JP2880264B2 - Substrate holding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention holds a substrate by vacuum-sucking the back surface of the substrate while maintaining the contact thermal resistance between the substrate and a holding table at a predetermined value or less. The present invention relates to a substrate holding device to be used.

[Conventional technology]

In an exposure apparatus of a semiconductor manufacturing apparatus, a substrate holding device for transferring a mask pattern onto a substrate such as a wafer is a substrate holding device that holds the back surface of the substrate by vacuum suction (for example, Japanese Patent Publication No. 1-17033). Gazette) is often used.

In general, when a substrate is held by a substrate holding device, when contact heat resistance between the substrate and a holding table of the substrate holding device is large, exposure energy for transferring a Max pattern onto the substrate is reduced from the substrate. Because it does not escape to the holding table,
This raises the temperature of the substrate and causes thermal deformation, thereby deteriorating the pattern transfer accuracy. In particular, in the case of a substrate holding device using vacuum suction, heat is released to a minute space formed between the back surface of the substrate and the chuck surface (the surface facing the sucked substrate) of the holding table. Since there is no gas as a heat medium, the pattern transfer accuracy is significantly deteriorated due to the temperature rise of the substrate.

Therefore, as a substrate holding device capable of controlling the temperature of the vacuum-sucked substrate during exposure and maintaining the flatness of the substrate, temperature-regulated water (hereinafter, referred to as "temperature-regulated water").
In order to control the temperature of the substrate by flowing a flow path provided in a holding table of the substrate holding apparatus, and to maintain the contact thermal resistance between the substrate and the holding table at a predetermined value or less, There is one that holds the substrate while keeping the internal pressure at a constant value.

FIG. 5 is a schematic configuration diagram showing one conventional example of an X-ray exposure apparatus having such a substrate holding device.

This X-ray exposure apparatus is, for example, a proximity system in which a mask 104 and a wafer 105 are arranged at a distance of several tens of microns and a mask pattern is transferred, as described in Japanese Patent Application No. 63-252991. Is an exposure apparatus.

The X-ray exposure apparatus includes a chamber 103 filled with a helium (He) gas that transmits X-rays generated by a storage ring or the like, and an X-ray transmission chamber provided in a part of the chamber 103. Beryllium window (hereinafter referred to as “Be window”) 102, second vacuum gauge 113 b for detecting pressure in chamber 103, and second H for supplying He gas into chamber 103.
e cylinder 116b, third gas control valve 115c for adjusting the supply amount of He gas into chamber 103, and third gas control valve 115c
It has a second controller 114b for opening and closing the substrate and a substrate holding device described below.

The substrate holding device of the X-ray exposure apparatus has a wafer chuck 106 as a holding table, a flow path 107 piped inside the wafer chuck 106, and a constant temperature bath 110 for circulating temperature regulating water in the flow path 107, The chuck surface 106 ₁ of the wafer chuck 106 (the sixth
Figure reference) and thereby connects the pump 117 is a vacuum source, an exhaust pipe 111 which connects the first He cylinder 116a is a source of the chucking surface 106 ₁ and He gas, an exhaust pipe 111
A first gas control valve 115a interposed between the wafer chuck 106 and the pump 117, and the wafer chuck 106 of the exhaust pipe 111.
A second gas regulating valve 115b interposed between the first gas cylinder 116a and the first He cylinder 116a, and between the wafer chuck 106 of the exhaust pipe 111 and the first and second gas regulating valves 115a and 115b. the first gauge 113a for detecting the pressure in the small space formed between the rear surface of the wafer 105 and the chuck face 106 ₁
And the first and second output signals from the first vacuum gauge 113a.
And a first controller 114a, which is a control means for controlling the gas control valves 115a and 115b. Where CPU 120
Together with the second controller 114b and the second vacuum gauge 113b
Also, the third gas control valve 115c is controlled by the output signal.
Also, a mask 104 for transferring a mask pattern is used.
Is installed in the chamber 103 with a certain gap (gap) from the wafer 105 that has been vacuum-sucked.

Also, as shown in FIG. 6, two concentric grooves 106 ₂
There together are formed in the chucking surface 106 ₁ of the wafer chuck 106, the chuck surface 106 ₁ of the central portion one groove 10 in
6 ₂ are formed, the exhaust pipe 111 is branched in the wafer chuck 106, and is opened in the groove 106 illustrated _second vertical and horizontal and the center of the concentric of each groove 106 _2.

 Next, the operation of the X-ray exposure apparatus will be described.

Before transferring the mask pattern to the wafer 105, the CPU
120 takes in the output signal of the second vacuum gauge 113b and controls the second controller 114b in accordance with the output signal to open and close the third gas control valve 115c, thereby increasing the pressure in the chamber 103 to 200 [Torr]. ]. Thereafter, when the wafer 105 to be vacuum-sucked is transferred to the position shown in the figure by a known transfer hand (not shown), the CPU 120 operates the first gas control valve.
The first controller 114a is controlled to open 115a.
When the first gas control valve 115a is opened, the exhaust pipe 111 is connected to the pump 117, and the back surface of the wafer 105 and the wafer chuck 10 are opened.
He gas existing in the minute space formed between the chuck surface 106 ₁ and the respective grooves 106 ₂ is sucked, and the pressure in the minute space is reduced. Of the wafer 105 due to the pressure difference
Adsorbed and held at 06.

Here, as one experimental result of this X-ray exposure apparatus, in order to maintain the vacuum suction force and the pattern transfer accuracy, for example, the contact thermal resistance between the wafer 105 and the wafer chuck 106 is set to 2 × 10 ⁻⁴ [ K · m ² / W] or less, and for that purpose, from the relationship between the wafer back pressure and the contact thermal resistance shown in FIG. 7, the wafer back pressure, that is, the pressure in the minute space, is about 50 [Torr]. It turns out that you need to.

Therefore, in this X-ray exposure apparatus, when the vacuum suction of the wafer 105 is started, the CPU 120 takes in the output signal of the first vacuum gauge 113a at a predetermined timing, and indicates the inside of the exhaust pipe 111 indicated by the output signal. The first controller 11 monitors the pressure and controls the first controller 11 so that the pressure in the exhaust pipe 111 is always 50 [Torr].
4a to control the first and second gas control valves 115a, 115b.
To open and close.

When the pressure of the exhaust pipe 111 is kept constant in this way, X
The transfer of the mask pattern is performed by irradiating the line 105 onto the wafer 105 through the Be window 102 and the mask 104. At this time, temperature control of the wafer 105 during exposure is performed by circulating temperature-regulated water in the flow path 107 by the thermostat 110 to keep the temperature of the wafer chuck 106 constant.

[Problems to be Solved by the Invention] However, in the conventional substrate holding apparatus described above, in order to suppress the temperature rise of the wafer 105 to about ± 0.06 [° C.] or less so as not to deteriorate the pattern transfer accuracy, for example, When the intensity of the X-ray irradiated on the wafer 105 is 150 [mW / cm ² ], the change in the contact thermal resistance is about ± 4.0 × 10 ⁻⁵ [K · m ² /
W], and the allowable value of the pressure change in the micro space at this time is within a range of about ± 5 [Torr] (see FIG. 7). The first vacuum gauge 113a for detecting the wafer chuck 1 of the exhaust pipe 111
06 and the first and second gas control valves 115a and 115b, the size of the warp of the wafer 105 and the roughness of the back surface thereof change temporarily, and When the amount of He gas flowing into the minute space is changed, chucking surface 106 ₁ of the wafer chuck 106 and the first vacuum gauge 113a
Due to the conductance between the first and second vacuum gauges, the reading of the first vacuum gauge 113a may change even if the pressure in the small space does not change. There is a problem that can not be.

SUMMARY OF THE INVENTION An object of the present invention is to provide a substrate holding device capable of accurately measuring pressure in a minute space and suppressing contact thermal resistance to a predetermined value or less, thereby preventing deterioration of pattern transfer accuracy.

[Means for Solving the Problems] A substrate holding apparatus according to the present invention comprises: a holding table having a chuck surface for sucking a substrate; and a vacuum for supplying the substrate to the chuck surface. An exhaust pipe to be formed, a measurement pipe having an opening on the chuck surface and formed on the holding stand separately from the exhaust pipe, and a pressure measuring means connected to the measurement pipe are provided.

A vacuum source is connected to the exhaust pipe via a regulating valve. Further, there is provided control means for controlling the regulating valve based on an output signal of the pressure measuring means. A gas supply source is connected to the exhaust pipe via another regulating valve. Further, there is provided a valve interposed between the exhaust pipe and the measurement pipe.

The substrate is a substrate to be exposed, and the substrate to be exposed is a wafer to which a mask pattern is transferred by X-ray irradiation.

[Operation] Since the substrate holding device of the present invention has the measuring tube connecting the pressure measuring means and the chuck surface of the holding table, the gas in the measuring tube is almost exhausted when the evacuation proceeds to some extent. Therefore, the value of the pressure indicated by the pressure measuring means matches the pressure in the minute space formed between the back surface of the substrate and the chuck surface of the holding table. If the control means controls the first and second gas regulating valves so that the internal pressure becomes a predetermined value, the pressure in the minute space can be accurately maintained at the predetermined value.

Further, by having a valve interposed between the exhaust pipe and the measurement pipe and controlled by the control means, if the vacuum suction is started after opening the valve by the control means, Since the gas in the measuring tube can be quickly exhausted through the valve, the pressure in the minute space can be accurately and promptly maintained at the predetermined value.

According to the substrate holding device of the present invention, the pressure in the minute space can be accurately measured and the contact thermal resistance can be suppressed to a predetermined value or less. When exposure is performed while holding a wafer on which a mask pattern is transferred by irradiation, deterioration of pattern transfer accuracy can be prevented.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of an X-ray exposure apparatus having a substrate holding device according to the present invention.

The X-ray exposure apparatus according to the present embodiment includes a chamber 3 filled with a helium (He) gas that transmits X-rays generated by a storage ring or the like, and an X-ray provided in a part of the chamber 3. A beryllium window (Be window) 2 for transmission, a second vacuum gauge 13b for detecting the pressure in the chamber 3, a second He cylinder 16b for supplying He gas into the chamber 3, and
It has a third gas control valve 15c for adjusting the supply amount of He gas supplied from the cylinder 16b into the chamber 3, and a second controller 14b for opening and closing the third gas control valve 15c.

Further, the substrate holding device includes a wafer chuck 6 serving as a holding table, a flow path 7 piped inside the wafer chuck 6, a constant temperature bath 10 for circulating temperature-regulated water through the flow path 7, and a chuck surface of the wafer chuck 6. 6 ₁ (see FIG. 2), a pump 17 as a vacuum source and a first He cylinder 16a as a source of He gas
Pipe 11 for connecting the wafer and the wafer chuck 6 of the exhaust pipe 11
A first gas control valve (regulating valve) 15a interposed between the pump and the pump 17, and a second gas control valve interposed between the wafer chuck 6 of the exhaust pipe 11 and the first He cylinder 16a. (Another regulating valve) 15b. The above points are the same as those of the conventional X-ray exposure apparatus shown in FIG.

However, this embodiment Shino X-ray exposure apparatus is measuring tube 30 having a free end is connected to the chuck surface ₆₁ of the wafer chuck 6, a chuck surface ₆₁ of the back surface of the wafer 5 and the wafer chuck 6 A first vacuum gauge 13a, which is a pressure measuring means for detecting a pressure in a minute space formed therebetween, is attached to a free end of a measuring pipe 30, and a valve 31 is connected to the exhaust pipe 11 for measuring. A microprocessor (CPU) 20 and a first controller 1 which are interposed between the pipe 30 and control means for controlling the first and second gas control valves 15a and 15b and the valve 31.
4a is operated by the output signal of the first vacuum gauge 13a.
This is different from the conventional example shown in FIG.

Further, as shown in FIG.
Chucking surface 6 of the concentric grooves 6 ₂ wafer chuck 6 ₁
Together they are formed in, the chuck surface 6 a groove 6 ₂ are formed also in the center of _1, the exhaust pipe 11 is concentric of the grooves 6 ₂
Although the point of branching into the groove 6 ₂ shown vertical and horizontal and the center of which is open is the same as the conventional wafer chuck 106 shown in FIG. 6, the measuring tube 30 is the chuck surface 6 ₁
Intermediate point that is open to is different from the conventional groove 6 ₂ and inner concentric grooves 6 ₂ in the center of.

The CPU 20 also controls the third gas control valve 15c based on the output signal of the second vacuum gauge 13b together with the second controller 14b. Further, a mask 4 for transferring a mask pattern is installed in the chamber 3 with a certain gap (gap) from the vacuum-sucked wafer 5.

Next, the operation of the X-ray exposure apparatus of the present embodiment will be described.

Before transferring the mask pattern to the wafer 5, the CPU 2
0 takes in the output signal of the second vacuum gauge 13b and controls the second controller 14b in accordance with the output signal to open and close the third gas control valve 15c, thereby increasing the pressure in the chamber 3 to 200 [ Torr]. Thereafter, when the wafer 5 to be vacuum-sucked is transported to a position shown in the figure by a known transport hand (not shown), the CPU 20 controls the first controller 14a to open the first gas control valve 15a and the valve 31. Control.
When the first gas control valve 15a and the valve 31 are opened, the exhaust pipe 1
1 and the measuring tube 30 is communicated with the pump 17, the minute space formed between the chucking surface ₆₁ and the grooves 6 ₂ of the rear surface of the wafer 5 and the wafer chuck 6 and the measuring tube 30 Exists
The He gas is sucked and the pressure in the minute space decreases, and the resulting pressure difference between the front and back surfaces of the wafer 5 causes the wafer 5 to be attracted and held by the wafer chuck 6.

When the vacuum suction of the wafer 5 is started in this way,
The He gas in the measurement tube 30 to which the first vacuum gauge 13a is attached is almost exhausted when the evacuation proceeds to some extent, and the flow of the He gas in the measurement tube 30 stops.
0 controls the first controller 14a to close the valve 31. Thereafter, in order to reduce the contact thermal resistance between the wafer 5 and the wafer chuck 6 to 2 × 10 ⁻⁴ [K · m ² / W] or less, the CPU 20 captures the output signal of the first vacuum gauge 13a at a predetermined timing. Then, the pressure in the measuring tube 30 indicated by the output signal is monitored, and the first and second gas control valves 15a and 15b are controlled so that the pressure in the measuring tube 30 is always 50 [Torr]. The first controller 14a is controlled to open and close. At this time, since the value of the pressure indicated by the first vacuum gauge 13a matches the pressure in the minute space, the pressure in the minute space is monitored accurately by monitoring the pressure in the measuring tube 30. [To
rr] can be kept constant.

After keeping the pressure in the micro space constant, X-ray
The mask pattern is transferred by irradiating the wafer 5 through the window 2 and the mask 4. At this time, the temperature of the wafer 5 during exposure is controlled by circulating temperature-regulated water in the flow path 7 through the thermostat 10 to keep the temperature of the wafer chuck 6 constant.

As a result, in the X-ray exposure apparatus of the present embodiment, since the pressure of the minute space and the pressure can be accurately maintained at 50 [Torr], the contact thermal resistance between the wafer 5 and the wafer chuck 6 is equal to or less than a value at which the pattern transfer accuracy is not deteriorated. About 2 × 10 ⁻⁴ [K · m ² / W].

Next, the operation and effect of the valve 31 in the present embodiment will be described.

Although the valve 31 is not always necessary, if it is assumed that the valve 31 is not provided, it takes a long time to reach the target pressure of 50 [Torr] in the minute space for the following reason. In comparison, the productivity becomes worse.

Chucking surface 6 of the wafer chuck 6 ₁ and the first gauge 13a
Exhaust of He gas present in the measuring tube 30 that connects the TMG, the central portion of the wafer chuck 6 via a minute space formed between the chucking surface ₆₁ of the central portion of the wafer 5 and the wafer chuck 6 grooves 6 ₂ and inner concentric grooves 6 ₂ (see FIG. 2)
However, since the minute space is very narrow, the flow path resistance is large, and it takes time to exhaust He gas. As a result, the gas (He gas) generated in the measurement tube 30 after a certain amount of time has not passed.
Therefore, the pressure indicated by the first vacuum gauge 13a does not match the pressure in the minute space.

Therefore, when starting vacuum suction, the CPU 20 controls the first controller 14a so as to open the valve 31, and the measurement tube 30
The He gas existing in the gas flows into the exhaust pipe 11 via the valve 31, thereby shortening the exhaust time of the He gas. Thereafter, when the CPU 20 confirms that the pressure in the exhaust pipe 11 indicated by the first vacuum gauge 13a has become equal to or lower than a predetermined value, the CPU 20 controls the first controller 14a so as to close the valve 31, and then controls the exhaust pipe 11 The output signal of the first vacuum gauge 13a is continuously taken at a predetermined timing until the internal pressure becomes 50 [Torr].

Next, various structures of the chuck surface of the wafer chuck will be described.

FIG. 3 is a diagram showing another structure of the chuck surface of the wafer chuck.

The wafer chuck 26, the which grooves 26 ₂ of the one near the outer periphery concentric chucking surface ₂₆₁ is formed, the exhaust pipe 11 to the shown vertical and horizontal of the concentric grooves 26 ₂ branches opening It is (shown above and below the exhaust pipe 11 is not shown), that the measuring tube 30 is opened in a central portion of the chucking surface ₂₆₁ is different from the wafer chuck 6 of Figure 2.

The wafer chuck 26 it is possible to increase the contact area between the wafer 5 and the chucking surface ₂₆₁ to be vacuum-suction, it is possible to reduce the contact thermal resistance than the wafer chuck 6 shown in Figure 2.

FIG. 4 is a view showing still another structure of the chuck surface of the wafer chuck.

The wafer chuck 36, similarly to the wafer chuck 26 shown in FIG. 3, the which grooves 36 ₂ of the one near the outer periphery concentric chucking surface 36 ₁ is formed, the concentric grooves 36 ₂ shown vertically and horizontally in the exhaust pipe 11 to be opened branched (exhaust pipe 11 shown vertically is not shown) in addition, connecting the measuring tube 30 that is open in the center and concentric grooves 36 ₂ three narrow groove ₃₆₃ is formed in the circumferential direction at equal intervals to be.

The wafer chuck 36, when there is no valve 31 shown in FIG. 1, since the three narrow groove ₃₆₃ is an exhaust passage of He gas is enhanced exhaust efficiency of the He gas measurement tube 30 There is an advantage.

The wafer chucks 6, 26, 3 shown in FIGS.
In FIG. 6, four exhaust pipes 11 were opened in each groove,
The number may be other than four as long as the openings are symmetrical.

In the above description, an example in which the substrate holding apparatus of the present invention is employed in an X-ray exposure apparatus has been described. For example, as in an exposure apparatus using light, the substrate is kept at a constant temperature and the front and back surfaces of the substrate are The present invention is applicable to all exposure apparatuses having a substrate holding device that holds the substrate by a pressure difference.

The object held by the substrate holding device of the present invention is not limited to a wafer, but may be a substrate such as a liquid crystal display on which a thin film transistor or the like is formed.

[Effects of the Invention] The present invention is configured as described above, and has the following effects.

The substrate holding device according to claim 1 has a measuring tube connecting the pressure measuring means and the chuck surface of the holding table, so that the gas in the measuring tube is almost exhausted when the evacuation proceeds to some extent. Therefore, the value of the pressure indicated by the pressure measuring means coincides with the pressure in the minute space formed between the vacuum-sucked substrate and the chuck surface of the holding table. There is an effect that the contact thermal resistance can be suppressed to a predetermined value or less by measuring accurately.

Further, when a valve is interposed between the exhaust pipe and the measuring pipe, the gas in the measuring pipe can be quickly exhausted through the valve at the start of vacuum suction, so Has an effect that the pressure can be accurately and promptly maintained at the predetermined value.

According to the substrate holding device of the present invention, the pressure in the minute space can be accurately measured, and the contact thermal resistance can be suppressed to a predetermined value or less. When used in an exposure device that
This has the effect of preventing deterioration of pattern transfer accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of an X-ray exposure apparatus having a substrate holding apparatus according to the present invention, FIG. 2 is a view showing a structure of a chuck surface of a wafer chuck, and FIG. FIG. 4 is a diagram showing still another structure of the chuck surface of the wafer chuck, FIG. 5 is a schematic configuration diagram showing one of X-ray exposure apparatuses having a conventional substrate holding device, FIG. 6 is a diagram showing the structure of the chuck surface of the wafer chuck of FIG. 5, and FIG. 7 is a diagram showing an example of the relationship between the wafer back pressure and the contact thermal resistance. 2 ... Be window, 3 ... chamber, 4 ... mask, 5 ... wafer, 6,
26,36… Wafer chuck, 6 ₁ , 26 ₁ , 36 ₁ … Chuck surface, 6
₂ , 26 ₂ , 36 ₂ ... groove, 7 ... flow path, 10 ... constant temperature bath, 11 ... exhaust pipe, 13a ... first vacuum gauge (pressure measuring means), 13b ... second vacuum gauge, 14a ... first Controller, 14b: second controller, 15a: first gas control valve (regulator valve), 15b: second controller
Gas control valve (another control valve), 15c: third gas control valve, 16a: first He cylinder (gas supply source), 16b: second
He cylinder, 20… CPU, 30… Measurement tube, 31… Valve, 36 ₃ … Narrow groove.

Claims (7)

(57) [Claims] A holding table having a chuck surface for sucking a substrate; an exhaust pipe formed on the holding table for supplying a vacuum for sucking the substrate on the chuck surface; and an opening in the chuck surface. A substrate holding apparatus, comprising: a measuring pipe formed on the holding table separately from the exhaust pipe; and pressure measuring means connected to the measuring pipe. 2. The substrate holding apparatus according to claim 1, wherein a vacuum generation source is connected to the exhaust pipe via an adjustment valve. 3. The substrate holding apparatus according to claim 2, further comprising control means for controlling said regulating valve in accordance with an output signal of said pressure measuring means. 4. The substrate holding device according to claim 2, wherein a gas supply source is connected to said exhaust pipe via another adjusting valve. 5. The substrate holding apparatus according to claim 1, further comprising a valve interposed between said exhaust pipe and said measuring pipe. 6. The substrate holding apparatus according to claim 1, wherein said substrate is a substrate to be exposed. 7. The substrate holding apparatus according to claim 6, wherein said substrate to be exposed is a wafer to which a max pattern is transferred by X-ray irradiation.