NuFlare has started development of multi-beam mask writer MBM-1000 aiming to apply to N5 and to release in Q4
2017. MBM-1000 is based on large area projection optics with shaping aperture array plate, blanking aperture array
(BAA) plate, single cathode and inline/realtime data path for vector data rasterization and bitmap dose correction. It is
designed to accomplish higher throughput than EBM series (variable shaped beam (VSB) writers) with massive beam
array, higher resolution by using 10-nm beam size and 10-bit dose control, and better writing accuracy with more write
passes. Configuration of MBM-1000 and flow of data path processing are described. Write time estimation suggests
MBM-1000 has advantage over VSB writer with shot count > 200 Gshot/pass and resist sensitivity >75 μC/cm2.
Printing test of 20 nm hp 1:1 line and space pattern with ZEP-520 resist showed better beam resolution of MBM-1000
alpha tool than EBM series.

Multi-Beam Mask Writer MBM-1000 and its Application Field

EUV lithography requirements continue to present new challenges and opportunities for multi-beam mask writer. Driven by sub-10nm node mask requirements for higher resolution, CD uniformity, pattern placement accuracy, lower line edge roughness (LER), and zero writer-induced defects, the multi-beam mask patterning technology must keep the pace, continue to innovate, and work hand-in-hand with mask makers to overcome these challenges to meet the mask and wafer manufacturing metrics and requirements.
In this paper we will review some of these challenges from the mask maker point of view. Also, we will shed light on a bigger challenge of transitioning to curvilinear mask ILT (Inverse Lithography Technology) data structure and the support needed from multi-beam writer to handle large data volume. Processing and managing this large growth of data helps the mask industry speed up the process of adapting to this technology and enabling EUV mask and wafer manufacturing reach its ultimate goals.

Multi-beam mask writer in EUV era: challenges and opportunities

Multi-beam mask writer MBM-1000 has been developed for N5. It is designed to accomplish high resolution with 10 nm beam and high throughput with 300 Gbps blanking aperture array (BAA) and inline real-time data path. It is equipped with function of pixel level dose correction (PLDC) to improve patterning resolution, which is method specific to multi-beam writer. Design concept of MBM-1000 is described. Writing test is carried out to demonstrate performance of MBM-1000 and PLDC function.

Multi-beam mask writer MBM-1000

A method for acquiring a settling time includes forming, using a deflector, a reference pattern so that a deflection movement amount of the beam may be smaller than an evaluation deflection movement amount; forming, while variably setting the settling time of the DAC amplifier, an evaluation pattern such that both ends of the width dimension of the evaluation pattern being the same design width dimension as that of the reference pattern, for each of times set variably, such that a deflection movement amount of a second beam shot of two beam shots successively shot is equivalent to the evaluation deflection movement amount; calculating a difference between the width dimension of the evaluation pattern concerned and that of the reference pattern, for each of the times set variably; and acquiring a settling time of the DAC amplifier necessary for the deflection movement amount, using the difference

Method for acquiring settling time

Semiconductor scaling is slowing down because of difficulties of device manufacturing below logic 7nm
node generation Various lithography candidates which include ArF immersion with resolution enhancement
technology (like Inversed Lithography technology), Extreme Ultra Violet lithography and Nano Imprint
lithography are being developed to address the situation In such advanced lithography, shot counts of mask
patterns are estimated to increase explosively in critical layers, and then it is hoped that multi beam mask
writer (MBMW) is released to handle them within realistic write time However, ArF immersion technology
with multiple patterning will continue to be a mainstream lithography solution for most of the layers Then,
the shot counts in less critical layers are estimated to be stable because of the limitation of resolution in ArF
immersion technology Therefore, single beam mask writer (SBMW) can play an important role for mask
production still, relative to MBMW Also the demand of SBMW seems actually strong for the logic 7nm
node To realize this, we have developed a new SBMW, EBM-9500 for mask fabrication in this generation A
newly introduced electron beam source enables higher current density of 1200A/cm2 Heating effect
correction function has also been newly introduced to satisfy the requirements for both pattern accuracy and
throughput In this paper, we will report the configuration and performance of EBM-9500

Electron beam mask writer EBM-9500 for logic 7nm node generation

The specifications for critical dimension (CD) accuracy and line edge roughness are getting tighter to promote every photomask manufacturer to choose electron beam resists of lower sensitivity. When the resist is exposed by too many electrons, it is excessively heated up to have higher sensitivity at a higher temperature, which results in degraded CD uniformity. This effect is called “resist heating effect” and is now the most critical error source in CD control on a variable shaped beam (VSB) mask writer. We have developed an on-tool, real-time correction system for the resist heating effect. The system is composed of correction software based on a simple thermal diffusion model and computational hardware equipped with more than 100 graphical processing unit chips. We have demonstrated that the designed correction accuracy was obtained and the runtime of correction was sufficiently shorter than the writing time. The system is ready to be deployed for our VSB mask writers to retain the writing time as short as possible for lower sensitivity resists by removing the need for increased pass count.

Correction of resist heating effect on variable shaped beam mask writer

Resist heating effect which is caused in electron beam lithography by rise in substrate temperature of a few tens or hundreds of degrees changes resist sensitivity and leads to degradation of local critical dimension uniformity (LCDU). Increasing writing pass count and reducing dose per pass is one way to avoid the resist heating effect, but it worsens writing throughput. As an alternative way, NuFlare Technology is developing a heating effect correction system which corrects CD deviation induced by resist heating effect and mitigates LCDU degradation even in high dose per pass conditions. Our developing correction model is based on a dose modulation method. Therefore, a kind of conversion equation to modify the dose corresponding to CD change by temperature rise is necessary. For this purpose, a CD variation model depending on local pattern density was introduced and its validity was confirmed by experiments and temperature simulations. And then the dose modulation rate which is a parameter to be used in the heating effect correction system was defined as ideally irrelevant to the local pattern density, and the actual values were also determined with the experimental results for several resist types. The accuracy of the heating effect correction was also discussed. Even when deviations depending on the pattern density slightly remains in the dose modulation rates (i.e., not ideal in actual), the estimated residual errors in the correction are sufficiently small and acceptable for practical 2 pass writing with the constant dose modulation rates. In these results, it is demonstrated that the CD variation model is effective for the heating effect correction system.

Study on modeling of resist heating effect correction in EB mask writer EBM-9000

A apparatus includes a unit to operate a first dose of a beam corrected for a proximity effect for each of second mesh regions of a second mesh size obtained by dividing the first mesh size by a product of a natural number and a number of passes, by using a dose model using a dose threshold; a unit to operate a representative temperature rising due to heat transfer originating from irradiation of the beam by using a dose for an applicable pass of the first dose and a unit to operate a polynomial having a term obtained by multiplying a dose modulation coefficient based on the representative temperature by a pattern area density as an element, and a dose that makes a difference between a value obtained by operating the polynomial and the dose threshold within a tolerance is used.

Charged particle beam writing apparatus and method for acquiring dose modulation coefficient of charged particle beam

A charged particle beam writing apparatus according to one aspect of the present invention includes: a first mesh division unit configured to virtually divide a pattern writing region of a target object into a plurality of first mesh regions in a first mesh size; a second mesh division unit configured to virtually divide the pattern writing region of the target object into a plurality of second mesh regions in a second mesh size obtained by dividing the first mesh size by a product of a natural number and a number of passes of multiple pattern writing performed by shifting a position; a first dose calculation unit configured to calculate a dose of a charged particle beam with corrected proximity effect for each of the plurality of second mesh regions by using a dose model using a dose threshold; a representative temperature calculation unit configured to calculate a representative temperature of the first mesh region rising due to heat transfer originating from irradiation of the charged particle beam by using a dose for an applicable pass of the multiple pattern writing of the calculated dose, for each pass of the multiple pattern writing and each of the plurality of first mesh regions; a polynomial calculation unit configured to calculate a polynomial having a term obtained by multiplying a dose modulation coefficient based on the representative temperature of each pass by a pattern area density for each of the plurality of second mesh regions as an element; and a pattern writing unit configured to write a pattern on the target object by using a charged particle beam of a dose of which the difference between a value obtained by calculating the polynomial and the dose threshold is within a tolerance value.

Mizuna Suganuma

Papers

Electron beam mask writer EBM-9500 for logic 7nm node generation

Correction of resist heating effect on variable shaped beam mask writer

Study on modeling of resist heating effect correction in EB mask writer EBM-9000

Charged particle beam writing apparatus and method for acquiring dose modulation coefficient of charged particle beam

Charged particle beam writing device and method for acquiring dose modulation coefficient