Method using a photoresist residue

Details Method using a photoresist residue Method using a photoresist residue

1999-02-24

2001-05-29

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

C438S584000, C438S628000, C438S648000, C438S758000, C438S761000, C438S763000, C438S791000

Reexamination Certificate

active

06239027

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an improved method for photoresist residue. More particularly, the present invention relates to an improved method for photoresist residue on a surface of a titanium nitride layer.
2. Description of Related Art
In semiconductor processes, a patterned method uses photoresist material to transfer patterns. Photoresist material is sensitive to light. Through exposure and development, a photoresist layer is formed to serve as an etching mask. With the photoresist layer serving as a mask, the underlayer is patterned.
Etching different material needs a suitable photoresist material serving as an etching mask. However, while etching titanium nitride, the photoresist material serving as a mask for etching the insulating layer causes damage to the titanium nitride. In a conventional method, a photoresist layer is directly formed on the titanium nitride. This causes a defect on the surface of the titanium nitride bottom electrode, and a portion of the photoresist material may remain on the surface of the bottom electrode.
A semiconductor process for a fingerprint sensor is taken as an example. After an interconnect is fabricated, a sensor region having an area of about 2.25 cm
2
which is like a finger is formed over a top surface of a semiconductor substrate. The layout of the sensor region has a capacitor with about 300 lines and about 300 rows. Titanium nitride is commonly used for a material for a bottom electrode of the capacitor. The fingers serve as an upper electrode of the capacitor. The capacitor in the fingerprint sensor is used to induce static electricity on a fingertip surface. The fingertip surface is composed of raised lines and depressions between the raised lines. The capacitance induced by the raised lines is different from that induced by the depressions, and this difference is read by the sensor. Finally, the signals are transformed into an image.
In fabrication of a conventional fingerprint sensor, after an interconnect is fabricated, a patterned titanium nitride layer is deposited to serve as a bottom electrode. Then an opening is formed in a silicon oxide layer between a pad and a titanium nitride layer to serve as a connection in a latter package process. While patterning the silicon oxide layer, a photoresist layer is formed on the silicon oxide layer and the titanium nitride layer. However, the titanium nitride layer is damaged by the photoresist material to cause a defect generated on a surface of the titanium nitride layer. Moreover, some photoresist residue remains on the surface of the titanium nitride layer. As a result, the quality of the capacitor is thus decreased.
SUMMARY OF THE INVENTION
The invention provides an improved method for photoresist residue. The method is used to prevent a material layer from being damaged by the photoresist residue. A semiconductor substrate is provided. An insulating layer is formed over the substrate. The patterned material layer is formed on the insulating layer. A thin dielectric layer is formed on the insulating layer and the material layer to protect the material layer. A patterned photoresist layer is formed on the dielectric layer. The insulating layer is defined. The photoresist layer is removed.
Additionally, the invention provides an improved method for fabricating a capacitor for a fingerprint sensor. The method is used after fabricating an interconnect. A semiconductor substrate is provided. A patterned first conductive layer is formed to serve as a pad. An insulating layer is formed on the first conductive layer. A second conductive layer is formed on the insulating layer. The second conductive layer is defined to form a bottom electrode of the subsequently formed capacitor. A first dielectric layer is formed on the bottom electrode and the insulating layer. A patterned photoresist layer is formed on the first dielectric layer. The first dielectric layer and the insulating layer are defined to form an opening until the first conductive layer is exposed. The photoresist layer is removed. A second dielectric layer is formed on the first dielectric layer wherein the first dielectric layer and the second dielectric layer form a dielectric film of the capacitor. The second dielectric layer is defined until the first conductive layer is exposed by the opening.
One advantage of the invention is the formation of a thin dielectric layer after the bottom electrode is formed. The thin dielectric layer serves as a part of a dielectric film of a capacitor, and, most importantly, it can protect the bottom electrode from contamination by photoresist residue in a later process.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 5693554 (1997-12-01), Lee

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