JP2831774B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of forming an alignment mark used for electron beam exposure.

(Prior Art) In recent years, the gate length of a FET structure using GaAs or the like has been reduced to 0.5 μm or less, and a gate is formed by electron beam exposure. At that time, an alignment mark was formed on the substrate and used for alignment for gate formation. For example, JP-A-63-308318 is known.

That is, as shown in FIG.
An underlying oxide film 22 is selectively deposited thereon (FIG. 2 (a)).

Next, a field oxide film 23 is deposited on the underlying oxide film 22 and on the semiconductor substrate 21.

Further, after forming a resist 24 on the field oxide film 23 and patterning the source, drain, and alignment mark forming positions, the field oxide film 23 is removed by etching using wet etching, and the semiconductor at the source and drain forming positions is removed. The surface of the substrate 21 and the underlying oxide film 22 under the alignment forming position are exposed. Next, an ohmic metal 25 is vapor-deposited on the resist 24 using a lift-off method, and an ohmic electrode 25-1 is formed on the exposed surface of the semiconductor substrate 21.
Is simultaneously formed on the exposed surface of the underlying oxide film 22 (FIG. 2 (c)).

Next, after removing the resist 24, heat treatment is performed (second
Figure (d).

Further, a resist 26 is applied by a lift-off method for forming a gate electrode, and the alignment mark 25-2 is scanned and positioned with an electron beam 27, and then exposed and developed to etch the gate pattern 28 (FIG. 2). (E)).

By this method, it was possible to improve the accuracy of gate electrode alignment by electron beam exposure. However, when the field oxide film 23 is wet-etched using the resist 24 as a mask to form an alignment mark, the field oxide film 23 is undercut. Electron beam 27
There is a disadvantage that the scanning accuracy is reduced because the undercut portion is read at the same time when scanning with.

(Problems to be Solved by the Invention) As described above, in the conventional method, when the field oxide film is etched using the wet etching method to form the alignment mark, an undercut occurs, and when the field oxide film is scanned by an electron beam, the undercut occurs. There has been a problem that reading accuracy is reduced due to the occurrence of cuts.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a method of manufacturing a semiconductor device which aims to form an alignment mark with good reading accuracy without undercut.

[Constitution of the Invention] (Means for Solving the Problems) In a method for manufacturing a semiconductor device according to the present invention, a step of forming an insulating film on a semiconductor substrate, a step of forming a resist layer on the insulating film, A step of pattern-exposing the resist layer, a step of baking the resist layer in an amine-based gas atmosphere, a step of selectively exposing an unexposed portion of the pattern-exposed resist layer, and a step of selectively exposing the resist layer and the insulating film. Exposing the semiconductor substrate by etching, exposing the unexposed resist layer and exposing the resist layer to expose the insulating film surface, exposing the insulating film surface, depositing a metal film, and removing the exposed semiconductor by a lift-off method. Simultaneously forming an electrode on the substrate and an alignment mark on the exposed insulating film.

(Operation) In this manufacturing method, when an alignment mark is formed on a semiconductor substrate, its position is determined by a resist, and an alignment mark with good reading accuracy is formed.

(Example) Hereinafter, an example of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view showing a method for manufacturing a semiconductor device according to the present invention in the order of steps.

Silicon oxide film 12 is deposited on semiconductor substrate 11 by CVD
Form about 0 °. On this silicon oxide film 12, a resist layer 13 (novolak-based resist such as NPR-820) which becomes soluble in an alkaline solution when exposed is deposited.

Next, the first exposure is performed by ultraviolet rays 15 using a mask 14 which is an inverted pattern of the originally used pattern to form an exposed portion and an unexposed portion 16. Further, baking is performed in an ammonia atmosphere at 90 to 100 ° C. At this time, the exposed portion of the resist layer 13 undergoes a decarboxylation reaction of the indene carboxylic acid to become alkali-insoluble indene (FIG. 1 (a)).

Next, a second exposure is performed, and only the ohmic electrode region 17 is selectively exposed. Then, an ohmic electrode region 17 that has been exposed for the second time is opened using an alkaline developing solution (FIG. 1B).

Further, the silicon oxide film 12 is removed by etching using the resist pattern 13 as a mask, and the semiconductor substrate 11 is removed.
Expose the surface. Subsequently, the unexposed portion 16 'in the resist pattern is exposed and developed to expose the silicon oxide film 12 (FIG. 1 (c)).

Next, using the resist 13 as a mask, the ohmic metal 18 is used.
Then, an ohmic electrode 18-1 is formed on the exposed surface of the semiconductor substrate 11 and an alignment mark 18-2 is formed on the exposed silicon oxide film 12 at the same time by a lift-off method (FIG. 1 (d)).

Next, the resist 13 is removed and heat treatment is performed. further,
A resist 19 is applied to form a gate electrode, and the alignment mark 18-2 is scanned and aligned with an electron beam 101, and then exposed and developed to form a gate pattern 102 (FIG. 1 (e)).

According to this embodiment, as in the related art, after forming an underlying oxide film on a semiconductor substrate, a field oxide film is formed and then patterned by a resist, and the position is determined by a resist without using a step of wet etching the field oxide film. Since the decision is made, no undercut of the field oxide film occurs. This makes it possible to improve the reading accuracy of the alignment mark when performing alignment by scanning with an electron beam.

[Effects of the Invention] From the above results, according to the manufacturing method of the present invention, it is possible to form an alignment mark with good alignment accuracy on an insulating film on a semiconductor substrate.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps, and FIG. 2 is a sectional view showing a method of manufacturing a semiconductor device according to the prior art in the order of steps. 11,21 ... Semiconductor substrate, 12 ... Silicon oxide film, 13,24 ... Resist layer, 14 ... Mask, 15 ... Ultraviolet, 16 ... Unexposed area, 18-1,25-1 ... Ohm Electrodes, 18-2, 25-2: alignment mark, 22: underlying oxide film, 23: field oxide film.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 21/027 H01L 21/338 H01L 29/812

Claims (1)

(57) [Claims] A step of forming an insulating film on a semiconductor substrate;
Forming a resist layer on the insulating film, pattern-exposing the resist layer, baking the resist layer in an amine-based gas atmosphere, and selecting an unexposed portion of the pattern-exposed resist layer. Step of selectively exposing, removing the selectively exposed resist layer,
Further removing the insulating film by etching to expose the semiconductor substrate, removing the resist layer after exposing the unexposed resist layer, exposing the insulating film surface,
Depositing a metal film and simultaneously forming an electrode on the exposed semiconductor substrate and an alignment mark on the exposed insulating film by a lift-off method.