JP2013165203A - Semiconductor device manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure continuity of a support film.SOLUTION: A semiconductor device manufacturing method comprises: forming a cylinder interlayer film, a support film and a sacrificial film by stacking; forming a plurality of cylinder holes which pierce the cylinder interlayer film, the support film and the sacrificial film, by arranging the plurality of cylinder holes at regular intervals along first and second directions which are orthogonal to each other; forming a plurality of electrodes each composed of a metal film which covers an internal surface of the cylinder hole; removing the sacrificial film to cause a part of each electrode to project from a top face of the support film; forming a mask film on the support film so as to fill between projections which are adjacent to each other in the first and second directions and to leave a clearance between the projections adjacent to each other in a third direction other than the first and second directions; etching back the mask film to expose a part of the support film; removing the exposed part of the support film to form a first opening; forming a reinforcement film for covering an exposed surface in the first opening so as not to completely fill the first opening; etching back the reinforcement film to form a second opening in the first opening; and removing the cylinder interlayer film through the second opening.

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device including a plurality of electrodes having a high aspect ratio arranged in an array.

  In a DRAM (Dynamic Random Memory) which is one of semiconductor devices, a cylinder type capacitor is used as a cell capacitor in order to secure the capacitance of the cell capacitor against a decrease in occupied area accompanying miniaturization.

  Since the lower electrode of the cylinder type capacitor has a high aspect ratio, it may collapse during manufacture. In order to prevent this collapse, the plurality of lower electrodes are connected to each other using a support film.

  A related semiconductor device manufacturing method is disclosed in Patent Document 1, for example.

  In the manufacturing method of Patent Document 1, a support film and an oxide film are sequentially formed on a cylinder interlayer film for forming a lower electrode. A cylinder hole for forming a lower electrode is formed so as to penetrate the oxide film, the support film, and the cylinder interlayer film, and a lower electrode is formed therein. The oxide film is removed and a part of the lower electrode is protruded. A mask film is formed on the support film so as to cover the protruding lower electrode. The mask film is etched back to expose a part of the support film. At this time, the mask film remains around the protruding portion of the lower electrode. The exposed support film is removed by etching using the remaining mask film as a mask to form an opening in the support film. The cylinder interlayer film under the support film is removed through the opening formed in the support film. Even if the cylinder interlayer film is removed, since the plurality of lower electrodes are interconnected by the support film, their collapse is prevented.

JP 2005-229097 A

  In the manufacturing method described in Patent Document 1, the mask film is left around the protruding portion of the lower electrode. If the mask films left around the adjacent lower electrodes are continuous with each other, even if an opening is formed in the support film using the mask films, the support films connect the adjacent lower electrodes to each other. This prevents the lower electrode from collapsing and prevents the occurrence of a short circuit due to the collapse.

  However, this method is based on the premise that the plurality of lower electrodes are all formed identically. That is, no consideration is given to variations in the size of the plurality of lower electrodes caused by manufacturing variations.

  More specifically, the range covered by the mask film remaining around the lower electrode depends on the film thickness. If the distance between adjacent lower electrodes is constant, the mask film remaining around the adjacent lower electrode can be made continuous by increasing the film thickness of the mask film larger than the distance. However, when a lower electrode having a small diameter is formed in a part of the plurality of lower electrodes due to manufacturing variations, the mask film remaining around the lower electrode is separated from the mask film remaining around the adjacent lower electrode. Become. When an opening is formed in the support film using such a mask film, the support film around the lower electrode having a small diameter is separated from the support films around the other lower electrodes. If the mask film is too thick, an opening cannot be formed in the support film.

  The diameter of the lower electrode depends on the diameter of the cylinder hole. With the progress of miniaturization, it has become difficult to form a large number of cylinder holes with uniform diameters, and the above problem is getting larger.

  A method of manufacturing a semiconductor device according to an embodiment of the present invention includes a cylinder interlayer film, a support film, and a sacrificial film stacked in this order, and a plurality of cylinder holes penetrating the sacrificial film, the support film, and the cylinder interlayer film. Are arranged at equal intervals along the first and second directions orthogonal to each other, a plurality of electrodes made of metal films respectively covering the inner wall surfaces of the plurality of cylinder holes are formed, and the sacrificial film is removed. A part of the plurality of electrodes projecting from the upper surface of the support film to form a plurality of projecting parts, filling between the projecting parts adjacent in the first and second directions, and the first and A mask film covering the plurality of protrusions is formed on the support film so as to leave a gap between the protrusions adjacent in the third direction other than the second direction, and the mask film is etched back to form the mask film. Support membrane Exposing the portion of the support film to form a first opening in the support film and exposing the first opening so as not to completely fill the first opening. Forming a reinforcing film covering the surface; etching back the reinforcing film to form a second opening in the first opening to expose a part of the upper surface of the cylinder interlayer film; and The cylinder interlayer film is removed through.

  According to the present invention, since the reinforcing film is formed, the isolated support film part is separated from the support film even if the isolated support film part exists when the first opening is formed in the support film. It can be connected to the part. Thereby, the lower electrode can be prevented from collapsing and the yield can be improved.

It is a figure for demonstrating the manufacturing method of the semiconductor device which concerns on the 1st Embodiment of this invention, Comprising: (a) Top view and (b) which show the state after forming the mask pattern for cylinder hole formation It is a BB sectional view. FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along the line BB for explaining the process following FIG. 1. FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along the line BB for explaining a process following FIG. 2. FIG. 4A is a plan view and FIG. 4B is a cross-sectional view taken along the line BB for explaining a process following FIG. 3. FIG. 5A is a plan view and FIG. 5B is a cross-sectional view taken along line BB for explaining the process following FIG. 4. 6A is a plan view and FIG. 6B is a cross-sectional view taken along the line BB for explaining the process following FIG. 5. FIG. 7A is a plan view and FIG. 7B is a cross-sectional view taken along line BB for explaining the process following FIG. 6. FIG. 8A is a plan view and FIG. 8B is a cross-sectional view taken along the line BB for explaining the process following FIG. 7. FIG. 9A is a plan view and FIG. 9B is a cross-sectional view taken along line BB for explaining the process following FIG. 8. FIG. 10A is a plan view and FIG. 10B is a cross-sectional view taken along the line BB for explaining the process following FIG. 9. FIG. 11A is a plan view and FIG. 11B is a cross-sectional view taken along the line BB for explaining the process following FIG. 10.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, a DRAM employing a cylinder type cell capacitor is illustrated as a semiconductor device, but the present invention is not limited to this and can be applied to various semiconductor devices.

  1 to 11 are views for explaining a method of manufacturing a semiconductor device according to the first embodiment of the present invention. Each drawing (a) is a plan view showing a part of a semiconductor device being manufactured in each step, and each drawing (b) is a sectional view taken along the line BB.

  A method for manufacturing a semiconductor device according to the first embodiment of the present invention will be described below.

  First, the state shown in FIGS. 1A and 1B is obtained using a known method.

  That is, a plurality of elements (not shown) are formed on a semiconductor substrate 11 such as a Si substrate. The plurality of elements include a plurality of cell transistors. The plurality of cell transistors are arranged along two directions intersecting each other.

  Next, a first interlayer insulating film (oxide film) 12 covering the element is formed on the semiconductor substrate 11. Then, a plurality of capacitive contacts 13 reaching the semiconductor substrate 11 through the first interlayer insulating film 12 are formed. The capacitor contact 13 electrically connects one of the source / drain regions of the cell transistor and a lower electrode described later. Capacitance contacts 13 are arranged along two directions intersecting each other according to the arrangement of the cell transistors. Here, it is assumed that they are arranged along first and second directions (vertical direction and horizontal direction in FIG. 1A) orthogonal to each other.

  A peripheral wiring 14 is formed on the first interlayer film 12.

  Next, a stopper nitride film 15 that covers the upper surface of the capacitor contact 13 and the peripheral wiring 14 is formed on the first interlayer film 12. Subsequently, on the stopper nitride film 15, a cylinder interlayer film (oxide film) 16, a support nitride film (support film) 17, an oxide film (sacrificial film) 18, an amorphous carbon film 19, an antireflection film 20, and Photoresist 21 is formed in this order. The stopper nitride film 15 functions as a stopper when the cylinder interlayer film is etched away later. The support nitride film 17 has an etching selectivity with respect to the cylinder interlayer film 16 and the oxide film 18.

  Next, a plurality of cylinder openings 22 are arranged in the photoresist 21. The arrangement of the plurality of cylinder openings 22 is matched with the arrangement of the capacitive contacts 13.

  In FIGS. 1A and 1B, a memory cell region 23 is a region where a plurality of cylinder openings 22 are arranged. Around the memory cell region 23, there is provided a peripheral circuit region 24 in which peripheral circuits for driving the memory cells are arranged.

  Here, the plurality of cylinder openings 22 are all designed to have the same diameter. However, in practice, not all cylinder openings 22 have the same diameter due to manufacturing variations. 1A and 1B, the cylinder opening 22 having a diameter within the proper range is indicated by a relatively large circle, and the cylinder opening 22 having a diameter outside the proper range is indicated by a relatively small circle. Note that the diameter variation of the cylinder opening 22 tends to be large in the peripheral portion of the memory cell region 23 where the continuity of the cylinder opening pattern is interrupted.

  Next, using the photoresist 21 as an initial mask, the antireflection film 20, the amorphous carbon film 19, the oxide film 18, the support nitride film 17, the cylinder interlayer film 16, and the stopper nitride film 15 are sequentially dry-etched, and FIG. As shown in (a) and (b), cylinder holes 25-1, 25-2 are formed. At this time, the cylinder hole 25-1 corresponding to the cylinder opening 22 having a large diameter reaches the capacity contact 13. On the other hand, the cylinder hole 25-2 corresponding to the cylinder opening 22 having a small diameter may not reach the capacity contact 13.

  During the formation of the cylinder hole 25, the photoresist mask 21 and the antireflection film 20 disappear. Thereafter, the amorphous carbon film 19 is removed, and the upper surface of the oxide film 18 is exposed.

  Next, as shown in FIGS. 3A and 3B, a metal film 31 to be a lower electrode is formed on the entire exposed surface. A CVD (Chemical Vapor Deposition) method or an ALD (Atomic Layer Deposition) method can be used so that a metal film is also formed on the inner wall surfaces of the cylinder holes 25-1 and 25-2. As the metal film 31, a titanium nitride (TiN) film can be used.

  Next, the entire metal film 31 is etched back by dry etching. As a result, as shown in FIGS. 4A and 4B, the metal film 31 is separated into portions corresponding to the cylinder holes 25-1 and 25-2, that is, the lower electrode 41. Hereinafter, the lower electrode 41 formed in the cylinder hole 25-1 may be referred to as a normal lower electrode, and the lower electrode formed in the cylinder hole 25-2 may be referred to as a defective lower electrode.

  Next, as shown in FIGS. 5A and 5B, the oxide film 18 is removed to expose the upper surface of the support nitride film 17, and a part of the lower electrode 41 protrudes from the upper surface of the support nitride film 17. Let For the removal of the oxide film 18, wet etching using hydrofluoric acid (HF) as an etchant can be used.

  The reason why the oxide film 18 is formed on the support nitride film 17 is to project a part of the lower electrode 41 on the support nitride film as described above. By projecting a part of the lower electrode 41, the support nitride film 17 can be self-aligned as described below.

  Next, as shown in FIGS. 6A and 6B, a mask oxide film 61 is formed. The formation of the mask oxide film 61 uses an ALD method having excellent embedding properties. The mask oxide film 61 covers the periphery of the protruding lower electrode 41 to form a cylindrical portion. As the thickness of the mask oxide film 61 increases, the columnar portions of the mask oxide film 61 covering the adjacent lower electrodes 41 are connected to each other. The columnar portions of the mask oxide film 61 covering the normal lower electrodes adjacent in the left and right direction (first direction) and the up and down direction (second direction) in FIG. The thickness of the mask oxide film 61 is set so that a gap 62 remains between the cylindrical portions adjacent to each other in the direction 3). As a result, a space 63 remains between the columnar portion of the mask oxide film 61 around the defective lower electrode 41 and the columnar portion of the mask oxide film 61 around the adjacent lower electrode 41.

  Next, the mask oxide film 61 is etched back to expose the upper surface of the support nitride film 17. Even by this etch back, the cylindrical portion of the mask oxide film 61 around the lower electrode 41 remains. That is, the support nitride film 17 is still covered with the mask oxide film 61 around the lower electrode 41. At this time, the columnar portion of the mask oxide film 61 around the defective lower electrode 41 is separated from the columnar portion of the surrounding mask oxide film 61 and is isolated.

  Next, using the mask oxide film 61 as a mask, the support nitride film 17 is etched to form an opening (first opening) in the support nitride film, and as shown in FIGS. The upper surface of the cylinder interlayer film 16 is exposed inside. At this time, the cylinder interlayer film 16 is also exposed in a region 72 (gap 62) surrounded on four sides by the columnar portion of the mask oxide film 61. Further, the support nitride film 17 around the columnar portion of the isolated mask oxide film 61 is also removed, and the portion of the support nitride film 17 covered with the columnar portion is isolated from the periphery. If the cylinder interlayer film 16 is removed in this state, there is no member that supports the defective lower electrode, and the defective lower electrode collapses.

  In order to prevent the collapse of the defective lower electrode, in this embodiment, a reinforced nitride film (reinforcing film) is formed prior to the removal of the cylinder interlayer film 16 as shown in FIGS. To do. The reinforcing nitride film 81 has the same composition as the support nitride film 17 and is formed on the entire exposed surface by using the ALD method. As a result, the reinforcing nitride film 81 is integrated with the support nitride film 17 and connects the support nitride film 17 around the defective defective lower electrode to the surrounding support nitride film 17.

  The film thickness of the reinforcing nitride film 81 is set in consideration of the amount that is reduced by wet etching when the cylinder interlayer film 16 is removed. The thickness of the mask oxide film 61 is a thickness that does not embed the region 72 surrounded by the four sides in other words, that is, a thickness that does not completely embed the first opening.

  The reinforcing nitride film 81 is etched back, and an opening (second opening) is formed in the reinforcing nitride film 81. As a result, the upper surface of the cylinder interlayer film 16 is exposed again in the second opening. At this time, the cylinder interlayer film 16 is also exposed in a region surrounded on all sides by the columnar portion of the mask oxide film 61.

  Next, the exposed cylinder interlayer film 16 is removed. As shown in FIGS. 9A and 9B, the cylinder interlayer film 16 located immediately below the support nitride film 17 is also completely removed by wet etching using hydrofluoric acid (HF) as an etchant.

  Since all the lower electrodes 41 including the defective lower electrode are connected to each other by the support nitride film 17 (including a part of the reinforcing nitride film 81), the collapse is prevented. Here, as understood from the comparison between FIG. 9A and FIG. 7A, the width of the connecting portion of the support nitride film 17 is expanded by the reinforcing nitride film 81. Thereby, the connection strength by the support nitride film 17 is improved, and the collapse of the lower electrode 41 is prevented with a higher probability.

  Next, as shown in FIGS. 10A and 10B, a capacitor insulating film 101 is formed on the entire exposed surface. Subsequently, a TiN film 101 and a B-SiGe layer serving as an upper electrode are formed on the capacitor insulating film 101. In this way, a cylindrical capacitor with an array formed is completed.

  Thereafter, as shown in FIGS. 11A and 11B, a tungsten film 111, interlayer insulating films 112 and 113, plugs 114 and 115, wirings 116 and 117, and the like are formed to complete the semiconductor device.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit of the present invention. The composition and formation method of each film are not particularly limited, and various known compositions and formation methods can be employed depending on the purpose.

DESCRIPTION OF SYMBOLS 11 Semiconductor substrate 12 1st interlayer insulation film 13 Capacitance contact 14 Peripheral line 15 Stopper nitride film 16 Cylinder interlayer film 17 Support nitride film 18 Oxide film 19 Amorphous carbon film 20 Antireflection film 21 Photo resist 22 Cylinder opening 23 Memory cell Region 24 Peripheral circuit region 25-1, 25-2 Cylinder hole 31 Metal film 41 Lower electrode 61 Oxide film for mask 62 Gap 63 Space 72 Region 81 Reinforced nitride film 101 Capacitive insulating film 102 TiN film 103 B-SiGe layer 111 Tungsten film 112,113 Interlayer insulating film 114,115 Plug 116,117 Wiring

Claims (5)

Cylinder interlayer film, support film and sacrificial film are laminated in this order,
A plurality of cylinder holes penetrating the sacrificial film, the support film, and the cylinder interlayer film are arranged at equal intervals along the first and second directions orthogonal to each other,
Forming a plurality of electrodes made of metal films respectively covering the inner wall surfaces of the plurality of cylinder holes;
Removing the sacrificial film and projecting a part of the plurality of electrodes from the upper surface of the support film to form a plurality of protrusions;
The plurality of the plurality of protrusions are filled between the protrusions adjacent in the first and second directions and leave a gap between the protrusions adjacent in the third direction other than the first and second directions. Forming a mask film covering the protrusion on the support film;
Etch back the mask film to expose a part of the support film,
Removing the exposed portion of the support film to form a first opening in the support film;
Forming a reinforcing film covering an exposed surface exposed in the first opening so as not to completely fill the first opening;
Etching back the reinforcing film to form a second opening in the first opening to expose a part of the upper surface of the cylinder interlayer film,
Removing the cylinder interlayer through the second opening;
A method for manufacturing a semiconductor device.   The method of manufacturing a semiconductor device according to claim 1, wherein the reinforcing film is a film having the same composition as the support film.   3. The method of manufacturing a semiconductor device according to claim 2, wherein a film having an etching selectivity with respect to the cylinder interlayer film and the sacrificial film is used as the support film and the reinforcing film.   4. The method of manufacturing a semiconductor device according to claim 2, wherein the reinforcing support film is formed using an ALD method. Before forming the cylinder interlayer film,
Forming an interlayer insulating film on the semiconductor substrate on which the element is formed;
A plurality of plugs that are connected to the element through the interlayer insulating film are arranged along the first and second directions so as to correspond to the plurality of cylinder holes,
Forming a stopper film on the interlayer insulating film so as to cover the plug;
The cylinder interlayer film is formed on the stopper film,
The cylinder hole is formed so as to penetrate the stopper film,
The method for manufacturing a semiconductor device according to claim 1, wherein:

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