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Microengineering MEMs and Interfacing - Danny Banks Part 8

Tham khảo tài liệu 'microengineering mems and interfacing - danny banks part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 120 Microengineering MEMS and Interfacing A Practical Guide Mosis Scmos layout rules-9-metal 2 Rule Description Lambda 9.1 Minimum width 3 9.2 Minimum spacing 3 9.3 Minimum overlap of via 1 1 9.4 Minimum spacing when either metal line is wider than 10 lambda 6 9.1 9.2a 9.2b Metal 1 c FIGURE 4.18 Continued Note Do not break design rules unless you are absolutely sure you know what you are doing. They are there for a purpose. It is usually desirable to exceed the design rules as far as possible. If a 4-pm overlap is specified an 8-pm overlap would be preferable. Furthermore it is helpful although not essential to work in multiples of the minimum feature size. 4.5.1 Developing Design Rules The first principle is to comply with the minimum feature size. No structures or gaps should have dimensions below the minimum feature size. This will set the absolute minimum width and separation rules Figure 4.19a . Process characteristics contribute to separation rules. Diffusion processes proceed laterally under the mask as well as into the silicon. The minimum separation between diffused impurities P-well or N-well is likely to be larger Figure 4.19b . Taking the process characteristics into account overlap requirements are set principally by the accuracy of alignment during photolithography. If it is possible to align one layer with another to 1 pm then an overlap of at least 2 pm would Copyright 2006 Taylor Francis Group LLC 122 Microengineering MEMS and Interfacing A Practical Guide Substrate A1 Substrate . Via V1 A1 Metal M1 Xvia Via V1 Metal M1 Xmetal a Xvia Xmetal b FIGURE 4.20 In a both Ml and V1 are aligned to a mark on the substrate with an error of 1 pm. This means that Xvia will be the nominal distance on the mask design X 1 pm. The same is true of Xmetal which means that Xvia can be as much as X 1 pm and Xmetal as little as X - 1 pm. The difference between the two structures on the final device will then be as great as 2 pm. This is addressed in b where M1 is .