JP4667737B2 - Method for forming metal pillar - Google Patents

Description

  The present invention relates to a method for forming a metal column serving as an electrode or a conductive wire on an IC pattern surface or a chip substrate.

  On the IC pattern surface, a metal column called a bump having a height of about 20 μm is formed as an electrode. Further, instead of wire bonding, a plurality of metal columns having a height of about 100 μm are provided on the chip itself, and the IC chip is mounted on the substrate through the metal columns.

  These metal pillars are formed by applying integrated circuit formation technology. Specifically, as shown in FIGS. 3A to 3D, a thick resist film is formed on the surface of the substrate or IC pattern, and a predetermined pattern mask is overlaid on the resist film surface and etched with oxygen gas plasma. Then, the opening formed by this etching is filled with metal by plating, and then the resist film is ashed.

  Etching plasma includes capacitively coupled plasma (CCP) and inductively coupled plasma (ICP), which is a pair of parallel plate electrodes. The inductively coupled plasma is generated by a coiled electrode having one end connected to a high frequency power source. The capacitively coupled plasma has an excellent etching rate in a low temperature range, but has a large damage to the object to be processed. The inductively coupled plasma has an excellent etching rate in a high temperature range and small damage, but is inferior in an etching rate in a low temperature range.

  The metal column that becomes the bump or the like has a high aspect ratio. For this reason, as shown in FIG. 3B, a resist film or a scum may remain on the bottom portion to be an opening at the time of pattern formation. If the plating process is carried out as it is, a metal column having a scum portion is formed as shown in FIG. 3 (d), which causes poor conduction, and the plating causes poor growth. It is conceivable to perform a discaming process. Patent Document 1 and Patent Document 2 disclose that the discum processing is performed on a pattern having a high aspect.

Japanese Patent No.-2623672, page 2, right column, lines 8 to 15 Japanese Patent No. 25222088, page 3, left column, lines 2-5, page 3, right column, lines 2-3

  If inductively coupled plasma (ICP) is used as the plasma for performing the discum treatment, the pattern shape is destroyed due to the high temperature treatment. Therefore, Patent Document 1 describes that a parallel plate type electrode (capacitive coupling type plasma) is used, and Patent Document 2 describes that a reactive ion etching apparatus is used.

  Using a parallel plate type electrode or a direct electrode disclosed in Patent Document 1 or Patent Document 2 and performing a discaming process with a pattern having a high aspect ratio resulted in large damage and poor uniformity.

  In order to solve the above-mentioned problems, the present invention forms a thick film resist on an IC pattern surface or a substrate surface, and exposes and develops the thick film resist to form openings serving as metal columns, and then oxygen gas plasma. When the metal column is formed by removing the thick film resist after the metal is filled in the opening by plating, the upper half is used as the plasma generation space, and the lower half is used as the plasma generation space. Is a downstream type plasma processing apparatus using a comb-like electrode in which the convex part of one sheet-like electrode enters the concave part of the other sheet-like electrode as a plasma generating electrode, The side wall of the opening was roughened.

  Among the downstream type plasma processing apparatuses, a comb-like electrode in which the convex portion of one sheet-like electrode enters into the concave portion of the other sheet-like electrode is used as a plasma generating electrode. Since the plasma is generated uniformly along the line, the efficiency of decomposing oxygen gas is higher than that of other capacitively coupled plasmas, a large amount of oxygen radicals are generated, and ashing at a low temperature becomes possible.

  When scum remains at the bottom of the opening, the scum is decomposed and gasified at the same time as the opening side wall is roughened.

  According to the present invention, a metal column having a high aspect ratio such as a bump can be formed on the IC pattern surface or the substrate surface without causing abnormal growth or abnormal shape. Therefore, it is possible to effectively stack circuits.

Further, according to the present invention, low-temperature processing is possible, so that deformation of the pattern shape due to thermal contraction of the photoresist (for example, enlargement of the opening) can be suppressed, the pattern shape after development can be maintained, and heat resistance can be maintained. Applicable to low resists. In particular, many resists having a film thickness exceeding 20 μm have low heat resistance, and the method of the present invention is advantageous.
Further, it is possible to cope with metal oxidation suppression and bump fine pitch.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram for explaining the method of the present invention in the order of steps, and FIG.

A thick resist film (20 μm or more) resist film formed on the IC pattern surface or the substrate surface is exposed and developed to form a resist pattern having openings for plating metal. This opening may or may not have scum.
As the resist to be used, for example, PMER-LA900 (manufactured by Tokyo Ohka Kogyo) or CA-1000 (manufactured by Tokyo Ohka Kogyo) is appropriate.

  Next, the resist pattern is lightly ashed using a downstream type plasma processing apparatus shown in FIG. In the plasma processing apparatus, a chamber 2 is disposed on a base 1. The chamber 2 has an upper half as a plasma generation space and a lower half as a plasma processing space.

  A pair of comb-like electrodes 4 and 5 are arranged outside the plasma generation space. The comb-like electrodes 4 and 5 are formed in a sheet shape and are attached so that the convex portion of one electrode 4 enters the concave portion of the other electrode 5. One electrode is connected to the high frequency power source 6, and the other electrode 5 Is grounded. Further, a table 7 grounded from below faces the plasma processing space, and a semiconductor wafer W or the like to be processed is set on the table 7.

  In the above, when oxygen gas is introduced from the reaction gas inlet 8 and the power is turned on, plasma is uniformly generated along the gaps between the comb-like electrodes 4 and 5, and the oxygen gas is decomposed and the plasma generation space 3a. To generate oxygen radicals. The generated oxygen radicals are guided to the lower plasma processing space 3b, and a discum treatment is performed by the oxygen radicals. That is, when scum is present due to oxygen radicals, the scum is decomposed, and the side wall of the opening is roughened regardless of the presence or absence of scum.

  As conditions for the discaming process, for example, the temperature of the table 7 is set to 80 ° C., the pressure of the introduced oxygen gas in the chamber is set to 300 mTorr, and the high frequency is set to 600 W. For the end point, the time is calculated from the amount of scum and the ashing rate, and the processing time is set slightly longer than the calculated time so that the amount of scum may vary. In this way, scum can be completely removed.

  Next, the opening is filled with metal (gold, copper, aluminum, etc.) in the opening, and then the resist film is removed by ashing to obtain a metal column. In this plating step, since the side wall of the opening is moderately roughened, the adhesion of plating is improved, so that a bump having a good shape along the resist pattern can be obtained.

Diagram explaining the method of the present invention in the order of steps Overall view of plasma processing equipment used for discum treatment A diagram explaining conventional problems

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Chamber, 3a ... Plasma generation space, 3b ... Plasma processing space 4, 5 ... Comb-shaped electrode, 6 ... High frequency power supply, 7 ... Table, 8 ... Reaction gas inlet, W ... To-be-processed object.

Claims (1)

A thick film resist is formed on the IC pattern surface or the substrate surface, and this thick film resist is exposed and developed to form an opening to be a metal pillar, and then a discum process is performed by oxygen gas plasma, and a plating process is performed. In the method for forming a metal column in which the thick film resist is removed after filling the metal into the opening, the discumbing process is performed downstream with the upper half as a plasma generation space and the lower half as a plasma processing space. a type of plasma processing apparatus, the convex portion of one of the sheet electrode as a plasma generating electrode using the comb-shaped electrode which enters the recess of the other sheet-like electrode, the temperature conditions of the descum process table temperature 80 ° C., the pressure in the chamber 300 mTorr oxygen gas introduced, the applied high frequency and 600W, also descum processing time Ska Is set longer than the time calculated in consideration of the variation in the amount of scum was completely removed, the descum process simultaneously with forming method of the metal posts, characterized in that roughening the side walls of the opening.