JP3028364B2 - Plasma processing apparatus and plasma 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 method of etching a back surface of a substrate to be processed, for example, a semiconductor wafer by plasma.
The present invention relates to a technique capable of quickly processing a thin film adhered to a back surface while removing a protective film on the front surface of a semiconductor wafer while preventing damage.

[0002]

2. Description of the Related Art When manufacturing semiconductor devices, a CVD (Chemical Vapor Deposition) is applied to the surface of a semiconductor wafer.
Is formed on the back surface of the wafer. Since the thin film on the back side of the wafer peels off from the wafer in the subsequent process and causes particles to be generated,
It is necessary to remove it. Since it is costly to perform the thin film removing process using a dedicated device, many semiconductor manufacturing plants use a plasma etcher to remove, for example, a polysilicon film attached to the back surface of a wafer.

The plasma etcher will be described with reference to FIG. 5. Reference numeral 1 denotes a protective cover. Inside the protective tube cover 1, a vacuum chamber 2 having an upper surface formed by a hemispherical member 22 is disposed. . The vacuum chamber 2 is partitioned by a mesh body 3 into a plasma generation chamber 2A and a plasma processing chamber 2B. In the plasma generation chamber 2A, the waveguide 11
Due to the energy of the microwave passing through, for example, C
The processing gas composed of the F ₄ gas and the O ₂ gas is turned into plasma, and the charged gas in the plasma is removed by the mesh body 3. At the bottom of the vacuum chamber 2, a plasma drawing electrode 10 is provided.
At the time of surface treatment, the gas body from which the charged particles in the plasma have been removed is drawn into the plasma processing chamber 2B,
Anisotropic etching is performed on the surface of the wafer W on the mounting table 61. In the figure, reference numeral 26 denotes an exhaust path.

When the back surface of the wafer W is etched (back-etched), the wafer W whose back surface is coated with a resist is mounted on a mounting table 61. In this process, isotropic etching is performed without using the electrodes 10. Do. Since the mounting table 61 is provided at two locations opposing each other in the radial direction, the plasma (radical) wraps around the back surface of the wafer W, and thereby, for example, the polysilicon film attached to the back surface of the wafer W is etched.

[0005]

Since the plasma temperature is high in the plasma generation chamber 2A, the wafer surface receives radiation heat from the plasma generation chamber 2A, and the resist on the plasma surface is damaged in the back etch step. If the damage is large, the resist is burned and cannot be removed in a later step. In order to prevent burning of the resist, the temperature of the plasma may be lowered by lowering the power of the microwave. In this case, however, the number of F radicals is reduced, and the etching rate is reduced.

In a single-wafer processing apparatus, a high throughput is required, so that a decrease in etching rate is very inefficient. In addition, since the apparatus is originally a plasma etcher, there is a burden on the user side that improvement for power down is required. Further, since the hardware of the apparatus has a structure for etching the front surface of the wafer W, there is a problem that the gap for the plasma wrap around to the rear surface side of the wafer W is narrow, and the etching rate is low from this point as well. .

SUMMARY OF THE INVENTION The present invention has been made under such an object, and an object of the present invention is to suppress damage to the surface of a substrate to be processed when etching the rear surface of the substrate to be processed, and to achieve a large etching. An object of the present invention is to provide a technology capable of securing a speed.

[0008]

According to the present invention, there is provided a structure in which a heat shield plate is provided opposite to a surface of a substrate to be processed in order to shield radiant heat radiated from the plasma generation chamber to the surface of the substrate. It is characterized by the following. In this case, it is preferable that the heat shield plate be detachably provided in the plasma processing chamber so that the surface treatment and the back surface etching can be performed by one apparatus.

Further, a first mounting unit and a second mounting unit each including a mounting unit for a substrate to be processed are used, and the first mounting unit is processed from the plasma generation chamber. In order to shield radiant heat radiated to the surface of the substrate, a heat shield plate provided so as to face the surface of the substrate to be processed is provided, and when etching a thin film attached to the back surface of the substrate to be processed, The first mounting unit may be mounted in the plasma processing chamber when the first mounting unit is processed, and the second mounting unit may be mounted in the plasma processing chamber when processing the surface of the substrate to be processed. This is advantageous in that the configuration can be adapted to the processing.

[0010]

FIG. 1 is a diagram showing an overall configuration of a plasma processing apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a protective cover. The protective cover 1 is disposed on a ring-shaped structure 21 made of, for example, aluminum.
A semi-spherical member (bell jar) 22 made of, for example, ceramic is provided in the protective cover 1 so as to cover a space above the opening of the structure 21. A cylindrical body 23 is provided below the structure 21 so as to close the opening on the lower surface of the structure 21. Hemispherical member 22 and structure 2
1 and between the lower surface of the structure 21 and the upper surface of the columnar body 23, sealing members 24 and 25 are interposed respectively. Has formed.

A cylindrical body 30 made of, for example, aluminum and having a lower side opening is fitted into the opening of the structure 21, and the upper surface of the cylindrical body 30 is located in the upper region of the vacuum chamber 2. And is configured as a mesh body 3 for removing charged particles in the plasma. The mesh body 3 is made of, for example, aluminum and has a large number of holes 31 formed therein. In this example, the upper region of the mesh body 3 in the vacuum chamber 2 forms the plasma generation chamber 2A, and the lower region of the mesh body 3 forms the plasma processing chamber 2B.

A waveguide 11 for guiding microwaves is connected to the upper surface of the protective cover 1 so that microwaves from a high-frequency power supply 12 are introduced into the plasma generation chamber 2A. In the plasma processing chamber 2B, a first mounting unit 4 is detachably attached to a cylindrical body 23 forming the bottom of the plasma processing chamber 2B by, for example, screws. As shown in FIG. 2, the mounting unit 4
A lift pin 41 for holding a wafer, a lifting unit 43 fixed to a mounting plate 42 and including, for example, an air cylinder for raising and lowering the lift pin 41, and a heat shield provided via a support rod 44 above the mounting plate 42 And a plate 5.

The lift pins 41 are for placing the wafer W thereon. The lift pins 41 are provided, for example, so as to hold three positions in the circumferential direction of the wafer W, and are provided between the transfer position of the wafer W and the processing position. Raise and lower between. At the transfer position, the wafer W is transferred to and from a transfer arm (not shown) outside the apparatus main body. At the processing position (the position indicated by the solid line in FIG. 1), the wafer W is approximately 30 mm from the bottom surface.
And the back surface is etched.

The heat shield plate 5 is made of aluminum having a thickness of, for example, 1 mm and is formed in a circular shape slightly larger than the wafer W, and is provided opposite to the wafer W, for example, at an upper position of 6 to 7 mm. Further, a gas supply pipe (not shown) is connected to the hemispherical member 22, and a processing gas is supplied from the gas supply pipe into the plasma generation chamber. On the other hand, an exhaust path 26 is formed in the cylindrical body 21 forming the bottom of the vacuum chamber 2, and the exhaust path 26 communicates with an exhaust pipe 27.

Next, the manner in which the above-described apparatus performs back etching on a wafer as a substrate to be processed whose surface is coated with a resist as a protective film will be described. First, the lift pins 41 are received so as to receive the wafer W at the position of the chain line.
The wafer W is transferred from the external load lock chamber onto the lift pins 41 by a transfer arm (not shown).
Next, the lift pins 41 are raised to place the wafer W at the processing position. Thereafter, a processing gas in which CF ₄ gas and O ₂ gas are mixed is introduced into the plasma generation chamber 2A, for example, at 70 SC, respectively.
CM and 30 SCCM are supplied, and the inside of the vacuum chamber 2 is maintained at a pressure of, for example, about 0.4 Torr.

Then, a microwave is generated at a power of 1000 W, and the processing gas in the plasma generation chamber 2A is turned into a plasma with the energy of the microwave. The charged particles are removed from the plasma when passing through the mesh body 3, and the remaining radical particles are introduced into the plasma processing chamber 2 </ b> B, diffused toward the back surface of the wafer W, and adhered to the back surface of the wafer W. Etch the silicon film. The temperature of the plasma becomes high in the plasma generation chamber 2A, and the heat is radiated into the plasma processing chamber 2B. However, since the heat shield plate 5 is provided above the wafer W, the radiant heat is blocked by the heat shield plate 5. Thus, damage to the resist on the wafer surface can be suppressed.

As described above, according to the above embodiment, even if the power of the microwave is increased, the damage to the resist can be suppressed. Therefore, the back etching is performed at a high etching rate, and the scorching of the resist is performed while securing a high throughput. Can be prevented. In addition, since the lift amount of the wafer W is increased by using the mounting unit dedicated to the back surface etching, the plasma sufficiently flows to the back surface side of the wafer W, and the etching rate also increases from this point.

Here, for example, if the wafer W is placed at the level of the receiving position and the bottom surface of the vacuum chamber 2 is lowered to secure a wide space on the back surface side of the wafer W, the amount of plasma wraparound increases. Then lift pin 41
Since the position of the lifting unit is lowered and the bottom surface of the cylindrical body 23 is lowered by that amount, the structure in which the wafer W is raised high as in the present embodiment is superior in that the size can be avoided.

The distance between the heat shield plate 5 and the wafer W is preferably as short as possible. The reason for this is that the amount of plasma wrapping around the front surface side of the wafer W is reduced, and damage to the resist can be further reduced. This is because the etching of the exposed portion can be suppressed. Further, the heat shield plate 5 is not limited to aluminum, but it is more preferable to use a material having a large heat capacity such as ceramics.

Since the heat shield plate 5 is provided on the mounting unit 4 and the mounting unit 4 is detachably mounted on the plasma processing chamber 2B, the mounting unit 4 is used for surface treatment. The surface treatment and the back etching can be performed by a common plasma processing apparatus by exchanging the mounting unit, and the cost can be significantly reduced as compared with the case where an apparatus dedicated to the back etching is manufactured. FIG. 3 shows a second mounting unit 6 used for back-etching the surface of the wafer W, and includes a mounting table 61 and a mounting table support 6.
The two assemblies are radially opposed to each other and are fixed on the mounting plate 63 by a supporter (not shown). Numeral 64 is a plasma drawing electrode, and numeral 65 is a lift pin elevating unit.

In the above description, the heat shield plate 5 may not be provided on the placement unit 4 but may be provided detachably on, for example, a cylindrical body 30 supporting the mesh body 3. When the back etching and the surface treatment are performed by a common apparatus, the heat shield plate 5 is preferably removed during the surface treatment. The reason is that the heat shield plate 5 deteriorates the uniformity of the flow of the plasma gas on the surface of the wafer W, and the in-plane uniformity of the etching rate.

Further, according to the present invention, the heat shield plate is not provided on the main body of the apparatus, but is directly mounted on the surface of the wafer, for example, and the wafer is loaded from the outside into the plasma processing chamber with the heat shield plate mounted thereon to perform the back etching. It may be performed. Furthermore, the present invention can also be applied to an apparatus that performs back etching on a plurality of wafers at a time. In this case, for example, a heat shielding plate may be directly mounted on the surface of each wafer.

[0023]

【Example】

(Embodiment) A wafer W having a surface coated with a resist and a polysilicon film and an oxide film (SiO ₂ film) formed in separate areas on the back surface was subjected to the pressure in the vacuum chamber 2 using the apparatus shown in FIG. The etching rate (etch rate) of the polysilicon film and the oxide film and the selectivity of the polysilicon film to the oxide film were examined by changing the power of the microwave and the power of the microwave. Aluminum having a thickness of 1 m was used as the heat shielding plate 5 and was placed 6 mm above the wafer W. The results are as shown in Examples 1 to 5 of FIG.

Comparative Example A similar test was performed using the conventional apparatus shown in FIG. The results are as shown in Comparative Examples 1 and 2 in FIG.

(Consideration) In Examples 1 to 5, the resist was not scorched when the microwave power was 1000 W or 1200 W, but the resist was scorched at 1000 W in the comparative example. Also, if the power is 100
When the wafer surface temperature was measured when etching was performed for 3 minutes at 0 W, the temperature was about 200 ° C. in the example, but was 350 ° C. or more in the comparative example. Since the resist does not burn up to about 200 ° C., it can be seen that the method of the present invention is effective. In the first to fifth embodiments, since the lift amount of the wafer W is large, compared with the conventional apparatus,
The amount of the plasma wrapping around the back surface of the wafer is large, so that the etching rate of the polysilicon film is considerably large and the selectivity is large.

In the case of the comparative example, the microwave power is set to 800
Burning of the resist can be avoided by dropping to W, but the etching rate is slow and the difference in etching rate between the edge and the center is large. However, even if the lift amount of the wafer is increased in the conventional apparatus, the etch rate of polysilicon becomes smaller than that in the case of 1000 W, and a high throughput cannot be obtained. This can be understood from the fact that the third embodiment has a higher polysilicon etch rate when the third embodiment is compared with the fifth embodiment.

[0027]

According to the first aspect of the present invention, when the back surface of the substrate to be processed is etched by plasma to remove the thin film adhering to the back surface, the heat shield plate is used, so that the protective film on the front surface is used. Damage can be suppressed, and a high throughput can be obtained. In this case, if the heat shield plate is detachably provided in the plasma processing chamber as in the second aspect of the present invention, and the surface treatment and the back surface etching are performed by a common apparatus, the cost can be reduced.

According to the third aspect of the present invention, if a placement unit dedicated to surface treatment and a placement unit dedicated to backside etching provided with a heat shield plate are prepared, the lift amount of the substrate to be processed during backside etching is provided. For example, the apparatus can be configured in accordance with each processing, such as by increasing the size, and the operation can be simplified by replacing the mounting table unit.

[Brief description of the drawings]

FIG. 1 is a vertical side view showing a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a mounting unit for back surface etching used in the embodiment of the present invention.

FIG. 3 is a vertical sectional side view showing a mounting unit for surface treatment used in the embodiment of the present invention.

FIG. 4 is a view showing a result of performing back surface etching using the apparatus of the present invention and a comparative apparatus.

FIG. 5 is a vertical sectional side view showing a conventional plasma processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Protective tube cover 11 Microwave waveguide 2 Vacuum chamber 2A Plasma generation chamber 2B Plasma processing chamber 22 Hemispherical member 26 Exhaust path 3 Mesh body 4 Placement unit 41 Lift pin 5 Heat shield plate W Semiconductor wafer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI H05H 1/46 H05H 1/46 B (58) Investigated field (Int.Cl. ⁷ , DB name) H01L 21/3065 C23C 16 / 56 C23F 4/00 H01L 21/205 H05H 1/46

Claims (4)

(57) [Claims] A plasma processing chamber in which a substrate to be processed is placed; and a plasma generation chamber provided to face the substrate to be processed, wherein plasma generated in the plasma generation chamber is generated by the plasma processing chamber. In the apparatus for etching the thin film adhered to the back surface of the substrate to be processed, in order to shield radiant heat radiated from the plasma generation chamber to the surface of the substrate to be processed, facing the surface of the substrate to be processed A plasma processing apparatus, wherein a heat shielding plate is provided. 2. A plasma processing chamber in which a substrate to be processed is placed, and a plasma generation chamber provided to face the substrate to be processed, wherein plasma generated in the plasma generation chamber is converted into plasma. In the apparatus for processing the substrate to be processed, in order to shield radiant heat radiated from the plasma generation chamber to the surface of the substrate to be processed, a heat shield plate at a position facing the surface of the substrate to be processed The heat shield plate is detachably provided in the plasma processing chamber, the heat shield plate is removed when processing the surface of the substrate to be processed, and the heat shield plate is attached when etching the thin film attached to the back surface of the substrate to be processed. A plasma processing apparatus characterized in that a surface treatment and a back surface etching are performed by a common device. 3. A plasma processing chamber in which a substrate to be processed is mounted, and a plasma generation chamber provided so as to face the substrate to be processed, wherein plasma generated in the plasma generation chamber is supplied to the plasma processing chamber. And an apparatus for processing a substrate to be processed, wherein the first mounting unit includes a first mounting unit and a second mounting unit each including a mounting unit for the processing substrate. The unit includes a heat shield plate provided to face the surface of the substrate to be processed in order to shield radiant heat radiated from the plasma generation chamber to the surface of the substrate to be processed, and adheres to the back surface of the substrate to be processed. The first mounting unit is mounted in the plasma processing chamber when the thin film is etched, and the second mounting unit is mounted in the plasma processing chamber when the surface of the substrate is processed. Oki Uni Placed on preparative mounting portion, the plasma processing apparatus characterized by performing the surface treatment and backside etching of the substrate by a common device. 4. A plasma processing chamber in which a substrate to be processed is mounted, and a plasma generation chamber provided to face the substrate to be processed, wherein plasma generated in the plasma generation chamber is supplied to the plasma processing chamber. In a device for etching a thin film adhered to the back surface of a substrate to be processed, a heat shield plate is interposed between the surface of the substrate to be processed and the plasma generation chamber, and the surface of the substrate to be processed is A plasma processing method, characterized in that a back surface of a substrate to be processed is etched while shielding radiant radiation heat by the heat shielding plate.