JPH10303185A - Etching apparatus and etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical etching apparatus and an etching method capable of effectively performing an etching at a process temperature lower than the plasma heating temperature. SOLUTION: The surface of a wafer 10 is etched by chemical species produced in a plasma produced in a space where the wafer 10 is. A cooling mechanism 4 cools the wafer 10 so that the process temperature at which the wafer 10 must be kept during etching is lower than the plasma heating temperature at which the wafer 10 reaches thermal equilibrium by the heat of the plasma and the temperature of the wafer 10 is kept equal to the process temperature while being etched. The heating mechanism 5 previously heats the wafer 10 so that the temperature of the wafer 10 reaches the process temperature when starting etching, stops heating when starting the etching or after the start, and switches to plasma heating of the wafer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching apparatus and a method for forming a plasma in a space facing a substrate and etching a surface of the substrate with chemical species generated by the plasma.

[0002]

2. Description of the Related Art An etching technique for etching the surface of a substrate with a chemical species generated by plasma is known as DR.
It has become an extremely important elemental technology for the manufacture of various semiconductor devices such as memories such as AM. Also, in the production of flat panel displays such as liquid crystal displays, etching is frequently used for forming circuit patterns and the like.

FIG. 4 is a schematic front view illustrating the structure of a conventional etching apparatus. The etching apparatus shown in FIG. 4 includes a processing vessel 1 in which a substrate 10 is disposed, a plasma forming means 2 for forming plasma in a space facing the substrate 10, and a position where predetermined chemical species generated by the plasma reach. And a substrate holder 3 on which the substrate 10 is arranged.

The processing container 1 is an airtight container provided with an exhaust system 11, and carries in and out the substrate 10 through a gate valve (not shown). Various types of plasma forming means 2 are known, but an inductive coupling type using a high-frequency coil 22 is employed in the apparatus shown in FIG. That is, the plasma forming means 2 includes a high frequency generator 21 for generating a high frequency of a predetermined frequency, and a high frequency generator 21.
A high-frequency coil 22 that transmits and excites the high-frequency waves generated in the high-frequency coil 22, a dielectric container 23 provided inside the high-frequency coil 22, and a gas introduction system 24 that introduces a plasma forming gas into the dielectric container 23. It is mainly composed of

The dielectric container 23 and the processing container 1 are airtightly connected, and a gas introduction system 24 introduces a gas for forming plasma into the dielectric container 23 via the processing container 1. The introduced gas is converted into plasma by the high frequency induced in the dielectric container 23, and the surface of the substrate 10 in the processing container 1 is etched by the action of active species and ions generated in the plasma. For example, in the case of etching silicon oxide (SiO ₂ ), a fluorinated carbon-based gas such as carbon tetrafluoride (CF ₄ ) is introduced together with a carrier gas such as hydrogen as a plasma forming gas, and is generated in the plasma. The fluorine-based ions and the fluorine-based active species reach the substrate 10, and the etching is performed by utilizing the reaction between these chemical species and silicon oxide.

In the conventional etching apparatus shown in FIG. 4, an electric field is applied between the plasma and the substrate 10 in order to positively use the ions in the plasma. May be caused. In this case, a substrate bias power supply 31 is connected to the substrate holder 3 as shown in FIG. The substrate bias power supply 31 generates a high frequency in many cases.
Substrate holder 3 via blocking capacitor 32
To be applied with a high frequency. Due to the interaction between the applied high frequency and the plasma, the surface of the substrate 10 is biased to a negative potential, and positive ions are extracted from the plasma and collide with the substrate 10. The surface of the substrate 10 is etched by utilizing the chemical action of ions or the physical action at the time of ion collision.

In the above-described etching process, the temperature of the substrate 10 during the etching is a very important parameter. For example, in the above-described etching of silicon oxide using carbon tetrafluoride, CF _x ions (X = 1,
Along with the etching of SiO ₂ according to (2) and (3), the deposition of the fluorocarbon film accompanying the reaction of the CF 4 gas in the plasma proceeds simultaneously. The deposition of the fluorocarbon film on the substrate 10 is affected by the temperature of the substrate 10, and the lower the temperature of the substrate 10, the higher the deposition rate of the fluorocarbon film. Since the fluorocarbon film hinders the etching of SiO ₂ by CF _x ions, when the deposition rate of the fluorocarbon film increases, normal etching does not proceed, and a correct etching pattern cannot be obtained.

The above points will be described in more detail with reference to FIG. FIG. 5 is a diagram illustrating a problem when the deposition rate of the fluorocarbon film is high. In FIG. 5, a silicon oxide film 100 is formed on a silicon substrate 10 to a predetermined thickness, and a photoresist 1 having plasma resistance is formed thereon.
The pattern No. 01 is formed as a mask. Substrate 1
0 is not low and the deposition rate of the fluorocarbon film is not high, the etching of the silicon oxide film 100 is performed as shown in FIG.
Then, etching is performed so as to dig substantially perpendicularly from the edge of the pattern of the photoresist 101, as shown by a dotted line.

However, when the temperature of the substrate 10 is lowered, the deposition rate of the fluorocarbon film is increased mainly near the edge of the pattern of the photoresist 101, and a large amount of the fluorocarbon film is deposited on this portion. Since this deposited film acts as a mask for etching,
As a result, the etching shape becomes tapered as shown by the solid line in FIG. In the etching of the silicon oxide film, a wiring material such as aluminum or tungsten is often embedded in the etched portion to establish conduction with the underlying silicon. However, if the tapered etching shape as described above occurs, the underlying silicon is etched. The contact portion between the semiconductor device and the contact wiring becomes small, the contact resistance increases, and the performance of the semiconductor device is easily deteriorated. On the other hand, if the temperature of the substrate 10 during the etching increases and exceeds the allowable temperature limit of the photoresist 101, thermal damage occurs to the photoresist 101, which may cause a problem such as pattern deformation.

Thus, in the etching process, the substrate 10
Is an important parameter and needs to be maintained at a predetermined temperature (hereinafter, process temperature) during etching. For this reason, in the conventional etching apparatus, the substrate 10 is placed on the substrate holder 3 with good thermal contact, and the substrate holder 3 is provided with a temperature adjusting mechanism so that the temperature of the substrate 10 is adjusted via the substrate holder 3. I have.

The temperature adjusting mechanism is specifically a cooling mechanism 4, which circulates a coolant in the substrate holder 3 and cools the substrate holder 3 to a predetermined temperature so that the temperature of the substrate 10 becomes the process temperature. Like that. That is, the substrate 10 is considerably heated by the plasma. This heating is mainly performed by ion bombardment from plasma or radiant heat of plasma emission. The temperature at which the substrate 10 reaches thermal equilibrium by this heating (hereinafter, plasma heating temperature) is higher than the above process temperature. Therefore, temperature control is required.

The temperature of the coolant is determined so that the temperature of the substrate 10 becomes a process temperature during the etching. That is, Qp is the heat given by the plasma, Qc is the amount of heat removed through the substrate holder 3 cooled by the refrigerant, and Q is the amount of heat released from the substrate 10 by other heat dissipation.
Substrate 1 that reaches equilibrium with Qp = Qc + Qd, where d
The temperature of the refrigerant is determined so that the temperature of 0 sufficiently matches the process temperature. For example, the input power for plasma formation is 1000 W, the pressure is 10 mTorr, and the process temperature is 87.
In the case of ° C., the temperature of the refrigerant is about 20 ° C.

[0013]

In the above-described conventional etching apparatus, since the temperature of the substrate is controlled only by cooling with a cooling medium, there are the following problems. This will be described with reference to FIG. FIG. 6 is a diagram for explaining a problem of the conventional etching apparatus. In FIG. 6, a curve indicated by -x- represents a temperature change of the substrate in the conventional apparatus.

In the above-described conventional etching apparatus,
The coolant is constantly circulating in the substrate holder, so that the temperature of the substrate holder at the start of etching is almost equal to the temperature of the coolant. Then, when the etching is started, as shown in FIG. 6, the substrate is heated by the plasma to gradually increase the temperature, and thereafter reaches thermal equilibrium and stabilizes. The time required to reach thermal equilibrium is about 55 seconds under the above-described conditions.

During the period in which the substrate temperature gradually increases at the beginning of the etching, the substrate temperature is naturally lower than the process temperature. For this reason, there is a problem that a problem such as a defective etching pattern due to an increase in the deposition rate of the fluorocarbon film is likely to occur. To solve this, it is effective to raise the temperature of the substrate at the start of etching up to about the process temperature.However, if this is performed only by setting the temperature of the coolant, the temperature of the substrate will be reduced during the etching. There is a problem that the temperature rises sharply beyond the temperature. For example, in the case where the process temperature is 87 ° C., if the etching is started in a state where the temperature of the coolant is 87 ° C. and the substrate holder is maintained at 87 ° C., the temperature of the substrate during the etching reaches an equilibrium at about 154 ° C. This temperature exceeds the heat resistance temperature of the photoresist of 120 ° C., and causes thermal damage to the photoresist.

Further, in the conventional configuration in which the temperature is controlled only by the refrigerant, there is a problem that the estimation of the etching time is difficult because the temperature of the substrate greatly changes as shown by a dotted line in FIG. That is, for example, in the case of etching silicon oxide with a fluorinated carbon-based gas described above, etching and deposition of a fluorocarbon film are proceeding in competition. That is,
The silicon oxide film is etched while etching the fluorocarbon film to be deposited. Therefore, the time required to complete the etching of the silicon oxide film having a predetermined thickness is affected by the deposition rate of the fluorocarbon film. When the temperature of the substrate greatly changes as shown in FIG.
The deposition rate of the fluorocarbon film also changes greatly. For this reason, it is difficult to estimate the time required for the completion of the etching, which causes a problem in process management.

The invention of the present application has been made to solve the above-described problems, and provides a practical etching apparatus and method capable of effectively performing an etching process in which the process temperature is lower than the plasma heating temperature. It is intended to provide.

[0018]

In order to solve the above-mentioned problems, the invention of claim 1 of the present application forms a plasma in a space facing a substrate, and etches a surface of the substrate by a chemical species generated by the plasma. A device,
A cooling mechanism for cooling the substrate and a substrate for heating the substrate in an etching apparatus in which the process temperature, which is the temperature of the substrate to be maintained during etching, is lower than the plasma heating temperature, which is the temperature at which the substrate reaches thermal equilibrium by heating from the plasma. A heating mechanism, wherein the cooling mechanism cools the substrate during etching so that the temperature of the substrate becomes the process temperature, and the heating mechanism heats the substrate in advance to start the etching. The temperature of the substrate is set to the process temperature, and the operation is stopped at the start of etching or thereafter. According to a second aspect of the present invention, in order to solve the above-mentioned problem, in the configuration of the first aspect, the cooling mechanism operates under the same condition as that during etching when being heated by the heating mechanism. The heating mechanism has a configuration in which the substrate holder is heated at the beginning of etching so that the thermal equilibrium temperature of the substrate holder reached by both the cooling by the cooling mechanism and the heating by the heating mechanism becomes the process temperature. . According to another aspect of the present invention, there is provided an etching method for forming a plasma in a space facing a substrate, and etching a surface of the substrate with a chemical species generated by the plasma. Process temperature, which is the temperature of the substrate to be
In an etching method that is lower than the plasma heating temperature at which the substrate reaches thermal equilibrium by heating from the plasma, the substrate is heated in advance by a heating mechanism so that the substrate temperature becomes the process temperature at the start of etching, and the etching is started. At or after that, the heating mechanism by the heating mechanism is stopped to switch to heating of the substrate by the plasma, and at the time of heating by the plasma, the cooling mechanism is operated to reach the substrate by both the cooling by the cooling mechanism and the heating by the plasma. Has a configuration in which the cooling mechanism is operated such that the thermal equilibrium temperature becomes the process temperature. According to a fourth aspect of the present invention, in order to solve the above-mentioned problem, in the configuration of the third aspect, upon heating by the heating mechanism, the cooling mechanism operates under the same conditions as those during the etching, The heating mechanism has a configuration in which the substrate is heated so that the thermal equilibrium temperature of the substrate reached by both the cooling by the cooling mechanism and the heating by the heating mechanism becomes the process temperature.

[0019]

Embodiments of the present invention will be described below. FIG. 1 is a schematic front view of an etching apparatus according to an embodiment of the present invention. The etching apparatus shown in FIG. 1 includes a processing vessel 1 in which a substrate 10 is disposed, and a substrate 1.
Forming means 2 for forming plasma in a space facing zero
A substrate holder 3 for arranging the substrate 10 at a position where predetermined chemical species generated by the plasma reach;
It mainly comprises a cooling mechanism 4 for cooling the substrate 10 and a heating mechanism 5 for heating the substrate 10.

The processing container 1 is an airtight container provided with an exhaust system 11, and is configured to carry in and out the substrate 10 through a gate valve (not shown). The exhaust system 11 employs a multi-stage vacuum exhaust system equipped with a vacuum pump such as a turbo molecular pump or a diffusion pump, and is configured to be able to exhaust the inside of the processing chamber 1 to, for example, about 10 ^-6 Torr.

Auxiliary magnets 12 are provided around the processing vessel 1 to prevent plasma loss on the walls of the processing vessel 1. FIG. 2 is a schematic plan view illustrating the configuration of the auxiliary magnet 12 in the apparatus of FIG. As shown in FIG. 1, the auxiliary magnets 12 are permanent magnets that are long in the vertical direction, and a plurality of auxiliary magnets 12 are provided around the processing container 1 at equal intervals as shown in FIG. Different magnetic poles appear on the inner surface of the adjacent auxiliary magnet 12, and a cusp magnetic field is set inside the wall of the processing container 1. Since it is difficult for the electrons constituting the plasma to move in the direction crossing the lines of magnetic force, the plasma is prevented from reaching the vessel wall of the processing vessel 1, and loss at the vessel wall is prevented. For this reason, it is possible to form high-density plasma inside the processing chamber 1.

In some cases, a load lock chamber (not shown) or the like is provided in the processing vessel 1 in an airtightly adjacent manner. When the apparatus in FIG. 1 is configured as a multi-chamber type apparatus, the processing container 1 is provided as one of a plurality of processing chambers disposed around the substrate transfer chamber.

In the present embodiment, a means for forming a helicon wave plasma is employed as the plasma forming means 2. This plasma forming means 2 includes a high frequency generator 21,
A loop antenna 25 for transmitting and exciting the high frequency generated by the high frequency generator 21;
, A magnet 26 disposed outside the loop antenna 25 to set a predetermined magnetic field in the dielectric container 23, and a gas for forming a plasma in the dielectric container 23. And a dielectric container 23 provided to surround the gas introduction system 24 for introducing the
And a magnet 26 for applying a predetermined magnetic field.

The high frequency generator 21 has a frequency of 13.56 MHz.
A magnetron or the like that generates a high-frequency wave is used. The generated high frequency is transmitted to a transmission path 27 such as a coaxial cable.
Is sent to the loop antenna 25 via the matching box 28. The loop-shaped antenna 25 has a configuration in which two ring-shaped antenna elements are vertically arranged at predetermined intervals and connected by a relay rod. Each antenna element is configured so that high-frequency currents flowing in opposite circumferential directions flow through each antenna element. The high frequency wave induced in the dielectric container 23 by the loop antenna 25 is a clockwise circularly polarized wave (helicon wave) similar to the Heusler wave.

The dielectric container 23 is a substantially cylindrical member having a hemispherical tip and an open lower end.
As a material, quartz glass or alumina is used. This dielectric container 23 is airtightly connected to the processing container 1. That is, the upper plate portion of the processing container 1 is provided with an opening adapted to the size of the lower end opening of the dielectric container 23, and the lower end opening of the dielectric container 23 is superimposed on this opening, so that both are airtight. It is connected.

The gas introduction system 24 introduces a gas for forming plasma into the dielectric container 23 via the inside of the processing container 1, and a gas cylinder (not shown) storing a predetermined gas and a gas cylinder (not shown). 241 connecting the processing container 1
And a valve 242 provided on the pipe 241 and a flow controller (not shown).

The gas introduced into the dielectric container 23 is given energy by a helicon wave induced by the loop antenna 25, and is turned into plasma. The formed plasma diffuses into the processing container 1 through the lower end opening of the dielectric container 23 and is used for etching the substrate 10. The ions in the plasma are
6 so as to be guided by the lines of magnetic force and reach the substrate 10 and used for etching. As the magnet 26, an electromagnet is used, and the magnetic flux density is about 100 gauss near the center axis of the dielectric container 23.

Helicon wave plasma has recently attracted attention as a technique capable of generating high-density plasma at a relatively low pressure, but the mechanism of energy transfer has not been completely elucidated. Generally, it is considered that energy is given to electrons from a high frequency by a phenomenon called Landau attenuation. In other words, when the moving speed of the electron moving while rotating by the magnetic field is equal to the phase speed of the helicon wave, the helicon wave is the same as stopping when viewed from the electron, so the electron is continuously accelerated from the helicon wave and energy is To generate a high-density plasma.

Next, details of the structure of the substrate holder 3 in which many features of the apparatus of the present embodiment appear will be described. FIG. 3 is a schematic front sectional view showing details of the configuration of the substrate holder 3 employed in the apparatus of FIG. As shown in FIG. 1, the substrate holder 3 is disposed below the dielectric container 23 so that plasma is formed so as to face the substrate 10 placed on the upper surface. As shown in FIG. 3, the substrate holder 3 has a mechanical clamp mechanism 6 for improving the contact between the substrate 10 and the substrate holder 3, and a substrate 1
A cooling mechanism 4 for cooling the substrate 10, a heating mechanism 5 for heating the substrate 10, and a substrate bias power supply 31 for applying a predetermined bias voltage to the substrate 10 are provided.

The substrate holder 3 comprises an upper first block 33 and a lower second block 34. The first block 33 is formed of a metal having excellent thermal conductivity such as copper, and the second block 34 is formed of a metal having good stability such as aluminum or stainless steel.
An adhesion sheet 35 is interposed between the first block 33 and the second block 34 to improve the adhesion. The adhesion sheet 35 is formed of, for example, indium, and improves the adhesion between the first block 33 and the second block 34 by forming a eutectic alloy or the like.

First, the mechanical clamp mechanism 6 mainly comprises a ring-shaped clamp 61 for pressing the peripheral portion of the substrate 10 placed on the substrate holder 3 from above, and a drive mechanism 62 for driving the clamp 61. ing. When the substrate 10 is placed on the substrate holder 3, the clamp 61 is located at the upper standby position by the driving mechanism 62. Substrate 10
Is transported in the horizontal direction, reaches the lower side of the clamp 61, and then descends and is placed on the substrate holder 3. Then, the driving mechanism 62 lowers the clamp 61 to move the substrate 10
Is placed on the peripheral portion of the substrate 10, and the clamp presses the peripheral portion of the substrate 10. Thereby, the substrate 10
The contact between the substrate holder 3 and the substrate holder 3 is improved, and the accuracy of temperature control described later is improved. In some cases, a spring member may be provided on the clamp 61 to press the clamp 61 against the substrate 10 by elastic force.

In order to further improve the thermal conductivity between the substrate 10 and the substrate holder 3, a helium chuck mechanism 7 is provided in the present embodiment. That is, a helium supply path 71 for supplying a gap between the substrate 10 and the substrate holder 3 is formed in the substrate holder 3. A helium cylinder 72 storing helium and a helium supply pipe 73 connecting the helium cylinder 72 and the supply path 71 are provided. Helium supplied to the gap between the substrate 10 and the substrate holder 3 promotes heat exchange between the substrate 10 and the substrate holder 3 and improves the accuracy of temperature control of the substrate 10 by the cooling mechanism 4 and the heating mechanism 5 described later. Improve.

The cooling mechanism 4 cools the substrate holder 3 by circulating a coolant in the substrate holder 3, and cools the substrate 10 via the substrate holder 3. Specifically, in the lower second block 34 of the substrate holder 3,
A refrigerant cavity 41 into which the refrigerant is introduced is formed. The refrigerant cavity 41 is a donut-shaped space having a rectangular cross section. The second block 34 has a refrigerant introduction path 42 for introducing the refrigerant into the refrigerant cavity 41 and a refrigerant discharge path 43 for discharging the refrigerant from the refrigerant cavity 41. And
A refrigerant introduction pipe 44 connected to the refrigerant introduction path 42, a refrigerant discharge pipe 45 connected to the refrigerant discharge path 43, and a refrigerant introduction pipe 4
A circulator 46 connecting the refrigerant discharge pipe 45 and the refrigerant discharge pipe 45 is provided. The circulator 46 has a built-in cooler, and the coolant cavity 4
1 is maintained at a predetermined temperature (hereinafter referred to as a refrigerant temperature).

The heating mechanism 5 mainly comprises a heater 51 embedded in the upper first block 33, a heater power supply 52 for supplying power to the heater 51, and a temperature sensor 53 for detecting the temperature of the substrate 10. Have been. The heating mechanism 5 generates Joule heat by energization and heats.
The heater 51 is composed of a filament formed of carbon or the like and an insulator such as ceramics surrounding the filament. The heater power supply 52 energizes the filament to generate heat to heat the insulator, thereby heating the first block 33. Further, the temperature sensor 53 is configured by a thermocouple or the like provided in contact with or near the back surface of the substrate 10. The detection signal of the temperature sensor 53 is sent to the heater power supply 52. This signal is sent to a control unit (not shown) provided in the heater power supply 52 to control the heat generation temperature of the heater 51 according to the temperature of the substrate 10.

The substrate bias power supply 31 applies a bias voltage to the substrate 10 for extracting ions from the plasma and causing the ions to collide with the substrate 10. As the substrate bias power supply 31, a power source that normally applies a high frequency of 13.56 MHz to the substrate holder 3 is employed, and a bias voltage of about -600 V is applied by the interaction between the high frequency and the plasma. The substrate bias power supply 31 is connected to a lower second block 34 via a blocking capacitor 32.

The side surface of the substrate holder 3 is entirely covered with a protective cover 36. The protective cover 36 is made of a heat-resistant and plasma-resistant material such as a Teflon insulator or the like, and prevents the substrate holder 3 from being damaged by plasma. The upper surface of the peripheral portion of the first block 33 is covered with an upper cover 37 to prevent the first block 33 from being exposed. The upper cover 36 is formed of a Teflon insulator or the like similarly to the protective cover 35, and prevents the first block 33 from being damaged by plasma. Also, although not shown in FIG. 1, the device of the present embodiment is:
A main control unit for controlling the operation of the entire apparatus is provided. The main control unit includes the exhaust system 11, the plasma forming means 2, the heating mechanism 5
And other operations are controlled.

Next, the operation of the etching apparatus according to the above-described embodiment will be described together with the description of the embodiment of the invention of the etching method. The major feature of the device of this embodiment is that
The point is that the heating mechanism 5 heats the substrate 10 to near the process temperature at the beginning of the etching. What is important in this respect is that the cooling mechanism 4 also cools the substrate 10 via the substrate holder 3. That is, the cooling mechanism 4 sets the temperature of the coolant so that the substrate 10 becomes the process temperature when the substrate 10 is heated only by the plasma without heating by the heating mechanism 5, and always cools the substrate holder 3. I have.

For example, when the input power for plasma formation is 1000 W and the pressure is 10 mTorr, the plasma heating temperature is 300 ° C., and when the process temperature is 87 ° C.,
The temperature of the refrigerant is set to about 20 ° C. At this time, the amount of heat (Qc) removed by the refrigerant from the substrate holder 3 is about 120 calories / second.

Then, the heating mechanism 5 supplements the heat taken from the substrate holder 3 by the cooling mechanism 4, and further applies heat to heat the substrate holder 3 to a temperature near the process temperature. That is, the temperature sensor 5 provided in the substrate holder 3
3 is sent to the heater power supply 52 and the temperature sensor 5
The heater power supply 52 controls the power supplied to the heater 51 so that the temperature detected by 3 becomes the process temperature. Heater 5
1 shows the amount of heat given by the heating mechanism 5 to the substrate holder 3 as Qh,
Assuming that the amount of heat dissipated by the substrate holder 3 to surrounding members and atmosphere is Qd, the substrate holder 3 is maintained at the process temperature in a state where the thermal equilibrium of Qh = Qc + Qd is achieved. According to the above example, Qh is 200 calories /
Second, and the power supplied to the heater 51 is 800 W
It is about.

In this state, when the substrate 10 is placed on the substrate holder 3, the thermal conductivity between the substrate 10 and the substrate holder 3 is extremely good by the mechanical clamp mechanism 6 and the helium chuck mechanism 7. The substrate 10 is instantaneously heated to and maintained at the process temperature. Further, the inside of the processing container 1 is preliminarily set
Exhausted to about ^-6 Torr. In this state, the gas introduction system 24 operates to adjust a predetermined gas at a predetermined flow rate.
An unillustrated evacuation speed adjuster provided in the evacuation system 11 adjusts the evacuation speed so that the inside of the processing chamber 1 has a predetermined pressure within a range of about 1 to 100 mTorr. Further, the substrate bias power supply 31 operates to apply a predetermined high frequency to the substrate 10.

In this state, the plasma forming means 2 operates. That is, the high frequency generator 21 operates to excite the loop antenna 25 at a predetermined high frequency, and induces a predetermined helicon wave in the dielectric container 23. Thereby, the dielectric container 2
Helicon wave plasma is formed in 3, and the plasma diffuses from the dielectric container 23 into the processing container 1. In particular, the ions in the plasma move along the lines of magnetic force set by the magnet 26 and reach the substrate 10.

The substrate 10 is biased to a negative potential by the interaction between the high frequency power supplied from the substrate bias power supply 31 and the plasma, and an electric field is set between the substrate 10 and the plasma. Positive ions in the plasma are extracted by the electric field and collide with the substrate 10 efficiently. Then, the substrate 10 is etched by the action of the positive ions and the action of the active species. The mechanism of etching differs depending on the material of the film to be etched and the type of gas. However, in the case of etching silicon oxide using a fluorinated carbon-based gas as described above, it is considered that fluorinated carbon ions are dominant. Can be

After performing such etching for a predetermined time, the plasma forming means 2 is stopped to end the etching. Thereafter, the substrate bias power supply 31 and the helium chuck mechanism 7 are stopped, the clamp 61 is raised, and then the substrate 10 is picked up from the substrate holder 3 and carried out of the processing vessel 1.

In the above-mentioned etching process, when the etching is started, the substrate 1 is heated by heat from the plasma.
0 is heated and the temperature gradually rises. Also, the heating mechanism 5
Is controlled by a main control unit (not shown), and stops the operation almost simultaneously with the start of etching. Therefore, the heating of the substrate 10 is switched from the heating by the heating mechanism 5 to the heating by the plasma at the start of the etching.

Here, the cooling mechanism 4 constantly cools the substrate holder 3, but at the beginning of the etching, the heating mechanism 5
, The temperature of the substrate 10 gradually increases in combination with the heating by the plasma. Then, when the residual heat of the heating mechanism 5 disappears, the heat is taken by the substrate holder 3 cooled by the cooling mechanism 4 and the temperature of the substrate 10 starts to decrease. Thereafter, the heat provided by the plasma, the heat taken by the cooling mechanism 4 and the natural heat radiation reach an equilibrium, and the temperature of the substrate 10 is settled to the process temperature.

The above temperature change is shown in FIG. 6 so that it can be compared with the conventional case. In FIG. 6, -O- indicates a temperature change of the substrate 10 in the operation of the above embodiment.
As is clear from FIG. 6, according to the operation of the above embodiment, the temperature change of the substrate 10 during the etching is much smaller than in the conventional case. That is, in the conventional apparatus, the substrate 10 greatly changes from the coolant temperature of 20 ° C. to the process temperature of about 87 ° C., but in the configuration of the present embodiment, the substrate 10 is suppressed to a range of about 87 ° C. to 96 ° C. I have. Therefore, there is no problem such as a large change in the deposition rate of the fluorocarbon film, which is observed when etching silicon oxide using a fluorinated carbon-based gas, in the configuration of the present embodiment.

The result of a specific etching experiment will be described. The silicon oxide film is formed by using the apparatus and the method according to the present embodiment having the above configuration so as to form a hole having an opening diameter of 0.35 μm and a depth of 1.5 μm. Taper angle (θ in FIG. 5) when etched by fluorinated carbon-based gas plasma
Is 89 ° and the diameter at the bottom of the hole (φ in FIG. 5) is 0.30.
μm. On the other hand, when etching was performed using a conventional apparatus and method to form similar holes, the taper angle was 86 °, and the diameter at the bottom of the holes was 0.14 μm.

From the above experimental results, according to the apparatus and method of the present embodiment, it is possible to perform highly accurate etching faithfully reflecting the pattern of the photoresist, and to obtain a good semiconductor device without a problem such as an increase in contact resistance. It can be seen that can be created.

In the configuration of the above embodiment, the cooling mechanism 4 is always operated, but in principle, it is not necessary to operate it before starting the etching. That is, before the start of etching, only the heating mechanism 5 may be operated to heat the substrate 10 to the process temperature, and the operation of the cooling mechanism 4 may be started simultaneously with the stop of the heating mechanism 5 at the start of etching. However, since there is a large difference in heat capacity between the substrate 10 and the substrate holder 3, there is a problem that the temperature of the substrate 10 greatly increases before the substrate 10 reaches the process temperature. But,
It is practical if the temperature rise is kept below the heat resistant temperature of the photoresist.

In the above-described embodiment, the heating mechanism 5 stops operating almost simultaneously with the start of etching. However, it may be possible to stop the operation several seconds later. As long as the temperature change of the substrate 10 does not cause any practical problem, the start of the etching and the stop of the operation of the heating mechanism 5 do not have to be strictly simultaneous. Therefore, immediately before the start of etching, the heating mechanism 5
May be stopped.

The etching apparatus according to the above-described embodiment is for forming a helicon wave plasma.
Other plasmas, for example, a high-frequency inductively coupled plasma using the above-described high-frequency coil 22, a parallel plate electrode type (DC or high-frequency) plasma found in a reactive ion etching apparatus, an electron cyclotron resonance (ECR) plasma, and a high-frequency capacity It can be configured as an apparatus utilizing various types of plasma such as coupled plasma.

In the above-described apparatus, in order to enhance the contact between the substrate 10 and the substrate holder 3, a mechanism for inducing static electricity on the surface of the substrate holder 3 and electrostatically attracting the substrate 10 may be employed. . This electrostatic suction mechanism can be used together with the mechanical clamp mechanism 6 described above.

As an example of the etching process,
In addition to the above-described etching of silicon oxide, etching of other materials such as aluminum alloy and polycrystalline silicon can be similarly performed, and the present invention is also applicable to an etch-back process for flattening the surface of the substrate 10.

Further, a field effect transistor (FET)
In this case, the present invention can be suitably applied to a low-concentration drain (LDD) process in which a low-concentration n-type region is provided near the drain to relax a high electric field near the drain to suppress hot carriers. In this process,
It is necessary to form a side wall spacer on the side wall of the gate electrode, and this side wall spacer can be obtained by etching the entire surface after forming a silicon oxide film on the entire surface. The configuration of the present invention can be applied to the entire surface etching.

In the field of products, the present invention is applicable not only to the manufacture of various semiconductor devices such as semiconductor memories and logics, but also to the manufacture of various products other than semiconductor devices such as liquid crystal displays.

[0056]

As described above, according to the first or third aspect of the present invention, in etching where the process temperature is lower than the plasma heating temperature, a change in the temperature of the substrate during etching can be reduced, so that good quality etching can be achieved. And the etching time can be easily estimated. Further, according to the invention of claim 2 or 4, the change in the temperature of the substrate during the etching can be further reduced, and the above effect is further improved.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic plan view illustrating a configuration of an auxiliary magnet 12 in the apparatus of FIG.

3 is a schematic front sectional view showing details of a configuration of a substrate holder 3 employed in the apparatus of FIG.

FIG. 4 is a schematic front view illustrating a configuration of a conventional etching apparatus.

FIG. 5 is a diagram illustrating a problem when a deposition rate of a fluorocarbon film is high.

FIG. 6 is a view for explaining a problem of the conventional etching apparatus, and also shows the effect of the configuration of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing container 10 Substrate 11 Exhaust system 2 Plasma formation means 21 High frequency generator 23 Dielectric container 24 Gas introduction means 25 Loop antenna 26 Magnet 3 Substrate holder 31 Substrate bias power supply 4 Cooling mechanism 41 Refrigerant cavity 42 Refrigerant introduction path 43 Refrigerant discharge path 44 Refrigerant introduction pipe 45 Refrigerant discharge pipe 46 Circulator 5 Heating mechanism 51 Heater 52 Heater power supply 53 Temperature sensor 6 Mechanical clamp mechanism 7 Helium chuck mechanism

Claims (4)

[Claims] 1. An etching apparatus for forming a plasma in a space facing a substrate and etching a surface of the substrate by a chemical species generated by the plasma, wherein a process temperature, which is a temperature of the substrate to be held during the etching, is: In an etching apparatus having a temperature lower than a plasma heating temperature at which a substrate reaches thermal equilibrium by heating from plasma, a cooling mechanism for cooling the substrate and a heating mechanism for heating the substrate are provided. To cool the substrate to the process temperature, the heating mechanism is to heat the substrate in advance so that the substrate temperature becomes the process temperature at the start of etching, and An etching apparatus wherein the operation is stopped at the start of or after the etching. 2. The cooling mechanism operates under the same conditions as during etching when heating by the heating mechanism, and the heating mechanism performs cooling by the cooling mechanism and heating by the heating mechanism. 2. The etching apparatus according to claim 1, wherein the substrate holder is heated at the beginning of the etching so that the thermal equilibrium temperature of the substrate holder reached by the both becomes the process temperature. 3. An etching method for forming a plasma in a space facing a substrate and etching a surface of the substrate by a chemical species generated by the plasma, wherein a process temperature which is a temperature of the substrate to be held during the etching is: In an etching method that is lower than the plasma heating temperature, which is the temperature at which the substrate reaches thermal equilibrium by heating from the plasma, the substrate is heated in advance by a heating mechanism so that the substrate temperature reaches the process temperature at the start of etching, and etching starts. When or after that, the operation of the heating mechanism is stopped to switch to heating of the substrate by plasma, and at the time of heating by the plasma, the cooling mechanism is operated to cool the substrate by both the cooling by the cooling mechanism and the heating by the plasma. Operate the cooling mechanism so that the thermal equilibrium temperature becomes the process temperature. Etching method comprising Rukoto. 4. When heating by the heating mechanism, the cooling mechanism operates under the same conditions as those operating during etching, and the heating mechanism performs cooling by the cooling mechanism and heating by the heating mechanism. 4. The etching method according to claim 3, wherein the substrate is heated such that a thermal equilibrium temperature of the substrate reached by the both becomes the process temperature.