JPS60145639A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a separating part between elements having a flat surface by slightly shortly developing as compared with the usual developing time, etching it, then again developing to remove the resist film of underetched part, burying with insulator by a lift-off method, and forming a burying groove. CONSTITUTION:When a photoresist film 5 is developed on a substrate 2 to open, it is developed slightly shorter than the optimum developing time to open the pattern 6 of the separating part between elements, the width is narrowed from the designed value. When chemical etching is perfored to etch the substrate 2, overhangs 8 are formed at a photoresist film 5 by the formation of underetching part 7. Then, the photoresist film for forming the overhangs 8 is dissolved by the redevelopment. Then, an insulating layer 10 is formed on the film 5 by a lifting method in the same manner as the conventional one, the film 5 is removed with a solvent, thereby forming the layer 10 having no groove.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a method for isolating elements of a semiconductor substrate having a flat surface.

(b) Technical Background Semiconductor devices, represented by ICs and LSIs, have many active elements such as diodes and transistors formed on a semiconductor substrate with a small area called a semiconductor chip.
A high-density electronic circuit is formed by connecting these circuits with wiring butter.In this case, the insulation between each element is
This is done effectively using a seed layer created by a pn junction.

On the other hand, silicon dioxide (Stop) and silicon nitride (SiiN4)
There are also devices that use insulators such as these to provide shielding between elements.

For example, in a solid-state image sensor using a charge injection device, the selection electrode and the five-edge protruding electrode are provided close to each other to form a unit pixel, and the other pixel is located on the semiconductor substrate. A large number of t3 green layers are formed on top of the t3 green layer. FIG. 1 is a plan view showing the pixel arrangement, and FIG. 1B is a sectional view taken along the line x-x'.

That is, the pixel 1 in which the selection i1t i and the readout 1d pole are configured adjacent to each other is formed on an insulating layer 3 provided on a semiconductor substrate 2 to form an MIS structure, and the elements of each pixel 1 Each selection '1 electrode is connected to a shift register, and each readout electrode is connected to a signal amplification circuit through wiring which is provided above the separation section 4 and alternates between main bodies. The element isolation section 4 is formed by etching a semiconductor substrate using photolithography and embedding an insulator therein.

The present invention relates to a method of forming such isolation between elements.

(e) Conventional technology and problems To form an isolation part between elements on a semiconductor substrate, after applying (transferring) a photoresist, selective exposure to ultraviolet rays is performed so that the irradiated part undergoes condensation polymerization and becomes insoluble (negative resist). Alternatively, it is formed by using a resist film that decomposes and becomes soluble in a developer (positive wave resist) to open a pattern of an element separation part in a resist film and then etching it.

FIG. 2 shows the process of forming the element isolation part using the chemical etching method. After opening the pattern 6 of the element isolation part in the photoresist film 5 using the above photolithography technique,
Figure A) A semiconductor substrate (substrate hereinafter) 2 is immersed in a chemical etching solution to chemically etch the window opening. An etched portion 7 is formed, thereby forming an eave 8 of the resist IM (FIG. B).

Next, an insulating material is deposited using a method such as high-frequency sputtering until the lY+; 10 is not formed (C in the same figure).

Therefore, what about the photoresist film 5? After dissolving and removing using medium No. 11, an inter-element separation area in which the under-etched area 7 is depressed is generated (FIG. 1)).

For this purpose, an insulating layer 3 is formed on a substrate 2 having a 1r'i portion corresponding to the amount of elements, and a conductive layer 11 is further formed; in this case, a groove 12 is formed on the under-etched portion 7 of the element isolation portion. (E in the same figure). The presence of this groove 12 is due to the t:d? of the wiring pattern formed through this portion. The cause of the line disturbance was the rti, which was a problem from the viewpoint of the 'Iff axis.

(d) Object of the Invention An object of the present invention is to provide a method for forming an element isolation part with a flat surface by eliminating grooves that occur in the element isolation part of a semiconductor substrate.

(e) Structure of the Invention The object of the present invention is to develop a resist film formed on a semiconductor substrate by exposing it to ultraviolet rays and developing it to open a window for isolation patterns between elements, by developing the resist film in a shorter time than the standard development time. After etching the substrate, it is developed again to remove the resist film on the under-etched area, and a lift-off method is used to fill the hole with an insulator to form a buried trench. (f) Embodiments of the Invention The present invention is to eliminate the eaves 8 of the photoresist film 5 that occur when chemically etching a substrate using photolithographic technology. It is something that makes things hot.

FIG. 3 is a process diagram according to the present invention, in which the photoresist film 5 on the substrate 2 is opened by photoetching, and the pattern 6 of the isolation part between elements is opened by developing the film for a shorter time than the optimum etching time. In this case, make the width narrower than the design value.

For example, when using positive resist 0FPR-800, it takes approximately 30 seconds of immersion to develop a 1 μm thick resist, but by keeping this for 20 seconds, the openings can be closed. It can be made narrower than a single stage (
Figure 3A).

Next, a chemical etching process i4 is performed to etch l+3iA'' 42, and at this time, a pressure j8 force i is generated on the photoresist 11g45 due to the shape l of the underetched portion 7 (FIG. 3B).

Next, the photoresist film forming the eaves 8 is dissolved by re-hulling and imaging according to the present invention.

For example, using 0FPR-800;
can be removed by dipping for 10 seconds (C in the same figure).

The reason for this is that the photoresist on the eaves 8 is a partially exposed portion, which is short and remains undissolved due to the 1) process. Next, as in the conventional method, an insulating layer 10 is formed on the potresist (rs<p) 5 using a lift-off method.
The insulating layer 10 without grooves can be formed by removing the photoresist film 5 using a solvent (see E in the same figure). are both flat.

(g) Effects of the Invention The present invention has the drawback that in the conventional device isolation method in which an insulating material is buried, a groove is formed along the buried insulating layer because an eaves are formed in the photoresist due to an under-etch phenomenon. By implementing the present invention, which removes the eaves of the photoresist, it is possible to separate elements with a flat surface.
This achieves improved reliability.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the separation between elements, the figure is a plan view, and a3) is an
A cross-sectional view of the X′ gland, and FIGS. 2(4) to (g) are explanations of the conventional process of separating elements, and FIGS. 3(4) to 3(g) are explanations of the steps according to the present invention. It is a diagram. In the figure, 2 is a substrate, 3 and 10 are insulating layers, 4 is an isolation portion, 5 is a photoresist film, 7 is an under-etched portion, 8 is an eaves, and 12 is a groove. Drop ↓-1-1

Claims (1)

[Claims] When a resist film formed on a semiconductor substrate is exposed to ultraviolet rays and developed to open a window for isolation patterns between elements, the resist film is developed for a shorter time than the standard development time to etch the substrate, and then the development process is performed again. Then, remove the resist film on the under-etched area, fill the hole with an insulator using the lift-off method, and form a buried groove! A method for manufacturing a semiconductor device having a j+ characteristic.