JPH04170026A - Dry etching - Google Patents

Abstract

PURPOSE:To make such dry etching possible as has excellent counter-resist selectivity and counter-silicon substrate selectivity, a high-speed performance and fewer particle contamination by using unsaturated fluorocarbon gas and by specifying the temperature of an etched substrate. CONSTITUTION:A layer-to-layer insulated film 3 is formed on a single-crystal silicon substrate 1. Then, a resist pattern 4 having an opening 4a is formed on the layer-to-layer insulated film 3 as an etching mask for the film 3. Nextly, the substrate is set in a magnetically enhanced microwave plasma etching device which is equipped with a cooling mechanism by which the temperature of an etched substrate is controlled. Then, the substrate is etched and then a contact hole 5 having a good anisotropic shape is formed rapidly. In the etching, an etching gas which contains fluorocarbon gas having at least one unsaturated bond among molecules is used and the temperature of the etched substrate 15 kept to 50 deg.C or lower. Consequently, a silicon compound layer can be subjected to such etching as has excellent counter resist selectivity and counter- silicon substrate selectivity, a high-speed performance and fewer particle contamination.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry etching method, and particularly to a dry etching method for a silicon compound layer that has excellent resist selectivity and silicon substrate selectivity, is fast, and has little particle contamination. Regarding.

[Summary of the invention]

The present invention is a dry etching method for etching a silicon compound layer formed on a substrate, using an etching gas containing a fluorocarbon gas having at least one unsaturated bond in the molecule to reduce the temperature of the substrate to be etched. By performing etching while controlling the temperature at 50° C. or lower, the polymerization of the carbon-based polymer in plasma is promoted and the resist selectivity and silicon base selectivity are improved.

Furthermore, the present invention etches the silicon compound layer to substantially just before the interface with the base substrate by the above-described process, and then etches the remaining portion by adding a hydrocarbon gas to the above-described etching gas. , which promotes the formation of deposits and particularly improves the selectivity to silicon substrates.

[Conventional technology]

VLS 1. As semiconductor devices such as ULSI devices become more advanced in miniaturization and integration, technical requirements for etching silicon compound layers such as silicon oxide are becoming increasingly strict.

First, as devices and chips become more highly integrated, the areas of devices and chips are expanding and wafers are becoming larger in diameter, while the patterns to be formed are also becoming finer. The mainstream of equipment is about to shift from the conventional batch type to the single wafer type. On this occasion,
In order to maintain the same productivity as before, it is essential to significantly improve the etching speed.

In addition, in order to increase the speed and miniaturization of vises, the junction depth of the impurity diffusion region has become shallow (and various deposited films have become thinner). For example, etching techniques for impurity diffusion regions formed in semiconductor substrates and SR etching techniques are required.
An example of this is etching of a silicon oxide interlayer insulating film using a silicon substrate or polycrystalline silicon layer as a base when forming contacts in the source/drain regions of PMO3 transistors used as resistive load elements in AM. It is.

However, characteristics such as high speed, high selectivity, and low damage are mutually selected, and it is extremely difficult to establish an etching process that satisfies all of them.

Conventionally, CHF3 gas and CF have been used to dry-etch a silicon compound layer such as silicon oxide while maintaining a high selectivity with respect to a silicon-based material layer.

/H, mixed gas, C! F@/CHF, mixed gas, etc. are typically used as the etching gas.

All of these are mainly fluorocarbon gases with an F/C ratio (ratio of the number of fluorine atoms to the number of carbon atoms in a molecule) of 4 or less. This is because (a) C contained in the fluorocarbon gas creates C-0 bonds on the surface of the silicon oxide layer, and has the effect of cutting or weakening the 5i-0 bonds; (b) the silicon oxide layer CF, which is the main etching species of silicon oxide (especially CF), can be produced; furthermore, relatively carbon-rich conditions are created in the (C) plasma, so that the oxygen in the silicon oxide is not present in the form of CO or CO2. On the other hand, carbon-based polymers are deposited on the surface of the silicon-based material layer due to the contribution of C, H, F, etc. contained in the gas system, reducing the etching rate and achieving a high selectivity with respect to the silicon-based material layer. This is based on reasons such as:

In response, the applicant of the present application previously proposed in Japanese Patent Application No. 2-75828 a method for dry etching a silicon compound layer using a saturated or unsaturated higher order fluorocarbon gas having 2 or more carbon atoms. There is. This is C! F
a, CsF*-C4F+. By using a high-order fluorocarbon gas such as , 04F8, etc., ions such as CFL are efficiently generated and etching speed is increased. However, if high-order fluorocarbon gas is used alone, it is not possible to obtain a sufficiently large selectivity to resist and selectivity to silicon substrate. For example, when etching a silicon oxide layer on a silicon substrate using C*Fs as an etching gas, high speed is achieved, but the selectivity to resist is as low as 1.3, and etching resistance is insufficient. A dimensional conversion difference occurs due to edge recession. Furthermore, since the selectivity to silicon is about 4.1, there remains a problem in overetching resistance.

Therefore, in order to solve these problems, in the above-mentioned prior art, etching using high-order fluorocarbon gas alone is stopped just before the underlying layer is exposed, and when etching the remaining part of the silicon compound layer, the etching is performed using a carbon-based polymer. A two-step etching process is performed in which a hydrocarbon-based gas is further added to this gas to promote etching.

[Problem to be solved by the invention]

However, in the current situation where the design rules of semiconductor devices are becoming highly miniaturized, the difference in dimension conversion between the etching mask and the etching mask is becoming almost intolerable. It is necessary to further improve the selectivity in the etching steps. In addition, with the progress of further miniaturization in the future, the influence of particle contamination due to carbon-based polymers may become more serious, so the amount of deposition gas such as hydrocarbon-based gas used in the second stage etching should be We also want to reduce this as much as possible.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method that has excellent resist selectivity and silicon underlayer selectivity, and allows high-speed etching of a silicon compound layer with less particle contamination.

[Means to solve the problem]

In order to achieve the above object, the present inventor conducted intensive studies and found that an etching gas containing a fluorocarbon gas having at least one unsaturated bond in the molecule is used for etching a silicon compound layer, and By controlling the temperature of the substrate to be etched to 50"C or less during etching, excellent resist selectivity and silicon substrate selectivity can be achieved without using a deposition gas, or at least with a very small amount of deposition gas. It was found that the generation of particles was also suppressed.

The present invention is proposed based on the above findings.

That is, the dry etching method according to the first aspect of the present invention uses an etching gas containing a fluorocarbon gas having at least one unsaturated bond in the molecule to control the temperature of the substrate to be etched to 50°C or less. This method is characterized in that the silicon compound layer formed on the substrate is etched at the same time.

Further, the dry etching method according to the second invention of the present invention includes etching the silicon compound layer to a depth that does not substantially exceed the thickness of the silicon compound layer according to the first invention, and then adding at least carbon to the etching gas. The remaining portion of the silicon-based material layer is etched by adding a gas containing hydrogen and hydrogen as constituent elements.

[Effect]

In the present invention, in etching a silicon compound layer,
An etching gas containing a fluorocarbon gas having at least one unsaturated bond in its molecule is used.

Since such a gas naturally has two or more carbon atoms in one molecule, the amount of CF and + produced from one molecule is similar to the higher-order fluorocarbon gas proposed earlier by the applicant. There will be more. Therefore, it is possible to speed up etching. In addition, when such gases are dissociated by plasma discharge, monoradicals or, in some cases, highly active biradicals (two-terminal free radicals) such as carbene are also generated, which attack the π electron system in the unsaturated bond. This accelerates the polymerization of carbon-based polymers. When this carbon-based polymer is deposited on the surface of a silicon-based material layer such as single crystal silicon or polycrystalline silicon or on the surface of a resist pattern, it may not be easily removed even by ion bombardment, etc.
At the surface of a silicon compound layer such as silicon oxide, oxygen contained in the layer is sputtered out and contributes to the decomposition of the carbon-based polymer, so it is easily removed. Therefore, increased deposition of carbon-based polymer improves resist selectivity and silicon underlayer selectivity.

Further, in the present invention, the temperature of the substrate to be etched during etching is controlled to 50° C. or less. This temperature control may be performed in the room temperature range or in the temperature range of 0° C. or lower, as in low-temperature etching, which has recently attracted attention in the field of dry etching. Normally, during the dry etching process, the temperature of the substrate to be etched is 200°C unless special cooling is performed.
It also increases in degree. However, if the temperature is controlled to 50°C or less, carbon-based polymers can be deposited efficiently due to the decrease in vapor pressure even if a deposition gas such as a hydrocarbon-based gas is not used or the amount used is extremely small. , and the selectivity can be improved as described above. Furthermore, since the amount of deposition gas added can be reduced by this, the risk of particle contamination is also reduced. The first aspect of the present invention
The second invention achieves this effect without using a deposition gas, and the second invention adds a deposition gas only when etching the silicon compound layer near the interface with the underlying layer. This aims to further improve the effectiveness.

Further, in the present invention, if low-temperature etching is performed by cooling the substrate to be etched to 0° C. or lower, the selectivity will be further improved. Etching of a resist material or a silicon-based material layer proceeds mainly through a chemical reaction by F'' (fluorine radicals), so when the temperature of the anti-1 system decreases and the movement of radicals is suppressed, the etching rate also decreases. On the other hand, etching of silicon compound layers such as silicon oxide proceeds physically, mainly through sputtering by ions, so the decrease in etching rate due to cooling is not as noticeable for resist materials or silicon-based materials. Therefore, a further improvement in the selection ratio can be expected.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

Example 1 This example applies the first aspect of the present invention and etches an interlayer insulating film made of silicon oxide using C4F gas, thereby etching an impurity diffusion layer formed in a silicon substrate. This is an example in which a facing contact hole is formed. This will be explained with reference to FIG. 1(A) and FIG. 1(B).

First, as shown in FIG. 1(A), an impurity diffusion layer (2
An interlayer insulating film (3) is formed on the single crystal silicon substrate (1) on which the interlayer insulating film (3) is formed, and openings (
4a) was formed.

Next, the substrate described above is set in a magnetic field microwave plasma etching apparatus equipped with a cooling mechanism that can control the temperature of the substrate (wafer) to below 0°C, and the substrate to be etched is etched using a chiller and ethanol coolant. about -50
Cooled to ℃. In this state, C4°F, gas flow rate 46
SCCM, gas pressure 1.3 Pa (#10 mTorr),
Etching was performed under the conditions of microwave power of 850 W and RF bias power of 400 W. The substrate temperature was maintained at -50° C. during etching. In this etching process, the carbon-based polymer (not shown) was efficiently deposited on the surface of the resist pattern (4), but the carbon-based polymer (not shown) was deposited on the surface of the interlayer insulating film (3) exposed in the opening (4a). The carbon-based polymer was also removed along with the etching removal.

As a result, a contact hole (5) with a good anisotropic shape as shown in FIG. is formed at high speed, and the resist pattern (
4) No significant decrease in film thickness, recession of pattern edges, or destruction of shallow junctions due to overetching were observed. At this time, the silicon selectivity was about 1O1 and the resist selectivity was about 4.

Example 2 This example applies the first aspect of the present invention and etches an interlayer insulating film made of silicon oxide using C4F gas, thereby etching an impurity diffusion layer formed in a silicon substrate. This is an example in which a facing contact hole is formed.

That is, the substrate in the state shown in FIG. 1(A) described above was set in a magnetron RIE (reactive ion etching apparatus), and C, F, gas flow rate 46 SCCM, gas pressure 2 Pa (,15 mTorr), RF Power density 2.0W/cm t, magnetic field strength 150 Gau
Etching was performed under conditions where the substrate temperature during etching was -50°C. Such etching also results in the image shown in Figure 1 (B
) A contact hole (5) having a good anisotropic shape was formed at high speed, and the selectivity to silicon was about 12 and the selectivity to resist was about 5.

In this embodiment and the above-mentioned embodiment 1, a great advantage is that etching can be performed in a single step without switching the gas system by slightly cooling with a simple cooling equipment.

Example 3 In this example, the second aspect of the present invention was applied, and an interlayer insulating film made of silicon oxide was etched using 04F gas up to just before the interface with the underlying layer, and the remaining portion was etched. This is an example in which C, H, and gases are added to the gas system. This will be explained with reference to FIG. 2 in addition to the above-described FIGS. 1(A) and 1(B).

That is, the substrate in the state shown in FIG.
rr).

Under the conditions of RF power density of 2.0 W/cm", magnetic field strength of 150 Gauss on the substrate to be etched, and substrate temperature of 50° C. during etching, the interlayer insulating film (3) was deposited to a depth that did not substantially exceed its layer thickness. Etched.

In this case, the end point of etching was determined by monitoring the emission spectrum at the point at which the C01 emission at 483.5 nm began to decrease. The state of the substrate at this time is as shown in Figure 2, with contact holes (5
) is formed up to the middle part, and an interlayer insulating film (3) is formed at the bottom.
A small amount of the remaining portion (3a) remained.

Next, C, F, gas flow rate is 46 SCCM, CtH4
Under the same conditions except that the gas flow rate was 3 SCCM,
When the remaining portion (3a) was etched, the first
As shown in Figure (B), the underlying impurity diffusion layer (2)
A contact hole (5) having a good anisotropic shape was formed without causing any damage.

In this example, although the substrate to be etched was not cooled to a temperature below 0° C., high anisotropy and high selectivity were achieved by using an unsaturated fluorocarbon gas. Furthermore, when etching the remaining portion (3a), a hydrocarbon gas is added, but the amount added is lower than the amount conventionally required to ensure a practically desirable selectivity of 10 or more. It only takes about 1/3 of the time. therefore,
Generation of particle contamination in the etching chamber is suppressed.

Here, in order to further prevent damage to the underlying layer, a relatively high RF power is applied while etching most of the interlayer insulating film (3) to maintain a practical etching speed, and the remaining When etching the portion (3a), it is effective to switch to a relatively low RF power to reduce the incident energy of ions.

In the above three examples, 04F, which has one double bond in the molecule, and C
Although sF* was used, the present invention is not limited to these, and among compounds having two or more double bonds, compounds having one or two or more triple bonds, and compounds having both double bonds and triple bonds. You can choose from a wide range of options. - For example, C2F4. C,F,, C,F,,
C, F, C, F, etc.

Gases containing at least carbon and hydrogen as constituent elements are not limited to the above-mentioned C, H, but also saturated hydrocarbons,
It can be selected from a wide range of compounds, such as unsaturated hydrocarbons or compounds containing other elements such as oxygen. - Examples include ethylene, acetylene, methane, ethane, methanol, etc.

However, from the viewpoint of promoting the production of a carbon-based polymer through polymerization, compounds containing carbon-carbon multiple bonds in the molecule are particularly preferred.

In the above gas system, an additional 0.0% was added to control the etching rate. Gas, etc. may be added, and He
, Ar, and other rare gases may be added as appropriate.

Furthermore, the material layer to be etched is not limited to the above-mentioned silicon oxide, but may also include PSG and BSG.

BPSG, As5G, AsPSG, AsBSG.

It may also be made of SiN or the like.

〔Effect of the invention〕

As is clear from the above explanation, in the present invention, by using an unsaturated fluorocarbon gas and controlling the temperature of the substrate to be etched to 50°C or less, a deposition gas is not used or a very small amount is added. A high selectivity to resist and a high selectivity to silicon underlayer can be achieved just by using this, and particle contamination is also reduced accordingly.

Therefore, the present invention is extremely effective in manufacturing semiconductor devices with high performance, high degree of integration, and fine patterns.

[Brief explanation of the drawing]

FIG. 1(A) and FIG. 1(B) are schematic cross-sectional views illustrating an example in which the first aspect of the present invention is applied to etching for opening a contact hole in an insulating film between the eyebrows according to the process order. 1(A) shows the state before the start of etching, and FIG. 1(B) shows the state at the end of etching. FIG. 2 is a schematic cross-sectional view showing a state in which etching of the interlayer insulating film has progressed halfway in the second aspect of the present invention. 1...Single crystal silicon substrate 2...Impurity diffusion layer 3...Interlayer insulating film 3a...Remaining part (of interlayer insulating film) 4
...Resist pattern 4a ...Opening 5 ...Contact hole patent applicant Sony Corporation representative Patent attorney Koike Mima Sakae Tamura - same Masaru Sahara

Claims (2)

[Claims] (1) Etching of a silicon compound layer formed on a substrate while controlling the temperature of the substrate to be etched to 50°C or less using an etching gas containing a fluorocarbon gas having at least one unsaturated bond in the molecule. A dry etching method characterized by performing. (2) Using an etching gas containing a fluorocarbon gas having at least one unsaturated bond in the molecule, the silicon compound layer formed on the substrate is substantially etched while controlling the temperature of the substrate to be etched to 50°C or less. a step of etching to a depth not exceeding the layer thickness; and a step of etching the remaining portion of the silicon-based material layer by adding a gas containing at least carbon and hydrogen as constituent elements to the etching gas. A dry etching method comprising: