JPH0471215A - Substrate retaining equipment and aligner provided with said equipment - Google Patents

Abstract

PURPOSE:To precisely measure pressure in a minute space, and prevent the deterioration of pattern transfer precision, by providing a pipe for measurement which connects a vacuum gauge and the check surface of a retaining stand. CONSTITUTION:In an X-ray aligner, a pipe 30 for measurement having a free end is connected with a chuck surface of a wafer chuck 6. A vacuum gauge 13a detecting pressure in a minute space formed between the rear of a wafer 5 and a chuck surface of the wafer chuck 6 is fixed on the free end of the pipe 30 for measurement. A valve 31 is interposed between an exhaust pipe 11 and the pipe 30 for measurement. A microprocessor (CPU) 20 and a first controller 14a which are controlling means to control a first and a second gas adjusting valves 15a, 15b and the valve 31 are operated by the output signal of the first vacuum gauge 13a.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is a method for holding a substrate by vacuum suction on the back surface of the substrate while keeping the contact thermal resistance between the substrate and the holding stand below a predetermined value. The present invention relates to a substrate holding device and an exposure apparatus including the device.

[Prior art 1] In an exposure apparatus of a semiconductor manufacturing device, 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 side of the substrate by vacuum suction (for example, a special substrate holding device). Publication No. 1-14703) is often used.

Generally, when a substrate is held by a substrate holding device, if the contact thermal resistance between the substrate and the holding stand of the substrate holding device is large, the exposure energy when transferring a mask pattern to the substrate is transferred from the substrate to the substrate holding device. Since the particles do not escape to the holding table, the temperature of the substrate increases and thermal deformation occurs, resulting in deterioration of pattern transfer accuracy. Particularly, in the case of a substrate holding device using vacuum suction, a small space is formed between the back surface of the substrate and the chuck surface of the holding table (the surface facing the suctioned substrate) to dissipate heat. Since there is no gas as a heat medium, the pattern transfer accuracy deteriorates significantly due to an increase in the temperature of the substrate.

Therefore, we have developed a substrate holding device that can control the temperature of vacuum-adsorbed substrates during exposure and also maintain the flatness of the substrates.
The temperature of the substrate is controlled by flowing temperature-controlled water (hereinafter referred to as "temperature-controlled water") into the channel provided in the holding stand of the substrate holding device, and the temperature between the substrate and the holding stand is controlled. In order to keep the contact thermal resistance between the substrates below a predetermined value, there is a method that holds the substrate while keeping the pressure within the microspace at a constant value.

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

This X-ray exposure apparatus is disclosed in, for example, Japanese Patent Application No. 63-25299.
Mask 104 and wafer 1 as described in No. 1
05 are arranged at a distance of several tens of microns and a mask pattern is transferred using a proximity type exposure apparatus.

This X-ray exposure apparatus consists of a chamber 103 filled with helium (He) gas that transmits X-rays generated by a storage ring, etc., and an X-ray transmitter installed in a part of the chamber 103. a beryllium window (hereinafter referred to as rBe window) 102, a second vacuum gauge 113b that detects the pressure inside the chamber 103, a second He cylinder 1]6b that supplies He gas into the chamber 103, It has a third gas control valve 115C that adjusts the amount of He gas supplied into the chamber 103, a second controller 114b that opens and closes the third gas control valve 115c, and a substrate holding device described below.

The substrate holding device included in this X-ray exposure apparatus includes a wafer chuck 106 that is a holding table, a flow path 107 piped inside the wafer chuck 106, and a constant temperature bath 110 that circulates temperature-controlled water in the flow path 107. The chuck surface 10L (see FIG. 6) of the wafer chuck 106 is connected to a pump 117 which is a vacuum generation source, and the chuck surface 10L is
．． and a first He cylinder 116a which is a supply source of He gas.
a first gas control valve 115a interposed between the wafer chuck 106 of the exhaust pipe 111 and the pump 117; and a first gas control valve 115a interposed between the wafer chuck 106 of the exhaust pipe 111 and the first He cylinder 116a. a second gas control valve 115b interposed between the wafer chuck 106 of the exhaust pipe 111 and the first and second gas control valves 115a;
115b, a first vacuum gauge 113a for detecting the pressure in the microspace formed between the back surface of the wafer 105 and the chuck surface 1061;
The first and second gas control valves 115a are activated by the output signal of the vacuum gauge 113a.

It has a microprocessor (hereinafter referred to as rcPUJ) 120, which is a control means for controlling the controller 115b, and a first controller 114a. Here, CPU
120, together with the second controller 114b, controls the third gas control valve 11 based on the output signal of the second vacuum gauge 113b.
A mask 104 for transferring the mask pattern is used to control the wafer 1 (15
It is installed in the chamber 103 with a certain gap between the two.

In addition, as shown in Fig. 6, two concentric circles of full 106
2 is the chuck surface 106. of the wafer chuck 106. and the chuck surface 106. One groove 106□ is also formed in the center of the
06. Grooves 1062 are opened at the top, bottom, left, right, and center of the figure.

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

Before transferring the mask pattern to the wafer 105, C.
The P U 120 takes in the output signal of the second vacuum gauge 113b, and controls the second controller 114b according to the output signal.
is controlled to open and close the third gas control valve 115c, thereby reducing the pressure inside the chamber 103 to 200 [Torrl].
Thereafter, when the wafer 105 to be vacuum-adsorbed is transported to the illustrated position by a known transport hand (not shown), the CPU 120 closes the first gas control valve 115a.
The first controller 114a is controlled to open the first controller 114a.

When the first gas control valve 115a is opened, the exhaust pipe 111
is communicated with the pump 1!7, and connects the back surface of the wafer 105, the chuck surface 1061 of the wafer chuck 106, and each groove 10.
The He gas present in the microspace formed between the wafer 105 and the 6 It is adsorbed and held by 106.

Here, as an experimental result using this X-ray exposure device,
In order to maintain vacuum suction force and pattern transfer accuracy, for example, the contact thermal resistance between the wafer 105 and the wafer chuck 106 must be 2 x 10-'(K-m''/W) or less, For this purpose, it was found that the wafer backside pressure, that is, the pressure in the microspace, needs to be about 50 Torrl from the relationship between the wafer backside pressure and the contact thermal resistance shown in FIG.

Therefore, in this X-ray exposure apparatus, when vacuum suction of the wafer 105 is started, the CPU 120 controls the first vacuum gauge 1.
13a at a predetermined timing and monitor the pressure in the exhaust pipe 111 indicated by the output signal, the first controller 114a is controlled so that the pressure in the exhaust pipe III is always 50 [Torrl]. control, first
and a second gas control valve 115a.

115b is opened and closed.

If the pressure in the exhaust pipe 111 is kept constant in this way,
The wire is connected to the wafer 1 through the Be window 102 and the mask 104.
By irradiating 05, the mask pattern is transferred. At this time, the temperature of the wafer 105 during exposure is controlled by circulating temperature-adjusted water through the channel 107 using a constant temperature bath 110 to keep the temperature of the wafer chuck 106 constant.

[Problems to be Solved by the Invention] However, in the conventional substrate holding device described above, in order to suppress the temperature rise of the wafer 105 to approximately ±0.06 ['C) or less and to prevent deterioration of pattern transfer accuracy, For example, if the intensity of the X-rays irradiated to the Eva 105 is 1
50 [mW/crn"l, it is necessary to keep the change in contact thermal resistance within the range of approximately ±4.OXl0-'[ni・m"/Wl, and the pressure change in the microspace at this time The allowable value is within the range of approximately ±5 [Torrl (7th
(see figure) is the first
A vacuum gauge 1138 connects the wafer chuck 106 of the exhaust pipe 111 and the first and second gas control valves 115a, 11
5b, if the degree of warpage of the wafer 105 or the roughness of its back surface changes,
When the amount of He gas flowing into the microspace from the atmosphere in the wafer chuck 106 changes, the chuck surface 106 of the wafer chuck 106 changes. The reading of the first vacuum gauge 1138 may change even if the pressure within the microspace does not change due to the conductance between the vacuum gauge 113a and the first vacuum gauge 113a. There is a problem that pressure cannot be measured accurately.

An object of the present invention is to provide a substrate holding device that can prevent deterioration of pattern transfer accuracy by accurately measuring the pressure in a microspace and suppressing contact thermal resistance to a predetermined value or less, and an exposure apparatus having the device. It is in.

[Means for Solving the Problems] A substrate holding device of the present invention includes: a holding table on which the back side of a substrate is held by vacuum suction; a chuck surface of the holding table and a vacuum generation source are connected; an exhaust pipe connecting the chuck surface of the stand and a gas supply source; a first gas control valve interposed between the holding stand of the exhaust pipe and the vacuum generation source; and the holding of the exhaust pipe. a second gas control valve interposed between the table and the gas supply source; a measuring tube connected to the chuck surface of the holding table and having a free end; and a protruding end of the measuring tube. a vacuum gauge attached to the substrate for detecting the pressure within the microspace formed between the back surface of the substrate and the chuck surface of the holding base; and control means for controlling the first and second gas control valves so that the gas control valve has a predetermined value.

Further, interposed between the exhaust pipe and the measurement pipe,
It may have a valve controlled by the control means.

An exposure apparatus of the present invention includes a substrate holding device according to claim 1 or 2.

[Function] The substrate holding device of the present invention has a measuring tube that connects the vacuum gauge and the chuck surface of the holding stand, so that most of the gas in the measuring tube is exhausted after exhaustion progresses to a certain extent. Therefore, the pressure value indicated by the vacuum gauge matches the pressure within the microspace formed between the back surface of the substrate and the chuck surface of the holding table, so the output signal of the vacuum gauge indicates the pressure within the microspace. If the control means controls the first and second gas regulating valves so that the pressure is at a predetermined value, the pressure within the microspace can be maintained at the predetermined value with high accuracy.

Further, interposed between the exhaust pipe and the measurement pipe,
By having a valve controlled by the control means,
If vacuum suction is started after the valve is opened by the control means, the gas in the measurement tube can be quickly exhausted through the valve, so the pressure in the microspace can be accurately and accurately evacuated. It is possible to quickly maintain the predetermined value.

By having the above-described substrate holding device, the exposure apparatus of the present invention can accurately measure the pressure within the microspace and suppress the contact thermal resistance to a predetermined value or less, thereby preventing deterioration of pattern transfer accuracy. .

[Example] Next, embodiments of the present invention will be explained 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 of the present invention.

The X-ray exposure apparatus of this embodiment includes a chamber 3 filled with helium (He) gas that transmits X-rays generated by a storage ring, etc., and an X-ray beam provided in a part of the chamber 3. A beryllium window (Be window) 2 for transmission, a second vacuum gauge 13b that detects the pressure inside the chamber 3, and a second He cylinder 16 that supplies He gas into the chamber 3.
b, and a third gas control valve 15c that adjusts the amount of He gas supplied into the chamber 3 from the He cylinder 16b.
and a second controller 14b that opens and closes the third gas control valve 15c.

Further, the substrate holding device is a wafer chuck 6 which is a holding stand.
, a flow path 7 piped inside the wafer chuck 6 , a constant temperature bath 10 for circulating temperature-controlled water through the flow path 7 , and a chuck surface 6 of the wafer chuck 6 . (see FIG. 2), an exhaust pipe 11 that connects a pump 17 that is a vacuum generation source, and a first He cylinder 16a that is a supply source of He gas, and a space between the wafer chuck 6 of the exhaust pipe 11 and the pump 17. and a second gas regulating valve 15b interposed between the wafer chuck 6 of the exhaust pipe 11 and the first) LE cylinder 16a. Regarding the above points, see Section 5.
This is the same as the conventional X-ray exposure apparatus shown in the figure.

However, in the X-ray exposure apparatus of this embodiment, the measurement tube 30 having a free end is connected to the chuck surface 6I of the wafer chuck 6, and the back surface of the wafer 5 and the chuck surface 6I of the wafer chuck 6 are connected to each other. A first vacuum gauge 13a is attached to the free end of the measuring tube 30 to detect the pressure in the microspace formed between the exhaust tube 11 and the measuring tube 30. It is interposed between the first. The fifth point is that the microprocessor (CPU) 20 and the first controller 14a, which are control means for controlling the second gas control valves 15a, 15b and the valve 31, operate based on the output signal of the first vacuum gauge 13a. This is different from the conventional example shown in the figure.

Further, as shown in FIG. 2, the wafer chuck 6 has two concentric grooves 6□ on the chuck surface of the wafer chuck 6.
1 and the chuck surface 6. A groove 62 is also formed in the center of the concentric groove 62, and the exhaust pipe 11 is opened by branching into the groove 62 at the top, bottom, left and right of the concentric groove 62 and at the center as shown in FIG. It is the same as the conventional wafer chuck 106, except that the measurement tube 30 is attached to the chuck surface 6. It differs from the conventional one in that it is opened midway between the central groove 6□ and the inner concentric groove 62.

The CPU 20, together with the second controller 14b, controls the third gas control valve 1 based on the output signal of the second vacuum gauge 13b.
5c is also controlled. Further, a mask 4 for transferring a mask pattern is installed in the chamber 3 with a certain gap from the wafer 5 which is vacuum-adsorbed.

Next, the operation of the X-ray exposure apparatus of this embodiment will be explained.

Before transferring the mask pattern to the wafer 5, the CPU
20 takes in the output signal of the second vacuum gauge 13b, controls the second controller 14b according to the output signal, and controls the third vacuum gauge 14b.
By opening and closing the gas control valve 15c, the pressure inside the chamber 3 is maintained at 200 Torrl. Thereafter, when the wafer 5 to be vacuum-adsorbed is transported to the illustrated position by a known transport hand (not shown), the CPU 20
The first controller 14a is controlled to open the gas control valve 15a and the valve 31. First gas control valve 15a
And when the valve 31 is opened, the exhaust pipe 11 and the measuring pipe 30
is communicated with the pump 17 and exists in the microspace formed between the back surface of the wafer 5 and the chuck surface 61 and groove 62 of the wafer chuck 6 and in the measurement tube 30.
The gas is sucked and the pressure in the microspace is reduced, 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, most of the He gas in the measurement tube 30 to which the first vacuum gauge 13a is attached is exhausted after the evacuation progresses to a certain extent, and the He gas in the measurement tube 30 is completely exhausted. Since the flow of He gas no longer exists, the CPU 20 controls the first controller 14a to close the valve 31. After that, the contact thermal resistance between the wafer 5 and the wafer chuck 6 is set to 2 x 10"'[K-m"
/W], the CPU 20 takes in the output signal of the first vacuum gauge 13a at a predetermined timing, monitors the pressure inside the measurement tube 30 indicated by the output signal, and also monitors the pressure inside the measurement tube 30. the first and second gas regulating valves 15a so that the pressure is always 50 Torrl.

The first controller 14a is controlled to open and close the first controller 15b. At this time, the pressure value indicated by the first vacuum gauge 13a matches the pressure in the microscopic space, so by monitoring the pressure in the measurement tube 30, the pressure in the microscopic space can be accurately measured by 50%. [Torrl can be kept constant.

After keeping the pressure in the microspace constant, the X-rays are
By irradiating the wafer 5 through the window 2 and the mask 4, the mask pattern is transferred. At this time, the temperature of the wafer 5 during exposure is controlled by the flow path 7 using the constant temperature bath 10.
This is done by circulating temperature-controlled water to keep the temperature of the wafer chuck 6 constant.

As a result of the above, in the x#lA exposure apparatus of this embodiment, since the pressure in the minute space can be maintained at a precision of 50 Torrl, the contact thermal resistance between the wafer 5 and the wafer chuck 6 can be set to a value that does not deteriorate the pattern transfer precision. Approximately 2 x 10-
'[ni・m''/Wl.

Next, the operation and effects of the valve 31 in this embodiment will be explained.

Although the valve 31 is not necessarily required, if the valve 31 were not provided, it would take a long time to bring the pressure in the microspace to the target of 50 Torrl, compared to the case where the valve 31 is provided, due to the following reasons. As a result, productivity deteriorates.

Chuck surface 6 of wafer chuck 6. and the first vacuum gauge 13
The He gas present in the measurement tube 30 connecting the wafer chuck 6 to the wafer chuck 6 is exhausted through the microspace formed between the wafer 5 and the chuck surface 61 at the center of the wafer chuck 6. Groove 62 and inner concentric groove 6□
(See Figure 2). However, since the microspace is very narrow, the flow resistance is large, and it takes a long time to exhaust the He gas. After a certain amount of time has elapsed, the first vacuum gauge 13
The pressure indicated by a does not match the pressure within the microspace.

Therefore, when starting vacuum adsorption, the CPU 20 controls the first controller 14a to open the valve 31, so that the He gas present in the measurement tube 30 flows to the exhaust pipe 11 via the valve 31. By doing so, the time for exhausting the He gas is shortened. 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 to close the valve 31, and then controls the exhaust pipe 11 to close the valve 31. The pressure inside is 5
The output signal of the first vacuum gauge 13a is continuously captured at a predetermined timing until the value reaches 0 [Torr].

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

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

This wafer chuck 26 has one concentric groove 262 formed near the outer periphery of the chuck surface 26.
Exhaust pipes 11 are branched and opened on the upper, lower, left and right sides of the concentric groove 262 (the upper and lower exhaust pipes 11 are not shown), and the measuring pipe 30 is connected to the chuck surface 26. It differs from the wafer chuck 6 in FIG. 2 in that it has an opening in the center.

Since this wafer chuck 26 can increase the contact area between the wafer 5 to be vacuum chucked and the chuck surface 26+, the contact thermal resistance can be made smaller than that of the wafer chuck 6 shown in FIG. 2.

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

This wafer chuck 36, like the wafer chuck 26 shown in FIG. Exhaust pipes 11 are branched and opened vertically and horizontally (the exhaust pipes 11 above and below are not shown), and a measuring pipe 30 opened in the center is connected to a concentric groove 36□. 3 thin grooves 36. are formed at equal intervals in the circumferential direction.

This wafer chuck 36 has three narrow grooves 36. when there is no valve 31 shown in FIG. Since this serves as a He gas exhaust passage, there is an advantage that the efficiency of exhausting He gas within the measurement tube 30 can be increased.

In addition, the wafer chuck 6.26 shown in FIGS. 2 to 4
．． In No. 36, four exhaust pipes 11 were opened in each valley groove, but the number may be other than four as long as the exhaust pipes 11 are opened symmetrically.

In the above description, an X-ray exposure apparatus was shown as an embodiment of the exposure apparatus of the present invention, but for example, an exposure apparatus that uses light maintains a substrate at a constant temperature and there is a pressure difference between the front and back surfaces of the substrate. Accordingly, the present invention is applicable to all exposure apparatuses having a substrate holding device for holding the substrate.

Further, 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] Since the present invention is configured as described above, it produces the following effects.

The substrate holding device according to claim 1 includes a measuring tube that connects the vacuum gauge and the chuck surface of the holding stand.
Since most of the gas in the measurement tube is exhausted after exhaustion has progressed to a certain extent, the pressure value indicated by the vacuum gauge is based on the minute pressure that is formed between the vacuum-adsorbed substrate and the chuck surface of the holding table. Since it matches the pressure within the space, it is possible to accurately measure the pressure within the microspace and suppress the contact thermal resistance to a predetermined value or less.

Further, the substrate holding device according to claim 2 has a valve that is interposed between the exhaust pipe and the measurement pipe and is controlled by the control means, so that when vacuum suction is started, the Since the gas in the measurement tube can be quickly exhausted, there is an effect that the pressure in the microspace can be accurately and quickly maintained at the predetermined value.

By having the substrate holding device according to claim 1 or 2, the exposure apparatus of the present invention can accurately measure the pressure within the microspace and suppress the contact thermal resistance to a predetermined value or less. This has the effect of preventing deterioration in pattern transfer accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an X-ray exposure apparatus having a substrate holding device of the present invention, FIG. 2 is a diagram showing the structure of the chuck surface of a wafer chuck, and FIG. 3 is a diagram showing the chuck surface of the wafer chuck. 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 the 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 shown in FIG. 5, and FIG. 7 is a diagram showing an example of the relationship between wafer back surface pressure and contact thermal resistance. 2... Be window, 3... Chamber, 4
... mask, 6.26.36 6+, 26+, 36t 62.26a, 36□ 7 ... flow path, 11 ... exhaust pipe, 13a ... first vacuum gauge, 13b ... th 2 vacuum gauge, 14a...first controller, 14b...second controller, 15a...first gas control valve, 15b...second gas control valve, 15c...second 3 gas control valve, 16a...first He cylinder, 16b...second He cylinder, 20...CPU, 30... measurement tube,
31... Valve, 363... Thin groove. 5... Sea urchin, wafer chuck, chuck surface, groove, 10... Constant temperature chamber,

Claims (1)

[Claims] 1. A holding table on which the back surface of the substrate is held by vacuum suction, a chuck surface of the holding table and a vacuum generation source are connected, and a gas supply source is connected to the chuck surface of the holding table. a first gas control valve interposed between the holding stand of the exhaust pipe and the vacuum generation source; and a first gas control valve interposed between the holding stand of the exhaust pipe and the gas supply source. a second gas control valve interposed between; a measuring tube having a free end connected to the chuck surface of the holding base; and a back surface of the substrate attached to the free end of the measuring tube; a vacuum gauge for detecting the pressure in the microspace formed between the chuck surface of the holding table; and a control means for controlling a second gas control valve. 2. Claim 1, characterized in that it has a valve that is interposed between the exhaust pipe and the measurement pipe and is controlled by a control means.
Substrate holding device as described in section. 3. An exposure apparatus comprising the substrate holding device according to claim 1 or 2.