TWI225680B - Method of fabricating a bottle shaped deep trench for trench capacitor dram devices - Google Patents

Abstract

A method for fabricating a bottle-shaped deep trench in a semiconductor substrate is disclosed. A pad stack layer is formed on a main surface of the semiconductor substrate. A deep trench is etched into the substrate through the pad stack layer. The deep trench has a vertical sidewall and a bottom surface. A CVD silicon nitride thin film is deposited on the interior surface of the deep trench. Subsequently, the upper portion of the CVD silicon nitride thin film is bombarded with inert gas ions by tilt-angle ion implantation. The bombarded upper portion of the CVD silicon nitride thin film is then selectively etched away to expose the substrate in the deep trench. The remaining CVD silicon nitride thin film at the lower portion of the deep trench serves as an oxidation mask. A thermal oxidation is carried out to oxidize the exposed substrate to form a silicon oxide layer at the neck of the deep trench. The oxidation mask is then stripped off to expose the lower portion of the deep trench, which is isotropically etched to form a bottle-shaped deep trench.

Description

1225680

FIELD OF THE INVENTION The present invention relates to a semiconductor process, and more particularly to a bottle-shaped trench in a semiconductor substrate. In the prior art, DRAM elements are required along with each meter. Under the trench capacitor space, Electricity (how to increase the capacity of capac charge information must comply with the structure of high parts, which is tied to the semiconductor, so it is possible. However, the area of the capacity i tance) is more difficult to detect and add capacitors. Life force, design of DRAM components

Deep trenches are carved in the bulk substrate of the high-density DRAM architecture widely used in trench capacitors and f-fields, and trenches are made in them ": the size of small memory cells, and the best use of crystal follower process lines The width is reduced to 0. U microns, and even it is reduced accordingly. The electric valley value that directly affects the insufficient capacitance value of the capacitor will cause the measurement stored in the capacitor to cause troubles in terms of interpolation. Therefore, the capacitance value It is a matter of urgency. As those skilled in the art know, one of the most direct and effective ways to increase the capacitance value is to increase the surface area of the capacitor. In the known technology, for example, the International Business Machines Corp. (IBM) company in 2001 U.S. Patent No. 6,448,131, filed on August 14th, entitled "Method for Increasing Trench Capacitance (METHOD FOR INCREASING THE CAPACITANCE OF A TRENCH CAPACITOR)" discloses the use of metal silicide to roughen the trench surface

Page 7 1225680 ____Case No. 92125401_Year Month_Amendment__ 5. Description of the invention (2) and then remove the metal silicide to obtain a larger capacitance area. By controlling the metal density, the thickness of the metal film, the metal phase of the silicide, and the selection of an appropriate metal, the degree of roughening of the trench surface can be determined. The conventional technology is also disclosed in the US patent No. 6555430 filed by IBM on November 18, 2000, entitled "A PROCESS FLOW FOR CAPACITANCE ENHANCEMENT IN A DRAM TRENCH". A discontinuous polycrystalline layer is first formed on the lower surface, and there are many gaps between the discontinuous polycrystalline layer, and then oxidized and etched to form a wavy trench surface, thereby Increase the capacitor area. Another method commonly used to increase the capacitance area is to further etch the lower part of the deep trench into a bottle-shaped. Such conventional technologies, such as Siemens Aktiengesellschaft and IBM Corporation, were shared on June 26, 1998. U.S. Patent No. 60181 74, filed on the same day, entitled "BOTTLE-SHAPED TRENCH CAPACITOR WITH EPI BURIED LAYER" was disclosed in a semiconductor substrate to form a deep trench with a bottle-shaped lower portion. Then, an epitaxial layer is formed on the bottle-shaped lower surface of the deep trench as a capacitor electrode.

For another example, Toshiharu et al. Filed an application on May 28, 1998. The patent right is US Patent No. 6,190,988 held by IBM Corporation, entitled "Controlled Bottle Trench System for DRAM Storage Electrodes (METHOD FOR

Page 8 1225680 _Case No. 92125401__ Year $ Day Amendment_ V. Description of the Invention (3) A CONTROLLED BOTTLE TRENCH FOR A DRAM STORAGE NODE ", discloses a method for forming a bottle-shaped trench in two etching steps. First, trenches of a first depth are etched into the substrate, and then the sidewalls of the trenches are protected by a silicon oxide layer and a silicon nitride layer, and then etching is continued to form deeper trenches. Then implanted doped on the inner wall of the trenches not covered by the protective layer. Then, the sidewalls of the doped doped trenches are etched away to form the lower part of the bottle-shaped trench. Finally, the silicon oxide layer and the silicon nitride layer on the sidewall of the trench neck are removed. For another example, Shiao et al. Filed an application on April 19, 2000. US Patent No. 6 3 6 548 5 held by Promos Tech, Inc. was titled "Forming in a Bottle-shaped Deep Trench." DRAM TECHNOLOGY OF BURIED PLATE FORMATION OF BOTTLE-SHAPED DEEP TRENCH ", reveals a method of bottle-shaped deep trenches, including etching deep trenches in the substrate and filling the dielectrics in the deep trenches. Layer, etch back the dielectric layer to a predetermined depth, and then form a silicon nitride sidewall on the sidewall of the deep trench on the dielectric layer, and then remove the dielectric layer to expose the silicon nitride sidewall below the silicon nitride sidewall. The side wall of the deep trench can then oxidize the substrate exposed at the lower part of the deep trench to form a silicon oxide layer. Finally, the stone layer can be etched away to obtain a bottle-shaped deep trench structure. However, the bottle-shaped trench method taught by the above-mentioned conventional techniques is still too complicated and complicated. The steps are too many and lengthy, which makes the cost higher, the efficiency is lower, and the productivity is reduced. From this, we can see that there is still room and necessity for further improvement of these techniques for bottle-shaped deep trench capacitors.

1225680 _ Case No. 92125401 V. Description of the Invention (4) Name Amendment Summary of the Invention According to this, the main object of the present invention is to provide an improved method for manufacturing a deep trench in a bottle shape, which can be applied to the manufacturing process of a trench capacitor DRAM integrated circuit. A preferred embodiment of the present invention discloses a method for manufacturing a bottle-shaped deep trench, which includes providing a substrate having a cushion layer thereon; etching the cushion layer and the substrate to form a deep trench having a vertical sidewall And a bottom surface; a silicon nitride protective layer is deposited on the vertical sidewalls and the bottom surface of the deep trench; the silicon nitride protective layer located on the upper part of the deep trench is bombarded with ions; and the silicon nitride is selectively etched away by the ion bombardment A protective layer exposes the substrate above the deep trench, and the silicon nitride protection layer located below the deep trench forms a silicon nitride mask; the exposed substrate above the deep trench is oxidized to form a neck A silicon oxide layer; selectively removing the silicon nitride mask; and using the neck silicon oxide layer as an etching mask to isotropically etch the vertical sidewalls and bottom surfaces of the deep trench not covered by the neck silicon oxide layer, This forms a bottle-shaped deep trench. This ion is made of an inert gas including argon and nitrogen. To 7. Left and right oblique angle method, the ion bombardment energy is about 20KeV, and the ion bombardment dose is about 1E15 to 1E16 atoms / cm2. In order to make your reviewers understand the features and technical contents of the present invention more closely, please refer to the following detailed description and drawings of the present invention. However, the drawings are only for reference and auxiliary explanation, and are not intended to be used for the present invention.

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Limiters. Embodiment 2 Refer to FIGS. 1 to 9, which are schematic cross-sectional views of bottle-shaped trenches made according to a preferred embodiment of the present invention. As shown in FIG. 1, a semi-conductive substrate is first provided, such as a silicon substrate, which has a main surface (main, surface) 11 and various semiconductor elements will be formed on the main surface n. Next, a silicon oxide-lined layer 12 and a silicon nitride-lined layer 4 are formed on the main surface of the semiconductor substrate 10 in sequence. The silicon-oxide-lined layer 2 can be grown to 50 angstroms or less by thermal oxidation. The thickness of the silicon nitride-lined layer 14 can be formed by a chemical vapor deposition (CVD) method. As shown in FIG. 2, a yellow light process is next performed to form a photoresist layer 15 ′ on the silicon nitride-lined layer 14. The photoresist layer 15 has openings 17 and defines the position and shape of a deep trench to be formed. As shown in FIG. 3, a deep trench dry etching process is then performed, and the silicon nitride liner layer 4, the silicon oxide liner layer 12, and the semiconductor substrate 10 are etched through the opening 17 of the photoresist layer 15 to form a deep trench 20. Its depth is about 7 microns or more below the surface of the substrate. The deep trench 20 has a vertical side wall 21 and a bottom surface 22. It should be noted that, during the deep trench dry etching process, the silicon oxide lining layer 12 near the mouth of the deep trench is engraved in the lateral direction, so that the silicon oxide lining layer 12 is pulled back slightly (puU back) and formed in the deep Annular notches near the ditch opening 2 5.

Page 11 1225680 ___ Case No. Amendment _V. Description of the Invention (6) As shown in Figure 4 ', perform a chemical vapor deposition process on the silicon nitride layer 14 and the vertical sidewall 21 of the deep trench 20. A silicon nitride protective layer 32 is deposited on the bottom surface 22 to a thickness of about 200 to 350 angstroms. The silicon nitride layer 32 simultaneously fills the annular gap 2 5 formed near the mouth of the bead trench. As shown in FIG. 5 ', an oblique angle ion bombardment process is then performed, using an inert gas ion, such as argon or nitrogen plasma, to incline 3 with the vertical axis of the main surface 11 of the semiconductor substrate 10. To 7. The left and right angles bombarded the silicon nitride protective layer 32 on the upper part of the deep trench. Taking nitrogen ion bombardment as an example, the dose is about 1E15 to 1E16 atoms / cm2, and the energy of the bombardment is about ^ 2 KeV. During the oblique angle ion bombardment (bombardment), the structure of the nitrided stone protective layer 3 2 in the upper part of the deep trench is loosened, and the etching rate difference with the unprotected layer 32 located in the lower part of the deep trench is loose. Yu. Fossil Yubao, the turmoil of Yiqing, shows the selectivity shown in Fig. 6. Layer 32, passes through the lower layer of the original protective layer 32 ~ 6: 1 (Nitride to protect the silicon), and exposes the ion bombardment, which is formed by the protection of ions with silicon phosphate. After layer 32 is formed, the solution subjected to deep trench semiconductor strike treatment is bombarded into layer 32. The structure is carved in deep trench wet M to form a ring-shaped silicon nitride substrate 10 which has been ion bombarded in the upper part. The preferred nitrogen according to the present invention The etching ratio of the silicon protective layer 32 and the deep-fossil protective layer 32 is about the same as that of wet etching). A silicon nitride mask 33 is formed below the deep trench. It should be noted that after the nitridation of the annular notch 25 near the mouth of the trench, the silicon nitride layer 3 4 remaining in the annular notch 2 5 remains. ^ 25680

As shown in Figure 7, the depth 4 of the cover, as in the case of the cover 33, the heat is as shown in the nitride method, using the hydrofluoric acid under the trench 42 of the hot silicon layer to perform an oxidation process, without the silicon nitride mask 3 A thermal oxide layer is formed on the surface of the cover / ditch 20, and the position of the thermal oxide layer between the ring-shaped silicon nitride layer 34 and the nitride trench 2 is at the upper part. According to a preferred implementation of the present invention, the thickness of the fossil evening layer 42 is between about 00 and about 350 angstroms. Shield $ and then 'selectively engraved $ = 33 located in the lower part of the deep trench, for example, using a known wet etch such as hot phosphoric acid solution: a part of the surface of the deep trench 20 is formed. As shown in Fig. 9 *, the silicon layer 42 is an etching mask, and the non-thermally oxidized portion δ) is etched with ammonia water. The side wall 21 and the bottom surface 22 of the channel 20 form a bottle-shaped deep liquid. . Afterwards, 'remove the thermal silicon oxide layer 42, for example, using the preferred embodiment of the interpretation, any application for specialization and modification according to the present invention' shall fall within the scope of the patent of the present invention. The range of equal change covers.

1225680 _ Case No. 92125401_ Year Month Amendment _ Brief Description of Drawings Brief Description of Drawings Figures 1 to 9 are schematic cross-sectional views of a bottle-shaped trench made in a preferred embodiment of the present invention.

Explanation of the symbols of the drawings 10 Semiconductor substrate 11 Main surface 12 Lined with silicon oxide layer 14 Lined with silicon nitride layer 15 Photoresist layer 17 Open V 20 Deep trench 21 Side wall 22 Bottom surface 25 Ring-shaped α 32 Silicon nitride protective layer 33 Silicon nitride Mask 34 Ring silicon nitride layer 42 Thermal silicon oxide layer 50 Lower part of deep trench

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Claims (1)

1225680 _Case No. 92125401_ Years and months of amendment_ VI. Application for patent scope 1. A method for making a bottle-shaped deep trench, comprising: providing a substrate with a cushion layer disposed thereon; etching the cushion layer and the substrate Forming a deep trench having vertical sidewalls and a bottom surface; depositing a silicon nitride protective layer on the vertical sidewalls and the bottom surface of the deep trench; bombarding the silicon nitride protective layer partially above the deep trench with ions; selectively Etching away the silicon nitride protective layer bombarded by ions, exposing the substrate above the deep trench, and leaving the silicon nitride protective layer below the deep trench to form a silicon nitride mask; oxidizing the deep The exposed substrate on the upper part of the trench forms a neck silicon oxide layer; selectively removing the nitride nitride mask; and using the neck silicon oxide layer as an etching mask, isotropic etching is not performed on the neck silicon oxide layer. The vertical sidewall and bottom surface of the deep trench are covered to form a bottle-shaped deep trench. 2. The method for making a bottle-shaped deep trench as described in item 1 of the scope of patent application, wherein the ion bombardment uses an inert gas. 3. The method for making a bottle-shaped deep trench as described in item 2 of the scope of patent application, wherein the inert gas includes argon and nitrogen. 4. The method of making a bottle-shaped deep trench as described in item 1 of the scope of the patent application, wherein the ion bombardment is performed at an oblique angle. Page 15 1225680 _ Case No. 92125401_ Year Month Date _f ^ L · _ VI. Patent Application Range 5. The method for making a bottle-shaped deep trench as described in item 1 of the patent application range, wherein the ion bombardment system uses 3 . To 7. Left and right oblique angle mode. 6. The method for making a bottle-shaped deep trench as described in item 1 of the scope of patent application, wherein the energy of the ion bombardment is about 20 KeV. 7. The method for making a bottle-shaped deep trench as described in item 1 of the scope of patent application, wherein the dose of the ion bombardment is about 1E15 to 1E16 atoms / cm2. 8. The method for making a bottle-shaped deep trench as described in item 1 of the scope of the patent application, wherein the liner layer is simultaneously etched to form a ring-shaped notch when the deep trench is etched, and the silicon nitride protective layer fills the ring-shaped notch. in.