&lt;title&gt;Physical and chemical factors governing dissolution of novolak resin films&lt;/title&gt;

2007

jjap

We have investigated the effect of a temperature change on photoresist critical dimension (CD) in a wafer during puddle development. The wafer temperature was decreased by the evaporation latent heat of developer solution during puddle development, and the rate of temperature decrease of the peripheral area was higher than that of the central area in the wafer. The temperature of the peripheral area was approximately 1.3 °C lower than that of the central area after 60 s. The temperature distribution was caused by the difference in heat capacitance in the wafer, which was mainly influenced by the wafer chuck. We investigated the influence of temperature on photoresist CD in the wafer, using a diazonaphthoquinone (DNQ)/novolac photoresist. Photoresist CD changed with temperature at a rate of approximately 5 nm/°C, and the CD of the peripheral area became smaller than that of the central area over time. We can improve the CD distribution by controlling the temperature during puddle development or by using a photoresist with a dissolution rate that is less sensitive to temperature.

Section: Introductionmentioning

confidence: 99%

Effect of Temperature on Photoresist Critical Dimension during Puddle Development

2007

jjap

“…These salts disturb the dissolution of a photoresist. 8,9) In this case, reaction products prevent the dissolution of a photoresist, resulting in a nonuniform dissolution. This leads to a decrease in CD uniformity.…”

mentioning

confidence: 99%

“…When a DNQ/novolac photoresist is dissolved in the TMAH developer solution, novolac resin reacts with TMA þ to generate a chargetransfer complex. 8,9) When the charge-transfer complex is generated, an absorption peak generally shifts to a longer wavelength. 12) In this case, the absorption peak shifted from 285 to 295 nm, and the peak width simultaneously extended.…”

mentioning

confidence: 99%

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Monitoring Reaction Products of Novolac Resists during Puddle Development

2007

jjap

We have developed a new technique for monitoring the concentration of reaction products during puddle development in ultralarge-scale integration (ULSI) lithography. Optical measurement has been employed for monitoring the concentration of reaction products by detecting reflected light from a wafer surface, and compared with the sampling method (UV-visible spectroscopy) for reaction products from a developer solution. A correlation coefficient of 0.89 was obtained, indicating a good correlation between this optical method and sampling method. We concluded that the newly developed optical monitoring technique is useful for measuring the concentration of reaction products.

“…Honda and coworkers reported that the reaction products of the reaction between diazonaphthoquinone ͑DNQ͒/novolac resist and tetramethyl ammonium hydroxide ͑TMAH͒ developer disturb the dissolution of photoresist. 8,9 The thickness of developer solution on the wafer is small in conventional puddle development. Therefore, it is easy for cellular convection such as Rayleigh-Benard convection or Marangoni convection to occur.…”

mentioning

confidence: 99%

Behavior of Reaction Products during Puddle Development in Fabrication of Ultralarge-Scale Integrations

2007

J. Electrochem. Soc.

The behavior of reaction products during puddle development was investigated in ultralarge-scale integration ͑ULSI͒ lithography. The concentration of reaction products originating from novolak photoresist was optically measured. Reaction products during puddle development migrated with time and gathered into cell-like structures. After 5 min from the developer puddle formation, the dissolution rate of photoresist at the cellular structures was about 10% lower than that in other areas. We examined two modified methods of puddle development in order to control the gathering phenomenon of reaction products: one is a method of agitating the reaction product by rocking the wafer, and the other is a method of heating the upper side of the developer solution.The distributions of the dissolution rate ͑3͒ for the former and latter methods were 5.9 and 5.3 nm/min, respectively. Compared with the distribution of the dissolution rate of 9.9 nm/min for conventional puddle development, both modified methods can improve the distribution of the dissolution rate. The migration of reaction products was large when the wafer temperature was high, and the Marangoni number was consistent with the critical value. Therefore, the cellular structures seem to be caused by Marangoni convection.