KR20040008904A - Method for forming storage node in semiconductor device - Google Patents

Abstract

PURPOSE: A method for forming a storage node of a semiconductor device is provided to prevent collapse of the storage node by forming an under-cut portion at lower part of an etch stop nitride layer. CONSTITUTION: An oxide layer(24) and an etch stop nitride layer(28) are sequentially formed on a semiconductor substrate(20) having a conductive layer. The etch stop layer and the oxide layer of a storage node contact region are selectively etched. A capacitor sacrificial oxide layer is formed on the resultant structure. The sacrificial oxide layer is selectively etched. An under-cut portion is formed at the lower part of the etch stop nitride layer(28) by partially wet-etching of the exposed oxide layer(24). Then, a storage node(26) is formed on the resultant structure.

Description

Method for forming a charge storage electrode of a semiconductor device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor manufacturing technology, and more particularly, to a process for forming a heavy charge storage electrode.

As high integration of semiconductor devices proceeds rapidly, design rules are rapidly reduced, and thus the layout area of capacitors is also reduced. Accordingly, the bottom CD (critical dimension) of the charge storage electrode is reduced, and this phenomenon causes various problems.

1A and 1B are process charts for forming an inner capacitor according to the prior art.

The inner capacitor forming process according to the prior art first selects an interlayer insulating film (not shown) covering the entire structure of the substrate on which the bit line 11 is formed on the lower layer 10 which has been subjected to a predetermined process as shown in FIG. 1A. Etching to form a charge storage electrode contact hole, a polysilicon film is deposited, and a CMP process is performed to form a contact plug 17. At this time, since the hard mask nitride film 12 on the bit line 11 is used as the polishing stop film during the CMP process of the polysilicon film, the interlayer insulating film does not remain on the bit line 11. Subsequently, an etch stop nitride film 14 is deposited on the entire structure, an etch stop nitride film 14 of the charge storage electrode contact region is etched, and then a charge storage electrode oxide film (sacrifice film) 15 is deposited on the entire structure. In addition, the charge storage electrode oxide layer 15 is etched through the photolithography and etching process using the charge storage electrode mask to open the contact, the polysilicon layer is deposited along the entire structure surface, and then the CMP process is performed to perform the unit charge storage electrode. Define (16). Reference numeral '13' represents the bit line sidewall spacer insulating layer.

Next, as shown in FIG. 1B, the charge storage electrode oxide layer 15 is wet-removed.

When the charge storage electrode is formed through the related art as described above, only a part of the charge storage electrode 16 is in contact with the lower contact plug (polysilicon) 17 in the bottom portion of the charge storage electrode 16. As a result, the adhesion is not strong. In this state, if the charge storage electrode oxide layer 15 is removed (it may not be removed, but should be removed to secure the capacitance), the charge storage electrode 16 is dependent only on the adhesive force with the lower contact plug 17. There is a problem of easily leaving by the impact.

In order to solve this problem, the charge storage electrode oxide layer 15 is deposited in two steps, but a method of disposing an oxide layer having a high etching rate with respect to the cleaning liquid on the lower side has been proposed. In this case, when the contact cleaning process is performed immediately after the process of etching the charge storage electrode oxide film 15 for opening the charge storage electrode contact, the area of the lower portion of the charge storage electrode 16 may be increased. Since only the contact area with) increases, there is a limit that does not significantly reinforce the adhesive force.

The present invention has been proposed to solve the above problems of the prior art, and an object of the present invention is to provide a method for forming a charge storage electrode of a semiconductor device capable of preventing the separation due to the lowering of the adhesion force of the charge storage electrode.

1A and 1B illustrate an inner capacitor forming process according to the prior art.

2A and 2B illustrate an inner capacitor forming process according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

24: oxide film

25: charge storage electrode oxide film

26: charge storage electrode

27: contact plug

28: etch stop nitride film

According to an aspect of the present invention for achieving the above technical problem, forming an oxide film and an etch stop nitride film on a substrate on which a lower layer including a predetermined conductive structure is formed; Etching the etch stop nitride layer and the oxide layer in the charge storage electrode contact region; Forming a sacrificial oxide film on the entire structure of the etch stop nitride film and the oxide film; Etching the sacrificial oxide layer in the charge storage electrode formation region; Partially etching the exposed oxide layer after the sacrificial layer is etched to cause an undercut under the etch stop nitride layer; And forming a conductive film for a charge storage electrode along the entire surface of the undercut induced structure.

In the present invention, it is noted that the line width of the etch stop nitride film does not change during the post-cleaning process of the etching process for opening the charge storage electrode contact. Form the jaw by forming a. Thereafter, the conductive film for the charge storage electrode fills the undercut region, and thus the charge storage electrode structure is supported by the jaw, thereby preventing separation. On the other hand, the present invention can also obtain the effect of securing the contact area as much as the undercut area.

Hereinafter, preferred embodiments of the present invention will be introduced in order to enable those skilled in the art to more easily carry out the present invention.

2A and 2B are flowcharts of forming an inner capacitor according to an embodiment of the present invention.

In the process of forming the inner capacitor according to the present embodiment, first, as shown in FIG. 2A, an interlayer insulating film (not shown) covering the entire structure of the substrate on which the bit line 21 is formed is formed on the lower layer 20 that has completed the predetermined process. Selectively etching to form a charge storage electrode contact hole, depositing a polysilicon film and then performing a CMP process to form a contact plug (27). At this time, since the hard mask nitride film 22 on the bit line 21 is used as the polishing stop film during the CMP process of the polysilicon film, the interlayer insulating film does not remain on the bit line 21, and The self-aligned contact may be formed by the bit line sidewall spacer insulating layer 23 formed on the sidewalls.

Subsequently, an oxide film 24 and an etch stop nitride film 28 are deposited on the entire structure, the etch stop nitride film 28 and the oxide film 24 in the charge storage electrode contact region are removed, and then the charge storage electrode oxide film is formed on the entire structure. The sacrificial film 25 is deposited, the charge storage electrode oxide film 25 is etched through the photolithography and etching process using the charge storage electrode mask to open the contact, and the cleaning process is performed. At this time, a portion of the oxide film 24 is isotropically etched by the cleaning solution (eg, hydrofluoric acid solution) so that the undercut is generated under the etch stop nitride film 28. On the other hand, CVD oxide films such as PSG, BPSG, PE-USG, PE-TEOS, etc. can be deposited to 200-3000 mm thick with the oxide film 24. For PSG, P concentrations of 2-15 wt% and P and B It is preferable to set the concentration to 2 to 15 wt%, respectively. In addition, it is preferable to deposit the charge storage electrode oxide film 25 with an oxide film of the same series as the oxide film 24.

Next, after the polysilicon film is deposited along the entire structure surface, the CMP process is performed to define the unit charge storage electrode 26. At this time, the polysilicon film fills the undercut region.

Subsequently, as shown in FIG. 2B, the charge storage electrode oxide layer 25 is wet-removed.

As described above, in the present invention, an oxide film 24 is further inserted below the etch stop nitride film 28, and the etching stop nitride film 28 is disposed below the etching stop nitride film 28 during the cleaning process performed after etching the charge storage electrode oxide film 25 for contact opening. An undercut was triggered to form the jaw. Subsequently, when the conductive film for the charge storage electrode is buried in the jaw, the charge storage electrode 26 is caught by the jaw, thereby preventing the charge storage electrode 26 from being separated by an external impact.

On the other hand, the contact area as much as the undercut area ('B' in Fig. 2b) is secured to obtain a side effect of improving the contact resistance. Compared to the contact width (X) according to the prior art shown in Figure 1b it can be easily confirmed by comparing the contact width (W) according to the present invention shown in Figure 2b.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

For example, in the above-described embodiment, the case where a polysilicon film is used as the conductive film for the charge storage electrode has been described as an example. However, the present invention is also applied to the case of using another conductive film instead of the polysilicon film.

The present invention described above has the effect of preventing the separation of the charge storage electrode pattern to improve the reliability and yield of the semiconductor device, it can be expected to the effect of improving the charge storage electrode contact resistance.

Claims (4)

Forming an oxide film and an etch stop nitride film on a substrate having a lower layer including a predetermined conductive structure; Etching the etch stop nitride layer and the oxide layer in the charge storage electrode contact region; Forming a sacrificial oxide film on the entire structure of the etch stop nitride film and the oxide film; Etching the sacrificial oxide layer in the charge storage electrode formation region; Partially etching the exposed oxide layer after the sacrificial layer is etched to cause an undercut under the etch stop nitride layer; And Forming a conductive film for a charge storage electrode along the entire surface of the undercut induced structure Method for forming a charge storage electrode of a semiconductor device comprising a. The method of claim 1, The oxide film is a charge storage electrode forming method of a semiconductor device, characterized in that any one of the CVD oxide film selected from PSG, BPSG, PE-USG, PE-TEOS. The method of claim 2, And the oxide film is formed to have a thickness of 200 to 3000 Å. The method according to any one of claims 1 to 3, And the oxide film and the sacrificial oxide film are formed of the same series of oxide films.