JPS61197500A - Cooler for substrate - Google Patents

Abstract

PURPOSE:When an ion is injected into the surface of a substrate such as a silicon wafer in a vacuum chamber, to cool the substrate effectively and to prevent damage by heat, by bringing the substrate into contact with a cooling plate having a great number of protrusions. CONSTITUTION:When the substrate such as a silicon wafer, etc. is placed on the vacuum chamber 2 and an ion is injected into it, the substrate 5 is damaged by rise in temperature accompanied by heat introduction of the ion injection. In order to prevent it, the substrate 5 is pushed against the surface 4 of the cooling plate 4 such as Cu, etc., having a lens-like surface and good heat conduction by the clamp 6. The cooling plate 4 is placed on the holder 2 made of Cu or Al equipped with the circulation path 3 of a refrigerant such as cooling water, etc. When the substrate 5 is heated by the heat introduction of the ion injection, the bottom of the substrate is curved and attached to the top of the cooling plate 4, the numerous protrusions 7 on the top of the cooling plate 4 come into the dents on the bottom of the substrate 5, the protrusions on the bottom of the substrate come into the dents between the protrusions on the surface of the cooling plate 4a, the contact area of is increased, the cooling effect is improved and damage by rise in temperature of the substrate 5 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an apparatus for cooling a substrate such as a silicon wafer used in the manufacture of semiconductors.

(Prior Art) Conventionally, in the manufacturing process of ICs, etc., ions are implanted into this type of substrate in a vacuum chamber to change the physical properties of the surface. Since there is a risk of damage due to temperature rise due to heat input from the substrate, the substrate is cooled by being brought into contact with the flat or lens-shaped front surface of a cooling plate through which cooling water is circulated. In this case, a thermally conductive rubber having high elasticity is provided between the cooling plate and the substrate, and the periphery of the substrate is clamped for attachment.

(Problem to be Solved by the Invention) When a silicon wafer is clamped around a substrate, the clamped portion of the substrate is pressed and deformed because its back surface is made of elastic rubber, and there is no rubber between the substrate and the rubber. There is a loose part that cannot be followed, and the actual contact area between the two is relatively small, making it unsuitable as a cooling device when, as in recent years, a large amount of power is required to process the substrate, and the amount of heat generated by the substrate increases. It is.

In addition, if the elastic rubber on the front surface of the cooling plate is removed and the board is brought into direct contact with the front surface, loose parts will still occur due to the unevenness of the board surface, reducing the contact area and making it difficult to make good contact. There is a disadvantage that cooling performance cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cooling device having a structure that allows a large contact area between a substrate to be processed in a vacuum and a cooling plate, thereby increasing heat transfer between the two.

(Means for Solving the Problems) In the present invention, a substrate to be subjected to ion implantation or other processing in a vacuum chamber is brought into contact with the front surface of a cooling plate cooled by circulation of cooling water, etc., so that the temperature rises as the processing progresses. In this device, a large number of protrusions are formed on the front surface of the cooling plate.

(Function) A substrate such as a silicon wafer is held in contact with the front surface of a cooling plate, and when it is subjected to heat injection processing such as ion implantation in a vacuum chamber, the temperature of the substrate rises. Since a large number of protrusions are formed on the front surface of the substrate, the protrusions of the cold plate enter into the recesses existing on the back surface of the substrate, and the protrusions present on the back surface fit into the valleys between the protrusions of the cooling plate. The substrate can come into contact with many of the protrusions of the cooling plate, increasing the contact area between the substrate and the cooling plate and improving cooling performance.

(Embodiment) To explain an embodiment of the present invention with reference to the drawings, in FIG. 1, (1) is a substrate holder placed in a vacuum chamber (2),
The substrate holder (1) is made of metal such as Cu, AI, etc., and has a circulation path for a coolant such as cooling water inside or on the back.
3) is provided.

(4) is Cu provided on the surface of the holder (1), that is, the cooling surface.
A cooling plate made of a metal with good thermal conductivity such as - is shown, and a substrate (5) such as a silicon wafer is pressed against the front surface (4a) of the cooling plate with a clamp (6). The clamp (6)
presses the periphery of the substrate (5), for example, at three locations, and holds the substrate (5) between this and the cooling plate (ω).

A large number of projections (7) are formed on the front surface (4a) of the cooling plate (4) as shown in FIG. The protrusions (7) may be formed into any shape, such as a rectangular shape, and the spacing and height of the protrusions (7) are determined by taking into account the average and degree of dispersion of the unevenness existing on the back surface of the substrate (5). When ions are implanted into the surface of the substrate (5) in the vacuum chamber (D) and the temperature rises, the substrate (ω) warps so that the ion-implanted surface side becomes a convex surface, so the front surface (4) of the cooling plate (4)
It is preferable that a) be formed in advance into a protruding lens-like shape as shown in the figure, so that it can fit and come into contact with the cooling plate (4) when the temperature of the substrate (5) increases.

When the ion implantation process is performed on the substrate (5), the temperature rises, and the amount of heat flows through the cooling plate (4) to the substrate holder (1) to prevent damage due to the high temperature. Board (4)
The protrusion (7) formed on the front surface (4a) of the front surface (4a)
enters the recess existing on the back side of the substrate (5) that comes into contact with the
The contact area between the substrate (5) and the cooling plate (4) is increased, and cooling performance is improved accordingly.

A polytetrafluoroethylene film (8) as shown in Fig. 5 may be layered on the top surface of each protrusion (7), and a metal film may be further coated on this, or as shown in Fig. 6. 1 on the entire front surface (4a) including the protrusion (7)! (8)
The substrate (5) is coated with the material of the cooling plate (4).
It is also possible to prevent contamination of the protrusions (υ) and to make contact with the substrate (5) wider by some elastic deformation of the layer (8).

In addition, instead of the layer (8), a layer formed by laminating thin or fibrous carbon, a thin metal film, or gold IIhII
A film formed by laminating fibers may also be used.

FIG. 7 shows the cooling performance of the substrate cooling device, in which curve A represents the temperature change of the substrate caused by a conventional cooling plate having a lens-shaped front surface protruding.

As the power of the ion beam and other heat input increases, the substrate temperature increases significantly, and when the input power approaches 1000 W, the temperature exceeds 300° C., which tends to cause damage to the substrate or the resist coated on the substrate. However, in the case of the present invention in which projections (7) were further formed on the cooling plate having a lens-shaped front surface, the temperature rise was prevented even when the input power increased, as shown by curves B and C1D. The one with curve B has a thickness of 0 on the top surface of the protrusion (7).
．． 1111 with polytetrafluoroethylene film (8), curve C has no film (8), and when the substrate (5) is brought into direct contact with the protrusion (7), the curve is This figure shows the temperature change of the substrate (5) when a film obtained by laminating thin carbon films is provided on the upper surface of the protrusion (7).

(Effects of the Invention) According to the present invention, since a large number of protrusions are formed on the front surface of the cooling plate against which the substrate comes into contact, the contact area between the substrate and the cooling plate is increased, thereby cooling the substrate. There are effects such as improved performance, and the ability to process substrates with increased input power without damaging them.

[Brief explanation of drawings]

Fig. 1 is a cutaway side view of an embodiment of the present invention, Fig. 2 is a perspective view of an example of a cooling plate, Figs. 3 and 4 are enlarged sectional views of the cooling plate, and Figs. 5 and 6 are An enlarged sectional view of a modified example of the cooling plate,
FIG. 7 is a diagram showing cooling performance. (No...Vacuum chamber (4)...Cooling plate (4)
a)...Front (ω...Substrate (7)
...Protrusion and 2 others Figure 1 Figure 2 Figure 4 Figure 6 Figure 7 υ Power (w)

Claims (1)

[Claims] In a device in which a substrate subjected to ion implantation or other processing in a vacuum chamber is brought into contact with the front surface of a cooling plate cooled by circulation of cooling water, etc., the temperature of the substrate rises due to processing is cooled. A substrate cooling device characterized by forming a large number of protrusions on the front surface of a cooling plate.