JP3752464B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dry etching technique suitable for processing fine and deep grooves and holes in a manufacturing process of a semiconductor device (semiconductor integrated circuit).
[0002]
[Prior art]
The dry etching technique is widely used in the manufacture of semiconductor integrated circuits (LSIs) because fine processing can be easily performed as compared with the wet etching technique using a chemical solution. When the conventional reactive ion etching (RIE) method is used, the gas pressure during etching is 10 mTorr to 100 mTorr, and the reactive gas flow rate is 10 sccm to 100 sccm. In the RIE method, discharge is unstable when the pressure is lower than the lower limit, and isotropic etching is performed when the pressure is higher than the upper limit. In a conventional dry etching apparatus, a pump having an exhaust speed of 1000 l / sec or less is frequently used, and the reaction gas flow rate is selected within a range in which the gas pressure can be set.
[0003]
Japanese Patent Publication No. 52-126174 and Solid State Devices and Materials p207, (1990) (Solid State Devices and Materials P207, (1990)) disclose microwave plasma etching (ECR) technology. In addition, in the dry process symposium p54, (1988), the magnetron discharge type RIE is described in Journal of Vacuum Science Technology B9 (2), 310 (1991) discloses a dry etching apparatus such as a helicon type RIE. The reaction gas pressure of these dry etching apparatuses is 0.5 mTorr or more, and the gas flow rate is 20 sccm or less. For example, in the case of the ECR etching method, the etching rate is polycrystalline silicon as an object to be etched and chlorine (Cl as a reactive gas). ₂ ), A gas pressure of 0.5 mTorr, and a gas flow rate of 20 sccm, a value of about 300 nm / min is obtained.
[0004]
As an example of a conventional dry etching apparatus, a microwave dry etching apparatus is shown in FIG. 101 is a microwave generation unit, 102 is a waveguide, 104 is a reaction gas inlet, 105 is a reaction gas pipe, 106 is a mass flow controller, 107 is an electromagnet for increasing the density of generated plasma, Reference numeral 109 denotes a silicon wafer, 110 denotes a sample stage, 111 denotes a chamber, 112 denotes a high-frequency power source, 114 denotes a vacuum pump, and 117 denotes an etching processing chamber. Microwaves generated by the microwave generation unit 101 travel along the waveguide 102 and are introduced into the chamber 111, and the reaction gas is turned into plasma in the chamber 111. The plasma etches the silicon wafer surface on the sample stage 110. In the dry etching apparatus, one kind of gas is introduced into the chamber 111 using one gas pipe 105 and one mass flow controller 105, and the gas pipe 105 is directly attached to the chamber 111. ing. The area of the opening of the gas inlet 104 is about the cross-sectional area of the gas pipe 105. The gas pressure in the chamber 111 increases as the flow rate of the reaction gas introduced into the chamber increases, and decreases as the effective exhaust speed in the chamber by the vacuum pump 114 increases. A value of several tens sccm is used when the gas pressure is 1 mtorr or higher, and a value of several sccm is used in a low gas pressure region of the order of 0.1 mtorr. The effective pumping speed is determined by the pumping speed of the vacuum pump and the conductance of the pumping system, and is 400 l / sec or less in the conventional apparatus.
[0005]
The processing chamber pressure with respect to the introduced gas flow rate is expressed by the following equation.
[0006]
P = (q + Q) / S (1) formula
Here, P (Torr) is the pressure in the processing chamber (when the pressure varies depending on the location in the processing chamber), q is the amount of leakage from the apparatus when no gas is introduced, and Q is the flow rate of the introduced gas ( Torr · l / sec), S is the effective pumping speed (l / sec) of the apparatus. In a normal case, q is 1/1000 or less of Q and can be almost ignored. In the conventional apparatus, for example, the pumping speed (S ₀ ) Has a turbo molecular pump of about 1000 l / sec or less, the exhaust conductance (C) of the processing chamber is 200 l / sec to 1000 l / sec, and the effective exhaust speed S0 at this time is the exhaust of multiple exhaust pumps From the speeds S1 to Sn (n is a numerical value indicating the number of pumps) and the exhaust conductance C of the vacuum processing chamber,
1 / S0 = (1 / ΣSn) + 1 / C (2)
Conventionally, exhaust was performed at an effective exhaust speed of 100 to 400 l / sec. Therefore, when the gas pressure is set to 0.5 mTorr, the gas flow rate that can be flowed is 4 to 20 sccm.
[0007]
On the other hand, as an amount representing the ease of gas flow in the vacuum processing chamber, there is a gas residence time in the processing chamber, which is expressed by the following equation.
[0008]
τ = V / S (= PV / Q) (3) formula
Here, V is the total volume of the vacuum processing chamber. In the conventional apparatus, as described above, the effective exhaust speed is 100 to 400 l / sec, the vacuum processing chamber volume is about 100 to 300 l, and the gas residence time is about 400 msec to 3000 msec.
[0009]
[Problems to be solved by the invention]
With the miniaturization of LSIs, processing technology for grooves and holes with dimensions of about 0.3 μm has been required. However, in dry etching using the conventional RIE method, the gas pressure is high, so ions in gas plasma are required. The directionality of ions incident on the substrate is disturbed due to scattering of light, and it is difficult to process grooves and holes with fine dimensions with high accuracy.
[0010]
By reducing the reaction gas pressure, ion scattering in the gas plasma can be prevented. In order to anisotropically process grooves and holes having the above dimensions, it is necessary to suppress the incident angle of oblique ions incident on the sample to 1 ° or less, and the reaction gas pressure (operating pressure) is preferably 1 mTorr or less. Needs to be 0.5 mTorr or less. However, in order to discharge the plasma stably, a pressure of 0.01 mTorr or more is necessary. Examples of the dry etching apparatus having a low reaction gas pressure include the ECR etching apparatus, the magnetron discharge RIE apparatus, and the helicon type RIE apparatus. However, in the conventional dry etching apparatus, when the reaction gas pressure is low, there arises a problem that the etching rate becomes small. That is, increasing the etching directionality and increasing the etching rate are in a drain-off relationship and are difficult to achieve at the same time.
[0011]
Furthermore, the diameter of the Si wafer forming the LSI is becoming larger. For example, in the ECR etching apparatus, a single wafer type dry etching apparatus is used in which the wafer is transferred to the vacuum processing chamber one by one and etched. It was. When such an apparatus is used, for example, in order to etch polysilicon having a thickness of 200 nm on a 6-inch wafer, a processing time of about 1 to 2 minutes is required at an etching rate of 200 to 300 nm / min. When an 8-inch diameter wafer is used, the etching rate decreases due to etching area dependency (so-called loading effect), the processing time increases to 2 to 4 minutes, and the etching processing rate (throughput) decreases. . When the input power of high frequency or microwave is increased to increase the etching rate and increase the throughput, there arises a problem that the ion energy is increased and the selectivity is lowered. By performing parallel processing using a plurality of the single wafer type dry etching apparatuses, it is possible to improve the throughput without changing the etching conditions, but the apparatus cost becomes enormous.
[0012]
In the ECR etching apparatus, since the cross-sectional area of the opening of the gas inlet is small, the effective exhaust speed is made larger than that of the conventional apparatus to increase the flow rate of gas flowing through the etching chamber 117, for example, If it is set to 1300 l / sec or more, the gas flow velocity when the gas flows into the chamber 111 from the gas inlet 104 increases to near the sonic velocity, a shock wave is generated in the flow, and the pressure in the flow becomes uneven. In this state, not only the gas density on the sample is uniform, but also plasma non-uniformity or instability due to discharge occurs, causing problems such as a reduction in uniformity of the etching rate. For this reason, the flow rate of gas needs to be less than or equal to the speed of sound, preferably less than or equal to 1/3 of the speed of sound.
[0013]
Further, in the configuration in which the gas inlet 104 is close to the side portion of the sample stage 110 that is the exhaust port of the etching process chamber 117, the exhaust port before the gas entering the chamber from the gas inlet spreads throughout the chamber. There is a problem that the gas is not efficiently used. In addition, depending on the chamber shape, there is a problem that the gas flow does not sufficiently spread to the center of the etching chamber 117.
[0014]
In addition, since only one mass flow controller 106 and one gas pipe are used to flow one kind of gas, the gas flow in the etching processing chamber 117 is biased, resulting in poor etching uniformity. was there.
[0015]
Further, the conventional apparatus has a problem that the gas flow does not spread sufficiently to the center of the etching chamber 117 as the wafer diameter increases.
[0016]
A main object of the present invention is to provide a method of manufacturing a semiconductor device using a dry etching technique capable of etching a groove or hole having a minute dimension with high accuracy and at high speed.
[0017]
Another object of the present invention is to provide a method of manufacturing a semiconductor device using a dry etching technique having a large throughput.
[0018]
Another object of the present invention is to provide a dry etching method and dry etching apparatus having high anisotropy.
[0019]
Another object of the present invention is to provide a method of manufacturing a semiconductor device using a dry etching technique with high selectivity.
[0020]
Another object of the present invention is a method of manufacturing a semiconductor device using a dry etching technique that obtains a high etch rate of 500 nm / min or more, preferably 1000 nm / min or more at a low gas pressure of 1 mTorr or less, preferably 0.5 mTorr or less. Is to provide.
[0021]
Another object of the present invention is to provide a method of manufacturing a semiconductor device using a dry etching technique with good uniformity.
[0022]
Another object of the present invention is to provide a method for manufacturing a semiconductor device using a dry etching technique that is less contaminated due to re-adhesion of reaction products on the wafer surface or processing chamber wall.
[0023]
[Means for Solving the Problems]
The main features of the present invention are as follows.
A step of preparing a semiconductor substrate having a mask having a predetermined pattern on a main surface; a step of installing the semiconductor substrate in an etching chamber; and a gas is supplied into the processing chamber to convert the gas into plasma, and the plasma is used to generate the semiconductor substrate. Forming a trench having a predetermined depth corresponding to the mask pattern on the main surface of the substrate, and in the trench formation step, the gas in the processing chamber is evacuated at a rate of 2000 l / s or more. A method of manufacturing a semiconductor device that exhausts air using
A more specific means is that the gas pressure in the vacuum processing chamber is 5 mTorr or less, preferably 1 mTorr or less, and the residence time of the reaction gas is 300 msec or less, preferably an effective pumping speed 1300 at an effective pumping speed of 500 l / sec or more. This is achieved by setting the residence time of the reaction gas to 100 msec or less at 1 / sec or more.
[0024]
FIG. 33 shows the specific exhaust speed, gas pressure control range, and effects of the present invention. As described above, the gas pressure is a parameter for controlling the etching directionality (anisotropy), and the exhaust speed is a parameter for controlling the etching speed. In conventional etching, since the effective exhaust speed is low speed of about 400 l / sec or less, there is a problem of low etch speed even if a high-density plasma etching apparatus such as microwave etching is used, and the direction of incident particles at low gas pressure. Even if the properties are uniform, high selectivity processing is actually difficult due to the small selection ratio with the mask.
[0025]
The main application range of the present invention can be divided into three regions shown in the figure. That is,
(1) Regardless of the gas pressure region, a region intended to increase the etching rate to a medium level 1.5 times or more than the conventional one, that is, a region requiring an effective exhaust speed of 800 l / sec or more,
(2) A region intended to achieve a medium etch rate of 1.5 times or more of the conventional level and a medium high anisotropy of 1.5 times or more of the conventional level, that is, an effective exhaust speed of 500 l / sec or more. A region requiring a gas pressure of 5 mTorr or less,
(3) A region aiming at a speed increase of 2 times or more of the conventional method and a high anisotropy of 2 times or more of the conventional method, that is, a region requiring an effective exhaust speed of 1300 l / sec or more and a gas pressure of 1 mTorr or less
It is.
[0026]
From the point of process improvement alone, the method of (3) is optimal, but since there are various processing steps in the semiconductor manufacturing process, in order to obtain the required performance at a low cost, considering the cost of the device, The application methods (1) and (2) are also possible.
[0027]
Since the relationship between the gas pressure P, the exhaust speed S, and the gas flow rate Q is expressed by P = Q / S according to the above equation (1), the gas flow rate necessary to satisfy the above means is the minimum required gas pressure. Is 0.5 mTorr, and the effective pumping speed is 800 l / sec, 32 sccm. However, since the gas pressure is actually finely adjusted, this variation is taken into consideration, and it is preferably 40 sccm or more.
[0028]
Here, since the discharge becomes unstable when the gas pressure is 0.01 mTorr or less, it is desirable that the lower limit of the gas pressure exceeds 0.01 mTorr.
[0029]
Also, the exhaust speed should not exceed the effective exhaust speed of 100,000 l / sec at the maximum considering the size of the apparatus.
[0030]
Further, the gas residence time should be 0.1 msec or more in consideration of the volume of the vacuum processing chamber, the upper limit of the exhaust speed, and the reaction time of the etching surface reaction.
[0031]
Also, the gas flow rate should not exceed 10,000 sccm, considering gas usage costs and gas flow control.
[0032]
Second, the purpose of the preceding paragraph is to widen the area of the gas introduction port so that the flow velocity of the introduction gas is 1/3 or less of the sound velocity, to provide a gas buffer chamber between the gas introduction port and the gas pipe, And a sample stage are provided close to each other, the gas inlet mounting position is separated from the sample stage and the chamber, and is provided in the center direction of the chamber. And mounting a plurality of gas inlets symmetrically around the chamber, providing a baffle plate for controlling the gas flow in the chamber, and setting the height / width ratio of the etching chamber to 0.5 or more, The height of the gas inlet is provided at a position within 1/3 from the upper part of the etching chamber, a vacuum buffer chamber is provided between the exhaust system and the etching chamber, and typically the pumping speed of the pump Effective by setting 2500 l / sec or more, desirably 4000 l / sec or more, exhaust conductance of 2000 l / sec or more, desirably 3000 l / sec or more, and effective exhaust conductance of 1300 l / sec or more. To be achieved.
[0033]
Thirdly, the object of the preceding paragraph is achieved by setting the residence time of the reactive gas in the chamber to 100 msec or less and batch processing a large number of large-diameter wafers simultaneously using a large vessel.
[0034]
Further, the above object is to provide an exhaust port at the center of the sample stage in the large vessel, to set the gas flow rate introduced into the vacuum chamber of the large vessel to 100 sccm or more, and to provide an electrode area of 5000 cm as the sample stage. ² With the above, the total exhaust conductance of the processing chamber and the exhaust pipe is set to 3300 l or more, an exhaust pump having an exhaust speed of 5000 l / sec or more is used, and the effective exhaust speed is set to 2000 l / sec or more. Is effectively achieved.
[0035]
In the conventional dry etching apparatus, when the gas pressure is lowered, the etching rate is remarkably reduced, and a practical etching rate cannot be obtained. This is considered to be because the number of ions in the reaction chamber decreases when the gas pressure is lowered. The inventors have made various studies in order to reduce the gas pressure and obtain a high etching rate. As a result, it was found that etching occurs when ions first collide with an object to be etched. That is, it has been found that if a large number of unreacted ions (reactive gas) are present in the reaction chamber as compared with the already reacted ions (reaction product), the etching rate can be increased even if the gas pressure is the same. Then, the factor which determines the ratio of unreacted ion and reaction product was further examined.
[0036]
FIG. 5 shows the calculation result of the incidence ratio R of the reactive gas and all incident particles (reactive gas + reaction product) to the substrate when the gas flow rate is changed. That is, the incidence ratio R is
R = 1 / (1 + 2.735 × 10 ² C ₁ ・ A ・ P / (α ・ Q)) (4)
Given in. Where C ₁ Is a constant determined by the object to be etched and the etching gas, and has a value in the range of 0.1 to 10. A is the area to be etched, P is the gas pressure, α is the gas utilization rate, and has a value in the range of 10 to 100%, which is a constant determined by the discharge efficiency of the introduced gas and the shape of the etching chamber in the etching apparatus. . Q is the gas flow rate. FIG. 5 shows an etching area A of 78.5 cm. ² The gas utilization rate α is 42% and the gas pressure is 0.5 mTorr. From this result, it can be seen that the proportion of the reactive gas increases with the gas flow rate. On the other hand, FIG. 6 shows a result obtained by calculating the change in the gas residence time when the gas flow rate is changed using the equation (3). As the gas flow rate increases, the gas residence time decreases rapidly. Therefore, as the gas flow rate increases, the residence time of the reaction product that inhibits the etching reaction decreases and is quickly exhausted out of the processing chamber, so that the etching reaction is accelerated and the etching rate is increased. However, simply increasing the gas flow rate increases the operating pressure (gas pressure) as shown in FIG. 17, resulting in a decrease in anisotropy. As for the method of increasing the gas flow rate without changing the operating pressure (gas pressure), as shown in FIG. 17, the larger the effective exhaust speed (gas flow rate in the etching process), the higher the gas at the gas inlet at the same operating pressure. The flow rate will increase. That is, the gas flow rate at the same operating pressure can be increased by increasing the effective exhaust speed.
[0037]
FIG. 7 shows the results of determining the relationship between the ratio of the reactive gas and all incident particles and the gas residence time using the equations (3) and (4). The total volume in the vacuum processing chamber is 100 l, and the etching area A is 78.5 cm. ² The gas utilization rate α was determined as 42%. From FIG. 7, it can be seen that the ratio of the reactive gas increases as the gas residence time decreases and changes significantly between 1 sec and 100 msec. Therefore, in order to efficiently perform the etching reaction, when the ratio of the reactive gas is 60% or more of the total particle incident on the wafer, the gas flow rate is 40 sccm or more, preferably 100 sccm or more from FIG. It can be seen that the staying time should be 100 msec or less, preferably 50 msec or less.
[0038]
When the volume in the etching chamber is 1000 l or less, the gas residence time can be realized by setting the flow rate of gas flowing through the chamber to 1300 l / sec or more. The total opening area of the gas inlet is 150 cm. ² As a result, the gas flow velocity at the gas inlet can be reduced to 1/3 or less of the sound velocity, and the gas flow can be prevented from becoming compressible. Thereby, the shock wave generated in the gas flow can be suppressed, and the instability and non-uniformity of the plasma can be suppressed.
[0039]
As a result of attaching the gas inlet to a position far from the horizontal part of the sample stage, which is the exhaust port of the etching chamber, the gas flow will spread sufficiently in the chamber, and the gas will be efficiently converted into plasma. Processing speed and uniformity increased. Further, since the direction is directed toward the center of the chamber, the gas can flow sufficiently in the direction of the center of the chamber, which improves the etching rate and uniformity.
[0040]
By controlling the gas flow rate with a mass flow controller and attaching a plurality of gas pipes that flow gas around the chamber with good symmetry, it was possible to prevent uneven gas flow in the chamber. As a result, the uniformity of etching increased. The gas flow uniformity was improved because of the symmetry of the gas inlet. In addition, by attaching a baffle plate, it became possible to control the flow of gas in the chamber, and in particular, it was possible to create a flow of gas at a place where plasma was generated, and the etching rate was increased.
[0041]
By setting the chamber height / width ratio to 0.5 or more, the gas flowed sufficiently toward the center of the chamber. This will be described with reference to FIG. The figure shows the result of simulating how the gas flow density in the etching chamber is affected by the height / width ratio of the etching chamber. It can be seen that increasing the height / width ratio of the etching chamber increases the flow density above the wafer, which is the center of the etching chamber, and improves uniformity. As described above, in the present invention, the gas can efficiently and uniformly flow to the center of the etching chamber, so that the plasma density is increased and the uniformity of the plasma is improved. As a result, even in a low pressure region, it is possible to perform etching with high uniformity and high etching speed.
[0042]
In the dry etching apparatus, as the operating pressure is lower, the frequency of scattering of ions incident on the wafer from the plasma is reduced, and the anisotropy of etching is increased. According to the present invention, anisotropic etching by low pressure operation can be performed with good uniformity at a practical etching rate.
[0043]
By performing dry etching using a large-sized vacuum processing chamber, a large number of samples can be processed at a time, so that the throughput can be improved. When a large vessel is used, it is particularly important to quickly exhaust reaction products generated by the etching reaction out of the processing chamber. Therefore, high speed exhaust is necessary. In the conventional apparatus, for example, a turbo molecular pump having a pump exhaust speed of about 1000 l / sec or less is provided, and an exhaust conductance C is 200 l / sec to 1000 l / sec, which is 100 to 400 l / sec. Therefore, when the gas pressure is set to 5 mTorr, the gas flow rate that can be flowed is 40 to 200 sccm. In the present invention, in a large vessel apparatus, an effective exhaust speed of 1300 l / sec or more, preferably 2000 l / sec or more can be flowed at a flow rate of 800 sccm at 5 mTorr by using a high-speed exhaust pump and a large exhaust conductance as described above. is there.
[0044]
FIG. 18 shows the relationship between the effective exhaust speed and the gas residence time when the vacuum processing chamber volume is changed from 100 l to 10000 l. By setting the effective pumping speed to 700 l / sec or more when the processing chamber volume is 100 l, the effective pumping speed is 3600 l / sec or more at a volume of 500 l, and 70000 l / sec or more at a volume of 10,000 l, thereby reducing the gas residence time. It can be set to 100 msec or less. As an example, in order to realize an effective exhaust speed of 70000 l / sec, if a pump with an exhaust speed of 140000 l / sec, for example, and a vacuum processing chamber with an exhaust conductance of 140000 l / sec are used, Good.
[0045]
Further, by providing the exhaust port at the center of the sample stage, the processing gas density at the center and the periphery of the sample stage can be made uniform.
[0046]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
One embodiment of a high-speed exhaust microwave plasma etching apparatus according to the present invention is shown in FIG. An etching gas is introduced into the vacuum processing chamber 1, a high frequency of 2.45 GHz is generated in the microwave generator 2, and this is transported to the discharge unit 4 by the waveguide 3 to generate a gas plasma 5. A solenoid coil 6 for generating a magnetic field is arranged around the discharge unit for high-efficiency discharge, and high-density plasma is generated by electron cyclotron resonance (ECR) by an 875 Gauss magnetic field. There is a sample stage 7 in the discharge part, and the wafer 8 placed thereon is etched by gas plasma. The processed etching gas is discharged from the gas inlet 9 to the outside of the vacuum processing chamber through the discharge unit 4 and the vacuum processing chamber 1 and from the exhaust pipe 10 by the exhaust pump 11. At this time, the exhaust speed can be changed by making the conductance valve 12 variable. The processing gas is introduced into the discharge unit 4 through the gas flow rate controller 13, the gas pipe 14, and the gas introduction port 9 through the buffer chamber 15 having a small hole in a mesh shape. Two or more gas inlets 9 were provided and arranged symmetrically with respect to the central axis of the discharge part. The gas pressure at the time of etching was measured by a gas pressure sensor 23 installed in the plasma discharge part. Thereby, the gas flow rate, gas pressure, gas exhaust speed, and gas residence time in the plasma discharge part can be determined. The sample stage on which the wafer is installed is provided with a cooling mechanism 16 for cooling the wafer to 0 ° C. or less, and an RF bias 17 of 13.56 MHz to 400 KHz can be applied. The vacuum processing chamber is provided with a heater 18 and can be heated to 50 ° C. or higher.
[0047]
Two turbo molecular pumps having an exhaust speed of 2000 l / sec were used as the exhaust pumps, and the exhaust pumps were arranged symmetrically with respect to the central axis of the discharge part at a total exhaust speed of 4000 l / sec. Further, the substantial gas exhaust port portion 10 of the vacuum processing chamber was also arranged in contrast to the wafer central axis. As a result, it was possible to contrast the gas flow with respect to the wafer center while increasing the exhaust conductance as much as possible. The total exhaust conductance of the discharge section, the vacuum processing chamber, the exhaust pipe, and the conductance valve, which are gas passages, was 4000 l / sec. For this purpose, the diameter of the lower part of the discharge part 4 is made larger than that of the upper part, and accordingly, the diameter of the magnetic field coil 6 installed in this part is also made larger than the diameter of the coil located above it. The wafer position at the time of etching is positioned below the center in the thickness direction of the lowermost coil, and the exhaust conductance below the discharge part is made as large as possible. At this time, the maximum effective exhaust speed is 2000 l / sec. The total volume of the discharge part, the vacuum processing chamber, and the exhaust pipe is 100 l, and the gas residence time in the vacuum processing chamber is 50 msec from the above-described equation (3).
[0048]
Using this high-speed exhaust microwave plasma etching apparatus, etching of the Si single crystal used for the Si trench was performed. The sample was formed by thermally oxidizing a Si substrate to a thickness of 500 nm, forming a photoresist mask thereon, dry etching the oxide film to form a hole pattern having a diameter of 0.1 μm to 1.0 μm, Remove photoresist to remove SiO ₂ A mask is formed. The etching gas is Cl ₂ The gas pressure was 0.5 mTorr, the microwave power was 500 W, the RF bias was 20 W at 2 MHz, the wafer temperature was −30 ° C., and the gas flow rate was varied from 2 to 100 sccm. The magnetic field strength distribution was small from the top to the bottom of the discharge part, and the position of 875 Gauss satisfying the ECR condition was 40 mm above the wafer. FIG. 2 shows the gas flow rate dependence of the Si etch rate at this time. At 2 sccm, the etch rate of 80 nm / min is Cl. ₂ It increased with the gas flow rate, and reached 1300 nm / min at 100 sccm. FIG. 3 shows the relationship between the gas pressure and the amount of undercut from the Si mask under similar etching conditions. Since the etching shape of Si is a low gas pressure of 0.5 mTorr, a high directionality is obtained, and the undercut amount of a Si deep hole having a depth of 5 μm is 0.03 μm or less, and there is almost no gas flow rate dependency. . FIG. 4 shows the gas pressure dependence of the Si etching rate when using an apparatus having an effective pumping speed of 2500 l / sec according to the present invention and a conventional apparatus having an effective pumping speed of 150 l / sec. Etching conditions are the same as those in the results of FIG. In the conventional etching apparatus, the etching rate of Si is greatly reduced as the gas pressure decreases. This is because the gas residence time is as long as 470 msec and the gas flow rate is reduced at a low gas pressure because the exhaust speed is slow. Using the apparatus of the present invention with a high pumping speed, an etching rate of 10 times or more of the conventional apparatus can be obtained at a low gas pressure of 0.5 mTorr or less, and high-speed etching of 1 μm / min or more can be performed at 0.5 mTorr or less. It was. On the other hand, the dependence of the etching rate on the hole diameter is small, and the difference in speed is within 3% for the hole diameters between 0.1 μm and 1.0 μm. Even if the gas flow rate is changed, SiO ₂ The etching rate of the SiO 2 used for the etching mask was almost unchanged at a gas flow rate of 100 sccm. ₂ (Si / SiO ₂ ) Was about 50.
[0049]
Also, the etching of phosphorus-doped polysilicon gives almost the same result as in FIG. 2 and FIG. ₂ The undercut amount was 0.03 μm or less at 1500 nm / min at a flow rate of 100 sccm.
[0050]
(Example 2)
SiO used for contact holes by the high-speed exhaust microwave plasma etching apparatus shown in FIG. ₂ Etching was performed. As a sample, a Si oxide film having a thickness of 2 μm was formed on a Si substrate by a CVD method, and a photoresist mask was formed thereon. Etching gas is CHF _Three A gas pressure of 0.5 mTorr, a microwave power of 500 W, an RF bias of 200 K at 800 KHz, a wafer temperature of −30 ° C., and a gas flow rate varied from 2 to 100 sccm. At 2 sccm, the etch rate of 50 nm / min is Cl. ₂ It increased with the gas flow rate, and reached 500 nm / min at 100 sccm. SiO ₂ Since the etching shape is low gas pressure of 0.5 mTorr, high directivity is obtained, and SiO 2 having a depth of 2 μm is obtained. ₂ The undercut amount of the deep hole was 0.05 μm or less, and there was almost no gas flow rate dependency. Further, the dependence of the etching rate on the hole diameter was small, and the difference in speed was within 3% for the hole diameters between 0.1 μm and 1.0 μm. In addition, when the gas flow rate is increased from 2 sccm to 100 sccm, SiO ₂ And the photoresist selectivity increased more than twice.
[0051]
Example 3
FIG. 8 shows an embodiment of a high-speed exhaust reactive ion etching (RIE) apparatus. Since it is a magnetic field application type equipped with a magnetic field coil, discharge is possible even at 1 mTorr or less. An etching gas is introduced into the vacuum processing chamber 1, and a gas plasma 5 is generated by discharging at a high frequency of 13.56 MHz. There is a sample stage 7 in the discharge part, and the wafer 8 placed thereon is etched by gas plasma. The processed etching gas is discharged from the gas inlet 9 through the vacuum processing chamber 1 and from the exhaust pipe 10 to the outside of the vacuum processing chamber by the exhaust pump 11. At this time, the exhaust speed can be changed by making the conductance valve 12 variable. The processing gas is introduced into the vacuum processing chamber 1 through the gas flow rate controller 13, the gas piping 14, and the gas introduction port 9 through the buffer chamber 15 having a small hole in a mesh shape. Two or more gas inlets 9 were provided and arranged symmetrically with respect to the central axis of the discharge part. The sample stage on which the wafer is installed is provided with a cooling mechanism 16 that cools the wafer to 0 ° C. or lower. The vacuum processing chamber is provided with a heater 18 and can be heated to 50 ° C. or higher.
[0052]
In the exhaust pump, two turbo molecular pumps having an exhaust speed of 2000 l / sec were arranged symmetrically with respect to the central axis of the discharge part. The total exhaust conductance of the discharge section, the vacuum processing chamber, the exhaust pipe, and the conductance valve, which are gas passages, was 4000 l / sec. At this time, the effective exhaust speed is 2000 l / sec. The total volume of the discharge part, the vacuum processing chamber, and the exhaust pipe is 100 l, and the gas residence time in the vacuum processing chamber is 50 msec from the above-described equation (3).
[0053]
The photoresist used for the multilayer resist mask was etched by the high-speed exhaust reactive ion etching apparatus shown in FIG. The sample was coated with a photoresist on a Si substrate to a thickness of 1.5 μm and baked to form an intermediate layer such as SOG (Spin-On-Glass) or titanium silica, and patterned on the photoresist. The intermediate layer is dry-etched to form a mask for etching the lower layer photoresist. Etching gas is O ₂ The gas pressure was 0.5 mTorr, the RF power was 500 W, the wafer temperature was −100 ° C., and the gas flow rate was changed from 2 to 100 sccm. At 2 sccm, the etch rate of 100 nm / min is Cl. ₂ It increased with the gas flow rate, and reached 1000 nm / min at 100 sccm. Since the etching shape of the resist is a low gas pressure of 0.5 mTorr, high directionality is obtained, and the undercut amount of the resist having a depth of 1.5 μm is 0.05 μm or less, and there is almost no gas flow rate dependency. . Further, the dependence of the etching rate on the hole diameter was small, and the difference in speed was within 3% for the hole diameters between 0.1 μm and 1.0 μm.
[0054]
(Example 4)
An embodiment of the present invention is shown in FIG. The microwave generated from the microwave generator 101 passes through the waveguide 102 and is sent to the etching processing chamber 117 in the chamber 111 through the microwave inlet. After the gas flow rate is adjusted by the mass flow controller 106, the gas is sent to the etching processing chamber 117 through the gas pipe 105. The gas spreads into the etching processing chamber 117 through the gas inlet 104 provided after the gas pipe 105.
[0055]
The gas entering the etching chamber 117 is controlled in flow by the baffle plate 108 and flows so that the density at the center of the etching chamber 117 is uniform. This gas flow is excited by microwaves on the upper portion of the wafer 109 to be in a plasma state. The plasma is used to generate active particles to etch the wafer. At this time, an external magnetic field is applied by the electromagnet 107 so that the microwave energy is efficiently transmitted to the plasma.
[0056]
A high frequency voltage can be applied to the sample stage by a high frequency power source 112. This power supply applies a bias voltage to the wafer 109 to control the directionality and energy of incident ions. If the sample stage is equipped with a cooling mechanism or a heating mechanism, etching with the wafer temperature controlled can be performed.
[0057]
A gas flow that enters the chamber 111 from the gas inlet 104 and enters a plasma state in the etching chamber 117 and is used for the etching reaction in the wafer 109 is a sample that is an exhaust port viewed from the etching chamber 117 along with the reaction product. The gas passes through the table 110 and is exhausted by the vacuum pump 114 through the exhaust buffer chamber 113.
[0058]
When a high pumping speed vacuum pump is used or when a plurality of vacuum pumps are used, the vacuum pump 114 is not directly attached to the chamber 111 but is attached to the chamber 111 via the exhaust buffer chamber 113 so that the etching processing chamber 117 can be removed. It is possible to equalize the exhaust speed next to the sample stage, which is the exhaust port. As a result, there is no unevenness in the gas flow, and etching with good uniformity becomes possible.
[0059]
The components for controlling the gas flow of this embodiment include a gas inlet 104, a baffle plate 108, and an exhaust buffer chamber 113.
[0060]
The gas introduction port 104 was not particularly treated in the conventional apparatus. The gas pipe 105 was directly connected to the chamber 111, and the connection position was not particularly considered. An example of a conventional apparatus is shown in FIG. The gas pipe 105 is directly attached to the chamber 111.
[0061]
The present invention is characterized in that the gas flow velocity does not exceed 1/3 of the sound velocity by expanding the area of the opening of the gas inlet. In the embodiment shown in FIG. 9, a gas introduction buffer chamber 116 is provided at a portion where the gas pipe 105 is connected to the chamber 111, and a plurality of gas introduction ports 104 are provided on the wall surface of the buffer portion, thereby opening the gas introduction port. The partial area is increased and the gas flow rate is suppressed to 1/3 or less of the sound velocity.
[0062]
The pressure of the gas flowing through the gas pipe 105 through the mass flow controller 106 is about 1 atm. When the gas is directly flowed into the chamber, the flow tends to be disturbed where the gas enters the chamber due to the pressure difference. In this embodiment, by providing the gas introduction buffer chamber 116 between the gas pipe 105 and the chamber 111, it is possible to suppress the flow disturbance due to the pressure difference.
[0063]
Further, in this embodiment, a plurality of gas pipes 105 including the mass flow controller 106 are attached around the chamber in consideration of symmetry, thereby improving the gas flow uniformity.
[0064]
When the plasma is generated near the center of the etching chamber, the active particles are efficiently incident on the wafer and the uniformity is increased. The flow of gas flowing along the wall surface of the etching chamber 117 has a small contribution to etching. Therefore, in this embodiment, the baffle plate 108 is attached to control the flow of the gas flowing on the wall surface of the chamber 111 so as to flow near the center of the chamber. Since the baffle plate 108 has a side effect of deteriorating the conductance of the flow, it may be adversely affected if a large one is attached. In this embodiment, the gap between the sample stage 110 and the chamber 111 that becomes the exhaust port of the etching chamber 117 is not visible from the gas introduction port 104 and is not exposed on the wafer 109.
[0065]
Further, in this embodiment, the exhaust buffer chamber 113 is installed between the chamber 111 and the vacuum pump 114, which is one of the features for controlling the flow. In order to make the flow uniform, it is desirable that the exhaust system also has good symmetry. However, it is necessary to connect a high-frequency power source 112 for bias application voltage to the sample stage 112 and to attach a cooling mechanism for flowing a coolant in order to perform low-temperature dry etching for controlling the temperature of the wafer 109. . Therefore, it is difficult to arrange the exhaust system including the vacuum pump with good symmetry. The vacuum buffer 113 attached in this embodiment has a function of uniformly applying the exhaust capability of the vacuum pump 114 to the exhaust portion of the etching processing chamber 117. Further, the exhaust buffer chamber 113 is highly effective in making the exhaust of the etching processing chamber 117 uniform even when a plurality of vacuum pumps are attached to increase the exhaust capability.
[0066]
FIG. 10 is a horizontal sectional view including the gas pipe 105 of the chamber 111 of this embodiment. Here, four gas pipes 105 are attached, but since there is a gas introduction buffer chamber 116, one gas pipe 105 may be provided. However, in order to make the flow uniform, it is better to attach a plurality of them in consideration of symmetry.
[0067]
Using the microwave dry etching apparatus configured as described above, holes and grooves of 0.3 to 0.5 μm were formed on the surface of the Si substrate. The sample used was a resist mask or a pattern formed with a SiO2 mask, and under the conditions of microwave power 400 W, pressure 0.5 mTorr, gas flow rate 50 sccm, RF bias 30 W (13.56 MHz), SF ₆ Gas was used. As a result, the etching rate was 500 nm / min or more. The side etch amount was 0.05 μm or less, and a good vertical shape could be obtained.
[0068]
(Example 5)
FIG. 11 shows another embodiment of the present invention. In this embodiment, the gas introduction buffer chambers 116 are not circumferential, but a number of isolated gas introduction buffer chambers 116 corresponding to the gas pipes 105 are attached. Compared to the uniformity, the embodiment shown in FIG. 9 is better, but the apparatus shown in FIG. 11 has the advantage that the embodiment shown in FIG. 11 can be made easier.
[0069]
There is a method in which the baffle plate 108 is not circular and a plurality of isolated ones are attached. Also, multiple circumferential baffles 108 can be installed at different heights in the chamber 111, or circumferential baffles and isolated baffles can be used in combination. It can be attached to various parts of the gas to control the gas flow. Thus, by providing the buffer chamber 116, the uniformity of the etching rate in the 8-inch wafer was improved more than twice compared with the case where the chamber was not provided, and could be ± 10% or less.
[0070]
(Example 6)
FIG. 12 illustrates another gas piping method as one embodiment of the present invention. In this example, the gas pipe 105 is connected to the chamber 111 at a plurality of portions, whereas the flow rate of the gas flowing from the cylinder 115 is controlled by only one mass flow controller 106. Since the flow rate is controlled by only one mass flow controller, there is an advantage that the flow rate can be accurately controlled and the structure of the apparatus can be simplified. On the other hand, the distance of the gas pipe 105 from the mass flow controller 106 to the chamber 111 changes. Therefore, there is a drawback that the uniformity of the gas flow in the etching chamber 117 is somewhat deteriorated. However, by changing the size of the gas inlet buffer chamber 116 depending on the location, changing the opening area and opening ratio of the gas inlet 104 depending on the location, and adjusting the mounting height, the gas flow uniformity can be improved. Since it can be adjusted as a system, the decrease in uniformity is not so much a problem in practice.
[0071]
Thus, by using a plurality of gas pipes 105, the uniformity of the etching rate in the 8-inch wafer can be improved more than twice compared with the case of a single gas pipe, and can be reduced to ± 10% or less. It was.
[0072]
(Example 7)
FIG. 13 illustrates another gas piping method as one embodiment of the present invention. A feature of the present embodiment is that the gas flow rate from one or more cylinders 115 is controlled by using one or more mass flow controllers 106 for a plurality of gas pipes 105 connected to the chamber 111. The flow of gas in the chamber 111 can be made uniform by adjusting the flow rate of gas flowing through each mass flow controller 106. In addition to the usage of making the gas flow uniform in the etching chamber by using multiple cylinders of the same gas type, different gas types of cylinders are used to mix different types of gas in the etching chamber. The method used can also be performed. By adjusting the number and position of gas pipes for each gas type and the flow rate of gas flowing through them, different types of gas are mixed uniformly and the flow of the mixed gas in the etching chamber is uniform. Can be. Thus, by using a plurality of gas pipes 105 and a plurality of gas cylinders, the uniformity of the etching rate in the 8-inch wafer is improved more than twice compared with the case of using a single gas pipe and a single gas cylinder, ± 10% or less could be achieved.
[0073]
(Example 8)
Another embodiment of the present invention is shown in FIG. In this embodiment, a gas introduction buffer chamber 116 is attached under the microwave introduction window 103, and the gas introduction port 104 is formed in the upper part of the wafer 109. This method has the advantage that the gas flow is more uniform and the gas flow density in the center of the chamber is increased. However, since a portion where the gas pressure is high is generated in the path of the microwave, there is a problem that the microwave may be prevented from traveling or a discharge may occur in the gas introduction buffer chamber 116. However, in order to suppress the adjustment of the power of the microwave, the electromagnet 107, and the pressure increase in the gas inlet buffer chamber 116, the gas flow rate is time-modulated, or the microwave is input in synchronization with the time modulation. This is practically not a problem because it can be avoided.
[0074]
Example 9
FIG. 19 shows an embodiment of a large vessel fast exhaust reactive ion etching (RIE) apparatus according to the present invention. An etching gas is introduced into the vacuum processing chamber 201, and a gas plasma 203 is generated by discharging at a high frequency 202 of 13.56 MHz. The vacuum processing chamber is a cylindrical type having a diameter of 120 cm and a height of about 40 cm, the electrode is a parallel plate type cathode coupling type, the upper electrode 204 is a ground potential, the lower electrode 205 is a high frequency application electrode, and the lower electrode is a wafer. It is a sample stage to be placed. The diameter of the lower electrode is 90 cm. To improve the uniformity of etching, an exhaust port 206 having a diameter of 10 cm that can exhaust the processing gas is provided at the center of the lower electrode, and exhausted from both the center and the periphery of the lower electrode outside the vacuum processing chamber. did. The electrode area is about 6300cm ² Yes, six 8-inch wafers 207 were placed and etched simultaneously. The exhaust speed of the processing gas can be changed by making the conductance valve 208 variable. The processing gas is introduced into the vacuum processing chamber 201 through the gas flow rate controller 209, the gas piping 210, and the gas introduction port 211 through the buffer chamber 212 having a small hole in a mesh shape. Two or more gas inlets 211 were provided and arranged symmetrically with respect to the central axis of the discharge part. The sample stage on which the wafer is installed is provided with a cooling mechanism 213 that cools the wafer to 0 ° C. or lower. The vacuum processing chamber is provided with a heater 214 and can be heated to 50 ° C. or higher.
[0075]
As the exhaust pump, two turbo molecular pumps having an exhaust speed of 6000 l / sec were arranged symmetrically with respect to the central axis of the discharge part. The total exhaust conductance of the discharge section, the vacuum processing chamber, the exhaust pipe, and the fully open conductance valve serving as a gas passage was 12000 l / sec. At this time, the effective exhaust speed is 6000 l / sec. The total volume of the vacuum processing chamber and the exhaust pipe is about 500 l, and the gas residence time in the vacuum processing chamber is 83 msec from the above-described equation (3).
[0076]
The Si single crystal was etched by the high-speed exhaust reactive ion etching apparatus shown in FIG. The sample was obtained by forming a photoresist mask on an 8-inch Si substrate, and six samples were placed on the sample stage at the same time. CF as etching gas _Four , Gas pressure 200mTorr, RF power 2KW (power density is 0.32W / cm ² The wafer temperature was −50 ° C., and the gas residence time was changed by changing the exhaust speed by changing the opening of the conductance valve. At this time, the gas pressure was constant and the gas flow rate was changed. FIG. 20 shows the gas flow rate dependence of the Si etch rate at this time. The Si etch rate was 100 nm / min when the gas flow rate was 50 sccm, but the etch rate increased to 800 nm / min when the gas flow rate was 900 sccm. At this time, etching was performed to a depth of 1 μm, and the amount of undercut from the Si mask was 0.1 μm or less. The selection ratio between Si and photoresist was 4.0. The uniformity of the etch rate within the wafer and between the wafers was ± 5% or less.
[0077]
(Example 10)
FIG. 21 shows an embodiment of a large vessel high-speed exhaust microwave plasma etching apparatus according to the present invention. Five vacuum discharge portions 216 are installed in the vacuum processing chamber 201, and the gas plasma 203 can be generated independently of each other. A total of five 8-inch wafers 207 were respectively placed under five microwave discharge portions on the sample stage placed in the vacuum processing chamber, and simultaneously etched. Gas exhaust ports 206 were provided in the vicinity of the five wafer placement portions inside the sample stage. The gas plasma is generated by introducing an etching gas into the vacuum processing chamber 201, generating a high frequency of 2.45 GHz in the microwave generator 217, and transporting this to the discharge unit 216 through the waveguide 218. A solenoid coil 219 for generating a magnetic field is disposed around the discharge unit for high-efficiency discharge, and high-density plasma is generated by electron cyclotron resonance (ECR) by an 875 Gauss magnetic field. The etching gas is discharged from the gas inlet 211 to the outside of the vacuum processing chamber by the exhaust pump 215 through the discharge unit 219 and the vacuum processing chamber 201. The exhaust speed can be changed by making the conductance valve 208 variable. The processing gas is introduced into the discharge unit 216 through the gas flow rate controller 209, the gas pipe 210, and the gas introduction port 211 through the buffer chamber 212 having a small hole in a mesh shape. Two or more gas inlets 211 were provided and arranged symmetrically with respect to the central axis of the discharge part. The sample stage on which the wafer is installed is provided with a cooling mechanism 213 that cools the wafer to 0 ° C. or less, and an RF bias 202 of 13.56 MHz to 400 KHz can be applied. The vacuum processing chamber is provided with a heater 214 and can be heated to 50 ° C. or higher.
[0078]
As the exhaust pump, two turbo molecular pumps having an exhaust speed of 20000 l / sec were arranged symmetrically with respect to the central axis of the discharge part. The total exhaust conductance of the discharge section, the vacuum processing chamber, the exhaust pipe, and the fully open conductance valve serving as a gas passage was 40000 l / sec. At this time, the effective exhaust speed is 20000 l / sec. The total volume of the vacuum processing chamber, the discharge part, and the exhaust pipe is about 2000 l, and the gas residence time in the vacuum processing chamber is 100 msec.
[0079]
The Si single crystal was etched by a large vessel high-speed exhaust microwave plasma etching apparatus shown in FIG. Samples were obtained by forming a photoresist mask on an 8-inch Si substrate, and five samples were placed on the sample stage simultaneously. CF as etching gas _Four The gas pressure was 5 mTorr, the microwave power was 2 KW, the RF bias was 200 W at 2 MHz, and the wafer temperature was −50 ° C. The Si etch rate at this time was 1.5 μm / min at a gas flow rate of 900 sccm. At this time, etching was performed to a depth of 1 μm, and the amount of undercut from the Si mask was 0.1 μm or less. The selection ratio between Si and photoresist was 3.0. The uniformity of the etch rate within the wafer and between the wafers was ± 5% or less.
[0080]
(Example 11)
With the high-speed exhaust microwave plasma etching apparatus shown in FIG. 1, patterns with different total areas were formed on an 8-inch wafer, and Al etching was performed. Etching conditions are Cl ₂ The gas pressure was 3 mTorr, the microwave power was 500 W, the RF bias was 50 W at 2 MHz, and the wafer temperature was 0 ° C. FIG. 22 shows the relationship between the effective evacuation rate (simply referred to as the evacuation rate in the following description of the embodiments) and the etch rate when the wafer diameter is changed from 6 inches to 8 inches. The etching area ratio in the wafer is 50%. Since the gas pressure is constant (3 mTorr), the gas flow rate (Q sccm) with respect to the exhaust speed (Sl / sec) is Q = 79.05 × S × 0.003.
[0081]
In the case of 6 inches in the conventional Al etching with low speed exhaust (about 200 l / sec), the etching rate was about 0.8 μm / min. When the exhaust speed is 500 l / sec, the etch rate is about 1.5 times 1.2 μm / min, and at 800 l / sec is about 1.8 times 1.4 μm / min, and at 1300 l / sec. It was doubled to 1.6 μm / min. In the 8-inch wafer, a more remarkable change was observed, which was 2.4 times the conventional value at 800 l / sec and about three times the conventional value at 1300 l / sec.
[0082]
Therefore, when trying to obtain 1.5 times or more of the conventional etch rate (6 inches, 200 l / sec) with an 8-inch wafer, it is found that at least 800 l / sec or more is necessary, and 2 times or more is obtained. Then, it was found that at least 1300 l / sec or more is necessary.
[0083]
The area dependence of the etching rate is almost the same with other materials such as Si in addition to Al. In order to obtain 1.5 times or more of the conventional etching rate with an 8-inch wafer, 800 l / sec. The above pumping speed was necessary. Similarly, in the case where etching conditions such as gas pressure, microwave power, sample temperature, and bias are different, an evacuation rate of 800 l / sec or more is required in order to obtain 1.5 times or more of the conventional etching rate with an 8-inch wafer. Was necessary.
[0084]
(Example 12)
Si etching was performed using the high-speed exhaust microwave plasma etching apparatus shown in FIG. 1 while changing the distance (ECR plane distance) between the ECR plane (the plane in which the magnetic field becomes 875 G in the plasma) and the wafer. Etching conditions are Cl ₂ The gas pressure was 0.5 mTorr, the microwave power was 500 W, the RF bias was 20 W at 2 MHz, and the wafer temperature was −30 ° C. FIG. 23 shows the relationship between the ECR surface distance and the etch rate when the exhaust speed is changed. With the conventional exhaust speed (200 l / sec), the etch rate decreased from 300 to 100 nm / min when the ECR surface distance was increased from 0 to 150 mm. On the other hand, even when the ECR surface distance is as long as 150 mm, the etching rate is 300 nm / min in the etching by high-speed evacuation of 500 l / sec, and increases to 1000 nm / min or more when the distance is further reduced. That is, it has been found that even if the ECR surface distance is increased to some extent by high-speed exhaust etching, an etching rate equal to or higher than that obtained when the ECR surface is brought closer is obtained.
[0085]
A problem when the ECR plane is brought close is that the plasma dissociation efficiency is high in the ECR region, so that the reaction product generated from the wafer is re-dissociated and redeposited on the wafer surface. This reduction may lead to etching shape deterioration and surface contamination. Further, when the ECR surface distance is reduced, the etching uniformity may be lowered. From the surface analysis, the amount of adsorption of the reaction product on the wafer was examined. As shown in FIG. 24, it was found that the amount of adsorption increased as the ECR surface distance decreased when the exhaust speed was 500 l / sec. When the exhaust speed is low (200 l / sec), the reaction product exhaust speed is slow, so even if the ECR plane distance is some distance away and re-dissociation is small, the amount of adsorption to the wafer increases. Therefore, for low-contamination and high-speed etching with little adsorption of reaction products, it is preferable to increase the ECR surface distance to some extent and exhaust at high speed. From the results of FIG. 24, it was found that it is appropriate to use an exhaust speed of 500 l / sec or more with an ECR surface distance of 40 mm or more.
[0086]
(Example 13)
Al was etched at a gas pressure of 1 to 10 mTorr using the high-speed exhaust microwave plasma etching apparatus shown in FIG. Etching conditions are Cl ₂ The gas pressure was 5 mTorr, the microwave power was 500 W, the RF bias was 20 W at 2 MHz, and the wafer temperature was 0 ° C. FIG. 25 shows the relationship between the exhaust speed and the Al etch speed. The gas flow rate is obtained by multiplying the gas pressure by the exhaust speed. The etch rate greatly increases at 500 l / sec or more. On the other hand, the exhaust speed dependency of the undercut amount is shown in FIG. Since the gas pressure is as high as 5 mTorr, undercut is likely to occur, and the tendency to increase is particularly large at an exhaust speed of 1300 l / sec or more. The reason why the undercut amount is small at an exhaust speed of 1300 l / sec or less is that the residence time of the reaction product is long, which deposits on the pattern side wall to prevent side etching. Therefore, in order to suppress the undercut amount to 0.1 μm or less at a high etch rate of 1000 nm / min or higher when etching that cannot suppress the undercut without using a sidewall deposition and a high etch rate is required. 500 l / sec was appropriate. A similar etching tendency was obtained at a pressure of 1 to 10 mTorr, and the exhaust speed satisfying an undercut amount of 0.1 μm or less was between 500 l / sec and 1300 l / sec at a high etch rate of 1000 nm / min or more. . The gas residence time was 300 msec at 500 l / sec.
[0087]
(Example 14)
By using the high-speed exhaust microwave plasma etching apparatus shown in FIG. _Three Al was etched using gas. Etching conditions are BCl _Three The gas pressure was 4 mTorr, the microwave power was 500 W, the RF bias was 20 W at 2 MHz, and the wafer temperature was 20 ° C. FIG. 27 shows the gas pressure dependence of the Al undercut amount. The exhaust speed was 800 l / sec. The undercut amount significantly decreased at 5 mTorr or less and became 0.1 μm or less. Cl ₂ Compared with etching by BCl _Three Now undercuts are reduced at higher gas pressures. This is because BCl _Three This is because there is an effect of depositing on the pattern side wall and protecting the side wall. On the other hand, FIG. 28 shows the exhaust rate dependency of microloading of Al etch rate (pattern size dependency: here 0.2 μm; ratio of etch rate of a and 10 μm; b groove pattern; a / b). The micro-loading decreased as the exhaust speed increased, and became 0.9 or more suitable for practical use at 800 l / sec or more. The reason why the micro-loading decreases with the increase in the exhaust speed is that the etching reaction particles are sufficiently supplied into the small groove due to the increase in the exhaust speed. Therefore, BCl _Three It has been found that in order to perform etching while suppressing undercutting and microloading in Al etching using, an exhaust speed of 800 l / sec or more is good at a gas pressure of 5 mTorr or less. Microrod is related to the amount of overetching required to etch the inside of a small groove to the end. In this case, since microloading is 0.9 or more, there is no practical problem, so the pumping speed is increased more than necessary. do not have to.
[0088]
(Example 15)
Al was etched by the high-speed exhaust microwave plasma etching apparatus shown in FIG. 1 and the reactive ion etching apparatus shown in FIG. Etching conditions are Cl in a microwave etching apparatus. ₂ Gas, microwave power 500W, RF bias 20W at 2MHz, wafer temperature 10 ° C, reactive ion etching with RF power 500W, Cl ₂ The gas and wafer temperatures were 10 ° C. FIG. 30 shows the relationship between the Al etch rate and the gas pressure. The exhaust speed was 500 l / sec. Since microwave etching can be performed at a low gas pressure, the undercut is 0.1 μm or less at 4 mTorr, and the etching rate is 1000 nm / min. In reactive ion etching, etching was not possible at a low gas pressure, the undercut was 0.2 μm at 10 mTorr, and the etch rate was 300 nm / min. In other words, microwave etching is capable of high-speed etching with low gas pressure and less undercut as compared with reactive ion etching. On the other hand, FIG. 31 shows the relationship between the Al etch rate and the exhaust rate. The gas pressure is 4 mTorr. As the pumping rate is increased, the Al etch rate is significantly increased in microwave etching than in reactive ion etching. This is because microwave etching has a higher surface reaction rate than reactive ion etching, so that the rate of supply of etching reaction particles is limited. Therefore, if the supply of etching reaction particles is increased by increasing the exhaust speed, the etching reaction is promoted. Because. In particular, the etch rate tended to be saturated at 500 l / sec or more. On the other hand, in reactive ion etching, the surface reaction rate is low and the reaction rate is limited. Therefore, even if the supply of etching reaction particles is increased by increasing the exhaust rate, the increase in the etch rate is small. Therefore, by using microwave plasma etching, in order to prevent undercut at low gas pressure and increase the etch rate by high-speed exhaust, the gas pressure should be 4 mTorr or less and the exhaust rate should be 500 l / sec or more. Suitable. The undercut becomes smaller as the gas pressure is lowered. However, the Al etch rate is greatly reduced at 0.5 mTorr or less to 300 nm / min or less, which is not very suitable for practical use.
[0089]
(Example 16)
Al was etched by the high-speed exhaust microwave plasma etching apparatus shown in FIG. 1 and the reactive ion etching apparatus shown in FIG. Etching conditions are Cl in a microwave etching apparatus. ₂ Gas pressure of 4 mTorr, microwave power of 500 W, RF bias of 20 W at 2 MHz, wafer temperature of 10 ° C., reactive ion etching with RF power of 500 W, Cl ₂ The gas pressure was 10 mTorr and the wafer temperature was 10 ° C. FIG. 32 shows the relationship between the Al etch rate and the gas residence time. Here, the gas flow rate was variable. Although the etching time tended to increase with any of the etching methods as the residence time decreased, the microwave etching significantly increased. The Al etch rate was 1000 nm / min at a residence time of 300 msec. Therefore, in order to obtain an etch rate of 1000 nm / min with an undercut of 0.1 μm or less, it is necessary to set the gas residence time to 300 msec or less at a gas pressure of 4 mTorr or less.
[0090]
【The invention's effect】
According to the present invention, the gas flow rate can be increased to 40 sccm or more under a high vacuum of 1 mTorr or less, and the gas residence time can be reduced to 100 msec or less. Therefore, undercut is prevented under a high vacuum, and a high etch rate is achieved at a large gas flow rate. This can be achieved, and the etching rate ratio (selection ratio) between the material to be etched and other materials can be increased. As a result, high aspect ratio (pattern width / etching depth ratio) etching of Si trenches, contact holes, and the like that require very high directivity can be processed at high speed and high accuracy.
[0091]
Further, even under a gas pressure of 1 mTorr or higher, undercutting can be prevented to some extent, and the etching rate and etching selectivity can be improved.
[0092]
In addition, since the redeposition of the reaction product is small, contamination of the wafer and the apparatus and abnormal etching shape can be reduced.
[0093]
The effects of the present invention are not limited to the above-described etching apparatus and etching material. For example, other apparatuses such as magnetron type RIE and helicon resonance type RIE, and other elements such as aluminum, tungsten, tungsten silicide, copper, GaAs, Si nitride film, etc. The same effect can be obtained with these materials.
[0094]
In addition, by using a large vessel, for example, a large number of wafers of 8 inches or more can be etched at the same time, and the etching rate can be made similar to the conventional one, so that the dry etching throughput can be improved and the cost of semiconductor products can be reduced. There is.
[0095]
The large-bore batch processing in the large vessel and high-speed exhaust processing apparatus according to the present invention has a great effect of increasing the throughput even in processes other than dry etching. For example, plasma CVD apparatus, sputtering apparatus, ion milling apparatus, plasma doping apparatus, etc. are examples. In any apparatus, when the vacuum processing chamber is enlarged, the amount of residual gas in the processing chamber increases, causing problems such as film quality deterioration due to residual gas mixing into the formed film, but such effects can be reduced by high-speed exhaust. High quality thin film can be formed. Furthermore, it is possible to shorten the time for the residual gas amount to be equal to or less than the value necessary for film formation by high-speed exhaust, and it is possible to improve the process throughput.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a high-vacuum high-speed exhaust type microwave plasma etching apparatus according to the present invention.
FIG. 2 is a diagram showing a relationship between a gas flow rate and an etching rate in Si etching using the high vacuum high speed exhaust type microwave plasma etching apparatus according to the present invention.
FIG. 3 is a diagram showing a relationship between a gas pressure and an undercut amount in Si etching using a high vacuum high speed exhaust type microwave plasma etching apparatus according to the present invention.
FIG. 4 is a diagram showing the relationship between gas pressure and etch rate in Si etching using a high-vacuum high-speed exhaust type microwave plasma etching apparatus according to the present invention.
FIG. 5 is a diagram showing a calculation result obtained by calculating an incidence ratio of a reactive gas and a reaction product to a substrate when a gas flow rate is changed.
FIG. 6 is a diagram showing a calculation result of obtaining a gas residence time when the gas flow rate is changed.
FIG. 7 is a diagram illustrating a calculation result of obtaining the incidence ratio of a reactive gas and a reaction product to a substrate when the gas residence time is changed.
FIG. 8 is a schematic sectional view of a high-vacuum high-speed exhaust type reactive ion etching (RIE) apparatus according to the present invention.
FIG. 9 is a schematic sectional view of a dry etching apparatus according to the present invention.
FIG. 10 is a partial plan view of a dry etching apparatus according to the present invention.
FIG. 11 is a partial plan view of a dry etching apparatus according to the present invention.
FIG. 12 is a plan view showing a configuration of a gas pipe of the dry etching apparatus according to the present invention.
FIG. 13 is a plan view showing a configuration of a gas pipe of the dry etching apparatus according to the present invention.
FIG. 14 is a schematic cross-sectional view of a dry etching apparatus according to the present invention.
FIG. 15 is a result of obtaining a relationship between the ratio of the height and width of the etching chamber and the gas flow density in the etching chamber by simulation.
FIG. 16 is a schematic cross-sectional view of a conventional dry etching apparatus.
FIG. 17 is a diagram showing the relationship between gas pressure and gas flow rate for different effective exhaust speeds.
FIG. 18 is a diagram showing the relationship between the effective exhaust speed and the gas residence time, with the vacuum processing chamber volume as a parameter.
FIG. 19 is a schematic view of a large vessel fast exhaust reactive ion etching (RIE) apparatus according to the present invention.
FIG. 20 is a diagram showing a relationship between a gas flow rate and an etching rate in Si etching using a high vacuum high speed exhaust type microwave plasma etching apparatus.
FIG. 21 is a schematic view of a large-sized vessel high-speed exhaust microwave plasma etching apparatus according to the present invention.
FIG. 22 is a graph of Al etch rate and effective exhaust rate according to the present invention.
FIG. 23 is a graph of Si etch rate and wafer-ECR surface distance according to the present invention.
FIG. 24 is a graph of the reaction product on the wafer surface and the wafer-ECR plane distance according to the present invention.
FIG. 25 is a graph of Al etch rate and effective exhaust rate according to the present invention.
FIG. 26 is a graph of the amount of Al undercut and the effective exhaust speed according to the present invention.
FIG. 27 is a graph of Al undercut amount and gas pressure according to the present invention.
FIG. 28 is a graph showing an Al etching depth ratio (depending on pattern size) and an effective exhaust speed according to the present invention.
FIG. 29 is a schematic view of a fast exhaust reactive ion etching (RIE) apparatus according to the present invention.
FIG. 30 is a graph of Al etch rate and gas pressure according to the present invention.
FIG. 31 is a graph of Al etch rate and effective exhaust rate according to the present invention.
FIG. 32 is a graph of Al etch rate and gas residence time according to the present invention.
FIG. 33 is a diagram showing a range of a processing gas pressure and an effective exhaust speed to which the effect of the present invention is applied.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum processing chamber, 2 ... Microwave generator, 3 ... Waveguide, 4 ... Discharge part, 5 ... Gas plasma, 6 ... Solenoid coil, 7 ... Sample stand, 8 ... Wafer, 9 ... Gas inlet, 10 DESCRIPTION OF SYMBOLS ... Exhaust pipe, 11 ... Exhaust pump, 12 ... Conductance valve, 13 ... Gas flow controller, 14 ... Gas piping, 15 ... Buffer chamber, 16 ... Cooling mechanism, 17 ... RF bias, 18 ... Heater, 19 ... Butterfly valve, 20 ... Gas flow, 21 ... Microwave introduction window, 22 ... Upper electrode, 23 ... Gas pressure sensor
DESCRIPTION OF SYMBOLS 101 ... Microwave generation part, 102 ... Waveguide, 103 ... Microwave introduction window, 104 ... Gas introduction port, 105 ... Gas piping, 106 ... Mass flow controller, 107 ... Electromagnet, 108 ... Baffle plate, 109 ... Wafer, 110 DESCRIPTION OF SYMBOLS ... Sample stage 111 ... Chamber, 112 ... High frequency power source, 113 ... Exhaust buffer chamber, 114 ... Vacuum pump, 115 ... Gas cylinder, 116 ... Gas introduction buffer chamber, 117 ... Etching processing chamber 201 ... Vacuum processing chamber, 202 ... High frequency, DESCRIPTION OF SYMBOLS 203 ... Gas plasma, 204 ... Upper electrode, 205 ... Lower electrode, 206 ... Gas exhaust port, 207 ... 8 inch wafer, 208 ... Conductance valve, 209 ... Gas flow controller, 210 ... Gas piping, 211 ... Gas inlet port, 212 ... buffer chamber, 213 ... cooling mechanism, 214 ... heater, 215 ... exhaust pump , 216 ... discharge unit, 217 ... microwave generator, RF bias, 218 ... waveguide, 219 ... solenoid coil, the flow of 220 ... gas.

Claims (2)

A step of preparing a Si substrate having a mask having a predetermined pattern on the main surface,
Installing the Si substrate in an etching chamber;
Supplying a processing gas containing Cl ₂ gas into the etching processing chamber, converting the processing gas into plasma,
The etching chamber gas pressure 0.5mTorr less, while maintaining the effective pumping speed above 500 l / s, viewed including the step of etching the Si substrate by a reactive gas generated by the plasma,
The method for manufacturing a semiconductor device, wherein a residence time of the processing gas in the processing chamber is 100 msec or less .   2. The method of manufacturing a semiconductor device according to claim 1, wherein the process gas is supplied at a flow rate of gas supplied to the process chamber of 100 sccm or more.

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