JP5785818B2 - Processing method by cluster - Google Patents

Description

  The present invention relates to a processing method for etching or cleaning a substrate surface by a reactive cluster generated from a reactive gas, and includes a reactive gas, an additive gas which is inert to the reactive gas and has a lower boiling point than the reactive gas. The mixed gas consisting of is cooled by a cooling source to a liquefaction temperature near the liquefaction temperature in the mixed gas supply path leading to the nozzle outlet, and blown into the vacuum processing chamber while adiabatically expanding from the nozzle outlet. This is a technique related to a processing method using a cluster that enables processing of a substrate surface at a high speed with little damage to the substrate by processing.

The present applicants have proposed a method using neutral reactive clusters as a method for solving the problems in the case of using cluster ions in etching and cleaning of a substrate (see, for example, Patent Document 1). ).
Further, conventionally, it is known that the nozzle portion is cooled by flowing a cooled dry nitrogen gas into a pipe attached to the nozzle portion, thereby enabling clustering of gases that could not be formed at room temperature (for example, , See Patent Document 2).

  Furthermore, conventionally, a silane gas is cooled with liquid nitrogen to generate a large silane cluster (for example, see Patent Document 3).

WO / 2010/021265 JP-A-8-127867 Japanese Utility Model Publication No. 62-190334

The conventional technique described in Patent Document 1 generates a neutral reactive cluster by using a reactive gas, and the reactive gas and an additive gas that is inert and has a lower boiling point than that. Because the reactive cluster collides with the substrate and reacts with the substrate surface, the substrate surface can be processed, and since it is a non-ionized electrically neutral cluster, it causes electrical damage to the substrate. Has no advantage.
However, this processing method has a problem that processing performance such as an etching rate is low.

  Generally, in order to increase the processing performance of the cluster, it is possible to increase the concentration of the reactive gas before cluster generation or increase the supply pressure. Such a method has a limit because the formation of clusters due to adiabatic expansion at the nozzle is prevented by liquefaction and separation in the supply path.

In Patent Documents 2 and 3, oxygen gas, nitrogen gas, argon gas or silane gas is cooled as a source gas for generating clusters, and a cluster is generated by jetting from a nozzle, and a substrate is processed by ionization. Have been described.
However, the conventional techniques described in Patent Documents 2 and 3 are both substrate gas processing methods using ionized clusters in which the source gas is not a mixed gas but a single gas, and the source gas is a reactive gas. And there is no suggestion about the action of the cooling of the raw material gas regarding the processing method by the reactive cluster generated from the mixed gas of the reactive gas and the inert and lower boiling point additive gas.

  In the conventional example described in Patent Document 1, the present invention is intended to solve the problem that the processing performance of a substrate by a neutral cluster is low, and is reactive gas, reactive gas, and inert. A mixed gas consisting of an additive gas having a lower boiling point is cooled by a cooling source to near the liquefaction temperature in the mixed gas supply path leading to the nozzle outlet, and blown into the vacuum processing chamber while adiabatically expanding from the nozzle outlet to generate It is an object of the present invention to provide a processing method in which the substrate surface is processed by the neutral reactive cluster, and the substrate can be processed at a high speed with little damage to the substrate.

Processing method according to the cluster of the present invention according to claim 1, the reactive gas, Ri Do from said reactive gas and low-boiling additive gas from the reactive gas an inert, generates a reactive cluster A mixed gas having a primary pressure for cooling from the liquefaction temperature of the mixed gas to a temperature range 10 ° C. higher than the liquefaction temperature by a cooling source in the mixed gas supply path to the nozzle outlet, and adiabatically expand from the nozzle outlet. The reactive cluster is ejected into the vacuum processing chamber to generate a reactive cluster, and the reactive cluster is jetted onto the substrate in the vacuum processing chamber to process the substrate surface.

  The processing method using clusters according to the second aspect of the present invention is the processing method according to the first aspect of the present invention, wherein the reactive gas is an interhalogen compound or hydrogen halide, and the additive gas is a rare gas. It is.

  A processing method using a cluster according to a third aspect of the present invention is the substrate to be processed, in addition to the configuration of the present invention according to the second aspect, wherein the reactive gas is chlorine trifluoride and the additive gas is argon. The surface is a silicon single crystal.

  In addition to the structure of the present invention according to any one of claims 1 to 3, the processing method using clusters according to the present invention according to claim 4 processes the substrate surface while maintaining the temperature of the substrate surface within a predetermined temperature range. It is what I did.

In the processing method using the cluster according to the first aspect of the present invention, the mixed gas is cooled by the cooling source from the liquefaction temperature of the mixed gas to a temperature range higher by 10 ° C. than the liquefaction temperature in the mixed gas supply path leading to the nozzle outlet. As a result, the substrate processing performance such as the etching rate is increased, the substrate is less damaged, and the substrate can be processed at high speed. It was.

  In addition to the effect of the present invention according to claim 1, the processing method using clusters according to the present invention according to claim 2 is because the reactive gas is an interhalogen compound or hydrogen halide, and the additive gas is a rare gas. The processing performance of the substrate can be made higher.

In addition to the effect of the present invention according to claim 2, the processing method using the cluster according to the present invention according to claim 3 is the substrate to be processed, wherein the reactive gas is chlorine trifluoride and the additive gas is argon. Since the surface is a silicon single crystal, processing such as etching in a manufacturing process of a semiconductor substrate or the like can be performed at high speed.
Further, since the reactive gas is chlorine trifluoride and has a high boiling point, the temperature of the cooling source can be increased, and the cost for cooling can be reduced.

  In addition to the effect of the present invention according to any one of claims 1 to 3, the processing method using clusters according to the present invention according to claim 4 processes the substrate surface while maintaining the temperature of the substrate surface within a predetermined temperature range. As a result, the processing performance and the surface state can be appropriately selected according to the required specifications of the substrate surface to be processed.

It is a schematic explanatory drawing which shows the outline of the processing method by the cluster of this invention. It is a figure showing the mixed gas temperature of the nozzle vicinity in the processing method by the cluster of this invention, and the etching rate of the substrate surface. It is a figure showing the temperature of the board | substrate surface and the etching rate of a board | substrate in the processing method by the cluster of this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
A processing method using clusters according to an embodiment of the present invention will be described with reference to the schematic explanatory diagram of FIG.

In FIG. 1, 1 is a mixed gas supply path, 2 is a nozzle, 3 is a cooling source, 4 is a vacuum processing chamber, and 5 is a substrate.
A mixed gas supply unit 11 is connected to the mixed gas supply path 1 via a pressure control valve 12 and a flow rate control valve 13.

As the mixed gas supply unit 11, a mixed gas 14 in which a reactive gas and a reactive gas and an additive gas that is inert and has a lower boiling point than the reactive gas are mixed in a predetermined ratio into a container at a predetermined pressure. In some cases, the gas 14 is stored and supplied, or the reactive gas and the additive gas are stored in separate containers, and the mixed gas 14 is supplied while being adjusted to a predetermined mixing ratio.
The reactive gas needs to have high reactivity with the substrate surface 51 to be processed. When the substrate surface 51 is a silicon single crystal, an interhalogen compound having high reactivity with silicon should be used. preferable.

Examples of the interhalogen compound include chlorine fluoride (ClF), chlorine trifluoride (ClF ₃ ), chlorine pentafluoride (ClF ₅ ), bromine trifluoride (BrF ₃ ), bromine monochloride (BrCl), five Iodine fluoride (IF ₅ ) and iodine heptafluoride (IF ₇ ) can be used.
The reactive gas is a metal material when the substrate surface 51 is a metal material or a semiconductor material other than silicon, such as gallium arsenide (GaAs), indium phosphide (InP), gallium nitride (GaN), or the like. It is preferable to use a hydrogen halide having high reactivity with.

As the hydrogen halide, hydrogen chloride (HCl), hydrogen bromide (HBr), hydrogen iodide (HI), or the like can be used.
In order to generate a reactive cluster, a predetermined pressure is required. However, the reactive gas has a high boiling point, and if the pressure is increased, it is condensed (liquefied) and cannot be adiabatically expanded at the nozzle. The pressure required to generate reactive clusters from only the reactive gas could not be obtained.

Therefore, by mixing an additive gas having a boiling point lower than that of a reactive gas such as an interhalogen compound and hydrogen halide, the partial pressure of the reactive gas is reduced and liquefaction of the reactive gas is prevented. However, a primary pressure sufficient to generate reactive clusters can be obtained.
Further, an additive gas having a boiling point lower than that of the reactive gas is selected in the mixed gas supply unit 11 and in the mixed gas supply path 1 so as to be inert with the reactive gas.

Examples of additive gases that are inert with the reactive gas and have a lower boiling point than the reactive gas include helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). From inert gas, nitrogen (N ₂ ), carbon dioxide (CO ₂ ), oxygen (O ₂ ), etc., select one that is inert and has a lower boiling point than the reactive gas. To do.
The reactive gas and the inert additive gas are selected because a reactive cluster is stably generated when the reactive gas and the additive gas react in the mixed gas supply unit 11 or the mixed gas supply path 1. This is because it may be difficult to process the substrate surface 51.

In this embodiment, the substrate surface 51 is made of silicon single crystal, the reactive gas is ClF ₃ , the additive gas is Ar, the antifreeze is used as the cooling source 3, the antifreeze is cooled by the Blainchler 31 and mixed. An annular antifreeze flow passage 32 is provided on the outer periphery of the gas supply path 1 and the nozzle 2, and the antifreeze flow passage 32 and the evaporator (not shown) of the blownler 31 are connected by a pipe 33 via a circulation pump (not shown). By connecting and circulating the antifreeze liquid, the mixed gas 14 is cooled to near the liquefaction temperature in the mixed gas supply path 1 leading to the nozzle outlet 21.
The vacuum processing chamber 4 is connected to an exhaust passage 44 having an open / close valve 41, a turbo molecular pump 42 and a dry pump 43, and the turbo molecular pump 42 and the dry pump 43 allow the interior of the vacuum processing chamber 4 to be reduced. The secondary pressure is 10 Pa (abs).

The nozzle 2 is a differential pressure between the primary pressure in the mixed gas supply path 1, for example, 0.68 MPa (abs) and the secondary pressure in the vacuum processing chamber 4, for example, 10 Pa (abs). It is an opening that can generate the reactive cluster 45.
In the present invention, in order to increase the processing performance of the reactive cluster 45, the mixed gas 14 composed of the reactive gas and the reactive gas and the additive gas that is inert and has a lower boiling point than the reactive gas, Cooling with the antifreeze liquid (cooling source 3) to near the liquefaction temperature in the mixed gas supply path 1 leading to the nozzle outlet 21, and spraying it into the vacuum processing chamber 4 while adiabatically expanding from the nozzle outlet 21, the neutral reactive cluster 45 Is generated.

As the control for cooling the mixed gas 14 to near the liquefaction temperature, for example, the temperature of the nozzle 2 is detected to control the circulation amount of the antifreeze liquid, or the outlet temperature of the antifreeze liquid in the blownler 31 is controlled by keeping the circulation amount of the antifreeze liquid constant. To do.
By cooling the mixed gas 14 to near the liquefaction temperature by the cooling source 3, the number of the neutral reactive clusters 45 ejected into the vacuum processing chamber 4 is increased or the size is increased (in one cluster). The number of molecules).

The neutral reactive clusters 45 generated in this way are sprayed onto the substrate surface 51 in the vacuum processing chamber 4 to process the substrate surface 51 at a high speed.
Reference numeral 52 denotes a substrate stand for fixing the substrate 5 at a predetermined position.

Here, according to Example 1 below, it was confirmed that the processing performance of the reactive cluster 45 can be improved by cooling the mixed gas 14 to near the liquefaction temperature by the cooling source 3.
Example 1
The substrate surface 51 processed by the reactive cluster 45 in the vacuum processing chamber 4 is made of silicon single crystal, the reactive gas is chlorine trifluoride (ClF ₃ ), and is inactive with the reactive gas (ClF ₃ ). The additive gas having a lower boiling point than the reactive gas (ClF ₃ ) was argon (Ar), and the mixing ratio of the mixed gas 14 was 6% by volume for ClF ₃ and 94% by volume for Ar.
The supply pressure (primary pressure) of the mixed gas 14 in the mixed gas supply path 1 is controlled by the pressure control valve 12 and the flow rate control valve 13 to 0.69 to 0.66 MPa (abs), and the pressure in the vacuum processing chamber 4 is changed. A vacuum of about 10 Pa (abs) was established by the turbo molecular pump 41 and the dry pump 42.
The distance between the nozzle outlet 21 and the substrate surface 51 was 13 mm, and the time for irradiating the reactive surface 45 to the substrate surface 51 was 2 min.
The temperature of the mixed gas 14 in the vicinity of the nozzle outlet 21 cooled by the antifreeze liquid in the mixed gas supply path 1 leading to the nozzle outlet 21 is measured with a thermocouple, and the etching rate of the substrate surface 51 is measured with a stylus type surface shape measuring instrument. Calculated.

FIG. 2 shows the temperature (° C.) of the mixed gas 14 near the nozzle outlet 21 on the horizontal axis and the etching rate (μm / min) of the substrate surface 51 on the vertical axis.
As can be seen from FIG. 2, the etching rate increases as the temperature of the mixed gas 14 decreases. However, when the temperature of the mixed gas 14 is −8 ° C. to −13 ° C., the etching rate decreases, and as the temperature decreases at −8 ° C. to −13 ° C., the flow rate of the mixed gas 14 increases. In the mixed gas supply path 1, liquefaction of ClF ₃ in the mixed gas 14 occurs, indicating that the generation of the neutral clusters 43 due to adiabatic expansion in the nozzle 2 has been partially inhibited. .

Therefore, the cooling of the mixed gas 14 in the mixed gas supply path 1 leading to the nozzle outlet 21 is preferably performed to near the liquefaction temperature of the mixed gas 14 in order to improve the processing performance by the neutral reactive cluster 45.
Here, “near the liquefaction temperature” means that the temperature range is 10 ° C. higher than the liquefaction temperature from the liquefaction temperature, and the boiling point of the reactive gas is higher than the boiling point of the additive gas at normal pressure. The boiling point of each gas is determined from the partial pressure based on the ratio, and it is close to the liquefaction temperature of any gas.

Incidentally, the boiling point of the ClF ₃ is a reactive gas in the first embodiment, since the primary pressure of the mixed gas 14 is ClF ₃ is 6 vol% in the 0.69 MPa (abs), as calculated from the partial pressure of ClF _3, -7.5 ° C.

Next, it was confirmed by Example 2 below how the temperature of the substrate surface 51 affects the processing by the neutral reactive cluster 45.
(Example 2)
In the second embodiment, since it is a confirmation of how the temperature of the substrate surface 51 affects the processing by the reactive cluster 45, the cooling of the mixed gas 14 in the first embodiment is not performed and the mixed gas is not performed. The temperature of the mixed gas 14 in the supply path 1 was normal temperature.
The substrate surface 51 processed by the reactive cluster 45 in the vacuum processing chamber 4 is a silicon single crystal, the reactive gas is chlorine trifluoride (ClF ₃ ), and the reactive gas (ClF ₃ ). The point that the additive gas having a low boiling point was argon (Ar), and the mixing ratio of the mixed gas was 6% by volume of ClF ₃ and 94% by volume of Ar, which was the same as in Example 1.
The supply pressure (primary pressure) of the mixed gas in the mixed gas supply path 1 is controlled by the pressure control valve 12 and the flow rate control valve 13 to 0.82 MPa (abs), and the pressure in the vacuum processing chamber 4 is set to the turbo molecular pump 41 and A vacuum of about 10 Pa (abs) was established by the dry pump 42.
The distance between the nozzle outlet 21 and the substrate surface 51 was 13 mm, and the time for irradiating the reactive surface 45 to the substrate surface 51 was 2 min.

In FIG. 3, the horizontal axis represents the temperature (° C.) of the substrate surface 51, the left vertical axis represents the etching rate of the substrate surface 51 (depth reference: μm / min), and the right vertical axis represents the etching rate of the substrate surface 51 (weight basis). : Mg / min).
According to FIG. 3, the depth-based etching rate (μm / min) increases as the temperature of the substrate surface 51 rises up to 50 ° C., but 50 under the conditions of this Example 2. Above ℃, the depth-based etching rate was almost saturated.

Further, according to FIG. 3, the weight-based etching rate (mg / min) increases even when the temperature of the substrate surface 51 is 50 ° C. or more as the temperature of the substrate surface 51 increases. This is isotropic due to atmospheric exposure. It can be presumed that etching has an influence.
And when the substrate surface 51 was observed after the etching process of the substrate surface 51 in this Example 2, the roughness of the substrate surface 51 tended to decrease by lowering the temperature of the substrate surface 51.

From the results of Example 2, the depth-based etching rate increases up to 50 ° C. by processing the substrate surface 51 by increasing the temperature of the substrate surface 51. Surface roughness becomes remarkable.
Therefore, it is preferable to process the substrate surface 51 while keeping the temperature of the substrate surface 51 in a predetermined temperature range so as to meet the required specifications of the processed substrate surface 51. In particular, the temperature of the substrate surface 51 is set to 50 ° C. More preferably, it is carried out while maintaining the following predetermined temperature range.

  In the conditions of Example 2, the mixed gas 14 was not cooled in order to simplify the conditions, and the mixed gas temperature in the mixed gas supply path 1 was normal temperature. As described above, even when the mixed gas 14 is cooled, the number of neutral reactive clusters 45 can be increased or the size can be increased. It can be assumed that the processing performance of the substrate surface 51 is the same regardless of whether or not the gas 14 is cooled.

In the example of the above embodiment, ClF ₃ is used as a reaction gas and Ar is used as an example of the mixed gas 14, but the mixed gas 14 is adiabatically expanded from the nozzle outlet 21 while being in the vacuum processing chamber 4. It is only necessary that the substrate surface 51 can be processed by the reactive cluster 45 generated by jetting to the surface, and the reactive gas is mixed with the reactive gas and an additive gas that is inert and has a lower boiling point than the reactive gas. If it is.
As the reactive gas, one having high reactivity with the substrate surface 51 to be processed is selected. Chlorine fluoride (ClF), chlorine trifluoride (ClF ₃ ), chlorine pentafluoride (ClF) ₅ ), interhalogen compounds such as bromine trifluoride (BrF ₃ ), bromine monochloride (BrCl), iodine pentafluoride (IF ₅ ), iodine heptafluoride (IF ₇ ), hydrogen chloride (HCl), bromide It is preferable to use a hydrogen halide such as hydrogen (HBr) or hydrogen iodide (HI).

As the additive gas, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and other rare gases, nitrogen (N ₂ ), carbon dioxide (CO ₂ ), oxygen (O ₂ ), etc., which are inert in relation to the selected reactive gas and have a lower boiling point than the reactive gas, are selected according to the physical properties and processing specifications of the substrate surface 51 to be processed. A gas is selected, and an additive gas suitable for the reactive gas is selected.
The mixing ratio of the mixed gas 14 depends on the kind of the reactive gas and the additive gas, the supply pressure of the mixed gas (primary pressure), the degree of vacuum in the vacuum processing chamber 4 (secondary pressure), and the substrate surface 51 to be processed. The physical properties and required processing specifications are comprehensively determined.

In the above embodiment, the mixed gas 14 is cooled by the antifreeze liquid (cooling source 3) cooled by the blownler 31 in the antifreeze flow passage 32 on the outer periphery of the mixed gas supply path 1 provided in the vacuum processing chamber 4. However, the mixed gas supply path 1 may be provided outside the vacuum processing chamber 4 so that the nozzle outlet 21 is opened in the vacuum processing chamber 4.
Further, as the cooling source 3, instead of the antifreeze liquid, the refrigerant of the refrigerator may be directly circulated. When the low-temperature cooling source 3 is required, liquid nitrogen may be used, and the mixed gas 14 is supplied to the nozzle outlet 21. Any cooling source 3 may be used as long as it can be cooled to near the liquefaction temperature in the mixed gas supply path 1 leading to.

In the above embodiment, the mixed gas 14 is cooled to near the liquefaction temperature to improve the processing performance of the substrate 5. The cooling to near the liquefaction temperature is as described above. The liquefaction temperature is cooled to a temperature range 10 ° C. higher than the liquefaction temperature .

DESCRIPTION OF SYMBOLS 1 Mixed gas supply path 2 Nozzle 3 Cooling source 4 Vacuum processing chamber 5 Substrate 14 Mixed gas 21 Nozzle outlet 45 Reactive cluster 51 Substrate surface

Claims (4)

And reactive gases, Ri Do from said reactive gas and low-boiling additive gas from the reactive gas an inert, a mixed gas having a primary pressure to produce reactive cluster, to the nozzle exit in the mixed gas supply passage from the liquefaction temperature of the mixed gas to 10 ° C. temperature range higher than the liquefaction temperature and then cooled by the cooling source is ejected into the vacuum processing chamber while adiabatic expansion from the nozzle outlet, the reactive cluster A processing method using a cluster, wherein the reactive cluster is generated and sprayed onto a substrate in a vacuum processing chamber to process the substrate surface.   2. The cluster processing method according to claim 1, wherein the reactive gas is an interhalogen compound or hydrogen halide, and the additive gas is a rare gas.   3. The cluster processing method according to claim 2, wherein the reactive gas is chlorine trifluoride, the additive gas is argon, and the substrate surface to be processed is a silicon single crystal.   The cluster processing method according to claim 1, wherein the substrate surface is processed while maintaining a temperature of the substrate surface within a predetermined temperature range.

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