KR100668075B1 - Etching method using neutral beam etching apparatus - Google Patents

Abstract

The present invention comprises the steps of extracting and accelerating an ion beam having a certain polarity from the ion source; Controlling the incident angle of the ion beam incident on the reflector to reflect the accelerated ion beam to convert the ion beam into a neutral beam; And etching the specific material layer on the etched substrate by the neutral beam by placing the etched substrate on the traveling path of the neutral beam, and in the ion beam extraction and acceleration step, CF as an etching gas. Provided is an etching method using a neutral beam etching apparatus, characterized in that the ion beam is extracted using a series of gases. Here, the etching gas is CF ₄ , the additive gas is preferably H ₂ . As a result, the selectivity between PR, silicon, and silicon oxide can be increased.

Neutral beam, grid, reflector, ion beam, angle of incidence, etching,

Description

Etching method using neutral beam etching apparatus

1 is a view schematically showing an etching apparatus using a neutral beam according to an embodiment of the present invention.

FIG. 2 is a perspective view schematically illustrating the ion beam source in FIG. 1.

3 is a perspective view schematically illustrating the neutral beam generator (reflector) in FIG. 1.

4 is a cross-sectional view illustrating an etched substrate to be etched by the neutral beam etching apparatus.

5 is a graph showing the change in etching rate according to the acceleration voltage when using a neutral beam etching apparatus, CF ₄ as the reaction gas.

6 is a graph showing the change in etching rate according to the CF ₄ gas supply when using a neutral beam etching apparatus, CF ₄ as the reaction gas.

7 is a graph showing the etching rate of silicon, silicon oxide, and PR according to the supply amount of the reaction gas and the additive gas when using a neutral beam etching apparatus, using CF ₄ gas as the reaction gas, H ₂ gas as the additive gas to be.

FIG. 8 is a graph showing an etching rate change of silicon and silicon oxide according to an acceleration voltage when a neutral beam etching apparatus is used and SF ₆ is used as a reaction gas. FIG.

※ Explanation of codes for main parts of drawing

10; Ion source 12; Induction coil

14; Grid 14a; Grid hole

40; Reflector 42; Reflector Hall

30; Semiconductor substrate 32; Etched material layer

34; Etch Mask Layer

The present invention relates to an etching method using a neutral beam etching apparatus, in particular CF-based gas, such as C _x F _y gas (X = 1 to 5, Y = 4 to 8), preferably CF ₄ gas and additive gas The present invention relates to an etching method using a neutral beam etching apparatus capable of etching intact (without side etching) a nanometer-class semiconductor device.

As the demand for high integration of semiconductor devices continues, design rules have been further reduced in the design of semiconductor integrated circuits in recent years, requiring a critical dimension of 90 nm or less. Currently, as an etching apparatus for implementing such a nanometer-class semiconductor device, ion-enhancing etching apparatuses such as a high density plasma etching apparatus and a reactive ion etching apparatus are mainly used. However, in such an etching apparatus, a large amount of ions exist to perform an etching process, and since these ions collide with the semiconductor substrate or a specific material layer on the semiconductor substrate with energy of several hundred eV, physical, Cause electrical damage.

For example, as physical damage, the surface of a crystalline substrate or a particular material layer that collides with these ions may be converted to an amorphous layer, and only some components of the material layer where some of the incident ions are adsorbed or collided selectively. The chemical composition of the surface layer to be detached and etched may be changed, and the atomic bonds of the surface layer may be broken by collision and become dangling bonds. These dangling bonds may cause not only physical damage to the material but also electrical damage, as well as notching of polysilicon due to chargeup damage of the gate insulating film or charging of the photoresist. Cause electrical damage. In addition to such physical and electrical damage, surface contamination may also occur due to the contamination of the chamber material or the reaction gas when the CF-based reaction gas is used.

Therefore, the physical and electrical damage caused by these ions in the nanometer-class semiconductor device is a factor that lowers the reliability of the device and further reduces the productivity, so that it will be applied in response to the trend of higher integration of the semiconductor device and a decrease in design rules. There is a demand for development of a new concept of semiconductor etching apparatus and etching method.

Among them, DBOakes et al. Proposed an intact etching technique using an overheated atomic beam in the paper "Selective, Anisotropic and Damage-Free SiO ₂ Etching with a Hyperthermal Atomic Beam." Takashi Yunogami et al. Used neutral beams and neutral radicals in the paper "Development of neutral-beam- assisted etcher" (J. Vac. Sci. Technol. A 13 (3), May / June, 1995). This paper suggests silicon oxide etching technology with very low damage, and MJ Goeckner et al. Induced Damage.May 13-14, Monterey, CA.) describes etching techniques for superheated neutral beams without charge instead of plasma.

However, the technique proposed by D.B.Oak et al. Has no electrical physical damage due to the absence of ions, and is expected to be less polluting, but it is difficult to achieve large area, and it is difficult to obtain anisotropy in ultra-fine devices. There is a disadvantage in that the technique proposed by Takashi Yunogami et al. Has the disadvantage that it is difficult to control the direction of the neutral beam and has a high possibility of contamination when extracting the ion beam, while the large area is easy. In addition, the technique proposed by M. J. Goeckner et al. Can achieve a large area and obtain a high neutral beam flux, while the direction of the neutral beam due to the recombination of ions and electrons is not obvious, and the ions are mixed. And, there is a disadvantage that the possibility of contamination during ion extraction is large.

On the other hand, the applicant of the present invention is based on the technical content of the document as described above, the 'neutral beam registered in Korean Patent Registration No. 10-412953 No.' neutral beam 'and' Neutral Beam No. 10-380660 'registered Etching method for a semiconductor device using the same and an etching apparatus therefor, and the above application describes a technique of a reflector for converting an ion beam into a neutral beam and an etching method using an apparatus having a reflector. It is incorporated herein by reference.

By the way, when using an etching apparatus using such a central island beam, the etching gas uses a florin-based gas, among which SF ₆ is used. The reason is that since SF ₆ gas does not contain carbon series in the gas, the contamination of the reflector is small during the neutralization of the ion beam, and a high etching rate can be obtained.

However, at present, since the narrow space problem of the reflector portion is improved according to the improvement of the etching apparatus, the problem of contamination due to the adsorption of gas by-products, especially carbon components, is improved, and thus the obstacle to the use of the CF-based etching gas is eliminated. have. When using Florin series (SF ₆ ) etching gas to etch silicon (Si), a high etching rate can be obtained, but there is a problem that the etching of silicon occurs spontaneously and the etching rate is too fast and side etching occurs. .

The following photograph 1 is a SEM photograph showing a state in which silicon is etched using SF ₆ as a reaction gas, and shows a state in which etching (indicated by an arrow) is performed on a side other than the vertical direction.

[Photo 1]

On the other hand, in the case of etching using a photoresist, the etching speed of the PR mask (CF series) is very fast, so that the etching was not easy.

The present invention has been invented to solve the above conventional problems, by etching the silicon layer and the silicon oxide layer using a CF-based gas, such as CF ₄ as an etching gas under a predetermined process conditions, side by spontaneous etching An object of the present invention is to provide an etching method using a neutral beam etching apparatus which prevents etching.

In addition, by using an additive gas together with a CF-based gas, such as CF ₄ gas, etching using a neutral beam etching apparatus that enables etching while adjusting the etching selectivity between the etched material (eg, silicon and silicon oxide) and PR. It is an object to provide a method.

In order to achieve the above object, the present invention, by extracting and accelerating the ion beam having a predetermined polarity from the ion source, by controlling the angle of incidence of the ion beam incident on the reflector to reflect the neutral ion beam And converting the beam into a beam, and etching the specific material layer on the substrate by the neutral beam by placing the substrate on the traveling path of the neutral beam, and extracting and accelerating the ion beam. In, the ion beam is used to extract the ion beam using the CF-based gas as an etching gas, or the ion beam using the CF-based gas and any one of the additive gas of O ₂ , Ar, N ₂ , H ₂ neutral An etching method using a beam etching apparatus is provided.

Preferably, the etching gas is preferably a gas of C _X F _Y (X = 1-5, Y = 4-8).

Preferably, the etching gas is CF ₄ , and the additive gas is H ₂ .

In addition, it is preferable that the incident angle of the ion beam is 5 ° or less.

In addition, the specific material layer on the etched substrate is preferably silicon, silicide, silicon oxide, silicon nitride, or silicon oxynitride.

In addition, the supply amount of CF ₄ as the etching gas is 15 sccm to 4.5 sccm, and the supply amount of H _{2 as} the additive gas is 0 to 10.5 sccm.

According to such process conditions, etching is easily performed while adjusting the etching selectivity ratio of PR and silicon or silicon oxide.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention in more detail. The present invention is not limited to the embodiments disclosed below, but can be practiced in various forms by those skilled in the art within the scope of the appended claims. Accordingly, the present embodiments are only provided to make the disclosure of the present invention more complete, and to more fully inform the person skilled in the art the scope of the present invention.

1 is a view schematically showing an etching apparatus using a neutral beam according to an embodiment of the present invention, Figure 2 is a perspective view of the ion source and grid of Figure 1, Figure 3 is a perspective view of the reflector of Figure 1 . 1 is a simplified diagram for explaining the principle of the present invention, wherein each component of FIG. 1 is provided in a vacuum chamber maintaining an appropriate degree of vacuum.

First, referring to the etching method of the present invention, after extracting and accelerating an ion beam having a predetermined polarity from the ion source 10, and converting the ion beam into a neutral beam by reflecting the accelerated ion beam to the reflector 40, The etched substrate 20 is placed on the path of the neutral beam to etch a specific layer of material (eg, silicon or silicon oxide) on the etched substrate by the neutral beam. In particular, in the present invention, the CF-based gas, preferably CF _4, is used as the etching gas in the ion beam extraction step, and H ₂ is used as the additive gas.

The present invention implements more preferable conditions for the etching process of the nanometer-class semiconductor device on the basis of the above theoretical basis, with reference to Figures 1 to 3 will be described in detail with respect to the etching apparatus used in the present invention.

Referring to FIG. 1, an ion beam generated from an ion source 10 passes through a plurality of grid holes 14a having a constant diameter of a grid 14 positioned at a rear end of an ion source 10 on a path of an ion beam. After the reflection on the surface of the reflector hole 42 formed in the reflector 40 is converted into a neutral beam, incident on the substrate 20 to be etched, a specific material layer (eg, silicon or silicon oxide) on the substrate 20 to be etched. Etch).

The ion source 10 is capable of generating an ion beam from various reaction gases. In this embodiment, an inductively coupled plasma (ICP) generator for generating a plasma by applying an induced power to the induction coil 12 is used. Of course, the ion source modified in various forms can be used.

The rear end of the ion source 10 is coupled to the cylindrical grid 14 formed with a plurality of grid holes 14a through which the ion beam can be accelerated by applying a voltage and through which the ion beam can pass.

The rear end of the grid 14 is in close contact with a reflector 40 which reflects the incident ion beam and converts it into a neutral beam. The reflector 40 may be made of a conductive material such as a semiconductor substrate, a mirror-like carbon (DLC), glassy carbon, or a conductive substrate such as a metal substrate, and may include a reflector hole in the reflector 40. Only the surface of 42 may be composed of these materials.

On the other hand, the reflector holes 42 are inclined at a predetermined angle with respect to the direction in which the ion beams are straight so that the ion beams passing through the grid holes 14a and going straight through are reflected in the reflector holes 42.

The reflector 40 is preferably grounded for discharge of charge generated by the incident ion beam. Although illustrated in FIG. 3 as a cylindrical shape, the reflector 40 is not necessarily limited to a cylindrical shape, and may be manufactured in various shapes, for example, a polygonal column such as a square.

In addition, in the drawing, although the reflector hole 42 is illustrated in a cylindrical shape, it is a matter of course that a plurality of pillar-shaped reflector holes 42 such as rectangular or polygonal may be formed. In particular, the inventors of the present invention form a slit inside the reflector 40 instead of the reflector hole 31 as described in the application number 2003-0042116 (03.06.26) when implementing the actual etching device. This formation of the slit portion solves the problem of narrowing the space of the reflector portion.

On the other hand, the inclination of the reflector hole is formed so that the ion beam going straight after passing through the grid hole is reflected only once in the reflector hole. In this embodiment, the inclination of the reflector hole is such that the angle of incidence of the ion beam incident on the inner surface of the reflector hole is within at least 15 °, and is preferably within the range of at least 3 ° to 15 °. The incidence angle of the ion beam in the range of at least 3 ° to 15 ° means that the angle of incidence based on a normal perpendicular to the surface of the reflector hole is at least 75 ° to 87 °.

Further, the reflection angle of the neutral beam reflected from the surface of the reflector hole in the reflector is set to be within 40 °, and preferably configured to be within the range of 3 ° to 40 °.

On the other hand, the etching target substrate 20 is disposed on the traveling path of the neutral beam reflected and converted from the reflector 40. The etched substrate 20 is mounted on a stage (not shown) in the reaction chamber maintained at a constant vacuum degree, and may be disposed perpendicular to the traveling path of the neutral beam, and at a predetermined angle according to the type of etching process. It is installed so that its position and direction are controlled so that it can be tilted.

FIG. 4 is a cross-sectional view illustrating the etched substrate 20 of FIG. 1 applied to an embodiment of the present invention, and looks at a change in etching speed according to each process condition of the present invention. Referring to FIG. 4, an etching target material layer 32 is formed on the semiconductor substrate 30, and a mask layer 34 having a predetermined pattern is formed thereon. In the present exemplary embodiment, an etching mask 34 coated with a silicon (Si) or silicon oxide (SiO ₂ ) layer as an etching target material layer 32 on a silicon substrate and patterned in a rod shape thereon is used.

Meanwhile, in the etching process using the neutral beam etching apparatus according to the present invention, the etching gas may be a CF-based gas such as CF ₄ , C ₂ F ₆ , C ₄ F ₈ ...., for etching silicon or silicon oxide. Etc. can be used, Preferably CF ₄ gas can be used.

FIG. 5 shows a change in the etching rate of PR (in a CF series) and silicon and silicon oxide according to an acceleration voltage when CF ₄ is used as an etching gas and 15 sccm. The incident angle to the reflector was 5 degrees and the RF power was 300W.

According to the graph of FIG. 5, as the acceleration voltage is changed from 100 V to 400 V, silicon and silicon oxide show similar etching rates, and when the acceleration voltage is 400 V, the maximum etching rate of silicon and silicon oxide is maximum (approximately, 180 to 180 V). 230 s / min). In addition, it can be seen that the etching rate between silicon and silicon oxide is almost the same as the acceleration voltage changes. That is, the etch rate of silicon and silicon oxide at an acceleration voltage of 100 V is approximately 25 kW / min, and the etching rate of silicon at an acceleration voltage of 200 V is approximately 47 kW / min, while the etching rate of silicon oxide is slightly larger than that. 49 Å / min, the etch rate of silicon is 75 Å / min at an acceleration voltage of 300 V, while the etch rate of silicon oxide is greater than 80 Å / min, and the etch rate of silicon is approximately 180 Å / min at an acceleration voltage of 400 V The etching rate of silicon oxide is larger than about 210 mA / min.

In FIG. 5, PR also shows that the etch rate increases with an increase in the acceleration voltage (approximately 400 μs / min at an acceleration voltage of 400 V), and the etching rate of the doubler PR is greater than that of silicon and silicon oxide. .

In FIG. 8, a neutral beam etching apparatus is used, and the other conditions are the same. The etching rate change of silicon and silicon oxide according to the acceleration voltage when SF ₆ and 15 sccm are used as the etching gas is shown.

Also in FIG. 8, the etching rate of silicon and silicon oxide increases with the change of acceleration voltage. However, the etching rate difference between silicon and silicon oxide is remarkably large when compared with FIG. That is, at 100V acceleration voltage, the etching rate of silicon is about 58nm / min while the etching rate of silicon oxide is much smaller than 2.2nm / min. The etching rate of oxide is about 5 nm / min smaller than that, and the etching rate of silicon is 110 nm / min at the acceleration voltage of 300V, while the etching rate of silicon oxide is about 10 nm / min, and the etching rate of silicon at the acceleration voltage of 400V. Is about 130 nm / min while the etching rate of silicon oxide is about 15 nm / min.

Therefore, according to the graph of FIG. 8, when the SF ₆ gas is used, the etching rate of silicon is much larger than the etching rate of silicon oxide (approximately 10 times). Therefore, SF ₆ is used as the etching gas. When using a neutral beam etching apparatus, it can be seen that it is not easy to etch silicon and silicon oxide together.

6 shows the etching rate of PR and silicon and silicon oxide by varying the flow rate of CF ₄ gas from ₄ sccm to 20 sccm. In the graph of FIG. 6, the incident angle of the ion beam to the reflector was 5 °, the RF power applied to the ion beam source was 300W, and the acceleration voltage was 400V.

In FIG. 6, as shown in FIG. 5, the etching rate difference between silicon and silicon oxide is small and increases constantly as the flow rate changes. On the other hand, in Figure 6, PR also can be seen that the etching rate is increased with the increase in the flow rate, it can be seen that the etching rate of the doubler PR than silicon and silicon oxide.

5 and 6, when using CF ₄ gas, it can be seen that silicon and silicon oxide are etched without spontaneous etching. That is, the graphs of FIGS. 5 and 6 show that the etching apparatus of the present invention, that is, the neutral beam etching apparatus, and the etching of silicon and silicon oxide can be etched using CF ₄ as an etching gas.

Meanwhile, silicon and silicon oxide may be etched using an additive gas together with the CF-based etching gas. As such additive gas, for example, O ₂ , Ar, N ₂ , H _2, or the like can be used, and preferably H ₂ gas is used.

7 shows that CF ₄ is used as an etching gas, H ₂ is used as an additive gas, and H ₂ / is increased while increasing the amount of H ₂ from 0 to 10.5 sccm while reducing CF ₄ from 15 sccm to 4.5 sccm. It is a graph showing the change of PR and the etching rate of silicon and silicon oxide when (H ₂ + CF ₄ )% is changed from 0% to 70%. In the graph of FIG. 7, the incident angle of the ion beam to the reflector was 5 degrees, the RF power applied to the ion beam source was 300W, and the acceleration voltage was 400V.

In FIG. 7, the region of H ₂ / (H ₂ + CF ₄ )% in the range of approximately 20% to 65% is important. That is, as the amount of H ₂ added increases from 3 sccm to 10.5 sccm, the etching rate of PR is lower than that of silicon and silicon oxide. That is, by using the additive gas H ₂ together with the CF ₄ gas, the etching selectivity of the etched material (eg, silicon and silicon oxide) and PR can be adjusted.

Photo 2 below is a SEM photograph showing a cross-sectional etching state of silicon etched using a neutral beam by CF ₄ , by adjusting the selectivity ratio of PR and silicon using CF ₄ gas and H ₂ gas to etch it. As shown in the drawing, the side is vertically etched without side etching.

[Photo 2]

According to the above description, in the present invention, by etching the silicon layer using CF ₄ as an etching gas, side etching is not performed by spontaneous etching, and symmetrical etching is performed as shown in the photograph 2.

Further, by using the added gases with a CF ₄ gas etching, because each substance able to adjust the etching selectivity ratio of the (e. G., Silicon and silicon oxide) and PR, CF ₄ for silicon and silicon oxide using a PR in an atmosphere easily Can be etched.

Claims (16)

Extracting and accelerating an ion beam having a constant polarity from the ion source; Converting the ion beam into a neutral beam by controlling the incident angle of the ion beam incident on the reflector in the accelerated ion beam etching apparatus; And placing an etched substrate on a path of the neutral beam to etch a material layer formed of at least one of silicon, silicide, silicon oxide, silicon nitride, and silicon oxynitride on the etched substrate by the neutral beam. Made up of steps, In the ion beam extraction and acceleration step, neutral etching method characterized in that for extracting the ion beam using a CF-based gas as an etching gas. The method of claim 1, wherein the CF-based gas is a gas of C _X F _Y (X = 1-5, Y = 4-8). The neutral beam etching apparatus of claim 1, further comprising, for example, O ₂ , Ar, N ₂ , or H ₂ as an additive gas together with the etching gas in the ion beam extraction and acceleration step. Etching method. The method of claim 1, wherein the reflector comprises a plurality of reflector holes or slit portions that are reflected after the incident ion beam collides at a predetermined incident angle. The method of claim 3, wherein the etching gas is CF ₄ and the additive gas is H ₂ . The etching method according to claim 1 or 4, wherein an incident angle of the ion beam incident on the surface of the reflector hole or the slit portion in the reflector is within 15 degrees. The etching method according to claim 1 or 4, wherein an angle of incidence of the ion beam incident on the surface of the reflector hole or the slit portion in the reflector is in the range of 3 ° to 15 °.  The etching method according to claim 1 or 4, wherein an incident angle of the ion beam incident on the surface of the reflector hole or the slit portion in the reflector is 3 °.  The etching method according to claim 1 or 4, wherein a reflection angle of the ion beam reflected from the surface of the reflector hole or the slit portion in the reflector is 40 ° or less. The neutralizer according to claim 1 or 4, wherein the reflector hole or the slit portion of the reflector is made of a conductive mirror surface or a metal substrate such as a semiconductor substrate, a diamond-like carbon (DLC), and a glassy carbon. Etching method using beam etching device. The method of claim 1, wherein the ion source is a capacitively coupled RF type ion beam source, a helicon wave coupled ion beam source, an anion source, an electron-cyclotron reactor (ECR) ion beam source, or an inductively coupled plasma source. Etching method using a neutral beam etching apparatus, characterized in that any one of. The method of claim 1, wherein the ion source is an inductively coupled plasma source. The method of claim 1, wherein the specific material layer on the etched substrate is silicon, silicide, silicon oxide, silicon nitride, or silicon oxynitride. The method of claim 5, wherein the supply amount of CF ₄ , which is the etching gas, is 15 sccm to 4.5 sccm, and the supply amount of H ₂ , which is the additive gas, is 0 to 10.5 sccm. The method of claim 1, wherein the RF power applied to the ion beam source is 300W, and the acceleration voltage of the ion beam incident on the reflector is 400V. The etching method according to claim 1 or 4, wherein the reflector hole or the slit portion in the reflector is inclined at a predetermined angle with respect to the direction in which the ion beam goes straight.

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