TABLE OF CONTENTS In this chapter, the basic patterning process step used for photoresist developing through final inspection (steps 5 through 10 of the basic process) are explained. The end of the chapter examines the processes used for mask making and a discussion of alignment error budgets.
Upon completion of this chapter, you should be able to:
Draw a cross section of a wafer before and after developing.
Make a list of the developing methods.
Explain the purpose and methods of hard bake.
List at least five reasons why a wafer can be rejected at develop inspect.
Draw a diagram of the develop-inspect-rework loop.
Explain the methods and relative merits of wet and dry etch.
Make a list of the resist strippers used to strip photoresist from oxide and metal films.
Explain the purpose and methods of final inspection.
After the wafer completes the alignment and exposure step, the device or circuit pattern is coded ( latent image) in the photoresist as regions of exposed and unexposed resist (Fig. 9.1). The pattern is developed in the resist by the chemical dissolution of the unpolymerized resist regions. Development processes are designed to form in the resist layer a pattern with the exact dimensions designated during the circuit design process. A problem resulting from a poor developing process (Fig. 9.1) is underdevelopment, which leaves the hole incompletely developed to the correct dimensions, or a coved sidewall. In some cases, the development will not...
