KR100573827B1 - Method for fabricating contact of semiconductor device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a contact of a semiconductor device in which a fine contact hole is formed by controlling a polymer that is unstable deposited on top of a contact hole during a plasma etching process for forming a contact hole. Forming a lower pattern having a lower layer, forming a buffer layer on the entire surface including the lower pattern, forming a hard mask pattern layer, and performing a first contact etching process using the hard mask pattern layer to remove a portion of the buffer layer; And removing the polymer generated during the first contact etching process, and performing the second contact etching to remove the remaining buffer layer of the contact region after removing the polymer to open the lower pattern.

ArF pattern, O₂ plasma, polymer, hard mask, contact hole

Description

Method for forming contact of semiconductor device {METHOD FOR FABRICATING CONTACT OF SEMICONDUCTOR DEVICE}             

1A to 1C are cross-sectional views of a process for forming a contact of a semiconductor device of the prior art;

2A and 2B are cross-sectional and planar configuration diagrams illustrating an unstable hole formation state by a polymer at the time of contact formation in the prior art;

3A to 3C are cross-sectional views illustrating a process for forming a contact of a semiconductor device according to the present invention;

4A to 4C are plan views showing the formation of contacts in the semiconductor device according to the present invention.

* Explanation of symbols for the main parts of the drawings

31 semiconductor substrate 32 lower pattern

33: buffer layer 34: hard mask pattern layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of semiconductor devices. Specifically, in the plasma etching process for forming contact holes, the contact formation of semiconductor devices capable of forming fine contact holes by controlling a polymer that is unstable deposited on the contact holes is formed. It is about a method.

Plasma etching devices and wet etching devices are used as etching devices used to form fine patterns in a semiconductor manufacturing process. Plasma etching devices exhibiting anisotropy have become mainstream as the degree of integration of semiconductor devices increases.

Sources of the plasma etching apparatus include radio frequency (RF) plasma, surface wave plasma (SWP), electron cyclotron resonance (ECR) plasma or helicon wave plasma.

Here, the high frequency (RF) plasma may be configured as an inductively coupled plasma (ICP) or a transformer coupled plasma (TCP).

Hereinafter, a contact forming process of a semiconductor device of the related art will be described with reference to the accompanying drawings.

1A to 1C are cross-sectional views of a process for forming a contact of a semiconductor device of the prior art, and FIGS. 2A and 2B are cross-sectional and planar views showing an unstable hole formation state by a polymer when forming a contact of the prior art.

In the prior art, a contact forming process using a hard mask is performed as follows to form an ultrafine pattern.

First, as shown in FIG. 1A, the hard mask layer 4 is formed to pattern the buffer layer 3 formed on the lower pattern 2 formed on the silicon substrate 1.

The lower pattern 2 may be an impurity junction region, a gate line, or a bit line, and the buffer layer 3 may be formed of a material such as BPSG (Boron Phosphorus Silicate Glass) or PSG (Phosphorus Silicate Glass).

In addition, the hard mask layer 4 formed for forming a deep contact having a high aspect ratio is usually formed of polysilicon.

Subsequently, an ArF photoresist pattern 5 is formed on the hard mask layer 4 and the etching process is performed using the ArF photoresist pattern 5 as shown in FIG. 1B.

The etching process forms a hard mask pattern layer 4a using a conventional TCP / ICP type plasma source for deep contact etch with high aspect-ratio.

In addition, the lower pattern 2 is opened by selectively etching the buffer layer 3 by an etching process using a high density plasma using the hard mask pattern layer 4a.

However, when forming ultra-fine contacts of 100 nm or less devices using an ArF photoresist pattern, deep contact formation having a high aspect ratio is required in accordance with chip shrinkage.

That is, as shown in Figure 1c, in order to etch the hard mask film as a barrier by using a high density plasma source of MERIE (Magnetic Enhanced Reactive Ion Etching) type by adjusting the ratio of CH _x F _x / CF _x / O ₂ As in (C), the C-Rich polymer is deposited and etched on the inner wall of the contact hole, with an uneven amount of polymer deposited inside each contact hole.

Part (a) shows the case where the amount of polymer deposited inside the contact hole is stable, and part (b) shows the instability.

When the etching is completed in the state having the unstable portion as described above, as shown in FIGS. 2A and 2B, the normal contact (d) and the abnormal contact (e) occur.

Figure 2a is a top view of the actual shape of the device 100nm or less in which this phenomenon occurs, which causes a lot of problems when forming a deep contact with a high aspect ratio using a hard mask for forming an ultra-fine pattern Let's do it.

As described above, in the manufacturing process of the prior art, a large amount of C generated during etching using a hard mask film as a barrier layer, which is required during the ultrafine patterning process in a semiconductor device, requires an ArF photoresist pattern and a deep contact is required. It does not solve the problem caused by the -rich polymer.

That is, due to contact hole striation due to unstable polymer deposition on the inner wall of the contact hole, it is difficult to secure an open area with the lower pattern.

This causes a reduction in the resistance characteristics of the ultra-fine device, which acts as a direct cause of lowering the device manufacturing yield.

The present invention has been proposed to solve the above problems of the prior art, a semiconductor that can form a fine contact hole by controlling a polymer that is unstable deposited on top of the contact hole during the plasma etching process for forming the contact hole It is an object of the present invention to provide a method for forming a contact of a device.

In order to achieve the above object, a method of forming a contact of a semiconductor device according to the present invention may include forming a conductive lower pattern on a semiconductor substrate, forming a buffer layer on the entire surface including the lower pattern, and forming a hard mask pattern layer. And forming a first contact hole by etching a portion of the buffer layer by performing a first contact etching process using the hard mask pattern layer, and removing a polymer generated during the first contact etching process. And performing a second contact etching process to form a second contact hole remaining after the first contact etching process and etching the buffer layer exposed through the first contact hole to expose the lower pattern. do.

Here, in the first and second contact etching processes, the ratio of C _x F _x : O ₂ : C _x / 2F _x / 2 is adjusted to about 2: 2: 1 during the etching process using the high density plasma of the MERIE type. It characterized in that to proceed to have an angle (88) to 89 °.

And the primary contacts etching process after that, the flow cut out (fluorine) based plasma C-rich polymer is an isotropic etching using O ₂ plasma from being deposited on the contact hole, the inner wall in an unstable state caused by the reaction by such as C _x F _x It is characterized by removing in the process.

Hereinafter, the most preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. .

3A to 3C are cross-sectional views illustrating a process for forming a contact of a semiconductor device according to the present invention, and FIGS. 4A to 4C are plan views illustrating contact formation of a semiconductor device according to the present invention.

In the process of fabricating a semiconductor device including logic, an O ₂ plasma polymer recess step for deep contact plasma etching with an ultrafine high aspect ratio using an ArF pattern is performed to control a polymer that is unstable to be deposited on an upper layer of a contact hole. By implementing contact profiles without contact hole striation, devices with sub-100nm tech are possible.

That is, in the ultra-fine patterning process, a large amount of C-rich polymer, which is generated at the time of etching the hard mask film as a barrier, is unreliably deposited on the inner wall of the contact hole.

First, as shown in FIGS. 3A and 3B, a material layer for forming a hard mask is formed in order to pattern the buffer layer 33 formed on the lower pattern 32 on the semiconductor substrate 31.

The lower pattern 32 may be an impurity junction region, a gate line, or a bit line, and the buffer layer 33 may be formed of a material such as BPSG (Boron Phosphorus Silicate Glass) or PSG (Phosphorus Silicate Glass).

In addition, the hard mask forming material layer formed for forming a deep contact having a high aspect ratio is usually formed of polysilicon.

Subsequently, an ArF photoresist pattern (not shown) is formed on the material layer for forming a hard mask and an etching process is performed using the ArF photoresist pattern.

The etching process forms a hard mask pattern layer 34 using a conventional TCP / ICP type plasma source for deep contact etch with high aspect-ratio.

The lower pattern 32 is opened by selectively etching the buffer layer 33 by an etching process using a high density plasma using the hard mask pattern layer 34.

Here, the process of opening the lower pattern 32 contact proceeds as follows.

First, as shown in FIGS. 3B and 4B, the plasma chamber and the polymer on the wafer are low-pressured using only O ₂ plasma before etching with an appropriate amount of target and etching the C-rich polymer unstable on the inner wall of the hole. The buffer layer 33 remaining inside the contact hole is etched after being etched and exhausted by isotropic etching under low pressure, low power, and high O ₂ conditions.

Detailed process conditions in the deep contact forming process having such a high aspect ratio are as follows.

In the etching process using MERIE type high density plasma as a hard mask layer, the ratio of C _x F _x : O ₂ : C _x / 2F _x / 2 is adjusted to 2: 2: 1 to about 88-89 °. Contact holes are formed to have an angle.

Here, the phenomenon that the C-rich polymer, which is generated in a large amount by the reaction by a fluorine-based plasma such as C _x F _x , is deposited on the inner wall of the contact hole in an unstable state is removed by an isotropic etching process using O ₂ plasma. .

As described above, the process of removing the buffer layer remaining inside the contasure hole after removing the polymer is performed in the same manner as in the etching process using the high density plasma of the MERIE type with the hard mask layer as a barrier C _x F _x : O ₂ : C _x / 2F _x Proceed by adjusting the ratio of / 2 to about 2: 2: 1 to form a contact hole to have an angle of about 88 ~ 89 °.

The primary buffer layer etching, polymer removal, and secondary buffer layer etching process are performed in-situ process.

And when performing the deep contact etching process, CH _x F _x (CHF ₃ , CH ₂ F ₂ , etc.) using C _x F _x (C ₃ F ₈ , C ₄ F ₈ , C ₄ F ₆ , etc.) as the main gas The process is performed by inducing a large amount of CH _x radicals using plasma.

In the etching process as described above, as shown in FIGS. 3C and 4C, the C-rich polymer 35 may be controlled in an appropriate amount to induce deposition of the inner wall of the hole in a stable state to form a normal contact.

The etching process of the buffer layer is etched by the following principle.

CF: SiO ₂ + 4CF → SiF ₄ + 2CO ↑ + 2C

CF ₂ : SiO ₂ + 2CF ₂ → SiF ₄ + 2CO ↑

CF ₃ : 3SiO ₂ + 4CF ₃ → 3SiF ₄ + 4O _{2 +} 4CO ↑

The plasma etch + O ₂ plasma polymer removal step such as C _x F _x controls the generation of C-rich polymer on the inner wall of the contact hole by repeating the in-situ sequence several times.

Here, in the MERIE type plasma source for etching to remove the polymer by O ₂ plasma isotropy, when constructing a relief, the O ₂ : Ar gas ratio is about 2 under a pressure condition of 15 to 30 mT using a power of 1000 W or less. The mixture is mixed at a ratio of 1, and 300 sccm to 400 sccm are injected to form a plasma to proceed to an isotropic etching process.

In addition, the process of eliminating the unstable contact hole inner wall deposition phenomenon of C-rich polymer by O ₂ plasma isotropic etching process is conventional MDS (Microwave Down Stream) type, ECR (Electron Cyclotron Resonance) type, HELICAL type, and faraday shield. The amount of c-rich polymer generated on the inner wall of the contact hole is controlled by an etching apparatus using an inductivity copled plasma (ICP) type plasma source.

The present invention can implement a contact profile without contact hole striation by controlling a polymer that is unstable to have an O ₂ plasma polymer removal step during an ultra-deep deep contact plasma etching process using a conventional ArF pattern. To be.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The above-described method for forming a contact of a semiconductor device according to the present invention solves a problem caused by unstable deposition of a polymer in a process of using a hard mask film as a barrier during an etching process for forming a deep contact having a high aspect ratio.

That is, the contact hole striation phenomenon generated by depositing on the inner wall of the contact hole in the unstable state of the C-rich polymer reacting with the fluorine-based plasma used in the etching process is removed from the lower pattern by removing the O ₂ plasma polymer. Enough area can be secured.

This ensures the resistance characteristics of ultra-fine devices, which has the effect of improving device implementation, device characteristics, and manufacturing yield.

Claims (7)

Forming a conductive lower pattern on the semiconductor substrate; Forming a buffer layer on the entire surface including the lower pattern and forming a hard mask pattern layer; Performing a first contact etching process using the hard mask pattern layer to etch a portion of the buffer layer to form a first contact hole; Removing the polymer generated during the first contact etching process; And Performing a second contact etching process to form a second contact hole remaining after the first contact etching process and etching the buffer layer exposed through the first contact hole to expose the lower pattern Contact forming method of a semiconductor device comprising a. The method of claim 1, The first and second contact etching process, In the etching process using MERIE type high density plasma, the ratio of C _x F _x : O ₂ : C _x / 2F _x / 2 is adjusted to 2: 2: 1 to have an angle of about 88 to 89 °. The method of forming a contact of a semiconductor device, characterized in that the progress. The method according to claim 1 or 2, After the primary contact etching process, The C-rich polymer generated by the reaction by the fluorine-based plasma, such as C _x F _x is deposited on the inner wall of the contact hole in an unstable state is removed by an isotropic etching process using O ₂ plasma Contact formation method. The method of claim 1, The method of claim 1, wherein the first contact etching process, the polymer removing process, and the second contact etching process are performed in-situ. The method of claim 1, When the first and second contact etching processes are performed, the process is performed by inducing a large amount of CH _x radicals using CH _x F _x (CHF ₃ , CH ₂ F ₂ ) plasma using C _x F _x as the main gas. A contact forming method of a semiconductor device, characterized in that. The method of claim 1, When the polymer is etched, the O ₂ : Ar gas ratio is mixed at a ratio of about 2: 1 by injection of 300 sccm to 400 sccm under a pressure condition of 15 to 30 mT using a power of 1000 W or less in a MERIE type plasma source. Forming a plasma and then proceeding to an isotropic etching process. The method of claim 1, And the hard mask layer is formed of a polysilicon layer, and the buffer layer is formed of any one of BPSG and PSG.

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