Shiro Ninomiya

Precise beam angle control in the S-UHE, SEN's single-wafer ultra-high energy ion implanter

In order to fabricate highly sensitive image sensors (IS), ultra-high energetic ion beams such as 5MeV of boron are required. In order to address the requirement as well as more aggressive requirements of leading-edge IS, SEN has developed the S-UHE, an ultra-high energy single-wafer ion implanter. One of the most important features in the S-UHE is a precise beam angle control system to obtain stable implant depth of ion species against angle-sensitive channeling effects. It is very important for the precise control both to design a sophisticated beam line and to measure beam angles accurately. In this report, measuring techniques of the beam angle and the results are presented.

Symmetric beam line technique for a single-wafer ultra-high energy ion implanter

In order to fabricate highly sensitive image sensors, ultra-high energy ion beams, such as 5 MeV of boron, are required. SEN has developed the S-UHE, a single-wafer ultra-high energy ion implanter, to obtain such ultra-high energy beams. The S-UHE has adopted an electrostatic and symmetric, parallelizing lens system, the concept of which is already used in the MC3-II, a medium-current ion implanter, and the SHX, a single-wafer high-current implanter. This system provides very good uniformity, even when a large amount of outgassing from photoresist materials is generated. Since the ion beam energy is so high at the lens system, a compound electrostatic parallelizing lens system is introduced. Beam angles have been controlled within 0.05° for any recipe in experiments with the electrostatic parallelizing lens system. Another beam line element specifically adopted in the S-UHE is an electric quadrupole lens installed between the two dipole magnets, in order to suppress beam current loss. This electric lens can easily form achromatic ion beam transportation without any significant deformation of the magnetic field.

Productivity Improvement for the SHX—SEN’s Single‐Wafer High‐Current Ion Implanter

Equipment productivity is a critical issue for device fabrication. For ion implantation, productivity is determined both by ion current at the wafer and by utilization efficiency of the ion beam. Such improvements not only result in higher fabrication efficiency but also reduce consumption of both electrical power and process gases. For high‐current ion implanters, reduction of implant area is a key factor to increase efficiency. SEN has developed the SAVING system (Scanning Area Variation Implantation with Narrower Geometrical pattern) to address this opportunity. In this paper, three variations of the SAVING system are introduced along with discussion of their effects on fab productivity.

MILD system: Maskless implantation for local doping

SEN Corporation has developed a very flexible dose pattern modulation system called “MIND+”. This system can be used for yield enhancement by compensating for variation induced by other processes. In this paper, another important feature of SEN’s single-wafer implanters is introduced. The system is called the “MILD” system, standing for “Maskless Implantation for Local Doping.” MILD provides the capability to implant dopants at any positions on a wafer without hard masks or photo-resist patterns. In this paper, MILD system operation and results will be described.

MIND+ system; More universal dose patterns by single-step ion implantation

Electrical characteristics of semi-conductor devices within a wafer are expected to be uniform based on control of the dose pattern during the ion implant process. SEN developed the MIND system (Mapping of Intentional Non-uniform Dosage), to provide such dose pattern control. This capability has been enhanced with MIND+. The new system provides improved two-dimensional dose pattern control with more degrees of freedom and greater accuracy than the original MIND system. In addition, MIND+ can generate practical dose patterns (see below) while using a single step implant. As a result, MIND+ provides a very powerful tool for yield enhancement without sacrificing throughput. This paper will provide more detail on the capabilities and practical applications of the MIND+ system.

Intentional Two-Dimensional Non-Uniform Dose Implant with High Dynamic Dose Range

Two-dimensional (2D) dose control is becoming well accepted for semiconductor device fabrication. At the same time, two specialized versions are arising; (1) High accuracy intentional non-uniform dose implant with relatively moderate dynamic dose range and (2) High dynamic dose range intentional non-uniform implant with relatively moderate dose accuracy. Sumitomo Heavy Industries Ion Technology (SMIT) has developed two-dimensional intentional non-uniform doseimplant methods for both demands. A method to carry out a high-accuracy intentional 2D non-uniform implant (MIND 2.0) will be presented at this conference. In this paper, our method to carry out a high-dynamic-range 2D non-uniform dose implant will be reported. A test implant was planned and carried out for an intentional doughnut-shape dose pattern by using the MC3-II/GP ion implanter. While the implant dose in the outmost region is neglected, we could obtain in the inner region about ten times smaller dose than in middle region in a wafer.

High-Accuracy Two-Dimensional Intentional Non-Uniform Dose Implant: MIND 2.0

Two-dimensional (2D) dose control is becoming well accepted for semiconductor device fabrication. At the same time, two specialized versions are arising; (1) High accuracy intentional non-uniform dose implant with relatively moderate dynamic dose range and (2) High dynamic dose range intentional non-uniform implant with relatively moderate dose accuracy. Sumitomo Heavy Industries Ion Technology (SMIT) has developed two-dimensional intentional non-uniform dose-implant methods for both demands. A method to carry out a highdynamic- range 2D non-uniform dose implant will be presented at this conference. In this paper, the method to carry out high-accuracy intentional 2D non-uniform implants (MIND 2.0) will be reported. The MIND 2.0 system has been installed on SMITs hybrid-scan single-wafer ion implanters. In order to obtain intentional non-uniform dosage, beam scanning patterns must be modified. For a high-accuracy intentional 2D non-uniform dose implant, an iterative method which includes actual dose-pattern checks has been implemented in MIND 2.0. In this way, appropriate beam scanning patterns for intended twodimensional non-uniform dose patterns are always obtained, no matter what a beam size is.

A Beam Quality Control Method in SAion Ion Implanter

The SAion is a leading-edge ion implanter developed for the upcoming generation. The SAion has extremely wide process coverage and high productivity throughout both the medium current (MC) and high current (HC) process ranges. In this paper, beam quality control method introduced for the SAion will be discussed. In order to carry out beam quality control, methods both to measure beam quality very precisely and to control beam quality very precisely must be satisfied simultaneously. These two technical elements have been developed and adopted in the SAion. A movable beam profiler has a beamangle measurement function in very high accuracy. A beam angle is measured very precisely at the wafer position. Based on the measurement, beam divergence control with extremely wide beam current coverage also can be carried out.

SEN's SAVING techniques for productivity enhancement

Needless to say, productivity of ion implantation processes is a very important issue for economical device fabrication. Reduction of implant areas is one of the essential keys to increase a beam utilization factor for high-current ion implanters. SEN already developed the X-, Y-, D-, and F-SAVING system to address this issue. This time, another SAVING system, the O-SAVING, has been developed for the SHX-III/S. In result, the system reduces implant time in 40% from the original implant and more than 10% from the F-SAVING. This system can freely change the beam scan widths and positions, keeping the beam scan frequency constant. In this manner not only good uniformity is ensured but also a shape of implant area can be freely selected from arbitrary shapes such as a circle, a triangle, a semicircle, and so on.

F-SAVING system productivity improvement for the SHX-III

Productivity of an ion implantation process is one of the critical issues for device fabrication. Reduction of implant area is a key factor to increase beam utilization for high-current implanters. SEN has already developed the X-, Y- and D-SAVING systems to address this issue. These allow reduction of beam scan length horizontally along the center line, vertically and horizontally along the right hand side of the wafer off the center line, respectively. These SAVING systems are is use for volume manufacturing by several semiconductor fabs. The F-SAVING system is the latest development for the SHX-III. One of the most important features in the F-SAVING system is the introduction of two-dimensional information on beam size for additional reduction of implant area. In this report, detail concepts of the F-SAVING system will be discussed.