JPH0622213B2 - Sample temperature control method and apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a sample temperature control method and apparatus, and more particularly to a sample temperature control method and apparatus suitable for controlling the temperature of a substrate.

[Background of the Invention]

One of the important applications of an apparatus that performs vacuum processing on a sample, for example, processing using plasma (hereinafter abbreviated as plasma processing), for example, a dry etching apparatus, is a fine pattern in the manufacture of minute solid state elements such as semiconductor integrated circuits There is the formation of.
This fine pattern is usually formed by dry etching using a pattern drawn by exposing and developing ultraviolet rays on a polymer material called a resist applied on a semiconductor substrate (hereinafter, abbreviated as a substrate) which is a sample, as a mask. It is done by transferring to.

During such dry etching of the substrate, the mask and the substrate are heated by heat of chemical reaction with the plasma and impact incident energy of ions or electrons in the plasma. Therefore, when sufficient heat radiation cannot be obtained, that is, when the temperature of the substrate is not well controlled, the mask is deformed or deteriorated so that a correct pattern cannot be formed, or it is difficult to remove the mask from the substrate after dry etching. It causes the inconvenience. Therefore, 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, Japanese Patent Publication No. 56-53.
As shown in Japanese Patent Publication No. 853, the sample table to which the output of the high frequency power source is applied is water-cooled, the material to be processed is placed on the sample table through the dielectric film, and the DC voltage of the sample table is changed. By applying a potential difference to the dielectric film through the plasma, the electrostatic attraction force generated by this causes the workpiece to be adsorbed to the sample stage, and reduces the thermal resistance between the workpiece and the sample stage. There are those that effectively cool the material to be processed.

In the conventional technique of the first example, even if the material to be processed and the sample stage are substantially brought into close contact with each other by electrostatic attraction as described above, they are not completely flat from a microscopic point of view. There is little contact between the material to be processed and the sample stage, and there are many minute gaps. Further, the process gas enters the gap, and the gas becomes a thermal resistance. In a general dry etching apparatus, the material to be processed is usually 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. Therefore, the reduction of the gap due to the electrostatic attraction force is almost the same from the viewpoint of the thermal resistance, and the effect is increased by the increase of the contact area. Therefore, in order to reduce the thermal resistance between the material to be processed and the sample table and cool the material to be processed more effectively, a large electrostatic attraction force is required. Therefore, such a technique has the following problems.

(1) It is difficult for the material to be processed to separate from the sample table.
It takes time to convey 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 substance to be processed, but if this potential difference becomes large, the substance to be processed,
That is, since the damage to the elements in the substrate becomes large, the yield deteriorates, and the fine processing of the thin gate film, which is required more and more as the integration degree of the integrated circuit increases, the yield becomes worse.

A second example of the prior art is, for example, Japanese Patent Laid-Open No. 57-14.
As disclosed in Japanese Patent No. 5321, there is a method in which a gas gas is blown from the back surface of the wafer to directly cool the wafer with the gas gas.

In the conventional technique of the second example, 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 gas gas flows into the etching chamber instead of staying on the cooling surface side of the wafer, an inert gas such as GHe has a large effect on the process.
Not available for all processes.

As a third example of the prior art, for example, E.I. J. Egerton
Others, Solid State Technology, Vol.25, No.8, P84
87 (1982-8), between an electrode, which is a water-cooled sample stage, and a substrate which is mounted on the electrode and whose outer periphery is pressed by the mechanical clamping means and fixed to the electrode. Further, there is a method in which GHe having a pressure of about 6 Torr is circulated to reduce the thermal resistance between the electrode and the substrate, thereby effectively cooling the substrate.

In the prior art of the third example, even if the outer periphery of the substrate is fixed by a clamp, the outflow of GHe into the vacuum processing chamber is unavoidable. Therefore, the same problem as in the above-mentioned second prior art is encountered. And also has the following problems.

(1) Since the mechanical clamping means presses the outer periphery of the substrate to fix the substrate to the electrodes, the substrate is circulated by GHe.
Due to the gas pressure of the above, it deforms to a convex shape in a middle height in the peripheral supporting state.
For this reason, the amount of the gap between the back surface of the substrate and the electrode becomes large, and the heat conduction characteristic between the substrate and the electrode is deteriorated accordingly. Therefore, the substrate cannot be cooled sufficiently effectively.

(2) Since the electrode is provided with a mechanical clamping means that presses and fixes the outer periphery of the substrate, the device manufacturing area in the substrate is reduced and the plasma uniformity is impaired. During operation of the means, there is a risk that reaction products adhering to the mechanical clamping means will fall off the mechanical clamping means and dust will be generated, and further, the substrate transfer becomes extremely complicated, resulting in an increase in size of the apparatus. Reliability decreases as it does.

As described above, these conventional techniques have not been sufficiently considered in terms of effective cooling of the sample, the influence of the gas flowing on the back surface of the substrate on the process, and the like.

[Object of the Invention]

An object of the present invention is to provide a sample temperature control method and apparatus that can effectively control the temperature of a sample to be vacuum-processed and reduce the influence of heat transfer gas on the process.

[Outline of Invention]

The present invention relates to the inside of the back surface which is the surface opposite to the surface to be processed of the sample to be vacuum-processed, at least the surface portion of the outer periphery of the sample and the surface at a position separated from the outer periphery in the sample center direction. Part of the sample is adsorbed and held on the sample table, and the heat transfer gas is supplied to the gap between the back surface of the sample and the sample table and other than the adsorbed and held surface part by the gas supply means. The deformation of the sample due to the gas pressure of the gas is prevented, the increase in the gap between the back surface of the sample held in close contact and the sample stage is suppressed, the temperature of the sample under vacuum is effectively controlled, and the heat transfer gas The effect of heat transfer gas on the process is reduced by suppressing the outflow into the vacuum processing chamber.

Example of Invention

As a device for vacuum-treating a sample, for example, a plasma treatment, there are a dry etching device, a plasma CVD device, a sputtering device and the like. Here, an embodiment of the present invention will be described taking the dry etching device as an example.

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

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 as a sample stage is electrically insulated and hermetically provided via an insulator 11. The vacuum processing chamber 10 has a discharge space 30 and a lower electrode.
An upper electrode 40 is provided inside so as to face 20 in the up-down direction.

An insulator 60 is embedded in the surface of the lower electrode 20 corresponding to the back surface which is the surface opposite to the surface to be processed of the substrate 50 which is a sample. Further, the lower electrode 20 is formed with a groove 21 that forms a heat transfer gas supply path. For the insulator 60 and the groove 21,
Details will be described later with reference to FIGS. 2 and 3. Lower electrode
The gas supply path 23a and the gas discharge path 23a communicate with the groove 21.
b and are formed. A coolant channel 22 is formed in the lower electrode 20. The lower electrode 20 has a coolant channel 22
A refrigerant supply path 24a and a refrigerant discharge path 24b are formed in communication with each other.

A conduit 70a connected to a gas source (not shown) is connected to the gas supply path 23a, and one end of a conduit 70b is connected to the gas discharge path 23b. A mass flow controller (hereinafter abbreviated as MFC) 71 is provided in the conduit 70a, and the conduit 70b is provided.
An adjusting valve 72 is provided in the. The other end of the conduit 70b is joined and connected to an exhaust conduit 12 that connects the vacuum processing chamber 10 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 conduit 90b is connected to the refrigerant discharge path 24b.

A high frequency power supply 101 is connected to the lower electrode 20 via a matching box 100, and a direct current power supply 103 is connected to the lower electrode 20 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 grounded.

Further, the upper electrode 40 is formed with a processing gas discharge hole (not shown) that opens into the discharge space 30 and a processing gas flow path (not shown) that communicates with the processing gas discharge hole. A conduit (not shown) connected to a processing gas supply device (not shown) is connected to the processing gas flow path.

Next, a detailed structure example of the lower electrode 20 shown in FIG. 1 is shown in FIGS.
It will be described with reference to the drawings.

In FIG. 2 and FIG. 3, the gas supply passage 23a shown in FIG.
In this case, the conduit 25a is formed, and in this case, the conduit 25a is provided so as to be movable up and down with the center of the substrate mounting position of the lower electrode 20 as an axis. Outside the conduit 25a, the conduit 25b is arranged to form the gas discharge passage 23b shown in FIG. Outside the conduit 25b, the refrigerant supply passage 24 shown in FIG. 1 is provided.
A conduit 25c is arranged to form a. On the outside of the conduit 25c, the refrigerant discharge passage 24b shown in FIG.
25d is provided. The upper end of the conduit 25b is connected to the electrode upper plate 26, and the upper end of the conduit 25d is connected to the electrode upper plate receiver 27 below the electrode upper plate 26. At the upper end of the conduit 25b, an empty space 28 is formed by the upper electrode plate 26, the upper electrode plate receiver 27, and the conduit 25b. A dividing plate 29 is internally provided in the empty chamber 28 to form the refrigerant flow path 22, and the upper end of the conduit 25c is connected to the dividing plate 29.

In this case, a plurality of radial heat transfer gas dispersion grooves 21a and circumferential heat transfer gas dispersion grooves 21b are formed on the surface of the electrode upper plate 26 on which the substrate (not shown) is placed. There is. The heat transfer gas dispersion grooves 21a and 21b are 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 placed. In this case, at least the outer peripheral surface of the sample in the surface on which the substrate is placed and the surface partial coating at a position more distant from the outer periphery in the sample center direction are coated.

In FIGS. 2 and 3, 110 is an electrode cover that protects the surface of the upper electrode plate 26 where the substrate is not placed, and 111 is an insulating cover that protects the lower electrode 20 except the surface of the upper electrode plate 26. , 112 is a shield plate. Further, at the upper end of the conduit 25a, a pin 113 for pointing the substrate from the back side when the substrate is placed on the electrode upper plate 26 and when the substrate is detached from the electrode upper plate 26.
However, in this case, three lines are arranged at intervals of 120 degrees.

In addition, the depth of the grooves 21a and 21b should be such that the gap between the back surface of the substrate and the bottom of the grooves 21a and 21b when the substrate is adsorbed (hereinafter referred to as the groove gap) is equal to or longer than the mean free path length of the heat transfer gas. For example, since the heat transfer effect of the heat transfer gas is reduced, it is preferable to select the depths of the grooves 21a and 21b so that the groove gap is preferably equal to or less than the average free path length of the heat transfer gas. good.

The area of the portion of the back surface of the substrate that is substantially adhered to the insulating film by electrostatic adsorption (hereinafter, abbreviated as an adsorption portion) depends on 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 the substrate from floating from the lower electrode 20, it is selected by the necessary electrostatic adsorption force determined by the pressure difference between the gas pressure of the heat transfer gas and the pressure of the vacuum processing chamber 10. For example, the pressure of the heat transfer gas is 1
When the pressure in the vacuum processing chamber 10 is 0.1 Torr in Torr, the electrostatic adsorption force required to prevent the substrate from rising from the lower electrode 20 is about 1.3 g / cm ² , and therefore, the electrostatic adsorption force is less than this. The area of the part is selected to be about ⅕ of the back surface area of the substrate. It is needless to say that this example is just an example, and if the area of the attraction portion is increased to almost the entire back surface of the substrate, the electrostatic attraction force can be reduced accordingly.

In the dry etching apparatus of FIGS. 1 to 3 configured as described above, the substrate 50 is transferred into the vacuum processing chamber 10 by a known transfer device (not shown), and then the outer periphery of the back surface is insulated. It is arranged on the lower electrode 20 corresponding to the object 60. After the placement of the substrate 50 on the lower electrode 20 is completed, the processing gas supplied from the processing gas supply device to the gas flow passage through the conduit flows through the gas flow passage and then the discharge space 30 from the gas discharge hole of the upper electrode 40. Is released to. 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 glow discharge occurs between the lower electrode 20 and the upper electrode 40. By this glow discharge, the processing gas in the discharge space 30 is turned into plasma, and the etching processing of the substrate 50 is started by this plasma. Also, along with this, the lower electrode
A DC voltage is applied to 20 from a DC power supply 103. substrate
When the etching treatment with plasma of 50 is started, the substrate 50 is electrostatically adsorbed to the lower electrode 20 by the self-bias voltage generated by this plasma treatment process and the DC voltage applied to the lower electrode 20 by the DC power supply 103,
The substantially entire surface including at least the surface portion of the outer periphery of the sample in the back surface of the substrate 50 and the surface portion at a position more distant from the outer periphery in the sample center direction are substantially brought into close contact with each other and fixed.
After that, the heat transfer gas, for example, GHe, is supplied to the grooves 21a and 21b from the gas source through the MFC 71 and the gas supply path 23a in order. As a result, the groove 21 is formed over the entire small gap between the back surface of the substrate and the lower electrode 20 which are substantially in contact with each other.
GHe is supplied from a and 21b. At this time, GHe is M
The gas amount is controlled and supplied by the operation of the FC 71 and the adjusting valve 72. In some cases, the back surface of the substrate and the lower electrode 20,
Specifically, it is possible to use GHe enclosed in the gap with the insulator 60. Further, in this case, by electrostatic attraction of the substantially entire back surface of the substrate 50, that is, at least the surface portion of the back surface of the substrate 50 at the outer periphery of the sample and the surface at a position separated from the outer periphery in the sample center direction. By electrostatic attraction with the part,
The substrate is held between the inside and the outside, and the substrate 50 is deformed into a convex shape having a middle height by the gas pressure, and the back surface of the substrate 50 and the lower electrode 2
The heat transfer gas is prevented from spreading to the substrate
Can be supplied over the entire back surface. As a result, the thermal resistance between the lower electrode 20 and the substrate 50, which is cooled by the coolant flowing through the coolant channel 22, for example, water or low temperature liquefied gas, is uniformly reduced over the entire back surface of the substrate, and the substrate 50. Are cooled effectively, that is, uniformly and efficiently. In other words, the substrate can be effectively cooled by adsorbing and holding at least the outer surface and the inner surface of the back surface of the substrate. afterwards,
When approaching the end of etching, the supply of GHe to the grooves 21a and 21b is stopped, and with the end of etching, the discharge space
The supply of the processing gas to 30 and the application of the DC voltage and the high frequency power to the lower electrode 20 are stopped. After that, continue to the substrate
The electrostatic attraction force generated in 50 is released. In this case, the pin 113, which is electrically kept at the same potential as the upper electrode plate 26, comes into contact with the substrate 50, whereby the static electricity is removed and the pin 113 is removed.
The substrate 50 is removed on the lower electrode 20 by the operation of.
After that, the substrate 50 is transferred to the vacuum processing chamber 10 by a known transfer device.
It is carried out. The static electricity can also be removed by stopping the application of the high-frequency power after stopping the application of the DC voltage.

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

(1) In addition to pressing and fixing the substrate to the lower electrode only on the outer periphery as in the past, at least the outer surface and the inner surface of the back surface of the substrate are adhered by electrostatic attraction. By fixing, substantially the entire back surface of the substrate can be fixed in close contact, so that the deformation of the substrate due to the gas pressure of the heat transfer gas GHe can be prevented, and the gap between the back surface of the substrate fixed to the lower electrode and the lower electrode can be prevented. An increase in quantity can be suppressed. Therefore, it is possible to prevent deterioration of the heat conduction characteristic between the substrate and the lower electrode, and to effectively cool the substrate.

(2) Since at least the outer periphery of the back surface of the substrate is adsorbed, GHe, which is a heat transfer gas, suppresses the outflow into the vacuum processing chamber at the adsorbing part, so the effect of GHe on the process is reduced, and Can be used in the process.

(3) In comparison with the conventional technique in which the contact area between the substrate and the lower electrode is increased by electrostatic adsorption to reduce the thermal resistance, in this embodiment, the magnitude of electrostatic adsorption force is GHe pressure and vacuum treatment. It may be of a size necessary to prevent the substrate from floating due to the pressure difference from the pressure inside the chamber. The pressure difference between the GHe pressure and the plasma pressure is determined by the thermal resistance between the back surface of the substrate and the lower electrode. By reducing the amount within the allowable range, the effect of cooling the substrate can be sufficiently obtained even if the electrostatic attraction force is reduced.

(4) Since the electrostatic adsorption force is small, the substrate can be easily detached from the lower electrode, the transport time of the substrate after the etching process can be shortened, and the substrate can be prevented from being damaged.

(5) Since the electrostatic attraction force may be small, the potential difference applied to the substrate is small and damage to the elements in the substrate can be reduced. Therefore, there is no concern that the yield will be deteriorated even by fine processing of a 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 decrease in the device manufacturing area within the substrate and maintain good plasma uniformity. There is no risk of dust being generated when the substrate is placed on the lower electrode and when the substrate is removed from the lower electrode, and the substrate can be easily transported. As a result, the size of the device can be suppressed and the reliability can be improved. 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 connected to the outside of the vacuum processing chamber 10 and the discharge space 30. Light path 12
0 is formed. A transparent window 121 is provided in an airtight manner outside the vacuum processing chamber 10 of the optical path 120. Outside the vacuum processing chamber 10 corresponding to the translucent window 121, temperature measuring means, for example, an infrared thermometer 122 is provided. Infrared thermometer
The output of 122 is input to the process control computer 124 via the amplifier 123, and
The command signal calculated by 4 is input to the MFC71. In addition, in addition, the same devices and the like as those in FIG.

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

(1) Adjusting the supply amount of GHe while measuring the substrate temperature,
That is, by connecting the MFC that supplies GHe with the process control computer and controlling the GHe supply amount from the relationship between the substrate temperature and the GHe supply amount obtained in advance, the substrate temperature can be kept constant. Can hold Such control is particularly effective in 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) When the plasma pressure is high, there is also a process in which the etching rate increases with the temperature rise of the substrate.In such a case, when the temperature of the substrate exceeds a preset constant temperature, It is possible to shorten the etching time while flowing GHe to enhance the cooling effect and prevent damage to the photoresist.

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

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

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, according to the present invention, at least the outer peripheral surface portion of the sample in the back surface, which is the surface opposite to the surface to be processed of the sample to be vacuum processed, is separated from the outer peripheral portion in the sample center direction. The surface portion of the position is adsorbed and held on the sample table, and the heat transfer gas is supplied to the minute gap between the back surface of the sample and the sample table which is adsorbed and held to prevent deformation of the sample due to the gas pressure of the heat transfer gas. Prevents the increase in the amount of gap between the back surface of the sample that has been adsorbed and held and the sample stage, effectively controls the temperature of the sample to be vacuum processed, and suppresses the flow of heat transfer gas into the vacuum processing chamber. Therefore, the effect of heat transfer gas on the process can be reduced.

[Brief description of drawings]

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. FIG. 4 is a block diagram showing another example of the dry etching apparatus embodying the present invention. 10 ... Vacuum processing chamber, 20 ... Lower electrode, 21, 21a, 21b ...
Groove, 22 ... Refrigerant flow path, 50 ... Substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukiya Hiratsuka 502 Jinritsucho, Tsuchiura-shi, Ibaraki Machinery Research Institute, Hiritsu Manufacturing Co., Ltd. (72) Inventor Fumio Shibata 794, Higashitoyoi, Kudamatsu, Yamaguchi Prefecture Hitachi, Ltd. Inside the Kasado Plant (72) Inventor Noriaki Yamamoto 794 Azuma Higashitoyo, Kudamatsu City, Yamaguchi Prefecture Stock Company Hitachi Ltd. Inside the Kasado Plant (72) Tsunehiko Tsubone, 794 Higashitoyoi, Kumamatsu City, Yamaguchi Prefecture Hitachi Ltd. (56) References JP 58-32410 (JP, A) Actual development 55-115047 (JP, U)

Claims (7)

[Claims] 1. A back surface which is the surface opposite to the surface to be processed of a sample to be vacuum-processed, and at least a surface portion of the outer periphery of the sample and a surface at a position separated from the outer periphery in the sample center direction. Part of the sample is adsorbed and held on the sample table, and is transferred to a gap between the back surface of the sample and the sample table and other than the surface part where the sample is adsorbed and held, via a gas supply path provided on the sample table. A method for controlling the temperature of a sample, which comprises supplying hot gas. 2. The temperature control method for a sample according to claim 1, wherein the adsorption of the sample is performed by electrostatic adsorption. 3. The surface portion of the sample on which the sample is adsorbed is required to prevent the sample from being lifted from the sample table due to the differential pressure between the gas pressure of the heat transfer gas and the pressure in the chamber for vacuum processing. The method for controlling the temperature of a sample according to claim 1, which has an area. 4. A back surface which is the surface opposite to the surface to be processed of a sample to be vacuum-processed, and at least a surface portion of the outer periphery of the sample and a surface portion at a position separated from the outer periphery in the sample center direction. And an adsorption means for adsorbing and holding the sample table on the sample table, and the heat transfer gas is supplied to a gap provided between the sample table and the back surface of the sample and the sample table other than the surface part held by the adsorption. A sample temperature control device comprising a gas supply path. 5. The sample temperature control device according to claim 4, wherein the adsorption means is an electrostatic adsorption means. 6. The electrostatic attraction means according to claim 5, wherein the electrostatic attraction means comprises an insulator provided on the sample table corresponding to the back surface of the sample and a DC power source connected to the sample table. Sample temperature control device. 7. The sample temperature control device according to claim 6, wherein the insulator is formed by coating an insulating film on a metal surface of the sample table.