JPH05291384A - Electrostatic attraction method - Google Patents

Abstract

PURPOSE:To provide an electrostatic attraction method by which a strong attracting force is uniformly obtained throughout the entire surface of a wafer even in plasma; the wafer temperature is evened: the wafer is completely chucked before/after plasma processing; and the wafer is easily removed. CONSTITUTION:An electrostatic attraction apparatus which sucks a wafer onto a flat plate insulator by applying positive and negative voltages to a pair of electrodes, respectively, embeded in the insulator and isolated from each other. For use in plasma processing, the electrostatic attraction apparatus is constituted as follows: negative voltage is changed into positive voltage during plasma processing (t3-t8) so that positive voltage is applied to both electrodes; the original state that positive and negative voltages are applied to a pair of electrodes, respectively, is restored just before the completion (t6-t7) of the plasma processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic attraction method mainly used in semiconductor manufacturing equipment. In a plasma processing apparatus such as a dry etching apparatus used for manufacturing a semiconductor device, a substrate to be processed (hereinafter referred to as a wafer)
An electrostatic chuck (hereinafter referred to as an electrostatic chuck) is often used to fix the wafer, but this electrostatic chuck can provide uniform adhesion over the entire surface even in plasma, and keep the wafer temperature uniform. Moreover, it is desired that the wafer can be easily removed after the plasma treatment.

[0002]

2. Description of the Related Art A conventional electrostatic chuck used for a stage of a plasma processing apparatus such as a dry etching apparatus is a one-pole type electrostatic chuck that applies a positive voltage to an electrode embedded in a flat plate-shaped insulator to adsorb a wafer. There are two types, one is a pair of electrodes and the other is a two-pole type in which positive and negative different voltages are applied to the respective electrodes to adsorb the wafer.

FIG. 8 is a diagram showing a conventional electrostatic attraction method using a one-pole type electrostatic chuck. (A) shows a case where a wafer is installed (without plasma) and (b) shows a case where it is in plasma, In the figure, 1 is a semiconductor wafer, 2 is a chuck electrode, 3 is a chuck dielectric (insulator), 4 is D.
C power source, 5 is plasma, G ₁ and G ₂ are ground, and CU is negative charge charged up by charged particles from the plasma.

In this one-pole type electrostatic chuck,
As indicated by reference numeral G ₁ in (a), the semiconductor wafer 1 which is the object to be adsorbed is not adsorbed unless it is grounded. When used in a plasma etching apparatus or the like, the wafer cannot be processed unless it is brought to a floating potential, so that the wafer 1 cannot actually be grounded G ₁ and therefore the suction force in this state cannot be obtained. However, during etching, as shown in Figure (b),
Since the wafer 1 is negatively biased by the charged particles from the plasma as indicated by the symbol UC, the attraction force can be obtained without grounding the wafer.

FIG. 9 is a diagram showing a conventional electrostatic attraction method using a two-pole type electrostatic chuck. Reference numerals 2A and 2B in FIG.
Indicates a pair of chuck electrodes, PC ₁ and PC ₂ indicate polarized charges, and other symbols indicate the same objects as in FIG.

In this two-pole type electrostatic chuck, 1
A positive voltage and a negative voltage having different polarities are applied to the pair of chuck electrodes 2A and 2B, respectively, to attract the wafer 1. Therefore, as shown in the figure, the wafer 1 has a characteristic that an attracting force can be obtained when the wafer 1 is at a floating potential.

[0007]

As described above, in the one-pole type electrostatic chuck, the attraction force does not work unless it is in plasma. Therefore, the wafer is likely to be displaced on the chuck before and after the wafer processing in which plasma is not generated, which hinders the transportation of the wafer. In addition, since excess electrons are accumulated on the wafer in the plasma, the chuck is turned off (O
(FF) Even if the wafer is forcibly peeled off due to the strong residual adsorption force, there were problems such as damage to the wafer and jumping of the wafer, resulting in misalignment.

When the bipolar electrostatic chuck as described above is used in a plasma device, as shown in FIG. 10 using the same reference numerals as those in FIGS. 8 and 9, the electrostatic chuck is applied to a wafer during plasma 5 treatment. Due to the negative (−) bias voltage (CU) applied, the repulsive force (F ₁ ) is applied to the wafer 1 on the negative electrode 2A of the chuck.
Will work. Therefore, on the negative electrode 2A, the wafer 1
However, there is a problem in that the heat conduction between the wafer 1 and the chuck is different between the negative electrode 2A and the positive electrode 2B due to the floating state, resulting in a large temperature distribution on the wafer 1. (F ₂ is a suction force) Therefore, in the present invention, even in plasma, a strong adsorption force is uniformly obtained over the entire surface of the wafer, the temperature of the wafer can be made uniform, and the adhesion before and after the plasma treatment is completely performed. It is another object of the present invention to provide an electrostatic adsorption method in which a wafer can be easily removed.

[0009]

To solve the above problems, a positive voltage and a negative voltage are applied to a pair of electrodes embedded in and separated from a plate-shaped insulator to form a substrate to be processed on the insulator. When an electrostatic adsorption device for adsorbing is used in plasma processing, the negative voltage is switched to a positive voltage during plasma processing to apply a positive voltage to all electrodes, or the plasma processing Immediately before the end of, the electrostatic attraction method according to the present invention includes a step of returning to the original state in which a positive voltage and a negative voltage are applied to the electrodes of the pair.

[0010]

FIG. 1 is a diagram for explaining the principle of the present invention, which is a time chart of the chuck voltage application method. In the figure, t ₁ is when the wafer is mounted, t ₂ is when the adsorption voltage is applied to the A electrode and the B electrode,
t ₃ is the start of plasma processing, t ₄ is the start of voltage inversion of the B electrode, t ₅ is the completion of voltage inversion of the B electrode, t ₆ is the start of voltage recovery of the B electrode, and t ₇ is the recovery of voltage of the B electrode Where t ₈ is the end of the plasma treatment, t ₉ is the stop of the voltage application to the A and B electrodes, t ₁₀ is the separation of the wafer, τ ₁ is the voltage rise time, τ ₂ is the voltage fall time, and T is the plasma. Indicates the processing time.

In the present invention, a bipolar electrostatic chuck having the same structure as the conventional one is used. And according to the invention,
A wafer is mounted on the electrostatic chuck (t ₁ ), and a positive (+) voltage is applied to the pair of electrodes, for example, the A electrode, and a negative (−) voltage is applied to the B electrode.
Voltage is applied to firmly adsorb and fix the wafer (t ₂ ). Next, while plasma is applied to the wafer and plasma processing is being performed (t _{3 to} t ₈ ), that is, T is A,
A positive (+) voltage is applied to both B electrodes. As a result, a negative (-) charge is supplied from the plasma and the wafer charged to a negative (-) potential is similarly attracted by the two electrodes, and the entire surface of the wafer is uniformly attracted and fixed on the electrostatic chuck. To be done. Therefore, the heat conduction from the entire surface of the wafer toward the electrostatic chuck is made uniform, so that the temperature distribution in the wafer surface during the plasma processing is made uniform.

Further, immediately before the plasma processing is completed (t ₈ ) (t ₇ ), the two electrodes are restored to the original state in which voltages having different polarities of positive (+) and negative (−) are applied again, and the wafer is restored. negative which has been excessively accumulated within (-) because it can escape the charge to the plasma, wafer removed and it is possible to reduce the residual adsorption force of the wafer leaving time t ₁₀ becomes easy, and the plasma treatment Positive (+) and negative (-) voltages are applied to the two electrodes except for medium (t _{3 to} t ₈ ), so the electrostatic chuck loses its attractive force even when it is not in plasma. It never happens.

When the polarity of the electrode voltage is switched, if a sharp change is applied, the potential of the device formed on the wafer will change instantaneously and a current will flow in the device, causing damage. Therefore, in the present invention, it is more desirable to prevent the damage on the device on the wafer by providing the rising time τ ₁ and the falling time τ ₂ of the voltage having a predetermined slope when switching the polarities.

[0014]

EXAMPLES The present invention will be described in detail below with reference to illustrated examples. 2 is a schematic diagram of a reactive ion etching (RIE) apparatus used in one embodiment of the present invention, FIG. 3 is a schematic diagram of a substrate stage section in the same embodiment, and FIG. 4 is a schematic diagram of an electrostatic chuck in the same embodiment. 5, FIG. 5 is a time chart diagram of the chuck voltage application method in the same embodiment, FIG. 6 is an in-plane temperature distribution diagram of the processed wafer in the same example, and FIG. 7 is an in-plane temperature distribution of the processed wafer in the conventional method. It is a figure. The same object is denoted by the same reference numeral throughout the drawings.

As shown in FIG. 2, the RIE apparatus used in one embodiment of the present invention attracts and holds the Si wafer 1 on the electrostatic chuck 6, and a fixed amount of the Si wafer 1 is supplied from the gas introduction port 8 through the mass flow controller 7. For example, argon (Ar) gas is introduced into the processing chamber 9, rf power is supplied to the rf electrode 11 by a high frequency (rf) power source 10, Ar plasma 5 is generated in the processing chamber 9, and the temperature at that time is transmitted through infrared rays. An infrared thermometer 13 including an infrared camera a and a main body b is used for measurement through a window 12, and further, an electrostatic chuck 6 is equipped with a DC power source 4, and electrodes of the DC power source 4 and the electrostatic chuck 6 are provided. A polarity switching means 14 is interposed between 2A and 2B.

FIG. 3 is a schematic cross-sectional view of the electrostatic chuck arrangement portion, that is, the substrate stage portion in the above RIE apparatus.
Shows when the wafer is adsorbed and (b) shows when the wafer is detached. In the figure, 1 is a Si wafer, 6 is an electrostatic chuck, 11 is an rf electrode, 15 is an eject pin projecting hole, 16 is an eject pin, and 17 is an eject pin. An insulator is shown, and the eject pin 16 projects from the eject pin projecting port 15 in the electrostatic chuck 6 so that the wafer 1 can be detached from the electrostatic chuck 6.

4A and 4B are schematic views of the electrostatic chuck used in the embodiment, where FIG. 4A is a plan view and FIG. 4B is a sectional view, in which 2A and 2B are made of Cu. Of the chuck electrode, 3 is a chuck dielectric, 15 is an eject pin protruding port, and 18 is an Al pedestal.

The chuck dielectric 3 of the electrostatic chuck 6 is made of alumina ceramics and has a thickness of 0.5 mm. The pair of A electrodes 2A and B electrodes 2B having different polarities are alternately arranged concentrically.

With this structure, in the present embodiment, the plasma treatment of one surface of the Si wafer was performed while applying the chuck voltage to the electrostatic chuck 6 according to the time chart shown in FIG.

That is, the wafer 1 is mounted on the electrostatic chuck 6 at t ₁ , and first, at t ₂ , for example, the A electrode 2A +
The wafer 1 is attracted by applying a DC voltage of -500V to the B electrode 2B of 500V. Then, at t ₃ , the rf electrode 11, 13.56MH
z, after generating plasma 5 to apply a high frequency power of 300 W, varying in t ₄ ~t ₅ for example the voltage of the B electrode 2B to + 500V. In this state, the Si wafer 1 is uniformly attracted by the negative (-) bias voltage given by the plasma 5 onto the electrostatic chuck 6 to which +500 V is applied to all the electrodes. And, t ₆ just before the end of the plasma treatment
After returning the voltage of the B electrode 2B to -500V at t _7, to end the cut plasma treatment rf power at t _8. After that, from t _{9 to} t ₁₀ , the A electrode 2A and the B electrode 2B are set to 0 V, and the wafer 1 is separated from the chuck 6.

FIG. 6 shows the temperature at each point on the diameter of the wafer 1 in the Ar plasma 5 in the above embodiment. As can be seen from this figure, the maximum temperature difference on the wafer in this example was about 16 ° C.

The above results show that during the plasma treatment, A and B were used all the time.
In the conventional method of applying +500 V and -500 V voltage to the electrode of No. 2 and adsorbing the wafer on the electrostatic chuck, the wafer after being exposed to Ar plasma generated with the same rf power as in the above embodiment for 2 minutes. The temperature difference is about 26 ° C. as shown in the temperature distribution chart of FIG. 7, which is a significantly improved value.

Further, in the above-described embodiment, since the voltages of the same height with different polarities, that is, + 500V and -500V, are applied to the A electrode and the B electrode again immediately before the plasma processing is finished, they are excessively accumulated in the wafer 1. The negative (-) charges that are generated can be released into the plasma, the residual adsorption force is lost, and the wafer can be detached very easily. It never happened.

Furthermore, since + 500V and -500V voltages are applied to the electrodes A and B, respectively, when the plasma processing is not performed, the plasma processing is performed like the conventional one-pole type electrostatic chuck. There will be no displacement of the wafer before and after.

Further, in the method of the present invention, in order to prevent damage to the semiconductor element formed in the Si wafer 1, it is desirable that the polarity of the chuck voltage is not rapidly changed. Set the rise time of the voltage of τ ₁ and the fall time of the voltage of τ ₂ shown in FIG. 5 to 1 second. Note that τ ₁ and τ
_{A value of 2} for 1 second or more is sufficient.

[0026]

As described above, according to the electrostatic adsorption method of the present invention, even in plasma, a strong adsorption force can be obtained uniformly over the entire surface of the wafer, and the wafer temperature can be made uniform, and the plasma The wafer is completely fixed before and after the treatment, and the wafer can be easily removed without damaging or misaligning the wafer.

Therefore, the present invention is extremely effective in improving the quality and yield of plasma processing.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a schematic diagram of an RIE device used in one embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of a substrate stage section in the example.

FIG. 4 is a schematic diagram of an electrostatic chuck in the same example.

FIG. 5 is a time chart diagram of a chuck voltage applying method in the embodiment.

FIG. 6 is an in-plane temperature distribution diagram of the wafer to be processed in the example.

FIG. 7 is an in-plane temperature distribution diagram of a wafer to be processed by a conventional method.

FIG. 8 is a diagram showing a conventional electrostatic attraction method using a one-pole type electrostatic chuck.

FIG. 9 is a diagram showing a conventional electrostatic attraction method using a two-pole type electrostatic chuck.

FIG. 10 is a diagram showing a problem of the conventional method in the two-pole type electrostatic chuck.

[Explanation of symbols]

t _{1 When} mounted on wafer t _{2 When} adsorption voltage is applied to A and B electrodes t _{3 When} plasma processing is started t _{4 When} voltage reversal of B electrode is started t ₅ When voltage reversal of B electrode is completed t ₆ Voltage recovery of B electrode is started Time t ₇ When voltage recovery of B electrode is completed t _{8 When} plasma processing is completed t _{9 When} voltage application to A electrode and B electrode is stopped t ₁₀ Wafer detachment τ ₁ voltage rise time, τ ₂ voltage fall time, T is plasma Processing time 1 Si wafer 2A Electrostatic chuck A electrode 2B Electrostatic chuck B electrode 3 Chuck dielectric 4 DC power supply 5 Ar plasma 6 Electrostatic chuck 7 Mass flow controller 8 Gas inlet 9 Processing chamber 10 rf power supply 11 rf electrode 12 Infrared transmission window 13 Infrared thermometer 14 Polarity switching device

Claims (3)

[Claims] 1. A plasma treatment of an electrostatic attraction device for applying a positive voltage and a negative voltage to a pair of electrodes embedded and separated in a plate-like insulator to attract a substrate to be treated onto the insulator. In the electrostatic adsorption method, the negative voltage is switched to a positive voltage and a positive voltage is applied to all the electrodes during the plasma treatment. 2. An electrostatic adsorption method characterized in that, immediately before the plasma processing according to claim 1 is finished, the electrodes are returned to the original state in which a positive voltage and a negative voltage are applied to the pair of electrodes, respectively. 3. The switching between the negative voltage and the positive voltage is not performed instantaneously, but the rising time or rising time and falling time of the voltage at the time of switching is controlled to a predetermined length. 2. The electrostatic adsorption method described in 2.