Electron Beam Writing Apparatus Back Surface Mask Holding
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Solution Overview
Problem
The existing electron beam writing apparatuses face challenges in maintaining writing accuracy due to vertical position displacement of masks held at their back surface, which is difficult to correct without increasing the adjustable range of the focal height adjustment mechanism.
Innovation Solution
An electron beam writing apparatus with a holding mechanism for the mask's back surface, incorporating an XY stage, a Z stage, and measuring means to calculate and adjust the height difference between the mask and the mark table, ensuring the focal height adjustment mechanism's middle value coincides with the mark table height, allowing the Z stage to move and align the mask's height with the mark table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the electronic optical lens barrel is brought close to the mask to enhance resolution for miniaturization, then the electron beam resolution is improved, but it becomes difficult to ensure space for the top reference piece of the clamp
Solution Approach 1:
The patent inverts the holding approach by switching from upper surface holding to back surface holding. Instead of holding the mask from the front (upper surface), the holding mechanism grasps the mask from the rear (back surface), allowing the reference piece to be positioned behind the mask rather than in front, thus clearing the space needed for high-resolution electron beam writing.
Solution Approach 2:
The patent transitions the holding mechanism from a two-dimensional upper surface clamp to a three-dimensional back surface holder that extends behind the mask. This dimensional change allows the reference piece to be positioned in the rear space, separating it from the front writing area and enabling closer proximity between the electron beam source and mask surface.
2Stability of the object's composition
If a back surface holding mechanism is used to hold the mask, then the holding stability is improved, but vertical position displacement occurs due to mask thickness tolerance
Solution Approach 1:
The patent incorporates a height measuring device that continuously monitors the vertical position of the mask surface and provides feedback to a control system. This feedback mechanism detects vertical displacements caused by mask thickness variations and triggers automatic height adjustment to maintain precise positioning during the writing process.
Solution Approach 2:
The patent employs an adjustable height mechanism that dynamically adapts to mask thickness variations. The holding mechanism's vertical position can be changed in real-time based on measured mask height, transforming a static holding system into a dynamic one that compensates for manufacturing tolerances and maintains optimal writing conditions.
3Manufacturing precision
If the focal height adjustable range is increased to correct vertical displacement, then the writing accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent divides the height correction function into two independent segments: (1) a height measuring device that detects mask surface position, and (2) a holding mechanism height adjustment system that physically repositions the mask. This segmentation allows each component to have a specialized, simpler design rather than requiring a single complex focal adjustment mechanism to handle both measurement and correction.
Solution Approach 2:
The patent introduces an intermediary height adjustment mechanism between the mask holding system and the electron beam writing system. This intermediary device acts as a buffer that absorbs vertical position variations, allowing the focal adjustment mechanism to operate within a fixed, limited range while still achieving accurate writing through coordinated height adjustment.
Data Source
AI summary
A Z stage is placed on an XY stage in avoidance of an area to which a mark table is fixed. The mask M is placed on a holding mechanism provided on the Z stage. A middle value of the range adjustable by the focal adjustment mechanism is made coincident with the height of the mark table. The height of the mark table is measured and the heights of plural measurement points of the mask M are measured. The Z stage is moved in such a manner that the height of a middle value between highest and lowest values of the heights of these measurement points coincides with the height of the mark table.