less show minimal lateral etching, thus enabling higher fidelity to pattern-plated traces. The problem with very thin copper foils is pinhole density and fragility in the laminate... 

---