JP2972315B2 - Vacuum processing equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum processing apparatus suitable for measuring the temperature of a substrate or a substrate when processing a substrate or a substrate in a vacuum such as a sputtering apparatus.

[Conventional technology]

When performing a certain process such as depositing a thin film on a substrate or performing etching in a vacuum, the temperature at which the process is performed is an important parameter in many cases. For example,
In general, in vapor deposition, the properties of a curtain formed by the temperature of a substrate are greatly affected. Therefore, it is necessary to control the temperature of the substrate at the time of starting the vapor deposition, during the vapor deposition, and after the vapor deposition is completed. For example, regarding the effect of the temperature of the substrate on the film formation during sputtering on the microstructure of the film,
Shin Solid Films, Vol. 171-531, 1989 JA Thornton and one other "Stress-Related Effect"
fects in Thin Films; Thin Solid Films, vol.171,
pp. 5-31 (1989)) is well known and describes in detail the effect of substrate temperature. Therefore, it is desirable that the temperature of the substrate is measured and controlled during, before, and after the film formation.

For example, to heat a substrate in a vacuum, lamp heating using an infrared lamp or the like is often used. However, since a heat transfer medium cannot be generally obtained in a vacuum, heating (cooling) by radiation involves a difference in the emissivity or absorptance of an object to be heated (cooled), in this example, the substrate. At this wavelength, the manner of absorption greatly differs, so that it is not easy to control the heating.

On the other hand, the method of filling the back surface of the substrate with gas is excellent as a method of controlling the temperature of the substrate. This heating method,
Alternatively, the method of transferring heat to the substrate is described in detail in JP-A-62-122118. In the following, a conventional technique for heating will be described. Even when cooling is required, the base may be cooled with some kind of refrigerant (for example, liquid nitrogen).

The control method for heating this substrate is as follows. The substrate to be heated is placed on a pre-heated base (hereinafter referred to as a heat block) and fixed so that the peripheral portion of the substrate is pressed against the heat block. Then, gas is introduced into an extremely narrow gap formed between the substrate and the heat block. The introduced gas is between the substrate and the heat block and acts as a heat transfer medium. The gas pressure on the back surface of the substrate is generally about several Torr. As a gas, Ar, which is a working gas for sputtering, is exclusively used in a sputtering apparatus. Ar gas introduced from the edge of the substrate,
It escapes as appropriate and acts to constitute part of the Ar gas pressure at which sputtering is performed. In a sputtering apparatus, glow discharge is generally performed at an Ar pressure of several mTorr. Helium may be used for cooling purposes.

At this time, the heat block and the back surface of the substrate need to be close to each other. This is because if the distance from the heat block to the substrate is large, the thermal resistance is large and efficient or rapid heating cannot be performed. In general, the distance between the substrate and the heat block is set as uniform as possible to 1 mm or less over the entire substrate.

If there is a depression or the like in the heat block, the temperature is lowered at the position of the substrate corresponding to that portion, and the uniformity of the substrate temperature is impaired.

Now, when Ar gas is introduced into the back surface of the substrate, substrate heating occurs rapidly, and this heating continues until the substrate temperature equilibrates with the heat block temperature. Further, as the temperature of the substrate approaches the heat block, the rate of temperature rise becomes slow.

[Problems to be Solved by the Invention] The above-mentioned prior art is a method in which the temperature of the substrate is actively balanced with the temperature of the heat block, but it takes a long time, and the temperature of the substrate is sufficiently balanced with the temperature of the heat block. In this case, the heat block temperature and the substrate temperature have a good correspondence, but there is a problem that the actual temperature of the substrate cannot be known during this heating process.
Further, in practice, the way in which the substrate is pressed onto the base is not constant, and this cannot be known even if the desired substrate temperature cannot be controlled.

SUMMARY OF THE INVENTION An object of the present invention is to provide a substrate heating control unit that can introduce a gas into a space between a substrate back surface and a heat block, and can further know an actual substrate temperature as a result of substrate heating. .

[Means for solving the problem]

In order to achieve the above object, in the present invention, the temperature of the substrate is known by observing the back surface of the substrate with an infrared thermometer. At this time, a small window is provided in the heat block so that gas heating can be performed without any problem, and the small window can be hermetically sealed so that observation of the back surface of the substrate with an infrared thermometer can be performed only when necessary through the small window. A lid was provided.

[Action]

The small window has a role of creating a space between the back surface of the substrate and the heat block. In order to observe the temperature on the back surface of the substrate with an infrared thermometer, an optical path for passing infrared radiation from the back surface of the substrate is required. However, simply providing an optical path on the back surface of the substrate results in a large gap between the substrate and the heat block, which is not preferable in terms of substrate temperature uniformity. For this reason, a small window is provided,
The substrate temperature may be measured by opening this window when temperature measurement is required.

When this small window is closed, it can be almost sealed,
The gas pressure required for heat transfer from the heat block on the back surface of the substrate to the substrate can be maintained.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.
In this embodiment, the case of controlling the heating of the substrate will be described. However, as described below, the purpose of the cooling control can be similarly achieved only by using the refrigerant.

Reference numeral 1 denotes a heat block, in which an electric heater 2 is provided. If a coolant such as liquid nitrogen is introduced into the heat block 1 instead of the heater, it can be used for cooling the substrate.

Reference numeral 3 denotes a small window provided in the heat block 1, which emits infrared radiation (radiation) from the back surface of a substrate (Si wafer in this example) 4 placed on the heat block 1.
It is provided to pass through the optical path 6 for observation by the thermometer 5.

The infrared thermometer 5 is installed in the atmosphere. Therefore, the optical path 6 must pass through the boundary between the atmosphere and the vacuum. Reference numeral 7 denotes a window for this purpose, and a material for efficiently transmitting infrared rays, for example, barium fluoride, calcium fluoride, or the like is used for the window material.

The pipe 8 has Ar in the space formed by the substrate 4 and the heat block.
It is for introducing gas. The substrate 4 is a substrate holder 9
By the heat block.

The small window 3 of the heat block 1 is closed by a lid 10. That is, the lid 10 is a crank-shaped drive shaft 11
, The drive shaft 11 can rotate up and down. In FIG. 1, the lid has been lowered to a halfway position, but the lid 10 can be further lowered to a position sufficiently below the heat block 1 and then rotated to observe the infrared thermometer. Can be retracted to a position that does not obstruct the optical path 6 for use.

On the contrary, the drive shaft 11 can be raised from the position shown in FIG. 1, and at the top dead center, the small window 3 of the heat block 1 can be completely closed by the lid 10 from below.

For this reason, the confidentiality of the space formed between the substrate 4 and the heat block 1 is maintained, and the pressure in this space is maintained at a preferable pressure within several Torr.

The substrate 4 is fixed to the heat block 1 by the substrate holder 9, and the end of the substrate and the end of the heat block are in close contact with each other, and the valve 13 is adjusted to a space between the surface of the substrate 4 and the heat block 1. For example, Ar gas is introduced.

At this time, the drive shaft 11 has risen to its top dead center, and the small window 3 of the heat block 1 is closed by the lid 10. By doing so, the transfer of heat from the heat block 1 to the substrate 4 starts, and the temperature of the substrate starts to rise quickly. Drive shaft 11 at appropriate time
Is rotated downward, the lid 10 is removed from the optical path 6, and the back surface of the substrate 4 can be observed by the infrared thermometer 5.

Since the gas pressure of several Torr cannot be maintained between the back surface of the substrate 4 and the heat block 1 due to the lowering of the lid 10, the temperature rise of the substrate 4 substantially stagnates.

If it is found that the substrate has a desired temperature, for example, a process such as film formation by sputtering may be started by a sputtering target 12 installed opposite to the substrate 4, or if the temperature is too low. If so, the lid 10 may be closed again, and heating may be continued by filling with gas.

The inventors have experimentally confirmed the effects of the present invention by using the Al film on a Si wafer by sputtering.

The method of heating the wafer by introducing Ar gas to the back side of the wafer depends on mechanical adjustment, but it is about 0.1%, that is, about one in 1,000 wafers, when the temperature starts film formation Was not heated to a predetermined temperature (300 ° C. in the experiments of the present inventors). This is because the wafer was not pressed sufficiently evenly on the heat block.

As is well known, when an Al film is formed at a low wafer temperature, a film having small crystal grains is formed. A film with small crystal grains has a lower resistance to electromigration when this Al film is used for a wiring than a film with large crystal grains. For this reason, as described above, if sufficient heating does not occur prior to film formation, the reliability of the Al wiring will be greatly reduced.

Also, in the case of an Al film, even if it is formed at a low wafer temperature,
The specular reflectance of the Al film does not decrease, and it is very difficult to visually identify such a defect.

〔The invention's effect〕

According to the present invention, the temperature of the wafer can be directly measured, so if a wafer that does not reach the desired temperature is found, additional heating or removal as a defective product from the beginning can be performed. As a result, shipment of defective products can be prevented.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and is an explanatory view showing an example in which the present invention is applied to a sputtering apparatus. 1: Heat block 2: Electric heater inside the heat block 3: Small window for temperature observation provided in the heat block 4: Si wafer (substrate) 5: Infrared thermometer 6: Optical path for observation of infrared thermometer 7: Peep window between atmosphere and vacuum 8: Heat transfer medium gas introduction pipe 9: Substrate holder 11: Drive shaft 12: Sputtering target 13: Gas introduction valve

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuji Yoneoka 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Pref. Hitachi Manufacturing Co., Ltd. (56) References JP-A-63-188940 (JP, A) JP-A-1-105530 (JP, A) JP-A-4-42025 (JP, A) JP-A-4-130746 (JP, A) JP-A-4-56145 (JP) , A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 21/66 H01L 33/00 H01L 21/31 G01J 5/00

Claims (1)

(57) [Claims] 1. A vacuum processing apparatus for performing processing by heating or cooling a substrate mounted on a base, a heating or cooling means for setting the base to a predetermined temperature, and an infrared ray for the back surface of the substrate. An observation hole provided in the base for observation by a thermometer, gas introduction means for filling a predetermined gas in a space formed by the substrate and the base, and the observation hole in the base. The observation hole is closed when the base or the substrate is being heated or cooled by the heating or cooling means, and is movably installed in an optical path to an infrared thermometer. A vacuum processing apparatus, comprising: a shutter for opening the observation hole and retracting from the optical path when measuring the temperature.