Paul F. Petric

REBL: A novel approach to high speed maskless electron beam direct write lithography

The system concepts used in a novel approach for a high throughput maskless lithography system called reflective electron beam lithography (REBL) are described. The system is specifically targeting five to seven wafer levels per hour throughput on average at the 45nm node, with extendibility to the 32nm node and beyond. REBL incorporates a number of novel technologies to generate and expose lithographic patterns at estimated throughputs considerably higher than electron beam lithography has been able to achieve as yet. A patented reflective electron optic concept enables the unique approach utilized for the digital pattern generator (DPG). The DPG is a complementary metal oxide semiconductor application specific integrated circuit chip with an array of small, independently controllable metallic cells or pixels, which act as an array of electron mirrors. In this way, the system is capable of generating the pattern to be written using massively parallel exposure by ∼1×106 beams at extremely high data rates ...

Reflective electron beam lithography: A maskless ebeam direct write lithography approach using the reflective electron beam lithography concept

Reflective electron beam litography (REBL) utilizes several novel technologies to generate and expose lithographic patterns at throughputs that could make ebeam maskless lithography feasible for high volume manufacturing. The REBL program was described in a previous article [P. Petric et al., J. Vac. Sci. Technol. B 27, 161 (2009)] 2 years ago. This article will review the system architecture and the progress of REBL in the past 2 years. The main technologies making REBL unique are the reflective electron optics, the rotary stage, and the dynamic pattern generator (DPG). Changes in how these concepts have been implemented in a new design will be discussed. The main disadvantage of today’s electron beam direct write is low throughput; it takes many tens of hours to expose a 300 mm wafer today using ebeam lithography. The projected system throughput performance with the integrated technology of the reflective optics, DPG, and a multiple wafer rotary stage will be shown incorporating the performance data for the new column design.Reflective electron beam litography (REBL) utilizes several novel technologies to generate and expose lithographic patterns at throughputs that could make ebeam maskless lithography feasible for high volume manufacturing. The REBL program was described in a previous article [P. Petric et al., J. Vac. Sci. Technol. B 27, 161 (2009)] 2 years ago. This article will review the system architecture and the progress of REBL in the past 2 years. The main technologies making REBL unique are the reflective electron optics, the rotary stage, and the dynamic pattern generator (DPG). Changes in how these concepts have been implemented in a new design will be discussed. The main disadvantage of today’s electron beam direct write is low throughput; it takes many tens of hours to expose a 300 mm wafer today using ebeam lithography. The projected system throughput performance with the integrated technology of the reflective optics, DPG, and a multiple wafer rotary stage will be shown incorporating the performance data for...

Optimization of variable axis immersion lens for resolution and normal landing

This paper describes a variable axis immersion lens system capable of better than 0.1‐μm resolution at 25 A/cm2 over a 10‐mm2 deflection field with perpendicular landing for both electrostatic (high speed) and magnetic deflections. Computer predictions of spot acuity and landing angles are compared to actual measurements for various degrees of field compensation accuracy.

EL-4 column and control

This article describes the electron optical column and some of its electronic controls for the new generation of electron‐beam lithography system at IBM, designated EL‐4. This new column utilizes variable shaped‐beam technology and incorporates dual shaping optics for both triangular and rectangular shapes and triple deflection. The EL‐4 system was designed for high‐throughput 1/4 μm lithography with an edge resolution of 50 nm (extendable to 1/10 μm groundrules) over a 10 mm×10 mm field. The beam deflection optics uses a dual variable axis immersion lens system to achieve two stages of magnetic deflection and one stage of electric deflection. By design, all three stages of deflection are telecentric to eliminate overlay errors resulting from target plane height variations. A pixel throughput increase from our existing state‐of‐the‐art system, the EL‐3, of over an order of magnitude was required for this new system to write the next generation circuit patterns within reasonable times. A unique mechanical ...

PREVAIL: Operation of the electron optics proof-of-concept system

A proof-of-concept (POC) system was built to prove the electron optics concept of PREVAIL as a viable technology for next generation lithography (NGL), and is described elsewhere (H. C. Pfeiffer et al., J. Vac. Sci. Technology B, these proceedings; W. Stickel et al. ibid., these proceedings). The primary objective of the PREVAIL POC system is the embodiment of the curvilinear variable-axis lens (CVAL) optics which provides superior performance in terms of minimum geometric aberrations over unusually large deflection distances off the system axis (see Stickel et al.). Another major benefit of the CVAL is the minimization of the Coulomb interaction blur, since this approach permits the reduction of the column length to the smallest practical dimensions. The implementation of the PREVAIL CVAL requires a much higher degree of complexity than that of probe-forming systems, even of those which incorporate variable-axis immersion lenses [M. A. Sturans et al., J. Vac. Sci. Technol. B 8, 1682 (1990)] in the projec...

Telecentric beam positioning for advanced e-beam lithography

Abstract Telecentric e-beam positioning systems are evaluated by computer simulation. Compared to post-lens double deflection and and deflection through the lens front focal point, the variable axis immersion lens (VAIL) concept is superior for applciation to lithography of pattern dimensions smaller than 0.5 um in fields larger than 4 mm. The simulations suggest that resolving power and telecentricity are conjugated in VAIL: Meeting the VAL condition is favorable for resolution, but not for perpendicular beam landing.

Modeling of counter streaming charged beams in MICHELLE-eBEAM

A new approach implemented in the MICHELLE-eBEAM code [Ovtchinnikov et al., J. Vac. Sci. Technol. B 28, C6J8 (2010)] is designed to take advantage of the graphics processing unit hardware acceleration using novel algorithms to capture inter-particle interactions accurately and efficiently. This approach is used in the simulation of counter streaming charged particle beams, where two beams are colocated in space while propagating in opposite directions, and has applications in lithographic devices such as in Reflective Electron Beam Lithography (REBL) [Petric et al., J. Vac. Sci. Technol. B 27, 161 (2009)]. Modeling such counter streaming beams presents different computational challenges depending on the specific device being modeled. These applications often require the modeling of both global and stochastic space charge, where the latter calls for accurate evaluation of Coulomb interactions. In this paper, the authors report on our progress and demonstrate, for a high current REBL application, the achiev...

High-current electron optical design for reflective electron beam lithography direct write lithography

The authors present the latest design and results for the second generation column used in the reflective electron beam lithography program. The previous magnetic prism based concept to separate the illumination and projection beams has been replaced with a Wien filter that allows the column to be shrunk in size by a factor of 3, resulting in reduced Coulomb blur and energy spread. Experimental data from the column are presented and compared to simulation. The authors also discuss design considerations for this and future columns, including beam voltage, numerical aperture selection, and cathode optimization.

Design of a high voltage electron gun for lithography applications

A development project was undertaken at IBM to meet the needs of production e‐beam lithography at increased beam energies up to 100 kV. The project was divided into two separate development efforts. The first part, which is the topic of this article, dealt with the gun vacuum and its overall design. The second half dealt with the high voltage design. This article describes the design of the overall gun and its vacuum system and the initial results of testing as they pertain to the vacuum system of the gun and its operation with the integral ion pump design.

Analysis of large electron optical systems with many interacting optical elements

Abstract The analysis of large electron optical systems depends on the accuracy of the field computation of the system. In turn, the accuracy of the computed fields is strongly dependent on the size and complexity of the system under investigation and the fineness used to convert the system to a discrete numerical model. This results in severe demands on computer memory and speed. In addition, the analysis of these complex electron optical systems having multiple optical elements requires a measure of flexibility in “adjusting” each elements contribution to the system independently. With this flexibility the entire system does not have to be solved again when a change is made to one element of the system. Two techniques have been developed to resolve these two limitations. One technique allows a large system to be broken into smaller sections by establishing the section boundary conditions using current loops. This permits the system problem to be solved using finer and finer discrete models of each section to increase the accuracy of the system solution. The second technique permits the field contribution of each optical element of the system to be computed individually, but as though all the elements of the system were operated at their nominal excitations.