JP5305734B2 - Dry etching method - Google Patents

Description

  The present invention relates to a dry etching method in a semiconductor device manufacturing process.

2. Description of the Related Art Conventionally, dry etching that forms deep holes and grooves (hereinafter referred to as trenches) and via holes in a substrate made of a silicon-based material in a semiconductor device manufacturing process is known. In order to form a trench, using an apparatus having a plasma generation source, sulfur hexafluoride (hereinafter referred to as SF ₆ ) and a deposition gas (that is, a protective film generation gas) that are etching gases in the reaction processing chamber. Patent Document 1 discloses a dry etching method in which octafluorocyclobutane (hereinafter referred to as C ₄ F ₈ ) is alternately switched and etching and deposition are repeated.

In dry etching, there is a problem of a black silicon phenomenon in which a reaction product during etching is deposited on a non-etched surface. Patent Document 2 discloses a dry etching method and a dry etching apparatus that can monitor the occurrence and signs of the black silicon phenomenon and prevent the occurrence of the black silicon phenomenon.
JP 2004-327606 A JP 2006-186221 A

In a conventionally known dry etching method, etching is optimized by changing conditions such as chamber pressure, electrode temperature, gas flow rate, high-frequency power supply power, and back He pressure. For example, a trench having a stable shape is formed by making the power of the high-frequency power source constant every time SF ₆ and C ₄ F ₈ flow in.

However, as the processing time of dry etching advances, C ₄ F ₈ is also generated from deposits (that is, neutral particles generated during deposition) attached to the side wall in the chamber, and SF ₆ is supplied during etching. There is a problem that the etchant at the time (that is, neutral particles generated during etching) is insufficient, the amount of deposit during deposition is larger than usual, and the trench shape is not uniform. In such a state, there is also a problem that leads to the occurrence of the black silicon phenomenon.

  The present invention has been made in view of the circumstances as described above, and even when the dry etching process time is long, while maintaining the balance between the etchant and the deposit at a constant condition, the trench shape is uniform. Provided is a dry etching method capable of preventing formation and occurrence of a black silicon phenomenon.

  In order to solve the above-described problem, a dry etching method for performing dry etching on a substrate to be processed in a reaction processing chamber having a supply port and an exhaust port, and protecting the etching gas and the reaction chamber through the supply port. A gas supply step for selectively supplying a film-forming gas; an energy supply step for supplying high-frequency energy into the reaction processing chamber in parallel with the gas supply step; and a predetermined time from the start of the gas supply step And adjusting the opening degree of the exhaust port according to the pressure in the reaction processing chamber, and adjusting the opening degree of the exhaust port to make the opening degree of the exhaust port constant after the predetermined time has elapsed. A dry etching method is provided.

  In the gas supply step, the flow rate of the etching gas may be set to 600 sccm, and the flow rate of the protective film generating gas may be set to 250 sccm. Further, in the energy supply step, the high frequency energy may be set to 1800 W at the time of supplying the etching gas, and 1500 W at the time of supplying the protective film forming gas.

The etching gas may be sulfur hexafluoride (SF ₆ ), and the protective film generation gas may be cyclooctane octafluoride (C ₄ F ₈ ).

  The gas supply step includes a step of supplying a reactive gas that reacts with the protective film formed by the protective film forming gas after the supply of the protective film generating gas and before the supply of the etching gas. May be included.

  While the etching gas and the protective film forming gas are alternately switched in the reaction processing chamber and supplied via the supply port, high frequency energy is supplied into the reaction processing chamber to perform dry etching, and within a predetermined time from the gas supply start time. Since the opening of the exhaust port of the reaction processing chamber is adjusted according to the pressure in the reaction processing chamber, and the opening of the exhaust port of the reaction processing chamber is adjusted to be constant after a predetermined time has elapsed, the dry etching processing time is long. Even in this case, it is possible to form a uniform trench shape and prevent the occurrence of the black silicon phenomenon while keeping the balance between the etchant and the deposit at a constant condition.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  First, a dry etching apparatus 10 used in a dry etching method as an embodiment of the present invention will be described in detail with reference to FIG.

As shown in FIG. 1, the dry etching apparatus 10 includes a reaction processing chamber 14 including a plasma generation unit 11, a diffusion unit 12, and a substrate installation unit 13. An antenna 15 that supplies high-frequency energy to the plasma generation unit 11 is disposed around the plasma generation unit 11, and a high-frequency power source 16 is connected to the antenna 15. A supply port 17 is provided in the upper part of the plasma generation unit 11, and flow rate control devices 19 a to 19 c including mass flow meters are connected to the supply port 17 through a supply line 18. An SF ₆ gas source 20a, a C ₄ F ₈ gas source 20b, and a He gas source 20c, which are supply gases, are connected to each of the flow rate control devices 19a to 19c.

  The diffusion unit 12 is provided with a pressure gauge 21 that measures the pressure inside the diffusion unit 12. Connected to the pressure gauge 21 is a valve control device 22 for adjusting the opening of a valve, which will be described later.

  The substrate installation unit 13 is provided with an exhaust port 23, and the exhaust port 23 is connected to a valve 24 for adjusting the opening degree and pressure of the exhaust port 23. A turbo molecular pump 26 is connected to the exhaust side of the valve 24 via an exhaust line 25. Further, a dry pump 27 is connected to the exhaust side of the turbo molecular pump 26 via an exhaust line 25.

  In addition, an electrode 28 is provided below the substrate setting portion 13, and a substrate holder 29 for mounting the substrate is provided on the electrode 28. A high frequency power supply 30 is connected to the electrode 28.

  Next, a dry etching method using the above-described etching apparatus 10 will be described in detail.

  First, the etching apparatus 10 is prepared, and a silicon substrate or an epi substrate and a substrate are inserted from a substrate insertion port (not shown) provided on the side surface of the substrate setting unit 13 and placed on the substrate holder 29. Note that a resist mask for forming a desired trench shape may be formed over the substrate.

Next, SF ₆ used as an etching gas and He used as a carrier gas are supplied to the plasma generation unit 11. At this time, the flow rate of SF ₆ is desirably set to 600 sccm by the flow rate control device 19a. The pressure measured by the pressure gauge 21 is preferably about 4 Pascals, and the pressure in the reaction processing chamber 14 may be controlled by the flow rate control devices 19a and 19c so as to be such pressure.

Next, in the plasma generator 11, high-frequency energy is supplied from the high-frequency power supply 16 through the antenna 15 in order to generate SF ₆ high-density plasma. At this time, the power value of the high frequency power supply is desirably set to 1800W. The high-density plasma of SF ₆ generated by supplying high-frequency energy moves in the direction of the substrate holder 29 on which the substrate is installed when a predetermined electrode is supplied to the electrode 28 (for example, 50 W). To do. The high-density plasma of SF ₆ that has moved to the substrate placement unit 13 comes into contact with the substrate and reacts (that is, the substrate is etched).

  The reactive gas or the unreacted gas in the substrate installation unit 13 is exhausted to the dry pump 27 side by the turbo molecular pump 26. At this time, the opening degree of the valve 24 is freely adjusted by the valve control device 22 according to the pressure measured by the pressure gauge 21. That is, when the pressure value in the diffusing unit 12 changes, the opening degree of the exhaust port 23 is adjusted by adjusting the opening degree of the valve 24 so as to keep the pressure value constant.

After supplying SF ₆ for 3.5 seconds, the supply of SF ₆ is stopped by the flow rate control device 19a. Simultaneously with the stop of the supply of SF ₆ , C ₄ F ₈ as a protective film generating gas is supplied by the flow rate control device 19b. At this time, it is desirable to set the flow rate of C ₄ F ₈ to 250 sccm by the flow rate control device 19b. The pressure measured by the pressure gauge 21 is preferably about 2.5 Pascals, and the pressure in the reaction processing chamber 14 may be controlled by the flow rate control devices 19a and 19c so as to be such pressure.

In the case where C ₄ F ₈ is supplied instead of SF ₆ and the plasma generator 11 is supplied, it is desirable to set the power value of the high frequency power supply to 1500 W. The high density plasma of C ₄ F ₈ generated by supplying the high frequency energy moves in the direction of the substrate holder 29 on which the substrate is installed. The high-density plasma of SF ₆ that has moved to the substrate placement unit 13 comes into contact with the substrate and reacts (that is, a protective film is formed on the substrate).

Even when C ₄ F ₈ is supplied to the plasma generator 11, the opening of the valve 24 is adjusted according to the pressure value so that the pressure value measured by the pressure gauge 21 is constant. The opening degree of 23 will be adjusted.

After supplying C ₄ F ₈ for 1.2 seconds, the supply of C ₄ F ₈ is stopped by the flow rate control device 19b. C ₄ SF _6, again at the same time supply and stop of F ₈ was supplied for 3.5 seconds, again supplying C ₄ F ₈ 1.2 seconds after the supply of SF _6. A desired trench shape is formed by alternately supplying such SF ₆ and C ₄ F ₈ .

Here, when the processing time of dry etching becomes longer, C ₄ F ₈ is generated from the deposit attached in the reaction processing chamber 14, and the pressure in the reaction processing chamber 14 increases. The amount of the supply amount is reduced etchant SF ₆ when the supply of SF ₆ by adjusting the degree of opening of the valve 24 in response to a pressure change becomes insufficient. Therefore, the following processing is performed.

After a predetermined time has passed since the supply of SF ₆ and C ₄ F ₈ is repeated, the valve 24 is adjusted to a constant opening without depending on the pressure value of the pressure gauge 21, and the opening of the exhaust port 23 is adjusted. To be constant. That is, the opening degree of the exhaust port 23 is always a constant opening degree without depending on the pressure value of the pressure gauge 21.

  Here, it is desirable that the timing of stopping the opening degree adjustment of the exhaust port 23 is a state in which the depth of the trench exceeds 30 μm. Therefore, the predetermined time mentioned above is a time obtained by calculating or measuring in advance a time when the depth of the trench exceeds 30 μm.

As described above, when the dry etching processing time exceeds a predetermined time (that is, when the trench depth is 30 μm or more), the deposition amount deposited in the reaction processing chamber 14 is kept constant by keeping the opening of the valve 24 constant. The constant SF ₆ can be always supplied without depending on the pressure change accompanying the amount of C ₄ F ₈ generated from the. Therefore, variations in trench shape can be prevented.

The process of supplying SF ₆ and C ₄ F ₈ is referred to as a gas supply process, the process of supplying high-frequency energy using the high-frequency power source 30 is referred to as an energy supply process, and the opening degree of the valve 24 is adjusted. The step of adjusting the opening degree of the exhaust port 23 depending on the pressure change or adjusting without depending on the pressure change is referred to as an exhaust port opening degree adjusting step.

  Next, the shape of the trench formed by the dry etching method as an embodiment of the present invention will be described in detail with reference to FIGS. 2 (a) and 2 (b).

  As shown in FIG. 2A, a pillar 42 having a predetermined thickness is formed on the upper surface (that is, the etching surface) of the substrate 41. For example, the pillar 42 may be formed in a U-shape as shown in FIG. Moreover, the pillar 42 may be formed in other shapes according to the resist mask. The height of the pillar 42 increases with the processing time of dry etching. That is, as the etching amount of the substrate 41 increases, the height of the pillar 42 increases. As shown in FIG. 2B, the side surface of the pillar 42 is formed in a wave shape including a portion where etching proceeds and a portion where etching does not proceed. Hereinafter, the wavy shape of the side surface of the pillar 42 is referred to as scallop.

  Next, the relationship between the width of the pillar 42 and the pressure value of the pressure gauge 21 will be described in detail with reference to FIG.

  The horizontal axis of the graph shown in FIG. 3 is the pressure value of the pressure gauge 21, and the vertical axis is the width of the pillar 42. In FIG. 3, the top three portions of pillars 42 (Piller tops [1] to [3]) that are farthest from the non-etched surface of the substrate 41 and the most non-etched surface of the substrate 41 The change of the width | variety of the bottom part 3 (Pillar bottom [1] to [3]) of the pillar 42 which is a part is shown. As shown in FIG. 3, when the pressure value is large, the variation in the width of the pillar 42 becomes large, and the trench shape varies. On the other hand, when the pressure value is small, the variation in the width of the pillar 42 is small, and the variation in the trench shape is also small. That is, when the opening degree of the valve 24 is reduced, the variation in the trench shape is large, and when the opening degree is increased, the variation in the trench shape is reduced. Therefore, it is desirable to increase the opening of the valve 24 and reduce the pressure in the reaction processing chamber 14.

Next, the relationship between the number of residues, the scallop width, and the etching rate with respect to the ratio of the set power of the high-frequency power supply 16 when SF ₆ is supplied and the set power of the high-frequency power supply 16 when C ₄ F ₈ is supplied will be described with reference to FIG. The details will be described.

The horizontal axis of the graph shown in FIG. 4 is the ratio between the set power of the high frequency power supply 16 when SF ₆ is supplied and the set power of the high frequency power supply 16 when C ₄ F ₈ is supplied, and the vertical axis is the number of residues and scallops. The width (μm) and the etching rate (μm / min).

As shown in FIG. 4, the set power of the high frequency power supply 16 when supplying SF ₆ during etching is higher than the set power of the high frequency power supply 16 when supplying C ₄ F ₈ during protective film generation. By doing so (that is, when the horizontal axis of the graph is smaller than 1.0), the etching rate can be increased, the number of residues can be reduced, and the scallop width can be increased. On the other hand, by setting the set power of the high-frequency power supply 16 at the time of supplying SF ₆ during etching to be lower than the set power of the high-frequency power supply 16 at the time of supplying C ₄ F ₈ at the time of protective film generation (ie, graph In the case where the horizontal axis is larger than 1.0), the etching rate can be lowered, the number of residues can be increased, and the scallop width can be reduced. That is, a desired scallop can be formed by adjusting the set power of the high-frequency power supply 16 without changing the supply amounts of SF ₆ and C ₄ F ₈ .

  In addition, when the horizontal axis is about 1.16 or more, the number of residues exceeds about 125. Hereinafter, such a state (that is, the horizontal axis is 1.16 or more) is referred to as a large residue region. The set power of the high frequency power supply 16 may be adjusted so that dry etching is not performed in the large residue region.

  As described above, according to the dry etching method of the present embodiment, the high-frequency energy is supplied into the reaction processing chamber while the etching gas and the protective film forming gas are alternately switched and supplied in the reaction processing chamber. Since the opening degree of the exhaust port is adjusted according to the pressure in the reaction processing chamber within a predetermined time from the start of supply, and the opening degree of the exhaust port in the reaction processing chamber is adjusted to be constant after the predetermined time has elapsed, the dry etching process Even when the time is long, it is possible to form a uniform trench shape and prevent the occurrence of the black silicon phenomenon while keeping the balance between the etchant and the deposit at a constant condition.

In the above-described embodiment, SF ₆ and C ₄ F ₈ are used as the reaction gas, but O ₂ may be used as the reaction gas. Specifically, the depot may be removed by supplying O ₂ for a predetermined time after supplying C ₄ F _{8 and} before supplying SF ₆ . Depot removal efficiency can be adjusted by adjusting the voltage setting of the high frequency power supply when O _{2 is} supplied. That is, if the voltage setting of the high-frequency power supply when O _{2 is} supplied is increased, the removal of the deposit is facilitated and the etching is facilitated. On the other hand, when the voltage setting of the high-frequency power supply during O ₂ supply is lowered, the lower part of the trench shape (that is, the part adjacent to the unetched substrate surface) becomes thinner, and a tapered shape can be formed.

1 is a schematic configuration diagram of a dry etching apparatus for carrying out a dry etching method as an embodiment of the present invention. (A) is a perspective view of a trench shape formed by a dry etching method as an embodiment of the present invention, and (b) is an enlarged view of a broken line part of FIG. 2 (a). It is a graph which shows the relationship between the pillar width formed by the dry etching method as an Example of this invention, and a pressure. It is the graph which showed the fluctuation | variation of the residue number with respect to the high frequency power supply power ratio in the dry etching method as an Example of this invention, a scallop, and an etching rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dry etching apparatus 14 Reaction processing chamber 16 High frequency power supply 17 Supply port 21 Pressure gauge 22 Valve control apparatus 23 Exhaust port 24 Valve 26 Turbo molecular pump 27 Dry pump

Claims (4)

A dry etching method for performing dry etching in a depth direction of at least one of a hole, a groove, and a via hole on a substrate to be processed in a reaction processing chamber having a supply port and an exhaust port,
A gas supply step of installing a substrate to be processed in the reaction processing chamber and selectively supplying an etching gas and a protective film forming gas into the reaction processing chamber through the supply port;
An energy supply step of supplying high-frequency energy into the reaction processing chamber in parallel with the gas supply step;
Within a predetermined time from the start of the gas supply step, the opening of the exhaust port is adjusted according to the pressure in the reaction chamber, and the opening of the exhaust port is made constant after the predetermined time has elapsed. possess an adjustment process, the,
In the gas supply step, the flow rate of the etching gas is set to 600 sccm, and the flow rate of the protective film generating gas is set to 250 sccm.
The dry etching method according to claim 1, wherein the predetermined time in the exhaust opening degree adjusting step is a time when at least one depth of the hole, groove and via hole is 30 μm . Wherein the energy supplying step, the said high-frequency energy during the etching gas supply and at 1800W, the dry etching method according to claim 1, characterized in that the at 1500W when the protective film forming gas supply. 3. The method according to claim 1, wherein the etching gas is sulfur hexafluoride (SF ₆ ) and the protective film forming gas is cyclobutane octafluoride (C ₄ F ₈ ). The dry etching method as described. The gas supplying step includes a step of supplying a reactive gas that reacts with the protective film formed by the protective film generating gas after the protective film generating gas is supplied and before the etching gas is supplied. the dry etching method according to claim 1 to 3 or 1, wherein the.

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