JPH0520891B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a plasma X-ray exposure apparatus, and in particular,
The present invention relates to a plasma X-ray exposure apparatus suitable for transferring submicron patterns using a plasma X-ray source that generates soft X-rays by discharge.

[Background of the invention]

There are various types of plasma X-ray sources, but
Methods that utilize gas discharge at a pressure lower than atmospheric pressure, such as plasma focus or gas puff type sparks, are considered suitable for X-ray exposure equipment because they have high X-ray generation efficiency and long electrode life. .

Typically, in such exposure equipment, an X-ray transparent window made of a material with high X-ray transmittance, such as beryllium, is installed in the discharge tube, and the X-rays are transmitted through this window into the atmosphere or into an exposure chamber where the air has been replaced with helium. It is installed and exposed.

However, since soft X-rays with a wavelength of 0.5 nm or more have a significantly high absorption coefficient, there is a problem in that the usable X-ray illuminance is significantly reduced due to absorption by the X-ray transmission window. In addition, electrons, ions, evaporated matter and scattered objects from the electrodes collide with the X-ray transmitting window due to discharge, damaging or contaminating the X-ray transmitting window, resulting in a decrease in transmittance or unevenness. As a result, the X-ray illuminance decreases or becomes uneven. For this reason, it is necessary to frequently replace the X-ray transmission window, but in this case, the above-mentioned normal exposure equipment
Since a pressure close to atmospheric pressure is applied to the X-ray transmission window, there is a problem in that it is necessary to bring the inside of the discharge tube to atmospheric pressure each time the X-ray transmission window is replaced.

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems in an exposure apparatus using a plasma X-ray source, to achieve high X-ray illuminance on the wafer surface, and to eliminate uneven illuminance.
An object of the present invention is to provide a plasma X-ray exposure apparatus that has a high wafer processing speed, that is, a high throughput.

[Summary of the invention]

A feature of the present invention is that it is equipped with a plasma X-ray source that generates soft X-rays by forming plasma in a discharge space filled with or injected with gas at a pressure lower than that of the atmosphere. In a plasma X-ray exposure apparatus for exposing a sample, the exposure chamber is separated into a preliminary chamber adjacent to the discharge space and a sample chamber in which a sample is mounted through an X-ray transmission film, and at least the preliminary chamber pressure is reduced. The discharge space is configured to be evacuated to a pressure equal to or lower than that of the discharge space.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described using the cross-sectional view shown in FIG. This is an example equipped with a plasma X-ray source of plasma focus type. In FIG. 1, 1 is an anode of a plasma focus X-ray source, 2 is a cathode disposed coaxially with the anode 1, and both are insulated by a glass 3. These are attached to one end face of the chamber 4,
Inside the chamber 4, a gas such as neon, argon, krypton, etc. is sealed at a pressure of 0.1 to 1 Torr to form a discharge space 7. A charged capacitor 5 is connected between the anode 1 and the cathode 2 via a switch 6, and when the switch 6 is short-circuited,
The voltage stored in the capacitor 5 is momentarily applied between the electrodes. First, a discharge occurs along the surface of the glass 3, and plasma is generated. The ions and electrons of the plasma are attracted by the electric field and move, and at the same time they receive force from the annular magnetic field that exists in the space between the anode 1 and the cathode 2, and move parallel to the electrodes toward the open ends of both electrodes. When the plasma passes the edge of the electrode, it is focused under the pressure of the magnetic field, and a hot spot of high-temperature, high-density plasma is generated on the central axis, emitting soft X-rays.

An exposure chamber is formed by a preliminary chamber 10 provided adjacent to the discharge space 7 through an X-ray transparent film 8, and a sample chamber 10' in which a sample to be exposed is mounted. Preliminary room 10 and sample room 1
0' are all evacuated to a pressure close to vacuum.
12 in the sample chamber 10' is an X-ray mask for exposure;
13 is a wafer coated with resist. In this embodiment, a gate valve 11 is provided between the preliminary chamber 10 and the sample chamber 10'. This is wafer 1
This is to enable the exchange of wafers 3 and 3 to be performed independently of the discharge space 7. When performing exposure, the gate valve 11 is opened and X-rays are irradiated, and when the wafer 13 is exchanged, the gate valve 11 is opened. is closed, the sample chamber 10' is returned to atmospheric pressure, the flange 14 is opened, and the wafer 13 is replaced. When the exchange is completed, the sample chamber 10' is evacuated and the gate valve 11 is opened.

15 is a plasma aperture, and 16 is a charged particle deflector, which is provided to prevent plasma from colliding with the X-ray transparent film 8. Even so, the X-ray transmissive membrane 8 may be damaged or contaminated and must be replaced. When the gas sealed in the discharge space 7 is repeatedly discharged, impurity elements are mixed in and the efficiency of light emission decreases, so the gas is evacuated at appropriate intervals and new gas is filled. According to this embodiment, the X-ray transmission membrane 8 is replaced during this evacuation time. That is, when the discharge space 7 is evacuated, the discharge space 7 and the preliminary chamber 1 are
Since there is no pressure difference between
The presser metal fitting 9' is loosened, the winding mechanism 9 for the X-ray transparent membrane 8 is operated, and the X-ray transparent membrane 8 is replaced with a new X-ray transparent membrane. When the replacement is completed, the presser metal fitting 9' is pressed, and the discharge space 7 is isolated from the preliminary chamber 10.
Filled with gas. Wafer 1
By performing the exchange described in step 3 and preparing for the next exposure, wasted time can be saved. In addition, 17,1
Reference numerals 8 and 19 are exhaust and air supply pipes provided in the discharge space 7, the preliminary chamber 10, and the sample chamber 10', respectively.

In the above embodiment, the preliminary chamber 10 forming the exposure chamber
A gate valve 11 is provided between the gate valve 11 and the sample chamber 10' so that the wafer 13 can be exchanged independently of the discharge space 7. However, in another embodiment, an X-ray transmitting A modification is possible in which a window is provided so that exposure can be performed while maintaining the sample chamber 10' at atmospheric pressure. The X-ray transmission window 11 provided in this case is not damaged and does not need to be replaced, but it is necessary to maintain the strength to withstand the pressure difference between the preliminary chamber 10 and the sample chamber 10'. If the attenuation of X-rays in the sample chamber 10' becomes a problem due to atmospheric pressure, the distance between the X-ray transmission window 11 and the wafer 13 may be reduced, or the air in the sample chamber 10' may be filled with helium. You can take measures such as replacing it.

Further, although the pressure in the preliminary chamber 10 is selected to be close to vacuum in the above-described embodiment, the pressure in the preliminary chamber 10 may be selected to be equal to or close to that of the discharge space 7. When the pressures in the preliminary chamber 10 and the discharge space 7 are equal, there is an advantage that the X-ray transparent membrane 8 can be replaced without waiting until the discharge space 7 is evacuated.

〔Effect of the invention〕

As described above, according to the present invention, the preliminary chamber is isolated from the plasma X-ray source by an X-ray transparent film, and the sample chamber adjacent to this preliminary chamber via the opening/closing mechanism or the X-ray transparent window is used for exposure. By forming a chamber and setting at least the preliminary chamber pressure to a pressure equal to or lower than that of the discharge space, absorption and scattering of X-rays in the exposure chamber can be reduced. The thickness of the X-ray transmissive membrane was required to withstand a pressure difference of 760 Torr in the conventional device, but with the present invention, it only has to withstand a pressure difference of about 1 Torr, and the thickness of the X-ray transmitting membrane was reduced to several tens of micrometers, which was conventionally used. It is now possible to change beryllium thick to several micrometers thick polymer, and the X
Attenuation of rays can be significantly reduced, and the price of the X-ray transparent membrane can be significantly reduced. Further, according to the present invention, during the time to exhaust gas in the discharge space, X
It has become easier to replace the radiation transmitting membrane, making it possible to always obtain uniform and strong X-ray illuminance.
By shortening the time required to replace the X-ray transparent membrane, the processing speed of wafers, that is, the throughput can be increased. Furthermore, in the present invention, when the pressure in the preliminary chamber disposed between the discharge space and the sample chamber is used as a pressure close to vacuum, shock waves due to the movement of plasma in the discharge space are transmitted through the X-ray transparent membrane. The X-ray mask can be prevented from being transmitted to the X-ray mask in the sample chamber 9, and the X-ray mask can be prevented from being displaced due to stress, and a remarkable effect can be exhibited in terms of accuracy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus according to an embodiment of the present invention. <Explanation of symbols>, 1... Anode, 2... Cathode, 4
... Chamber, 5 ... Capacitor, 7 ... Discharge space, 8 ... X-ray transmission membrane, 9 ... Winding mechanism, 9'
... Holding metal fitting, 10 ... Preparation chamber, 10' ... Sample chamber, 11 ... Gate valve or X-ray transmission window, 12
... X-ray mask, 13 ... wafer, 14 ... flange, 15 ... plasma aperture, 16 ... charged particle deflector, 17, 18, 19 ... piping.

Claims (1)

[Claims] 1. A plasma X-ray source that generates soft X-rays by forming plasma in a discharge space filled or injected with gas at a pressure lower than that of the atmosphere, and that guides the soft X-rays to an exposure chamber. In a plasma X-ray exposure apparatus that exposes a sample, the exposure chamber is separated into a preparatory chamber adjacent to the discharge space and a sample chamber in which a sample is mounted via an X-ray transmission film, and at least the preparatory chamber pressure is adjusted to the above level. A plasma X-ray exposure apparatus characterized in that the discharge space is evacuated to a pressure equal to or lower than that of the discharge space. 2. In the plasma X-ray exposure apparatus according to claim 1, when the X-ray transmissive film is replaced with a new part of the film by operating the exchange mechanism when there is no pressure difference between the discharge space and the preliminary chamber. 1. A plasma X-ray exposure apparatus characterized in that the X-ray transmission film is replaced by an X-ray transmissive film. 3. The plasma X-ray exposure apparatus according to claim 1 or 2, characterized in that the preliminary chamber of the exposure chamber and the sample chamber are separated by an opening/closing mechanism. Exposure equipment. 4. In the plasma X-ray exposure apparatus according to claim 1 or 2, a preliminary chamber of the exposure chamber and a sample chamber are separated by an X-ray transmission window, and the sample chamber is large. A plasma X-ray exposure device characterized by being maintained at a pressure close to atmospheric pressure.