Pressing plate for improving damage to back surface of substrate in ion implantation process

Abstract

The utility model discloses a pressing plate for improving the damage of the back surface of a substrate in an ion implantation process, which comprises a pressing plate body, a buffer layer is arranged on the pressing plate body, and the friction coefficient between the buffer layer and the back surface of the substrate is smaller than that between the pressing plate body and the back surface of the substrate; the buffer layer is provided with a through hole for the substrate ejector pin to pass through and a heat dissipation hole. And the buffer layer is made of an insulating material. According to the application, the condition of contact damage after ion implantation on the back surface of the 300mm substrate can be effectively avoided, the appearance damage of the substrate is improved, and the particle pollution risk in the subsequent process is reduced.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of semiconductor production, concretely relates to a press plate for improving substrate back surface damage in ion implantation process. BACKGROUND

[0002] Ion implantation is a technology for doping semiconductor surface, and its purpose is to change the carrier concentration and conductive type of semiconductor. Ion implantation equipment is widely used in doping process, can satisfy the requirements such as shallow junction, low temperature and accurate control, and has become the indispensable key equipment in integrated circuit manufacturing process. At present, ion implantation machine is applied to many fields, including integrated circuit, IGBT (insulated gate bipolar transistor) manufacturing field, solar cell production field, AMOLED (active matrix organic light emitting diode) panel manufacturing and the like.

[0003] With the reduction of semiconductor process size, the number of chips integrated on each wafer is more and more, and the cost of single wafer is also increased, and any tiny defect can cause chip function failure or even scrap, therefore, how to avoid wafer damage is the most important in each process.

[0004] The characteristic of ion implantation is that the ion beam is vertically or at a certain angle incident to the substrate. The current mainstream ion implantation equipment is to implant the whole surface by fixing the ion beam and moving or rotating the substrate up and down; the substrate movement is mainly realized by rotating the large disc type (multiple pieces) or moving up and down by the platen (Platen) elevator (single piece).

[0005] The method for using the platen (Platen) elevator is as follows: in the ion implantation process, the platen adsorbs the substrate by electrostatic force, and moves the substrate up and down in the vertical direction to implant ions. Since the platen and the substrate back surface must be in contact, in the moving process, tiny relative displacement will leave scratches or contact marks on the substrate back surface; these damages can cause particle contamination or impurity introduction problem in the later process; therefore, how to reduce or avoid such contact damage is a widespread concern in the industry. UTILITY MODEL CONTENTS

[0006] The utility model aims at providing a press plate for improving substrate back surface damage in ion implantation process to solve the problems in the prior art.

[0007] The utility model aims at providing a press plate for improving substrate back surface damage in ion implantation process to solve the problems in the prior art.

[0008] A press plate for improving substrate back surface damage in ion implantation process, comprising a press plate body,

[0009] The buffer layer is provided on the pressing plate body, and the friction coefficient between the buffer layer and the back surface of the substrate is less than the friction coefficient between the pressing plate body and the back surface of the substrate.

[0010] The buffer layer is provided with a through hole for the substrate pin to pass through and a heat dissipation hole.

[0011] The buffer layer is of insulating material.

[0012] Preferably, the static friction coefficient between the buffer layer and the back surface of the substrate is ≤0.15us, and the dynamic friction coefficient is ≤0.1uk.

[0013] Preferably, the buffer layer is a polytetrafluoroethylene buffer layer.

[0014] Preferably, the thickness of the buffer layer is ≤1mm.

[0015] Preferably, the polytetrafluoroethylene buffer layer is provided on the pressing plate body by a thermal spraying process.

[0016] Preferably, the heat dissipation holes are annularly and uniformly distributed in the edge region of the buffer layer.

[0017] The present application can effectively avoid the case of contact damage of the 300mm substrate after ion implantation, improve the appearance damage of the substrate, and reduce the risk of particle contamination in subsequent processes. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a schematic diagram of the front structure of the pressing plate provided by the present application;

[0019] Fig. 2 is a schematic diagram of the top structure of the pressing plate provided by the present application;

[0020] Fig. 3 is an application reference state diagram of the pressing plate provided by the present application;

[0021] Fig. 4 is an AOI Map diagram of the substrate after ion implantation using the original pressing plate;

[0022] Fig. 5 is an AOI Map diagram of the substrate after ion implantation using the pressing plate with the HDPE buffer layer;

[0023] Fig. 6 is an AOI Map diagram of the substrate after ion implantation using the pressing plate with the PTFE buffer layer;

[0024] BRIEF DESCRIPTION OF DRAWINGS

[0025] 1-pressing plate body; 2-buffer layer; 3-pin hole; 4-heat dissipation hole; 5-substrate; 6-pin. DETAILED DESCRIPTION

[0026] The main steps of the substrate during ion implantation process are as follows: (1) the front arm of the machine transfers the substrate in the box to the pre-evacuation chamber; (2) the pre-evacuation chamber is evacuated; (3) the rear arm transfers the substrate from the pre-evacuation chamber to the platen of the vacuum process chamber (the platen and the substrate are horizontally placed); (4) the platen is vertically erected after electrostatic adsorption of the substrate; (5) the elevator drives the platen to move up and down for ion implantation; (6) after the implantation is completed, the elevator returns to the initial position, the platen is restored to the horizontal position and the adsorption is released; (7) the rear arm transfers the substrate back to the pre-evacuation chamber; (8) the pre-evacuation chamber is broken; (9) the front arm transfers the substrate from the pre-evacuation chamber back to the box.

[0027] During the ion implantation process, the substrate is adsorbed on the platen by electrostatic force, moves up and down with the elevator for full-surface implantation, and the back surface of the substrate must be in close contact with the platen. The speed of the elevator moving up and down can reach 12 inch / s. The platen body is generally made of SiC ceramic material, and the static friction coefficient between the platen body and the substrate is about 0.29us, and the dynamic friction coefficient is about 0.26uk. The back surface of the substrate is easily damaged by the friction force generated on the surface of the platen.

[0028] In view of the above technical problems, the application provides an improved platen structure, as shown in Figs. 1-3 A buffer layer 2 is provided on the platen body 1, and the friction coefficient between the buffer layer and the back surface of the substrate is less than the friction coefficient between the platen body and the back surface of the substrate, which can reduce the damage to the back surface of the substrate.

[0029] Since the platen body is provided with a thimble 6, when the arm takes and places the substrate 5, the thimble needs to be raised to support the substrate, then the arm is retracted, the thimble is lowered, and the platen body 1 adsorbs the substrate by electrostatic force. Therefore, the buffer layer 2 needs to reserve a thimble hole 3 for the thimble to pass through. In addition, in order not to affect the electrostatic force of the platen body, the buffer layer 2 needs to be made of insulating material.

[0030] During ion implantation, a certain high temperature may be generated, therefore, the buffer layer 2 also needs to have certain high temperature resistance and is provided with heat dissipation holes 4, which is beneficial to control the temperature of the substrate. Preferably, the heat dissipation holes are annularly and uniformly distributed in the edge region of the buffer layer, which helps to improve the heat dissipation efficiency.

[0031] Preferably, the static friction coefficient between the buffer layer and the back surface of the substrate is ≤0.15us; and the dynamic friction coefficient is ≤0.1uk.

[0032] The buffer layer is preferably a polytetrafluoroethylene (PTFE) buffer layer. PTFE has a very low intermolecular force of the surface fluorine-carbon chain due to its high lubrication and non-stickiness. Compared with other materials in the prior art, such as HDPE (high-density polyethylene) material, polyamide material, polyvinyl chloride material, and polytetrafluoroethylene propylene material, the static and dynamic friction coefficients are extremely small (the static friction coefficient with steel is 0.10μs, and the dynamic friction coefficient is 0.05μk; the static friction coefficient with plastic is 0.04μs, and the dynamic friction coefficient is 0.04μk), which is much smaller than the body of the pressing plate, and the surface is smooth. Therefore, the friction between the substrate and the pressing plate can be reduced, thereby avoiding the generation of contact-type damage and improving the yield of the substrate.

[0033] Preferably, the thickness of the buffer layer 2 is ≤1mm. The thickness is thin, which can avoid affecting the electrostatic field of the pressing plate, maintain the adsorption capacity of the pressing plate to the substrate, and avoid the risk of falling off. At the same time, under this thickness, when the arm (provided with a substrate support table to support the substrate) extends into the pressing plate body and the substrate, the arm body maintains a certain gap with the lower pressing plate body and the upper substrate, which can prevent collision with the substrate and the pressing plate body and avoid scratching the arm and the substrate.

[0034] Preferably, the polytetrafluoroethylene buffer layer is provided on the pressing plate body by a thermal spraying process.

[0035] Embodiment 1

[0036] A layer of polytetrafluoroethylene buffer layer is provided on the pressing plate body, with a thickness of 1mm. The polytetrafluoroethylene buffer layer is provided with heat dissipation holes and pin holes. The pressing plate provided with a high-density polyethylene buffer layer and the original SiC ceramic material pressing plate are used as controls.

[0037] Three groups of AOI (automatic optical inspection) appearance inspection substrates without abnormalities are prepared, and after cleaning, the three kinds of pressing plates are used for ion implantation on the same ion implanter using the same program.

[0038] After ion implantation, the two groups of substrates are subjected to AOI appearance inspection, and it is found that:

[0039] (1) After ion implantation using the original SiC pressing plate, the back surface of the substrate is seriously scratched, with a total scratch length of 2048.2mm;

[0040] (2) After ion implantation using the pressing plate with a HDPE buffer layer, the back surface of the substrate is heavily scratched, with a total scratch length of 1386.3mm;

[0041] (3) After ion implantation using the pressing plate with a PTFE buffer layer, the back surface of the substrate is basically not scratched, with a total scratch length of 4.1mm.

[0042] The substrate AOI appearance detection picture is shown in Figs. 4-6 .

[0043] The above-mentioned pressing plate with polytetrafluoroethylene buffer layer is subjected to adsorption capacity test, and it is found that the substrate does not fall off at different lifting rates and speeds, which proves that the polytetrafluoroethylene buffer layer does not have adverse effect on the electrostatic adsorption capacity of the pressing plate.

[0044] The above-mentioned results fully prove that the pressing plate with polytetrafluoroethylene buffer layer provided by the application can obviously improve or even avoid the damage of the substrate caused by contacting the pressing plate during ion implantation process, compared with the original pressing plate and the pressing plate with buffer layer made of other materials.

[0045] Therefore, the application can effectively avoid the situation that the 300mm substrate appears contact damage after ion implantation on the back surface, improve the appearance damage of the substrate, and reduce the risk of particle pollution in subsequent process.

[0046] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including all the preferred embodiments and all changes and modifications falling within the scope of the present application. Obviously, those skilled in the art can make various modifications and changes to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and changes of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and changes.

Claims

1. A pressure plate for improving damage to the back side of a substrate during ion implantation, comprising a pressure plate body, characterized in that, The pressure plate body is provided with a buffer layer, and the coefficient of friction between the buffer layer and the back of the substrate is less than the coefficient of friction between the pressure plate body and the back of the substrate. The buffer layer is provided with ejector pin holes and heat dissipation holes for the ejector pins of the substrate to pass through; The buffer layer is made of insulating material.

2. The pressure plate for improving substrate backside damage during ion implantation as described in claim 1, characterized in that, The static friction coefficient between the buffer layer and the back of the substrate is ≤0.15µs; the dynamic friction coefficient is ≤0.1µk.

3. The pressure plate for improving substrate backside damage during ion implantation as described in claim 1, characterized in that, The buffer layer is a polytetrafluoroethylene buffer layer.

4. The pressure plate for improving substrate backside damage during ion implantation as described in claim 1, characterized in that, The thickness of the buffer layer is ≤1mm.

5. The pressure plate for improving substrate backside damage during ion implantation as described in claim 3, characterized in that, The polytetrafluoroethylene buffer layer is applied to the pressure plate body via a thermal spraying process.

6. The pressure plate for improving substrate backside damage during ion implantation as described in claim 1, characterized in that, The heat dissipation holes are evenly distributed in a ring shape at the edge region of the buffer layer.

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