JP2626618B2 - Sample holding method for vacuum processing 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 method for holding a sample in a vacuum processing apparatus, and more particularly to a method for holding and holding a substrate by electrostatic attraction.

[0002]

2. Description of the Related Art One of the important applications of a vacuum processing, for example, a plasma processing (hereinafter abbreviated as "plasma processing"), for example, a dry etching apparatus is one of the important uses of a micro solid state device such as a semiconductor integrated circuit. Formation of fine patterns in the manufacture of This fine pattern is usually formed by dry etching using a pattern drawn by exposing and developing a polymer material called a resist applied on a semiconductor substrate (hereinafter abbreviated to “substrate”) as a mask as a mask. It is performed by transferring to.

At the time of dry etching of such a substrate, the mask and the substrate are heated by heat of chemical reaction with plasma or impact incident energy such as ions or electrons in the plasma. Therefore, when sufficient heat radiation cannot be obtained, that is, when the temperature of the substrate is not properly controlled, the mask is deformed or deteriorated, and a correct pattern cannot be formed.
A disadvantage arises in that it is difficult to remove the mask from the substrate after the dry etching. In order to eliminate these inconveniences, the following techniques have been conventionally used and proposed. Hereinafter, these conventional techniques will be described.

As a first example of the prior art, for example, as shown in Japanese Patent Publication No. 56-53853, a sample table to which an output of a high-frequency power supply is applied is cooled with water, and a work piece is processed on the sample table. A substance is placed via a dielectric film, and a DC voltage is applied to the sample stage to apply a potential difference to the dielectric film via plasma. In some cases, the thermal resistance between the workpiece and the sample stage is reduced to effectively cool the workpiece.

As a second example of the prior art, for example, as disclosed in Japanese Patent Application Laid-Open No. 57-145321, a gas gas is blown from the back surface of a wafer and the wafer is directly cooled by the gas gas. is there.

As a third example of the prior art, for example, EJ
Egerton et al., Solid State Technology, Vol. 25, No.
8, pages 84 to 87 (1982-8), an electrode which is a water-cooled sample stage, and a substrate which is mounted on the electrode and whose outer periphery is pressed against the electrode by mechanical clamping means and fixed thereto. In some cases, GHe having a pressure of about 6 Torr is passed between the electrodes to reduce the thermal resistance between the electrode and the substrate, thereby effectively cooling the substrate.

[0007]

However, these prior arts are not sufficiently considered in terms of effective cooling of the sample and the effect of the gas flowing on the back surface of the substrate on the process. There was such a problem.

In the first prior art, even if the above-described operation is performed, there is still little contact between the material to be processed and the sample table, and there is a slight gap when viewed microscopically. . Further, a process gas enters the gap, and this gas becomes a thermal resistance. In general dry etching equipment,
Usually, the material to be processed is etched by a process gas pressure of about 0.1 Torr, and the gap between the material to be processed and the dielectric film is smaller than the average free path length of the process gas. The reduction in the gap is almost the same in terms of the thermal resistance, and the effect is increased by the increase in the contact area. Therefore, a large electrostatic attraction force is required to reduce the thermal resistance between the material to be processed and the sample stage and to cool the material to be processed more effectively. For this reason, such a technique has the following problems.

(1) Since the material to be processed hardly separates from the sample table, it takes time to transport the material to be processed after the etching process is completed, or the material to be processed is damaged.

(2) In order to generate a large electrostatic attraction force,
It is necessary to give a large potential difference between the dielectric film and the material to be processed. However, if this potential difference is large, the material to be processed, that is, the element in the substrate is greatly damaged, and the yield is reduced. In the case of fine processing of a thin gate film, which is increasingly required as the integration degree of an integrated circuit increases, the yield is further reduced.

In the second prior art, the cooling efficiency of the wafer can be improved by using a gas gas having excellent thermal conductivity such as helium gas (hereinafter abbreviated as GHe). However, such a technique has the following problems.

(1) Since a large amount of gaseous gas flows into the etching chamber instead of staying on the cooling surface side of the wafer, even an inert gas such as GHe has a large effect on the process. Can not.

In the third prior art, even if the outer periphery of the substrate is fixed by a clamp, the flow of GHe into the vacuum processing chamber is unavoidable. Therefore, the same problem as in the above second prior art is obtained. Problem, and also has the following problem.

(1) Since the outer periphery of the substrate is pressed by the mechanical clamping means to fix the substrate to the electrode, the substrate is deformed to a convex shape at a middle height in the peripheral support state by the gas pressure of the flowing GHe. For this reason, the gap amount between the back surface of the substrate and the electrode increases, and accordingly, the heat conduction characteristics between the substrate and the electrode deteriorate. Therefore, the cooling of the substrate cannot be performed sufficiently effectively.

(2) Since the electrode is provided with mechanical clamping means for pressing and fixing the outer periphery of the substrate, the area for manufacturing the element in the substrate is reduced, and the uniformity of plasma is impaired. During the operation of the mechanical clamping means, there is a risk that reaction products adhered to the mechanical clamping means fall off the mechanical clamping means and generate dust,
Substrate transport becomes extremely complicated, resulting in an increase in the size of the apparatus and a decrease in reliability.

An object of the present invention is to provide a method for holding a sample in a vacuum processing apparatus using an electrostatic attraction force, the method comprising:
An object of the present invention is to provide a method for holding a sample of a vacuum processing apparatus which can be reduced .

[0017]

According to the present invention, at least the outer periphery of a sample to be vacuum-processed and the direction of the sample center more than the outer periphery.
Electrostatic adsorption and a position spaced on the sample stage in the vacuum processing chamber,
Holding, the back surface of the sample and the sample table held by suction
The heat transfer gas supplied to the gap between the front differential pressure between the heat transfer gas pressure in the sample back surface and said vacuum processing chamber of the processing gas pressure
Range in which the thermal resistance between the sample and the sample stage is sufficiently reduced.
And reducing the electrostatic attraction force in a range where the floating of the sample is prevented .

According to a feature of the present invention, the area of the adsorption portion electrostatically adsorbed to the insulating film on the back surface of the sample is determined by the difference between the gas pressure of the heat transfer gas and the pressure of the vacuum processing chamber. In order to prevent the air from rising, the pressure is selected based on the required electrostatic attraction force determined by the pressure difference between the gas pressure of the heat transfer gas and the pressure of the vacuum processing chamber. The area of the portion where the sample is adsorbed on the sample table by the electrostatic attraction force is preferably at least 1/5 of the area of the back surface of the sample.

[0019]

According to the present invention, the differential pressure between the processing gas pressure in the vacuum processing chamber and the heat transfer gas pressure on the back surface of the sample is determined by comparing the sample and the sample stage with each other.
Between the ranges where the thermal resistance during
In addition, by reducing the electrostatic attraction force within a range where the floating of the sample is prevented , a large electrostatic attraction force is not required,
An increase in the amount of gap between the back surface of the sample and the sample stage can be suppressed. In other words, since the electrostatic attraction force can be reduced,
Damage can be reduced.

According to the present invention, even when the electrostatic adsorption force is reduced, the cooling effect of the sample can be reduced as compared with the prior art in which the contact area between the sample and the lower electrode is increased by electrostatic adsorption to reduce the thermal resistance. Is sufficiently obtained. Since the electrostatic attraction force is small, it is easy to separate the sample from the lower power, and it is possible to shorten the transport time of the sample after the etching process,
Sample damage can be prevented. Further, since the electrostatic attraction force may be small, the potential difference applied to the sample is small, and damage to elements in the sample can be reduced. Therefore, there is no fear that the yield is deteriorated even in the fine processing of the thin gate film.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Vacuum processing of a sample, for example, plasma processing, includes dry etching equipment and plasma CVD.
Although there are an apparatus, a sputtering apparatus, and the like, an embodiment of the present invention will be described using a dry etching apparatus as an example.

An embodiment of the present invention will now be described with reference to FIGS.
This will be described below.

FIG. 1 shows a schematic configuration of a dry etching apparatus. On the bottom wall of the vacuum processing chamber 10 in this case, a lower electrode 20 serving as a sample stage is electrically insulated and provided airtight through an insulator 11. An upper electrode 40 is provided in the vacuum processing chamber 10 so as to have a discharge space 30 and face the lower electrode 20 in the vertical direction.

In this case, an insulator 60 is buried on the surface of the lower electrode 20 corresponding to the back surface of the substrate 50 corresponding to the periphery of the back surface of the substrate 50 in this case. Insulator 60
A groove 21 forming a heat transfer gas supply path is formed in the lower electrode 20 on the inside. The groove 21 communicates with the discharge space 30 when the substrate 50 is not placed. In addition, a groove (not shown) for gas dispersion connected to the groove 21 is formed in the insulator 60. The lower electrode 20 has a gas supply passage 23a and a gas discharge passage 23b formed in communication with the groove 21. In the lower electrode 20, a coolant channel 22 is formed. The lower electrode 20 is formed with a refrigerant supply path 24a and a refrigerant discharge path 24b in communication with the refrigerant flow path 22.

A gas supply passage 23a is connected to a conduit 70a connected to a gas source (not shown).
One end of a conduit 70b is connected to 3b. Conduit 7
A mass flow controller (hereinafter abbreviated as MFC) 71 is provided at 0a, and an adjustment valve 72 is provided at a conduit 70b. The other end of the conduit 70b is connected to the vacuum processing chamber 10
And a vacuum conduit 80 that connects the vacuum pump 80 and the vacuum pump 80. A conduit 90a connected to a refrigerant source (not shown) is connected to the refrigerant supply path 24a, and a refrigerant discharge pipe 90b is connected to the refrigerant discharge path 24b.

The lower electrode 20 has a matching box 1
A high-frequency power supply 101 is connected via a high-frequency circuit 00 and a DC power supply 103 is connected via a high-frequency cutoff circuit 102. The vacuum processing chamber 10, the high-frequency power supply 101, and the DC power supply 103 are each grounded.

The upper electrode 40 has a processing gas discharge hole (not shown) opened to the discharge space 30 and a processing gas flow path (not shown) communicating with the processing gas discharge hole. A processing gas supply device (not shown) is provided in the processing gas passage.
Are connected to each other (not shown).

Next, an example of the detailed structure of the lower electrode 20 of FIG. 1 will be described with reference to FIGS.

2 and 3, the gas supply path 2 shown in FIG.
3a is formed in this case by a conduit 25a,
In this case, is provided so as to be able to move up and down about the center of the substrate mounting position of the lower electrode 20 as an axis. Outside the conduit 25a, the gas discharge passage 23b shown in FIG.
5b is provided. Outside the conduit 25b, a conduit 25c is provided by forming the refrigerant supply passage 24a shown in FIG. Outside the conduit 25c, a conduit 25d is formed by forming the refrigerant discharge passage 24b shown in FIG. The upper end of the conduit 25b is connected to the upper electrode plate 26, and the conduit 25d
Is connected to an electrode upper plate receiver 27 below the electrode upper plate 26. An empty space 28 is formed at the upper end of the conduit 25b by the upper electrode plate 26, the upper electrode plate receiver 27, and the conduit 25b. A dividing plate 29 is formed in the vacant space 28 so as to form the refrigerant passage 22, and the upper end of the conduit 25 c is connected to the dividing plate 29.

An upper electrode plate 2 on which a substrate (not shown) is placed
In this case, a plurality of grooves 21a for dispersing heat transfer gas radially and grooves 21b for dispersing heat transfer gas circumferentially are formed on the surface of 6 in this case. Grooves 21a and 21b for dispersing heat transfer gas
Is connected to the conduits 25a and 25b. An insulator 60 is provided on the surface of the electrode upper plate 26 on which the substrate is mounted. In this case, the insulating film is coated.

In FIGS. 2 and 3, reference numeral 110 denotes an electrode cover for protecting the surface of the electrode upper plate 26 where the substrate is not mounted, and reference numeral 111 denotes a portion for protecting the lower electrode 20 other than the surface of the electrode upper plate 26. The insulating cover 112 is a shield plate. Further, at the upper end of the conduit 25a, pins 113 for supporting the substrate from the back side when the substrate is mounted on the electrode upper plate 26 and when the substrate is detached from the electrode upper plate 26, in this case, three pins at 120 ° intervals. This is installed.

The depth of the grooves 21a and 21b is determined by the gap between the back surface of the substrate and the bottom of the grooves 21a and 21b at the time of substrate suction (hereinafter, abbreviated as groove gap). In this case, the heat transfer effect of the heat transfer gas is reduced. Therefore, the depth of the grooves 21a and 21b is selected so that the groove gap is preferably equal to or less than the average free path length of the heat transfer gas. Good to do.

The area of the portion of the back surface of the substrate that is electrostatically attracted to the insulating film (hereinafter, abbreviated as the absorptive portion) is determined by the pressure difference between the gas pressure of the heat transfer gas and the pressure of the vacuum processing chamber 10. In order to prevent floating from the lower electrode 20, the selection is made based on a required electrostatic attraction force determined by a differential pressure between the gas pressure of the heat transfer gas and the pressure of the vacuum processing chamber 10. For example, if the pressure of the heat transfer gas is 1
When the pressure of the vacuum processing chamber 10 is 0.1 Torr and the pressure of the vacuum processing chamber 10 is 0.1 Torr, the required electrostatic attraction force for preventing the substrate from floating from the lower electrode 20 is about 1.3 g / cm ^2. The area of the portion is selected to be about 1/5 of the rear surface area of the substrate.

In the dry etching apparatus of FIGS. 1 to 3 configured as described above, the substrate 50 is loaded into the vacuum processing chamber 10 by a known transfer device (not shown).
The outer peripheral portion of the lower electrode is made to correspond to the insulator 60 so that the lower electrode 2
0. After the mounting of the substrate 50 on the lower electrode 20 is completed, the processing gas supplied to the gas flow passage from the processing gas supply device via the conduit flows through the gas flow passage, and then flows from the gas discharge hole of the upper electrode 40 to the discharge space 30. Will be released. After adjusting the pressure in the vacuum processing chamber 10, high-frequency power is applied to the lower electrode 20 from the high-frequency power supply 101, and a glow discharge occurs between the lower electrode 20 and the upper electrode 40. The processing gas in the discharge space 30 is turned into plasma by the glow discharge, and the etching of the substrate 50 is started by the plasma. At the same time, a DC voltage is applied to the lower electrode 20 from the DC power supply 103. The substrate 50 is electrostatically attracted to the lower electrode 20 and fixed by the self-bias voltage generated by the plasma processing process and the DC voltage applied to the lower electrode 20 by the DC power supply 103 when the etching process of the substrate 50 by the plasma is started. Is done. After that, the grooves 21a and 21b receive M
Heat transfer gas through the FC 71 and the gas supply path 23a in order,
For example, a processing gas is supplied. At this time, the processing gas is supplied in a controlled amount by operating the MFC 71 and the adjustment valve 72, and in some cases, the processing gas can be used in a space on the back surface of the substrate. Thereby, the thermal resistance between the lower electrode 20 and the substrate 50, which are cooled by the refrigerant flowing through the refrigerant flow path 22, for example, water or low-temperature liquefied gas, is reduced, and the substrate 50 is effectively cooled. Thereafter, when the end of the etching is approached, the grooves 21a,
The supply of the processing gas to 21b is stopped, and the supply of the processing gas to the discharge space 30 and the application of the DC voltage and the high-frequency power to the lower electrode 20 are stopped with the end of the etching. Thereafter, the electrostatic attraction force generated on the substrate 50 is subsequently released, and in this case, the static electricity is removed by the contact of the electrically grounded pin 113 with the substrate 50,
The substrate 50 is removed from the lower electrode 20 by the operation of the pin 113. Thereafter, the substrate 50 is carried out of the vacuum processing chamber 10 by a known transfer device. The static electricity can also be removed by stopping the application of the DC voltage and then stopping the application of the high-frequency power.

As described above, according to the present embodiment, the following effects can be obtained.

(1) Since the substrate can be fixed to the lower electrode using not only the outer periphery of the back surface of the substrate but also other portions of the back surface, deformation of the substrate due to the gas pressure of the processing gas as a heat transfer gas is prevented. Thus, it is possible to suppress an increase in the amount of gap between the lower electrode and the back surface of the substrate fixed to the lower electrode. Therefore, it is possible to prevent deterioration of the heat conduction characteristic between the substrate and the lower electrode, and it is possible to efficiently cool the substrate.

(2) Since at least the outer periphery of the back surface of the substrate is adsorbed, the processing gas, which is a heat transfer gas, is suppressed from flowing into the vacuum processing chamber at the adsorption section. Less and can be used for all processes.

(3) Compared with the prior art in which the contact area between the substrate and the lower electrode is increased by electrostatic attraction to reduce the thermal resistance, in this embodiment, the magnitude of the electrostatic attraction force is larger than that of the processing gas. The pressure may be large enough to prevent the substrate from rising due to the pressure difference between the pressure and the pressure in the vacuum processing chamber.The pressure difference between the processing gas pressure and the plasma pressure is determined by the difference between the back surface of the substrate and the lower electrode. Even if the electrostatic attraction force is reduced, the effect of cooling the substrate can be sufficiently obtained by reducing the thermal resistance within the range permitted by the thermal resistance.

(4) Since the electrostatic attraction force is small, it is easy to separate the substrate from the lower electric power, and it is possible to shorten the transport time of the substrate after the etching process and prevent the substrate from being damaged.

(5) Since the electrostatic attraction force may be small, the potential difference applied to the substrate is small, and damage to elements in the substrate can be reduced. Therefore, there is no fear that the yield is deteriorated even in the fine processing of the thin gate film.

(6) Since the substrate is fixed to the lower electrode by electrostatic attraction without using mechanical clamping means, it is possible to prevent a reduction in the element manufacturing area within the substrate and to maintain good plasma uniformity. Also, there is no danger of generating dust when the substrate is placed on the lower electrode and when the substrate is removed from the lower electrode, and further, the substrate can be easily transported, and as a result, the size of the apparatus can be suppressed. In addition, reliability can be improved.

FIG. 4 shows another example of the dry etching apparatus embodying the present invention. The top wall of the vacuum processing chamber 10 and the upper electrode 40 are provided outside the vacuum processing chamber 10 and the discharge space 30.
And an optical path 120 is formed. Light path 120
On the outside of the vacuum processing chamber 10, a light-transmitting window 121 is provided in an airtight manner. Vacuum processing chamber 10 corresponding to translucent window 121
Externally, a temperature measuring means, for example, an infrared thermometer 122
Is provided. The output of the infrared thermometer 122 is input to the process control computer 124 via the amplifier 123, and the command signal calculated by the process control computer 124 is input to the MFC 71. In addition, the same devices and the like as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

According to this embodiment, the following effects can be further obtained.

(1) The supply amount of the processing gas is adjusted while measuring the temperature of the substrate, that is, the MFC for supplying GHe is connected to the process control computer, and the difference between the substrate temperature and the supply amount of GHe determined in advance is obtained. By controlling the supply amount of GHe from the relationship, the substrate temperature can be maintained at a constant temperature. Such control is particularly effective at the time of dry etching of the Al-Cu-Si material, and the residue of the material to be etched can be reduced by controlling the temperature to a high temperature within a range where the photoresist is not damaged.

(2) In the case where the plasma pressure is high, there is also a process in which the etching rate increases with an increase in the temperature of the substrate. In such a case, the temperature of the substrate exceeds a predetermined temperature. In this case, the etching time can be reduced while flowing GHe to increase the cooling effect and prevent damage to the photoresist.

In the above-described embodiment, the electrostatic attraction force is used for the substrate attraction, but the vacuum attraction force can be used in a process in which the pressure of the plasma gas is high. Alternatively, the positive electrode and the negative electrode may be alternately arranged on the lower surface of the insulator to apply electrostatic attraction to the substrate. Further, in the case where overetching is further performed after the base material starts to be exposed, the supply of GHe is stopped when the base material starts to be exposed, and a DC voltage is applied reversely to the lower electrode. With this configuration, the electrostatic force remaining on the substrate at the end of the etching can be further reduced, so that the substrate is not damaged at the time of unloading the substrate, and the time required for unloading the substrate can be shortened. However, in this case, it is necessary to control so that the temperature of the substrate during etching is reduced by the temperature rise during over-etching. In addition, hydrogen gas,
A gas having good heat conductivity such as neon gas may be used.

The present invention has a similar effect in controlling the temperature of a sample that is placed and held on another substrate substrate to be cooled and subjected to vacuum processing.

[0048]

As described above, according to the present invention,
As compared with the conventional technique in which the contact area between the sample and the lower electrode is increased by electrostatic adsorption to reduce the thermal resistance, the effect of cooling the sample can be sufficiently obtained even if the electrostatic adsorption force is reduced.
Since the electrostatic attraction force is small, the sample can be easily detached from the lower power, and the transport time of the sample after the etching process can be shortened, and the sample can be prevented from being damaged. Also,
Since the electrostatic attraction force may be small, the potential difference applied to the sample is small, and damage to elements in the sample can be reduced. Therefore, there is no fear that the yield is deteriorated even in the fine processing of the thin gate film.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a dry etching apparatus embodying the present invention.

FIG. 2 is a detailed plan view of a lower electrode of FIG. 1;

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a configuration diagram showing another example of the dry etching apparatus embodying the present invention.

[Explanation of symbols]

10: vacuum processing chamber, 20: lower electrode, 21, 21a, 2
1b: groove, 22: refrigerant flow path, 23a: gas supply path, 24
a: refrigerant supply path, 50: substrate.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yukiya Hiratsuka 502 Kandamachi, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. Notoaki, Yamamoto, Inventor Noriaki Yamamoto, 794, Higashi-Toyoi, Katsumatsu-shi, Yamaguchi Pref.Hitachi, Ltd.Kasato Plant, Hitachi, Ltd. (56) References JP-A-58-32410 (JP, A) JP-A-58-132937 (JP, A) JP-A-55-115047 (JP, U) JP-B-56-53853 (JP, B2)

Claims (2)

(57) [Claims] (1) at least an outer periphery of a sample to be vacuum-processed;
A position separated in the sample center direction from the outer periphery is electrostatically adsorbed and held on the sample table in the vacuum processing chamber, and a heat transfer gas is supplied to a gap between the back surface of the sample and the sample table held by suction. Then, a differential pressure between the processing gas pressure in the vacuum processing chamber and the heat transfer gas pressure on the back surface of the sample is set between the sample and the sample stage.
A sample holding method for a vacuum processing apparatus, characterized in that the sample is reduced in a range where the thermal resistance is sufficiently reduced and the electrostatic attraction force is reduced in a range in which the sample is prevented from floating. 2. The vacuum according to claim 1, wherein an area of a portion where the sample is adsorbed on the sample table by the electrostatic attraction force is equal to or more than ５ of an area of the back surface of the sample. Sample holding method for processing equipment.