Contrast Enhancing Additives for Positive Photoresist

Pampalone, T. R.; Kuyan, F. A.

doi:10.1149/1.2095639

Cited by 11 publications

(4 citation statements)

References 2 publications

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“…Measurement of photoresist contrast.--Contrast was determined as previously described (3). Each resist was spincoated on 3 in.…”

Section: Addition Of Indenecarboxylic Acid To Photoresist--az M)mentioning

confidence: 99%

“…The latter occurs when the resin at the surface of the resist cross-links to form an insoluble surface skin (2). The degree and extent of surface cross-linking is increased by the addition of catalytic amounts of acidic organic compounds, such as phenols and carboxylic acids (3). Indenecarboxylic acid, therefore, would also be expected to enhance the surface skin formation and the subsequent contrast of positive photoresist when used as an additive.…”

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Contrast Enhancement of Positive Photoresist Due to Indenecarboxylic Acid

Pampalone

Piazza

1988

J. Electrochem. Soc.

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It is well known that the major photolytic decomposition product of positive photoresist is 3-indenecarboxylic acid (1). The photogenerated acid increases the developer-solubility of the exposed portions of the positive resist, and in this way the mask pattern is reproduced in the resist. The major role of the phenolic resin component of the resist is as a vehicle for the photoactive component (PAC); however, under certain circumstances, the phenolic resin participates significantly to improve the resolution and profile of the resultant images. The latter occurs when the resin at the surface of the resist cross-links to form an insoluble surface skin (2). The degree and extent of surface cross-linking is increased by the addition of catalytic amounts of acidic organic compounds, such as phenols and carboxylic acids (3). Indenecarboxylic acid, therefore, would also be expected to enhance the surface skin formation and the subsequent contrast of positive photoresist when used as an additive. However, since indenecarboxylic acid occurs normally in positive photoresist before exposure as a thermal degradation product (4), its natural presence may be contributing to the resist contrast observed in resist usage. This paper discusses the contribution of indenecarboxylic acid in enhancing the contrast of positive photoresist. Experimental Addition of indenecarboxylic acid to photoresist.--AZ m)1350J-SF photoresist (American Hoechst Corporation) was spin-coated on 50 3 in. wafers and baked at 90~ for 10 min in a Wafertrac (a) oven (GCA Corporation) to give 2.0 ~m film thickness. The wafers were flood-exposed until the resist was completely bleached, i.e., the absorption curve remained unchanged. The exposed resist was dissolved from the wafers with acetone and the resultant solution evaporated to dryness under vacuum. 0.25 and 0.10g amounts of the red residue were each dissolved into a 100g portion of AZ 1350J-SF and the two resist solutions were filtered.Measurement of photoresist contrast.--Contrast was determined as previously described (3). Each resist was spincoated on 3 in. silicon wafers and baked in a track oven at 95~ for 10 min to give 1.76 ~m film thickness. They were then exposed stepwise on a TRE-800 (m stepper (TRE Semiconductor Equipment Corporation) from 0-250 ms in 10 ms increments through a clear reticle, and spray-developed on a GCA developer track using AZ 422 developer. The thickness remaining corresponding to each exposure dose was measured using a film thickness monitor, and best-fit plotted as normalized thickness remaining after development with log exposure dose. (Since the intensity of the stepper lamp is constant during wafer exposure, exposure time is used as exposure dose.) The correlation coefficient of each plot was at least 0.99. The photosensitivity value (where normalized thickness remaining was 0) and contrast value (slope of the best-fit plot) were measured from the characteristic exposure curve (Fig. 1) and tabulated in Table I.Technique of photoresist pre-exposure.--Wafers were baked...

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“…Measurement of photoresist contrast.--Contrast was determined as previously described (3). Each resist was spincoated on 3 in.…”

Section: Addition Of Indenecarboxylic Acid To Photoresist--az M)mentioning

confidence: 99%

mentioning

confidence: 99%

Contrast Enhancement of Positive Photoresist Due to Indenecarboxylic Acid

Pampalone

Piazza

1988

J. Electrochem. Soc.

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“…A variety of dyes have been proposed as absorbers for photoresists (1)(2)(3). The nonbleachable absorbance incorporated in this way can result in a reduction in standing waves (4) and/or reflective notching (nonuniform linewidths due to reflections off the substrate) (5).…”

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Dyed Positive Photoresist Employing Curcumin for Notching Control

Renschler

Lemen

Rodriquez

et al. 1989

J. Electrochem. Soc.

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“…In general, adding more dye to the photoresist improves the linewidth control, but at the expense of longer exposure times and reduced wall angles (6). Recently (7), heavily dyed photoresists have been developed which show excellent resolution and linewidth control with no loss in wall angles and only a small penalty in exposure time. However, the linewidth control using heavily dyed photoresist on highly reflective substrates is still not good enough for submicron patterning (8).…”

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confidence: 99%

Improved Photoresist Patterning over Reflective Topographies Using Titanium Oxynitride Antireflection Coatings

Pampalone¹,

Camacho²,

Lee³

et al. 1989

J. Electrochem. Soc.

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The resolution and linewidth control of photoresist patterns over highly reflective substrates, such as aluminum and tantalum disilicide, are significantly improved by the use of reactive-sputtered titanium oxynitride as an antireflection coating. The substrate reflectivities are reduced from over 85% to less than 25%, and when patterned with heavily dyed photoresist on a g-line stepper, or undyed resist on an i-line stepper, submicron resolutions over topography are demonstrated. The TiON thicknesses can be selected to provide the m a x i m u m process latitude and antireflection, while still permitting stepper alignment. TiON is easily etched in plasmas eontaining chlorine, thereby reproducing the photoresist patterns in the substrates with no extra plasma processing steps. The remaining TiON can either be removed with the photoresist or left as a passivation layer, depending on the photoresist stripping conditions used.The difficulty in high-resolution patterning of photoresist on reflective topography is well documented (1). The exposing light couples with the light reflected from the substrate, creating standing waves and distortions in the photoresist coating. Pattern distortions are also caused by the light reflected angularly from topological features. Figure 1 illustrates both kinds of reflective distortions for undyed resist patterned on tantalum disilicide. The linewidth variability on top of the island is due to the interference effects resulting from variations in the resist thickness over the island. The degradation of the photoresist line in the island recess is due to light reflection off the walls of the recess.Several lithographic techniques have been presented for patterning on reflective topography. One approach, "ARC" (2), uses a thin polyamic acid film containing an absorbing dye between the substrate and the photoresist. The organic film is partially polymerized by baking so that its solubility matches the solubility of the exposed photoresist in the aqueous, alkaline developer. If the ARC baking temperature or time are not exactly controlled, the resultant images will be either undersized from too little, or oversized from too much baking.Multilayer imaging systems eliminate substrate reflections with a heavily dyed planarization layer (3). A thin photoresist coating is imaged and the pattern transferred to the suhstrate by plasma etching. Although effective, multilayer imaging systems are still considered too complex for patterning most device levels.Another approach to reduce reflective distortions proposes using a thin, inorganic, "antireflective" coating, such as 160/~ of amorphous silicon (4) over the reflective substrates. The reflectivity of the wafer depends critically on the thickness of the silicon coating. For instance, the reflectivity of aluminum decreases from 38 to 7% as the thickness of the amorphous silicon antireflection coating increases from 100 to 200/k (4). Since depo~tion thicknesses are generally controllable to only _+ 100A in production, using less than 300A of si...

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Contrast Enhancing Additives for Positive Photoresist

Cited by 11 publications

References 2 publications

Contrast Enhancement of Positive Photoresist Due to Indenecarboxylic Acid

Contrast Enhancement of Positive Photoresist Due to Indenecarboxylic Acid

Dyed Positive Photoresist Employing Curcumin for Notching Control

Improved Photoresist Patterning over Reflective Topographies Using Titanium Oxynitride Antireflection Coatings

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