^{1,a)}and Leonidas E. Ocola

^{1}

### Abstract

The authors report experimental data on the dose contribution of backscattered electrons on a silicon substrate. The backscattered electron intensity, i.e., the relative dose contribution from backscattered electrons with respect to direct write dose, is not constant, but varies with the percentage of the total dose received by backscattered electrons. In order to measure the backscattered electron contribution, the position and number of electrons are controlled by electron beam lithography. The dose contribution is measured using a negative electron beam resist, which quantifies the electron interactions in a nanoscale volume on the surface of the substrate. The data presented here will lead to improvements in proximity effect correction algorithms and ultimately improve pattern creation using electron beam lithography.

This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility under Contract No. DE-AC02-06CH11357.

I. INTRODUCTION

II. THEORY

III. EXPERIMENT

IV. RESULTS AND DISCUSSION

V. SUMMARY AND CONCLUSIONS

### Key Topics

- Backscattering
- 41.0
- Electron beams
- 15.0
- Height measurements
- 10.0
- Silicon
- 6.0
- Negative resistance
- 5.0

##### G03F7/00

##### H01J37/317

##### H01L21/02

##### H01L21/70

## Figures

(Color online) Schematic of the pattern used to measure the relative dose contribution of backscattered electrons. The pattern consists of intersecting lines and a torus with inner radius, R in, and outer radius, R out. The pattern is exposed, developed, and the height of the resist exposed at the center of the intersecting lines is measured. This height is used as a means to quantify the electron interactions with a nanoscale volume of the resist on the surface of the substrate.

(Color online) Schematic of the pattern used to measure the relative dose contribution of backscattered electrons. The pattern consists of intersecting lines and a torus with inner radius, R in, and outer radius, R out. The pattern is exposed, developed, and the height of the resist exposed at the center of the intersecting lines is measured. This height is used as a means to quantify the electron interactions with a nanoscale volume of the resist on the surface of the substrate.

(Color online) Example graph showing the expected relation between the normalized resist height and the torus dose. The solid lines represent the normalized resist height for a given write dose. The direct write dose of the lines is highest for D line 1 and lowest for D line 5. Subsequently, the torus doses need to be increased as the line dose is decreased to achieve the same resist height.

(Color online) Example graph showing the expected relation between the normalized resist height and the torus dose. The solid lines represent the normalized resist height for a given write dose. The direct write dose of the lines is highest for D line 1 and lowest for D line 5. Subsequently, the torus doses need to be increased as the line dose is decreased to achieve the same resist height.

(Color online) Graph of the normalized resist height as a function of the direct write dose. The circles are the raw data. The solid line represents a least squares fit of the data to a saturating exponential function, characterized by two parameters: a minimum printing dose below which no features are left after development and a slope of the curve related to the sensitivity of the resist.

(Color online) Graph of the normalized resist height as a function of the direct write dose. The circles are the raw data. The solid line represents a least squares fit of the data to a saturating exponential function, characterized by two parameters: a minimum printing dose below which no features are left after development and a slope of the curve related to the sensitivity of the resist.

(Color online) Graph showing the normalized resist height as a function of the modified torus dose for seven different write doses. The symbols represent the measured data. The solid lines represent a least squares fit of the data to a saturating exponential function. The solid horizontal line at 0.5 normalized height is used to visualize the individual values for the different D line curves. These values are used to calculate the relative backscattered dose contribution, η, for the different curves.

(Color online) Graph showing the normalized resist height as a function of the modified torus dose for seven different write doses. The symbols represent the measured data. The solid lines represent a least squares fit of the data to a saturating exponential function. The solid horizontal line at 0.5 normalized height is used to visualize the individual values for the different D line curves. These values are used to calculate the relative backscattered dose contribution, η, for the different curves.

(Color online) Graph showing the relative backscattered dose contribution, η, as a function of the percentage normalized backscatter dose contribution. The symbols represent the calculated values for η. The solid lines around the symbols represent the calculated error for the corresponding values of η. The solid line represents a continuous function used to extrapolate values for points in between the measured data points.

(Color online) Graph showing the relative backscattered dose contribution, η, as a function of the percentage normalized backscatter dose contribution. The symbols represent the calculated values for η. The solid lines around the symbols represent the calculated error for the corresponding values of η. The solid line represents a continuous function used to extrapolate values for points in between the measured data points.

## Tables

Fit parameters for the raw data for the contrast curve and the different line doses. The units of D line, D min, ΔD min, s, Δs, and 0.5 h are μC/cm2. η and Δη are dimensionless parameters.

Fit parameters for the raw data for the contrast curve and the different line doses. The units of D line, D min, ΔD min, s, Δs, and 0.5 h are μC/cm2. η and Δη are dimensionless parameters.

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