JPH09213780A - Electrostatic chuck device, and method of separating electrostatic chuck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the separation of a wafer and prevent the breakage of a wafer when attracting and holding a wafer where an insulating layer such as a thermal oxide film or the like is made on the backside, by an electro static chuck using ceramics such as an aluminum oxide (Al2 O3 ), aluminum nitride (AlN), etc. SOLUTION: When attracting a wafer W with an electrostatic chuck 3, DC voltage (reverse voltage) of reverse polarity to that of the DC voltage applied between electrodes 4A and 4B is applied to it in separation. The range of the reverse voltage capable of separating it depends upon the DC voltage V1 and the temperature of the wafer W at attraction, therefore these relation is grasped by test in advance, and on the basis of the data, the value of the reverse voltage is adjusted to a proper value by a control means, according to the DC voltage V1 and the temperature of the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck device for sucking and holding a semiconductor wafer, for example, and a method for separating the electrostatic chuck.

[0002]

2. Description of the Related Art In a single-wafer type semiconductor processing apparatus, one semiconductor (hereinafter referred to as a wafer) is placed on a mounting table in a chamber and a predetermined processing is performed on the surface of the wafer. In that case, it is necessary to hold the wafer on the mounting table in order to surely process the semiconductor wafer. In recent years, the wafer is electrostatically charged without using mechanical holding means such as a clamp. An electrostatic chuck type mounting table structure, which is adapted to be held by suction on the mounting table, is being adopted.

This electrostatic chuck, as shown in FIG.
For example, the electrostatic chuck 12 is provided on the upper surface (mounting surface) of the mounting table 11 made of aluminum. The electrostatic chuck 12 is configured by providing a pair of electrodes 14 made of, for example, tungsten foil in a dielectric body 13.
4 is a DC power source 1 via a lead wire 15 and a switch 16
7 is connected.

This kind of electrostatic chuck is, for example, a plasma CVD (Chemical Vapor Deposi).
However, it is applied to a plasma processing apparatus for plasma etching or plasma etching. By the way, as the dielectric 13 used for the electrostatic chuck 12, a polyimide sheet or the like has been conventionally used. However, since the ECR plasma treatment causes a large amount of damage due to plasma, the inventors of the present invention have used Al ₂ O ₃ and Al.
We are considering using ceramics such as N.

In this processing apparatus, the wafer carried into the reaction container is placed on the electrostatic chuck 12, and the switch 1
6 is turned on to form a line of electric force by applying a DC voltage between the electrodes 14 and 14, whereby an electrostatic attractive force is generated between the wafer W and the electrostatic chuck 12, and the mounting table 1
The wafer W is adsorbed and held on the wafer 1. When the wafer W is removed after the plasma processing, the switch 16 is turned off to stop the application of the DC voltage. However, since the residual charge is large, the wafer W is irradiated with the plasma to remove the electric charge, and then a pusher pin (not shown) is mounted. The wafer W is floated by protruding from the upper surface of the mounting table 11, and the wafer is unloaded by a transfer arm (not shown).

[0006]

By the way, it has been found that when ceramics such as Al ₂ O ₃ and AIN are used as the dielectric 13, the residual adsorption force is considerably large for the wafer which has been subjected to the thermal oxidation treatment. This is because when a wafer is subjected to thermal oxidation in a heating furnace, a thermal oxide film is also formed on the back surface of the wafer, and this thermal oxide film has a high insulating property and the ceramics have a considerably large dielectric constant (insulating property). Is high).

However, if the residual suction force is large as described above, the wafer W may be cracked when the pusher pin is pushed up to separate the wafer W from the electrostatic chuck 12. Further, when the gate oxide film of the transistor is already formed in the circuit portion on the wafer W,
At the time of separation, excessive charged particles flowed in, which sometimes destroyed the gate oxide film.

As a method for separating the bipolar electrostatic chuck as described above, Japanese Patent Laid-Open No. 4-230051 discloses that a DC voltage having a polarity opposite to that of a DC voltage at the time of adsorption is applied to remove residual charges. However, when an insulating layer such as a thermal oxide film or a thermal nitride film is formed on the back surface of the wafer W, it is difficult to separate the wafer W by simply applying a reverse voltage. Knows.

The present invention has been made under the above circumstances, and an object thereof is to provide an electrostatic chuck device and a method of separating an electrostatic chuck that can easily separate a held body. It is in.

[0010]

According to the present invention, for example, a wafer having a backside surface (mounting surface side) on which a thermal oxide film is formed is attracted to an electrostatic chuck device, and the polarity is opposite to the DC voltage applied at the time of attraction. When a DC voltage (reverse voltage) is applied to release the reverse voltage, there is a range in which the reverse voltage can be detached and the range is different for each dielectric material. It was made based on the understanding that it depends on the temperature and.

That is, according to the first aspect of the invention, the mounting surface portion of the mounting table is made of a dielectric material, and a pair of electrodes are provided in the dielectric material to form an electrostatic chuck. In the electrostatic chuck device for applying a DC voltage for application to the dielectric body to electrostatically attract the held object, a reverse voltage having a polarity opposite to the DC voltage for attraction between the pair of electrodes. And a control means for adjusting the reverse voltage value according to the DC voltage value for adsorption and the temperature of the object to be held.

According to a second aspect of the invention, in the first aspect of the invention, the held body is a semiconductor wafer having an insulating layer formed on the back surface.

The invention of claim 3 is characterized in that, in the invention of claim 1 or 2, the dielectric is ceramics.

According to a fourth aspect of the present invention, the mounting surface portion of the mounting table is made of a dielectric material, and a pair of electrodes are provided in the dielectric material to form an electrostatic chuck. In an electrostatic chuck device for applying a DC voltage to electrostatically attract a held body to the dielectric, a DC voltage opposite to the DC voltage for attraction after the held body is electrostatically attracted to the dielectric. The reverse voltage is applied between the electrodes to perform a test for detaching the retained body, and the value of the reverse voltage at which the retained body can be detached, the value of the DC voltage for adsorption, and the temperature of the retained body The step of previously obtaining the data indicating the relationship between the data and the object to be held is electrostatically adsorbed to the dielectric, and then adjusted according to the temperature of the data and the electrostatic chuck and the DC voltage for adsorption. Applying a reverse voltage between the pair of electrodes to release the held body. And butterflies.

[0015]

1 is a diagram showing an electrostatic chuck device according to an embodiment of the present invention. Reference numeral 2 in FIG. 1 denotes a mounting table for a held object, for example, a wafer W. The mounting table 2 is configured by providing a heater 22 and an electrostatic chuck 3 in this order on a mounting table body 21 made of, for example, aluminum. . The mounting table 2 is provided with a pusher pin 23 that is lifted and lowered between a position retracted downward from the mounting surface and a position protruding upward by a lifting mechanism (not shown). Also, the mounting table body 2
A coolant passage 24 is formed in the heater 1,
Together with this, it constitutes a wafer temperature adjusting means.

The electrostatic chuck 3 constitutes the mounting table surface of the mounting table 2, and is a thin circular plate-shaped dielectric 41 having a thickness of 4 mm, for example.
A pair of electrodes 4A made of, for example, tungsten foil,
4B is embedded. Each of the electrodes 4A and 4B is formed in a semicircular shape in plan view as shown in FIG. 2, for example, and the feed lines 43A and 43B passed through the through holes 42 formed in the mounting table 2 in the vertical direction. It is electrically connected to one end.

The other ends of the power supply lines 43A and 43B are connected to the power supply section 5. The power supply unit 5 includes a DC power supply unit 51 whose voltage value can be varied, a power supply disconnection switch 52 for disconnecting a DC voltage from the DC power supply unit 51 between the power supply lines 43A and 43B, and the power supply line 43A. , 43B, and a polarity switching switch 53 for switching the polarity of the DC voltage applied.

The polarity switch 53 is used for the wafer W.
This is for applying a DC voltage (reverse voltage) having a polarity opposite to that of the DC voltage at the time of adsorption to the electrodes 4A and 4B at the time of disconnection of the switch 53 in this embodiment. The DC power supply unit 51 constitutes a reverse voltage applying means which is a constituent element of the present invention.

The DC voltage value of the DC power supply 51 and the switches 52 and 53 are controlled by the control means 6. The control means 6 includes a memory 61 that stores a table showing the relationship between the suction DC voltage value, the temperature of the wafer W, and the detachable reverse voltage value, a CPU (central processing unit) 62, and a switch switching unit 63. , And a voltage adjusting unit 64.

The CPU 62 gives a control signal to the switch switching section 63 for controlling ON / OFF of the power supply / disconnection switch 52 and switching control of the polarity switching switch 53 based on a predetermined sequence program, and also to the control means 6. The temperature of the wafer W during the process and the input DC voltage value for adsorption (DC voltage value given during adsorption) and the memory 61 which are input.
It has a function of giving an appropriate reverse voltage command value to the voltage adjusting unit 64 based on the table in FIG. Voltage adjusting unit 64
Is the DC power supply unit 51 based on the command value from the CPU 62.
Is controlled so that the reverse voltage value between the electrodes 43A and 43B is adjusted to an appropriate value, that is, the command value.

However, regarding the method of setting the reverse voltage value,
In addition to the above-described method, for example, as shown in FIG. 3, a recipe for the electrostatic chuck 3 in which the suction DC voltage value, the temperature of the wafer W, and the reverse voltage value are written in advance is determined for each wafer processing type. Alternatively, these recipes may be stored in the memory, the recipe corresponding to the wafer processing may be selected, and the DC power supply unit 51 may be controlled based on the reverse voltage value written in the recipe.

Next, setting of table data and recipe data in the memory 61 will be described. In order to obtain this data, the present inventor adhered an aluminum block to the surface of a 6-inch wafer, electrostatically attracted it to the electrostatic chuck shown in FIG. 1, attached one end of the wire to the aluminum block, and The other end was passed through a pulley, a 2 kg weight was attached, and a test was conducted to see how long the wafer was released from the electrostatic chuck after applying a reverse voltage between the electrodes.

Specifically, a direct-current voltage V1 for adsorption is applied between the electrodes for a time long enough to generate residual adsorption, in this example, for 2 minutes, and then a reverse voltage V2 is applied between the electrodes. The time from the application to the separation of the wafer was measured. As the wafer, one having a thermal oxide film with a thickness of about 3000 angstrom formed on the back side was used.

FIG. 4 is a graph in which the horizontal axis represents the reverse voltage value and the vertical axis represents the detachment time.
Temperature is 160 ° C., V1 is 1000 V and 16
This is the case when the voltage is set to 00V. However, the dielectric is AlN
(Aluminum nitrogen) is used. As can be seen from this graph, when the value of the reverse voltage V2 is small, it is difficult to separate (the separation time is long), and the larger the value of V2, the easier the separation becomes. However, it is not necessary that the value of V2 is large.
The larger the value of 2, the more difficult it is to come off.
That is, it can be seen that there is a range of reverse voltage V2 that can be separated.

In the actual electrostatic chuck, when the wafer is pushed up by the pusher pin, the wafer can be smoothly detached from the electrostatic chuck, and the detachment time of 60 seconds or less is sufficient in the above experimental apparatus. Has been confirmed in advance. Therefore, if the time that can be separated is 60 seconds or less,
The range of the removable reverse voltage V2 is about 100V to 1250V when V1 is 1000V, and V2 is 1600.
In the case of V, it is approximately 200V to 1100V.

When such a test is performed for each temperature of the wafer W while fixing the value of the DC voltage V1 for adsorption, for example, V1
Is 1000 V, it is possible to understand how the range of the removable reverse voltage V2 changes depending on the temperature. FIG. 5 shows such data with V1 of 500 V and 1000
3 is a graph in which the abscissa represents the temperature of the wafer W and the ordinate represents the reverse voltage V2. The inside of the graph connecting these plots is the range of reverse voltage that can be separated. Incidentally, in FIG. 6, Al ₂ is used as a dielectric.
The test results when O ₃ (aluminum oxide) is used are also shown.

When a data table or recipe is actually stored in the memory 61 shown in FIG. 1, under the conditions determined by the material of the dielectric material, the DC voltage V1 for adsorption and the temperature of the wafer W as described above. The reversible reverse voltage V2 value is written.

Next, the overall structure of the ECR plasma device to which the above electrostatic chuck device is applied will be briefly described with reference to FIG. This ECR plasma device includes a high frequency power supply unit E1 in a plasma chamber 71 on the upper side of the vacuum container 7.
For example, 2.45 GHZ microwave is guided from the waveguide 72 through the transmission window 73, and a plasma gas such as Ar gas or O ₂ gas is supplied from the plasma gas nozzle 74 into the plasma chamber 71 to further generate plasma. A magnetic field B is applied by an electromagnetic coil 75 provided outside the chamber 71 to generate electron cyclotron resonance. In addition, in the reaction chamber 76 on the lower side of the vacuum container 7, the reactive gas nozzle 77 is projected and at the bottom, the above-described mounting table 2 is placed.
Is provided. 23 is a pusher pin lifting mechanism 78
Is an exhaust pipe, 79 is a gate valve, and E2 is a plasma drawing power source.

Next, the operation of the above embodiment will be described. First, when the temperature of the wafer W and the DC voltage value for adsorption are input to the control means 6, these input conditions and the memory 61 are input.
The reverse voltage value is determined based on the data table in FIG. Further, as shown in FIG. 3, when the conditions regarding the electrostatic chuck 3 are incorporated in the recipe corresponding to the type of plasma processing, the reverse voltage value is determined by the selection of the recipe.

Then, the gate valve 79 shown in FIG. 7 is opened, and the wafer W is mounted on the mounting table 2, that is, the electrostatic chuck 3 by the cooperative operation of the transfer arm (not shown) and the pusher pin 23. 79 is closed and the inside of the vacuum container 1 is evacuated to a predetermined vacuum degree. At this time, a DC voltage of, for example, 1000 V is applied between the electrodes 4A and 4B of the electrostatic chuck 3 from the power supply section 5, and the wafer W is electrostatically adsorbed to the electrostatic chuck 3. Then, the wafer W is heated to a predetermined temperature, for example, 120 ° C. by the combination of the heater 22 and the coolant in the coolant channel 24, and, for example, Ar gas and O ₂ gas are discharged from the nozzle 74 to the nozzle 77.
, For example, SiH ₄ gas is introduced into the vacuum container 7,
SiH is generated by plasma ions flowing into the reaction chamber 76.
₄ is activated to form a SiO ₂ film on the wafer W.

After the plasma processing is completed, the switch contact of the switch 53 of the power feeding section 5 is switched to apply a reverse voltage value between the electrodes 4A and 4B of the electrostatic chuck 3. The application of the reverse voltage value is performed by the CPU 62 reading the reverse voltage value determined as described above and adjusting the voltage value of the DC power supply unit 51 by the voltage adjusting unit 64. This reduces the residual charge on the wafer W, weakens the electrostatic attraction force due to the residual charge, and pushes up the pusher pin 23 to separate the wafer W from the electrostatic chuck 3. Thereafter, the wafer W is transferred to a transfer arm (not shown) and unloaded from the vacuum container 7.

According to the above-described embodiment, the wafer W has already been subjected to the thermal oxidation treatment, the thermal oxide film which is the insulating film is formed on the back surface side, and ceramics is used as the dielectric 41 of the electrostatic chuck 3. When used, the range of the reverse voltage that can reduce the large residual charges existing in the wafer W after the direct-current voltage for adsorption is cut off to the extent that the separation of the wafer W is not affected is the range of the reverse voltage for each adsorption material. Since it is found that it depends on the DC voltage value and the temperature of the wafer W, and is configured to be adjusted to an appropriate reverse voltage value according to the conditions based on the data obtained by performing a test in advance, The wafer W can always be smoothly detached from the electrostatic chuck 3, and therefore the wafer W is not likely to be cracked, and the gate oxide film in the device of the wafer W is not likely to be broken. Therefore, it is very effective especially when ceramics are used as the dielectric.

However, the insulating film formed on the back surface of the wafer W is not limited to the thermal oxide film and may be, for example, a silicon nitride film. The processing device to which the electrostatic chuck device of the present invention is applied is not limited to the ECR plasma processing device, and may be applied to a CVD device, an etching device, a sputtering device, an ion implantation device, or the like. Furthermore, the electrostatic chuck device is not limited to the mounting table and may be used in combination with a transfer arm or the like.

[0034]

As described above, according to the present invention, when an object to be held is attracted and held by the electrostatic chuck, an appropriate reverse voltage according to the conditions is applied between the electrodes. It can be easily detached, and the held object can be prevented from cracking.
The present invention is particularly effective when a wafer on which an insulating film such as a thermal oxide film is formed is attracted and held by an electrostatic chuck using ceramics.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an electrostatic chuck device according to an embodiment of the present invention.

FIG. 2 is a plan view showing an electrostatic chuck.

FIG. 3 is an explanatory diagram showing data defining the usage conditions of the electrostatic chuck.

FIG. 4 is a graph showing a relationship between a reverse voltage and a detachment time in a wafer detachment test.

FIG. 5 is a graph showing a relationship between a wafer temperature and a range of reversible reverse voltage when Al ₂ O ₃ is used as a dielectric.

FIG. 6 is a graph showing the relationship between the wafer temperature and the range of reversible reverse voltage when AlN is used as a dielectric.

FIG. 7 is a vertical cross-sectional side view showing an example in which the electrostatic chuck device according to the embodiment of the present invention is applied to an ECR plasma processing apparatus.

FIG. 8 is a configuration diagram showing a conventional electrostatic chuck device.

[Explanation of symbols]

 2 Mounting Table 22 Heater 23 Pusher Pin 24 Refrigerant Flow Path 3 Electrostatic Chuck 4A, 4B Electrode 41 Dielectric 5 Feeding Unit 51 DC Power Supply 52, 53 Switch 6 Control Means 7 Vacuum Container 71 Plasma Chamber 75 Electromagnetic Coil 76 Reaction Chamber

Front page continued (72) Inventor Gohei Kawamura 1-24-1 Machiya, Shiroyama-cho, Tsukui-gun, Kanagawa Prefecture Tokyo Electron Tohoku Co., Ltd. Sagami Business Office

Claims (4)

[Claims] 1. A mounting surface portion of a mounting table is made of a dielectric material, and a pair of electrodes are provided in the dielectric material to form an electrostatic chuck, and a DC voltage for attraction is applied between the electrodes. In the electrostatic chuck device that electrostatically attracts the held body to the dielectric, a reverse voltage, which is a DC voltage having a polarity opposite to that of the DC voltage for attraction, is applied between the pair of electrodes at the time of separation. An electrostatic chuck device comprising: a reverse voltage applying unit; and a control unit that adjusts the reverse voltage value according to a DC voltage value for adsorption and a temperature of a held body. 2. The electrostatic chuck device according to claim 1, wherein the held body is a semiconductor wafer having an insulating layer formed on the back surface. 3. The electrostatic chuck device according to claim 1, wherein the dielectric is ceramics. 4. The mounting surface portion of the mounting table is made of a dielectric material, and a pair of electrodes are provided in the dielectric material to form an electrostatic chuck, and a DC voltage for attraction is applied between the electrodes. Then, in the electrostatic chuck device that electrostatically attracts the held body to the dielectric, after the held body is electrostatically attracted to the dielectric, a reverse voltage that is a DC voltage opposite to the DC voltage for attraction is applied. A test for releasing the held body by applying it between the electrodes is performed, and the value of the reverse voltage at which the held body can be released and the value of the direct-current voltage for adsorption,
A step of preliminarily obtaining data indicating the relationship with the temperature of the held body; and after the held body is electrostatically adsorbed to the dielectric, the temperature of the data and the electrostatic chuck, and a DC voltage for adsorption. And a step of applying a reverse voltage adjusted in accordance with the above-mentioned method between the pair of electrodes to separate the held body.