KR20000000761A - Method for forming capacitor of semiconductor memory device - Google Patents

Abstract

PURPOSE: A method for forming a capacitor of a semiconductor memory device is provided to obtain a large capacitance in a predetermined cell area regardless of density of a polysilicon at a lower electrode of a capacitor. CONSTITUTION: The method for forming a capacitor of a semiconductor memory device comprises: a step to form a insulation layer(102) on a semiconductor substrate(100); a step form a contact hole(103) by etching the insulation layer until the surface of the semiconductor substrate(100) is exposed using a mask for forming the contact hole; a step to form a storage electrode(104) electrically connected to the semiconductor substrate(100)by filling the contact hole with conductive matter; and a step to form a metal film(106) of hemisphere on the surface of the storage electrode(104).

Description

A METHOD OF FABRICATING CAPACITOR FOR SEMICONDUCTOR MEMORY DEVICE

The present invention relates to a method of manufacturing a semiconductor memory device, and more particularly to a method of manufacturing a capacitor of a semiconductor memory device.

As semiconductor devices become more integrated, the cell unit area decreases and thus the surface area of the unit cell decreases.However, the capacitance of the capacitor that stores the actual electrical signal must be maintained at a constant amount regardless of the increase in integration. Processing is possible.

In particular, in semiconductor devices that store information such as DRAMs, capacitance is a very important factor in refresh, speed, and reliability.

Therefore, various methods have been used as a method of increasing the capacitance by increasing the surface area. For example, there are methods using a one cylinder stacked cell (OCS), a double cylinder stacked cell (DCS), a micro trench stacked cell (MTS), and a fin structure. However, these methods also all have a disadvantage in that the process is complicated, and as the design rules decrease, there is a problem in process reproducibility and mass productivity.

Another method of increasing the surface area is hemi-spherical grain (HSG). The HSG is a polysilicon grain having hemispherical crystal grains on its surface, and is migrated between particles by annealing at an intermediate temperature between an amorphous phase and a polycrystalline phase by changing the growth conditions of the polysilicon. ) Is formed. The HSG can increase the capacitance required by the DRAM by increasing the surface area of the capacitor in a relatively easier way than the aforementioned methods.

The increase in the surface area of the capacitor may be obtained by changing process conditions such as stabilization temperature, seeding process, annealing temperature, and polysilicon concentration during HSG growth.

Among the above conditions, the lower the polysilicon concentration is, the easier HSG growth is, and thus the surface area of the capacitor can be increased to increase the capacitance.

However, when data is actually stored in a capacitor, a depletion layer is formed on polysilicon to reduce the capacitance. As the concentration of polysilicon decreases, the thickness of the depletion layer formed in the polysilicon increases. Thus, in terms of capacitance, there is a constraint that the concentration of polysilicon indefinitely cannot be lowered in order to maximize HSG growth.

In order to solve this problem, a storage electrode is formed of low-concentration polysilicon, and HSG growth is performed on the storage electrode to maximize the increase of the surface area, and then, by doping PH ₃ again to the polysilicon surface, the concentration is increased. Other methods are used to minimize the pip layer.

During HSG seeding, polysilicon seeds generate selectivity loss that is formed not only on the surface of the storage electrode but also on the insulating film exposed between the electrodes. Since the polysilicon seeds formed on the insulating film due to the selectivity loss may cause a bridge between the storage electrodes, there is a problem that a process of removing the unnecessary polysilicon seeds formed on the insulating film by wet etching or the like is necessary before the dielectric film is formed. .

The present invention has been proposed to solve the above-described problems, and provides a method of manufacturing a capacitor of a semiconductor memory device capable of securing a large capacitance in the same cell area regardless of the concentration of polysilicon of the capacitor lower electrode. There is a purpose.

1A and 1B are flowcharts sequentially showing processes of a capacitor manufacturing method of a semiconductor memory device according to an embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

100 semiconductor substrate 102 insulating film

103: contact hole 104: storage electrode

106: metal film 108: dielectric film

110: conductive film

(Configuration)

According to the present invention for achieving the above object, a capacitor manufacturing method of a semiconductor memory device comprises the steps of forming an insulating film on a semiconductor substrate; Forming a contact hole by etching the insulating layer until the surface of the semiconductor substrate is exposed using a contact hole forming mask; Filling the contact hole with a conductive material to form a storage electrode electrically connected to the semiconductor substrate; Forming a hemispherical metal film on a surface of the storage electrode.

(Action)

Referring to FIG. 1A, in a method of manufacturing a capacitor of a novel semiconductor memory device according to an embodiment of the present invention, a contact hole is formed by etching an insulating film until the surface of the semiconductor substrate is exposed using a contact hole forming mask. . After forming the storage electrode electrically connected to the semiconductor substrate by filling the contact hole with a conductive material, a hemispherical metal film is formed on the surface of the storage electrode. In such a method of manufacturing a capacitor of a semiconductor memory device, by forming a hemispherical metal film instead of an HSG film on the surface of the storage electrode, it is selectively formed only on polysilicon to prevent bridges, and the dielectric constant of the depletion layer in the storage electrode It can be prevented from being reduced and a large capacitance can be secured by increasing the surface area of the storage electrode.

(Example)

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1A to 1B.

1A and 1B are flowcharts sequentially illustrating processes of a capacitor manufacturing method of a semiconductor memory device according to an embodiment of the present invention.

Referring to FIG. 1A, a gate electrode layer is formed on a semiconductor substrate 100 having active and inactive regions defined therein (not shown). An insulating film 102 is formed on the semiconductor substrate 100 including the gate electrode layer. ) Is formed.

The insulating layer 102 is etched by using the contact hole forming mask until the surface of the semiconductor substrate 100 is exposed to form the contact hole 103. A conductive film is formed on the insulating film 102 including the contact hole 103 (not shown). The conductive film is made of polysilicon.

A photoresist pattern for forming a storage electrode is formed on the conductive layer. (Not shown in the drawing) The conductive layer is etched using the photoresist pattern as a mask to form a storage electrode 104. The storage electrode 104 also serves as a lower electrode of the capacitor but at the same time secures an electrode area of the three-dimensional capacitor.

The metal film 106 is formed on the storage electrode 104. The metal film 106 is formed of, for example, aluminum (Al), and is deposited by a chemical vapor deposition (CVD) process. The metal film 106 is selectively formed only on the storage electrode 104 and has a hemispherical surface. In the CVD process, the metal film 106 may be formed at a low temperature of 200 ° C. because the metal organic compound is a deposition source.

Since the metal film 106 is grown by nucleation and growth mechanism at a suitable temperature according to the process conditions, the metal film 106 has a hemispherical surface. In addition, the hemispherical metal film 106 may increase the surface area of the electrode as in the case of HSG growth of polysilicon.

In the case of increasing the surface area using the conventional HSG, as mentioned above, HSG cannot grow indefinitely because the degree of HSG growth and the formation of a depletion layer are closely related to the doping concentration of polysilicon.

However, in the present invention, since there is no formation of a depletion layer in the metal film 108, the value of equivalent thickness of oxide (Toxeq) is influenced by the thickness of the dielectric film to be formed in a subsequent process, thereby freely controlling the growth of the hemispherical metal film. Can be.

In addition, in the subsequent process, polysilicon has a disadvantage of increasing the value of Toxeq due to the generation of dielectric material by oxidation (oxidation), whereas in the present invention, when using a dense oxide film such as aluminum, it is possible to prevent the above problems have.

In a practical process, both the HSG or the hemispherical metal film 106 according to the present invention should be formed only on the storage electrode for separation between cells.

Since the hemispherical metal film 106 formed by the CVD process according to the present invention exhibits excellent selective deposition characteristics compared to the HSG, the selectivity margin is improved.

The capacitor dielectric layer 108 is formed on the insulating layer 102 including the metal layer 106. The capacitor dielectric layer 108 is formed of, for example, NO, ONO, SiO _2, or the like. A conductive layer 110 is formed on the capacitor dielectric layer 108 to form a capacitor as shown in FIG. 1B.

In another embodiment, a hemispherical metal film may be applied to most capacitors, such as trench type capacitors, in addition to the stack type capacitors as described above.

According to the present invention, by forming a hemispherical metal film instead of an HSG film on the surface of the storage electrode, it is selectively formed only on polysilicon to prevent the bridge, and to prevent the dielectric constant from being reduced by the depletion layer in the storage electrode. Increasing the surface area of the storage electrode has the effect of ensuring a large capacitance.

Claims (4)

Forming an insulating film (102) on the semiconductor substrate (100); Forming a contact hole (103) by etching the insulating film (102) until the surface of the semiconductor substrate (100) is exposed using a contact hole forming mask; Filling the contact hole (103) with a conductive material to form a storage electrode (104) electrically connected to the semiconductor substrate (100); Forming a hemispherical metal film (106) on a surface of the storage electrode (104). The method of claim 1, The hemispherical metal film (106) is a capacitor manufacturing method of a semiconductor memory device is deposited by a chemical vapor deposition (CVD) process. The method according to claim 1 and 2, The metal film (106) is, for example, aluminum (Al) capacitor manufacturing method of a semiconductor memory device. The method of claim 3, wherein The deposition of the aluminum is carried out at a temperature of 200 ℃ capacitor manufacturing method of a semiconductor memory device.