Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
2002-12-17
2004-02-17
Nguyen, Thanh T. (Department: 2813)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S386000, C438S736000
Reexamination Certificate
active
06693006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a method for increasing the area of the trench capacitor for dynamic recess random memory (DRAM). In particular, the present invention relates to a method for increasing the area of the trench capacitor using nitride refill.
2. Description of the Related Art
DRAM is used to store data by the charging state of the memory cell. If the capacitors of DRAM can store more charges, that is, the capacitors have higher capacitance, the noise effect, such as soft errors from a particles, occurring in data reads, can be effectively reduced, as is the refresh frequency. In other words, the higher the capacitance, the more stable the data stored in the memory. Therefore, improving the capacitance of the capacitor is an important topic for research.
SUMMARY OF THE INVENTION
A method for increasing area of a trench capacitor is provided. First, a first oxide layer and a first nitride layer are sequentially formed on a substrate. An opening is formed through the first oxide layer and the first nitride layer into the substrate to expose the first oxide layer and the substrate, wherein the opening has a lower portion and an upper portion. A part of the first oxide layer exposed in the opening is removed to form a first recess between the first nitride layer and the substrate. A second nitride layer is formed in the first recess between the first nitride layer and the substrate. A second oxide layer is formed on the first nitride layer and the opening. The second oxide layer in the upper portion of the opening is removed. A third nitride layer is formed in the upper portion of the opening. The second oxide layer in the lower portion of the opening is removed. The substrate in the opening is etched using the first nitride layer, the second nitride layer and the third nitride layer as a mask to form a second recess in the substrate in the lower portion of the opening. The second nitride layer and the third nitride layer are removed.
According to the present invention, the area of the capacitor is increased; therefore, the capacitance of the capacitor is also improved. The nitride refill step is introduced after forming the first recess between the first nitride layer and the substrate in the opening, hence the first oxide layer cannot be undercut, that is, the pad oxide layer and the etching solution used to enlarge the surface area of the lower portion of the opening provide numerous options.
REFERENCES:
patent: 6140175 (2000-10-01), Kleinhenz et al.
patent: 6426254 (2002-07-01), Kudelka et al.
patent: 6458647 (2002-10-01), Tews et al.
Chen Yi-Nan
Ho Hsin-Jung
Huang Tung-Wang
Wu Chang Rong
Nanya Technology Corporation
Nguyen Thanh T.
Quintero Nelson A.
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