JPH06151711A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a polycrystalline Si storage electrode with a roughened surface. CONSTITUTION:An oxide film 2 and a polycrystalline Si layer 3 are successively grown on an Si substrate 1, and after a mask 4 has been formed by optical lithography, an anisotropic storage electrode 5 is formed by dry-etching. Then, the surface of the anisotropically etched storage electrode can be reprocessed into a storage electrode 6 having semispherical rugged shape by making accumulation reaction of dry etching compete with reaction of etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a method of forming a storage electrode.

[0002]

2. Description of the Related Art Conventionally, there is a stack type storage electrode as a typical example of the structure of a storage electrode portion of a DRAM or a capacitor. One way to secure a large number of sufficiently large storage capacitors in a limited area is to use the electrode area, but in order to secure the area, the storage electrode must be made high.

However, if this method is simply used, a large step is formed between the memory cell section and the peripheral circuit section, and if this step becomes larger than the focus margin in the photolithography process, it is impossible to form a mask with high accuracy. Occurs. Therefore, the height of the storage electrode cannot be unnecessarily increased.

Therefore, a method of increasing the surface area by devising the shape of the storage electrode can be considered as follows. Using the LPCVD method, polycrystalline Si having a hemispherical uneven shape is grown on the entire surface of the stacked storage electrode to form an uneven surface, and the polycrystalline Si is dry-etched while maintaining the uneven shape of the storage electrode. Separate the storage electrodes of.

However, the growth temperature of the polycrystalline Si having the hemispherical concavo-convex shape is extremely limited to 550 ° C., so that there is a problem in reproducibility.

FIG. 1 shows the relationship between the polycrystalline Si deposition temperature and the amount of accumulated charge when the polycrystalline Si is used for the lower electrode of the stack type accumulation electrode. When polycrystal Si is deposited at around 550 ° C. and polycrystalline Si is used for the lower electrode, the accumulated charge amount is about doubled, but the temperature range is extremely narrow.

[0007]

As mentioned above, L
In the PCVD method, polycrystalline Si having a hemispherical uneven shape is used.
The temperature at which to grow is very limited. for that reason,
Although highly accurate temperature control is required, it becomes difficult to control the temperature uniformly in the substrate surface as the silicon substrate area increases. As a result, the manufacturing yield of a semiconductor device having a large storage capacity may decrease.

An object of the present invention is to provide a method of manufacturing a semiconductor device having a large storage capacity by forming polycrystalline Si having a hemispherical uneven shape by dry etching without using the conventional LPCVD method. .

[0009]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having an electrode forming step and an etching processing step, wherein the electrode forming step is The anisotropic storage electrode is formed on the semiconductor substrate, and the etching process is a dry etching process of the storage electrode surface into a hemispherical uneven shape.

[0010]

[Function] After anisotropically dry-etching the storage electrode,
By competing the deposition reaction and the etching reaction of dry etching, the surface of the anisotropically etched storage electrode can be reprocessed into a storage electrode having a hemispherical uneven shape.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 2A to 2C are sectional views of a semiconductor chip for explaining one embodiment of the present invention.

First, a method of forming a storage electrode on a semiconductor substrate will be described. As shown in FIG. 2A, the Si substrate 1
After forming the SiO ₂ film 2 thereon, a polycrystalline Si layer 3 is formed on the SiO ₂ film 2 by the LPCVD method, and then phosphorus is thermally diffused to reduce the sheet resistance of the polycrystalline Si layer 3 to 600Ω / □
And Then, after forming a photoresist layer, patterning is performed by a photolithography technique to form a mask 4. The dry etching apparatus uses a cathode-coupled parallel plate type batch-type etcher that uses 13.56 MHz high-frequency discharge. H as etching gas
60 with a mass flow controller using Br gas
SCCM flow, pressure 100mTorr, RF power is 1
Etching is performed under the condition of 50 W so that the etching shape of the storage electrode becomes vertical. 3 more after etching
By adding 0% additional etching, polycrystalline S
Make sure that there is no etching residue on the i layer 3. After that, a CF ₄ (2
%) + O ₂ discharge for 20 seconds, followed by O ₂ discharge to 90
The resist is peeled off by exposing for 2 seconds, and a large number of anisotropic storage electrodes 5 are formed as shown in FIG.

Next, the flow rate of the mixed gas of HBr + N ₂ was changed (N ₂ 17%, 50%, 83%) and the total flow rate was 60 s.
It is controlled by a mass flow controller so that it becomes ccm. Both the pressure and the RF power are the same as the above conditions.
The results of etching under the above conditions are shown in FIGS.
Shown in. When the amount of N ₂ added was 17%, irregularities began to appear on the silicon surface, and when the amount of added N was 50%, the silicon surface had
It is processed into a hemispherical irregular shape of about 00Å.

However, when the addition amount is 83%, etching does not proceed and the surface is flat. N ₂ addition amount is about 3
In the range of 0% to 60%, the silicon surface is processed into a hemispherical uneven shape. According to this mechanism, when N ₂ is added and polycrystalline Si is etched, silicon nitride is generated in plasma, and this is deposited on the surface of polycrystalline Si. Since HBr etches silicon, the deposition reaction and the etching reaction compete with each other to process the surface of polycrystalline Si into an uneven shape. Therefore, HBr (50%) + N ₂ (5
When the storage electrode 5 is etched with (0%) mixed gas, a storage electrode 6 having a hemispherical uneven shape can be formed as shown in FIG.

In the present invention, the etching gas is HBr + N.
₂ was used, but if it is a gas that etches Si, by adding a gas that causes a deposition reaction, the surface of polycrystalline Si can be processed into a hemispherical uneven shape,
It is possible to manufacture a semiconductor device having a large storage capacity. In addition, in the embodiment, the etching device has 13.56 MH.
Although the cathode-coupled parallel plate type batch etcher utilizing the high frequency discharge of z was used, the same parallel plate type etching apparatus using a single-wafer type, the etching method using electron cyclotron resonance, etc. Needless to say, can be applied.

[0016]

As described above, according to the present invention, L
The polycrystalline Si surface can be processed into a hemispherical uneven shape by dry etching without using the PCVD method, and the storage electrode can be formed with extremely good reproducibility. Therefore, a semiconductor device having a large storage capacity can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a formation temperature of polycrystalline Si having an uneven surface on the surface by an LPCVD method and a storage capacitance.

FIG. 2 is a sectional view of a semiconductor chip for explaining one embodiment of the present invention.

FIG. 3 is a micrograph showing the N ₂ addition rate to HBr gas and the degree of unevenness of the silicon surface.

[Explanation of symbols]

1 Si substrate 2 SiO ₂ film 3 polycrystalline Si layer 4 mask 5 storage electrode 6 storage electrode having a hemispherical uneven shape

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[Procedure amendment]

[Submission date] July 19, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

FIG. 3 is a micrograph of a crystal structure showing the N ₂ addition rate to HBr gas and the degree of uneven shape of the silicon surface.

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device comprising an electrode forming step and an etching processing step, wherein the electrode forming step forms an anisotropic storage electrode on a semiconductor substrate. Is a method for manufacturing a semiconductor device, characterized in that the surface of the storage electrode is dry-etched into a hemispherical uneven shape.