JPH0831448B2 - Low temperature dry etching equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus suitable for fine processing of a surface, and more particularly to a low temperature dry etching apparatus particularly suitable for anisotropic etching of semiconductor wafers.

[0002]

2. Description of the Related Art As the degree of integration of semiconductor integrated circuits increases from LSI to VLSI, the dimensions of integrated devices have become smaller and smaller. When a resist image having a pattern of 1 μm or less is used as a mask to etch a substance thereunder, the reaction products can be easily removed by using a low-pressure gas plasma, and ions generated by an electric field as in reactive etching are used. It is expected that the use of this acceleration will reduce the problem of undercutting and facilitate the creation of fine patterns.

So-called dry etching, in which etching is performed using gas without using a solution, is an indispensable technique for VLSI manufacturing. However, in order to prevent alteration of the resist mask, a sample to be mounted is placed on the sample. Cooling a table is well known. Water cooling is the most common method of cooling, but gas is also used for some of them. For example, Nuclear Instruments and Methods (Nuclear Instrumennts and
Methods] 189 (1981) pp. 169-173. In all of these, the sample stage is cooled to a temperature of 120 to 150 ° C. or lower at which the resist is denatured, and the temperature control range is 20 to 100 ° C. Furthermore, Japanese Patent Application Laid-Open No. 60-158627 discloses a technique for cooling a sample to a temperature below room temperature, that is, a number of minus 10 ° C. or less by using a heat pipe to prevent side etching. In dry etching, high-energy particles such as ions and electrons and neutral particles such as radicals simultaneously enter the horizontal surface of the sample, while only neutral particles enter the pattern sidewall. In the above prior art, the number of samples is minus one.
When cooled to a low temperature of 0 ° C., the reaction rate between the sample and neutral particles is remarkably reduced and the side wall of the pattern is not etched, but high energy particles such as ions and electrons collide with the horizontal surface. Therefore, a pseudo high temperature state is created on the very surface and etching progresses. As a result, anisotropic etching with less side etching is achieved.

Further, in JP-A-60-50923, an etching gas containing a halogen element and a gas for forming a thin film on the surface of a material to be etched are alternately introduced into a vacuum container and excited from these gases. A technique is disclosed in which anisotropic etching is performed while alternately repeating etching and thin film formation on the surface of the material to be etched in plasma.

[0005]

The above-mentioned prior art requires time for forming a thin film on the surface of the material to be processed, in addition to the time for etching the surface of the material to be processed, which tends to increase the processing time. . Further, in the case of implementing the above-mentioned conventional technique, since the heat pipe is used as the cooling device, the controllable temperature range is narrow. For example, the temperature control range in the case of a heat pipe using liquid nitrogen is approximately -203 to -160 ° C. However, practically, it is desirable to set the optimum temperature for each material and etching gas within a range of 0 to −200 ° C., which is far wider than this temperature range.

The present invention has been made in order to solve the above-mentioned problems. The material to be treated is cooled to a low temperature of 0 ° C., preferably -50 ° C. or lower to improve the thin film forming efficiency and shorten the thin film forming time. At the same time, the side etching prevention effect due to low temperature reduces the number of repeated cycles for thin film formation, and further expands the low temperature range corresponding to changes in etching conditions to arbitrarily set the sample to the desired temperature range. It is an object of the present invention to provide a low-temperature dry etching apparatus equipped with a sample stage capable of performing the above.

[0007]

The above object is to provide a circuit for controlling the sample stage temperature by an apparatus that uses both a cooling by a liquefied gas and a heater and a material to be etched at 0 to -200.degree.
As a means for cooling the gas to a temperature range and alternately introducing the etching gas and the thin film forming gas into the vacuum vessel, a low-temperature dry etching apparatus is used, which is performed via a device that sets the timing of automatic opening and closing of the gas line valve. It is possible. Further, a heating chamber for raising the temperature of the material to be etched after etching to room temperature is independently provided adjacent to the processing chamber to improve processing efficiency.

[0008]

When the material to be etched is set to a predetermined temperature within the above temperature range and cooled, the composition particles of the film are easily adsorbed on the surface of the material to be etched, and neutral radicals and patterns that cause side etching The reaction efficiency with the side surface is reduced, and at the same time, the vapor pressure of the reaction product is reduced. These synergistic effects increase the thin film formation rate and reduce the side etching amount. That is, even if the thin film formation time is shortened by increasing the thin film formation rate, side etching can be suppressed. Further, by providing a heating chamber that raises the temperature of the material to be etched after processing to room temperature independently of the processing chamber, it is not necessary to raise the temperature of the sample table in the processing chamber, resulting in remarkable processing efficiency. improves.

[0009]

EXAMPLE 1 FIG. 1 is a diagram for explaining an example of the present invention. In FIG. 1, the processing chamber 1 is of a load-lock type, and by being separated from each other by a sample exchange chamber (heating chamber) 2 and a gate valve 3, moisture in the atmosphere causes dew condensation on a sample table 7 in the processing chamber 1. Is prevented. Liquid nitrogen 10 is placed inside the sample table 7.
Was introduced and cooled, and heating was performed by the electric heater 9, and the temperature sensor 18 was further arranged. Reference numeral 17 represents a Teflon table, 19 represents a thermometer, 20 represents an insulator, and 21 represents a liquefied gas container. In this embodiment, the sample table 7 is made of copper in order to enhance the cooling efficiency of the material to be etched 8, and in order to prevent contamination by spattering of copper, the sample table 7 is covered with the quartz cover 6 except the portion on which the material to be etched 8 is placed. Has been done. The thickness of the quartz cover 6 is preferably 5 mm or more in order to prevent the surface of the quartz cover 6 from being cooled and to prevent the reaction gas and reaction products from adhering. Acts as a trap for SF ₆ gas, and it is difficult to control the gas pressure. Further, the quartz cover 6 can be replaced by a Teflon cover depending on the implementation conditions, and the vacuum seal portion where the inside of the sample stage 7 and the processing chamber 1 are in contact is kept airtight by the metal O-ring 5. The voltage supplied to the electric heater 9 was a pulse voltage, and the pulse interval was set in the range of 0.1 to 60 seconds depending on the set temperature of the sample table 6. Further, the output signal from the temperature sensor 18 was sent to the heater power source 12 and the gas supply control system 23 via the feedback circuit 22 to control the heating and cooling of the sample table 7. As a result, the temperature of the sample table 7 could be controlled to the set value ± 2 ° C. The sample exchange chamber 2 precools the material 8 to be etched before it is transferred to the processing chamber 1 and heats the material 8 to be etched after processing. Sample stand 13 provided in the sample exchange chamber 2
A quartz table 16 (which can be replaced by Teflon is also provided) is provided on the surface that comes into contact with the material to be etched 8. A gas cooled by liquid nitrogen flows in from the cooling gas supply port 14 to cool the material 8 to be etched. Etching material 8
In order to prevent damage to the sample, the flow rate of the cooling gas was gradually increased and gradually cooled until the temperature of the sample stage 7 of the processing chamber 1 was reached. After the etching process is completed, the material to be etched 8
Is transported to a sample table 13 provided in the sample exchange chamber 2 and heated to room temperature by a heating lamp 15.

In etching using the above apparatus, Si is used as the material to be etched, the temperature is −80 ° C., the etching gas is SF ₆ , the film forming gas is CCl ₄ , and SF.
₆ and CCl ₄ were set to 40 seconds and 5 seconds in one cycle, respectively, and the etching treatment was performed for a total of 225 seconds in 5 cycles. As a result, the etching depth was 1 μm and the side etching amount was 0.1 μm or less. . On the other hand, in order to obtain the same result as above without cooling the material to be etched,
SF ₆ and CCl ₄ 1 cycle each set time is 2
The etching processing time was set to 0 second, and a total of 12 cycles required an etching treatment time of 480 seconds. That is, by alternately introducing the etching gas and the film-forming gas to cool the material to be etched, in this example, the processing time could be shortened by about 47%.

Next, the temperature of the sample table 7 was changed in the range of 0 to -150 ° C., and the etching shapes of Si were compared. Figure 3 is a diagram showing the relationship between the temperature of the sample table and the side etching amount. At a temperature of -80 ° C or less, a remarkable side-etching decrease tendency is seen, and the side etching amount at -100 ° C decreases to 0.05 μm or less. did. Further, when the temperature is −120 ° C. or lower, the etching rate is lowered, which is not preferable.
From this result, the optimum etching temperature in this example is −
It turns out that it is 100-120 degreeC.

In the etching using the etching apparatus shown in FIG. 1, when SiCl ₄ was used as the etching gas instead of SF ₆ , the optimum temperature was -80 to -1.
00 ° C, side etching amount is about 0.05 μm
Reduced to

When W was used as the material to be etched, the effect of reducing the side etching amount was observed from -20 ° C, and the optimum temperature was in the range of -40 to -80 ° C.

Other materials to be etched are Al,
_{SiO 2, Si 3 N 4,} Mo, Ti, Ta, for even such as photoresist, although each approximately difference, the effect of side-etching inhibition due to cooling were observed.

Further, in the apparatus shown in FIG. 1, when liquid helium was used as the liquefied gas for cooling instead of liquid nitrogen, the cooling efficiency was high and the sample stage could be cooled in a shorter time than liquid nitrogen. . Other gases such as liquid ammonia and trichloromonofluoromethane can also be used practically.

<Embodiment 2> FIG. 2 shows another embodiment of the present invention, showing an example of an apparatus using microwave plasma etching. The same reference numerals as those in FIG. 1 represent the same parts as in FIG. Reference numeral 24 represents an apparatus for setting the timing time for automatically opening and closing the gas line valve in order to alternately introduce the etching gas and the thin film forming gas into the processing chamber 1. The microwave excited by the magnetron 25 is guided to the waveguide 26 to generate plasma in the processing chamber 1. The magnet 27 functions to increase the excitation efficiency by the ECR (electron cyclotron resonance) action. Si etching was performed using the apparatus having the above-mentioned configuration, and the gas supply time for one cycle of SF ₆ and CCl ₄ was set to 20 seconds and 3 seconds, respectively. According to this apparatus, the ionization efficiency is high, and the density of active species is higher than that of the apparatus shown in FIG. 1, so that an etching amount of 1 μm in depth was obtained in a total processing time of 92 seconds for 4 cycles. Without cooling, the processing time of each cycle was 20 seconds, and the same etching amount was obtained in 160 seconds by repeating this for 4 cycles. Therefore, the total processing time was reduced to 58%. In addition, using this device, SF ₆ gas
On the other hand, the amount of side etching when etched in the temperature range of −80 to −120 ° C. was 0.05 μm or less.

In this embodiment, the electric heater is used as the heating heater, but the heater may be used with other heat sources.

[0018]

As a result of the practice of the present invention, the optimum temperature for the material to be etched and the processing gas can be set in a wide range, and the results are recognized in shortening the etching processing time and suppressing side etching. It showed a remarkable effect in improving accuracy. Further, the processed material is conveyed to the sample exchange chamber (heating chamber) and heated to room temperature, so there is no risk of dew condensation when taken out to the outside. Further, since the temperature of the sample table provided in the processing chamber does not rise to room temperature, the time required for the next etching is shortened and the processing efficiency is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a curve diagram showing the relationship between the temperature of the sample table and the amount of side etching.

[Explanation of symbols]

1 ... Treatment room, 2 ... Sample exchange room (warming room), 3 ... Gate valve, 4 ... Processing gas supply port, 5 ... O ring, 6 ... Quartz cover, 7 ... Sample stand, 8 ... Etching material, 9 ... Electrothermal heater, 10 ... Liquid nitrogen, 11 ... RF power source, 12 ... Heater power source, 13 ... Sample stage, 14 ... Cooling gas supply port, 15 ... Heating lamp, 16 ... Quartz stage, 17 ... Teflon stage, 18
... Temperature sensor, 19 ... Thermometer, 20 ... Insulator, 21 ... Liquefied gas container, 22 ... Feedback circuit, 23 ... Liquefied gas supply control system, 24 ... Reactive gas opening / closing control system, 25 ... Magnetron, 26 ... Waveguide , 27 ... Magnet, 100 ...
plasma.

Claims (5)

[Claims] 1. A processing chamber for etching a cooled material to be etched using plasma of a processing gas, and a processing chamber provided separately from the processing chamber and carrying in the material to be etched etched in the processing chamber. A low temperature dry etching apparatus comprising: a heating chamber that heats the carried etching target material to raise the temperature of the etching target material to room temperature. 2. The low temperature dry etching apparatus according to claim 1, wherein the heating chamber is provided adjacent to the processing chamber. 3. The low temperature dry etching apparatus according to claim 1, wherein the heating chamber has a means for heating the material to be etched by a heating lamp. 4. The low-temperature dry etching apparatus according to claim 1, wherein the heating chamber has means for heating the material to be etched by a heater. 5. The etching in the processing chamber comprises:
The low temperature dry etching apparatus according to any one of claims 1 to 4, wherein the temperature of the material to be etched is 0 to -200 ° C.