JPS62232141A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To decrease birds' beaks, improving electric characteristics and to obtain a minute semiconductor device in simple processes, by using a silicon nitride film, which is etched with mixed gas of SF6 and He, performing selective oxidation, and performing oxidation and etching of the silicon surface before forming a gate oxide film. CONSTITUTION:A silicon substrate 11 undergoes thermal oxidation, and a first silicon oxide film 12 is formed. A silicon nitride film 13 is deposited thereon. Then, with photoresist 14 as a mask, the silicon nitride film 13 undergoes dry etching by using mixed gas of SF6 and He. Then, with the silicon nitride film 13 as a mask, a field oxide film 16 is grown. Thereafter, the silicon nitride film 13 and the first silicon oxide film 12 are removed, and the silicon surface in an active region is exposed. Then, thermal oxidation is performed and second silicon oxide film 10 is formed. The silicon oxide film 10 is removed with aqueous solution of fluoric acid again. Then a gate oxide film 17 is grown. After a gate electrode 18 comprising polycrystalline silicon is patterned, a source and a drain 19 are formed, Thus an MOS transistor is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and in particular to an element isolation technique for insulating each element on a semiconductor substrate from each other using a field oxide film using 8-selective oxidation. It is.

[Summary of the invention]

The present invention makes it possible to thin the base oxide film and thicken the silicon nitride film for the oxidation mask when selectively oxidizing the entire field oxide film for element isolation in the manufacture of semiconductor devices, thereby making it possible to make a bird's beak? At the same time, the one-temperature characteristics of the device are completely improved.

[Conventional technology]

Conventionally, for element isolation in the manufacture of MO8 semiconductor devices, for example, a selective oxidation technique called the Locos method using a silicon window film as an oxidation mask has often been used, as described in Japanese Patent Laid-Open No. 47-2517. .

For example, as shown in FIG.
First silicon oxide film 2 serving as a base of 00 to 1000A
After forming 2, a silicon nitride film 23 of 1400 to 160 QA is deposited depending on the vapor phase bottom length, a patterned photoresist 24t-mask is used, and dry etching is performed using a mixed gas plasma of OF and OL. Boron-gold ions are implanted (Figure 2-
a).

Next, the silicon nitride film 25' described above is formed by water vapor oxidation (selectively oxidized using a mask to form a field oxide film 26' of about 6000 to 800 OA (FIG. 2-b)), and then the silicon nitride film 23 is heated using hot phosphoric acid. Then, the first silicon oxide film 22 is etched by etching (step 217-c). Subsequently, a gate oxide film 27 is formed, and a gate electrode 28 made of multilayer silicon or the like is patterned on top of the gate oxide film 27, and all phosphorous ions are implanted to form a self-aligned gate electrode. drain region 29
-z formation and N-channel λ4013) run sister is formed (Fig. 2-d).

[Problem that the invention seeks to solve]

However, the conventional method has the following problems. First of all, silicon M film 25? ! - In the case of etching with a mixed gas plasma of CF4 and Ot, the selectivity to the silicon oxide film is about 12.0, so the thickness of the silicon oxide film 22 of process 1, which is the base layer, is equal to that of the silicon nitride film 25. The etching speed of the silicon nitride film is 900A.
/ minute; 1 degree, which causes problems with the throughput of the equipment, and if the etching time exceeds 2 minutes, the resist will be damaged and general sulfuric acid peeling etc. will not be possible, so the thickness [1400
It is regulated to about ~1600A. However, if all selective oxidation is performed with this forgery, the bird's beak in which the field oxide film sinks under the silicon nitride film reaches 1.2 to 1.5 μm VC-, making it difficult to miniaturize LSI.

Furthermore, although the length of the bird's beak itself can be reduced by thinning the first silicon oxide film serving as the base and by making the silicon nitride film 'a-J' thinner, the silicon substrate is exposed directly to the plasma during etching of the silicon nitride film. This leads to various problems such as etch bits and crystal defects, stress on the silicon nitride film itself, white ribbon, etc., deterioration of transistor gate breakdown voltage, and increase in junction leakage.

The present invention eliminates the above-mentioned drawbacks, makes it possible to create a structure in which the underlying silicon oxide film is made thinner and the silicon nitride film is made thicker, thereby improving the device characteristics and reducing the need for bird's beak. , LSI with minute rules? It is a stable supply.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes at least 600A
A step of forming a silicon nitride film with a thickness of 1800 Å or more with the following first silicon oxidation process, a step of selectively oxidizing the silicon nitride film t mask by dry etching it into a desired pattern using a mixed gas of 8Fa and He, and a step of selectively oxidizing the silicon nitride film t mask. a step of completely removing the silicon nitride film and the first silicon oxide film;
The method is characterized by a step of completely forming a second silicon oxide film on the silicon surface of the active region, and after removing the entire surface of the second silicon oxide film u1, a step EV is performed to form the entire gate oxide film.

[Middle example]

Hereinafter, the present invention will be explained in detail based on a central example.

FIG. 1 shows a method of manufacturing an MO8 type semiconductor device according to the present invention. For example, a P-well is formed and a first silicon oxide film 12 of about 60 OA is thermally oxidized on a fLt silicon substrate 11.
A silicon nitride film 13' having a length of 1800 Å (photoresist which was deposited and buttered after being deposited) is dry etched on the silicon nitride film 13' in a reduced pressure vapor phase (Fig. 1-a). ). At this time, the φ condition of dry etching is a parallel plate dry etching device, using a mixed gas of SFa and Bθ, a pressure lower than α4tOrr, a mixture ratio of SF6 of 20φ, and an A selection ratio of 5.
-4.01, and the etch rate was also 140OA for 1 minute or more. At this time, unlike conventional methods, no deformation of the resist surface or etch focus on the silicon substrate was observed.

Note that 15 is a channel stopper region into which boron ions are implanted. Next, using a silicon nitride film 137 mask, a field oxide film 16 of 800 OA was formed in a high-pressure steam oxidation furnace.
After growing the silicon nitride film 15 using hot phosphoric acid (FIG. 1-b), the first silicon oxide film 12 is grown using a hydrofluoric acid aqueous solution. Remove active area silicon surface? After exposing, 1000
A second silicon oxide film 10i of 400 to 600 A is formed by thermal oxidation in an oxygen atmosphere (Fig. 1-c), and the second silicon oxide film 10 is removed again with a hydrofluoric acid aqueous solution (Fig. 11-d). . It was confirmed that the L9 white ribbon was removed by this oxide etching, and that stacking faults in the active region were reduced if an oxygen atmosphere containing chlorine was used during etching. Next, a gate alpha film 1711 of 40OA is grown, and a multilayer film 1711 is grown.
1m1B gate made of DM silicon? After r patterning, phosphorous ions are implanted to form the source and drain 197 shapes in a self-aligned manner (Fig. The 7CMO8 semiconductor device I was manufactured through the same engineering process as above, and the bird's beak was reduced to about 18 μm, and there were no problems with gate breakdown voltage deterioration or contact leakage. In addition, a silicon nitride film with a thickness of 2000 A and a first silicon oxide film as the base of 1200 to 400 A was also manufactured through the process of the present invention, but the bird's beak was 05 μm and 8 degrees, and there were no problems with the electrical characteristics. Fine MO8) Successful production of Run Sister. In the practical example of the present invention, an N-channel MOS semiconductor device will be explained, and next, a two-way MOS semiconductor device and a C! An MO8 semiconductor device can also be fabricated, and the gate structure can also be applied to silicide or salicide.

〔Effect of the invention〕

The effect of the present invention is that the silicon nitride film is selectively oxidized by etching with SF and nu gases, and the silicon surface is selectively oxidized before forming the gate oxide film. Through oxidation and etching, the bird's beak tα can be reduced to 5 μm or less, the electrical characteristics can be improved, and fine semiconductor devices can be supplied with a simple process.

[Brief explanation of drawings]

1A to 1E are schematic cross-sectional views showing the manufacturing process of the semiconductor device of the present invention. Figures 2a to 2d are schematic cross-sectional views showing the manufacturing process of a conventional semiconductor device. 10... Second silicon oxide film 11.21... Silicon substrate 12.22... First silicon oxide film 15.25... Silicon nitride film 14.24... Photoresist 15.25...・Channel stopper 16, 26・
...Field oxide film 17.27...Gate oxide film 18.28...Gate electrode 19.29...More than source and drain

Claims (1)

[Claims] Step of forming at least a first silicon oxide film with a thickness of 600 Å or less and a silicon nitride film with a thickness of 1800 Å or more on a semiconductor substrate, and select the silicon nitride film dry-etched into a desired pattern with a mixed gas of SF_6 and He as a mask. a step of oxidizing, a step of completely removing the silicon nitride film and the first silicon oxide film, a step of forming a second silicon oxide film on the silicon surface of the active region, and after completely removing the second silicon oxide film, A method for manufacturing a semiconductor device, comprising the step of forming a gate oxide film.