TWI401741B - Plasma etching method - Google Patents

Description

Plasma etching method

The present invention relates to a plasma etching method including an engineering of etching a processed object using plasma.

In the manufacturing process of a semiconductor device, the process of etching the laminated film is repeatedly performed using a patterned photoresist or the like. For example, in the manufacturing process of the gate electrode, a ruthenium oxide film or a tantalum nitride film which is to be a gate insulating film and a polysilicon layer to be a gate electrode are formed on the semiconductor substrate in this order. A hard mask film made of tantalum nitride or the like, an anti-reflection film made of ruthenium oxide or the like, and a photoresist film. Then, the photoresist film patterned by photolithography is used as a mask to dry-etch the anti-reflection film and the hard mask. Then, after removing the photoresist film by ashing, the hard mask is used as a mask. The process of etching the polysilicon layer by the curtain performs gate electrode formation.

At this time, when the antireflection film and the hard mask film are etched, a plasma etching apparatus for etching an insulating film is used, and when the polysilicon is etched, a plasma etching apparatus dedicated to ruthenium etching is used. Furthermore, the ashing removal of the photoresist is performed using a dedicated ashing device.

Further, for the tantalum substrate, the STI (Shallow Trench Isolation) for forming the trench for element isolation is prepared by, for example, laminating a tantalum oxide film, a tantalum nitride film, or a silicon oxynitride (SiON) film on the tantalum substrate. , oxide cover film and photoresist film. Then, the photoresist formed by photolithography is used as a mask to etch the oxide mask film, yttrium oxynitride (SiON) film, tantalum nitride film, and hafnium oxide film. Next, an oxide mask, a silicon oxynitride (SiON) film, and a nitride film are used as a mask to etch the germanium substrate, and a trench is formed on the germanium substrate. At this time, when etching the oxide mask film, the yttrium oxynitride (SiON) film, the tantalum nitride film, and the hafnium oxide film, an etching device for etching an insulating film is used, and when etching the germanium substrate, germanium etching is used. Special etching device. Furthermore, the ashing removal of the photoresist is performed using a dedicated ashing apparatus.

As described above, the conventional etching process must be performed by first etching the hard mask using a photoresist film to transfer the photoresist pattern to the hard mask before etching the germanium layer, and then performing at least two stages of the germanium etching using the hard mask. Etching works. This is because when the photoresist is to be etched as a mask, the mask selection ratio cannot be sufficiently obtained, and it is difficult to ensure the etching rate, or the density of the pattern such as the line and the pitch or the central portion of the semiconductor wafer. The in-plane position of the peripheral portion or the like causes a difference in an etching shape such as an angle or a critical dimension (CD: Critical Dimensin) of the trench sidewall formed by the etching.

In addition, since the gas system used for the etching of the insulating film and the etching is different, the etching is mainly performed by a gas having a strong corrosiveness, or the etching precision of each gas is lowered, etc., and the insulating film must be used separately for the object to be etched. The etching apparatus and the etching apparatus dedicated to the crucible (for example, Patent Document 1).

[Patent Document 1] Japanese Patent Laid-Open No. Hei 7-263415 (paragraphs 0006 to 0010)

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plasma etching method which can ensure a sufficient mask selection ratio and etching rate, and which uses a photoresist as a mask to etch a layer of tantalum in a laminated film. In addition to this, it is also provided that in the above etching, there is no plasma etching method which causes a difference in etching shape due to the density of the pattern or the position on the object to be processed.

In order to solve the above problems, the plasma etching method according to the first aspect of the present invention is directed to a ruthenium layer having ruthenium as a main component and a photoresist film formed on the ruthenium layer and patterned in advance. The treatment body is etched by using the plasma generated from a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas as a mask. The above-mentioned layer of engineering.

Further, in the plasma etching method according to the second aspect of the present invention, in the processing chamber of the plasma processing apparatus, at least a tantalum layer containing ruthenium as a main component and at least an upper layer than the tantalum layer are laminated. The film, the tantalum nitride film, and the object to be processed which is patterned in advance, use a plasma generated from a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas, and The photoresist film is used as a mask to etch the tantalum nitride film, the tantalum oxide film, and the tantalum layer together.

In the above first aspect and second aspect, the fluorocarbon gas is preferably CF ₄ gas, C ₂ F ₆ gas, C ₃ F ₈ gas or C ₄ F ₈ gas. Further, the hydrofluorocarbon gas is preferably CHF ₃ gas, CH ₂ F ₂ gas or CH ₃ F gas.

Further, the flow rate of the fluorocarbon gas is preferably 10 to 50 mL/min. Further, the flow rate of the above O ₂ gas is preferably from 1 to 30 mL/min. Further, the flow ratio (hydrogen fluoride gas flow rate/rare gas flow rate) of the hydrofluorocarbon gas to the rare gas is preferably from 0.019 to 0.173.

Further, the treatment pressure is preferably 8 to 12 Pa.

Further, in the first aspect and the second aspect described above, it is preferable to control the critical dimension after etching of the portion of the pattern and the close portion by the flow rate of the fluorocarbon gas or the O ₂ gas. Further, the critical dimension after the in-plane etching of the object to be processed is controlled by the flow rate of the fluorocarbon gas.

Further, in the second aspect, the processing pressure at the time of etching the tantalum layer is lowered with respect to the processing pressure at the time of etching the tantalum nitride film, or when the tantalum nitride film is etched The flow rate of the hydrofluorocarbon gas is preferably such that the flow rate of the hydrofluorocarbon gas at the time of etching the tantalum layer is lowered.

Further, in the above first aspect and second aspect, it is preferable that the tantalum layer is a polycrystalline germanium or a single crystal germanium as a main component.

A third aspect of the present invention provides a control program for operating on a computer, and controlling the plasma processing apparatus to perform a plasma etching method of the first aspect or the second aspect during execution.

A fourth aspect of the present invention provides a computer readable memory medium readable by a computer for storing a control program for operating on a computer In the media, when the control program is executed, the plasma processing apparatus is controlled to perform the plasma etching method of the first aspect or the second aspect.

According to a fifth aspect of the present invention, there is provided a plasma processing apparatus comprising: a processing chamber for performing a plasma etching treatment on a target object; a support body on which the object to be processed is placed in the processing chamber; a gas exhausting means for supplying a processing gas into the processing chamber; and a control portion for controlling the plasma etching method of the first aspect or the second aspect in the processing chamber.

According to the plasma etching method of the present invention, etching can be sufficiently ensured by using a gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas as a processing gas. Rate, and the photoresist is used as a mask to perform etch etching.

Furthermore, by adjusting the flow rate of the fluorocarbon gas or the O ₂ gas, the angular difference of the side wall of the etching groove due to the density of the pattern or the critical dimension after etching due to the position on the object to be processed can be removed. Poor, uniformizing the etching shape.

Therefore, with the plasma etching method of the present invention, in the germanium etching process, substantial reduction of the number of engineering and shortening of the processing time can be achieved. Further, since the plasma method of the present invention can make the etching shape uniform, it is advantageously used in a semiconductor device having high reliability, and can correspond to a semiconductor The design rules of the body device are fine and high.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic cross-sectional view showing a magnetron RIE plasma etching apparatus 100 which can be optimally used in the plasma etching method of the present invention. The plasma etching apparatus 100 is formed into a cylindrical shape having a step formed by the small-diameter upper portion 1a and the large-diameter lower portion 1b, and the wall portion is, for example, a chamber (processing container) 1 made of aluminum.

In the chamber 1, a support base 2 for horizontally supporting a semiconductor wafer (hereinafter referred to as "wafer") W as a single crystal Si substrate to be processed is provided. The support base 2 is made of, for example, aluminum and is supported by the support base 4 of the conductor via the insulating plate 3. Further, on the periphery of the support base 2, a focus ring 5 formed of a material other than Si such as quartz is provided. The support base 2 and the support base 4 are lifted and lowered by a ball screw mechanism including a ball screw 7, and the drive portion below the support base 4 is covered by a bellows 8 made of stainless steel (SUS). A bellows cover 9 is provided on the outer side of the bellows 8. Further, a baffle 10 is provided on the outer side of the focus ring 5, and is electrically connected to the chamber 1 through the baffle 10, the support base 4, and the bellows 8. The chamber 1 is grounded.

An exhaust port 11 is formed on a side wall of the lower portion 1b of the chamber 1, and an exhaust system 12 is connected to the exhaust port 11. Then, by operating the vacuum pump of the exhaust system 12, the inside of the chamber 1 can be depressurized to a specific degree of vacuum. another Further, on the upper side of the side wall of the lower portion 1b of the lower portion 1 of the chamber 1, a gate valve 13 for opening and closing the inlet of the switch wafer W is provided.

The high frequency power source 15 for plasma formation is connected to the support base 2 via the integrator 14, and high frequency power of a specific frequency such as 13.36 MHz is supplied from the high frequency power source 15 to the support table 2. Further, a shower head 20 is disposed in parallel with the support table 2, and the shower head 20 is grounded. Therefore, the support base 2 and the shower head 20 function as a pair of electrodes.

An electrostatic chuck 6 for holding the wafer W by electrostatic attraction is provided on the surface of the support base 2. The electrostatic chuck 6 is configured such that an electrode 6a is formed between the insulators 6b, and a DC power source 16 is connected to the electrodes 6a. Then, a voltage is applied from the power source 16 to the electrode 6a, and the wafer W is adsorbed by the electrostatic force such as Coulomb force.

A cold coal chamber 17 is disposed inside the support base 2, and cold coal is introduced into the cold coal introduction pipe 17a, and is discharged from the cold coal discharge pipe 17b to circulate, and the cold heat is passed through the support base 2 The wafer W is heat transferred, whereby the processed surface of the wafer W is controlled to a desired temperature.

Furthermore, even if the chamber 1 is kept evacuated by the exhaust system 12, the wafer W can be effectively cooled by the cold coal circulating in the cold coal chamber 17, and the cooling gas is supplied to the gas introduction mechanism 18 by means of the gas introduction mechanism 18. The gas supply tube 19 is introduced between the surface of the electrostatic chuck 6 and the back surface of the wafer W. By introducing the cooling gas in this way, the cold heat of the cold coal is efficiently transmitted to the wafer W, and the cooling efficiency of the wafer W can be improved. As the cooling gas, for example, He or the like can be used.

The above-described shower head 20 is disposed to face the support base 2 in the wall portion of the chamber 1. The shower head 20 is provided with a plurality of gas discharges underneath The hole 22 has a gas introduction portion 20a at the upper portion, and a space 21 is formed inside thereof. A gas supply pipe 24 having a valve 23 is connected to the gas introduction portion 20a, and a process gas supply system 25 for supplying a processing gas composed of an etching gas and a diluent gas is connected to the other end of the gas supply pipe 24.

The processing gas supply system 25 has a CF ₄ gas supply source 41, a CHF ₃ gas supply source 42, an Ar gas supply source 43, and an O ₂ gas supply source 44 as shown in Fig. 2, and is supplied from the gas supply sources. The piping is provided with a mass flow controller 45 and a valve 46, respectively. Then, CF ₄ gas/CHF ₃ gas/Ar gas/O ₂ gas as an etching gas is supplied from the gas supply pipe 24 and the gas introduction unit 20a to the respective shower heads 20 through the gas supply pipe 20 and the gas introduction unit 20a. The space 21 is discharged from each of the gas discharge holes 22.

Further, a dipole ring magnet 30 is concentrically arranged around the upper portion 1a of the chamber 1. The dipole ring magnet 30 is formed as shown in the horizontal cross-sectional view of Fig. 3, and a plurality of anisotropic segmented columnar magnets 31 are attached to the outer casing 32 of the annular magnetic body. In this example, 16 anisotropic segmented columnar magnets 31 constituting a columnar shape are arranged in a ring shape. In Fig. 3, the arrow shown in the anisotropic segmented columnar magnet 31 indicates the direction of magnetization, and as shown in the figure, the magnetization of the most anisotropic segmented columnar magnet 31 is shifted little by little. In the direction, the entire horizontal magnetic field B is formed in one direction.

Therefore, in the space between the support base 2 and the shower head 20, as shown schematically in Fig. 4, the electric field EL in the vertical direction is formed by the high-frequency power source 15, and the level is formed by the dipole ring magnet 30. Magnetic field B, by doing so The resulting orthogonal electromagnetic field generates a magnetron discharge. Accordingly, a plasma of an etching gas of a high energy state is formed, and the wafer W is etched.

Further, each component of the plasma etching apparatus 100 is configured to be connected to a process controller 50 including a CPU. The process controller 50 is connected to a user interface 51 such as a keyboard that is displayed by the engineering manager to manage the input operation of the plasma etching apparatus 100, or a display that visualizes the operating state of the plasma etching apparatus 100. .

Further, the process controller 50 is connected with a memory portion 52 storing a process recipe for recording a control program or processing condition for realizing various processes performed by the plasma etching device 100 by the control of the process controller 50. Information, etc.

Then, according to the instruction from the user interface 51, the process controller 50 is executed by calling the arbitrary process recipe from the memory unit 52, and under the control of the process controller 50, the plasma etching apparatus 100 is used. Execute what you want. Furthermore, the process recipe can be stored at any time by a computer-readable memory medium such as a CD-ROM, a hard disk, a floppy disk, a flash memory, or the like, or transmitted from other devices via, for example, a dedicated return line. Use it.

Next, an etching method of the present invention which performs electro-crystalline etching on a wafer W having a tantalum layer (single crystal germanium or polycrystalline germanium) will be described with reference to the plasma etching apparatus 100 configured as described above.

First, the gate valve 13 is opened, and the wafer W is introduced into the chamber 1. After being placed on the support base 2, the support base 2 is raised to the position shown in the figure, and the vacuum pumping of the exhaust system 12 is performed.埠11 inside the exhaust chamber 1.

Then, the processing gas supply system 25 introduces a processing gas containing an etching gas and a diluent gas into the chamber 1 at a specific flow rate, so that the inside of the chamber 1 becomes a specific pressure, and the state is supplied from the high-frequency power source 15 in a specific state. High frequency power to the support base 2. At this time, the wafer W is applied to the electrode 6a of the electrostatic chuck 6 from the DC power source 16 by the specific voltage, for example, by the Coulomb force, and is held by the electrostatic chuck 6, and belongs to the shower head 20 belonging to the upper electrode and belongs to the lower electrode. A high frequency electric field is formed between the support seats 2. Since the horizontal magnetic field B is formed by the dipole ring magnet 30 between the shower head 20 and the support base 2, an orthogonal electromagnetic field is formed in the processing space between the electrodes of the wafer W, and magnetic waves are generated according to the drift generated thereby. Control the discharge. Then, the wafer W is etched in accordance with the plasma of the etching gas formed by the discharge of the magnetron.

It is preferable to use a gas containing CF ₄ , CHF ₃ , or O ₂ as an etching gas from the viewpoint of ensuring sufficient selection of the mask ratio and etching rate, and performing control of the etching shape. The CF ₄ gas generates a F radical (F*) mainly contributing to etching by a reaction mainly represented by CF ₄ →CHF ₃ *+F* in the plasma. The F radical is etched by reacting a ruthenium oxide film, a tantalum nitride film, or a ruthenium layer into the following formula (Reaction 1) to (Reaction 3).

(Reaction 1) SiO ₂ +4F* → SiF ₄ ↑+O ₂

(Reaction 2) Si ₃ N ₄ +12F* → 3SiF ₄ ↑+2N ₂ ↑

(Reaction 3) Si+4F* → SiF ₄ ↑

When the CHF ₃ gas is added to the CF ₄ described above, HF is generated to reduce the F radical, and by forming a CH or CF-based polymer, these functions as a protective film, and the selectivity to the photoresist is increased.

The Ar gas acts to promote the dissociation reaction of the above-mentioned F radicals, and has the effect of maintaining the uniformity of the radical distribution in the plasma. Further, there is also an effect of removing a film which is an etching reaction by sputtering.

Further, the O ₂ gas is on the bottom surface of the groove or the hole after the etching, and has an excessive stack of the polymer preventing the CH or CF system.

In order to make the etching shape good, it is also effective to adjust the temperature of the wafer W. Therefore, a cold coal chamber is provided, and the cold coal chamber 17 is circulated to cool coal, which heat is transferred to the wafer W via the support base 2, and the treated surface of the wafer W is controlled to a desired temperature.

In order to form a desired plasma, the high frequency power source 15 for plasma generation appropriately sets the frequency and output. In the ruthenium etching, it is preferable to set the frequency to, for example, 13.56 MHz or more in order to increase the plasma density immediately above the wafer W.

In order to increase the plasma density directly above the wafer W, the dipole ring magnet 30 applies a magnetic field to the processing space between the support 2 and the shower head 20 belonging to the counter electrode, in order to effectively exert the effect, so that the processing space is formed. The strength of the magnetic field of 10000 μT (100 G) or more is preferred. Although the stronger the magnetic field strength, the effect of increasing the plasma density should be increased, but from the viewpoint of safety, it is preferably 100000 μT (1 kg) or less.

The optimum conditions for collectively etching the laminated film using the plasma etching apparatus 100 are as follows.

For example, CF ₄ can be set to 10 to 50 mL/min (sccm), more preferably 20 to 40 mL/min (sccm), and CHF ₃ can be set to 10 to 100 mL/min (sccm). More preferably, it is 20 to 70 mL/min (sccm), Ar can be set to 100 to 2000 mL/min (sccm), more preferably 300 to 1200 mL/min (sccm), and O ₂ can be set to 1 to 30 mL/ Min (sccm) is preferred, and more preferably 6 to 15 mL/min (sccm).

Furthermore, since the etching rate is ensured and the uniformity of the etching shape is ensured (that is, the inclination angle difference of the side wall of the etching groove due to the density of the pattern is suppressed, the critical dimension difference due to the in-plane position of the wafer is suppressed) From the viewpoint, it is preferable to set the flow ratio to CF ₄ /CHF ₃ /Ar/O ₂ =1~3/2~4/20~40/0.5~2.

The treatment pressure is preferably from 1.3 to 40 Pa, more preferably from 5 to 13.3 Pa, from the viewpoint of ensuring etching of the ruthenium oxide film, the tantalum nitride film, and the tantalum layer.

Further, from the viewpoint of increasing the degree of dissociation of the etching gas, the frequency of the high frequency of the high frequency power source 15 is set to 13.56 MHz, and the high frequency power is set to divide the high frequency power supplied to the lower electrode by the surface area of the substrate. The size of the electric power is preferably 300 W to 500 W (0.96 W/cm ² to 1.59 W/cm ² ).

Further, from the viewpoint of controlling the anisotropy of the etching shape to be good, it is preferable to adjust the wafer temperature to, for example, 40 to 70 °C.

[First Embodiment]

Fig. 5 is a view schematically showing a cross-sectional structure of a target object 110 such as a semiconductor wafer W to which the plasma etching method of the first embodiment is applied. The body 110 is to be processed in the upper silicon substrate 101 is formed a silicon oxide (SiO ₂₎ in order from below the membrane 102, silicon nitride (Si ₃ N ₄₎ film 103, the polysilicon layer 104; silicon nitride (Si ₃ N ₄ The film 105 and the inorganic anti-reflection film (Barc) 106 are formed thereon with a photoresist (PR) 107 formed in advance. This etching process is to form the gate electrode by using the polysilicon layer 104 as an electrode layer, and the yttrium oxide (SiO ₂ ) film 102 and the tantalum nitride (Si ₃ N ₄ ) film 103 serve as a gate insulating film.

In the conventional etching method, in the object to be processed 110 in the state of FIG. 5, the photoresist (PR) 107 is first used as the mask etching antireflection film 106 and the tantalum nitride (Si ₃ N ₄ ) film 105. Next, after the photoresist (PR) 107 is removed by ashing, the tantalum nitride (Si ₃ N ₄ ) film 105 is used as a hard mask to etch the polysilicon layer 104. Then, when the anti-reflection film 106 and the tantalum nitride (Si ₃ N ₄ ) film 105 are etched, an etching device dedicated to etching an insulating film is used, and when the polysilicon layer 104 is etched, an etching device dedicated to ruthenium is used. Further, the ashing removal of the photoresist (PR) 107 is performed using a dedicated ashing apparatus.

On the other hand, in the plasma etching method according to the present embodiment, a plasma containing fluorocarbon gas, hydrofluorocarbon gas, rare gas, and O ₂ gas, such as CF ₄ /, is used in the plasma etching apparatus 100. CHF ₃ /Ar/O ₂ is used as a processing gas, and the photoresist (PR) 107 is used as a mask to etch the anti-reflection film (Barc) 106 and the tantalum nitride (Si ₃ N ₄ ) film 105 according to the pattern thereof. The polysilicon layer 104, the tantalum nitride (Si ₃ N ₄ ) film 103, and the hafnium oxide (SiO ₂ ) film 102. By collectively etching the laminated film, in one stage of etching, as shown in Fig. 6, the concave portion 108 can be formed.

[Second Embodiment]

Fig. 7 is a view schematically showing a cross-sectional structure of a target object 210 such as a semiconductor wafer to which the plasma etching method of the second embodiment is applied. The object to be processed 210 is formed above the tantalum substrate 201, and a tantalum oxide (SiO ₂ ) film 202, a tantalum nitride (Si ₃ N ₄ ) film 203, a hafnium oxynitride (SiON) film 204, and tantalum oxide are sequentially formed from below. The (SiO ₂ ) film 205 is further formed thereon with a photoresist (PR) 206 formed in advance. This etching process is one of the trenches 207 for forming an insulating film for embedding on the germanium substrate 201 by STI.

In the conventional etching method, the object to be processed 210 in the state of FIG. 7 is first etched with a photoresist (PR) 206 as a mask to etch a yttrium oxide (SiO ₂ ) film 205 and a yttrium oxynitride (SiON) film. 204, a tantalum nitride (Si ₃ N ₄ ) film 203 and a yttrium oxide (SiO ₂ ) film 202, and then, after removing the photoresist (PR) 206 by ashing, the yttrium oxide (SiO ₂ ) film 205, oxygen nitrogen The bismuth (SiON) film 204 and the tantalum nitride (Si ₃ N ₄ ) film 203 are used as a mask to etch the substrate 201. Then, when the yttrium oxide (SiO ₂ ) film 205, the yttrium oxynitride (SiON) film 204, the tantalum nitride (Si ₃ N ₄ ) film 203, and the yttrium oxide (SiO ₂ ) film 202 are etched, the insulating film is used for etching. The etching apparatus uses an etching apparatus dedicated to ruthenium when the ruthenium substrate 201 is etched. Furthermore, the ashing removal of the photoresist (PR) is performed using a dedicated ashing apparatus.

On the other hand, in the plasma etching method according to the present embodiment, the plasma etching apparatus 100 is used, and a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas, such as CF ₄ /CHF, is used. ₃ /Ar /O ₂ as a processing gas, thereby etching a yttrium oxide (SiO ₂ ) film 205, a yttrium oxynitride (SiON) film 204, a tantalum nitride (Si ₃ N ₄ ) film 203, and yttrium oxide (SiO ₂ ) film 202 and tantalum substrate 201. By etching the laminated film together, the trench 207 for insulating film can be formed on the germanium substrate 201 as shown in FIG. 8 in one etching process.

As is apparent from the above first and second embodiments, by using the processing gas of the specific combination described above, it is possible to etch a laminate containing at least a tantalum layer and an insulating film in a single process by using a single etching apparatus. Subtraction of devices derived from sharing, and significant reductions in engineering numbers and processing time.

Next, the present invention will be further described by way of examples and test examples, but the present invention is not limited to the examples.

Example 1

For the object to be processed 110 having the laminated structure shown in FIG. 5, the plasma etching apparatus 100 is used, and etching is performed using CF ₄ /CHF ₃ /Ar/O ₂ as an etching gas, and the photoresist (PR) is used. 107 is used as a mask to form a recess 108. Here, as the photoresist (PR) 107, a material having a film thickness of 400 nm and an elemental composition of C, H, F, and O is used, and a film thickness of the anti-reflection film (Barc) 106 is 58 nm, and tantalum nitride ( The film thickness of the Si ₃ N ₄ ) film 105 was 60 nm, and the film thickness of the polysilicon layer 104 was 65 nm. Further, the line and pitch of the photoresist (PR) 107 pattern were set to be 0.6 μm in line and 0.24 μm in pitch.

The etching conditions are as follows.

CF ₄ /CHF ₃ /Ar/O ₂ =20/25/300/10mL/min(sccm)

Pressure = 13.3Pa (100mTorr)

RF frequency (high frequency power supply 15) = 13.56MHz

RF power = 400W (1.27W/cm ² )

Back pressure (center/edge) = 1066Pa/2000Pa (8/15 Torr; He gas)

Distance between upper and lower electrodes = 27mm

Temperature (upper electrode / chamber side wall / lower electrode) = 60 ° C / 60 ° C / 30 ° C

Etching time = 11 seconds

The results of the etching time are shown in Table 1.

The upper CD (CD of the interface between the anti-reflection film (Barc) 106 and the tantalum nitride film 105; Critical Dimension) is also in the center portion and the edge portion of the wafer W (see FIG. 9(c)). It is 270 nm and can be uniformly etched in the plane of the wafer W. Further, it was confirmed that the remaining film thickness of the photoresist (PR) 107 was sufficient to ensure the selection ratio of the photoresist mask. Further, the "plane" in the residual film thickness of the resist in the table means the film thickness of the flat surface of the photoresist (PR) 107 (the total thickness of the photoresist), and the "abrasive surface" means the ion sputtering or the like. When the corner portion of the photoresist (PR) 107 is collapsed (so-called shoulder peeling), the thickness of the shoulder-removed portion is reduced by the full thickness of the photoresist (PR) film 107.

Example 2

For the object to be processed 210 having the laminated structure shown in Fig. 7, the plasma etching apparatus 100 is used, and etching is performed using CF ₄ /CHF ₃ /Ar/O ₂ as an etching gas, and the photoresist (PR) is used. 206 acts as a mask to form a trench 207. Here, as the photoresist (PR) 206, a material having a film thickness of 320 nm and an elemental composition of C, H, F, and O is used, and a cerium oxide (SiO ₂ ) film 205 having a film thickness of 20 nm is used, and the film thickness is The film is a 32 nm yttrium oxynitride (SiON) film 204, a tantalum nitride (Si ₃ N ₄ ) film 203 having a film thickness of 265 nm, and a yttrium oxide (SiO ₂ ) film 202 having a film thickness of 8 nm. Further, the photoresist (PR) 206 pattern has a line width of 0.17 μm and a trench width of 0.18 μm.

The etching conditions are as follows.

CF ₄ /CHF ₃ /Ar/O ₂ =20/25/300/10mL/min(sccm)

Pressure = 13.3Pa (100mTorr)

RF frequency (high frequency power supply 15) = 13.56MHz

RF power = 400W (1.27W/cm ² )

Back pressure (center/edge) = 933Pa/5332Pa (7/40 Torr; He gas)

Distance between upper and lower electrodes = 27mm

Temperature (upper electrode / lower electrode) = 60 ° C / 30 ° C

Etching time = 130 seconds

The results of the etching time are shown in Table 2.

Even in the central portion and the edge portion of the wafer W, the upper CD (the CD at the interface between the yttrium oxide film 202 and the tantalum nitride film 203 in this experiment) is 206 nm, and the CD at the bottom of the trench 207 is 174 nm, so in the crystal Uniform etching in the surface of the circle.

Further, it is shown that the trench depth and the sidewall angle (180°-θ; refer to FIG. 8) of the substrate 201 to be formed are the same in the center portion and the edge portion of the wafer W, and high in-plane uniformity is obtained for the etching shape. .

Next, tests were conducted on the effects of the etching rate, the mask selection ratio, and the etching shape. In this test, a sample wafer having the laminated structure shown in Fig. 9(a) was used. The sample wafer has a structure in which a tantalum oxide (SiO ₂ ) film 302, a tantalum nitride (Si ₃ N ₄ ) film 303, and a photoresist film 304 are laminated on a tantalum substrate 301. Then, using CF ₄ /CHF ₃ /Ar/O ₂ as a processing gas, etching was performed according to the experimental method shown in Table 3 to change the etching conditions, and the concave portion 305 was formed. The etching rate at this time, the selection ratio of the photoresist mask, and the etching shape were measured.

Further, in terms of other conditions in the etching, the RF frequency (high-frequency power source 15) is 13.56 MHz, the RF power is 300 W (0.96 W/cm ² ), and the back pressure (center portion/edge portion) is 933 Pa/ 2666 Pa (7/20 Torr; He gas), the distance between the upper and lower electrodes was 27 mm, and the temperature (upper electrode/lower electrode) was 60 ° C / 30 ° C.

The results of the etching rate and the selection ratio of the photoresist mask are shown in Table 4 and Figures 10 to 13. Further, the results of etching the shape are shown in Table 5 and Figs. 14 to 21. Further, in Fig. 10 to Fig. 13, the horizontal axis represents the flow ratio of CHF ₃ /AF, and the vertical axis represents the processing pressure.

Fig. 10 is a graph showing the etching selectivity of the tantalum nitride (Si ₃ N ₄ ) film 303 to the photoresist film 304. Therefore, if the mask selection ratio of the yttrium nitride (Si ₃ N ₄ ) film 303 is set to 1 or more, it can be seen from Fig. 10 that a sufficient mask can be obtained substantially within the set condition range. Choose ratio. Further, by selecting the condition that the flow ratio of CHF ₃ /Ar is large and the processing pressure is high (the upper right area of Fig. 10), the mask selection ratio can be improved.

Fig. 11 is a view showing the etching rate of the tantalum nitride (Si ₃ N ₄ ) film 303. From Fig. 11, it can be seen that the treatment pressure is not effective as a condition for increasing the etching rate of the tantalum nitride (Si ₃ N ₄ ) film 303. Instead, the flow ratio of CHF ₃ /Ar is increased in the set condition range. effective.

The twelfth graph etches the etching selectivity of the photoresist film 304 of the substrate 301 to the photoresist film 304. Since the selection ratio of the mask to the mask is one or more, it can be seen from Fig. 12 that substantially the mask selection ratio is substantially obtained in the set condition range. Further, by selecting the condition that the flow ratio of CHF ₃ /Ar is large and the processing pressure is high (the region on the upper right in Fig. 12), the mask selection ratio in the ruthenium etching can be further improved.

Fig. 13 is a view showing the etching rate of the germanium substrate 301. This Fig. 13 shows that in the set condition range, when the flow ratio of CHF ₃ /Ar is large, the processing pressure is small to obtain a high etching rate, and when the flow ratio of CHF ₃ /Ar is small, the processing pressure is large. One side achieves a high etching rate.

Based on the above results, in order to improve the mask selection ratio when the tantalum nitride (Si ₃ N ₄ ) film 303 and the tantalum substrate 301 are used, in the condition range of Table 3, high pressure is set and high CHF ₃ is set. The /Ar flow ratio is valid. At this time, the etching rate of the tantalum nitride (Si ₃ N ₄ ) film 303 is also improved. Further, when the etching rate of the ruthenium substrate 301 is emphasized, as shown in Fig. 13, when the flow ratio of CHF ₃ /Ar is large, the processing pressure is preferably small, and the flow ratio of CHF ₃ /Ar is preferably For the hour, the processing pressure is preferably good, and the flow rate of CHF ₃ or the processing pressure is preferably changed during the etching.

For example, in the stage of etching the tantalum nitride (Si ₃ N ₄ ) film 303, sufficient mask selection ratio and etching rate should be obtained, and the high pressure and CHF ₃ /Ar flow ratio are set in the condition range of Table 3, At the stage of the ruthenium etching after the concave portion 305 reaches the ruthenium substrate 301, the flow rate of the CHF ₃ is kept as it is, so that the processing pressure is lowered, or the opposite processing pressure is maintained as it is, so that the flow rate of the CHF ₃ is lowered, thereby improving the etching rate of the ruthenium substrate 301. At this time, if the selection ratio of the mask to the mask is one or more, it can be seen from the result of FIG. 12 that there is no fear of increasing the selection ratio of the mask.

Further, at the stage of etching the tantalum nitride (Si ₃ N ₄ ) film 303, the processing pressure and the CHF ₃ /Ar flow ratio can be set low in the condition range of Table 3, and at this time, the concave portion 305 is reached. The ruthenium etching stage after the substrate 301, for example, the CHF ₃ flow rate is maintained as it is, so that the processing pressure is increased, or the processing pressure is kept constant, so that the CHF ₃ flow rate is increased, whereby the etching rate of the ruthenium substrate 301 can be improved.

Next, the results of the "angle difference of the side walls between the dense patterns" in Table 5 and the results of Figs. 14 to 17 corresponding to the above will be described.

As a result of Table 5, since the uniformity of the etching shape on the wafer W was confirmed, the difference in the inclination angle of the side wall of the groove in the measuring device was measured by the following method. The difference in the inclination angle of the side wall is measured by the inclination angle θ 1 of the side wall of the concave portion 305 of the dense portion shown in Fig. 9(b) and the inclination angle θ 2 of the side wall of the concave portion 305 of the sparse portion, by the difference [(the inclination angle of the side wall of the sparse portion) θ 2) - (the side wall inclination angle θ 1 of the dense portion) is calculated.

Fig. 14 to Fig. 17 are Table 5 showing the results relating to the difference in the inclination angle of the side wall, and the dispersion analysis was performed. From this, the tendency of the side wall inclination angle to fluctuate with respect to the fluctuation of each process parameter (pressure, CF ₄ flow rate, CHF ₃ /Ar flow ratio, O ₂ flow rate) is known.

More specifically, as shown in Fig. 9 (a) to (c), the inclination angles of the side walls of the portion where the pattern is separated from the center portion and the edge portion of the wafer W are measured at three places, and the average value thereof is obtained. value. Similarly, the inclination angle of the side wall of the dense portion of the center portion and the edge portion of the wafer W was measured at three places, and the average value was obtained. Then, the difference between the average value of the inclination angles of the side walls of the alienation portion and the average value of the inclination angles of the side walls of the tight portion is determined, and the vertical axis (unit: degree) of the graphs of Figs. 14 to 17 is obtained. It means that the absolute value of the vertical axis is small, and the difference in the density of the inclination angle of the side wall is smaller.

According to Fig. 14, it is shown that, for the pressure, among the set conditions, 9.3 to 10.6 Pa (70 to 80 mTorr) is good, and when the pressure is larger or smaller, the inclination angle of the side wall caused by the density of the pattern is different. The tendency to expand.

According to Fig. 15, for the flow ratio of CHF ₃ and Ar to CHF ₃ /Ar, it is found that when the flow ratio becomes larger (that is, the CHF ₃ flow rate is increased), there is a difference in the inclination angle of the side wall due to the density of the pattern. In the tendency to expand, it is difficult to cancel the difference in the inclination angle of the side wall by the flow ratio CHF ₃ /Ar.

From Fig. 16, it can be confirmed that the CF ₄ flow rate tends to decrease as the side wall tilt angle difference generated by the pattern is reduced as the flow rate is increased in the set condition range. Similarly, with reference to Fig. 17, it is also confirmed that the O ₂ flow rate tends to decrease as the side wall inclination angle difference decreases as the flow rate is increased within the set condition range. Therefore, it can be seen that by adjusting the CF ₄ flow rate and/or the O ₂ flow rate, it is possible to control the difference in the inclination angle of the side wall due to the pattern density.

Next, the results of "CD difference in the wafer surface" in Table 5 and the results of Figs. 18 to 21 corresponding thereto will be described.

As a result of the results shown in Table 5, since the uniformity of the etching shape of the wafer W was confirmed, the difference in the critical dimension (CD: Critical Dimension) in the wafer surface was measured by the following method. The CD was obtained by measuring the width at the interface between the yttrium oxide (SiO ₂ ) film 302 and the tantalum nitride (Si ₃ N ₄ ) film 303 as shown in Fig. 9(b).

More specifically, the CD of the center portion and the edge portion of the wafer W was measured at each of three places, and the average value was obtained. Then, the average value of the CD of the center portion and the difference between the average values of the CDs at the edge portions are obtained as "CD difference in the wafer surface" in Table 5. The dispersion analysis was performed on the results of the CD difference in Table 5, which is the 18th to 21st drawings. Accordingly, it can be seen that the difference in CD in the wafer surface tends to vary with respect to each of the process parameters (pressure, CF ₄ flow rate, CHF ₃ /Ar flow ratio, O ₂ flow rate). Therefore, the vertical axis of the graph is the CD difference (in nm) in the wafer plane.

With the 18th and 21st drawings, there is not much difference in the set pressure range for the treatment pressure and the O ₂ flow rate. According to Fig. 19, for the flow ratio CHF ₃ /Ar, it is confirmed that the flow ratio is increased in the set condition range (that is, the CHF ₃ is increased), and the CD difference tends to be smaller, suggesting that Adjusting the flow ratio to CHF ₃ /Ar, you can control the in-plane difference of the CD.

Furthermore, with reference to Fig. 20, it was confirmed that the CF ₄ flow rate tends to decrease in the in-plane difference of the CD as the flow rate is increased in the set condition range. Accordingly, it was found that by adjusting the CF ₄ flow rate, the in-plane difference of the CD can be controlled.

When the above results (Fig. 14 to Fig. 21) are combined, it is effective to adjust the flow rate of the CF ₄ flow rate in order to improve the difference in the inclination angle of the side wall caused by the density of the pattern and the CD difference in the in-plane position. In order to achieve this, it is preferred to set the flow rate of CF ₄ to, for example, 20 to 40 mL/min (sccm). Further, in order to improve the difference in the inclination angle of the side wall caused by the density of the pattern, it is also effective to adjust the flow rate of O ₂ , and in order to achieve the object, it is preferable to set the flow rate of O ₂ to 6 to 15 mL/min (sccm).

As a result, according to the plasma method of the present invention, the photoresist can be used as a mask to etch the insulating film and the laminate film including the tantalum layer. According to this, it is possible to greatly shorten the formation of, for example, the gate electrode of the transistor or the formation of the trench for element isolation by STI.

Further, it is possible to suppress variations in the shape of the wafer W in the in-plane, or to change the etching shape due to the density of the pattern, and to ensure uniformity of the etching shape.

Therefore, the transistor etching method of the present invention can be suitably utilized in the manufacture of various semiconductors.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above embodiment, the dipole ring magnet is used as the magnetic field forming means of the magnetron RIE plasma etching apparatus. However, the present invention is not limited thereto, and it is not always necessary to form a magnetic field. Further, if the plasma can be formed by the gas type of the present invention, any device can be used, and each of a capacitive coupling type or an inductive coupling type can be used. A plasma etching device.

[Industrial use feasibility]

The present invention can be suitably used in the process of manufacturing various semiconductor devices such as transistors.

1‧‧‧chamber (processing container)

2‧‧‧Support (electrode)

12‧‧‧Exhaust system

15‧‧‧High frequency power supply

18‧‧‧ gas introduction mechanism

20‧‧‧Sprinkler

25‧‧‧Processing gas supply system

30‧‧‧ Dipole ring magnet

101‧‧‧矽 substrate

102‧‧‧Oxide film (SiO ₂ )

103‧‧‧ nitride film (Si ₃ N ₄ )

104‧‧‧Polysilicon layer

105‧‧‧ nitride film (Si ₃ N ₄ )

106‧‧‧Anti-reflection film (Barc)

107‧‧‧Light Resistance (PR)

110‧‧‧Processed body

201‧‧‧矽 substrate

202‧‧‧Oxide (SiO ₂ ) film

203‧‧‧ nitrided (Si ₃ N ₄ ) film

204‧‧‧ oxynitride (SiON)

205‧‧‧Oxide (SiO ₂ ) film

206‧‧‧Light Resistance (PR)

301‧‧‧矽 substrate

302‧‧‧Oxide (SiO ₂ ) film

303‧‧‧ nitrided (Si ₃ N ₄ ) film

304‧‧‧Light Resistance (PR)

W‧‧‧ wafer

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view showing a magnetron RIE plasma etching apparatus which is an implementation of the method of the present invention.

Fig. 2 is a structural view of the processing gas supply system in Fig. 1.

Fig. 3 is a horizontal sectional view schematically showing a dipole ring magnet arranged around the chamber of Fig. 1.

Fig. 4 is a schematic view for explaining an electric field and a magnetic field formed in a chamber.

Fig. 5 is a schematic cross-sectional view showing a laminated structure of a semiconductor wafer to which the present invention is applied.

Fig. 6 is a view showing a cross section of the semiconductor wafer after etching.

Fig. 7 is a schematic view showing a cross section of a laminated structure of a semiconductor wafer to which another example of the method of the present invention is applied.

Fig. 8 is a view showing a cross section of the semiconductor wafer after etching.

Fig. 9 is a view showing a sample wafer (a) used in the test, (a) showing a cross section before etching, (b) showing a cross section after etching, and (c) showing a measurement position of a CD on the surface of the sample wafer.

Figure 10 shows the nitridation when the gas flow ratio and pressure are changed. The etch film is selected for the etching of the photoresist mask.

Fig. 11 is a view showing the etching rate of tantalum nitride when the gas flow rate ratio and the pressure are changed.

Figure 12 is a graph showing the etching selectivity of the photoresist mask when the gas flow ratio and pressure are changed.

Fig. 13 is a view showing the etching rate of 矽 when the gas flow rate ratio and pressure are changed.

Fig. 14 is a view showing a change in the inclination angle of the side wall due to the density of the pattern when the pressure is changed.

Fig. 15 is a view showing a change in the inclination angle of the side wall due to the density of the pattern when the CHF ₃ /Ar flow ratio is changed.

Fig. 16 is a view showing a change in the inclination angle of the side wall due to the density of the pattern when the flow rate of CH ₄ is changed.

Fig. 17 is a view showing a change in the inclination angle of the side wall due to the density of the pattern when the flow rate of O ₂ is changed.

Fig. 18 is a view showing a change in critical dimension difference due to the in-plane position of the wafer when the pressure is changed.

Fig. 19 is a view showing a change in the inclination angle of the side wall due to the in-plane position of the wafer when the CHF ₃ /Ar flow ratio is changed.

Fig. 20 is a view showing a change in critical dimension difference due to the in-plane position of the wafer when the CF ₄ flow rate is changed.

Fig. 21 is a view showing a change in critical dimension difference due to the in-plane position of the wafer when the flow rate of O ₂ is changed.

1‧‧‧chamber (processing container)

2‧‧‧Support plate (electrode)

3‧‧‧Insulation board

4‧‧‧Support table

5‧‧‧ Focus ring

7‧‧‧Ball screw

8‧‧‧ Bellows

9‧‧‧Corrugated tube cover

10‧‧ ‧Band

11‧‧‧Exhaust gas

12‧‧‧Exhaust system

14‧‧‧matcher

15‧‧‧High frequency power supply

17‧‧‧Cold coal room

18‧‧‧ gas introduction mechanism

19‧‧‧ gas supply pipe

20‧‧‧Sprinkler

21‧‧‧ Space

22‧‧‧ gas discharge hole

23‧‧‧Valves

24‧‧‧ gas supply piping

25‧‧‧Processing gas supply system

30‧‧‧ Dipole ring magnet

W‧‧‧ wafer

Claims (6)

A plasma etching method comprising: a tantalum layer having a tantalum-based composition, and an uppermost layer of the tantalum layer, at least a laminated tantalum oxide film, tantalum nitride, and light patterned in advance The object to be treated of the resist film is a plasma generated from a processing gas containing a fluorocarbon gas, a hydrofluorocarbon gas, a rare gas, and an O ₂ gas, and the photoresist film is used as the resist film. The ruthenium oxide film and the tantalum nitride film are etched by a mask, and the fluorocarbon gas is controlled at 20 to 40 mL/min, and the O ₂ gas is controlled at 6 to 15 mL/min. The plasma etching method according to claim 1, wherein the fluorocarbon gas is CF ₄ gas, C ₂ F ₆ gas, C ₃ F ₈ gas or C ₄ F ₈ gas. The plasma etching method according to claim 1, wherein the hydrofluorocarbon gas is CHF ₃ gas, CH ₂ F ₂ gas or CH ₃ F gas. The plasma etching method according to the first aspect of the invention, wherein the flow ratio of the hydrofluorocarbon gas to the rare gas (hydrofluorocarbon gas flow rate/rare gas flow rate) is from 0.019 to 0.173. The plasma etching method according to the first aspect of the invention, wherein the processing pressure is 8 to 12 Pa. The plasma etching method according to claim 1, wherein the tantalum layer is mainly composed of polycrystalline germanium or single crystal germanium.