JP2985761B2 - Sample processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample processing method utilizing electrostatic adsorption.

[0002]

2. Description of the Related Art A conventional apparatus is disclosed in, for example,
As described in JP-A-286249, a first electrode is provided inside an insulating layer or at a boundary between an insulating layer and a substrate, and a second electrode penetrating the insulating layer is exposed to or exposed from the surface of the insulating layer. In some cases, the wafer is made to protrude and a voltage is applied between the two electrodes to attract the wafer.

[0003]

The prior art described above does not consider the reliability of wafer suction, and is good for sucking a wafer without warpage when the second electrode is exposed. However, in the case of adsorbing a warped wafer, the second electrode may not be adsorbed without coming into contact with the wafer. Conversely, when the second electrode is protruded, it is good for sucking a warped wafer, but when sucking a wafer that does not warp, the second electrode is obstructive. There is a possibility that the wafer and the insulating layer do not completely adhere to each other and cannot be attracted. Further, since the wafer is in contact with the second electrode at the ground potential during the etching process, non-uniform distribution of ions incident on the wafer occurs, which adversely affects the etching characteristics, particularly the uniformity of the etching rate. There is fear.

An object of the present invention is to provide a sample processing method which can improve the reliability of wafer suction and does not adversely affect plasma processing characteristics.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a sample processing method in which a wafer is held on a sample table provided in a vacuum processing chamber by electrostatic attraction and the wafer is plasma-processed in the vacuum processing chamber. The elastic member provided on the sample stage corresponding to a part of the sample stage is set to the ground potential, the wafer is placed on the sample stage, the wafer is brought into contact with the elastic member, and then a negative voltage is applied to the sample stage to sample the wafer. After the wafer is electrostatically attracted, a heat transfer gas is introduced to the back of the wafer after the wafer is electrostatically attracted, and when the wafer is cooled to the target temperature, the elastic member is electrically floated to generate plasma in the vacuum processing chamber.
Is not carried out plasma treatment of the upper blade performs supply stop of the plasma extinguished and the heat transfer gas When plasma treatment is completed, the elastic member to re-ground potential, a positive voltage is applied a predetermined time to the other sample table, then the sample This is achieved by stopping the voltage application to the stage and transferring the wafer from the sample stage.

[0006]

An elastic member which can be connected to the ground potential is provided on the back surface of the wafer, the elastic member is set to the ground potential, the wafer is placed on the sample table, the wafer is brought into contact with the elastic member, and then a negative voltage is applied to the sample table. The wafer is electrostatically attracted to the sample table. As a result, the elastic member is deformed to the same level as the surface of the sample table by the weight of the wafer and the electrostatic attraction force, and the elastic member can be reliably brought into contact with the wafer regardless of whether or not the wafer is warped. Reliability can be improved. After the wafer is electrostatically attracted, a heat transfer gas is introduced into the back surface of the wafer, and when the wafer is cooled to a target temperature, the elastic member is electrically floated to generate plasma and perform plasma processing. As a result, the ions in the plasma do not locally flow through the wafer, and the adverse effect on the plasma processing characteristics can be prevented. When the plasma processing is completed, the plasma is extinguished and the supply of the heat transfer gas is stopped, the elastic member is set to the ground potential again, and a positive voltage is applied to the sample stage for a certain period of time, after which the voltage application to the sample stage is stopped. Thus, the wafer can be easily removed from the sample table, and the wafer can be transferred from the sample table.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In this case, the plasma processing apparatus is applied to, for example, a magnetic field microwave apparatus. A discharge tube 2 made of, for example, quartz is provided above the vacuum chamber 1 to form a vacuum processing chamber. The vacuum chamber 1 is provided with a gas supply hole 6 connected to a gas supply source (not shown) for supplying a processing gas for plasma processing, for example, an etching process in the vacuum processing chamber. An exhaust port 7 connected to a vacuum pump 9 for depressurizing and evacuating via a pressure adjusting valve 8 is provided.

[0008] A waveguide 3 surrounding the discharge tube 2 is provided outside the discharge tube 2, and a solenoid coil 5 for generating a magnetic field in the discharge tube 2 is provided outside the waveguide 3. At the end of the waveguide 3, a magnetron 4 for emitting microwaves is provided.

At the bottom of the vacuum chamber 1, there is provided a sample stage 11 on which a wafer 18 to be processed can be placed via an insulating material 10. An insulating film 17 is provided on the upper surface of the sample stage 11 by coating, for example, and the wafer 18 is disposed on the insulating film 17. The sample stage 11 is connected to a DC power source 22 via a high-frequency power source and a low-pass filter 28 so that high-frequency power and DC voltage can be applied to the sample stage 11. The DC power supply 22 can be switched between positive and negative voltages by a changeover switch 23.

A coolant channel 12 is provided in the sample stage 11, and a coolant supply device 13 for circulating a coolant capable of cooling the sample stage 11 is connected thereto. At the center of the sample stage 11,
Push-up pins 14 used for transferring the wafer 18 are provided, and the push-up pins 14 are connected to a push-up device 15. A heat transfer gas, for example, He gas can be supplied through a valve 19 and a mass flow controller 20 to a gap in a space provided with the push-up pins 14 at the center of the sample table 11. It can be supplied.
Further, an exhaust passage for He gas connected to the vacuum pump 9 via the valve 21 is provided in the gap.

Further, as described in detail in FIGS. 2 and 3, a conductive member, which is an elastic member, is provided on the upper portion of the sample stage 11 at a position corresponding to the back surface of the wafer 18 outside the convex portion on the upper surface of the sample stage 11. A leaf spring 25 is provided, and the conductive leaf spring 25 is supported by a susceptor 24 and fixed with screws 26. A lead wire 27 is connected to the conductive leaf spring 25, and the other end is grounded via a low-pass filter 28 and a switch 29. The lead wire 27 is led out of the vacuum chamber 1 through the feedthroughs 31 and 32.

The changeover switch 23 and the switch 29 of the DC power supply 22 are operably connected by a control signal from the control device 30. The control device 30 controls the wafer 18
Switch, the changeover switch 23 is connected to the contact a, a negative voltage is applied to the sample table 11, and the switch 29 is connected to the ground. The controller 30 turns off the switch 29 during the plasma processing of the wafer 18 so as to be in an electrically floating state. In some cases, it may be connected to the ground during processing. The control device 30 controls the wafer 1
To remove 8 from the sample stage 11, the changeover switch 23 is connected to the contact b, and a positive voltage is applied to the sample stage 11, and in this case, the switch 29 is connected to the ground.

The apparatus configured as described above allows the processing gas introduced from the gas supply holes 6 into the vacuum processing chamber to interact with the microwave electric field generated by the magnetron 4 and the magnetic field generated by the solenoid coil 5. The wafer 1 is turned into plasma by using the same, and high-frequency power is applied to the sample table 11 by the high-frequency power supply 16 to control the energy of ions in the plasma incident on the wafer 18 while controlling the wafer
8 is etched.

At this time, the sample stage 11 is
Is cooled by the coolant supplied to the coolant channel 12. Thereby, the wafer 18 is cooled using the He gas supplied to the back surface of the wafer 18 as a heat transfer medium. At this time, the valve 19 is open and the valve 21 is closed.

Here, after the wafer 18 is placed and held on the sample stage 11 and processed,
The process of removing from the sample stage 11 will be described with reference to FIG. First, the conductive leaf spring 25 is set to the ground potential by the switch 29 (this is shown in step 31), and in this state, the wafer 18 is placed on the sample table 11 by the transfer device (this is shown in step 32). It should be noted that the details of the arrangement of the wafers 18 are loaded into the vacuum processing chamber by a transfer means (not shown), and the loaded wafers 18 are loaded.
Is lifted up by the push-up pins 14, and after the transfer means escapes, the push-up pins 14 are lowered to place the wafer 18 on the sample stage 1.
1 above. As a result, the wafer 18 is
When it is arranged on the upper side, the conductive leaf spring 25 contacts the back surface of the wafer 18.

Next, the changeover switch 23 is operated by the control device 30, a negative voltage is applied to the sample stage 11 by the DC power supply device 22, and the wafer 18 is electrostatically attracted to the sample stage 11 (this is referred to as step 33). Shown). In this state, the valve 19 is opened to introduce He gas into the back surface of the wafer 18 (this is shown in step 34). As a result, the temperature of the wafer 18 rapidly drops to substantially the same temperature as the temperature of the sample stage 11. Then, when the wafer 18 is cooled to the target temperature (this is shown in step 35), the conductive leaf spring 2
5 is turned off by turning off the switch 29 (this is shown in step 36), and plasma is generated to start etching (step 37).
Shown in After that, when the etching process is completed, the plasma is extinguished (this is shown in step 38). At the same time, the valve 19 is closed to stop the He gas (step 39).
Shown in ), Again by the switch 29, the conductive leaf spring 25
To the ground potential (this is shown in step 40).
Then, in this state, the changeover switch 23 is operated by the control device 30, and a positive voltage is applied to the sample stage 11 by the DC power supply device 22 for a certain period of time (this is shown in step 41). As a result, the charge on the insulating film 8 is erased, and the removal of the wafer 7 is facilitated. After a certain period of time, the changeover switch 23 is set in a floating state, the output from the DC power supply 22 is set to 0 V (this is shown in step 42), the valve 21 is opened, and the inside of the flow path for supplying heat transfer gas is exhausted. (This is shown in step 43).

With the above operation, one etching process is completed, and the wafer 7 is transferred to another station by the transfer device (this is shown in step 44).

As described above, according to the present embodiment, when the wafer 18 is placed on the sample stage 11, the conductive plate spring 25 comes into contact with the wafer 18 on the back surface of the wafer 18, and the conductive plate 25 The wafer 18 by electrostatic attraction force
As a result, the wafer 18 is securely held by suction on the sample table 11. Thereby, the reliability of wafer suction is improved. Further, during the plasma processing, the switch 29 is set in an electrically floating state to perform the wafer processing.
The ions in the plasma do not locally flow through the wafer 18 and do not adversely affect the plasma processing characteristics. In addition, when removing the wafer, a positive voltage can be applied to the sample stage 11, so that the removal of the wafer 18 can be performed easily. Further, the conductive leaf spring 25 is covered by the susceptor 24 and the wafer 18, protected by He gas leaking from the back surface of the wafer 18, and the plasma is applied to the conductive leaf spring 2.
Since it does not penetrate into the five parts, the conductive leaf spring is not damaged.

Next, another embodiment of the present invention will be described with reference to FIGS. In this figure, the same reference numerals as those in FIGS. 1 to 3 denote the same members, and a description thereof will be omitted. This drawing differs from FIGS. 1 and 2 in that the conductive leaf spring 25 is
Is provided at the upper end of the. In this case, the lead wire 27 goes out of the vacuum chamber 1 through the inside of the push-up pin 14.

In the apparatus configured as described above, processing is performed in the same steps as in the above-described embodiment. As a result, the same effect as in the first embodiment can be obtained. Further, in this embodiment, since the conductive leaf spring 25 is provided on the push-up pin 14, there is an effect that the configuration of the sample stage is simplified. In this embodiment, the elastic member is a conductive leaf spring. However, a conductive material may be provided at the tip of an elastic member such as a leaf spring or a coil spring.

[0021]

According to the present invention, there is an effect that the reliability of wafer suction can be improved and that the plasma processing characteristics can be prevented from being adversely affected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a detailed sectional view of a conductive leaf spring portion of FIG. 1;

FIG. 3 is a plan view of FIG. 2 as viewed from A.

FIG. 4 is a step diagram for implementing the present invention using the apparatus of FIG. 1;

FIG. 5 is a configuration diagram illustrating a plasma processing apparatus according to a second embodiment of the present invention.

FIG. 6 is a detailed cross-sectional view of the conductive plate spring section of FIG. 5;

[Explanation of symbols]

2 ... discharge tube, 4 ... magnetron, 5 ... solenoid coil, 11 ... sample stand, 14 ... push pin, 17 ... insulating film, 1
8 wafer, 22 DC power supply device, 23 switch, 25 conductive plate spring, 29 switch, 30 control device.

Continuation of front page (58) Fields investigated (Int.Cl. ⁶ , DB name) H01L 21/68 C23F 4/00 H05H 1/46 C23C 16/50 H01L 21/3065

Claims (1)

(57) [Claims] In a sample processing method for holding a wafer on a sample stage provided in a vacuum processing chamber by electrostatic attraction and performing plasma processing on the wafer in the vacuum processing chamber, the wafer is made to correspond to a part of the back surface of the wafer. The elastic member provided on the sample stage is set to the ground potential, the wafer is placed on the sample stage, the wafer is brought into contact with the elastic member, and then the wafer is applied by applying a negative voltage to the sample stage. Electrostatically adsorbed to the sample stage, a heat transfer gas is introduced to the back surface of the wafer after the electrostatic adsorption of the wafer, and the elastic member is electrically floated when the wafer is cooled to a target temperature,
Plasma is generated in the vacuum processing chamber to perform plasma processing on the wafer, and when the plasma processing is completed, the plasma is extinguished and the supply of the heat transfer gas is stopped, the elastic member is again set to the ground potential, and the other A sample processing method, comprising: applying a positive voltage to a table for a certain period of time; thereafter, stopping applying voltage to the sample table, and transporting the wafer from the sample table.